Studies of cobalt carbonyls on oxide supports. 4. Nitric oxide reactions with cobalt carbonyls

Nitric oxide was reacted with the cobalt carbonyls Co/sub 2/(CO)/sub 8/ and Co/sub 4/(CO)/sub 12/ supported on silica, ..gamma..-alumina, Na-Y and Na-X zeolites, and magnesia. IR spectroscopy, manometry, mass spectrometry, and isotropic exchange experiments disclosed, in each case, the conversion of the supported carbonyl compound to an intermediate Co(CO)/sub 3/NO (I) and then to a trinitrosyl of cobalt (II). The IR spectra observed for I on the supports agreed quite closely with those reported for the corresponding pure compound. Indeed, I could be added directly from the vapor phase to the supports where it displayed properties identical with those of the intermediate observed in the surface nitrosylation process. Although the intermediate was observed only fleetingly on the Na-X zeolite and not at all on ..gamma..-Al/sub 2/O/sub 3/ during the conversion of the starting carbonyl to II, direct addition of I to both these supports resulted in spontaneous conversion to II. Moreover, when NO was added to supported II formed in this manner, the IR spectrum of II increased 2-3-fold in intensity, indicating that bare cobalt atoms formed in the spontaneous conversion of I to II may be nitrosylated to yield more II. The identity of II is more ambiguous because it could not be extracted from any of the surfaces for direct comparison with appropriate cobalt nitrosyl species. Analogy with known preparative solution chemistry comparison with reported IR spectra, and interpretation of observations of the gas phase above the surface species lead to the conclusion that II is the zero valent Co(NO)/sub 3/ complex, although the possibility that it is (Co(NO)/sub 3/)/sup 2 +/ cannot be ruled out. 19 references, 5 figures.