Synthesis and Investigation of a Soluble Distannene with no Trans-Bent Angle or Twisting in the Solid-State

By treating KSiiPr3 with Sn[N(SiMe3)2]2 the distannene Sn2(TIPS)4 (TIPS=SiiPr3) is formed in a metathesis reaction. The crystal structure analysis of Sn2(TIPS)4 reveals a planar arrangement of the substituents in the solid-state and hence the second planar alkene like distannene of its kind. Due to the TIPS substituents, Sn2(TIPS)4 is well soluble in all commonly used organic solvents, opening the door for various analytics and reactivity studies. Due to its stability in solution, various reactions can be performed such as cycloaddition reactions with 2,3-dimethyl-1,3-butadiene (DMBD) and TMS-azide.

Structure and Bonding in a Diamond-Shaped Tin Cluster Possessing a cyclo-Sn4 Core

A tetrameric cluster composed entirely of (aryl)Sn units, [DMPSn]₄ (DMP=2,6-dimesitylphenyl), has been prepared by reduction of [DMPSnCl]₂ with a variety of reductants. This cluster was characterized in solution by multinuclear NMR spectroscopies, as well as in the solid-state by single crystal X-ray diffraction analysis. This species is stereochemically nonrigid in solution and possesses a cyclo-Sn₄ core whose DMP substituents are equivalent at higher temperatures. The solid-state molecular structure is remarkably unsymmetrical and possesses a nearly planar cyclo-Sn₄ core. The DMP substituents are arranged such that three are approximately coplanar, while one is nearly perpendicular to the cyclo-Sn₄ core. Density functional theory calculations for a [PhSn]₄ model system show that this distorted geometry about the cyclo-Sn₄ core maximizes σ-bonding between the Sn centers in a manner reminiscent of trans-bent bonding in the heavy group 14 analogues of alkenes and alkynes.

Reductive dehydrocoupling of diphenyltin dihydride with LiAlH4: selective synthesis and structures of the first bicyclo[2.2.1]heptastannane-1,4-diide and bicyclo[2.2.2]octastannane-1,4-diide

The reaction of diphenyltin dihydride with LiAlH4 gives access to a set of charged tin cages as their lithium salts. Variation in the ratio of reactants provides a perstannabicyclooctane dianion and a perstannanorbornane as the di- and monoanions. These compounds can be synthesised selectively by careful stoichiometric control and have been characterised by single crystal X-ray diffractometry, NMR and UV-vis spectroscopy. Computational exploration of the electronic structures of these compounds was undertaken and, in agreement with structural and spectroscopic features, indicated significant σ-delocalisation in the tin skeletons.

Deprotonation of Organogermanium and Organotin Trihydrides

Terphenyltin and terphenylgermanium trihydrides were deprotonated in reaction with strong bases, such as LiMe, LDA, or KBn. In the solid state, the Li salts of the germate anion 4 and 4a exhibit a Li-Ge contact. In the Li salt of the dihydridostannate anion 6a, the Li cation is not coordinated at the tin atom instead an interaction of the Li cation with the hydride substituents was found. Evidenced by ¹H-⁷Li-HOESY NMR spectroscopy the Li-salt of the deprotonated tin hydride 6a exhibits in toluene solution a contact between Li cation and hydride substituents, whereas in the ¹H-⁷Li-HOESY NMR spectrum of the homologous germate salt 4a, no crosspeak between hydride and Li signals was found. The organodihydridogermate and -stannate react as nucleophiles with low-valent Group 14 electrophiles. Thus, three compounds were synthesized: Ar-Ë'-EH₂-Ar (E', E = Sn, Ge; Pb, Ge; Pb, Sn; Ar = Ar', Ar*). Following an alternative synthesis Ar'SnH₂PbAr* was synthesized in reaction between [(Ar*PbH)₂] and [(Ar'SnH)₄] generated in situ. In reaction between low-valent organotin hydride [(Ar*SnH)₂] and organdihydridostannate [Ar*SnH₂]^- formation of distannate [Ar*₂Sn₂H₃]^- was found.

Reductive Elimination of Hydrogen from Bis(trimethylsilyl)methyltin Trihydride and Mesityltin Trihydride

Alkyltin trihydride [(Me₃ Si)₂ CHSnH₃ ] was synthesized and the reductive elimination of hydrogen from this species was investigated. A methyl-substituted N-heterocyclic carbene reacts with the organotrihydride in dependence on stoichiometry and solvent to give a series of products of the reductive elimination and dehydrogenative tin-tin bond formation. Besides characterization of the carbene adduct of the alkyltin(II) hydride, a Sn₄ chain was also isolated, encompassing two stannyl-stannylene sites, which are stabilized each as NHC-adducts. Complete dehydrogenation resulted to give either a carbene-stabilized distannyne or a metalloid Sn₉ -cluster salt. Reductive elimination of hydrogen was also achieved with an excess of diethylmethylamine to give the alkyltin(II) hydride as a Lewis base free tetramer [(RSnH)₄ ]. The method of cluster formation at low temperatures by hydrogen elimination was also transferred to the mesityl-substituted tin trihydride MesSnH₃ . In this case [(MesSn)₁₀ ], showing a [5]prismane structure, was isolated in good yield and characterized. NMR spectroscopic features of the propellane-type cluster [Trip₆ Sn₆ ] are reported.

