Platinum nonlinear optical properties

Platinum polyynes represent one of the most interesting and well-studied classes of linear metallopolymers (Chapters, Section 5.2). Dendritic analogues of these materials have been prepared by a variety of methodologies [94—96]. One example is the nonametallic dendrimer 8.43, which was prepared by a convergent route as illustrated in Eq. 8.9 [94]. Dendrimers based on ruthenium polyyne architectures have also been prepared, and promising nonlinear optical properties have been identified [97, 98]. 

The auxiliary phosphine ligands also play an important role in controlling the physical properties of platinum(ii) alkynyl complexes. Monomeric complexes of trans-[Pt(PR3)2(C=CR )2] usually exist in the crystalline state at room temperature. Cooper et al. recently communicated the synthesis and isolation of platinum alkynyls in the liquid state at room temperature using trioctylphosphine as the auxiliary ligands [97]. It was proposed that these liquids may possess enhanced nonlinear optical properties. 

Alkynyl complexes contain metal-carbon bonds in which the metal is bound to the sp-hybridized carbon at the terminus of a metal-carbon triple bond. The materials properties of these complexes have been investigated extensively. The properties of these complexes include luminescence, optical nonlinearity, electrical conductivity, and liquid crystallinity. These properties derive largely from the extensive overlap of the metal orbitals with the ir-orbitals on the alkynyl ligand. The M-C bonds in alkynyl complexes appear to be considerably stronger than those in methyl, phenyl, or vinyl complexes. Alkynyl complexes are sometimes prepared from acetylide anions generated from terminal alkynes and lithium bases (e.g., method A in Equation 3.42), but the acidity of alkynyl C-H bonds, particularly after coordination of the alkyne to the transition metal, makes it possible to form alkynyl complexes from alkynes and relatively weak bases (e.g., method B in Equation 3.42). Alkynyl copper complexes are easily prepared and often used to make alkynylnickel, -palladium, or -platinum complexes by transmetallation (Equation 3.43). This reaction is a step in the preparation of Ni, Pd, or Pt alkynyl complexes from an alkyne, base, and a catalytic amoimt of Cul (Equation 3.44). This protocol for... 

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