THE SYNTHESIS, STRUCTURE AND NUCLEAR-MAGNETIC-RESONANCE PROPERTIES OFSOME TITANIUM RELATIVES OF AMAVADIN - [DELTA-TI(R,R-HIDPA)(2)](2-), [DELTA,LAMBDA-TI(R,R-HIDPA)(2)](2-) AND [DELTA,LAMBDA-TI(HIDA)(2)](2-) [H(3)HIDPA = 2,2'-(HYDROXYIMINO)DIPROPIONIC ACID, H(3)HIDA = N-HYDROXYIMINODIACETIC ACID]

The compound [TiO(acac)(2)] (acac = acetylacetonate) reacts with N-hyd roxyiminodiacetic acid (H(3)hida) or (R,R)-2,2'-(hydroxyimino)dipropio nic acid (R,R-H(3)hidpa) to yield [Ti(hida)(2)](2-) or [Ti(R,R-hidpa)( 2)](2-), respectively. The anion [Ti(R,R-hidpa)(2)](2-) has been obtai ned from H2O in the presence of Ca2+ as 2O)(4)][Ca(H2O)(5)](3)-[Delta- Ti(R,R-hidpa)(2)](4) . 2H(2)O 3 which crystallises in the space group P2(1) (no. 4) with a = 14.258(2), b = 16.516(3), c = 19.169(3) Angstro m, beta = 110.907(9)degrees; least-squares refinement of 6082 reflecti ons and 1126 variables converged with agreement factors of R = 0.069 a nd R' = 0.054. The anions possess the co-ordination geometry identifie d for other Amavadin-style complexes, viz. eight-co-ordination achieve d by the ligation of two mutually trans and staggered eta(2)-NO groups and four unidentate carboxylate oxygen atoms; Ti-N(NO) 2.04(1)-2.10(1 ), Ti-O(NO) 1.962(9)-2.001(9), Ti-O(CO2) 2.024(9)-2.100(9), N-O 1.38(1 )-1.44(1) Angstrom. The lattice of compound 3 comprises of parallel zi gzag strands of alternating [Delta-Ti(R,R-hidpa)(2)](2-) and [Ca(H2O)( x)](2+) (x = 4 or 5) linked interstrand by Ca-II binding to carboxylat o-oxygen atoms and intra-and inter-strand by hydrogen bonding from the H2O molecules to the oxygen atoms of the anions. The anions are obtai ned exclusively in the Delta-helical form and this has enabled H-1 and C-13 NMR studies to follow epimerisation at the Ti-IV centre to produ ce a mixture of the Delta- and Lambda-helical forms Carbon-13 NMR spec troscopy has been used to investigate the interaction of the carboxyla to groups of[Ti(hida)(2)](2-) with solvents.