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1.
Ravi Shankar Vandana Shahi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):7816-7826
The polysilanes [RMe2Si(CH2)x(Me)Si]n [x = 2, 3; R = 2‐Fu ( 1, 2 ), 5‐Me‐2‐Fu ( 3, 4 )] bearing furyl‐substituted carbosilyl side chains have been synthesized by dehalocondensation reaction (Wurtz coupling) of the corresponding carbosilanes using sodium dispersion in refluxing toluene. On the other hand, analogous polysilanes with appended thienyl groups [x = 2, 3; R = 2‐Th ( 5, 6 ), 4‐Me‐2‐Th ( 7, 8 )] are only accessible by the reaction of the corresponding carbosilane precursors under mild Wurtz coupling conditions (THF, RT). These polysilanes reveal monomodal molecular weight distribution with Mw/PDI = 3.3–5.4 × 104/1.22–1.47 ( 1–4 ) and 9.1–14.4 × 104/1.45–1.61 ( 5–8 ) and are characterized by FT‐IR, multinuclear (1H, 13C{1H}, 29Si{1H}) NMR, and UV/PL spectral studies as well as thermogravimetric analysis (TGA). Preliminary studies on the reactivity of polysilane 2 with palladium acetate (toluene, RT) reveal the formation of spherical palladium nanoparticles of size 8.2 ± 0.6 nm, which remain stable in solution for several weeks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7816–7826, 2008 相似文献
2.
Reactions of Pentafulvene Complexes of Titanium with Nitriles and iso‐Nitriles — Synthesis and Isomerizations of σ, π‐Chelat Complexes with Cp∼N‐Ligands The reactions of fulvene complexes Cp*Ti{η6—C5H4=C(R)(R')}Cl (R = H, R' = tBu ( 1 ); R = Me, R' = iPr ( 4 )) with nitriles and iso‐nitriles, leading to σ, π‐chelat complexes with Cp∼N‐ligands, have been examined and the formed products characterized. Whereas in the reactions of 1 and 4 , respectively, with nitriles a 1, 2‐mono‐insertion of the CN‐group in the Ti—C(R)(R') (Fv) bond is observed, the reaction with iso‐nitrils leads to the insertion of two molecules iso‐nitrile. The nitrile insertion product of 1 is characterized by an imine‐enamine tautomerization. Whereas the primary built meta stable imine species ( 3 ) was only identified by NMR measurements in solution, the enamine tautomer ( 2 ) crystallized from n‐hexane, so that the crystal structure could be determined. The primary formed iminoacyl complex ( 7 ) rearranges due to the electrophilicity of the titanium centre and builds a Ti—N bond with significant N(pπ) → Ti(dπ) bonding character. 相似文献
3.
Nilo Zanatta Elizandra C. S. Lopes Leonardo Fantinel Helio G. Bonacorso Marcos A. P. Martins 《Journal of heterocyclic chemistry》2002,39(5):943-947
The synthesis of a novel series of twelve 4‐(trihalomethyl)dipyrimidin‐2‐ylamines, from the cyclo‐condensation reaction of 4‐(trichloromethyl)‐2‐guanidinopyrimidine, with β‐alkoxyvinyl trihalomethyl ketones, of general formula: X3C‐C(O)‐C(R2)=C(R1)‐OR, where: X = F, Cl; R = Me, Et, ‐(CH2)2‐, ‐(CH2)3‐; R1 = H, Me; R2 = H, Me, ‐(CH2)2‐, ‐(CH2)3‐, is reported. The reactions were carried out in acetonitrile under reflux for 16 hours, leading to the dipyrimidin‐2‐ylamines in 65‐90% yield. Depending on the substituents of the vinyl ketone, tetrahydropyrimidines or aromatic pyrimidine rings were obtained from the cyclization reaction. When X = Cl, elimination of the trichloromethyl group was observed during the cyclization step. The structure of 4‐(trihalomethyl)dipyrimidin‐2‐ylamines was studied in detail by 1H‐, 13C‐ and 2D‐nmr spectroscopy. 相似文献
4.
