[Ni(NHC)(2)] as a Scaffold for Structurally Characterized trans [H−Ni−PR(2)] and trans [R(2)P−Ni−PR(2)] Complexes

The addition of PPh(2)H, PPhMeH, PPhH(2), P(para‐Tol)H(2), PMesH(2) and PH(3) to the two‐coordinate Ni(0) N‐heterocyclic carbene species [Ni(NHC)(2)] (NHC=IiPr(2), IMe(4), IEt(2)Me(2)) affords a series of mononuclear, terminal phosphido nickel complexes. Structural characterisation of nine of these compounds shows that they have unusual trans [H−Ni−PR(2)] or novel trans [R(2)P−Ni−PR(2)] geometries. The bis‐phosphido complexes are more accessible when smaller NHCs (IMe(4)>IEt(2)Me(2)>IiPr(2)) and phosphines are employed. P−P activation of the diphosphines R(2)P−PR(2) (R(2)=Ph(2), PhMe) provides an alternative route to some of the [Ni(NHC)(2)(PR(2))(2)] complexes. DFT calculations capture these trends with P−H bond activation proceeding from unconventional phosphine adducts in which the H substituent bridges the Ni−P bond. P−P bond activation from [Ni(NHC)(2)(Ph(2)P−PPh(2))] adducts proceeds with computed barriers below 10 kcal mol(−1). The ability of the [Ni(NHC)(2)] moiety to afford isolable terminal phosphido products reflects the stability of the Ni−NHC bond that prevents ligand dissociation and onward reaction.