Synthesis of new organophosphorus‐substituted mono‐ and bis(trimethylsilyl)amines with PCH2N fragments and their derivatives

Convenient procedures for the synthesis of new organophosphorus‐substituted mono‐ and bis(trimethylsilyl)amines with PCH₂N moiety are proposed, starting from trimethylsilyl esters of organophosphorus acids, as well as 1,3,5‐trialkylhexahydro‐1,3,5‐triazines and N‐alkoxymethyl bis(trimethylsilyl)amines as aminomethylating reagents. Certain properties of the resulting compounds are presented. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:71–77, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20580     

meso‐Bis{η5‐1‐[1‐(dimethylamino)ethenyl]‐3‐(trimethylsilyl)cyclopentadienyl}iron(II) and the cobalt(II) analogue

The two title crystalline compounds, viz.meso‐bis{η⁵‐1‐[1‐(dimethylamino)ethenyl]‐3‐(trimethylsilyl)cyclopentadienyl}iron(II), [Fe(C₁₂H₂₀NSi)₂], (II), and meso‐bis{η⁵‐1‐[1‐(dimethylamino)ethenyl]‐3‐(trimethylsilyl)cyclopentadienyl}cobalt(II), [Co(C₁₂H₂₀NSi)₂], (III), were obtained by the reaction of lithium 1‐[1‐(dimethylamino)ethenyl]‐3‐(trimethylsilyl)cyclopentadienide with FeCl₂ and CoCl₂, respectively. For (II), the trimethylsilyl‐ and dimethylaminoethenyl‐substituted cyclopentadienyl (Cp) rings present a nearly eclipsed conformation, and the two pairs of trimethylsilyl and dimethylaminoethenyl substituents on the Cp rings are arranged in an interlocked fashion. In the case of (III), the same substituted Cp rings are perfectly staggered leading to a crystallographically centrosymmetric molecular structure, and the two trimethylsilyl and two dimethylaminoethenyl substituents are oriented in opposite directions, respectively, with the trimethylsilyl group of one Cp ring and the dimethylaminoethenyl group of the other Cp ring arranged more closely than in (II).     

Metallierung und C‐C‐Kupplung von 2‐Pyridylmethylamin: Synthese und Strukturen von Methylzink‐2‐pyridylmethylamid,Tris(trimethylsilyl)methylzink‐2‐pyridylmethylamid und (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethen

Metalation and C‐C Coupling Reaction of 2‐Pyridylmethylamine: Synthesis and Structures of Methylzinc‐2‐pyridylmethylamide, Tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide and (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethene The metalation of 2‐pyridylmethylamine with dimethylzinc yields methylzinc‐2‐pyridylmethylamide ( 1 ), which shows a dimer‐trimer equilibrium in solution. Compound 1 crystallizes trimeric with a Zn₃N₃‐cycle in boat conformation. The endocyclic Zn‐N distances vary between 202 and 206 pm. Heating of this compound in toluene in the presence of dimethylzinc leads to the precipitation of zinc metal and to the formation of a few crystals of bis—[methylzinc‐2‐pyridylmethylamido]‐N, N′‐bis(methylzinc)‐2,3,5,6—tetrakis(2‐pyridyl)‐1,4‐diazacyclohexane ( 2 ). The protolysis of this solution with acetamide gives yellowish (Z)‐1‐amino‐1,2‐dipyridylethene ( 3 ) in a rather poor yield. The enamine tautomer is stabilized by N‐H···N hydrogen bridges. The demanding tris(trimethylsilyl)methyl group at the zinc atom allows the isolation of the dimeric tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide (4) ₂ in good yield. A C‐C coupling reaction of this compound with dimethylzinc is not possible.     

Kristallstrukturen und spektroskopische Eigenschaften von 2λ3‐Phospha‐1, 3‐dionaten und 1, 3‐Dionaten des Calciums ‐ ein Vergleich am Beispiel der 1, 3‐Diphenyl‐ und 1, 3‐Di(tert‐butyl)‐Derivate

