Rhodium pentamethylcyclopentadienyl complexes

Systems which fulfil these conditions are tris(2,2 -bipyridyl)rhodium complexes [63] and, more effectively, substituted or unsubstituted (2,2 -bipyridyl) (pentamethylcyclopentadienyl)-rhodium complexes [64], Electrochemical reduction of these complexes at potentials between — 680 mV and — 840 mV vs SCE leads to the formation of rhodium hydride complexes. Strong catalytic effects observed in cyclic voltammetry and preparative electrolyses are... 

Some rhodium complexes are more promising in the hydrogenation of arenes. The pentamethylcyclopentadienyl rhodium complex [ RhCUCi -CsMes) ], for instance, is stereoselective in the reduction of CgD6, yielding the all-m product almost exclusively, without the formation of cyclohexene.179... 

E. Pentamethylcyclopentadienyl Cobalt and Rhodium Complexes Derived from OFCOT... 

F. Reactions of Pentamethylcyclopentadienyl Cobalt and Rhodium Complexes of OFCOT with Exogenous Ligands... 

The same system was employed in the reduction of 4-phenyl-2-butanone to (S)-4-phenyl-2-butanol using HLADH as well as 5-ADH from Rhodococcus sp. with high enantioselectivity [113]. With pentamethylcyclopentadienyl-4-ethoxy-methyl-2,2 -bipyridinechloro-rhodium(III) as mediator and HLADH as catalyst, after 5 h 70% of 4-phenyl-2-butanone was reduced to (S)-4-phenyl-2-butanol with 65% ee. Using 5-ADH. 76% of the ketone was converted to the (S)-alcohol after 5 h with 77% ee. Furthermore, this system has been applied in an electrochemical EMR with a polymer bound rhodium complex as mediator. 

A method for the stabilization of the isocyano metabolites by formation of rhodium complexes has been developed. The (r 5-pentamethylcyclopentadienyl)- or (r 5-ethyltetramethylcyclopenta-dienyl)-di- i-thiocyanato rhodium complexes of the isocyanides (eg 129) normally provide stable, crystalline compounds, thus facilitating the analysis and the purification of these metabolites [139,140]. 

Rigby W, Bailey PM, McCleverty JA, MaitUs PM (1979) Pentamethylcyclopentadienyl-rhodium and -iridium complexes 19. Preparation and reactions of azido-, cyanato-, tMocya-nato-, nitrito-, and nitrato-rhodium complexes. J Chem Soc Dalton Trans 371—381... 

The dichlororuthenium arene dimers are conveniently prepared by refluxing ethanolic ruthenium trichloride in the appropriate cyclohexadiene [19]. The di-chloro(pentamethylcyclopentadienyl) rhodium dimer is prepared by refluxing Dewar benzene and rhodium trichloride, whilst the dichloro(pentamethylcyclo-pentadienyl)iridium dimer is prepared by reaction of the cyclopentadiene with iridium trichloride [20]. Alternatively, the complexes can be purchased from most precious-metal suppliers. It should be noted that these ruthenium, rhodium and iridium arenes are all fine, dusty, solids and are potential respiratory sensitizers. Hence, the materials should be handled with great care, especially when weighing or charging operations are being carried out. Appropriate protective clothing and air extraction facilities should be used at all times. 

Several dyes or transition-metal complexes can be used as redox mediators in indirect electrolyses. Pentamethylcyclopentadienyl-rhodium(bipyridine) complexes [Cp Rhnl(bpy)(H20)]2+ 9 [33], which were pioneered and intensively studied by Steckhan et al. [34—36], are very versatile catalysts for the reduction of cofactors. 

Recently, the use of pentamethylcyclopentadienyl(l,10-phenanthrohne-5,6-di-one)chloro rhodium(III) hexafluorophosphate [(Cp )Rhm(phend)Cl]PF6, 11 (Fig. 43.4) has been reported for the electrochemical NAD+ reduction. TONs between 7 and 453 h-1 have been achieved by varying pH, temperature and the complex concentrations [44]. This study reveals only preliminary results, so the mechanism of cofactor reduction is not explained however, due to the structural... 

The coordination properties of this phosphine-alane were further investigated by Fontaine et al. toward the rhodium(III) precursor [RhCp Me2(DMSO)] (Cp =pentamethylcyclopentadienyl, DMSO = dimethylsulfoxide).78 According to the spectroscopic data, the DMSO molecule is retained in the corresponding complex 96, most probably by interaction of its oxygen atom with the pendant alane moiety (Scheme 55). Trimethylaluminium was added to 96 to trap DMSO and generate complex 97 related to 96. But the competition between the external and... 

Pentamethylcyclopentadienyl complexes CpjAnX, 4, 207 Cp AnX2 and Cp AnX, 4, 206 Cp MX compounds, 4, 62 with iridium amidinates, 7, 366 mono(Cp ) actinide(IV) compounds, 4, 207 with Ni-C cr-bonded ligands, 8, 108-109 with rhodium, 7, 152 with ruthenium, 6, 632 tris(Cp ) actinide(IV) compounds, 4, 219 with zirconium amidinates, 12, 730 l, 2, 3, 4, 5 -Pentamethyl-l-formylruthenocene, preparation, 6, 643... 

The pyrazolate ligand plays an important role in the addition of HPPh2 to complexes containing the (C5Me5)RhH1 fragment, allowing new links to the pentamethylcyclopentadienyl-rhodium(III) phosphido chemistry, which is very scarcely represented. 

Recently, it was also shown [74] that pentamethylcyclopentadienyl rhodium and iridium complexes with labile dative ligands catalyze the borylation of alkanes at the terminal position under thermal conditions (Scheme 9). It was proposed that Ir(V) and Rh(V) boryl complexes act as intermediates in these reactions. Reaction of Cp IrH4 with HBpin gives Cp Ir(Bpin)(H)3 and Cp Ir(Bpin)2(H)2. Both of the two Ir(V) boryl complexes react with octane to give octylboronate ester [75], though it is still unclear regarding the role... 

R1 = Me, R2 = H), however, an unexpected inversion took place to afford a mixture of two phosphines (59, and 592). The phosphines (59, and 592) were reacted with bis[(pentamethylcyclopentadienyl)rhodium dichloride to furnish the corresponding rhodium(III) complexes (60, and 602) (Scheme 27) [38],... 

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