Synthesis of Bis(2,6-dimesityl-4-methylphenyl)phosphaarsene and EPR of its Radical Anion

Abstract

Novel bis(2,6-dimesityl-4-methylphenyl)phosphaarsene was synthesized by the coupling reaction of 2,6-dimesityl-4-methylphenylphosphine with dichloro(2,6-dimesityl-4-methylphenyl)arsine in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene and isolated as stable crystals. The radical anion generated by the sodium metal reduction of the phosphaarsene was investigated by X-band EPR.

Isolation of Carbene‐Stabilized Arsenic Monophosphide [AsP] and its Radical Cation [AsP]+. and Dication [AsP]2+

“…ORTEP diagramoft he cationicpart in [(IMes)As(Cl)P(IDipp)]Cl (3) with thermaldisplacement parameters drawn at 50 %p robability level. The simulation afforded coupling constants of A( 75 As) = 21.7 G, A( 31 P) = 42.2 G, and A( 14 N) = 1.5 G( not resolved), in excellent agreement with the EPR spectrum recorded in situ for the arsaphosphene radical anion [RAsPR] À· (R = 2,6-(Mes) 2 -4-MeC 6 H 2 ), which afforded as imilar" pseudosextet"p attern with A( 75 As) = 23 Ga nd A( 31 P) = 48 G. [31] The calculated spin density is distributeds ymmetrically between the arsenic (0.39 e)a nd phosphorusa toms (0.31 e)w ith only little additional localization on each of the four nitrogen atoms (approx.0.04 e, Figure 4, right).Furthero xidationo f5 + +· ,o rt wo-electron oxidation of 4,f urnishedt he dication [(IMes)AsP(IDipp)] 2+ + (6 2+ + )h owever,i ti sa lso conveniently accessible from 3 through abstraction of the two chloride ions with two equivalents of gallium trichloride. [23] It also falls in the range established for other AsÀPs ingleb onds, as for instancei nc yclodiarsadiphosphanes, [27] or in complexes containing the tetrahedral AsP 3 ligand.…”

Synthesis and photolysis of phosphiranes and diphosphiranes carrying sterically protecting groups on the phosphorus atoms

“…Similar differences of photoreactivity between the 2,4,6-tri-t-butylphenyl and the 2,6-dimesityl-4-methylphenyl derivatives were also observed in the photolysis of bis(2,6-dimesityl-4-methylphenyl)-diphosphene (17) and bis(2,6-dimesityl-4-methylphenyl)phosphaarsene (18) [9]. Irradiation of the diphosphene 17 and the phosphaarsene 18 resulted in recovery of the starting materials, and no products, including Z-isomers, were observed.…”

“…2,6-Dimesityl-4-methyliodobenzene (7), which was prepared according to Hart's procedure [11], was lithiated with butyllithium and allowed to react with phosphorus trichloride to give the dichlorophosphine 8 [9,10]. The dichlorophosphine 8 was converted to the air-stable primary phosphine 9 by LiAlH 4 reduction.…”

“…Although the cyclization of the tosylate 10 to the phosphirane 5 with butyllithium was not effective, 10 was accidentally converted to 5 by passing a solution of 10 through a silica-gel column. Attempted synthesis of 1-(2,6-dimesityl-4-methylphenyl)-2-phenylphosphirane was not successful either by the procedure of Oshikawa and Yamashita [15] or by ours [13], but the reaction of bis(2,6-dimesityl-4-methylphenyl)diphosphene (17) [9,10] with excess diphenyldiazomethane afforded the corresponding diphosphirane, although only in a trace amount.…”

“…However, in the course of our study, the significance of participation of the ortho tbutyl substituents became clear, and we therefore desired to study the behavior of a sterically protecting group with comparable bulkiness but less reactivity as compared with the 2,4,6-tri-t-butylphenyl group. Recently, we [9] and others [10] have reported the application of the 2,6-diarylphenyl-type of sterically protecting group, which can easily be synthesized by the Hart reaction [11], and such protecting groups have been successfully used for stabilizing low-coordinated main-group element as well as transition metal compounds, as reported by He et al [12], for diphosphenes and a phosphaarsene. Thus, we prepared 2,6-dimesityl-4-methylphenylphosphirane 5 as a possible phosphinidene precursor bearing a protecting group with less reactivity.…”