1 Electrophilic RhI catalysts for arene H/D exchange in acidic media
... based on Ir and Rh have been shown to be active for benzene C−H activation [50-61]. Rhodium complexes are particularly attractive due to the possibility of C−H activation by RhI [62] or RhIII [55]. Further, oxidation of the rhodium center can be achieved with air recyclable Cu(II) salts, which provi ...
... based on Ir and Rh have been shown to be active for benzene C−H activation [50-61]. Rhodium complexes are particularly attractive due to the possibility of C−H activation by RhI [62] or RhIII [55]. Further, oxidation of the rhodium center can be achieved with air recyclable Cu(II) salts, which provi ...
University of Groningen Reactivity of rare earth metal
... combine high catalyst activity, selectivity, and broad substrate scope. Organo rare earth metal catalysts show good activities, but heteroatom-containing substrates have barely been investigated.5 Although these metals are hard Lewis acids, the high kinetic lability of their complexes provides inter ...
... combine high catalyst activity, selectivity, and broad substrate scope. Organo rare earth metal catalysts show good activities, but heteroatom-containing substrates have barely been investigated.5 Although these metals are hard Lewis acids, the high kinetic lability of their complexes provides inter ...
Metal Complexation of Thiacrown Ether Macrocycles by
... macrocycles directly complexed with the metal ions of interest. ESI-MS provides complementary information not available with (i) the purely elemental capabilities of ICPMS and ICP-AES, which are commonly used for heavy metal detection, (ii) NMR analysis, which often requires higher concentrations of ...
... macrocycles directly complexed with the metal ions of interest. ESI-MS provides complementary information not available with (i) the purely elemental capabilities of ICPMS and ICP-AES, which are commonly used for heavy metal detection, (ii) NMR analysis, which often requires higher concentrations of ...
metal ion complexing properties of the highly preorganized ligands
... Highly preorganized ligands have shown greater stability constants as well as increased metal-ion selectivities over their straight-chain analogs. The preorganized ligand 8-quinolyl1,10-phenanthroline (8QP) was studied to determine its formation constants with various aqueous metal-ions as well as i ...
... Highly preorganized ligands have shown greater stability constants as well as increased metal-ion selectivities over their straight-chain analogs. The preorganized ligand 8-quinolyl1,10-phenanthroline (8QP) was studied to determine its formation constants with various aqueous metal-ions as well as i ...
inorganic chemistry and spectroscopy ( a systematic approach)
... Cu+ is diamagnetic while Co+2 is paramagnetic. In the highest oxidation states, the transition metal show acidic character and form cationic complexes. Zn, Cd and Hg have relatively lower melting points than the other d-block element as they have completely filled (n-1) d-orbitals, their atoms are n ...
... Cu+ is diamagnetic while Co+2 is paramagnetic. In the highest oxidation states, the transition metal show acidic character and form cationic complexes. Zn, Cd and Hg have relatively lower melting points than the other d-block element as they have completely filled (n-1) d-orbitals, their atoms are n ...
PDF File
... substrate (S) or the guanosine nucleophile (G), leading to stronger binding of the second substrate. Recent work showed that the two substrates are bridged by a metal ion that coordinates both the nonbridging reactive phosphoryl oxygen of S and the 2 ' -OH of G. These results suggest that the energy ...
... substrate (S) or the guanosine nucleophile (G), leading to stronger binding of the second substrate. Recent work showed that the two substrates are bridged by a metal ion that coordinates both the nonbridging reactive phosphoryl oxygen of S and the 2 ' -OH of G. These results suggest that the energy ...
Diamagnetic Corrections and Pascal`s Constants
... often conflicting values are given in different sources owing to the different interpretations of diamagnetic susceptibilities that arose in the early 20th century (8). In this article we present an explanation for the origin of the diamagnetic correction factors, organized tables of constants compi ...
... often conflicting values are given in different sources owing to the different interpretations of diamagnetic susceptibilities that arose in the early 20th century (8). In this article we present an explanation for the origin of the diamagnetic correction factors, organized tables of constants compi ...
