Formation of Mixed-Ligand Complexes

Anation of [M(NH3)sOH2] (M = Co or Cr) by NCS ion has been studied in aqueous-organic solvents (alcohols, dioxane).  

Ammination of rra/is-[Cr(l,3-pn)2BrF] with liquid ammonia yields pure rrans-[Cr(l,3-pn)2(NH3)F] ion. The X-ray structure of the product is reported.  

The rates of Sul methylation of coordinated thiolates, selenates and sulfenates (e.g., [Cr(en)2(SCH2CH2NH2)] ) by Mel have been 

A D mechanism has been established for substitution reactions of chloro(tetraphenylporphinato)chromium(III), [Cr(TPP)(L)(Cl], where L (and incoming ligand X) includes methylimidazole (Melm), py, and PR3 (R = Ph, C2H4CN, pr ). 

Reaction of [Co(NH3)4(0-N)] ions (0-N = amino acid) with [Cr(H20)6] gives the 0-bonded amino acid complexes [(H20)sCrO- 

Formation of [Cr(edta)] from the reaction of edta with the cis-[Cr(ox)2(OH2)2] ion has been studied in alkaline solutions. Both the uncatalyzed and HCOJ-catalyzed reactions were investigated. The initial step involves deprotonation of a coordinated water molecule, or its reaction with HCO J ion, followed by oxalate displacement by Hedta , either directly or via oxalate chelate-ring opening.  

Formation of several chromium(III) complexes with tetra-azama-crocycles have been reported. The fra s-[Cr(L)(OH2)2f ion (L = 5, 

14- tetramethyl-1,4,8,11 -tetra-azacyclotetradeca-4,6,11,13-tetraene) is formed via the reaction of [Cr(H20)6] and L 2HC104. The fra s-[Cr(L)-(SH)(0H2)] ion was also prepared, and the kinetics of the reactions of this and trans-[Cr(L)(OH2)2] with the unidentate ligands NCS , NJ, CP, pyridine, and imidazole investigated. The coordinated water molecules are less acidic than those in [Cr(H20)6f , and more labile. Interestingly, the frans-[Cr(L)(SH)(OH2] ion reacts more slowly than tra/is-[Cr(L)(OH)-(OH)2r with the azide ion.  

A high-yield synthetic route to the trans-[Cr(cyclam)(CN)2] ion has appeared from the reaction of cis- or frans-[Cr(cyclam)Cl2] with the CN ion in DMSO solution. Conversion to /ra/j5-[Cr(cyclam)(NCS)2] was possible. The photochemistry of trans-[Cr(cyclam)(CN)2] is considered later. 

14- hexamethyl-l,4,8,ll-tetra-azacyclotetradecane) is especially inter-esting.  

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Heterocyclic nitrogen donors and their adducts with zinc chloride have been studied.623,624 A large number of other ligand systems have also been characterized, for example, zinc halide adducts of 2,2-dimethylpropane-1,3-diamine and hexamethylphosphoramide have been studied.625,626 The formation of mixed ligand complexes with chloride and substituted pyridines has been studied.627 The zinc tris(pyridyl) chloride anion has also been structurally characterized.628 Manganese(II) ions have been used to probe the stereochemistry in reactions of zinc halides with pyrazine.629... 

The addition of phenylenediammonium to a mixture of 19 and 21 thus caused two distinct rearrangements to occur initial (covalent) imine exchange followed immediately by (coordinative) ligand exchange, resulting in the exclusive formation of mixed-ligand complex 22. 

Van der Linden WE, Beers C (1975) Formation constants of mercury(II) with some buffer/ masking agents and the formation of mixed-ligand complexes. Talanta 22 89-92... 

The formation of mixed-ligand complexes by co-proportionation of homoleptic complexes has been considered theoretically. The crucial issue is... 

Equation 1.8 suggests that the co-proportionation constant, calculated on a statistical basis, will always be above unity. Thus, the statistical redistribution of ligands will favor the formation of mixed-ligand complexes. 

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