Synthesis and characterization of heterodinuclear IrCo, RuCo, IrNi, and RnNi complexes containing pyrazolate and pyrazolylborate ligands

Treatment of the metallo ligands [ML(pz)(2)(Hpz)] (pz = pyrazolate; L = C(5)Me(5), M = Ir (1); L = mesitylene, M = Ru (3)) with [M'Cl{HB(3-i-Pr-4-Br-pz)(3)}] (M' = Co (4), Ni (5)) yields heterodinuclear complexes of formula [LM(mu-pz)(2)(mu-Cl)M'{HB(3-i-Pr-4-pz)(3)}] (L = C(5)Me(5); M = Ir; M' = Co (6), Ni (7). L = mesitylene; M = Ru; M' = Co (8)). The related complex [Ru(eta(6)-p-cymene)(pz)(2)(Hpz)] (2) reacts with equimolar amounts of 4 or 5 to give mixtures of the corresponding bis(mu-pyrazolato) mu-chloro complexes [(eta(6)-p-cymene)Ru(mu-pz)(2)(mu-Cl)-M'{HB (3-i-Pr-4-Br-pz)(3)}] (M' = Co (9), Ni (10)) and the triply pyrazolato-bridged complexes [(eta(6)-p-cymene)-Ru(mu-pz)(3)M'{HB(3-i-Pr-4-Br-pz)(3)}] (M' = Co (11), Ni (12)). Complex 1 reacts with 5 in the presence of KOH to give the IrNi complex [(eta(5)-C(5)Me(5))Ir(mu-pz)(3)Ni{HB(3-i-Pr-4-Br-pz)(3)}] (13) whereas its reaction with 4 and KOH rendered the bis(mu-pyrazolato) eta-hydroxo complex [(eta(5)-C(5)Me(5))Ir(mu-pz)(2)(mu-OH)Co{HB(3-i-Pr-4-Br-pz)(3)}] (14). The molecular structure of the heterobridged-IrCo complex (6) and those of the homobridged RuNi (12) and IrNi (13) complexes have been determined by X-ray analyses. Compound 6 crystallizes in the monoclinic space group P2(1)/n, with a = 10.146(5) Angstrom, b = 18.435(4) Angstrom, c = 22.187(13) Angstrom, beta = 97.28(4)degrees, and Z = 4. Complex 12 is monoclinic, space group P2(1), with a 10.1169(7) Angstrom, b = 21.692(2) Angstrom, c = 11.419(1) Angstrom, beta = 112.179(7)degrees, and Z = 2. Compound 13 crystallizes in the monoclinic space group Cc, with a 13.695(2) Angstrom, b = 27.929(6) Angstrom, c = 13.329(2) Angstrom, beta = 94.11(4)degrees, and Z = 4. All the neutral complexes 6, 12, and 13 consist of linear M ... M'... B backbones with two (6) or three (12, 13) pyrazolate ligands bridging the dimetallic M ... M' units and three substituted 3-i-Pr-4-Br-pz groups joining M' to the boron atoms. The presence in the proximity of the first-row metal M' of the three space-demanding isopropyl substituents of the pyrazolate groups induces a significant trigonal distortion of the octahedral symmetry, yielding clearly different M'-N bond distances on both sides of the ideal octahedral coordination sphere of these metals.