19-20 - TAMU Chemistry
... Q. What happens to rates of (A) and (D) type when one has a bulky ligand? A. (D) should be more favored – rates of loss of the bulky ligand would increase. (A) should be less favored – rates of adding a new ligand to the “already crowded” coordination environment should be ...
... Q. What happens to rates of (A) and (D) type when one has a bulky ligand? A. (D) should be more favored – rates of loss of the bulky ligand would increase. (A) should be less favored – rates of adding a new ligand to the “already crowded” coordination environment should be ...
Metallocene Organoactinide Complexes
... that the 6d orbitals are chiefly involved in interactions with ligand-based orbitals. While the 5f orbital energy drops across the series, creating an energy match with ligand-based orbitals, spatial overlap is poor, precluding strong metal–ligand bonding [44]. Thorium lies early in the actinide seri ...
... that the 6d orbitals are chiefly involved in interactions with ligand-based orbitals. While the 5f orbital energy drops across the series, creating an energy match with ligand-based orbitals, spatial overlap is poor, precluding strong metal–ligand bonding [44]. Thorium lies early in the actinide seri ...
Room temperature ionic liquid as a novel medium for liquid/liquid
... facilitates the formation of deprotonated dithizone because the solvation energy of deprotonated dithizone in IL is higher than that in chloroform [31]. This argument is further supported from the absorption spectrum of dithizone in [C4 mim][PF6 ], as shown in Fig. 2, that only one absorption maximu ...
... facilitates the formation of deprotonated dithizone because the solvation energy of deprotonated dithizone in IL is higher than that in chloroform [31]. This argument is further supported from the absorption spectrum of dithizone in [C4 mim][PF6 ], as shown in Fig. 2, that only one absorption maximu ...
PDF document
... complexes.16 Metal ions may change the bio-availability of quinolones by changing their solubility or their lipophilicity. The metal complexes of quinolones may have new biological properties in terms of altered minimal inhibitory concentration, antibacterial spectrum, etc.17 Recently, three novel g ...
... complexes.16 Metal ions may change the bio-availability of quinolones by changing their solubility or their lipophilicity. The metal complexes of quinolones may have new biological properties in terms of altered minimal inhibitory concentration, antibacterial spectrum, etc.17 Recently, three novel g ...
IOSR Journal of Applied Chemistry (IOSR-JAC)
... The efficiency of the process is relatively low (84%), suggesting that for every incremental increase in the oxidative peak, there is no corresponding increase in the reduction peak. It is interesting to note that the Pb2+ redox center is not observed but there is a positive shift in the oxidative p ...
... The efficiency of the process is relatively low (84%), suggesting that for every incremental increase in the oxidative peak, there is no corresponding increase in the reduction peak. It is interesting to note that the Pb2+ redox center is not observed but there is a positive shift in the oxidative p ...
Matrix Isolation and Transient Photochemistry of Ru( d m ~ e ) ~ H
... 56 OC, 9 OC lower than normal. The matrix IR bands of the precursor were reduced in intensity by a factor of 4.3 for the same deposition time, but the UV/vis product bands were observed at 459,543, and 755 nm, close to their previous positions. Selective photolysis with X = 432-440 nm shifted the ce ...
... 56 OC, 9 OC lower than normal. The matrix IR bands of the precursor were reduced in intensity by a factor of 4.3 for the same deposition time, but the UV/vis product bands were observed at 459,543, and 755 nm, close to their previous positions. Selective photolysis with X = 432-440 nm shifted the ce ...
Product Selectivity in Homogeneous Artificial Photosynthesis Using
... for economic reasons, catalysis has played a major role in the development of industrial chemistry [2]. The continuous enhancement of catalysts is also driven by the intellectual insatiable desire of keeping up with nature’s highly selective operating enzymes, whose activity has been optimized to pe ...
... for economic reasons, catalysis has played a major role in the development of industrial chemistry [2]. The continuous enhancement of catalysts is also driven by the intellectual insatiable desire of keeping up with nature’s highly selective operating enzymes, whose activity has been optimized to pe ...
Ternary metal-carbon-hydrogen compounds of some transition metals
... zirconium and hafnium specimens of low carbon content were cut to the desired size with a water cooled abrasive wheel. Those specimens with a higher carbon content and the vana dium specimen were broken into pieces just small enough to fit into the quartz furnace tube. ...
