Trivalent phosphorus atom

Fe—Fe bond can be assigned structures 201 or 202 based on spectral data. The other product of this reaction is 193 (R = r-Bu), however, it is produced in minor amounts. Complexes 199 (R = R = r-Bu, R = Ph, R = r-Bu) were obtained. Reaction of 146 (M = Mo, R = Ph, R = R = Ft, R = r" = Me) with (benzyli-deneacetone)iron carbonyl gives rise to the bimetallic complex 200 (M = Mo), which reacts further with the free phosphole to form the bimetallic heteronuclear sandwich 203. The preferable coordination of the molybdenum atom to the dienic system of the second phosphole nucleus is rather unusual. The molybdenum atom is believed to have a greater tendency to coordinate via the trivalent phosphorus atom than via the dienic system. 

The trivalent phosphorus atom in triphenylphosphine is quantitatively oxidized by in-situ-generated or isolated DMD, to afford triphenylphosphine oxide under a variety of conditions Recently, the selective oxidation of the phosphite functionality in nucleosides was reported to produce the corresponding nucleotides in nearly quantitative yields". One example of such an oxidation is shown in equation 16, to illustrate that this phosphorus oxidation may offer an expedient way of preparing unusual nucleotides. 

Phosphaalkenes, P=C compounds with a trivalent phosphorus atom, can react with various C=C compounds, like maleimide (Scheme 9) <2002JOM(643)409>, cyclobutadienes (Equation 27) <1994T759>, and C C compounds, like ynamines (Scheme 10) <2003EJ0512>, to afford the corresponding phosphetanes and phosphetenes. 

Oxidation of the trivalent phosphorus atoms in the tetrasubstituted [l,4,2,3]diazadiphospholo[3,2-6]diazadiphosphole (82) is accompanied by rupture of the P—P bond to give the 9-oxa-2,4,6,8-tetraaza-l,5-diphosphabicyclo[3.3.1]nonane-3,7-dione 1,5-dioxide (83), whereas reaction with sulfur at 180-200 °C gives the corresponding 2,3-disulfide without cleaving the P—P bond (81CB2132). 

Fig. 1. Molecular structure of P408 schematic illustration of the different P—0 linkages. (H) P(III)—Oa ( ) P(III)—Ob (El) P(V)—Ob and ( ) P(V)—Oc. To specify the different atoms forming the phosphorus oxide molecules, the following nomenclature will be used P(III) denotes a formally trivalent phosphorus atom P(V), a formally pentavalent phosphorus atom. Oa denotes a bridging oxygen atom between two P(III) atoms Ob, a bridging atom between a P(III) and a P(V) atom and Oc, a bridging oxygen atom between two P(V) atoms. Od denotes a terminally bonded oxygen atom.

Cationic polymerization of cyclic compounds containing trivalent phosphorus atom has also been reported. Monomers include cyclic phoshites (a) [223,224], phosphonites (b) [225-227], and deoxophosphones (c) [228] ... 

The trivalent phosphorus atom bears a lone pair of electrons and therefore can be used as a nucleophilic reagent for substitution. Triphenylphosphine displacements on alkyl halides give phosphonium salts which, after the conversion into phosphorus ylides by strong bases. 

In this case the water attacks and hydrolyzes not a cation but a small, highly charged center (the trivalent phosphorus atom) re.sulting from the inductive effect of the chlorine atoms. 

A combination of TMEDA and MCjSiCl makes benzylic copper reagents more stable and permits their applications to conjugate addition to a,P-unsaturated esters. Chelation control is manifested in the cuprate addition to conjugate esters by a trivalent phosphorus atom 8 bonds away. ... 

Interest has continued in the extent to which factors affecting the planarity of the trivalent phosphorus atom have a bearing on the aromaticity and other properties of the phosphole ring system, and a review has appeared. A study of the coordination chemistry of phospholes bearing a sterically bulky substituent at phosphorus has shown that coordination to platinum results in increased pyramidality at phosphorus. In the same vein, an ab initio theoretical study of the triphosphole (357) has shown that the steric interac-... 

In general, therefore, our research results are related to the study of the electrophilic properties of the two-coordinate, trivalent phosphorus atom in (methylene)phosphine (1) and the isoelectronic phosphinimine (2). In particular, the novel reactions of these compounds with allenes, acetylenes, acetylenic halides and alcohols as well as selected diketones will be described in this paper. 

The mechanism of asymmetric induction at a trivalent phosphorus atom was explained by formation of pentacoordinated transition state b, pseudo-rotation, and exchange of ligands at a pentacoordinated phosphorus atom, resulting in the thermodynamically more stable diastereoisomer. The effect of the reaction conditions on the diastereoisomeric ratio of products c shows thermodynamic control. For example, a decrease of the reaction temperature reduces the stereoselectivity, which is impossible with kinetic control, because the temperature lowering leads to a deceleration of the equilibrium establishment of pentacoordinated intermediate complex (Scheme 16) [33]. 

Scheme 16 The mechanism of asymmetric induction at the trivalent phosphorus atom...

When trivalent phosphorus atoms link together as in diphosphine, P2H4 (3.10a), each P atom contributes an electron to form the single covalent bond. A similar situation exists with pentavalent derivatives such as hypophosphoric acid, H4P2O6 which can be represented as in (3.10b). The phosphoryl bonds in the compound are donor type as in POCI3 above, with two electrons being provided by each P atom to complete the formal octet around the O atoms. It is, however, usually more convenient to represent the electronic formulae as in (3.10c). Examples of donor-type P — P linkages are known but these are very rare. In MejP — PFj, both electrons for the bond are provided by the same P atom (3.10d). 

Cationic ROP of cyclic monomers, containing trivalent phosphorus atom, °° proceeds by two mechanisms of propagation ionic and/or covalent. These both can be visualized best for the polymerization of structure 49. Monomer 49 polymerizes by CFsSOsMe initiator... 

The planarity of phosphinines and the formal /7 -hybridization of the phosphorus atom do not allow the introduction of P-stereogenic centers within the heterocycle, as it is common for classical phosphines based on a trivalent phosphorus atom. 

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