The electrochemical behavior of the N-heterocyclic carbene bisphenolate complex of nickel(ii) Ni(L)Py (L – 1,3-bis(3,5-di-tert-butyl-2-phenolato)-5,5-dimethyl-(4,6-dihydropyrimidin-2-ylidene)) was studied using cyclic voltammetry and EPR spectroelectrochemistry. According to the obtained experimental data supplemented by quantum chemical calculations, the electrochemical properties of this complex differ significantly from those of its benzimidazolylidene and imidazolylidene analogs. The oxidation of the Ni(L)Py complex is a ligand-centered process, and the phenoxyl radical group formed is susceptible to decoordination and interaction with the NHC-fragment of the complex to form benzoxazole, the crystal structure of which was determined by X-ray diffraction.

The nickel(II) complex Ni(L)Py (I) (L is 1,3-bis(3,5-di-tert-butyl-2-phenolato)-5,5-dimethyl-(4,6-dihydropyrimidin-2-ylidene)) containing the dianionic bonded N-heterocyclic carbene (NHC) bis(phenolate) ligand is synthesized. In the presence of a stronger base (4-dimethylaminopyridine (DMAP)), the exchange reaction occurs with the replacement of pyridine in complex I by the DMAP molecule to form complex Ni(L)(DMAP) (II), the crystal structure of which is determined by XRD. The synthesized compounds are characterized by elemental analysis, mass spectrometry, and NMR spectroscopy. The spectral characteristics of the compounds are studied.

A novel organonickel sigma-complex [NiBr(Tcpp)(bpy)], where Tcpp is 2,4,6-tricyclopentylphenyl, bpy is 2,2'-bipyridine has been generated in solution by electrochemical macroscale synthesis. The monitoring of the macroscale electrosynthesis and also the cyclic voltammetric measurements have shown that the organonickel sigma-complex is formed at the electrolysis but, in contrast to its analogues with ortho -substituted aromatic fragments, is unstable and decomposes to the homo-coupling product, namely, the earlier unknown sterically hindered biaryl derivative 2,2',4,4',6,6'-hexacyclopentyl-1,1'-biphenyl, the molecular and crystal structure of which are described by NMR spectroscopy and X-ray diffraction techniques.

An Erratum to this paper has been published: https://doi.org/10.1134/S1023193524010087

New bis-chelate cobalt(II) complex [Co(DPG) 2 (DMF) 2 ] ( 1 ), where DPG is N -(2,5-bis(methoxycarbonyl)phenyl)-α-diphenylphosphorylglycinate, has been prepared and characterized. The complex is the first example of cobalt complex containing phosphorylated derivative of α-amino acid. Octahedral coordination geometry of the cobalt complex 1 has been determined by X-ray diffraction. Electrochemical reduction of the obtained complex has been found to be irreversible two-electron process ( E_p^red = –1.70 V vs Ag/AgNO 3 , 1 × 10 –2 М in CH 3 CN), resulting in formation of cobalt metal adsorbed on the surface of working electrode.

The low-stable organonickel sigma-complex (2,2'-bipyridyl)bromo(2,4,6-tricyclopentylphenyl)nickel(II) [NiBr(Tcpp)(bpy)] was obtained by a modified procedure of preparative electrochemical synthesis and isolation. The crystal structure of the resulting organonickel complex was determined by the X-ray diffraction method. Its structure was compared with that of its more stable analogue [NiBr(Tchp)(bpy)], where Tchp is 2,4,6-tricyclohexylphenyl. It was found that a more efficient network of intermolecular interactions is formed in the [NiBr(Tchp)(bpy)] crystal, which is responsible for its higher stability, whereas [NiBr(Tcpp)(bpy)] is more likely to enter into an equilibrium Schlenk reaction, leading to its decomposition.

An Erratum to this paper has been published: https://doi.org/10.1134/S0022476623010080

Получен и охарактеризован новый бисхелатный комплекс кобальта (II) [Co(DPG) 2 (DMF) 2 ] ( 1 ), где DPG – N -(2,5- бис (метоксикарбонил)фенил)-α-дифенилфосфорилглицинат, являющийся первым примером комплекса кобальта, содержащего в своей структуре фосфорилированное производное α-аминокислоты. Методом рентгеновской дифракции определена октаэдрическая координационная геометрия комплекса кобальта 1 . Установлено, что электрохимическое восстановление полученного комплекса кобальта является необратимым двухэлектронным процессом ( E p red = –1.70 В отн. Ag/AgNO 3 , 1 × 10 –2 М в CH 3 CN), приводящим к образованию металлического кобальта, адсорбированного на поверхности рабочего электрода.

The organonickel σ-complex 2,3,4,5,6-pentamethylphenyl-nickel(II)-bromide-2,2′-bipyridine is synthesized electrochemically. This is the first example from a series of [NiBr(Aryl)(bpy)] complexes containing a meta-substituted aromatic moiety (Pmp is 2,3,4,5,6-pentamethylphenyl). The obtained compound is characterized in solution by 1H, 13С{1H}, and 1H13С{1H}–HSQC NMR and UV spectroscopy and ESI mass spectrometry. The crystal structure is determined by X-ray diffraction. The electrochemical properties of the complex are studied by cyclic voltammetry. It is found that in the DMF solution, a ligand exchange reaction occurs, resulting in the formation of a [Ni(Pmp)(bpy)(DMF)]+ derivative with elimination of the bromide anion. Similar cationic derivatives are active in catalytic processes of oligo- and polymerization of olefins, which indicates the importance of data obtained in this work for the development of the chemistry of nickel(II) organometallic complexes.

Электрохимически синтезирован никельорганический сигма-комплекс 2,3,4,5,6-пентаметилфенил-никель(II)-бромид-2,2'-бипиридил, являющийся первым примером из серии комплексов [NiBr(Aryl)(bpy)], содержащим мета-замещенный ароматический фрагмент (Pmp - 2,3,4,5,6-пентаметилфенил). Полученное соединение охарактеризовано в растворе методами 1H, 13С{1H} и 1H13С{1H}–HSQC ЯМР и УФ–спектроскопии и ИЭР масс-спектрометрии. Кристаллическая структура определена методом рентгеновской дифракции. Электрохимические свойства комплекса исследованы с помощью циклической вольтамперометрии. Обнаружено, что в растворе ДМФА происходит реакция лигандного обмена, приводящая к образованию производного [Ni(Pmp)(bpy)(DMF)]+ с элиминированием бромид-аниона. Подобные катионные производные являются активными в каталитических процессах олиго- и полимеризации олефинов, что свидетельствует о важности полученных в настоящей работе данных для развития химии металлоорганических комплексов никеля (II).