Synthesis and oxidation of bis(triphenylgermyl)zinc

Bis(triphenylgermyl)zinc (Ph₃Ge)₂Zn (1), prepared by the reaction of diethylzinc (Et₂Zn) with two molar amounts of triphenylgermane (Ph₃GeH), was easily reacted by a small amount of oxygen to give tetrameric oxide (Ph₃GeZnO)₄ (2). Four zinc and four oxygen atoms in 2 are arranged such that a cube is formed as determined by X-ray diffraction analysis. Further oxidation of 2 led to the formation of digermoxane, (Ph₃Ge)₂O as a final product.     

Crystallographic report: Polymeric [3‐(triphenylgermyl)‐3‐o‐methoxyphenylpropionato]trimethyltin(IV)

The polymeric chains of [Sn(CH₃)₃(C₂₈H₂₅O₃Ge)]_n contain trimethyltin moieties bridging two neighboring 3‐(triphenylgermyl)‐3‐o‐methoxypropionate ligands via carboxyl groups. The germanium atom has a distorted tetrahedral geometry and the tin atom has a distorted trigonal‐bipyramidal geometry, the latter with three methyl groups in the equatorial plane and oxygen atoms defining the axial positions. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis and Structures of some Trisorganylstannyl Boranes and Triorganylstannyl Borates [1]

New stannylboranes were prepared from tetramethylpiperidino dichloroborane or B‐bromo‐pentamethylborazine with lithium triorganylstannides LiSnR₃. Only double stannylation was possible with tmpBCl₂ and LiSnMe₃, while tmpBCl(SnPh₃) was obtained by employing LiSnPh₃. This chloride reacted with LiGePh₃ to the stannyl germyl borane tmpB(GePh₃)(SnPh₃). On the other hand, PhMeNBCl₂ and an excess of LiSnMe₃ gave the borate Li[B(NMePh)(SnMe₃)₃], which was isolated as a solvate with 4 molecules of THF. The compound is present in the solid state as a solvent separated ion pair. The borate Li(H₃BSnMe₃) · 2 THF is dimeric in the solid state. Dimerization occurs via two single Li–H–B bridges and a Li–H(B)–Li bridge. The B–Sn bonds in the borates are practically of the same lengths as those in the boranes. In solution all BH bonds of this trihydridoborate are equivalent.     

Synthesis and reactivity of 3-(trichlorogermyl)propanoic acid and 3-(triphenylgermyl) propanoic acid

3-(Trichlorogermyl)propanoic acid (la) reacts with phenylmagnesium bromide in malar ratio 1:4 to give 3-(triphenylgermyl)propanoic acid (2a).In the compounds la and 2a theβ-carboxylic functional group shows some unusual properties when they react with excess of phenylmagnesium bromide.The compound la reacts with phenylmagnesium bromide in molar ratio 1:5 to give phenyl 2-(triphenylgermyl)ethylketone (3a) and in molar ratio 1:6 to give l,l-diphenyl-3-(triphenylgermyl)propanol (4a).The compound 2a reacts with phenylmagnesium bromide in molar ratio 1:2 to give 3a and in molar ratio 1:3 to give 4a also.Dehydration of the compound 4a with dilute hydrochloric acid seems especially easy.Moreover,the compound la reacted with phenylmagnsium bromide in molar ratio 1:6,then the mixture was treated with dilute hydrochloric acid to give 1,1-diphenyl-3-(triphenylgermyl)-1-propene (5a) in one pot reaction.Alkyl Ge-C bond in the compound 5a can be cleaved selectively by lithium aluminium hydride ( LiAlH4) in good yiel     

Germanium(II)‐, Zinn(II)‐ und Blei(II)‐Derivate des polycyclischen Alumosiloxans [Ph2SiO]8[Al(O)OH]4

