Allylic derivatives of nickel and palladium

Abstract

The synthesis of novel allylic derivatives of Ni and Pd incorporating the bispyrazolylgallate ligand Me2Ga(N2C5H7)2− is described. Pyrazolyl-bridged homobinuclear and trinuclear nickel allyl systems are also presented. Crystal structures of [Me2Ga(N2C5H7)2]Ni(η3-C3H5) and [(η3-C3H5)Ni(N2C5H7)2]2Ni are described. Crystals of the former are triclinic, a = 8.265(1), b = 10.487(1), c = 11.755(2) Å, α = 72.60(1), β = 87.28(1), γ = 67.58(1)°, Z = 2, space group [Formula: see text] and crystals of the latter are monoclinic, a = 7.9172(3), b = 10.6929(1), c = 16.9118(6) Å, β = 102.887(2)°, Z = 2, space group P21/c. Both structures were solved by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to R = 0.026 and 0.025 for 3329 and 2914 reflections with I ≥ 3σ(I) respectively. In both structures the M—(N—N)2—M rings are in the boat conformation and the allyl groups display twofold orientational disorder. In [Me2Ga(N2C5H7)2]Ni(η3-C3H5) the nickel coordination may be regarded as square-planar with the allyl ligand occupying two coordination sites and the coordination about the gallium is distorted tetrahedral. Important bond lengths (corrected for libration) are: Ni—N, 1.926(2) and 1.929(2), Ni—C, 1.971(5)–2.025(3), Ga—N, 1.994(2) and 1.996(2), Ga—C, 1.966(3) and 1.988(3) Å. The trinuclear complex [(η3-C3H5)Ni(N2C5H7)2]2Ni is centrosymmetric with the central Ni(1) atom bonded to four pyrazolyl nitrogen atoms in square-planar fashion. The outer Ni(2) atom is bonded to two pyrazolyl nitrogens and to an allyl group and also has square-planar coordination geometry. Important bond distances in this complex are: Ni(1)—N, 1.897(1) and 1.901(1), Ni(2)—N, 1.908(2) and 1.912(2), Ni(2)—C, 1.97(l)–2.022(3) Å.