Phenoxo and diphenoxo complexes of titanium(II) and vanadium(III): synthesis and X-ray structure

Abstract

Reaction of [TiCl₃(thf)₃] and [VCl₃(thf)₃](thf = tetrahydrofuran) with 2,6-Bu^t₂C₃H₃ONa and 2,6-Me₂C₆H₃ONa respectively, led to the monomeric five-co-ordinate complexes [TiCl₂(2,6-Bu^t₂C₆H₃O)(thf)₂], (1), and [VCl₂(2,6-Me₂C₆H₃O)(thf)₂], (2). Both metal atoms have a trigonal bipyramidal co-ordination, the equatorial plane being defined by the two chloride and the phenoxo ligands. The axial positions are filled by two thf molecules. Phenoxo parameters are: Ti–O 1.807(8) and V–O 1.803(5)Å; Ti–O–C 174.2(9) and V–O–C 135.9(5)°. Reaction of the sodium salt of benzene-1,2-diol (H₂cat) with [VCl₃(thf)₃] led to the isolation of a binuclear complex [V₂(µ-cat)₂Cl₂(thf)₄], (3), while the reaction with the sodium salt of bis(2-hydroxy-5-methyl-3-t-butylphenyl)methane (H₂bhm) gave the mononuclear complex [V(bhm)Cl(thf)₂](4). Complex (3) has a planar V₂(µ-cat)₂Cl₂ skeleton with molecules of thf above and below the plane, and vanadium(III) achieves six-co-ordination by sharing the oxygens of the catecholato dianion. Complex (4) has a monomeric structure with the diphenolato anion (bhm) forming an eight-membered ring and vanadium(III) having a pseudo-trigonal-bipyramidal co-ordination. Compounds (1)–(4)(all monoclinic) were characterized by single-crystal X-ray analysis: (1), space group P2₁/c, a= 10.483(1), b= 10.771 (1), c= 24.847(2)Å, β= 95.61 (1)°, Z= 4, R 0.064 for 1 051 observed reflections; (2), space group P2₁/n, a= 7.329(1), b= 13.195(1), c= 19.687(2)Å, β= 94,58(1)°, Z= 4, R 0.057 for 1 226 observed reflections; (3), space group P2₁/n, a= 17.743(2), b= 9.238(1), c= 9.522(1)Å, β= 97.35(1)°, Z= 2, R 0.043 (R′ 0.047) for 1 264 observed reflections; (4), space group P2₁/c, a= 9.327(1), b= 13.814(2), _c= 24.577(2)Å, β= 93,54(1)°, Z= 4, R 0.059 (R′ 0.065) for 2 390 observed reflections.