TETRAHEDRAL GOLD PHOSPHINE CLUSTERS - A RELATIVISTIC MOLECULAR-ORBITAL STUDY

The recently characterized cluster [{Au(PBu3t)}4]2+ has been investiga ted by the quasi-relativistic and relativistic versions of the LCAO-SC F molecular orbital approach at the non-empirical CNDO/1 level. The op timized geometry agrees well with available experimental data. The nak ed gold cluster alters its properties dramatically when phosphine liga nds are added. The simple phosphine PH3 is a rather poor model of more complex phosphines, like PBu(t)3. The former is not capable of suffic ient donation and thus it induces an instability with respect to reduc tion. The polar environment assists positively in the redox stabilizat ion of the cluster. The effect of the phosphine ligands lies in the sa turation of the high electron affinity of the {Au4}2+ core and in the population of the d5/2 sublevel.