Correlation of Mo-95 NMR chemical shifts, electronic absorption bands, and solvent donor numbers for some dimeric Mo-2(O2CR)(4)L-2 solvent adducts

摘要

The Mo-95 NMR chemical shifts are reported for two series of solvent adducts of the dimeric molybdenum(II) complexes Mo-2(O2CR)(4)L-2 (R = CF3, Bu-t; L = solvent). The large deshielding effect (over 450 ppm for the R = CF3 series as the solvent changes from chloroform to hexamethylphosphoramide) correlates well with the donor number of the solvent. The lowest energy electronic absorption band corresponding to the delta-delta* transition also moves to longer wavelength with the more strongly coordinating solvents, which is consistent with weakening of the Mo=Mo quadruple bond and the dominance of the Delta E parameter in the paramagnetic term which controls the magnitude of delta(Mo-95). (C) 1997 Elsevier Science Ltd. [References: 26]