Two modifications of a five-coordinate silicon complex

TBPY-5-34-(Butane-1,4-diyl)(2-{[1-(2-oxidophenyl)ethylidene-kO] amino-kN}ethanolato-kO) silicon, C14H19NO2Si, crystallizes in two modi cations. The monoclinic form, (IIm), was obtained by crystallization over a period of 2 d at room temperature; the orthorhombic form, (IIo), crystallized overnight at 248 K. The main difference between the two molecular structures involves the angles in the equatorial plane of the trigonal bipyramid around silicon. Form (IIm) has an O - Si - O angle of ca 121 degrees and O - Si - C angles of ca 121 and 116 degrees. In form (IIo), the corresponding angles are similar to 123, 124 and 111 degrees. There are also significant differences in the packing: (IIm) shows pi stacking, whereas (IIo) does not.