Synthesis, structure, and reactions of vanadium acid esters VO(OR)(3): Transesterification and reaction,vith oxalic acid

The reaction of tert.-Butyl Vanadate VO(O-tert.-Bu)(3) (1) with H2C2O4 in t he primary alcohols ethanol and propanol results in the formation of (ROH)( RO)(2)OVV-(C2O4)(VO)-O-V(OR)(2)(HOR) (with R = C2H5 2 and R = C3H7 3). Comp ounds 2 and 3 are the first structurally characterized neutral, binuclear o xo-oxalato-complexes with pentavalent vanadium. The two vanadium atoms are connected by a bisbidentate oxalate group. The {VO6} coordination at each v anadium site is completed by a terminal oxo group, an alcohol ligand and tw o alcoxide groups. The binuclear molecules are connected to chains by hydro gen bonding. In the case of 2 a reversible isomorphic phase transition in t he temperature range of -90 degrees C to -130 degrees C is observed. From m ethanolic solution the polymeric Methyl Vanadate (1)(infinity)[VO(OMe)(3)] (4) was obtained by transesterification. A report on the crystal structures of 1, 2 and 3 as well as a redetermination of the structure of 4 is given. Crystal data 1, orthorhombic, Cmc2(1), a = 16.61(2) Angstrom, b = 9.274(6) Angstrom, c = 10.784(7) Angstrom, V = 1662(2) Angstrom(3), Z = 4, d(c) = 1. 144 gcm(-1); 2 (-90 degrees C), monoclinic, I2/a, a = 33.502(4) Angstrom, b = 7.193(1) Angstrom, c = 15.903(2) Angstrom und beta = 143.060(3)degrees, V = 2303(1) Angstrom(3), Z = 3. d(c) = 1.425 gcm(-1); 2 (-130 degrees C), m onoclinic, I2/a, a = 33.274(4) Angstrom, b = 7.161(1) Angstrom, c = 47.554( 5) Angstrom, beta = 142.798(2)degrees, V = 6851(1) Angstrom(3), Z = 12, d(c ) =1.438 gcm(-1); Angstrom, triklinic, P (1) over bar, a = 9.017(5) Angstro m, b = 9.754(5) Angstrom, c = 16.359(9) Angstrom, alpha = 94.87(2)degrees, beta = 93.34(2)degrees, gamma = 90.42(2)degrees, V = 1431(1) Angstrom(3), Z = 2, d(c) = 1.340 gcm(-1); 4, triklinic, P (1) over bar, a = 8.443(2) Angs trom, b = 8.545(2) Angstrom, c = 9.665(2) Angstrom, alpha = 103.202(5)degre es, beta = 96.476(5)degrees gamma = 112.730(4)degrees, V = 610.2(2) Angstro m(3), Z = 4, d(c) = 1.742 gcm(-1).