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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)2(η5-C2B9H11) (4, diene = COD; 5, diene = NBD) or (CO)(PPh3)Rh(μ-H)Ru(PPh3)2(η5-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.

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Iridium pincer complexes [C 6 H 3 2,6 (OPBu t 2 ) 2 ]Ir(H)Cl (10) and [4 EtOOCC 6 H 2 2,6 (OPBu t 2 ) 2 ]Ir(H)Cl (11) react with protic acids undergoing metallation of one of the tert butyl groups to form double cyclometallated products [4 R C 6 H 2 2 (OPBu t 2 ) 6 (OP(Bu t )CMe 2 CH 2 )]IrCl (12, R = H; 13, R = COOEt), which are stable in air. Complex 12 reacts with CO and Bu t NC giving the corresponding 18 electron complexes [C 6 H 3 2 (OP Bu t 2 ) 6 (OP(Bu t )CMe 2 CH 2 )]Ir(L)Cl (14, L = CO; 15, L = CNBu t ). The structure of com pound 14 was established by X ray diffraction analysis.Homogeneous catalytic dehydrogenation of saturated hydrocarbons is one of the most important problems of organometallic chemistry, the solution of which should promote more rational use of hydrocarbon raw materials. 1 At the same time, the solution of this problem will allow one to accomplish functionalization of a wide class of com pounds containing unactivated C-H bonds. 2 Iridium compounds play an important role here. 3 In the field of study of homogeneous catalysts for dehydrogenation, 4 the most prominent results were achieved using complexes of the type A and B (see .Several years ago, we also began our study on dehydro genation of alkanes. We succeded in the development of complexes of the type C containing pincer ligands based on metallocenes (ferrocene and ruthenocene), 9 which ex hibited unprecedent activity in the dehydrogenation of alkanes and at present are the most active catalysts for this reaction.A necessity to compare electronic and steric properties of the pincer ligands obtained by us with analogous prop erties of ligands studied by other researches was the reason for the synthesis and more detailed study of chemical prop erties of complexes of the type B (for example, we de scribed reactions of complex 3 with CO and CNBu t ).In addition, in order to immobilize dehydrogenation catalysts on polymeric (or dendrimeric) supports we in troduced various functional groups (COOR, CONR 2 , CH 2 NR 2 ) into the pincer ligand of complexes of the type B.In the attempt to modify the substituents indicated, it was found that acidic or basic reagents very often react with the iridium atom instead of a functional group to form a mixture of unidentified products. These observations prompted us to more detailed study of the reaction of known 8 iridium bis(phosphinite) complex 10 and its ana logs with various reactive compounds, in particular, with protic acids.

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