870097-00-0Relevant academic research and scientific papers
Mechanistic information on the reductive elimination from cationic trimethylplatinum(IV) complexes to form carbon-carbon bonds
Procelewska, Joanna,Zahl, Achim,Liehr, Guenter,Van Eldik, Rudi,Smythe, Nicole A.,Williams, B. Scott,Goldberg, Karen I.
, p. 7732 - 7742 (2008/10/09)
Cationic complexes of the type fac-[(L2)PtIVMe 3(pyr-X)][OTf] (pyr-X = 4-substituted pyridines; L2 = diphosphine, viz., dppe = bis(diphenylphosphino)ethane and dppbz = o-bis(diphenylphosphino)benzene; OTf = trifluoromethane-sulfonate) undergo C-C reductive elimination reactions to form [L2PtIIMe(pyr-X)] [OTf] and ethane. Detailed studies indicate that these reactions proceed by a two-step pathway, viz., initial reversible dissociation of the pyridine ligand from the cationic complex to generate a five-coordinate PtIV intermediate, followed by irreversible concerted C-C bond formation. The reaction is inhibited by pyridine. The highly positive values for ΔS ?obs = +180 ± 30 J K-1 mol -1, ΔH?obs = 160 ± 10 kJ mol-1, and ΔV?obs = +16 ± 1 cm3 mol-1 can be accounted for in terms of significant bond cleavage and/or partial reduction from PtIV to PtII in going from the ground to the transition state. These cationic complexes have provided the first opportunity to carry out detailed studies of C-C reductive elimination from cationic PtIV complexes in a variety of solvents. The absence of a significant solvent effect for this reaction provides strong evidence that the C-C reductive coupling occurs from an unsaturated five-coordinate PtIV intermediate rather than from a six-coordinate PtIV solvento species.