Crystal Structures and Spectroscopic Properties of 2λ³‐Phospha‐1, 3‐dionates and 1, 3‐Dionates of Calcium ‐ Comparative Studies on the 1, 3‐Diphenyl and 1, 3‐Di(tert‐butyl) Derivatives A hydrogen‐metal exchange between dibenzoylphosphane and calcium carbide in tetrahydrofuran (THF) followed by addition of the ligand 1, 3, 5‐trimethyl‐1, 3, 5‐triazinane (TMTA) furnishes the binuclear complex bis[(tmta‐N, N′, N″)calcium bis(dibenzoylphosphanide)] ( 1a ) co‐crystallizing with benzene. Similarly, reaction of bis(2, 2‐dimethylpropionyl)phosphane with bis(thf‐O)calcium bis[bis(trimethylsilyl)amide] in 1, 2‐dimethoxyethane (DME) gives bis(dme‐O, O′)calcium bis[bis(2, 2‐dimethylpropionyl)phosphanide] ( 1b ) in high yield. The carbon analogues 1, 3‐diphenylpropane‐1, 3‐dione (dibenzoylmethane) or 2, 2, 6, 6‐tetramethylheptane‐3, 5‐dione (dipivaloylmethane) and bis(thf‐O)calcium bis[tris(trimethylsilylmethyl)zincate] in DME afford bis(dme‐O, O′)calcium bis(dibenzoylmethanide) ( 2a ) and the binuclear complex (μ‐dme‐O, O′)bis[(dme‐O, O′)calcium bis(dipivaloylmethanide)] ( 2b ), respectively. Dialkylzinc formed during the metalation reaction shows no reactivity towards the 1, 3‐dionates 2a and 2b . Finally, from the reaction of the unsymmetrically substituted ligand 2‐(methoxycarbonyl)cyclopentanone and bis(thf‐O)calcium bis[bis(trimethylsilyl)amide] in toluene, the trinuclear complex 3 is obtained, co‐crystallizing with THF. The β‐ketoester anion bridges solely via the cyclopentanone unit.     

Stereoselective Peterson Olefinations from Bench‐Stable Reagents and N‐Phenyl Imines

The synthesis of bench‐stable α,α‐bis(trimethylsilyl)toluenes and tris(trimethylsilyl)methane is described and their use in stereoselective Peterson olefinations has been achieved with a wide substrate scope. Product stereoselectivity was poor with carbonyl electrophiles (E/Z ～1:1 to 4:1) though this was significantly improved by employing the corresponding substituted N‐benzylideneaniline (up to 99:1) as an alternative electrophile. The olefination byproduct was identified as N,N‐bis(trimethylsilyl)aniline and could be easily separated from product by aqueous acid extraction. Evidence for an autocatalytic cycle has been obtained.     

Regioselective Synthesis of Trichloromethyl‐Substituted Salicylates and Cyclohexenones by One‐Pot Cyclizations of 1,3‐Bis(trimethylsilyloxy)buta‐1,3‐dienes

A variety of 6‐(trichloromethyl)salicylates (=2‐hydroxy‐6‐(trichloromethyl)benzoates) were prepared by TiCl₄‐mediated cyclization of 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1,1,1‐trichloro‐4,4‐dimethoxybut‐3‐en‐2‐one. The employment of trimethylsilyl trifluoromethanesulfonate (Me₃SiOTf) as Lewis acid resulted in the formation of trichloromethyl‐substituted cyclohexenones. The cyclizations proceeded with good‐to‐very‐good regioselectivities.     

1,1‐Organoboration of bis(trimethylstannyl)ethyne with trimethylsilyl‐ and dimethylsilyl‐dialkylboryl‐substituted alkenes: organometallic‐substituted allenes

The reactions of bis(trimethylstannyl)ethyne, Me₃Sn–C?C–SnMe₃ ( 4 ), with trimethylsilyl‐ or dimethylsilyl‐dialkylboryl‐substituted alkenes 1 – 3 afford organometallic‐substituted allenes 5 , 6 and 8 , 9 in high yield. In the case of (E)‐2‐trimethylsilyl‐3‐diethylboryl‐2‐pentene ( 1) , a butadiene derivative 7 could be detected as an intermediate prior to rearrangement into the allene. All reactions were monitored by ²⁹Si and ¹¹⁹Sn NMR, and the products were characterized by an extensive NMR data set (¹H, ¹¹B, ¹³C, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd.     

