Structural and electron paramagnetic resonance studies of the square pyramidal to trigonal bipyramidal distortion of vanadyl complexes containing sterically crowded Schiff base ligands

[N,N'-Ethylenebis(o-(tert-butyl-p-methylsalicylaldiminato)] oxovanadium(IV) (1), [N,N'-propanediylbis(o-(tert-butyl-p-methylsalicylaldiminato)]oxovanadium(IV) (2), bis(N-methylsalicylaldiminato)oxovanadium(IV) (3), bis(N-isopropyl-o-methylsalicylaldiminato)oxovandium(IV) (4), and, bis(N-methyl-o-(tert-butyl-p-methylsalicylaldiminato)- oxovanadium(IV) (5) were prepared and characterized by X-ray crystallography and EPR spectroscopy. Complexes 1 and 2 are best described as square pyramids, while complexes 3-5 are distorted trigonal bipyramids, demonstrating that oxovanadium(IV) complexes can readily adopt a trigonal bipyramidal geometry. All five compounds give nearly the same parallel hyperfine coupling constant (A,) regardless of the fact that the geometry about the vanadium changes from square pyramidal to trigonal bipyramidal. Crystal data for 1: space group <P(1)over bar>, a = 7.9382(3) Angstrom, b = 12.6749(7) Angstrom, c = 13.8353(7) Angstrom, alpha = 109.608(5)degrees, beta = 96.552(5)degrees, gamma = 96.589(5)degrees, Z = 2. Crystal data for 2: space group I4(1)/a, a = 16.1895(6) Angstrom, b = 16.1895(6) Angstrom, c = 41.117(3) Angstrom, Z = 16. Crystal data for 3: space group C2/c, a = 18.8230(17) Angstrom, b = 7.5118(5) Angstrom, c = 11.7460(10) Angstrom, beta = 112.229(7)degrees, Z = 4. Crystal data for 4: space group P2(1)/c, a = 9.7086(6) Angstrom, b = 11.4554(7) Angstrom, c = 20.866(2) Angstrom, beta = 103.943(6)degrees, Z = 4. Crystal data for 5: space group Pbca, a = 10.667(3) Angstrom, b = 25.549(5) Angstrom, c = 18.322(4) degrees, Z = 8.