Isolation of [Ru(IPr)2(CO)H]+ (IPr = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene) and reactivity towards E-H (E = H, B) bonds

Ian M Riddlestone, David McKay, MJ Gutmann, Stuart Macgregor, MF Mahon, Hazel A Sparkes, Michael K. Whittlesey

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Abstract

Halide abstraction from the ruthenium N-heterocyclic carbene complex Ru(IPr)2(CO)HCl (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with NaBAr4F (BAr4F = B{C6H3(3,5-CF3)2}4) gave the salt [Ru(IPr)2(CO)H]BAr4F (2), which was shown through a combined X-ray/neutron structure refinement and Quantum Theory of Atoms in Molecules (QTAIM) study to contain a bifurcated Ru···η3-H2C ξ-agostic interaction involving one iPr substituent of the IPr ligand. This system complements the previously reported [Ru(IMes)2(CO)H]+ cation (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene: Organometallics 2009, 28, 1758) where a non-agostic form is favored. Treatment of 2 with CO, H2 and the amine-boranes H3B·NR2H (R = Me, H) gave [Ru(IPr)2(CO)3H]BAr4F (3), [Ru(IPr)2(CO)(η2-H2)H]BAr4F (4) and [Ru(IPr)2(CO)(κ2-H2BH·NR2H)H]BAr4F (R = Me, 5, R = H, 6) respectively. Heating 5 in the presence of Me3SiCH=CH2 led to alkene hydroboration and formation of the C-H activated product [Ru(IPr)(IPr)'(CO)]BAr4F (7). X-ray characterization of 3 and 5-7 was complemented by DFT calculations and the mechanism of H2/H exchange in 4 was also elucidated. Treatment of 2 with HBcat resulted in Ru-H abstraction to form the boryl complex [Ru(IPr)2(CO)(Bcat)]BAr4F (8), which proved to be competent in the catalytic hydroboration of 1-hexene. In 8, a combined X-ray/neutron structure refinement and QTAIM analysis suggested the presence of a single Ru···η2-HC ξ-agostic interaction.
Original languageEnglish
Pages (from-to)1301-1312
Number of pages12
JournalOrganometallics
Volume35
Issue number9
Early online date26 Apr 2016
DOIs
Publication statusPublished - 9 May 2016

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