Metallacycles of 1,4-Bis(3-thiophenyl)-1,3-butadiyne in Mixed Metal Clusters Derived by C−C Bond Coupling of Alkynyls

Reaction of cis-Pt(C⋮CTp)2(dppe) (Tp = thiophene) with Ru3(CO)11(CH3CN) in refluxing toluene for 1 h resulted in head-to-head C−C bond coupling of the alkynyl ligands forming 1,4-bis(3-thiophenyl)buta-1,3-diyne, which afforded an extraordinal 1,4-heterodimetalla[5,6-b]thienopentalene, [PtRu3{μ4-η1:η1:η1:η1:η4:η4-C4H2S-CCC(H)CTp}(μ-CO)2(CO)6(dppe)] (1) (Tp = 3-thiophene), in 54% yield. Its crystal structure shows that a hydrogen shift occurs from the thiophene substituent to an end carbon atom of the 1,3-diyne, transforming 1,4-bis(3-thiophenyl)buta-1,3-diene, which results in formations of PtC4 and RuC4 rings, both with metallacyclopenta-2,4-diene. The Ru3(μ-CO)2(CO)6 moiety conforms to an open cluster, and its central ruthenium atom forms a RuCp ring whose carbon atoms bond to two ruthenium atoms by eight Ru−C π-bonds. Reactions of the acetylides with single metal media, Fe(CO)5, gave rise to annealation of alkynyls via both cyclic and acyclic dimerization processes, affording extraordinal metallacycles of 1,3-diyne, a platinacyclobutene consisting of a cyclone, [FePt{μ2-η1:η1:η4-(C4Tp2-CO)-CO}(CO)3(dppe)] (2), and a 1,2-heterodimetallacyclo-3-penten-5-one, [FePt(μ2-η1:η1:η2-TpCCCCTp-CO)(μ-CO)(CO)2](dppe)] (3), in 15 and 16% yields, respectively.