A Simple and Convenient Preparation of [(Ph3P)4Rh2(.mu.-OH)2] and Its Reactions with C-H, O-H, and M-H Acids
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Cited by 70 publications
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Rh(I) carbonyl carboxylato complexes: Spectral and structural characteristics. Some reactions of coordinated formate group
Dirhodium(I) di( µ -carboxylato) tetracarbonyls[ Rh ( µ -RCOO )( CO ) 2 ] 2 were obtained for the first time by reacting rhodium(I) carbonyl chloride dimer [ Rh ( µ -Cl )( CO ) 2 ] 2 with silver carboxylates [1]. The authors [1] synthesized and characterized acetate, trifluoroacetate, p -fluorobenzoate, and phthalate complexes of this type and some bis(phosphine) derivatives, such as transRh ( RCOO )( PPh 3 ) 2 ( CO ) . Later, some other methods were developed for synthesizing [ Rh ( µ -RCOO )( CO ) 2 ] 2 complexes with R = CH 3 ( II ), CF 3 ( III ) [2-4] and their monocarbonyl triphenylphosphine derivatives transRh ( RCOO )( PPh 3 ) 2 ( CO ) [2,[5][6][7][8][9][10][11][12]. The authors of [4] reported the results of X-ray diffraction study of [ Rh ( µ -The structure of transRh ( CF 3 COO )( PPh 3 ) 2 ( CO ) was previously determined in [13].Rhodium(I) formate complexes became available considerably later. Thus, the carbonyl formate dimer [ Rh ( µ -HCOO )( CO ) 2 ] 2 ( I ) was synthesized for the first time via a reaction of dirhodium(II) tetraacetate with carbon monoxide in formic acid [14]. Some other methods of synthesis of this compound were reported later on in [15,16]. A series of bis(phosphine) complexes trans -Rh ( HCOO )( PR 3 ) 2 ( CO ) was also synthesized [17][18][19]. The molecular structure of transRh ( HCOO )( PPh 3 ) 2 ( CO ) ( IV ) was determined by X-ray diffraction method [17]. It should be noted that in subsequent years, rhodium(I) formate complexes with carbonyl and some other π -acceptor ligands (olefins, phosphines) were studied more intensively than other carboxylate derivatives. This is quite natural, since formate group is a C 1 ligand with composite structure and high reactivity.It is noteworthy that though separate IR and NMR parameters of Rh(I) carbonyl carboxylate complexes were reported in some of the above-mentioned papers, their comparison is difficult, since they were determined under different conditions. In this work, simple reaction is suggested that can be used to synthesize [ Rh ( µ -HCOO )( CO ) 2 ] 2 complex and its crystal structure is determined. The latter complex is shown to be suitable starting reagent in synthesis of Rh(I) carbonyl hydride HRh ( PPh 3 ) 3 ( CO ) . X-ray diffraction data available in the literature for bis(triphenylphosphine) complexes of the composition transRh ( RCOO )( PPh 3 ) 2 ( CO ) with R = H, CF 3 [13, 17] are supplemented with the data we obtained for analogous acetate complex. IR and NMR measurements of carbonyl formate complexes [ Rh ( µ -HCOO )( CO ) 2 ] 2 and of trans -Rh ( HCOO )( PPh 3 ) 2 ( CO ) together with their acetate and trifluoroacetate analogs made it possible to obtain for the first time a set of comparable spectral parameters that indicates a transfer of electronic effects of the ligands through a central atom. The results of this work were partially reported in the previous publications [20][21][22]. Abstract-Complexes[Rh(µ-RCOO)(CO) 2 ] 2 , where R = H, CH 3 , CF 3 (I, II, III, respectively) are synthesized by reacting anhyd...
Rh(I) carbonyl carboxylato complexes: Spectral and structural characteristics. Some reactions of coordinated formate group
Dirhodium(I) di( µ -carboxylato) tetracarbonyls[ Rh ( µ -RCOO )( CO ) 2 ] 2 were obtained for the first time by reacting rhodium(I) carbonyl chloride dimer [ Rh ( µ -Cl )( CO ) 2 ] 2 with silver carboxylates [1]. The authors [1] synthesized and characterized acetate, trifluoroacetate, p -fluorobenzoate, and phthalate complexes of this type and some bis(phosphine) derivatives, such as transRh ( RCOO )( PPh 3 ) 2 ( CO ) . Later, some other methods were developed for synthesizing [ Rh ( µ -RCOO )( CO ) 2 ] 2 complexes with R = CH 3 ( II ), CF 3 ( III ) [2-4] and their monocarbonyl triphenylphosphine derivatives transRh ( RCOO )( PPh 3 ) 2 ( CO ) [2,[5][6][7][8][9][10][11][12]. The authors of [4] reported the results of X-ray diffraction study of [ Rh ( µ -The structure of transRh ( CF 3 COO )( PPh 3 ) 2 ( CO ) was previously determined in [13].Rhodium(I) formate complexes became available considerably later. Thus, the carbonyl formate dimer [ Rh ( µ -HCOO )( CO ) 2 ] 2 ( I ) was synthesized for the first time via a reaction of dirhodium(II) tetraacetate with carbon monoxide in formic acid [14]. Some other methods of synthesis of this compound were reported later on in [15,16]. A series of bis(phosphine) complexes trans -Rh ( HCOO )( PR 3 ) 2 ( CO ) was also synthesized [17][18][19]. The molecular structure of transRh ( HCOO )( PPh 3 ) 2 ( CO ) ( IV ) was determined by X-ray diffraction method [17]. It should be noted that in subsequent years, rhodium(I) formate complexes with carbonyl and some other π -acceptor ligands (olefins, phosphines) were studied more intensively than other carboxylate derivatives. This is quite natural, since formate group is a C 1 ligand with composite structure and high reactivity.It is noteworthy that though separate IR and NMR parameters of Rh(I) carbonyl carboxylate complexes were reported in some of the above-mentioned papers, their comparison is difficult, since they were determined under different conditions. In this work, simple reaction is suggested that can be used to synthesize [ Rh ( µ -HCOO )( CO ) 2 ] 2 complex and its crystal structure is determined. The latter complex is shown to be suitable starting reagent in synthesis of Rh(I) carbonyl hydride HRh ( PPh 3 ) 3 ( CO ) . X-ray diffraction data available in the literature for bis(triphenylphosphine) complexes of the composition transRh ( RCOO )( PPh 3 ) 2 ( CO ) with R = H, CF 3 [13, 17] are supplemented with the data we obtained for analogous acetate complex. IR and NMR measurements of carbonyl formate complexes [ Rh ( µ -HCOO )( CO ) 2 ] 2 and of trans -Rh ( HCOO )( PPh 3 ) 2 ( CO ) together with their acetate and trifluoroacetate analogs made it possible to obtain for the first time a set of comparable spectral parameters that indicates a transfer of electronic effects of the ligands through a central atom. The results of this work were partially reported in the previous publications [20][21][22]. Abstract-Complexes[Rh(µ-RCOO)(CO) 2 ] 2 , where R = H, CH 3 , CF 3 (I, II, III, respectively) are synthesized by reacting anhyd...
