title: New RuII (arene) complexes with halogen-substituted bis- and tris(pyrazol-1-yl)borate ligands.
abstract: [RuCl(arene)(μ-Cl)]2 dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis- and tris(pyrazolyl)borate ligands [Na(Bp(Br3))], [Tl(Tp(Br3))], and [Tl(Tp(iPr, 4Br))]. Mononuclear neutral complexes [RuCl(arene)(κ(2)-Bp(Br3))] (1: arene=p-cymene (cym); 2: arene=hexamethylbenzene (hmb); 3: arene=benzene (bz)), [RuCl(arene)(κ(2)-Tp(Br3))] (4: arene=cym; 6: arene=bz), and [RuCl(arene)(κ(2)-Tp(iPr, 4Br))] (7: arene=cym, 8: arene=hmb, 9: arene=bz) have been always obtained with the exception of the ionic [Ru2 (hmb)2-(μ-Cl)3][Tp(Br3)] (5'), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru-(CH3OH)(cym)(κ(2)-Bp(Br3))][X] (10: X=PF6, 12: X=O3SCF3) and the neutral [Ru(O2CCF3)(cym)(κ(2)-Bp(Br3))] (11) have been obtained by a metathesis reaction with corresponding silver salts. All complexes 1-12 have been characterized by analytical and spectroscopic data (IR, ESI-MS, (1)H and (13)C NMR spectroscopy). The structures of the thallium and calcium derivatives of ligand Tp(Br3), [Tl(Tp(Br3))] and [Ca(dmso)6][Tp(Br3)]2 ⋅2 DMSO, of the complexes 1, 4, 5', 6, 11, and of the decomposition product [RuCl(cym)(Hpz(iPr, 4Br))2][Cl] (7') have been confirmed by using single-crystal X-ray diffraction. Electrochemical studies showed that 1-9 and 11 undergo a single-electron Ru(II) →Ru(III) oxidation at a potential, measured by cyclic voltammetry, which allows comparison of the electron-donor characters of the bis- and tris(pyrazol-1-yl)borate and arene ligands, and to estimate, for the first time, the values of the Lever EL ligand parameter for Bp(Br3), Tp(Br3), and Tp(iPr, 4Br). Theoretical calculations at the DFT level indicated that both oxidation and reduction of the Ru complexes under study are mostly metal-centered with some involvement of the chloride ligand in the former case, and also demonstrated that the experimental isolation of the μ(3)-binuclear complex 5' (instead of the mononuclear 5) is accounted for by the low thermodynamic stability of the latter species due to steric reasons.
authors.affiliation: School of Science and Technology, Chemistry Section, University of Camerino, S. Agostino 1, 62032 Camerino MC (Italy).
authors.forename: Serena
authors.initials: S
authors.lastname: Orbisaglia
authors.forename: Corrado
authors.initials: C
authors.lastname: Di Nicola
authors.forename: Fabio
authors.initials: F
authors.lastname: Marchetti
authors.forename: Claudio
authors.initials: C
authors.lastname: Pettinari
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pettinari
authors.forename: Luísa M D R S
authors.initials: LM
authors.lastname: Martins
authors.forename: Elisabete C B A
authors.initials: EC
authors.lastname: Alegria
authors.forename: M Fátima C Guedes
authors.initials: MF
authors.lastname: da Silva
authors.forename: Bruno G M
authors.initials: BG
authors.lastname: Rocha
authors.forename: Maxim L
authors.initials: ML
authors.lastname: Kuznetsov
authors.forename: Armando J L
authors.initials: AJ
authors.lastname: Pombeiro
authors.forename: Brian W
authors.initials: BW
authors.lastname: Skelton
authors.forename: Alexandre N
authors.initials: AN
authors.lastname: Sobolev
authors.forename: Allan H
authors.initials: AH
authors.lastname: White
mesh_terms: D001881:Borates / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011720:Pyrazoles / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D001881:Borates; D008024:Ligands; D009942:Organometallic Compounds; D011720:Pyrazoles; D012428:Ruthenium
keywords: arenes; borates; density functional calculations; ligands; ruthenium