Germanium(II)‐, Tin(II)‐ and Lead(II)‐Derivatives of the polycyclic Alumosiloxane [Ph₂SiO]₈[Al(O)OH]₄ Five new derivatives of the polycyclic alumosiloxane [Ph₂SiO]₈[Al(O)OH]₄ have been synthesized by replacement of the protic hydrogen atoms on the hydroxy‐groups attached to the aluminium atoms by the divalent group 14 elements germanium, tin and lead. The compounds can be divided in those with one metal atom per alumosiloxane moiety, [Ph₂SiO]₈[Al(O)OH]₂[AlO₂]M (M=Ge, Sn), and those with complete substitution of the protic hydrogen atoms by metal atoms like [Ph₂SiO]₈[AlO₂]₄M₂ (M= Sn, Pb). Always one element of the series Ge, Sn, Pb is missing in the two types of compounds. Crystal structure analyses of [Ph₂SiO]₈[Al(O)OH]₂[AlO₂]₂M · 2 C₄H₈O₂ (M= Ge ( 1 ), Sn ( 2a )), [Ph₂SiO]₈[Al(O)OH]₂[AlO₂]₂Sn · 2 THF ( 2b ) and [Ph₂SiO]₈[AlO₂]₄M₂ (M= Sn ( 3 ), Pb ( 4 )) have been performed elucidating either polycyclic basket‐type ( 1 , 2a , 2b ) or closed polyhedral structures ( 3 , 4 ).     

Reduction of Digallane [(dpp‐bian)Ga?Ga(dpp‐bian)] with Group 1 and 2 Metals

The reduction of digallane [(dpp‐bian)Ga? Ga(dpp‐bian)] ( 1 ) (dpp‐bian=1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene) with lithium and sodium in diethyl ether, or with potassium in THF affords compounds featuring the direct alkali metal–gallium bonds, [(dpp‐bian)Ga? Li(Et₂O)₃] ( 2 ), [(dpp‐bian)Ga? Na(Et₂O)₃] ( 3 ), and [(dpp‐bian)Ga? K(thf)₅] ( 7 ), respectively. Crystallization of 3 from DME produces compound [(dpp‐bian)Ga? Na(dme)₂] ( 4 ). Dissolution of 3 in THF and subsequent crystallization from diethyl ether gives [(dpp‐bian)Ga? Na(thf)₃(Et₂O)] ( 5 ). Ionic [(dpp‐bian)Ga]^?[Na([18]crown‐6)(thf)₂]⁺ ( 6 a ) and [(dpp‐bian)Ga]^?[Na(Ph₃PO)₃(thf)]⁺ ( 6 b ) were obtained from THF after treatment of 3 with [18]crown‐6 and Ph₃PO, respectively. The reduction of 1 with Group 2 metals in THF affords [(dpp‐bian)Ga]₂M(thf)_n (M=Mg ( 8 ), n=3; M=Ca ( 9 ), Sr ( 10 ), n=4; M=Ba ( 11 ), n=5). The molecular structures of 4 – 7 and 11 have been determined by X‐ray crystallography. The Ga? Na bond lengths in 3 – 5 vary notably depending on the coordination environment of the sodium atom.     

Synthese,Struktur und Eigenschaften von [nacnac]MX3‐Verbindungen (M = Ge,Sn; X = Cl,Br, I)

Synthesis, Structure, and Properties of [nacnac]MX₃ Compounds (M = Ge, Sn; X = Cl, Br, I) Reactions of [nacnac]Li [(2,6‐ⁱPr₂C₆H₃)NC(Me)C(H)C(Me)N(2,6‐ⁱPr₂C₆H₃)]Li ( 1 ) with SnX₄ (X = Cl, Br, I) and GeCl₄ in Et₂O resulted in metallacyclic compounds with different structural moieties. In the [nacnac]SnX₃ compounds (X = Cl 2 , Br 3 , I 4 ) the tin atom is five coordinated and part of a six‐membered ring. The Sn–N‐bond length of 3 is 2.163(4) Å and 2.176(5) Å of 4 . The five coordinated germanium of the [nacnac]GeCl₃ compound 5 shows in addition to the three chlorine atoms further bonds to a carbon and to a nitrogen atom. In contrast to the known compounds with the [nacnac] ligand the afore mentioned reaction creates a carbon–metal‐bond (1.971(3) Å) forming a four‐membered ring. The Ge–N bond length (2.419(2) Å) indicates the formation of a weakly coordinating bond.     

