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Crumpton-Bregel DM, Goldberg KI: 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.
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. |
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