Equatorial ligand field strength

Substituting Equation 1 into Equation 5 and defining Dg and Dq as the equatorial (in-plane) and axial (out-of-plane) ligand field strengths, respectively, then (48) ... 

The unique electronic structure of these (L-A3)MoO(dithiolene) complexes arises from two basic factors. The first is the strong axial a- and Ji-donor properties of the terminal oxo ligand, which dominates the ligand field and predetermines the energy of the Mo-based dxz, dyz, and dzi acceptor orbitals. The second is the equatorial dithiolene sulfur donors, from which the low-energy LMCT transitions arise. Dithiolene covalency contributions to the electroactive C, or redox, orbital can be directly probed via the relative oscillator strengths of the / —> ixy and /fp —> (/", transitions (see above). These three wave functions may be expanded in terms of Mo- and dithiolene sulfur-based functions ... 

The location of the unpaired electron in the equatorial plane of the molecule has also been indicated by the i F n.m.r. data, for OsOFj in WF, solution. Unexpectedly, a F resonance, which could only be attributed to OsOFj, was found at a field strength corresponding to that at which the quintent of ReOF, (also in WFg solution) also occurs. The OsOFj resonance, corresponding to the ReOFj doublet, was not found. It was argued that the broad unresolved OsOFj resonance was that of the unique fluorine. The absence of a doublet resonance was ascribed to broadening consequent upon the delocalisation of the unpaired spin over the fluorine ligands in that plane. 

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