Reaction Mechanism of the Symmetry‐Forbidden [2+2] Addition of Ethylene and Acetylene to Amido‐Substituted Digermynes and Distannynes Ph2NEENPh2, (E=Ge,Sn): A Theoretical Study

Quantum chemical calculations of reaction mechanisms for the formal [2+2] addition of ethylene and acetylene to the amido‐substituted digermyne and distannyne Ph₂N?EE?NPh₂ (E=Ge, Sn) have been carried out by using density functional theory at the BP86/def2‐TZVPP level. The nature and bonding situations were studied with the NBO method and with the charge and energy decomposition analysis EDA‐NOCV. The addition of ethylene to Ph₂N?EE?NPh₂ takes place through an initial [2+1] addition to one metal atom and consecutive rearrangement to four‐membered cyclic species, which feature a weak E?E bond. Rotation about the C?C bond with concomitant rupture of the E?E bond leads to the 1,2‐disubstituted ethanes, which have terminal E(NPh₂) groups. The overall reaction Ph₂N?EE?NPh₂+C₂H₄→(Ph₂N)E?C₂H₄?E(NPh₂) has very low activation barriers and is slightly exergonic for E=Ge but slightly endergonic for E=Sn. The analysis of the electronic structure shows that there is charge donation of nearly one electron to the ethylene moiety already in the first part of the reaction. The energy partitioning analysis suggests that the HOMO(Ph₂N?EE?NPh₂)→LUMO(C₂H₄) interaction has a similar strength as the HOMO(C₂H₄)→LUMO(Ph₂N?EE?NPh₂) interaction. The [2+2] addition of acetylene to Ph₂N?EE?NPh₂ also takes place through an initial [2+1] approach, which eventually leads to 1,2‐disubstituted olefins (Ph₂N)E?C₂H₂?E(NPh₂). The formation of the energetically lowest lying conformations of cis‐(Ph₂N)E?C₂H₂?E(NPh₂), which occurs with very low activation barriers, is clearly exergonic for the germanium and the tin compound. The trans‐coordinated isomers of (Ph₂N)E?C₂H₂?E(NPh₂) are slightly lower in energy than the cis form but they are separated by a substantial energy barrier for the rotation about the C?C bond. The energy decomposition analysis indicates that the initial reaction takes place under formation of electron‐sharing bonds between triplet fragments rather than HOMO–LUMO interactions.     

Mesoionic Dithiolates (MIDts) Derived from 1,3-Imidazole-Based Anionic Dicarbenes (ADCs)

Mesoionic dithiolates [(MIDt^Ar)Li(LiBr)₂(THF)₃] (MIDt^Ar={SC(NDipp)}₂CAr; Dipp=2,6-iPr₂C₆H₃; Ar=Ph 3 a , 3-MeC₆H₄ (3-Tol) 3 b , 4-Me₂NC₆H₄ (DMP) 3 c ) and [(MIDt^Ph)Li(THF)₂] ( 4 ) are readily accessible (in≥90 % yields) as crystalline solids on treatments of anionic dicarbenes Li(ADC^Ar) ( 2 a - c ) (ADC^Ar={C(NDipp)₂}₂CAr) with elemental sulfur. 3 a - c and 4 are monoanionic ditopic ligands with both the sulfur atoms formally negatively charged, while the 1,3-imidazole unit bears a formal positive charge. Treatment of 4 with (L)GeCl₂ (L=1,4-dioxane) affords the germylene (MIDt^Ph)GeCl ( 5 ) featuring a three-coordinated Ge atom. 5 reacts with (L)GeCl₂ to give the Ge−Ge catenation product (MIDt^Ph)GeGeCl₃ ( 6 ). KC₈ reduction of 5 yields the homoleptic germylene (MIDt^Ph)₂Ge ( 7 ). Compounds 3 a - c and 4 – 7 have been characterized by spectroscopic studies and single-crystal X-ray diffraction. The electronic structures of 4 – 7 have been analyzed by DFT calculations.     

Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)methanide Ligands

A study of the coordination chemistry of different bis(diphenylphosphino)methanide ligands [Ph₂PC(X)PPh₂] (X=H, SiMe₃) with Group 4 metallocenes is presented. The paramagnetic complexes [Cp₂Ti{κ²‐P,P‐Ph₂PC(X)PPh₂}] (X=H ( 3 a ), X=SiMe₃ ( 3 b )) have been prepared by the reactions of [(Cp₂TiCl)₂] with [Li{C(X)PPh₂}₂(thf)₃]. Complex 3 b could also be synthesized by reaction of the known titanocene alkyne complex [Cp₂Ti(η²‐Me₃SiC₂SiMe₃)] with Ph₂PC(H)(SiMe₃)PPh₂ ( 2 b ). The heterometallacyclic complex [Cp₂Zr(H){κ²‐P,P‐Ph₂PC(H)PPh₂}] ( 4 aH ) has been prepared by reaction of the Schwartz reagent with [Li{C(H)PPh₂}₂(thf)₃]. Reactions of [Cp₂HfCl₂] with [Li{C(X)PPh₂}₂(thf)₃] gave the highly strained corresponding metallacycles [Cp₂M(Cl){κ²‐P,P‐Ph₂PC(X)PPh₂}] ( 5 aCl and 5 bCl ) in very good yields. Complexes 3 a , 4 aH , and 5 aCl have been characterized by X‐ray crystallography. Complex 3 a has also been characterized by EPR spectroscopy. The structure and bonding of the complexes has been investigated by DFT analysis. Reactions of complexes 4 aH , 5 aCl , and 5 bCl did not give the corresponding more unsaturated heterometallacyclobuta‐2,3‐dienes.     

Syntheses and Molecular Structures of [(thf)4Li] [{(thf)Li}M(C4H8)3] (M = Zr,Hf) and Their Solution Behavior

The reaction of MCl₄(thf)₂ (M = Zr, Hf) with 1,4-dilitiobutane in diethyl ether at –25 °C or at 0 °C with a molar ratio of 1 : 3 yields the homoleptic “ate” complexes [(thf)₄Li] [{(thf)Li}M(C₄H₈)₃] 1 - Zr (M = Zr) and 1 - Hf (M = Hf). The crystalline compounds form ion lattices with solvent-separated [(thf)₄Li]⁺ cations and [{(thf)Li}M(C₄H₈)₃]^– anions. The NMR spectra at –20 °C show magnetic equivalence of the M–CH₂ and of the β-CH₂ groups of the butane-1,4-diide ligands on the NMR time scale. Analogous reactions of MCl₄(thf)₂ with 1,4-dilithiobutane with a molar ratio of 1 : 2 proceed unclear. However, single crystals of [Li(thf)₄] [HfCl₅(thf)] ( 2 ) can be isolated with the hafnium atom in a distorted octahedral coordination sphere of five chloro and one thf ligand. NMR spectra allow to elucidate the time-dependent degradation of 1-Hf and 1-Zr in THF and toluene at 25 °C via THF cleavage. Addition of tmeda to a solution of 1-Zr allows the isolation of intermediately formed [{(tmeda)Li}₂Zr(nBu)₂(C₄H₈)₂] ( 3 ).     

Synthesis and Characterisation of N,N′-Disubstituted 1,2-phenylenebis(amido)tin(II) Compounds; X-Ray structures of 1,2- and of [1,2- (tmeda)

Cyclic bis(amido)tin(II) compounds 1,2- [R = SiMe₃] ( 4 ), SiMe₂Bu^t ( 5 ) and CH₂Bu^t ( 6 )], as well as ( 4 )₂(μ-tmeda) 7 have been obtained either from (i) the corresponding dilithium compound 1,2-C₆H₄[N(R)Li]₂ 1–3 and SnCl₂ for 4–6 , respectively, (or for 4 ) 2 1 + [Sn(μ-Cl){N(SiMe₃)₂}]₂; or (ii) 1,2-C₆H₄[N(H)R]₂ + Sn[N(SiMe₃)₂]₂ for 4–6 ; or for 7 from 4 and tmeda. Compounds 4–6 are monomeric, yellow, thermochromic (becoming redder on heating), diamagnetic, crystalline and are lipophilic and sublimable in vacuo. Compound 7 is colourless. The molecular structures of 6 and 7 have been determined from single crystal X-ray diffraction data. Compound 6 crystallises in bimolecular aggregates, in which there is a weak η-C₆ … Sn contact.     

Oxidative P−P Bond Addition to Cobalt(−I): Formation of a Low‐Spin Cobalt(III) Phosphanido Complex

The first homoleptic cobalt phosphanido complex [K(thf)₄][Co{1,2‐(Pt Bu₂)₂C₂B₁₀H₁₂}₂] ( 1 ) was prepared by an unprecedented oxidative P−P bond addition of an ortho ‐carborane‐substituted 1,2‐diphosphetane to cobalt(−I) in [K(thf)_0.2][Co(η⁴‐cod)₂)] (cod=1,5‐cycloctadiene). Compound 1 is a rare distorted tetrahedral 3d⁶ complex with a low‐spin ground state configuration. Magnetic measurements revealed that the complex is diamagnetic between 2 to 270 K in the solid state and at 298 K in [D₈]THF solution. Based on DFT calculations, the unusual singlet ground state is caused by the strong σ‐donor and moderate π‐donor properties of the bis(phosphanido) ligand.     

