Polycarbonates made using high activity catalysts

Polycarbonates having M.sub.n ranging from about 5,000 to about 40,000 and a molecular weight distribution ranging from 1.05 to 2.0 are prepared from epoxides and CO.sub.2 using a catalyst which has a Zn center and two ligands where one of the ligands is a propagating group and the other of the ligands is not a propagating group and an activity of at least one turnover per hour, preferably at least 100 turnovers per hour. Preferred catalysts have a ##STR1## moiety with group on each nitrogen containing a phenyl moiety.

TECHNICAL FIELD 
The invention is directed at novel high activity zinc containing catalysts 
for producing polycarbonates from epoxide and carbon dioxide, to a process 
for producing polycarbonates using the catalysts and to the polycarbonates 
produced thereby. 
BACKGROUND OF THE INVENTION 
Polycarbonates are useful, for example, for packaging materials and 
coatings and are of special interest because they are biodegradable. 
Consideration has been given to a phosgene-free synthesis of polycarbonates 
using epoxides and carbon dioxide monomers and various catalysts, in most 
instances zinc-containing catalysts. 
lnoue, S., et al., J. Poly. Sci. Lett. B7, 287-292 (1969) discloses use of 
a poorly defined heterogenous catalyst made by partially hydrolyzing 
diethyl zinc. The catalyst has a very low activity requiring days for 
polycarbonate production. 
Aida, T., et al., J. Am. Chem. Soc. 105, 1304-1309 (1983) teaches an 
aluminum porphyrin catalyst which has very low activity (&lt;0.3 
turnovers/hr). 
Darenbourg, D. J., et al., Macromolecules, 28, 7577-7579 (1995) teaches a 
catalyst having the structure 
##STR2## 
This catalyst provides higher activity (2.4 turnovers per hour) than 
previously described but said activity is still too low for a commercially 
competitive product. In the case of this catalyst, the ligands become part 
of the polymer chain end. 
Super, M., et al., Macromolecules, 30, 368-372 (1997) discloses an ill 
defined catalyst made by reacting zinc oxide and 
##STR3## 
This catalyst provided an activity of 8.4 turnovers per hour, which is 
higher than achieved before but which still is quite low. Moreover, it 
requires running the polymerization in supercritical CO.sub.2. In the case 
of this catalyst, the ligands become part of the chain end. 
Moreover, conventional zinc (II) dicarboxylates and dialkoxides exhibit low 
activities and presumably lose their initial ligands during the 
polymerization reaction. 
The catalysts heretofore exhibit polymerization rates that are far too low 
for an efficient industrial process. The polycarbonates made from epoxide 
and carbon dioxide up to now have not made much commercial impact because 
they are expensive due to time-consuming preparation because of the low 
activity of known catalysts. 
Due to the inexpensive and accessible monomers used in the process 
(epoxides from olefins and O.sub.2, CO.sub.2) and the attractive 
properties and potential of polycarbonates, the development of a new, 
category of catalysts for this polymerization process is a significant 
scientific goal. 
SUMMARY OF THE INVENTION 
It has been discovered herein that catalysts competitive with and in many 
cases at least 10 times faster than catalysts heretofore known for 
catalyzing the reaction of epoxide and CO.sub.2 to form polycarbonate have 
a zinc center and two ligands where one of the ligands is a propagating 
group and the other of the ligands is not a propagating group. These 
catalysts have an activity of at least one turnover per hour and preferred 
catalysts have an activity of at least 100 turnovers per hour, for 
catalyzing the reaction of epoxide and CO.sub.2 to form polycarbonate. 
In one embodiment of the invention herein, there is provided a catalyst for 
use in a method of polymerizing epoxide and carbon dioxide to produce 
polycarbonate where the catalyst has a zinc center and two ligands where 
one of the ligands does not become part of the polymer chain. 
One group of catalysts herein have the formula 
##STR4## 
where each R.sub.1 is selected from the group consisting of C.sub.1 
-C.sub.20 alkyl where one or more hydrogens is optionally replaced by 
halogen, e.g., chlorine or fluorine, and C.sub.6 -C.sub.20 aryl where one 
or more hydrogens is optionally replaced by halogen, e.g., chlorine or 
fluorine, and where the C.sub.6 -C.sub.20 includes the carbon atoms in 
aryl ring and carbon atom(s) in substituent(s) on aryl ring and each 
R.sub.1 is the same or different, and each R.sub.2 is selected from the 
group consisting of hydrogen, cyano, C.sub.1 -C.sub.20 alkyl where one or 
more hydrogens is optionally replaced by halogen, e.g., chlorine or 
fluorine, and C.sub.6 -C.sub.20 aryl where one or more hydrogens is 
optionally replaced by halogen, e.g., chlorine or fluorine, and where the 
C.sub.6 -C.sub.20 includes the carbon atoms in aryl ring and carbon in 
atom(s) in substituent(s) on aryl ring and each R.sub.2 is the same or 
different, and R is selected from the group consisting of C.sub.1 
-C.sub.20 allyl, C.sub.6 -C.sub.20 aryl where the C.sub.6 -C.sub.20 
includes the carbon atoms in aryl ring and carbon atom(s) in 
substituent(s) on aryl ring and polymer of weight average molecular weight 
up to 1,000,000 having at least one pendant carboxyl group, or dimer 
thereof, the compound of formula (I) or dimer thereof being effective to 
catalyze the reaction of epoxide and CO.sub.2 to form polycarbonate. 
