Synthesis, reactions, and [sup 77]Se NMR studies of [eta][sup 5]-selenophene complexes of chromium, manganese, ruthenium, and iridium

The series of [eta][sup 5]-selenophene transition metal complexes ([eta][sup 5]-Seln)Cr(CO)[sub 3] (1-3), [([eta][sup 5]-Seln)Mn(CO)[sub 3]]SO[sub 3]CF[sub 3] (4-6), [([eta][sup 5]-Seln)RuCp*] SO[sub 3]CF[sub 3] (7-9), and [([eta][sup 5]-Seln)IrCp*](BF[sub 4])[sub 2] (10-12), where Seln = selenophene (Sel), 2-methylselenophene (2-MeSel), or 2,5-dimethylselenophene (2,5-Me[sub 2]Sel), were synthesized and characterized by [sup 1]H, [sup 13]C, and [sup 77]Se NMR and IR spectroscopy. The molecular structure of ([eta][sup 5]-2,5-Me[sub 2]Sel)Cr(CO)[sub 3] (3) was determined. Reactions of [([eta][sup 5]-Sel)Mn(CO)[sub 3]]SO[sub 3]CF[sub 3] (4) with nucleophiles (Nuc = H[sup [minus]], CN) give the neutral addition products [(Sel-Nuc)Mn(CO)[sub 3]] [Nuc = H[sup [minus]] (4a), Nuc = CN[sup [minus]] (4b)] in which three carbon atoms and the Se are bonded to the Mn. The reaction of [([eta][sup 5]-Sel)RuCp*]SO[sub 3]CF[sub 3] (7) with H[sup [minus]], however, results in cleavage of the C-Se bond to form a butadiene selenide complex (([eta][sup 5]-SeCH=CHCH=CH[sub 2])RuCp*) (7a). Still another type of product results from the reaction of [([eta][sup 5]-2,5-Me[sub 2]Sel)IrCp*](BF[sub 4])[sub 2] (12) with 2 equiv of H[sup [minus]]; in this case, the H[sup [minus]] acts as a reducing agent to give the ring-opened complex (C, Se-2,5-Me[sub 2]Sel)IrCp* (12a). 45 refs., 4 figs., 4 tabs.