Sulfur-Bridged Co~(III)Pt~(II)Co~(III) Trinuclear Complexes with Mixed Aliphatic and Aromatic Thiolate Ligands:Effect of Nonbridging Ligands on the Homochiral Linkage of Cobalt(lll) Octahedrons by Platinum(ll)

摘要

The reaction of [Ni{Co(aet)_2(pyt)}_2]~(2+) (aet = 2-aminoethanethiolate,pyt = 2-pyridinethiolate) with [PtCI_4]~(2-) gave an S-bridged Co~(III)Pt~(II)Co~(III) trinuclear complex composed of two [Co(aet)_2(pyt)] units,[Pt{Co(aet)_2(pyt)}_2]~92+) ([1]~(2+)).When a 1:1 mixture of [Ni{Co(aet)_2(pyt)}_2]~(2+) and [Ni{Co(aet)_2(en)}_2]~(4+) was reacted with [PtCI_4]~(2-),a mixed-type S-bridged Co~(III)Pt~(II)Co(III) complex composed of one [Co(aet)_2(pyt)] and one [Co(aet)_2(en)]~+ units,[Pt{Co(aet)_2(en)}-{Co(aet)_2(pyt)}]~(3+) ([2]~+),was produced,together with [1]~(2+) and [Pt{Co(aet)_2(en)}_2]~(4+).The corresponding Co~(III)Pt~(II)-Co trinuclear complexes containing pymt (2-pyrimidinethiolate),[Pt{Co(aet)_2(pymt)}_2]~92+) ([3]~(2+)) and [Pt{Co(aet)_2-(en)}{Co(aet)_2(pymt)}]~(3+) ([4]~(3+)),were also obtained by similar reactions,using [Ni{Co(aet)_2(pymt)}_2]~(2+) instead of [Ni{Co(aet)_2(pyt)}_2]~(2+).While [Pt{Co(aet)_2(en)}_2]~(4+) formed both the AA (meso) and AA/AA (racem/c) forms in a ratio of ca.1:1,the preferential formation of the AA/AA form was observed for [1]~(2+) (ca.DELTALAMBDA:DELTADELTA/LAMBDALAMBDA = 1:3) and [2]~(3+) (ca.DELTA_(en)LAMBDA_(PYT)/LAMBDA_en)DELTA_(pyt):DELTALAMBDA/LAMBDALAMBDA = 1:2).Furthermore,[3]~(2+) and [4]~(3+) predominantly formed the DELTADELTA/LAMBDALAMBDA form.These results indicate that the homochiral selectivity for the S-bridged Co~(III)Pt~(II)Co~(III) trinuclear complexes composed of two octahedral [Co(aet)_2(L)]~0 or + units is enhanced in the order L = en < pyt < pymt.The isomers produced were separated and optically resolved,and the crystal structures of the meso-type AA-[1]CI_2-4H_20 and the spontaneously resolved AA-[4](CI0_4)_3-H_20 were determined by X-ray analyses.In AA-[1]~(2+),the A and A configurational mer(S)-trans(N_(aet))-[Co(aet)_2(pyt)] units are linked by a square-planar Pt~(II) ion through four aet S atoms to form a linear-type S-bridged trinuclear structure.In DELTADELTA-[4]~(3+),a similar linear-type trinuclear structure is constructed from the DELTA-met(S)-trans(N_(aet))-[Co(aet)_2(pymt)] and LAMBDA-C_2-cis(S)-[Co(aet)_2(en)]~+ units that are bound by a Pt ion with a slightly distorted square-planar geometry through four aet S atoms.