Substituted cyclic phosphine oxides

A cyclic phosphine oxide of the formula ##STR1## in which R.sup.1 is an alkyl or an aryl radical having up to 14 carbon atoms, PA1 R.sup.2, r.sup.3 and R.sup.4 each independently is a C.sub.1 -C.sub.4 -alkyl radical, hydrogen, chlorine or bromine, PA1 X and Y each independently is oxygen or sulfur, PA1 a, b, and c each independently is 0 or 1, and PA1 R.sup.5 is a C.sub.1 -C.sub.12 -alkyl radical and, where a = 0, also an aryl radical and, where a = 1, an equivalent of a cation, PA1 R.sup.6 is a C.sub.1 -C.sub.12 -alkyl radical and, where b = 0, also an aryl radical and, where b = 1, an equivalent of a cation, Is produced by reacting an unsaturated 5-membered cyclic phosphine oxide of the formula ##STR2## with a compound containing a phosphorus-hydrogen bond and of the formula ##STR3## in which R.sup.7 is a C.sub.1 -C.sub.12 -alkyl radical or, where a = 0, also an aryl radical, and PA1 R.sup.8 is a C.sub.1 -C.sub.12 -alkyl radical or, where b = 0, also an aryl radical, In the presence of free radicals at a temperature of about 50.degree. C to about 300.degree. C, and the reaction product is optionally hydrolyzed and converted into a salt.

This invention relates to new substituted cyclic phosphine oxides 
corresponding to the general formula (I): 
##STR4## 
in which R.sup.1 represents an alkyl or an aryl radical having up to 14 
carbon atoms, 
R.sup.2 r.sup.3 and R.sup.4 represent a C.sub.1 -C.sub.4 -alkyl radical, 
hydrogen, chlorine or bromine, 
R.sup.5 represents a C.sub.1 -C.sub.12 -alkyl radical and, where a = 0, an 
aryl radical and, where a = 1, 1/n of an n-valent cation, such as a metal, 
ammonium, guanidinium, phosphonium or hydrogen, 
R.sup.6 represents a C.sub.1 -C.sub.12 -alkyl radical and, where b = 0, an 
aryl radical and, where b = 1, 1/n of an n-valent cation such as, for 
example, a metal, ammonium, guanidinium, phosphonium or hydrogen, 
X and Y represent oxygen or sulfur, and 
a, b and c = 0 or 1, 
and to a process for the production of these new compounds. 
Among the tertiary phosphine oxides, those with a 4-membered or 5-membered 
saturated or unsaturated ring system, the so-called phosphetane or 
phospholine or phospholane ring systems, are distinguished by particularly 
high activity as catalysts in the formation of carbodiimides from 
isocyanates (cf. for example German Offenlegungsschrift No. 1,130,594). 
The process for the production of the compounds according to the invention 
is distinguished by the fact that unsaturated 5-membered cyclic phosphine 
oxides corresponding to the general formulae: 
##STR5## 
in which R.sup.1, R.sup.2, R.sup.3, R.sup.4 and X have the same meaning as 
in formula (I), are reacted in the presence of free radicals at a 
temperature of about 50.degree. C to about 300.degree. C with a compound 
containing a phosphorus-hydrogen and of the formula 
##STR6## 
in which a, b, c and Y have the same meaning as in formula (I) and in 
which R.sup.7 represents an alkyl radical or, where a = 0, also an aryl 
radical and R.sup.8 represents an alkyl radical or, where b = 0, also an 
aryl radical, 
The primary products of formula (V): 
##STR7## 
in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.7, R.sup.8, X, Y, a, b 
and c have the same meaning as in formulae (II), (III), and (IV), 
may be converted either by acid-catalyzed or by alkali catalyzed hydrolysis 
into the corresponding acids of the formula (VI) 
##STR8## 
in which 
R.sup.5 represents hydrogen where a = 1, or R.sup.5 = R.sup.7 where a = 0, 
R.sup.6 represents hydrogen where b is 1, or R.sup.6 = R.sup.8 where b = 
0, 
or into their salts and, when both a and b in formula (V) represent the 
number 1, into the acids corresponding to the formula (VII): 
##STR9## 
or their salts. The aforementioned salts may of course also be obtained 
from the acids of formulae (VI) and (VII) by neutralization with monomeric 
or polymeric amines or other nitrogen-containing bases, with phosphines, 
ammonium, phosphonium or arsonium hydroxides, ammonium or phosphonium 
salts of weak acids with a pK.sub.s -value of greater than 2, with metal 
oxides, metal hydroxides, metal salts of weak acids with a pK.sub.s -value 
of greater than 2, and by reacting the acids of formulae (VI) and (VII) 
with base metals and by so-called double decomposition with metal salts or 
with monomeric or polymeric ammonium or phosphonium salts or the salts of 
other nitrogen-containing bases. 
