SYNTHESIS, CHARACTERIZATION AND INVESTIGATION OF MOLECULAR-MOTION BY VARIABLE-TEMPERATURE H-1-NMR OF THE BIS(QUADRIDENTATE)ZIRCONIUM(IV) COMPLEXES YLIDENE-CIS-1,2-DIAMINOCYCLOHEXANATO)ZIRCONIUM(IV) AND DENE-TRANS-1,2-DIAMINOCYCLOHEXANATO)ZIRCONIUM(IV), AND COMPARISONS WITH ISALICYLIDENE-1,2-PHENYLENEDIAMINATO)ZIRCONIUM(IV) - CRYSTAL AND MOLECULAR-STRUCTURE OF THE RACEMIC ZR(TRANS-DSD)2 AND ZR(S,S-TRANS-DSD)2 COMPLEXES

Variable temperature H-1 NMR over the range from 165.9 to 19.9-degrees -C in d6-dimethyl sulfoxide and 22.1 to -95.4-degrees-C in d2-methylen e chloride is employed to investigate the molecular motions in the eig ht-coordinate zirconium complexes lidene-cis-1,2-diaminocyclohexanato) zirconium(IV), Zr(cis-dsd)2; dene-trans-1,2-diaminocyclohexanato)zirco nium(IV), Zr(trans-dsd)2; and alicylidene-1,2-phenylenedi-aminato)zirc onium(IV), Zr(dSP)2. For Zr(cis-dsd)2, the resolution of one methine s ignal into separate axial (upfield) and equatorial (downfield) signals at low temperature is consistent with the chair-to-chair interconvers ion of the fused cyclohexane ring becoming slow on the NMR time scale. A coalescence temperature of c. -47-degrees-C and a thermodynamic bar rier of DELTAG(not-equal)(298)=46.5+/-0.9 kJ mol-1, DELTAH(not-equal)= 27+/-3 kJ mol-1 and DELTAS(not-equal)=-66+/-13 J mol-1 K-1 are obtaine d for this process. The resolution of six imine signals at -95.4-degre es-C from two ambient temperature imine signals is attributed to slow interconversion of isomers which arise from different ligand wrapping geometries, cyclohexane ring conformations, and/or polytopal coordinat ion geometries. For Zr(trans-dsd)2, the resolution of a second set of salicylidene NMR signals as the temperature is decreased is likewise a ttributed to the slow interconversion of isomers. However, since only one set of averaged signals is observed at high temperature, these iso mers Must possess symmetrical salicylidene moieties. For Zr(dSP)2, com parable changes were not observed over the temperature range studied, despite the fact that both dsp(2-) and dsd(2-) ligands are capable of considerable non-planarity. The two new zirconium complexes, Zr(cis-ds d)2, and Zr(trans-dsd)2, are synthesized from Zr(O-n-CH9)4 butanol sol vate and Schiff bases made from cis- and trans-diaminocyclohexane (DAC H), and characterized by elemental analysis, IR, UV-Vis, H-1 and C-13 NMR (the latter able to distinguish Zr(R,R-trans-dsd)(S,S-trans-dsd) f rom other Zr(trans-dsd), isomers), thermogravimetric analysis, optical rotation for the separate enantiomers Zr(R,R-trans-dsd), and Zr(SS-tr ans-dsd)2, and single crystal X-ray diffraction analysis for Zr(trans- dsd)2. Hitherto unpublished C-13 NMR results for Zr(dsp)2 are included in order to facilitate making assignments. Details of the crystallogr aphy include: formula C40H40N4O4Zr, space group Fddd with a=15.232(3), b=16.994(4), c=26.711(5) angstrom, V=6914(2) angstrom3, Z=8, and D(ca lc)=1.406 g CM-3 ; refinement of 152 variables using 2283 reflections collected (1820 independent and observed) converge at R=3.84%. Details of the crystallography for the Zr(S, S-trans-dsd)2 isomer, space grou p P1BAR, can be obtained. Testing of the new complexes for anticancer activity was performed by Bristol-Myers and was negative.