Nickel complexes arsenic ligands

The corresponding palladium compound (157) must be formulated as [Pd(TA)Br]+Br. The cation is essentially square-planar, but the bromine atom is displaced 10° out of the arsenic-palladium plane. Such a distortion is very unusual for palladium, and may be due to a steric effect of the alkyl chains in the arsine ligand. This might similarly account for the distortion of the nickel complex from a square pyramidal shape. 

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. 

The most common nickel(O) complexes are those containing phosphorus, arsenic and antimony as donor atoms. Besides the Malatesta and Cenini book/1 which specifically deals with metal(O) complexes, nickel(O) complexes have been summarized in books and review articles which report complexes with phosphine, arsine and stibine ligands.31-37 Actually the nickel(O) complexes with these ligands amount to hundreds and the number of new complexes which are synthesized is increasing very rapidly, making nickel(0) phosphine chemistry a very extensive topic. 

Hydrated nickel(II) salts in the presence of the ligand p3 react with both white phosphorus and yellow arsenic, breaking up the structure of the tetraatomic P4 and As4 molecules to form triatomic cyclo-triphosphorus and cyc/o-triarsenic species. These fragments act as trihapto ligands yielding double sandwich complexes (equation 99).292 The compounds are air-stable both in the solid state and in solution. Upon reduction with NaBH the complexes of equation... 

A typical structure of these so called triple-decker sandwich complexes is that of the complex [(p3)Ni -(j)3-P3) Ni(p3)](BPh4)2-2.5Me2CO (73). In each complex the trihapto P3 (or trihapto As3) groups form a bridge between the two Ni(p3) residues.292 Each nickel atom is thus six-coordinated by three phosphorus atoms from the ligand p3 and by three phosphorus atoms from the cyclo-P3 (or arsenic atoms from the cyclo-As ), which acts as a three-electron-donor ligand. 

The ligands triphos or/ and np in presence of compounds of iron, cobalt, nickel, rhodium, iridium and palladium, by reaction with THF solutions of white phosphorus, P, or yellow arsenic, As, form mononuclear or dinuclear sandwich complexes containing the cyclo-triphosphorus or cyclo-triarsenic units which behave as 3n-electrons rings. 

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