Ruthenium carborane complexes

As indicated earlier, when symmetry is not evident, there is no advantage in either cylindrical or spherical nomenclature. An example of this is the ruthenium-carborane complex illustrated in Figure 25, which has as its Cartesian name ... 

Ruthenium Carborane Complexes in Atom Transfer Radieal Polymerization... 

Figure 1. Structures of the examined ruthenium carborane complexes.

Ruthenium carborane complexes 1-8, were synthesized under argon using anhydrous solvents, according to procednres described in the literatnre (14-16). Coimnercial phosphines and diphosphines (Strem Chemicals) were nsed. The obtained prodncts were isolated and pnrified by colnnrn chromatography nsing silica gel Merck (230 00 mesh). 

Polymerization of methyl methacrylate (MMA) and styrene in bulk via ruthenacarboranes and carbon tetrachloride was investigated first, ft was found that proposed ruthenium complexes were able to efficiently catalyze polymerization of MMA in conjunction with carbon tetrachloride as an initiator. Moreover, as follows from the data obtained (Table I), high conversion of the monomer is achieved in a number of cases. The structure of ruthenium carborane complexes closo or exo-nido) has a substantial effect on the kinetic parameters of MMA and styrene polymerization, as well as on the molecular-weight characteristics of synthesized polymers. 

A small number of carborane complexes containing ruthenium-ruthenium bonds has been reported, drawing on the formal relationship between the pentahapto bonding modes of cyclopentadienyl ligands and certain carboranes. 

Incorporation of rhodium triphenylphosphine moieties into carboranes has led to HRh(C2B9Hn)(PPh3)2 complexes, which are formally hydri-dorhodium(III) dicarbollides and which catalyze olefin hydrogenation under mild conditions (527). Iridium and ruthenium analogs are also known, including complexes with carboranylphosphine ligands, e.g., HRuCl(PPh3)(l-P(CH3)2-l,2-C2B, Hn]2 (,527-530). 

Ruthenium complexes bearing anionic carborane-phosphine and dicarbol-lide ligands. 

Arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal(O) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. 

Cyclopentadienyl derivatives of ruthenium were first complexes of this metal which were found to be able to catalyze ATRP 1, 7-10). Subsequently carborane (11-12) and alkylidene (13) rathenium complexes were employed as ATRP catalysts. 

Demonceau and Vinas et al. [68] demonstrated cyclopropanation of several olefins with ruthenium and rhodinm complexes 62-66 of m7/o-carboranes (Scheme 22.19, Figure 22.23) [65,68]. They observed a conversion between 90% and 98% for both of the ruthenium complexes, where activated olefins, such as styrene and derivatives thereof, were used as substrates (Table 22.28). The yields were significantly lower with cyclic olefins or terminal linear mono-olefins (51-65%). Similar results... 

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