Divergent Reactivity of a Cyclic Bis-Hydridostannylene: A Masked Sn(I) Diradicaloid

Herein, reactivity studies of a cyclic bis-hydridostannylene [(ADC)SnH]2 (1-H2) (ADC=PhC{(NDipp)C}2; Dipp=2,6-iPr2C6H3) with various unsaturated organic substrates are reported. Reactions of terminal alkynes (RC≡CH) with 1-H2 afford mixed acetylide-vinyl-functionalized bis-stannylenes via dehydrogenation and hydrostannylation. Treatment of 1-H2 with PhC≡CCH3 gives a unique distannabarrelene via dehydrogenative C(sp3)-H stannylation and hydrostannylation of the C≡CCH3 moiety. 1-H2 undergoes dehydrogenative [2+2]-cycloaddition reactions with diphenylacetylene, azobenzene, acetone, benzophenone, and benzaldehyde to form the 1,4-distannabarrelene derivatives. The elimination of H2 in these reactions suggests the masked-diradical property of 1-H2. In fact, these [2+2]-cycloaddition products are also accessible on treatments of the Sn(I) diradicaloid [(ADC)Sn]2 (1) with appropriate reagents. All compounds have been characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction. Moreover, the catalytic activity of 1-H2 has been shown for the hydroboration of unsaturated substrates.

The First Planar, Not Twisted, Distannene - A Structural Alkene Analog. Synthesis, Isolation and X-ray Crystallography Characterization

The tetrasilyl-substituted distannene, (tBu2 HSi)2 Sn=Sn(SiHtBu2 )2 6, was synthesized by mild thermolysis (70 °C in hexane) of tris(di-tert-butyl-hydridosilyl)stannane 4. The X-ray crystallography structure of 6 reveals the following unusual structural properties: a planar geometry around both Sn atoms (Σ∡Sn=359.87°), a non-twisted Sn=Sn double bond, and the shortest Sn=Sn double bond of 2.599 Å among all acyclic distannenes. Thus, compound 6 is the first reported distannene having a structure closely analogous to a classic alkene. Reactions of 6 with CCl4 or with 2,3-dimethylbuta-1,3-diene to produce 1,2-dichlorodistannane 9 and the [2+4] cycloadduct 10, respectively, are characteristic for a Sn=Sn double bond.

Dimetalloylene (M-E-M) Complexes of Heavier Main Group Elements Ge, Sn, Pb, Bi via Cleavage of E-X Bonds (X=N(SiMe3 )2 , OtBu) with an Iridium Hydride

Reactions of the IrV hydride [Me BDIDipp ]IrH4 {BDI=(Dipp)NC(Me)CH(Me)CN(Dipp); Dipp=2,6-iPr2 C6 H3 } with E[N(SiMe3 )2 ]2 (E=Sn, Pb) afforded the unusual dimeric dimetallotetrylenes ([Me BDIDipp ]IrH)2 (μ2 -E)2 in good yields. Moreover, ([Me BDIDipp ]IrH)2 (μ2 -Ge)2 was formed in situ from thermal decomposition of [Me BDIDipp ]Ir(H)2 Ge[N(SiMe3 )2 ]2 . These reactions are accompanied by liberation of HN(SiMe3 )2 and H2 through the apparent cleavage of an E-N(SiMe3 )2 bond by Ir-H. In a reversal of this process, ([Me BDIDipp ]IrH)2 (μ2 -E)2 reacted with excess H2 to regenerate [Me BDIDipp ]IrH4 . Varying the concentrations of reactants led to formation of the trimeric ([Me BDIDipp ]IrH2 )3 (μ2 -E)3 . The further scope of this synthetic route was investigated with group 15 amides, and ([Me BDIDipp ]IrH)2 (μ2 -Bi)2 was prepared by the reaction of [Me BDIDipp ]IrH4 with Bi(NMe2 )3 or Bi(OtBu)3 to afford the first example of a "naked" two-coordinate Bi atom bound exclusively to transition metals. A viable mechanism that accounts for the formation of these products is proposed. Computational investigations of the Ir2 E2 (E=Sn, Pb) compounds characterized them as open-shell singlets with confined nonbonding lone pairs at the E centers. In contrast, Ir2 Bi2 is characterized as having a closed-shell singlet ground state.