Another group of catalysts herein have the formula 
##STR5## 
where each R.sub.1 is defined the same as for (I) and each R.sub.1 is the 
same or different and each R.sub.2 is defined the same as for (I) and each 
R.sub.2 is the same or different and R.sub.3 is selected from the group 
consisting of hydrogen, C.sub.1 -C.sub.20 alkyl, C.sub.6 -C.sub.20 aryl 
where the C.sub.6 -C.sub.20 includes the carbon atoms in aryl ring and 
carbon atom(s) in substituent(s) on aryl ring and polymer of weight 
average molecular weight up to 1,000,000 having at least one pendant 
hydroxyl group, or dimer thereof, the compound of formula (II) or dimer 
thereof being effective to catalyze the reaction of epoxde and CO.sub.2 to 
form polycarbonate. 
Another embodiment herein is directed to a method of preparing a 
polycarbonate, said method comprising copolymerizing monomers comprising 
carbon dioxide and epoxide selected from the group consisting of C.sub.2 
-C.sub.20 alkylene oxides, C.sub.4 -C.sub.12 cycloalkene oxides and 
styrene oxide in the presence of a catalyst which has a Zn center and two 
ligands where one of the ligands is a propagating group and the other of 
the ligands is not a propagating group and an activity of at least one 
turnover per hour, often an activity of at least 100 turnovers per hour. 
Exemplary of the catalysts are those defined above in conjunction with 
formulas (I) and (II) and dimers thereof. 
Another embodiment herein is directed to polycarbonate having an M.sub.n 
ranging from about 5,000 to about 40,000 and a molecular weight 
distribution (i.e., M.sub.w /M.sub.n) ranging from 1.05 to 2.0, e.g., from 
1.05 to 1.25. 
As used herein, the term "propagating group" means the group bound to the 
zinc center into which the monomers insert. In the case of catalysts (I) 
and (II), the ligands which are propagating groups are respectively --OCOR 
and --OR.sub.3. 
The term "turnovers per hour," sometimes abbreviated "TO/hr," means the 
number of moles of epoxide monomer per mole of zinc center polymerized per 
hour. The turnovers per hour may be referred to as "TOF" which stands for 
turnover frequency. The turnover number or TON is the turnover frequency 
multiplied by the time of reaction. 
The M.sub.n referred to above is the number average molecular weight and is 
determined by gel permeation chromatography, versus monodispersed 
polystyrene standards. 
The molecular weight distribution is M.sub.w /M.sub.n (i.e., weight average 
molecular weight divided by number average molecular weight) and is 
determined by gel permeation chromatography. 
DETAILED DESCRIPTION 
As indicated above, the catalysts here have an activity of at least one 
turnover per hour and preferably at least 100 turnovers per hour. The 
catalysts have an activity, for example, ranging from 100 to 750 turnovers 
per hour or ranging from about 200 to 600 turnovers per hour. 
We turn now to the catalysts having the formula (I) described above. 
When R is a polymer having at least one pendant carboxyl group, it normally 
has a weight average molecular weight of at least 1,000 and preferably is 
either polyethylene oxide with at least one pendant carboxyl group or 
polybutadiene with at least one pendant carboxyl group. 
One group of preferred catalysts contains a phenyl moiety in R.sub.1 of 
formula (I). 
One class of catalysts herein having the formula (I) and containing a 
phenyl moiety in R.sub.1 of formula (I) have the formula 
##STR6## 
where R.sub.4 is methyl, R.sub.5 is hydrogen or cyano, R.sub.6 and R.sub.7 
are the same or different and are C.sub.1 -C.sub.3 alkyl, R.sub.8 is 
hydrogen and R.sub.9 is hydrogen, and OAc is acetate, or is dimer thereof. 
The compounds of formula (V) normally exist in both monomeric and dimeric 
form in solution and in the dimeric form in the solid state. 
One catalyst of formula (V) is the compound having the formula 
##STR7## 
where .sup.i Pr is isopropyl and OAc is acetate and is the compound of 
formula (V) where R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is 
isopropyl, R.sub.7 is isopropyl, R.sub.8 is hydrogen, and R.sub.9 is 
hydrogen. This catalyst is referred to as Catalyst A hereinafter. A 
variation on this catalyst has the structure (III) except that one or both 
of the outer R.sub.2 groups in formula (I) is triluoromethyl instead of 
methyl. 
Another catalyst of formula (V) is the compound having the formula 
##STR8## 
where Et is ethyl and OAc is acetate, and is the compound of formula (V) 
where R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is ethyl, R.sub.7 is 
ethyl, R.sub.8 is hydrogen, and R.sub.9 is hydrogen. This catalyst is 
referred to as Catalyst B hereinafter. 
Catalysts of formula (I) and the catalysts of formula (V) can be prepared 
in a process characterized by ease of execution wherein two equivalents of 
C.sub.1 -C.sub.20 primary amine are refluxed with 2,4-pentane dione 
(unsubstituted or substituted at the one, three and/or five positions) in 
acidic ethanol and deprotonating the resulting .beta.-diimine at 0.degree. 
C. with butyllithium (BuLi) and then reacting with zinc salt of aliphatic 
or aromatic acid corresponding to R and purifying the resulting complex. 
The primary amine determines R.sub.1 and the dione determines each 
R.sub.2. 
The .beta.-diimine has the formula 
##STR9## 
where R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 become 
R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, and R.sub.9 in the catalysts 
having corresponding formulas where that the ring hydrogen is converted to 
&gt;ZnOCOR in the case of compounds of formula (V) and to &gt;ZnOR.sub.3 in the 
case of compounds of formula (VII) discussed below. 
