MgO-supported manganese carbonyl complexes were prepared by chemical vapor deposition of Mn(CO)5CH3 on partially dehydroxylated, high-area MgO powder. X-ray absorption spectra identify the resultant surface species, on average, as Mn(CO)4(Os)2 (where the two oxygen ligands are part of the MgO surface), and infrared spectra show that the chemisorption results from the reaction of Mn(CO)5CH3 with OH groups of the MgO surface. Electron paramagnetic resonance and X-ray absorption near edge data indicate that the manganese was in a positive oxidation state other than +2, but the value is not determined, and the IR spectra indicate the presence of a mixture of manganese carbonyls. Extended X-ray absorption fine structure spectra determine the average Mn-CO bond distance to be 1.87 Å and the average Mn-O bond distance to be 2.12 Å. The surface complex was found to be stable in O2 at room temperature.