Syntheses, structures, and reactions of η⁶ complexes of iridathiabenzene with chromium, molybdenum, and tungsten carbonyls

The iridathiabenzene analogues [η⁶-Cp*Ir(C,S-2,5-Me₂T)]M(CO)₃, where M = Cr (3), Mo (5), W (7), of (η⁶-arene)M(CO)₃ are prepared from M(CO)₃(NCMe)₃ and Cp*Ir(C,S-2,5-Me₂T) (2), where C,S-2,5-Me₂T is ring-opened 2,5-dimethylthiophene. The high reactivity and coordination flexibility of the η⁶-Cp*Ir(C,S-2,5-Me₂T) ligand leads to a variety of products upon reaction with phosphine ligands. The reaction of 3 with PEt₃ leads to PEt₃ adduct formation at the Ir in the product [η⁶-Cp*Ir(PEt₃)(C,S-2,5-Me₂T)] [Cr(CO)₃] (17). On the other hand, reaction of the analogous tungsten complex 7 with PEt₃ yields the adduct [η⁴-Cp*Ir(C,S2,5-Me₂T)]W(CO)₂(PEt ₃)(μ-CO) (19), in which PEt₃ adds to the W atom. These and other studies show that the iridathiabenzene ligand is capable of coordination to Cr, Mo, or W through one, four, five, or six of its ring atoms. When 7 is reacted with CF₃SO₃H, protonation occurs at the tungsten, as occurs in the protonation of the analogous arene complex (η⁶C₆Me₆)W(CO)₃. Structures of four of the complexes were established by X-ray studies.