Rational synthesis of anionic, neutral and cationic palladium(I) dinuclear complexes containing bridging conjugated dienes

Abstract

Addition of conjugated diene to an equimolar mixture of palladium(I1) halides and a palladium(0) complex induces facile Pd-Pd bond formation to give anionic, neutral and cationic PdrPdI dinuclear complexes containing bridging 1,3-diene ligands.Increasing attention has been paid to organopalladium complexes containing a Pd-Pd bond bridged by 4e-donating hydrocarbon ligands, such as alkyne, ally1,2 allenyl/prop-2-yny1,3 cyclopentadienyl,2 or a~-ene.~ Another ubiquitous 4e donor, 1,3-diene, has been used only rarely as a bridging ligand at Pd-Pd, an example being [(isoprene)Pd2(p-PBut2)(PH-But&]+, recently prepared by exchange of a bridging PHBut2 ligand on Pd-Pd with the diene;5 by contrast the 1,3-diene chemistry of mononuclear palladium-(11) and -(O) complexes has been extensively developed.6 We report here a convenient method for the synthesis of 1,3-diene complexes containing Pd-Pd moieties, including two new fragments, [Pd2X2(pX)]-and [Pd2X(p-X)(PPh3)], which involves a directed Pd-Pd bond formation as a key step. This method is novel when compared to those for the known 1,3-diene complexes of di-or poly-nuclear metal systems7 employing a simple ligand substitution on the pre-formed metal-metal bond,? as above.5A mixture of [Pd2&(PPh3)2] (X = C1, Br, I) and [Pd2(dba)3] (dba = dibenzylideneacetone) was stirred in CH2C12, through which buta-1,3-diene was bubbled for 0.5 h at room temperature, to give a deep-red solution.

Dipalladium(I) Terphenyl Diphosphine Complexes as Models for Two-Site Adsorption and Activation of Organic Molecules

“…The lack of butadiene displacement by MeCN is consistent with the plethora of stable s- trans -diene-bridged dipalladium compounds in the literature. 19,20,39 …”

From mononuclear to multinuclear complexes of palladium containing unsaturated hydrocarbon ligands

“…However, only a limited number of diene Pd-Pd complexes had been isolated previously, e.g., those shown in Scheme 10 [15,21]. We made efforts to gain a series of l-butadiene Pd-Pd complexes by the reaction of Pd(II) complex with Pd(0) complex in the presence of the diene (Scheme 11) [22]. Remarkably, no Pd-Pd bond was formed from the reactants used in Scheme 11 unless butadiene is added.…”

A topological isomer of ferrocene: Theoretical approach for transition metal complexes with conjugated all trans cyclodecapentaene

“…Considering the importance of orbital conjugation in the diene complexes, we investigated the complexation of extended conjugated system, i.e., a,x-diphenylpolyenes, to prepare dinuclear tetraene and pentaene complexes 1-3 bearing Ru(acac) 2 [11,12]. Kurosawa et al reported several linear palladium clusters supported by two polyene ligands [13].According to crystallographic data, the s-trans diene ligand in these s-trans complexes is highly distorted from the planarity, two terminal carbon-carbon bonds being deformed about 30°. We anticipate that it may be possible to create cyclic polyene coordinating systems, the smallest one being all-trans cyclodeca-1,3,5,7,9-pentaene (DPEN).…”

“…Considering the importance of orbital conjugation in the diene complexes, we investigated the complexation of extended conjugated system, i.e., a,x-diphenylpolyenes, to prepare dinuclear tetraene and pentaene complexes 1-3 bearing Ru(acac) 2 [11,12]. Kurosawa et al reported several linear palladium clusters supported by two polyene ligands [13].…”