Dismantling of Vinyl Ethers by Pentanuclear [(iPr3 P)Ni]5 H6 : Facile Cooperative C-O, C-C and C-H Activation Pathways.

The [(iPr3 P)Ni]5 H6 cluster (1) and H2 C=CHOtBu react at room temperature to form the new pentanuclear NiH carbide [(iPr3 P)Ni]5 H4 (C)(CO) (3), along with an equivalent of isobutylene. This transformation requires the activation of multiple unreactive bonds, including C-H, C-C, and C(sp3 )-O bond cleavage. Analysis of the reaction mixture by 1 H NMR revealed the production of two additional paramagnetic species, assigned as [(iPr3 P)Ni]4 H4 (C-CH3 )NiOtBu (4 a) and [(iPr3 P)Ni]4 H4 (C-CH2 OtBu)NiOtBu (5 a), which arise from C(sp2 )-O bond cleavage and CH bond rearrangements. The reaction of 1 with H2 C=CHOSiMe2 CH2 Ph produced the isolable 4 a analogue [(iPr3 P)4 Ni5 ]H4 (CCH3 )(OSiMe2 CH2 Ph) (4 c). An isolable analogue of 5 a was obtained from the reaction of 1 with H2 C=CHOAd (Ad=1-admantyl), which produced [(iPr3 P)4 Ni5 ]H4 (CCH2 OAd)(OAd) (5 d). The utilization of both cluster faces and vertices for bonding substrate fragments in these transformations demonstrates the remarkable flexibility of the robust Ni5 H4 core in the cooperative activation of multiple C-O, C-C and C-H bonds.