Synthese und Metallierung des Diaminosiloxans O(SiiPr2NH2)2

Synthesis and Metalation of the Diaminosiloxane O(SiiPr₂NH₂)₂ The 1,3‐diaminoldisiloxane O(SiiPr₂NH₂)₂ ( 1 ) was obtained from the reaction of O(SiiPr₂Cl)₂ with NH₃. The reactions of 1 with AlEt₃ or GaEt₃ produced the compounds [O{SiiPr₂N(H)MEt₂}{SiiPr₂NMEt}]₂ ( 2 : M = Al; 3 : M = Ga). The crystal structures of 2 and 3 were determined by single crystal X‐ray diffraction, showing a polycyclic M₄N₄Si₄O₂ core structure of these molecules.     

P(SiiPr3)3: the First Trisilylphosphane Derivative with an almost Planar Three‐Coordinated Phosphorus Atom

The title compound ( 1 ) was obtained by salt‐metathesis reaction of iPr₃SiPLi₂ with two molar equiv. of iPr₃SiOTf (OTf = OSO₂CF₃) in 34% yield. Surprisingly, ( 1 ) consists of an 4 : 1 mixture of the two diastereomers ( 1 a ) and ( 1 b ), which do not interconvert to each other even at their decomposition temperature (> 70 °C). They represent different iPr‐rotational isomers which are separated by an unusual high rotational barrier (> 25 kcal mol^–1), resulting from hindered rotations around the Si–C and C–C bonds. The unexpectedly small magnitude of the ¹J(Si, P) coupling constant of ( 1 a ) (9.4 Hz) and ( 1 b ) (9.0 Hz) reflects unusual electronic properties of the Si₃P skeleton. Hitherto only ( 1 a ) could be isolated in the form of single‐crystals and its structure was determined by X‐ray diffraction analysis. The P‐atom in ( 1 a ) is almost planar coordinated (sum of bond angles = 359.789(3)°), but the Si–P‐distance (2.264(7) Å) resembles those values of related silylphosphanes with pyramidally coordinated P atoms. Although MNDO calculations revealed two other iPr‐rotational isomers with similar energy, they prove that the Si₃P skeleton prefers the trigonal‐planar arrangement due to steric congestion.     

Theoretical Study of Pd11Si6 Nanosheet Compounds Including Seven‐Coordinated Si Species and Its Ge Analogues

Nanosheet compounds Pd₁₁(SiiPr)₂(SiiPr₂)₄(CNtBu)₁₀ ( 1 ) and Pd₁₁(SiiPr)₂(SiiPr₂)₄(CNMes)₁₀ ( 2 ), containing two Pd₇(SiiPr)(SiiPr₂)₂(CNR)₄ plates (R=tBu or Mes) connected with three common Pd atoms, were investigated with DFT method. All Pd atoms are somewhat positively charged and the electron density is accumulated between the Pd and Si atoms, indicating that a charge transfer (CT) occurs from the Pd to the Si atoms of the SiMe₂ and SiMe groups. Negative regions of the Laplacian of the electron density were found between the Pd and Si atoms. A model of a seven‐coordinated Si species, that is, Pd₅(Pd?SiMe), is predicted to be a stable pentagonal bipyramidal molecule. Five Pd atoms in the equatorial plane form bonding overlaps with two 3p orbitals of the Si atom. This is a new type of hypervalency. The Ge analogues have geometry and an electronic structure similar to those of the Si compounds. But their formation energies are smaller than those of the Si analogues. The use of the element Si is crucial to synthesize these nanoplate compounds.     

