Molecular rearrangement accompanied by solid-state isomerization of {N,N′-Di-3-ethoxysalicylidene-(R,S)(S,R)-1,2-diphenyl-1,2-ethanediamine} oxovanadium(IV)

Two geometrical isomers, exo- and endo-[VO(3-EtOsal-meso-stien)] (H-2(3-EtOsal-meso-stien) = N,N'-di-3-ethoxy-silicylidene-(R,S)(S,R)-1,2-diphenyl-1,2-ethanediamine), were selectively prepared separately. X-Ray structure analyses were carried out for two different crystals of the endo-isomer: endo-[VO(3-EtOsal-meso-stien)]. 3H(2)O, (A), monoclinic P2(1)/c, a = 10.435(3), b = 9.696(3), c = 30.938(3) Angstrom, beta = 94.87(2)degrees, V = 3120(1) Angstrom(3) and Z = 4; endo-[VO(3-EtOsal-meso-stien)]. CH3CN, (B), monoclinic P2(1)/c, a = 15.935(3), b = 9.510(2), c = 20.891(2) Angstrom, beta = 100.58(1)degrees, V = 3112(1) Angstrom(3) and Z = 4. Under an argon atmosphere, the endo-isomer in both crystals A and B isomerized to the exo-isomer completely upon heating at 210 degrees C for 20 h. The X-ray powder diffraction patterns of the heated crystals A' and B' were approximately identical with that of exo-[VO(3-EtOsal-meso-stien)]. H2O (C). In the latter the V=O bonds are arranged in crystals to form a fairly weak linear chain structure (V=O ... V=O ...). The drastic rearrangement of the metal complexes in the solid state accompanied by the isomerization reaction indicates that the thermal reaction proceeds in a non-topochemical fashion.