Process for homogeneous hydrogenation of esters

A novel process is described for the homogeneous hydrogenation of carboxylic acid esters to primary alcohols utilizing anionic Group VIII metal hydride compositions as catalysts which contain phosphorus, arsenic or antimony organoligands. Use of these anionic catalysts allows the process to be conducted in solution under mild conditions of temperature and pressure with high selectivity and eliminates the disadvantages of utilizing heterogeneous catalysts. A process is also described for decarbonylating formate esters utilizing said compositions as catalysts.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for homogeneously hydrogenating 
carboxylic acid esters to primary alcohols in solution under mild 
conditions utilizing anionic Group VIII metal hydride compositions as 
catalysts. 
2. Brief Description of the Background of the Invention Including Prior Art 
Carboxylic acid esters, as a class, are not readily susceptible to 
hydrogenation to produce primary alcohols under mild conditions. 
Generally, very forcing conditions are required, such as temperatures well 
above 150.degree. C. together with reaction pressures in the order of 
2000-3000 psig. In addition, the hydrogenation process generally requires 
a heterogeneous catalyst, which are frequently not selective such as Raney 
nickel, copper-chromite, or zinc-chromium oxide. See Organic Reactions, 
Vol. 8, pages 1-27 (John Wiley, 1954). 
Catalytic hydrogenation of carboxylic acid esters represents an 
importantindustrial source of primary alcohols, which are useful in a wide 
variety of known applications such as in producing gums, resins, perfumes, 
wetting agents and the like. For example, 1-decanol is commercially 
produced by catalytic hydrogenation of coconut oil fatty acids and their 
esters under high pressure. Sulfonated derivatives of 1-decanol are useful 
as surface-active agents. Also, trifluoroethanol, CF.sub.3 CH.sub.2 OH, 
useful as an intermediate in producing the anesthetic, CF.sub.3 
CHClOCHF.sub.2, is produced by the heterogeneous catalytic hydrogenation 
of trifluoroethyltrifluoroacetate, CF.sub.3 COOCH.sub.2 CF.sub.3, as 
described in U.S. Pat. No. 4,072,726 (Nychka et al. to Allied Chemical 
Corporation 1978). 
Homogeneous catalytic hydrogenation of acyclic and cyclic carboxylic acid 
anhydrides to the corresponding esters and lactones by the use of soluble 
ruthenium catalysts is described in U.S. Pat. No. 3,957,827 (1976) and 
J.C.S. Chem. Comm. p. 412-413 (1975). However, no specific mention is made 
of the reduction of esters to the corresponding primary alcohols. 
New and improved catalysts for catalytic hydrogenation of carboxylic esters 
to primary alcohols are constantly being searched for and especially for 
homogeneous catalysts that can overcome the known attendant disadvantages 
of the use of heterogeneous catalysts. 
SUMMARY OF THE INVENTION 
We have unexpectedly found that the anionic Group VIII metal hydride 
compositions, described by Guido Pez and Roger Grey in U.S. Application, 
Ser. No. 972,147 now abandoned are very effective catalysts in the 
hydrogenation of carboxylic acid esters to primary alcohols. 
The invention process generally involves subjecting a solution of a 
carboxylic acid ester and catalyst composition, neat or in a suitable 
inert solvent, to an atmosphere containing hydrogen gas under mild 
conditions, preferably at temperatures below 150.degree. C. and pressures 
below 150 psig, whereby high yields and high selectivities of the 
resulting primary alcohol are obtained. 
In accordance with this invention there is provided a process for 
hydrogenating an ester group in a cyclic or acyclic saturated aliphatic 
mono- or dicarboxylic ester, thereby converting the acid moiety of said 
ester to a primary alcohol group, said acid moiety containing at least two 
carbon atoms, comprising contacting a solution of hydrogenation catalyst 
and said ester neat or in an inert solvent therefore, with an atmosphere 
containing hydrogen gas, at a temperature of about 0.degree. to 
150.degree. C., under a pressure of about 0 to 150 psig, said catalyst 
being a composition of the formula: 
EQU [(L.sub.a L.sub.b 'L.sub.c "M).sub.x H.sub.y ].sub.z.sup.r- Q.sub.s.sup.q+ 
including dimers, trimers and tetramers thereof, wherein L, L' and L" are 
independently selected from organoligands containing phosphorus, arsenic 
or antimony elements, each ligand being free of carbonyl and containing at 
least one said element, M being a Group VIII metal, H being hydrido, Q 
being acation, wherein a, b and c are integer values of 0 or 1, the sum of 
a, b, c being of from 1 to 3, x being a value 1 or 2, y being an integer 
value of from 1 to 3x, x being defined above, r and s independently being 
integer values of 1 or 2, and z and q independently being integer values 
of from 1 to 3, wherein said composition is electrically neutral and 
contains a minimum of one and a maximum of three atoms of phosphorus, 
arsenic, antimony, or mixtures thereof, per Group VIII metal atom. 
Further provided is a process for decarbonylating an alkyl formate ester 
thereby producing an alkyl alcohol and carbon monoxide comprising 
contacting said alkyl formate ester with the catalyst composition 
described hereinabove, neat or in an inert solvent therefor, at a 
temperature of about 0.degree. to 150.degree. C., under a dry atmosphere. 