Mariya Edeleva Sylvain R. A. Marque Kuanish Kabytaev Yohann Guillaneuf Didier Gigmes Elena Bagryanskaya 《Journal of polymer science. Part A, Polymer chemistry》2013,51(6):1323-1336
Thermal decomposition of four tertiary N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines (SG1‐C(Me)2‐C(O)‐OR, R = Me, tBu, Et, H) has been studied at different experimental conditions using 1H and 31P NMR spectroscopies. This experiment represents the initiating step of methyl methacrylate polymerization. It has been shown that H‐transfer reaction occurs during the decomposition of three alkoxyamines in highly degassed solution, whereas no products of H‐transfer are detected during decomposition of SG1‐MAMA alkoxyamine. The value of the rate constant of H‐transfer for alkoxyamines 1 (SG1‐C(Me)2‐C(O)‐OMe) and 2 ( SG1‐C(Me)2‐C(O)‐OtBu) has been estimated as 1.7 × 103 M?1s?1. The high influence of oxygen on decomposition mechanism is found. In particular, in poorly degassed solutions, nearly quantitative formation of oxidation product has been observed, whereas at residual pressure of 10?5 mbar, the main products originate from H‐atom transfer reaction. The acidity of the reaction medium affects the decomposition mechanism suppressing the H‐atom transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
5.
Dr. Shubhankar Kumar Bose Dipak Kumar Roy Pritam Shankhari K. Yuvaraj Bijan Mondal Amrita Sikder Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(7):2337-2343
Room temperature photolysis of a triply‐bridged borylene complex, [(μ3‐BH)(Cp*RuCO)2(μ‐CO)Fe(CO)3] ( 1 a ; Cp*=C5Me5), in the presence of a series of alkynes, 1,2‐diphenylethyne, 1‐phenyl‐1‐propyne, and 2‐butyne led to the isolation of unprecedented vinyl‐borylene complexes (Z)‐[(Cp*RuCO)2(μ‐CO)B(CR)(CHR′)] ( 2 : R, R′=Ph; 3 : R=Me, R′=Ph; 4 : R, R′=Me). This reaction permits a hydroboration of alkyne through an anti ‐ Markovnikov addition. In stark contrast, in the presence of phenylacetylene, a metallacarborane, closo‐[1,2‐(Cp*Ru)2(μ‐CO)2{Fe2(CO)5}‐4‐Ph‐4,5‐C2BH2] ( 5 a) , is formed. A plausible mechanism has been proposed for the formation of vinyl‐borylene complexes, which is supported by density functional theory (DFT) methods. Furthermore, the calculated 11B NMR chemical shifts accurately reflect the experimentally measured shifts. All the new compounds have been characterized in solution by mass spectrometry and IR, 1H, 11B, and 13C NMR spectroscopies and the structural types were unequivocally established by crystallographic analysis of 2 , 5 a , and 5 b . 相似文献
6.
U. N. Tripathi G. Venubabu Mohd. Safi Ahmad S. S. Rao Kolisetty A. K. Srivastava 《应用有机金属化学》2006,20(10):669-676
Diorganotin(IV) dipyrazolinates of the type R2Sn(C15H12N2OX)2 [where C15H12N2OX = 3(2′‐Hydroxyphenyl)‐5(4‐X‐phenyl)pyrazoline {where X = H ( a ); CH3 ( b ); OCH3 ( c ); Cl ( d ) and R = Me, Prn and Ph}] have been synthesized by the reaction of R2SnCl2 with sodium salt of pyrazolines in 1:2 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement as well as spectral [IR and multinuclear NMR (1H, 13C and 119Sn)] studies. The bidentate behaviour of the pyrazoline ligands was confirmed by IR, 1H and 13C NMR spectral data. A distorted trans‐octahedral structure around tin(IV) atom for R2Sn(C15H12N2OX)2 has been suggested. The free pyrazoline and diorganotin(IV) dipyrazolinates have also been screened for their antibacterial and antifungal activities. Some diorganotin(IV) dipyrazolinates exhibit higher antibacterial and antifungal effect than free ligand and some of the antibiotics. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
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. 相似文献
8.