Synthese und Kristallstrukturen von [Li(thf)4]2[Bi4I14(thf)2], [Li(thf)4]4[Bi5I19] und (Ph4P)4[Bi6I22]

Synthesis and Crystal Structure of [Li(thf)₄]₂[Bi₄I₁₄(thf)₂], [Li(thf)₄]₄[Bi₅I₁₉], and (Ph₄P)₄[Bi₆I₂₂] Solutions of BiI₃ in THF or methanol react with MI (M = Li, Na) to form polynuclear iodo complexes of bismuth. The syntheses and results of X-ray structure analyses of compounds [Li(thf)₄]₂[Bi₄I₁₄(thf)₂], [Li(thf)₄]₄[Bi₅I₁₉], [Na(thf)₆]₄[Bi₆I₂₂] and (Ph₄P)₄[Bi₆I₂₂] are described. The anions of these compounds consist of edge-sharing BiI₆ and BiI₅(thf) octahedra. The Bi atoms lie in a plane and are coordinated by bridging and terminal I atoms and by THF ligands in a distorted octahedral fashion. [Li(thf)₄]₂[Bi₄I₁₄(thf)₂]: Space group P1 (No. 2), a = 1 159.9(6), b = 1 364.6(7), c = 1 426.5(7) pm, α = 114.05(3), β = 90.01(3), γ = 100.62(3)°. [Li(thf)₄]₄[Bi₅I₁₉]: Space group P2₁/n (No. 14), a = 1 653.0(9), b = 4 350(4), c = 1 836.3(13) pm, β = 114.70(4)°. [Na(thf)₆]₄[Bi₆I₂₂]: Space group P2₁/n (No. 14), a = 1 636.4(3), b = 2 926.7(7), c = 1 845.8(4) pm, β = 111.42(2)°. (Ph₄P)₄[Bi₆I₂₂]: Space group P1 (No. 2), a = 1 368.6(7), b = 1 508.1(9), c = 1 684.9(8) pm, α = 98.28(4), β = 95.13(4), γ = 109.48(4)°.     

Thermal reactivity of cis- and trans-bis(triphenylgermyl)bis(tertiary phosphine)platinum(II)

The complex cis-Pt(Ph₃Ge)₂(PMe₂Ph)₂ underwent smooth isomerization to give the trans-isomer at room temperature via an associative five-coordinated intermediate. Thermodynamic parameters and activation energy for the cis to trans isomerization were obtained, ΔH^# = 105 kJ mol⁻¹, ΔS^# = 12.5 J mol⁻¹ K⁻¹, and Ea = 107 kJ mol⁻¹, respectively. Heating of trans-Pt(Ph₃Ge)₂(PMe₂Ph)₂ at 50 °C for 36 days produced trans-PtPh(Ph₃Ge)(PMe₂Ph)₂ followed by the formation of trans-PtPh₂(PMe₂Ph)₂, Pt(PMe₂Ph)₄, and Ph₄Ge finally via elimination of the phenyl group from Ph₃Ge ligand with liberation of the Ph₂Ge unit and subsequent reductive elimination of the remaining Ph₃Ge ligand at 80 °C for 1 month.     