Synthese,Kristallstrukturen und quantenchemische Untersuchung von Verbindungen mit leiterartigem Al4P4‐ und hexagonal prismatischem Al6P6‐Grundgerüst

The reaction of AlCl₃ with Li₂PR (R = SiiPr₃, SiMeiPr₂) in a mixture of heptane and ether yields in the polycyclic compounds [(AlCl)₄(μ₃‐PR)₂(μ‐PR)₂(Et₂O)₂]( 1a : R = SiiPr₃; 1b : SiMeiPr₂) with a ladder‐shaped Al₄P₄ core. The coordination sphere of the outer aluminium atoms in these compounds is completed by ether ligands. In contrast, the reaction of AlCl₃ with Li₂PSiiPr₃ in pure heptane yields in the formation of the hexagonal prismatic compound [(AlCl)₆(μ₃‐PSiiPr₃)₆]( 2 ). 1 and 2 were characterized by single crystal X‐ray diffraction analysis as well as by ³¹P{1H} and ²⁷Al NMR spectroscopy. The structure determining effect of the solvent can be rationalized by quantumchemical calculations, which also show that the hexagonal prismatic structure is the most stable of the investigated oligomers in absence of ether.     

Synthese von verbrückend substituierten sekundären Phosphanen sowie deren Reaktionen mit Triisopropylindium

In this work we report the synthesis and characterisation of the 1.5‐diphosphanyldiethylether O{C₂H₄PH(SiiPr₃)}₂ ( 2 ) in which two silyl‐substituted phosphine groups are linked by an ether bridge as well as the compound O(SiiPr₂PHEt)₂ ( 3 ) where two ethyl substitute phosphine groups are connected by a siloxane bridge. In addition, we describe the metalation of 2 and 3 with triisopropylindium. These reactions lead to the compounds [O{C₂H₄P(SiiPr₃)IniPr₂}₂] ( 4 ) and [O{SiiPr₂P(Et)IniPr₂}₂] ( 5 ) with In₂P₂ ring structures.     

Metalated diphosphanylsiloxanes with polycyclic and polymeric structures

The reactions of the diphosphanylsiloxane O(SiiPr₂PH₂)₂ (1) with MiPr₃ (M = Ga, In) produced the polycyclic compounds [O{SiiPr₂(PH)MiPr₂}{SiiPr₂(P)MiPr}] ₂ (2, 3). Compounds 2 and 3 are composed of three M₂P₂ rings forming a ladder structure and two OSi₂P₂M rings. By reactions of 1 with n-BuLi the polymeric compound [O(SiiPr₂PHLi)₂(THF)(TMEDA)] · THF (4) was obtained.     

[iPr2P]2P?SiMe3 und [iPr2P]2PLi – Synthese und Reaktionen Struktur des [iPr2P]2P?P[PiPr2]2

[iPr₂P]₂P? SiMe₃ and [iPr₂P]₂PLi – Synthesis and Reactions Structure of [iPr₂P]₂P? P[PiPr₂]₂ [iPr₂P]₂P? SiMe₃ 1 and [iPr₂P]₂PLi 2 were prepared to investigate the influence of the bulky alkyl groups on formation and properties of the ylides R₂P? P?P(X)R₂ (R = iPr, tBu; X = Br, Me) in reactions of 1 with CBr₄ and of 2 with 1,2-dibromoethane or MeCl, resp. Compared to the iPr groups the tBu groups favour the formation of ylides. With CBr₄ 1 forms iPr₂P? P?P(Br)iPr₂ 5 just as a minor product which decomposes already below ?30°C. With 1,2-dibromoethane 2 yields only traces of 5 but [iPr₂P]P? P[P(iPr)₂]₂ 7 as main product. With MeCl 2 gives iPrP? P?P(Me)iPr₂ 9 and [iPr₂P]₂PMe 10 in a molar ratio of 1:1. 9 is considerably more stable than 5. 7 crystallizes triclinic in the space group P1 (No. 2) with a = 10.813 Å, b = 11.967 Å, c = 15.362 Å, α = 67.90°, β = 71.36°, γ = 64.11° and two formula units in the unit cell.     

