Synthesis and structure of [EtV~(+centre dot)]5[Ag_(12)(mu_(12)-Ag){mu_3-Fe(CO)_4}_8] centre dot 4 DMF:the missing [Ag_(13)Fe_8(CO)_(32)]~(5-)pentaanion as ethylviologen(EtV)salt

摘要

The reaction in MeCN of [Ag_5Fe_4(CO)_(16)]~(3-)in its Na~+ salt with EtV~(2+)2I~-leads to precipitation of [EtV~(+centre dot)]_5[Ag_(13)Fe_8(CO)_(32)].Its DMF solution is deep-green,displays infrared carbonyl absorptions very similar to those of the paramagnetic [Ag_(13)Fe_8(CO)_(32)]~(4-)tetraanion and only shows the EPR signal of the EtV~(+centre dot)radical cation.The colour of the solution and the IR spectrum suggest the presence of a charge-transfer salt.Crystallisation of the precipitate from DMF and isopropyl alcohol affords brown crystals of [EtV~(+centre dot)]_5[Ag_(13)Fe_8(CO)_(32)]_4 DMF,which are insoluble in all organic solvents,DMF included.X-ray analysis of the crystals provided the structure of the yet uncharacterised [Ag_(13)Fe_8(CO)_(32)]~(5-)pentaanion and allowed the first determination of the structure of the ethylviologen radical cation.The latter gives rise to stacks in which weakly-bound pentameric moieties are clearly identifiable.The structural findings are implemented by spectroscopic measurements and EHMO calculations.