Synthesis of homo- and heterodinuclear metal complexes with dimethylsilylene bridged unsymmetrical bis(cyclopentadienyl) ligand

The reaction of the dilithium salt Li2[Me2Si(C5H4)(C5Me4)] (2) of Me2Si(C5H5)(C5HMe4) (1) with [MCl(C8H12)]2 (M=Rh, Ir) and [RhCl(CO)2]2 afforded homodinuclear metal complexes [{Me2Si(η5-C5H4)(η5-C5Me4)}{M(C8H12)}2] (M=Rh: 3; M=Ir: 4) and [{Me2Si(η5-C5H4)(η5-C5Me4)}Rh2(CO)2(μ-CO)] (5), respectively. The reaction of 2 with RhCl(CO)(PPh3)2 afforded a mononuclear metal complex [{Me2Si(C5HMe4)(η5-C5H4)}Rh(CO)PPh3] (6) leaving the C5HMe4 moiety intact. Taking advantage of the difference in reactivity of the two cyclopentadienyl moieties of 2, heterodinuclear complexes were prepared in one pot. Thus, the reaction of 2 with RhCl(CO)(PPh3)2, followed by the treatment with [MCl(C8H12)]2 (M=Rh, Ir) afforded a homodinuclear metal complex [Rh(CO)PPh3{(η5-C5H4)SiMe2(η5-C5Me4)}Rh(C8H12)] (7) consisting of two rhodium centers with different ligands and a heterodinuclear metal complex [Rh(CO)(PPh3){(η5-C5H4)SiMe2(η5-C5Me4)}Ir(C8H12)] (8). The successive treatment of 2 with [IrCl(C8H12)]2 and [RhCl(C8H12)]2 provided heterodinuclear metal complex [Ir(C8H12){(η5-C5H4)SiMe2(η5-C5Me4)}Rh(C8H12)] (9). The reaction of 2 with CoCl(PPh3)3 and then with PhCCPh gave a mononuclear cobaltacyclopentadiene complex [{Me2Si(C5Me4H)(η5-C5H4)}Co(CPhCPhCPhCPh)(PPh3)] (10). However, successive treatment of 2 with CoCl(PPh3)3, PhCCPh and [MCl(C8H12)]2 in this order afforded heterodinuclear metal complexes [M(C8H12){(η5-C5H4)SiMe2(η5-C5Me4)}Co(η4-C4Ph4)] (M=Rh: 11; M=Ir: 12) in which the cobalt center was connected to the C5Me4 moiety. Although the heating of 10 afforded a tetraphenylcyclobutadiene complex [{Me2Si(C5Me4H)(η5-C5H4)}Co(η4-C4Ph4)] (13), in which the cobalt center was connected to the C5H4 moiety, simple heating of the reaction mixture of 2, CoCl(PPh3)3 and PhCCPh resulted in the formation of a tetraphenylcyclobutadiene complex [{Me2Si(C5H5)(η5-C5Me4)}Co(η4-C4Ph4)] (14), in which the cobalt center was connected to the C5Me4 moiety. The mechanism of the cobalt transfer was suggested based on the electrophilicity of the formal trivalent cobaltacyclopentadiene moiety. In the presence of 1,5-cyclooctadiene, the reaction of 2 with CoCl(PPh3)3 provided a mononuclear cobalt cyclooctadiene complex [{Me2Si(C5Me4H)(η5-C5H4)}Co(C8H12)] (15). The reaction of 15 with n-BuLi followed by the treatment with [MCl(C8H12)]2 (M=Rh, Ir) afforded the heterodinuclear metal complexes of [Co(C8H12){(η5-C5H4)SiMe2(η5-C5Me4)}M(C8H12)] (M=Rh: 16; M=Ir: 17). Treatment of 6 with Fe2(CO)9 at room temperature afforded a heterodinuclear metal complex [{Me2Si(C5HMe4)(η5-C5H4)}{Rh(PPh3)(μ-CO)2Fe(CO)3}] (18) in which the C5HMe4 moiety was kept intact. Treatment of dinuclear metal complex 5 with Fe2(CO)9 afforded a heterotrinuclear metal complex [{(η5-C5H4)SiMe2(η5-C5Me4)}{Rh(CO)Rh(μ-CO)2Fe(CO)3}] (19) having a triangular metal framework. The crystal and molecular structures of 3, 11, 12, 18 and 19 have been determined by single-crystal X-ray diffraction analysis.