Bs. Williams et Ki. Goldberg, Studies of reductive elimination reactions to form carbon-oxygen bonds from Pt(IV) complexes, J AM CHEM S, 123(11), 2001, pp. 2576-2587
The platinum(IV) complexes fac-L(2)PtMe3(OR) (L-2 = bis(diphenylphosphino)e
thane, o-bis(diphenylphosphino)benzene, R = carboxyl, aryl; L = PMe3, R = a
ryl) undergo reductive elimination reactions to form carbon-oxygen bonds an
d/or carbon-carbon bonds. The carbon-oxygen reductive elimination reaction
produces either methyl esters or methyl aryl ethers (anisoles) and L2PtMe2,
while the carbon-carbon reductive elimination reaction affords ethane and
L2PtMe(OR). Choice of reaction conditions allows the selection of either ty
pe of coupling over the other. A detailed mechanistic study of the reductiv
e elimination reactions supports dissociation of the OR- ligand as the init
ial step for the C-O bond formation reaction. This is followed by a nucleop
hilic attack of OR- upon a methyl group bound to the PL(IV) cation to produ
ce the products MeOR and L2PtMe2. C-C reductive elimination proceeds from L
2PtMe3(OR) by initial L (L = PMe3) or OR- (L2 = dppe, dppbz) dissociation,
followed by C-C coupling from the resulting five-coordinate intermediate. O
ur studies demonstrate that both C-C and C-O reductive elimination reaction
s from Pt(IV) are more facile in polar solvents, in the presence of Lewis a
cids, and for OR- groups that contain electron withdrawing substituents.