Ether complexes of tungsten with two different binding modes: An O-bound ether and an eta(2)-(C=C) vinyl ether. Evidence for C-H center dot center dot center dot O hydrogen bonding of vinylic C-H groups

The reaction of PhCH(OCH3)(2) with Cp(CO)(3)WH and HOTf gives [Cp(CO)(3)W(PhCH(2)OCH(3))](+)OTf(-). The structure of this benzyl methyl ether complex was determined by single crystal X-ray diffraction and was shown to have the ether bonded to tungsten through the oxygen. This compound was isolated as a kinetic product of the reaction; it decomposes in solution by releasing free PhCH(2)OCH(3) and forming Cp(CO)(3)WOTf. An analog with the BAr4'(-) counterion [Ar'=3,5-bis(trifluoromethyl)phenyl] is more stable. The reaction of the vinyl acetal CH2=CHCH(OEt)(2) with Cp(CO)(3)WH and HOTf produces [Cp(CO)(3)W(eta(2)-EtOCH=CHCH3)](+)OTf(-), in which the ether is bonded to tungsten through the C=C bond of the vinyl ether. The crystal structure of this compound shows that the W-C(OEt) distance (2.69(3) Angstrom) is significantly longer than the W-C(CH3) distance (2.37(3) Angstrom). There are weak C-H ... O hydrogen bonds between both vinyl CH's and oxygens of triflate counterions. Evidence is presented that some of these weak hydrogen bonds are maintained in CD2Cl2 solution but not in CD3CN.