The coordinated OH group in cationic complexes [(η nring)M(NOH)(Solv)][SbF 6 ] and [(η n -ring)M(NOH){(R)-P1}][SbF 6 ] 2 ((η n -ring)M = (η 5 -C 5 Me 5 )Rh, (η 5 -C 5 Me 5 )Ir, (η 6 -p-MeC 6 H 4 iPr)Ru; NOH = hydroxypyridine ligand; (R)-P1 = (R)-monophos) is deprotonated by Na 2 CO 3 , rendering bi-or mononuclear compounds of formulas [{respectively. The complexes have been characterized by analytical and spectroscopic means, including the determination of the crystal structures of) by X-ray diffractometric methods. In complexes [(η n -ring)M(NOH)(P*)][SbF 6 ] 2 (P* = chiral phosphoramidite ligand) the proton of the coordinated hydroxypyridine ligand is able to activate the carbonyl group of methyl 3,3,3-trifluoropyruvate toward the Friedel−Crafts addition of indoles. In most cases, quantitative conversion is achieved in a few minutes, at −70 °C, with an ee of up to 82%. NMR data support the activation of the pyruvate by interaction between its carbonyl oxygen and the OH group of the coordinated hydroxymethylpyridine. Therefore, the metallic complexes act as Lewis acid assisted Brønsted acid catalysts.

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The synthesis and characterization of cationic iridium(III) aqua complexes of the formula [IrH(H 2 O)(PN*)(PP)][SbF 6 ] 2 (PN* = chiral phosphano−oxazoline ligand; PP = diphosphane) as well as that of the OPOF 2 -containing complex [IrH(OPOF 2 )(PNiPr)(dppp)][SbF 6 ] (10) are reported. The X-ray molecular structures of [IrH(H 2 O)-(PNInd)(dppe)][SbF 6 ] 2 (1), [IrH(H 2 O)(PNInd)(dppen)][SbF 6 ] 2 (2), and 10a have been determined. Dichloromethane solutions of these aqua complexes efficiently catalyze the enantioselective 1,3-dipolar cycloaddition of the nitrone N-benzylidenephenylamine N-oxide to methacrolein and Diels−Alder reactions between cyclopentadiene and trans-β-nitrostyrenes. In the first case, the catalytic reaction occurs with excellent endo selectivity and ee up to 85%; the Diels−Alder reaction occurs rapidly at room temperature with good endo:exo selectivity and ee up to 90%. The dipolar cycloaddition intermediates [IrH(methacrolein)(PNInd)(PP)][SbF 6 ] 2 (PP = (S,S)-chiraphos ( 11), (R)-prophos ( 12)) have been characterized, and the molecular structure of 11 has been determined by an X-ray structural analysis.