COORDINATION OF (O-AMINOPHENYL)DIPHENYLPHOSPHINE IN COMPLEXES CONTAINING THE [MV=O]3+ (M=TC OR RE) CORE

Reduction-substitution reactions of [TcO4]- with (o-aminophenyl)diphenylphosphine (HL) at a strictly controlled stoichiometric metal/ligand ratio gave neutral oxotechnetium(V) complexes of the type [TcOL2(OR)] (R = Me 1 or Et 2): Analogous [ReOL2(OR)] species (R = H 3, Me 4, Et 5, Pr 6, Bu 7, C2H4OH 8, C3H6OH 9, Ph 10 or OCMe 11) are instead produced via ligand-exchange reactions in basic media starting from (ReOCl4]-. Compounds 1-11 are referred to as 'equatorial' because the co-ordination of both bidentate L- chelates occurs symmetrically in the equatorial plane orthogonal to the M=O moiety, with a mutual cis-phosphorus configuration. The site trans to the oxo group is always occupied by an oxygen-containing monodentate ligand the co-ordination of which determines the stability of this class of octahedral complexes. Nevertheless the -OR group is easily exchangeable with other nucleophiles available in the reaction mixture by the mass effect and/or donor ability of the incoming ligand. The crystal structures of complexes 1 and 5 have been determined: 1, monoclinic, space group P2(1)/c, Z = 4, a = 12.156(3), b = 26.005(6), c =1 0.953(2) angstrom, beta = 102.49(2)-degrees, R' 0.0611 using 1766 observed reflections; Tc-O(1) 1.700(8), Tc-O(2) 1.999(8), Tc-P 2.511(3) and 2.503(4), Tc-N 1.972(10) and 1.976(8) angstrom; O(1)-Tc-N 105.8(4) and 103.6(4), 0(l)-Tc-P 88.1(3) and 88.9(2), 0(l)-Tc-O(2) 158.3(3)-degrees; 5, monoclinic, space group P2(1)/c, Z = 4, a = 12.056(3), b 26.303(6), c = 11.005(3) angstrom, beta = 102.32(2)-degrees, R' 0.0614 using 4752 observed reflections; Re-O(1) 1.692(7), Re-O(2) 2.004(7), Re-P 2.495(2) and 2.493(3), Re-N 1.990(8) and 2.003(7) angstrom; O(1)-Re-N 104.6(3) and 102.6(3), O(1)-Re-P 89.1(2) and 88.8(2), 0(l)-Re-0(2) 160.8(3)-degrees. By treatment of [MOL,(OR)] solutions with HX (X = halide), further reduction to lower-oxidation-state species occurs when M = Tc, while another class of stable and neutral oxo complexes, termed 'twisted', is produced when M = Re. Two mutually orthogonal L- chelates co-ordinate the metal while still preserving the cis-phosphorus configuration, one ligand bridging an equatorial and an apical position (with the phosphinoamido nitrogen trans to the Re-O linkage) and the other two equatorial positions. The equatorial plane is completed by a halide atom. The chloro derivative [ReOL2Cl] exhibits two crystalline forms, alpha (12) and beta (13), the crystal structures of which have been determined: 12, monoclinic, space group P2(1)/n, Z = 4, a = 9.594(l), b =18.565(4), c = 17.656(2) angstrom, beta = 91.00(1)-degrees, R' 0.0477 using 2979 observed reflections; Re-0 1.767(7), Re-Cl 2.436(3), Re-P(1) 2.429(3), Re-P(2) 2.479(3), Re-N(1) 1.986(9), Re-N(2) 2.029(8) angstrom; O-Re-N(2) 162.8(3), O-Re-N(l) 108.6(3)-degrees; 13, orthorhombic, space group P2(1)2(1)2(1), Z = 4, a = 10.196(5), b = 14.047(6), c = 21.987(8) angstrom, R' 0.0671 using 2501 observed reflections; Re-0 1.69(l), Re-Cl 2.422(6), Re-P(1) 2.434(5), Re-P(2) 2.476(5), Re-N(l) 2.01(l), Re-N(2) 2.04(1) angstrom; O-Re-N(2) 162.7(6), O-Re-N(l) 109.0(7)-degrees. The interconversion between 'equatorial' and 'twisted' species is discussed. Elemental analyses, FAB mass, IR, electronic, H-1 and P-31 NMR spectra are reported. The P-31 NMR signal is diagnostic for both classes of complexes in solution, being a singlet for the 'equatorial' and two doublets for the 'twisted' species, respectively.