Organometallics 2008, 27, 3297–3302
3297
Synthesis and Characterization of Chalcogenolato-Bridged Allyl
Palladium Complexes: Versatile Precursors for Palladium
Chalcogenides
Ninad Ghavale, Sandip Dey,* Amey Wadawale, and Vimal K. Jain*
Chemistry DiVision, Bhabha Atomic Research Centre, Mumbai-400085, India
ReceiVed January 29, 2008
The complexes [Pd(µ-ER)(η3-allyl)]2 (ER ) EMes; E ) S, Se; allyl ) C3H5, C4H7) have been isolated
by the reaction of [Pb(ER)2]n with [Pd2(µ-Cl)2(η3-allyl)2]. Similar reactions with [Pb(SeCH2CH2NMe2)2]n
resulted in the formation of a trinuclear complex [Pd3Cl2(κ2-Se,N-SeCH2CH2NMe2)(η3-allyl)3]. Treatment
of [Pd(µ-SR)(η3-C4H7)]2 with [Pd(SMes)2]n in 1:1 ratio yielded [Pd3(µ-SMes)4(η3-C4H7)2]. These complexes
were characterized by elemental analyses and mass, UV-vis, and NMR spectroscopy. The structures of
[Pd2(µ-EMes)2(η3-C4H7)2] (E ) S, Se) were established by single-crystal X-ray diffraction analysis, which
revealed a syn configuration. Two new structural motifs for [Pd3Cl2(κ2-Se,N-SeCH2CH2NMe2)(η3-C3H5)3]
and [Pd3(µ-SMes)4(η3-C4H7)2] have also been identified. Pyrolysis of [Pd(µ-ER)(η3-C4H7)]2 yielded
palladium chalcogenides, which were characterized by powder XRD and EDAX.
semiconducting materials (e.g., PdS: Eg ) ∼2.0 eV).12 The
utility of palladium sulfides has been demonstrated in a wide
range of catalytic reactions13–15 such as dehydrosulfurization
of thiophenes13 and dehydrogenation.14 Besides the reactions
of palladium salts with H2S or Na2S for the preparation of
PdS,16,17 classical complexes [Pd(S2COPri)2]18 and [Pd(S2CN-
MeHex)2]19 have been used for the deposition of thin films of
PdS. The allylpalladium complexes [Pd2(µ-SR)2(η3-C4H7)2]4 and
[Pd(η3-C3H5)(S2CNMeHex)],11 in contrast, yield palladium-rich
sulfides, Pd4S and Pd2.8S, respectively. The allyl thiolate
complexes are formed by the reactions of [Pd2(µ-Cl)2(η3-allyl)2]
with the alkali metal thiolate salts. Thus, the reactions of [Pd2(µ-
Cl)2(η3-allyl)2] with 1,1-dithiolates give [Pd(η3-allyl)(SkS]
complexes,1 while with simple thiols binuclear derivatives are
formed.4 Studies of heavier chalcogenolate complexes are rather
scanty.4 In the above perspective the present investigation on
allylpalladium complexes containing both bulkier and internally
functionalized chalcogenolate ligands has been undertaken.
Introduction
The chemistry of η3-allylpalladium complexes has been a
subject area of extensive research for the past several decades.1
There are several obvious reasons for this sustained interest.
These include their diverse reactivity and utility in palladium-
catalyzed organic transformations2,3 and more recently in
materials science.4 The allylpalladium complexes are usually
isolated as mono- and binuclear derivatives with a few examples
of tri-5 and high-nuclearity complexes.6
The lability of the allyl group has made these complexes,
such as [Pd(η3-allyl)2] (allyl ) C3H5 or C4H7),7 [Pd(Cp)(η3-
C3H5)2],7 [Pd(η3-allyl)(ꢀ-diketonate)],8 and [Pd(η3-allyl)(ꢀ-
ketoiminato)],9 attractive precursors for deposition of high-
quality palladium films under mild conditions. Similarly the
binuclear complex [Pd2(µ-Cl)2(η3-C3H5)2] has been used for the
preparation of palladium nanoparticles.10 The lability of the allyl
group has also led to the development of single-source precur-
sors for palladium sulfides.4,11
Palladium forms a range of palladium chalcogenides differing
in stoichiometry and structures, and several of them are
Results and Discussion
Synthesis and Spectroscopy. Reactions of chloro-bridged
allylpalladium complexes with lead salts of organochalcogeno-
late ligands gave bi- and trinuclear chalcogenolato-bridged
allylpalladium complexes (Scheme 1). With mesityl chalco-
genolate, binuclear complexes [Pd2(µ-EMes)2(η3-allyl)2] (1-4)
are formed as yellow-orange crystalline solids, whereas with
internally functionalized chalcogenolate ligand, Me2NCH2CH2-
Se-, trinuclear complexes [Pd3Cl2(κ2-Se,N-SeCH2CH2NMe2)(η3-
allyl)3] (6, 7) are isolated, in which selenolate selenium atom
* Corresponding authors. E-mail: dsandip@barc.gov.in.
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10.1021/om8000795 CCC: $40.75
2008 American Chemical Society
Publication on Web 06/10/2008