title: Imidazolin-2-iminato complexes of rare earth metals with very short metal-nitrogen bonds: experimental and theoretical studies.
abstract: The reactions of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH, 1-H) with trimethylsilylmethyl lithium (LiCH(2)SiMe(3)) and anhydrous rare earth metal trichlorides MCl(3) afforded the imidazolin-2-iminato complexes [(1)MCl(2)(THF)(3)] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) and [(1)GdCl(2)(THF)(2)] x [LiCl(THF)(2)] (2d). Treatment of complexes 2 with dipotassium cyclooctatetradienide, K(2)(C(8)H(8)) resulted in the formation of two- or three-legged piano-stool complexes of the type [(eta(8)-C(8)H(8))M(1)(THF)(n)] (3a, M = Sc, n = 1; 3b, M = Y, n = 2; 3c, M = Lu, n = 2; 3d, M = Gd, n = 2). X-ray diffraction analyses of all eight complexes 2 and 3 revealed the presence of very short metal-nitrogen bonds, which are among the shortest ever observed for these elements. [(eta(8)-C(8)H(8))Sc(1)(THF)] (3a) reacted with 2,6-dimethylphenyl isothiocyanate (Xy-NCS) to form the [2 + 2]-cycloaddition product 4, which contains a thioureato-N,N' moiety. The related COT-titanium complex [(eta(8)-C(8)H(8))TiCl(1)] (6) could be obtained from [(1)TiCl(3)] (5) by reaction with K(2)(C(8)H(8)) and was structurally characterized. As a theoretical analysis of the nature of the metal-nitrogen bond, density functional theory (DFT) calculations have been carried out for complexes 3a and 6 and also for the model complexes [(eta(8)-C(8)H(8))Sc(NIm(Me))] (7), [(eta(8)-C(8)H(8))Ti(NIm(Me))](+) (8), and [(eta(8)-C(8)H(8))Ti(NXy)] (9), revealing a marked similarity of the bonding in imidazolin-2-iminato and conventional imido metal complexes.
authors.affiliation: Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina, Hagenring 30, 38106 Braunschweig, Germany.
authors.forename: Tarun K
authors.initials: TK
authors.lastname: Panda
authors.forename: Alexandra G
authors.initials: AG
authors.lastname: Trambitas
authors.forename: Thomas
authors.initials: T
authors.lastname: Bannenberg
authors.forename: Cristian G
authors.initials: CG
authors.lastname: Hrib
authors.forename: Sören
authors.initials: S
authors.lastname: Randoll
authors.forename: Peter G
authors.initials: PG
authors.lastname: Jones
authors.forename: Matthias
authors.initials: M
authors.lastname: Tamm
mesh_terms: D002712:Chlorides / Q000737:chemistry; D048288:Imidazolines / Q000737:chemistry*; D007097:Imines / Q000737:chemistry; D008674:Metals, Rare Earth / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D014025:Titanium / Q000737:chemistry
chemical_list: D002712:Chlorides; D048288:Imidazolines; D007097:Imines; D008674:Metals, Rare Earth; D009942:Organometallic Compounds; D014025:Titanium; D009584:Nitrogen