Lewis Base Behavior of Bridging Nitrido Ligands of Titanium Polynuclear Complexes |
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Authors: | Jorge J. Carbó Dr. Noelia Martínez‐Espada Miguel Mena Dr. Marta E. G. Mosquera Dr. Josep‐M. Poblet Prof. Carlos Yélamos Dr. |
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Affiliation: | 1. Department de Química Física i Inorgánica, Universitat Rovira i Virgili, Marcel‐lí Domingo s/n, 43007 Tarragona (Spain), Fax: (+34)?977‐559563;2. Departamento de Química Inorgánica, Universidad de Alcalá, 28871 Alcalá de Henares‐Madrid (Spain), Fax: (+34)?91‐8854683 |
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Abstract: | The Lewis base behavior of μ3‐nitrido ligands of the polynuclear titanium complexes [{Ti(η5‐C5Me5)(μ‐NH)}3(μ3‐N)] ( 1 ) and [{Ti(η5‐C5Me5)}4(μ3‐N)4] ( 2 ) to MX Lewis acids has been observed for the first time. Complex 1 entraps one equivalent of copper(I ) halide or copper(I ) trifluoromethanesulfonate through the basal NH imido groups to give cube‐type adducts [XCu{(μ3‐NH)3Ti3(η5‐C5Me5)3(μ3‐N)}] (X=Cl ( 3 ), Br ( 4 ), I ( 5 ), OSO2CF3 ( 6 )). However, the treatment of 1 with an excess (≥2 equiv) of copper reagents afforded complexes [XCu{(μ3‐NH)3Ti3(η5‐C5Me5)3(μ4‐N)(CuX)}] (X=Cl ( 7 ), Br ( 8 ), I ( 9 ), OSO2CF3 ( 10 )) by incorporation of an additional CuX fragment at the μ3‐N nitrido apical group. Similarly, the tetranuclear cube‐type nitrido derivative 2 is capable of incorporating one, two, or up to three CuX units at the μ3‐N ligands to give complexes [{Ti(η5‐C5Me5)}4(μ3‐N)4?n{(μ4‐N)CuX}n] (X=Br ( 11 ), n=1; X=Cl ( 12 ), n=2; X=OSO2CF3 ( 13 ), n=3). Compound 2 also reacts with silver(I ) trifluoromethanesulfonate (≥1 equiv) to give the adduct [{Ti(η5‐C5Me5)}4(μ3‐N)3{(μ4‐N)AgOSO2CF3}] ( 14 ). X‐ray crystal structure determinations have been performed for complexes 8 – 13 . Density functional theory calculations have been carried out to understand the nature and strength of the interactions of [{Ti(η5‐C5H5)(μ‐NH)}3(μ3‐N)] ( 1′ ) and [{Ti(η5‐C5H5)}4(μ3‐N)4] ( 2′ ) model complexes with copper and silver MX fragments. Although coordination through the three basal NH imido groups is thermodynamically preferred in the case of 1′ , in both complexes the μ3‐nitrido groups act as two‐electron donor Lewis bases to the appropriate Lewis acids. |
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Keywords: | cage compounds cubanes density functional calculations nitrides titanium |
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