Synthesis of ONO‐Ligated Tetrylenes Based on 2,6‐bis(2‐Hydroxyphenyl)pyridines: Influence of Ligand Sterics on the Structure of the Products

Abstract

A series of novel tetrylenes based on three 2,6‐bis(2‐hydroxyphenyl)pyridines 4 a–4 c have been obtained by the reaction of Lappert's tetrylenes E[N(SiMe3)2]2 (E=Ge, Sn) with corresponding tridentate pyridine‐linked phenol‐based ligands. It was found that the structure of the ligand and the size of the atom of the group 14 element drastically affect the structure of the reaction product. Ligand 4 c with a bulky tert‐butyl group leads to monomeric tetrylenes, while ligands with less bulky groups lead to bis‐ligand derivatives of M(IV) (M=Ge, Sn) and a coordination polymer. Also, derivatives of germanium (IV) and tin (IV) were obtained by the metathesis reaction of MCl4 (M=Ge, Sn) with lithium phenoxides. The compositions and structures of the novel compounds were established by elemental analysis and 1H, 13C, 119Sn (5–7), 1H DOSY (6) NMR spectroscopy, in the solid state by X‐ray diffraction analysis (germylene 10, stannylene 6, Ge4+ compound 8, Sn4+ compound 7) and 119Sn Mössbauer spectrum of tin complex 6. All the synthesized tetrylenes are monomeric. Tetrylenes 6 and 10 were characterized by cyclic voltammetry. A study of the redox behavior of 6, 10 by cyclic voltammetry on a glassy carbon working electrode in acetonitrile solution of 0.1 M Bu4NPF6 as a supporting electrolyte showed that these compounds can be both oxidized and reduced electrochemically in the accessible potential range.

Germanium Complexes with ONO Tridentate Ligands: O-H Bond Activation Control According to DFT Calculations

“…Thus, for 4-H d (Ge-O) 1.859 Å, d (Ge-N) 2.057 Å, angles N-Ge-N 179.5° and O-Ge-O 178.0°; for 6-H d (Ge-O) 1.882 Å, d (Ge-N) 2.076 Å, angles O-Ge-O 94.8° and O-Ge-N 86.6° (cf. the structural data for compound D [ 62 , 63 ], Scheme 6 ), which is indicative of a good correlation and, thereby, of the accuracy and correctness of our calculations. The modeled reactions represent a “classical” single-site O-H activation (cf.…”

“…At the same time, research concerning the controlled balance between reactivity and stabilization governed by the polydentate ligand structure is missing, thus making our investigation unprecedented. As we have established earlier by synthetic experiments, in interaction with Lappert’s germylene, [(Me 3 Si) 2 N] 2 Ge: substituted 2,6-pyridinobis(phenols) ( Scheme 3 ) form bis -liganded Ge(+4) complexes or monoliganded Ge(+2) (germylenes) species [ 62 , 63 ], where the steric size of the substituents in ligands determines the type of the product. Indeed, sterically unhindered ligands lead to Ge(+4) complexes, whereas voluminous ligands (containing bulky groups in α-positions in relation to donor atoms) lead to expected Ge(+2) complexes.…”