COPPER(II) COMPLEXES WITH TRIDENTATE O,N,O-CHELATE DIANIONS AND ADDITIVE MONODENTATE DONOR LIGANDS-I - CRYSTAL-STRUCTURES AND EPR RESULTS OF UREA ADDUCTS OF N-SALICYLIDENE-ALPHA-AMINOACIDATO-COPPER(II) COMPARED WITH N-SALICYLIDENEGLYCINATO-THIOUREA-COPPER(II)

Dinuclear Cu(II) complexes with the tridentate N-salicylideneglycinate (saa(2-)) or N-salicylidenemethylalaninate dianion (sab(2-)) and urea (Ur) or thiourea (Tu) as additional monodentate donor ligand were pre pared and characterised, namely [(saa)Cu(Ur)](2) (1), [(sab)Cu(Ur)](2) (Ur)(2) (2) and [(saa)Cu(Tu)](2) (3). The urea adducts crystallise in the triclinic space group P (1) over bar with a=7.611(1), b=7.815(1), c=10.078(1) Angstrom; alpha=98.06(1), beta=110.31(1), gamma=95.91(1)de grees for 1 and a=8.820(1), b=9.712(1), c=10.317(1) Angstrom; alpha=66 .208(5), beta=88.722(5), gamma=83.364(6)degrees for 2; in each case Z= 2 refering to the mononuclear constituents of centrosymmetric dimers. In the crystal structure of the thiourea derivative (monoclinic space soup I2/a: a=12.353(1), b=14.315(1), c=13.670(1) Angstrom; beta=91.62( 1)degrees; Z=8), however, the dimers have C-2 symmetry due to a shift of the ligands into cis position. In all three cases the phenoxy-O lig ands act as bridges in connecting monomeric units. Each one of them is part of the basal plane of one Cu ion and acts as an apical ligand to the copper centre of the second monomeric complex. The copper ions ad opt (4+1) square-pyramidal geometry with relatively short apical Cu-O distances of about 2.4 Angstrom in the case of 1 and 2 compared to abo ut 2.8 Angstrom for 3. Minor structural alterations in changing from 1 to 2 give rise to a significant impact in spectroscopic data, especia lly in the EPR parameters. The results are interpreted as consequences of (i) the electron inducing effect due to alkylation of the tridenta te ligand and (ii) the intercalation of urea dimers in the case of 2 s tabilised by hydrogen bonds. (C) 1998 Elsevier Science S.A.