4268
Organometallics 1997, 16, 4268-4275
P a lla d iu m -Allyl Com p lexes Ba sed on
3,17-Dioxo-4-a n d r osten e. Th e Solid -Sta te Str u ctu r e of
[P d (η3-C19H29O2)(R-Bin a p )]P F 6
Dario Drommi, Reinhard Nesper, Paul S. Pregosin,* Gerald Trabesinger, and
Fabio Zu¨rcher
Laboratorium fu¨r Anorganische Chemie, ETH Zu¨rich, Universita¨tstrasse 6,
CH-8092 Zu¨rich, Switzerland
Received April 16, 1997X
Several π-allyl compounds of the form [Pd(η3-C19H29O2)(bidentate)](anion), derived from
3,17-dioxo-4-androstene, have been prepared (bidentate ) R-Binap, 3a ; S,S-Chiraphos, 3b;
(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(3,5-di-tert-butylphenylphosphine), MeO-Biphep, 3c; the
P,S-chelate (2,3,4,6-tetra-O-acetyl-1-(2-diphenylphosphino)benzylthio)-â-D-glucopyranose),
7, phenanthroline, 8, and neocuproin, 9). The solid-state structure of [Pd(η3-C19H29O2)(R-
Binap)]PF6 has been determined by X-ray diffraction methods. It is suggested that 3a (and
presumably other relatively large allyl complexes) accommodates the two large ligands by
both hinging the allyl plane away from the Binap and rotating the allyl ligand. Selected
aspects of the solution dynamics for 3a , 3c, and 9 have been followed by NOESY methods.
Allyl 13C NMR data are reported for the complexes.
In tr od u ction
refers to the steric interactions between sections of the
coordinated allyl and, e.g., the phosphorus substituents.
These steric effects will depend on the size and bite
angle of the chelate as well as its 3-D structure.
Intuitively, one would expect that the structure of the
allyl must also be an important factor in determining
enantioselectivity, in addition to the nature of the
chelate; however, there is relatively little on the effect
of allyl size in the literature. We have recently shown15
that the organic allyl derived from the diterpene carvone
is still quite modest in size and in terms of its solution
dynamics behaves like a 2-methylallyl ligand.
The chemistry of π-allyl-palladium complexes con-
tinues to attract interest in that these molecules provide
useful preparative tools.1 A variety of Pd-allyl com-
plexes are isolable and readily accommodate both mono-
and bidentate phosphine and nitrogen compounds as
accompanying ligands.1-4
In the enantioselective allylic alkylation reaction,
phosphine, pyrazole, and oxazoline complexes have been
employed as auxiliaries, among others, with varying
degrees of success in terms of enantioselectivity.5-14 In
this area, one finds an increasing amount of literature
concerned with defining the “chiral pocket” experienced
by the coordinated allyl ligand.7b,13a,14 In effect, this
X Abstract published in Advance ACS Abstracts, August 15, 1997.
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