Untersuchungen zu Reaktionen des Diphosphanylsilans iPr2Si(PH2)2 mit Erdalkalimetallsilazaniden

The reaction of iPr₂Si(PH₂)₂ ( 1 ) with [Ca{N(SiMe₃)₂}₂(THF)₂] at 25 °C in molar ratio 1:1 yields the compound [Ca₃{iPr₂Si(PH)₂}₃(THF)₆] ( 2 ). Compound 2 consists of two Ca₂P₃ trigonal bipyramids with one conjoint calcium corner and SiiPr₂ bridged phosphorus atoms. In contrast, the same reaction at 60 °C yield the complex [Ca({P(SiiPr₂)₂PH}₂(THF)₄] ( 3 ). The isotype strontium compound [Sr({P(SiiPr₂)₂PH}₂(THF)₄] ( 4 ) was obtained from the reaction of iPr₂Si(PH₂)₂ with [Sr{N(SiMe₃)₂}₂(DME)₂]. The Compounds 2 – 4 were characterised by single crystal X‐ray diffraction, elemental analysis as well as IR and NMR spectroscopic techniques.     

Sterically Tuned P‐Phosphanylamino Phosphaalkenes (Me3Si)2C=PN(R)PPh2 and (iPrMe2Si)2C=PN(R)PPh2

Deprotonation of the aminophosphanes Ph₂PN(H)R 1a – 1h [R = tBu ( 1a ), 1‐adamantyl ( 1b ), iPr ( 1c ), CPh₃ ( 1d ), Ph ( 1e ), 2,4,6‐Me₃C₆H₂ (Mes) ( 1f ), 2,4,6‐tBu₃C₆H₂ (Mes*) ( 1g ), 2,6‐iPr₂C₆H₃ (DIPP) ( 1h )], followed by reactions of the phosphanylamide salts Li[Ph₂PNR] 2a , 2b , 2g , and 2h with the P‐chlorophosphaalkene (Me₃Si)₂C=PCl, and of 2a – 2g with (iPrMe₂Si)₂C=PCl, gave the isolable P‐phosphanylamino phosphaalkenes (Me₃Si)₂C=PN(R)PPh₂ 3a , 3b , 3g , and (iPrMe₂Si)₂C=PN(R)PPh₂ 4a – 4g . ³¹P NMR spectra, supported by X‐ray structure determinations, reveal that in compounds 2a , 2b , 3a , and 3b , with bulky N‐alkyl groups the Si₂C=P–N–P skeleton is non‐planar (orthogonal conformation), whereas 3g , 3h , and 4g with bulky N‐aryl groups exhibit planar conformations of the Si₂C=P–N–P skeleton. Solid 3g and 4g exhibit cisoid orientation of the planar C=P–N–C units (planar I) but in solid 3h the transoid rotamer is present (planar II). From 3g , 4d , and 4g mixtures of rotamers were detected in solution by pairs of ³¹P NMR patterns ( 3h : line broadening).     

Borderline of hydrogen bonding of silanols

Two new silanols bearing very bulky silyl groups, (i-Pr₃ Si)₃SiOH and (t − BuMe₂Si)₃SiOH were prepared by peracidoxidation of their respective silanes. The X − ray crystallographic analysis revealed that (t − BuMe₂Si)₃ SiOH forms a dimeric structure with hydrogen bonding, while (i − Pr₃ Si)₃ SiOH exists as a monomer in the crystal. The effects of the size of the substituents as well as the reactivity of these silanols are discussed.     

