Some Ruthenium Derivatives of Penta-1,4-diyn-3-one

Abstract

The reaction between Ru(CCH)(dppe)Cp* (1) and oxalyl chloride affords ({Ru(dppe)Cp*}CC) 2 CO (2) in 72% yield. Methylation (MeOTf) of 2 occurs first on the carbonyl oxygen, affording [({Ru(dppe)Cp*}CC) 2 C-(OMe)]OTf ([3]OTf). A second methylation of [3] + on the alkynyl C β proceeds slowly, affording [{Cp*(dppe)Ru}-CCMeC(OMe)CC{Ru(dppe)Cp*}][OTf] 2 ([4][OTf] 2 ), whereas protonation of [3] + occurs readily to give crystallographically characterized [{Cp*(dppe)Ru}CCHC(OMe)CC-{Ru(dppe)Cp*}][OTf] 2 ([5][OTf] 2 ). The molecular structures of [3]OTf and [5][OTf] 2 suggest that polarization by the CO group results in significant contributions from the alkynyl-allenylidene or alkynyl-carbyne mesomers, respectively. Reaction of 2 in refluxing MeOH containing [NH 4 ]PF 6 results in partial methanolysis to give Ru{CCC(O)CH CH(OMe)}(dppe)Cp* (6). Knovenagel condensation of 2 with CH 2 (CN) 2 affords {[Ru(dppe)Cp*]CC} 2 CC(CN) 2 (7). The related asymmetric complex {Cp*(dppe)Ru}CC[CC(CN) 2 ]CCCC{Ru(dppe)Cp*} (8) was obtained from the reaction between Ru{CCC(CN)C(CN) 2 }(dppe)Cp* and lithiated Ru(CCCCH)(dppe)Cp*. Single-crystal structural determinations of 2, [3]OTf, [5][OTf] 2 , 6, 7, and 8 are reported, together with a supporting computational study of relevant electronic structures.

Mixed‐Valent Compounds and their Properties – Recent Developments

“…In cross‐conjugated ligands, the situation is a first sight similar, but a careful inspection reveals that the electron transfer path contains somewhere a succession of two formally single bonds. Typical examples are penta‐1,4‐diyn‐3‐one[28a] or geminal‐diethynylethene[28b], [28c], [28d] (Figure ). (One can remark that the number of carbon atoms constituting the bridge is odd).…”

“…The effect of cross‐conjugation (and even hyperconjugation through a sp3 carbon or silicon) is similarly found in organic mixed‐valent compounds. [28e]…”

Twists and turns: Studies of the complexes and properties of bimetallic complexes featuring phenylene ethynylene and related bridging ligands

“…In this context of metal alkynyl and polyynyl complexes, early examples of such processes would include the deprotonation of terminal ynyl ligands (or masked equivalents such as -CCSiMe 3 [169,170] and terminal vinylidenes [171,172]) and subsequent reactions with electrophiles [173][174][175]. The high nucleophilicity of the alkynyl C  carbon in complexes such as [Ru(CCH)(dppe)Cp*] also raises interesting options for 'chemistry on the complex' synthetic strategies based on direct reactions of this species with electrophiles [176,177]. However, with a view to the preparation of the phenyl ethynyl based systems the Sonogashira cross-coupling reaction using either terminal ynyl complexes {L n M}{(CC) x H} or {L n M}(CCArCCH) [154,173,178,179] or arylhalide substituted metal -ethynyl complexes [180] as coupling partners with aryl halides or 1-alkynes, respectively, has been shown to be a powerful,…”

Reactions of Ruthenium Complexes Containing Pentatetraenylidene Ligand

“…A proposed mechanism for the formation of 13 is shown in Scheme . Treatment of 12 with HBF 4 produces allenylidene complex G . Then, addition of MeOH would take place at C α =Cβ to form H , which readily transforms to 13 , because the keto form is more favorable than the enol form.…”