(η6-Arene) ruthenium(ii) complexes and metallo-papain hybrid as Lewis acid catalysts of Diels-Alder reaction in waterElectronic supplementary information (ESI) available: Synthetical procedures, X-ray crystallographic data of 1a·BF4, kinetics data of aquation of 1a and anation of 1b and of Diels-Alder reactions. CCDC reference number 742394. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c001630f

Covalent embedding of a (η 6 -arene) ruthenium( ii ) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water. Covalent embedding of a (η 6 -arene) ruthenium( ii ) complex within the protein papain gives rise to a metalloenzyme catalysing a Diels-Alder reaction in water at a rate enhanced by two orders of magnitude.