Versatile conversion of N-heterocyclic silylene to silyl metal compounds by insertion of divalent silicon into metal-carbon and metal-hydrogen bonds

The facile one-pot reaction of the stable N-heterocyclic silylene LSi: 1 (L=(ArN)C(=CH(2))CH=C(Me)(NAr), Ar=2,6-iPr(2)C(6)H(3)) with Me(2)Zn, Me(3)Al, H(3)Al-NMe(3), and MeLi has been investigated. The silicon(II) atom in 1 is capable of insertion into the corresponding M-C and Al-H bonds under very mild reaction conditions. Thus, Me(2)Zn furnishes the bis(silyl) zinc complex LSi(Me)ZnSi(Me)L 2 as the sole product, irrespective of the molar ratio of the starting materials applied. Moreover, the reactions of 1 with Me(3)Al, H(3)Al-NMe(3), and MeLi lead directly to the 1,1-addition products LSi(Me)(Al(thf)Me(2)) 3, LSi(H)(AlH(2)(NMe(3))) 4, and LSi(Me)Li(thf)(3) 5, respectively. All new compounds 2-5 were fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.     

Rare‐Earth‐Metal–Hydrocarbyl Complexes Bearing Linked Cyclopentadienyl or Fluorenyl Ligands: Synthesis,Catalyzed Styrene Polymerization,and Structure–Reactivity Relationship

A series of rare‐earth‐metal–hydrocarbyl complexes bearing N‐type functionalized cyclopentadienyl (Cp) and fluorenyl (Flu) ligands were facilely synthesized. Treatment of [Y(CH₂SiMe₃)₃(thf)₂] with equimolar amount of the electron‐donating aminophenyl‐Cp ligand C₅Me₄H‐C₆H₄‐o‐NMe₂ afforded the corresponding binuclear monoalkyl complex [({C₅Me₄‐C₆H₄‐o‐NMe(μ‐CH₂)}Y{CH₂SiMe₃})₂] ( 1 a ) via alkyl abstraction and C? H activation of the NMe₂ group. The lutetium bis(allyl) complex [(C₅Me₄‐C₆H₄‐o‐NMe₂)Lu(η³‐C₃H₅)₂] ( 2 b ), which contained an electron‐donating aminophenyl‐Cp ligand, was isolated from the sequential metathesis reactions of LuCl₃ with (C₅Me₄‐C₆H₄‐o‐NMe₂)Li (1 equiv) and C₃H₅MgCl (2 equiv). Following a similar procedure, the yttrium‐ and scandium–bis(allyl) complexes, [(C₅Me₄‐C₅H₄N)Ln(η³‐C₃H₅)₂] (Ln=Y ( 3 a ), Sc ( 3 b )), which also contained electron‐withdrawing pyridyl‐Cp ligands, were also obtained selectively. Deprotonation of the bulky pyridyl‐Flu ligand (C₁₃H₉‐C₅H₄N) by [Ln(CH₂SiMe₃)₃(thf)₂] generated the rare‐earth‐metal–dialkyl complexes, [(η³‐C₁₃H₈‐C₅H₄N)Ln(CH₂SiMe₃)₂(thf)] (Ln=Y ( 4 a ), Sc ( 4 b ), Lu ( 4 c )), in which an unusual asymmetric η³‐allyl bonding mode of Flu moiety was observed. Switching to the bidentate yttrium–trisalkyl complex [Y(CH₂C₆H₄‐o‐NMe₂)₃], the same reaction conditions afforded the corresponding yttrium bis(aminobenzyl) complex [(η³‐C₁₃H₈‐C₅H₄N)Y(CH₂C₆H₄‐o‐NMe₂)₂] ( 5 ). Complexes 1 – 5 were fully characterized by ¹H and ¹³C NMR and X‐ray spectroscopy, and by elemental analysis. In the presence of both [Ph₃C][B(C₆F₅)₄] and AliBu₃, the electron‐donating aminophenyl‐Cp‐based complexes 1 and 2 did not show any activity towards styrene polymerization. In striking contrast, upon activation with [Ph₃C][B(C₆F₅)₄] only, the electron‐withdrawing pyridyl‐Cp‐based complexes 3 , in particular scandium complex 3 b , exhibited outstanding activitiy to give perfectly syndiotactic (rrrr >99 %) polystyrene, whereas their bulky pyridyl‐Flu analogues ( 4 and 5 ) in combination with [Ph₃C][B(C₆F₅)₄] and AliBu₃ displayed much‐lower activity to afford syndiotactic‐enriched polystyrene.     

