RHENIUM(V) AND TECHNETIUM(V) COMPLEXES OF BIDENTATE (0, 0) MONOBASIC 3-OXY-4-PYRONATO AND -4-PYRIDINONATO LIGANDS - X-RAY STRUCTURES OF CIS-BROMOBIS(3-METHYL-2-OXY-4-PYRONATO)OXORHENIUM(V), TETRA-N-BUTYLAMMONIUM TRIBROMO(3-METHYL-2-OXY-4-PYRONATO)OXORHENATE(V), AND TETRA-N-BUTYLAMMONIUM TRICHLORO(3-METHYL-2-OXY-4-PYRONATO)OXOTECHNETATE(V)

A series of technetium(V) and rhenium(V) complexes of the form [MOXL2], where L is a bidentate (0, 0) monobasic ligand, 2-methyl-3-oxy-4-pyronate (maltolate, ma-) or 1,2-dimethyl-3-oxy-4-pyridinonate (dpp-), and X is a halo ligand, X = Cl (M = Tc) or Br (M = Re), have been synthesized by ligand substitution on [TcOCl4]- or [ReOBr4]- anions in nonaqueous solutions. Trihalo(maltolato)oxometalate complexes of technetium(V) and rhenium(V), [MOX3(ma)]- (M = Tc, X = Cl; M = Re, X = Br), were also prepared as tetra-n-butylammonium (M = Tc, Re) or tetraphenylarsonium (M = Re) salts. The complexes have been studied by IR, IH NMR, and mass spectra. The X-ray structures of [ReOBr(ma)2], [(n-Bu)4N][ReOBr3(ma)] and [(n-Bu)4N][TcOCl3(ma)] were determined. Crystals of [ReOBr(ma)2] (C12H10BrO7Re) are triclinic, P1BAR, with a = 20.846(2) angstrom, b = 8.484(2) angstrom, c = 8.4809(8) angstrom, alpha = 85.89(1)-degrees, beta = 89.831(9)-degrees, gamma = 89.80(1)-degrees, V = 1496.0(4) angstrom3, and Z = 4; those of [(n-Bu)4N][ReOBr3(ma)] (C22H41Br3NO4Re) are monoclinic, P2(1)/n, with a = 11.074(3) angstrom, b = 15.713(4) angstrom, c = 17.370(4) angstrom, beta = 104.77(2)-degrees, V = 2923(2) angstrom3, and Z = 4; and those of [(n-Bu)4N][TcOCl3(ma)] (C22H41Cl3NO4Tc) are monoclinic, P2(1)/c, with a 10.724(2) angstrom, b = 11.327(2) angstrom, c = 23.651(2) angstrom, beta = 101.46(1)-degrees, V = 2815.6(8) angstrom3, and Z = 4. The structures were solved by the Patterson method ([(n-Bu)4N] [ReOBr3(ma)]) or a combination of the Patterson and direct methods ([ReOBr(ma)2] and [(n-Bu)4N][TcOCl3(ma)]). They were refined by full-matrix least-squares procedures to R = 0.043, 0.033, and 0.034 and R(w) = 0.050, 0.027, and 0.030 for 4524, 3250, and 4338 observed reflections (I greater-than-or-equal-to 3sigma(I)) for [ReOBr(ma)2], [(n-Bu)4N][ReOBr3(ma)], and [(n-Bu)4N][TcOCl3(ma)], respectively. For [ReOBr(ma)2], the solution H-1 NMR spectrum and the crystal structure both demonstrate cis-geometry, with the Re atom being in the center of a highly distorted octahedron of cis-(bromo, oxo) donors and ketonic oxygen and hydroxy oxygen donors of the two mutually orthogonal maltolato ligands. In [(n-Bu)4N] [ReOBr3(ma)] and [(n-Bu)4N]-[TcOCl3(ma)], the [MOX3(ma)]- anions are isostructural; the metal atom is also in a highly distorted octahedral environment in each case, with the maltol hydroxy oxygen trans to the oxo group.