Synthesis, structure, and properties of {((t)Bu(2)PC(2)H(4)P(t)Bu(2))Ni}(2)(mu-eta(2):eta(2)-C6H6) and ((t)Bu(2)PC(2)H(4)P(t)Bu(2))Ni(eta(2)-C6F6)

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))NiCl2 with Mg* in THF/benzene affords a solution of mononuclear ((t)Bu(2)PC(2)H(4)P(t)Bu(2))Ni(eta(2)-C6H6) (1) and dinuclear {((t)Bu(2)PC(2)H(4)P(t)Bu(2))Ni}(2)(mu-eta(2):eta(2)-C6H6) (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 C6F6 affords mononuclear ((t)Bu(2)PC(2)H(4)P(t)Bu(2))Ni(eta(2)-C6F6) (5) for which the molecular structure is also reported.