Darstellung,Eigenschaften und Reaktionsverhalten von 2-(Dimethylaminomethyl)phenyl- und 8-(Dimethylamino)naphthylsubstituierten Lithiumhydridosilylamiden – Bildung von Silaniminen durch Lithiumhydrideliminierung

Preparation, Properties, and Reaction Behaviour of 2-(Dimethylaminomethyl)phenyl- and 8-(Dimethylamino)naphthylsubstituted Lithium Hydridosilylamides – Formation of Silanimines by Elimination of Lithium Hydride The hydridosilylamines Ar(R)Si(H)–NHR′ ( 2 a : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = CMe₃; 2 b : Ar = 2-Me₂NCH₂C₆H₄, R = Ph, R′ = CMe₃; 2 c : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = SiMe₃; 2 d : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = CMe₃; 2 e : Ar = 8-Me₂NC₁₀H₆, R = Ph, R′ = CMe₃; 2 f : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = SiMe₃) have been synthesized from the appropriate chlorosilanes Ar(R)SiHCl either by reaction with the stoichiometric amount of Me₃CNHLi ( 2 a , 2 b , 2 d , 2 e ) or by coammonolysis in liquid NH₃ with chlorotrimethylsilane in molar ratio 1 : 3 ( 2 c , 2 f ). Treatment of 2 a–2 f with n-butyllithium in equimolar ratio in n-hexane resulted in the lithiumhydridosilylamides Ar(R)Si(H)–N(Li)R′ 3 a–3 f . The frequencies of the Si–H stretching vibration and ²⁹Si–¹H coupling constants in the amides are smaller than in the analogous amines indicating a higher hydride character for the hydrogen atom of the Si–H group in the amides compared to the amines. Results of NMR spectroscopic studies point to the existence of a (Me₂)N → Si coordination bond in the 8-(dimethylamino)naphthyl-substituted amines and amides. The amides 3 a–3 c are stable under refluxing in m-xylene. At the same conditions 3 d and 3 e eliminate LiH and the silanimines 8-Me₂NC₁₀H₆(R)Si=NCMe₃ ( 4 d : R = Me, 4 e : R = Ph) are formed. The amides 3 a–3 d und 3 f react with chlorotrimethylsilane in THF to give the corresponding N-substitution products Ar(R)Si(H)–N(SiMe₃)R′ 6 a–6 d and 6 f in good yields. 4 d is formed as a byproduct in the reaction of 3 d with chlorotrimethylsilane. In n-hexane and m-xylene these amides are little reactive opposite to chlorotrimethylsilane. 6 a–6 d and 6 f are obtained in very small amounts. In the case of 3 d besides the N-substitution product 6 d the silanimine 4 d is obtained. In contrast to chlorotrimethylsilane the amides 3 a and 3 f react well with chlorodimethylsilane in m-xylene producing 2-Me₂NCH₂C₆H₄(H) SiMe–N(SiHMe₂)CMe₃ ( 7 a ) and 8-Me₂NC₁₀H₆(H)SiMe–N(SiHMe₂)SiMe₃ ( 7 f ).     

A Heteroleptic (E)-1,2-Diaryl-1,2-disilyldistannene without Donor Stabilization

The reaction of the stannylene R₂Sn : (R = 2-tBu-4,5,6-Me₃C₆H) with R′₂Sn (R′ = Si(SiMe₃)₃) proceeds with substituent exchange to afford the heteroleptic stannylene RR′Sn : which, in the solid state, forms the distannene RR′Sn = SnRR′ ( 7 ). The X-ray structure analysis of 7 reveals a trans-bent arrangement of the substituents with a large fold angle of 44.9° and an Sn–Sn double bond length of 279.14(4) pm.     

