Synthesis, spectroscopic and structural studies on transition metal carbonyl complexes of cyclic di- and tetra-selenoether ligands

Reaction of [M(CO)(4)(nbd)] (M = Cr or Mo, nbd = norbornadiene) or [W(CO)(4 )(TMPA)] (TMPA = N,N,N',N'-tetramethyl-1,3-propanediamine) with [8]aneSe(2) (1,5-diselenacyclooctane) yielded the cis-disubstituted tetracarbonyl spec ies [M(CO)(4)([8]aneSe(2))] (M = Cr, Mo or W). The complexes [M'X(CO)(5)] ( M' = Mn, X = Cl, Br or I; M' = Re, X = Cl or Br) reacted similarly with [8] aneSe(2) to give fac-[M'X(CO)(3)([8]aneSe(2))] in high yield. Infrared and multinuclear NMR spectroscopic studies confirmed these assignments and indi cated a single species in solution; delta(Mn-55) lies in the same range as observed for other fac-[MnX(CO)(3)(diselenoether)] complexes, while for all of the compounds delta(Se-77) is to low frequency of [8]aneSe(2) itself (d elta 137). Crystal structures of [W(CO)(4)([8]aneSe(2))], [MnBr(CO)(3)([8]a neSe(2))] and [ReBr(CO)(3)([8]aneSe(2))] show the cyclic diselenoether chel ating and adopting a chair-boat conformation. The compounds [16]aneSe(4) (1 ,5,9,13-tetraselenacyclohexadecane) and L(1,6-diselena-3,4-benzocyclononane ) reacted with the metal(II) species [{MoBr2(CO)(4))}(2)] or [MI2(CO)(3)(NC Me)(2)] in CH2Cl2 solution to give seven-co-ordinate [{MoX2(Co)(3)}(2)([16] aneSe(4))], [WI2(CO)(3)([16]aneSe(4))], [MoX2(CO)(3)(L)] and [WI2(CO)(3)(L) ], although these species decompose rapidly in co-ordinating solvents. Reac tion of [16]aneSe(4) with two molar equivalents of [M'Cl(CO)(5)] yielded th e dinuclear complex [{MnCl(CO)(3)}(2)([16]aneSe(4))] (in which the tetrasel enoether is thought to bind in a bidentate manner to each Mn) and the monon uclear complex [ReCl(CO)(3)([16]aneSe(4))] (which is thought to involve bid entate ligation to [16]aneSe(4) with two free Se donors). The cationic spec ies fac-[Mn(CO)(3)(eta(3)-[16]aneSe(4))]CF3SO3 was generated by treatment o f [MnCl(CO)(5)] with AgCF3SO3 in Me2CO followed by addition of [16]aneSe(4) .