Isolation and Reactivity of Stannylenoids Stabilized by Amido/Imino Ligands

The reaction of the lithium aryl(silyl)amide Dipp(ⁱ Pr₃ Si)NLi (Dipp=2,6-ⁱ Pr₂ C₆ H₃ ) with one equivalent of SnCl₂ in THF gave a novel stannylenoid Dipp(ⁱ Pr₃ Si)NSnCl⋅LiCl(THF)₂ . Heating the solution of amidostannylenoid in toluene to 80 °C resulted in dimeric amido(chloro)stannylene [Dipp(ⁱ Pr₃ Si)NSnCl]₂ , which can be converted to bis(amido)stannylene Sn[N(Dipp)(ⁱ Pr₃ Si)]₂ and amido(imino)stannylene Sn[N(Dipp)(ⁱ Pr₃ Si)][IPrN] (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-imino). Treatment of bis(imino)stannylenoid [IPrN]₂ Sn(Cl)Li with N₂ O resulted in the dimeric complex [IPrNSn(Cl)OLi]₂ . All compounds were characterized by NMR, elementary analysis, and X-ray structural determination.

Fully Tin-Coated Coinage Metal Ions: A Pincer-Type Bis-stannylene Ligand for Exclusive Tetrahedral Complexation

The synthesis of a novel bis-stannylene pincer ligand and its complexation with coinage metals (Cu^I , Ag^I and Au^I ) are described. All coinage metal centres are in tetrahedral coordination environments in the solid state and are exclusively coordinated by four neutral Sn^II donors. ¹¹⁹ Sn NMR provided information about the behaviour in solution. All of the isolated compounds have photoluminescent properties, and these were investigated at low and elevated temperatures. Compared to the free bis-stannylene ligand, coordination to coinage metals led to an increase in the luminescence intensity. The new compounds were investigated in detail through all-electron relativistic density functional theory (DFT) calculations.

Intramolecularly Double-Donor-Stabilized Stannylene and Its Coordination towards Ag(I) and Au(I) Centers

The intramolecularly double-donor-stabilized stannylene 1 has been synthesized from the salt-metathesis reaction between two equivalents of lithium pyridine ene-amide L1 and SnCl₂ . Compound 1 exhibits dipolar behavior when reacted with B(C₆ F₅ )₃ leading to the zwitterionic compound 2. The reaction of 1 with one equivalent and 0.5 equivalent of AgOTf (OTf=trifluoromethane sulfonate) result in the formation of a stannylene-AgOTf complex 3 and a homoleptic distannylene-silver ionic complex 4, respectively. Analogous to complex 4, the gold(I) complex 5 has been synthesized from the reaction between two equivalents of 1 and 0.5 equivalent of AuCl.SMe₂ /Me₃ SiOTf. Complex 5 is the first example of homoleptic stannylene-Au(I) ionic complex among the very scarce reports on stannylene-gold(I) coordination complexes. All compounds have been structurally characterized using single crystal X-ray crystallography. Solution-state characterization have been performed using multinuclear NMR techniques. Detailed DFT calculations on the optimized geometries 1 o, 3 o-5 o reveal the change in sp- hybridization on the pyramidal Sn(II) center upon metal coordination and their bonding overlaps.

A 1,5-Oligosilanylene Dianion as Building Block for Oligosiloxane Containing Cages, Ferrocenophanes, and Cyclic Germylenes and Stannylenes

Starting out from dipotassium 1,5-oligosiloxanylene diide 2, a 3,7,10-trioxa-octasilabicyclo[3.3.3]undecane was prepared, which represents the third known example of this cage structure type. Reaction of 1,3-dichlorotetramethyldisiloxane with 1,1'-bis[bis(trimethylsilyl)potassiosilyl]ferrocene gave a ferrocenophane with a disiloxane containg bridge. The compound can be further derivatized by conversion into a 1,5-oligosilanyl diide. Reacting 1,5-oligosiloxanylene diide 2 with SnCl2 or GeCl2·dioxane in the presence of PMe3 gave cyclic disilylated tetrylene PMe3 adducts. Release of the base-free stannylene led to a dimerization process which gave a bicyclic distannene as the final product. Abstraction of the PMe3 from the cyclic disilylated germylene PMe3 adduct with B(C6F5)3 caused oxidative addition of the germylene into a para-C-F bond of Me3P·B(C6F5)3.

An indenide-tethered N-heterocyclic stannylene

Analysis of the coordination of the Sn to the indenyl ring shows that the Sn inter­acts in an η² fashion. A database survey showed that whilst this coordination mode is unusual for Ge and Pb compounds, Sn displays a wider range of coordination modes to cyclo­penta­dienyl ligands and their derivatives.

