29Si and17O NMR investigations on Si−O−Ti bonds in solutions of diphenylsilanediol and titanium-tetra-isopropoxide
✍ Scribed by Dagobert Hoebbel; Thomas Reinert; Helmut Schmidt
- Publisher
- Springer
- Year
- 1996
- Tongue
- English
- Weight
- 816 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0928-0707
No coin nor oath required. For personal study only.
✦ Synopsis
The structural units in diphenylsilanediol/titanium-isopropoxide solutions with molar ratio Si:Ti between 1 :O. 1 and I:5 were examined by means of 29Si and "0 NMR. The main component in solutions with molar ratio Si/Ti = 1 :O. 1 is the chain-like octaphenyltetrasiloxanediol.
With increasing Ti-isopropoxide content (1:0.25-1 :0.5) Si-0-Ti units of the spirocyclic titanosiloxane Ti[05Si4(C6Hs)s)]2 prevail in the solutions accompanied by the chain-like tetrasiloxanediol. The 29Si NMR spectra of 1: 1 solutions indicate a lot of different Si containing building units with chemical shifts mainly between -40 and -46 ppm. The signals with a chemical shift between -40 and -46 ppm are probably caused by Si atoms which are connected via oxygen bridges directly (Si-0-Ti) or indirectly (s-0-Si-0-Ti) with titanium. Contrary to the 1: 1 solutions only one or two different species with Si-0-Ti units are present in high Ti-alkoxide containing solutions (15). 29Si and "0 NMR results reveal a quick hydrolysis of the Ti-0-Si bonds to titanium-oxo-hydroxo-polymers and phenylsiloxanediols or their isopropyl esters after the addition of water to the solutions. This separation into species only containing either Ti-0-Ti or Si-0-Si bonds can entail a decreased homogeneity of the reaction products on a molecular level.