Ethylene/1-hexene copolymerization by salicylaldiminato vanadium(III) complexes activated with diethylaluminum chloride

Mono salicylaldiminato vanadium（Ⅲ） complexes（1a-1f）[RN = CH（ArO）]VCl₂（THF）₂（Ar = C₆H₄（1a-1e）,R = Ph,1a;R = p-CF₃Ph,1b;R = 2,6-Me₂Ph,1c;R = 2,6-iPr₂Ph,1d;R = cyclohexyl,1e;Ar = C₆H₂tBu₂（2,4）,R = 2,6-iPr₂Ph, 1f） and bis（salicylaldiminato） vanadium（Ⅲ） complexes（2a-2f）[RN = CH（ArO）]₂VCl（THF）_x（Ar = C₆H₄（2a-2e）,x = 1 （2a-2e）,R = Ph,2a;R =p-CF₃Ph,2b;R = 2,6-Me₂Ph,2c;R = 2,6-iPr₂Ph,2d;R = cyclohexyl,2e;Ar = C₆H₂tBu₂（2,4）,R = 2,6-iPr₂Ph,x = 0,2f） have been evaluated as the active catalysts for ethylene/1-hexene copolymerization in the presence of Et₂AlCl.The ligand substitution pattern and the catalyst structure model significantly influenced the polymerization behaviors such as the catalytic activity,the molecular weight and molecular weight distribution of the copolymers etc.The highest catalytic activity of 8.82 kg PE/（mmol_V·h） was observed for vanadium catalyst 2d with two 2,6-diisopropylphenyl substituted salicylaldiminato ligands.The copolymer with the highest molecular weight was obtained by using mono salicylaldiminato vanadium catalyst 1f having ligands with tert-butyl at the ortho and para of the aryloxy moiety.     

Homoleptische Amide von Zink,Cadmium und Quecksilber

Homoleptic Amides of Zinc, Cadmium, and Mercury ZnCl₂, CdCl₂ and HgCl₂ react with the lithium salts ( 1 a–5 a ) of the sterically demanding secundary amines HN(SiMe₃)Ph ( 1 ), HN(SiMe₃)C₆H₃Me₂‐2,6 ( 2 ), HN(SiMe₃)C₆H₃ⁱPr₂‐2,6 ( 3 ), HN(SiMe₃)C₆H₃^tBu₂‐2,5 ( 4 ), and HN(SiMe₂NMe₂)C₆H₃ⁱPr₂‐2,6 ( 5 ) yielding the corresponding homoleptic metal amides Zn[N(SiMe₂R′)R]₂ ( 1 b–5 b ), Cd[N(SiMe₂R′)R]₂ ( 1 c , 5 c ), and Hg[N(SiMe₂R′)R]₂ ( 1 d–5 d ), respectively. Except the dimeric {Zn[N(SiMe₃)Ph]₂}₂ ( 1 b ), all complexes are monomeric. The compounds were characterized by elemental analyses, molecular weight determinations, NMR and mass spectra. Furthermore, the zinc amides ( 1 b–5 b ) and the mercury amides 1 d–3 d and 5 d were characterized by single crystal X‐ray structure analysis. Except 1 b and 5 b , they show a linear N–M–N arrangement.     

Distibanes and Distibenes from Reduction of Sb(NONR)Cl by using MgI Reagents

The bis(amidodimethyl)disiloxane antimony chlorides Sb(NON^R)Cl (NON^R=[O(SiMe₂NR)₂]²⁻; R=tBu, Ph, 2,6-Me₂C₆H₃=Dmp, 2,6-iPr₂C₆H₃=Dipp, 2,6-(CHPh₂)₂-4-tBuC₆H₂=tBu-Bhp) are reduced to Sb^II and Sb^I species by using Mg^I reagents, [Mg(BDI^R′)]₂ (BDI=[HC{C(Me)NR′}₂]⁻; R′=2,4,6-Me₃C₆H₂=Mes, Dipp). Stoichiometric reactions with Sb(NON^R)Cl (R=tBu, Ph) form dimeric Sb^II stibanes [Sb(NON^R)]₂, shown crystallographically to contain Sb−Sb single bonds. The analogous distibane with R=Dmp substituents has an exceptionally long Sb−Sb interaction and exhibits spectroscopic and reactivity properties consistent with radical character in solution. When R=Dipp, reductions with Mg^I reagents directly give distibenes [Sb(μ-NON^Dipp)Mg(BDI^R′)(THF)_n]₂ (R′=Mes, n=1; R′=Dipp, n=0). Crystallographic analysis shows a trans-substitution of the Sb=Sb double bond, with bridging NON^Dipp-ligands between the Sb^I and Mg^II centres. An attempt to access the NON^Ph-analogue using the same protocol afforded the polystibide cluster Sb₈[μ₄,η^2:2:2:2-Mg(BDI^Mes)]₄, which co-crystallized with the ligand transfer product, [Mg(BDI^Mes)]₂(μ-NON^Ph).     

