CRYSTAL-STRUCTURE OF BIS-[DIHYDRIDO(3,5-DIMETHYL-1-PYRAZOLYL) (3,5-DIPHENYL-1-PYRAZOLYL)BORATE]ZINC(II), [ZN(H2B(3,5-ME2PZ)(3,5-PH2PZ))2]1

Crystals of the title compound are monoclinic, a = 13.796(1), b = 16.727(1), c = 16.1937(8) angstrom, beta = 102.063(5)-degrees, V = 3654.3(4)angstrom3, space group P2(1)/c, Z = 4. The crystal structure was solved by Patterson and Fourier methods and refined to R = 0.033 for 3883 unique reflections with F(o) > 3 sigma(F(o)). The metal atom is tetrahedrically coordinated to two bidentate ligands with Zn-N distances and N-Zn-N angles in the range 1.982(2)-2.019(2)angstrom and 100.3(1)-119.5(1)-degrees. The boat conformations of both BN4Zn chelate rings are unusually asymmetric (quasi-sofa), with the B atoms at 0.71 angstrom from the N4 mean plane, while the Zn atoms are at only 0.07 angstrom. Zn ... B distances (3.784 and 3.794 angstrom) and nu(B-H) stretching frequencies (2497 and 2400 cm-1) rule out agostic bonds. Overall the molecule displays approximate C2 symmetry. The temperature-dependent NMR spectra show no fluxional behavior in solution.