Chains of Palladium

Movements of mononuclear and dinuclear Pd moieties have been observed along the 71-conjugated five-carbon chain with subsequent bonding rearrangement providing cumelenyl-type compounds.  

The stepwise growth of a Pd chain of up to four metals has been achieved within the sandwich polyene framework. Dipalladium(I) compound sandwiched by 1,4-diphenyl-1,3-butadiene (dpbd) is obtained from the reaction of 

The same compound was isolated in 69% yield by applying 2 equivalents of Pd and 2 equivalents of Pd° in the form of [Pd2(CH3CN)g][BF4]2 and Pd2(dba)3, respectively, with o-dpbb and a subsequent anion exchange of BF4 with BAr.  

The X-ray structure of [Pd5(p-bpbb)2][BAr ]2 reveals a V-shaped Pds chain sandwiched between two p-bpbb ligands via the p5-ri ri ri ri ri mode. The Pds chain is bent at the central Pd3 atom (Pd2-Pd3-Pd4 121.81(4)°), which is coordinated to the p-phenylene moieties. A formal quinoid character of the CH(p-C6H4)CH moiety of the p-bpbb ligand is suggested by examination of coordination modes and by the alteration in C-C bond lengths. 

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