Synthesis and dynamic NMR studies of stereochemical non-rigidity in rhenium(I) complexes of 2,6-bis[1-(phenylimino)ethyl]pyridine derivatives

Conformational analysis via calculations and NMR spectroscopy for isomers of the mono(imino)pyridine ligand, 2-{(2,6-Me2-C6H3)NC(i-Pr)}C5H4N

“…It is notable that these authors do not invoke E/Z isomerization as an explanation for the fluxional behavior observed by NMR spectroscopy; presumably, the primary alkyl substituents on the imino carbon positions (methyl 20,21 or butyl 21 ) render the E,E-isomer energetically favorable. This is in contrast to studies by Orrell et al where a symmetric bis(imino)pyridine ligand serves a bidentate ligand for Pd(II) or Pt(II), 22 Re(I) 23,24 and Pt(IV), 25 and E/Z isomerization of the non-coordinated imine arm is invoked in combination with atropisomerism (again, with methyl substituents on the imino carbon positions). Finally, an account from 1987 with the closest structural similarity to our work describes theoretical identification of two atropisomers of the E-isomer of mono (imino)pyridine 2-(HNLCH)C 5 H 4 N. 26 Herein, we describe the preparation and conformational analysis of the sterically hindered mono(imino)pyridine, 2-{(2,6-Me 2 -C 6 H 3 )NC(i-Pr)}C 5 H 4 N (1).…”

Iron-Based and Cobalt-Based Olefin Polymerisation Catalysts

“…Generally for a given aniline, the condensation reaction occurs more readily for 2,6-pyridinedicarboxaldehyde than for 2,6-diacetylpyridine, while 2,6-dibenzoylpyridine is much less reactive under these conditions. Using this simple approach a wide variety of symmetrical examples of 1 have been prepared in which the steric bulk and electronic properties of the aryl groups have been systematically varied (see Tables 1 and 2 for complexed examples [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,17,20,21,24,26,27,29,28,32,33,36,37,38,39,40,41,42,44,48,18,16,19,22,23,25,30,31,34,35,45,43,46,…”

Molecular and Electronic Structures of Bis(pyridine-2,6-diimine)metal Complexes [ML2](PF6)n (n = 0, 1, 2, 3; M = Mn, Fe, Co, Ni, Cu, Zn)

“…Recently, an example for bidentate coordination of a pyridine-2,6-bis(imine) ligand has been provided in fac-[ReCl-(CO) 3 L 0 ]. 18 In this work we show that octahedral complexes [ML 2 ] n+ of the ligand 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine 5,22 and a first-row transition metal ion (M ) Mn, Fe, Co, Ni, Cu, Zn) can exist as tri-, di-, or monocations and even as neutral complexes [ML 2 ] 0 . For each complex we will carefully address the question of the actual oxidation level of the ligands that can be coordinated as a neutral ligand L 0 or as radical monoanion (L 1 ) 1-.…”