Synthesis, Spectral Studies, Structural Elucidation and Magnetic Properties of Metallasiloxanes containing Main Group and Transition Metals

Abstract

In recent years, metallasiloxanes have been shown as potential model compounds for zeolites. In view of this, the synthesis and characterization of novel metallasiloxanes are of paramount importance and for this the silanols serve as suitable starting materials. Recently, the N-bonded silanetriol, RSi(OH)3 [R = (2,6-iPr2C6H3)N(SiMe3)] has been shown as a precursor due to its interesting solubility and stability. Using this silanetriol, a large number of metallasiloxanes have been obtained by reacting it with metal alkyls and metal alcoholates. Nevertheless, the reaction of the same with metal amides is poorly studied. In order to overcome this deficiency, it was planned to study the reaction of this aminosilanetriol with various main group and transition metal amides. The thesis reports the results obtained from such studies. For this investigation, the group 14 metallasiloxanes Ge(II), Sn(II), and Pb(II) amides were reacted with N-bonded silanetriol. In the case of Ge(II) amide, a cubic metallasiloxane with terminal Ge-H bonds was obtained by means of an unprecedented oxidative addition reaction. In the reaction with Sn(II) and Pb(II) amides, cage compounds with (SnO)6 and (PbO)6 motifs in ladder form were trapped by two R2Si2O3 fragments. For group 15 metallasiloxanes the reaction of N-bonded silanetriol with Sb(III) and Bi(III) amides were carried out. With Sb(III) amide, a cubic metallasiloxane was obtained whereas with Bi(III) amide, a metallasiloxane with 12 bismuth atoms and 4 bridging chlorine atoms was the result. To study the transition metal containing metallasiloxanes Group 8 and 9 metal amides namely Fe(II), Fe(III) and Co(II) amides were used. With Fe(III) amide, a cubic structure was obtained, in case of Fe(II) a novel Fe8 cluster and in case of Co(II) amide, an interesting hetero-cubane-like architecture resulted. All these new metallasiloxanes were thoroughly characterized by means of various spectroscopic techniques. Also, their solid state structures were determined by means of single crystal X-ray diffraction analysis. The paramagnetic metallasiloxanes were studied for their magnetic behaviour by means of magnetic susceptibility measurements.