Phosphine tertiary alkyl derivatives

The tertiary phosphine-stabilized alkyl derivatives Co(R)(CO)3(PMePh2) (R = Me, CH20Me) undergo carbon monoxide insertion, as expected. On the other hand. 

Structural studies " by X-ray diffraction methods have shown that tertiary phosphine-substituted alkyl and acyl tricarbonyl derivatives of formula Co(R)(CO)3(PR3) have a distorted trigonal-bipyramidal structure, with the R and PR3 ligands in the following axial arrangement ... 

Tertiary oxides containing a hydroxy groups are less stable than simple alkyl derivatives, and undergo thermal decomposition at about 100°C to form secondary phosphine oxides (6.120). Tertiary oxides can be reduced to tertiary phosphines with lithium aluminium hydride (6.58). Alkali hydrides form phosphinite derivatives (6.121). 

PH3 itself is cytotoxic and used as a fumigant against pests in stored products. It inhibits mitochondrial respiration but the details of the process are unclear. The oxidation pathways for PH3 differ significantly from those of tertiary phosphines PR3 and for these the available pathways depend on the substituents R. Pathways involving radicals usually lead to p-sdssion when R = aryl but a-scission when R = alkyl. The autoxidation of alkyl phosphines is usually rapid compared to aryl phosphines. Similar differences exist in the reduction of disulphide bonds the alkyl derivatives are more reactive. 

Advances in the use of anionic stereogenic phosphorus have been interesting. Acylation of lithium o-anisylphenylphosphide with chloro-formates bearing chiral alkyl groups provided a diastereomeric mixture that could be induced to undergo an inversion at phosphorus (at relatively low temperature) to form the more favorable diastereoisomer in a crystalline lattice.186 Subsequent conversion to the quaternary phos-phonium species was followed by removal of the acyl group and isolation of the chiral tertiary phosphine as the borane derivative (Equation 3.10). 

Amphiphilic tertiary phosphines have their phosphorus donor atom located somewhere in the hydrophobic part of the molecule and should have at least one long alkyl or alkyl-aryl chain carrying a polar head group (Scheme 4. 10). Some of them, such as the sulfonated derivatives, are quite well soluble in water, others, such as Ph2P(CH) COOH (n = 3, 5, 7, 9, 11) are practically insoluble, however, can be easily solubilized with common surfactants (SDS, CTAB etc.). 

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. 

The photochemistry of these aryl complexes has been briefly investigated by Nesmeyanov and co-workers (98,98a) and is quite similar to that of the analogous alkyl complexes. Irradiation of CpFe(CO)2Ar complexes in the presence of tertiary phosphines at room temperature led to the formation of the corresponding monosubstituted derivatives (98) [Eq. (96)]. Prolonged irradiation in the presence of triphenylphosphite... 

The combination of triphenylphosphine with esters of trihaloacetic acids provides a reagent system for the stereo- and regio-selective conversion of alcohols into alkyl halides.The bromine-triphenylphosphine adduct has been used at low temperatures (-50 C in dichloromethane) for the removal of the tetrahydropyranyl protecting group from tetrahydropyranyl ethers derived from secondary and tertiary alcohols.The reactions of tertiary phosphines (and other trivalent phosphorus compounds) with iodine in aprotic solvents have received further study, a range of species being identified.The first reported study of the reactions of trivalent phosphorus compounds with monopositive astatine has led to the identification of stable complexes with triphenylphosphine, trioctylphosphine, and triethylphosphite. 

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