Gallaphosphene L(Cl)GaPGaL: A novel phosphinidene transfer reagent

Gallaphosphene 1 serves as a phosphinidene transfer reagent in reactions with ^RNHCs and isonitriles, to give ^RNHC-coordinated phosphinidenes 2 and 1,3-phosphaazaallenes 3, respectively. NHC-coordinated phosphinidene 2 b reacted with THF ⋅ BH₃ with selective B−H bond activation to the unique NHC-stabilized borane complex 4.

Abstract

Gallaphosphene L(Cl)GaPGaL 1 (L=HC[C(Me)N(Ar)]₂; Ar=2,6-iPr₂C₆H₃) reacts with N-heterocyclic carbenes ^RNHC (^RNHC=[CMeN(R)]₂C; R=Me, iPr) to ^RNHC-coordinated phosphinidenes ^RNHC→PGa(Cl)L (R=Me 2 a, iPr 2 b) and with isonitriles RNC (R=iPr, Cy) to 1,3-phosphaazaallenes L(Cl)GaP=C=N−R (R=iPr 3 a, Cy 3 b), respectively. Quantum chemical calculations reveal that 2 a/2 b possess two localized lone pair of electrons, whereas 3 a/3 b only show one localized lone pair as was reported for gallaphosphene 1. 2 b reacts with 2.5 equivalents of a borane (THF ⋅ BH₃) to the NHC-stabilized phosphinidene-borane complex [ ^iPrNHC→P(BH₂)]₂(BH₃)₃ 4 with concomitant formation of LGa(H)Cl 5. 2–5 are characterized by heteronuclear (¹H, ¹³C{¹H}, ³¹P{¹H}) NMR and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction (sc-XRD).

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