Influence of substituents within bidentate nitrogenous bases on the spectra of mixed-ligand (1,1-dithiolato)copper(II) and nickel(II) chelates

Characterization and DNA-interaction studies of 1,1-dicyano-2,2-ethylene dithiolate Ni(II) mixed-ligand complexes with 2-amino-5-methyl thiazole, 2-amino-2-thiazoline and imidazole. Crystal structure of [Ni(i-MNT)(2a-5mt)2]

“…The very strong bands at 2175 cm À1 and in the region 1356-1436 cm À1 have been assigned to m(C"N) and m(C@C), respectively, of the i-MNT ligand. 19 Upon coordination, these bands are shifted to higher wavenumbers: the former by 28-53 cm À1 and the latter by 35-93 cm À1 compared to the free i-MNT ligand. These shifts reveal an increase of the order of the C"N and C@C bonds, since the planar extensive p-conjugated system of the i-MNT ligand facilitate a drift of electron density towards the sulfur atoms that results in a shortening of the C"N and C@C bonds.…”

“…The small S-Ni-S chelation angle of 78.85(2)°indi-cates that it is determined by the geometry of the rigid i-MNT ligand. 19,20 On the other hand, as a result of the relatively small separation of the coordinated nitrogen atoms of the flexible 2a-5mt ligands (2.851 Å in comparison to 3.10 Å, which is the sum of their van der Waals radii) the opposite N-Ni-N angle appears greater than the ideal value of 90°[95.26(7)°]. The two Ni-S distances are very close to each other and have a mean value of 2.189(1) Å, which is in very good agreement with the corresponding ones observed in other dithiolato complexes, having the Ni(II) atom in a square-planar coordination.…”

Copper Complexes with (2,7‐Di‐tert‐butylfluoren‐9‐ylidene)methanedithiolate: Oxidatively Promoted Dithioate Condensation

“…[23] The Cu II complexes are represented by the mononuclear species [Cu(i-mnt) 2 ] 2-, [12,24] [Cu(ded) 2 ] 2-, [25,26] and [Cu(i-mnt)(N-N)] (N-N = 1,2-ethanediamines). [27] The Cu III complex [Cu(ded) 2 ] -has also been prepared by the oxidation of [Cu(ded) 2 ] 2-with H 2 O 2 , I 2 , or Cu 2+ ions. [25,26] Part of our recent research in this field has been devoted to the coordination chemistry of the (fluoren-9-ylidene)me-thanedithiolato ligand and its 2,7-disubstituted derivatives.…”