Hydrido(hydrosilylene)tungsten Complexes: Dynamic Behavior and Reactivity Toward Acetone

Reaction of a labile tungsten nitrile complex, [(Cp*)W(CO)₂(NCMe)Me] (Cp*=η⁵‐C₅Me₅), with H₃SiC(SiMe₃)₃ gave the hydrido(hydrosilylene) complex [(Cp*)(CO)₂(H)W?Si(H){C(SiMe₃)₃}] ( 1a ). The hydrido(silylene) complex [(η⁵‐C₅Me₄Et)(CO)₂(H)W?SiMes₂] ( 2 ) (Mes=2,4,6‐Me‐C₆H₂) was synthesized by a similar reaction with H₂SiMes₂. There is a strong interligand interaction between the hydrido and silylene ligands of these complexes; this was confirmed by a neutron diffraction study of [D₂] 1b , that is, the deuterido and η⁵‐C₅Me₄Et derivative of 1a . The exchange between the W? H and the Si? D groups was observed in the deuterido complex [D] 1a . This H/D exchange proceeded slowly at room temperature, but very rapidly under UV irradiation. Variable‐temperature NMR spectroscopy measurements show the dynamic behavior of carbonyl ligands in 1a . Complex 1a reacted with acetone at room temperature to give mainly a hydrosilylation product, [(Cp*)(CO)₂(H)W?Si(OiPr){C(SiMe₃)₃}] ( 3a ), along with a siloxy complex, [(Cp*)(CO)₂WO(Si(H)iPr{C(SiMe₃)₃})] ( 4a ). At low temperature, a different reaction, namely, α‐H abstraction, proceeded to give an equilibrium mixture of 1a and a dihydrido(silyl) complex, [(Cp*)(CO)₂(H)₂W(Si(H){OC(?CH₂)Me}{C(SiMe₃)₃})] ( 5 ).     

UV–visible spectroscopy for zirconocene activation by MAO in olefin polymerization: activity versus wavenumber

Activation of ansa‐zirconocenes of the type Rac [Zr{1‐Me₂Si(3‐R‐(η⁵‐C₉H₅))(3‐R′‐(η⁵‐C₉H₅))}Cl₂] [R = Et, R′ = H ( 1 ); R = Pr, R′ = H ( 2 ); and R = Et, R′ = Pr ( 3 ), R, R′ = Me ( 4 ) and R, R′ = Bu ( 5 )] by MAO has been studied by UV–visible spectroscopy. Compounds 1–3 have been tested in the polymerization of ethylene at different Al:Zr ratios. UV–vis spectroscopy was used to determine a correlation between the electronic structures of ( 1–5 ) and their polymerization activity. Copyright © 2009 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.     

Isolation of a Cationic Platinum(II) σ‐Silane Complex

The platinum complex [Pt(I^tBuⁱPr′)(I^tBuⁱPr)][BAr^F] interacts with tertiary silanes to form stable (<0 °C) mononuclear Pt^II σ‐SiH complexes [Pt(I^tBuⁱPr′)(I^tBuⁱPr)(η¹‐HSiR₃)][BAr^F]. These compounds have been fully characterized, including X‐ray diffraction methods, as the first examples for platinum. DFT calculations (including electronic topological analysis) support the interpretation of the coordination as an unusual η¹‐SiH. However, the energies required for achieving a η²‐SiH mode are rather low, and is consistent with the propensity of these derivatives to undergo Si?H cleavage leading to the more stable silyl species [Pt(SiR₃)(I^tBuⁱPr)₂][BAr^F] at room temperature.     

Catalytic diversity of diene complexes of niobium and tantalum on polymerizations of ethylene,norbornene, and methyl methacrylate

Half‐metallocene diene complexes of niobium and tantalum catalyzed three‐types of polymerization: (1) the living polymerization of ethylene by niobium and tantalum complexes, MCl₂(η⁴‐1,3‐diene)(η⁵‐C₅R₅) ( 1‐4 ; M = Nb, Ta; R = H, Me) combined with an excess of methylaluminoxane; (2) the stereoselective ring opening metathesis polymerization of norbornene by bis(benzyl) tantalum complexes, Ta(CH₂Ph)₂(η⁴‐1,3‐butadiene)(η⁵‐C₅R₅) ( 11 : R = Me; 12 : R = H) and Ta(CH₂Ph)₂(η⁴‐o‐xylylene)(η⁵‐C₅Me₅) ( 16 ); and (3) the polymerization of methyl methacrylate by butadiene‐diazabutadiene complexes of tantalum, Ta(η²‐RN=CHCH=NR)(η⁴‐1,3‐butadiene)(η⁵‐C₅Me₅) ( 25 : R = p‐methoxyphenyl; 26 : R = cyclohexyl) in the presence of an aluminum compound ( 24 ) as an activator of the monomer.     

