NiLX2 (X = ClO4, BF4, I, Cl, Br, SCN, NO3; L = the lipophilic tetramine macrocycle 1-hexadecyl-1,4,8,11-tetraazacyclotetradecane) were prepd. and dissolve in noncoordinating solvents such as CH2Cl2 and CHCl3 as intact NiLX2, whose spin state and color depend on the coordinating tendencies of the apically bound X- anions: Cl-, and SCN-, blue, high-spin complexes; ClO4-, BF4-, and L-, yellow, low-spin complexes. NiLBr2 exists in soln. as an equil. mixt. of the blue and yellow species and the blue-to-yellow conversion is exothermic; moreover, the equil. is displaced to the right on further addn. of the background electrolyte, R4NBr (R = alkyl) or Et4PBr. A general model is proposed to explain the thermodn. aspects of the high-spin/low-spin interconversion in both coordinating (e.g. water) and noncoordinating media. Finally, NiLX2 in CH2Cl2 soln. (0.1 mol dm-3 Bu4NX) undergo reversible 1-electron oxidn. processes to give [NiLX2]X. The NiIII-NiII redox potential decreases dramatically with increasing coordinating tendency of the X- ions. A spectrochem. series was obtained for electrochem. inert inorg. anions. On this basis, it appears that ClO4- is a more strongly coordinating ligand than BF4-.
Solution chemistry in noncoordinating solvents (methylene chloride, chloroform) of nickel(II) and nickel(III) complexes of the lipophilic macrocycle 1-hexadecyl-1,4,8,11-tetraazacyclotetradecane. The emphasized role of the anion coordination
DI CASA, MICHELINA;FABBRIZZI, LUIGI;
1990-01-01
Abstract
NiLX2 (X = ClO4, BF4, I, Cl, Br, SCN, NO3; L = the lipophilic tetramine macrocycle 1-hexadecyl-1,4,8,11-tetraazacyclotetradecane) were prepd. and dissolve in noncoordinating solvents such as CH2Cl2 and CHCl3 as intact NiLX2, whose spin state and color depend on the coordinating tendencies of the apically bound X- anions: Cl-, and SCN-, blue, high-spin complexes; ClO4-, BF4-, and L-, yellow, low-spin complexes. NiLBr2 exists in soln. as an equil. mixt. of the blue and yellow species and the blue-to-yellow conversion is exothermic; moreover, the equil. is displaced to the right on further addn. of the background electrolyte, R4NBr (R = alkyl) or Et4PBr. A general model is proposed to explain the thermodn. aspects of the high-spin/low-spin interconversion in both coordinating (e.g. water) and noncoordinating media. Finally, NiLX2 in CH2Cl2 soln. (0.1 mol dm-3 Bu4NX) undergo reversible 1-electron oxidn. processes to give [NiLX2]X. The NiIII-NiII redox potential decreases dramatically with increasing coordinating tendency of the X- ions. A spectrochem. series was obtained for electrochem. inert inorg. anions. On this basis, it appears that ClO4- is a more strongly coordinating ligand than BF4-.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