Reactivity of Dialumane and “Dialumene” Compounds toward Alkenes

The reactions of dialumane [L(thf)Al? Al(thf)L] ( 1 , L=[{(2,6‐iPr₂C₆H₃)NC(Me)}₂]^2?) with stilbene and styrene afforded the oxidation/insertion products [L(thf)Al(CH(Ph)? CH(Ph))AlL] ( 2 ) and [L(thf)Al(CH(Ph)? CH₂)Al(thf)L] ( 3 ), respectively. In the presence of Na metal, precursor 1 reacted with butadienes, possibly through the reduced “dialumene” or the “carbene‐like” :AlL species, to yield aluminacyclopentenes [LAl(CH₂C(Me)?C(Me)CH₂)Na]_n ( 4 a ) and [Na(dme)₃][LAl(CH₂C(Me)?CHCH₂)] ( 4 b , dme=dimethoxyethane) as [1+4] cycloaddition products, as well as the [2+4] cycloaddition product 1,6‐dialumina‐3,8‐cyclodecadiene, [{Na(dme)}₂][LAl(CH₂C(Me)?C(Me)CH₂)₂AlL] ( 5 ). The possible mechanisms of the cycloaddition reactions were studied by using DFT computations.     

A Gallium‐Substituted Distibene and an Antimony‐Analogue Bicyclo[1.1.0]butane: Synthesis and Solid‐State Structures

RGa {R=HC[C(Me)N(2,6‐iPr₂C₆H₃)]₂} reacts with Sb(NMe₂)₃ with insertion into the Sb? N bond and elimination of RGa(NMe₂)₂ ( 2 ), yielding the Ga‐substituted distibene R(Me₂N)GaSb?SbGa(NMe₂)R ( 1 ). Thermolysis of 1 proceeded with elimination of RGa and 2 and subsequent formation of the bicyclo[1.1.0]butane analogue [R(Me₂N)Ga]₂Sb₄ ( 3 ).     

Experimental and Theoretical Studies on Arene‐Bridged Metal–Metal‐Bonded Dimolybdenum Complexes

The bis(hydride) dimolybdenum complex, [Mo₂(H)₂{HC(N‐2,6‐iPr₂C₆H₃)₂}₂(thf)₂], 2 , which possesses a quadruply bonded Mo₂^II core, undergoes light‐induced (365 nm) reductive elimination of H₂ and arene coordination in benzene and toluene solutions, with formation of the Mo^I₂ complexes [Mo₂{HC(N‐2,6‐iPr₂C₆H₃)₂}₂(arene)], 3?C₆H₆ and 3?C₆H₅Me , respectively. The analogous C₆H₅OMe, p‐C₆H₄Me₂, C₆H₅F, and p‐C₆H₄F₂ derivatives have also been prepared by thermal or photochemical methods, which nevertheless employ different Mo₂ complex precursors. X‐ray crystallography and solution NMR studies demonstrate that the molecule of the arene bridges the molybdenum atoms of the Mo^I₂ core, coordinating to each in an η² fashion. In solution, the arene rotates fast on the NMR timescale around the Mo₂‐arene axis. For the substituted aromatic hydrocarbons, the NMR data are consistent with the existence of a major rotamer in which the metal atoms are coordinated to the more electron‐rich C?C bonds.     

