[Ni(NHC)<sub>2</sub>] as a Scaffold for Structurally Characterized <i>trans</i> [H−Ni−PR<sub>2</sub>] and <i>trans</i> [R<sub>2</sub>P−Ni−PR<sub>2</sub>] Complexes
Sara Sabater, David Schmidt, Heidi Schmidt, Maximilian W. Kuntze‐Fechner, Thomas Zell, Connie J. Isaac, Nasir A. Rajabi, Harry Grieve, William J. M. Blackaby, John P. Lowe, Stuart A. Macgregor, Mary F. Mahon, Udo Radius, Michael K. Whittlesey
Abstract
Abstract 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=I i Pr 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 >I i Pr 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.