Divalent phosphorus ligands

Thus it has so far proved possible to isolate stable derivatives of monomeric metaphosphoric acid and of metathio- and metaselenophosphoric acid, which, understandably, generally bear tert-butyl and/or trimethylsilyl substituents u. Specifically, we know aminobisiminophosphoranes (3, Z = NR2, X = Y = NR)2,3,4), aminoiminothio (or seleno)phosphoranes (5, Z = NR2, X = NR, Y = S or Se)5), and aminoiminomethylenephosphoranes (1, R = NR2, X = NR)6>. Conspicuously, no stable phosphorus(V) three-coordinate compounds have been synthesized with oxygen as divalent ligand. 

Neutral phosphorus(V) compound containing divalent tridentate azo ligands were studied by Cavell and coworkers.83 The 31P and, 9F chemical shifts and /(31P, 19F) coupling constants are collected in Tables 9 and 10 for (2,2 -azophenoxy)trifluorophosphorus (22), /rans-(2,2 -azophenoxy)(trifluoro-methyl)difluorophosphorus (23) and cis-(2,2 -azophenoxy)(trifluoromethyl) difluorophosphorus (24). 

Cavell et al. have synthesised and characterised a series of neutral, hexaco-ordinate phosphorus compounds containing divalent, tridentate diphenol imine, azo and thio ligands. For example, the reaction of silylated Schiff base ligands e.g. 112) with PCI5 gave the neutral, hexacoordinate compound 113 by... 

The synthesis and characterisation of neutral hexacoordinate phosphorus(V) compounds (perphosphoranides) containing divalent tridentate diphenol imino, azo and thio ligands has also been reported.The hexacoordination was revealed by their high-field 53ip values, characteristic Jpp coupling and crystal structures. Two compounds of particular interest are the trihaloperphosphoranides (77 Hal = Cl, F), with respective Ssip values of —136.4 and —136.9. 

Additives that are typically effective as antioxidants and UV stabilisers include hindered phenols, aromatic amines, hindered amines (only those that have a tendency to form N-oxides), hydroxylamines, benzofuranones, divalent sulfur compounds, phosphorus(III) compounds (phosphines and phosphites, with phosphites most common) and multidentate metal ligands (such as ethylenediaminetetracetic acid). Polymers to be processed above 300 C are exceptions as there are no commercial antioxidants thermally stable enough to be processed at that temperature. 

Other Lewis base derivatives are known as for example, with Et20, acetone, pyridine MeCN, BuNC. In the X-ray structure of the complex Cp2YbCl(Me2PCH2PMe2) (Tilley et al. 1983) where divalent Yb is oxidized by YbCls to the trivalent metallocene, Yb is coordinated to the two Cp ligands, to the chlorine and to one phosphorus of the dmpm ligand in a nearly tetrahedral arrangement. Yb-Cl bond length is 2.532(2), Yb-P is 2.941(3)A. 

Coleman and Gadian (1976) studied developing frog (Xenopus laevis) embryos. They deduced that the ATP molecules are liganded to divalent cations other than Mn, probably Ca or Mg. The internal pH of the embryo was found to be 6.8. Changes in Pj levels and levels of other phosphorus-containing compounds occurred during development of the embryo. 

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