Synthesis, stereochemistry and crystal structures of cobalt(III) complexes containing 5,8-diphenyl-2,11-dithia-5,8-diphosphadodecane or 5,9-diphenyl-2,12-dithia-5,9-diphosphatridecane

Twelve new cobalt(III) complexes containing a tetradentate phosphine ligand of the type MeS(CH 2 ) 2 PPh(CH 2 ) n PPh(CH 2 ) 2 SMe (n = 2 L 1 or 3 L 2 ) were prepared. Their structures were assigned on the basis of electronic absorption and 1 H NMR spectra and the molecular structures of cis-α-[CoCl 2 {rac(P)-L 1 }]BF 4 and trans-[CoCl 2 {meso(P)-L 2 }]BF 4 were determined by single-crystal X-ray diffraction. The last two complexes comprise a slightly distorted octahedron with bond distances Co–P 2.210(1), Co–S 2.254(1) and Co–Cl 2.281(1) and Co–P 2.227(3), Co–S 2.327(3) and Co–Cl 2.241(3) ∠ (all averages) respectively. The differences in Co–S and Co–Cl bond distances are attributable to the strong trans influence of the phosphino group. Acetylacetonate complexes of rac(P)-SPPS in organic solvents form equilibrium mixtures of the cis-α and cis-β isomers, the molar ratio in MeNO 2 solution at 60 °C being 2∶1 for the L 1 complex and 3∶2 for the L 2 complex.