Substitution reactions of [MBr(π allyl)(CO)2(LL)] complexes (M = Mo,W; L-L = 2,2 -bipyridine 1,2-bis(diphenylphosphine)ethane) with xanthates and dithiocarbamates

The complexes [MBr(π-allyl)(CO)₂(bipy)] (M = Mo, W, bipy = 2,2′-bipyridine) react with alkylxanthates (M^IRxant), and N-alkyldithiocarbamates (M^IRHdtc) (M^I = Na or K), yielding complexes of general formula [M(S,S)- (π-allyl)(CO)₂(bipy)] (M = Mo, (S,S) = Rxant (R = Me, Et, t-Bu, Bz), RHdtc (R = Me, Et); M = W, (S,S) = Extant). A monodentate coordentate coordination of the (S,S) ligand was deduced from spectral data. The reaction of [MoBr(π-allyl)(CO)₂(bipy)] with MeHdtc and Mexant gives the same complexes whether pyridine is present or not. The complexes [Mo(S,S)(π-allyl)(CO)₂(bipy)] ((S,S) = MeHdtc, Mexant) do not react with an excess of (S,S) ligand and pyridine.No reaction products were isolated from reaction of [MoBr(π-allyl)(CO)₂(dppe)] with xanthates or N-alkyldithiocarbamates.     

Nickel Tetracarbonyl as Starting Material for the Synthesis of NHC-stabilized Nickel(II) Allyl Complexes

A novel, useful in situ synthesis for NHC nickel allyl halide complexes [Ni(NHC)(η³-allyl)(X)] starting from [Ni(CO)₄], NHC and allyl halides is presented. The reaction of [Ni(CO)₄] with (i) one equivalent of the corresponding NHC and (ii) with an excess of the corresponding allyl chloride at room temperature leads with elimination of carbon monoxide to complexes of the type [Ni(NHC)(η³-allyl)(X)]. This approach was used to synthesize the complexes [Ni(tBu₂Im)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 2 ), [Ni(iPr₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 3 ), [Ni(iPr₂Im)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 4 ), [Ni(iPr₂Im)(η³-H₂C -C (H)-C (Me)₂)(Br)] ( 5 ), [Ni(Me₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 6 ), and [Ni(EtiPrIm^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 7 ). The complexes 1 to 7 were characterized using NMR and IR spectroscopy and elemental analysis, and the molecular structures are provided for 2 and 7 . The allyl nickel complexes 1 – 7 are stereochemically non-rigid in solution due to (i) NHC rotation about the nickel-carbon bond, (ii) allyl rotation about the Ni–η³-allyl axis and (iii) π–σ–π allyl isomerization processes. The allyl halide complexes can be methylated as was demonstrated by the methylation of a number of the complexes [Ni(NHC)(η³-allyl)(X)] with methylmagnesium chloride or methyllithium, which led to isolation of the complexes [Ni(Me₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 8 ), [Ni(tBu₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 9 ), [Ni(iPr₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Me)] ( 10 ), [Ni(iPr₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 11 ), [Ni(iPr₂Im)(η³-H₂C -C (H)-C (Me)₂)(Me)] ( 12 ), and [Ni(EtiPrIm^Me)(η³-H₂C -C (Me)-C H₂)(Me)] ( 13 ). These complexes were fully characterized including X-ray molecular structures for 10 and 11 .     

