Synthesis and structural characterization of cobalt(III) complexes of hybrid donor-type didentate or tetradentate ligands bearing dimethylphosphino and thioether groups

Abstract

The preparation and characterization of new hybrid donor-type phosphine-thioether ligands, a linear tetradentate Me 2P(CH 2) 2S(CH 2) 3S(CH 2) 2PMe 2 (dmdtn) and a didentate Me 2P(CH 2) 2SR [R = Me (mtdmp) or Et (etdmp)], and their cobalt(III) complexes are described. The reaction of trans-[CoCl 2(PY) 4]C1 (py = pyridine) with dmdtn, followed by anion metathesis with NaPF 6, afforded green crystals of trans( Cl,Cl-[CoCl 2{ meso(S)-dmdtn}]PF 6 (1), whose geometrical structure and configuration around S atoms were determined by X-ray analysis. Further reaction of 1 with Li(acac) (acac = pentane-2,4-dionate) and crystallization with LiBF 4 gave red crystals of the acac complex 2. The X-ray analysis of 2 confirmed the structure and configuration of cisβ-[Co(acac){ racemic(S)-dmdtni}(BF 4) 2, indicating the configurational inversion at one sulfur during the derivation of complex 2. An analogous N,N-dimethyldithiocarbamate (dtc) complex 3 was also prepared, and the electrochemical properties of complexes 1– 3 were discussed. For analogous mtdmp and etdmp (P-S) complexes, trans(Cl,Cl)cis(P,P)-[CoCl 2(P-S) 2]PF 6 reacted with Li(acac) to give not only trans(P,S)-[Co(acac)(P-S) 2](PF 6) 2 but also [Co(acac) 2(P-S)]PF 6. Similar reactions with Na(dtc) yielded cis-[Co(dtc) 2(P-S-κ P) 2] ( 14 for P-S = mtdmp), together with trans(P,S)-[Co(dtc)(P-S) 2](PF 6) 2 and [Co(dtc) 2(P-S)]PF 6. The structures of these complexes were characterized by NMR and UV-visible spectroscopy and X-ray analysis of 14. These results suggested that the didentate ligands were hemilabile as similar to previously described SPPS-type tetradentate ligands, but the tetradentate dmdtn ligand was not.