Oxodienyl/alkyne coupling reactions in half-open ruthenocenes(II) and related species of Ru(IV)

A successful synthesis of Cp*Ru(eta(5)-CH2CHCHCHO) (1) was obtained by chromatography on neutral deactivated alumina of Cp*Ru(1-4-7-eta-CH2CHCHCHOSiMe3)Cl (2). The disproportionation reaction of 2 affords compounds 1 and Cp*Ru(1-3-eta-endo-syn-CH2CHCHCHO)Cl-2 (3). Reaction of compound 1 with diphenylacetylene affords compounds Cp*Ru[1-5-eta-syn-CH(Ph)C(Ph)CHCHCH(CHO)] (6), Cp*Ru[1,4,5-eta-C(Ph)C(Ph)CH2CHCH2]CO (7), Cp*Ru(1-3-eta-CH2CHCHCHO)(eta(2)-PhC CPh) (8), and compounds with cyclic structures, such as Cp*Ru[1,6,7,10,11-eta-CH(CH)(4)CCHC(Ph)CH(CH)(2)C(O)CH(C6H4)CH(Ph)] (9) and Cp*Ru[3,4,5-eta-C(Ph)C(Ph)CHCHCHC(O)](eta(2)-PhCH=CHPh) (10). Reaction of compound 3 with diphenylacetylene shows the syn-aldehyde derivative 6, as well as the corresponding kinetic isomer 11, in which the terminal aldehyde group is in anti-position. Treatment of [Cp*RuCl2](2) with CH2CHCHCHOSiMe3 affords compound Cp*Ru[1-3-eta-endo-syn-(Me)CHCHCH(OEt)]Cl-2 (5). The Ru(IV) complex 5 reacts with diphenylacetylene to give the cyclic 1,2-diphenyl-3-methylcyclopentadienyl complex Cp*Ru[eta(5)-C(Ph)C(Ph)C(Me)CHCH] (12). The investigation of the reactivity of the 2,4-dimethyl-oxopentadienyl of Cp*Ru[eta(5)-CH2C(Me)CHC(Me)O] (4) with excess of diphenylacetylene or dimethyl acetylenedicarboxylate showed the oxopentadienyl/alkyne coupling products Cp*Ru[1-5-eta-syn-CH(Ph)C(Ph)CHC(Me)CH(COMe)] (13) and Cp*Ru[1-5-eta-syn-CH(COOMe)C(COOMe)CHC(Me)CH(COMe)] (16), along with small amounts of Cp*Ru[1-5-eta-syn-CH(Ph)C(Ph)CHC{CH2C(Ph)CH(Ph)}CH(COMe)] (14) and Cp*Ru[1-5-eta-syn-CH(COOMe)C(COOMe)CHC{CH2C(COOMe)CH(COOMe)}CH(COMe)] (17), which are products of a second coupling reaction through the activation of one of the C-H bonds of the 2-methyl substituent. Crystallographic studies are reported for compounds 6, 9, 13, 14, and 17. Cp*Ru[1-5-eta-CH2C(Me)CHC{CH2C(Me)(2)CH2C(O)}CH] (18) was also studied in solid state and in solution.