Coordination of Tetrakis(pyrazolyl)borate in Rhenium Complexes Containing the [Re^VO]³⁺ Core

The complex [ReO{η3-B(pz)4}(OMe)2] (1) reacts with potentially bidentate protic substrates yielding several monomeric and dimeric oxorhenium compounds in which the tetrakis(pyrazolyl)borate presents different coordination modes: [ReO(acac){η2-B(pz)4}(OMe)] (3), [ReO(acac){η2-B(pz)4}]2(μ-O) (4), [ReO{η2-B(pz)4}(quinolin-8-olate)(OMe)] (5), [ReO{η2-B(pz)4}(OMe)(pz*)(pz*H)] (pz* = pz (6) or 3,5-Me2pz (7)), [ReO{η2-B(pz)4}(μ-pz*)]2(μ-O) (pz* = pz (9) or 3,5-Me2pz (10)), [ReO(HNCH2CH2NH){η3-B(pz)4}] (14), and [ReO(m-nitrophenyl-o-diaminate){η3-B(pz)4}] (15). Using the analogous alkoxide [ReO{η3-B(pz)4}(OEt)2] (2), the compound [ReO{η2-B(pz)4}(OEt)(pz)(pzH)] (8) has also been obtained. Compounds 3 and 5 react with trimethylsilyl chloride providing the monochlorides [ReO(acac){η2-B(pz)4}Cl] (12) and [ReO{η2-B(pz)4}(quinolin-8-olate)Cl] (13), respectively. Compounds 9, 10, and 14 were also prepared by reacting [ReO(μ-O){B(pz)4}]2 (11) with the respective substrates. The new compounds 3−10 and 12−15 were characterized by elemental analysis and IR and 1H NMR spectroscopies. Compounds 3, 4, and 9 have also been characterized by X-ray crystallography. Compounds 3 and 4 both crystallize in the monoclinic space group P21/c, with a = 7.862(1) Å, b = 14.152(2) Å, c = 19.975(3) Å, β = 91.79(1)°, V = 2221(1) Å3, and Z = 4 (3) and a = 13.547(2) Å, b = 9.959(1) Å, c = 15.878(2) Å, β = 102.00(1)°, V = 2095(1) Å3 and Z = 2 (4). Compound 9 crystallizes in the monoclinic space group P21, with cell parameters a = 11.086(2) Å, b = 15.269(1) Å, c = 12.133(1) Å, β = 93.51(1)°, V = 2050(1) Å3 and Z = 2.