Syntheses of soluble polymeric Lewis bases and their adducts with metal alkyls

Abstract

The pendant double bonds in polybutadiene have been hydrosilated by the reaction of polybutadiene with chloro-dimethylsilane in toluene using H₂PtCl₆ as catalyst. The hydrosilated polybutadiene was further functionalised with 2-picolyl, 4-picolyl, 4-dimethylaminophenyl and diphenylphosphinomethyl Lewis base groups thereby obtaining a series of new polymeric Lewis bases. All the polymers were found to react with group 13 metal alkyls and the 2- or 4-substituted pyridine functionalised polymers were also found to react with group 12 metal alkyls to form soluble polymer adducts. The polymers have been characterised by ¹H nuclear magnetic resonance (NMR) spectroscopy, ¹³C NMR and elemental analysis. Integration of ¹H NMR resonances indicates that polymer adducts with M : N or M : P ratios close to 1.0 are obtained when using group 13 metal alkyls, whereas polymer adducts with M : N ratios close to 0.5 are obtained when using group 12 metal alkyls. The metal alkyls are easily lost during vacuum drying. The ¹H NMR resonances from the alkyl groups on the metal centre shift to a high field upon coordination with N-containing polymeric Lewis bases whilst small downfield shifts are observed upon coordination of Me₃M (M = Ga or In) with the P-containing polymeric Lewis bases.