Thio derivatives of β-diketones and their metal chelates. II. α-Substituted Monothio-β-diketones as ligands

The α-methyl substituted monothio-β-diketones, 4-mercapto-3-methylpent-3-en-2-one, MeC(SH)=C(Me)COMe, and 3-mercapto-2-methyl-1,3-diphenylprop-2-en-1-one, PhC(SH)=C(;Me)COPh, were prepared; the former was not obtained pure. The complexing ability of these ligands appears to be weaker than that of other monothio-β-diketones; this can be partly explained on the basis of steric hindrance caused by the methyl group attached to the central carbon atom. The diamagnetic complexes, Ni(MeCS=CMeCOMe)2, Co(MeCS=CMeCOMe)3, and Ni(PhCS=CMeCOPh)2 were obtained but attempts to prepare other metal complexes of these ligands were unsuccessful. The infrared spectra of the three metal chelates display four characteristic bands for which assignments are given: 1570-1540 cm-1, v (C--C); 1525-1500 cm-1, v (C-0); 1230-1223 cm-1, v (C--8); 497-458 cm-1, v (M-0).