It has surprisingly been found that the phosphorus-hydrogen compounds of 
formula (IV) are added to the cyclic phosphine oxides of formulae (II) and 
(III), because the double bonds in the cyclic phosphine oxides (II) and 
(III) have proved to be sluggish with respect to radical polymerization 
and because there are also no terminal double bonds. 
The starting materials for the process according to the invention 
corresponding to formulae (II) and (III) are known or may be obtained by 
known methods (cf. G.M. Kosolapoff, L. Maier, Organic Phosphorus 
Compounds, Wiley-Interscience, New York, 1972 et seq. vol 3, pages 
370-371, pages 458-463 and vol 4, pages 9-10, page 48). The following are 
examples of 5-membered unsaturated phosphine oxides of this kind, whose 
double bonds may be situated either in the 2,3- or in the 3,4-position: 
1-methyl-1-oxophospholine 
1-ethyl-1-oxophospholine 
1-butyl-1-oxophospholine 
1-(2-ethylhexyl)-1-oxophospholine 
1-methyl-1-thiophospholine 
1-(2-chloroethyl)-1-oxophospholine 
1-phenyl-1-oxophospholine 
1-p-tolyl-1-oxophospholine 
1-chloromethyl-1-oxophospholine 
1,3-dimethyl-1-oxophospholine 
1,2-dimethyl-1-oxophospholine 
1-methyl-3-chloro-1-oxophospholine 
1-methyl-3-bromo-1-oxophospholine 
1-chlorophenyl-1-oxophospholine 
1,3,4-trimethyl-1-oxophospholine 
1,2,4-trimethyl-1-oxophospholine 
1,2,2-trimethyl-1-oxophospholine 
1-phenyl-1-thiophospholine 
1-phenyl-3-methyl-1-oxophospholine 
1-phenyl-2,3-dimethyl-1-oxophospholine 
The following compounds for example may be used as the phosphorus-hydrogen 
compounds in the process according to the invention: 
dimethyl phosphite 
diethyl phosphite 
di-isopropyl phosphite 
di-n-propyl phosphite 
di-i-butyl phosphite 
di-n-octyl phosphite 
di-decyl phosphite 
methyl-ethyl phosphite 
methane phosphonous acid methyl ester 
methane phosphonous acid ethyl ester 
methane phosphonous acid-n-butyl ester 
ethane phosphonous acid methyl ester 
ethane phosphonous acid-2-ethylhexyl ester 
benzene phosphonous acid methyl ester 
benzene phosphonous acid-i-propyl ester 
dimethyl phosphine oxide 
methylethyl phosphine oxide 
di-n-butyl phosphine oxide 
methylphenyl phosphine oxide 
diphenyl phosphine oxide 
dimethyl thiophosphite 
diethyl thiophosphite 
di-i-butyl thiophosphite 
methane thiophosphonous acid methyl ester 
dimethyl phosphine sulfide 
dimethyl phosphine 
diethyl phosphine 
diphenyl phosphine 
methylphenyl phosphine 
dibutoxy phosphine 
methyl phosphine 
ethyl phosphine 
phenyl phosphine 
Suitable catalysts are the free radicals produced by radical formers active 
at temperatures in the range of from about 50.degree. to 300.degree. C 
which primarily belong to the groups of organic peroxides, aliphatic azo 
compounds and high-energy radiation, for example dialkyl peroxides, such 
as di-tert.-butyl peroxide; diacyl peroxides, such as dibenzoyl peroxide, 
p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, succinyl peroxide, 
nonanoyl peroxide and lauroyl peroxide; peroxy esters, such as tert.-butyl 
peroctoate, tert.-butyl perisobutyrate, tert.-butyl peracetate, 
tert.-butyl perbenzoate, tert.-butyl perpivalate; and also peroxy ketals 
and percarbonates, azoisobutyronitrile, azo-bis-isobutanol diacetate, and 
also UV-rays, X-rays or .gamma.-rays. Other equivalent radical formers are 
known among experts. Their suitability may readily be determined by simply 
preliminary tests. 