EINIGE NEUE THIOPHOSPHINSÄUREAMIDE R2P(S)NHR': SYNTHESE UND KERNRESONANZSPEKTROSKOPISCHE UNTERSUCHUNGEN

Abstract

P.P-Dialkylthiophosphinsäureamide R₂P(S)NHR' (R=Me, 'Pr, 'Bu; R'=Me, Et, ⁱPr. ^cHex. ^tBu. Ph. etc.) wurden erhalten durch Umsetzung von R₂PNHR' mit Schwefel oder durch Reaktion von Me₂P(S)CI mit primaren Aminen. Ihre ³¹P- und ¹³C-NMR-Spektren werden diskutiert. Insbesondere die Di-t-butylthiophosphinsäureamide sind auszilg;ergewöhnlich stabil gegen Hydrolyse und Luftsauerstoff. P,P-Dialkylthiophosphinic acid amides R₂P(S)NHR' (R=Me. ⁱPr. ^tBu; R'=Me, Et, ⁱPr, ^cHex. ^tBu, Ph. etc.) have been obtained by reaction of the corresponding aminophosphines with sulfur or by reaction of dimethylthiophosphorylhalides with primary amines. Their ³¹P- and ¹³C-NMR spectra are discussed. The di-t-butylthiophosphinic compounds proved to be remarkably stable against moisture and oxygen.     

Functionalization of Pentaphosphorus Cations by Complexation

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P₅R₂]⁺ cations with cyclopentadienyl metal complexes. The reaction of [Cp^ArFe(μ‐Br)]₂ (Cp^Ar=C₅(C₆H₄‐4‐Et)₅) with [P₅R₂][GaCl₄] (R=iPr and 2,4,6‐Me₃C₆H₂ (Mes)) afforded bicyclo[1.1.0]pentaphosphanes ( 1‐R , R=iPr and Mes), showing an unsymmetric “butterfly” structure. The same products 1‐R were formed from K[Cp^Ar] and [P₅R₂][GaCl₄]. The cationic complexes [Cp^ArCo(η⁴‐P₅R₂)][GaCl₄] ( 2‐R [GaCl₄], R=iPr and Cy) and [(Cp^ArNi)₂(η^3:3‐P₅R₂)][GaCl₄] ( 3‐R [GaCl₄]) were obtained from [P₅R₂][GaCl₄] and [Cp^ArM(μ‐Br)]₂ (M=Co and Ni) as well as by using low‐valent “Cp^ArM^I” sources. Anion metathesis of 2‐R [GaCl₄] and 3‐R [GaCl₄] was achieved with Na[BArF₂₄]. The P₅ framework of the resulting salts 2‐R [BArF₂₄] can be further functionalized with nucleophiles. Thus reactions with [Et₄N]X (X=CN and Cl) give unprecedented cyano‐ and chloro‐functionalized complexes, while organo‐functionalization was achieved with CyMgCl.     

Facile Synthetic Access to Rhenium(II) Complexes: Activation of Carbon–Bromine Bonds by Single‐Electron Transfer

The five‐coordinated Re^I hydride complexes [Re(Br)(H)(NO)(PR₃)₂] (R=Cy 1 a , iPr 1 b ) were reacted with benzylbromide, thereby affording the 17‐electron mononuclear Re^II hydride complexes [Re(Br)₂(H)(NO)(PR₃)₂] (R=Cy 3 a , iPr 3 b ), which were characterized by EPR, cyclic voltammetry, and magnetic susceptibility measurements. In the case of dibromomethane or bromoform, the reaction of 1 afforded Re^II hydrides 3 in addition to Re^I carbene hydrides [Re(?CHR¹)(Br)(H)(NO)(PR₃)₂] (R¹=H 4 , Br 5 ; R=Cy a , iPr b ) in which the hydride ligand is positioned cis to the carbene ligand. For comparison, the dihydrogen Re^I dibromide complexes [Re(Br)₂(NO)(PR₃)₂(η²‐H₂)] (R=Cy 2 a , iPr 2 b ) were reacted with allyl‐ or benzylbromide, thereby affording the monophosphine Re^II complex salts [R₃PCH₂R′][Re(Br)₄(NO)(PR₃)] (R′=? CH?CH₂ 6 , Ph 7 ). The reduction of Re^II complexes has also been examined. Complex 3 a or 3 b can be reduced by zinc to afford 1 a or 1 b in high yield. Under catalytic conditions, this reaction enables homocoupling of benzylbromide (turnover frequency (TOF): 3 a 150, 3 b 134 h^?1) or allylbromide (TOF: 3 a 575, 3 b 562 h^?1). The reaction of 6 a and 6 b with zinc in acetonitrile affords in good yields the monophosphine Re^I complexes [Re(Br)₂(NO)(MeCN)₂(PR₃)] (R=Cy 8 a , iPr 8 b ), which showed high catalytic activity toward highly selective dehydrogenative silylation of styrenes (maximum TOF of 61 h^?1). Single‐electron transfer (SET) mechanisms were proposed for all these transformations. The molecular structures of 3 a , 6 a , 6 b , 7 a , 7 b , and 8 a were established by single‐crystal X‐ray diffraction studies.     

