Reaction of [ ( R u ( ~~-C , M ~~) ( ~~-C I ) ) ~]with 2 equivalents of REER (E = S, Se or Te; R = ferrocenyl) gave novel ferrocenylchalcogenolate-bridged diruthenium complexes [{ Ru(q 5-CSMe,)Cl(p-ER)} 2] in good yields. Reduction of these by sodium amalgam in the presence of buta-l,3-diene afforded [ { R u ( ~~-C , M ~, ) ( ~-E R ) } ~-(p-s-trans-q2 : q2'-CH2=CHCH=CH2)], whereas treatment with AgOS02CF3 produced the co-ordinatively unsaturated complexes [Cl(q5-CSMe5)Ru(p-ER)2Ru(q5-CSMe,)][OS02CF3]. The structures of five of the complexes have been defined by X-ray crystallography.Considerable attention has recently been focused on transitionmetal complexes with chalcogen ligands as synthetic models of active sites of several metalloenzymes and heterogeneous sulfide catalysts. We have recently found that the chloride ligands inl 2 can be readily displaced by p-ER (E = S 3 or Se;4 R = alkyl or aryl) or p-RTeTeR4 units, upon treatment with various thiol, thiolate, selenolate or tellurolate reagents, to form a series of dinuclear (q '-C,Me,)Ru complexes with ruthenium-( 11) and/or -(m) centres. 5-7 Subsequent studies have shown that these diruthenium complexes provide well defined bimetallic reaction sites for unique activation and transformation of organic substrates including alkynes,* organic halidesg and hydrazines. '* Interestingly these reactions are surprisingly sensitive to the nature of the diruthenium centre, and this has led us to develop a general synthetic methodology for diruthenium complexes possessing bridging chalcogen ligands.A promising approach to compounds of this class would be oxidative addition of the diorganodichalcogenides to lowvalent diruthenium complexes. ' ' However, such reactions reported to date usually result in the formation of mixtures of several products, and the desired diruthenium species can only be isolated in low yields. Previously, Killops and Knoxwith REER (ER = SMe, SEt, SCH2Ph or SePh), under UV irradiation, gives a mixture of the spectroscopically characterized complexes [Ru(qs-C,H5)(CO),(ER)] and [(Ru(q5-C5HS)(CO)(p-ER)}2] in low yields. Schermar and Baddley observed that thermal reaction of [ R U ~( C O ) ~~] with PhSeSePh affords [{Ru(CO),(p-SePh)},] (10% yield), the structure of which has recently been crystallographically determined by Cabeza and co-workers.6b We have now found that the tetranuclear ruthenium(m) complex [( Ru(q 5-C5Me,)(p3-Cl)}4] 212 readily reacts with REER (E = S, Se or Te; R = ferrocenyl) at room temperature to form the ferrocenylchalcogenolate-bridged diruthenium complexes [(Ru-(q5-C,Me5)C1(p-ER)},1 (E = S 3, Se 4 or Te 5)13 in good yields. Reported herein are the syntheses and crystal structures of these complexes together with their transformation into the s-truns-buta-l,3-diene complexes [(Ru(q'-C,Me,)(p-Selected bond distances (A) and angles (") for [(Ru(q5-Ru-Ru* Ru-CI Ru-E Ru-E* Ru-C(1) Ru-C(2) Ru-C(3) Ru-C(4) Ru-C( 5 ) E-C(l1)