The process according to the invention is generally carried out by adding 
the 5-membered unsaturated phosphine oxide dropwise to the 
phosphorus-hydrogen compound in a molar ratio of approximately 1:0.1 to 
1:1. There is no need for a solvent, although if desired an inert solvent 
may be used. The radical former is used in a quantity of about 0.1 to 20 
mole % and preferably in a quantity of about 0.5 to 5 mole %, based on the 
5-membered unsaturated cyclic phosphine oxide, and is added with the 
latter to the reaction mixture. Before use, the radical former may be 
dissolved either in an inert solvent or in one of the reactants. It is 
also possible, however, optionally to mix the reactants with a small 
quantity of the radical former and subsequently to heat the mixture to the 
reaction temperature. Portions of radical formers, which have a 
sufficiently short half life at the reaction temperature, are then 
periodically added to the mixture at the reaction temperature. 
The reaction temperatures are in the range of from about 50.degree. to 
300.degree. C and preferably in the range of about 100.degree. to 
200.degree. C. Depending upon the size of the reaction mixture and upon 
the reaction conditions, the reaction takes about 0.5 to 30 hours, i.e. 
the reaction time may be varied within wide limits. 
The reaction is preferably carried out under normal pressure, although it 
may also be carried out under elevated or reduced pressure. The atmosphere 
under which the reaction is carried out may consist of air or an inert 
gas. 
The reaction gives the products according to the invention in high yields. 
Unused starting materials may readily be recovered, for example by 
distillation. In general, the reaction products accumulate in the form of 
liquids after the excess starting materials have been distilled off. In 
some cases, these liquids may be further purified by distillation. 
According to analysis by spectroscopic methods, the reaction products are 
mixtures of stereoisomeric and positionally isomeric forms of compounds 
corresponding to formula (V). 
The compounds according to the invention are valuable catalysts for the 
formation of carbodiimides from isocyanates. By comparison with catalysts 
of the kind normally used for carbodiimide formation, they enable activity 
to be strictly graduated by varying the substituents introduced by the 
process according to the invention. 
In addition, they afford the possibility of producing catalysts for 
carbodiimide formation which are insoluble in the isocyanate-carbodiimide 
system. Thus, it is possible to produce low molecular weight carbodiimides 
from diisocyanates, polyisocyanates or mixtures of isocyanates differing 
in their functionality by separating off the catalyst insoluble in the 
system by simple operations, such as filtration or decantation, after a 
predetermined level of carbodiimide formation has been reached, thereby 
stopping carbodiimide formation at that level. In addition, the valuable 
and expensive catalyst may be recovered and repeatedly used. 
The high volatility of the catalyst, which has frequently been found to 
give rise to difficulties in the production of monomeric carbodiimides 
from isocyanates by means of 1-methyl-1-oxophospholine, insofar as it can 
leave the end product with impurities after distillation, is either 
completely absent or present to only a very minimal extent in the 
substances according to the invention. 
The ability of the compounds according to the invention to extract metal 
ions and metal salts, for example zinc chloride, from aqueous solutions, 
is superior to that of the phosphine oxides hitherto proposed for this 
purpose.

The process according to the invention is illustrated by the following 
Examples: 
EXAMPLE 1 
Production of 1-methyl-1-oxophospholane phosphonic acid dimethyl ester 
A total of 117 g of an approximately 1:1-mixture of 
1-methyl-1-oxophospholine-2 and 1-methyl-1-oxophospholine-3 is added 
dropwise with intensive stirring over a period of 1 hour at a temperature 
of 113.degree. to 115.degree. C to 550 g of dimethyl phosphite 
accommodated in a 1 liter glass flask. At the same time, a suspension of 8 
g of dibenzoyl peroxide in silicone oil is added dropwise over the 
reaction time. All the materials used have been freed from traces of 
oxygen by repeated evacuation and venting with nitrogen. 
On completion of the reaction, first the dimethyl phosphite and then the 
unreacted part of the 1-methyl-1-oxophospholine (81 g), which consists of 
substantially equal parts of the two isomers, are distilled off in vacuo. 
28 g of an almost colorless oil (b.p. .sub.0.5 :185.degree. to 190.degree. 
C) distil over during distillation of the residue, thickening in the 
receiver into a white crystalline paste which becomes liquid again between 
40.degree. and 55.degree. C. 
