pH-Metric Studies on the Interaction of Ni-Containing Anderson Type Heteropolyanions in Aqueous Solution

Synthesis and Characterization of the First Nickel(II)‐Centered Single‐Side Tris‐Functionalized Anderson‐Type Polyoxomolybdate

“…In accordance with the occurrence of only two sodium cations per cluster and the weak acidic environment (pH = 6.5), it can be assumed that the amino groups of the Tris ligands (both the grafted and free ligands) are protonated. The Ni–O bond lengths are in the range of 2.024(11)–2.048(15) Å and the µ 3 ‐O–C bond lengths are in the range of 1.426(2)–1.440(2) Å, which is in good agreement with those observed for the parent[12a] and bifunctionalized [H 2 NiMo 6 O 18 {(OCH 2 ) 3 CCH 2 OH} 2 ] 2–[5a] anions. The structure analysis indicates that the lengths of all three types of Mo–O bonds (Mo–µ 2 ‐O, Mo–µ 3 ‐O, Mo=O terminal ) are close to those of the parent species [Ni(OH) 6 Mo 6 O 18 ] 4–[12a] and of the Tris‐functionalized POMo analogues…”

“…The IR spectrum of NiMo 6 –Tris–NH 3 is typical for Anderson‐type POMs, and the characteristic bands of the core structure are all in agreement with the bands observed in the spectrum of Na 4 [Ni(OH) 6 Mo 6 O 18 ] · 16H 2 O[12a] (see Figure S1, Supporting Information). The stretching vibrations of the terminal Mo=O units appear at 926 cm –1 , whereas the bands at 883 cm –1 and in the region of 440–800 cm –1 correspond to the asymmetric and symmetric deformation vibrations of the Mo–O–Mo and Mo–O–Ni bridging fragments, respectively.…”

“…For the synthesis, the parent Anderson POMo, Na 4 [Ni(OH) 6 Mo 6 O 18 ] · 16H 2 O,[12a] was dissolved in water (pH = 6.5) and heated to reflux. Then a twofold excess of Tris–NH 2 over the parent anion was added, and after double recrystallization from aqueous solution, single‐side‐functionalized Na 2 [NH 3 C(CH 2 OH) 3 ][Ni(OH) 3 Mo 6 O 18 (OCH 2 ) 3 CNH 3 ] · 11.75H 2 O ( 1 ) was obtained (see Scheme ) in high yield (72 % based on Mo).…”

“…The destruction of [Ni(OH) 6 Mo 6 O 18 ] 4– occurs at temperatures above 250 °C. [12a] The last mass loss in the TG curve occurs between 350 and 650 °C and is presumably caused by the loss of the grafted organic ligand and the three OH groups from the Ni II coordination sphere.…”

“…Materials and Instrumentation: Reagents were used as purchased from Sigma–Aldrich without further purification. Na 4 [Ni(OH) 6 Mo 6 O 18 ] · 16H 2 O was obtained according to a reported procedure,[12a] and its identity was confirmed by IR spectroscopy. Attenuated total reflection Fourier‐transform infrared spectroscopy was performed with a Bruker Tensor 27 IR spectrometer equipped with a single‐reflection diamond ATR unit.…”