the-synthesis-sn10-si-sime3-3-42-using-metastable-sn-i-halide

The Synthesis of [Sn10(Si(SiMe3)3)4]2- Using a Metastable Sn(I) Halide Solution Synthesized via a Co-condensation Technique

The number of well-characterized metalloid tin clusters, synthesized by applying the disproportionation of a metastable Sn(I) halide in the presence of a ...

University of Tübingen

Very recently it was shown that Sn monohalides can be prepared in preparative scale applying a preparative co-condensation technique. Here, a first reaction of Sn(i)Br is presented leading to the metalloid cluster compound Sn(10)[Si(SiMe(3))(3)](6) 1. This reaction can be seen as a first step to metalloid cluster compounds applying the disproportionation reaction of a metastable Sn monohalide. The ten tin atoms in 1 are arranged in the form of a centaur polyhedron, representing a novel structural motif in tin chemistry. The structural and electronic properties of 1 and its relation to the phase transition alpha<-->beta tin are discussed with the aid of quantum chemical calculations as well as (119)Sn Mössbauer spectroscopy.

The formation of a metalloid Sn(10)[Si(SiMe(3))(3)](6) cluster compound and its relation to the alpha<-->beta tin phase transition.

In the course of the disproportionation reaction of a monohalide beside metalloid clusters like Sn(10)[Si(SiMe(3))(3)](6) also molecular compounds with an average oxidation state of the tin atoms larger than one must be present. First results of such oxidized species are presented where the bonding is strongly influenced by the steric bulk of the ligands leading to the shortest tin-tin double bond.

Sn[Si(SiMe3)3]3- and Sn3[Si(SiMe3)3]4: first insight into the mechanism of the disproportionation of a tin monohalide gives access to the shortest double bond of tin.

[Sn4Si{Si(SiMe3)3}4{SiMe3}2]: a model compound for the unexpected first-order transition from a singlet biradicaloid to a classical bonded molecule.

The disproportionation reaction of the subvalent metastable halide SnBr proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Hence, the neutral metalloid cluster compound Sn(10)[Si(SiMe(3))(3)](6) (3) was synthesized from the reaction of SnBr with LiSi(SiMe(3))(3). In the course of the reaction anionic clusters might also be present, and we now present the first anionic cluster compound {Sn(8)E[Si(SiMe(3))(3)](3)}(-) (E = Si, Sn), where one position in the cluster core is occupied by a silicon or a tin atom, giving further insight into structural variations of E(9) cages in metalloid group 14 cluster compounds.

{Sn9[Si(SiMe3)3]3}− and {Sn8Si[Si(SiMe3)3]3}−: variations of the E9 cage of metalloid group 14 clusters.

The disproportionation reaction of the subvalent metastable halide SnCl proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Now we present the synthesis and structural characterization of the anionic metalloid cluster compound [Sn(9)[Si(SiMe(3))(3)](2)](2-)3 where the oxidation state of the tin atoms is zero. Quantum chemical calculations as well as Mössbauer spectroscopic investigations show that three different kinds of tin atoms are present within the cluster core. Compound 3 is highly reactive as shown by NMR investigations, thus being a good starting material for further ongoing research on the reactivity of such partly shielded metalloid cluster compounds.

{Sn9[Si(SiMe3)3]2}2-: a metalloid tin cluster compound with a Sn9 core of oxidation state zero.

The reaction of a Sn(I) Cl solution with LiSi(SiMe3 )3 gave the anionic metalloid tin cluster {Sn10 [Si(SiMe3 )3 ]4 }(2-) (7) in good yield. The arrangement of the ten tin atoms in the cluster core can be described as a distorted centaur polyhedron. Quantum chemical calculations suggest that there are 26 bonding electrons in the cluster core, which may be described as an arachno cluster in agreement with Wade's rules. NMR and mass spectrometric investigations showed that 7 is highly reactive, which may be due to the open ligand shell. The easily available tin atoms in 7 thereby open the door to further subsequent reactions, in which 7 may act as a building block to larger cluster aggregates.

{Sn10 [Si(SiMe3 )3 ]4 }(2-) : A highly reactive metalloid tin cluster with an open ligand shell.

Chemistry that uses metalloid tin clusters as a starting material is of fundamental interest towards understanding the reactivity of such compounds. Since we identified {Sn10[Si(SiMe3)3]4}(2-) 7 as an ideal candidate for such reactions, we present a further step in the understanding of metalloid tin cluster chemistry. In contrast to germanium chemistry, ligand elimination seems to be a major reaction channel, which leads to the more open metalloid cluster {Sn10[Si(SiMe3)3]3}(-) 9, in which the Sn core is only shielded by three Si(SiMe3)3 ligands. Compound 9 is obtained through different routes and is crystallised together with two different countercations. Besides the structural characterisation of this novel metalloid tin cluster, the electronic structure is analysed by (119)Sn Mössbauer spectroscopy. Additionally, possible reaction pathways are discussed. The presented first step into the chemistry of metalloid tin clusters thus indicates that, with respect to metalloid germanium clusters, more reaction channels are accessible, thereby leading to a more complex reaction system.

Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}(2-): Ligand Elimination versus Coordination Chemistry.