Strukturen zweifach metallierter Derivate von 3, 3‐Dimethyl‐1, 5‐bis(trimethylsilyl)‐1, 5‐diaza‐pentan mit Lithium und Aluminium sowie zweier Donor‐substituierter Digallane

Structural Characterization of Bis(metallated) Derivatives of 3, 3‐Dimethyl‐1, 5‐bis(trimethylsilyl)‐1, 5‐diaza‐pentane with Lithium and Aluminum and of two Donor‐substituted Digallanes The diaminopropane derivative Me₂C[CH₂N(H)SiMe₃]₂ is metallated with n‐butyllithium and lithium tetrahydridoaluminate to obtain Me₂C[CH₂N(Li)SiMe₃]₂ and Me₂C[CH₂N(Li)SiMe₃][CH₂N(AlH₂)SiMe₃], respectively. Both compounds exhibit a central eight‐membered ring, Li₄N₄ or Li₂Al₂N₄. Me₂C[CH₂N(Li)SiMe₃]₂ reacts with Ga₂Cl₄ · 2dioxane under formation of the corresponding tetra(amino)digallane. This is monomeric, in contrast to a dimeric tetraalkoxy‐substituted digallane, Ga₄O^tBu₈. All compounds were characterized by single crystal X‐ray crystallography.     

Synthese und Molekülstrukturen von N‐substituierten Diethylgallium‐2‐pyridylmethylamiden

Synthesis and Molekular Structures of N‐substituted Diethylgallium‐2‐pyridylmethylamides (2‐Pyridylmethyl)(tert‐butyldimethylsilyl)amine ( 1a ) and (2‐pyridylmethyl)‐di(tert‐butyl)silylamine ( 1b ) form with triethylgallane the corresponding red adducts 2a and 2b via an additional nitrogen‐gallium bond. These oily compounds decompose during distillation. Heating under reflux in toluene leads to the elimination of ethane and the formation of the red oils of [(2‐pyridylmethyl)(tert‐butyldimethylsilyl)amido]diethylgallane ( 3a ) and [(2‐pyridylmethyl)‐di(tert‐butyl)silylamido]diethylgallane ( 3b ). In order to investigate the thermal stability solvent‐free 3a is heated up to 400 °C. The elimination of ethane is observed again and the C‐C coupling product N, N′‐Bis(diethylgallyl)‐1, 2‐dipyridyl‐1, 2‐bis(tert‐butyldimethylsilyl)amido]ethan ( 4 ) is found in the residue. Substitution of the silyl substituents by another 2‐pyridylmethyl group and the reaction of this bis(2‐pyridylmethyl)amine with GaEt₃ yield triethylgallane‐diethylgallium‐bis(2‐pyridylmethyl)amide ( 5 ). The metalation product adds immediately another equivalent of triethylgallane regardless of the stoichiometry. The reaction of GaEt₃ with 2‐pyridylmethanol gives quantitatively colorless 2‐pyridylmethanolato diethylgallane ( 6 ).     

Synthesis of Bis(2,4‐diarylimidazol‐5‐yl) Diselenides from N‐Benzylbenzimidoyl Isoselenocyanates

The reaction of N‐benzylbenzamides 6 with SOCl₂ under reflux gave the corresponding N‐benzylbenzimidoyl chlorides 7 . Further treatment with KSeCN in dry acetone yielded imidoyl isoselenocyanates 3 (Scheme 2). These compounds, obtained in satisfying yields, proved to be stable enough to be purified and analyzed. Reaction of 3 with morpholine in dry acetone led to the corresponding selenourea derivatives 8 . On treatment with Et₃N, the 4‐nitrobenzyl derivatives of type 3 were transformed into bis(2,4‐diarylimidazol‐5‐yl) diselenides 9 (Scheme 3). This transformation takes place only when the benzyl residue bears an NO₂ group and the phenyl group is not substituted with a strong electron‐donating group. A reaction mechanism for the formation of 9 is proposed in Scheme 4. The key structures have been established by X‐ray crystallography.     

N‐Silylaminotitanium Chlorides — Synthesis,Structures, Multinuclear Magnetic Resonance,and some Applications

