Reaction of Mo≡Mo triply bonded complexes [η 5 -RC 5 H 4 Mo(CO) 2 ] 2 with the Fe/S butterfly compound (μ-PhS) 2 Fe 2 (CO) 6 in refluxing xylene gives two corresponding Mo Mo doubly bonded complexes (η 5 -RC 5 H 4 ) 2 Mo 2 (CO) 2 (μ-PhS) 2 . Each of the complexes consists of two isomers, namely trans/anti and trans/syn, in terms of the relative arrangement of the RC 5 H 4 and CO ligands and the mutual orientation of the phenyl groups on the bridging sulfur atoms. The two isomers with R=MeCO are convertible to each other in xylene at reflux and have been crystallographically determined by X-ray diffraction. Further reactions of the R=MeCO complex with NaBH 4 and MeMgI afford two corresponding functional hydroxyl derivatives [η 5 -MeCH(OH)C 5 H 4 ] 2 Mo 2 (CO) 2 (μ-PhS) 2 and [η 5 -Me 2 C(OH)C 5 H 4 ] 2 Mo 2 (CO) 2 (μ-PhS) 2 .