Synthesis and Reactivity of Pt^II Methyl Complexes Supported by Pyrazolate Pincer Ligands

Abstract

Multidentate pyrazolate ligands, 2-(5-tert-butylpyrazol-3-yl)-6-(diethylaminomethyl)­pyridine ( H NNN) Et and 2,6-bis­(5-tert-butyl-1H-pyrazol-3-yl)­pyridine ( H NNN H ), were metalated with PtII to form neutral Pt­(*NNN)EtCH3 and anionic [Y]­[Pt­(*NNN*)­CH3] (Y = Li­(THF)−Cl−Li­(THF)3; Y = PPN) (* denotes that the pyrazolate N has been deprotonated). Reactions of these PtII–CH3 complexes with acids were investigated. Protonation occurs preferentially at the pyrazolate site, and the release of methane requires additional acid.

Selective Luminescent Chemosensing of Chloride Based on a Cyclometalated Platinum(II) Complex in Water: Crystal Structures, Spectroscopic Studies, Extraction, and Bioimaging

“…X-ray structural analysis of 1 shows a dihydrated complex [Pt­(N^C^N)­NCCH 3 ]­OTf·2H 2 O, where Pt­(II) atoms possess a distorted-square-planar geometry. The platinum–nitrogen (acetonitrile) bond distances Pt–N = 2.070(8) and 2.098(6) Å (the unit cell contains two independent molecules, Table S3) are significantly larger than those found for related cationic complexes featuring (N^N^N) ligands, such as [Pt­(terpy)­NCCH 3 ]­(OTf) 2 (1.986 Å), [Pt­(terpy)­NCCH 3 ]­(SbF 6 ) 2 (1.996 Å), [Pt­( H N^N^N H )­NCCH 3 ]­(BF 4 ) 2 (1.983 Å), and ( H N^N^N H = 5tertbutyl-1,3-bis­(pyrazol-3-yl)­pyridine). This difference can be assigned to the trans influence exerted by the anionic benzene moiety opposite of acetonitrile .…”

“…35,38 We previously demonstrated successful anion sensing applications based on a pincer Pt(II)-N^C^N complex involving enhanced emission analytical response in micellar aqueous media. 39 Cyclometalated Pt(II)-N^C^N complexes (N^C^N = 1,3-bis(phenylbenzimidazolyl)benzene) are typically highly luminescent green-emitting compounds (λ em ∼ 500−550 nm) 40−42 with lifetimes in the microsecond range and applications in light-emitting devices 43,44 photochromism, 45−47 catalysis, 48 metallophilic interactions, 49 and recently in bioimaging research. 50,51 However, anion coordination/ sensing in an aqueous phase remains largely unexplored.…”

“…Reports in the area of bioorganometallic chemistry have displayed that the cationic compounds [Ru­(en)­(tetrahydroanthracene)­(H 2 O)] 2+ and [Rh­(cyclopentadienyl)­(ferrozine)­(H 2 O)] 2+ are able to selectively coordinate Cl – in aqueous media with binding constants in the range of 10 2 –10 3 M –1 via direct coordination to the metal atom. , However, the creation of a chemosensor with higher Cl – affinity is not a trivial task and clearly requires elaborate molecular strategy and synthetic approaches to chemical affinity and size selectivity. , We previously demonstrated successful anion sensing applications based on a pincer Pt­(II)-N^C^N complex involving enhanced emission analytical response in micellar aqueous media . Cyclometalated Pt­(II)-N^C^N complexes (N^C^N = 1,3-bis­(phenylbenzimidazolyl)­benzene) are typically highly luminescent green-emitting compounds (λ em ∼ 500–550 nm) − with lifetimes in the microsecond range and applications in light-emitting devices , photochromism, − catalysis, metallophilic interactions, and recently in bioimaging research. , However, anion coordination/sensing in an aqueous phase remains largely unexplored. Taking this into account, we surmised that an efficient luminescent chloride sensor could be achieved by using a water-soluble cationic [Pt­(N^C^N)] + complex containing an available coordination site and hydrogen bond donor groups as cooperative recognition points.…”

Organic platinum compounds containing one platinum–carbon bond. Synthesis, structure, possibilities of practical application

“…Реакции металлирования 2-(5-трет-бутилпиразол-3-ил)-6-(диэтиламинометил)пиридина (HNNN)Et и 2,6-бис(5-трет-бутил-1H-пиразол-3-ил)пиридина (HNNNH) соединениями Pt(II) приводит к образованию нейтральных комплексов Pt(*NNN)EtCH 3 (4), для которых исследованы реакции с кислотами [4]. Показано, что протонирование происходит преимущественно на пиразолатном участке (комплекс (5)), а для высвобождения метана требуется дополнительная кислота (комплекс (6)).…”

“…Показано, что улучшенные люминесцентные свойства йодсодержащего соединения 125 обусловлены меньшей синглеттриплетной энергетической щелью ΔEST по сравнению с хлорсодержащим аналогом. Также был исследовано влияние йод-лигандов на триплетные и синглетные состояния и на спинорбитальное взаимодействие (СОС) в аналогичных фосфоресцентных комплексах моноплатины(II) (126, 127).Фотофизические свойства описаны для нового биядерного комплекса Pt 2 L(PF 6 ) 2 (128) на основе макроциклического каликс[4]имидазолилиден[2]пиразолатного лиганда. Комплекс был получен депротонированием in situ соли тетраимидазолия H 6 L(PF 6 ) 4 [62].…”