Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

Abstract

The methylene-bridged complex, [IrOs(CO) 3 (μ-CH 2 )(dppm) 2 ][BF 4 ] (dppm = μ-Ph 2 PCH 2 PPh 2 ) (2), reacts with allene, resulting in C−C bond formation, to yield an equilibrium mix of two isomers of [IrOs(CO) 3 (μ-η 3 :κ 1 -C(CH 2 ) 3 )(dppm) 2 ][BF 4 ] (3/3a), in which the hapticity of the trimethylenemethane ligand with respect to the two metals, as well as the carbonyl ligand arrangement, is different in each isomer. Reaction of 2, as the triflate salt (2-CF 3 SO 3 ), with methylallene also yields two isomers, [IrOs(CO) 3 (μ-η 3 :κ 1 -C(CHCH 3 )(CH 2 ) 2 )(dppm) 2 ][CF 3 SO 3 ] (4/4a); however, in this case, the binding mode of the substituted trimethylenemethane moiety is the same in each isomer and differs only in the position of the methyl group on the allylic moiety. The addition of 1,1-dimethylallene to 2-CF 3 SO 3 results in loss of 4-methyl-1,3pentadiene and subsequent reaction of the remaining "[IrOs(CO) 3 (dppm) 2 ] + " species with excess 1,1-dimethylallene to give [IrOs(CO) 3 (μ-η 3 :κ 1 -CH 2 CCMe 2 )(dppm) 2 ][CF 3 SO 3 ] (5), in which the dimethylallene moiety is κ 1 -bound to Os through the central carbon and η 3 -bound to Ir. Both allene and methylallene react with the tetracarbonyl complex, [IrOs(CO) 4 (dppm) 2 ]-[BF 4 ] (6), to generate analogous products, [IrOs(CO) 3 (μ-η 3 :κ 1 -CH 2 CCHR)(dppm) 2 ][BF 4 ] (R = H (7), CH 3 (8), respectively). Reaction of 6-CF 3 SO 3 with 1,1-dimethylallene yields [IrOs(CO) 4 (μ-CC(H)C(CH 3 )CH 2 )(dppm) 2 ][CF 3 SO 3 ] (9), the result of activation of the geminal C−H bonds of the unsubstituted end of the allene, and additional activation of a methyl C−H bond. The addition of 1,1-difluoroallene to 6-CF 3 SO 3 yields [IrOs(CO) 4 (μ-κ 1 :κ 1 -F 2 CCCH 2 )(dppm) 2 ][CF 3 SO 3 ] (10), in which this cumulene bridges both metal centers through the central carbon and the CH 2 end of the substrate. These reactivities are compared to those of related Ir 2 , Rh/Ru, Rh/Os, and Ir/Ru complexes.

Carbon–Carbon Bond Coupling of Vinyl Molecules with an Allenyl Ligand at a Diruthenium Complex

“…Salient 13 C NMR features are provided by the two terminal carbonyl ligands (197–204 ppm) and the five carbons directly involved in metal coordination [e.g., in the case of 4 : δ/ppm = 39.2 (C 1 ), 70.9 (C 2 ), 73.7 (C 3 ), 76.0 (C 4 ), and 67.8 (C 5 )]. This set of data supports the best description of the pentacarbon ligand as alkenyl-allyl. ,, …”

Bimetallic Carbonyl Complexes Based on Iridium and Rhodium: Useful Tools for Hydrodefluorination Reactions

“…Cowie et al. reported several compounds characterized by various metal combinations including Ir/Ir, [2c,o] Rh/Rh, [4] Ir/Rh, [2c,e,i,k, ° ,p] Ir/Ru, [2m,n] and Ir/Os [2f,g,m] . The Ir/Ir carbonyl complexes [Ir 2 (CH 3 )(CO) 2 (dppm) 2 ][CF 3 SO 3 ] (dppm=bis(diphenylphosphino)methane) and [Ir 2 (CO) 3 ( μ ‐H)(depm) 2 ][BAr F 4 ] (depm=bis(diethylphosphino)methane enabled the C−F bond activation reactions of various polyfluorinated ethylene derivatives [5] .…”