Arsines as ligands

Nickel(I) complexes are far less numerous than those of nickel(0). Like nickel(0) complexes, nickel(I) complexes are generally obtained with ligands having -acceptor capability. Most complexes of nickel(I) which have been isolated as solids contain tertiary phosphines (or arsines) as ligands and are sufficiently stable in the absence of air to allow them to be studied with several physicochemical techniques. 

C4C im][PF6] [C5C qm] [various] [C6py]Cl PdCl2 Pd(OAc)2 NaHC03 Et3N 40-200 °C. Phosphines and arsines as ligands arylation of acrylates product extracted with hexane. [58]... 

It was during this period from the second World War to around 1965 that the unique character of the phosphines and arsines as ligands was established. It was also during this period that the fundamentally important qualities of hydride and ligands attached through carbon to transition metals were discovered. Here it is not possible to do more than summarize these developments,t which are elaborated more fully where appropriate in other chapters. 

It was also shown that phosphines and arsines as ligands have fairly high -effects, so that although one, two, or rarely three monophosphine... 

Tertiary arsines have been widely employed as ligands in a variety of transition metal complexes (74), and they appear to be useful in synthetic organic chemistry, eg, for the olefination of aldehydes (75). They have also been used for the formation of semiconductors (qv) by vapor-phase epitaxy (76), as catalysts or cocatalysts for a number of polymeri2ation reactions (77), and for many other industrial purposes. 

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. 

In view of the excellent donor properties of tertiary arsines, it is of interest to inquire whether these cyc/o-polyarsanes can also act as ligands. Indeed, (MeAs)s can displace CO from metal carbonyls to form complexes in which it behaves as a uni-, bi- or triden-tate ligand. For example, direct reaction of (MeAs)5 with M(CO)6 in benzene at 170° (M = Cr, Mo, W) yielded red crystalline compounds [M(CO)3( -As5Me5)] for which the structure... 

The number of gold complexes containing tertiary phosphines, arsines, or stibines as ligands is large because of the wide use of the fragment AuL+, mainly with L = PPh3, in the synthesis of... 

The As—N bond is labile and this has been widely exploited in synthetic arsenic chemistry. Some idea of the versatility168 can be seen from Schemes 1 and 2. Refluxing secondary amines with tris(dimethylamino)arsine effects transamination (equation 6). These tris(dialkyl-amino)arsines undergo the general reactions in Scheme 1, enabling ready access to a wide variety of compounds, many of them finding use as ligands in transition metal complexes (see Chapter 14 of this work). 

Routes have been developed to the hitherto unobtainable arsine—alkene ligands (CH2=CHCH2 CH2 ) As(CH2 CH2 CH2 AsMe2 )3 (n = 1, tasol, but-3-enylbis(3-dimethyl-... 

Trialkyl and triphenyl substituted tertiary arsines and stibines are, like the phosphine analogues, suitable as ligands in transition metal complexes in several oxidation states, due to their low reduction potentials (cf Table 7 in Section III.A.l) and relatively high oxidation potentials (cf Table 14 in Section V.A). 

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