Metal–ligand cooperativity across two sites of a square planar iron(ii) complex ligated by a tetradentate PNNP ligand

2020 ◽  
Vol 56 (61) ◽  
pp. 8611-8614 ◽  
Author(s):  
Gregory P. Hatzis ◽  
Christine M. Thomas
Keyword(s):  
Electron Process ◽  
Square Planar ◽  
Metal Ligand

A square planar (PNNP)FeII complex is shown to readily activate two B–H bonds across the Fe–amide linkages in an overall four-electron process facilitated by metal–ligand cooperativity.

Tuning the thermoelectric performance of π–d conjugated nickel coordination polymers through metal–ligand frontier molecular orbital alignment

2018 ◽  
Vol 6 (40) ◽  
pp. 19757-19766 ◽  
Author(s):  
Xue Yong ◽  
Wen Shi ◽  
Gang Wu ◽  
Shermin S. Goh ◽  
Shiqiang Bai ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Power Factor ◽  
High Mobility ◽  
Frontier Molecular Orbital ◽  
Phonon Coupling ◽  
Thermoelectric Power Factor ◽  
Square Planar ◽  
Electron Phonon Coupling ◽  
Weak Electron ◽  
Metal Ligand

A good frontier molecular orbital alignment between the square planar metal-tetrasulfide fragment and the organic π-conjugated spacers results in a weak electron-phonon coupling, a high mobility and eventually a higher thermoelectric power factor.

scholarly journals Insights into metal–ligand hydrogen transfer: a square-planar ruthenate complex supported by a tetradentate amino–amido-diolefin ligand

2016 ◽  
Vol 52 (36) ◽  
pp. 6138-6141 ◽  
Author(s):  
Demyan E. Prokopchuk ◽  
Alan J. Lough ◽  
Rafael E. Rodriguez-Lugo ◽  
Robert H. Morris ◽  
Hansjörg Grützmacher
Keyword(s):  
Hydrogen Transfer ◽  
Oxidative Addition ◽  
Square Planar ◽  
Elimination Reactions ◽  
Metal Ligand

A unique square planar anionic ruthenium(0) complex with amido and amine donors undergoes rapid NH oxidative addition/elimination reactions.

scholarly journals Reactivity of Iridium Complexes of a Triphosphorus-Pincer Ligand Based on a Secondary Phosphine. Catalytic Alkane Dehydrogenation and the Origin of Extremely High Activity

2021 ◽  
Author(s):  
Benjamin Gordon ◽  
Nicholas Lease ◽  
Thomas Emge ◽  
Faraj Hasanayn ◽  
Alan Goldman
Keyword(s):  
High Catalytic Activity ◽  
Iridium Complexes ◽  
Major Goal ◽  
Alkane Dehydrogenation ◽  
Chemical Catalysis ◽  
Coordination Site ◽  
Selective Functionalization ◽  
Alkyl Groups ◽  
Square Planar ◽  
Metal Ligand

The selective functionalization of alkanes and alkyl groups is a major goal of chemical catalysis. Toward this end, a bulky triphosphine with a central secondary phosphino group, bis(2 di-t-butyl-phosphinophenyl)phosphine (tBuPHPP), has been synthesized. When complexed to iridium it adopts a meridional (“pincer”) configuration. The secondary phosphino H atom can undergo migration to iridium to give an anionic phosphido-based-pincer (tBuPPP) complex. We describe novel metal-ligand cooperativity of the iridium-phosphido unit. Stoichiometric reactions of the (tBuPPP)Ir complexes reflect a distribution of steric bulk around the iridium center in which the coordination site trans to the phosphido group is quite crowded, one coordination site cis to the phosphido is even more crowded, while the remaining site is particularly open. The (tBuPPP)Ir precursors are the most active catalysts reported to date for dehydrogenation of n-alkanes, by about two orders of magnitude. The electronic properties of the iridium center are very similar to that of well-known analogous (RPCP)Ir catalysts. Accordingly, DFT calculations predict that (tBuPPP)Ir and (tBuPCP)Ir are, intrinsically, comparably active for alkane dehydrogenation. While dehydrogenation by (RPCP)Ir proceeds through an intermediate trans-(PCP)IrH2(alkene), (tBuPPP)Ir follows a pathway proceeding via cis-(PPP)IrH2(alkene), thereby circumventing unfavorable placement of the alkene at the bulky site trans to phosphorus. (tBuPPP)Ir and (tBuPCP)Ir, however, have analogous resting states: square planar (pincer)Ir(alkene). Alkene coordination at the crowded trans site is therefore unavoidable in the resting states. Thus the resting state of the (tBuPPP)Ir catalyst is destabilized by the unusual architecture of the ligand, and this is largely responsible for its unusually high catalytic activity.

