Can Electrochemistry Distinguish Classical from Nonclassical Transition-Metal Polyhydrides?

Abstract

The present article intends to propose electrochemistry as a tool to distinguish classical hydride coordination to metal centers from nonclassical dihydrogen complexation. The successful application to a series of Group VIII metal-polyhydride complexes of the type [(XP₃)MH₂] + (XP₃ = X(CH₂CH₂PPh₂)₃ (X = P, N); M = Co, Rh, Ir), in which classical and nonclassical hydrides are present, induces us to think that such a technique, notably less demanding of sophisticated instrumentations than established crystallographic, NMR and IR techniques, might play some role in the future for what concerns the yet elusive characterization of dihydrogen complexes. The limitations of such an electrochemical approach are put in evidence. The scattered and sometimes disputed data in the literature are also discussed.

Key Words:

• electrochemistry as a tool to discriminate classical from nonclassical polyhydride metal complexes