New Derivatives of PCP-Type Pincer Complexes of Nickel

The pincer-type complexes (PCsp3Pi-Pr)NiR (PCsp3Pi-Pr = (i-Pr2PCH2CH2)(2)CH) react with HBF4 (R = C equivalent to CMe, Ph, Me) or AgBF4 (R = Br) to give (PCsp3 Pi-Pr)Ni(BF4), 1, which was found to involve fluxional Ni-F-BF3 interactions. Competition experiments revealed that the relative ease of protonation of the Ni-hydrocarbyl moiety follows the order Ni-Me > Ni-C equivalent to CMe > Ni-Ph. Complex 1 reacts with water to give [(PCsp3Pi-Pr)Ni(H2O)][BF4], 2, that in turn undergoes H2O exchange with CH3CN, i-PrNH2, and CO to give the corresponding cationic adducts 3, 4, and 5; alternatively, 3-5 can also be obtained directly from the reaction of 1 with CH3CN, i-PrNH2, and CO, respectively. Deprotonation of complex 2 gives the neutral hydroxo complex (PCsp3Pi-Pr)Ni(OH), 6. All complexes have been characterized by NMR spectroscopy and, in the case of 2-6, by X-ray crystallography.