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  • Title: Homo and heteropolymetallic Group 4 molecular nitrides.
    Author: Caballo J, Greño M, Mena M, Pérez-Redondo A, Yélamos C.
    Journal: Dalton Trans; 2015 Nov 07; 44(41):18145-57. PubMed ID: 26419656.
    Abstract:
    Treatment of [{Ti(η(5)-C5Me5)(μ-NH)}3(μ3-N)] (1) with zirconium or hafnium tetrachloride adducts [MCl4(thf)2] affords complexes [Cl3M{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (M = Zr (2), Hf (3)). Titanium chloride complexes [Cl2Ti{(μ3-N)2(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (4) and [(Me2NH)ClTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (5) are obtained by reaction of 1 with [TiCl4-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(η(5)-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(η(5)-C5Me5)3(μ3-N)}] (R = η(5)-C5H5 (7), N(SiMe3)2 (8)). The reaction of the zirconium trichloride complex 2 with [Tl(C5H5)] yields exclusively the dichloride-monocyclopentadienyl derivative [(η(5)-C5H5)Cl2Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-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 [(η(5)-C5H5)Zr{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (10) via intermediates [(η(5)-C5H5)2ClZr{(μ3-N)Ti3(η(5)-C5Me5)3(μ-NH)2(μ3-N)}] (11) and [(η(5)-C5H5)ClZr{(μ3-N)2(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (12). Treatment of 2 or 9 with [Mg(C5H5)2] leads to the magnesium derivative [(η(5)-C5H5)Mg(μ-Cl)2(η(5)-C5H5)Zr{(μ4-N)(μ3-N)(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (13), which can be visualized as a result of the incorporation of one [Mg(η(5)-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(η(5)-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(η(5)-C5Me5)3(μ3-N)}] (15) or the ion pair [K(crypt-222)][Cl3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (16). The X-ray crystal structures of 2, 8, 13 and 15 have been determined.
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