Synthesis of highly branched polyethylene using para‐phenyl‐substituted α‐diimine nickel catalysts
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A series of para‐phenyl‐substituted α‐diimine nickel complexes, [(2,6‐R2‐4‐PhC6H2N═C(Me))2]NiBr2 (R = iPr ( 1 ); R = Et ( 2 ); R = Me ( 3 ); R = H ( 4 )), were synthesized and characterized. These complexes with systematically varied ligand sterics were used as precatalysts for ethylene polymerization in combination with methylaluminoxane. The results indicated the possibility of catalytic activity, molecular weight and polymer microstructure control through catalyst structures and polymerization temperature. Interestingly, it is possible to tune the catalytic activities ((0.30–2.56) × 106 g (mol Ni·h)?1), polymer molecular weights (Mn = (2.1–28.6) × 104 g mol?1) and branching densities (71–143/1000 C) over a very wide range. The polyethylene branching densities decreased with increasing bulkiness of ligand and decreasing polymerization temperature. Specifically, methyl‐substituted complex 3 showed high activities and produced highly branched amorphous polyethylene (up to 143 branches per 1000 C). 相似文献
9.
Reaction between an aqueous ethanol solution of tin(II) chloride and that of 4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl‐3 H‐pyrazol‐3‐one in the presence of O2 gave the compound cis‐dichlorobis(4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl‐3 H‐pyrazol‐3‐onato) tin(IV) [(C26H26N4O4)SnCl2]. The compound has a six‐coordinated SnIV centre in a distorted octahedral configuration with two chloro ligands in cis position. The tin atom is also at a pseudo two‐fold axis of inversion for both the ligand anions and the two cis‐chloro ligands. The orange compound crystallizes in the triclinic space group P 1 with unit cell dimensions, a = 8.741(3) Å, b = 12.325(7) Å, c = 13.922(7) Å; α = 71.59(4), β = 79.39(3), γ = 75.18(4); Z = 2 and Dx = 1.575 g cm–3. The important bond distances in the chelate ring are Sn–O [2.041 to 2.103 Å], Sn–Cl [2.347 to 2.351 Å], C–O [1.261 to 1.289 Å] and C–C [1.401 Å] the bond angles are O–Sn–O 82.6 to 87.7° and Cl–Sn–Cl 97.59°. The UV, IR, 1H NMR and 119Sn Mössbauer spectral data of the compound are reported and discussed. 相似文献
10.
Walid Fathalla Pavel Pazdera Michal ajan Jaromír Marek 《Journal of heterocyclic chemistry》2002,39(6):1145-1152
Regioselective reactions of morpholine‐1‐carbothioic acid (2‐phenyl‐3H‐quinazolin‐4‐ylidene) amide ( 1 ) with electrophiles and nucleophiles were studied. The compound ( 1 ) reacts with alkyl halides in basic medium to afford S‐substituted isothiourea derivatives, with amines to give 1,1‐disubstituted‐3‐(2‐phenyl‐3H‐quinazolin‐4‐ylidene) thioureas and l‐substituted‐3‐(2‐phenyl‐quinazolin‐4‐yl) thioureas via transami‐nation reaction. The reaction of ( 1 ) with amines in the presence of H2O2 provided N4‐disubstituted‐N'4‐(2‐phenylquinazolin‐4‐yl)morpholin‐4‐carboximidamide via oxidative desulfurization. Estimation of reactivity sites on ( 1 ) was supported using the ab initio (HF/6‐31G**) quantum chemistry calculations. The ir, 1H nmr, 13C nmr, mass spectroscopy and x‐ray identified the isolated products. 相似文献
11.
