Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes

TY - JOUR

T1 - Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes

AU - Birk, T.

AU - Magnussen, M.J.

AU - Piligkos, Stergios

AU - Weihe, H.

AU - Holten, Anders

AU - Bendix, J.

PY - 2010/9

Y1 - 2010/9

N2 - Interaction of robust chromium(III) fluoride complexes with sodium or lithium cations in solution lead to hypsochromic spectral shifts of increasing magnitude along the series: trans-[CrF2(py)4]+, mer-[CrF3(terpy)], and fac-[CrF3(Me3tacn)]. Crystalline products isolated from solution exhibit μ2-bridging by the fluoride ligands in a linear fashion between Na+-ions and chromium centres in catena-[Na(H2O)4(μ-F)-trans- {CrF(py)4}](HCO3)2 and in the dimers [Li(H 2O)n(μ-F)-trans-{CrF(py)4}]2+ (n = 3, 4). The uncharged chromium complexes fac-[CrF3(Me 3tacn)] and mer-[CrF3(terpy)] have been synthesized from mer-[CrF3(py)3] and shown to precipitate sodium salts from solution, of which 3[CrF3(Me3tacn)]·2Na(Bph 4)·solv and 6[CrF3(terpy)]·4Na(Bph 4)·solv have been crystallographically characterized. In these clusters, the neutral fluoride complexes bring the Na+ cation separation down to 3.610 and 3.369 Å, respectively, which is much closer than the inter-cation distance in NaCl and comparable to that of NaF. DFT calculations support the notion of a strong interaction between Na+ ions and neutral chromium(III) fluoride complexes. The calculations reproduce the magnitude and the counter-intuitive sign of the spectral shifts induced by second sphere complexation in solution, which originates in a breakdown of the assumption of parameter transferability in ligand-field descriptions.

AB - Interaction of robust chromium(III) fluoride complexes with sodium or lithium cations in solution lead to hypsochromic spectral shifts of increasing magnitude along the series: trans-[CrF2(py)4]+, mer-[CrF3(terpy)], and fac-[CrF3(Me3tacn)]. Crystalline products isolated from solution exhibit μ2-bridging by the fluoride ligands in a linear fashion between Na+-ions and chromium centres in catena-[Na(H2O)4(μ-F)-trans- {CrF(py)4}](HCO3)2 and in the dimers [Li(H 2O)n(μ-F)-trans-{CrF(py)4}]2+ (n = 3, 4). The uncharged chromium complexes fac-[CrF3(Me 3tacn)] and mer-[CrF3(terpy)] have been synthesized from mer-[CrF3(py)3] and shown to precipitate sodium salts from solution, of which 3[CrF3(Me3tacn)]·2Na(Bph 4)·solv and 6[CrF3(terpy)]·4Na(Bph 4)·solv have been crystallographically characterized. In these clusters, the neutral fluoride complexes bring the Na+ cation separation down to 3.610 and 3.369 Å, respectively, which is much closer than the inter-cation distance in NaCl and comparable to that of NaF. DFT calculations support the notion of a strong interaction between Na+ ions and neutral chromium(III) fluoride complexes. The calculations reproduce the magnitude and the counter-intuitive sign of the spectral shifts induced by second sphere complexation in solution, which originates in a breakdown of the assumption of parameter transferability in ligand-field descriptions.

KW - Bridging

KW - Cr(III)

KW - Robust

KW - Linear

KW - Chain

KW - FIELD ABSORPTION-BANDS

KW - RAY CRYSTAL-STRUCTURE

KW - NMR-SPECTRA

KW - SOLID-STATE

KW - ANIONS

KW - SOLVATOCHROMISM

KW - TITANIUM(III)

KW - PYRIDINE

KW - ENERGY

KW - APPROXIMATION

U2 - 10.1016/j.jfluchem.2010.06.003

DO - 10.1016/j.jfluchem.2010.06.003

M3 - Journal article

SN - 0022-1139

VL - 131

SP - 898

EP - 906

JO - Journal of Fluorine Chemistry

JF - Journal of Fluorine Chemistry

IS - 9

ER -