The fulvalene diiridium platform was scrutinized for its potential to effect double vicinal C-H activation of C 6 H 6 and C 6 H 12 , respectively. For this purpose, an improved preparation of Fv[Ir(CO) 2 ] 2 was developed, and the syntheses of the new complexes FvIr(CO) 2 Ir(CO)(η 2 -C 6 F 6 ), Fv[Ir(CO)(η 2 -C 6 F 6 )] 2 , Fv[Ir(CH 2 =CH 2 ) 2 ] 2 (X-ray), Fv[Ir(PMe 3 )(H) 2 ] 2 (X-ray), and (2,2′,3,3′-tetra- tert -butylFv)[Ir(CO) 2 ] 2 were accomplished. When irradiated in C 6 H 6 , these molecules succeeded to varying degrees, and best for (2,2′,3,3′-tetra- tert -butylFv)[Ir(CO) 2 ] 2 , in the double metalation of the aromatic ring to engender ligating Ir 2 (ortho - μ -C 6 H 4 )(CO) 2 (Ir - Ir) moieties, in addition to their precursor mono(phenyliridium hydride) constructs. A competing photochemical pathway is evident by the formation of diastereomers of Fv (or 2,2',3,3'-tetra- tert -butylFv) [Ir(CO)(Ph)(H)] 2 and the resulting dehydrogenated ligated [Ir(CO)(Ph)] 2 (Ir - Ir). The structures of FvIr 2 (ortho - μ -C 6 H 4 )(CO) 2 (Ir - Ir) and trans -Fv[Ir(CO)(Ph)] 2 (Ir - Ir) were corroborated by X-ray analyses. Efforts to realize C-H bond activations with C 6 H 12 generally failed or fared very poorly, with the exception of the tert -butylFv system, which enabled single, but not further, insertion to give (2,2′,3,3′-tetra- tert -butylFv)[Ir(CO)(Cy)(H)][Ir(CO) 2 ] in 34% yield. To explore the relevant chemistry of phenyl- and alkyliridium species attached to Fv, several such derivatives were made by independent routes, adding knowledge to the fundamental behavior of this category of molecules. Where appropriate and for comparative purposes, similar reactions were performed on the corresponding Cp- and 1,2-di- tert -butylCpIr(CO) 2 relatives.
ASJC Scopus subject areas
- Organische Chemie