Crystal‐to‐Crystal Transformations in a Seven‐Coordinated Scandium Complex

Abstract

Aquatris(3‐cyanopentane‐2, 4‐dionato)scandium(III) undergoes two transformations which can be monitored by X‐ray diffraction as well as solid‐state NMR spectroscopy: At 145 K, the mononuclear complex shows a reversible phase transition; in agreement with the symmetry principle, this transition of the t2 type proceeds from the monoclinic room temperature phase to triclinic twins at low temperature, the twin law corresponding to a twofold rotation. Under vacuum at room temperature, the aqua ligand of the complex is irreversibly eliminated and the structure rearranges, forming a 1D chain polymer. In both phases of the mononuclear complex as well as in the polymer, the coordination polyhedra around the ScIII atom represent distorted capped trigonal prisms. Solid‐state 45Sc NMR spectroscopic investigations on powder samples reveal a reversible phase transition of the monoclinic complex at low temperatures. Changes of the NMR signal line shapes for the room and low temperature complex as well as the 1D chain polymer are a fingerprint for different scandium bonding situations.

The ephemeral dihydrate of sulfanilic acid

“…The unit-cell volume shrank by ca 25 Å 3 per H 2 O molecule during the irreversible topotactic dehydration of silver isonicotinate (Kalf et al, 2010). The irreversible loss of an Sc-bonded aqua ligand was associated with a volume difference of ca 23 Å 3 (Merkens et al, 2013) and the reversible removal of a coordinated water molecule in an Eu complex with a volume difference of ca 30 Å 3 (Englert et al, 1998). CSD-based volume considerations by Hofmann (2002) suggest 22 Å 3 as the lower limit for such an effect.…”

3-(4-Pyridyl)-acetylacetone – a fully featured substituted pyridine and a flexible linker for complex materials

“…The nitrile-substituted HacacCN may essentially be regarded as an acetylacetonate; this functional group allows coordination to a broad range of di-and trivalent cations. The additional donor properties of the CN group are, however, less pronounced; its coordination is restricted to Ag I cations (Kondracka & Englert, 2008;Burrows et al, 2007; or to secondary interactions in the solid state (Merkens, Pecher et al, 2013). The original designers of HacacPy also started with the acetylacetonate functionality of their ligand in mind: their first reaction involved O,O 0 chelation to Al III (Mackay et al, 1995).…”

Crosslinking of the Pd(acacCN)2 building unit with Ag(i) salts: dynamic 1D polymers and an extended 3D network

“…For reasons of symmetry, the palladium center and its four coordinating oxygen atoms are exactly coplanar. 23 In the chain polymers 2-6, Pd building blocks and AgIJI) cations are arranged in an alternating sequence, thus forming one-dimensional cationic scaffolds with the counterions included in voids of the crystal structures, in direct neighborhood of the AgIJI). In crystalline 1, the molecules are arranged in parallel stacks.…”

“…This was confirmed in reports about the coordination chemistry of the mono-pyridyl ligands a [10][11][12][13][14] and b, 15 and of the di-pyridyl derivative c. 16, 17 3-IJ4-Pyridyl)acetylacetone (Scheme 1, a) has also been employed in halogen-and hydrogen-bonded extended structures. 22,23 All previous examples with the exception of a Cu-Ag bimetallic ladder structure involve coordination numbers of at least 6 at the cations; 19 no square-planar complexes based on acacCN have been structurally characterized to date, although this coordination mode has been encountered for the unsubstituted parent ligand acac and several of its substitution products. Earlier work with this ligand has covered the O, O′ coordination chemistry of Cu, Fe, 19 Cr, 20 Al, 21 and rare earth cations.…”

“…Earlier work with this ligand has covered the O, O′ coordination chemistry of Cu, Fe, 19 Cr, 20 Al, 21 and rare earth cations. 22,23 All previous examples with the exception of a Cu-Ag bimetallic ladder structure involve coordination numbers of at least 6 at the cations; 19 no square-planar complexes based on acacCN have been structurally characterized to date, although this coordination mode has been encountered for the unsubstituted parent ligand acac and several of its substitution products. [24][25][26] In this contribution, we report the synthesis and characterization of the square-planar complex PdIJacacCN) 2 , 1, and its use as a building block for bimetallic extended solids based on PdIJII) and AgIJI) cations.…”