The crystal structure of [SnLCl3] has been determined and shown to consist ol discrete distorted fac-octahedral molecules [L = tris(3,5-dimethylpyrazolyl)hydroborate]. The single-crystal EPR spectra, at room temperature and Q-band frequencies, of [MoE(L)Cl2] and [MoO(L)(NCS)2], E = O or S, diluted in the structurally similar [SnLCl3] have been recorded. The data from the different possible diluent sites in [SnLCl3] are consistent with exact, or nearly exact, monoclinic EPR symmetry for each of the molybdenum compounds which involves a rotation of the g and A tensors about an axis perpendicular to the mirror plane in each molecule. The angles of rotation are in the range 30-38-degrees and are in good agreement with those obtained via simulation of the frozen-solution X-band EPR spectra of the compounds. The relationships between the g and A tensors, the molecular geometries, and the electronic structures are discussed.

The synthesis and crystallographic characterization of three oxovanadium(IV) complexes as solvates are reported: (a) [{HB(Me2PZ)3}VOCl(Me2pzH)].2MeCN (I.2MeCN), (b) [{HB(Me2PZ)3}VO(benzoate)(Me2PzH)].0.4toluene (II.0.4toluene), and (c) [{HB(MC2PZ)3}VO(mu-Malonate)VO(Me2pzH){HB(Me2PZ)3}].2toluene (III.2toluene), where Me2PZ = 3,5-dimethylpyrazolyl. I.2MeCN: blue rhombs; triclinic, P1BAR; a = 9.986(3), b = 10.898(3), c = 16.007(3) angstrom; alpha = 71.50(2), beta = 79.86(2), gamma = 65.70(2)-degrees; Z = 2. II.0.4toluene: purple hexagonal prisms; trigonal P3BAR; a = 24.320(3), c = 9.233(l) angstrom; Z = 6. III.2toluene: purple/blue rhombs; triclinic P1BAR; a = 13.859(4), b = 13.843(3), c = 16.860(4) angstrom; alpha = 76.07(2), beta = 72.50(2), gamma = 73.77(2); Z = 2. In each case the metal is found in a distorted octahedral environment with a short vanadium to terminal oxygen distance: (I) 1.599(4), (II) 1.590(8), (III) 1.587(9), 1.592(9) angstrom. The hydrotris(3,5-dimethylpyrazolyl)borate ion acts as a facially coordinating, uninegative tridentate ligand, and in each case one neutral pyrazole molecule is used to complete six-coordination at the metal. In II the benzoate anion acts as a monodentate ligand, and in III the malonate anion is monodentate with respect to one vanadium center and bridges to the other, forming a six-membered chelate ring system, such that one carboxylate functionality forms the bridge unit. The neutral pyrazole molecule is held in the same relative position by hydrogen bonding in complexes II and III but has a different orientation with respect to the LVO fragment in I. The three complexes have been characterized by infrared, electronic absorption and ESR spectroscopy and by cyclic voltammetry at a platinum working electrode. The ESR spectra recorded in dichloromethane solution are consistent with a monomer structure for I and II and with the retention of a dimer for III. Double-integrated ESR signal intensities measured in the temperature range 300-3.6 K for II and III in CH2Cl2 solution show an antiferromagnetic coupling interaction in III of ca. 3 cm-1.

The results of a single crystal ESR study of LMoOCl2 diluted in the isostructural host LSnCl3 are reported. These results confirm the monoclinic ESR symmetry deduced previously from frozen solution measurements giving the rotation angle between the tensor axes as 35° compared with 33° in previous study. The single crystal data show that none of the principal g- or A-tensor axes coincide with metal-ligand directions.