New stable monomeric germanium(II) and tin(II) compounds M(OCH 2 CH 2 NMe 2 ) 2 (M ) Ge (1); M ) Sn (2)), stabilized by two intramolecular coordination MrN bonds and containing no bulky groups on the metal atoms, were synthesized. The molecular and crystal structures of these compounds, and that of the previously synthesized compound (ArO) 2 Sn (3; Ar ) 2,4,6-(Me 2 NCH 2 ) 3 C 6 H 2 ), were determined by X-ray diffraction analysis. The electronic structures of 1 and 2 were studied by the DFT method.
The first monomeric germanethiocarbamyl halides containing a chelating β-diiminate
ligand, L2(Cl)GeY (L2 = PhNC(Me)CHC(Me)NPh; Y = S (2), Y = Se (3)), have been prepared
by the reaction of the corresponding heteroleptic halogermylene L2(Cl)Ge (1) with elemental
sulfur or black selenium in refluxing toluene. Single-crystal X-ray structural analyses of 2
and 3 reveal that the germanium centers reside in highly distorted tetrahedral environments
in these compounds; short Ge−Y distances (Ge−S = 2.07 Å (2); Ge−Se = 2.21 Å (3)) are
indicative of an unsaturated character of these germanium−chalcogen bonds. Selective
reactions between 2 or 3 and MeLi afforded the corresponding alkylated germanechalcogenones L2(Me)GeY (Y = S (4), Se (5)).
An experimental and theoretical study of the heteroleptic divalent germanium compounds containing the bidentate coordinating monoanionic β-diketiminate ligand L 2 GeΣ (L 2 ) PhNC-(Me)CHC(Me)NPh; Σ ) Cl (1), I (2), Me (3), OMe (4)) has been performed in this contribution. The new stable germanium(II) compounds 3 and 4 have been synthesized by reaction of 1 with RLi (R ) Me, OMe) and fully characterized. The crystal structures of 1-3 and their electronic structures have been determined by X-ray diffraction and UV-photoelectron spectroscopy (UPS), respectively. DFT calculations on 1 and 3 were carried out at the B3LYP level of theory. Natural bond orbital analysis for the model molecules 1′ and 3′ (without phenyl) gives information on the Ge-Σ bonding. It turns out from the NMR, mass spectroscopy, and X-ray molecular geometry properties together with the ab initio calculations that the three-coordinated germanium(II) compound L 2 GeX is best described by a model structure corresponding to a divalent germanium species weakly coordinated with the halide group, L 2 Ge + ‚‚‚X -. This view is confirmed by the particularly low energetic values of the X atom lone-pair ionizations.
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