A series of quadruply bonded dimolybdenum compounds of form Mo(2)(EE'CC≡CPh)(4) (EE' = {NPh}(2), Mo(2)NN; {NPh}O, Mo(2)NO;{NPh}S, Mo(2)NS; OO, Mo(2)OO) have been synthesised by ligand exchange reactions of Mo(2)(O(2)CCH(3))(4) with the acid or alkali metal salt of {PhC≡CCEE'}(-). The compounds Mo(2)NO, Mo(2)NS and Mo(2)OO were structurally characterised by single crystal X-ray crystallography. ...