Polyether polymerization process

A process 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 in a semi-batch process in which the catalyst complex and starter are charged to a reaction vessel, the catalyst complex is activated and at least a portion of the alkylene oxide is thereafter added to the reaction vessel containing the activated catalyst complex and starter under polymerization conditions without removal of product until all of the alkylene oxide has been added, wherein the catalyst complex is a mixture of a zinc hexacyanocobaltate catalyst and one or more of aluminum oxide, iron oxide, hafnium oxide, gallium oxide and indium oxide present in an amount sufficient to provide 0.002 to 10 moles of aluminum, iron, hafnium, gallium or indium per mole of cobalt provided by the zinc hexacyanocobaltate catalyst.