DESCRIPTION OF INVENTION AND PREFERRED EMBODIMENTS 
The novelty of the invention process resides in the fact that the anionic 
Group VIII metal hydride compositions described in U.S. Application 
972,147 by Guido Pez and Roger Grey, hereby incorporated by a reference, 
are very efficient catalysts for the hydrogenation of carboxylic esters 
thus producing the corresponding primary alcohols. A complete and thorough 
description of the anionic hydride compositions, their structure,synthesis 
and physical properties thereof, are adequately described in the 
above-mentioned reference. For purposes of this invention, the scope of 
the compositions useful as catalysts in the instant invention process is 
identical to the scope of the compositions disclosed in the 
above-described reference. By the terms "hydrogenation catalyst" and 
"catalyst composition" as used herein, is meant the compositions described 
above. 
The Group VIII metals present in the compositions useful as catalysts in 
the invention process include iron, cobalt, nickel, ruthenium, rhodium, 
palladium, osmium, iridium and platinum and preferably ruthenium, rhodium, 
iron, and platinum, designated as M in the above-described formula. 
Organoligands, independently designated L, L' and L", present in the 
compositions include the coordinating elements phosphorus, arsenic and 
antimony and preferably those of phosphorus and arsenic. The number of 
ligands present is 1 to 3 per Group VIII metal atom, designated by the sum 
of a, b, and c, and the value of x, in which each ligand is carbonyl free 
and contains at least one P, As or Sb element, and included in the total 
number of ligands, is a maximum of three atoms of said elements present 
per Group VIII metal atom in the molecule. A maximum of three atoms of P, 
As or Sb, or mixtures thereof, per Group VIII metal atom is a limitation 
because we believe that more than this number interferes in the catalytic 
process. For example, it has been found by us that when the anionic tris 
(triphenylphosphine)ruthenium complex, is employed during the homogeneous 
catalytic hydrogenation of ketones or esters, additional 
triphenylphosphine has an adverse effect upon catalytic reactivity, 
wherein we believe the anionic tetrakis(triphenylphosphine)ruthenium 
complex is formed under the conditions. 
It is also considered that carbonyl ligands generally withdraw electronic 
charge from the respective metal atom, to which they are attached, thus 
rendering any hydride ligand attached to the metal atom less hydridic in 
character. Since it is considered that the effectiveness of the subject 
compositions as homogeneous catalysts is a function of the hydridic nature 
of the hydride ligands, the subject compositions do not contain carbonyl 
ligands. Further, we have found that the presence of carbon monoxide acts 
as a catalyst poison in the homogeneous hydrogenation of esters utilizing 
the catalyst compositions described herein. 
Included among ligands applicable in the compositions are those wherein L, 
L' and L" are independently of the formulae: 
(R'R"G.sub.1), (R'R"R"'G.sub.1) or (R'R"G.sub.1 --R--G.sub.2 R"'R"") 
wherein G.sub.1 and G.sub.2 are independently phosphorus, arsenic or 
antimony and R', R", R"' and R"" are independentlyselected from C.sub.1 
-C.sub.18 linear or branched alkyl, phenyl, C.sub.1 -C.sub.18 linear or 
branched alkylphenyl and phenyl-substituted C.sub.1 -C.sub.18 linear or 
branched alkyl, and R being a C.sub.1 -C.sub.4 divalent alkyl bridging 
group between G.sub.1 and G.sub.2, wherein said alkyl and phenyl groups 
can also be substituted with groups inert toward metal arenes (such as 
potassium naphthalene), such as C.sub.1 -C.sub.4 alkoxy, being linear or 
branched, and the like. Bidentate ligands are considered as being one 
ligand in the above-described formula for the subject compositions andmay 
form two points of attachment per Group VIII metal atom, or be bridged 
between two Group VIII metal atoms. 
Representative examples of organoligands applicable in the compositions (Ph 
being used hereinafter to designate phenyl) are triphenylphosphine 
(Ph.sub.3 P), diphenylmethylphosphine (Ph.sub.2 CH.sub.3 P), 
diphenylphosphide (Ph.sub.2 P), triphenylarsine (Ph.sub.3 As), 
diphenylmethylarsine (Ph.sub.2 CH.sub.3 As), trimethylphosphine, 
triethylphosphine, trioctadecylphosphine, tri-n-octylphosphine, 
triisopropylphosphine, tri-secondary-butylphosphine, 
tricyclohexylphosphine, tri(pentamethylphenyl)phosphine, 
tri(p-tolyl)phosphine, tri(p-n-octadecylphenyl)phosphine, 
tri(p-n-octylphenyl)phosphine, tri(2-phenethyl)phosphine, 
tribenzylphosphine, tri(2-phenyl-isooctadecyl)phosphine, 
tri(p-methoxyphenyl)phosphine, tri(2-methoxyethyl)phosphine, 
tri(p-tertiary-butoxyphenyl)phosphine, triphenylstibine, 
dimethylphosphinoethane (Me.sub.2 PCH.sub.2 CH.sub.2 PMe.sub.2) and 
diphenylphosphinoethane (Ph.sub.2 PCH.sub.2 CH.sub.2 PPh.sub.2). 
Preferred ligands are those of organophosphorus and organoarsine types and 
particularly preferred are those of organophosphorus, particularly 
triphenylphosphine, diphenylmethylphosphine and diphenylphosphide. 
The charge on the anion in the composition, designated as r, can be -1 or 
-2, and the number ofanions in the composition, designated by z, can be 
from 1 to 3. 