CycloSiFA: The Next Generation of Silicon-Based Fluoride Acceptors for Positron Emission Tomography (PET)

The ring-opening Si-fluorination of a variety of azasilole derivatives cyclo-1-(iPr₂Si)−4-X−C₆H₃−2-CH₂NR ( 4 : R=2,6-iPr₂C₆H₃, X=H; 4 a : R=2,4,6-Me₃C₆H₂, X=H; 9 : R=2,6-iPr₂C₆H₃, X=tBuMe₂SiO; 10 : R=2,6-iPr₂C₆H₃, X=OH; 13 : R=2,6-iPr₂C₆H₃, X=HCCCH₂O; 22 : R=2,6-iPr₂C₆H₃, X=tBuMe₂SiCH₂O) with different ¹⁹F-fluoride sources was studied, optimized and the experience gained was used in a translational approach to create a straightforward ¹⁸F-labelling protocol for the azasilole derivatives [¹⁸F] 6 and [¹⁸F] 14 . The latter constitutes a potential clickable CycloSiFA prosthetic group which might be used in PET tracer development using Cu-catalysed triazole formation. Based on our findings, CycloSiFA has the potential to become a new entry into non-canonical labelling methodologies for radioactive PET tracer development.     

O-Halogensilyl-N,N-bis(trimethylsilyl)hydroxylamine – Synthese,Kristallstruktur und Reaktionen

O-Halogenosilyl-N,N-bis(trimethylsilyl)hydroxylamines – Synthesis, Crystal Structure, and Reactions The substitution of halogenosilanes on lithiated N,O-bis(trimethylsilyl)-hydroxylamine in the molar ratio of 1 : 1 occurs on the oxygen atom. The O-halogenosilyl-N,N-bis(trimethylsilyl)hydroxylamines were prepared: RSiF₂ON · (SiMe₃)₂ (R = CMe₃ 1 , CHMe₂ 2 , CH₂C₆H₅ 3 , C₆H₂(CMe₃)₃ 4 ), RR′SiFON(SiMe₃)₂ (R = CMe₃, R′ = C₆H₅ 5 ; R = Me, R′ = C₆H₅ 6 ; R = C₆H₂Me₃, R′ = C₆H₂Me₃ 7 ; R = CH₂C₆H₅, R′ = CH₂C₆H₅ 8 ; R = CHMe₂, R′ = CHMe₂ 9 ; R = CMe₃, R′ = CMe₃ 10 ), RSiCl₂ON(SiMe₃)₂ (R = CMe₃ 11 ; R = Cl 12 ). The reaction of fluorosilanes with lithiated N,O-bis(trimethylsilyl)hydroxylamine in the molar ratio of 1 : 2 leads to the formation of O,O′-fluorosilyl-bis[N,N-bis(trimethylsilyl)hydroxylamines]: RSiF[ON(SiMe₃)₂]₂ (R = CMe₃ 13 ; R = C₆H₅ 14 ). 13 could be prepared in the reaction of 1 with LiON(SiMe₃)₂. Lithiated dimethylketonoxime reacts with 1 to Me₂C=NOSiRF–ON(SiMe₃)₂ [R = CMe₃ ( 15 )]. The first crystal structure of a tris(silyl)hydroxylamine ( 4 ) is shown. The angle at the nitrogen prove a pyramidal geometry.     

