First agostic closo-metallacarboranes with eta(3)-cyclooctenyl type ligand: synthesis and structural characterization of closo-3-[eta(3)-(endo-1,5-dimethylcycloocten-1-yl)]-1,2-mu-(1 ',2 '-xylylene)-3,1,2-IrC2B9H9 and its isomerization to closo-3-[et

摘要

The reaction of a new iridium reagent [Ir(eta(4)-1,5-Me2COD)Cl](2) (1) with [nido-7,8-mu-(1',2'CH2 in solution Of C6H6-MeOH mixture or in C6H6 afforded either an agostic (C-H... Ir) closo-3-[eta(3)-(endo-1,5-Me2COD)]-1,2-mu-(1',2'CH2C6H4CH2-)-3,1,2-IrC,B9H 9 (3) along with closo-3-[eta(3)-(endo-1,5-Me2COD)]-1,2-mu-(1',2'-CH2-C6H4CH2-)-8-(EtO)-3,1 ,2IrC(2)B(8)H(8) (4) or the only complex 3 in high yield. Complex 3 in dichloromethane solution is quantitatively converted to isomeric eta(3)-exo-allylic complex closo-3-[eta(3)-(l-exo-CH2-5-MeC8H12)]-1,2-mu-[eta(2)-(1',2'-CH2C6H4CH2-)] -3,1,2-IrCB9H9 (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 eta(2)-coordination of the metal atom with one of the aromatic bonds of orthoxylylene cage substituent in 5. The normal and low-temperature H-1- and C-13/C-13 {H-1}-NMR spectra as well as 2D COSY/HETCOR NMR data obtained for the studied complexes are discussed in details. (C) 2003 Elsevier Science B.V. All rights reserved. [References: 58]