Organometallic Compounds of the Lanthanides. 127 [1] Synthesis of Monomeric Bis(cyclopentadienyl)lanthanide Tetrahydroborates with Bulky Cyclopentadienyl Ligands. Single Crystal X-ray Structures of [(η5-C5Me5)2SmBH4(THF)] and [(η5-C5Me4Et)2Y(μ-H)2BH2(THF)]

The trichlorides of yttrium, samarium, and lutetium react with 2 equivalents of Na[C₅H₄ ^tBu] and 1 equivalent of NaBH₄ to give [(η⁵-C₅H₄ ^tBu)₂LnBH₄(THF)] (Ln = Y ( 1 ), Sm ( 2 ), Lu ( 3 )) or with 2 equivalents of Na[C₅Me₄R] and 1 equivalent of NaBH₄ to form [(η⁵-C₅Me₄R)₂ · LnBH₄(THF)] (R = H, Ln = Y ( 4 ), Sm ( 5 ), Lu ( 6 ); R = Me, Ln = Y ( 7 ), Sm ( 8 ), Lu ( 9 ); R = Et, Ln = Y ( 10 ), Sm ( 11 ), Lu ( 12 ); R = ⁱPr, Ln = Y ( 13 ), Sm ( 14 ), Lu ( 15 )). The new compounds have been characterized by elemental analysis, NMR spectroscopy and mass spectrometry. The crystal structures of 8 and 10 were determined by single crystal X-ray diffraction.     

Zur kenntnis der cyclopentadienyl-nitrosyl-carbonyl-isonitril-komplexe der VI. Und der cyclopentadienyl-dicarbonyl-isonitril-komplexe der VII. Nebengruppe

The nitrosylcarbonylisonitrile complexes η⁵-C₅H₅M(NO)(CO)CNR (R = Me for Cr, Mo, W; R = Et, SiMe₃, GeMe₃, SnMe₃ for Mo) are formed by treatment of the nitrosylcarbonylcyanometalates Na[η⁵-C₅H₅M(NO)(CO)CN] with [R₃O]BF₄ (R = Me, Et), Me₃SiCl, Me₃GeCl or Me₃SnCl. The isoelectronic dicarbonylisonitrile compounds η⁵-C₅H₅Mn(CO)₂CNR (R = SiMe₃, GeMe₃, SnMe₃, PPh₂, AsMe₂) and η⁵-C₅H₅Re(CO)₂CNAsMe₂ are obtained by analogous reactions of Na[η⁵-C₅H₅M(CO)₂CN] (M = Mn, Re) with Me₃ECl (E = Si, Ge, Sn), Ph₂PCl and Me₂AsBr.With phosgene the anionic complexes Na[η⁵-C₅H₅M(CO)₂CN] (M = Mn, Re) can be transformed into the new carbonyldiisocyanide-bridged dinuclear complexes η⁵-C₅H₅M(CO)₂CN-C(O)-NC(OC)₂M-η⁵-C₅H₅. Finally, the reactions of η⁵-C₅H₅M(NO)(CO)CNMe (M = Cr, Mo, W) with NOPF₆, leading to the cationic dinitrosylisonitrile complexes [η⁵-C₅H₅M(NO)₂CNMe]⁺, are described.     

Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: synthesis, structure, and reactivity toward biomass-derived furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me₃TACD^?) are reported. Upon treatment of the neutral allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] with Brønsted acids, monocationic allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)(thf)₂][B(C₆X₅)₄] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me₃TACD)H₂]_n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me₃TACD)R₂]_n (R=η³‐C₃H₅, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions.     

