Homo and heteropolymetallic Group 4 molecular nitrides

Abstract

Treatment of [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)] (1) with zirconium or hafnium tetrachloride adducts [MCl₄(thf)₂] affords complexes [Cl₃M{(μ₃-N)(μ₃-NH)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (M = Zr (2), Hf (3)). Titanium chloride complexes [Cl₂Ti{(μ₃-N)₂(μ₃-NH)Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (4) and [(Me₂NH)ClTi{(μ₃-N)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (5) are obtained by reaction of 1 with [TiCl_4−x(NMe₂)_x] (x = 2, 3). The dimethylamine ligand in 5 is displaced by pyridine to give the analogue complex [(py)₂ClTi{(μ₃-N)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-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{(μ₃-N)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (R = η⁵-C₅H₅ (7), N(SiMe₃)₂ (8)). The reaction of the zirconium trichloride complex 2 with [Tl(C₅H₅)] yields exclusively the dichloride-monocyclopentadienyl derivative [(η⁵-C₅H₅)Cl₂Zr{(μ₃-N)(μ₃-NH)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (9). However, the treatment of 2 with excess [Na(C₅H₅)] causes further chloride replacement in 9 and subsequent cyclopentadiene elimination to give [(η⁵-C₅H₅)Zr{(μ₃-N)₃Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (10) via intermediates [(η⁵-C₅H₅)₂ClZr{(μ₃-N)Ti₃(η⁵-C₅Me₅)₃(μ-NH)₂(μ₃-N)}] (11) and [(η⁵-C₅H₅)ClZr{(μ₃-N)₂(μ₃-NH)Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (12). Treatment of 2 or 9 with [Mg(C₅H₅)₂] leads to the magnesium derivative [(η⁵-C₅H₅)Mg(μ-Cl)₂(η⁵-C₅H₅)Zr{(μ₄-N)(μ₃-N)(μ₃-NH)Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (13), which can be visualized as a result of the incorporation of one [Mg(η⁵-C₅H₅)Cl] moiety to complex 12. In contrast to the metathesis process with [M(C₅H₅)_x] derivatives and subsequent C₅H₆ eliminations, the reaction of 2 with potassium pentamethylcyclopentadienide in toluene produces the paramagnetic derivative [K(μ-Cl)₃Zr{(μ₃-N)(μ₃-NH)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (14) and C₁₀Me₁₀. Complex 14 reacts with one equivalent of 18-crown-6 or cryptand-222 to give the molecular complex [(18-crown-6)K(μ-Cl)₃Zr{(μ₃-N)(μ₃-NH)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (15) or the ion pair [K(crypt-222)][Cl₃Zr{(μ₃-N)(μ₃-NH)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (16). The X-ray crystal structures of 2, 8, 13 and 15 have been determined.