N‐Silylaminotitanium trichlorides, Me₃S(R)N‐TiCl₃ ( 18 ) [R = ^tBu ( a ), SiMe₃ ( b ), 9‐borabicyclo[3.3.1]nonyl (9‐BBN)( c )], and (CH₂SiMe₂)₂N‐TiCl₃ ( 18d ) were obtained in high yield and high purity from the reaction of the respective bis(silylamino)plumbylene with an excess of titanium tetrachloride. The crystal structure of 18a was determined by X‐ray analysis. The reactions of the analogous stannylenes with an excess of TiCl₄ did not lead to 18 . N‐Lithio‐trimethylsilyl[9‐(9‐borabicyclo[3.3.1]nonyl)]amine ( 8 ) was prepared, structurally characterized and used for the synthesis of a new bis(amino)stannylene 10 and a plumbylene 11 . The compounds 18a—d served as ideal starting materials for the synthesis of bis(silylamino)titanium dichlorides, where the silylamino groups can be identical ( 19 ) or different ( 20 ). This was achieved either by the reaction of 18 again with bis(amino)plumbylenes or with lithium N‐silylamides. In contrast to the direct synthesis starting from titanium tetrachloride and two equivalents of the respective lithium amide, which in general affords 19 with identical amino groups only in low yield, the procedure starting from 18 is much more versatile and gave the pure compounds 19 or 20 in almost quantitative yield. Further treatment of the dichlorides 19 or 20 with lithium amides led to tris(amino)titanium chlorides 21 . The dichlorides 19 or 20 reacted with two equivalents of alkynyllithium reagents to give the first well characterized examples of di(alkyn‐1‐yl)bis(N‐silylamino)titanium compounds 22 — 27 . These compounds reacted with trialkylboranes (triethyl or tripropylborane) by 1, 1‐organoboration. In some cases, the extremely reactive reaction products could be identified as novel 1, 1‐bis(silylamino)titana‐2, 4‐cyclopentadienes 28 — 31 bearing a dialkylboryl group in 3‐position. In solution, the proposed structures of all products were deduced from a consistent set of data derived from multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, ¹⁴N, ¹⁵N, ²⁹Si, ³⁵Cl NMR).     

Oxidation of E,E‐bis(3‐bromo‐1‐chloro‐1‐propen‐2‐yl) chalcogenides and use of E,E‐bis(3‐bromo‐1‐chloro‐1‐propen‐2‐yl)sulfone in heterocyclization with primary amines

Oxidation of E,E‐bis(3‐bromo‐1‐chloro‐1‐propen‐2‐yl) sulfide and selenide with hydrogen peroxide in chloroform/acetic acid or acetic acid affords previously unknown E,E‐bis(3‐bromo‐1‐chloro‐1‐propen‐2‐yl) sulfoxide, selenoxide, and sulfone. The reaction of E,E‐bis(3‐bromo‐1‐chloro‐1‐propen‐2‐yl) sulfone with primary amines in ethanol in the presence of NaHCO₃ or Na₂CO₃ is found to lead not only to heterocyclization but also to alcoholysis of the chloromethylidene groups in the intermediate bis(chloromethylidene) derivatives of thiomorpholine‐1,1‐dioxides to afford N‐organyl‐2(E),6(E)‐bis(ethoxymethylidene) thiomorpholine‐1,1‐dioxides as final products.     

The Synthesis of 1,4‐Bis[N‐(4/6‐Substituted Benzothiazole‐2‐yl)‐N′‐Glycosylguanidino]Benzenes

The starting material O‐protected glycosyl isothiocyanate ( 1?3 ) was refluxed with 1,4‐diaminobenzene in CHCl₃ under nitrogen atmosphere to give 1,4‐bis(N‐glycosyl)thioureidobenzene ( 4?6 ). Then 1,4‐bis[N‐(4/6‐substituted benzothiazole‐2‐yl)‐N′‐glycosylguanidino]benzenes ( 8a?8e , 9a?9e , 10a?10e ) were obtained in good yield by reaction of compounds ( 4?6 ) with 2‐amino‐4/6‐benzothizoles ( 7a?7e ) and HgCl₂ in the presence of TEA in DMF. The structures of all 18 new compounds were confirmed by IR, ¹H NMR, LC‐MS and elemental analysis. The bioactivity of anti‐HIV‐1 protease (HIV‐1 PR) and against angiotensin converting enzyme (ACE) have been evaluated.     

1,2‐Diaza‐3‐silacyclopent‐5‐ene – Synthese und Reaktionen

1,2‐Diaza‐3‐silacyclopent‐5‐ene – Synthesis and Reactions The dilithium salt of bis(tert‐butyl‐trimethylsilylmethylen)ketazine ( 1 ) forms an imine‐enamine salt. 1 reacts with halosilanes in a molar ratio of 1:1 to give 1,2‐diaza‐3‐silacyclopent‐5‐enes. Me₃SiCH=CCMe₃ [N(SiR,R′)‐N=C‐C]HSiMe₃ ( 2 ‐ 7 ). ( 2 : R,R′ = Cl; 3 : R = CH₃, R′ = Ph; 4 : R = F, R′ = CMe₃; 5 : R = F, R′ = Ph; 6 : R = F, R′ = N(SiMe₃)₂; 7 : R = F, R′ = N(CMe₃)SiMe₃). In the reaction of 1 with tetrafluorosilane the spirocyclus 8 is isolated. The five‐membered ring compounds 2 ‐ 7 and compound 9 substituted on the silicon‐fluoro‐ and (tert‐butyltrimethylsilyl) are acid at the C(4)‐atom and therefore can be lithiated. Experiments to prepare lithium salts of 4 with MeLi, n‐BuLi and PhLi gave LiF and the substitution‐products 10 ‐ 12 . 9 forms a lithium salt which reacts with ClSiMe₃ to give LiCl and the SiMe₃ ring system ( 13 ) substituted at the C(4)‐atom. The ring compounds 3 ‐ 7 and 10 ‐ 12 form isomers, the formation is discussed. Results of the crystal structure and analyses of 8 , 10 , 12 , and 13 are presented.     

