The synthesis, structure, and full characterization of a redox‐switchable germylene based on a 3ferrocenophane ligand arrangement, Fc(NMes)2Ge (4), is presented. The mesityl (Mes)‐substituted title ...compound is readily available from Fc(NHMes)2 (2) and Ge{N(SiMe3)2}2, or from the dilithiated, highly air‐ and moisture‐sensitive compound Fc(NLiMes)2⋅3 Et2O (3) and GeCl2. Cyclic voltammetry studies are provided for 4, confirming the above‐mentioned view of a redox‐switchable germylene metalloligand. Although several 1:1 RhI and IrI complexes of 4 (5–7) are cleanly formed in solution, all attempts to isolate them in pure form failed due to stability problems. However, crystalline solids of Mo(κ1Ge‐4)2(CO)4 (8) and W(κ1Ge‐4)2(CO)4 (9) were isolated and fully characterized by common spectroscopic techniques (8 by X‐ray diffraction). DFT calculations were performed on a series of model compounds to elucidate a conceivable interplay between the metal atoms in neutral and cationic bimetallic complexes of the type Rh(κ1E‐qE)(CO)2Cl0/+ (qE=Fc(NPh)2E with E=C, Si, Ge). The bonding characteristics of the coordinated Fc‐based metalloligands (qE/qE+) are strongly affected upon in silico oxidation of the calculated complexes. The calculated Tolman electronic parameter (TEP) significantly increases by approximately 20 cm−1 (E=C) to 25 cm−1 (E=Si, Ge) upon oxidation. The change in the ligand‐donating abilities upon oxidation can mainly be attributed to Coulombic effects, whereas an orbital‐based interaction appears to have only a minor influence.
The redox‐switchable germylene Fc(NMes)2Ge, based on a 3ferrocenophane ligand arrangement, alongside some transition‐metal complexes are reported. The changes in the ligating properties upon oxidation were elucidated by DFT calculations on neutral and cationic bimetallic model complexes.
The isolation and characterization of the first silicon analogue of the aromatic cyclobutadiene dication is reported. The aromatic 2π-electron tetrasilacyclobutadiene dication in (L Ph Si)4(BPh4)2 ...(L Ph = PhC(NtBu)2) has been obtained in a simple and straightforward synthesis, from L Ph SiCl, L Ph SiSiL Ph and NaBPh4, and fully characterized. The molecular structure reveals a four-membered Si4-dication in an almost perfect square-planar geometry. Theoretical calculations support the interpretation of the title compound as a classical 2π-aromatic species with a singlet ground state.
Selective substitution and insertion reactions of silylenes into the cyclo-P5 ring of Cp*Fe(η5-P5) are reported. The selective substitution of one P atom by an isoelectronic LSi fragment (L = PhC(N ...t Bu)2) leads to (η4-P4SiL)FeCp* and LSi(Cl)P-SiL(Cl)2. To elucidate the reaction mechanism, {LSi(N(SiMe3)2)}{(η4-P5)FeCp*}, in which the silicon atom binds to the cyclo-P5 ring, was synthesized as a model compound for the reaction intermediate. The insertion of LSi-SiL into the cyclo-P5 ring of Cp*Fe(η5-P5) resulted in {η4-P5(SiL)2}FeCp* featuring a cyclo-P5(SiL)2 ring, which corresponds to the largest silicon–polyphosphorus ring known in a complex.
We report on the successful synthesis of Si5Mes6 (Mes = 2,4,6-trimethylphenyl), which consists of an archetypal 1.1.1 cluster core featuring two ligand-free, “inverted tetrahedral” bridgehead silicon ...atoms. The separation between the bridgehead Si atoms is much longer, and the bond strength much weaker, than usually observed for a regular Si−Si single bond. A detailed analysis of the electronic characteristics of Si5Mes6 reveals a low-lying excited triplet state, indicative of some biradical(oid) character. Reactivity studies provide evidence for both closed-shell and radical-type reactivity, confirming the unusual nature of the stretched silicon−silicon bond in this “nonclassical” molecule.
The novel tin(II) oxychloride BMImSn5O2Cl7 (BMIm = 1-butyl-3-methylimidazolium) is obtained by the room-temperature reaction (25 °C) of black SnO and SnCl2 in BMImCl/SnCl2 as an ionic liquid. The ...title compound can be described as composed of noncharged, infinite ∞ 1(Sn2OCl2) strands that are embedded in a saline matrix of BMIm+ and SnCl3−. The ∞ 1(Sn2OCl2) strands consist of a backbone of edge-sharing OSn4/2 tetrahedra, which represent one-dimensional (1D) strands cut out of the layer-type structure of SnO. In BMImSn5O2Cl7, the ∞ 1(Sn2OCl2) strands, which mimic a 1D semiconductor, are terminated by chlorine atoms, whereas they are interconnected by oxygen atoms in the 2D semiconductor SnO. The view of the noncharged ∞ 1(Sn2OCl2) strands in a saline BMImSnCl3 matrix is validated by dissolution experiments. Thus, electron microscopy and Raman spectroscopy show a deconstruction of BMImSn5O2Cl7 single crystals after treatment with chloroform with a dissolution of BMImSnCl3, the formation of SnCl2 needles, and tin oxide as a solid remain.