CH Bond Activation during and after the Reactions of a Metallacyclic Amide with Silanes: Formation of a μ‐Alkylidene Hydride Complex,Its H–D Exchange,and β‐H Abstraction by a Hydride Ligand

Metallacyclic complex [(Me₂N)₃Ta(η²‐CH₂SiMe₂NSiMe₃)] ( 3 ) undergoes C?H activation in its reaction with H₃SiPh to afford a Ta/μ‐alkylidene/hydride complex, [(Me₂N)₂{(Me₃Si)₂N}Ta(μ‐H)₂(μ‐C‐η²‐CHSiMe₂NSiMe₃)Ta(NMe₂)₂] ( 4 ). Deuterium‐labeling studies with [D₃]SiPh show H–D exchange between the Ta?D ?Ta unit and all methyl groups in [(Me₂N)₂{(Me₃Si)₂N}Ta(μ‐D)₂(μ‐C‐η²‐CHSiMe₂NSiMe₃)Ta(NMe₂)₂] ([D₂]‐ 4 ) to give the partially deuterated complex [D_n]‐ 4 . In addition, 4 undergoes β‐H abstraction between a hydride and an NMe₂ ligand and forms a new complex [(Me₂N){(Me₃Si)₂N}Ta(μ‐H)(μ‐N‐η²‐C,N‐CH₂NMe)(μ‐C‐η²‐C,N‐CHSiMe₂NSiMe₃)Ta(NMe₂)₂] ( 5 ) with a cyclometalated, η²‐imine ligand. These results indicate that there are two simultaneous processes in [D_n]‐ 4 : 1) H–D exchange through σ‐bond metathesis, and 2) H?D elimination through β‐H abstraction (to give [D_n]‐ 5 ). Both 4 and 5 have been characterized by single‐crystal X‐ray diffraction studies.     

Stabilization of a Silaaldehyde by its η2 Coordination to Tungsten

Treatment of pyridine‐stabilized silylene complexes [(η⁵‐C₅Me₄R)(CO)₂(H)W?SiH(py)(Tsi)] (R=Me, Et; py=pyridine; Tsi=C(SiMe₃)₃) with an N‐heterocyclic carbene ^MeIⁱPr (1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) caused deprotonation to afford anionic silylene complexes [(η⁵‐C₅Me₄R)(CO)₂W?SiH(Tsi)][H^MeIⁱPr] (R=Me ( 1‐Me ); R=Et ( 1‐Et )). Subsequent oxidation of 1‐Me and 1‐Et with pyridine‐N‐oxide (1 equiv) gave anionic η²‐silaaldehydetungsten complexes [(η⁵‐C₅Me₄R)(CO)₂W{η²‐O?SiH(Tsi)}][H^MeIⁱPr] (R=Me ( 2‐Me ); R=Et ( 2‐Et )). The formation of an unprecedented W‐Si‐O three‐membered ring was confirmed by X‐ray crystal structure analysis.     

Synthese und Charakterisierung neuer intramolekular stickstoffstabilisierter Organoaluminium‐ und Organogalliumalkoxide

