MO-2(O)(OCH(2)(T)BU)(4)(PME(3))(4-CENTER-DOT) PREPARATION AND CHARACTERIZATION OF A PARTIAL HYDROLYSIS PRODUCT OF MO-2(OCH(2)(T)BU)(6)

Partial hydrolysis of Mo-2(OCH(2)(t)Bu)(6) in the presence of excess t rimethylphosphine produced the novel compound Mo-2(PMe(3))(4)(mu-O)(mu -OCH(2)(t)Bu) (OCH(2)(t)Bu)(3) (1). The solid-state molecular structur e of 1 as determined by single crystal X-ray diffraction revealed an M o-Mo double bond [2.4931(9) Angstrom] between the metal centers which are in local octahedral and trigonal bi-pyramidal coordination geometr ies, respectively. The complex possesses an asymmetric oxo bridge [1.9 96(4) Angstrom and 1.874(4) Angstrom] as well as a bridging alkoxide l igand. Based on the coordination geometries, as well as the metal-meta l separation, it is proposed to contain metal centers with formal oxid ation states Mo(4+) (d(2)) and (Mo+) (d(4)). In solution 2 is evidentl y non-fluxional on the NMR timescale and maintains a geometry akin to that seen in the solid state. Compound 1 reacted with carbon monoxide (1 equiv.) giving a 1 : 1 adduct, 2, wherein the d(4)-Mo(2+) center is ligated by CO. Thermolysis of 2 does not yield oxidation products, i. e. Me(3)PO or CO2, but does show evidence for the formation of (PMe(3) )(4)Mo(CO)(2) along with other uncharacterized molybdenum alkoxide pro ducts. While 2 may be formally derived from the oxidative cleavage of CO2 by reaction with Mo-2(OCH(2)(t)Bu)(4)(PMe(3))(4), the latter inser ts CO2 into the Mo-OR bonds, as does Mo-2((OPr)-Pr-i)(4)(dmpe)(2), whe re dmpe = Me(2)PCH(2)CH(2)PMe(2). Copyright (C) 1996 Elsevier Science Ltd