FLUXIONAL BEHAVIOR OF SOME DINUCLEAR IRON AND COBALT HEXACARBONYL COMPOUNDS WITH ALKYLSULFUR AND DIALKYLPHOSPHORUS, DIALKYLARSENIC, DIALKYLGERMANIUM, AND DIALKYLTIN BRIDGES
FLUXIONAL BEHAVIOR OF SOME DINUCLEAR IRON AND COBALT HEXACARBONYL COMPOUNDS WITH ALKYLSULFUR AND DIALKYLPHOSPHORUS, DIALKYLARSENIC, DIALKYLGERMANIUM, AND DIALKYLTIN BRIDGES
复制标题
DOI：
10.1021/ic50148a038
复制
发表时间：
1975-01-01
影响因子：
4.6
通讯作者：
MIHICHUK, L
中科院分区：
文献类型：
--
作者：
ADAMS, RD;COTTON, FA;MIHICHUK, L
A number of compounds of the general type (OC) 3M (a-ERn) 2M (CO) 3, in which M= Fe while ER «is PMez, AsMePh, AsMez, SMe, or SEt and M= Co while ERn= GeMez or SnMez, have been prepared and their dynamical properties studied by 13C and> H NMR spectroscopy at temperatures from-130 to+ 150. The RS-bridged compounds show no evidence of axial-equatorial R group exchange prior to the onset of irreversible thermolysis. of the phosphino-and arsino-bridged iron compounds show R group exchange with coalescence temperatures in the range 50-100, while the germylyl-and silylyl-bridged cobaltcompounds exhibit R groupexchange with coalescence temperatures around-55. Interconversion of symmetrical and unsymmetrical isomers of the AsMePh-bridged iron compound requires a period of many hours at ca. 150 to attain equilibrium. Rapidexchange of nonequivalent carbonylgroups proceeds at very low temperatures in all cases, with coalescence temperatures around-70. Thus, there appear to be three essentiallyindependent processes which are, in order of decreasing rate,(1) CO scrambling,(2) axial-equatorial R group exchange in a concerted fashion such that it occurs in both ERz groups simultaneously, and (3) axial-equatorial R group exchange in such a way that isomers of an ERR'-bridged species are interconverted. The low activation energy for process 1 is not inconsistent with observations on many other M (CO) 3-containing molecules, and the very high activation energy for process 3 is consistent with the need for inversion of the configuration of pyramidal P or As ligands in a bridge-opened intermediate. The mechanism of process 2 remains debatable butit may proceed without bridge opening.
