Polyether polymerization process

A method for producing a polyether, the method forming a reaction mixture comprising a hydroxyl-containing starter, at least one alkylene oxide and a catalyst complex, and polymerizing the alkylene oxide onto the hydroxyl-containing starter to produce the polyether in the presence of no more than 0.01 moles of a carbonate precursor per mole of alkylene oxide, wherein the catalyst complex is a mixture of a zinc hexacyanocobaltate catalyst and a particulate M3 metal or semi-metal oxide wherein the M3 metal or semi-metal is one or more of aluminum, iron, hafnium, gallium and indium and the M3 metal or semi-metal oxide is present in an amount sufficient to provide 0.002 to 10 moles of M3 metal or semi-metal per mole of cobalt provided by the zinc hexacyanocobaltate catalyst, and further wherein the hydroxyl concentration during at least a portion of the polymerization is in the range of 4.25 to 20% by weight of the reaction mixture.