RESUMO
The reactions of 1-methyl-1,3-dihydro-2H-benzimidazole-2-selone, H(sebenzimMe), towards the zinc and cadmium halides, MX2 (M = Zn, Cd; X = Cl, Br, I), afford the adducts, [H(sebenzimMe)]2MX2, which have been structurally characterized by X-ray diffraction. The halide ligands of each of these complexes participate in hydrogen bonding interactions with the imidazole N-H moieties, although the nature of the interactions depends on the halide. Specifically, the chloride and bromide derivatives, [H(sebenzimMe)]2ZnX2 and [H(sebenzimMe)]2CdX2 (X = Cl, Br), exhibit two intramolecular N-Hâ¢â¢â¢X interactions, whereas the iodide derivatives, [H(sebenzimMe)]2ZnI2 and [H(sebenzimMe)]2CdI2, exhibit only one intramolecular N-Hâ¢â¢â¢I interaction. Comparison of the M-Se and M-Cl bond lengths of the chloride series, [H(sebenzimMe)]2MCl2 (M = Zn, Cd, Hg), indicates that while the average M-Cl bond lengths progressively increase as the metal becomes heavier, the variation in M-Se bond length exhibits a non-monotonic trend, with the Cd-Se bond being the longest. These different trends provide an interesting subtlety concerned with use of covalent radii in predicting bond length differences. In addition to tetrahedral [H(sebenzimMe)]2CdCl2, [H(sebenzimMe)]3,CdCl2â¢[H(sebenzim)Me]4CdCl2, which features both five-coordinate and six-coordinate coordinate centers, has also been structurally characterized. Finally, the reaction between CdI2 and H(sebenzimMe) at elevated temperatures affords the 1-methylbenzimidazole complex, [H(sebenzimMe)]-[H(benzimMe)]CdI2, a transformation that is associated with cleavage of the C-Se bond.
RESUMO
In the new tin(IV) and copper(II) complexes, cis-dichlorido-trans-dimethyl-cis-bis(N,N',N''-tricyclohexylphosphoric triamide-κO)tin(IV), [Sn(CH(3))(2)Cl(2)(C(18)H(36)N(3)OP)(2)], (I), and trans-diaquabis(N,N',N''-tricyclohexylphosphoric triamide-κO)copper(II) dinitrate-N,N',N''-tricyclohexylphosphoric triamide (1/2), [Cu(C(18)H(36)N(3)OP)(2)(H(2)O)(2)](NO(3))(2)·2C(18)H(36)N(3)OP, (II), the N,N',N''-tricyclohexylphosphoric triamide (PTA) ligands exist as hydrogen-bonded dimers via P=O···H-N interactions around the metal center. The asymmetric unit in (I) consists of one complete complex molecule located on a general position. The Sn(IV) coordination geometry is octahedral with two cis hydrogen-bonded PTA ligands, two cis chloride ligands and two trans methyl groups. The asymmetric unit in (II) contains one half of a [Cu(PTA)(2)(H(2)O)(2)](2+) dication on a special position (site symmetry Ì 1 for the Cu atom), one nitrate anion and one free PTA molecule, both on general positions. The complex adopts a square-planar trans-[CuO(2)O(2)] coordination geometry, with the Cu(II) ion coordinated by two PTA ligands and two water molecules. Each of the noncoordinated PTA molecules is hydrogen bonded to a neighboring coordinated PTA molecule and an adjacent water molecule; the phosphoryl O atom acts as a double-H-atom acceptor. The P atoms in the PTA ligands of both complexes and in the noncoordinated hydrogen-bonded molecules in (II) adopt a slightly distorted tetrahedral environment.
