~ Pergamon 0277-5387(94)00278-9 Polyhedron Vol. 14, No. 5, pp. 617420, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0277 5387/95 $9.50+0.00 SOLID STATE STRUCTURES AND 13C NMR SPECTRA OF THE SEVEN-COORDINATE COMPLEXES [WI2(CO)3(NCR)2] (R=Me or Et) MICHAEL G. B. DREW* Department of Chemistry, University of Reading, Whiteknights, Reading RG6 2AD, U.K. PAUL K. BAKER,* ELAINE M. ARMSTRONG, STUART G. FRASER and DAVID J. MULDOON Department of Chemistry, University of Wales, Bangor, Gwynedd LL57 2UW, U.K. and AIDAN J. LAVERY* and ANDREW SHAWCROSS ZENECA Specialities, PO Box 42, Hexagon House, Blackley, Manchester M9 3DA, U.K. (Received 17 May 1994; accepted 19 July 1994) Abstract--The X-ray crystal structures of the two seven-coordinate complexes [WI2(CO)3(NCR)2] {R = Me (1) or Et (2)} have been determined. In both structures, the molecules have crystallographic m symmetry. The geometries of the metal coordination spheres are very similar, conforming reasonably well to distorted capped octahedra. The 13C NMR spectra of 1 and 2 are also described, and for the case of complex 1 can be correlated with the crystallographically observed geometry. In 1960, Nigam et alJ described the preparation of the seven-coordinate complexes [MoX2(CO)3 (diars)] (X = Br or I; diars = 1,2-Me2AsC6H4 AsMe2). Since this early report the synthesis and molecular structures of seven-coordinate complexes of molybdenum(II) and tungsten(II) have been widely explored. 2-'~ The structures of seven-coor- dinate complexes have generally been found 12'13to have (i) capped octahedral, (ii) capped trigonal pris- matic, (iii) pentagonal bipyramidal, or (iv) the so- called "4 : 3" geometry. The most common geometry for complexes of the type [MX2(CO)3L2] (M = Mo or W; X = halide; L = neutral donor ligand) is capped octahedralJ 4 In 1982, Colton and Kevekordes ~5 described how J3C NMR spec- troscopy could be used to correlate the solid state structure with the carbonyl region of the solution * Authors to whomcorrespondenceshouldbe addressed. state 13C NMR spectrum for a capped octahedral complex containing a carbonyl ligand in the unique capping position. In this paper we describe the X-ray crystal struc- tures and ~3CNMR spectra of the seven-coordinate bis(nitrile) complexes [WI2(CO)3(NCR)2] (R = Me or Et). A communication describing part of this work ~6 has been reported previously. EXPERIMENTAL The complex [WI2(CO)3(NCMe)2] (1) was pre- pared by reacting fac-[WI2(CO)3(NCMe)3] (pre- pared in situ) with an equimolar amount of 12 at 0°C, ~7 whereas the bis(proprionitrile) complex [WI2(CO)3(NCEt)2] (2) was prepared by reacting [WI2(CO)3(NCMe)2] with an excess of NCEt in CH2C12 at room temperature. TM The ~3CNMR spec- tra for the seven-coordinate bis(nitrile) complexes [WI2(CO)3(NCR)2] (R = Me or Et) were recorded 617