## Homo and heteropolymetallic Group 4 molecular nitrides†

### Abstract

Treatment of [{Ti(η^{5}-C_{5}Me_{5})(μ-NH)}_{3}(μ_{3}-N)] (**1**) with zirconium or hafnium tetrachloride adducts [MCl_{4}(thf)_{2}] affords complexes [Cl_{3}M{(μ_{3}-N)(μ_{3}-NH)_{2}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (M = Zr (**2**), Hf (**3**)). Titanium chloride complexes [Cl_{2}Ti{(μ_{3}-N)_{2}(μ_{3}-NH)Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**4**) and [(Me_{2}NH)ClTi{(μ_{3}-N)_{3}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**5**) are obtained by reaction of **1** with [TiCl_{4−x}(NMe_{2})_{x}] (*x* = 2, 3). The dimethylamine ligand in **5** is displaced by pyridine to give the analogue complex [(py)_{2}ClTi{(μ_{3}-N)_{3}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**6**). Treatment of the titanium chloride complexes **4** and **5** with sodium cyclopentadienide or lithium bis(trimethylsilyl)amide reagents leads to the cube-type nitrido derivatives [RTi{(μ_{3}-N)_{3}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (R = η^{5}-C_{5}H_{5} (**7**), N(SiMe_{3})_{2} (**8**)). The reaction of the zirconium trichloride complex **2** with [Tl(C_{5}H_{5})] yields exclusively the dichloride-monocyclopentadienyl derivative [(η^{5}-C_{5}H_{5})Cl_{2}Zr{(μ_{3}-N)(μ_{3}-NH)_{2}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**9**). However, the treatment of **2** with excess [Na(C_{5}H_{5})] causes further chloride replacement in **9** and subsequent cyclopentadiene elimination to give [(η^{5}-C_{5}H_{5})Zr{(μ_{3}-N)_{3}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**10**) *via* intermediates [(η^{5}-C_{5}H_{5})_{2}ClZr{(μ_{3}-N)Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ-NH)_{2}(μ_{3}-N)}] (**11**) and [(η^{5}-C_{5}H_{5})ClZr{(μ_{3}-N)_{2}(μ_{3}-NH)Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**12**). Treatment of **2** or **9** with [Mg(C_{5}H_{5})_{2}] leads to the magnesium derivative [(η^{5}-C_{5}H_{5})Mg(μ-Cl)_{2}(η^{5}-C_{5}H_{5})Zr{(μ_{4}-N)(μ_{3}-N)(μ_{3}-NH)Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**13**), which can be visualized as a result of the incorporation of one [Mg(η^{5}-C_{5}H_{5})Cl] moiety to complex **12**. In contrast to the metathesis process with [M(C_{5}H_{5})_{x}] derivatives and subsequent C_{5}H_{6} eliminations, the reaction of **2** with potassium pentamethylcyclopentadienide in toluene produces the paramagnetic derivative [K(μ-Cl)_{3}Zr{(μ_{3}-N)(μ_{3}-NH)_{2}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**14**) and C_{10}Me_{10}. Complex **14** reacts with one equivalent of 18-crown-6 or cryptand-222 to give the molecular complex [(18-crown-6)K(μ-Cl)_{3}Zr{(μ_{3}-N)(μ_{3}-NH)_{2}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**15**) or the ion pair [K(crypt-222)][Cl_{3}Zr{(μ_{3}-N)(μ_{3}-NH)_{2}Ti_{3}(η^{5}-C_{5}Me_{5})_{3}(μ_{3}-N)}] (**16**). The X-ray crystal structures of **2**, **8**, **13** and **15** have been determined.