Preparation and thermochemistry of complexes of Δ2-tetrazaborolines with titanium tetrachloride, boron trichloride, antimony pentachloride, and stannic chloride

Abstract

A study was made of the adducts of 1,4,5-trimethyltetrazaboroline with a number of main-group electron acceptors including the trichlorides of boron, aluminium, and gallium, germanium tetrachloride, stannic chloride, and antimony pentachloride. New complexes were isolated from the reactions with the latter two acceptors and with boron trichloride having stoicheiometries SnCl₄,2L, SbCl₅,L, and BCl₃,L, respectively. With titanium tetrachloride, three types of adduct of tetrazaborolines were prepared. Compounds of the stoicheiometries 2TiCl₄,1·5L (L = Me₂N₄BMe, Me₂N₄BCl and Me₂N₄BPh), 2TiCl₄,L,toluene, (L = Me₂N₄BMe and Me₂N₄BCl) and 2TiCl₄,-Me₂N₄BPh,0·5C₆H₅CH₃ were identified. The condensed-phase heats of formation of the complexes between 1,4,5-trimethyltetrazaboroline and boron trichloride, stannic chloride, and antimony pentachloride and of the series 2TiCl₄,1·5L were measured by a hydrolytic method in a reaction calorimeter. Attempts were made to measure the heats of vaporisation of some of the complexes in order to derive their gas-phase heats of formation. It is concluded that, towards BCl₃, SbCl₅, and SnCl₄, the tetrazaboroline ring behaves as a monodentate ligand, whilst with TiCl₄, bridged complexes are probably formed.