Phosphiranes

Phosphirane, (CH2)2PH, mp = -121°C, bp = 36.5°C, can be made by reacting dichloroethane with sodiophosphine at low temperatures (6.831). At room temperature, this compound decomposes, yielding ethylene and other products [26]. Various other syntheses of phosphiranes have now been devised and known derivatives include those of types (6.832). The 5-coordinated derivatives appear to be very unstable. 

Methods of synthesis include rearrangement of compounds (6.624) and the use of terminal phosphinidene complexes (Chapter 8). 

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Unlike the other stmctural isomers of C2H N, /V-methylenemethylamine (33,34), ethylideneimine (35), and vinylamine [593-67-9] (36,37) and the analogous phosphoms compound, phosphirane (38), ethyleneimine is stable at room temperature provided CO2 is excluded from the air (39). Unexpectedly, ethyleneimine has the highest calculated relative heat of formation of the C2H N isomers (40). Relative calculated heats of formation are ethylideneimine. 

The proton affinities (gas phase) of thiirane and other three-membered heterocycles have been determined azirane (902.5), thiirane (819.2), phosphirane (815.0), oxirane (793.3 kJ moF ) (80JA5151). Increasing s character in the lone electron pairs decreases proton affinities. Data derived from NMR chemical shifts in chloroform indicate the order of decreasing basicity is azirane > oxirane > thiirane (73CR(B)(276)335). The base strengths of four-, five- and six-membered cyclic sulfides are greater than that of thiirane. 

Phosphetanium tetrachloroaluminum salt, 1-chloro-2,2,3-trimethyl-1-phenyl-synthesis, 1, 524 Phosphindole synthesis, 1, 517 Phosphine, pyrazol-l-yl-synthesis, 5, 236 Phosphirane, 1-phenyl-synthesis, 1, 525 Phosphirane, 1,2,3-tri-t-butyl-... 

Bachrach has argued against the surface delocalization by comparing the electron density at the centers of the banana bonds to that of the centers of cyclopropane 1 and phosphirane 10 (Scheme 3) [22]. Density is spread over the ring in 1, but not... 

It must be noted that the saturated ring system, the 1 -chloro-A -phosphirane was synthesized [84] a cyclic phospheniiun cation was postulated which is stable towards ring opening [85]. A corresponding cation could not be isolated, due to a methanid shift from a trimethylsilyl substituent. 

The most widely employed electrophilic phosphinidene complexes are generated from M(C0)5 (M=W, Mo, Cr) complexed 7-phosphanorbornadienes 7, which were reported by Marinetti et al. in 1982 [46]. They trapped the transient phosphinidene complex 8 at 110 °C (or at 55 °C if CuCl was used as catalyst) with olefins and alkynes to obtain three-membered phosphiranes and phosphirenes, respectively. 

Amino-substituted phosphirane complexes undergo retro-cycloaddition at 70-90 °C to give the trappable (OC)5WPNEt2 phosphinidene complex [55]. Other substituted phosphiranes are not suited to generate phosphinidenes because they require elevated temperatures, which typically induce thermal degradation instead. 

Treatment of the A -methylpyridinium salt of (65) with phosphiran gave a solid complex, pentacarbonylphosphiranmolybdenum(O) (66). 

EH MO calculations on the phosphiran (109) are relevant to microwave studies of compounds in this series. - The calculations suggest that inversion involves all the atoms of the ring, including the hydrogens, and that although the 3c/-orbitals of phosphorus do not participate very much... 

Recently, [2+3] cycloaddition reaction of 2-acetyl-[l,2,3]diazaphosphole (6) with 9-diazofluorenes (96) has been reported [105, 106], From the reaction in cyclohexane at rt, bicyclic phosphirane 97 was obtained as a result of the loss of nitrogen from the initial cycloadduct (Scheme 30). The cycloadduct, 3-spiro substituted 3H-[l,2,4]diazaphospholo-fused [l,2,3]diazaphosphole (98) could be isolated in good yield at room temperature in one case (R=/Bu) its stability was assigned to the presence of bulky fert-butyl group at 7-position. Use of polar solvent like dichloromethane led to the cyclic trimeric compound 99 (Scheme 30). 

Borst et al. <2005CEJ3631> conducted a study on the synthesis of strained bicyclic phosphirane and phosphirene iron-tetracarbonyl complexes (Scheme 11). It was shown that, depending on the ring size of the resulting heterocycle, electrophilic phosphinidene [Ri-PrNP=Fe(CO)4] could be trapped intramolecularly with both double and triple bonds (compounds 146-150). The phosphinidene addition was found to be reversible at room temperature and when using phenylacetylene as solvent, exchange between phenylacetylene and the phosphinidene group took place. Compound 151 was isolated as the dimer, compound 152. 

The appearance potentials of HPC+ and DPC+ from methylidynephosphine (155) and its deuteriated analogue are close to the theoretical values.21 The mass spectra and ion-molecule reactions of phosphiran (156) and of mixtures of phosphiran with ammonia and deuterio-ammonia show that all the important product ions are formed by PH group-transfer reactions where ethane is generated as a neutral particle. 

These unusual shifts may be an indication of a significant d orbital participation, especially in phosphiran which probably has a nearly planar geometry and may possess some aromatic character as in the parent cyclopropanes [the P-H coupling in 3 of 155 Hz is between that found in PH2s (138 Hz) and PH3 (182 Hz)]. The same conclusions would to some extent apply to organogermyl-, organostannyl- and organosilyl-phosphines recently discussed by Schumann/1969,14)... 

With benzaldazine, a criss-cross-type cycloaddition takes place reaction with diphenyldiazomethane yields a bicyclic phosphirane (49) among other products <87CB597). 

The reaction of 1,2,3-diazaphospholes 110 with diazodiphenylmethane leads directly to bicyclic phosphiranes 117 (184). The analogous product 118 was obtained using a 1,3,4-thiaazaphosphole (185). It is reasonable to assume that these phosphiranes result from a 47i-electrocyclization of the bis(methylene)phos-phorane unit of a reaction intermediate analogous to 115. 

The P=C bond of ), a -phosphoranes is also accessible to a 1,3-dipolar cycloaddition reaction. The formation of 97 (Scheme 8.23), of 3,5-dihydro-1,2,4-diazaphosphole sulfide 132 from an amino(methylene)thioxophosphorane (190) and of phosphirane imine 133 from an amino(imino)alkylidenephosphorane (191) (Scheme 8.29) illustrate the chemical behavior of phosphaalkenes containing a A, a -phosphoms atom. 

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