Novel insertion of ethynylbenzene derivatives bearing an electron-withdrawing substituent at the 4-position into a P–C bond and their transannular insertion between a metal atom and an ipso-carbon atom of the phosphine ligand †

2000 ◽  
pp. 2896-2897 ◽  
Author(s):  
Yasuhiro Yamamoto ◽  
Kenichiro Sugawara
Keyword(s):  
Carbon Atom ◽  
Metal Atom ◽  
Phosphine Ligand

3,5-Dimethylpyrazolylphosphine molybdenum(0) and tungsten(0) carbonyl complexes

1980 ◽  
Vol 58 (2) ◽  
pp. 151-158 ◽  
Author(s):  
Harry B. Davis ◽  
James K. Hoyano ◽  
Ping Yuen Leung ◽  
Louis K. Peterson ◽  
Brian Wolstenholme
Keyword(s):  
General Formula ◽  
Metal Atom ◽  
Phosphorus Atom ◽  
Phenyl Ring ◽  
Octahedral Geometry ◽  
Phosphine Ligand ◽  
Carbonyl Complexes ◽  
Coordination Sites ◽  
And Tungsten

Complexes with the general formula [LnM(CO)m], where [Formula: see text] x = 0–2, n = 1 or 2, M = Mo(0) or W(0), m = 3 or 4, were prepared by thermal or photolytic methods by the reaction of the appropriate 3,5-dimethylpyrazolyl phosphine ligand with M(CO)6, norbornadienemetaltetracarbonyl [C7H8M(CO)4], cycloheptatrienylmetaltricarbonyl [C7H8M(CO)3], [(Me2N(CH2)3NMe2)M(CO)4], [(CH3CN)2M(CO)4], or [(CH3CN)3M(CO)3]. Structural evidence indicates octahedral geometry about the metal atom centre, and several modes of coordination for the ligands in those complexes isolated and characterized. For x = 2, the ligand [Formula: see text] was monodentate, via phosphorus in [Formula: see text] and bidentate in [Formula: see text] where coordination by P and the 2N site of the pyrazolyl ring yielded four-membered [Formula: see text] metallocycles. For x = 1, the [Formula: see text] ligand was bidentate, via the phosphorus atom and one of the 2N sites of one of the pyrazolyl substituents, thus giving the four-membered [Formula: see text] metallocycle in [Formula: see text] and tridentate in [Formula: see text] where three facial CO's, two 2N atoms of the pyrazolyl rings, and a part of the phenyl ring occupy the six coordination sites. For x = 0, the P(Me2pz)3 ligand was tridentate via the 2N atoms of all three pyrazolyl rings, thus giving tricyclic systems [P(Me2pz)3M(CO)3] (VIII, IX).

Metallaborane Reaction Chemistry. Part 7. B-Frame Supported Bimetallics: Ligand-to-β-Metal Organometallic Interaction in Dimetallaboranes and an Interesting Ligand Displacement Cascade

1999 ◽  
Vol 64 (6) ◽  
pp. 938-946 ◽  
Author(s):  
Young-hee Kim ◽  
Yvonne M. McKinnes ◽  
Paul A. Cooke ◽  
Robert Greatrex ◽  
John D. Kennedy ◽  
...  
Keyword(s):  
Metal Atom ◽  
Phenyl Group ◽  
Phosphine Ligand ◽  
Platinum Atom ◽  
Displacement Cascade ◽  
Ligand Displacement

Reaction of [PtCl2(PMe2Ph)2] with [(PMe2Ph)2PtB10H12] generates [(PMe2Ph)2-μ-η1(Pt)- η1-(Pt')-{PMe2(C6H4)}-closo-Pt2B10H9(PMe2Ph)] in which the phenyl group of a phosphine ligand on one platinum atom exhibits ortho-cyclometallation to the second metal atom, whereas reaction of PPh3 with [(PMe2Ph)2PtB9H9Ru(pcym)] generates [(PMe2Ph)2-μ-η6(Ru)- η1(Pt)-(C6H5PPh2)-closo-PtRuB9H9] in which the phenyl group of a phosphine ligand on the platinum atom exhibits tridentate η6 coordination to the second metal atom.

scholarly journals Carbones and Carbon Atom as Ligands in Transition Metal Complexes

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4943 ◽  
Author(s):  
Lili Zhao ◽  
Chaoqun Chai ◽  
Wolfgang Petz ◽  
Gernot Frenking
Keyword(s):  
Carbon Atom ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Metal Atom ◽  
Lanthanide Complexes ◽  
Theoretical Studies ◽  
Complete Coverage ◽  
Review Reports ◽  
Experimental And Theoretical Studies

This review summarizes experimental and theoretical studies of transition metal complexes with two types of novel metal-carbon bonds. One type features complexes with carbones CL2 as ligands, where the carbon(0) atom has two electron lone pairs which engage in double (σ and π) donation to the metal atom [M]⇇CL2. The second part of this review reports complexes which have a neutral carbon atom C as ligand. Carbido complexes with naked carbon atoms may be considered as endpoint of the series [M]-CR3 → [M]-CR2 → [M]-CR → [M]-C. This review includes some work on uranium and cerium complexes, but it does not present a complete coverage of actinide and lanthanide complexes with carbone or carbide ligands.