Cation Q in the composition has a positive charge from +1 to +3 designated 
by q, and the composition can have from one to three cations, designated 
by s. Representative examples of cations applicable in the composition 
include the Group IA alkali metals, such as Li, Na, K, Rb and Cs, the 
Group IIA alkaline earth metals, such as Be, Mg, Ca, Ba and Sr, Group IIIA 
metals such as Al, and Ga, divalent and trivalent lanthanide elements such 
as La.sup.+3 and Eu.sup.+2, "metallocene" sandwich-type organo-metallic 
gegencations, such as (C.sub.5 H.sub.5).sub.2 Ti.sup.+, and (C.sub.5 
H.sub.5).sub.2 V.sup.+, and divalent transition metals such as V, Cu, Mn 
and Fe. Preferred cations in the compositions are K.sup.+, Li.sup.+, 
La.sup.+3 and V.sup.+2. The total cationic and anionic charges in the 
composition are equivalent in absolute value such that the resulting 
composition is electrically neutral. 
The number of hydrogen atoms also termed "hydride" or "hydrido" ligands, 
attached to the Group VIII metal atoms in the compositions is from 1 to 
3x, ("x" being defined above) designated by the symbol y, and can be from 
1-6 and preferably two or four. It is believed that where one hydrogen 
atom is present per two Group VIII metal atoms, the hydrogen atom is 
bridged between the two respective metal atoms. One of the hydride ligands 
present can be formed by an ortho metallation process as described below. 
The number of hydride ligands is easily established in the molecule by the 
well-known technique of reacting one gram mole of said composition in a 
pure state with at least about one gram-mole of hydrogen chloride, 
producing one gram-mole of hydrogen gas per gram-atom of hydride ligand 
present in the composition. Stoichiometrically, the reaction requires one 
gram-mole of hydrogen chloride, but in practice, a slight excess over this 
amount is used to insure complete reaction. 
Representative examples of compositions applicable in the process are 
illustrated by the following formulas which are approximate structural 
formulas, as regarded by us, on the basis of present available evidence: 
[(Ph.sub.3 P).sub.3 RuH].sup.- K.sup.+ ; [(Ph.sub.3 P) (Ph.sub.2 
P)RuH].sub.2.sup.- K.sub.2.sup.+ ; ](Ph.sub.3 P).sub.2 RuH].sup.- K.sup.+ 
; 
[(Ph.sub.2 P).sub.2 Fe.sub.2 H].sup..dbd. K.sub.2.sup.+, [(Ph.sub.3 
P).sub.3 RuH].sup.- Na.sup.+ ; [(Ph.sub.3 P).sub.3 RuH].sup.- Li.sup.+ ; 
[(Ph.sub.3 P).sub.3 RuH].sub.2.sup.- Mg.sup.+2 ; [(Ph.sub.3 P).sub.2 
RuH].sup.- Li.sup.+ ; [(Ph.sub.3 P).sub.2 RuH].sup.- Cs.sup.+ ; 
[(Ph.sub.2 CH.sub.3 P).sub.3 RuH].sup.- K.sup.+ ; [(Ph.sub.3 P).sub.2 
PtH].sup.- K.sup.+ ; [(Ph.sub.3 P).sub.3 RhH].sup.- K.sup.+ ; 
[(Ph.sub.3 P).sub.2 RuH.sub.2 ].sup.- K.sup.+ ; [(Ph.sub.3 P).sub.2 
RuH.sub.3 ].sup.- K.sup.+. 
Preferred compositions for use in the process are listed below giving their 
approximate structural formulas, assigned Roman numerals, used herein for 
convenient referral thereto, and chemical names. 
______________________________________ 
Roman 
Formula Numerals Chemical Name 
______________________________________ 
[(Ph.sub.3 P).sub.3 RuH].sup.- K.sup.+ 
I potassium tris(triphenyl 
phosphine) ruthenium 
hydride 
[(Ph.sub.3 P) (Ph.sub.2 P) RuH].sup.- K.sup.+ 
II potassium triphenylphos- 
phine diphenylphosphide 
ruthenium hydride 
[(Ph.sub.3 P).sup.2 RuH].sup.- K.sup.+ 
III potassium bis(triphenyl- 
phosphine)ruthenium 
hydride 
______________________________________ 
The molecular structure of the compositions are fairly complex and have 
only been rigorously studied in detail in a few cases. For example, 
structure (I) behaves chemically as a dihydride and, on the basis of its 
infrared and nuclear magnetic resonance spectra and chemical properties, 
can be more properly represented as being ortho-metallated by the formula: 
##STR1## 
In the case of compound (II) it is felt that ortho-metallation occurs, but 
it is not shown in the formula since it is not known which specific 
phosphine (or phosphide) moiety is in fact ortho-metallated. We have shown 
that on the basis of chemical reactivity that the compound is a dihydride 
and also on the basis of proton and .sup.- P nuclear magnetic resonance 
spectra that the compound is a dimer. Thus, for purposes of this 
disclosure, the following approximate structural formulas are considered 
to be equivalent: 
[(Ph.sub.3 P).sub.2 (Ph.sub.2 P).sub.2 Ru.sub.2 H.sub.4 ].sup.= 
K.sub.2.sup.+ ; 
[(Ph.sub.3 P) (Ph.sub.2 P)RuH.sub.2 ].sub.2.sup.- K.sub.2.sup.+ ; 
[(Ph.sub.3 P) (Ph.sub.2 P)RuH].sub.2.sup.- K.sub.2.sup.+ ; and 
[(Ph.sub.3 P) (Ph.sub.2 P)RuH].sup.- K.sup.+. 
