An investigation of the electronic factors that influence structural differences between cis-(CpMoCl)2([mu],[eta]4-Ar4C4) (Ar = p-tolyl or phenyl) and trans-(CpNbCO)2(Ph2C2)2

Abstract

The influence of geometric factors, such as cis/trans isomerism, and electronic factors, such as [pi] donor vs [pi] acceptor ligands and coupled and uncoupled acetylene ligands, on the stability of cis-(CpMoCl)2([mu],[eta]4-Ar4C4) and trans-(CpNbCO)2(Ph2C2)2 is investigated through patterns in molecular orbital diagrams, size of HOMO/LUMO gap and total energies. The comparison between the two dimers involves rationalization of why the observed structures appear so different, when in fact both clusters have the same number of valence electrons. In the course of the investigation, other stable niobium chlorine complexes are discussed and the kinetic vs thermodynamic stability of trans-(CpNbCO)2 (Ph2C2)2 is analysed.