Complexes of the fac-{Re(CO)(3)}(+) core with tridentate ligands derived from arylpiperazines

摘要

Arylpiperazines, XC6H4N(CH2CH2)(2)NH, are readily alkylated to give the N-alkylpiperazines of the type XC6H4N(CH2CH2)(2)N(CH2)(n)NH2. The amine functions of these derivatives are in turn easily subjected to mono- or dialkylation to provide potentially tridentate ligands of the types XC6H4N(CH2CH2)(2)N(CH2)(n)N(H)(CH2Y) and XC6H4N(CH2CH2)(2)N(CH2)(n) N(CH2Y)(CH(2)Z), respectively. The latter class of dialkylated derivatives may be symmetrically (Y = Z) or unsymmetrically (Y not equal Z) substituted. The donor groups Y and Z of this Study include pyridine, imidazole, methyl-imidazole, thiazole, carboxylate and thiolate. The reactions of these ligands with [NEt4](2)[Re(CO)(3)Br] yield complexes of the type [Re(CO)(3){(YCH2)N(H)(CH2)(n)(H)(x)N (CH2CH2)(2)N(H)yC(6)H(4)X}](n) and [Re(CO)(3){(ZCH(2))(YCH2)N(CH2)(n)(H)(x)N(CH2CH2)(2)N(H)(y)C6H4X}](n) where the molecular charge n (0, +1. or +2) depends on the nature of the donor groups Y and Z (whether neutral or anionic or a combination of neutral and anionic) and on the degree of protonation of the piperazine unit (x = 0 or 1 y = 0 or 1). This variety of tridentate chelators provides complexes with fac-{Re(CO)(3)N-3}, {Re(CO)(3)N2O}, {Re(CO)(3)NO2}, Re(CO)(3)N2S and {Re(CO)(3)NS2} coordination geometries. The structures of the model compound [Re(CO)(3){(CH3N2C3H2CH2)N(H)CH2CH2-piperidine}](BrH2O)-H-., [Re(CO)(3) {(CH3N2 C3H2CH2)N(H)CH2CH2-Fphenpip}]Br, [Re(CO)(3){(NC5H4CH2)N(H)CH2CH2-Fpheiipip}]Br, [Re(CO)(3){(O2CCH2)(2)NCH2CH2 CH2-CH(3)OphenpipH}](.)xCH(3)OH (x approximate to 0.875), [Re(CO)(3){(NC5H4CH2)(2)NCH2CH2CH2-CH(3)OpheiipipH}]Br(2)(.)2CH(2)Cl(2) (.) H2O and [Re(CO)(3) {(CH3N2C3H2CH2)(O2CCH2)NCH2CH2CH2-CH(3)OpheiipipH(2)}]BrCl (.) 1.5CH(3)OH (.) H2O are discussed (phenpip: phenylpiperazine, -C6H4N(CH2CH2)(2)N-). (C) 2003 Elsevier B.V. All rights reserved. [References: 75]