SPIN DISTRIBUTION AND BONDING IN [MO(OD2)(6)](3+)

Polarized neutron diffraction results from a CsMo(SO4)(2) . 12D(2)O si ngle crystal have enabled the spin distribution within the [Mo(OD2)(6) ](3+) ion to be determined with sufficient precision to permit a close examination of the metal-water bonding interactions. Most of the spin (ca. 90%) is concentrated in the molybdenum(III) t(2g) orbitals, but there is significant spin transfer to the ligand. The water molecule b ound to molybdenum(III) has trigonal planar coordination about the oxy gen atom, and the spatial distribution of the spin about the ligand is defined with good precision. The spin about the oxygen atom is concen trated in the Mo-O interbond region (-0.017(3) mu B) and in orbitals w hich are out of the plane of the water molecule (0.035(5) mu(B)). A si mple 10 parameter model which includes oxygen-centered sp(2) hybrid or bitals fits the 178 observations with R(w) = 0.0336 and chi(2) = 1.23. These results provide unequivocal evidence for the presence of metal- water pi-bonding normal to the plane of the water molecule and the abs ence of significant in-plane metal-ligand spin transfer implies that m etal-ligand pi interaction is highly anisotropic. The anisotropy of th e metal-ligand pi interaction may lead to Jahn-Teller distortions in c ases where there is uneven occupancy of the t(2g) orbitals.