Transfer of ketyls from alkali metals to transition metals. Formation and diverse reactivities of D-block transition-metal ketyls

Article abstract of DOI:10.1021/om981013c

This paper reports our studies on the preparation of d-block transition-metal ketyls via metathesis reactions of alkali-metal ketyls with transition-metal chlorides as well as via deprotonation of pinacols with a transition-metal base. The metathesis reaction of sodium fluorenone ketyl with (C₅Me₅)₂ZrCl₂ in THF gave the corresponding zirconium fluorenone ketyl complex (C₅Me₅)₂Zr(OC₁₃H₈)Cl (1), which represents the first example of a structurally characterized d-block transition-metal ketyl complex. In the case of sodium benzophenone ketyl, further reaction between the ketyl radical and a C₅Me₅ ligand took place to give finally the zirconium bis(alkoxide) complex (η⁵-C₅Me₅)(η⁵:η ¹-C₅Me₄CH₂C(Ph) ₂O)Zr(OCHPh₂) (2). In contrast, the similar reaction of [(C₅Me₅)Ir(μ-Cl)Cl]₂ with sodium fluorenone ketyl yielded the iridium carbonyl complex (C₅Me₅)Ir(CO)(C₁₂H₈) (5), as a result of decarbonylation of fluorenone. When [(C₅Me₅)Ir(μ-H)Cl]₂ was used to react with sodium fluorenone or benzophenone ketyl, the dechlorination (reduction) product [(C₅Me₅)Ir(μ-H)]₂ (8), together with fluorenone or benzophenone, formed selectively. The ketone-free 8 could be obtained in high yields by reaction of [(C₅Me₅)Ir(μ-H)Cl]₂ with 2 equiv of K or Na in THF. The reaction of 1,2-bis(biphenyl-2,2′-diyl)ethane-1,2-diol (9) with the iridium imido complex (C₅Me₅)IrN^tBu in THF gave a mixture of 5 (30%) and 8·2(fluorenone) (30%). However, when the reaction was carried out in benzene, the pinacolate complex (C₅Me₅)Ir(O₂C₂₆H₁₆) (10) was formed as a major product (73%) together with a small amount of 5 (9%) and 8 (13%).