A series of iodo- and hydroxorhodium(I) complexes of the general composition trans-[RhX(=C=C=CRR')(PiPr3)2] (X = I: 5-7; X = OH: 8-11) was prepared from the related chlororhodium(I) precursors. The hydroxo compounds behave as organometallic Brønsted bases and react with acids like MeCO2H, PhCO2H, PhOH, or TsOH by elimination of water to give the substitution products trans-[RhX'(=C=C=CRR')(PiPr3)2] (X' = MeCO2: 12, 13; X' = PhCO2: 14; X' = PhO: 15, 16; X' = TsO: 17, 18) in good to excellent yields. In contrast to the tosylates 17, 18, which react with CO by cleavage of the allenylidene-metal bond to give trans-[Rh(OTs)(CO)(PiPr3)2] (19), treatment of the acetato and phenolato derivatives 12, 13 and 15, 16 with CO affords by migratory insertion of the allenylidene unit into the Rh-O bond the alkynyl complexes trans-[Rh[C(triple bond)CCR(R')X'](CO)(PiPr3)2] (X' = MeCO2: 20, 21; X' = OPh: 22, 23). Similarly, the reactions of the hydroxo compounds 8, 10, and 11 with CH2(CN)2 and either CO or CNMe yield the carbonyl and the isocyanide complexes trans-[Rh[C(triple bond)CCR(R')CH(CN)2](L')(PiPr3)2] (L' = CO: 25-27; L' = CNMe: 28-30), respectively. By protolytic cleavage of the Rh-C sigma bond the gamma-functionalized alkynes HC(triple bond)CCR(R')CH(CN)2 (31, 32) are generated from 25, 26 and HCl in benzene. The molecular structure of 22 was determined by X-ray crystallography.
Reductive dehalogenation -one of the earliest reactions described in the organic chemical literature -has achieved special significance since the 1980s when the harmful properties of numerous halogenated (chiefly chlorinated) hydrocarbons became clear. The identification of methods capable of neutralizing or, at least, diminishing these dangers, remains a major challenge for chemistry. It is reasonable to convert stocks of the prohibited chemicals (e.g., polychlorobiphenyls, PCBs; chlorofluorocarbons, CFCs) to valuable products as far as possible. At the same time, the halogen-containing wastes should be detoxified by degradation. During the past two decades, the mainly heterogeneous (but also homogeneous) catalytic dehalogenation provided a major share towards solving these problems. Within this period, substantial progress was also made in the application of these reactions in organic syntheses.Hydrodehalogenation -that is, hydrogenolysis of the carbon-halogen bondinvolves the displacement of a halogen bound to carbon by a hydrogen atom. This chapter is devoted to dehalogenations mediated by transition-metal complexes (Eq. (1)): ÀC j j ÀX reducing agent L n Mj 3 ÀC j j ÀH Y 1 where X = F, Cl, Br, I, and [L n M] = a transition metal complex. The use of a wide variety of reducing agents (H 2 , hydrides of metals and metalloids, organic reductants, etc.) under the most diverse reaction conditions (e.g., one-or two-phase systems) has been reported. Organic halides have also been reduced by electrochemical and photochemical methods in the presence of compounds of the type [L n M]. Reductive transformations of organic halides not relevant to Eq.(1) (e.g., coupling reactions) and dehalogenation of acyl halides will not be included here. 513The Handbook of Homogeneous Hydrogenation. Edited by J. G. de Vries and C. J. ElsevierThe reactivity of the carbon-halogen bond in Eq. (1) depends on several factors: · the nature of the halogen atom; · the environment of the halogen atom in the molecule; and · the reagents and conditions used in Eq. (1) [1].The order of reactivity of the C-X bond (generally: I > Br > Cl > F) is consistent with its strength. For instance, the experimentally found dissociation energies for phenyl halides (D Ph-X ) are 528, 402, 339, and 272 kJ mol -1 at 298 K for X = F, Cl, Br, and I, respectively [2]. Consequently, catalytic defluorination in the literature is comparatively rare. The different reactivity of the C-X bonds renders possible the selective dehalogenation of compounds containing two dissimilar halides, leaving intact the stronger C-X bond.
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