期刊
CHEMICAL SCIENCE
卷 6, 期 5, 页码 2893-2902出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c5sc00404g
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资金
- Nanyang Technological University
- A*STAR of Singapore [PSF/SERC 1321202066]
The reactivity of a tricoordinate organoboron L2PhB: (L = oxazol-2-ylidene) 1 towards metal precursors and its coordination chemistry were comprehensively studied. While the boron center in 1 is reluctant to coordinate to the alkali metals in their trifluoromethanesulfonate salts (MOTf) (M = Li, Na, K), the unprecedented compound 2 containing two L2PhB: units linked by a cyclic Li(OTf)(2)Li spacer was obtained from the reaction of 1 with LiOTf. Treatment of 1 with group 9 metal complexes [MCl(COD)](2) (M = Rh, Ir) afforded the first zwitterionic rhodium(I)-boronium complex 3 and the iridium(III)-borane complex 4, respectively. The reaction pathway may involve C-H activation followed by proton migration from the metals to the boron center, demonstrating the first example of the deprotonation of metal hydrides by a basic boron. In the reactions with coinage metals, 1 could act as a two-electron reducing agent towards the metal chlorides MCl (M = Cu, Ag, Au). Meanwhile, the reaction of 1 with gold chloride supported by a N-heterocyclic carbene (NHC) produced a heteroleptic cationic gold complex [(L2PhB) Au(NHC)] Cl (6) featuring both carbene and L2PhB: ligands on the gold atom. In contrast, an isolable gold chloride complex (L2PhB) AuCl (8) was obtained by direct complexation between 1 and triphenylphosphine-gold chloride via ligand exchange. X-ray diffraction analysis and computational studies revealed the nature of the B: -> Au bonding interaction in complexes 6 and 8. Natural Population Analysis (NPA) and Natural Bond Orbital (NBO) analysis support the strong sigma-donating property of the L2PhB: ligand. Moreover, preliminary studies showed that complex 8 can serve as an efficient precatalyst for the addition of X-H (X = N, O, C) to alkynes under ambient conditions, demonstrating the first application of a metal complex featuring a neutral boron-based ligand in catalysis.
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