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High‐spin square planar iron(II) alkali metal siloxide complexes – influence of the alkali metal and reactivity towards O 2 and NO
Author(s) -
Beckmann Fabian,
Kass Dustin,
Keck Matthias,
Yelin Stefan,
Hoof Santina,
Cula Beatrice,
Herwig Christian,
Krause Konstantin B.,
Ar Deniz,
Limberg Christian
Publication year - 2021
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.202100059
Subject(s) - chemistry , alkali metal , deprotonation , crystallography , metal , adduct , counterion , inorganic chemistry , ligand (biochemistry) , ion , organic chemistry , biochemistry , receptor
Complexes [L 2 Fe][Li(DME)] 2 , 1(DME) , {[L 2 Fe][Na 2 (DME) 3 ]} ∞ , 2(DME) and [L 2 Fe][K(DME) 2 ] 2 , 3(DME) were synthesized by deprotonation of LH 2 (LH 2 =O(SiPh 2 OH) 2 ) with the respective alkali metal tert ‐butoxides followed by recrystallization from DME. It turned out that upon crossing over from Li + via Na + to K + counterions the structures of the high‐spin iron(II) complexes are increasingly distorted from a square planar towards a tetrahedral structure so that 3(DME) represents a borderline case, as indicated by the τ ‐values. The distortions are also reflected in the Mössbauer spectra through the quadrupole splittings. The compounds behave inert in contact with O atom transfer reagents but react rapidly with dioxygen. The reaction rates are too high to be determined even by stopped‐flow measurements quantitatively, but qualitatively it emerged that the rates increase from Li to Na to K. Using NO as an O 2 surrogate an NO adduct with an S = 3/2 ground state was isolated where NO is coordinated in an end‐on binding mode, formally as a NO − ligand, with a significantly weakened NO bond.