Synthesis and Reactivity of Low‐Valent Group 14 Element Compounds

The tetravalent germanium and tin compounds of the general formulae Ph*EX₃ (Ph* = C₆H₃Trip‐2,6, Trip = C₆H₂iPr₃‐2,4,6; E = Sn, X = Cl ( 1a ), Br ( 1b ); E = Ge, X = Cl ( 2 )) are synthesized by reaction of Ph*Li·OEt₂ with EX₄. The subsequent reaction of 1a , b with LiP(SiMe₃)₂ leads to Ph*EP(SiMe₃)₂ (E = Sn ( 3 ), Ge ( 4 )) and the diphosphane (Me₃Si)₂PP(SiMe₃)₂ by a redox reaction. In an alternative approach 3 and 4 are synthesized by using the corresponding divalent compounds Ph*ECl (E = Ge, Sn) in the reaction with LiP(SiMe₃)₂. The reactivity of Ph*SnCl is extensively investigated to give with LiP(H)Trip a tin(II)‐phosphane derivative Ph*SnP(H)Trip ( 6 ) and with Li₂PTrip a proposed product [Ph*SnPTrip]^– ( 7 ) with multiple bonding between tin and phosphorus. The latter feature is confirmed by DFT calculations on a model compound [PhSnPPh]^–. The reaction with Li[H₂PW(CO)₅] gives the oxo‐bridged tin compound [Ph*Sn{W(CO)₅}(μ‐O)₂SnPh*] ( 8 ) as the only isolable product. However, the existence of 8 as the bis‐hydroxo derivative [Ph*Sn{W(CO)₅}(μ‐OH)₂SnPh*] ( 8a ) is also possible. The Sn^IV derivatives Ph*Sn(OSiMe₃)₂Cl ( 9 ) and [Ph*Sn(μ‐O)Cl]₂ ( 10 ) are obtained by the oxidation of Ph*SnCl with bis(trimethylsilyl)peroxide and with Me₃NO, respectively. Besides the spectroscopic characterization of the isolated products compounds 1a , 2 , 3 , 4 , 8 , and 10 are additionally characterized by X‐ray diffraction analysis.     

Bis(1,2‐diselenoquadratato)metallate

Bis(1,2‐diselenosquarato) Metalates A series of 1,2‐diselenosquarato metalates [M(dssq)₂]^2– (M = Pd²⁺, Pt²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺, VO²⁺) was available by direct synthesis from the appropriate metal salt with dipotassium 1,2‐diselenosquarate in deoxygenized water under an argon athmosphere. The copper(II)complex, [Cu(dssq)₂]^2–, and the oxovanadium(IV)complex, [VO(dssq)₂]^2–, were identified in solution by EPR spectroscopy (parameters: [Cu(dssq)₂]^2–: g₀ = 2.073; a = –76.0 · 10^–4 cm^–1, a = 47.0 · 10^–4 cm^–1; [VO(dssq)₂]^2–: g₀ = 1.986; a = 74.9 · 10^–4 cm^–1). The complexes bis(tetraphenylphosphonium)[bis(1,2‐diselenosquarato)nickelate(II)], (Ph₄P)₂[Ni(dssq)₂], and bis(tetraphenylphosphonium)[bis(1,2‐diselenosquarato)zincate(II)], (Ph₄P)₂[Zn(dssq)₂], were characterized by X‐ray structure analysis. The square‐planar Ni^II complex (Ph₄P)₂[Ni(dssq)₂] crystallizes in the monoclinic spacegroup P2₁/n with the unit cell parameters a = 11.1472(8) Å, b = 15.331(1) Å, c = 14.783(1) Å, β = 94.441(1)° and Z = 2. The Zn^II‐complex (Ph₄P)₂[Zn(dssq)₂] is tetrahedral coordinated and crystallizes in the monoclinic spacegroup P2₁/c with the unit cell parameters a = 9.4238(1) Å, b = 18.5823(3) Å, c = 29.5309(5) Å, β = 96.763(1)° and Z = 4.     

Fluoroborates by Cleavage of Trimethylamine‐bis(trifluoromethyl)boranes with NEt3 × 3 HF. Structures of C6F5(CF3)2B · NMe3, K[C6H5CH2(CF3)2BF], and K[C6H5(CF3)2BF]

Trimethylamine‐bis(trifluoromethyl)boranes R(CF₃)₂B · NMe₃ (R = cis/trans‐CF₃CF=CF ( 1/2 ), HC≡C ( 3 ), H₂C=CH ( 4 ), C₂H₅ ( 5 ), C₆H₅CH₂ ( 6 ), C₆F₅ ( 7 ), C₆H₅ ( 8 )) react with NEt₃ × 3 HF depending on the nature of R at 155–200 °C under replacement of the trimethylamine ligand to form the corresponding fluoro‐bis(trifluoromethyl)borates [R(CF₃)₂BF]^– ( 1 a/2 a – 8 a ). The structures of 7 , K[C₆H₅CH₂(CF₃)₂BF] ( K‐6 a ), and K[C₆H₅(CF₃)₂BF] ( K‐8 a ) have been investigated by single‐crystal X‐ray diffraction. In 7 the CF₃ groups make short repulsive contacts with NMe₃ and C₆F₅ entities – the B–CF₃ bonds being unusually long. The B–F bond lengths of K‐6 a and K‐8 a (1.446(3) and 1.452(2) Å, respectively) are long for a fluoroborate.     