Synthesis and Characterization of New Intramolecularly Nitrogen‐stabilized Organoaluminium‐ and Organogallium Alkoxides The intramolecularly nitrogen stabilized organoaluminium alkoxides [Me₂Al{μ‐O(CH₂)₃NMe₂}]₂ ( 1a ), Me₂AlOC₆H₂(CH₂NMe₂)₃‐2,4,6 ( 2a ), [(S)‐Me₂Al{μ‐OCH₂CH(i‐Pr)NH‐i‐Pr}]₂ ( 3a ) and [(S)‐Me₂Al{μ‐OCH₂CH(i‐Pr)NHCH₂Ph}]₂ ( 4 ) are formed by reacting equimolar amounts of AlMe₃ and Me₂N(CH₂)₃OH, C₆H₂[(CH₂NMe₂)₃‐2,4,6]OH, (S)‐i‐PrNHCH(i‐Pr)CH₂OH, or (S)‐PhCH₂NHCH(i‐Pr)CH₂OH, respectively. An excess of AlMe₃ reacts with Me₂N(CH₂)₂OH, Me₂N(CH₂)₃OH, C₆H₂[(CH₂NMe₂)₃‐2,4,6]OH, and (S)‐i‐PrNHCH(i‐Pr)CH₂OH producing the “pick‐a‐back” complexes [Me₂AlO(CH₂)₂NMe₂](AlMe₃) ( 5 ), [Me₂AlO(CH₂)₃NMe₂](AlMe₃) ( 1b ), [Me₂AlOC₆H₂(CH₂NMe₂)₃‐2,4,6](AlMe₃)₂ ( 2b ), and [(S)‐Me₂AlOCH₂CH(i‐Pr)NH‐i‐Pr](AlMe₃) ( 3b ), respectively. The mixed alkyl‐ or alkenylchloroaluminium alkoxides [Me(Cl)Al{μ‐O(CH₂)₂NMe₂}]₂ ( 6 ) and [{CH₂=C(CH₃)}(Cl)Al{μ‐O(CH₂)₂NMe₂}]₂ ( 8 ) are to obtain from Me₂AlCl and Me₂N(CH₂)₂OH and from [Cl₂Al{μ‐O(CH₂)₂NMe₂}]₂ ( 7 ) and CH₂=C(CH₃)MgBr, respectively. The analogous dimethylgallium alkoxides [Me₂Ga{μ‐O(CH₂)₃NMe₂}]₂ ( 9 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)NH‐i‐Pr}]_n ( 10 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)NHCH₂Ph}]_n ( 11 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)N(Me)CH₂Ph}]_n ( 12 ) and [(S)‐Me₂Ga{μ‐OCH₂(C₄H₇NHCH₂Ph)}]_n ( 13 ) result from the equimolar reactions of GaMe₃ with the corresponding alcohols. The new compounds were characterized by elemental analyses, ¹H‐, ¹³C‐ and ²⁷Al‐NMR spectroscopy, and mass spectrometry. Additionally, the structures of 1a , 1b , 2a , 2b , 3a , 5 , 6 and 8 were determined by single crystal X‐ray diffraction.     

Halogenid‐Ionen als Katalysator: Metallzentrierte C–C‐Bindungsknüpfung ausgehend von Acetontril

Halide Ions as Catalyst: Metalcentered C–C Bond Formation Proceeded from Acetonitril AlMe₃ reacts at 20 ?C in acetonitrile to the complex [Me₃Al(NCMe)] ( 1 ). By addition of cesium halides (X^– = F^–, Cl^–, Br^–) a trimerisation to the heterocycle [Me₂Al{HNC(Me)}₂C(CN)] ( 2 ) has been observed. The reaction might be carried out under catalytic conditions (1–2 mol% CsX). The gallium complex [Me₂Ga{HNC(Me)}₂ · C(CN)] ( 3 ), generated under similar reaction conditions, can be converted to the silylated compound [Me₂Ga{Me₃SiNC(Me)}₂C(CN)] ( 4 ) by successive treatment with two equivalents n‐butyllithium and Me₃SiCl. 3 reacts under hydrolysis conditions (1 M hydrochloric acid) to the iminium salt [{H₂NC(Me)}₂C(CN)]Cl ( 5 ). A mixture of H₂O, Ph₂PCl and 3 in THF/toluene leads in a unusual conversion to the diphospane derivative [Ph₂P–P(O)(Me₂GaCl)] ( 6 ). 1 , 2 , 4 , 5 and 6 have been characterized by NMR, IR and MS techniques. X‐ray structure analyses were performed with 1 , 2 , 4 and 6 · 0.5 toluene. According this 1 possesses an almost linear axis AlNCC [Al1–N1–C3: 179,5(2)?; N1–C3–C4: 179,7(4)?]. 2 is an AlN₂C₃ six‐membered heterocycle with two iminium fuctions. One N–H group is responsible for a intermolecular chain‐formation through hydrogen bridges to an adjacent nitrile group along the direction [010]. The basic structural motif of the heterocycle 3 has been maintained after silylation to 4 . In 6 · 0.5 toluene an unit Me₂GaCl, originated from 3 , is coordinated to the oxygen atom of the diphosphane oxide Ph₂P–P(O)Ph₂.     

