Transition-Metal Fluoro Compounds Containing Carbonyl, Phosphine, Arsine andStibine Ligands

摘要

This review describes the considerable variety of transition-metal fluorocompounds containing carbonyl, phosphine, arsine, and stibine ligands reported in the literature. Included are a number of stable low-valent organometallic fluorides, a class of compounds frequently assumed to be inaccessible on the basis of hard/soft acid/base predictions. A wide range of metal ligand environments can support fluoro ligands. In fact, fluoro complexes are more stable in many instances than the corresponding heavier halogen analogues. Tables II-IX provide a comprehensive survey of the methods used to prepare metal fluoro complexes. From the compounds and chemistry described in this review, several features emerge concerning the reactivity of the transition-metal fluoro compounds containing carbonyl, phosphine, arsine and stibine ligands. The combination of soft low-valent transition-metal centers and hard fluoride ions can produce unusual compounds with new reactivity patterns (e.g., RhF(PCy3)2). Fluoride appears to promote ligand-substitution lability at metal centers; this effect, combined with the stability of metal fluoride bonds, suggests promised for the use of organometallic fluoro compounds as catalysts and reagents in aprotic media. Fluoro ligands can also be useful sites for reaction chemistry; the propensity of F to form hydrogen bonds to hydroxylic compounds and the extremely strong Si-F bond can be used in synthetic schemes to prepare transition-metal compounds not accessible from chloro, bromo, or iodo starting materials.