It is believed that the subject compositions can also exist in dimer, 
trimer and tetramer forms of their basic empirical formulas. 
It is not clearly understood, but is felt that the compositions possess the 
ability to undergo "ortho-metallation", a process whereby an "unfilled" 
coordination site on the Group VIII metal atom becomes attached by 
substitution onto the ortho position of a neighboring phenyl radical, as 
present in triphenylphosphine. The bond formation between the metal atom 
and the ortho carbon on the phenyl ring displaces the ortho hydrogen atom 
which then attaches to the metal atom thus forming a dihydride as 
indicated by the horizontal bracket on the above-described formula. It is 
considered that "ortho-metallation" in solution, is a dynamic, reversible 
process in which the ortho-metallated material can react back to the 
non-ortho-metallated form. This ortho-metallation behavior may be present 
in the other catalyst compositions and can be observed by a dihydride 
behavior of the substance in that one gram-atom of hydride ligand in the 
catalyst composition will liberate one gram-mole of hydrogen gas upon 
reaction with at least about one gram-mole of hydrogen chloride. 
Other chemical characteristics of the catalyst compositions are that one 
gram-atom of hydrido ligand in the subject composition will liberate one 
gram-mole of methane upon reaction with at least about one gram-mole of 
methyl iodide. 
The infrared spectra of the compositions exhibit metal-hydride absorption 
maxima in the infrared region of about 1600 to 1900 cm.sup.-1 and usually 
about 1750 to 1850 cm.sup.-1. 
The catalyst compositions can exist in the "free form" as described by the 
above structural formula and can also exist wherein the cation is 
complexed with an organic solvent in adduct form, or as a complex with a 
chelating agent for said cation. For example, structure I can exist as an 
etherate, being complexed with one mole of diethyl ether per mole of 
composition. The catalyst composition can also form adducts with aromatic 
hydrocarbons, such as naphthalene and toluene and chelates with chelating 
agents, such as crown ethers, e.g. 18-crown-6, cryptates, being 
bicyclic-nitrogen bridged diamines having oxyethylene bridges, such as 
2,2,2-crypt, and the like. Adducts and chelates of the compositions, in 
some cases, display better crystalline properties than the free-form 
composition, and are more convenient for handling and operability. 
However, for purposes of this invention the free-form composition and 
adducts and chelates thereof, are considered to be equivalents as 
compositions and within the scope of the applicable compositions. 
The anionic Group VIII metal hydride compositions applicable herein can be 
prepared by reacting a neutral Group VIII metal complex, metal halide, 
hydrido-halide or hydride, with a metal cationic radical anion complex, 
hereinafter referred to as "metal arene," such as potassium naphthalene, 
in a suitable solvent, such as tetrahydrofuran or diethylether, at a 
temperature of about -111.degree. C. to +80.degree. C., under vacuum or 
under an inert atmosphere. The product is easily isolated and purified 
from the reaction mixture. A description of apparatus found useful in 
preparing the composition is described in J. Amer. Chem. Soc., 98, 8072 
(1976), hereby incorporated by reference. 
Carboxylic acid esters, comprised of an acid moiety and alcohol moiety, and 
by the term "alcohol moiety", is meant to include aromatic hydroxy moiety, 
e.g., phenols and naphthols as well, which are applicable in this 
invention process, include those wherein the acid moiety is derived from a 
C.sub.2 -C.sub.18 linear or branched alkyl monocarboxylic acid, C.sub.2 
-C.sub.6 linear or branched alkyl dicarboxylic acid, C.sub.7 -C.sub.8 
cycloalkyl monocarboxylic acid, C.sub.2 -C.sub.4 fluorinated 
monocarboxylic acid, containing 1-7 fluorine atoms, and said alcohol 
moiety of said ester is derived from a C.sub.1 -C.sub.4 linear or branched 
alkyl alcohol, C.sub.1 -C.sub.4 linear or branched fluorinated alcohol, 
containing 1-7 fluorine atoms, C.sub.7 -C.sub.9 aralkyl alcohol, or 
C.sub.6 -C.sub.10 aromatic hydroxy compound. 
Representative examples of carboxylic acids providing the acid moiety in 
said ester are acetic acid, propionic acid, butyric acid, isobutyric acid, 
n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, 
n-decanoic acid, n-pentadecanoic acid, n-octadecanoic acid, oxalic acid, 
malonic acid, succinic acid, adipic acid, cyclohexylcarboxylic acid, 
cyclohexylacetic acid, fluoroacetic acid, difluoroacetic acid, 
trifluoroacetic acid, trifluoropropionic acid and trifluorobutyric acid, 
and the like. 
Representative examples of alcohols and aromatic hydroxy compounds 
providing the alcohol moiety in said ester are methanol, ethanol, 
propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, 
2,2,2-trifluoroethanol (hereinafter referred to as "trifluoroethanol"), 
monofluoromethanol, difluoromethanol, 1,3-difluoro-2-propanol, benzyl 
alcohol, phenethyl alcohol, phenol, 2-naphthol, and the like. 