Analysis: C.sub.7 H.sub.16 O.sub.4 P.sub.2 calculated: 27.4%, P; 37.2% C; 
7.1%, H. found: 28.0%, P; 36.8%, C; 7.0%, H. 
According to analysis by gas chromatography, 4 different isomers are 
present. 
EXAMPLE 2 
Production of 1-methyl-1-oxophospholane phosphonic acid dimethyl ester 
2900 g of 1-methyl-1-oxophospholine (isomer mixture as in Example 1) and 
200 g of tert.-butyl peroctoate, dissolved in 750 ml of dimethyl 
phosphite, are added dropwise with stirring over a period of 4 hours at 
110.degree. to 115.degree. C to 5500 g of dimethyl phosphite. The reaction 
takes place under a nitrogen atmosphere. Removal of the excess dimethyl 
phosphite and the unreacted phospholine oxide (170 g) by distillation 
leaves 5250 g of 1-methyl-1-oxophospholane phosphonic acid dimethyl ester 
(93% of the theoretical) as a residue which solidifies at 50.degree. to 
60.degree. C. 
Analysis: C.sub.7 H.sub.16 O.sub.4 P.sub.2 calculated: 27.4% P; 37.2% C; 
7.1% H. found: 27.2% P; 37.0% C; 7.0% H. 
EXAMPLE 3 
Production of 1-methyl-1-oxophospholane phosphonic acid diethyl ester 
1380 g of diethyl phosphite are heated under nitrogen to 160.degree. C. 348 
g of 1-methyl-1-oxophospholine and 18 g of tert.-butyl peroxide are 
simultaneously added dropwise over a period of 2 hours at the 
above-mentioned temperature to the intensively stirred reaction mixture. 
Unreacted diethyl phosphite is distilled off in vacuo. The residue 
consists of a yellow liquid (775 g) which, according to analysis and the 
NMR-spectrum, has the constitution of a 1-methyl-1-oxophospholane 
phosphonic acid diethyl ester. The liquid can be distilled at 220.degree. 
to 225.degree.C/1 mm Hg with some slight decomposition. 
Analysis: C.sub.9 H.sub.20 O.sub.4 P.sub.2 calculated: 24.4% p; 42.5% C; 
7.9% H. found: 24.2% P; 42.8% C; 7.8% H. 
EXAMPLE 4 
Production of 1-methyl-1-oxophospholane phosphonic acid diisopropyl ester 
500 g of diisopropyl phosphite are heated to 110.degree. C. 116 g of 
1-methyl-1-oxophospholine and 6 g of tert.-butyl peroctoate in 30 ml of 
diisopropyl phosphite are simultaneously added over a period of 30 minutes 
under a nitrogen atmosphere to the thoroughly stirred reaction mixture. 
After removal of the unreacted starting materials by distillation, 248 g 
of 1-methyl-1-oxophospholane phosphonic acid diisopropyl ester are left in 
the form of a substantially colorless liquid which begins to decompose at 
a temperature above 160.degree. C. 
EXAMPLE 5 
Production of 1-methyl-1-oxophospholane phosphonic acid di-i-butyl ester 
A total of 116 g of 1-methyl-1-oxophospholine and 6 g of tert.-butyl 
peroctoate in 30 ml of di-i-butyl phosphite are simultaneously added 
dropwise over a period of 30 minutes under nitrogen at 115.degree. C to 
582 g of diisobutyl phosphite. Removal of the unreacted starting materials 
by distillation leaves 270 g of a substantially colorless liquid which 
consists predominantly of 1-methyl-1-oxophospholane phosphonic acid 
di-i-butyl ester. For further purification, the product is dissolved in 
300 ml of water, 3.9 g of sodium hydroxide are added, the solution is 
briefly heated to 70.degree. C and, after testing for neutral reaction, is 
extracted 3 times with 100 ml of methylene chloride. Removal of the 
methylene chloride by distillation leaves 223 g of pure 
1-methyl-1-oxophospholane phosphonic acid di-i-butyl ester. 
EXAMPLE 6 
770 g of dimethyl phosphite and 116 g of 1-methyl oxophospholine are mixed 
in a 1 liter flask, freed from oxygen by passing through a stream of 
nitrogen and heated to 90.degree. C. 20 g of tert.-butyl peroctoate, 
dissolved in 80 ml of dimethyl phosphite, are added dropwise with stirring 
over a period of 10 hours. After another 15 hours at 90.degree. C, 
dimethyl phosphite and 1-methyl-1-oxophospholine are distilled off. 
