Synthesis, Structure, and Reactivity of (tBu₂PC₂H₄PtBu₂)Ni(CH₃)₂ and {(tBu₂PC₂H₄PtBu₂)Ni}₂(μ-H)₂

Oxidative addition of CH 3 I to (d t bpe)Ni(C 2 H 4 ) (d t bpe = t Bu 2 PC 2 H 4 P t Bu 2 ) affords (d t bpe)Ni(I)CH 3 ( 1 ). The reaction of (d t bpe)NiCl 2 or 1 with the stoichiometric quantity of (tmeda)Mg(CH 3 ) 2 yields (d t bpe)Ni(CH 3 ) 2 ( 2 ). (d t bpe)Ni(I)CD 3 ( 1 - d 3 ) and (d t bpe)Ni(CD 3 ) 2 ( 2 - d 6 ) have been prepared analogously. Thermolysis of 2 in benzene affords {(d t bpe)Ni} 2 (μ-η 2:η 2 -C 6 H 6 ) ( 4 ). The reaction of either 2 or 4 with hydrogen (H 2, HD, D 2 ) gives {(d t bpe)Ni} 2 (μ-H) 2 ( 3 ) and the isotopomers {(d t bpe)Ni} 2 (μ-H)(μ-D) ( 3 - d ) and {(d t bpe)Ni} 2 (μ-D) 2 ( 3 - d 2 ). According to the NMR spectra, the structure of 3 is dynamic in solution. The crystal structures of 2 and 3 have been determined by X-ray crystallography. Solution thermolysis of 2 or reduction of (d t bpe)NiCl 2 with Mg* in the presence of alkanes probably involves σ-complex-type intermediates [(d t bpe)Ni(η 2 -R‘H)] (R‘ = e.g. C 2 H 5, A ). While the nonisolated [(d t bpe)Ni 0 ] σ-complexes A are exceedingly reactive intermediates, isolated 3 and 4 represent easy to handle starting complexes for [(d t bpe)Ni 0 ] reactions. Partial protolysis of 2 with CF 3 SO 3 H affords (d t bpe)Ni(CH 3 )(OSO 2 CF 3 ) ( 5 ). Complex 5 reacts slowly with 2 equiv of ethene to give equimolar amounts of [(d t bpe)Ni(C 2 H 5 )] + (OSO 2 CF 3 - ) ( 6 ) and propene. The reaction is thought to be initiated by an insertion of ethene into the Ni−CH 3 bond of 5 to form the intermediate [(d t bpe)Ni(C 3 H 7 )(OSO 2 CF 3 )] ( G ), followed by elimination of propene to give the hydride intermediate [(d t bpe)Ni(H)(OSO 2 CF 3 )] ( H ), which on insertion of ethene into the Ni−H bond affords 6 .