An air-stable iron cluster alkoxide complex Na-2[Fe-6(OCH2CH2OCH3)(18)(mu(6)-O)] was prepared from the reaction of iron(III) chloride and sodium 2-methoxyethoxide. The complex was used to prepare Sr2FeMoO6, which spin-coated film:shows a very high positive magnetoresistance of 25% with a magnetic field of 0.8 T at 300 K.