OXIDATIVE ADDITION-REACTIONS OF SATURATED SI-X BONDS (X = H, F, C, OR SI) TO PT(PH3)2 - AN ABINITIO MO/MP4 STUDY

Oxidative addition reactions of the saturated C-H, C-C, and Si-X bonds (X = H, F, C, or Si) to Pt(PH3)2 are theoretically investigated with the ab initio MO/MP4 method. The activation barrier (E(a)) increases in the order Si-H (0.7) < Si-Si (17.4) < Si-F (25.8) < C-H (28.7) < Si-C (29.5) < C-C (60.7), while the exothermicity (E(exo)) decreases in the order Si-Si (46.4) > Si-H (26.4) > Si-C (14.1) > C-C (0.9) > Si-F (-3.5) > C-H (-6.5), where the values in parentheses (MP4(SDQ) level: kcal/mol unit) represent either the E(a) or the E(exo) (the endothermicity is represented by a negative value). These results can explicate experimental findings that the Si-H and Si-Si oxidative additions proceed but the Si-F oxidative addition does not. The C-H, C-C, and Si-F reactions with Pt(PH3)2 are characterized as the typical oxidative addition, while the Si-H and Si-Si reactions with Pt(PH3)2 are considered as the rearrangement of covalent bonds rather than the oxidative addition. Electronic factors determining the exothermicity and the activation barrier are discussed in detail.