... zirconium and hafnium specimens of low carbon content were cut to the desired size with a water cooled abrasive wheel. Those specimens with a higher carbon content and the vana dium specimen were broken into pieces just small enough to fit into the quartz furnace tube. ...
Document
... complexed metal ions. The resulting chromatogram (metal ion concentration as a function of elution volume) is presented in Figure 3. Given the specifically high affinity for Sc(III), it is ...
... complexed metal ions. The resulting chromatogram (metal ion concentration as a function of elution volume) is presented in Figure 3. Given the specifically high affinity for Sc(III), it is ...
Direct Observation of Early-Stage Quantum Dot
... multistage process. First, the freezing string method86 was used to provide an interpolated path connecting the geometryoptimized reactant and product structures. In this method, linear synchronous transition (LST) is used for the initial interpolation of new path images that grow inward from reacta ...
... multistage process. First, the freezing string method86 was used to provide an interpolated path connecting the geometryoptimized reactant and product structures. In this method, linear synchronous transition (LST) is used for the initial interpolation of new path images that grow inward from reacta ...
Spin crossover
Spin Crossover (SCO), sometimes referred to as spin transition or spin equilibrium behavior, is a phenomenon that occurs in some metal complexes wherein the spin state of the complex changes due to external stimuli such as a variation of temperature, pressure, light irradiation or an influence of a magnetic field.With regard to a ligand field and ligand field theory, the change in spin state is a transition from a low spin (LS) ground state electron configuration to a high spin (HS) ground state electron configuration of the metal’s d atomic orbitals (AOs), or vice versa. The magnitude of the ligand field splitting along with the pairing energy of the complex determines whether it will have a LS or HS electron configuration. A LS state occurs because the ligand field splitting (Δ) is greater than the pairing energy of the complex (which is an unfavorable process).Figure 1 is a simplified illustration of the metal’s d orbital splitting in the presence of an octahedral ligand field. A large splitting between the t2g and eg AOs requires a substantial amount of energy for the electrons to overcome the energy gap (Δ) to comply with Hund’s Rule. Therefore, electrons will fill the lower energy t2g orbitals completely before populating the higher energy eg orbitals. Conversely, a HS state occurs with weaker ligand fields and smaller orbital splitting. In this case the energy required to populate the higher levels is substantially less than the pairing energy and the electrons fill the orbitals according to Hund’s Rule by populating the higher energy orbitals before pairing with electrons in the lower lying orbitals. An example of a metal ion that can exist in either a LS or HS state is Fe3+ in an octahedral ligand field. Depending on the ligands that are coordinated to this complex the Fe3+ can attain a LS or a HS state, as in Figure 1.Spin crossover refers to the transitions between high to low, or low to high, spin states. This phenomenon is commonly observed with some first row transition metal complexes with a d4 through d7 electron configuration in an octahedral ligand geometry. Spin transition curves are a common representation of SCO phenomenon with the most commonly observed types depicted in Figure 2 in which γHS (the high-spin molar fraction) is plotted vs. T. The figure shows a gradual spin transition (left), an abrupt transition with hysteresis (middle) and a two-step transition (right). For a transition to be considered gradual, it typically takes place over a large temperature range, even up to several hundred K, whereas for a transition to be considered abrupt, it should take place within 10 K or less.These curves indicate that a spin transition has occurred in a metal complex as temperature changed. The gradual transition curve is an indication that not all metal centers within the complex are undergoing the transition at the same temperature. The abrupt spin change with hysteresis indicates a strong cooperativity, or “communication”, between neighboring metal complexes. In the latter case, the material is bistable and can exist in the two different spin states with a different range of external stimuli (temperature in this case) for the two phenomena, namely LS → HS and HS → LS. The two-step transition is relatively rare but is observed, for example, with dinuclear SCO complexes for which the spin transition in one metal center renders the transition in the second metal center less favorable.There are several types of spin crossover that can occur in a complex; some of them are light induced excited state spin trapping (LIESST), ligand-driven light induced spin change (LD-LISC), and charge transfer induced spin transition (CTIST).