Issue 9, 1986

The reactivity of diphosphenes towards electrophilic and nucleophilic reagents

Abstract

The reaction of P2[C(SiMe3)3]2(2) with a stoicheiometric quantity of HCI leads to (Me3Si)3CP(H)–P(Cl)C(SiMe3)3 whilst an excess of this reagent causes P[double bond, length half m-dash]P cleavage and results in the formation of PH(Cl)[C(SiMe3)3]. The corresponding reaction with RP[double bond, length half m-dash]PR (R = 2,4,6-But3C6H2), (1), results in PH(Cl)R, even when 1 equivalent of HCl is used. Protonation of compound (2) with HBF4·Et2O at –78 °C results in the phosphonium salt [PH3{C(SiMe3)3}][BF4]. Protonation of (1) with HBF4·Et2O is more complex and leads ultimately to P[double bond, length half m-dash]P bond cleavage and insertion of a cationic phosphorus centre into a C–H bond of an ortho-But group. The dication [R(Ag)P[double bond, length half m-dash]P(Ag)R]2+ and the monocation [R(Ag)P[double bond, length half m-dash]PR]+ and [RP[double bond, length half m-dash]P(AuPEt3)R]+ are formed on treatment of (1) with Ag[SO3CF3] or [Au(PEt3)][PF6]. The reaction of (1) with excess of sulphur in the presence of 1,5-diazabicyclo[5.4.0] undec-5-ene results in P[double bond, length half m-dash]P bond cleavage and formation of a cyclic dithiophosphinic acid. The diphosphene, (1), reacts with LiMe to afford the anion [RP–P(Me)R]. Quenching with MeOH affords the diphosphine R(H)P–P(Me)R, whilst treatment of [RP–P(Me)R] with OH causes P–P bond cleavage and formation of the phosphine oxides PH2RO and PH(Me)RO. Treatment of [RP–P(Me)R] with HBF4·Et2O produces PH2R and the phosphonium salt [PH2(Me)R][BF4]. Treatment of (1) with LiBut also results in anion formation, viz. [RP–P(But)R], as the major product which on protonation with MeOH gives the diphosphine R(H)P–P(But)R. The corresponding reaction with LiBun gives the related anion and diphosphine. The reaction of (1) with K[BHBus3] results only in the diphosphine R(H)P–P(H)R.

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1986, 1801-1808

The reactivity of diphosphenes towards electrophilic and nucleophilic reagents

A. H. Cowley, J. E. Kilduff, N. C. Norman and M. Pakulski, J. Chem. Soc., Dalton Trans., 1986, 1801 DOI: 10.1039/DT9860001801

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