title: Establishing the Family of Diruthenium Water Oxidation Catalysts Based on the Bis(bipyridyl)pyrazolate Ligand System.
abstract: A bis(bipyridyl)pyrazolate ((Me)bbp(-)) has recently been introduced as a rugged dinucleating, bis(tridentate) ligand for the formation of efficient diruthenium water oxidation catalysts (J. Am. Chem. Soc. 2014, 136, 24-27). Now, detailed protocols for the synthesis of a whole family of such dinuclear ruthenium complexes [{Ru(pyR(2))2}2(μ-(R1)bbp)(X,Y)](2+) based on the bis(bipyridyl)pyrazolate scaffold are reported. The isolation of a synthetic key intermediate allowed the straightforward introduction of different pyridines as axial ligands. Thereby, a set of complexes with different substituents at the pyrazolate backbone (R(1) = Br, H, Me), different pyridines as axial ligand (R(2) = H, NMe2, SO3), and different (non)bridging units in the in,in-position (X,Y = Cl, H2O, OAc) has been prepared and thoroughly characterized. Complexes of the type [{Ru(pyR(2))2}2(μ-(R1)bbp)(μ-OAc)](2+), with an exogenous acetato bridge, have been used as catalyst precursors in catalytic water oxidation experiments with a sacrificial oxidant. The effect of substitution on the pyrazole core of the (R1)bbp(-) ligand as well as on the pyridine ligands on both electrochemistry and catalytic activity has been systematically investigated. The catalyst stability, reflected by the turnover number, is crucially determined by the substituent at the pyrazolate ligand (R(1) = Me > H > Br). In contrast, the axial pyridine ligands modulate the rate of the catalytic process, expressed by the initial turnover frequency (R(2) = H > NMe2H(+)).
authors.affiliation: Institute of Inorganic Chemistry, Georg-August-University , Tammannstrasse 4, D-37077 Göttingen, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Neudeck
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ) , Av. Països Catalans 16, 43007 Tarragona, Spain.
authors.forename: Somnath
authors.initials: S
authors.lastname: Maji
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ) , Av. Països Catalans 16, 43007 Tarragona, Spain.
authors.forename: Isidoro
authors.initials: I
authors.lastname: López
authors.affiliation: Institute of Inorganic Chemistry, Georg-August-University , Tammannstrasse 4, D-37077 Göttingen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Dechert
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ) , Av. Països Catalans 16, 43007 Tarragona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Benet-Buchholz
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ) , Av. Països Catalans 16, 43007 Tarragona, Spain.|Departament de Química, Universitat Autònoma de Barcelona , 08460 Cerdanyola del Vallès, Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Llobet
authors.affiliation: Institute of Inorganic Chemistry, Georg-August-University , Tammannstrasse 4, D-37077 Göttingen, Germany.|International Center for Advanced Studies of Energy Conversion (ICASEC), Georg-August-University , D-37077 Göttingen, Germany.
authors.forename: Franc
authors.initials: F
authors.lastname: Meyer