Coordination chemistry of polynitriles. Part 9. Decacyanoferrocene revisited: crystal and molecular structure of cis-[{C5(CN)5}2(MeCN)4Fe

Karlheinz Sünkel,Tobias Blockhaus

doi:10.1107/s2053229622000365

Abstract

The reaction of Ag[C5(CN)5] with anhydrous FeCl2 in acetonitrile leads to colourless crystals of tetrakis(acetonitrile-κN)bis(pentacyanocyclopentadienido-κN)iron(II) acetonitrile 1.8-solvate, [Fe(C10N5)2(CH3CN)4]·1.8CH3CN or cis-[{C5(CN)5}2(MeCN)4Fe]·1.8MeCN. The compound crystallizes in the triclinic space group P-1 as monomers, which exhibit weak C-H...N and π-π interactions. The crystals contain ca 20% solvent-accessible voids, which are nearly completely filled by two MeCN molecules.

Highlights

The term ‘decacyanoferrocene’ appeared first in a publication about ‘diazotetracyanocyclopentadiene’ (Webster, 1966) and later in two US patents by the same author (Webster, 1970, 1974)
The compound crystallizes in the triclinic space group P1 as monomers, which exhibit weak C—HÁ Á ÁN and – interactions
It was used for the reaction product from silver pentacyanocyclopentadienide and FeCl2 in acetonitrile, which led to ‘light-green crystals of decacyanoferrocene’, which were characterized, after drying at 112 C under vacuum, by elemental analysis and IR and UV spectroscopy as ‘C20N10FeÁxH2O’

Summary

Introduction

The term ‘decacyanoferrocene’ appeared first in a publication about ‘diazotetracyanocyclopentadiene’ (Webster, 1966) and later in two US patents by the same author (Webster, 1970, 1974) It was used for the reaction product from silver pentacyanocyclopentadienide and FeCl2 in acetonitrile, which led to ‘light-green crystals of decacyanoferrocene’, which were characterized, after drying at 112 C under vacuum, by elemental analysis and IR and UV spectroscopy as ‘C20N10FeÁxH2O’. Within the last 15 years, the coordination chemistry of the pentacyanocyclopentadienide anion has been studied intensively by us and others (Sunkel & Reimann, 2013; Sunkel & Nimax, 2018; Nimax et al, 2018; Blockhaus & Sunkel, 2021; Bacsa et al, 2011; Less et al, 2013) These studies showed that [C5(CN)5]À could behave either as a noncoordinating anion or use one to its five cyano groups for coordination, sometimes even in a bridging 2-1:1 fashion. All attempts to obtain crystals of this product by dissolution in a noncoordinating solvent met with failure

Refinement

Results and discussion

Conclusion