Rhodium i Complexes

Biimidazole and bibenzimidazole with [(ri -2-RC3H )Pd(p-Cl)]2 (R = H, Me) taken in the 2 1 molar ratio in the presence of methanolic potassium hydroxide give complexes of the type 146 (83JCS(D)1729) and with [(ti -2-RC3H ) Pd(Mc2C0) ](C10 ) - 147. When the ratio of 2,2 -biimidazole or 2,2 -bibenz-imidazole and [(Ti -2-RC3H )Pd(p-Cl)]2 (R = H, Me) is 1 1, the homo-tetranuclear species 148 result. Heterotetranuclear palladium(II)-rhodium(I) complexes 149 (L2 = cod) follow from [(TiLcod)Rh(Hbim)] and [(ri -2-R-C3H )Pd(acac)]. They are readily carbonylated with complete substitution of... 

An example of a rhodium(I) complex with a tridentate phosphine is shown in Figure 2.16 it is formed by the usual route, reaction of the phosphine with [RhCl(cycloocta-1,5-diene)]2. 

Figure 2.16 Bond lengths in a rhodium(I) complex of a tridentate phosphine compared with...

Like other planar rhodium(I) complexes, Rh(RNC)4 undergoes oxidative addition with halogens to form 18-electron rhodium(III) species and also add other small molecules (S02, NO+) (Figure 2.31). 

ESCA data support a rhodium(II) oxidation state in these compounds. Therefore, the Rh 3d5//2 binding energy is c. 309.2 eV in simple car-boxylates, midway between those in typical rhodium(I) complexes (c. 308.5 eV) and rhodium(III) complexes (c. 310.7 eV) [72],... 

The ethanol is implicated in forming a rhodium(I) complex that catalyses the reaction. The second method produces a mixture... 

Complexes of trimethylphosphine (cone angle 118°) [115]. Syntheses are shown in Figure 2.63. The rhodium(III) complexes can be made by the usual routes or by oxidation of rhodium(I) complexes. Note that in contrast with the bulkier PPh3, refluxing RhCl3 with PMe3 does not result in reduction. 

Rhodium(—I) complexes, 4,904,905 Rhodium(Q) complexes, 4,905,906 triphenylphosphine, 4,905 Rhodium(I) complexes, 4,906-929 anionic, 4,906 bidentate anions... 

A novel chiral dissymmetric chelating Hgand, the non-stabiUzed phosphonium ylide of (R)-BINAP 44, allowed in presence of [Rh(cod)Cl]2 the synthesis of a new type of eight-membered metallacycle, the stable rhodium(I) complex 45, interesting for its potential catalytic properties (Scheme 19) [81]. In contrast to the reactions of stabihzed ylides with cyclooctadienyl palladium or platinum complexes (see Scheme 20), the cyclooctadiene is not attacked by the carbanionic center. Notice that the reactions of ester-stabilized phosphonium ylides of BINAP with rhodium(I) (and also with palladium(II)) complexes lead to the formation of the corresponding chelated compounds but this time with an equilibrium be-... 

The preparations of a number of rhodium(I) complexes of isocyanides, some of them new, have been described. The newtetrakis(methyl isocyanide) complex, [Rh(CNCH3)4], was isolated as salts of various anions from reactions of RhClj -3H20 or [(l,S-CgH,2)RhCl]2 and this isocyanide ligand (11), and several [Rh(CNR)4]+ alkyl and aryl isocyanide complexes (R= Bu, Pr, /)-C6H4C1, /.-CSH4CH3, and P-C6H4OCH3) have... 

Rhodium(I) complexes are effective reagents and/or catalysts for the decarbonylation of acyl halides and aldehydes 9 11,34,195,230,231,236). The compound Rh(PPh3)3Cl, especially, has received considerable attention. The first step in such reactions involves oxidative addition to Rh(I) of the organic molecule, exemplified by the following ... 

An example of a large scale application of the aqueous biphasic concept is the Ruhrchemie/Rhone-Poulenc process for the hydroformylation of propylene to n-butanal (Eqn. (15)), which employs a water-soluble rhodium(I) complex of trisulphonated triphenylphosphine (tppts) as the catalyst (Cornils and Wiebus, 1996). 

Rhodium(I) complexes anchored by phosphine ligands usually have high selectivity but low stability.270-273 One of the possible way to tackle this problem is to bond the metal complexes by oxygen-containing anchoring ligands (14 in Fig. 7.12).274 275... 

Li-tetrafluorobenzenedicarboxylatobis [trans-carbonylbis(triphenylphos-phine)rhodium(I)] complexes in pyridine resulted in hemidecarboxylation in each case [Eq. (98)] (79). Prolonged heating in an attempt to... 

Several rhodium(I) complexes have also been employed as ATRP catalysts, including Wilkinson s catalyst, (177),391 421 422 ancj complex (178).423 However, polymerizations with both compounds are not as well-controlled as the examples discussed above. In conjunction with an alkyl iodide initiator, the rhenium(V) complex (179) has been used to polymerize styrene in a living manner (Mw/Mn< 1.2).389 At 100 °C this catalyst is significantly faster than (160), and remains active even at 30 °C. A rhenium(I) catalyst has also been reported (180) which polymerizes MM A and styrene at 50 °C in 1,2-dichloroethane.424... 

Chiral thioureas have been synthesized and used as ligands for the asymmetric hydroformylation of styrene catalyzed by rhodium(I) complexes. The best results were obtained with /V-phenyl-TV -OS )-(l-phenylethyl)thiourea associated with a cationic rhodium(I) precursor, and asymmetric induction of 40% was then achieved.387,388 Chiral polyether-phosphite ligands derived from (5)-binaphthol were prepared and combined with [Rh(cod)2]BF4. These systems showed high activity, chemo- and regio-selectivity for the catalytic enantioselective hydroformylation of styrene in thermoregulated phase-transfer conditions. Ee values of up to 25% were obtained and recycling was possible without loss of enantioselectivity.389... 

The combination of [Rh(Cl(NBD)]2 and ligands 89, 90, 91, or 92 with diphenylsilane asymmetrically reduces aryl alkyl ketones, including acetophenones, in excellent yields and in 81 to 90% ee (Eq. 346).574 The best results are with ferrocene 91 and acetophenone in toluene.575 Other phosphine-substituted ferrocenes do not give comparable results. Rhodium(I) complexes of TADDOL-derived... 

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