Nickel(0) and Palladium(0) Complexes with (Z,Z)-Ph2PCH2C(t-Bu)=N-N=C(t-Bu)CH2PPh2. Alkyne-to-Alkenyl Conversion in [Pd(MeOCOCCCOOMe){(Z,Z)-Ph2PCH2C(t-Bu)=N-N=C(t-Bu)CH2PPh2}]

Novel zero-valent metal complexes [ML 2 {( Z,Z )-Ph 2 PCH 2 C( t -Bu)=N-N=C( t -Bu)CH 2 PPh 2 }] (M = Ni, L = CO, t -BuNC) with the azine diphosphine chelating in a nine-membered ring were prepared. The nickel dicarbonyl complex was found to be in an equilibrium with its isomer containing ( E,Z )-chelated azine diphosphine, the equilibrium being on the side of the ( Z,Z )-isomer below 60 °C. A similar palladium complex (M = Pd, L 2 = CH 3 OCOC≡CCOOCH 3 ) prepared earlier was found to undergo a rearrangement with simultaneous alkyne-to-alkenyl conversion of the acetylenedicarboxylate dimethyl ester ligand.