Titanium Tetrachloride(TiCl4) is a dense, colourless distillable liquid,
although crude samples may be yellow or even red-brown. It is one of the rare
transition metal halides that is a liquid at room temperature, VCl4 being
another example. This property reflects the fact that Titanium
Tetrachloride(TiCl4) is molecular; that is, each Titanium Tetrachloride(TiCl4)
molecule is relatively weakly associated with its neighbours. Most metal
chlorides are polymers, wherein the chloride atoms bridge between the metals.
The attraction between the individual TiCl4 molecules is weak, primarily van
der Waals forces, and these weak interactions result in low melting and boiling
points, similar to those of CCl4.
Ti4+ has a "closed" electronic shell, with the same number of
electrons as the inert gas argon. The tetrahedral structure for TiCl4 is
consistent with its description as a d0 metal center (Ti4+) surrounded by four
identical ligands. This configuration leads to highly symmetrical structures,
hence the tetrahedral shape of the molecule. Titanium Tetrachloride(TiCl4)
adopts similar structures to TiBr4 and TiI4; the three compounds share many
similarities. TiCl4 and TiBr4 react to give mixed halides TiCl4−xBrx, where x = 0, 1,
2, 3, 4. Magnetic resonance measurements also indicate that halide exchange is
also rapid between TiCl4 and VCl4.
Titanium Tetrachloride(TiCl4) is soluble in toluene and chlorocarbons, as
are other non-polar species. Evidence exists that certain arenes form complexes
of the type [(C6R6)TiCl3]+. TiCl4 reacts exothermically with donor solvents
such as THF to give hexacoordinated adducts. Bulkier ligands (L) give
pentacoordinated adducts TiCl4L.
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