Synthesis and Structure of Novel RuII–N≡C–Me Complexes and their Activity Towards Nitrile Hydrolysis: An Examination of Ligand Effects

Joaquim Mola; David Pujol; Montserrat Rodríguez; Isabel Romero; Xavier Sala; Néstor Katz; Teodor Parella; Jordi Benet-Buchholz; Xavier Fontrodona; Antoni Llobet

doi:10.1071/CH08563

RESEARCH ARTICLE

Synthesis and Structure of Novel Ru^II–N≡C–Me Complexes and their Activity Towards Nitrile Hydrolysis: An Examination of Ligand Effects

Joaquim Mola ^A , David Pujol ^A , Montserrat Rodríguez ^A , Isabel Romero ^A ^E , Xavier Sala ^B , Néstor Katz ^C , Teodor Parella ^D , Jordi Benet-Buchholz ^B , Xavier Fontrodona ^A and Antoni Llobet ^B ^D ^E

+ Author Affiliations

- Author Affiliations

^A Departament de Química and Serveis Tècnics de Recerca (STR), Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain.

^B Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 Tarragona, Spain.

^C Instituto de Química Física, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán Ayacucho 491, (T4000INI) San Miguel de Tucumán, Argentina.

^D Departament de Química and Servei de RMN Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Barcelona, Spain.

^E Corresponding authors. Email: marisa.romero@udg.es; allobet@iciq.es.

Australian Journal of Chemistry 62(12) 1675-1683 https://doi.org/10.1071/CH08563
Submitted: 23 December 2008 Accepted: 14 May 2009 Published: 10 December 2009

Abstract

The synthesis and isolation of new Ru^II–acetonitrile complexes, of general formula trans,fac-[Ru(bpea)(B)(MeCN)](BF₄)₂ (bpea = N,N-bis(2-pyridylmethyl)ethylamine; B = bpy, 2,2′-bipyridine, 4; B = dppe, 1,2-bis(diphenylphosphino)ethane, 5), together with a synthetic intermediate trans,fac-[Ru(NO₃)(bpea)(dppe)](BF₄), 6, are described. Ru(bpea)Cl₃, 1, is used as the starting material for the synthesis of all complexes 2–6 presented in this paper, which are characterized by analytical, spectroscopic (IR, UV/Vis, 1D and 2D NMR), and electrochemical techniques (cyclic voltammetry). Furthermore, complexes 4, 5, and 6 have also been characterized in the solid state by single crystal X-ray diffraction analysis. Their structures show a distorted octahedral geometry where the bpea ligand binds in a facial mode, the bidentate ligands bpy and dppe bind in a chelate manner, and finally the MeCN or the NO₃ ^– ligand occupy the sixth position of the octahedral Ru metal centre. The kinetics of the basic hydrolysis of the coordinated MeCN ligand for complexes 4 and 5 and for the related complex [Ru(phen)(MeCN)([9]aneS₃)](BF₄)₂, 7, which contains the 1,4,7-trithiacyclonane ligand ([9]aneS₃) and 1,10-phenanthroline (phen) is also described. Second-order rate constants for acetonitrile hydrolysis measured at 25°C of k = 1.01 × 10^–3 M^–1 s^–1 for 4, 1.08 × 10^–4 M^–1 s^–1 for 5, and 6.8 × 10^–3 M^–1 s^–1 for 7, have been obtained through UV-vis spectroscopy. Activation parameters have also been determined over the temperature range 25.0–45.0°C and agree with a mechanism that involves an associative rate-determining step. Finally the electronic and steric influence of the auxiliary ligands on this reaction for the above and related complexes is discussed.

Acknowledgements

This research has been financed by MEC of Spain through projects, CTQ2006-15634, CTQ2007-60476/PPQ, CTQ2007-67918, and CSD2006-0003. JM is grateful for the allocation of a FI doctoral grant of the Generalitat de Catalunya. X.S. thanks MICINN for a Torres Quevedo contract. I.R. and A.L. also thank Johnson and Matthey for the loan of RuCl₃·xH₂O.

References

Synthesis and Structure of Novel RuII–N≡C–Me Complexes and their Activity Towards Nitrile Hydrolysis: An Examination of Ligand Effects

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Synthesis and Structure of Novel Ru^II–N≡C–Me Complexes and their Activity Towards Nitrile Hydrolysis: An Examination of Ligand Effects