It is to be understood that esters produced from combinations of the 
above-described acids and alcohols in known manner are deemed to be 
applicable within the scope of this invention process. Representative 
examples of esters useful in the invention process are methyl acetate, 
ethyl acetate, methyl n-octadecanoate, isobutyl decanoate, t-butylnonoate, 
phenyl acetate, 2-naphthyl propionate, dimethyl oxalate, diethyl oxalate, 
dimethyl malonate, diethyl malonate, dimethyl succinate, diethyl 
succinate, dimethyl adipate, diethyl adipate,methyl cyclohexylcarboxylate, 
ethyl cyclohexylacetate, n-butyl fluoroacetate, methyl difluoroacetate, 
n-propyl trifluoropropionate, methyl trifluorobutyrate, isopropyl acetate, 
sec-butyl propionate, fluoromethyl acetate, difluoromethyl acetate, 
1,3-difluoro-2-propyl octanoate, benzyl acetate, phenethyl acetate, methyl 
trifluoroacetate andtrifluoroethyl trifluoroacetate. Preferred examples of 
esters in the invention process are dimethyl oxalate, methyl acetate, 
ethyl acetate, methyl propionate, methyl trifluoroacetate and 
trifluoroethyl trifluoroacetate. Particularly preferred ester in the 
invention process is trifluoroethyl trifluoroacetate. 
The hydrogenation of the carboxylic acid ester group in a compound in the 
process leads to the production thereby of primary alcohol, produced from 
the carboxylic acid moiety, and regeneration of the alcohol or aromatic 
hydroxy compound from the alcohol moiety in the ester. In the case of 
dicarboxylic acid esters, the invention process leads to hydrogenation of 
generally only one ester group, at temperatures below 150.degree. C. and 
pressures below 150 psig, thus producing mainly the 
mono-alcohol-mono-ester, as in the case of dimethyl oxalate in which 
methyl glycolate is the principal product. It is considered that more 
forcing conditions, i.e. temperatures higher than 150.degree. C. and 
pressures higher than 150 psig, will result in hydrogenation of both ester 
groups thus yielding a diol. 
In addition to the esters described hereinabove, cyclic "inner esters", 
i.e. lactones, are also applicable in the invention process, which can be 
hydrogenated to yield diols, useful in the synthesis of polyesters. The 
scope of lactones applicable in the invention process include C.sub.3 
-C.sub.12 alkyl lactones, such as propiolactone, butyrolactone, 
valerolactone, octanoic lactone, caprolactone and 1,12-dodecalactone. 
Preferred are alkyl lactones in which the lactone functional group is 
formed between the first and terminal carbon atoms in the precursor 
hydroxy alkyl carboxylic acid. Thus, butyrolactone canbe hydrogenated to 
yield, 1,4-butanediol and the above-described lactones will yield diols in 
like manner. 
The amount of carboxylic acid ester substrate present in the process is not 
critical and is generally about 1 to 100,000 parts by weight of substrate 
per part of catalyst composition and preferably, about 10 to 1,000 parts 
by weight of ester substrate per part of catalyst composition. However, 
larger or smaller amounts of substrate may effectively be used. 
The process can be conducted in the neat state, i.e. no solvent, providing 
said ester is liquid at the reaction temperature employed and the catalyst 
is soluble therein. However, it is preferred to conduct the reaction in 
the presence of an inert solvent for both the carboxylic ester substrate 
and catalyst composition. The solubility of the respective materials in 
the solvent should be significantly large enough to initiate and maintain 
the hydrogenation process. 
Solvents which are applicable in the invention process must be inert toward 
hydrogenation under the reaction conditions and possess adequate solvating 
ability for the substrate carboxylic acid ester and catalyst, should 
preferably be anhydrous, and include C.sub.6 -C.sub.12 non-fused benzenoid 
hydrocarbons, and C.sub.2 -C.sub.18 alkyl derivatives thereof, C.sub.5 
-C.sub.10 linear or branched saturated aliphatic or alicyclic 
hydrocarbons, C.sub.4 -C.sub.6 saturated aliphatic cyclic mono- or 
diethers and C.sub.2 -C.sub.6 linear or branched saturated aliphatic mono- 
or diethers, C.sub.7 -C.sub.14 aromatic ethers, or mixtures thereof. By 
the term "non-fused benzenoid hydrocarbon" is meant that if more than one 
benzene ring is present in the hydrocarbon, they are not fused together. 
Thus, the term includes biphenyl but not naphthalene. 
Representative examples of specific solvents useful in the invention 
process are benzene, toluene, xylene, hexamethylbenzene, biphenyl, 
n-octadecylbenzene, pentane, cyclopentane, cyclohexane, methylcyclohexane, 
hexane, isooctane, decane, cyclodecane, tetrahydrofuran, p-dioxane, 
2,5-dimethyltetrahydrofuran, methyl tetrahydrofurfuryl ether, dimethyl 
ether, 1,2-dimethoxyethane, diglyme, diethylether, diisopropyl ether, 
anisole, diphenyl ether, and mixtures thereof. 
Preferred solvents in the invention process are toluene, benzene, 
cyclohexane, hexane, tetrahydrofuran, p-dioxane, diethyl ether or 
1,2-dimethoxyethane. Particularly preferred solvents are benzene and 
toluene. Preferred solvents for the hydrogenation of C.sub.2 -C.sub.18 
linear or branched alkyl monocarboxylic acids are the relatively non-polar 
hydrocarbons, described above, particularly toluene. 
