Boron chlorination on a Cp*Rh-coordinated bis(2-mercapto-1-arylimidazolyl)borate [H₂B(tim^Ar)₂]⁻: [Cp*Rh{κ²-S,S′-ClHB(tim^Ar)₂}Cl] and [Cp*Rh{κ³-H,S,S′-ClHB(tim^Ar)₂}][BF₄]⋅H₂O

Abstract

Interaction of [Cp*Rh(μ-Cl)Cl]₂ with two equiv. of Na[H₂B(tim^Ar)₂] (tim^Ar = 1-(4-chloro-phenyl)-imidazole-2-thione) in THF afforded [Cp*Rh{κ²-S,S′-H₂B(tim^Ar)₂}Cl] (1). Treatment of 1 with AgBF₄ in THF gave [Cp*Rh{κ³-H,S,S′-H₂B(tim^Ar)₂}][BF₄] (2) with an agostic B–H⋯Rh bond, whereas 1 in a stirring CHCl₃ solution led to isolation of [Cp*Rh{κ²-S,S′-ClHB(tim^Ar)₂}Cl] (3) with a B–Cl bond. Similarly, treatment of 3 with AgBF₄ in THF gave the cationic complex [Cp*Rh{κ³-H,S,S′-ClHB(tim^Ar)₂}][BF₄]⋅H₂O (4⋅H₂O) with both agostic B–H⋯Rh and terminal B–Cl bonds, isolated from the solution of 2 in CHCl₃. All complexes were spectroscopically characterized and structures of 3 and 4⋅H₂O have been established by X-ray crystallography.

Graphical Abstract

Two rhodium(III) complexes [Cp*Rh{κ²-S,S’-ClHB(tim^Ar)₂}Cl] and [Cp*Rh{κ³-H,S,S’-ClHB(tim^Ar)₂}][BF₄]⋅H₂O with the terminal B−Cl bonds were isolated by reaction of boron-chlorination and structurally characterized by X-ray crystallography.

Keywords:

• Rhodium complex
• Dihydrobis(mercaptoimidazolyl) borate ligand
• Agostic B–H⋯Rh bond
• B–Cl bond
• Boron chlorination
• Crystal structure

Funding

This project was supported by the Natural Science Foundation of China (21201003 and 21372007). X.H. Huang thanks Zhejiang Province Natural Science Foundation of China (LY12B03010) for the assistance.