The compound of the formula (III) is readily prepared by refluxing two 
equivalents of 2,6-diisopropyl aniline with 2,4-pentane dione as described 
in Feldman, J., et al., Organometallics, 16, 1514-1516 (1997), hereinafter 
Feldman, which is incorporated herein by reference, and reacting the 
resulting .beta.-diimine with one equivalent of butyllithium and one 
equivalent of zinc acetate at 0.degree. C. in tetrahydrofuran and 
purifying by crystallizing from methylene chloride. For a variation where 
one or two of the R.sub.2 groups is trifluoromethyl, the diones are 
1,1,1-trifluoro-2,4-pentane dione and 1,1,1,5,5,5-hexafluoro-2,4-pentane 
dione respectively. 
The compound of the formula (VI) can be prepared the same way as just 
described for the compound of the formula (III) except that 2,6-diethyl 
aniline is used in place of 2,6-diisopropyl aniline. 
We turn now to the catalysts having the formula (II) described above. 
When R.sub.3 is a polymer having at least one pendant hydroxyl group, it 
normally has a weight average molecular weight of at least 1,000 and 
preferably is either polyethylene oxide with at least one pendant hydroxyl 
group or polybutadiene with at least one pendant hydroxyl group. 
One group of preferred catalysts contains a phenyl moiety in R.sub.1 of 
formula (II). 
One class of catalysts herein having the formula (II) and containing a 
phenyl moiety in R.sub.1 of formula (II) have the formula 
##STR10## 
wherein R.sub.4 is methyl, R.sub.5 is hydrogen or cyano, R.sub.6 and 
R.sub.7 are the same or different and are C.sub.1 -C.sub.3 alkyl, R.sub.8 
is hydrogen or chloro, and R.sub.9 is hydrogen and Me is methyl, or is 
dimer thereof. 
The compounds of formula (VII) normally exist mostly in the monomeric form 
and some in the dimeric form in solution and in the dimeric form in the 
solid state. 
One catalyst of formula (VII) is compound having the formula 
##STR11## 
where .sup.i Pr is isopropyl and Me is methyl and is the compound of 
formula (VII) where R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is 
isopropyl, R.sub.7 is isopropyl, R.sub.8 is hydrogen, and R.sub.9 is 
hydrogen. This compound is considered to exist as the dimer in the solid 
state. This compound is referred to as Catalyst C hereinafter. A variation 
on this catalyst has the structure (IV) except that one or both of the 
outer R.sub.2 groups in formula (II) is trifluoromethyl instead of methyl. 
Another catalyst of formula (VII) is compound having the formula 
##STR12## 
where Et is ethyl and Me is methyl and is the compound of formula (VII) 
where R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is ethyl, R.sub.7 is 
ethyl, R.sub.8 is hydrogen, and R.sub.9 is hydrogen. This compound exists 
as the dimer in the solid state. This compound is referred to as Catalyst 
D hereinafter. A structure for the dimer is set forth below. 
##STR13## 
Still another catalyst of formula (VII) is compound having the formula 
(VII) wherein R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is 
isopropyl, R.sub.7 is methyl, R.sub.8 is hydrogen, and R.sub.9 is 
hydrogen. This compound exists as the dimer in the solid state. This 
compound is referred to as Catalyst E hereinafter. 
Still another catalyst of formula (VII) is compound having the formula 
(VII) wherein R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is 
isopropyl, R.sub.7 is ethyl, R.sub.8 is hydrogen, and R.sub.9 is hydrogen. 
This compound exists as the dimer in the solid state. This compound is 
referred to as Catalyst F hereinafter. 
Still another catalyst of formula (VII) is compound having the formula 
(VII) wherein R.sub.4 is methyl, R.sub.5 is hydrogen, R.sub.6 is ethyl, 
R.sub.7 is ethyl, R.sub.8 is chloro, and R.sub.9 is hydrogen. This 
compound exists as the dimer in the solid state. This compound is referred 
to as Catalyst G hereinafter. 
Yet another catalyst of formula (VII) is compound having the formula (VII) 
wherein R.sub.4 is methyl, R.sub.5 is cyano, R.sub.6 is ethyl, R.sub.7 is 
ethyl, R.sub.8 is hydrogen, and R.sub.9 is hydrogen. This compound exists 
as dimer in the solid state. This compound is referred to as Catalyst H 
hereinafter. 
Catalysts of formula (II) and the catalysts of formula (VII) can be 
prepared in a process characterized by ease of execution where 
.beta.-diimine prepared as described in conjunction with preparation of 
compounds of the formula (V) is reacted with two equivalents of diethyl 
zinc at 0.degree. C. One of the equivalents of diethyl zinc reacts and the 
other is removed. The resulting product is reacted with one equivalent of 
R.sub.3 OH to replace the ethyl on the reacted zinc atom with OR.sub.3, 
thereby to form catalysts of formula (II) and the catalysts of formula 
(VII). 
The compound of the formula (IV) can be prepared by reacting the 
.beta.-diimine used for producing compound of formula (III), with two 
equivalents of diethyl zinc in toluene at 0.degree. C. and removing 
unreacted diethyl zinc and solvent in vacuo and then reacting with 
methanol. 
The compound of formula (VIII) can be prepared in the same way as the 
compound of formula (IV) except that the .beta.-diimine is the same as 
that used for preparation of compound of formula (VI). 
