Dynamic NMR studies of ring rotation in substituted ferrocenes and ruthenocenes

Redox-Switchable Hydroelementation of a Cobalt Complex Supported by a Ferrocene-Based Ligand

“…The electronic structure of the compound was investigated by the Evans method, which yielded a magnetic susceptibility of 4.34 µB, suggesting an S = 3/2 d 7 cobalt, as expected for a tetrahedral geometry. Previously reported square planar cobalt(II) salen complexes exhibit magnetic susceptibilities near 1.7 µB, indica- 49 Compound 2 was found to undergo a one-electron oxidation in the presence of acetylferrocenium [BAr F 4] (Ar F = 3,5-(CF3)2-C6H3) to produce the stable and isolable species [Co(salfen)][BAr F 4] (3, Scheme 1). Complex 3 could be reduced back to 2 by the addition of cobaltocene.…”

Preparation and Reactions of Base-Free Bis(1,2,4-tri-tert-butylcyclopentadienyl)uranium Oxide, Cp‘2UO

“…As the rings rotate about this axis they pass through several conformations, each of which has a different free energy and symmetry, which are related by different energy barriers. 25,26 The largest barrier presumably involves a conformation in which the Me 3 C-groups at the back of the wedge pass through an eclipsed conformation. Since the Cp'(cent)-U-Cp'(cent) angles are essentially the same for 1, 4, and 17, Table 3, it follows that the solution barriers should be nearly identical.…”

Ruthenocenes and Osmocenes

“…72 For l,r,3,3'-tetraalkylruthenoeenes (alkyl = Bu\ r-pentyl) the major process is exchange between a mirror pair of structures (6) with both C 5 rings eclipsed and staggered alkyl groups although, for the Bu l derivative, a pair o f staggered ring rotamers also contributes to the line shape. 71 Some determined values for £ a (reorientation) are: ; for the high-and low-temperature forms, E z values are 19.lk.Jmor 1 and 21.6 kJ mol" 1 , respectively. 74 Rc M (CONMe 2 ) 2 shows A G * for rotation of the amide carbonyl groups of 61.1kJmor'; similar morpholine and thiomorpholine derivatives have values between 54.5 kJ mol" 1 and 64.1 kJ mol" 1 .…”

“…71 Solid-state crosspolarization and magic angle spinning (CP-MAS) 13 C NMR measurements indicate fast ring rotation i n OsCp* 2 at room temperature. 46 Reorientation barriers o f the Cp rings in solid metallocenes are determined mainly by intermolecular interactions.…”