From 2-Phosphino-2H-Phosphirene to 1-Phosphino-1H-Phosphirene, 1λ5,2λ3-Diphosphete, and 1,2-Dihydro-1λ3,2λ3-Diphosphete: an Experimental and Theoretical Study

Abstract

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Isolable Phosphanylidene Phosphorane with a Sterically Accessible Two‐Coordinate Phosphorus Atom

“…Notably, the attempt by Protasiewicz and co‐workers to generate the analogous bis(borane) adduct from the sterically encumbered phosphanylidene phosphorane (2,6‐Mes 2 C 6 H 3 )‐PPMe 3 5 a failed and only the monoborane adduct 5 a ⋅BH 3 was isolated and spectroscopically characterized 2b,d. Also, Bertrand and co‐workers report only the monoborane adduct 6 ⋅BH 3 upon reaction of the parent crowded cyclic phosphanylidene‐σ 4 ‐phosphorane 6 with BH 3 ⋅SMe 2 3d. The (spectroscopically characterized) bis(borane) adduct Me 3 PPCF 3 ⋅2 BH 3 thus represents the only other example of a phosphine‐donor‐stabilized neutral phosphorus atom acting as a double donor to two borane units 8.…”

Stable Carbenes

“…160 Similarly, the phosphinosilylcarbene XIa reacts at -30°C with a slight excess of tert-butylphosphaalkyne cleanly affording the 2-phosphino-2H-phosphirene 76. 166 The reaction leading to 76 is related to that observed on reacting transient dichlorocarbene with the tert-butylphosphaalkyne, in which the transient 2H-phosphirene 78 was postulated. 167 At room temperature, the three-membered heterocycle 76 appeared to be rather unstable and rearranged quantitatively to afford the 1λ 5 ,2λ 3 -diphosphete 77 after 3 h (Scheme 17).…”

Unusual Formation of an Azaphospholene from 1,3,4,5-Tetramethylimidazol-2-ylidene and Di(isopropyl)aminophosphaalkyne

“…The reaction of the Bertrand phosphanylsilyl carbene with the phosphaalkyne 3 a proceeds in the same manner. The primarily formed 2‐phosphanyl‐2 H ‐phosphirene is stabilized by ring opening under preservation of the C−C carbene bond, and breaking of the P−C carbene bond to yield the 1 λ 5 ,2 λ 3 ‐diphosphetene 5. Herein we report the synthesis of an isolable 1:1 adduct between the N‐heterocyclic carbene 2 and the phosphaalkyne 3 b , which results in the formation of a P−C carbene bond, and we propose a mechanism for this novel reaction on the basis of quantum‐chemical calculations.…”