The compound of Catalyst E can be prepared in the same way as the compound 
of formula (IV) except that the .beta.-diimine is prepared by refluxing 
two equivalents of 2-isopropyl-6-methyl aniline with 2,4-pentane dione by 
the method described in Feldman. 
The compound of Catalyst F can be prepared in the same way as the compound 
of formula (IV) except that the .beta.-diimine is prepared by refluxing 
two equivalents of 2-ethyl-6-isopropyl aniline with 2,4-pentane dione by 
the method described in Feldman. 
The compound of Catalyst G can be prepared in the same way as the compound 
of formula (IV) except that the .beta.-diimine is prepared by refluxing 
two equivalents of 2,6-diethyl-3-chloro aniline with 2,4-pentane dione by 
the method described in Feldman. 
The compound of Catalyst H can be prepared in the same way as the compound 
of formula (IV) except that the .beta.-diimine is prepared by reacting 
.beta.-diimine the same as used for preparing compound of the formula 
(VI), with 1 equivalent of n-butyllithium at -78.degree. C. in 
tetrahydrofuran (THF), followed by stirring with 1 equivalent of 
p-toluenesulfonyl cyanide at -78.degree. C. for two hours, then warming to 
room temperature, then removing solvent in vacuo, and then isolating the 
product by extracting the solid residue with methylene chloride, washing 
with water and drying in vacuo. 
We turn now to the embodiment herein directed to a method of preparing a 
polycarbonate, said method comprising copolymerizing monomers comprising 
carbon dioxide and epoxide selected from the group consisting of C.sub.2 
to C.sub.20 alkylene oxides, C.sub.4 to C.sub.12 cycloalkene oxides and 
styrene oxide in the presence of a catalyst which has a Zn center and two 
ligands where one of the ligands is a propagating group and the other of 
the two ligands is not a propagating group and an activity of at least one 
turnover/hour, often an activity of at least 100 turnovers per hour, where 
examples of the catalysts are those defined above in conjunction with 
formulas (I) and (II), or dimers thereof, and examples of preferred 
catalysts are those described above in conjunction with formulas (V) and 
(VII), and examples of very preferred catalysts are Catalysts A, B, C, D, 
E, F, G, and H. 
Examples of alkylene oxides include ethylene oxide, propylene oxide, and 
oxabicycloheptane. 
Examples of cycloalkene oxides include cyclopentene oxide, cyclohexene 
oxide, cyclooctene oxide, and vinylcyclohexene diepoxide (which results in 
clear cross-linked polycarbonate). Cyclohexene oxide, i.e., 
1,2-epoxycyclohexane, is normally taken as a benchmark in the art for 
comparing activity of catalysts and determining efficiency of a 
polycarbonate preparation process. 
The mole ratio of catalyst to epoxide normally should range from 1:100 to 
1:4000, e.g., from 1:100 to 1:1500, with 1:1000 being preferred. 
The temperature at which reaction is carried out normally ranges from 
20.degree. C. to 110.degree. C. with 50.degree. C. being preferred. 
The reaction can be carried out at a pressure (caused by CO.sub.2) ranging 
from 20 psi to 800 psi, preferably from 20 psi to 500 psi, e.g., 100 psi. 
The reaction can be carried out, for example, over a period of 1 to about 
24 hours, preferably 11/2 to 6 hours, e.g., 2 hours. 
The reaction is normally carried out with the epoxide monomer functioning 
as the reaction solvent, i.e., without other reaction solvent being 
present. The catalysts thus function in solution and are considered to 
function in the monomeric form and in the dimeric form in solution. 
We turn now to the embodiment herein directed to polycarbonate having a 
M.sub.n ranging from about 5,000 to about 40,000 and a molecular weight 
distribution ranging from 1.05 to 2.0, e.g., 1.05 to 1.25. The molecular 
weight distribution range means that the product is very homogeneous. The 
product typically has 85% or more carbonate linkages, often 95% or more 
carbonate linages. A product obtained by copolymerizing cyclohexene oxide 
and carbon dioxide is poly(cyclohexenylene carbonate) and comprises 
##STR14## 
where n ranges from 50 to 500 and contains at least 85%, often at least 
95% polycarbonate linkages. The product is biodegradable and is suitable 
for packaging material and for coatings. 
The invention is illustrated by the following specific examples:

EXAMPLE I 
Catalyst A 
To a solution of .beta.-diimine formed from 2,4-pentane dione and two 
equivalents of 2,6-diisopropyl aniline as described in Feldman, J., et al. 
Organometallics, 16, 1514-1516 (1997), hereinafter H(BDI)-1, (0.535 g, 
1.28 mmol) in tetrahydrofuran, denoted THF hereinafter (10 ml) was slowly 
added n-BuLi (1.6M in hexane, 0.88 ml, 1.41 mmol) at 0.degree. C. After 
stirring for 5 min at 0.degree. C., the solution was cannulated to a 
solution of zinc acetate (0.240 g, 1.41 mmol) in THF (15 ml). After 
stirring overnight at room temperature, the suspension was filtered over a 
frit and the clear solution was dried in vacuo. The light yellow solid was 
recrystallized from a minimum amount of methylene chloride at -20.degree. 
