Polyphosphine metal complexes

Polydentate polyphosphine metal complexes freqnently show greater catalytic activity than the monophosphine-type complexes so far discussed. In addition, asymmetric polydentate complexes (whether the asymmetry arises on the P atom or another atom) may catalyse asymmetric syntheses, that is, the production of a single optical isomer, sometimes of nearly 100% optical purity (Chapter 13.2). In the presently known field of asymmetric catalytic ligands, P componnds figure prominently and are of ever-growing importance. BINAP (12.372d) represents a family of such ligands, many of which have C2 symmetry (12.373). 

M. Reactions of Metal Complexes with Polyphosphines and Polyarsines... 

By using a combination of known reactions, synthetic chemistry, and electrochemistry, new catalysts for the electrochemical reduction of CO2 have been developed. Consideration of the electrochemical properties of a variety of transition metal complexes containing polyphosphine ligands led to a more detailed study of metal complexes of the type [M(PP2)(PR3)HbF )2 (where M is Ni, Pd, and Pt ... 

More recent work on the hydrogenation of thiophenic molecules catalyzed by water-soluble metal complexes is pursuing the use of polyphosphine ligands (cf. Section 3.2.2). These studies follow the success obtained with the tridentate phosphine MeC (CH2PPh2)3 (TRIPHOS), which forms rhodium and iridium catalysts for the hydrogenation, hydrogenolysis, and desulfurization of various thiophenic... 

Of the 33 papers presented at the symposium 32 are included in this volume. They are of two general types. One type discusses inorganic compounds exhibiting a specific property, most frequently electrical or photochemical. The second type reviews recent developments in the synthetic chemistry of a class of inorganic compounds— most often transition metal or lanthanide complexes— which are of potential interest to persons looking for new systems with unusual properties. Classes of compounds covered by this second type include metal alkyls, metal alk-oxides, metal alkylamides, metal chelates, and metal clusters as well as metal complexes with polyboranes, polyphosphines, macrocyclic derivatives, di- and triketones, and polypyrazolylborates as ligands. 

Keiter s data suggest that the best results are obtained by building the polyphosphine from a vinylphosphine ligand bonded to the transition metal complex of interest. This approach should be limited only by the lability of the complex and the susceptibility of other attached ligands to reaction under the experimental conditions employed. It should also lead to syntheses of new cyclic and acyclic tri- and tetra-phosphines coordinated to the metal (or cluster) used for the template. 

A. Caminade, J.-P. Majoral, and R. Mathieu, Synthesis of polyphosphine and phosphene transition metal complexes, Chem. Revs., 91, 575, 1991. 

Phosphinidenes, RP, although not radicals (Table 13.12), can be identified as species formed on thermolysis or photolysis of polyphosphines such as (PPh)5 (Chapter 6.17). They also form metal complexes (Chapter 8). The first phosphinidene, which was observed in 1994 by Caspar et al. using ESR spectroscopy, was (13.146a) [18-20]. 

OsA Studies of (o-metallated phosphine) (polyphosphine) complexes 20000M2310, 20000M1166... 

Metal carbonyl complexes are reported for triphenylcyclotriphosphine Ph3P3210 and the polyphosphines (12) and (13).211 Peaks associated with the ionization of the phosphorus lone-pair electrons of (13) and the analogous pentamer can be assigned in the photoelectron spectra, giving values which imply that any (p-d)ir-bonding must be relatively unimportant.212 Anion... 

Generally, these compounds form complexes with alkaline-earth metals that are less stable than the corresponding complexes of the polyphosphonic acids. WeiB and Hagele [96] investigated the chromatographic behavior of a variety of aliphatic and olefinic polyphosphonic and polyphosphinic acids, respectively, with 1 to 4 phosphorus atoms [87,88], that are applied in medicine and in pharmaceutical chemistry. 

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