Chiral propionate enolate equivalents for the stereoselective synthesis of threo- or erytho-α,-methyl-β-hydroxy acids

The aluminium and copper enolates derived from (η⁵-C₅H₅)Fe(CO)(PPh₃)COCH₂CH₃ are chiral propionate enolate equivalents which on reaction with aldehydes (RCHO, RMe.Et,ⁱPr,^tBu) provide stereoselective syntheses of threo- and erytho-α-methyl-β-hydroxy acids respectively.     

Regioselectivity in the amination of azines: Reaction of pyrazine derivatives with <Emphasis Type="Italic">O</Emphasis>-mesitylenesulfonylhydroxylamine

Treatment of 2-X-substituted pyrazines [X = H, Me, Et, Pr, i-Pr, t-Bu, MeCH(OH), H₂N, AcNH] with O-mesitylenesulfonylhydroxylamine gave the corresponding 2-X- and 3-X-(1-amino)pyrazin-1-ium mesitylenesulfonates. 2-Alkylpyrazines (X = Me, Et, Pr, i-Pr) displayed a correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations and substituent steric constants. Wider series of substituted pyrazines [X = H, Me, Et, Pr, i-Pr, MeCH(OH), H₂N, AcNH] conformed to a multiparameter correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations, on the one hand, and substituent constants σ_I, σ_R^o, and E _s^o, on the other. The obtained data on the regioselectivity of amination of pyrazines were interpreted in terms of DFT/PBE/3Z quantum-chemical calculations.     

Methylidene Rare‐Earth‐Metal Complex Mediated Transformations of CN,NN and N?H Bonds: New Routes to Imido Rare‐Earth‐Metal Clusters

Three new patterns of reactivity of rare‐earth metal methylidene complexes have been established and thus have resulted in access to a wide variety of imido rare‐earth metal complexes [L₃Ln₃(μ₂‐Me)₃(μ₃‐Me)(μ ‐ NR)] (L=[PhC(NC₆H₃iPr₂‐2,6)₂]^?; R=Ph, Ln=Y ( 2 a ), Lu ( 2 b ); R=2,6‐Me₂C₆H₃, Ln=Y ( 3 a ), Lu ( 3 b ); R=p‐ClC₆H₄, Ln=Y ( 4 a ), Lu ( 4 b ); R=p‐MeOC₆H₄, Ln=Y ( 5 a ), Lu ( 5 b ); R=Me₂CHCH₂CH₂, Ln=Y ( 6 a ), Lu ( 6 b )) and [{L₃Lu₃(μ₂‐Me)₃(μ₃‐Me)}₂(μ ‐ NR′N)] (R′=(CH₂)₆ ( 7 b ), (C₆H₄)₂ ( 8 b )). Complex 2 b was treated with an excess of CO₂ to give the corresponding carboxylate complex [L₃Lu₃(μ‐η¹:η¹‐O₂CCH₃)₃(μ‐η¹:η²‐O₂C‐CH₃)(μ‐η¹:η¹:η²‐O₂CNPh)] ( 9 b ) easily. Complex 2 a could undergo the selective μ₃‐Me abstraction reaction with phenyl acetylene to give the mixed imido/alkynide complex [L₃Y₃(μ₂‐Me)₃(μ₃‐η¹:η¹:η³‐NPh)(μ₃‐C?CPh)] ( 10 a ) in high yield. Treatment of 2 with one equivalent of thiophenol gave the selective μ₃‐methyl‐abstracted products [L₃Ln₃(μ₂‐Me)₃(μ₃‐η¹:η¹:η³‐NPh)(μ₃‐SPh)] (Ln=Y ( 11 a ); Lu ( 11 b ). All new complexes have been characterized by elemental analysis, NMR spectroscopy, and most of the structures confirmed by X‐ray diffraction.     

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(?CH₂) CH?C(Me)(NAr), Ar=2,6‐iPr₂C₆H₃) with Me₂Zn, Me₃Al, H₃Al‐NMe₃, 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, Me₂Zn 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 Me₃Al, H₃Al‐NMe₃, and MeLi lead directly to the 1,1‐addition products LSi(Me)(Al(thf)Me₂) 3 , LSi(H)(AlH₂(NMe₃)) 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.     

