Infrared Spectroelectrochemistry of Boron-Hydrogen Stretches: A Tool for Diagnosis of Delocalization in Mixed-Valent Metallacarborane Complexes

Precise control of the degree and regioselectivity of functionalization in nitro- and amino-functionalized di(trispyrazolylborato)iron(ii) spin crossover complexes

“…The strength of the B-H bond is inversely correlated with the electronic density at the boron. 53 Thus, as expected, coordination of a ligand to the iron center, drawing electronic density away from the ligand, increases the B-H wavenumber by 20 to 40 cm -1 . Trends between the complexes give us some insight into the impact of pyrazole functionalization on the electronic density at the boron.…”

Precise control of the degree and regioselectivity of functionalization in nitro- and amino-functionalized di(trispyrazolylborato)iron(II) spin crossover complexes

“…The strength of the B-H bond is inversely correlated with the electronic density at the boron. 62 Thus, as expected, coordination of a ligand to the iron center draws electronic density away is drawn away from the ligand and increases the B-H wavenumber by 20 to 40 cm -1 . No correlation was observed between the amplitude of this shift and the spin state of the complex.…”

Valence delocalisation in a strongly coupled (Kc = 1014) molecule-bridged cyanodiiron(III,II) species

“…2). The direction of shifts of the typically single band (very close A 1 , B 1 and B 2 features) corresponds to charge alteration, [11][12][13] however, the oxidation to a metal-based mixed-valent species and the reduction to a ligand-centered radical complex produce rather similar amounts of high-and low-energy shifts, respectively. As noted previously, 11 such band energy differences are thus not suitable to unambiguously clarify the site of electron addition or removal.…”

“…The question of localisation or delocalisation in mixed-valent complexes in solution may be most elegantly answered by vibrational spectroscopy. 12,13 On the corresponding time scale of about 10 212 s the appearance of averaged bands in relation to the neighbouring oxidation states suggests delocalisation whereas the appearance of separate or broadened features indicates localisation. The redox system 1 n2 was thus studied in the cyanide stretching region for n = 3, 4 and 5 (Fig.…”