The first 4π‐electron resonance‐stabilized 1,3‐digerma‐2,4‐diphosphacyclobutadiene LH2Ge2P2 4 (LH=CHCHNDipp2 Dipp=2,6‐iPr2C6H3) with four‐coordinate germanium supported by a β‐diketiminate ligand and ...two‐coordinate phosphorus atoms has been synthesized from the unprecedented phosphaketenyl‐functionalized N‐heterocyclic germylene LHGe‐P=C=O 2 a prepared by salt‐metathesis reaction of sodium phosphaethynolate (P≡C−ONa) with the corresponding chlorogermylene LHGeCl 1 a. Under UV/Vis light irradiation at ambient temperature, release of CO from the P=C=O group of 2 a leads to the elusive germanium–phosphorus triply bonded species LHGe≡P 3 a, which dimerizes spontaneously to yield black crystals of 4 as isolable product in 67 % yield. Notably, release of CO from the bulkier substituted LtBuGe‐P=C=O 2 b (LtBu=CHC(tBu)N‐Dipp2) furnishes, under concomitant extrusion of the diimine Dipp‐NC(tBu)2, the bis‐N,P‐heterocyclic germylene DippNC(tBu)C(H)PGe2 5.
Elusive Ge≡P: A 4π‐electron resonance‐stabilized 1,3‐digerma‐2,4‐diphosphacyclobutadiene derivative LH2Ge2P2 (3; LH=CHCHN(2,6‐iPr2C6H32), could be synthesized, isolated, and structurally characterized. This compound resulted from the phosphaketenyl‐functionalized germylene LHGe(P=C=O) (1) through photolytic release of CO and subsequent head‐to‐tail dimerization of the presumed phosphagermyne intermediate, LHGe≡P (2).
The production of phosphoryl species (PO, PO2, HOPO) is believed to be of great importance for efficient flame‐retardant action in the gas phase. We present a detailed investigation of the thermal ...decomposition of dimethyl methylphosphonate (DMMP) probed by vacuum ultraviolet (VUV) synchrotron radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. This technique provides a snapshot of the thermolysis process and direct evidence of how the reactive phosphoryl species are generated during heat exposure. One of the key findings of this work is that only PO is formed in high concentration upon DMMP decomposition, whereas PO2 is absent. It can be concluded that the formation of PO2 needs an oxidative environment, which is typically the case in a real flame. Based on the identification of products such as methanol, formaldehyde, and PO, as well as the intermediates OPCH3, H2CPOH, and H2CP(O)H, supported by quantum chemical calculations, we were able to describe the predominant pathways that lead to active phosphoryl species during the thermal decomposition of DMMP.
Molecular fire extinguishers: The production of phosphoryl species is believed to be of great importance for efficient flame‐retardant action in the gas phase. A detailed investigation on the pathways to the PO radical from thermally cracked dimethyl methylphosphonate is presented.
Metal-catalyzed asymmetric processes offer one of the most straightforward ways to introduce stereogenic centers. Hence, the development of novel chiral ligands that can effectively induce asymmetry ...in reactions is crucial in modern organic synthesis. While many established chiral ligands bind to a metal through heteroatoms, structures that coordinate to metals through carbon atoms have received little attention so far. Here, we highlight the increasing number of such chiral chelating olefin ligands as well as their application in a variety of metal-catalyzed transformations.
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•Phosphinines with different coordination modes.•Phosphinines in metal–ligand cooperativity.•Phosphinines in the activation of small molecules.•Phosphinines in catalysis.•Phosphinines ...in material science.•Phosphinines in light-induced transformations.
This review covers the progress that has been made during the last 10 years in the coordination chemistry of 1-phosphinines, 1,4-diphosphinines and 1,3,5-triphosphinines and related ligands. There is particular emphasis on the reactivity and application of phosphinine-containing transition metal complexes in relation to the electronic, structural and coordination properties of the corresponding phosphorus heterocycle.
The development of an efficient catalytic process that mimics the enzymatic function of alcohol dehydrogenase is critical for using biomass alcohols for both the production of H2 as a chemical energy ...carrier and fine chemicals under waste-free conditions. Dehydrogenation of alcohol-water mixtures into their corresponding acids with molecular hydrogen as the sole by-product from the reaction can be catalysed by a ruthenium complex with a chelating bis(olefin) diazadiene ligand. This complex, K(dme)2Ru(H)(trop2dad), stores up to two equivalents of hydrogen intramolecularly, and catalyses the production of H2 from alcohols in the presence of water and a base under homogeneous conditions. The conversion of a MeOH-H2O mixture proceeds selectively to CO2/H2 gas formation under neutral conditions, thereby allowing the use of the entire hydrogen content (12% by weight). Isolation and characterization of the ruthenium complexes from these reactions suggested a mechanistic scenario in which the trop2dad ligand behaves as a chemically 'non-innocent' co-operative ligand.
Stable Aminyl Radical Metal Complex Bůttner, Torsten; Geier, Jens; Frison, Gilles ...
Science (American Association for the Advancement of Science),
01/2005, Letnik:
307, Številka:
5707
Journal Article
Recenzirano
Metal-stabilized phenoxyl radicals appear to be important intermediates in a variety of enzymatic oxidations. We report that transition metal coordination also supports an aminyl radical, resulting ...in a stable crystalline complex: Rh(I)(trop₂Nsuperscript .)(bipy)⁺OTf⁻ (where trop is 5-H-dibenzoa,dcycloheptene-5-yl, bipy is 2,2'-bipyridyl, OTf⁻ is trifluorosulfonate). It is accessible under mild conditions by one-electron oxidation of the amide complex Rh(I)(trop₂N)(bipy), at a potential of -0.55 volt versus ferrocene/ferrocenium. Both electron paramagnetic resonance spectroscopy and density functional theory support 57% localization of the unpaired spin at N. In reactions with H-atom donors, the Rh-coordinated aminyl behaves as a nucleophilic radical.
Cellulose nanocrystals (CNCs) with >2000 photoactive groups on each can act as highly efficient initiators for radical polymerizations, cross‐linkers, as well as covalently embedded nanofillers for ...nanocomposite hydrogels. This is achieved by a simple and reliable method for surface modification of CNCs with a photoactive bis(acyl)phosphane oxide derivative. Shape‐persistent and free‐standing 3D structured objects were printed with a mono‐functional methacrylate, showing a superior swelling capacity and improved mechanical properties.
All‐rounder: Multifunctional cellulose nanocrystals were achieved by facile surface immobilization of photoactive groups. They serve as highly efficient visible light photoinitiators, cross‐linkers and covalently embedded nanofillers for 3D printing of nanocomposite hydrogels, using a mono‐functional methacrylate as monomer without any conventional cross‐linkers.
Abstract
Small organic molecules provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. Herein, we report that ...diolefin–ruthenium complexes containing the chemically and redox non-innocent ligand trop
2
dad catalyse the production of H
2
from formaldehyde and water in the presence of a base. The process involves the catalytic conversion to carbonate salt using aqueous solutions and is the fastest reported for acceptorless formalin dehydrogenation to date. A mechanism supported by density functional theory calculations postulates protonation of a ruthenium hydride to form a low-valent active species, the reversible uptake of dihydrogen by the ligand and active participation of both the ligand and the metal in substrate activation and dihydrogen bond formation.
Simple basic ingredients are at the origin of the synthesis of Na(OCP), the phosphorus analogue of sodium cyanate. Na(OCP) is obtained from NaPH2 (made from Na, P, and a proton source) and CO ...(from carbon and air). This salt is remarkably stable, in complete contrast to HCP discovered 50 years ago.
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