Isolation and characterization of the chelate exo-nido-ruthenacarborane intermediates formed in the thermal exo-nido-to-closo conversion of [exo-nido-5,6,10-{Cl(Ph3P)2Ru}-5,6,10-(μ-H)3-10-H-7,8-R2-7,8-C2B9H6] (R = H or Me) upon the triphenylphosphine liga

Reactions of [exo-nido-5,6,10-{Cl(Ph3P)2Ru}-5,6,10-(μ-H)3-10-H-7,8-R2-7,8-C2B9H6] (1, R = H; 2, R = Me) with the chiral (2S,4S)-2,4-bis(diphenylphosphino)pentane (3,S,S-bdpp) ligand proceed in benzene with replacement of both PPh3 ligands on the metal center with the diphosphine affording the chelate exo-nido complexes [exo-nido-5,6,10-{Cl(S,S-bdpp)Ru}-5,6,10-(μ-H)3-10-H-7,8-R2-7,8-C2B9H6] (7, R = H) and (8, R = Me), respectively. A relatively fast and irreversible rearrangement of 7 into its closo isomer [closo-3,3-(S,S-bdpp)-3-Cl-3-H-3,1,2-RuC2B9H11] (4) occurs in solution already at room temperature. On the contrary, exo-nido-to-closo conversion of 8 proceeds in benzene (or much faster in toluene) only on heating and yields 17-electron paramagnetic complex [closo-3,3-(S,S-bdpp)-3-Cl-1,2-Me2-3,1,2-RuC2B9H9] (9). All exo-nido- and closo-ruthenacarboranes obtained were characterized by a combination of analytical, multinuclear NMR or EPR spectroscopic data and, in addition, by X-ray diffraction studies of both dimethylated complexes 8 and 9.

The phosphine–diphosphine displacement reactions of [exo-nido-5,6,10-{Cl(Ph3P)2Ru}-5,6,10-(μ-H)3-10-H-7,8-R2-7,8-C2B9H6] (R = H or Me) with the chiral (2S,4S)-(−)-2,4-bis(diphenylphosphino)pentane (S, S-bdpp) ligand has been found to proceed via the corresponding exo-nido intermediate [exo-nido-5,6,10-{Cl(S,S-bdpp)Ru}-5,6,10-μ-(H)3-10-H-7,8-R2-7,8-C2B9H6] to form the chelate closo complexes either of 18- or 17-electron structure, depending on whether substituted or non-substituted starting exo-nido complexes are used.Figure optionsDownload as PowerPoint slide