1,1‐Ethylboration of alkyn‐1‐yl‐chloro(methyl)silanes: alkenes with chloro(methyl)silyl and diethylboryl groups in cis positions

The 1,1‐ethylboration of alkyn‐1‐yl‐chloro(methyl)silanes, Me₂Si(Cl)? C?C? R ( 1 ) and Me(H)Si(Cl)? C?C? R ( 2 ) [R = Bu ( 2a ), CH₂NMe₂ ( 2b )] requires harsh reaction conditions (up to 20 days in boiling triethylborane), and leads to alkenes in which the boryl and silyl groups occupy cis ((E)‐isomers: 3a , 3b , 5a , 5b ) or trans positions ((Z)‐isomers in smaller quantities: 4b and 6b ). The alkenes are destabilized in the presence of SiH(Cl) and CH₂NMe₂ units ( 5b , 6b ). NMR data indicate hyper‐coordinated silicon by intramolecular N? Si coordination in 3b and 5b , by which, at the same time, weak Si? Cl? B bridges are favoured. Copyright © 2005 John Wiley & Sons, Ltd.     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Synthesis and Characterization of m‐Terphenyl (1,3‐Diphenylbenzene) Compounds Containing Trifluoromethyl Groups

The bis(silyl)triazene compound 2,6‐(Me₃Si)₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 4 ) was synthesized by double lithiation/silylation of 2,6‐Br₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 1 ). Furthermore, 2,6‐bis[3,5‐(CF₃)₂‐C₆H₃]‐4‐Me‐C₆H₂‐1‐(N?N? NC₄H₈)C₆H₂ derivative 6 can be easily synthesized by a C,C‐bond formation reaction of 1 with the corresponding aryl‐Grignard reagent, i.e., 3,5‐bis[(trifluoromethyl)phenyl]magnesium bromide. Reactions of compound 4 with KI and 6 with I₂ afforded in good yields novel phenyl derivatives, 2,6‐(Me₃Si)₂‐4‐MeC₆H₂? I and 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]‐4‐MeC₆H₂? I ( 5 and 7 , resp.). On the other hand, the analogous m‐terphenyl 1,3‐diphenylbenzene compound 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]C₆H₃? I ( 8 ) could be obtained in moderate yield from the reaction of (2,6‐dichlorophenyl)lithium and 2 equiv. of aryl‐Grignard reagent, followed by the reaction with I₂. Different attempts to introduce the ^tBu (Me₃C) or neophyl (PhC(Me)₂CH₂) substituents in the central ring were unsuccessful. All the compounds were fully characterized by elemental analysis, melting point, IR and NMR spectroscopy. The structure of compound 6 was corroborated by single‐crystal X‐ray diffraction measurements.     

