Stabilization of p-block organoelement terminal hydroxides, thiols, and selenols requires newer synthetic strategies

Abstract

Metal hydroxides represent a very interesting and highly useful class of compounds that have been known to chemists for a very long time. While alkali and alkaline earth metal hydroxides (s-block) are commonplace chemicals in terms of their abundance and their use in a chemical laboratory as bases, the interest in Bronsted acidic molecular terminal hydroxides of p-block elements, such as aluminum and silicon, has been of recent origin, with respect to the variety of applications these compounds can offer both in materials science and catalysis. Moreover, these systems are environmentally friendly, relative to the metal halides, owing to their -OH functionality (resembling that of water). Design and conceptualization of the corresponding terminal thiols, selenols, and tellurols (M=SH, M=SeH, and M=TeH) offer even more challenging problems to synthetic inorganic chemists. This concept summarizes some of the recent strategies developed to stabilize these otherwise very unstable species. The successful preparation of a number of silicon trihydroxides a few years back resulted in the generation of several model compounds for metal-silicates. The recent synthesis of unusual aluminum compounds such as RAl(OH)₂, RAl(SH)₂, and RAl(SeH)₂ with terminal EH (E=O, Se, or Se) groups is likely to change the ways in which some of the well-known catalytic conversions are being carried out. The need for very flexible and innovative synthetic strategies to achieve these unusual compounds is emphasized in this concept.