Phosphine pseudohalide

Ligand A anionic (e.g., halides, pseudohalides, alkyl, aryl, thiolate, alkoxide) ligand N neutral (e.g., amines, imines, phosphines, carbenes, nitriles, isonitriles, NO, CO) ligand C cationic (e.g., NO+)... 

A major group of rhenium(II) complexes is characterized by two chelating bis-phosphines forming the equatorial plane of a distorted octahedron (263). The axial ligands can be varied and representatives with halides, pseudohalides, thiolates, and nitriles have been studied extensively. 

Lever has successfully predicted Mn"/ potentials of 24 Mn-carbonyl complexes containing halide, pseudohalide, isonitrile, and phosphine co-ligands, with additivity parameters derived from the potentials of Ru "/" couples [39]. An important consideration for heteroleptic complexes is the influence of isomerism on redox thermodynamics. For Mn(CO) (CNR)6- complexes, with n = 2 or 3, the Mn"/ potentials for cis/trans and fac/mer pairs differ by as much as 0.2 V [40]. The effect arises from the different a-donor and 7r-acceptor abilities of carbonyl (CO) and isocyanide and their influence on the energy of the highest energy occupied molecular orbital (HOMO). 

The hydride complexes [MoH(CO)2(chel)2]+ (chel = variety of chelating diphosphines and arsines) are prepared by protonation of the parent Mo° dicarbonyls and appear to have a monocapped octahedral structure in solution, with the fluxional hydride moving around the possible capping positions. This process has been extensively studied by NMR.65 A number of other cationic seven-coordinate analogues [MoX(CO)2(chel)2]+ (X = halide or pseudohalide chel = chelating ligand usually phosphine or arsine) are also known (Table 5).la... 

R = alkyl, aryl, acyl X = halide or pseudohalide L = phosphine ligand... 

Tertiary phosphines form a wide range of complexes of the type PtX2(PR3)2 (X - halide, pseudohalide R = alkyl, aryl or mixed alkylaryl). Space limitations preclude this chapter becoming a compendium of known compounds, therefore for each individual complex the reader is directed to Chemical Abstracts, Gmelin or the book by McAuliffe which contains extensive tabulations of compounds.1225 In this chapter we outline the general methods of synthesis, the properties, and the structures and spectral features which we expect to be found with this class of compounds. 

Among these, halide and pseudohalide complexes of the general formula AgP X (where X = halide or pseudohalide, P = phosphine and n = 1-4) have been studied in detail. 

Table 25 Distances (pm) in some Silver Halide (or Pseudohalide) Phosphines (for Ag—X and X—X, the maximum and minimum values are given if available)...

Other pseudohalides are carbonylated. Benzoic acid derivatives are prepared from arenediazonium salts at room temperature without addition of a phosphine ligand [223], For example, the acid anhydride 457 is prepared by the carbonylation of the benzenediazonium salt 456 in the presence of AcONa. By this method, nitrobenzene can be converted to benzoic acid indirectly. 

Aryl chlorides are more reluctant to participate in amination than most other aryl halides/pseudohalides. To tackle this problem, Caddick et al. examined the effect of palladium-N-heterocyclic carbenes as catalysts in rapid microwave-promoted reactions [87]. Para-tolyl and -anisyl chloride were reacted with aromatic and aliphatic amines in mostly good yields within 6 minutes of heating at 160 °C. Reactions using anisyl, tolyl or phenyl chlorides and aliphatic amines have also been reported by Maes et al. using a phosphine ligand and a strong base, which creates the desired products after 10 minutes of heating at 110-200 °C [88]. 

The precise nature of the product obtained depends on the cation used and also on the halide and the solvent. There is a variety of halide complexes with other ligands present such as Mnl2(thf)3, trnns-[MnCl4(H20)2]2 , and amine and phosphine species. Homoleptic pseudohalide complexes are represented by [Mn(NCS)6]4 and [Mn(CN)6]4, as well as Prussian blue-like analogues, e.g., K2Mnu[Mnn(CN)6], that are ferrimagnetic.3... 

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