Synthesis of Diaminophosphonium Salts [Ph2(ArNH)2P]+Br− (Ar = o-MeC6H4, p-MeC6H4, p-Pr i C6H4, p-EtO2CC6H4, p-MeOC6H4)

The behavior of different anilines H₂NC₆H₄R (R = o-Me, p-Me, o-, m- and p? ⁱ Pr, p-OMe, p-CO₂Et) and 2,6-Me₂C₆H₃NH₂ towards trihalophosphoranes was studied. 2,6-Me₂C₆H₃NH₂ failed to form the diaminophosphonium salt [Ph₂PNH(2,6-Me₂C₆H₃)₂]Br, and the aminophosphine oxide Ph₂(2,6-Me₂C₆H₃NH)PO was the only isolated product. Both o- and p-toluidine gave the corresponding diaminophosphonium salts; however in the case of o-toluidine, the yield was low and a mixture with the respective aminophosphine oxide was observed. Anilines containing methoxy and ethoxycarbonyl groups in para-position form the diaminophosphonium salts in reasonable yields.     

Aminosilylgermylenes: (E)-Digermene versus Germylene Crystallization [1]

The diaminosilylene tBuNCH₂CH₂NtBuSi: reacted with the diaminogermylenes RNCH₂CH₂NRGe: R = 2,6-Me₂C₆H₃, iPr, by silylene insertion into one of the Ge–N bonds to furnish the aminosilylgermylenes 8 , R = 2,6-Me₂C₆H₃, and 9 , R = iPr. The X-ray structure analyses of these compounds revealed that 8 remains monomeric in the crystal with weak Ge … Ge interactions to the germanium atom of a neighbouring germylene molecule, whereas 9 dimerizes to give the strongly twisted (E)-1,2-diamino-1,2-disilyldigermene (E)- 10 with a long Ge–Ge double bond of 246 pm and a large trans-bent angle of 47.3°.     

Synthesis and Structural Characterization of Some Novel Trialkylsilyl‐substituted Lithium Benzyl Complexes [Li(tmeda)][CHRSiMe2R′] (R = Ph, 3,5‐Me2C6H3; R′ = Me,tBu, Ph)

The reactions of PhCH₂SiMe₃ ( 1 ), PhCH₂SiMe₂^tBu ( 2 ), PhCH₂SiMe₂Ph ( 3 ), 3,5‐Me₂C₆H₃CH₂SiMe₃ ( 4 ), and 3,5‐Me₂C₆H₃CH₂SiMe₂^tBu ( 5 ) with ⁿBuLi in tetramethylethylenediamine (tmeda) afford the corresponding lithium complexes [Li(tmeda)][CHRSiMe₂R′] (R, R′ = Ph, Me ( 6 ), Ph, ^tBu ( 7 ), Ph, Ph ( 8 ), 3,5‐Me₂C₆H₃, Me ( 9 ), and 3,5‐Me₂C₆H₃, ^tBu ( 10 )), respectively. The new compounds 5 , 7 , 8 , 9 and 10 have been characterized by ¹H and ¹³C NMR spectroscopy, compounds 7 , 8 and 9 also by X‐ray structure analysis.     

Complexes of N-Phosphorylated Thioureas RNHC(S)NHP(O)(OiPr)2 (R = 2-MeC6H4, 2,6-Me2C6H3, 2,4,6-Me3C6H2) With Nickel(II)

The reaction of O,O′-diisopropylphosphoric acid isothiocyanate (iPrO)₂P(O)NCS with 2-methylaniline 2-MeC₆H₄NH₂, 2,6-dimethylaniline 2,6-Me₂C₆H₃NH₂, or 2,4,6-trimethylaniline 2,4,6-Me₃C₆H₂NH₂ leads to the N-phosphorylated thioureas RNHC(S)NHP(O)(OiPr)₂ (R = 2-MeC₆H₄?, HL^I ; 2,6-Me₂C₆H₃?, HL^II ; 2,4,6-Me₃C₆H₂?, HL^III ). Reaction of the potassium salts of HL^{I –III} with Ni(II) in aqueous EtOH leads to [Ni(L^I–III-N,S)₂] ([NiL^I–III ₂ ]) chelate complexes. The compounds obtained were investigated by ¹H, ³¹P{¹H} NMR spectroscopy and microanalysis. The molecular structure of the thiourea HL^III was elucidated by single crystal X-ray diffraction analysis. Single crystal X-ray diffraction studies showed that HL^III forms both intra- and intermolecular hydrogen bonds, which in turn leads to the formation of polymeric chains. One of the intermolecular hydrogen bonds is of the type N?H…S. Moreover, the formation of intermolecular C?H…η⁶-phenyl interactions was established.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Effect of para-Substituents in Ethylene Copolymerizations with 1-Decene, 1-Dodecene,and with 2-Methyl-1-Pentene Using Phenoxide Modified Half-Titanocenes-MAO Catalyst Systems