The amount of solvent, when used, is not critical provided sufficient 
solvent is present to dissolve the carboxylic acid ester substrate and 
catalyst and to initiate and maintain the hydrogenation reaction. In 
general, about 1 to 100 parts by weight of solvent per part of ester is 
used, although not limited thereto, larger or smaller amounts being 
effective with the above proviso. 
As described above, the composition catalysts exist in the free form or can 
be present as an adduct or chelate with another organic molecule. 
Chelating agents of the type described above may be employed, such as 
crown ethers, including 15-crown-5, 18-crown-6, dibenzo and dicyclohexyl 
derivatives thereof; cryptates, such as 2.2.2-crypt, hexacyclen, the 
nitrogen analog of 18-crown-6 crown ether, and tertiary amines such as 
N,N,N'-tetramethylethylenediamine and the like. A preferred chelating 
agent is 18-crown-6. If a chelating agent is used, normally it is used in 
a molar ratio of chelating agent to catalyst of about 1:1 to 2:1 and 
preferably in slight excess over the stated 1:1 molar ratio. 
In general, the hydrogenation of esters with the catalyst compositions may 
be sensitive to the solvent or additive used to complex the cation. It is 
preferred to use the non-fused benzenoid hydrocarbons in the hydrogenation 
of the above-described C.sub.2 -C.sub.18 alkyl esters, and preferably in 
the absence of chelating agents. It is also preferred to utilize chelating 
agents in the hydrogenation of dicarboxylic esters, and particularly 
dimethyl oxalate. Fluorine-containing carboxylic esters are hydrogenated 
equally well in non-polar and polar solvents, described above, and in the 
presence of chelating agents. However, it is preferred to utilize the 
non-polar solvents described above, for the hydrogenation in the absence 
of chelating agents, since the rate of hydrogenation is usually faster, 
such as for trifluoroethyl trifluoroacetate. 
Temperature in the process is normally in the range from about 0.degree. 
C., to about 150.degree. C. and preferably in the range of about 
80.degree. to 100.degree. C. However, higher temperatures under more 
severe conditions can also be employed and are considered to be equivalent 
to the stated preferred ranges. 
The pressure in the reaction process is usually about 0 psig (101 to 1135 
KPa absolute) to 150 psigat the reaction temperature and preferably at 
about 80 to 100 psig (653 to 690 KPa absolute) at the reaction 
temperature. However, higher pressures under more severe conditions can be 
employed and are considered to be equivalent to the stated preferred 
ranges. The term "psig" refers to pounds per square inch gauge and 0 psig 
corresponds to 1 atmosphere, and 150 psig corresponds to about 11 
atmospheres. 
The process is conducted under an atmosphere containing hydrogen gas, being 
the active reducing agent. The atmosphere above the reaction mixture can 
also contain an inert gas such as nitrogen, argon, mixtures thereof, and 
the like, as long as sufficient hydrogen gas is present to maintain the 
hydrogenation reaction. It is preferred to conduct the process under an 
atmosphere consisting essentially of hydrogen gas, and particularly 
preferred at a pressure of about 80-100 psig. 
Conversions of esters in the process range from 30 to 100% of theory based 
on the starting amount of ester substrate. 
Selectivities in the process for production of primary alcohols from esters 
is in the range of about 90 to 100%, being defined as (moles primary 
alcohol produced/divided by moles ester hydrogenated) .times. 100. 
The invention process can be modified for a batch type process for 
fluorinated esters wherein the catalyst is recycled after use in one run. 
After the process has been conducted, the product, solvent and volatiles 
are removed by distillation under reduced pressure and fresh solvent added 
and the resulting solution stirred under about 5 to 10 psig of hydrogen 
gas for about 5 to 10 minutes. The solution is then preferably frozen and 
hydrogen removed by distillation under reduced pressure. Fresh substrate 
is then added and the reaction process run through another cycle. By 
performing this recycled step, catalyst from the original run can be used 
for about 4 to 5 additional runs. 
In the case of easily hydrogenated esters, such as the fluorine-containing 
alkyl esters, further recycle can be conducted by employing a catalyst 
regeneration agent. Said regeneration agent has the formula CBH(OR).sub.3 
or CBHR.sub.3, where R is C.sub.1 -C.sub.4 linear or branched alkyl 
including methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl 
and n-butyl, and C is lithium, sodium, potassium or cesium cation. 
Preferred agent is sodium trimethoxy borohydride. The regeneration 
procedure is generally conducted after a run by distilling off all solvent 
and volatile materials. The regeneration agent is then added in an amount 
of about 3:1 to 7:1 molar ratio of agent to said catalyst. An ether, such 
as tetrahydrofuran or glyme, is added and the resulting solution stirred 
under reduced pressure at room temperature for about 1 hour. The ether and 
other volatiles are removed by distillation under reduced pressure leaving 
dry catalyst and agent residue. Solvent and new ester substrate are then 
added and a new run is commenced. Addition of regeneration agent prolongs 
catalyst life times such that about 20-50 additional runs of the reaction 
process can be conducted. 
The product primary alcohol can be isolated from the process and purified 
by conventional methods such as extraction, followed by fractional 
distillation or column or gas chromatographic techniques. 