C. to produce compound of formula (III), i.e., Catalyst A (0.436 g, 63% 
yield). .sup.1 H NMR (25 mg complex in 0.55 ml C.sub.6 D.sub.6, 300 MHz, 
"M" denotes monomer, "D" denotes dimer) .delta.7.11 (18H, M+D, m, ArH), 
4.93 (1H, s, .beta.- CH, m), 4.64 (2H, s, .beta.-CH, D), 3.29 (12H, m, 
CHMe.sub.2, M+D), 1.73 (6H, s, OC(O)Me, D), 1.67 (6H, s, .alpha.-Me, M), 
1.55 (12 H, s, .alpha.-Me, D), 1.41 (12H, d, J=6.4 Hz, CHMeMe', M), 1.31 
(3H, s, OC(O)Me, M), 1.19 (24H, d, J=7.0 Hz, CHMeMe', D), 1.14 
(24H,d,J=7.0 Hz, CHMeMe', D), 0.87 (12H, d, J=6.4 Hz, CHMe,Me', M). X-ray 
diffraction data: monoclinic, P2.sub.1 /n, colorless; .alpha.=13.0558(3) 
.ANG., b=15.1725(4) .ANG., c=15.9712(2) .ANG.; .beta.=106.142(1); 
V=3038.99(11); Z=4; R=0.535; GOF=1.121. Analysis of the compound by X-ray 
crystallography revealed the compound exists as the dimer in the solid 
state. 
EXAMPLE II 
Catalyst B 
To a solution of .beta.-diimine formed from 2,4-pentane dione and two 
equivalents of 2,6-diethyl aniline as described in Feldman for H(BDI)-1 
(hereinafter H(BDI)-2) (0.501 g, 1.38 mmol) in THF (10 ml) was slowly 
added n-BuLi (1.6M in hexanes, 0.95 ml, 1.52 mmol) at 0.degree. C. After 
stirring for 5 min at 0.degree. C., the solution was cannulated to a 
suspension of zinc acetate (0.266 g, 1.45 mmol) in THF (15 ml). After 
stirring overnight at room temperature the suspension was filtered over a 
frit and the clear solution was dried in vacuo. The crude material was 
dissolved in 20 ml toluene; the insoluble precipitate was filtered over a 
frit. The clear solution was concentrated and then recrystallized at 
-30.degree. C. (0.323 g, 48%) to provide compound of formula (VI), i.e., 
Catalyst B. Analysis of the compound by X-ray crystallography revealed the 
compound exists as the dimer in the solid state. 
EXAMPLE III 
Catalyst C 
To a solution of diethyl zinc (0.61 ml, 5.95 mmol) in toluene (10 ml) was 
slowly added H(BDI)-1 produced as in Example I (0.501 g. 1.196 mmol) in 
toluene (10 ml) at 0.degree. C. After stirring overnight at 80.degree. C., 
the clear solution was dried in vacuo, giving a quantitative yield (0.61 
g) of intermediate (BDI-1)ZnEt. .sup.1 H NMR (C.sub.6 D.sub.6, 300 MHz) 
.delta.7.07 (6H, m, ArH), 4.98 (1H, s, .beta.-CH), 3.18 (4H, m, 
CHMe.sub.2), 1.69 (6H, s, .alpha.-Me), 1.25 (12H, d, J=7.0 Hz, CHMeMe'), 
1.14 (12H, d, J=7.0 Hz, CHMeMe'), 0.89 (3H, t, J=8.0 Hz, CH.sub.2 
CH.sub.3), 0.24 (2H, q, J=8.0 Hz, CH.sub.2 CH.sub.3). To a solution of 
(BDI)ZnEt-1 (1.196 mmol) in toluene (10 ml) was added methanol (0.24 ml, 
5.91 mmol) at room temperature (RT). After stirring for an hour at room 
temperature, the clear solution was dried in vacuo to produce compound of 
formula (IV), i.e., Catalyst C (0.604 g), 98% yield. .sup.1 H NMR (C.sub.6 
D.sub.6, 300 MHz) .delta.7.13 (6H, m, ArH), 4.87 (1H, s, .beta.- CH), 3.30 
(3H, s, OCH.sub.3), 2.97 (4H, m, CHMe.sub.2), 1.53 (6H, s, .alpha.-Me), 
1.20 (12H, d, J=6.5 Hz, CHMeMe'), 1.16 (12H, d, J=6.5 Hz, CHMeMe'). 
Analysis of the compound by X-ray crystallography revealed the compound 
exists as the dimer in the solid state. 
EXAMPLE IV 
Catalyst D 
To a solution of diethyl zinc (0.61 ml, 5.95 mmol, 2 eq) in toluene (5 ml) 
was slowly added H(BDI)-2 produced as in Exanmple II (1.077 g, 2.971 mmol, 
1 eq) in toluene (5 ml) at 0.degree. C. After stirring overnight at 
80.degree. C., the clear solution was dried invacuo, giving a quantitative 
yield (1.35 g) of intermediate compound (BDI-2)ZnEt. .sup.1 H NMR (C6D6, 
300 MHz) .delta.7.04 (6H, b, ArH), 4.92 (1H, s, .beta.-CH), 2.60 (4H, m, 
J=7.5 Hz, CH.sub.2 CH.sub.3), 2.45 (4H, m, J=7.5 Hz, CH.sub.2 CH.sub.3), 
1.62 (6H, s, .alpha.-Me), 1.16 (12H, t, J=7.5 Hz, CH.sub.2 CH.sub.3), 0.95 
(3H, t, J=8.0 Hz, CH.sub.2 CH.sub.3), 0.25 (2H, q, J=8.0 Hz, CH.sub.2 
CH.sub.3). To a solution of the intermediate compound (BDI) ZnEt-2 (1.35 
g, 2.97 mmol, 1 eq) in toluene (10 ml) was added methanol (0.13 ml, 3.20 
mmol, 1.1 eq)at room temperature (RT). After stirring for an hour at RT, 
the clear solution was dried in vacuo and then recrystallized from a 
minimum amount of toluene at -30.degree. C. (0.98 g, 72%) to produce 
compound of formula (VIII), i.e., Catalyst D. .sup.1 H NMR(C6D6, 300 MHz) 
.delta.7.09 (6H, m, ArH), 4.64 (1H, s, .beta.-CH), 3.53 (3H, s, OCH.sub.3) 
2.55 (4H, m, J=7.5 Hz, CH.sub.2 CH.sub.3), 2.20 (4H, m, J=7.5 Hz, CH.sub.2 
CH.sub.3), 1.41 (6H, s, .alpha.-Me), 1.13 (12H t, J=7.5 Hz, CH2CH.sub.3). 
