Bidentate phosphorous

Fig. 7 Two configurations of a bidentate phosphorous ligand with rhodium...

Sasaki, Y., Umetani, S. 2006. Comparison of four bidentate phosphoric and diamide compounds for the extractability of actinides. Journal of Nuclear Science and Technology 43(7) 794-797. 

Enantioselective telomerization reactions of the dicarborative type are achieved using homogeneous palladium catalysts derived from palladium(ll) salts [Pd(OAc)2] which are chirally modified with bidentate phosphorous ligands such as 4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-l,3-dioxolane (Diop), (2R,3R)-2,3-bis(diphenylphosphino)bicyclo[2.2.1]hept-5-ene... 

There are few examples where the absolute stereochemistry is determined in the PKR. Verdaguer has demonstrated the use of a bidentate phosphorous-sulphur ligand to provide an enantiopure cyclopentenone in for the synthesis of the HIV drug (-)-abacavir. The achiral alkyne cobalt complex is generated first in 1 h at room temperature. Heating with enantiopure R,S-ligand 102 provides a separable mixture of diastereomeric... 

SCHEME 20.7 Examples using bidentate phosphorous hgands. 

Abstract This chapter focuses on carbon monoxide as a reagent in M-NHC catalysed reactions. The most important and popular of these reactions is hydro-formylation. Unfortunately, uncertainty exists as to the identity of the active catalyst and whether the NHC is bound to the catalyst in a number of the reported reactions. Mixed bidentate NHC complexes and cobalt-based complexes provide for better stability of the catalyst. Catalysts used for hydroaminomethylation and carbonyla-tion reactions show promise to rival traditional phosphine-based catalysts. Reports of decarbonylation are scarce, but the potential strength of the M-NHC bond is conducive to the harsh conditions required. This report will highlight, where appropriate, the potential benefits of exchanging traditional phosphorous ligands with iV-heterocyclic carbenes as well as cases where the role of the NHC might need re-evaluation. A review by the author on this topic has recently appeared [1]. 

Amides of phosphorous acid (e.g., P(NMe2)3 and the bicyclic compound (L16)) are useful ligands for cross-coupling of arylboronic acids with aryl bromides and chlorides (system Pd(OAc)2/2L, Cs2C03, toluene, 80 °C), the bicyclic amide being markedly more effective than simple acyclic ones.421 Amides of phosphinous acids are also excellent bidentate ligands with PN coordination mode ((L6), Section 9.6.3.4.2). 

Monodentate (monometallic monoconnective) phosphor-1,1-dithiolato ligands are rare. Bidentate (monometallic biconnective) form chelate rings and three sub-types can be distinguished according to the degree of asymmetry (Scheme 2). The most asymmetric type (anisobidentate) occurs when a covalent bond is associated with a secondary bond this takes place mostly in main-group metal complexes. The second type is rare and is the result of the association between a covalent and a dative coordinate bond. The symmetric bidentate bonding (isobidentate) is found mainly in transition metal complexes. 

The coordination patterns of dithioarsinates identified so far are similar to those of phosphor-1,1-dithiolates, i.e. monodentate, bidentate chelating (symmetrical and unsymmetrical) and bridging. 

Recovery of actinides at the RFP with an organic phosphorous bidentate extractant has been proposed. A conceptual production flow sheet is shown in Figure 3. The bidentate reagent, dihexyl-N, N-diethylcarbamoylmethylenephosphonate (DHDECMP), is especially attractive since it can recover actinides from MSE residues containing aluminum. The cation exchange process is unable to effect actinide purification when aluminum is present. (DHDECMP extracts actinides and lanthanides, but does not extract common RFP contaminants, e.g., aluminum. No lanthanides are used in process streams at RFP.)... 

Mercury(II) reacts with phosphines to form 1 1 or 1 2 complexes of the general type HgLX2, where X is an anionic ligand such as halide or nitrate. The values of the coupling constants are useful in elucidating the structures of these compounds. Complexes with bidentate ligands that contain phosphorous and group 16 donor atoms (S, Se) are also known. These have been characterized by P, Se, and Se, and Hg NMR spectroscopy and by electrochemical... 

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