C-P vs C-H Bond Cleavage of Triphenylphosphine at Platinum(0): Mechanism of Formation, Reactivity, Redox Chemistry, and NMR Chemical Shift Calculations of a μ-Phosphanido Diplatinum(II) Platform

Transition-metal phosphanides M-PR2 are key intermediates in catalytic C-P bond functionalization. M-PR2 formation from tertiary phosphines through P-C bond cleavage widens the scope beyond P-H functionalized substrates, but mechanistic understanding of this reaction still is fragmentary. Starting from a defined coordination complex has allowed monitoring the reaction of a Pt-PPh3 moiety and Pt(0) by NMR spectroscopy. Initial Pt(0) transfer is rate-limiting and leads to products from PPh3-borne ortho-C-H and C-P bond cleavage along kinetically distinct pathways. Albeit kinetically favored, the reversibility of C-H bond cleavage eventually leads to thermodynamically preferred C-P bond scission. This pathway affords a robust [Pt(mu-PPh2)Pt] core structure whose redox chemistry and reactivity toward external ligands are reported. Organometallic products have been substantiated by a combination of magnetic resonance and absorption spectroscopies, X-ray diffraction, and DFT computations.