Mechanism of alkyne conversion to carbyne by 14- or 16-electron Os(H)2ClL2X (L = PiPr3; X = OTf or B(C6H3(CF3)2)4)

The mechanism of conversion of terminal alkynes RCtriple bond; length of mdashCH to coordinated carbyne Ostriple bond; length of mdashCCH2R by Os(H)2ClXL2 (L = PiPr3) has been studied for X = OTf and View the MathML sourceBArF4 (ArF = 3,5-di(CF3)2(C6H3). Ready loss of these X makes possible detection of η2-RCCH (4-electron donor) and double bond; length as m-dashCH(CH2R) intermediates, and D-labeling (RCCD) gives OsDClX(CCH2R)L2. The energy of various intermediates, including the only experimentally unobserved one, η2-vinyl, was evaluated with DFT(PBE) calculations.