Distillation of the residue gives 146 g of 1-methyl-1-oxophospholane 
phosphonic acid dimethyl ester. 
EXAMPLE 7 
Production of 1-methyl-1-oxophospholanyl methyl phosphinic acid methyl 
ester 
A total of 116 g of 1-methyl-1-oxophospholine and 6 g of tert.-butyl 
peroctoate in 30 g of methane phosphonous acid methyl ester are 
simultaneously added dropwise with stirring at 120.degree. C to 282 g of 
oxygen-free methane phosphonous acid methyl ester. The reaction time is 90 
minutes. Excess methane phosphonous acid methyl ester and a little 
1-methyl oxophospholine are distilled off. For purification, the residue 
of 205 g of 1-methyl-1-oxophospholanyl methyl phosphinic acid methyl ester 
is distilled in vacuo (b.p. 210.degree. -220.degree. C) and gives 186 g of 
a pure product which hardens very slowly into star-shaped crystals which 
become liquid again at a temperature above 70.degree. C. 
EXAMPLE 8 
Production of 1-methyl-1-thiophospholane phosphonic acid dimethyl ester 
132 g of 1-methyl-1-thiophospholine are added dropwise under nitrogen over 
a period of 1 hour at a temperature of 115.degree. to 120.degree. C to 550 
g of dimethyl phosphite. 1 g of tert.-butyl peroctoate in 40 ml of 
dimethyl phosphite is added dropwise over the same period. Excess dimethyl 
phosphite and part of the unreacted 1-methyl-1-thiophospholine are 
recovered by distillation at a sump temperature of up to 130.degree.C/1 mm 
Hg. The residue (148 g) consists of 1-methyl-1-thiophospholane phosphonic 
acid dimethyl ester which is contaminated by approximately 10% of 
1-methyl-1-thiophospholine. Dissolution in 500 ml of water, followed by 
extraction with 40 ml of trichlorethylene, gives an aqueous solution, free 
from 1-methyl-1-thiophospholine, from which 118 g of 
1-methyl-1-thiophospholane phosphonic acid dimethyl ester can be 
re-extracted with chloroform. 
EXAMPLE 9 
Production of 1-methyl-1-oxophospholane thiophosphonic acid dimethyl ester 
58 g of 1-methyl-1-oxophospholine and 3 g of tert.-butyl peroctoate in 5 ml 
of 1-methyl-1-oxophospholine are simultaneously added dropwise with 
stirring under nitrogen atmosphere to 132 g of dimethyl thiophosphite. The 
reaction temperature is 120.degree. to 125.degree. C. Removal of the 
dimethyl thiophosphite and a small quantity of 1-methyl-1-oxophospholine 
by distillation leaves 121 g of 1-methyl-1-oxophospholane thiophosphonic 
acid dimethyl ester which crystallizes on cooling. The colorless crystals 
become liquid again at a temperature above 80.degree. C. 
EXAMPLE 10 
Production of 1-methyl-1-oxophospholanyl dimethyl phosphine oxide 
116 g of 1-methyl-1-oxophospholine and 6 g of tert.-butyl perpivalate in 
dibutyl phthalate are added dropwise with stirring under an oxygen-free 
atmosphere to 234 g of dimethyl phosphine oxide. The reaction temperature 
is 75.degree. to 80.degree. C. The starting materials are then distilled 
off. The residue consists of 185 g of 1-methyl-1-oxophospholanyl dimethyl 
phosphine oxide. 
EXAMPLE 11 
Production of 1-methyl-1-oxophospholane phosphonic acid 
226 g of 1-methyl-1-oxophospholane phosphonic acid dimethyl ester are 
heated for 3 days to boiling point with 500 g of water and 300 g of 36% 
hydrochloric acid. Methyl chloride and methanol distil off. After 
concentration by evaporation in vacuo, a total of 6 ml of product is taken 
up with 200 g of water and reconcentrated by evaporation. Thereafter no 
more chloride can be detected in the residue, and pure 
1-methyl-1-oxophospholane phosphonic acid is left behind. Equivalent 
weight: found 98.2, calculated 99. 
