A General Synthetic Route to NHC‐Phosphinidenes: NHC‐mediated Dehydrogenation of Primary Phosphines

Abstract

Abstract The dehydrocoupling of primary phosphines with N ‐heterocyclic carbenes (NHCs) to yield NHC‐phosphinidenes is reported. The reaction of two equivalents of the NHCs Me 2 Im (1,3‐dimethylimidazolin‐2‐ylidene), Me 4 Im (1,3,4,5‐tetramethylimidazolin‐2‐ylidene), i Pr 2 Im (1,3‐di‐ iso ‐propylimidazolin‐2‐ylidene) and Mes 2 Im (2,4,6‐trimethylphenylimidazolin‐2‐ylidene) with PhPH 2 and MesPH 2 led to the NHC stabilized phosphinidenes (NHC)PAr: ( i Pr 2 Im)PPh ( 1 ), (Mes 2 Im)PPh ( 2 ), (Me 4 Im)PPh ( 3 ), (Mes 2 Im)PMes ( 4 ), (Me 2 Im)PMes ( 5 ), (Me 4 Im)PMes ( 6 ) and ( i Pr 2 Im)PMes ( 7 ). The reaction of t BuPH 2 with two equivalents of the NHCs afforded the corresponding NHC stabilized parent phosphinidenes (NHC)PH: ( i Pr 2 Im)PH ( 8 ), (Mes 2 Im)PH ( 9 ) and (Me 4 Im)PH ( 10 ). Reaction of 1 with oxygen and sulfur led to isolation of i Pr 2 Im‐P(O) 2 Ph ( 11 ) and i Pr 2 Im‐P(S) 2 Ph ( 12 ), whereas the reaction with elemental selenium and tellurium gave (NHC)PPh cleavage with formation of ( i Pr 2 Im)Se ( 13 ), i Pr 2 ImTe ( 14 ) and different cyclo ‐oligophosphines. Furthermore, the complexes [{( i Pr 2 Im)PPh}W(CO) 5 ] ( 15 ), [Co(CO) 2 (NO){( i Pr 2 Im)PPh}] ( 16 ) and [(η 5 ‐C 5 Me 5 )Co(η 2 ‐C 2 H 4 ){( i Pr 2 Im)PPh}] ( 17 ) have been prepared starting from 1 and a suitable transition metal complex precursor. The complexes 16 and 17 decompose in solution upon heating to ca . 80 °C to yield the NHC complexes [Co( i Pr 2 Im)(CO) 2 (NO)] and [(η 5 ‐C 5 Me 5 )Co( i Pr 2 Im)(η 2 ‐C 2 H 4 )] with formation of cyclo ‐oligophosphines. The reaction of 1 with [Ni(COD) 2 ] afforded the diphosphene complex [Ni( i Pr 2 Im) 2 ( trans ‐PhP=PPh)] 18 .