Synthesis of chiral thiourea ligands and their transition metal complexes

[摘要] ENGLISH ABSTRACT:Modification of chitosan with benzoylisothiocyanate was attempted, however due tosolvent problem the study was left incomplete till appropriate solvent is designed.N,N-diethyl-N -camphanoylthiourea (HL8), N-piperidyl-N '-camphanoylthiourea (HL9),N-pyrrolidyl-N -camphanoylthiourea (HL10) and N,N-diethyl-N -adamantylcarbonylthiourea (HL11)have been synthesised and characterised for the first time. Two ofthese ligands HL8 and HL11, were used to form a number of transition metalcomplexes, namely H30+{fae-[Co(L8-S,Obn, cis-[Ni(L8-S,0)2], trans-[Cu(L8-S,0)2],translcis-[Zn(L 8_S,0)2], translcis-[Pt(L 8_S,0)2], Ag2[(HL8-S)(L-J.1-S,O)]2, translcis-[Ni(L11-S,O)2]and translcis-[Cu(L11_S,O)2]. The new products are fully characterisedby means of MS, IR spectroscopy, NMR spectroscopy, elemental (C, H, Nand S)analysis and melting point determinations. The H30+{fae-[Co(L8-S,Obn, cis-[Ni(L8-S,O)2], trans-[Cu(L8-S,O)2] and Ag2[(HL8-S)(L-J.1-S,O)]2 are also characterised by Xraydiffraction analysis.The structure of the new chiral N,N-dialkyl-N' -camphanoylthiourea ligand (HL8) has asignificant effect on its coordination chemistry with transition metal ions. This ligandforms H30+ {fae-[Co(L8-S,Obn, cis-[Ni(L8-S,0)2], trans-[Cu(L-S,O)2] and Ag2[(HL8-S)(L8-J.1-S,O)]2 complexes with the Co(II), Ni(II), Cu(II) and Ag(I) metal ionsrespectively. The spectroscopic and X-ray diffraction results of these complexesindicate a bidentate mode of coordination of the ligand (with its Sand °donoratoms) to the Co(II), Ni(II) and Cu(II) metal ions. The reaction of this ligand withsilver(I) however affords the formation of a binuclear silver(I) complex exhibitingmonodentate and bidentate modes of coordination within the same complex. Theexclusive formation of trans-[Cu(L8-S,0)2] is a new phenomenon for the HL typethiourea ligands with Sand °donor atoms. Up to this point a maximum of 15 %trans-isomer has been reported in ltterature.All the transition metal complexes made with HL8and HL11are air stable in both theliquid and solid states except the H30+{fae-[Co(L 8-S,Ob]} Interestingly the deepgreen fae- H30+{fae-[Co(L8-S,Obn complex is air sensitive and the Co(II) oxidizes toCo(III) in the complex by atmospheric O2. The oxidation of Co(II) to Co(III) in thecomplex is confirmed by 1Hand 13CNMR spectra as well as by UV-Visible spectra of the complex. The NMR spectra of the complexes indicated the presence of oneisomer in each complex except for the NMR spectra of the platinum complex of theHL8 ligand. The presence of the minor trans-[Pt(L8-S,Q)21 isomer in combination withthe major cis-[Pt(L8-S,Q)21 isomer in the platinum complex was indicated by the 1H,13Cand 195ptNMR spectra of the complex.

[发布机构] Stellenbosch University