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Lewis Base Behavior of Bridging Nitrido Ligands of Titanium Polynuclear Complexes
Author(s) -
Carbó Jorge J.,
MartínezEspada Noelia,
Mena Miguel,
Mosquera Marta E. G.,
Poblet JosepM.,
Yélamos Carlos
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901598
Subject(s) - chemistry , trifluoromethanesulfonate , adduct , lewis acids and bases , copper , crystal structure , medicinal chemistry , titanium , stereochemistry , base (topology) , halide , reagent , crystallography , inorganic chemistry , organic chemistry , catalysis , mathematical analysis , mathematics
The Lewis base behavior of μ 3 ‐nitrido ligands of the polynuclear titanium complexes [{Ti(η 5 ‐C 5 Me 5 )(μ‐NH)} 3 (μ 3 ‐N)] ( 1 ) and [{Ti(η 5 ‐C 5 Me 5 )} 4 (μ 3 ‐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{(μ 3 ‐NH) 3 Ti 3 (η 5 ‐C 5 Me 5 ) 3 (μ 3 ‐N)}] (X=Cl ( 3 ), Br ( 4 ), I ( 5 ), OSO 2 CF 3 ( 6 )). However, the treatment of 1 with an excess (≥2 equiv) of copper reagents afforded complexes [XCu{(μ 3 ‐NH) 3 Ti 3 (η 5 ‐C 5 Me 5 ) 3 (μ 4 ‐N)(CuX)}] (X=Cl ( 7 ), Br ( 8 ), I ( 9 ), OSO 2 CF 3 ( 10 )) by incorporation of an additional CuX fragment at the μ 3 ‐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 μ 3 ‐N ligands to give complexes [{Ti(η 5 ‐C 5 Me 5 )} 4 (μ 3 ‐N) 4− n {(μ 4 ‐N)CuX} n ] (X=Br ( 11 ), n =1; X=Cl ( 12 ), n =2; X=OSO 2 CF 3 ( 13 ), n =3). Compound 2 also reacts with silver( I ) trifluoromethanesulfonate (≥1 equiv) to give the adduct [{Ti(η 5 ‐C 5 Me 5 )} 4 (μ 3 ‐N) 3 {(μ 4 ‐N)AgOSO 2 CF 3 }] ( 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(η 5 ‐C 5 H 5 )(μ‐NH)} 3 (μ 3 ‐N)] ( 1′ ) and [{Ti(η 5 ‐C 5 H 5 )} 4 (μ 3 ‐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 μ 3 ‐nitrido groups act as two‐electron donor Lewis bases to the appropriate Lewis acids.