Synthesis, Structures, and Reactivity of Single and Double Cyclometalated Complexes Formed by Reactions of [Cp*MCl2]2 (M = Ir and Rh) with Dinaphthyl Phosphines.

Abstract

Reactions of two dinaphthyl phosphines with [Cp*IrCl2]2 have been carried out. In the case of di(α-naphthyl)phenylphosphine (1a), a simple P-coordinated neutral adduct 2a is obtained. However, tert-butyldi(α-naphthyl)phenylphosphine (1b) is cyclometalated to form [Cp*IrCl(P^C)] (3b). Complexes 2a and 3a undergo further cyclometalation to give the corresponding double cyclometalated complexes [Cp*Ir(C^P^C)] (4a,b) upon heating. In the presence of sodium acetate, reactions of 1a,b with [Cp*IrCl2]2 directly afford the final double cyclometalated complexes (4a,b). In the absence of acetate, [Cp*RhCl2]2 shows no reaction with 1a,b, whereas with acetate the reactions form the corresponding single cyclometalated complexes [Cp*RhCl(P^C)] (5a,b), which react with tBuOK to form the corresponding rhodium hydride complexes (6a,b). Treatment of 4a with CuCl2 or I2 leads to opening of two Ir–C σ bonds to yield the corresponding P-coordinated iridium dihalide (7 or 8) by means of an intramolecular C–C coupling reaction. A new chiral phosphine (11) is formed by the ligand-exchange reaction of 8 with PMe3. Reactions of the single cycloiridated complex 3b with terminal aromatic alkynes result in the corresponding five- and six-membered doubly cycloiridated complex 12 and/or η2-alkene coordinated complexes 13–15; the latter discloses that the electronic effect of terminal alkynes affects the regioselectivity. While the single cyclorhodated complex 5b reacts with terminal aromatic alkynes to form the corresponding six-membered cyclometalated complexes 16a–c by vinylidene rearrangement/1,1-insertion. Plausible pathways for formation of insertion products 13–16 were proposed. Molecular structures of twelve new complexes were determined by X-ray diffraction.