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

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 (1,3dimethylimidazolin-2-ylidene), Me 4 Im (1,3,4,5-tetramethylimidazolin-2-ylidene), iPr 2 Im (1,3-di-iso-propylimidazolin-2ylidene) and Mes 2 Im (2,4,6-trimethylphenylimidazolin-2-ylidene) with PhPH 2 and MesPH 2 led to the NHC stabilized phosphinidenes (NHC)PAr: (iPr 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 (iPr 2 Im)PMes ( 7). The reaction of tBuPH 2 with two equivalents of the NHCs afforded the corresponding NHC stabilized parent phosphinidenes (NHC)PH: (iPr 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 iPr 2 Im-P(O) 2 Ph (11) and iPr 2 Im-P(S) 2 Ph (12), whereas the reaction with elemental selenium and tellurium gave (NHC) PPh cleavage with formation of (iPr 2 Im)Se ( 13), iPr 2 ImTe (14) and different cyclo-oligophosphines. Furthermore, the complexes [{(iPr 2 Im)PPh}W(CO) 5 ] (15), [Co(CO) 2 (NO){(iPr 2 Im)PPh}] (16) and [(η 5 -C 5 Me 5 )Co(η 2 -C 2 H 4 ){(iPr 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(iPr 2 Im)(CO) 2 (NO)] and [(η 5 -C 5 Me 5 )Co(iPr 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(iPr 2 Im) 2 (trans-PhP = PPh)] 18.

N‐Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Adducts of Antimony(III)

“…Over the last few years we and others reported on the reactivity of NHCs and related molecules towards compounds of group 13, [1d,j,m,3] 14 [1d,j,m,4] and 15 [1m,j,5] elements. A plethora of NHC ligated phosphorus compounds is known, [6] including phosphorus in low oxidation states as in phosphinidenes (NHC ⋅ PR) [5b,7] and molecules with uncommon binding modes such as carbene stabilized P 2 , P 4 and P 12 [6l,8] . In contrast, reports on carbene stabilized compounds of the heavier homologues arsenic [6h,9] and bismuth [9b,10] are rather scarce, whereas some antimony compounds are known.…”

N-Heterocyclic carbene and cyclic (alkyl)(amino)carbene complexes of vanadium(iii) and vanadium(v)

“…All reactions and subsequent manipulations involving organometallic reagents were performed under an argon atmosphere by using standard Schlenk techniques or in a Glovebox (Innovative Technology Inc. and MBraun Uni Lab) as reported previously. 30 All reactions were carried out in oven-dried glassware. Toluene, n -hexane and THF were purified using a solvent purification system (Innovative Technology).…”

Subvalent group 13 molecules by carbene-induced hydrogen abstraction

“…We reported the dehydrocoupling of triorganotin monohydrides induced by the small NHCs iPr 2 Im and iPr 2 Im Me with the formation of distannanes, 7 and demonstrated that iPr 2 Im can be used in the transition metal-free dehydrogenative coupling of secondary and primary phosphines. 8 Depending on the stoichiometry between the phosphine and the NHC used, the formation of diphosphines, cyclic oligophosphines and NHC phosphinidene adducts was observed. Wesemann and co-workers reported the NHC-induced reductive elimination of dihydrogen from tin hydrides in some detail.…”