Kai Li Hongjian Sun Wenjing Yang Yajie Wang Shangqing Xie Xiaoyan Li Olaf Fuhr Dieter Fenske 《应用有机金属化学》2020,34(3):e5337
A series of phosphorus-chalcogen chelated hydrido iron (II) complexes 1–7 , (o-(R'2P)-p-R-C6H4Y)FeH (PMe3)3 ( 1 : R = H, R' = Ph, Y = O; 2 : R = Me, R' = Ph, Y = O; 3 : R = H, R' = iPr, Y = O; 4 : R = Me, R' = iPr, Y = O; 5 : R = H, R' = Ph, Y = S; 6 : R = Me, R' = Ph, Y = S; 7 : R = H, R' = Ph, Y = Se), were synthesized. The catalytic performances of 1–7 for dehydration of amides to nitriles were explored by comparing three factors: (1) different chalcogen coordination atoms Y; (2) R' group of the phosphine moiety; (3) R substituent group at the phenyl ring. It is confirmed that 5 with S as coordination atom has the best catalytic activity and 7 with Se as coordination atom has the poorest catalytic activity among complexes 1 , 5 and 7 . Electron-rich complex 4 is the best catalyst among the seven complexes and the dehydration reaction was completed by using 2 mol% catalyst loading at 60 °C with 24 hr in the presence of (EtO)3SiH in THF. Catalyst 4 has good tolerance to many functional groups. Among the seven iron complexes, new complexes 3 and 4 were obtained via the O-H bond activation of the preligands o-iPr2P(C6H4)OH and o-iPr2P-p-Me-(C6H4)OH by Fe(PMe3)4. Both 3 and 4 were characterized by spectroscopic methods and X-ray diffraction analysis. The catalytic mechanism was experimentally studied and also proposed. 相似文献
12.
Nikolaus Gorgas Berthold Stger Luis F. Veiros Karl Kirchner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(39):14012-14017
Herein, we report on the first synthesis and structural characterization of the iron based aminoborane complexes [Fe(PNP)(H)(η2:η2‐H2B=NR2)]+ (R=H, Me). These species are formed upon protonation of the borohydride complex [Fe(PNP)(H)(η2‐BH4)] by ammonium salts [NH2R2]+ (R=H, Me). For R=Me, the reaction proceeds via the cationic dinuclear intermediate [{Fe(PNP)(H)}2(μ2,η2:η2‐BH4)]+. A mechanism for the reaction is proposed based on DFT calculations that also indicate the final aminoborane complex as the thermodynamic product. All complexes were characterized by NMR spectroscopy, HRMS, and X‐ray crystallography. 相似文献
13.
BYABARTTA Prithwiraj 《中国化学》2008,26(8):1515-1518
Reaction of [Au(DAPTA)(Cl)] with RaaiR’ in CH2Cl2 medium following ligand addition leads to [Au(DAPTA)(RaaiR’)](Cl) [DAPTA=diacetyl-1,3,5-triaza-7-phosphaadamantane, RaaiR’=p-R-C6H4-N=N- C3H2-NN-1-R’, (1—3), abbreviated as N,N’-chelator, where N(imidazole) and N(azo) represent N and N’, respectively; R=H (a), Me (b), Cl (c) and R’=Me (1), CH2CH3 (2), CH2Ph (3)]. The 1H NMR spectral measurements in D2O suggest methylene, CH2, in RaaiEt gives a complex AB type multiplet while in RaaiCH2Ph it shows AB type quartets. 13C NMR spectrum in D2O suggest the molecular skeleton. The 1H-1H COSY spectrum in D2O as well as contour peaks in the 1H-13C HMQC spectrum in D2O assign the solution structure. 相似文献
14.
