title: Reaction of Ketones with 1,4-Diaza-1,3-diene Zirconium and Hafnium Complexes: First Example of a 1,3-Dipolar Cycloaddition Reaction of 1,4-Diaza-1,3-diene Complexes of Early Transition Metals.
abstract: The novel complexes M[O(R)PhCH{CH=N(tBu)}N(tBu)](2) [M = Zr, R = Me (4a), R = Ph (4b) and M = Hf, R = Me (5a), R = Ph (5b)] have been prepared in almost quantitative yield by reaction of (tBu-DAD)(2)Zr (1) and (tBu-DAD)(2)Hf (2) [tBu-DAD = (tBu)N=CHCH=N(tBu)] with 2 equiv of the ketones MeCOPh (3a) or PhCOPh (3b). The reaction proceeds via a 1,3-dipolar cycloaddition of the C=O bond across the M-N-C unit of the DAD complexes. The molecular structures of the complexes 4a and 5b have been determined by a single-crystal X-ray diffraction study (4a, triclinic, space group P&onemacr;; a = 10.395(2) Å, b = 10.865(2) Å, c = 16.842(3) Å, alpha = 93.80(3) degrees, beta = 99.84(3) degrees, gamma = 106.12(3) degrees, V = 1787.4(6) Å(3), Z = 2, R1 = 0.035 (wR2 = 0.101) for 6963 reflections with I > 2sigma(I); 5b, monoclinic, space group P2(1)/c, a = 19.961(4) Å, b = 10.482(2) Å, c = 20.150(4) Å, beta = 91.30(1) degrees, V = 4215(1) Å(3), Z = 4, R1 = 0.036 (wR2 = 0.097) for 4650 reflections with I > 2sigma(I)). The metal atoms in 4a and 5b adopt a pseudooctahedral coordination sphere consisting of four nitrogen and two oxygen atoms. The distortion is a consequence of the [2.2.1] bicyclic structure of the newly formed tridentate ligands which are not able to span three regular octahedral positions.
authors.affiliation: Institut für Anorganische Chemie, Martin-Luther-Universität Halle-Wittenberg, Geusaer Strasse, D-06217 Merseburg, Germany, and Max-Planck-Gesellschaft, Arbeitsgruppe "CO(2)-Chemie" an der Friedrich-Schiller-Universität Jena, Lessingstrasse 12, D-07743 Jena, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Scholz
authors.forename: Helmar
authors.initials: H
authors.lastname: Görls