Anionic pyrazolyl-bridged nickel nitrosyl complexes. Synthesis, structure, and reactivity

Abstract

A series of anionic pyrazolyl-bridged nickel nitrosyl complexes, M+[(ON)Ni(μ-L2)(μ-X)Ni(NO)]− (where L = pyrazolyl, N2C3H3, or 3,5-dimethylpyrazolyl, N2C5H7; X = Cl, Br, I, or N2C5H7; and M = Na, (CH3)4N, or (C2H5)4N) is described. Crystallographic analyses have been carried out on two of these complexes. Crystals of [(C2H5)4N]+[(ON)Ni(μ-I)(μ- N2C5H7)2Ni(NO)]− are orthorhombic, a = 19.910(1), b = 14.0330(7), c = 9.3195(9) Å, Z = 4, space group Pn21a and crystals of [(C4H8O)2Na][(ON)Ni(μ-N2C5 H7)3Ni(NO)] are orthorhombic, a = 19.897(2), b = 19.529(3), c = 15.894(2) Å, Z = 8, space group Pbca. Both structures were solved by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to R = 0.027 and 0.057 for 2572 and 2168 reflections with I ≥ 3σ(I) respectively. The structure of [(C2H5)4N]+[(ON)Ni(μ-I)(μ-N2C5H7)2Ni(NO)]− consists of discrete cations and binuclear anions which have approximate C2v symmetry. The nickel atoms have distorted tetrahedral coordination geometry. Important mean molecular dimensions (distances corrected for libration) are: Ni—I—Ni, 73.67(2)°, Ni—I, 2.765(3), Ni—NO, 1.649(5), Ni—N(pyrazolyl), 1.980(14) Å, and Ni—N—O, 172.5(18)°. The structure of [(C4H8O)2Na][(ON)Ni(μ-N2C5 H7)3Ni(NO)] consists of discrete ion-pair units in which the two NiNO moieties are bridged by three N2C5H7 ligands, two of which are coordinated to the sodium ion via a novel η2(N,N) π-interaction (mean Na—N = 2.61(3) Å). The sodium is also coordinated to two tetrahydrofuran oxygen atoms to give a distorted tetrahedral coordination geometry about the sodium (Na—O = 2.301(6) and 2.266(5) Å). Except for disordered tetrahydrofuran carbon atoms, the molecular unit has approximate C2v symmetry. The nickel atoms have distorted tetrahedral coordination geometry, the mean distances being Ni—NO, 1.591(6), Ni—N(pyrazolyl), 1.985(2) for the unique pyrazolyl group and 2.016(5) Å for the pyrazolyl nitrogen atoms coordinated to Na. The mean Ni—N—O angle is 176.9(11)°.