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The conformational analyses of PPh3 1 and the representative achiral metal complexes Al(PPh3)(Me)3 2, Fe(PPh3)(CO)4 7 and Ir(PPh3)2(CO)3+ 8 possessing tetrahedral and trigonal-bipyramidal geometries are reported, and comparisons between the calculated and solid-state structures are made. The intramolecular non-bonded interactions which govern the conformational preferences of PPh3 in both the free and complex-bound state are characterised. The equilibrium between the opposing inter ring–ring and inter ring–ligand interactions which govern the minimum energy conformations of these complexes is examined. Analysis of the conformational preferences of PPh3 ligands in metal complexes is facilitated by the introduction of the novel concept of the plane of nadir energy.
Costello et al. (Thu,) studied this question.