π-Coordinated arene metal complexes and catalysis

Abstract

Metal complexes formed from π-coordination of aromatic groups to metal centres may undergo reactions at the coordinated arene that do not occur for the unbound arene. Upon completion of such reactions, the coordinated arene product can be liberated from the metal complex by thermal or photolytic methods. A catalytic approach can also be envisaged in which the arene transiently π-coordinates to the metal centre, reacts and then undergoes arene exchange for further starting arene. The significant challenge to this catalytic approach is to balance reactivity with arene exchange. In this review, we summarise the synthesis and reactivity of π-arene metal complexes. We go on to discuss the features of arene exchange and conclude with a comprehensive review of catalytic reactions proceeding via π-arene intermediates.

Aluminum Species and the Synthesis Mechanism of AlCl3–CuCl–Arene Solutions

“…23 The synthesis and catalysis of transition-metal−arene complexes were discussed in detail by Walton and Shvydkiy. 24,25 Complexes such as Hg(arene) 2 (AlCl 4 ) 2 and Ti(arene) 2 (AlCl 4 ) 2 were used in the alkylation of aromatics and alkenes 26 or alkene oligomerization, 27 respectively. However, there was little literature reporting the application of AlCl 3 −CuCl−arene solutions in chemical reactions.…”

Experimental and Computational Evaluation of Tantalocene Hydrides for C–H Activation of Arenes

“…As such, the π-complex is expected to exist in much higher concentration than the σ-complex under the reaction conditions, which enables aromatic C–H activation to outcompete benzylic activation. Arene π-complexation to coordinatively unsaturated metal centers is typically stabilizing, and is known to often precede and direct C–H activation. , …”

As Nice as π: Aromatic Reactions Activated by π‐Coordination to Transition Metals

“…The early work on p-arene transition metal complexes focussedo n[ ( h 6 -C 6 H 6 )Cr(CO) 3 ]a nd related complexes to develop the fundamental understanding of the reactivity of the coordinated arene.T he reader is guided to several excellent reviews and book chapterso nt he early understanding of this complex and itsd erivatives. [4,6] More recently,t he reactivity of these Cr speciesh as furtherd eveloped into CÀHa ctivation and ar ange of Pd-catalysed couplingp rocesses, which have also been reviewed. [5,7]…”