177 zyxwvuts Journal of Organometallic Chemistry, 205 (1981) 177-183 Elsevier Sequoia S.A., Lausanne -Printed in The Netherlands zyxwvutsrqponmlkjihgfedcbaZYXWV SYNTHESIS OF THE PENTACARBONYL(CHALCOCARBONYL)- CHROMIUM(O) COMPLEXES, Cr(CO),(CX) (X = S, Se) ANN M. ENGLISH, KEITH R. PLOWMAN, IONE hf. BAIBICH, JAMES P. HICKEY, IAN S. BUTLER * Department of Chemistry, McGill University, Montreal, Quebec H3A 2K6 (Canada) GERARD JAOUEN * and PAUL LEMAUX Laboratoire de Chimie des OrganomCtaNiques, UniversiN de Rennes, 35042 Rennes Ce’dex (France) (Received June 4th, 1980) The arene complexes, ($-C,H,)Cr(CO),(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60°C to produce the Cr(CO),(CX) complexes in high yield. The IR and NlMR (13C and 170) spectra of these complexes are in complete accord with the expected C,,, molecular symmetry. Like the analogous W( CO),(CS) complex, both compounds react with cyclohexylamine to give Cr( CO),( CNC,H 1 1). However, while W(CO),( CS) undergoes stereospecific CO substitution with halide ions (Y -) to form zyxwvutsrqponmlkj trans- [W(CO),(CS)Y] -, the two chromium chalcocarbonyl complexes apparently un- dergo both CO and CX substitution to afford mixtures of [Cr(CO),Y] - and tram-[Cr(CO),(CX)Y]-. Introduction Sodium amalgam reduction of the Group VIB metal hexacarbonyls in tetra- hydrofuran leads to mixture of metal carbonyl anions, chiefly [M2(CO)J *- (M = Cr, MO, W) [ 11, and addition of excess thiophosgene (Cl&S) to these solutions affords the M(CO),(CS) complexes in very poor yields (usually <5%) [ 23. Furthermore, these thiocarbonyl products are heavily contaminated with large amounts of M(CO),, which is regenerated during the reactions, thus neces- sitating tedious physical or chemical separations. Moreover, this route cannot be extended to the synthesis of the analogous selenocarbonyl complexes, M(CO),(CSe), owing to the apparent nonexistence of Cl&Se. Earlier, we communicated [3] an alternative route to Cr(CO),(CS) (eq. 1) in