MOLECULAR AND CRYSTAL-STRUCTURES OF TRANS-[VOCL2(H2O)2] HYDROGEN-BONDED ADDUCTS WITH 15-CROWN-5 AND BENZO-15-CROWN-5 ETHER

The crystal structures of molecular adducts of vanadyl complex of trans[VOC]2(H2O)2] with 15-crown-5 (15C5). benzo-15-crown-5 (B15C5) have been studied by X-ray diffraction at ambient temperature. The adduct of the same complex with 18-crown-6 (18C6) recrystallized from a solvent different from that previously reported, has been also re-refined and the unresolved chloro position has been resolved into two disordered positions. The Cl-V-Cl bond angles in the 15C5 and B15C5 adduct are 143-degrees and 145-degrees. respectively, which are smaller than the O-V-O bond angles of 153-degrees and 154-degrees. There appear eclipsed type H2O-VCl2 conformations in all the adducts. These observations can be ascribed to the steric repulsion between the chloro ligands and aqua hydrogen atoms as well as to the coulombic repulsion between the chloro and oxido ligand. The crystals are composed of adduct polymers with 1 : 1 stoichiometry in which the chromophore and crown ether alternate along the polymer axis. The polymers are formed by hydrogen bonding between the aqua ligand and the oxygen atoms on the crown ring. The crown ethers adopt invariably all-gauche C-C conformation. The O-C bonds are of trans conformation except for a gauche O-C bond in 15C5. ESR parameters of trans-[VOCl2(H2O)2] observed for the 15C5 adduct powder are also presented.