Die Tris(triisopropylsilyl)pnikogene: Synthese und Charakterisierung von [E(SiiPr3)3] (E = P,As, Sb)

The Tris(triisopropylsilyl)pnikogenes: Synthesis and Characterisation of [E(Si ⁱ Pr₃)₃] (E = P, As, Sb) The compounds [E(SiⁱPr₃)₃] (E = P, As, Sb) ( 1 – 3 ) were prepared in high yields by the reaction of (Na/K)₃E with ⁱPr₃SiCl in DME. They were characterised by ¹H‐, ¹³C‐, ²⁹Si‐ and ³¹P‐NMR spectroscopy, mass spectrometry and single crystal X‐ray diffraction. Compound 1 , recently obtained in a different way, shows an unusual trigonal planar coordination of the central phosphorus atom. However, 2 and 3 , featuring increasing covalence radii of the central atoms, show an increasingly pyramidal structure. 1 – 3 crystallise isotyp in the cubic spacegroup Pa 3, the lattice constants are: 1 : a = 1860.1(2) pm, 2 : a = 1873.6(2) pm, 3 : a = 1897.1(2) pm.     

Preparation and characterization of tris(iso‐propyl)stibine complexes of palladium and platinum

Tris(iso‐propyl)stibine complexes of palladium and platinum of the type [MX₂(SbⁱPr₃)₂] [M, X = Pd, Cl (1a), Pd, Br (1b), Pd, I (1c), Pt, Cl (2)] have been prepared and characterized by elemental analysis, IR and ¹H NMR spectral data. The structure of 1a, established by X‐ray structural analysis, revealed that the palladium atom is in a square planar environment with mutually trans SbⁱPr₃ ligands. Copyright © 2001 John Wiley & Sons, Ltd.     

Unusual Pathway Taken in the Reaction of Bis(alkynyl)diisopropylaminoboranes with B(C6F5)3

The bis(alkynyl)diisopropyl‐aminoboranes 7 were prepared by treatment of iPr₂NBCl₂ with two molar equivalents of 1‐pentynyl lithium or lithium phenylacetylenide, respectively. Their reaction with one molar equivalent of B(C₆F₅)₃ resulted in the formation of the 1,1‐carboboration products 8 that were subsequently stabilized by adduct formation ( 9 ) with tert‐butyl isocyanide. Thermolysis of 8a (R=nPr) proceeded with hydride transfer from a N‐isopropyl substituent to the distal carbon atom of the remaining pentynyl unit at boron to give the zwitterionic five‐membered heterocyclic product 10a in good yield. The analogous product 10b (R=Ph) was obtained upon photolysis of 8b . The compounds 7b , 9b , 10a , and 10b were characterized by X‐ray crystal structure analysis.     

Synthesis,Structure, and Stability of Lithium Arylphosphanidyl-diarylphosphane Oxide

The reaction of LiP(H)Tipp ( 2a ) and KP(H)Tipp ( 2b , Tipp = C₆H₂-2,4,6-iPr₃), which are accessible via metalation of Tipp-PH₂ ( 1 ), with bis(4-tert-butylphenyl)phosphinic chloride yields Tipp-P=P(OM)Ar₂ [M = Li ( 3a ) and K ( 3b )]. These complexes show characteristic chemical ³¹P shifts and large ¹J_PP coupling constants. These compounds degrade with elimination of the phosphinidene Tipp-P: and the alkali metal diarylphosphinites M–O–PAr₂ [M = Li ( 4a ) and K ( 4b )]. The phosphinidene forms secondary degradation products (like the meso and R,R/S,S-isomers of diphosphane Tipp-P(H)–P(H)Tipp ( 5 ) via insertion into a P–H bond of newly formed Tipp-PH₂), whereas the crystallization of [Tipp-P=P(OLi)Ar₂ · LiOPAr₂ · LiCl · 2Et₂O]₂ (i.e. [ 3a·4a· LiCl · 2Et₂O]₂) succeeds from diethyl ether. The metathesis reactions of LiP(SiiPr₃)Tipp and LiP(SiiPr₃)Mes (Mes = C₆H₂-2,4,6-Me₃) with Ar₂P(O)Cl yield Ar*-P=P(OSiiPr₃)Ar₂ (Ar* = Mes, Tipp) which degrade to Ar₂POSiiPr₃ and other secondary products.     

