The synthesis of (eta5-cyclohexadienyl)Mn(CO)3-based planar chiral ligands is realized by an efficient lithiation/electrophilic quench procedure, and the coordinating properties of one of them are highlighted together with its optical resolution.

Addition of a Grignard reagent to keto-substituted (η 5 -cyclohexadienyl)Mn(CO) 3 complexes leads to the corresponding alcohols in very good yields. After acidic treatment, dehydration occurs, which gives rise to the formation of unprecedented (η 5 -cyclohexadienyl)Mn(CO) 3 complexes substituted by a double bond conjugated to the π system as the major compounds, along with uncoordinated trienones due to the rearrangement of the intermediate carbocation. The structure of one of these η 5 complexes has been determined by X-ray crystallography as well as one of the corresponding cationic (η 6 -arene)Mn(CO) 3 complexes formed upon hydride abstraction.

Hydroxyalkylcyclohexadienyl)tricarbonylmanganese complexes 3a and 3b have been prepared, and their rearomatization delivered compounds 5 and 6, the first benzylic alcohol derivatives coordinated to the cationic Mn(CO) 3 tripod. The structure of 5 has been determined by X-ray crystallography. 1-Hydroxyalkyl 3a, 7, 8, 2-hydroxyalkyl 19, 20, and 3-hydroxyalkyl 25, 26 (η 5cyclohexadienyl)tricarbonylmanganese complexes have been synthesized and studied toward trifluoroacetylation of the hydroxy group when submitted to the action of NEt 3 and (CF 3 CO) 2 O. Only the 2hydroxyalkyl-substituted complexes eclipsed by a Mn-CO bond of the Mn(CO) 3 tripod gave the expected trifluoroacetate derivatives 21 and 22. For the 1-hydroxyalkyl-substituted complexes, elimination of the trifluoroacetoxy group took place followed by decoordination of the Mn(CO) 3 moiety and trifluoroacetylation, giving rise to trifluoromethyltrienones 10, 11, and 12, whose stuctures were established by X-ray analysis. For 3-hydroxyalkyl-substituted complexes, elimination of the trifluoroacetoxy group also occurred, yielding free arenes 27 and 28 by decoordination of the Mn(CO) 3 entity.

Mono-and bidentate ligands (5À8, 15À18, 20, 29À31) have been synthesized in which the phosphinyl group substitutes a (η 5 -cyclohexadienyl)Mn(CO) 3 scaffold. In the case of one of the bidentate ligands, 15, the formation of the corresponding Pd complex was studied. The complex unexpectedly afforded two bimetallic complexes depending on the solvent of the reaction: the neutral complex 33 and the cationic complex 34, whose X-ray structures were established. The catalysts carrying the new ligands demonstrated high activity (99% conversion) in the palladium-catalyzed allylic substitution. The resolution of three of the ligands, 6, 8, and 15, was achieved, and the catalyst with the enantioenriched PÀN ligand 15 delivered fairly good enantioselectivity in asymmetric allylic substitution.

First Suzuki-Miyaura coupling reactions applied to (η(5)-chloro-cyclohexadienyl)Mn(CO)3 complexes are described and lead to the syntheses of (η(5)-aryl-cyclohexadienyl)Mn(CO)3 and of cationic (η(6)-arene)Mn(CO)3 complexes after rearomatization. The structures of two of the new complexes have been investigated by X-ray diffraction study.