G. Bellachioma et al., CATIONIC ACETYL COMPLEXES OF IRON(II) AND RUTHENIUM(II) BEARING NEUTRAL N,O LIGANDS - SYNTHESIS, CHARACTERIZATION, AND INTERIONIC SOLUTION STRUCTURE BY NOESY NMR-SPECTROSCOPY, Organometallics, 17(23), 1998, pp. 5025-5030
The reactions of complexes trans, cis-M(PMe3)(2)(CO)(2)(Me)I (M = Fe (
1a), Ru (1b)) with N,O ligands [2-acetylpyridine (2-apy), 2-benzoylpyr
idine (2-bzpy), and 2,2'-dipyridyl ketone (2,2'-dpk)] in the presence
of NaBPh4 afford a mixture of the two possible stereoisomers trans-[M(
PMe3)(2)(CO)(COMe)(N, O)]BPh4 having the N arm cis (A) or trans (B) to
the acetyl group. The stereochemistry of the complexes was determined
by H-1 NOESY NMR spectra. For all the iron complexes the major stereo
isomer is B, while for ruthenium complexes it is A. When A/B mixtures
are left in methylene chloride, the concentration of A increases, indi
cating that A and B are the thermodynamic and kinetic reaction product
s, respectively. Furthermore, the more basic the N,O ligands, the more
B stereoisomer that forms. The solid-state structure of 4b was obtain
ed using single-crystal X-ray diffraction. For all the complexes, the
ion-pair structures and the localization of the counterion in solution
with respect to the organometallic moiety were investigated by the de
tection of interionic contacts in the H-1 NOESY NMR spectra. Specific
interactions were observed that indicate that the counterion is locali
zed in solution in front of the face determined by PMe3 and the two ar
ms of the N,O ligands.