Synthese und Charakterisierung neuer cyclischer und käfigartiger Indium‐Phosphor‐ und Indium‐Arsen‐Verbindungen

Synthesis and Characterization of New Cyclic and Cage‐like Indium — Phosphorus and Indium — Arsenic Compounds The reaction of InEt₃ with H₂ESiiPr₃ initially yields the cyclic compound [Et₂InP(H)SiiPr₃]₂ ( 2 ). 2 appears as a mixture of cis and trans isomers and has been characterized by ³¹P‐NMR spectroscopy, IR spectroscopy, and mass spectrometry. 2 decomposes in solution under elimination of ethane during a few days to form [EtInPSiiPr₃]₄ ( 3 ) with a cage‐like structure. The analogous arsenic compound [EtInAsSiiPr₃]₄ ( 4 ) can be prepared by reaction of InEt₃ with H₂AsSiiPr₃. Central structural motif of 3 and 4 is an In₄E₄ heterocubane like structure (E = P, As), whereas the reaction of InEt₃ with H₂PSiMe₂Thex (Thex = CMe₂iPr) yields [EtInPSiMe₂Thex]₆ ( 5 ) with a hexagonal prismatic structure.     

8‐Amidoquinoline, 8‐(Trialkylsilylamido)quinoline, 2‐Pyridylmethylamide,and (2‐Pyridylmethyl)(trialkylsilyl)amide Complexes of Gallium

Lithium 8‐amidoquinoline ( 1 ) and lithium 8‐(trialkylsilylamido)quinoline [SiMe₂tBu ( 2 ), SiiPr₃ ( 3 )] react with dimethylgallium chloride to the metathesis products dimethylgallium 8‐amidoquinoline ( 4 ) as well as dimethylgallium 8‐(trialkylsilylamido)quinoline [SiMe₂tBu ( 5 ), SiiPr₃ ( 6 )]. The gallium atoms are in distorted tetrahedral environments. During the synthesis of 5 , orange dimethylgallium 2‐butyl‐8‐(tert‐butyldimethylsilylamido)quinoline ( 7 ) was found as by‐product. The metathesis reactions of Me₂GaCl with LiN(R)CH₂Py (Py = 2‐pyridyl) yield the corresponding 2‐pyridylmethylamides Me₂Ga‐N(H)CH₂Py ( 8 ), Me₂Ga‐N(SiMe₂tBu)CH₂Py ( 9 ) and Me₂Ga‐N(SiiPr₃)CH₂Py ( 10 ). In these complexes the gallium atoms show a distorted tetrahedral coordination sphere. However, derivative 8 crystallizes dimeric with bridging amido units whereas in 9 and 10 the 2‐pyridylmethylamido moieties act as bidentate ligands leading to monomeric molecules.     

Iridium(I)‐ und Iridium(III)‐Komplexe mit Triisopropylarsan als Ligand

Iridium(I) and Iridium(III) Complexes with Triisopropylarsane as Ligand The ethene complex trans‐[IrCl(C₂H₄)(AsiPr₃)₂] ( 2 ), which was prepared from [IrCl(C₂H₄)₂]₂ and AsiPr₃, reacted with CO and Ph₂CN₂ by displacement of ethene to yield the substitution products trans‐[IrCl(L)(AsiPr₃)₂] ( 3 : L = CO; 4 : L = N₂). UV irradiation of 2 in the presence of acetonitrile gave via intramolecular oxidative addition the hydrido(vinyl)iridium(III) compound [IrHCl(CH=CH₂)(CH₃CN)(AsiPr₃)₂] ( 5 ). The reaction of 2 with dihydrogen led under argon to the formation of the octahedral complex [IrH₂Cl(C₂H₄)(AsiPr₃)₂] ( 7 ), whereas from 2 under 1 bar H₂ the ethene‐free compound [IrH₂Cl(AsiPr₃)₂] ( 6 ) was generated. Complex 6 reacted with ethene to afford 7 and with pyridine to give [IrH₂Cl(py)(AsiPr₃)₂] ( 8 ). The mixed arsane(phosphane)iridium(I) compound [IrCl(C₂H₄)(PiPr₃)(AsiPr₃)] ( 11 ) was prepared either from the dinuclear complex [IrCl(C₂H₄)(PiPr₃)]2 ( 9 ) and AsiPr₃ or by ligand exchange from [IrCl(C₂H₄)(PiPr₃)(SbiPr₃)] ( 10 ) und triisopropylarsane. The molecular structure of 5 was determined by X‐ray crystallography.     

