Transformations in Transition-Metal Carbonyls Containing Arsenic: Exploring the Chemistry of [Et4N]2[HAs{Fe(CO)4}3] in the Search for Single-Source Precursors for Advanced Metal Pnictide Materials

The chemistry of [Et4N]2[HAs­{Fe­(CO)4}3] ([Et4N]2[I]) has
been explored with the goal of preparing heterometallic compounds
for use as single-source precursors to metal pnictide phases. Reaction
of AgPF6 with [Et4N]2[I] in THF produces [Et4N]­[HAs­{Fe2(CO)6(μ-CO)­(μ-H)}­{Fe­(CO)4}] in 12% yield, but the
yield is improved to 71% if the reaction is carried out with added
[Et4N]­[HFe­(CO)4]. The structure possesses rare
As–H and {Fe2(CO)6(μ-CO)­(μ-H)}
fragments. The addition of [CPh3]­[BF4] to [Et4N]2[I] in THF gives [Et4N]­[Fe3(CO)9(μ-CO)­{μ3-AsFe­(CO)4}] in 45% yield. This compound is also obtained
as a minor product from oxidation of [Et4N]2[I] with 1 equiv of AgPF6, AsCl3, SbCl3, or BiCl3 in THF. The cluster consists
of an Fe3As tetrahedron with an isolated Fe­(CO)4 unit bound to the arsenic in a spiked-tetrahedral arrangement. Refluxing
[Et4N]2[I] with 1 equiv of AgPF6 in THF produces [Et4N]­[(μ-H)2Fe3(CO)9)­{μ3-AsFe­(CO)4}]. This cluster is similar to [Et4N]­[Fe3(CO)9(μ-CO)­{μ3-AsFe­(CO)4}] with the bridging CO being replaced by two bridging hydride ligands.
Treatment of [Et4N]2[I] with 1
equiv of Mn­(CO)5Br in THF gives the spirocyclic compound
[Et4N]­[{FeMn­(CO)8}­(μ4-As)­{Fe2(CO)6(μ-CO)­(μ-H)}] in 52% yield. Refluxing
this cluster in the presence of triethylamine and an additional 1.8
equiv of Mn­(CO)5Br gives [Et4N]­[Fe3(CO)9(μ-CO)­{μ3-AsMn­(CO)4Br-cis}] in low yield. Alternatively, treating [Et4N]­[{FeMn­(CO)8}­(μ4-As)­{Fe2(CO)6(μ-CO)­(μ-H)}] with triflic acid or an
oxidant ([Ox] = Cu+, Ag+, Cu2+, CPh3+) in dichloromethane produces the two neutral
compounds (μ-H)2Fe3(CO)9{μ3-AsMn­(CO)5} and {FeMn­(CO)8}­(μ4-As)­{Fe2(CO)8} in trace amounts and
high yield, respectively. The former could be removed by treatment
with base in nonpolar solvents. Neutral {FeMn­(CO)8}­(μ4-As)­{Fe2(CO)8} can then be isolated
by filtration and evaporation in 74% yield. An improved synthesis
of the known [Fe3(CO)9(μ-CO)­{μ3-PFe­(CO)4}]− as its tetraethylammonium
salt is also included. All compounds were characterized by spectroscopy,
by ESI-mass spectrometry, and by single-crystal X-ray diffraction.

对[Et4N]2[HAs{Fe(CO)4}3] ([Et4N]2[I])的化学性质进行了研究，旨在制备适用于作为金属氮化物相单源前驱体的异金属化合物。在四氢呋喃中，AgPF6与[Et4N]2[I]反应，生成[Et4N][HAs{Fe2(CO)6(μ-CO)(μ-H)}{Fe(CO)4}]，产率为12%，若在反应中加入[Et4N][HFe(CO)4]，产率可提升至71%。该结构具有罕见的As-H和{Fe2(CO)6(μ-CO)(μ-H)}片段。在四氢呋喃中，将[CPh3][BF4]加入[Et4N]2[I]，可生成[Et4N][Fe3(CO)9(μ-CO){μ3-AsFe(CO)4}]，产率为45%。该化合物也是通过在四氢呋喃中用等摩尔量的AgPF6、AsCl3、SbCl3或BiCl3氧化[Et4N]2[I]所得的次要产物。该簇由一个Fe3As四面体组成，其中孤立的Fe(CO)4单元以尖锥四面体结构连接到砷上。在四氢呋喃中，将[Et4N]2[I]与等摩尔量的AgPF6回流，生成[Et4N][(μ-H)2Fe3(CO)9){μ3-AsFe(CO)4}]。该簇与[Et4N][Fe3(CO)9(μ-CO){μ3-AsFe(CO)4}]相似，但桥连的CO被两个桥连氢化物配体取代。在四氢呋喃中，用1等摩尔量的Mn(CO)5Br处理[Et4N]2[I]，生成螺环化合物[Et4N][{FeMn(CO)8}(μ4-As){Fe2(CO)6(μ-CO)(μ-H)}]，产率为52%。在存在三乙胺和额外的1.8等摩尔量的Mn(CO)5Br的情况下，回流该簇，产率较低地生成[Et4N][Fe3(CO)9(μ-CO){μ3-AsMn(CO)4Br-顺式}]。或者，用三氟乙酸或氧化剂([Ox] = Cu+、Ag+、Cu2+、CPh3+)在二氯甲烷中处理[Et4N][{FeMn(CO)8}(μ4-As){Fe2(CO)6(μ-CO)(μ-H)}]，分别以痕量和高效产率生成两个中性化合物(μ-H)2Fe3(CO)9{μ3-AsMn(CO)5}和{FeMn(CO)8}(μ4-As){Fe2(CO)8}。前者可以通过在非极性溶剂中用碱处理去除。中性{FeMn(CO)8}(μ4-As){Fe2(CO)8}可以通过过滤和蒸发以74%的产率分离。还包括已知[Fe3(CO)9(μ-CO){μ3-PFe(CO)4}]−的改进合成，其作为四乙铵盐。所有化合物均通过光谱学、电喷雾质谱和单晶X射线衍射进行了表征。