PREPARATION AND REACTIONS OF RHENIUM(VII) TRIOXO HYDROGENDIOLATO COMPLEXES AND RHENINM(VI) OXO BIS(DIOLATO) COMPLEXES

The compound Re2O7, Re2O7. 2H(2)O or [ReO3(OSiMe3)] reacted with H(2)d iol to form complexes having the general formula [ReO3(Hdiol)] where H (2)diol = 2,3-dimethylbutane-2,3-diol (H(2)pin) or 1,1'-bicyclohexane- 1,1'-diol (H(2)bicy). In the case of H(2)pin the complex [ReO3(Hpin)]. H(2)pin is formed initially in the reaction of rhenium(VII) oxides wi th an excess of pinacol. The hydrogen bonded free pinacol molecule can be removed by sublimation. The monomethyl derivative of pinacol, HMep in, reacts in a similar way to form the complex [ReO3(Mepin)]. In the rhenium(VII) compounds the Re atom has a distorted trigonal bipyramida l co-ordination geometry. Pale yellow solutions of [ReO3(Hdiol)] in CH 2Cl2 slowly become orange and red crystals having the formula [ReO(dio l)(2)] may be isolated. The reaction of rhenium(VII) oxides with H(2)d iol and PPh3 in the presence of drying agents in CH2Cl2 produced the s ame compounds in high yield. The crystal structures of the rhenium(VI) complexes reveal that the rhenium(VI) cations have square pyramidal c o-ordination geometries. The rhenium(VI) oxo bis(diolato) complexes ar e thermally stable and do not readily undergo oxidation in dry air.