Synthesis of a C(sp2)-bridged Phosphine-Borane by Ionic Coupling

The vinyl carbenoid H₂C=CBr(Li) has been used as key precursor to prepare a geminal C(sp²)-bridged phosphine-borane. Starting from bromoethene, two sequences of lithiation/electrophilic trapping, with ClPiPr₂ and FBMes₂ respectively, affords iPr₂P–C(=CH₂)–BMes₂ 3 [Mes = 2,4,6-(H₃C)₃C₆H₂]. This new phosphine-borane 3 was characterized by multi-nuclear NMR and mass spectroscopy. It adopts a monomeric open structure without P→B interaction. A few crystals of a secondary product 4 were analyzed by X-ray diffraction, revealing an unusual dimeric structure.     

Pr4S3[Si2O7] und Pr3Cl3[Si2O7]: Durch weiche Fremdanionen modifizierte Derivate von Praseodymdisilicat

Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇]: Derivatives of Praseodymium Disilicate Modified by Soft Foreign Anions For synthesizing both the disilicate derivatives Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇], Pr, Pr₆O₁₁ and SiO₂ are brought to reaction with S and PrCl₃, respectively, in suitable molar ratios (850 °C, 7 d) in evacuated silica tubes. By using NaCl as a flux, Pr₄S₃[Si₂O₇] crystallizes as pale green, transparent single crystals (tetragonal, I4₁/amd, a = 1201.6(1), c = 1412.0(2) pm, Z = 8) with the appearance of slightly compressed octahedra. On the other hand, Pr₃Cl₃[Si₂O₇] emerges as pale green, transparent platelets and crystallizes monoclinically (space group: P2₁, a = 530.96(6), b = 1200.2(1), c = 783.11(8) pm, β = 109.07(1)°, Z = 2). In both crystal structures ecliptically conformed [Si₂O₇]^6– units of two corner‐linked [SiO₄] tetrahedra with Si–O–Si bridging angles of 131° in the sulfide and 148° in the chloride disilicate are present. In Pr₄S₃[Si₂O₇] both crystallographically independent Pr³⁺ cations show coordination numbers of 8 + 1 (5 S^2– and 3 + 1 O^2–) and 9 (3 S^2– and 6 O^2–). For Pr1, Pr2 and Pr3 in Pr₃Cl₃[Si₂O₇] coordination numbers of 10 (5 Cl^– and 5 O^2–) and 9 (2 ×; 4 Cl^– and 5 O^2– or 3 Cl^– and 6 O^2–, respectively) occur.     

N‐Heterocyclic Carbene Coordinated Neutral and Cationic Heavier Cyclopropylidenes

Cyclopropylidene is a transient intermediate of the allene–propyne–cyclopropene isomerization. The incorporation of heavier Group 14 elements into the cyclopropylidene scaffold has to date been restricted to the formal replacement of the carbenic carbon atom by a base‐coordinated silicon(II) center. Herein we report the synthesis and characterization of NHC‐coordinated heavier cyclopropylidenes (Si₂GeR₃X, and Si₃R₃Br; X=Cl, Mes; R=Tip=2,4,6‐iPr₃C₆H₂) in which the three‐membered ring is exclusively formed by silicon and germanium. In case of the chloro‐substituted Si₂Ge‐cyclopropylidene, a stable heavier cycloprop‐1‐yl‐2‐ylidene cation is obtained by NHC‐induced chloride dissociation.