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New Ru II (arene) Complexes with Halogen‐Substituted Bis‐ and Tris(pyrazol‐1‐yl)borate Ligands
Author(s) -
Orbisaglia Serena,
Di Nicola Corrado,
Marchetti Fabio,
Pettinari Claudio,
Pettinari Riccardo,
Martins Luísa M. D. R. S.,
Alegria Elisabete C. B. A.,
Guedes da Silva M. Fátima C.,
Rocha Bruno G. M.,
Kuznetsov Maxim L.,
Pombeiro Armando J. L.,
Skelton Brian W.,
Sobolev Alexandre N.,
White Allan H.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201304406
Subject(s) - hexamethylbenzene , chemistry , medicinal chemistry , ligand (biochemistry) , metathesis , ruthenium , nuclear magnetic resonance spectroscopy , crystallography , stereochemistry , benzene , catalysis , organic chemistry , receptor , polymerization , biochemistry , polymer
[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 Br 3)], [Tl(Tp Br 3)], and [Tl(Tp i Pr, 4Br )]. Mononuclear neutral complexes [RuCl(arene)(κ 2 ‐Bp Br 3)] ( 1 : arene= p ‐cymene (cym); 2 : arene=hexamethylbenzene (hmb); 3 : arene=benzene (bz)), [RuCl(arene)(κ 2 ‐Tp Br 3)] ( 4 : arene=cym; 6 : arene=bz), and [RuCl(arene)(κ 2 ‐Tp i Pr, 4Br )] ( 7 : arene=cym, 8 : arene=hmb, 9 : arene=bz) have been always obtained with the exception of the ionic [Ru 2 (hmb) 2 (μ‐Cl) 3 ][Tp Br 3] ( 5′ ), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru(CH 3 OH)(cym)(κ 2 ‐Bp Br 3)][X] ( 10 : X=PF 6 , 12 : X=O 3 SCF 3 ) and the neutral [Ru(O 2 CCF 3 )(cym)(κ 2 ‐Bp Br 3)] ( 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 Br 3, [Tl(Tp Br 3)] and [Ca(dmso) 6 ][Tp Br 3] 2 ⋅ 2 DMSO, of the complexes 1 , 4 , 5′ , 6 , 11 , and of the decomposition product [RuCl(cym)(Hpz i Pr, 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 E L ligand parameter for Bp Br 3, Tp Br 3, and Tp i Pr, 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.