408346-84-9Relevant academic research and scientific papers
Mesityl-vanadium(III)-phenolate complexes: Synthesis, structure, and reactivity
Thiele,Goerls,Imhof,Seidel
, p. 107 - 118 (2008/10/08)
Protolysis reactions of [VMes3(THF)] with ortho-substituted phenols (2-iso-propyl-(H-IPP), 2-tert-butyl-(H-TBP), 2,4,6-trimethylphenol (HOMes) and 2.2′biphenol (H2-Biphen) yield the partially and fully phenolate substituted complexes [VMes(OAr)2(THF)2] (OAr = IPP (1), TBP (2)), [VMes2(OMes)(THF)] (4), [V(OAr)3(THF)2] (OAr = TBP (3), OMes (5)), and [V2(Biphen)3(THF)4] (6). Treatment of 6 with Li2Biphen(Et2O)4 results in formation of [{Li(OEt2)}3V(Biphen)3] (7) and with MesLi complexes [{Li(THF)2}2VMes(Biphen)2] · THF (8) and [{Li(DME)}-VMes2(Biphen)] (9) are formed. Reacting [VCl3(THF)3] with LiOMes in 1:1 to 1:4 ratios yields the componds [VCl3-n(OMes)n(THF)2] (n = 1 (5b), 2 (5a), 3 (5)) and [{Li(DME)2}V(OMes)4] (5c), the latter showing thermochromism due to a complexation/decomplexation equilibrium of the solvated cation. The mixed ligand mesityl phenolate complexes [{Li(DME)n}{VMes2(OAr)2}] (OAr = IPP (10), TBP (11), OMes (12) (n = 2 or 3) and [{Li(DME)2}-{VMes(OMes)3}] (15) are obtained by reaction of 1, 2, 5 a and 5 with MesLi. With [{Li(DME)2(THF)}{VMes3(IPP)}] (13) a ligand exchange product of 10 was isolated. Addition of LiOMes to [VMes3(THF)] forming [Li(THF)4][VMes3-(OMes)] (14) completes the series of [Li(solv.)x][VMes4-n-(OMes)n] (n = 1 to 4) complexes which have been oxidised to their corresponding neutral [VMes4-n(OMes)n] derivatives 16 to 19 by reaction with p-chloranile. They were investigated by epr spectroscopy. The molecular structures of 1, 3. 5, 5a, 5a-Br, 7, 10 and 13 have been determined by X-ray analysis. In 1 (monoclinic, C2/c, a = 29.566(3) A, b = 14.562(2) A, c = 15.313(1) A, β = 100.21(1)°, Z = 8), 3 (orthorhombic, Pbcn, a = 28.119(5) A, b = 14.549(3) A, c = 17.784(4) A, β = 90.00°, Z = 8), (5) (triclinic, P1, a = 8.868(1) A, b = 14.520(3) A, c = 14.664(3) A, α = 111.44(1)°, β = 96.33(1)°, γ = 102.86(1)°, Z = 2), 5a (monoclinic, P21/c, a = 20.451(2) A. b = 8.198(1) A, c = 15.790(2) A, β = 103.38(1)°, Z = 4) and 5a-Br (monoclinic, P21/c, a = 21.264(3) A, b = 8.242(4) A, c = 15.950(2) A, β = 109.14(1)°, Z = 4) the vanadium atoms are coordinated trigonal bipyramidal with the THF molecules in the axial positions. The central atom in 7 (trigonal, P3c1, a = 20.500(3) A, b = 20.500(3) A, c = 18.658(4) A, Z = 6) has an octahedral environment. The three Li(OEt2)+ fragments are bound bridging the biphenolate ligands. The structures of 10 (monoclinic, P21/c, a = 16.894(3) A, b = 12.181(2) A, c = 25.180(3) A, β = 91.52(1)°, Z = 4) and 13 (orthorhombic, Pna21, a = 16.152(4) A, b = 17.293(6) A, c = 16.530(7) A, Z = 4) are characterised by separated ions with tetrahedrally coordinated vanadate(III) anions and the lithium cations being the centres of octahedral and trigonal bipyramidal solvent environments, respectively.