Analysis of the compound by X-ray crystallography revealed that the 
compound exists as the dimer in the solid state. 
EXAMPLE V 
Catalyst E 
To a solution of diethyl zinc (0.59 ml, 5.76 mmol, 5 eq) in toluene (5 ml) 
was slowly added .beta.-diimine formed from 2,4-pentane dione and two 
equivalents of 2-isopropyl-6-methyl aniline as described in Feldman 
(H(BDI)-3) (0.415 g, 1.14 mmol, 1 eq) in toluene (5 ml) at 0.degree. C. 
After stirring overnight at 80.degree. C., the clear solution was dried in 
vacuo, giving a quantitative yield(0.522 g) of the desired intermediate 
compound, designated (BDI-3)ZnEt. To a solution of (BDI) ZnEt-3 (0.522 g, 
1.14 mmol, 1 eq) in toluene(10 ml) was added methanol (0.047 ml, 1.16 
mmol, 1 eq) at room temperature (RT). After stirring for an hour at RT, 
the clear solution was dried in vacuo and then recrystallized from a 
minimum amount of toluene at -30.degree. C.(0.254 g, 49%) to provide 
compound constituting Catalyst E. Analysis of the compound by X-ray 
crystallography revealed that the compound exists as the dimer in the 
solid state. 
EXAMPLE VI 
Catalyst F 
To a solution of diethyl zinc (0.56 ml, 5.46 mmol, 5 eq) in toluene (5 ml) 
was slowly added .beta.-diimine formed from 2,4-pentane dione and two 
equivalents of 2-ethyl-6-isopropyl anline as described in Feldman 
(H(BDI)-4) (0.426 g, 1.09 mmol, 1 eq) in toluene (5 ml) at 0.degree. C. 
After stirring overnight at 80.degree. C., the clear solution was dried in 
vacuo, giving a quantitative yield (0.528 g) of the desired intermediate 
compound, designated (BDI-4) ZnEt. To a solution of (BDI)ZnEt-4 (0.528 g, 
1.09 mmol) in toluene(10 ml) was added methanol (0.15 ml, 3.386 mmol, 3.4 
eq) at room temperature (RT). After stirring for an hour at RT, the 
suspension was filtered over a frit and the clear solution was dried in 
vacuo and then recrystallized from a minimum amount of toluene at 
-30.degree. C. to provide compound constituting Catalyst F (0.201 g, 38%). 
Analysis of the compound by X-ray crystallography revealed that the 
compound exists as the dimer in the solid state. 
EXAMPLE VII 
Catalyst G 
To a solution of diethyl zinc (0.64 ml, 6.25 mmol, 5 eq) in toluene (5 ml) 
was slowly added .beta.-diimine formed from 2,4-pentane dione and two 
equivalents of 2,6-diethyl-3-chloro aniline as described in Feldman 
(H(BDI)-5) (0.537 g, 1.24 mmol, 1 eq) in toluene (5 ml) at 0.degree. C. 
After stirring overnight at 80.degree. C., the clear solution was dried in 
vacuo, giving a quantitative yield (0.652 g) of the desired intermediate 
compound, designated (BDI-5)ZnEt. To a solution of (BDI)ZnEt-5 (0.652 g, 
1.24 mmol, 1 eq) in toluene (30 ml) was added methanol (0.25 ml, 6.15 
mmol, 5 eq) at room temperature (RT). After stirring for 5 min at RT, the 
clear solution was dried in vacuo. The crude material was dissolved in 
hexanes (20 ml); the insoluble precipitate was filtered over a frit. The 
clear solution was concentrated and then recrystallized at 5.degree. C. to 
provide compound constituting Catalyst G. Analysis of the compound by 
X-ray crystallography revealed that the compound exists as the dimer in 
the solid state. 
EXAMPLE VIII 
Catalyst H 
To a solution of diethyl zinc (0.53 ml, 5.17 mmol, 5 eq) in toluene (5 ml) 
was slowly added .beta.-diimine (H(BDI)-6) (0.401 g, 1.04 mmol, 1 eq) in 
toluene (5 ml) at 0.degree. C. where the H(BDI)-6 was prepared by reacting 
H(BDI)-2 with one equivalent of n-butyllithium at -78.degree. C. in THF 
followed by stirring with one equivalent of p-toluenesulfonyl cyanide at 
-78.degree. C. for two hours, then warming to room temperature, removing 
solvent in vacuo, and isolating the product by extracting the solid 
residue with methylene chloride, washing with water and drying in vacuo. 
