Synthesis of novel quadruply bridged M2Se4 clusters trans/anti and trans/syn-[(η5-RC5H4)2M2(μ-Se)2(μ-SeCH2Ph)2] (M=Mo, W) via an unexpected reaction of MM triply bonded complexes [(η5-RC5H4)2M2(CO)4] with dibenzyl diselenide. Crystal structures of a pair

The unexpected reaction of triply bonded complexes [(η5-RC5H4)2M2(CO)4] with dibenzyl diselenide (PhCH2)2Se2 in toluene at reflux gave a series of isomeric M2Se4 clusters trans/anti-[(η5-RC5H4)2M2(μ-Se)2(μ-SeCH2Ph)2] (1a, M=Mo, R=MeCO; 2a, Mo, MeO2C; 3a, Mo, EtO2C; 4a, W, MeCO; 5a, W, MeO2C; 6a, W, EtO2C) and trans/syn-[(η5-RC5H4)2M2(μ-Se)2(μ-SeCH2Ph)2] (1b, M=Mo, R=MeCO; 2b, Mo, MeO2C; 3b, Mo, EtO2C; 4b, W, MeCO; 5b, W, MeO2C; 6b, W, EtO2C) in combined 20–41% yields. In addition, the reaction of [(η5-MeO2CC5H4)2W2(CO)4] with (PhCH2)2Se2 in solid state at 90°C also afforded 5a and 5b in a total of 32% yield. The structures of these new clusters were fully characterized by elemental analysis and spectroscopy; those for 3a and 3b were confirmed by single-crystal X-ray diffraction techniques.