ETHER COMPLEXES OF TUNGSTEN WITH 2 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 ethe r complex was determined by single crystal X-ray diffraction and was s hown to have the ether bonded to tungsten through the oxygen. This com pound 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 b ond of the vinyl ether. The crystal structure of this compound shows t hat the W-C(OEt) distance (2.69(3) Angstrom) is significantly longer t han 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 counte rions. Evidence is presented that some of these weak hydrogen bonds ar e maintained in CD2Cl2 solution but not in CD3CN.