Synthesis, chemistry, and structures of mono-η⁶-arene complexes of chromium(II) bearing trichlorosilyl and carbon monoxide ligands

(η6-Arene)chromium tricarbonyl complexes have been photolyzed in the presence of trichlorosilane. The first reaction to take place is the expected loss of CO followed by oxidative addition to yield (η6-arene)-Cr(CO)2(H)(SiCl3). However, further photolysis causes the elimination of H2 and formation of (η6-arene)Cr(CO)2(SiCl3)2. During this process the arene ligand becomes labilized and undergoes exchange with other arene ligands present. In some instances, the hydride intermediate is too short-lived to be isolated and the -Cr(CO)2(SiCl3)2 derivative is preferentially formed. Evidence is presented that the presence of the SiCl3 groups helps labilize the η6 arene group both thermally and photochemically. Attempts to incorporate heteroatom-containing arenes are discussed, and X-ray structural elucidations of (η6-mesitylene)Cr(CO) 2(SiCl3)2 and square-planar (2,4,6-collidine)2CrCl2 are presented