SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF METALLACARBORANE POLY(PYRAZOLYL)BORATE COMPLEXES

The mixed-ligand poly(1-pyrazolyl)borate–dicarbollide metallacarborane complexes closo-3-{η3-HB(pz)3}-3, 1, 2-RhC2B9H11 (3a), closo-2-(η3-HB(pz)3)-2, 1,7-RhC2B9H11 (3b), and [closo-3-(η2-Ph2B(pz)2)-3,1,2-NiC2B9H11]− ([5]−) (pz = 1-pyrazolyl) have been prepared and characterized by a combination of spectroscopic techniques, elemental analysis, and X-ray crystallography. Complex 3a crystallizes in the space group P21 with a = 8.874 (1) Å, b = 10.786 (1) Å, c = 10.604 (1) Å, β = 109.284 (3)°, V = 960 Å3, and Z = 2. Data were collected to a maximum of 2θ = 55°, giving 2322 unique reflections. The final discrepancy index was R = 0.042 (Rw = 0.054) for 1969 independent reflections. Complex 3b crystallizes in the space group C2/c with a = 14.830 (2) Å, b = 27.059 (3) Å, c = 20.298 (2) Å, β = 108.907 (3)°, V = 7706 Å3, and Z = 16. Data were collected to a maximum of 2θ = 50°, giving 4672 unique reflections. The final discrepancy index was R = 0.048 (Rw = 0.063) for 3525 independent reflections. Compound [NMe4][5] crystallizes in the space group P21/a with a = 17.437 (6) Å, b = 9.631 (3) Å, c = 19.695 (4) Å, β = 92.271 (8)°, V = 3305 Å3, and Z = 4. Data were collected to a maximum of 20 = 45°, giving 4332 unique reflections. The final discrepancy index was R = 0.082 (Rw = 0.091) for 1585 independent reflections. The anion [5]− is oxidized by ferric chloride to the neutral species closo-3-(η2-Ph2B(pz)2)-3,1,2-NiC2B9H11 (6). NMR spectral data for 3a, 3b, and [5]− indicate fluxional solution behavior such that pyrazole ring environments are equilibrated on the NMR time scale. Complex [5]− exhibits an unusual carborane cage distorion resulting from an intramolecular influence of the axial phenyl group of the [η2-Ph2B(pz)2]− ligand. © 1990, American Chemical Society. All rights reserved.