Coordination Modes, Oxidation, and Protonation Levels of 2,6-Pyridinediimine and 2,2':6',2'́-Terpyridine Ligands in New Complexes of Cobalt, Zirconium, and Ruthenium. An Experimental and Density Functional Theory Computational Study

Mei Wang; Christina Römelt; Thomas Weyhermüller; Karl Wieghardt

doi:10.1021/acs.inorgchem.8b01949

Coordination Modes, Oxidation, and Protonation Levels of 2,6-Pyridinediimine and 2,2':6',2'́-Terpyridine Ligands in New Complexes of Cobalt, Zirconium, and Ruthenium. An Experimental and Density Functional Theory Computational Study

Inorg Chem. 2019 Jan 7;58(1):121-132. doi: 10.1021/acs.inorgchem.8b01949. Epub 2018 Dec 7.

Authors

Mei Wang^{1

2}, Christina Römelt², Thomas Weyhermüller², Karl Wieghardt²

Affiliations

¹ Key Laboratory of Marine Chemistry, Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering , Ocean University of China , Quingdao , 266100 , PR China.
² Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36 , D- 45470 Mülheim an der Ruhr , Germany.

PMID: 30525542
DOI: 10.1021/acs.inorgchem.8b01949

Abstract

The syntheses and molecular and electronic structures of the following complexes have been established by single crystal X-ray crystallography and UV-vis-NIR spectroscopy, and verified by density functional theory calculations (DFT B3LYP): [(η⁵-Cp)₂Zr^IV(tpy^2-)]⁰ ( S = 0) 1, [(η⁵-Cp)₂Zr^IV(^OMepdi^2-)]⁰ ( S = 0) 2, [Co^II(^OMepdi^•)(η²-BH₄)]⁰ ( S = 0) 4, [Ru^II(^OMepdi-H)Cl(PPh₃)₂]⁰ ( S = 0) 5, cis-[Ru^II(^OMepdi⁰)Cl₂(PPh₃)]⁰ ( S = 0) 6, and [Ru^II(η²-^OMepdi⁰)(η²-^OMepdi-H)₂]⁰ ( S = 0) 7, with (tpy⁰) being neutral 2,2':6',2'́-terpyridine, (tpy^•)^1- its π radical anion, (tpy^2-)^2- its dianion; (^OMepdi⁰) neutral 2,6-bis(4-methoxyphenylmethylimine)pyridine, (^OMepdi^•)^1- its radical anion and (^OMepdi^2-)^2- its dianion; (^OMepdi-H)^1- represents the deprotonated form of the (^OMepdi⁰) ligand where deprotonation takes place at the meta-position of the pyridine ring. Density functional theory calculations using the B3LYP functional were performed, establishing geometry optimized molecular and electronic structures. The structural parameter Δ = [(average distance C_py-C_imine) - (av. distance C_py-N_py + av. distance C_imine-N_imime)] is introduced for the characterization of the oxidation level of pdi (and analogously of tpy) ligands of M(pdi) (or M(tpy)) motifs for first row transition metals. The M(L⁰) unit in second and third row low-valent transition metal ion complexes may exhibit significant π-backdonation M → L⁰ structural effects.