A variety of vinylidene−ruthenium complexes [trans-RuCCHR(Cl)(dppe)2]PF6 (2) are obtained by reaction of RuCl2(dppe)2 (1) with terminal alkynes and NaPF6. On treatment with a base, complexes 2 afford the alkynyl−ruthenium derivatives trans-Ru−C⋮C−R(Cl)(dppe)2 (3). trans-Ru(C⋮CR)2(dppe)2 4 are prepared under mild conditions via the reaction of RuCl2(dppe)2 with terminal alkynes HC⋮C−R (R = Ph, nBu, SiMe3, C10H21, CH2OSiMe3, CH2OMe) in the presence of an excess amount of NaPF6 and NEt3, whereas trans-Ru(C⋮CH)2(dppe)2 (5) was obtained directly from HC⋮C−SnBu3 and precursor 1. In contrast, unsymmetrically substituted complexes trans-Ru(C⋮CR1)(C⋮CR2)(dppe)2 (6) were built from the vinylidenes 2 in the presence of another alkyne, NaPF6, and NEt3. On protonation with NH4 +PF6 -, the bis(alkynyl) derivatives 4 lead to the release of RC⋮CH and the formation of trans-[Ru(NH3)(C⋮CR)(dppe)2]PF6 complexes 7. The structure of trans-[Ru(NH3)(C⋮CC6H5)(Ph2PCH2CH2PPh2)]PF6 (7a) has been determined by X-ray diffraction.

The reaction of 1,4-diethynylbenzene with cis-RuCl2(dppe)2 and iodoferrocene gave the homobimetallic systems Cl(dppe)2RuC⋮CC6H4C⋮CRu(dppe)2Cl (2) and (η5-C5H5)Fe(η5-C5H4)C⋮CC6H4C⋮C(η5-C5H4)Fe(η5-C5H5) (3), respectively. The organometallic terminal alkynes Cl(dppe)2RuC⋮CC6H4C⋮CH (6) and (η5-C5H5)Fe(η5-C5H4C⋮CC6H4C⋮CH) (8), obtained by desilylation of the corresponding complexes Cl(dppe)2RuC⋮CC6H4C⋮CSiiPr3 (5) and (η5-C5H5)Fe(η5-C5H4C⋮CC6H4C⋮CSiiPr3) (7), were used as key starting products for access to the heterotrimetallic systems trans-(PnBu3)2Pd[−C⋮CC6H4C⋮CRu(dppe)2Cl]2 (10; 53%) and trans-(PnBu3)2Pd[(−C⋮CC6H4C⋮CC5H4-η5)Fe(η5-C5H5)]2 (11; 73%) by reaction with PdCl2(PBu3)2. The cyclic voltammetry studies of the complexes 2 and 3 have shown that the electrochemical response was strongly dependent on the connection type between the two terminal organometallic fragments and the organic bridge and that the insertion of the palladium moiety trans-Pd(PBu3)2 in the trimetallic complexes 10 and 11 induced totally different electrochemical behavior.

A variety of neutral ruthenium−carbene complexes RuCl2(carbene)(arene) 1 (carbene = C(NR)C6H4(NR), R = Me (a), Et (b); arene = p-Me-C6H4-iPr (1), C6H3Me3 (2), C6Me6 (3)) have been prepared by reaction of [RuCl2(arene)]2 precursors with the enetetraamines (RN)C6H4(RN)CC(NR)C6H4(NR) I (R = Me) and II (R = Et). RuC(NCH2Ph)CH2CH2(NCH2Ph)Cl2(p-cymene) (4) was prepared similarly, whereas the reaction of [RuCl2(cycloocta-1,5-diene)] n with I led to the formation of the 16-electron neutral complex RuCl2[C(NMe)C6H4(NMe)]3 (6). One of them (3a) was transformed into the dihydride derivative RuH2(C(NMe)C6H4NMe)(C6Me6) (5). The cyclic voltammograms of derivatives 1−3 show that they are oxidized in the range E1/2 = 1.03−1.31 V vs SCE and are more electrophilic than the isoelectronic RuCl2(PR3)(arene) complexes. Derivatives 1a, 3a, and 3b act as efficient catalyst precursors for the electrophilic activation of the C⋮C bond of (Z)-3-methylpent-2-en-4-yn-1-ol to afford 2,3-dimethylfuran in good yield via intramolecular cyclization.