Calcium–Amidoborane–Ammine Complexes: Thermal Decomposition of Model Systems

Hydrocarbon‐soluble model systems for the calcium–amidoborane–ammine complex Ca(NH₂BH₃)₂ ? (NH₃)₂ were prepared and structurally characterized. The following complexes were obtained by the reaction of RNH₂BH₃ (R=H, Me, iPr, DIPP; DIPP=2,6‐diisopropylphenyl) with Ca(DIPP‐nacnac)(NH₂) ? (NH₃)₂ (DIPP‐nacnac=DIPP? NC(Me)CHC(Me)N? DIPP): Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)₂, Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)₃, Ca(DIPP‐nacnac)[NH(Me)BH₃] ? (NH₃)₂, Ca(DIPP‐nacnac)[NH(iPr)BH₃] ? (NH₃)₂, and Ca(DIPP‐nacnac)[NH(DIPP)BH₃] ? NH₃. The crystal structure of Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)₃ showed a NH₂BH₃^? unit that was fully embedded in a network of BH???HN interactions (range: 1.97(4)–2.39(4) Å) that were mainly found between NH₃ ligands and BH₃ groups. In addition, there were N? H???C interactions between NH₃ ligands and the central carbon atom in the ligand. Solutions of these calcium–amidoborane–ammine complexes in benzene were heated stepwise to 60 °C and thermally decomposed. The following main conclusions can be drawn: 1) Competing protonation of the DIPP‐nacnac anion by NH₃ was observed; 2) The NH₃ ligands were bound loosely to the Ca²⁺ ions and were partially eliminated upon heating. Crystal structures of [Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)]_∞, Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃) ? (THF), and [Ca(DIPP‐nacnac){NH(iPr)BH₃}]₂ were obtained. 3) Independent of the nature of the substituent R in NH(R)BH₃, the formation of H₂ was observed at around 50 °C. 4) In all cases, the complex [Ca(DIPP‐nacnac)(NH₂)]₂ was formed as a major product of thermal decomposition, and its dimeric nature was confirmed by single‐crystal analysis. We proposed that thermal decomposition of calcium–amidoborane–ammine complexes goes through an intermediate calcium–hydride–ammine complex which eliminates hydrogen and [Ca(DIPP‐nacnac)(NH₂)]₂. It is likely that the formation of metal amides is also an important reaction pathway for the decomposition of metal–amidoborane–ammine complexes in the solid state.     

Regiospecific Formation and Unusual Optical Properties of 2,5‐Bis(arylethynyl)rhodacyclopentadienes: A New Class of Luminescent Organometallics

A series of 2,5‐bis(arylethynyl)rhodacyclopentadienes has been prepared by a rare example of regiospecific reductive coupling of 1,4‐(p‐R‐phenyl)‐1,3‐butadiynes (R?H, Me, OMe, SMe, NMe₂, CF₃, CO₂Me, CN, NO₂, ?C?C‐(p‐C₆H₄?NHex₂), ?C?C?(p‐C₆H₄?CO₂Oct)) at [RhX(PMe₃)₄] ( 1 ) (X=?C?C?SiMe₃ ( a ), ?C?C‐(p‐C₆H₄?NMe₂) ( b ), ?C?C?C?C?(p‐C₆H₄?NPh₂) ( c ) or ?C?C?{p‐C₆H₄‐C?C?(p‐C₆H₄‐N(C₆H₁₃)₂)} ( d ) or Me ( e )), giving the 2,5‐bis(arylethynyl) isomer exclusively. The rhodacyclopentadienes bearing a methyl ligand in the equatorial plane (compound 1 e ) have been converted into their chloro analogues by reaction with HCl etherate. The rhodacycles thus obtained are stable to air and moisture in the solid state and the acceptor‐substituted compounds are even stable to air and moisture in solution. The photophysical properties of the rhodacyclopentadienes are highly unusual in that they exhibit, exclusively, fluorescence between 500–800 nm from the S₁ state, with quantum yields of Φ=0.01–0.18 and short lifetimes (τ=0.45–8.20 ns). The triplet state formation (Φ_ISC=0.57 for 2 a ) is exceptionally slow, occurring on the nanosecond timescale. This is unexpected, because the Rh atom should normally facilitate intersystem crossing within femto‐ to picoseconds, leading to phosphorescence from the T₁ state. This work therefore highlights that in some transition‐metal complexes, the heavy atom can play a more subtle role in controlling the photophysical behavior than is commonly appreciated.     