Also a subject of this invention is a process for decarbonylating an alkyl 
formate ester to an alkyl alcohol and carbon monoxide as illustrated in 
the following reaction scheme: 
##STR2## 
The process comprises contacting an alkyl formate ester with the catalyst 
described herein, being neat or in an inert solvent therefor, under a dry 
atmosphere, at a temperature of about 0.degree. to 150.degree. C., thereby 
resulting in the corresponding alkyl alcohol and carbon monoxide 
respectively. 
The process variables in this process are identical to the first-described 
process for hydrogenation of an ester with respect to temperature, 
pressure, solvent, catalyst composition, catalyst and solvent 
concentration, catalyst recycle and apparatus and need not be reiterated. 
The main difference between the two processes are that an atmosphere 
containing hydrogen gas is not required, for formate decarbonylation inert 
gases such as nitrogen, argon or solvent vapor being sufficient. 
Formates which are applicable in this process are alkyl formates, wherein 
the alkyl radical therein being C.sub.1 -C.sub.18 linear or branchedalkyl 
wherein said alkyl radical can also be substituted with groups inert under 
the reaction conditions such as C.sub.1 -C.sub.4 linear or branched alkyl 
or C.sub.1 -C.sub.4 linear or branched alkoxy. 
Representative examples of formates applicable in the process are methyl 
formate, ethyl formate, isobutyl formate, isoamyl formate, octyl formate 
and the like. 
Preferred method for carrying out the decarbonylation process is where 
[(Ph.sub.3 P).sub.3 RuH].sup.- K.sup.+ is the catalyst, the reaction is 
conducted neat, 80.degree.-100.degree. C. is the temperature, 50-70 psig 
is the pressure, in an argon atmosphere, and said reaction is carried out 
for about 16 hours thereby resulting in the corresponding alcohol and 
generated carbon monoxide. Pressure in the process will of course increase 
due to the generation of carbon monoxide and the pressure in the reaction 
will increase above initial pressure to about 200 to 300 psig. 
Apparatus for conducting the invention process can be any conventional 
pressure apparatus, glass or steel, in which the operations of charging 
the reactant materials, heating, cooling, stirring, introduction of 
hydrogen gas, isolation and purification the final products can be 
conducted substantially in the absence of air and moisture. Such apparatus 
and procedure for carrying out the invention process will be obvious to 
one skilled in the art from this disclosure.

The following examples are illustrative of the best mode of carrying out 
the invention as contemplated be us and should not be construed as being 
limitations on the scope and spirit of the instant invention. 
EXAMPLE 1 
Catalytic Hydrogenation of Dimethyl Oxalate 
A glass pressure tube was charged with 40 mg of the bis-phosphine catalyst 
[(Ph.sub.3 P)(Ph.sub.2 P)RuH.sub.2 ].sub.2.sup.- K.sub.2.sup.+, (prepared 
by reacting bis(triphenylphosphine)ruthenium hydridochloride.toluene dimer 
with potassium naphthalene in about a 1:2 molar ratio in tetrahydrofuran 
at about -80.degree. C. underreduced pressure), 0.5 gram (4.23 mmol) of 
dimethyl oxalate and 5 ml of toluene. The reaction solution was 
pressurized with 100 psig of hydrogen and allowed to react in the absence 
of moisture and molecular oxygen at 90.degree. C. for 16 hours. Gas 
chromatographic analysis of the reaction mixture showed 95% conversion of 
the dimethyl oxalate to methanol and methyl glycolate as the only 
products. 
EXAMPLE 2 
Catalytic Hydrogenation of Methyl Acetate 
A glass pressure tube was charged with 40 mg of the bis-phosphine catalyst 
described in Example 1, 0.47 gram (6.3 mmol) of methyl acetate and 5 ml of 
toluene. The reaction solution was pressurized with 100 psig of hydrogen 
and allowed to react at 90.degree. C. for 16 hours. Gas chromatographic 
analysis of the reaction mixture showed 35% conversion of the methyl 
acetate to methanol, ethanol and ethyl acetate as the only products. 
EXAMPLE 3 
Catalytic Hydrogenation of Methyl Trifluoroacetate 
A glass pressure tube was charged with 20 mg of the bis-phosphine catalyst 
described in Example 1, 0.72 gram (5.6 mmol) of methyl trifluoroacetate 
and 3 ml of toluene. The reaction solution was pressurized with 90 psig of 
hydrogen and allowed to react in the absence of moisture and molecular 
oxygen at 90.degree. C. for 16 hours. Gas chromatographic analysis of the 
reaction mixture showed 88% conversion of the methyl trifluoroacetate to 
2,2,2-trifluoroethanol and methanol in a selectivity of about 98%. 
EXAMPLE 4 
Catalytic Hydrogenation of Trifluoroethyl Trifluoroacetate 
(a) Hydrogenation 
A glass pressure tube was charged with 20 mg of the bis-phosphine catalyst 
described in Example 1, 1.1 gram (5.7 mmols) of trifluoroethyl 
trifluoroacetate and 3 ml of toluene. The reaction solution was 
pressurized with 90 psig of hydrogen and allowed to react in the absence 
of moisture and molecular oxygen at 90.degree. C. for 4 hours. Gas 
chromatographic analysis of the reaction mixture showed 99% conversion of 
the ester to 2,2,2-trifluoroethanol in a selectivity of about 98%. 