EXAMPLE 12 
Production of the monosodium and disodium salts of 
1-methyl-1-oxophospholane phosphonic acid 
The addition of 200 g of sodium hydroxide to 99 g of 
1-methyl-1-oxophospholane phosphonic acid in 300 ml of water gives a 
solution with a pH-value of 5.3. Concentration of part of this solution by 
evaporation at 150.degree.C/1 mm Hg gives the monosodium salt of 
1-methyl-1-oxophospholane phosphonic acid in the form of a hygroscopic 
white crystalline substance having the composition: C.sub.5 H.sub.11 
O.sub.4 P.sub.2 Na.2H.sub.2 O. 
The addition of more sodium hydroxide to the residual solution up to pH 9.0 
gives the disodium salt of 1-methyl-1-oxophospholane phosphonic acid which 
is obtained in pure crystalline form by concentrating the solution by 
evaporation at 100.degree.C/1 mm Hg. Its composition corresponds to the 
formula C.sub.5 H.sub.10 O.sub.4 P.sub.2 Na.sub.2.9H.sub.2 O. 
EXAMPLE 13 
Production of the zinc salt of 1-methyl-1-oxophospholane phosphonic acid 
A solution of 20 g of 1-methyl-1-oxophospholane phosphonic acid in 100 ml 
of water is poured over 13 g of zinc oxide. The zinc oxide is partly 
dissolved by thorough stirring for 1 hour. The undissolved fraction is 
filtered off and the solution is concentrated at 120.degree.C/1 mm Hg, 
leaving behind white crystals of the zinc salt having the composition: 
C.sub.5 H.sub.10 O.sub.4 P.sub.2 Zn.H.sub.2 O. 
EXAMPLE 14 
Production of the monosodium salt of 1-methyl-1-oxophospholane phosphonic 
acid monomethyl ester 
22.6 g of 1-methyl-1-oxophospholane phosphonic acid dimethyl ester in 100 
ml of water are stirred with 4 g of sodium hydroxide for approximately 3 
hours at room temperature and then for 10 minutes at 100.degree. C. 
Thereafter less than 1% of the alkali used is still present. Concentration 
by evaporation at 200.degree. C/1 mm Hg gives the monosodium salt of 
1-methyl-1-oxophospholane phosphonic acid monomethyl ester in the form of 
a colorless, highly hygroscopic powder. 
EXAMPLE 15 
The neutralization of 22.6 g of 1-methyl-1-oxo-phospholane phosphonic acid 
with 10.5 g of diethanolamine gives the diethanol ammonium salt of 
1-methyl-1-oxophospholane phosphonic acid in the form of a viscous oil. 
EXAMPLE 16 
200 ml of a so-called weakly basic anion exchanger in ball form (diameter 
0.3 - 1.6 mm) based on polystyrene and containing dimethyl-amino groups, 
regenerated with sodium hydroxide, are treated in a column with 30 g of 
1-methyl-1-oxophospholane phosphonic acid in 300 ml of water. The 
exchanger resin has a macroporous structure and a total capacity of 1.9 
val/1. The resin charged with 1-methyl-1-oxophospholane phosphonic acid is 
washed with 3 liters of water and then dried in vacuo at 90.degree. C. The 
dried exchanger resin contains approximately 30% by weight of 
1-methyl-1-oxophospholane phosphonic acid. In contact with isocyanates, 
the resin thus prepared brings about the formation of carbodiimides. 
EXAMPLE 17 
When the procedure of Example 16 is repeated with 300 ml of a macroporous 
(&gt;50% pore volume, 200-400 A pore diameter, 40-50 pore surface/g), 
strongly basic anion exchanger (ball form, diameter 0.3-1.5 mm) based on 
polystyrene with 5% divinylbenzene with a total capacity of 1.2 val/1, in 
which trimethyl ammonium ions are attached to the solid phase, a resin 
containing approximately 20% by weight of 1-methyl-1-oxophospholane 
phosphonic acid is obtained, showing similar activity with respect to 
isocyanates. 
EXAMPLE 18 
71 g of 1-methyl-1-oxophospholane phosphonic acid in the form of a 14% 
solution in water are added to 500 ml of strongly basic polystyrene-based 
exchanger resin regenerated with sodium hydroxide. The resin has a 
macroporous structure (ball form 0.3 -1.5 mm diameter) and a total 
capacity of 1.2 val/1 and contains dimethyl hydroxyethyl ammonium ions as 
anchor groups in the solid phase. After a contact time of 30 minutes, the 
charged resin is washed with 3 1-liter portions of water and the dried in 
vacuo. Approximately 30 g of 1-methyl-1-oxophospholane phosphonic acid are 
bonded per 100 g of dried resin. 
