Halide Effects on the Stability of Osmium Indenylidene Complexes: Isolation, Characterization, and Reactivities

Abstract

[(η6-p-cymene)­OsI2]2 was found to be a good catalyst for the cyclopropanation reaction of isobutyl vinyl ether with 3-tert-butyldiazoindene. In contrast, the complexes [(η6-p-cymene)­OsX2]2 (X = Cl, Br) are poorer catalysts for the reaction. The interesting halide effect can be related to the tendency of osmium indenylidene complexes [(η6-p-cymene)­OsX2(indenylidene)] (6) (derived from the reactions of [(η6-p-cymene)­OsX2] (5) with diazoindene, X = Cl, Br, I) to undergo migratory insertion reactions to give η5-haloindenyl complexes. While the chloro indenylidene complex 6Cl readily rearranges to the corresponding η5-chloroindenyl complex 8Cl, the iodo indenylidene complex 6I can be stored in solutions for weeks without appreciable decomposition. The thermal stability of the bromo indenylidene 6Br is between those of Cl- and I-substituted indenylidenes. Computational studies have been carried out to understand the experimental observations. The indenylidene complexes described here represent the first well-characterized mononuclear indenylidene complexes synthesized from diazoindene precursors.

Repercussion of a 1,3-Hydrogen Shift in a Hydride-Osmium-Allenylidene Complex

“…Indenylidene complexes display a marked tendency to evolve to indenyl derivatives by 1,2-shift of an 1-e – donor ligand, including chloride, from the metal center to the carbenic carbon atom. , In addition, it has been argued that one of the difficulties in the synthesis of metalanaphthalene compounds could be due to its lower stability relative to the indenyl derivatives. So, the stability of 4 and 5 first surprised us and then encouraged us to promote their transformation to indenyl species, in particular that of 4 .…”

Cytotoxicity of osmium(ii) and cycloosmated half-sandwich complexes from 1-pyrenyl-containing phosphane ligands

“…Highresolution mass analyses (HRMS) were carried out using electrospray ionisation (ESI). The metallic dimers of formula [MX (μ-X)(η 6 -p-cymene)] 2 (M = Ru, Os; X = Cl, I) [41][42][43][44][45] and diphosphane ligands PPyriPr 2 27 and PPyrPh 2 25 were prepared following reported procedures.…”

Arene-Osmium(II) Complexes in Homogeneous Catalysis

“…Scheme 13. Osmium-catalyzed cyclopropanation of styrene derivatives.More recently, the cyclopropanation of isobutyl vinyl ether with 3-tert-butyldiazoindene was studied using dimers [{OsX(µ-X)(η 6 -p-cymene)} 2 ] (X = Cl, Br, I) as catalysts (Scheme 14)[85]. A marked effect of the halides on the effectiveness of the process was observed and positive results were only obtained with [{OsBr(µ-Br)(η 6 -p-cymene)} 2 ] and [{OsI(µ-I)(η 6 -p-cymene)} 2 ].…”