Ionic‐Liquid‐Based Synthesis of the Germanium‐Iron Carbonyls FeI₄{GeI₃Fe(CO)₃}₂ and (GeI₃)₂Fe(CO)₄

Abstract

Dark red and brick red transparent crystals of FeI4{GeI3Fe(CO)3}2 (1) and (GeI3)2Fe(CO)4 (2) were obtained by reacting GeI4 and Fe2(CO)9 or Fe3(CO)12 in a mixture of [BMIM]Cl and AlCl3 as ionic liquid (BMIm = 1‐butyl‐3‐methylimidazolium). According to X‐ray structure analysis based on single crystals, the title compounds exhibit cluster units with Fe–Ge bonds. FeI4{GeI3Fe(CO)3}2 consists of two GeI2I1/2‐Fe(CO)3I2/2 units that are interlinked by a distorted octahedral FeI6/2 group. (GeI3)2Fe(CO)4 consists of two GeI3 units that are connected by a square planar Fe(CO)4 group with a linear Ge–Fe–Ge unit. Depending on the synthesis conditions, interestingly, (GeI3)2Fe(CO)4 crystallizes either in P21/n (2a) or in P1 (2b). 2a exhibits a more dense packing, whereas 2b exhibits shorter intermolecular I–I distances. Both title compounds are temperature labile and highly sensitive to oxygen, moisture and illumination, including X‐ray irradiation. They decompose with release of CO in absence of certain CO atmosphere. In addition to crystal structure analysis the compounds were characterized by energy dispersive X‐ray (EDX) analysis, thermogravimetry (TG) and infrared spectroscopy (FT‐IR).

Ge−Fe Carbonyl Cluster Compounds: Ionic Liquids‐Based Synthesis, Structures, and Properties

“…After approximately two weeks, bright‐red needles of the already known compound Fe(CO) 4 {GeI 3 } 2 ( I ) were formed. This finding is not surprising since Fe(CO) 4 {GeI 3 } 2 was also directly formed in absence of Ph 3 GeCl [12] . 1 crystallizes in the monoclinic space group P2 1 /c and contains [BMIm] + cations and [(FeI 2 ) 0.75 {Fe(CO) 2 I(GeI 3 ) 2 } 2 ] 2− anions (Table 1, Figure 2).…”

“…First of all, a decisive parameter to influence the realization of a specific carbonyl cluster compound in the Ge−Fe system relates to the type, and especially, to the Lewis acidity of the IL (Figure 4). Already for the previously reported compounds, we have observed that (GeI 3 ) 2 Fe(CO) 4 ( I ) was obtained with a 1 : 1 mixture of [BMIm]Cl/AlCl 3 [12] . Upon increasing the amount of AlCl 3 to a 1 : 2 a mixture of [BMIm]Cl/AlCl 3 , GeI 3 Fe(CO) 3 } 2 FeI 4 ( II ) was formed [12] .…”

“…For the system Ge−Fe, we could already realize three different carbonyl cluster compounds with Ge−Fe bonds. These are (Fe(CO) 4 (GeI 3 ) 2 , FeI 4 {GeI 3 Fe(CO) 3 } 2 , and Ge 12 {Fe(CO) 3 } 8 (μ‐I) 4 , [9,12] which were all prepared by ionic‐liquid‐based synthesis. Based on the success of this synthesis route, we have examined the Ge−Fe system in more detail, resulting in six additional compounds: [EMIm][Fe(CO) 3 I(GeI 3 )], [EHIm][Fe(CO) 3 I(GeI 3 )], [BMIm][GeI 2 {Fe(CO) 4 } 2 (μ‐I)][AlCl 4 ] 2 , [GeI 2 {Fe(CO) 4 } 2 (μ‐I)][Fe(AlBr 4 ) 3 ], [BMIm] 2 [(FeI 2 ) 0.75 {Fe(CO) 2 I(GeI 3 ) 2 } 2 ], and [EHIm][Fe(CO) 4 (GeI 2 ) 2 Fe(CO) 3 GeI 3 ] (EMIm: 1‐ethyl‐3‐methylimidazolium, EHIm: 1‐ethylimidazolium, BMIm: 1‐butyl‐3‐methylimidazolium).…”

“…Selected examples comprise the adamantane‐type Fe 4 Sn 6 cluster core in [{Fe(CO) 3 } 4 {SnI} 6 I 4 ] 2− , [8] the Ge 12 Fe 8 germanium‐iron cluster core in Ge 12 {Fe(CO) 3 } 8 (μ‐I) 4 , [9] [SnI 8 {Fe(CO) 4 } 4 ] 2+ containing a highly coordinated Sn +II I 8 subunit, [10] or an anti‐(WCl 2 ) 6 ‐like [(Pb 6 I 8 ){Mn(CO) 5 } 6 ] 2− cluster [11] . Especially, reactions of Fe(CO) 5 or Fe 2 (CO) 9 with Lewis‐acidic metal iodides (e. g., SnI 4 , GeI 4 ) resulted in a series of novel carbonyl cluster compounds that are specifically designated by the absence of alkyl and aryl ligands [8–12] . Thus, a synthesis of such highly labile compounds is possible although the electronic and/or sterical stabilization of alkyl/aryl ligands is missing [13]…”

Pseudohalogen Chemistry in Ionic Liquids with Non‐innocent Cations and Anions

“…Besides application in classic solid state chemistry, ILs can be used as reaction media to prepare (oligomeric) metal complexes, metal organic frameworks, coordination polymers [25–35] or cluster compounds incorporating main group elements [36–41] . Within SPP 1708, the synthesis of intermetallic cluster and nanoparticles, [3,42–56] the controlled synthesis of polyanions and cations, [57–61] solvent‐free chalcogenidometal‐containing materials, [62–75] deposition of nanocrystalline materials, [76–80] ionic liquids as precursors for inorganic materials, [81–83] ionic‐liquid‐modified hybrid materials, [84–87] as well as the low‐temperature synthesis of thermoelectric materials [88–92] were investigated. Moreover, theoretical [93–106] and solubility [107–114] aspects during the synthesis process were studied.…”