As/Se-units as building blocks in cobalt complexes containing the C 5Me 4Et ligand. Crystal structure of ( η5-C 5Me 4Et)Co( η4-As 6Se)

Abstract

The reaction of Cp∗ 2 Co 2(CO) 2 1 (Cp∗=C 5Me 4Et) with equimolar amounts of As 4Se 4 was investigated at different temperatures and compared to the reaction of 1 with As 4S 4. In boiling toluene the formation of Cp∗ 2 Co 2As 2Se 3 (4-Se) and Cp∗ 3 Co 3As 2Se 4 (5-Se) was observed, whereas in boiling xylene in addition to 4-Se and 5-Se Cp∗CoAs 6Se (7) was formed. Spectroscopic investigations show that the structures of 4-Se and 5-Se are analogous to those of the known compounds Cp∗ 2 Co 2As 2S 3 (4-S) and Cp∗ 3 Co 3As 2S 4 (5-S). As 7 is the first complex derived from selenium substituted E 7 3− (E=P, As, Sb) Zintl ions, an X-ray diffraction analysis was carried out showing that it consists of a norbornadiene-like cage of the main group elements to which a Cp∗Co fragment is coordinated via four As atoms as a four-electron ligand.