Ligand Redox Effects in the Synthesis, Electronic Structure, and Reactivity of an Alkyl−Alkyl Cross-Coupling Catalyst (original) (raw)
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Functionalised Terpyridines and Their Metal Complexes—Solid-State Interactions
Chemistry: A European Journal, 2021
Analysis of the weak interactions within the crystal structures of 33 complexes of various 4′-aromatic derivatives of 2,2′:6′,2″-terpyridine (tpy) shows that interactions that exceed dispersion are dominated, as expected, by cation⋯anion contacts but are associated with both ligand–ligand and ligand–solvent contacts, sometimes multicentred, in generally complicated arrays, probably largely determined by dispersion interactions between stacked aromatic units. With V(V) as the coordinating cation, there is evidence that the polarisation of the ligand results in an interaction exceeding dispersion at a carbon bound to nitrogen with oxygen or fluorine, an interaction unseen in the structures of M(II) (M = Fe, Co, Ni, Cu, Zn, Ru and Cd) complexes, except when 1,2,3-trimethoxyphenyl substituents are present in the 4′-tpy.
Journal of Chemical Sciences, 2007
In this paper, we study the reactivity of diimines like 2,2′-bipyridine and its analogues using reactivity descriptors. We discuss evaluation of local descriptors using relaxed as well as frozen approximation and characterize the σ/π acceptance/donor characteristics of the above ligands. The intermolecular reactivity sequence for the same systems is examined by the global and local philicity index. In addition, electron density analysis has been carried out to highlight the possible strengths of interaction of the bipyridine and its analogues with metal ions.
2011
The Schiff base ligand, N-Propylidene-2-methylpyridylamine was obtained from the condensation of 2- aminomethypyridine and propanal.Also, its complexes with Cu(II),Ni(II),Zn(II),Co(II) and Mn(II) were prepared with terpyridine as co-ligand by boiling the mixture under reflux. The synthesized ligand and its metal complexes have been characterized by elemental analysis and spectroscopic (i.r. and electronic) methods. An octahedral geometric structure is proposed for the metal complexes. The six coordinate environment of the metals is composed of N5X core with thr ee nitrogen atoms from the tridentate terpyridine co-ligand and two from the Schiff base and the anions X = NO3-, CH3COO- or SO4 2- completing the octahedral geometry.
Royal Society Open Science
A series of different substituted terpyridine (tpy)-based ligands have been synthesized by Kröhnke method. Their binding behaviour was evaluated by complexing them with Co(II), Fe(II) and Zn(II) ions, which resulted in interesting coordination compounds with formulae, [Zn(tpy) 2 ]PF 6 , [Co(tpy) 2 ](PF 6 ) 2 , [Fe(tpy) 2 ](PF 6 ) 2 and interesting spectroscopic properties. Their absorption and emission behaviours in dilute solutions were investigated in order to explain structure–property associations and demonstrate the impact of different aryl substituents on the terpyridine scaffold as well as the role of the metal on the complexes. Photo-luminescence analysis of the complexes in acetonitrile solution revealed a transition from hypsochromic to bathochromic shift. All the compounds displayed remarkable photo-luminescent properties and various maximum emission peaks owing to the different nature of the functional groups. Furthermore, the anti-microbial potential of ligands and comp...
Substituted 2,2′-Bipyridines by Nickel Catalysis: 4,4′-Di-tert-butyl-2,2′-bipyridine
Synthesis, 2013
A simple, ligand-free synthesis of the important bipyridyl ligand 4,4′-di-tert-butyl-2,2′-bipyridine is presented. 5,5′-Bis(trifluoromethyl)-2,2′-bipyridine is also synthesized by the same protocol. The syntheses efficiently couple the parent 2-chloropyridines by a nickel-catalyzed dimerization with manganese powder as the terminal reductant.
Inorganic Chemistry, 2007
A series of dinuclear metal terpyridine (M-tpy; M) Ru, Os, Fe, and Co) complexes with a photochromic dithienylethene bridge were designed and synthesized through either a convergent or a divergent approach. The open forms of the complexes containing Ru II and Fe II centers were found to be inert to ultraviolet photoirradiation but could be cyclized electrochemically as revealed by a cyclic voltammetric study. On the contrary, the Co II complex underwent efficient photochemical but not electrochemical cyclization. The corresponding Os II complex was neither photochromic nor electrochromic.
Inorganic Chemistry
Transition metal complexes of 2-[4′-(2,2′:6′,2′′-terpyridyl)]-(4,4,5,5-tetramethylimidazolinyl-3-oxide-1-oxyl) (terpy-NIT) and 2-[4′-(2,2′:6′,2′′-terpyridyl)]-(4,4,5,5-tetramethylimidazolinyl-1-oxyl) (terpy-IM) have been prepared. Whereas the pyridyl fragments of the free ligands are in an anti conformation, the complexes are obtained by coordination of two terpyridines in a syn conformation, forming a distorted octahedron around the metal center: [M(terpy-NIT) 2 ](ClO 4) 2 (M) Ni(II) 1, Zn(II) 2, Cu(II) 3) and [M(terpy-IM) 2 ](ClO 4) 2 (M) Ni(II) 4, Zn(II) 5). The ligands and their complexes have been characterized by FAB-MS, UV-vis, FT-IR spectroscopies, elemental analysis, and by EPR spectroscopy and susceptibility measurements. Single-crystal X-ray diffraction have been performed on the terpy-NIT ligand and on complexes 1, 4, and 5 giving following crystal data: terpy-NIT, monoclinic, P2 1 /c, Z) 4, a) 14.2186(5), b) 12.9129(6), c) 11.704(1) Å,) 108.615(4)°; 1, orthorhombic, P(n a 2 1), Z) 4, a) 23.6367(6), b) 8.7836(1), c) 24.2748(7) Å; 4, monoclinic, P2 1 , Z) 1, a) 8.738(1), b) 25.010(1), c) 11.704(1) Å,) 102.849(3)°; 5, monoclinic, P2 1 , Z) 1, a) 8.7463(2), b) 25.0833(5), c) 11.8168(3) Å,) 102.757(3)°. For complexes 1 and 3, an antiferromagnetic behavior has been found and parametrized by considering a symmetric magnetic trimer, highlighting a strong intramolecular coupling between the metal and the radicals (average values 2J M-NIT)-19.6 K for M) Ni and-22.8 K for M) Cu). In the case of compound 4, an asymmetric magnetic trimer has been used to model the antiferromagnetic interactions (2J Ni-IM1)-13.0 K, 2J Ni-IM2)-5.6 K). The shape of the EPR spectra of complexes 2, 3, and 5 in solution indicates the intermediate exchange limit, of the order of a few mK, between the two nitroxide radicals through the pyridyl-metal-pyridyl fragment.