18. "Platinum-Catalyzed Acrylonitrile Hydrophosphination. P-C Bond Formation via Olefin Insertion into a Pt-P Bond," Denyce K. Wicht, Igor V. Kourkine, Ivan Kovacik, David S. Glueck, Thomas E. Concolino, Glenn P. A. Yap, Christopher D. Incarvito, and Arnold L. Rheingold, Organometallics 1999, 18, 5381-5394.

The acrylonitrile complexes Pt(diphos)(CH₂CHCN) [diphos = dppe (1), dcpe (2) (dppe = Ph₂PCH₂CH₂PPh₂, dcpe = Cy₂PCH₂CH₂PCy₂, Cy = cyclo-C₆H₁₁)] are catalyst precursors, and, for some substrates, resting states, during addition of P-H bonds in primary and secondary phosphines across the C=C double bond of acrylonitrile (hydrophosphination). Oxidative addition of P-H bonds to related catalyst precursors gives the phosphido hydride complexes Pt(diphos)(PRR')(H) (diphos = dppe, R = H, R' = Mes* (20), R = R' = Mes (21); diphos = dcpe, R = H, R' = Mes* (22) (Mes = 2,4,6-Me₃C₆H₂, Mes* = 2,4,6-(t-Bu)₃C₆H₂)). Acrylonitrile does not insert into the Pt-H bond of these hydrides to give cyanoethyl ligands; the putative products, phosphido complexes Pt(diphos)(CH₂CH₂CN)(PRR') (diphos = dppe, R = H, R' = Mes* (9), R = R' = Mes (10); diphos = dcpe, R = H, R' = Mes* (11)) were prepared independently and found to be stable to P-C reductive elimination. Instead, catalysis appears to occur by selective insertion of acrylonitrile into the Pt-P bond to yield the alkyl hydrides Pt(diphos)[CH(CN)CH₂PRR'](H), followed by C-H reductive elimination and regeneration of 1 or 2.

This insertion was observed directly in model methyl phosphido complexes M(dppe)(Me)(PRR') (M = Pt, R = H, R' = Mes* (12), R = R' = Mes (13); M = Pd, R = H, R' = Mes* (17)), yielding M(dppe)[CH(CN)CH₂PRR'](Me), (14, 15, 18). Similarly, treatment of Pt(dcpe)(PHMes*)(H) (22) with acrylonitrile gives Pt(dcpe)[CH(CN)CH₂PHMes*](H) (24) as a mixture of diastereomers; the isomeric Pt(dcpe)[PMes*(CH₂CH₂CN)](H) (25), which was prepared independently, was also observed during this reaction. Both 24 and 25 decompose in the presence of acrylonitrile to form Pt(dcpe)(CH₂CHCN) (2) and PHMes*(CH₂CH₂CN) (3a). The C-H reductive elimination step was modeled by studies of Pt(dcpe)[CH(Me)(CN)](H) (26). Another isomer, Pt(dcpe)[CH(Me)(CN)](PHMes*) (29), which formally results from insertion of acrylonitrile into the Pt-H bond of 22, was formed by decomposition of complex 2 during catalysis. Complex 29 is inactive in catalysis, but decomposes to partially regenerate the active catalyst 2. The cyanoethyl compounds Pt(dcpe)(CH₂CH₂CN)(PHMes*) (11), trans-Pt(PPh₃)₂(CH₂CH₂CN)(Br) and PMes₂(CH₂CH₂CN) (23) were structurally characterized by X-ray crystallography.