[Cl5ta(Mu-O)Tacl3{(Prs)-Pr-I(Ch2)(2)(Spr)-Pr-I}] And [(Tacl4)(2)(Mu-O)(Mu-Me2se2)]: Two Chalcogenoether Complexes Of Ta2ocl8 With Very Different Geometries

The title compounds, [1,2-bis(isopropylsulfanyl)ethane-2 kappa S-2,S']octachlorido-1 kappa Cl-5,2 kappa Cl-3-mu-oxido-ditantalum(V), [Ta2Cl8O(C8H18S2)], (I), and mu-dimethyldiselane-kappa Se-2:Se'-mu-oxido-bis[tetrachloridotantalum(V)], [Ta2Cl8O(C2H6Se2)], (II), contain six-coordinate Ta-V centres linked by a nonlinear oxide bridge. Compound (I) contains one Ta-V centre bonded to a chelating dithioether and three terminal chloride ligands, with the second Ta-V centre bonded to five terminal chloride ligands. In (II), two tetrachloridotantalum(V) residues are bridged by the diselenide, giving a puckered five-membered Ta/O/Ta/Se/Se ring. The Ta-O distances in the bridges are short in both compounds, indicating that significant multiple-bond character is retained despite the deviation from linearity, and the bond lengths reveal a clear trans influence order of O > Cl > S > Se on the hard Ta-V centre. The structures are compared with the [Ta2Cl10O](2-) anion, which contains a linear oxide bridge.