Structure and bonding of group 4-nickel heterobimetallics supported by 2-(diphenylphosphino)pyrrolide ligands

• Published in: Dalton transactions : an international journal of inorganic chemistry 2016-01, Vol.45 (24), p.9892-991
• Main Authors: Dunn, Peter L, Carlson, Rebecca K, Gagliardi, Laura, Tonks, Ian A
• Format: Article
• Language: English
• Subjects: Bonding; Chemical bonds; Intermetallics; Nickel; Nickel titanides; Reduction; Shape memory alloys; Titanium
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c6dt00431h

The synthesis of a full series of group 4/nickel complexes supported by a 2-(diphenylphosphino)pyrrolide (NP) ligand is reported. Treatment of the homoleptic, 8-coordinate M(NP) 4 monometallic precursors with Ni(COD) 2 (COD = 1,5-cyclooctadiene) yielded the heterobimetallic complexes (κ 2 -NP)M(μ 2 -NP) 3 Ni (M = Ti, Zr, Hf). Although X-ray crystallographic analysis reveals similarly short metal-metal distances in all three complexes, quantum chemical calculations indicate that ZrNi ( 5 ) and HfNi ( 6 ) contain only single Ni → M dative bonds while TiNi ( 4 ) has an additional Ti-Ni π-bond. All three complexes have quasireversible reductions by cyclic voltammetry, and 1-electron chemical reduction of 4 by Na(Hg) yields the anion, [Na][(κ 2 -NP)Ti(μ 2 -NP) 3 Ni] ( 7 ). X-ray and computational analysis indicate that the 1-electron reduction of 4 completely breaks the metal-metal bond, yielding a formally Ti III -Ni 0 complex. Ti-Ni bonding can also be disrupted by coordination of CO, wherein Ni → CO backbonding effectively outcompetes Ni → Ti dative bonding. The synthesis of a full series of group 4/nickel complexes supported by a 2-(diphenylphosphino)pyrrolide (NP) ligand is reported.