Photochemical synthesis and stereochemistry of cobalt(III) complexes containing pyrimidine-2-thionate and derivatives

Abstract

Three series of mixed-ligand cobalt(III) complexes containing four-membered N,S chelates [CoL_n-(en)_3–n]^(3–n)+[n= 1, 2 and/or 3; HL = pyrimidine-2-thiol (Hpymt), 4-methylpyrimidine-2-thiol (Hmpymt), or 4,6-dimethylpyrimidine-2-thiol (Hdmpymt); en = ethane-1,2-diamine] have been photochemically prepared from robust [Co(en)₃]³⁺ and the free ligand in moderate yields and characterized by their elemental analyses, UV/VIS absorption and ¹H and ¹³C NMR spectra. The crystal structure of [Co(mpymt)(en)₂][ClO₄]₂ was determined from 3329 reflections to R= 0.043 (R′= 0.062): space group P2₁/n(monoclinic) with a= 10.122(8), b= 9.003(6), c= 20.35(2)Å, β= 100.17(7)° and Z= 4. The mpymt ligand co-ordinates through N and S donors and the complex adopts a remote linkage form where the C⁴ methyl group is distant from the en chelate rings. The Co–N bond length trans to the sulfur atom is slightly longer (0.013 Å) than the cis one.