Energetics of Homogeneous Intermolecular Vinyl and Allyl Carbon−Hydrogen Bond Activation by the 16-Electron Coordinatively Unsaturated Organometallic Fragment [Tp‘Rh(CNCH2CMe3)]

Reaction of the complex Tp‘Rh(CNneo)(CHCH2)Cl (neo = CH2CMe3, Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with Cp2ZrH2 leads to the formation of Tp‘Rh(CNneo)(CHCH2)H. This complex is also formed upon photolysis of a solution of Tp‘Rh(CNneo)(PhNCNneo) containing ethylene or by thermal reaction of Tp‘Rh(CNneo)(c-hexyl)H with ethylene. The vinyl hydride complex rearranges to the more stable η2-ethylene complex with a half-life of 8 h at 22 °C. Photolysis of a solution of Tp‘Rh(CNneo)(PhNCNneo) in liquid propylene produces the allylic activation product Tp‘Rh(CNneo)(CH2CHCH2)H, which rearranges (t1/2 = 3 days at 22 °C) to the η2-propylene complex. Allylic activation is also seen with isobutylene, but loss of olefin is observed at 22 °C in benzene solution to generate Tp‘Rh(CNneo)(Ph)H (t1/2 = 16.6 h). Photolysis of a tert-butylethylene solution of Tp‘Rh(CNneo)(PhNCNneo) produces the trans vinyl hydride complex, which loses tert-butylethylene to generate Tp‘Rh(CNneo)(Ph)H (t1/2 = 113 days at 22 °C). A comb...