Oxygen uptake and evolution by iron porphyrin enzymes

1959 ◽  
Vol 12 (1) ◽  
pp. 47
Author(s):  
NK King ◽  
ME Winfield
Keyword(s):  
Ascorbic Acid ◽  
Carbon Atom ◽  
Oxygen Uptake ◽  
Cytochrome Oxidase ◽  
Metal Atom ◽  
Iron Porphyrin ◽  
Reduction Step ◽  
The Third ◽  
Catalase Peroxidase ◽  
Electron Deficiency

Three detailed mechanisms are considered for the catalatic decomposition of H2O2. It is shown that the first of these, akin to the earlier hypotheses for catalase action, cannot satisfy the magnetic, titrimetric, and kinetic evidence. The second mechanism involves oxidation of the FeIII porphyrin to the equivalent of FeV. The electron deficiency is distributed over the ligands so that even in the most oxidized complex the iron is in the FeIV or possibly even the FeIII state. In the third scheme it is suggested that the reduction step (in which O2 is liberated) takes place at a carbon atom, while the site of the oxidation is the metal atom as commonly supposed. The liberation of O2 from H2O2 can be catalysed by 6-coordinate ruthenium II complexes. In the catalytic cycle, the metal appears to be oxidized to Rdv, then reduced to RuII. Ethanol or ascorbic acid can substitute for H2O2 in the reduction. Evidence for H2O2 attack on the ligands is suggestive but not conclusive. A brief comment is made on the bonding of oxygen to haemoglobin and myoglobin. The accumulated evidence for the structures of catalase, peroxidase, and myoglobin complexes is utilized in a scheme for the uptake of oxygen by cytochrome oxidase.

An atomic resolution study of a carbide phase in platinum

1992 ◽  
Vol 50 (1) ◽  
pp. 20-21
Author(s):  
M.J. Witcomb ◽  
M.A. O'Keefe ◽  
CJ. Echer ◽  
C. Nelson ◽  
J.H. Turner ◽  
...  
Keyword(s):  
Solid Solution ◽  
Carbon Atom ◽  
Carbide Phase ◽  
Structural Changes ◽  
Critical Role ◽  
Alloy System ◽  
Atomic Resolution ◽  
Excess Carbon ◽  
Interstitial Carbon ◽  
Resolution Study

Under normal circumstances, Pt dissolves only a very small amount of interstitial carbon in solid solution. Even so, an appropriate quench/age treatment leads to the formation of stable Pt2C {100} plate precipitates. Excess (quenched-in) vacancies play a critical role in the process by accommodating the volume and structural changes that accompany the transformation. This alloy system exhibits other interesting properties. Due to a large vacancy/carbon atom binding energy, Pt can absorb excess carbon at high temperatures in a carburizing atmosphere. In regions rich in carbon and vacancies, another carbide phase, Pt7C which undergoes an order-disorder reaction was formed. The present study of Pt carburized at 1160°C and aged at 515°C shows that other carbides in the PtxC series can be produced.

Electronic properties of quasi two-dimensional transition metals chalcogenides with low-dimensional magnetism

Doklady BGUIR ◽  
2020 ◽  
Vol 18 (7) ◽  
pp. 87-95
Author(s):  
M. S. Baranava ◽  
P. A. Praskurava
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Exchange Interaction ◽  
Electronic Properties ◽  
Metal Atom ◽  
Transition Metal Atom ◽  
Two Dimensional ◽  
Transition Metal Atoms ◽  
Ground Magnetic ◽  
Low Dimensional

The search for fundamental physical laws which lead to stable high-temperature ferromagnetism is an urgent task. In addition to the already synthesized two-dimensional materials, there remains a wide list of possible structures, the stability of which is predicted theoretically. The article suggests the results of studying the electronic properties of MAX3 (M = Cr, Fe, A = Ge, Si, X = S, Se, Te) transition metals based compounds with nanostructured magnetism. The research was carried out using quantum mechanical simulation in specialized VASP software and calculations within the Heisenberg model. The ground magnetic states of twodimensional MAX3 and the corresponding energy band structures are determined. We found that among the systems under study, CrGeTe3 is a semiconductor nanosized ferromagnet. In addition, one is a semiconductor with a bandgap of 0.35 eV. Other materials are antiferromagnetic. The magnetic moment in MAX3 is localized on the transition metal atoms: in particular, the main one on the d-orbital of the transition metal atom (and only a small part on the p-orbital of the chalcogen). For CrGeTe3, the exchange interaction integral is calculated. The mechanisms of the formation of magnetic order was established. According to the obtained exchange interaction integrals, a strong ferromagnetic order is formed in the semiconductor plane. The distribution of the projection density of electronic states indicates hybridization between the d-orbital of the transition metal atom and the p-orbital of the chalcogen. The study revealed that the exchange interaction by the mechanism of superexchange is more probabilistic.

Mass spectra of 4,4-dimethyl-A-homo-4a,6-cholestadien-3-ols, 4,4-dimethyl-A-homo-5-cholestene-3,4a-diols and their derivatives

1982 ◽  
Vol 47 (10) ◽  
pp. 2768-2778
Author(s):  
Antonín Trka ◽  
Helena Velgová
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions

Partial electron impact induced mass spectra are given of 3α-hydroxy-, 3β-hydroxy-, 3β-methoxy-, 3α-acetoxy- and 3β-acetoxy-4,4-dimethyl-A-homo-4a,6-cholestadienes, 3α,5α-epoxy-4,4-dimethyl-A-homo-5-cholestane, isomeric 4,4-dimethyl-A-homo-5-cholestene-3α(β),4aα(β)-diols, their 3-acetoxy derivatives and 3-methyl ethers. The fragmentation of the molecular ions of these substances involves the usual elimination of substituents (in the form of H2O, CH3OH, CH3COOH, CH2CO), but the most abundant and characteristic ions are products of the contraction of ring A (to a six- or five-membered one), accompanied by expulsion of a fragment containing the carbon atom C(4) with both methyls.

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