Ate complexes of Ge(II) and Sn(II) with bidentate ligands [LiE(OCH2CH2NMe2)3]2 (E=Ge, Sn): synthesis and structure

The reaction of equimolar quantities of LiOCH₂CH₂NMe₂ and E¹⁴(OCH₂CH₂NMe₂)₂ (E¹⁴=Ge, Sn) in ether yielded new ate complexes [LiE¹⁴(OCH₂CH₂NMe₂)₃]₂ (E¹⁴=Ge (1), Sn (2)) with bidentate ligands. The compounds 1 and 2 are white crystalline substances which are highly soluble in THF and pyridine and very sensitive to the traces of oxygen and moisture. The structures of these compounds are studied by X-ray diffraction analysis. The ate complexes 1 and 2 are powerful nucleophiles and may be employed as ligands (neutral) in the coordination chemistry of the transition metals. The electronegative O-substituents at the divalent E¹⁴ atoms render them less oxidizable than alkyl- or aryl-substituted derivatives, and the bidentate ligands, owing to intramolecular donor-acceptor interactions, make them more thermodynamically stable compared to monodentate ligands.     

Some further studies of estertin compounds. crystal structures of [NEt4][MeO2CCH2CH2Sn(dmio)2] (dmio = 1,3-dithiole-2-one-4,5-dithiolato) and (MeO2CCH2CH2)2SnX2[X2 = I2, (NCS)2 or Cl, Br]

Estertn compounds, (MeO₂CCH₂CH₂)₂SnX₂ [X₂ = I₂ (2); X₂ = Br₂ (9); X₂ = Cl, Br (4)) or X₂ = (NCS)₂ (3)] have been obtained by halide exchange reactions of (MeO₂CCH₂CH₂)₂SnCl₂. Crystal structure determinations of 2–4 revealed chelating MeO₂CCH₂CH₂ units with distorted octahedral geometries at tin. The Sn---O bond lengths in the isothiocyanato complex, 3, are shorter [2.390(11) to 2.498(12), mean 2.439 Å], with the chelate bite angles, C---Sn---O, larger [74.3(7) to 78.2(6), mean 76.0°] than those in the halide analogues 2 and 4 [Sn---O = 2.519(2) to 2.541(8), mean 2.530 Å; C---Sn---O 72.8(3) to 73.9(4), mean 73.3°]. ¹H, ¹³C and ¹¹⁹Sn NMR and IR spectra of 2–4 and 9 were determined in CDCl₃ solution: the NMR spectra of (MeO₂CCH₂CH₂)₂SnX₂ show the following trends: (i) both δ¹H and δ¹³C, increase and (ii) both ²J (Sn---H) and ¹J(Sn---C) decrease in the sequence X₂ = (NCS)₂, Cl₂, ClBr, Br₂ and I₂. The MeO₂CCH₂CH₂ and dmio groups (dmio = 1,3-dithiole-2-one-4,5-dithiolato) are all chelating groups in (MeO₂CCH₂CH₂)₂Sn(dmio) (5). As shown by X-ray crystallography, the tin atom in the anion of solid [Q][MeO₂CCH₂CH₂Sn(dmio)₂] 6 (Q = NEt₄) forms 5 strong bonds [to C and the 4 thiolato S atoms, Sn---S 2.459(2) to 2.559(2) Å], arranged in a near trigonal bipyramidal array. There is an additional Intramolecular but weaker, interaction with the carbonyl oxygen atom [Sn---O = 3.111(5) Å]; v(C=O) = 1714 cm⁻¹ in solid 6 (Q = NEt₄). NMR spectra of 5 and 6 are also reported.     

Synthesis,spectroscopic characterization and thermal behavior of cadmium(II) complexes of S-methyldithiocarbazate (SMDTC) and S-benzyldithiocarbazate (SBDTC): X-ray crystal structure of [Cd(SMDTC)3] · 2NO3

Two new cadmium(II) complexes of the empirical formulae [Cd(SMDTC)₃] · 2NO₃ (1) and [Cd(SBDTC)₂] · 2NO₃ (2) have been synthesized and characterized by elemental analyses, UV–Vis, IR, ¹H NMR and TGA techniques. In complex 1, the six coordination sites around cadmium are occupied by three neutral SMDTC molecules with N and S donor atoms from each ligand molecule, whereas in complex 2 the cadmium center is four coordinated with two relatively larger SBDTC ligands chelating with N and S donor atoms in the neutral thione form. In the solid state, thermal gravimetric analysis shows that both complexes are relatively volatile in nature and undergo facile thermal decomposition above 120 °C to form the metal sulfide followed by stepwise loss of ligand molecules. The crystal and molecular structure of complex 1 has been established by the X-ray diffraction method. The central cadmium(II) atom has an octahedral geometry with three five-membered chelate rings formed by SMDTC ligands. The crystal structure consists of parallel layers of cations and anions. The SMDTC molecules in cations are arranged with their N donor groups directed towards the anion layer in an alternating fashion and form hydrogen bonds with the O atoms of the anion.