Polysulfonylamines. CXXIV. Preparation of Organylmercury(II) Di(methanesulfonyl)amides and Crystal Structure of Ph–Hg–N(SO2Me)2 Four N,N‐disulfonylated organylmercury(II) amides R–Hg–N(SO2Me)2, where R is Me, iPr, Me3SiCH2 or Ph, were obtained on treating the appropriate chlorides RHgCl with AgN(SO2Me)2, and characterized by 1H and 13C NMR spectra. In the crystal structure of the phenyl compound (orthorhombic, space group Pbca, Z = 8, X‐ray diffraction at –95 °C), the molecule exhibits a covalent and significantly bent C–Hg–N grouping [bond angle 172.7(3)°; Hg–C 204.0(8), Hg–N 209.1(7) pm]. One sulfonyl oxygen atom forms a short intramolecular Hg…O contact [296.1(5) pm] and simultaneously catenates glide‐plane related molecules via a second Hg…O interaction 297.6(5) pm], thus conferring upon HgII the effective coordination number 4 and a geometrically irregular coordination polyhedron (bond angles from 173 to 54°). 相似文献
15.
Dirk Steinborn Tobias Hoffmann Michael Gerisch Clemens Bruhn Harry Schmidt Karsten Nordhoff Julian A. Davies Kristin Kirschbaum Ingo Jolk 《无机化学与普通化学杂志》2000,626(3):661-666
The platina‐β‐diketones [Pt2{(COR)2H}2(μ‐Cl)2] ( 1 , R = Me a , Et b ) react with phosphines L in a molar ratio of 1 : 4 through cleavage of acetaldehyde to give acylplatinum(II) complexes trans‐[Pt(COR)Cl(L)2] ( 2 ) (R/L = Me/P(p‐FC6H4)3 a , Me/P(p‐CH2=CHC6H4)Ph2 b , Me/P(n‐Bu)3 c , Et/P(p‐MeOC6H4)3 d ). 1 a reacts with Ph2As(CH2)2PPh2 (dadpe) in a molar ratio of 1 : 2 through cleavage of acetaldehyde yielding [Pt(COMe)Cl(dadpe)] ( 3 a ) (configuration index: SP‐4‐4) and [Pt(COMe)Cl(dadpe)] (configuration index: SP‐4‐2) ( 3 b ) in a ratio of about 9 : 1. All acyl complexes were characterized by 1H, 13C and 31P NMR spectroscopy. The molecular structures of 2 a and 3 a were determined by single‐crystal X‐ray diffraction. The geometries at the platinum centers are close to square planar. In both complexes the plane of the acyl ligand is nearly perpendicular to the plane of the complex (88(2)° 2 a , 81.2(5)° 3 a ). 相似文献
16.
Synthesis and Structure of Highly Functionalized 2, 3‐Dihydro‐1H‐1, 3, 2‐diazaboroles A series of differently substituted 2, 3‐dihydro‐1H‐1, 3, 2‐diazaboroles has been prepared by various methods. 1, 3‐Di‐tert‐butyl‐2‐trimethylsilylmethyl‐1H‐1, 3, 2‐diazaborole ( 7 ), 2‐isobutyl‐1, 3‐bis(1‐cyclohexylethyl)‐1H‐1, 3, 2‐diazaborole ( 8 ), 1, 3‐bis‐(1‐cyclohexylethyl)‐2‐trimethylsilylmethyl‐1H‐1, 3, 2‐diazaborole ( 9 ) 1, 3‐bis(1‐methyl‐1‐phenyl‐propyl)‐2‐trimethylsilylmethyl‐1H‐1, 3, 2diazaborole ( 10 ) and 2‐bromo‐1, 3‐bis(1‐methyl‐1‐phenyl‐propyl)‐1H‐1, 3, 2‐diazaborole ( 11 ) were formed by reaction of the corresponding 1, 4‐diazabutadienes with the boranes Me3SiCH2BBr2, iBuBBr2 and BBr3 followed by reduction of the resulting borolium salts [R1 = tBu, Me(cHex)CH, [Me(Et)Ph]C; R2 = Me3SiCH2, iBu, Br] with sodium amalgam. Treatment of 11 and 12 with silver cyanide afforded the 2‐cyano‐1, 3, 2‐diazaboroles 13 and 14 . An alternative route to compound 8 is based on the alkylation of 2‐bromo‐1, 3, 2‐diazaborole 12 with isobutyllithium. Equimolar amounts of 13 and isobutyllithium give rise to the formation of 15 . The new compounds were characterized by 1H‐, 13C‐, 11B‐NMR, IR and mass spectra. The molecular structures of 7 and meso ‐10 were confirmed by x‐ray structural analysis. 相似文献
17.
