Compounds of Rhodium l

Many compounds of rhodium (III) may readily be obtained by this general catalytic procedure. Rhodium(III) bromide may be substituted for the rhodium trichloride, and weakly basic nitrogenous ligands (2,2 -bipyridine, o- (or l,10-)phen-anthroline, or dioximes) for the pyridine. The products all have the halogen atom in trans positions. 

Rhodium-catalysed addition (10) of hydridosilanes (Chapter 17) to a/3-unsaturated carbonyl compounds can be performed regioselectively, to afford either the product of 1,2-addition, or, perhaps more usefully, that of 1,4-addition, i.e. the corresponding silyl enol ether this latter process is an excellent method for the regiospecific generation of silyl enol ethers. Of all catalyst systems investigated, tris(triphenylphosphine)rhodium(l) chloride proved to be the best. 

A very extensive and detailed study of the cationic rhodium(i)-catalyzed isomerization of allylic alcohols demonstrated that mono- and disubstituted allylic alcohols can be efficiently isomerized to the corresponding carbonyl compounds through the corresponding enol compounds (Scheme 20).45 The isomerization using cationic rhodium(l)... 

In order to probe the mechanism, this transformation was conducted under molecular deuterium atmosphere with cationic rhodium(l) complex (Scheme 110). The final compound 440 showed the incorporation of two deuterium atoms in each double bond. This is in agreement with a heterolytic activation of D2. Two different pathways are proposed. The first one involves the formation of a rhodacycle 438 followed by reductive elimination. The second one consists of a deuteriorhodation/carborhodation sequence, affording the same intermediate 437. A vinylrhodium... 

Analysis of the Mukaiyama-type aldol coupling (Eq. 2) and the well-known hydrosilyla-tion of a,/l-unsaturated carbonyl compounds 11 in the presence of a rhodium catalyst, indicate that both can be explained by the intervention of the rhodium enolate 13. This line of reasoning provided the impetus to develop a new crossed aldol coupling using a hydrosilane, an a,yS-unsaturated ketone 11, and an aldehyde to form 15 (Scheme 6.4). 

Chick embryos exposed to rhodium on the eighth day of incubation were stunted mild reduction of limb size and feather growth inhibition were also observed. A number of rhodium compounds have tested positive in bacterial assays for genetic altering capability. The 2003 ACGIH threshold limit valuetime-weighted averages (TLV-TWAs) are 1.0 mg/m for the metal, l.Omg/m as Rh, insoluble compounds, and 0.01 mg/m as Rh, soluble compounds. 

Compounds of the 3-metalla -l,2-dioxolane type were unknown in rhodium and iridium chemistry until 2001 [65] when Gal reported the preparation of some examples through sohd-gas reactions, quite an imcommon type of chemistry. They were initially obtained from the cationic complex [Rh(/c -tpa)(C2H4)] (tpa = Ar,Nd, -tris(2-pyridylmethyl)amine), and then extended to the iridium counterparts and the rhodium [66] compoimds [Rh(/c -dpda-Me2)(C2H4)] (Fig. 1) (the aromatic circles for the pyridine rings have been omitted for clarity). 

Rhodium-catalyzed hydroformylation of -(substituted amino)benzyl-amines (387, X = H2) and -(substituted amino)benzamides (387, R = H, X = O) in the presence of rhodium(II) acetate dimer and triphenylphos-phine in deoxygenated ethyl acetate gave a 7 3 mixture of 1,2,3,4,4 ,5-hexahydro-6//-pyrido[l,2-a]quinazolines (388, X = H2,0) and isomeric 3-methyl-l,2,3,3fl,4,5-hexahydropyrrolo[l,2-a]quinazolines (389, X = H2, O) (94AJC1061). The methyl derivative of benzylamine 387 (R = Me, X = H2) afforded a mixture of diastereoisomers 390 and 391 (X = H2). Their ratio depended on the reaction time. Longer reaction times gave more 391 (X = H2), containing the methyl group in an equatorial position. Compound 390 isomerized into 391 (X = H2), under the aforementioned conditions. The benzamide derivative (387, R = Me, X = O) yielded only one isomer (391, X = O), independent of the reaction period. 

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