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Reaction of BiX3 (X = Cl, Br, I) with [PtMe2(P-P)], (1a, P-P = dppm; 1b, P-P = dppe), occurs easily to yield a mixture of platinum(II) complexes [PtMeX(P-P)], 2, and [PtX2(P-P)], 3, and the binuclear complex [Pt2Me2(µ-X)(μ-dppm)2]X, 4. On the basis of 31P NMR and UV-vis spectroscopy, a mechanism is proposed in which the rate determining step is conversion of the yellowish Pt(II)-BiX3 adduct BiI3·[PtMe2(dppm)], A, into the Pt(IV)-Bi(III) intermediate [PtMe2(BiX2)X(P-P)], IM1. Density functional theory (DFT) studies suggest that intermediate IM1 may be formed in acetone solution which undergoes the Bi-C reductive elimination process before formation of complexes 2 and 3. The structures of intermediates IM1 were theoretically determined using DFT calculations. In dilute acetone solution, as monitored by UV-vis spectroscopy, the oxidative addition processes follow first order kinetics. The overall reaction is slower for heavier halide. [ABSTRACT FROM AUTHOR]

The cyclometalated platinum(II) complexes [PtMe(C ∧ N)(L)] [ 1 PS : C ∧ N = 2-phenylpyridinate (ppy), L = SMe 2 ; 1 BS : C ∧ N = benzo[h]quinolate (bhq), L = SMe 2 ; 1 PP : C ∧ N = ppy, L = PPh 3 ; and 1 BP : C ∧ N = bhq, L = PPh 3 ] containing two different cyclometalated ligands and two different ancillary ligands have been investigated in the reaction with CX 3 CO 2 H (X = F or H). When L = SMe 2 , the Pt-Me bond rather than the Pt-C bond of the cycloplatinated complex is cleaved to give the complexes [Pt(C ∧ N)(CX 3 CO 2 )(SMe 2 )]. When L = PPh 3 , the selectivity of the reaction is reversed. In the reaction of [PtMe(C ∧ N)(PPh 3 )] with CF 3 CO 2 H, the Pt-C ∧ N bond is cleaved rather than the Pt-Me bond. The latter reaction gave [PtMe(κ 1 N-Hppy)(PPh 3 )(CF 3 CO 2 )] as an equilibrium mixture of two isomers. For L = PPh 3 , no reaction was observed with CH 3 CO 2 H. The reasons for this difference in selectivity for complexes 1 are computationally discussed based on the energy barrier needed for the protonolysis of the Pt-C sp 3 bond versus the Pt-C sp 2 bond. Two pathways including the direct one-step acid attack at the Pt-C bond (S E 2) and stepwise oxidative-addition on the Pt(II) center followed by reductive elimination [S E (ox)] are proposed. A detailed density functional theory (DFT) study of these protonations along with experimental UV-vis kinetics suggests that a one-step electrophilic attack (S E 2) at the Pt-C bond is the most likely mechanism for complexes 1 , and changing the nature of the ancillary ligand can influence the selectivity in the Pt-C bond cleavage. The effect of the nature of the acid and cyclometalated ligand (C ∧ N) is also discussed.

The rollover cyclometalated platinum(II) complexes [PtMe(2,X'-bpy-H)(PPh 3 )], (X = 2, 1a; X = 3, 1b; and X = 4, 1c) containing two potential nucleophilic centers have been investigated to elucidate which center is the stronger nucleophile toward methyl iodide. On the basis of DFT calculations, complexes 1b and 1c are predicted reacting with MeI through the free nitrogen donor to form N-methylated platinum(II) complexes, while complex 1a reacts through oxidative addition on platinum to give a platinum(IV) complex, which is in agreement with experimental findings. The reasons for this difference in selectivity for complexes 1a-1c are discussed based on the energy barrier needed for N-methylation versus oxidative addition reactions.