Ligand displacement reactions with ethers

Apart from the metal atom aggregation reactions described below, bis(arene)metal complexes of the early transition metals are resistant to ligand displacement The rings on the corresponding bis(naphthalene)metal species (41) are by, contrast, labile. Polymer-supported analogs of these naphthalene compounds with vanadium and chromium are known (42), but Ti atoms attack the polymer at the silicon ether linkage. These and other hybrid polymers can be further modified once the metal atom is incorporated. Thus a-methyl naphthalene is displaced from the hybrid organometallic polymer shown in Scheme 7 (43). 

In these and related reactions, the ether and alcohol ligands dissociate readily. The coordinated THF dissociates from the zirconium methyl complex to allow olefin polymerization, albeit more slowly than in the absence of THF. The ether dissociates from palladium and nickel to allow olefin to bind to the cationic palladium and nickel species, and alcohol and water are easily displaced from related Pt(II) complexesby hydrocarbons prior to C-H activation processes. Likewise, the THF and phosphine oxide ligands reversibly dissociate from the zirconium knido complex (Equation 2.18) prior to [2+2] additions with alkynes. - ... 

Although the metathesis of terminal alkynes also proceeds rapidly, polymerization of the terminal alkynes displaces the carbyne exchange reactions towards the wrong side towards the starting terminal alkyne that polymerizes except if suitable parameters are ad usted such as temperature, solvent diethyl ether and especially the presence of the potential ligand quinuclidine together with the... 

Mixed Ligand Carbonyls.—General. Solvent and structural effects on reactivities of metal carbonyl halides towards carbon monoxide replacement have been probed for manganese, iron, and ruthenium compounds. The compounds were MnX(CO>5, where X == Br or I, RuX(CO)2(/i -C6H6), where X = Cl or Br, and FeX(CO)2(/i -C3H5), where X = Br or I. The displacing nucleophiles were triphenylphosphine or triphenyl phosphite the solvents were n-octane, xylene, di-n-butyl ether, or nitrobenzene. Kinetic parameters for some of these reactions, with some earlier values for related systems for comparison, are listed in Table 1. The main conclusion... 

Carreira has reported a conceptually different class of chiral ligands for iridium-catalyzed allylic displacement reactions (Equation 6) [87]. The use of chiral diene 89 in combination with Ir(I) led to kinetic resolution of racemic allylic carbonates. The resulting allylic ethers (cf 90) and recovered starting allylic carbonates are obtained with high enantioselectivity. The modular chiral diene ligands, exemplified by 89, are readily available by a short synthetic sequence starting from carvone. 

Trans effects. In these square-planar olefin complexes, ligands which are trans to the olefin readily undergo displacement reactions [91,92,93]. The trans effect of ethylene is apparent in the greater stability of the white cir-bis-ethylene complex cu-(C2H4)2PtCl2 compared with the very unstable yellow trans isomer [48,14]. The Ironr-isomer readily isomerizes to the cir-isomer in ether solution [94]. 

By taking advantage of the C(2) activation, 2-allyloxy-3-iodopyridine (173) was prepared by an SNAr displacement of 2-chloro-3-iodopyridine with sodium allyloxide [137]. 2-Chloro-3-iodopyridine was prepared by orrto-lithiation of 2-chloropyridine followed by iodine quench. The intramolecular Heck reaction of allyl ether 173 under Jeffery s ligand-free conditions resulted in 3-methylfuro[2,3-6]pyridine (174). 

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