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

Thereaction between Ru(CCH)(dppe)Cp* (1)and oxalyl chloride affords ({Ru(dppe)Cp*}CC)2CO(2) in 72% yield. Methylation (MeOTf) of 2occurs first on the carbonyl oxygen, affording [({Ru(dppe)Cp*}CC)2C(OMe)]OTf ([3]OTf). A second methylation of[3]+on the alkynyl Cβproceedsslowly, affording [{Cp*(dppe)Ru}CCMeC(OMe)CC{Ru(dppe)Cp*}][OTf]2([4][OTf]2), whereas protonationof [3]+occurs readily to give crystallographicallycharacterized [{Cp*(dppe)Ru}CCHC(OMe)CC{Ru(dppe)Cp*}][OTf]2([5][OTf]2). The molecular structures of[3]OTf and [5][OTf]2suggestthat polarization by the CO group results in significant contributionsfrom the alkynyl-allenylidene or alkynyl-carbyne mesomers, respectively.Reaction of 2in refluxing MeOH containing [NH4]PF6results in partial methanolysis to give Ru{CCC(O)CHCH(OMe)}(dppe)Cp*(6). Knövenagel condensation of 2with CH2(CN)2affords {[Ru(dppe)Cp*]CC}2CC(CN)2(7). The related asymmetriccomplex {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 8are reported, together with a supportingcomputational study of relevant electronic structures. [ABSTRACT FROM AUTHOR]