Structurally Defined Potassium‐Mediated Zincation of Pyridine and 4‐R‐Substituted Pyridines (R=Et,iPr, tBu,Ph, and Me2N) by Using Dialkyl–TMP–Zincate Bases

Two potassium–dialkyl–TMP–zincate bases [(pmdeta)K(μ‐Et)(μ‐tmp)Zn(Et)] ( 1 ) (PMDETA=N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine, TMP=2,2,6,6‐tetramethylpiperidide), and [(pmdeta)K(μ‐nBu)(μ‐tmp)Zn(nBu)] ( 2 ), have been synthesized by a simple co‐complexation procedure. Treatment of 1 with a series of substituted 4‐R‐pyridines (R=Me₂N, H, Et, iPr, tBu, and Ph) gave 2‐zincated products of the general formula [{2‐Zn(Et)₂‐μ‐4‐R‐C₅H₃N}₂ ? 2{K(pmdeta)}] ( 3 – 8 , respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51 %, respectively; the treatment of 2 with 4‐tBu‐pyridine gave [{2‐Zn(nBu)₂‐μ‐4‐tBu‐C₅H₃N}₂ ? 2{K(pmdeta)}] ( 9 ) in an isolated crystalline yield of 58 %. Single‐crystal X‐ray crystallographic and NMR spectroscopic characterization of 3 – 9 revealed a novel structural motif consisting of a dianionic dihydroanthracene‐like tricyclic ring system with a central diazadicarbadizinca (ZnCN)₂ ring, face‐capped on either side by PMDETA‐wrapped K⁺ cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3 , 7 , 8 , and 9 appear to be essentially clean reactions, in contrast to those producing 4 , 5 , and 6 , which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium–zincate base acts as an amido transfer agent with a subsequent ligand‐exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4‐coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl–zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn? N bonds for efficient zincation.     

Reaktionen von metall-koordiniertem kohlenmonoxid mit yliden: XVII. Darstellung eines molybdän- und wolframkomplexes mit η3-gebundenem trimethylsiloxybutenon-liganden durch silylierung der phosphonium-metall-enolat-vorstufe

The reaction of the phosphonium metallates Me₄P[C₅R₅(CO)(Me₃P)$\text{MC(O)=CHC(O}$)R′] (M = W, R = H, R′ = Et (1a); M = Mo, R = Me, R′ = Me (1b)) with the silylating reagent Me₃SiOSO₂CF₃ yields the neutral complexes C₅R₅(CO)(Me₃P)$\text{MC(OSiMe}{}_3\text{)=CHC(O}$)R (2a, 2b) bearing a chelating O(2), C(4)-trimethylsiloxybutenone ligand. The structure of the new compounds is established by the IR, ¹H and ³¹P NMR spectra.     

Synthesis and Characterization of Intramolecularly Stabilized Chiral Dimethylindium Alkoxides and their Use as Cross Coupling Reagents

The enantiomerically pure dimeric N, O‐5‐chelates [Me₂In(μ‐OCH₂CH(R)NMe₂)]₂ {R = Me (S) ( 2 ); R = ⁱPr (S) ( 3 ); R = ⁱBu (S) ( 4 ); R = Bz (S) ( 5 )}, and [Me₂In‐{μ‐(1R, 2S)‐OCH(Ph)CH(Me)NMe₂}]₂ ( 6 ), as well as the achiral dimeric N, O‐6‐chelate [Me₂In(μ‐O(CH₂)₃NMe₂)]₂ ( 7 ) have been synthesized from trimethylindium and equimolar amounts of the corresponding enantiomerically pure dimethylamino alcohols or of the achiral dimethylaminopropanol by elimination of methane. Their ¹H NMR, ¹³C NMR, and mass spectra as well as the X‐ray single crystal structure analyses of [Me₂In{μ‐O(CH₂)₂NMe₂}]₂ ( 1 ), 3, 5, 6 and 7 are described and discussed. The coordinative N→In bonds of the five‐coordinate indium complexes show dynamic dissociation/association processes. 1—6 were found to be useful reagents for the partial kinetic resolution of 2‐carbomethoxy‐1, 1′‐binaphthyl triflate.