Investigation of structures of mono- and diorgano-substituted oligosiloxanes containing transition metal atoms

Abstract

Oligomeric linear copper-containing diorganosiloxanes with a variable Cu : Si ratio and branched Cu- and Ni-containing organosiloxanes containing the γ-aminopropyl group at the Si atom were investigated. IR spectroscopic studies demonstrated that the distribution of metal atoms throughout the metallosiloxane chain in compounds with a high metal content (M : Si≥2) is rather uniform. According to the data from electronic spectroscopy, compounds under study are complexes of metal ions characterized by d-d transitions and an octahedral configuration of the coordination units. The Cu^II and Ni^II ions are coordinated by the NH₂ groups primarily through interchain interactions. ESR spectroscopic studies demonstrated that the Cu^II ions are located predominantly in the main chain to form −O−Cu−O− fragments. The coordination polyhedron changes from a nearly planar square (in the solid phase) to an elongated tetragonal bipyramid (in solution). The spectral parameters of the Cu-containing oligomer containing the γ-aminopropyl group at the Si atom indicate that the N atoms of the amino groups are located in the equatorial plane of the Cu-containing coordination polyhedron.