Premium
Two reversible enantiotropic phase transitions in a pentacoordinate silicon complex with an O , N , O ′‐tridentate valinate ligand
Author(s) -
Schwarzer Anke,
Fels Sabine,
Böhme Uwe
Publication year - 2015
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229615009778
Subject(s) - monoclinic crystal system , orthorhombic crystal system , crystallography , chemistry , ligand (biochemistry) , isopropyl , phase transition , group (periodic table) , silicon , phase (matter) , yield (engineering) , crystal structure , stereochemistry , materials science , condensed matter physics , physics , medicinal chemistry , biochemistry , receptor , organic chemistry , metallurgy
Dimethyl[ N ‐(4‐oxidopent‐3‐en‐2‐ylidene)valinato‐κ 3 O , N , O ′]silicon(IV), C 12 H 21 NO 3 Si, (II), crystallizes in the orthorhombic space group P 2 1 2 1 2 1 . The chiral compound undergoes two sharp enantiotropic phase transitions upon cooling. The first transformation occurs at 163 K to yield a unit cell with one axis having double length. This intermediate‐temperature form has the monoclinic space group P 2 1 . The second transition takes place at 142 K and converts the single crystal into the low‐temperature form in the orthorhombic space group P 2 1 2 1 2 1 . This transition proceeds under tripling of the a axis of the high‐temperature form. Both phase transitions are fully reversible and correspond to order–disorder transitions of the isopropyl group of the valine unit in the ligand backbone. The phase transitions presented here raise questions, since they do not fit into the rules of group–subgroup relationships.