Migrations of Alkyl and Aryl Groups from Silicon to Nitrogen in Silylated Aryloxyiminoquinones

Silylation of the oxidized ligand in lead­(II) bis­(3,5-tert-butyl-1,2-quinone-(3,5-di-tert-butyl-2-hydroxy-1-phenyl)­imine),
Pb­(ONOQ)2, with chlorosilanes RSiX2Cl (R = Me, Ph; X = Me, Ph, Cl) results in the tetracyclic, pentacoordinate
silicon compounds (ON­[R]­O)­SiX2 with a reduced, dianionic
amine-bisphenolate ligand in which the methyl or phenyl group has
migrated to nitrogen. Methyl migration is observed exclusively over
phenyl migration, though phenyl migration is observed if no alkyl
groups are present on silicon. Chlorotriphenylstannane reacts similarly,
with migration of the phenyl group from tin to nitrogen. The five-coordinate
products adopt a trigonal-bipyramidal geometry with long bonds to
the apical amine donors (d(Si–N) = 2.3–2.9
Å). Chlorine occupies the other axial position in strong preference
to methyl or phenyl, while methyl has a modest preference for the
axial position in comparison to phenyl (8.7:1).