A new simple synthetic route to M3Se7 (M = Mo or W) core containing complexes: crystal structure and characterisation of [M-3(mu(3)-Se)(mu-Se-2)(3)(dtc)(3)](2)Se

The reaction of M(CO)(6). (M = Cr, Mo or W), with elemental Se and (Et2NCS2 )(2) in refluxing 1,2-dichlorobenzene has been studied. For M = Mo the prev iously unknown compound [Mo-3(mu (3)-Se)(mu -Se-2)(3)(dtc)(3)](2)Se (1)(dtc = Et2NCS2) was obtained. A single crystal X-ray crystallographic study sho ws that 1 contains two [Mo-3(mu (3)-Se)(mu -Se-2)(3)(dtc)(3)] subunits join ed by a bridging selenium atom which is coordinated to the three axial Se a toms of the three Se, moieties in each subunit. The results of vibrational spectroscopic and mass spectrometric studies back up this crystallographic investigation. Similar reactions where Cr(CO)(6) or W(CO)(6) replace Mo(CO) (6) in the reaction mixture give, with Cr(CO)(6), the well-known complex [C r(dtc)(3)] or, with W(CO)(6), a mixture of products including 2 which is th e tungsten analogue of 1. (C) 2000 Elsevier Science B.V. All rights reserve d.