Studies of niobium selenido-halides: crystal structure of [Nb2Cl4(Se2)2(SMe2)4]

Abstract

The reactions of [NbCl₃Se] with the sulphur-donor ligands dimethyl sulphide (dms), tetrahydrothiophen (tht), and 1,2-bis(phenylthio)ethane(bpte), and the reaction of [NbBr₃Se] with tht under moisture- and oxygen-free conditions are described. The reactions gave insoluble products with analyses close to those expected for 1:2 (dms, tht) or 1:1 (bpte) adducts. Recrystallisation of the product from the reaction of [NbCl₃Se] with dms, nominally ‘NbCl₃Se·2dms’, yielded the niobium(IV) compound [(dms)₂Cl₂Nb(Se₂)₂NbCl₂(dms)₂] whose structure has been determined. Crystals are monoclinic, space group P2₁/n with a= 8.366(10), b= 13.121 (14), c= 11.204(14)Å, β= 99.53(10)°, and Z= 2. 1 855 Reflections above background were collected on a diffractometer; the structure was solved by direct methods and has been refined to R= 0.068. The structure contains centrosymmetric dimers in which each niobium atom is bonded to two chlorine atoms [Nb–Cl 2.527(5), 2.510(5)Å], four selenium atoms in two bridging Se₂^2– groups [Nb–Se 2.638(2), 2.630(2), 2.640(2), 2.625(3)Å], and two sulphur atoms from the dms group [Nb–S 2.739(4), 2.739(4)Å].