Organometallics 1982,1, 274-279
274
nicating his results prior to publication. Registry No. (OMN)Cr(C0)3,79391-56-3;(OMN)Mo(CO),, 79391-57-4;(OMN)W(CO)S, 79391-58-5;(OMN)Cr(C0)2(PPhS), 79391-59-6;( ~ ~ ~ O ) - [ O M N . M A ] C ~ (79391-60-9; CO)~, (ero)-[OMN. MA]Cr(C0)3, 79434-50-7;(endo)-OMNSMA, 36744-72-6;(exo)OMNqMA, 36744-73-7;Cr(CO)S(P(OMe)3),, 17764-72-6;Cr(CO)B,
13007.92-6; (CH&N)IMo(CO)S, 15038-48-9;(CH&N)SW(CO)s, 16800-47-8; MA, 108-31-6.
Supplementary Material Available: Listings of the observed and calculated structure factors used in the crystallographic analyses (21 pages). Ordering information is given on any current masthead page.
Further Studles on the Molecular Dynamics of the Four-Electron Brldglng Carbonyl John A. Marsella and Kenneth 0. Caulton' Department of Chemistry, Indiana Universw, Bloomington, Indiana 4 7405
Received Ju& 14, 1987
Both Mn2(CO)6(dpm)z, which contains only terminal carbonyls, and Mn2(CO)6(dpm)z, which contains one p:q2 (four-electrondonor) carbonyl, are shown to be fluxional by 13C NMR spectroscopy. Scrambling in the hexacarbonyl occurs over both metal atoms with E, = 10.2 kcal/mol and log A = 12.1,while that in pentacarbonyl involves only a wagging motion which results in disruption of the Dewar-Chatt portion of the four-electron donor carbonyl with E, = 17.0 kcal/mol and log A = 15.0. By selective 31Pdecoupling experiments, the chemical shift of the four-electroq donor carbon 1 is shown to fall in the chemical shift region normally attributed to terminal carbonyls. Coupling of JC to 31Pis small (
