12-ELECTRON TETRANUCLEAR TUNGSTEN ALKOXIDE CLUSTERS ARE NOT TETRAHEDRAL - PREPARATION, STRUCTURE AND BONDING IN W4(O)(OPRI)10 AND W4(O)(CL)(OPRI)9 - COMPARISONS WITH THE BONDING IN CARBONYL CLUSTERS

Addition of H2O (0.5 equiv) to a hexane/PriOH solution of W4(OPri)12 yields W4(O)(OPri)10 (II) which reacts further with NH4Cl to give W4(O)(Cl)(OPri)9 (I). The NMR data for I and II are indicative of common structural features and the molecular structure of I has been determined in the solid state by a single crystal X-ray diffraction study. At -146°C: a = 41.172(18), b = 9.185(2), c = 22.718(8) Å, β = 97.15(2)°, Z = 4 and dcalc = 2.113 g cm-3. A WCl(OPri) moiety caps a basal W3(μ-O)(μ-OPri)2(OPri)6 moiety. The local WO4 geometry for the tungsten atoms in the basal plane is square planar. Of particular note are the short WW distances involving the capping WCl(OPri) moiety (ca 2.45 Å) relative to those WW distances in the basal plane (ca 2.90 Å). The bonding in compounds I and II, modelled as W4(O)(Cl)(OH)9 and W4(O)(OH)10, respectively, has been investigated by MO calculations employing the method of Fenske and Hall. The combination of the d4-WCl(OH) fragment with the d8-W3(O)(OH)8 fragment yields multiple MM bond character between the capping tungsten atom and the three WW atoms in the basal plane. Interesting analogies are seen between carbonyl and alkoxide clusters based on the isolobal principle d3-W(OR)3 ↔ d9-Co(CO)3 ↔ d9-Os(CO)3- and d4-WX2 ↔ d10-PtL2. Specific comments are made with respect to the bonding in M4(OR)12 (M = Mo, W), M4(CO)12 (M = Co, Rh, Ir) (I, II) and Os3Pt(H)2(CO)(PR3). © 1990.