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)oxovanadium(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
(Az) regardless of the fact that the
geometry about the vanadium
changes from square pyramidal to trigonal bipyramidal. Crystal
data for 1:  space group P1̄, a
= 7.9382(3) Å,
b = 12.6749(7) Å, c = 13.8353(7)
Å, α = 109.608(5)°, β = 96.552(5)°, γ =
96.589(5)°, Z = 2. Crystal data
for 2:  space group
I41/a, a =
16.1895(6) Å, b = 16.1895(6) Å, c
= 41.117(3) Å, Z = 16. Crystal data for
3: 
space group C2/c, a =
18.8230(17) Å, b = 7.5118(5) Å, c
= 11.7460(10) Å, β = 112.229(7)°, Z =
4. Crystal
data for 4:  space group
P21/c, a =
9.7086(6) Å, b = 11.4554(7) Å, c
= 20.866(2) Å, β = 103.943(6)°, Z =
4.
Crystal data for 5:  space group Pbca,
a = 10.667(3) Å, b = 25.549(5) Å,
c = 18.322(4) Å, Z = 8.