Titanium(III) chloride is the inorganic compound with the formula TiCl₃. At least four distinct species have this formula; additionally hydrated derivatives are known. TiCl₃ is one of the most common halides of titanium and is an important catalyst for the manufacture of polyolefins.

In TiCl₃, each Ti atom has one d electron, rendering its derivatives paramagnetic, i.e. the substance is attracted into a magnetic field. The trihalides of hafnium and zirconium: in these heavier metals engage in metal-metal bonding. Solutions of titanium(III) chloride are violet, which arises from excitations of its d-electron. The colour is not very intense since the transition is forbidden by the Laporte selection rule.

Four solid forms or polymorphs of TiCl₃ are known. All feature titanium in an octahedral coordination sphere. These forms can be distinguished by crystallography as well as by their magnetic properties, which probes exchange interactions. β-TiCl₃ crystallizes as brown needles. Its structure consists of chains of TiCl₆ octahedra that share opposite faces such that the closest Ti—Ti contact is 2.91 Å. This short distance indicates strong metal-metal interactions (See Figure in upper right). The three violet "layered" forms, named for their color and their tendency to flake, are called alpha, gamma, and delta. In α-TiCl₃, the chloride anions are hexagonal close-packed. In γ-TiCl₃, the chlorides anions are cubic close-packed. Finally, disorder in shift successions, causes an intermediate between alpha and gamma structures, called the delta (δ) form. The TiCl₆ share edges in each form, with 3.60 Å being the shortest distance between the titanium cations. This large distance between titanium cations precludes direct metal-metal bonding. In contrast, direct Zr-Zr bonding is indicated in zirconium(III) chloride. The difference between the Zr(III) and Ti(III) materials is attributed in part to the relative radii of these metal centers.

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