Chromium arene complexes in organic synthesis

Abstract

The complexation of an arene to a chromium tricarbonyl unit changes its chemical behavior, giving rise to unprecedented transformations. The electron-withdrawing effect of the unit allows efficient nucleophilic attack (S(N)Ar and dearomatization reactions), stabilizes negative charges in benzylic positions and activates C(Ar)-halogen bonds for cross-coupling reactions. In addition, the Cr(CO)(3) moiety exerts great facial control so it can be used as an auxiliary that can easily be removed. The 1,2- and 1,3-unsymmetrically disubstituted complexes are planar chiral and there are various ways to prepare them in enantiomerically pure form. Planar chiral chromium complexes are becoming useful intermediates and ligands for asymmetric catalysis. This mature field of organometallic chemistry has given rise to several synthetic applications of chromium arene complexes in the synthesis of natural products. This chemistry is overviewed in this tutorial review, giving special attention to the most recent and outstanding contributions in the area.

Cr(CO)3‐Activated Diels–Alder Reaction on Single‐Wall Carbon Nanotubes: A DFT Investigation

“…[13] Although the effect of high pressure on cycloaddition reactions is well documented, [14] the activating effect of the [Cr(CO) 6 ] complex on the reactivity of CNs towards the DA reactions raises many interesting questions concerning the reaction mechanism. According to previous experimental investigations, thermolysis of [Cr(CO) 6 ] gives rise to mostly chromium tricarbonyl, Cr(CO) 3 , [15,16] which avidly coordinates to arene rings in a h 6 fashion. [15,16] The pronounced electronwithdrawing properties of the Cr(CO) 3 …”

Half-Sandwich Complexes of an Extremely Electron-Donating, Redox-Active η6-Diborabenzene Ligand

“…Reaction of 1 with lithium metal for 5 d provides the dianion as its dilithium compound, Li 2 (THF) 2 [1] (6) in 68% yield (Scheme 4). The compound has a deep purple colour in solution, appearing black in the solid state.…”

“…Since the isolation of [(η 6 -C 6 H 6 )Cr(CO) 3 ] by Fischer and Öfele in 1957 (Figure 1), the discovery that coordination to the Cr(CO) 3 fragment makes arenes susceptible to nucleophilic substitution has been instrumental in organic synthesis. [1][2] Although less well studied than their all-carbon analogues, a variety of heteroarene complexes of the Group 6 M(CO) 3 series are also known. Pyridines, typically η 1 donor ligands, can be coerced into η 6 coordination by use of bulky substituents in the 2 and 6 positions, [3][4] while halfsandwich complexes of η 6 phosphabenzene, [5][6][7] arsabenzene, [8][9] and stibabenzene 9 ligands have also been reported.…”

Thermally induced inter-ring haptotropic rearrangements in π-complexes of molybdenum with nitrogen containing polyaromatic heterocycles: A DFT study

“…Recently, the ability of such complexes to catalyze many organic reactions was fully recognized [3]. Their catalytic action is often [5]. All of this has led to significant prospects of transition metal PAL complexes in the fields of material chemistry [6] and pharmacology [7].…”