Mono- and dinuclear Ni(I) products formed upon bromide abstraction from the Ni(I) ring-expanded NHC complex [Ni(6-Mes)(PPh3)Br]

William J. M. Blackaby, Sara Sabater, Rebecca C. Poulten, Michael J. Page, Andrea Folli, Vera Krewald, Mary F. Mahon, Damien M. Murphy, Emma Richards, Michael K. Whittlesey

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Abstract

Bromide abstraction from the three-coordinate Ni(I) ring-expanded N-heterocyclic carbene complex [Ni(6-Mes)(PPh3)Br] (1; 6-Mes = 1,3-bis(2,4,6-trimethylphenyl) 3,4,5,6-tetrahydropyrimidin-2-ylidene) with TlPF6 in THF yields the T-shaped cationic solvent complex, [Ni(6-Mes)(PPh3)(THF)][PF6] (2), whereas treatment with NaBArF4 in Et2O affords the dimeric Ni(I) product, [{Ni(6-Mes)(PPh3)}2(µ-Br)][BArF4] (3). Both 2 and 3 act as latent sources of the cation [Ni(6-Mes)(PPh3)]+, which can be trapped by CO to give [Ni(6-Mes)(PPh3)(CO)]+ (5). Addition of [(Et3Si)2(µ-H)][B(C6F5)4] to 1 followed by work up in toluene results in the elimination of phosphine as well as halide to afford a co-crystallised mixture of [Ni(6-Mes)(η2-C6H5Me)][B(C6F5)4] (4), and [6MesH⋅ C6H5Me][B(C6F5)4]. Treatment of 1 with sodium salts of more strongly coordinating
anions leads to substitution products. Thus, NaBH4 yields the neutral, diamagnetic dimer [{Ni(6-Mes)}2(BH4)2] (6), whereas NaBH3(CN) gives the paramagnetic monomeric cyanotrihydroborate complex [Ni(6-Mes)(PPh3)(NCBH3)] (7). Treatment of 1 with NaOtBu/NHPh2 affords the three-coordinate Ni(I) amido species, [Ni(6-Mes)(PPh3)NPh2] (8). The electronic structures of 2, 5, 7 and 8 have been analysed in comparison to that of previously reported 1 using a combination of EPR spectroscopy and density functional theory.
Original languageEnglish
Pages (from-to)769-782
Number of pages14
JournalDalton Transactions
Volume47
Issue number3
Early online date5 Dec 2017
DOIs
Publication statusPublished - 1 Jan 2018

ASJC Scopus subject areas

  • Inorganic Chemistry

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