Synthesis of novel 4-(4-methylsulfonylphenyl)-3-phenyl-2(3H)-thiazole thione derivatives with functionalized diarylheterocycle pharmacophore as potential COX-2 inhibitors was described. The title compounds were synthesized by cyclocondensation of corresponding dithiocarbamate and 2-bromo-1-(4-methylsulfonylphenyl)ethanone, followed by dehydration with H2SO4. All of the target compounds were characterized by ^1H NMR, IR and mass spectral data. 相似文献
18.
Man Yan Zai‐Gang Luo Xiao‐Fei Zhu De‐Qing Shi 《Journal of heterocyclic chemistry》2008,45(4):1045-1049
19.
Sadiq‐ur‐Rehman Bilal Ahmad Khan Muhammad Aziz Chaudhary Khawaja Ansar Yasin Saqib Ali 《Heteroatom Chemistry》2015,26(6):417-425
Di‐ and triorganotin(IV) carboxylates, RnSn(OCOC(R2)=CHR1)4–n (n = 2 and 3; R = Me, Et, n‐Bu, Ph; R1 = 3‐CH3O‐4‐OHC6H3, R2 = C6H5) were prepared by reacting the corresponding organotin(IV) chloride with the silver salt of the (E)‐3‐(4‐hydroxy‐3‐methoxyphenyl)‐2‐phenylpropenoic acid. The title compounds were investigated and characterized by elemental analysis, infrared (FT‐IR), multinuclear (1H, 13C, 119Sn) NMR, and mass spectrometry, and possible structures were proposed. The complexes and ligand acid ( HL ) have been evaluated in vitro against various bacteria and fungi. The results noticed during the biocidal activity screenings proved their in vitro biological potential. They were also tested for cytotoxicity. 相似文献
20.
Jens Beckmann Dainis Dakternieks Andrew Duthie Edward R. T. Tiekink 《无机化学与普通化学杂志》2002,628(13):2948-2953
The six‐, eight‐ and twelve‐membered cyclo‐siloxanes, cyclo‐[R2SiOSi(Ot‐Bu)2O]2 (R = Me ( 1 ), Ph ( 2 )), cyclo‐(t‐BuO)2Si(OSiR2)2O (R = Me ( 3 ), Ph ( 4 )), cyclo‐R2Si[OSi(Ot‐Bu)2]2O (R = Me ( 5 ), Ph ( 6 )) and cyclo‐[(t‐BuO)2Si(OSiMe2)2O]2 ( 3a ) were synthesized in high yields by the reaction of (t‐BuO)2Si(OH)2 and [(t‐BuO)2SiOH]2O with R2SiCl2 and (R2SiCl)2O (R = Me, Ph). Compounds 1 — 6 were characterized by solution and solid‐state 29Si NMR spectroscopy, electrospray mass spectrometry and osmometric molecular weight determination. The molecular structure of 4 has been determined by single crystal X‐ray diffraction and features a six‐membered cyclo‐siloxane ring that is essentially planar. The reduction of 1 — 6 with i‐Bu2AlH (DIBAL‐H) led to the formation of the metastable aluminosiloxane (t‐BuO)2Si(OAli‐Bu2)2 ( 7 ) along with Me2SiH2 and Ph2SiH2. 相似文献