Three 2,5‐dialkoxy‐1,4‐diethynylbenzene derivatives

2,5‐Diethoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene, C₂₀H₃₀O₂Si₂, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5‐dialkoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu‐catalysed cross‐coupling. 2,5‐Diethoxy‐1,4‐diethynylbenzene, C₁₄H₁₄O₂, (II), results from protodesilylation of (I). 1,4‐Diethynyl‐2,5‐bis(heptyloxy)benzene, C₂₄H₃₄O₂, (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)–(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C—H...π interactions between the methylene H atoms and the acetylenic C atom. Compound (II) shows π–π interactions between the acetylenic C atoms, complemented by C—H...π interactions between the methyl H atoms and the acetylenic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen‐bond‐type interactions between the acetylenic H atoms and the ether O atoms.     

An Efficient Synthesis of Novel Benzo‐Fused Macrocyclic Dilactams

A facile synthetic approach was adopted towards the synthesis of benzo‐fused macrocyclic lactams 2a – 2g via the base‐catalyzed condensation reaction of 2,2′‐[alkanediylbis(oxy)]bis[benzaldehydes] 3a – 3c with N,N′‐substituted bis[2‐cyanoacetamide] derivatives 7a – 7c (Scheme 2). The latter compounds were obtained by the reaction of the appropriate diamines 6a – 6c with ethyl 2‐cyanoacetate ( 4 ). Attempts to prepare the oxaaza macrocycles 2 by alternative pathways were also investigated. The novel pyrazolo‐fused macrocycles 13a and 13b were obtained in 48 and 52% yield, respectively, upon treatment of 2d and 2g with NH₂NH₂?H₂O at 100° (Scheme 4).     

Hydrogen‐bonded ribbons in ethyl (E)‐3‐[2‐amino‐4,6‐bis(dimethylamino)pyrimidin‐5‐yl]‐2‐cyanoacrylate and 2‐[(2‐amino‐4,6‐di‐1‐piperidylpyrimidin‐5‐yl)methylene]malononitrile

The pyrimidine rings in ethyl (E)‐3‐[2‐amino‐4,6‐bis(dimethylamino)pyrimidin‐5‐yl]‐2‐cyanoacrylate, C₁₄H₂₀N₆O₂, (I), and 2‐[(2‐amino‐4,6‐di‐1‐piperidylpyrimidin‐5‐yl)methylene]malononitrile, C₁₈H₂₃N₇, (II), which crystallizes with Z′ = 2 in the space group, are both nonplanar with boat conformations. The molecules of (I) are linked by a combination of N—H...N and N—H...O hydrogen bonds into chains of edge‐fused R₂²(8) and R₄⁴(20) rings, while the two independent molecules in (II) are linked by four N—H...N hydrogen bonds into chains of edge‐fused R₂²(8) and R₂²(20) rings. This study illustrates both the readiness with which highly‐substituted pyrimidine rings can be distorted from planarity and the significant differences between the supramolecular aggregation in two rather similar compounds.     

Nucleophilic Cyclopropanation Reaction with Bis(iodozincio)methane by 1,4‐Addition to α,β‐Unsaturated Carbonyl Compounds

Treatment of α,β‐unsaturated ketones with an electrophilic site at the γ‐position in the presence of trimethylsilyl cyanide with bis(iodozincio)methane afforded the (Z)‐silyl enol ether of the β‐cyclopropyl substituted ketone in good yields. The reaction proceeds by 1,4‐addition to form an enolate, and its sequential intramolecular nucleophilic attack to an adjacent electrophilic site. The reaction of γ‐ethoxycarbonyl‐α,β‐unsaturated ketone and bis(iodozincio)methane in the presence of trimethylsilyl cyanide afforded 1‐ethoxy‐1‐trimethylsiloxycyclopropane derivatives, which can be regarded as the homoenolate equivalent. Additionally, reaction of the obtained homoenolate equivalents with imines give 1‐(E)‐alkenyl‐2‐(1‐aminoalkyl)alkanols diastereoselectively.     