Effect of para-substituents in the ethylene (E) copolymerization with 1-decene (DC), 1-dodecene (DD), and with 2-methyl-1-pentene (2M1P) using a series of Cp*TiCl₂(O-2,6-ⁱPr₂-4-R-C₆H₂) [R=H ( 1 ), ^tBu ( 2 ), Ph ( 3 ), CHPh₂ ( 4 ), CPh₃ ( 5 ), SiMe₃ ( 6 ), SiEt₃ ( 7 ), and newly prepared 4-^tBuC₆H₄ ( 8 ) and 3,5-Me₂C₆H₃ ( 9 )]-MAO catalyst systems has been studied. The activities in these copolymerization reactions were affected by the para-substituent, and the SiMe₃ ( 6 ), SiEt₃ ( 7 ) and 3,5-Me₂C₆H₃ ( 9 ) analogues showed the higher activities at 50 °C in the E copolymerization reactions with DC (1.06–1.44×10⁶ kg-polymer/mol-Ti⋅h), DD (1.04–1.88×10⁶ kg-polymer/mol-Ti⋅h) than the others, whereas no significant differences were observed in the comonomer incorporations. Complexes 6 and 7 also showed the higher activities at 50 °C in the E/2M1P copolymerization, and the 2M1P incorporation was affected by the para-substituent and the polymerization temperature; complex 9 showed better 2M1P incorporation at 25 °C.     

Über die Si---N-bindung : XLIV. Die umsetzung von benzophenon mit bis- und tris(trimethylsilyl)amin

The thermal LiHal elimination of

- and

functional compounds provides a simple synthetic route to four-membered SiC and SiN rings. In attempts to inhibit dimerisation sterically, bulky silylmethyl and silylamino substituents were introduced (I–III). (Me₃Si)₃CSiF₂R reacts with LiNHR′, 1,3- migration of a silyl group from carbon to the nitrogen (I, R′= 2,4,6-Me₃C₆H₂) taking place. Substitution occurs for R′ = SiMe₂CMe₂, (II, III) only.Dichloro-bis(trimethylsilyl)methane reacts with halogenosilanes and lithium in THF to give bis(trimethylsilyl)-halogenosilaethanes (Me₃Si)₂CHSi(Hal)RR′; R= Me, R′ = N(SiMe₃)₂, IV, Hal = F; V, Hal = Cl. However a reductive THF cleavage accompanied by a silyl group migration to the oxygen occurs and 1-halogenosilyl-1- trimethylsilyl-5-trimethylsiloxi-pent-1-ene,(Me₃Si)(RR′SiHal)CCH(CH₂)₃OSiMe₃, Are The main products (VII–X) of these reactions. Disubstitution occurs with F₃Si-i-Pr (VI). (Me₃Si)₃CSiFNHSiMe₂CMe₃ (II) reacts with C₄H₉Li in a molar ratio $\text{1}\text{2}$ to give an 1-aza-2,3-disilacyclobutane (XI), involving substitution, LiF elimination, and nucleophilic migration of a methanide ion of the unsaturated precusor.(Me₃Si)₂CHSiFMeN (2,4,6-Me₃C₆H₂)SiMe₃ cyclizes under comparable conditions in the reaction with MeLi via a methylene group of the mesityl group (XII).     

