Tertiary stibines complexes

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. 

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... 

Tertiary stibines have been widely employed as ligands in a variety of transition metal complexes (99), and they appear to have numerous uses in synthetic organic chemistry (66), eg, for the olefination of carbonyl compounds (100). They have also been used for the formation of semiconductors by the metal—organic chemical vapor deposition process (101), as catalysts or cocatalysts for a number of polymerization reactions (102), as ingredients of light-sensitive substances (103), and for many other industrial purposes. 

From a structural point of view the complexes with tertiary stibine ligands are very uniform. The predominant type is rj coordination (type 1), with electron pair donation of the Sb atom to the metal centre.1,2,6,8 However, complexes with bridging stibine ligands (type 2) are also known.13,14 (Scheme 1). 

Recently, also the coordination of a tertiary stibine to antimony acceptors with formation of a coordinative Sb-Sb bond was investigated. Examples are the complexes of Me3Sb with SbMeI2,47 Sbl348 or Me2Sb +. 49... 

Related to tertiary stibines is the (Me3Si)3Sb ligand. Recent studies of this ligand comprise coordination on transition metal and main group element centers. An example for a transition metal complex with a known crystal structure is [(CO)5CrSb(SiMe3)3],5° the structure of which is depicted in Fig. 2. 

A novel type of ligands are tertiary stibines containing heterocyclic aromatic groups (Y-2-C4H3)3Sb (Y = S, O, or NMe) which with silver nitrate form polymeric 2 1 complexes, [ (Y-2-C4H3)3Sb 2AgN03]x.56... 

Bridging coordination of a tertiary stibine ligand (type 2) occurs in binuclear complexes of rhodium (Equation 1).13,14... 

When a RSb moiety is coordinated to two or three 17-e- complex fragments the resulting compounds compare well with tertiary stibines,... 

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... 

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. 

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). 

It is a singular circumstance that the known chemistry of the tertiary phosphite complexes of osmium differs quite significantly from that of the tertiary phosphines, arsines and stibines. The closest analogue to P(OR)3 in osmium coordination chemistry would seem to be PF3, but even here the similarities are not marked. The oxidation states found are 0, II, III and IV (there are no established zerovalent unsubstituted osmium phosphine complexes), and the phosphites form unsubstituted species of the type OsL and [OsL ] " which have no counterparts in phosphine chemistry. The reason for these differences must be associated in part at least with the different cone angles and basicities of P(OR)3 ligands as against PR3. Further similarities and differences between the chemistries of osmium phosphines, phosphites and phosphorus trihalide complexes would obviously constitute a worthwhile study. 

Complexes with monodentate tertiary phosphines, arsines and stibines Complexes with alkyl and aryl phosphites as ligands Complexes with bidentate tertiary phosphines, arsines and stibines... 

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