Pentavalent phosphorus oxide

SPO compounds are in equilibrium, which could lead to the pentavalent phosphorus oxide preligand and the trivalent phosphinous acid ligand. 

Pentavalent phosphorus derivatives can be converted to phosphonyl halides or phosphine oxides by partial hydrolysis or by other oxygen donors. 

Compounds of tnvalent phosphorus are generally oxidized to pentavalent phosphorus denvaPves bis(fluoroalkyl) and tns(fluoroalkyl) phosphites are oxi dized to the corresponding[106, lOI] (equation 92)... 

A case of a pentavalent phosphorus-atom oxidation is documented for a.a-dicarbonyl-phosphoranes (equation 17)". When treated with DMD, the corresponding a tricarbonyl... 

As a potential class of compounds we came to consider phosphine oxides, reasoning that pentavalent phosphorus compounds are certain not to interact strongly with Ru. 

Compounds of trivalcnl phosphorus are generally oxidized to pentavalent phosphorus derivatives, which in turn can be oxidized to a higher oxidation state. The oxidation of phosphanes takes place readily and is accomplished by a series of reagents. For example, the oxidation of bis(pentafluorobenzyl)phosphanc is accomplished simply by stirring a solution of the substrate in an open flask for several hours (Table 17).269... 

Three phosphonites (RO)2PR have also been found to add to la. The products contained the bicyclo[l.l.l]pentane cage inserted into the P—C bond and were isolated after oxidation to stable pentavalent phosphorus derivatives125. In a related process involving... 

Phosphacyclobutene P-oxides 64 are produced by the reaction of titanacyclobutenes with dichlorophenylphosphine <07CEJ4077>. The large instability of heterophosphete compounds 65, composed of a four-membered unsaturated ring with a pentavalent phosphorus atom and a heteroatom, has been identified and characterised by first-principle molecular orbital computations, at several levels of theory showing that strong electron-... 

The Michaelis-Arbuzov reaction is the most used and well-known method for the synthesis of phosphonates and their derivatives and may also be used to synthesize phosphinates and tertiary phosphine oxides. The simplest form of the Michaelis-Arbuzov reaction is the reaction of a trialkyl phosphite, 3, with an alkyl halide, 4, to yield a dialkyl alkylphosphonate, 6, and new alkyl halide, 7 (Scheme 2). During this transformation the phosphorus atom of a ter-valent phosphorus(III) species (3) acts as a nucleophile resulting in the formation of an intermediate alkoxy phosphonium salt 5, containing a new [P—C] bond. The precise structure of the intermediates 5 is a subject of debate—as reflected by common reference to them as pseudophosphonium salts —with a penta-coordinate species (containing a [P—X] bond) being proposed and detected in some cases.18 Decomposition (usually rapid under the reaction conditions) of the intermediate 5 by nucleophilic attack of X- on one of the alkyl groups R1, with concomitant formation of a [1 =0] bond yields the product pentavalent phosphorus(V) compound (6) and the new alkyl halide, 7. 

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.

Many chemical molecules that are not stable under normal conditions at room temperature are found in high-temperature vapors. These include gaseous molecular forms of compounds such as metal oxides or chlorides that are normally encountered as solids at room temperature. Other species found in high-temperature vapors have unusual valencies and coordination numbers. Examples are the molecules OPCl and O2PCI, which contain unusual two-coordinate trivalent and three-coordinate pentavalent phosphorus atoms, respectively. It is of interest to study such species to extend our knowledge of the structure and bonding of small molecules to new regions of the periodic table. Moreover, many such species are proposed chemical reaction intermediates. 

In this ehapter, DN agents are defined as OP eompounds of pentavalent phosphorus that produee OPIDN. Examples shown in Figure 57.3 are ethyl -oetylphosphonofluoridate (EOPF) and 2-(2-methylphenoxy)-4iT-l,3,2-benzodiox-aphosphorin-2-oxide [2-(2-methylphenoxy)-BDPO], the active metabolite of the arehetypal DN agent, tri-o-eresyl phosphate (TOCP) (Wu and Casida, 1995). 

Treatment of diphenyl diselenide with tributylphosphine in an alkaline medium generates a benzeneselenolate anion [24], which reacts with various electrophiles, such as halides, epoxides, a, -unsaturated ketones, to generate various selenides [24,25]. The mechanism for the generation of the benzeneselenolate is proposed as shown in Scheme 17 [25]. A selenophosphonium ion and/or a pentavalent phosphorus species are initially formed in the reaction of diphenyl diselenide and tributylphosphine, and then the addition of sodium hydroxide liberates the benzeneselenolate and phosphine oxide. 

A similar oxidation of trivalent phosphorus to pentavalent phosphorus occurs in trialkyl or triaryl phosphites. Triphenyl phosphite is converted by ozone in dichloromethane at 5-10 C into triphenyl phosphate in 95% yield [775] and by argentic oxide in 30% yield [557] (equation 538). 

The l,3-azaphospholo[5,l-i]benzothiazole (36) does not react with 2,3-dimethylbutadiene or with isoprene alone. However, if the reaction is carried out in the presence of O2, Sg or Se , the [4 + 2]-cycloadduct (37 X = O, S, Se) with pentavalent phosphorus is obtained (Equation (3)). The reaction with isoprene occurs regioselectively <93PS(77)235>. It is suggested that the phosphorus is first oxidized to give a transient species with a three-coordinate pentavalent phosphorus, which subsequently... 

Oxidation of trifluorophosphine by halogens is well known (282) and although corresponding reactions with alkyl or aryl fluorophosphines have received only little attention, it has become apparent that oxidation to the pentavalent phosphorus fluorides can be brought about by a wide variety of reagents. In certain cases the reducing property of the fluoro-phosphine has been utilized in the synthesis of zero-valent transition metal fluorophosphine complexes (Section IX). 

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