Syntheses and structures of chalcogen-bridged binuclear group 5 and 6 metal complexes

Syntheses and structural elucidations of a series of chalcogen stabilized binuclear complexes of group 5 and 6 transition metals have been described. Room temperature reaction of [Cp*CrCl] 2 (Cp* = η 5 -C 5 Me 5 ) with Li[BH 3 (SePh)] afforded a Se inserted binuclear chromium complex, [(Cp*Cr) 2 ( µ- Se 2 SePh) 2 ], 1 . In an attempt to make the analogous complexes with heavier group 6 metals, reactions of [Cp*MCl 4 ] (M = Mo and W) with Li[BH 3 (SePh)] were carried out that yielded Se inserted binuclear complexes [(Cp*M) 2 ( µ- Se) 2 ( µ- SePh) 2 ], 2 and 3 ( 2 : M = Mo and 3 : M = W) along with known [(Cp*M) 2 B 5 H 9 ], 4a – b ( 4a : M = Mo and 4b : M = W). Similarly, the reactions of [Cp*NbCl 4 ] with Li[BH 3 (EPh)] (E = S or Se) followed by thermolysis led to the formation of binuclear chalcogen complexes [(Cp*Nb) 2 ( µ- E 2 ) 2 ], 5 and 6 ( 5 : E = S and 6 : E = Se) and known [(Cp*Nb) 2 (B 2 H 6 ) 2 ], 7 . All these complexes have been characterized by 1 H and 13 C NMR spectroscopy and mass spectrometry. The structural integrity of complexes 1 , 3 , 5 and 6 was established by the X-ray diffraction studies. The DFT studies further exemplify the bonding interactions present in these complexes, especially the multiple bond character between the metals in 1–3 . Graphic abstract The syntheses and structural characterizations of three chalcogen-bridged bimetallic complexes of group 5 and 6 metals, such as [(Cp*Nb) 2 ( µ- E 2 ) 2 ] (E = S and Se) (right), [(Cp*Cr) 2 ( µ- Se 2 SePh) 2 ] (centre) and [(Cp*M) 2 ( µ- Se) 2 ( µ- SePh) 2 ], (M = Mo and W) (left) are reported.