The structure of (μ-1κN:2(η²),κ²N,N′-(2-{[2,6-bis(propan-2-yl)phen­yl]aza­nid­yl}eth­yl)[2-(1H-inden-1-yl)eth­yl]aza­nido)(1,4,7,10,13,16-hexa­oxa­cyclo­octa­dec­ane-1κ⁶O)lithiumtin, [LiSn(C₈H₁₆O₄)(C₂₅H₃₁N₂)], at 100 K has monoclinic (P2₁/n) symmetry. Analysis of the coordination of the Sn to the indenyl ring shows that the Sn inter­acts in an η² fashion. A database survey showed that whilst this coordination mode is unusual for Ge and Pb compounds, Sn displays a wider range of coordination modes to cyclo­penta­dienyl ligands and their derivatives.

Rational Syntheses and Serendipity: Complexes [LSnPtCl2 (SMe2 )]2 , [{LSnPtCl(SMe2 )}2 SnCl2 ], [(LSn)3 (PtCl2 )(PtClSnCl){LSn(Cl)OH}], and [O(SnCl)2 (SnL)2 ] with L=MeN(CH2 CMe2 O)2

Syntheses and molecular structures of the dimeric tin-platinum complex [LSnPtCl₂ (SMe₂ )]₂ (2), the tin-platinum clusters [{LSnPtCl(SMe₂ )}₂ SnCl₂ )] (3) and [(LSn)₃ (PtCl₂ )(PtClSnCl)(LSnOHCl)] (6) (L=MeN(CH₂ CMe₂ O^- )₂ ), and of the unprecedented tin(II) aminoalkoxide-tin oxide chloride complex [O(SnCl)₂ ⋅(SnL)₂ ] (5) are reported. The compounds were characterized by NMR spectroscopy (¹ H, ¹³ C, ¹¹⁹ Sn, ¹⁹⁵ Pt), ¹¹⁹ Sn Mössbauer spectroscopy (1-3, 6), electrospray ionization mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses (2⋅CH₂ Cl₂ , 3⋅2 C₄ H₈ O, 5, 6⋅3CH₂ Cl₂ ). The tin(II) aminoalkoxide [MeN(CH₂ CMe₂ O)₂ Sn]₂ (1) behaves like a neutral ligand, inserts into a Pt-Cl bond, or is involved in rearrangement reactions with the different behavior occurring even within one compound (3, 6). DFT calculations show that the tin-platinum compounds behave like electronic chameleons.

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.

Bis-Sulfonyl O,C,O-Chelated Metallylenes (Ge, Sn) as Adjustable Ligands for Iron and Tungsten Complexes

The synthesis and characterization of an E2 CE2 bis-sulfonyl aryl pincer ligand and its efficiency for the stabilization of compounds containing low-valent Group 14 elements (Ge and Sn) are reported. Complexation reaction of these metallylenes with iron or tungsten complexes resulted in the modulation of the oxygen atoms of the sulfonyl groups implicated in the stabilization of the Group 14 elements, demonstrating the original adjustable character of the bis-sulfonyl O2 S-C-SO2 aryl pincer.

η(3) -Allyl coordination at tin(II)-reactivity towards alkynes and benzonitrile

We herein report the synthesis and characterization of a terphenyl-substituted Sn(II) allyl compound featuring an η(3)  coordination mode in solution and in the solid state. Two examples for the interesting reactivity of the allyl Sn(II) molecule are presented: Reactions with terminal alkynes result in the formation of tricyclic compounds by CC bond formation and the dimerization of two Sn moieties whereas the reaction with benzonitrile leads to a sixteen-membered ring system through CH activation.

Performance of Møller-Plesset second-order perturbation theory and density functional theory in predicting the interaction between stannylenes and aromatic molecules

The performances of Møller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT) have been assessed for the purposes of investigating the interaction between stannylenes and aromatic molecules. The complexes between SnX2 (where X = H, F, Cl, Br, and I) and benzene or pyridine are considered. Structural and energetic properties of such complexes are calculated using six MP2-type and 14 DFT methods. The assessment of the above-mentioned methods is based on the comparison of the structures and interaction energies predicted by these methods with reference computational data. A very detailed analysis of the performances of the MP2-type and DFT methods is carried out for two complexes, namely SnH2-benzene and SnH2-pyridine. Of the MP2-type methods, the reference structure of SnH2-benzene is reproduced best by SOS-MP2, whereas SCS-MP2 is capable of mimicking the reference structure of SnH2-pyridine with the greatest accuracy. The latter method performs best in predicting the interaction energy between SnH2 and benzene or pyridine. Among the DFT methods, ωB97X provides the structures and interaction energies of the SnH2-benzene and SnH2-pyridine complexes with good accuracy. However, this density functional is not as effective in reproducing the reference data for the two complexes as the best performing MP2-type methods. Next, the DFT methods are evaluated using the full test set of SnX2-benzene and SnX2-pyridine complexes. It is found that the range-separated hybrid or dispersion-corrected density functionals should be used for describing the interaction in such complexes with reasonable accuracy.