Bridged rings palladium complexes

Both the mononuclear palladium complexes, with a chiral alkyl chain in the ether substituent of one of the aromatic rings of the Schiff base, and the dinuclear complexes, where the bridge joining the two palladium atoms is itself chiral, exhibit a blue phase in a glassy state.Pure, they form a cholesteric phase, right-handed for the (5)-Pd (5)-(6.24) derivative and left-handed for the (/f)-Pd2 (R)-(6.25) derivative (Figure 6.15). 

The soluble portion of the product possessed a molecular weight of 1000 and was shown by X-ray analysis to be a hexamer. A cyclic structure containing the six nickel atoms in a planar hexagon was proposed. The nickel atoms are bridged with ethylthio groups above and below the plane of the nickel ring as shown in structure [13]. The authors also proposed this structure for the analogous palladium complexes. This structure, of course, has the same repeat units as that proposed in 1935 by Mann and Purdie [5]. 

In nickel and palladium dithiobenzoato complexes, four-membered chelate rings are formed (366), whereas, in the corresponding phenyl-dithio acetates [M2(S2CCH2Ph)4], the dithio ligands act as bridging groups between the two metal atoms, with the formation of binuclear units (367). The molecular structure of the latter compounds shows that each metal atom is coordinated to four sulfur atoms and to the other metal atoms in a square-pyramidal geometry. Other evidence for... 

Reactions carried out with M2(DBA)3 (M — Pd, Pt DBA = dibenzylidene-acetone) and 3,5-di-t-butyl-l,2-benzquinone gave as major products the M(DBSQ)2 complexes [229]. In the case of palladium, an additional product Pd2[Pd(DBSQ)2]2 was detected, whose molecular structure consists of two planar cw-Pd(DBSQ)2 units bridged by two Pd atoms. The Pd atoms are sandwiched between semiquinone rings of adjacent Pd(DBSQ)2 units with three Pd — C lengths and an allyl structure 961 for the semiquinone rings ... 

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