Reaktionen von Lithiumhydridosilylamiden RR′(H)Si–N(Li)R″ mit Chlortrimethylsilan in Tetrahydrofuran und unpolaren Lösungsmitteln: N‐Silylierung und/oder Cyclodisilazanbildung

Reactions of Lithium Hydridosilylamides RR′(H)Si–N(Li)R″ with Chlorotrimethylsilane in Tetrahydrofuran and Nonpolar Solvents: N‐Silylation and/or Formation of Cyclodisilazanes The lithiumhydridosilylamides RR′(H)Si–N(Li)R″ ( 2 a : R = R′ = CHMe₂, R″ = SiMe₃; 2 b : R = R′ = Ph, R″ = SiMe₃; 2 c : R = R′ = CMe₃, R″ = SiMe₃; 2 d : R = R′ = R″ = CMe₃; 2 e : R = Me, R′ = Si(SiMe₃)₃, R″ = CMe₃; 2 f – 2 h : R = R′ = Me, f : R″ = 2,4,6‐Me₃C₆H₂, g : R″ = SiH(CHMe₂)₂, h : R″ = SiH(CMe₃)₂; 2 i : R = R′ = CMe₃, R″ = SiH(CMe₃)₂) were prepared by reaction of the corresponding hydridosilylamines RR′(H)Si–NHR″ 2 a – 2 i with n‐butyllithium in equimolar ratio in n‐hexane. The unknown amines 1 e – 1 i and amides 2 f – 2 i have been characterized spectroscopically. The wave numbers of the Si–H stretching vibrations and ²⁹Si–¹H coupling constants of the amides are less than of the analogous amines. This indicates a higher hydride character for the hydrogen atom of the Si–H group in the amide in comparison to the amines. The ²⁹Si‐NMR chemical shifts lie in the amides at higher field than in the amines. The amides 2 a – 2 c and 2 e – 2 g react with chlorotrimethylsilane in THF to give the corresponding N‐silylation products RR′(H)Si–N(SiMe₃)R″ ( 3 a – 3 c , 3 e – 3 g ) in good yields. In the reaction of 2 i with chlorotrimethylsilane in molar ratio 1 : 2,33 in THF hydrogen‐chlorine exchange takes place and after hydrolytic work up of the reaction mixture [(Me₃C)₂(Cl)Si]₂NH ( 5 a ) is obtained. The reaction of the amides 2 a – 2 c , 2 f and 2 g with chlorotrimethylsilane in m(p)‐xylene and/or n‐hexane affords mixtures of N‐substitution products RR′(H)Si–N(SiMe₃)R″ ( 3 a – 3 c , 3 f , 3 g ) and cyclodisilazanes [RR′Si–NR″]₂ ( 6 a – 6 c , 6 f , 6 g ) as the main products. In case of the reaction of 2 h the cyclodisilazane 6 h was obtained only. 2 c – 2 e show a very low reactivity toward chlorotrimetyhlsilane in m‐xylene and toluene resp.. In contrast to Me₃SiCl the reactivity of 2 d toward Me₃SiOSO₂CF₃ and Me₂(H)SiCl is significant higher. 2 d react with Me₃SiOSO₂CF₃ and Me₂(H)SiCl in n‐hexane under N‐silylation to give RR′(H)Si–N(SiMe₃)R″ ( 3 d ) and RR′(H)Si–N(SiHMe₂)R″ ( 3 d ′) resp. The crystal structures of [Me₂Si–NSiMe₃]₂ ( I ) ( 6 f , 6 g and 6 h ) have been determined.     

Isospecific Polymerization of Methyl Methacrylate by Intramolecular Rare‐Earth Metal Based Lewis Pairs†

A series of cationic rare‐earth aryloxide complexes, i.e., [LREOAr']⁺[B(C₆F₅)₄]^– (L = CH₃C(NAr)CHC(CH₃)(NCH(R)CH₂PPh₂); RE = Y, Lu; Ar' =2,6‐tBu₂‐C₆H₃, 2,6‐(PhCMe₂)₂‐4‐Me‐C₆H₂; Ar = 2,6‐iPr₂‐C₆H₃, 2,6‐(Ph₂CH)₂‐4‐iPr‐C₆H₂; R = H, CH₃, iPr, Ph), were prepared and applied to the Lewis pair polymerization of methyl methacrylate (MMA). The stereoregularity of the resulting PMMA was significantly affected by the R substituent on the pendant arm of the tridentate NNP ligand, and was found to increase with increase in the steric hindrance of R. When using a Ph group as R, the Y complex produced a highly isotactic polymer with an mm value of 95% and a T_g of 54.6 ^oC. In contrast, the steric hindrance of the Ar and Ar' groups had no effect on the tacticity of the resulting polymer, presumably because these two substituents were situated such that they pointed outward from the cyclic intermediates. Kinetics studies demonstrated that the polymerization was a first‐order process with regard to the monomer concentration prior to catalyst deactivation. End group analysis indicated that the polymerization was accompanied by two possibly competing chain‐termination side reactions that proceeded via intramolecular backbiting cyclization.     

