Ligand solvents

Attempts to prepare the mono(cyclopenta-dienyl) derivatives are sometimes frustrated by a Schlenk-type equilibrium (see p. 132), but judicious choice of ligands, solvent etc. occasionally permits the isolation of such compounds, e.g. the centrosymmetric halogen-bridged dimer (t - -C5Me5)Ca(/i-l)(lhf)2 2] which cry.stallizes from toluene solution. The complex is isostruc-tural with the dimeric organosamarium(ll) analogue. - ... 

Metal type ligand solvent solvent ligand... 

Macroinitiator1 Monomer 2a Catalyst /Ligand Solvent Temp. °C... 

Use of the above conditions in conjunction with the enol tosylate 32, provided only low yields of 22, prompting an extensive screening of structurally diverse phosphine ligands/solvents and palladium sources to attempt to define suitable conditions. Quite quickly a number of conditions were found to be effective, with chelating diphosphines being superior to monodentate phosphines (Table 9.7). In... 

Reaction type Catalyst precursor Ligand Solvent system Pressure (MPa) scC02 Pressure (MPa) h2 Conversion (%) Selectivity (%) UOLc Selectivity (%) SALd... 

The need for multiple desolvation of the metal ion in some systems may provide a barrier to complex formation which is reflected by lower formation rates - especially for inflexible macrocycles such as the porphyrins. Because of the high energies involved, multiple desolvation will be unlikely to occur before metal-ion insertion occurs rather, for flexible ligands, solvent loss will follow a stepwise pattern reflecting the successive binding of the donor atoms. However, because of the additional constraints in cyclic systems (relative to open-chain ones), there may be no alternative to simultaneous (multiple) desolvation during the coordination process. 

Core Structure Compound/Ligands (Solvent) Xmax (nm) 8 (M 1 cm ") Resonance Raman Spectrum (cm-1) (lsO Data) Cu-Cu Distance (A)... 

Entry Substituents Ligand Solvent Temp. (°C) % ee (Config.)... 

Entry Substrate 114 Ligand Solvent 115a 115b... 

Entry Olefin Ligand Solvent Time (h) Product ee (%, config.)... 

The palladium-catalyzed reaction of iodobenzene and an allenyl malonate provided vinylcyclopropane in a highly regioselective manner (Scheme 16.7) [11, 12]. A jT-allylpalladium complex, generated by the addition of PhPdl to a 2-allenyl malonate, can be trapped by an internal malonate anion to afford a vinylcyclopropyl derivative. The site selectivity in this cyclization is dependent on the nature of the entering RX groups, catalytic systems involving phosphine ligands, solvents and bases. 

Usually there is no ambiguity about the choice of components to form the species often they are metal ions, ligands, solvent molecules, protons etc. 

No Substrate Metal/ Ligand Solvent Product Yield % Ref. 

We conclude that in this simple model there are two contributions to the ligand-ligand correlation, hence to the cooperativity one due to direct ligand-ligand interaction [/(1,1) and the other due to ligand-solvent interaction. The latter part of the indirect correlation is transmitted by solvent molecules. The extent of this correlation depends on the presence of the adsorbent molecule. 

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