scholarly journals Synthesis, Spectral Characterization and X–Ray Diffraction Studies of some Pd(II) Complexes with Schiff Bases

2014 ◽  
Vol 36 ◽  
pp. 272-280
Author(s):  
Julekha A. Shaikh
Keyword(s):  
Thermal Analysis ◽  
Schiff Bases ◽  
Molar Conductivity ◽  
Planar Geometry ◽  
Monoclinic Crystal System ◽  
X Ray Diffraction ◽  
Monoclinic Crystal ◽  
X Ray ◽  
Square Planar ◽  
Metal Ligand

The synthesis, spectroscopic and X – Ray Diffraction studies of some Pd(II) complexes with bidentate Schiff bases are reported here. These Schiff bases were derived by condensing aldehydes like 2-hydroxy-1-naphthaldehyde, 5-chloro salicyladehyde with amines like 4-nitro aniline, 4-methyl aniline and 4-methoxy aniline. The complexes were characterized on the basis of elemental analysis, molar conductivity, spectral (IR, 1H and electronic) as well as thermal analysis. All the Pd (II) complexes exhibit square planar geometry with 1:2 (metal : ligand) stoichiometry. The X- ray diffraction studies suggest monoclinic crystal system for these complexes.

Isotopic Studies of the Metal–Ligand Bond. Part III. The Far Infrared Spectra of Some Tetragonal Diamine Complexes of Cobalt(II) and Nickel(II): Studies of the Metal–Nitrogen Bond, as a Function of Metal Ion and of Spin State

1973 ◽  
Vol 51 (10) ◽  
pp. 1567-1581 ◽  
Author(s):  
A. B. P. Lever ◽  
Elvio Mantovani
Keyword(s):  
Infrared Spectra ◽  
Metal Ion ◽  
Far Infrared ◽  
Geometric Factors ◽  
Square Planar ◽  
Isotopic Studies ◽  
First Time ◽  
Far Infrared Spectra ◽  
Metal Ligand ◽  
Nitrogen Bond

The far infrared spectra of 35 complexes of the formula M(diamine)2X2 are reported where M = Co(II) and Ni(II), X = Cl−, Br−, I−, NO3−, SCN−, ClO4−, and AgI2− and the diamine is ethylenediamine or its N,N-symmetric or antisymmetrically substituted dimethyl or diethyl derivative. Isotopic substitution studies with 62Ni and with 2H are carried out with eleven characteristic complexes and assignments for the metal–nitrogen modes in both octahedral and square planar complexes so deduced. In most cases the appropriate number of metal–ligand modes, based on symmetry considerations, are observed. The variations in observed M—N frequencies are discussed in terms of the electronic and geometric factors previously utilized for the corresponding copper(II) complexes. In complexes containing the asymmetric ligands, stretching vibrations arising from the two types of metal–nitrogen bond can be separately identified. Isotopic studies of pairs of complexes containing the same ligand and metal ion but with the latter in alternate spin states are reported here for the first time. All of the cobalt(II) complexes and several of the nickel(II) complexes are reported here for the first time.