Mono(amidinate) rare earth metal bis(alkyl) complexes: Synthesis,structure and their activity for l-lactide polymerization

Alkane elimination reaction between Ln(CH₂SiMe₃)₃(THF)₂ (Ln = Y, Lu) with one equivalent of the amidines with different steric demanding HL ([CyC(N-2,6-ⁱPr₂C₆H₃)₂]H (HL₁), [CyC(N-2,6-Me₂C₆H₃)₂]H (HL₂), [PhC(N-2,6-Me₂C₆H₃)₂]H (HL₃)) in THF afforded a series of mono(amidinate) rare earth metal bis(alkyl) complexes [CyC(N-2,6-ⁱPr₂C₆H₃)₂]Ln(CH₂SiMe₃)₂(THF) (Ln = Y (1), Lu (3)), [CyC(N-2,6-Me₂C₆H₃)₂]Ln(CH₂SiMe₃)₂(THF)₂ (Ln = Y (4), Lu (6)), and [PhC(N-2,6-Me₂C₆H₃)₂]Y(CH₂SiMe₃)₂(THF)₂ (7) in 75–89% isolated yields. For the early lanthanide metal Nd, THF slurry of NdCl₃ was stirred with three equiv of LiCH₂SiMe₃ in THF, followed by addition of one equiv of the amidines HL₁ or HL₂ gave an “ate” complex [CyC(N-2,6-ⁱPr₂C₆H₃)₂]Nd(CH₂SiMe₃)₂(μ-Cl)Li(THF)₃ (2) in 48% yield and a neutral [CyC(N-2,6-Me₂C₆H₃)₂]Nd(CH₂SiMe₃)₂(THF)₂ (5) in 52% yield, respectively. They were characterized by elemental analysis, FT-IR, NMR spectroscopy (except for 2 and 5 for their strong paramagnetic property). Complexes 2, 3, 4 and 5 were subjected to X-ray single crystal structure determination. These neutral mono(amidinate) rare earth metal bis(alkyl) complexes showed activity towards l-lactide polymerization to give high molecular weight and narrow molecular weight distribution polymers.     

1‐Azonia‐2‐boratanaphthalenes

The 1‐azonia‐2‐boratanaphthalenes (NH)(BX)C₈H₆ can be synthesized from 2‐aminostyrene and the dihaloboranes XBHal₂ ( 1 ‐ 4 : X = Cl, Br, iPr, tBu). Further derivatives (NH)(BX)C₈H₆ are obtained from 1 by replacing Cl by alkoxy or alkyl groups [ 5 ‐ 8 : X = OMe, OtBu, Me, (CH₂)₃NMe₂]. The hydrolysis of 1 gives a mixture of the bis(azoniaboratanaphthyl) oxide [(NH)BC₈H₆]₂O ( 9 ) and the hydroxy derivative (NH)[B(OH)]C₈H₆ ( 10 ). The diboryl oxide 9 crystallizes in the space group C2/c. The lithiation of 4 at the nitrogen atom gives [NLi(tmen)](BtBu)C₈H₆ ( 11 ), which upon reaction with the diborane(4) B₂Cl₂(NMe₂)₂ yields the 1, 2‐bis(azoniaboratanaphthyl)diborane B₂[N(BtBu)C₈H₆]₂(NMe₂)₂ ( 12 ). The 2‐chloro‐1‐methyl‐4‐phenyl derivative (NMe)(BCl)C₈H₅Ph ( 13 ) of the parent (NH)(BH)C₈H₆ can be synthesized from the aminoborane BCl₂(NMePh) and phenylethyne. Substitution of Cl in 13 gives the derivatives (NMe)(BX)C₈H₅Ph [ 14 ‐ 20 : X = N(SiMe₃)₂, Me, Et, iBu, tBu, CH₂SiMe₃, Ph] and the reaction of 13 with Li₂O affords the bis(azoniaboratanaphthyl) oxide [(NMe)BC₈H₅Ph]₂O ( 21 ). The reaction of 16 or 19 with [(MeCN)₃Cr(CO)₃] yields the complexes [{(NMe)(BX)C₈H₅Ph}Cr(CO)₃] ( 22 , 23 : X = Et, CH₂SiMe₃), in which the chromium atom is hexahapto bound to the homoarene part of 16 or 19 , respectively. The complex 23 crystallizes in the space group P2₁/c. Upon reaction of the phenols para‐C₆H₄R(OH) with the aryldichloroboranes ArBCl₂ and subsequent condensation of the products with phenylethyne, the 1‐oxonia‐2‐boratanaphthalenes O(BAr)C₈H₄RPh with R in position 6 and Ph in position 4 are formed ( 24 ‐ 26 : Ar = Ph, R = H, Me, OMe; 27 ‐ 29 : Ar = C₆F₅, R = H, Me, OMe). The azoniaboratanaphthalenes 1 ‐ 23 were characterized by NMR methods.     

