Synthesis, Structure, and Properties of {( t Bu 2 PC 2 H 4 P t Bu 2 )Ni} 2 (μ-η 2 :η 2 -C 6 H 6 ) and ( t Bu 2 PC 2 H 4 P t Bu 2 )Ni(η 2 -C 6 F 6 ) 1

Thermolysis of ( t Bu 2 PC 2 H 4 P t Bu 2 )NiMe 2 in benzene or reduction of ( t Bu 2 PC 2 H 4 P t Bu 2 )NiCl 2 with Mg* in THF/benzene affords a solution of mononuclear ( t Bu 2 PC 2 H 4 P t Bu 2 )Ni(η 2 -C 6 H 6 ) ( 1 ) and dinuclear {( t Bu 2 PC 2 H 4 P t Bu 2 )Ni} 2 (μ-η 2:η 2 -C 6 H 6 ) ( 2 ) in equilibrium. Complex 2 has been isolated; the X-ray structure analysis reveals an antifacial coordination of the [( t Bu 2 PC 2 H 4 P t Bu 2 )Ni 0 ] moieties to adjacent C C bonds of a formal cyclohexatriene ligand. According to solid-state and solution NMR the structure of 2 is static in the solid and fluxional in solution. Displacement of the benzene ligand in 1 or 2 by C 6 F 6 affords mononuclear ( t Bu 2 PC 2 H 4 P t Bu 2 )Ni(η 2 -C 6 F 6 ) ( 5 ) for which the molecular structure is also reported.