Synthesis and crystal structures of three silicon complexes with N -[(2-hydroxynaphthalen-1-yl)methylidene]alanine

The reaction of the Schiff base ligand N -[(2-hydroxynaphthalen-1-yl)methylidene]alanine, H 2 L , with dichlorodiorganosilicon compounds, Cl 2 Si R 2 , yields silicon complexes L Si R 2 . The crystal structure analyses of ( RS )-dimethyl{ N -[(2-oxidonaphthalen-1-yl)methylidene]alaninato}silicon, C 16 H 17 NO 3 Si, ( 1 ), ( RS )-diethenyl{ N -[(2-oxidonaphthalen-1-yl)methylidene]alaninato}silicon, C 18 H 17 NO 3 Si, ( 2 ), and ( RS )-methyl{ N- [(2-oxidonaphthalen-1-yl)methylidene]alaninato}phenylsilicon chloroform hemisolvate, 2(C 21 H 19 NO 3 Si)·CHCl 3 , ( 3 ), allow a detailed analysis of the coordination geometries of the pentacoordinated silicon complexes. All three complexes adopt a distorted trigonal–bipyramidal coordination geometry. The apical positions in these coordination polyhedra are occupied by the oxygen atoms O1 and O2, whereas the equatorial positions are occupied by the nitrogen atoms N1 and the carbon atoms of the organic groups at the silicon atom. In all three compounds, the O3 oxygen atoms interact in bifurcated C—H...O interactions with the imine hydrogen atoms, leading to stable zigzag chains. Differences between the three structures are found in the support of this interaction via other C—H...O or aryl interactions. While 1 exhibits π–π stacking, 2 and 3 shows C—H...π contacts. This study demonstrates the ability of the H 2 L ligand to form hypercoordinate silicon complexes.