(b) Catalyst Recycle of Trifluoroethyl Trifluoroacetate 
Trifluoroethanol and toluene were removed from the above reaction mixture 
by vacuum distillation at room temperature. Toluene (3 ml) was distilled 
into the pressure tube containing the dry catalyst residue and this 
solution stirred under 5 psig of hydrogen for 5 minutes. The solution was 
frozen, the hydrogen pumped off and 1.1 gram (5.7 mmols) of trifluoroethyl 
trifluoroacetate distilled in under vacuum. The resulting solution was 
warmed to room temperature under a hydrogen atmosphere, pressurized to 90 
psig of hydrogen and allowed to react at 90.degree. C. for 7 hours. The 
resulting product mixture was analyzed by gas chromatography and showed a 
99% conversion and 98% selectivity for trifluoroethanol. 
(c) Catalyst Regeneration 
After five cycles similar to the one described above, the gas 
chromatographic analysis showed only 80% conversion to trifluoroethanol 
and the catalyst was then regenerated in the following manner. The 
pressure tube containing the catalyst residue (originally 0.03 mmol) was 
charged with 20 mg (0.25 mmol) of NaBH(OCH.sub.3).sub.3, in a dry box. 
Tetrahydrofuran (3 ml) was distilled into the tube under vacuum and the 
solution stirred at room temperature for one hour. The solvent and other 
volatiles were removed in vacuo and the residue evacuated to dryness. The 
pressure tube was then charged with toluene (3 ml) and 1.1 gram (5.7 
mmols) of ester and the hydrogenation was conducted as described in part 
(a). 
In subsequent catalyst recycles, the concentration of ester was gradually 
increased to 50% volume/volume in toluene, then neat ester was finally 
used. A lifetime study included 22 catalyst recycles and four regeneration 
steps in which the equivalent of 3400 gms of ester were reduced per gram 
of original catalyst present. 
EXAMPLE 5 
The following runs were made utilizing the apparatus and procedure as 
described in Example 1. The pressure of hydrogen gas used in the runs was 
90 psig and the temperature in each run was conducted at 90.degree. C. for 
a period of not more than 16 hours. The following table lists and 
summarizes the alkyl ester substrate used, the solvent, chelating agent if 
used, and calculated N number in the process for the product resulting 
from the hydrogenation. 
TABLE I 
______________________________________ 
Catalytic Hydrogenation of Esters* 
Cata- Sol- Re- 
lyst.sup.+ 
Substrate vent Additive 
N marks 
______________________________________ 
II Methyl acetate.sup.a 
THF 2 
" " toluene 38 
" " toluene 18-crown-6 
2 e 
I Dimethyl oxalate.sup.b 
THF 6 
" " toluene 20 
II " THF 2 
" " THF KBr 80 f 
" " toluene 80 
" " toluene 18-crown-6 
80 f 
" Methyl Trifluoro- 
acetate.sup.c 
THF 100 
" Methyl Trifluoro- 
toluene 100 g 
acetate.sup.c 
" Methyl Trifluoro- 
toluene 18-crown-6 
75 h 
acetate.sup.c 
I Trifluoroethyl 
toluene 40 
Trifluoroacetate.sup.d 
IV Trifluoroethyl 
toluene 40 
Trifluoroacetate.sup.d 
V toluene 40 
II Trifluoroethyl 
toluene 180 
Trifluoroacetate.sup.d 
" Trifluoroethyl 
toluene 18-crown-6 
120 h 
Trifluoroacetate.sup.d 
" Trifluoroethyl 
neat 460 
Trifluoroacetate.sup.d 
ester 
" Trifluoroethyl 
neat 390 
Trifluoroacetate.sup.d 
ester 
______________________________________ 
*catalyst conc. = 0.01M; volume of system = 98 cc; concentration of 
substrate: a = 1.26M, b = 1.1M, c and d = 1.84M. Remarks: e = additive 
inhibits reaction, f = additive promotes reaction, g = initial rates are 
faster than THF reaction, h = additive decreases rate; N = number of mole 
of ester hydrogenated per mole of catalyst in one batch reaction. 
##STR3## 
II = [(Ph.sub.3 P)(Ph.sub.2 P)RuH].sub.2.sup.- K.sub.2.sup.+ 
IV = [(Ph.sub.3 P).sub.3 RhH].sup.- K.sup.+, 
V = [(Ph.sub.2 CH.sub.3 P).sub.3 RuH].sup.- K.sup.+ 
EXAMPLE 6 
Catalytic Decarbonylation of Ethyl Formate 
A glass pressure tube was charged with 40 mg of bright yellow 
tris-phosphine catalyst, 
##STR4## 
produced by reacting tris(triphenylphosphine)ruthenium hydridochloride 
with potassium naphthalene in about 1:2 molar ratio in tetrahydrofuran at 
-80.degree. C. under reduced pressure, and 4 grams (54 mmols) of ethyl 
formate. The reaction was pressurized with 50 psig of hydrogen. The 
reaction solution was stirred at 90.degree. C. for two hours and the 
pressure increased to 235 psig. Gas chromatographic analysis of the 
reaction mixture showed ethanol and carbon monoxide as the only products 
produced in a 92% conversion. Methyl formate under similar conditions was 
decarbonylated in a conversion of about 90%. 
The hydrogenation of dimethyl adipate was unsuccessfully attempted in 
toluene solvent at 90.degree. C. in the presence of the bis-phosphine 
catalyst described in Example 1. However, we believe that dimethyl adipate 
ester can be reduced under other conditions as described herein, and thus 
regard adipate ester as being also within the scope of the invention 
process.