Hydrogen migration mechanism for ligand substitution reactions in metal carbonyl hydrides

Autor: Peter C. Ford, Heiko. Mauermann, Howard W. Walker, Ralph G. Pearson
Rok vydání: 1981
Předmět:
Zdroj: Inorganic Chemistry. 20:2741-2743
ISSN: 1520-510X
0020-1669
DOI: 10.1021/ic50222a078
Popis: It has been known for some time that certain transition metal carbonyl hydrides are unusually labile in ligand substitution processes. A mechanism explaining this unusual lability was offered involving a ligand migration of hydrogen to a carbonyl group, attack at the vacated coordination site y the entering ligand, loss of a CO ligand, and back-migration of H to the metal. The following recent experiments offer strong support for this hydride migration. (A) In acetone at -70/sup 0/C H/sub 2/Fe(CO)/sub 4/ reacts within 3 min with PPh/sub 3/ to give H/sub 2/Fe(CO)PPh/sub 3/ and with P(OMe)/sub 3/ to give H/sub 2/Fe(CO)/sub 3/P(OMe)/sub 3/ and H/sub 2/Fe(CO)/sub 2/(P(OMe)/sub 3/)/sub 2/. The phosphine and phosphites are cis to both hydrogens, and the hydrogens are probably cis to each other. The same results are found in methanol at room temperature. These substitutions are at least 30 times as fast as the thermal decomposition of H/sub 2/Fe(CO)/sub 4/ in methanol. H/sub 2/Fe(CO)/sub 3/PPh/sub 3/ decomposes at a rate similar to that of H/sub 2/Fe(CO)/sub 4/ and yields trans-Fe(CO)/sub 3/(PPh/sub 3/)/sub 2/ in the presence of triphenylphosphine. (B) H/sub 2/Ru(CO)/sub 4/ in acetone at -70/sup 0/C also gives H/sub 2/Ru(CO)/sub 3/P(OMe)/sub 3/ in a few minutesmore » with the phosphite cis to hydrogen. Upon warming H/sub 2/Ru(CO)/sub 2/(P(OMe)/sub 3/)/sub 2/ is formed. (C) In methanol at 25/sup 0/C the ion HRu(CO)/sub 4//sup -/, as the PPN/sup +/ salt, is converted immediately into HRu/sub 3/(CO)/sub 11//sup -/. Adding excess sodium methoxide (about 0.4 M) slows the reaction time down to about 15 min, but the same product is formed.« less
Databáze: OpenAIRE
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