The heteroleptic iodo complexes (DIP2pyr)MI(THF) n (M = Ca, Sr (n = 3); Ba (n = 4); (DIP2pyr)− = 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl) were synthesized by reaction of (DIP2pyr)K ...with anhydrous alkaline earth metal diiodides. All complexes are monomeric in the solid state. A κ3-coordination mode of the (DIP2pyr)− ligand was observed for the strontium and the barium compounds, while the analogous calcium derivative is κ2-coordinated in the solid state. However, VT-1H NMR studies of (DIP2pyr)CaI(THF)3 indicate a symmetrically coordinated (DIP2pyr)− ligand in solution. Computational studies confirm the different coordination modes in solution and in the solid state. The preferred κ2-coordination mode observed in the solid state might be a result of temperature or/and crystal-packing effects. Furthermore, the calcium and strontium amido complexes (DIP2pyr)M{N(SiMe3)2}(THF)2 (M = Ca, Sr) were prepared by reaction of (DIP2pyr)MI(THF) n (M = Ca, Sr (n = 3)) with K{N(SiMe3)2}. Both compounds were investigated for the intramolecular hydroamination of aminoalkenes. Both catalysts showed a good activity, and the best results were obtained for the calcium complex (DIP2pyr)Ca{N(SiMe3)2}(THF)2.
The positively charged and weakly polarizable s‐block metals commonly do not usually have phosphine ligands in molecular complexes. Herein, we report mono‐ and dinuclear small diamidophosphine ...complexes of the alkaline‐earth metals Mg, Ca, and Sr, which were prepared from simple precursors and a phosphine‐functionalized diamine ligand N,N‐bis(2‐(diphenyl‐phosphino)phenyl)ethane‐1,2‐diamine (PNHNHP). The alkaline‐earth metal based complexes (PNNP)Mg2 and (PNNP)M(thf)3 (M=Ca, Sr), exhibit unusual coordination spheres and show bright fluorescence, both in the solid state and in solution. For comparison, the even stronger luminescent Al and Zn complexes (PNNP)Zn2 and (PNNP)AlCl were prepared. Emission lifetimes in the nanosecond range and high photoluminescence quantum yields up to 93 % are observed at room temperature.
Unusual coordination spheres: As phosphine ligands are not commonly used in s‐block chemistry, the preparation of mono‐ and dinuclear diamidophosphine complexes of the alkaline‐earth metals, aluminum, and zinc gives rise to unusual coordination spheres. All compounds feature bright fluorescence both in the solid state and in solution, as well as high quantum yields up to 93 % at room temperature.
The synthesis of a 1,2,3,4-tetramethylcyclopentadienyl (Cp
4
) substituted four-membered N-heterocyclic silylene {PhC(N
t
Bu)
2
}Si(C
5
Me
4
H) is reported first. Then, selected reactions with ...transition metal and a calcium precursor are shown. The proton of the Cp
4
-unit is labile. This results in two different reaction pathways: (1) deprotonation and (2) rearrangement reactions. Deprotonation was achieved by the reaction of {PhC(N
t
Bu)
2
}Si(C
5
Me
4
H) with suitable zinc precursors. Rearrangement to {PhC(N
t
Bu)
2
}(C
5
Me
4
)SiH, featuring a formally tetravalent silicon R
2
C&z.dbd;Si(R′)-H unit, was observed when the proton of the Cp
4
ring was shifted from the Cp
4
-ring to the silylene in the presence of a Lewis acid. This allows for the coordination of the Cp
4
-ring to a calcium compound. Furthermore, upon reaction with transition metal dimers MCl(cod)
2
(M = Rh, Ir; cod = 1,5-cyclooctadiene) the proton stays at the Cp
4
-ring and the silylene reacts as a sigma donor, which breaks the dimeric structure of the precursors.
A cyclopentadienyl functionalized silylene or its derivatives can be coordinated in all three forms: silylene (
A
), anion (
B
), and sila fulvene (
C
).
To study the influence of heteroatoms on the photophysical properties of divalent Eu and Sr complexes, the synthesis of the phospholyl and arsolyl compounds {(Dtp)(thf)M}2{μ-η8:η8-C8H8} (M = EuII ...and SrII; Dtp = 3,4-dimethyl-2,5-bis(tert-butyl)phospholyl) and {(Dtas)(thf)M}2{μ-η8:η8-C8H8} (M = EuII and SrII; Dtas = 3,4-dimethyl-2,5-bis(tert-butyl)arsolyl) is reported. Organometallic compounds of divalent europium with P and As heterocyclic ligands have not been described previously. They were prepared by salt elimination reactions from potassium phospholyl or arsolyl, K2C8H8, and EuI2(thf)2 or SrI2. Photophysical properties were investigated alongside a reference cyclopentadienyl complex with a comparable structure. Critically, the influence of the heteroatom on the photoluminescence emission and excitation and quantum yields of the complexes is significant. Density functional theory calculations were performed to rationalize the ligand influences.
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