Nitro‐substituted iron(II) tridentate bis(imino)pyridine complexes as high‐temperature catalysts for the production of α‐olefins

A new series of nitro‐substituted bis(imino)pyridine ligands {2,6‐bis[1‐(2‐methyl‐4‐nitrophenylimino)ethyl]pyridine, 2,6‐bis[1‐(4‐nitrophenylimino)ethyl]pyridine, (1‐{6‐[1‐(4‐nitro‐phenylimino)‐ethyl]‐pyridin‐2‐yl}‐ethylidene)‐(2,4,6‐trimethyl‐phenyl)‐amine, and 2,6‐bis[1‐(2‐methyl‐3‐nitrophenylimino)ethyl]pyridine} and their corresponding Fe(II) complexes [{p‐NO₂? o‐Me? Ph? N?C(Me)? Py? C(Me)?N? Ph? o‐ Me? p‐NO₂}FeCl₂ ( 10 ), L₂FeCl₂ ( 11 ), {m‐NO₂? o‐Me? Ph? N?C(Me)? Py? C(Me)?N? Ph? o‐Me? m‐NO₂}FeCl₂ ( 12 ), and {p‐NO₂? Ph? N?C(Me)? Py? C(Me)?N? Mes}FeCl₂ ( 14 )] were synthesized. According to X‐ray analysis, there were shortenings of the axial Fe? N bond lengths (up to 0.014 Å) in para‐nitro‐substituted complex 10 and (up to 0.015 Å) in meta‐nitro‐substituted complex 12 versus the Fe(II) complex without nitro groups [{o‐Me? Ph? N?C(Me)? Py? C(Me)?N? Ph? o‐Me}FeCl₂ ( 1 )]. Complexes 10 , 12 , and 14 afforded very active catalysts for the production of α‐olefins and were more temperature‐stable and had longer lifetimes than parent non‐nitro‐substituted Fe(II) complex 1 . The reaction between FeCl₂ and a sterically less hindered ligand [p‐NO₂? Ph? N?C(Me)? Py? C(Me)?N? Ph? p‐NO₂] resulted in the formation of octahedral complex 11 . A para‐dialkylamino‐substituted bis(imino)pyridine ligand [p‐NEt₂? o‐Me? Ph? N?C(Me)? Py? C(Me)?N? Ph? o‐Me? p‐NEt₂] and the corresponding Fe(II) complex [{p‐NEt₂? o‐Me? Ph? N?C(Me)? Py? C(Me)?N? Ph? o‐Me? p‐NEt₂}FeCl₂ ( 16 )] were synthesized to evaluate the effect of enhanced electron donation of the ligand on the catalytic performance. According to X‐ray analysis, there was a shortening (up to 0.043 Å) of the axial Fe? N bond lengths in para‐diethylamino‐substituted complex 16 in comparison with parent Fe(II) complex 1 . © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2615–2635, 2006     

Synthesis and characterization of the first examples of 1,3,2‐diazastibole and 1,3,2‐diazabismole ring compounds

Reaction of either 9,10‐phenanthrenedione (phenanthrenequinone) or diphenylethanedione (benzil) with two equivalents of Li[N(SiMe₃)₂], followed by quenching of the reaction with excess ClSiMe₃, produces the corresponding N,N′‐bis(trimethylsilyl)‐α‐diimines in high yields (85–95%). Subsequent dehalosilylation/ring‐closure reactions with SbCl₃ and BiCl₃ produce, in 90–95% yields, the first examples of 1,3,2‐diazaheterole ring compounds containing antimony or bismuth. These 2‐chloro‐1,3,2‐diazaheteroles can be further functionalized at the pnictogen by reaction with, for example, Li[N(SiMe₃)₂], to produce the corresponding 2‐bis(trimethylsilyl)amido‐1,3,2‐diazaheteroles. All of these new main group element–containing heterocycles have been characterized through ¹H and ¹³C NMR, elemental analysis, and two of the diazastiboles have been structurally characterized by single‐crystal X‐ray analysis, confirming the ring structures. Both of these diazastiboles exist as associated dimers in the solid state; half of the dimer represents the asymmetric unit. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 423–429, 1999