Arsine complexes rhodium

There are no tertiary arsine complexes of rhodium(II). Early reports of such complexes are erroneous.5,6 The complexes have been shown to be hydridorhodium(III) species. 

Apart from the triethylarsine972 and the tribenzylarsine974 complexes the remaining tertiary arsine complex is formed by the ditertiary arsine l,2-(Ph2As)2C2H4 clearly this cannot adopt structure (80). However, the ditertiary stibine complexes976 may well adopt structure (80), since their stoichiometry implies that only half the antimony atoms are coordinated to rhodium. 

The tertiary arsine complexes were first prepared by Dwyer and Nyholm,5 but, before the advent of NMR spectrometry, were erroneously considered to be rhodium(II) complexes.989 Further investigations have shown that in preparations starting from rhodium trihalides using a higher tertiary arsine rhodium ratio and lower reaction temperatures favor the formation of the p isomer (equations 205 and 206).986... 

The tertiary arsine complexes (Table 74) are much less numerous than those containing tertiary phosphines. They are usually prepared by the interaction of tertiary arsines with rhodium trihalides. The poorer reducing properties of tertiary arsines make it much less likely that rhodium(I) complexes will be formed in this reaction. 

One interesting reaction undergone by the tri(styryl)arsine complexes is the bromination of the C=C bond by bromine in CC14 (equation 217).1013 Similar behavior970 is exhibited by the few tertiary stibine complexes (Table 75) that have been isolated. Few physical properties of these complexes have been investigated, but the 121 Sb Mossbauer parameters for both rhodium(III) complexes and the free ligands have been determined.1016... 

However, over the last 60 years a new type of chemistry has emerged. Although the first examples, tertiary arsine complexes, were initially prepared as an extension of classical rhodium(III) chemistry, the newer complexes containing tt-bonding ligands have been a consequence of the intense interest in the catalytic properties of rhodium(I) complexes. Examples of these ligands also include tertiary phosphines and stibines, although it is debatable to what extent they act as r-acids when coordinated to rhodium(III). 

Chlorocarbonylbis(triphenylphosphine)rhodium and chlorocarbonylbis(triphenylarsine)rhodium form bright yellow crystalline solids which are readily soluble in chloroform and dichloromethane, moderately soluble in benzene and carbon tetrachloride, and sparingly soluble in ether and aliphatic hydrocarbons. The phosphine complex (m.p. 195 to 197°) and the arsine complex (m.p. 242 to 244°) are reported to have carbonyl stretching frequencies (using KBr disks) at 1960 and 1963 cm., respectively. ... 

The first report on rhodium-catalyzed [2 + 2 + 2] cycloaddifion of alkynes is the intermolecular cyclotrimerization of dimethyl acetylenedicarboxylate (DMAD) catalyzed by a neutral rhodacyclopentadiene/arsine complex in 1968 [6]. After this initial report, various neutral rhodium(I) complexes were developed for intermolecular [2 + 2 + 2] cycloaddition of internal alkynes (Scheme 4.1) [7-13], Among them, (T) -cyclopentadienyl)rhodium(I) complexes [7-9,13] are the best-investigated catalysts. Neutral rhodium(ni) complexes have also been employed as catalysts [14,15], A RhCls/amine system effectively catalyzes [2 + 2 + 2] cycloaddition of internal alkynes [15]. 

Although trialkyl- and triarylbismuthines are much weaker donors than the corresponding phosphoms, arsenic, and antimony compounds, they have nevertheless been employed to a considerable extent as ligands in transition metal complexes. The metals coordinated to the bismuth in these complexes include chromium (72—77), cobalt (78,79), iridium (80), iron (77,81,82), manganese (83,84), molybdenum (72,75—77,85—89), nickel (75,79,90,91), niobium (92), rhodium (93,94), silver (95—97), tungsten (72,75—77,87,89), uranium (98), and vanadium (99). The coordination compounds formed from tertiary bismuthines are less stable than those formed from tertiary phosphines, arsines, or stibines. 

Rhodium(III) forms a wide range of complexes with tertiary phosphines and arsines [108, 109], though in some cases other oxidation states are possible. Table 2.5 summarizes the complexes produced from reaction of RhCl3 with stoichiometric quantities of the phosphine. 

