Two reversible enantiotropic phase transitions in a pentacoordinate silicon complex with an O,N,O′-tridentate valinate ligand

摘要: Dimeth­yl[N-(4-oxidopent-3-en-2-yl­idene)valinato-κ3O,N,O′]silicon(IV), C12H21NO3Si, (II), crystallizes in the ortho­rhom­bic space group P212121. The chiral compound undergoes two sharp enanti­otropic phase transitions upon cooling. first transformation occurs at 163 K to yield a unit cell with one axis having double length. This inter­mediate-temperature form has monoclinic P21. second transition takes place 142 K and converts single crystal into low-temperature proceeds under tripling of high-temperature form. Both are fully reversible correspond order–disorder isopropyl valine ligand backbone. presented here raise questions, since they do not fit rules group–subgroup relationships.