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Structure of 7t-CóH6CoS2C2(CN) 2 1123 conformations should allow estimates of these -bond energies and will be reported in a later paper.The second form of evidence suggesting multiple bonding between the metal atom and the pyridine groups comes from the metal-nitrogen atom bond lengths. The values determined here are nearly equal and average 2.187 Á. Values of 2.12 and 2,14 A have been reported for this distance in Co(NCS)2(py)22S and CoCl2(py)2,29 where the cobalt atom in both cases is octahedrally coordinated through bridging by the nonpyridine ligands; however, both of these structures were done only with projections and no reliable estimate of the errors involved is available. Further, these distances might also be shortened from the ideal single-bond distance.The value for hypothetical single-bond distances for the fifth and sixth coordination positions of a cobalt acetylacetonate is needed, and the structure6 of Co(AA)2(H20)2 provides that information. There is little reason to believe that there is any double bonding between the cobalt atom and the water (28) M. A. Porai-Koshits and G. N. Tischenko, Kristallografiya, 4, 239 (1959).