New Insight into the Nature of Bonding in the Dimers of Lappert's Stannylene and Its Ge Analogs: A Quantum Mechanical Study

The strength and nature of the connection in Lappert's stannylene dimer ({Sn[CH(SiMe3)2]2}2) and its smaller analogs, simplified stannylenes, as well as similar Ge complexes were studied by means of DFT-D3 calculations, energy decomposition analysis (EDA), electrostatic potential (ESP), and natural population analysis. The trans-bent structure of the investigated molecules was rationalized by means of EDA, ESP, and molecular orbital (MO) analyses. The different ESPs for the monomers studied are a result of different hybridization of the Sn (Ge) atoms. The comparably strong stabilization in the largest and the smallest systems with a dramatically different substituent size is explained by the different nature of the binding between monomers. For all complexes, it has been found that the total attractive interaction is mostly provided by the electrostatic component (>50%), followed by orbital interaction and dispersion. In the largest molecule (Lappert's stannylene), the dispersion interaction plays a more significant role in stabilization and its magnitude is comparable to that of orbital interaction; on the other hand in the smallest molecule (SnH2), where bulky substituents are replaced by H only, the dispersion energy is less important and the E-E bond is more of a charge-transfer character, caused by donor-acceptor orbital interactions. The charge transfer in Ge dimers is greater than in the Sn ones due to shorter distances between monomers, which cause better ⟨HOMO/LUMO⟩ overlaps. The easier dimerization of Lappert's stannylene as compared to Kira's ({Sn[(Me3Si)2CHCH2CH2CH(SiMe3)2-κ(2)C,C']}) stannylene is explained by the different orientation of their substituents-asymmetry promotes dimerization.

Synthesis and solid state structure of a metalloid tin cluster [Sn10(trip8)]

The Mg(i) compound (LMg)₂ reacts with (trip₂Sn)₂ with formation of the metalloid Sn₁₀trip₈ cluster 1, which contains Sn atoms in the formal oxidations states 0, +I and +II, while the stronger Mg(i) reductant (L′Mg)₂ yielded elemental tin. The reaction demonstrates the promising potential of Mg(i) compounds to serve as soluble reductants for cluster synthesis.

Si(SiMe3)2SiPh3 - a ligand for novel sub-valent tin cluster compounds

For the synthesis of metalloid tin cluster compounds applying the disproportionation reaction of a Sn(i) halide, silyl ligands, especially the symmetric Si(SiMe3)3 has proven to be extremely useful. Silyl ligands of lower symmetry where e.g. one SiMe3 group is substituted with SiPh3 are thereby unexplored, although the synthesis of the anionic silyl precursors is quite easy, referring to previously described methods. Here the synthesis of the silanide [Si(SiMe3)2(SiPh3)](-) as its potassium () as well as its lithium salt () in excellent yield is presented. proved to be a suitable starting material for the synthesis of subvalent tin compounds as shown by the reaction with tin halides in oxidation state +2 (SnCl2) and +1 (SnCl); i.e. on the one hand the anticipated stannide [Sn(Si(SiMe3)2SiPh3)2Cl](-) could be isolated and on the other hand the unexpectedly partly substituted ring compound Cl4Sn4[Si(SiMe3)2SiPh3]4 is obtained. As no elemental tin is formed during the reaction with SnCl, metalloid tin clusters may be present in solution too, which is supported by the nearly black color of the reaction mixture, showing that might be a suitable ligand for the synthesis of such cluster compounds.

Metalloid Sn clusters: properties and the novel synthesis via a disproportionation reaction of a monohalide

Metalloid cluster compounds of tin of the general formulae SnnRm with n>m (R=organic ligand), where beside ligand-bound tin atoms also “naked” tin atoms, that only bind to other tin atoms, are present, represent a novel class of cluster compounds in tin chemistry. As the “naked” tin atoms inside these clusters exhibit an oxidation state of 0, the average oxidation state of the tin atoms within such metalloid tin clusters is in between 0 and 1. Thus, these cluster compounds may be seen as intermediates on the way to the elemental state. Therefore, interesting properties are expected for these compounds, which might complement results from nanotechnology. During the last years, different syntheses of such novel cluster compounds have been introduced, leading to several metalloid tin cluster compounds, which exhibit new and partly unusual structure and bonding properties. In this review, recent results in this novel field of group 14 chemistry are discussed, whereby special attention is focused on the novel synthetic route applying a disproportionation reaction of metastable Sn(I) halides.