Complexes of Sterically Hindered Thiolate Ligands

Abstract

This chapter discusses the chemistry of sterically hindered thiolate complexes. The chapter presents a survey that covers the chemistry of transition metal and main group complexes of sterically hindered thiolates up to the end of 1991. Emphasis is placed on their syntheses, structural types, and reactivity. Generally, only those complexes that contain at least 50% of sterically hindered thiolate ligands in the coordination sphere are discussed in the chapter on the basis that a lower proportion would not be sufficient to dominate the coordination chemistry. The account covers 2,6- and 2,4,6-alkyl and silyl-substituted aromatic thiolate complexes in reasonable depth. Halogenated aromatic thiolate and sterically hindered aliphatic thiolate complexes are discussed in the chapter. The chapter focuses on monodentate thiolate ligands. The structures and abbreviations for the most commonly used bulky 2,6- and 2,4,6-substituted aromatic thiols are presented. These aromatic thiols have the advantage over those with aliphatic groups that the tendency for C–S bond cleavage is virtually eliminated that in turn lessens the probability of generating unreactive sulfidebridged polymers. The ability of sterically hindered thiols to generate mononuclear species with unusual geometries and oxidation states has arguable relevance to the metal sites found in metalloproteins with cysteine coordination.