Ruthenium or Ferrocenyl Homobimetallic and RuPdRu and FePdFe Heterotrimetallic Complexes Connected by Unsaturated, Carbon-Rich −C⋮CC6H4C⋮C− Bridges

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.