Identification of diastereoisomeric tetracarbonyl[o-phenylenebis(methylphenylarsine)]molybdenum complexes by means of 1H and 13C fourier nuclear magnetic resonance spectroscopy

Abstract

The diastereoisomers of o-phenylenebis(methylphenylarsine), (I), have been unambiguously identified . by examining ¹³C n.m.r. spectra of their corresponding tetracarbonylmolybdenum(0) complexes. An investigation into the nature of the triphenylphosphine-substituted complexes fac-[Mo(CO)₃(PPh₃)L][L =(I)] has provided insight into the mechanism of the carbonyl-substitution reaction and an alternative means of identifying diastereoisomeric diarsines. Oxidation of the diastereoisomeric molybdenum tetracarbonyl complexes is also described. Fluxional behaviour of the seven-co-ordinate complexes [Mo(CO)₃(I)₂L] has been observed in solution and studied over the temperature range –90 to +35 °C using ¹H n.m.r. techniques. The stereochemistry of these complexes in solution is related to their crystal structures in the solid state.