Containing Nickel, Palladium, and Platinum Chains

Compounds Containing Nickel, Palladium, and Platinum Chains... 

Inner Transition Metal Complexes With Chains of Metal Atoms 103 9.2.12.1. Compounds Containing Nickel, Palladium, and Platinum Chains 9.2.12.1.4. Halogen-Oxidized Complexes Containing 7t-Delocalized Ligands. 

The first pol5unetallaynes contained nickel, palladium, or platinum atoms in the main chain and were isolated in 1977 as yellow, film forming materials (203-205). These were prepared by efficient copper halide-catalyzed coupling processes (eg, eq. 36) and possessed estimated molecular weights (Mw) from 13,000 to 120,000. 

The first systematic study of d-block metallomesogens were carried out by Giroud and Mueller-Westerhoff [11] and marked, in 1977, the beginning of interest in metal-containing systems. They were dithiolene complexes of nickel, palladium and platinum with two p-alkyl phenyl substituents (see structure 3). Nickel and platinum complexes showed nematic and smectic phases, depending on the chain length. Palladium analogs do not possess any mesomorphic properties [81]. 

Square-planar complexes of platinum(II) and palladium(II) have been known for a long time the comparatively simple unit cells of compounds such as K2PdCl4, K2PtCl4, and Pd(NH3)4Cl2H20 led to early elucidation of the structures (257) and they all contain square-planar ions. The simple halides PdCl2 and Pt,Cl2 (71) consist of chains in which the metal is bonded from the corners of a square. Nickel chloride, on the other hand, has a layer lattice in which the nickel is octahedrally coordinated, and in the halide complexes the coordination is tetrahedral, as described in Section IV,B. 

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