EXAMPLE 19 
500 ml of a medium-basic gel-form exchanger (ball form, diameter 0.3-1.2 
mm) based on a polycondensation resin, which in addition to dimethylamine 
groups also contains trimethyl ammonium groups bonded to the solid phase, 
are regenerated with sodium hydroxide and washed with water until neutral. 
The exchanger with a total capacity of 2.2 val/1 is brought into contact 
with 600 ml of an 18% aqueous 1-methyl-1-oxophospholane phosphonic acid 
solution containing 0.16 mole of hydrochloric acid. After a contact time 
of 2 hours, the aqueous phase is removed, the solid phase washed 4 times 
with 4 1-liter portions of water and then dried in vacuo. The dry 
preparation contains 36% of 1-methyl-1-oxophospholane phosphonic acid. 
EXAMPLE 20 
This Example shows the use of the compounds according to the instant 
invention: 
a. Ionic fixation of the catalyst to insoluble matrices 
200 ml of a so-called "weak-basic" commercial anion exchanger based on a 
polystyrene containing --N--(CH.sub.3).sub.2 -groups, which has been 
regenerated with sodium hydroxide solution, are treated in a column with 
30 g of 1-methyl-1-oxophospholane phosponic acid in 300 ml of water. The 
exchanger resin has a macroporous structure and a total capacity of 1.9 
val/1. When the resin has been laden with 1-methyl-1-oxophospholane 
phosphonic acid, it is washed with 3 1 of water and dried in a vacuum at 
90.degree. C. The dried exchanger resin contains approximately 30%, by 
weight, of 1-methyl-1-oxophospholane phosphonic acid. 
b. Preparation of a catalyst consisting of a matrix and 
1-methyl-1-oxophospholane phosphonic acid 
Approximately 30 parts, by weight, of 1-methyl-1-oxophospholane phosphonic 
acid are fixed to 70 parts, by weight, of a very strongly basic anion 
exchanger on a basic of polystyrene (5%, by weight, of divinyl benzene as 
cross-linking component) which has been prepared as described above and 
has a macroporous structure and contains --N.sub..sym. (CH.sub.3).sub.3 
-anchoring groups. This matric has a pore volume of about 55%, a pore 
surface from 40 to 50 m.sup.2 per gram of dry substance and an average 
pore diameter of from about 200 to 400 Angstrom units. The particle size 
is in the region of from 0.3 to 1.5 mm. The capacity of this matrix to 
swell in aliphatic poly-isocyanates is from about 30 to 40 vol.-%, 
measured by the increase in volume of the beads, and its capacity to swell 
in aromatic isocyanates, such as phenyl isocyanate or 
tolylene-2,4-diisocyanate, is from approximately 90 to 130 vol.-%. The 
matrix contains 2 .times. 10.sup.18 basic goups per mg of dry substance. 
The following demonstrates the surprising selectivity of such a catalyst 
described above (matrix on a basis of polystyrene with strongly basic 
anchoring groups): 
500 parts, by weight, of 4,4'-diisocyanatodiphenyl methane (2 mol) and 34.8 
parts, by weight, (0.2 mol) of a mixture of 80 parts, by weight, of 
tolylene-2,4-diisocyanate and 20 parts, by weight, of 
tolylene-2,6-diisocyanate are heated to 165.degree. C for 35 minutes with 
4 parts, by weight, of the above mentioned catalyst. Carbodiimidisation of 
the tolylene diisocyanate proceeds strictly selectively and a solution of 
about 7%, by weight, of the compound: 
##STR10## 
in 4,4-diisocyanatodiphenylmethane is obtained. This solution has the 
remarkably low viscosity of only about 68 cP/20.degree. C and an 
isocyanate content of about 31.5%. 
More than 70%, by weight, of the diisocyanato-carbodiimide formed is in 
equilibrium with a triisocyanato-uretone imine of the idealised formula: 
##STR11## 
It is surprisingly found that even at concentrations of only about 7%, by 
weight, the diisocyanato-carbodiimide or its uretone imine triisocyanate 
is capable of liquefying 4,4'-diisocyanatodiphenylmethane which is 
crystalline at room temperature. 
It will be appreciated that the instant specification and claims are set 
forth by way of illustration and not limitation, and that various 
modifications and changes may be made without departing from the spirit 
and scope of the present invention.