Oxidative cleavage of tetraaryltetraphosphane-1,4-diides by nickel(II) and palladium(II): formation of unusual Ni(0) and Pd(0) diaryldiphosphene complexes

[Na(2)(thf)(4)(P(4)Mes(4))] (1) (Mes = 2,4,6-Me(3)C(6)H(2)) reacts with one equivalent of [NiCl(2)(PEt(3))(2)], [NiCl(2)(PMe(2)Ph)(2)], [PdCl(2)(PBu(n)(3))(2)] or [PdCl(2)(PMe(2)Ph)(2)] to give the corresponding nickel(0) and palladium(0) dimesityldiphosphene complexes [Ni(eta(2)-P(2)Mes(2))(PEt(3))(2)] (2), [Ni(eta(2)-P(2)Mes(2))(PMe(2)Ph)(2)] (3), [Pd(eta(2)-P(2)Mes(2))(PBu(n)(3))(2)] (4) and [Pd(eta(2)-P(2)Mes(2))(PMe(2)Ph)(2)] (5), respectively, via a redox reaction. The molecular structures of the diphosphene complexes 2-5 are described.