Synthesis and theoretical study of a series of dipalladium(I) complexes containing the Pd2(mu-CO)2 core

The complex [PBu4]2[Pd2(mu-CO)2Cl4] has been prepared in high yields by carbonylation of [PBu4]2[Pd2Cl6]. Methanol, potassium acetate, or CO readily reacted under ambient conditions to quantitatively afford a series of dipalladium(I) complexes, namely [Pd2(mu-CO)2Cl3(OCH3)]2-, [Pd2(mu-CO)2Cl3(OC(O)CH3)]2-, [Pd2(mu-CO)2Cl3(CO)]-, and [Pd2(mu-CO)2Cl2(OCH3)(CO)]-, all of which have the Pd2(mu-CO)2 core preserved. All these complexes have been characterized by infrared and NMR spectroscopies; the high nu(CO) stretching wavenumbers observed and the diamagnetic character of these complexes prompted us to perform theoretical calculations to describe the electronic structure of the Pd2(mu-CO)2 core and to gain an intimate description of the Pd-CO bonds. The pairing of the two lonely electrons of the Pd d9 atoms is due to the delocalization along the CO bridging ligands.