Rhodium complexes bridging ligands

Since the hydroformylation reaction for most substrates shows a first order dependence on the concentration of rhodium hydride, the reaction becomes slower when considerable amounts of rhodium are tied up in dimers. This will occur at low pressures of hydrogen and high rhodium concentrations. Dimer formation has mainly been reported for phosphine ligands [17, 42, 45], but similar dimeric rhodium complexes from monophosphites [47] and diphosphites [33, 39] have been reported. The orange side product obtained from HRh(15)(CO)2 was characterized as the carbonyl bridged, dimeric rhodium species Rh2(15)2(CO)2 [39]. 

Pyrazine, bridged supramolecular complexes, 46 206-213, 240-243 p-Pyrazine complexes, osmium, 37 307 Pyrazolates, ligand with rhodium complex, 44 278 Pyrazoles... 

Rasmussen, S.C., Richter, M.M., Yi, E., Place, H. and Brewer, KJ. (1990) Synthesis and characterization of a series of novel rhodium and iridium complexes containing polypyridyl bridging ligands Potential uses in the development of multimetal catalysts for carbon dioxide reduction. Inorg. Chem., 29, 3926—3932. 

G. Dinuclear Indenyl Rhodium Complexes with Bridging OFCOT Ligands... 

Finally, the generality of this bonding situation was illustrated by preparing the rhodium complex 90 upon treatment of 7b with the [Rh(p-Cl)(nbd)]2 precursor (Scheme 51).22 The bridging coordination of the PB ligand across the Rh-Cl bond was supported both experimentally (NMR spectroscopy and X-ray diffraction) and theoretically. 

Recently, Hartwell (57) reported a rhodium complex, [(C elT bSbJr CH2RhCOCl 2, in which stibinomethane also acts as a bridging ligand. 

Fig. 2.26 The cover of the review summarizing our work on the chemistry of dinuclear rhodium complexes with bridging Phosphine, arsine and stibine ligands (from Angew. Chem. Int. Ed. 41, 938-954 (2004), reproduced with permission of Wiley-VCH)...

G. E. Herberich, B. Hessner, G. Huttner, and L. Zsolnai, A Triple-Decker Sandwich Complex of Rhodium with Dibora benzene as the Bridging Ligand, Angew. Chem. Int. Ed. Engl. 20, 472-473 (1981). 

The complexes included in this section are those in which rhodium and at least one other metallic element are present. Normally the second metal is not bound to rhodium although complexes in which a metal-metal bond is supplemented by a bridging ligand are also included. 

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