Thermolysis phosphorus compounds

Amino, alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

Various methods, such as thermolysis, photolysis, interaction with triva-lent phosphorus compounds [e.g., PR3, P(NR2)3, P(OR)3] or bases, and reaction with nickel catalysts or oxidizing agents (e.g., H2O2, RCO3H), are useful for the ring-contraction reaction of heterocycles by sulfur extrusion. In a number of cases, the reagent adds to the sulfur atom in a first reaction step (Scheme 4). Hence, instead of elemental sulfur, its derivatives are eliminated in the subsequent ring contraction, such as SO2 in the presence... 

The generation of an aryl phosphenite (150) from a 7-phospha-norbornene derivative (151) by thermolysis or photolysis has been investigated. Thermolysis gave a condensate containing some (150) besides dimers and trimers photolysis, however, gave no fragmentation products from (151) or from similar phospha-norbornenes unless alcohols were present. Photolysis of 7-phospha-norbomenes is therefore not a route to two-co-ordinate phosphorus compounds, as assumed earlier. 

Sulphur-Nitrogen-Phosphonis Compounds.—Thermolysis of compounds of the t3rpe RgPCl N—SOgX (R = Cl, Me, or Ph X = F or Cl) has been shown 2 to result in the formation of the compounds R2P(0)C1 and [NS(0)X] . Pyrolysis of phosphorus-sulphur-nitride halides with longer chains yields, amongst others, the cyclic compounds (37) and (38). The... 

The preparation of similar precursors suitable for the deposition of metal nitrides is analogous to the preparations of phosphorus and arsenic compounds. The initial reaction of metal trialkyls MR3 (M = A1, Ga, In) with amines (NHR 2) results in the formation of oligomeric amido compounds [R2MNR 2] (n = 2 or 3) which eliminate alkanes on thermolysis. The incorporation of a proton as a substituent on the pnictide bridging ligand has been examined, and many compounds of the type [R2MNHR ]2 have been synthesized. The presence of this proton may facilitate /3-elimination, allowing lower deposition temperatures to be used. 

Betaines 261 are stable crystalline compounds. Knowledge of their chemical reactions is still limited. Alkaline hydrolysis of aryl derivatives (261 R = Ar) gives the 2-azobenzoic acids 266 but the mechanism of this rearrangement is unknown. Reduction by tin and hydrochloric acid gives the hydrazides 267. Thermolysis of the p-tolyl compound (261 R = p-MeC6H4) (120 C at 0.1 mm Hg) gives the isomeric triazine (268 R = >-MeC6H4). Phosphorus pentasulfide converts the 2-methyl derivative (261 R = Me) into 2-methyl l,2,3-benzotriazinium-4-thiolate (272 R = Me) (Section in,B,15). 

Since 1965 we have found an unexpected number of binary phosphorus hydrogen compounds in addition to the well-known hydrides PH and 2H4 (Table I). These phosphanes have been detected in the hydrolysis products of calcium phosphide or in the thermolysis products of 2H4 mass spectroscopy. Only the compounds... 

A fascinating analogy between cp and Ps became apparent by the isolation of the mixed ferrocene cp Fe(P5), where cp represents pentamethylcyclopentadienyl and (P5) the planar, strictly pentagonal phosphoras unit (52). The compound is prepared in the thermolysis of [cp Fe(CO)2]2 in the presence of white phosphorus. The Ps unit, which clearly acts as a six-electron donor in this mononuclear complex, can also function as a central unit in a cationic triple-decker cation [(cp)Fe(P5)Fe(cp )]+ (53).i ... 

Bis(diisopropylamino)phosphanyl(trimethylsilyl)diazomethane 6, easily available by treatment of chlorobis(diisopropylamino)phosphane with lithiated diazo(trimethylsilyl)methane, provides upon flash thermolysis at 250"C the so-called stable carbene 7.38,39,40 behaves partly as a nucleophilic carbene and reacts only with electron-deficient alkenes such as methyl propenoate or diethyl fumarate under cyclopropanation." In the former case only the Z-isomer 8 is formed. Cyclopropane 9 is thermally unstable and is, therefore, oxidized in situ at the phosphorus atom with elemental sulfur to provide cyclopropane 10, Cyclopropanes 8 and 9 are also generated from the diazo compound 6 and the appropriate alkene by photolysis." ... 

Addition compounds form between aluminium chloride and the silylphosphines Me3SiPEt2 or Me H3 SiPMe2, which on heating lose methylsilyl chloride, giving trimeric aluminium-phosphorus heterocycles such as (29). The thermolysis product from the adduct Me3SiPMe2,H2AlCl is similar to (29), but the... 

NMR spectroscopy has shown that many compounds, previously described as (1-hydroxyalkylidene)bisphosphonic esters, are actually either totally rearranged compounds or mixtures of initial and rearranged compounds. Such was the case with the products from dialkyl hydrogenphosphonates and dialkyl acylphosphonates, for which, when R R the potential for confusion is obvious (Scheme 18). Provided that the compounds 104 are not heated above 80 °C, they may sometimes be isolated by crystallization, but others, e.g. 104 (R = Ph or aryl), rearrange very easily and cannot be isolated. (1-Hydroxyethylidene)bisphosphonic acid is stable in solution at pH 1.6 up to 125 °C, and in alkaline solutions at pH 8.5-11.5 up to 195 °C the compound then undergoes thermolysis with fission of the carbon-phosphorus bond to give, initially, acetylphosphonic and (1-hy dr oxyethy l)phosphonic acids ... 

The well-known retro-Diels-Alder expulsion of SO2 and liberation of buta-1,3-diene when their adduct is heated has analogies in the phosphorus field. Flash thermolyses of the cyclic phosphonic ester 493 (R = OMe) and of the phosphinic ester 493 (R = 2,4,6-trimethylphenyl) afford buta-1,3-diene and the highly reactive metaphosphate 494 (R = OMe) or metaphosphonate 494 (R = 2,4,6-trimethylphenyl) species. The elimination of phenylmetaphosphonate or an analogous species was observed during the thermolysis of the 1,3,2-dioxaphospholanes 495 [Ar = (a) Ph or (b) (l,l -biphenyl)-2-yl or (c) 2,4,6-tri-tcrt-butylphenyl ] at 700-800 °C here the respective metaphosphonates were characterized through the formation of the indicated known products. The compound 496 (Ar = Ph)... 

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