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

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)(2)ZrCl2 in THF gave the corresponding zirconium fluorenone ketyl complex (C5Me5)(2)Zr(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 (eta(5)-C5Me5)(eta(5):eta(5)-C5Me4CH2C(Ph)(2)O)Zr(OCHPh2) (2). In contrast, the similar reaction of [(C5Me5)Ir(mu-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(mu-H)Cl](2) was used to react with sodium fluorenone or benzophenone ketyl, the dechlorination (reduction) product [(C5Me5)Ir(mu-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(mu-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)(IrNBu)-Bu-t 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%).