The influence of the stabilizing ligand on the physical and chemical properties of a metalloid cluster compound is important for nanotechnology as metalloid clusters are ideal model compounds for metal nanoparticles. Here we present the synthesis of a differently substituted metalloid {Ge9R3}(-) cluster: {Ge9[Si(SiMe3)2(SiPh3)]3}(-) 1, which is obtained in good yield by the reaction of K4Ge9 with ClSi(SiMe3)2(SiPh3). 1 is characterized via NMR and mass spectrometry, but crystallization is hindered. However, the reaction with HgCl2 gives the neutral compound HgGe18[Si(SiMe3)2(SiPh3)]6 2, which can be crystallized and structurally characterized. The presented results are a first step for the investigation of the ligand's influence on the properties of a metalloid germanium cluster compound.

{Ge9[Si(SiMe3)2(SiPh3)]3}(-): Ligand Modification in Metalloid Germanium Cluster Chemistry.

The oxidation of [Ge9(Hyp)3](-) (Hyp=Si(SiMe3 )3) with an Fe(II) salt leads to Ge18 (Hyp)6 (1), the largest Group 14 metalloid cluster that has been structurally characterized to date. The arrangement of the 18 germanium atoms in 1 shows similarities to that found in the solid-state structure Ge(cF136). Furthermore, 1 can be described as a macropolyhedral cluster of two Ge9 units. Quantum-chemical calculations further hint at a strained arrangement so that 1 can be considered as a first trapped intermediate on the way from Ge9 units to elemental germanium with the clathrate-II structure (Ge(cF136)).

The Largest Metalloid Group 14 Cluster, Ge18[Si(SiMe3)3]6 : An Intermediate on the Way to Elemental Germanium.

Recently the metalloid cluster compound [Ge9Hyp3]- 1 (Hyp = Si(SiMe3)3), was oxidatively coupled by an Iron(II) salt to give the largest metalloid group 14 cluster Ge18Hyp6. The redox chemistry is also possible with different transition metal salts TM2+ (TM = Fe, Co, Ni) to give the TM+1 complexes [Fe(dppe)2][Ge9Hyp3] 3 (dppe = 1,2-bis(diphenylphosphino)ethane), [Co(dppe)2][Ge9Hyp3] 4, {Ni(dppe)[Ge9Hyp3]} 5 and {[Ni(dppe)]2[Ge9Hyp3]}+ 6. Such a redox reaction does not proceed for Mn, where a salt metathesis gives the first open shell [Hyp3Ge9-M-Ge9Hyp3] cluster 2 (M = Mn). The bonding of the transition metal atom to 1 is also possible for Ni, where one or even two nickel atoms can bind to 1. In contrast to this in case of the Fe and Co compound 3 and 4 the transition metal atom is not bound to the Ge9 core of 1. The synthesis and the experimentally determined structures of 2 - 6 are presented. Additionally the bonding within 2 - 6 are analyzed and discussed with the aid of EPR measurements and quantum chemical calculations.

Article	Year
The formation of a metalloid Sn(10)[Si(SiMe(3))(3)](6) cluster compound and its relation to the alpha<-->beta tin phase transition. Dalton transactions (Cambridge, England : 2003)\| PubMed ID: 20449434	2010
Sn[Si(SiMe3)3]3- and Sn3[Si(SiMe3)3]4: first insight into the mechanism of the disproportionation of a tin monohalide gives access to the shortest double bond of tin. Chemical communications (Cambridge, England)\| PubMed ID: 20717582	2010
[Sn4Si{Si(SiMe3)3}4{SiMe3}2]: a model compound for the unexpected first-order transition from a singlet biradicaloid to a classical bonded molecule. Angewandte Chemie (International ed. in English)\| PubMed ID: 21698735	2011
{Sn9[Si(SiMe3)3]3}− and {Sn8Si[Si(SiMe3)3]3}−: variations of the E9 cage of metalloid group 14 clusters. Inorganic chemistry\| PubMed ID: 22436071	2012
{Sn9[Si(SiMe3)3]2}2-: a metalloid tin cluster compound with a Sn9 core of oxidation state zero. Inorganic chemistry\| PubMed ID: 22804582	2012
{Sn10 [Si(SiMe3 )3 ]4 }(2-) : A highly reactive metalloid tin cluster with an open ligand shell. Chemistry (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 25430476	2015
Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}(2-): Ligand Elimination versus Coordination Chemistry. Chemistry (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 25892180	2015
Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}(2-): Ligand Elimination versus Coordination Chemistry. Chemistry (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 26095993	2015
{Ge9[Si(SiMe3)2(SiPh3)]3}(-): Ligand Modification in Metalloid Germanium Cluster Chemistry. Inorganic chemistry\| PubMed ID: 26154728	2015
The Largest Metalloid Group 14 Cluster, Ge18[Si(SiMe3)3]6 : An Intermediate on the Way to Elemental Germanium. Angewandte Chemie (International ed. in English)\| PubMed ID: 26822765	2016
Reactivity of [Ge9{Si(SiMe3)3}3]- towards transition metal M2+ cations : coordination and redox chemistry. Chemistry (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 27796057	2016

Claudio Schrenk

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