Die Hydroaluminierung von 1,1,4,4‐Tetramethyl‐2,3‐diazabutadien mit Dialkylaluminiumhydriden – Synthese von Dialkylaluminiumhydrazoniden

The Hydroalumination of 1,1,4,4‐Tetramethyl‐2,3‐diazabutadiene by Dialkylaluminium Hydrides – Synthesis of Dialkylaluminium Hydrazonides 1,1,4,4‐Tetramethyl‐2,3‐diazabutadiene reacted with dimethylaluminium hydride by hydroalumination of only one C=N double bond. The hydrazone derivative [Me₂Al–N(CHMe₂)–N=CMe₂]₂ ( 1 ) was formed which gave a dimer possessing a six‐membered Al₂N₄ heterocycle. The hydroalumination of both C=N double bonds was not observed. Also an excess of di(tert‐butyl)‐ or bis(trimethylsilylmethyl)aluminium hydride afforded only the product of a single hydroalumination step, a second dialkylaluminium hydride molecule was attached via a coordinative interaction between its central aluminium atom and the nitrogen atom of the C=N double bond and in addition via a 3 c‐2 e Al–H–Al bond. Compounds [(Me₃C)₂Al][(Me₃C)₂AlH]N(CHMe₂)NCMe₂ ( 2 ) and [(Me₃SiCH₂)₂Al][(Me₃SiCH₂)₂AlH]N(CHMe₂)NCMe₂ ( 3 ) were formed which have five‐membered Al₂N₂H heterocycles. Thermolysis of 2 gave by C–H activation compound [(Me₃C)₂Al]₂[CH₂C(Me)=N–]₂ ( 4 ) in trace amounts which possesses two anellated AlN₂C₂ rings with a common N–N bond. In contrast, the thermal decomposition of 3 yielded by the cleavage of the N–N bond a dimeric dialkylaluminium methylideneamide ( 5 ) which has two intact C=N double bonds. Up to now our attempts to insert a C=N double bond into an Al–C bond remained unsuccessful, and only the formation of an adduct [(Me₃C)₃Al(–N=CMe₂)₂] ( 6 ) was observed upon treatment of tri(tert‐butyl)aluminium with the diazabutadiene derivative.     

Bisaminophosphane – Synthese,Struktur und Reaktivität

Bisaminophosphanes – Synthesis, Structure, and Reactivity Different pathways for the synthesis of bis(alkylamino)phosphanes RP(N(H)R′)₂ are described. t‐BuP(N(H)‐ Dipp)₂ (Dipp = 2,6‐i‐Pr₂–C₆H₃) was structurally characterized by single crystal X‐ray diffraction. The reactivity of the compounds was examplarily investigated using t‐BuP(N(H)t‐Bu)₂. Its reaction with Me₃Al and R₂AlH (R = Me, Et, i‐Bu) in 1 : 1 and 1 : 2 stoichiometrie yield monosubstituted compounds of the type t‐BuP(N(H)t‐Bu)(N(AlR₂)t‐Bu).     

Gemischte Sandwichkomplexe der 4 f‐Elemente: Enantiomerenreine Cyclooctatetraenyl‐Cyclopentadienyl‐Komplexe des Samariums und Lutetiums mit donorfunktionalisierten Cyclopentadienylliganden

Organometallic Compounds of the Lanthanides. 139 Mixed Sandwich Complexes of the 4 f Elements: Enantiomerically Pure Cyclooctatetraenyl Cyclopentadienyl Complexes of Samarium and Lutetium with Donor‐Functionalized Cyclopentadienyl Ligands The reactions of [K{(S)‐C₅H₄CH₂CH(Me)OMe}], [K{(S)‐C₅H₄CH₂CH(Me)NMe₂}] and [K{(S)‐C₅H₄CH(Ph)CH₂NMe₂}] with the cyclooctatetraenyl lanthanide chlorides [(η⁸‐C₈H₈)Ln(μ‐Cl)(THF)]₂ (Ln = Sm, Lu) yield the mixed cyclooctatetraenyl cyclopentadienyl lanthanide complexes [(η⁸‐C₈H₈)Sm{(S)‐η⁵ : η¹‐C₅H₄CH₂CH(Me)OMe}] ( 1 a ), [(η⁸‐C₈H₈)Ln{(S)‐η⁵ : η¹‐C₅H₄CH₂CH(Me)NMe₂}] (Ln = Sm ( 2 a ), Lu ( 2 b )) and [(η⁸‐C₈H₈)Ln{(S)‐η⁵ : η¹‐C₅H₄CH(Ph)CH₂NMe₂}] (Ln = Sm ( 3 a ), Lu ( 3 b )). For comparison, the achiral compounds [(η⁸‐C₈H₈)Ln{η⁵ : η¹‐C₅H₄CH₂CH₂NMe₂}] (Ln = Sm ( 4 a ), Lu ( 4 b )) are synthesized in an analogous manner. ¹H‐, ¹³C‐NMR‐, and mass spectra of all new compounds as well as the X‐ray crystal structures of 3 b and 4 b are discussed.     