Crystal chemistry of high-Tc superconductors

1990 ◽  
Vol 48 (4) ◽  
pp. 1118-1119
Author(s):  
Maryvonne Hervieu
Keyword(s):  
Oxygen Deficiency ◽  
Large Family ◽  
Copper Oxides ◽  
High Tc Superconductors ◽  
High Tc ◽  
Single Mechanism ◽  
Square Planar ◽  
History Of ◽  
Bismuth Cuprates ◽  
New Compounds

Four years after the discovery of superconductivity at high temperature in the Ba-La-Cu-O system, more than thirty new compounds have been synthesized, which can be classified in six series of copper oxides: La2CuO4 - type oxides, bismuth cuprates, YBa2Cu3O7 family, thallium cuprates, lead cuprates and Nd2CuO4 - type oxides. Despite their quite different specific natures, close relationships allow their structures to be simply described through a single mechanism. The fifth first families can indeed be described as intergrowths of multiple oxygen deficient perovskite slabs with multiple rock salt-type slabs, according to the representation [ACuO3-x]m [AO]n.The n and m values are integer in the parent structures, n varying from 0 to 3 and m from 1 to 4; every member of this large family can thus be symbolized by [m,n]. The oxygen deficient character of the perovskite slabs involves the existence or the co-existence of several types of copper environment: octahedral, pyramidal and square planar.Both mechanisms, oxygen deficiency and intergrowth, are well known to give rise easily to nonstoichiometry phenomena. Numerous and various phenomena have actually been characterized in these cuprates, strongly depending on the thermal history of the samples.

On the Conrotatory Ring Opening of 3-Carbomethoxycyclobutene Vis-À-Vis 3-Carbomethoxy-1,2-Benzocyclobutene and the Predominant Inward Opening of 3-Dimethylaminocarbonyl-1,2-Benzocyclobutene

2018 ◽  
Author(s):  
Veejendra Yadav ◽  
Dasari L V K Prasad ◽  
Arpita Yadav ◽  
Maddali L N Rao
Keyword(s):  
Transition State ◽  
Ring Opening ◽  
Electron Process ◽  
Ring Opening Reaction ◽  
Stable Species ◽  
Electron Event

<p>The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by p<sub>C1C2</sub>→s*<sub>C3C4</sub> and s<sub>C3C4</sub>→p*<sub>CO</sub> interactions in the transition state in a 4-electron process as opposed to only s<sub>C3C4</sub>→p*<sub>CO</sub> interaction in an apparently 8-electron event in 3-carbomethoxy-1,2-benzocyclobutene. The ring opening of 3-carbomethoxy-1,2-benzocyclobutene is sufficiently endothermic. We therefore argue that the reverse ring closing reaction is faster than the forward ring opening reaction and, thus, it establishes an equilibrium between the two and subsequently allows formation of the more stable species <i>via</i> outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.</p>

New Platinum (II) Ternary Complexes of Formamidine and Pyrophosphate: Synthesis, Characterization and DFT Calculations and In vitro Cytotoxicity

2020 ◽  
Vol 23 (7) ◽  
pp. 611-623
Author(s):  
Ahmed A. Soliman ◽  
Fawzy A. Attaby ◽  
Othman I. Alajrawy ◽  
Azza A.A. Abou-hussein ◽  
Wolfgang Linert
Keyword(s):  
Cell Line ◽  
Cancer Cell ◽  
Theoretical Calculations ◽  
Thermal Analyses ◽  
Cancer Cell Line ◽  
Cellular Growth ◽  
Planar Geometry ◽  
Square Planar ◽  
Vis Spectroscopy

Aim and Objective: Platinum (II) and platinum (IV) of pyrophosphate complexes have been prepared and characterized to discover their potential as antitumor drugs. This study was conducted to prepare and characterize new ternary platinum (II) complexes with formamidine and pyrophosphate as an antitumor candidate. Materials and Methods: The complexes have been characterized by mass, infrared, UV-Vis. spectroscopy, elemental analysis, magnetic susceptibility, thermal analyses, and theoretical calculations. They have been tested for their cytotoxicity, which was carried out using the fastcolorimetric assay for cellular growth and survival against MCF-7 (breast cancer cell line), HCT- 116 (colon carcinoma cell line), and HepG-2 (hepatocellular cancer cell line). Results: All complexes are diamagnetic, and the electronic spectral data displayed the bands due to square planar Pt(II) complexes. The optimized complexes structures (1-4) indicated a distorted square planar geometry where O-Pt-O and N-Pt-N bond angles were 82.04°-96.44°, respectively. Conclusion: The complexes showed noticeable cytotoxicity and are considered as promising antitumor candidates for further applications.

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