Chalcogenide Derivatives of Imidotin Cage Complexes

Reaction of the secocubane [Sn₃(μ₂‐NHtBu)₂(μ₂‐NtBu)(μ₃‐NtBu)] ( 1 ) with dibutylmagnesium produces the heterobimetallic cubane [Sn₃Mg(μ₃‐NtBu)₄] ( 4 ) which forms the monochalcogenide complexes of general formula [ESn₃Mg(μ₃‐NtBu)₄] ( 5 a , E=Se; 5 b , E=Te) upon reaction with elemental chalcogens in THF. By contrast, the reaction of the anionic lithiated cubane [Sn₃Li(μ₃‐NtBu)₄]^? with the appropriate quantity of selenium or tellurium leads to the sequential chalcogenation of each of the three Sn^II centres. Pure samples of the mono‐ or dichalcogenides are, however, best obtained by stoichiometric redistribution reactions of [Sn₃Li(μ₃‐NtBu)₄]^? and the trichalcogenides [E₃Sn₃Li(μ₃‐NtBu)₄]^? (E=Se, Te). These reactions are conveniently monitored by using ¹¹⁹Sn NMR spectroscopy. The anion [Sn₃Li(μ₃‐NtBu)₄]^? also acts as an effective chalcogen‐transfer reagent in reactions of selenium with the neutral cubane [{Snμ₃‐N(dipp)}₄] ( 8 ) (dipp=2,6‐diisopropylphenyl) to give the dimer [(thf)Sn{μ‐N(dipp)}₂Sn(μ‐Se)₂Sn{μ‐N(dipp)}₂Sn(thf)] ( 9 ), a transformation that results in cleavage of the Sn₄N₄ cubane into four‐membered Sn₂N₂ rings. The X‐ray structures of 4 , 5 a , 5 b , [Sn₃Li(thf)(μ₃‐NtBu)₄(μ₃‐Se)(μ₂‐Li)(thf)]₂ ( 6 a ), [TeSn₃Li(μ₃‐NtBu)₄][Li(thf)₄] ( 6 b ), [Te₂Sn₃Li(μ₃‐NtBu)₄][Li([12]crown‐4)₂] ( 7 b′′ ) and 9 are presented. The fluxional behaviour of cubic imidotin chalcogenides and the correlation between NMR coupling constants and tin–chalcogen bond lengths are also discussed.     

Zinn in der Peripherie von Bis(aren)metall‐Komplexen des Vanadiums und Chroms

Metal π Complexes of Benzene Derivatives. 53 [1] Tin in the Periphery of Bis(arene)metal Complexes of Vanadium and Chromium By means of metal‐atom ligand‐vapor cocondensation as well as via wet chemical methods (lithiation and follow‐up reaction) the first organostannyl substituted bis(arene)metal complexes (R₃Sn‐η⁶‐C₆H₅)₂M have been prepared: 15 (R = Me, M = V), 16 (R = Ph, M = V), 13 (R = Me, M = V), 17 (R = Ph, M = Cr). Despite the bulkiness of the Ph₃Sn groups the geometry of the central sandwich unit in 17 deviates only marginally from that of the parent complex (C₆H₆)₂Cr ( 2 ). The triclinic unit cell of 17 (space group: P1; a = 9.414(4), b = 9.877(5), c = 11.012(13) Å; α = 83.51(7), β = 87.95(7), γ = 72.67(4)°) contains one independent molecule. Perturbation of the electronic structure of the bis(arene)metal unit by organostannyl groups appears to be minute because EPR spectra of the M(d⁵) species fail to reveal deviations from axial symmetry. The potentials for reversible oxidation of the Me₃Sn‐substituted complexes 13 and 15 differ insignificantly (anodic shifts ≤ 20 mV) from those of the parent species 1 and 2 ; reductions are irreversible in both cases. More sizeable anodic shifts are observed for the Ph₃Sn‐derivatives 16 and 17 ; here as well, only the redox pairs 0/+ are reversible. The resistance of the neutral complexes to protic media contrasts to ready hydrodestannylation of the complex cations. By way of metal exchange, employing n‐butyl lithium, 13 affords (Li‐η⁶‐C₆H₅)₂Cr strictly 1,1′‐disubstituted and devoid of auxiliary base.