Synthesis and characterization of sulfur-capped trinuclear group 6B metal clusters

Article abstract of DOI:10.1021/om00088a029

The sulfur-capped trinuclear chromium carbonyl cluster S[Cr(CO)₄]₃^2- has been synthesized and shown to arise via carbon monoxide loss from the CO-saturated S[Cr(CO)₅]₃^2- species. The carbon monoxide ligands display complete stereochemical nonrigidity at ambient temperature. In a low-energy process that occurs below -60°C the bridging carbon monoxide groups and the set of terminal CO groups that are cis to the capping sulfide moiety undergo fast exchange when compared to their chemical shift differences (1218 Hz at 50.3 MHz). A subsequent, higher energy exchange process of these carbon monoxide ligands with the remaining terminal carbonyl sites (those trans to the sulfide cap) occurs at temperatures greater than -20°C. Addition of Cr(¹³CO)₅THF to the S[Cr(CO)₄]₃^2- trimer results in formation of (CO)₅CrS[Cr(CO)₄]_32-, where the ¹³CO ligands are shown to be statistically distributed throughout the tetrameric species.