First agostic closo-metallacarboranes with η3-cyclooctenyl type ligand: synthesis and structural characterization of closo-3-[η3-(endo-1,5-dimethylcycloocten-1-yl)]-1,2-μ-(1′,2′-xylylene)-3,1,2-IrC2B9H9 and its isomerization to closo-3-[η3-(exo-1-methylen

The reaction of a new iridium reagent [Ir(η4-1,5-Me2COD)Cl]2 (1) with [nido-7,8-μ-(1′,2′-CH2C6H4CH2)-7,8-C2B9H10]−K+ (2) in solution of C6H6–MeOH mixture or in C6H6 afforded either an agostic (CH⋯Ir) closo-3-[η3-(endo-1,5-Me2COD)]-1,2-μ-(1′,2′-CH2C6H4CH2)-3,1,2-IrC2B9H9 (3) along with closo-3-[η3-(endo-1,5-Me2COD)]-1,2-μ-(1′,2′-CH2C6H4CH2)-8-(EtO)-3,1,2-IrC2B9H8 (4) or the only complex 3 in high yield. Complex 3 in dichloromethane solution is quantitatively converted to isomeric η3-exo-allylic complex closo-3-[η3-(1-exo-CH2-5-MeC8H12)]-1,2-μ-[η2-(1′,2′-CH2C6H4CH2)]-3,1,2-IrC2B9H9 (5) for a few days. All new complexes 3, 4 and 5 were characterized by single-crystal X-ray diffraction studies, which confirmed the existence of an agostic CH⋯Ir interaction in 3 and revealed a weak η2-coordination of the metal atom with one of the aromatic bonds of ortho-xylylene cage substituent in 5. The normal and low-temperature 1H- and 13C/13C{1H}-NMR spectra as well as 2D COSY/HETCOR NMR data obtained for the studied complexes are discussed in details.