The versatile coordination modes of monophosphine-o-carborane in the formation of iridium and rhodium complexes: synthesis, reactivity, and characterization.
Monophosphine-o-carborane has four competitive coordination modes when it coordinates to metal centers. To explore the structural transitions driven by these competitive coordination modes, a series of monophosphine-o-carborane Ir,Rh complexes were synthesized and characterized. [Cp*M(Cl)(2){1-(PPh(2))-1,2-C(2)B(10)H(11)}] (M=Ir (1a), Rh (1b); Cp*=η(5)-C(5)Me(5)), [Cp*Ir(H){7-(PPh(2))-7,8-C(2)B(9)H(11)}] (2a), and [1-(PPh(2))-3-(η(5)-Cp*)-3,1,2-MC(2)B(9)H(10)] (M=Ir (3a), Rh (3b)) can be all prepared directly by the reaction of 1-(PPh(2))-1,2-C(2)B(10)H(11) with dimeric complexes [(Cp*MCl(2))(2)] (M=Ir, Rh) under different conditions. Compound 3b was treated with AgOTf (OTf=CF(3)SO(3) (-)) to afford the tetranuclear metallacarborane [Ag(2)(thf)(2)(OTf)(2){1-(PPh(2))-3-(η(5)-Cp*)-3,1,2-RhC(2)B(9)H(10)}(2)] (4b). The arylphosphine group in 3a and 3b was functionalized by elemental sulfur (1 equiv) in the presence of Et(3)N to afford [1-{(S)PPh(2)}-3-(η(5)-Cp*)-3,1,2-MC(2)B(9)H(10)] (M=Ir (5a), Rh (5b)). Additionally, the 1-(PPh(2))-1,2-C(2)B(10)H(11) ligand was functionalized by elemental sulfur (2 equiv) and then treated with [(Cp*IrCl(2))(2)], thus resulting in two 16-electron complexes [Cp*Ir(7-{(S)PPh(2)}-8-S-7,8-C(2)B(9)H(9))] (6a) and [Cp*Ir(7-{(S)PPh(2)}-8-S-9-OCH(3)-7,8-C(2)B(9)H(9))] (7a). Compound 6a further reacted with nBuPPh(2), thereby leading to 18-electron complex [Cp*Ir(nBuPPh(2))(7-{(S)PPh(2)}-8-S-7,8-C(2)B(9)H(10))] (8a). The influences of other factors on structural transitions or the formation of targeted compounds, including reaction temperature and solvent, were also explored.
Huo
Xian-Kuan
XK
Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Department of Chemistry, Fudan University, Shanghai 200433, P.R. China.
Su
Ge
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Jin
Guo-Xin
GX