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Selectivity for the methoxycarbonylation of ethylene versus CO-ethylene copolymerization with catalysts based on C4-bridged bidentate phosphines and phospholes

Lookup NU author(s): Dr Simon Doherty, Dr Edward Robins, Dr Julian Knight, Dr Barrie Rhodes, Paul Anthony Champkin, Emeritus Professor Bill Clegg

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Abstract

The C4-bridged phospholes 11,12-bis(2,3,4,5-tetramethylphospholylmethyl)-9,10-dihydro-9,10-ethano- anthracene (cis, 4a; trans, 4b) and diphosphines 11,12-bis(diphenylphosphinomethyl)-9,10-dihydro-9,10-ethano-anthracene (cis, 5a; trans, 5b) and their corresponding palladium complexes [(P-P)PdCl2] (6a-d) have been prepared and characterized. Single-crystal X-ray analyses of 6a-d have been undertaken and they reveal that 4a and b and 5a and b coordinate in a bidentate manner forming seven-membered chelate rings with natural bite angles between 98.62 and 100.30°. The palladium-catalyzed carbonylation of ethylene has been studied using 4a and b and 5a and b. Catalyst mixtures generated from 4a and b, palladium acetate and methanesulfonic acid are selective for the copolymerization of ethylene with carbon monoxide, generating low molecular weight polymers. Surprisingly, the activity of catalyst systems based on cis-(4a) is markedly higher than that based on its trans-isomer, 4b. The marked influence of the nature of the four-carbon tether is highlighted by comparative catalyst testing with [{1,4-bis(2,3,4,5-tetramethylphospholyl)butane}Pd(OAc)2], which rapidly decomposes under the conditions used for copolymerization. In contrast, under identical conditions catalyst mixtures formed from 5a and b show a marked dependence of the selectivity on the stereochemistry of the ethano-anthracene tether, the former generating a low molecular weight copolymer while the latter generate mainly methyl propanoate. Interestingly, polyketone generated from catalysts based on bisphosphole 4a has a markedly higher average molecular weight than that formed using its diphenylphosphino counterpart, 5a.


Publication metadata

Author(s): Champkin PA; Doherty S; Robins EG; Rhodes B; Clegg W; Knight JG; Newman CR

Publication type: Article

Publication status: Published

Journal: Journal of Organometallic Chemistry

Year: 2001

Volume: 640

Issue: 1-2

Pages: 182-196

ISSN (print): 0022328X

ISSN (electronic): 1872-8561

Publisher: Elsevier B.V.

URL: http://dx.doi.org/10.1016/S0022-328X(01)01180-9

DOI: 10.1016/S0022-328X(01)01180-9


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