Synthesis, structure, and reactivity of ((Bu2PC2H4PBu2)-Bu-t-Bu-t)Ni(CH3)(2) and {((Bu2PC2H4PBu2)-Bu-t-Bu-t)Ni}(2)(mu-H)(2)

Oxidative addition of CH3I to (d(t)bpe)Ni(C2H4) (d(t)bpe = (Bu2PC2H4PBu2)-B u-t-Bu-t) affords (d(t)bpe)-Ni(I)CH3 (I). The reaction of (d(t)bpe)NiCl2 or 1 with the stoichiometric quantity of (tmeda)Mg(CH3), yields (d(t)bpe)Ni(C H3)(2) (2). (d(t)bpe)Ni(I)CD3 (1-d(3)) and (d(t)bpe)Ni(CD3)(2) (2-d(6)) hav e been prepared analogously. Thermolysis of 2 in benzene affords {(d(t)bpe) Ni}(2)(mu-eta(2):eta(2)-C6H6) (4). The reaction of either 2 or 4 with hydro gen (H-2, HD, D-2) gives {(d(t)bpe)Ni}(2)(mu-H)(2) (3) and the isotopomers {(d(t)bpe)Ni}(2)(mu-H)(mu-D) (3-d) and {(d(t)bpe)Ni}(2)(mu-D)(2) (3-d(2)). According to the NMR spectra, the structure of 3 is dynamic in solution. Th e crystal structures of 2 and 3 have been determined by X-ray crystallograp hy, Solution thermolysis of 2 or reduction of (dtbpe)NiCl2 with Mg* in the presence of alkanes probably involves a-complex-type intermediates [(d(t)bp e)Ni(eta(2)-R'H)] (R' = e.g. C2H5, A). While the nonisolated [(d(t)bpe)Ni-0 ] a-complexes A are exceedingly reactive intermediates, isolated 3 and 4 re present easy to handle starting complexes for [(d(t)bpe)Ni-0] reactions. Pa rtial protolysis of 2 with CF3SO3H affords (d(t)bpe)Ni(CH3)(OSO2CF3) (5). C omplex 5 reacts slowly with 2 equiv of ethene to give equimolar amounts of [(d(t)bpe)Ni(C2H5)](+)(OSO2CF3-) (6) and propene. The reaction is thought t o be initiated by an insertion of ethene into the Ni-CH3 bond of 5 to form the intermediate [(d(t)bpe)Ni(C3H7)(OSO2CF3)] (G), followed by elimination of propene to give the hydride intermediate [(d(t)bpe)Ni(H)(OSO2CF3)] (H), which on insertion of ethene into the Ni-H bond affords 6.