After stirring overnight at 80.degree. C., the clear solution was dried in 
vacuo, giving a quantitative yield (0.498 g) of the desired intermediate 
compound, designated (BDI-6)ZnEt. To a solution of(BDI)ZnEt-6 (0.498 g, 
1.04 mmol, 1 eq) in methylene chloride (30 ml) was added methanol (0.015 
ml, 1.23 mmol, 1.2 eq) at room temperature (RT). After stirring for 4 
hours at RT, the clear solution was dried in vacuo (.sup.1 H NMR showed 
only 50% conversion). Then extra methanol (0.031 ml, 0.763 mmol, 0.73 eq) 
was added at RT. After stirring for 2 hours at RT, the clear solution was 
dried invacuo (.sup.1 H NMR showed 100% conversion) and then 
recrystallized from a minimum amount of methylene chloride at -30.degree. 
C. to provide compound constituting Catalyst H. (0.297 g, 60%). Analysis 
of the compound by X-ray crystallography revealed that the compound exists 
as the dimer in the solid state. 
SUMMARY OF EXAMPLES I-VIII 
A summary of Examples I-VIII is provided in Table 1 below wherein Me is 
methyl, iPr is isopropyl and Et is ethyl. 
TABLE 1 
______________________________________ 
Example Associated 
Number Catalyst Formula R.sub.4 R.sub.5 R.sub.6 R.sub.7 R.sub.8 
______________________________________ 
R.sub.9 
I A V Me H iPr iPr H H 
II B V Me H Et Et H H 
III C VII Me H iPr iPr H H 
IV D VII Me H Et Et H H 
V E VII Me H iPr Me H H 
VI F VII Me H iPr Et H H 
VII G VII Me H Et Et Cl H 
VIII H VII Me CN Et Et H H 
______________________________________ 
EXAMPLE IX 
In a drybox, Catalyst A produced as in Example I (20 mg, 
3.7.times.10.sup.-5 mol) and cyclohexene oxide (CHO, 3.8 ml, 3.7 g, 
3.7.times.10.sup.-2 mol) and a magnetic stir bar were placed in a 60 ml 
Fischer-Porter bottle. The vessel was pressurized to 100 psig with 
CO.sub.2 and allowed to stir at 50.degree. C. for 2 h. After a small 
sample of the crude material was removed for characterization, the product 
was dissolved in 5 ml of methylene chloride and precipitated from 20 ml of 
methanol. The product was then dried in vacuo to constant weight (2.56 g, 
494 moles of CHO consumed per mole of zinc, 247 moles of CHO consumed per 
mole of zinc per hour). The polymer contained 96% carbonate linkages 
(determined by .sup.1 H NMR spectroscopy). Characterization of the product 
by gel-permeation chromatography revealed a M.sub.n of 31,000 g/mole, and 
a M.sub.w /M.sub.n of 1.11. 
EXAMPLE X 
In a drybox, Catalyst B produced as in Example II (18.4 mg, 0.0189 mmol) 
and cyclohexene oxide (CHO, 3.9 ml, 3.7 g, 3.8.times.10.sup.-2 mol) and a 
magnetic stir bar were placed in a 60 ml Fischer-Porter bottle. The vessel 
was pressurized to 100 psig with CO.sub.2 and allowed to stir at 
50.degree. C. for 2 hours. The crude product was dried in vacuo, then was 
dissolved in a minimum amount (5 ml) of methylene chloride and 
precipitated from 20 ml of methanol. The product was then dried in vacuo 
to constant weight (470 moles of CHO consumed per mole of zinc, 235 moles 
of CHO consumed per mole of zinc per hour). The polymer contained 96% 
carbonate linkages (determined by .sup.1 H NMR spectroscopy). 
Characterization of the product by gel-permeation chromatography revealed 
a M.sub.n of 22,000 g/mol and a M.sub.w /M.sub.n of 1.12. 
EXAMPLE XI 
In a drybox, Catalyst C produced as in Example III (25 mg, 
4.4.times.10.sup.-5 mol) and cyclohexene oxide (CHO, 4.5 ml, 4.4 g, 
4.4.times.10.sup.-2 mol) and a magnetic stir bar were placed in a 60 ml 
Fischer-Porter bottle. The vessel was pressurized to 100 psig with 
CO.sub.2 and allowed to stir at 50.degree. C. for 2 h. After a small 
sample of the crude material was removed for characterization, the product 
was dissolved in 5 ml of methylene chloride and precipitated from 20 ml of 
methanol. The product was then dried in vacuo to constant weight (2.76 g, 
449 moles of CHO consumed per mole of zinc, 224 moles of CHO consumed per 
mole of zinc per hour). The polymer contained 95% carbonate linkages 
(determined by .sup.1 H NMR spectroscopy). Characterization of the product 
by gel-permeation chromatography revealed a M.sub.n of 19,100 g/mole, and 
a M.sub.w /M.sub.n of 1.07. 
EXAMPLE XII 
In a drybox, Catalyst D produced as in Example IV (18.4 mg, 0.0201 mmol) 
and cyclohexene oxide (CHO, 4.1 ml, 3.9 g, 4.0.times.10.sup.-2 mol) and a 
magnetic stir bar were placed in a 60 ml Fischer-Porter bottle. The vessel 
was pressurized to 100 psig with CO.sub.2 and allowed to stir at 
50.degree. C. for 2 hours. The crude product was dried in vacuo, then was 
dissolved in a minimum amount (5 ml) of methylene chloride and 
precipitated from 20 ml of methanol. The product was then dried in vacuo 
to constant weight (477 moles of CHO consumed per mole of zinc, 239 moles 
of CHO consumed per mole of zinc per hour). The polymer contained 96% 
carbonate linkages (determined by .sup.1 H NMR spectroscopy). 
