carbon monoxide in tetrahydrofuran byproducts: [(C6H5)3PH](1+)*BF4(1-), (C6H5)3P; (Ar),to nickel complex added THF previously saturated with CO, then CO passed in at -78°C for 24 h; filtered, evapd., treated with pentane, benzene, hot toluene, elem. anal., IR;