[2+4] and [2+2] Cycloaddition Reactions of N‐Sulfinyl Carboxylic Acid Amides with (CF3)2BNMe2. Crystal Structure of cyclo‐(CF3)2B‐NMe2‐S(=O)‐N=C(p‐CH3C6H4)‐O

N‐sulfinylacylamides R‐C(=O)‐N=S=O react with (CF₃)₂BNMe₂ ( 1 ) to form, by [2+4] cycloaddition, six‐membered rings cyclo‐(CF₃)₂B‐NMe₂‐S(=O)‐N=C(R)‐O for R = Me ( 2 ), t‐Bu ( 3 ), C₆H₅ ( 4 ), and p‐CH₃C₆H₄ ( 5 ) while N‐sulfinylcarbamic acid esters R‐O‐C(=O)‐N=S=O react with 1 to yield mixtures of six‐membered (cyclo‐(CF₃)₂B‐NMe₂‐S(=O)‐N=C(OR)‐O) and four‐membered rings (cyclo‐(CF₃)₂B‐NMe₂‐S(=O)‐N(C=O)OR) for R = Me ( 6 and 9 ), Et ( 7 and 10 ), and C₆H₅ ( 8 and 11 ). The structure of 5 has been determined by X‐ray diffraction.     

Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC–Silicon(I) Radical and an NHC–Parent‐Silyliumylidene Cation

The trapping of a silicon(I) radical with N‐heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAAC_Me] (cAAC_Me=:C(CMe₂)₂(CH₂)NAr, Ar=2,6‐i Pr₂C₆H₃) with H₂SiI₂ in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAAC_Me)₂Si:^.]⁺I⁻ ( 1 ), which features a cationic cAAC–silicon(I) radical, and [cAAC_Me−H]⁺I⁻. In addition, the reaction of the NHC–iodosilicon(I) dimer [I_Ar(I)Si:]₂ (I_Ar=:C{N(Ar)CH}₂) with 4 equiv of I_Me (:C{N(Me)CMe}₂), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(I_Me)₂SiH]⁺I⁻ ( 2 ) comprising the first NHC–parent‐silyliumylidene cation. Its further reaction with fluorobenzene afforded the C_Ar−H bond activation product [1‐F‐2‐I_Me‐C₆H₄]⁺I⁻ ( 3 ). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1 . Compounds 1 – 3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X‐ray crystallography.     

Synthesis of a “Masked” Terminal Zinc Sulfide and Its Reactivity with Brønsted and Lewis Acids

The “masked” terminal Zn sulfide, [K(2.2.2‐cryptand)][^MeLZn(S)] ( 2 ) (^MeL={(2,6‐ⁱPr₂C₆H₃)NC(Me)}₂CH), was isolated via reaction of [^MeLZnSCPh₃] ( 1 ) with 2.3 equivalents of KC₈ in THF, in the presence of 2.2.2‐cryptand, at ?78 °C. Complex 2 reacts readily with PhCCH and N₂O to form [K(2.2.2‐cryptand)][^MeLZn(SH)(CCPh)] ( 4 ) and [K(2.2.2‐cryptand)][^MeLZn(SNNO)] ( 5 ), respectively, displaying both Brønsted and Lewis basicity. In addition, the electronic structure of 2 was examined computationally and compared with the previously reported Ni congener, [K(2.2.2‐cryptand)][^tBuLNi(S)] (^tBuL={(2,6‐ⁱPr₂C₆H₃)NC(^tBu)}₂CH).