Characterization of the product by gel-permeation chromatography revealed 
a M.sub.n of 23,700 grams/mole, and a M.sub.w /M.sub.n of 1.14. 
EXAMPLE XIII 
In a drybox, Catalyst E produced as in Example V (18.8 mg, 0.0205 mmol) and 
cyclohexene oxide (CHO, 6.4 ml, 6.1 g, 6.2.times.10.sup.-2 mol) and a 
magnetic stir bar were placed in a 60 ml Fischer-Porter bottle. The vessel 
was pressurized to 100 psig with CO.sub.2 and allowed to stir at 
50.degree. C. for 2 hours. The crude product was dried in vacuo, then was 
dissolved in a minimum amount (5 ml) of methylene chloride and 
precipitated from 20 ml of methanol. The product was then dried in vacuo 
to constant weight (418 moles of CHO consumed per mole of zinc, 209 moles 
of CHO consumed per mole of zinc per hour). The polymer contained 94% 
carbonate linkages (determined by .sup.1 H NMR spectroscopy). 
Characterization of the product by gel-permeation chromatography revealed 
a M.sub.n of 17,000 grams/mole, and a M.sub.w /M.sub.n of 1.21. 
EXAMPLE XIV 
In a drybox, Catalyst F produced as in Example VI (12.5 mg, 0.0129 mmol) 
and cyclohexene oxide (CHO, 4.0 ml, 3.8 g, 3.8.times.10.sup.-2 mol) and a 
magnetic stir bar were placed in a 60 ml Fischer-Porter bottle. The vessel 
was pressurized to 100 psig with CO.sub.2 and allowed to stir at 
50.degree. C. for 2 hours. The crude product was dried in vacuo, then was 
dissolved in a minimum amount (5 ml) of methylene chloride and 
precipitated from 20 ml of methanol. The product was then dried in vacuo 
to constant weight (622 moles of CHO consumed per mole of zinc, 311 moles 
of CHO consumed per mole of zinc per hour). The polymer contained 99% 
carbonate linkages (determined by .sup.1 H NMR spectroscopy). 
Characterization of the product by gel-permeation chromatography revealed 
a M.sub.n of 25,400 grams/mole, and a M.sub.w /M.sub.n of 1.22. 
EXAMPLE XV 
In a drybox, Catalyst G produced as in Example VII (12.5 mg, 0.0119 mmol) 
and cyclohexene oxide (CHO, 3.7 ml, 3.5 g, 3.6.times.10.sup.-2 mol) and a 
magnetic stir bar were placed in a 60 ml Fischer-Porter bottle. The vessel 
was pressurized to 100 psig with CO.sub.2 and allowed to stir at 
50.degree. C. for 2 hours. The crude product was dried in vacuo, then was 
dissolved in a minimum amount (5 ml) of methylene chloride and 
precipitated from 20 ml of methanol. The product was then dried in vacuo 
to constant weight (744 moles of CHO consumed per mole of zinc, 372 moles 
of CHO consumed per mole of zinc per hour). The polymer contained 97% 
carbonate linkages (determined by .sup.1 H NMR spectroscopy). 
Characterization of the product by gel-permeation chromatography revealed 
a M.sub.n of 22,900 grams per mole, and a M.sub.w /M.sub.n of 1.11. 
EXAMPLE XVI 
In a drybox, Catalyst H produced as in Example VIII (10.0 mg, 0.0104 mmol) 
and cyclohexene oxide (CHO, 6.4 ml, 6.1 g, 6.2.times.10.sup.-2 mol) and a 
magnetic stir bar were placed in a 60 ml Fischer-Porter bottle. The vessel 
was pressurized to 100 psig with CO.sub.2 and allowed to stir at 
50.degree. C. for 2 hours. The crude product was dried in vacuo, then was 
dissolved in a minimum amount (5 ml) of methylene chloride and 
precipitated from 20 ml of methanol. The product was then dried in vacuo 
to constant weight (1116 moles of CHO consumed per mole of zinc, 558 moles 
of CHO consumed per mole of zinc per hour). The polymer contained 89% 
carbonate linkages (determined by .sup.1 H NMR spectroscopy). 
Characterization of the product by gel-permeation chromatography revealed 
a M.sub.n of 31,300 grams per mole, and a M.sub.w /M.sub.n of 1.20. 
SUMMARY OF EXAMPLES IX-XVI 
A summary of Examples IX-XVI is provided in Table 2 below wherein GPC 
stands for gel-permeation chromatography. 
TABLE 2 
__________________________________________________________________________ 
Reaction 
% 
Pressure length carbonate M.sub.n (.times. 10.sup.-3) M.sub.w 
/M.sub.n TOF 
Example Catalyst Temp (.degree. C.) (psig) (h) linkages (GPC (GPC) TON 
(h.sup.-1) 
__________________________________________________________________________ 
IX A 50 100 2 96 31.0 1.11 
494 
247 
X B 50 100 2 96 22.0 1.12 470 235 
XI C 50 100 2 95 19.1 1.07 449 224 
XII D 50 100 2 96 23.7 1.14 477 239 
XIII E 50 100 2 94 17.0 1.21 418 209 
XIV F 50 100 2 99 25.4 1.22 622 311 
XV G 50 100 2 97 22.9 1.11 744 372 
XVI H 50 100 2 89 31.3 1.20 1,116 558 
__________________________________________________________________________ 
Variations 
Many variations of the above will be obvious to those skilled in the art. 
Thus, the scope of the invention is defined by the claims.