Phosphorus ligands derived from terpene alcohols as stereochemical probes
Date
2018-07-19
Authors
Wang, Jihong
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Abstract
A series of optically active tertiary phosphorus ligands, [special characters omitted] (R = bornyl,
menthyl, or isopinocamphyl; n = 1, 2, or 3, 1 – 9), containing chiral alkoxy groups
derived from natural terpene alcohols, menthol, borneol, and isopinocampheol, are
synthesized and characterized by various spectroscopic techniques. The reactions of
these ligands with iron and cobalt carbonyl complexes are carried out, giving monomeric
mono- and di-substituted iron(0) and dimeric di-substituted cobalt carbonyl complexes
[special characters omitted]. The characterization of these
complexes by IR and NMR spectrometries is discussed. Results of preliminary studies
on hydroformylation reaction under oxo conditions catalysed by several cobalt
complexes are presented.
Pyrazolyl bridged di-iridium(I) systems, [special characters omitted], are prepared as diastereomers with unequal
thermodynamic distribution. The X-ray crystal structure of 41 shows cocrystallization
of the two diastereomers in the same unit cell, which provides 1:1 kinetic distribution
of the two isomers. Kinetic studies of the interconversion from the kinetic ratio to the
thermodynamic ratio of the two diastereomers in 41 indicates the existence of a slow
inversion process of the six-membered central metallocycle in 41. Oxidative addition of
Mel to 41 generates a pair of diastereomeric adducts (43) in kinetic distribution, which
is slowly converted to its thermodynamic distribution, implying a very slow reductive
elimination of Mel.
Oxidative additions of exo- and endo-norbornyl iodide to [special characters omitted] results
in same product (44). Possible mechanisms for this process are discussed.
Bisdiphenylphosphinoalkylsilane containing chiral menthoxy group [special characters omitted] is prepared and characterized. Its four-coordinate square
planar platinum complex [special characters omitted] and five-coordinate
iridium(I) complex [special characters omitted] are synthesized.
Isomerizations of 49 and its CO adducts, [special characters omitted] (55 and
56), are studied in relation to their methyl analogues.
Description
Keywords
Ligands, Terpenes, Stereochemistry