Organometallics 2003, 22, 3025-3027
3025
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of a Novel
Dip a lla d iu m Com p lex w ith a n Un p r eced en ted P d CN
Bon d in g Motif
Gareth R. Owen, Ramo´n Vilar,* Andrew J . P. White, and David J . Williams
Department of Chemistry, Imperial College London,
South Kensington, London SW7 2AZ, U.K.
Received April 1, 2003
Sch em e 1. P ossible Coor d in a tion Mod es of
Meta l-Im id oyl (a ) a n d Meta l-Im in e (b) Moieties
Summary: Removal of the chloride atom from Pd{C-
(dNXy)CH3}(Cl)(But bipy) initiates a series of reactions
2
that lead to the formation of the novel dipalladium
complex [Pd(But bipy){η2-[Pd(But bipy){N(Xy)dC(CH3)-
2
2
C(CH3)dNXy}]}][BF4]2. In this process, two imidoyl
groups undergo a C-C coupling reaction generating a
bis-imino ligand that coordinates to two palladium cen-
ters, one of which is bound to a C-N bond of the ligand
giving an unprecedented three-membered PdCN ring.
complexes,4 with the softer late transition metals
η1-coordination is usually observed. In group 10, for ex-
ample, only nickel complexes have been reported to
display η2-coordination to the imidoyl group.5 The first
fully characterized example of this type of complexs
with a nickel(II) centerswas reported in 1990 by Car-
mona et al.5a Similarly, imines tend to form η1 (σ-co-
ordinated) complexes with the late transition metals
rather than η2-species. In group 10, although several
nickel(0) complexes with η2-coordination of imines have
been reported,6 very few are known with palladium7 or
platinum.8
Insertion of small molecules such as CO, C2H4, and
CNR into metal-carbon bonds has proven to be an
efficient route for the synthesis of novel organic species
and polymeric materials.1,2 The migratory insertion of
isocyanides (which are generally regarded as better
σ-donors and weaker π-acceptors than CO)3 into metal-
carbon bonds yields imidoyl groups, which, in principle,
can be coordinated to the metal in either an η1- or
η2-fashion (see Scheme 1). While the lanthanides, ac-
tinides, and early transition metals tend to form η2-
* Corresponding author. Fax: (+44) 20-7594-5880. E-mail: r.vilar@
imperial.ac.uk.
As part of a systematic investigation into metal-
mediated C-C and C-N bond formation,9 we have
recently studied the reactivity of palladium-imidoyl
complexes with a range of unsaturated species (such as
olefins and isocyanates). By analogy with the work
recently reported by Sen10 and Arndtsen,11 we investi-
gated the possibility of inserting imines into the pal-
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10.1021/om030235u CCC: $25.00 © 2003 American Chemical Society
Publication on Web 06/25/2003