Organophosphorus π-Conjugated Materials

Ligand design is becoming an increasingly important part of the synthetic activity in chemistry. This is of course because of the subtle control that ligands exert on the metal center to which they are coordinated. Ligands which contain significantly different chemical functionalities, such as hard and soft donors, are often called hybrid ligands and find increasing use in molecular chemistry. Although the interplay between electronic and steric properties has long been recognized as essential in determining the chemical or physical properties of a complex, predictions remain very difficult, not only because of the considerable diversity encountered within the Periodic Table-different metal centers will behave differently towards the same ligand and different ligands can completely modify the chemistry of a given metal-but also because of the small energy differences involved. New systems may-even through serendipity-allow the emergence of useful concepts that can gain general acceptance and help design molecular structures orientated towards a given property. The concept of ligand hemilability, which finds numerous illustrations with hybrid ligands, has gained increased acceptance and been found to be very useful in explaining the properties of metal complexes and in designing new systems for molecular activation, homogeneous catalysis, functional materials, or small-molecule sensing. In the field of homogeneous enantioselective catalysis, in which steric and/or electronic control of a metal-mediated process must occur in such a way that one stereoisomer is preferentially formed, ligands containing one or more chiral oxazoline units have been found to be very valuable for a wide range of metal-catalyzed reactions. The incorporation of oxazoline moieties in multifunctional ligands of increasing complexity makes such ligands good candidates to display hemilabile properties, which until recently, had not been documented in oxazoline chemistry. Herein, we briefly recall the definition and scope of hemilabile ligands, present the main classes of ligands containing one or more oxazoline moieties, with an emphasis on hybrid ligands, and finally explain why the combination of these two facets of ligand design appears particularly promising.

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline‐Based Systems

The structural chemistry of metal thiolate complexes

5.1.2. Viscosity and Thermal Denaturation 1874 5.1.3. Induced Circular Dichroism 1875 5.1.4. Competitive Fluorescence Spectroscopy 1875 5.1.5. Closed Circular DNA 1876 5.1.6. Stereochemical Changes in DNA 1876 5.1.7. Site-Specific Intercalation 1877 5.1.8. Other Mononuclear Intercalators 1877 5.1.9. Multinuclear Intercalators 1878 5.2. Covalent Binding to Biomolecules 1881 5.3. Labeling Biomolecules 1882 5.4. Cytotoxicity 1885 5.4.1. Chemotherapeutic Agents 1886 5.4.2. Radiotherapeutic Agents 1892 6. Conclusion 1892 7. Acknowledgments 1892 8. References 1893

Square-planar Pd(II), Pt(II), and Au(III) terpyridine complexes: their syntheses, physical properties, supramolecular constructs, and biomedical activities.

Chiral sulfur ligands for asymmetric catalysis.

The binuclear complexes of the type (±)-[(Me3PtX)2MeE(CHR)nEMe](E = S or Se; X = Cl, Br, or I; R = H or Me; n= 0 or 1) have been shown to exhibit a remarkable series of fluxional phenomena over a range of temperatures; most notable of these is an intermetallic commutation by the two donor atoms of the bidentate sulphur and selenium ligands.

Novel fluxional rearrangements in binuclear platinum complexes; intermetallic ligand atom switching

Organometallic compounds containing metal-metal bonds

Photolysis of the complex [Mo(σ-[graphic omitted])(CO)3(η-C5H5)] causes elimination of carbon monoxide and formation of [Mo(η2-[graphic omitted])(CO)2(η-C5H5)] in which the ring behaves as a di-hapto, formally three-electron donor.

σ-η2 Transformation of an electron-rich thioarsenic heterocyclic ligand: X-ray crystal structure of [Mo(η2-AsSCH2CH2S)(CO)2(η-C5H5)]

A synthetic route to the platinum(IV) complexes [(PtXMe3)2([graphic omitted]HMe)](X = Cl, Br or I) has been established. Solution NMR and other evidence favour the ligand adopting a boat conformation and bridging the two platinum(IV) centres across an –SCH2S–portion of the ring, with the ring methyl group in an equatorial environment. Only very weak evidence was obtained for the existence of the –SCHMeS– bridged ligand complex despite the occurrence of a fluxional process involving 60° pivots of the ligand about individual S–Pt bonds which must proceed via the –SCHMeS– bridged species. Activation energies and a proposed mechanism for the process are presented. Some rare examples of 2J(PtIVPtIV) scalar couplings are reported.

Nuclear magnetic resonance investigations of configurational non-rigidity in dinuclear platinum(IV) complexes. Part 8. Fluxional properties of complexes [(PtXMe3)2(SCH2SCH2SCHMe)](X = Cl, Br or I)

Edward W. Abel

Papers

Novel fluxional rearrangements in binuclear platinum complexes; intermetallic ligand atom switching

Organometallic compounds containing metal-metal bonds

σ-η2 Transformation of an electron-rich thioarsenic heterocyclic ligand: X-ray crystal structure of [Mo(η2-AsSCH2CH2S)(CO)2(η-C5H5)]

Nuclear magnetic resonance investigations of configurational non-rigidity in dinuclear platinum(IV) complexes. Part 8. Fluxional properties of complexes [(PtXMe3)2(SCH2SCH2SCHMe)](X = Cl, Br or I)

Homogeneous catalysis by transition-metal complexes