Trimethylene-bridged Tetraorganodistannoxanes {[Me3SiCH2(RCOO)Sn(CH2)3Sn(OOCR)CH2SiMe3]O}n (R = Ph, 2,4-Me2C6H3): Control of Structure by Variation of R

The synthesis of trimethylene-bridged carboxylate-substituted tetraorganodistannoxanes {[Me₃SiCH₂(RCOO)Sn(CH₂)₃Sn(OOCR)CH₂SiMe₃]O} _n (1, R = Ph; 2, R = 2,4-Me₂C₆H₃) is reported. Depending on the structure of R, in the solid state these compounds are either dimers (1, n = 2, cis-isomer) with a ladder-type structure or tetramers (2, n = 4) with a double ladder-type structure.     

Styrene polymerization with nickel complexes/methylaluminoxane catalytic system

Polymerization of styrene using β‐diketiminate nickel (II) bromide complexes CH{C(R)NAr}₂NiBr (R = CH₃, Ar = 2,6‐ⁱPr₂C₆H₃, 1 ; R = CH₃, Ar = 2,6‐Me₂C₆H₃, 2 ; R = CF₃, Ar = 2,6‐ⁱPr₂C₆H₃, 3 ; R = CF₃, Ar = 2,6‐Me₂C₆H₃, 4 ) in the presence of methylaluminoxane was studied. Compound 3 is the most active styrene polymerization catalyst of all the nickel complexes tested. The activity of these catalysts increases with increases in steric bulk of the substituents on the aryl rings. The electronic nature of the ligand backbone also affects the activity. Weight‐average molecular weight of the prepared polystyrene ranges from 21 000 to 72 000, with polydispersity indexes of 1.95–2.78. The microstructure of the obtained products is atactic polystyrenes from NMR analyses. Copyright © 2008 John Wiley & Sons, Ltd.     

Steric effects in oxidative addition and reductive elimination reactions of rhodium pentafluorophenylthiolate complexes

The complexes [cis-Rh(SC₆F₅)(PPh₃)₂(L)] (L = py, 3-Mepy, isoquin, N-Melm; py = pyridine, 3-Mepy = 3-methylpyridine, isoquin = isoquinoline, N-Melm = N-methylimidazole) readily undergo oxidative addition of HR (R = H, SC₆F₅, C₂Ph) to give [RhH(R)(SC₆F₅)(PPh₃)_n(L)_3−n] (n = 1, 2) whereas the complexes [cis-Rh(SC₆F₅)(PPh₃)₂(L′)] (L′ = 2-Mepy, 2,6-Me₂py, quin; 2-Mepy = 2-methylpyridine; 2,6-Me₂py = 2,6-dimethylpyridine, quin = quinoline) react only where R = C₂Ph. Where conditions favour the formation of [RhH(R)(SC₆F₅)(PPh₃)_n(L′)_3−n] reductive elimination of H₂ (R = H) or C₆F₅SH (R = SC₆F₅, C₂Ph) occurs.