Coupling of co-ordinated acetylide ligands with and without CO on chalcogen-stabilised mixed-metal clusters. Synthesis and characterisation of [M<SUB>2</SUB>Fe<SUB>3</SUB>(L)<SUB>2</SUB>(CO)<SUB>6</SUB>(μ<SUB>3</SUB>-E)<SUB>2</SUB>{μ-CC(Ph)C(Ph)C}] and [M<SUB>2</SUB>Fe<SUB>2</SUB>(L)<SUB>2</SUB>(CO)<SUB>4</SUB>(μ<SUB>3</SUB>-E)<SUB>2</SUB>{μ-CC(Ph)(CO)C(Ph)C}] (L = η<SUP>5</SUP>-C<SUB>5</SUB>Me<SUB>5</SUB> or η<SUP>5</SUP>-C<SUB>5</SUB>H<SUB>5</SUB>, M = Mo or W, E = S, Se or Te)

Thermolysis of a toluene solution containing [Fe3(CO)9(μ3-E)2] (E = S or Se) and [M(L)(CO)3(CCPh)], M = Mo or W, resulted in coupling of co-ordinated acetylide ligands with and without CO and formation of mixed-metal clusters [M2Fe3(L)2(CO)6(μ3-E)2{μ-CC(Ph)C(Ph)C}] (L = η5-C5Me5, M = Mo, E = S 1 or Se 2; M = W, E = S 3 or Se 4; M = W, E = Te 5; L = η5-C5H5, M = Mo, E = S 6 or Se 7; M = W, E = S 8 or Se 9 and [M2Fe2(L)2(CO)4(μ3-E)2{μ-CC(Ph)(CO)C(Ph)C}] (L = η5-C5H5, M = Mo, E = S 10 or Se 11; M = W, E = S 12 or Se 13). From the thermolysis reaction of [Mo(η5-C5H5)(CO)3(C≡CPh)], the new compound [{Mo(η5-C5H5)(CO)2}2{μ-C(Ph)C(CO)C≡C(Ph)}] 15 was isolated. All compounds have been characterised by IR and 1H, 13C and 77Se or 125Te NMR spectroscopy. The crystal structures of 8, 12 and 15 were elucidated by X-ray diffraction methods