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Synthesis of Mixed-Metal (Ru−Rh) Bimetallacarboranes via exo-nido- and closo-Ruthenacarboranes. Molecular Structures of (η4-C8H12)Rh(μ-H)Ru(PPh3)25-C2B9H11) and (CO)(PPh3)Rh(μ-H)Ru(PPh3)25-C2B9H11) and Their Anionic closo-Ruthenacarborane Precursors

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journal contribution
posted on 28.01.1999, 00:00 by Igor T. Chizhevsky, Irina A. Lobanova, Pavel V. Petrovskii, Vladimir I. Bregadze, Fyodor M. Dolgushin, Alexandr I. Yanovsky, Yuri T. Struchkov, Anatolii L. Chistyakov, Ivan V. Stankevich, Carolyn B. Knobler, M. Frederick Hawthorne
The reaction of exo-nido-5,6,10-[Cl(PPh3)2Ru]-5,6,10-(μ-H)3-10-H-7,8-C2B9H8) (1) with [(η4-diene)RhCl]2 in EtOH or with [(CO)2RhCl]2 in MeOH in the presence of KOH produced novel mixed-metal bimetallacarboranes (η4-diene)Rh(μ-H)Ru(PPh3)25-C2B9H11) (4, diene = COD; 5, diene = NBD) or (CO)(PPh3)Rh(μ-H)Ru(PPh3)25-C2B9H11) (10) along with a small amount of the mononuclear complexes closo-(CO)2(PPh3)Ru(η5-C2B9H11) and closo-(CO)(PPh3)2Ru(η5-C2B9H11), respectively. Complexes 4 and 10 were characterized by single-crystal X-ray diffraction studies which revealed the existence of two types of bridging bonds Ru−H−Rh and B−H···Rh in these species. The bridging hydrogen atoms are asymmetrically disposed within these linkages. Several separate experiments have been carried out for the synthesis of the anionic complex [closo-3,3-(PPh3)2-3-H-3,1,2-RuC2B9H11]-, which is proposed to be the key intermediate in the reaction of 1 with [(η4-diene)RhCl]2. The reaction of (PPh3)3RuHCl with [7,8-C2B9H12][Me3NH] under reflux in THF in the presence of Et4NCl yielded [closo-3,3-(PPh3)2-3-Cl-3,1,2-RuC2B9H11][Et4N] (7), which after reduction by LiAlH4 in THF afforded [closo-3,3-(PPh3)2-3-H-3,1,2-RuC2B9H11][Et4N] (8) in poor yield. Alternatively, treatment of (PPh3)3RuHCl with Tl2[7,8-C2B9H11] in THF at ambient temperature led to 8 in 84% yield. The anionic complex 8 and the known neutral closo-3,3-(PPh3)2-3-Cl-3-H-3,1,2-RuC2B9H11 (6) have been substituted for 1 in the synthesis of 4 under the same conditions. Structures of both anionic closo-ruthenacarboranes 7 and 8 have been confirmed by single-crystal X-ray diffraction studies. The NMR data [1H, 13C{1H}, 31P{1H}, and 11B] for the new mononuclear and binuclear ruthenacarborane complexes are discussed in detail.