Mechanisms of C-C and C-H alkane reductive eliminations from octahedral Pt(IV): reaction via five-coordinate intermediates or direct elimination?

Dawn M Crumpton-Bregel; Karen I Goldberg

doi:10.1021/ja029140u

Mechanisms of C-C and C-H alkane reductive eliminations from octahedral Pt(IV): reaction via five-coordinate intermediates or direct elimination?

J Am Chem Soc. 2003 Aug 6;125(31):9442-56. doi: 10.1021/ja029140u.

Authors

Dawn M Crumpton-Bregel¹, Karen I Goldberg

Affiliation

¹ Department of Chemistry, Box 351700, University of Washington, Seattle, Washington 98195-1700, USA.

PMID: 12889975
DOI: 10.1021/ja029140u

Abstract

The Pt(IV) complexes P(2)PtMe(3)R [P(2) = dppe (PPh(2)(CH(2))(2)PPh(2)), dppbz (o-PPh(2)(C(6)H(4))PPh(2)); R = Me, H] undergo reductive elimination reactions to form carbon-carbon or carbon-hydrogen bonds. Mechanistic studies have been carried out for both C-C and C-H coupling reactions and the reductive elimination reactions to form ethane and methane are directly compared. For C-C reductive elimination, the evidence supports a mechanism of initial phosphine chelate opening followed by C-C coupling from the resulting five-coordinate intermediate. In contrast, mechanistic studies on C-H reductive elimination support an unusual pathway at Pt(IV) of direct coupling without preliminary ligand loss. The complexes fac- P(2)PtMe(3)R (P(2) = dppe, R = Me, H; P(2) = dppbz, R = Me) have been characterized crystallographically. The Pt(IV) hydrides, fac-P(2)PtMe(3)H (P(2) = dppe, dppbz), are rare examples of stable phosphine ligated Pt(IV) alkyl hydride complexes.