For this reason Long (7, 8) and Erskine 8—11) prepared two series of ligands the ortho, meta and para-styryl dimethyl arsines Long), and the o, m and -allylphenyldimethylarsines Erskine) and studied the bromination of these compounds, their methiodides and their platinum (II) and rhodium(III) complexes. 

The rhodium(III) complexes of the isomeric st oryl dimethyl arsines were all of the type RhBrs (arsine) 3 and all reacted with an excess of bromine (> 6 mols) giving complexes of the t3 e RhBrs (arsine Br2)3, in which all the double bonds of the ligands have been saturated by addition of bromine. No difference in reactivity between any of the isomers was noted (5). 

Phosphines and arsines containing more than one olefinic group were neglected as possible multidentate ligands until Hall prepared the tris (orfAo-vinylphenyl) derivatives of phosphorus, arsenic and antimony (tvpp, tvpa and tvps) and their platinum(II) (48) and rhodium(I) (49) complexes. 

The reactions of dihydrobilin (1,19-dideoxybiladiene-a, c) with transition metals are strongly influenced by the nature of the metal ion. Thus with Mn(OAc)3 or FeClj the corresponding metallocorrolates have been obtained in high yield, in the presence of chromium or ruthenium salts the reaction product isolated has been the metal free macrocycle, while coordination of rhodium requires the presence of an axial ligand such as a phosphine, arsine or amine [21]. Neutral pentacoordinated rhodium complexes have thus been obtained. Although analysis of the electronic spectra of the reaction mixtures demonstrated that cyclization of the open-chain precursor and formation of metallocorrolates occur even in the absence of extra ligands, no axially unsubstituted rhodium derivative has been reported. 

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)...

To some extent this situation has been rectified by a number of reviews of more limited range. Among these are the review by Robinson on the rhodium(II) carboxylates,19 and the reviews on the chemistry of [RhCl(PPh3)3]20 and [RhH(CO)(PPhj)3].21 The tertiary phosphine, arsine and stibine complexes of the element have also been covered in two reviews of these ligands complexes with the transition elements.22... 

Rhodium(Il) complexes with tertiary arsines were erroneously reported over 40 years ago. These complexes were, with the advent of NMR spectrometry, later proved to be hydridorhodium(III) complexes. Nevertheless, the only stable isolable monomeric rhodium(II) complexes are those containing tertiary phosphine and other similar group VB ligands. 

There is an extensive chemistry of tertiary phosphine rhodium(III) complexes. However, there are comparatively few complexes of monodentate tertiary arsines, although the complexes of ditertiary arsines are more numerous. There are virtually no tertiary stibine complexes. The two main preparative routes to the complexes described in this section are (i) direct reaction pf the ligands with rhodium trichloride, which usually yields trichloro complexes and (ii) oxidative addition to rhodium(I) tertiary phosphine complexes, which gives rise to more diverse products of the type [RhXYZ(PRj) ], Metathetical reactions on the complexes prepared by either method (i) or (ii) have been used to prepare most of the remaining compounds. 

These complexes are produced when rhodium trichloride is allowed to react with two, or less, equivalents of tertiary phosphine or arsine (equation 199). Their physical properties are listed in Table 68, and the complexes have been shown to adopt the non-centrosymmetric structure (80).977 This is in agreement with the dipole moment972 and 3IP NMR spectrum978 of the tributylphosphine... 

The other hydrogen halides add oxidatively to rhodium(I) complexes of ditertiary phosphines or arsines giving rise to numerous monohydrido complexes, whose physical properties are also listed in Table 79. However, it is possible to prepare certain monohydrido complexes from rhodium(III) halides. One interesting reaction, carried out under an atmosphere of CO, gives rise to dicar-bonyldichlororhodate(I) salts (equation 241).226... 

Tetrafluoroborate,223 tetraphenylborate and iodide227 salts of a large range of rhodium(I) complex cations react oxidatively with dioxygen (equation 242). The physical properties of the dioxygen complexes are given in Table 80. The claim that a rhodium(I) species containing a ditertiary arsine... 

A rhodium(III) perchlorate complex containing two molecules of the tritertiary arsine can also... 

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