Search

(R)-3-[(tert-Butoxycarbonyl)amino]piperidine and (R)-3-[(tert-butoxycarbonyl)amino]azepane were prepared in two steps starting from d-ornithine and d-lysine, respectively. In the key step, N-Boc-protected 3-aminolactams were converted into imido esters by O-alkyl­ation and then hydrogenated to amines, under mild conditions (5 bar H2, room temperature) and without isolation, over a standard hydrogenation catalyst (5% Pt/C).

In contrast to the reaction of vinyl(alkynyl)silanes with 9-BBN-H, leading to the quantitative formation of 5-R-4-(9-BBN)-2,3-dihydro-1H-siloles, treatment of bis(alkynyl)silanes bearing one terminal alkynyl group with 2 equiv of 9-BBN-H followed by methanolysis afforded 5-R-4-(9-BBN)-2,5-dihydro-1H-siloles with yields of 85-90% (by NMR integration). The reaction proceeds via a double 1,2-hydroboration of the terminal triple bond with the formation of the geminal diborane followed by ring closure via intramolecular 1,1-carboboration of the remaining alkynyl fragment. Depending on the nature of the substituent R in position 5, the allylic BBN group locates in position 3 (R = Ph) or position 5 (R = SiHMe2, SiMe3) to give 2,3- or 2,5-dihydrosiloles, respectively. The protodeborylation of the allylic BBN group with MeOH of both 3,4-(9-BBN)2-2,3-dihydro- and 4,5-(9-BBN)2-2,5-dihydrosiloles results in the exclusive formation of 4-(9-BBN)-2,5-dihydrosiloles. In all cases, the formation of 10-12% of 2-R-2,4-(9-BBN)2-2,3-dihydrosilole minor isomers has been observed, which occurs from vicinal diboranes formed as side products by a second hydroboration of the terminal triple bond. Similarly, treatment of the tri- and tetraalkynes containing a terminal triple bond with 2 equiv of 9-BBN-H followed by treatment with methanol resulted in the high-yield formation of 1,2,6,6a-tetrahydro-1,6-disilapentalenes and 2,6,7,7a-tetrahydro-1,6,7-trisila-1H-cyclopenta[a]pentalenes, respectively.

Methyl-camouflaged dicarbaboranes closo-1,2- and 1,10-H2C2B8Me8 have been prepared in high yields either from nido-5,6-H2C2B8H10 or closo-1,2-H2C2B8H8 via electrophilic methylation reactions and cl...

Despite the apparent diversity of the protocols developed for the synthesis of helicenes, they essentially follow the same strategy: the closure of one, or several, internal rings in a key step. Herein, we report the synthesis of a new family of the heterohelicenes consisting of fused silacyclopentadiene rings formed via a facile and novel process. The treatment of oligo(alkynilydenesilylene) precursors of type H2 C=CH-(SiMe2 -C≡C)n -R (n=3-7), bearing a vinyl group on the terminal silicon atom, with 9-borabicyclononane leads first to 1,2-hydroboration of the terminal double bond which then continues with a cascade of intramolecular 1,1-carboboration reactions accompanied with the closure of a new silole ring after each step affording the target silahelicenes with, currently, up to seven condensed silole rings and with excellent yields. According XRD analysis, the seven fused silole rings of the heptacyclic compound 11 b form an almost complete turn of a helix. The presented one-pot sequence of reactions is the first example of ring-by-ring knitting of a helical framework starting from easily available linear precursors.

New preparative methods for halogenation of the cage producing the corresponding [2-NH3-B10X9]- species (2- to 4-, X = Cl, Br, I) have been developed using halogenations by elemental halogens in a glass pressure vessel. Compared to similar icosahedral species of formulation [1-H3N-B12X11]- (X = Cl, Br), the N-alkylation reactions in 10-vertex series proceed significantly more easily. The reason for this difference is conceivably due to the two orders of magnitude lower basicity of the amino group, with pKa values in the interval from 9.27 to 8.37, and slightly lower steric strain around the reaction centre. Thus methylations with MeI under mild conditions provided the whole series of corresponding quarternary amines of the formulation [2-Me3N-B10X9]- (5- to 7-, X = Cl, Br, I). The effect of the steric strain of the surrounding halogens on the reactivity at the NH3- centre could then be better seen from reactions with bulkier benzyl bromide. Under comparable conditions, these reactions resulted in the ready formation of disubstituted compounds in case of X = Cl (8-), mixture of mono and disubstituted derivatives for X = Br (9-, 10-) or in monosubstited product for X = I (11-) only. Dibenzyl derivative of the nonaiodinated products (12-) could be still obtained, however only under more forcing conditions. The single-crystal X-ray diffraction structures of all three polyhalogenated derivatives 2- to 4- are presented along with that for benzyl derivative 10-, spectral and physicochemical properties of these polyhalogenated systems are outlined along with specific insights into specific properties of the NH3 group.

Alkylation of the [nido-5,6-R12C2B8H9]− anions (where R1 = H and Me) with alkyl halides (RX, where R = primary and secondary alkyls) in boiling tetrahydrofuran (THF) proceeds via unusual H2 elimination, followed by cage closure to give a series of the neutral closo-1,2-R12C2B8H7-3-R derivatives in ∼70–80% yields. In contrast, treatment of the unsubstituted [nido-5,6-C2B8H11]− anion with tert-butyl bromide (t-BuBr) led to the formation of the parent closo-1,2-C2B8H10 in >85% yield. The constitution of all compounds isolated has been confirmed unambiguously by multinuclear (11B, 1H, and 13C) nuclear magnetic resonance measurements and α-shift correlation assessments.

A direct dicarbon insertion into nine-vertex arachno cages resulting in the formation of C-substituted dicarbollides [7,8-R2-nido-7,8-C2B9H10]− Et3NH+via reactions between 4-Et3N-arachno-B9H13 and alkynes in refluxing toluene (yields 65–85%) is reported.

Reported are procedures leading to the first types of methyl camouflaged dicarbadecaboranes with fewer than eleven vertices. The compounds contain the closo-1,6-C2B8 scaffolding inside the egg-shaped hepta – decamethyl sheath, which imparts unusually high air and solvolytic stability to all of these compounds.

The principles of a new α-shift correlation (ASC) NMR method are demonstrated on a model series of substituted derivatives of o-carborane for which reliable NMR data are available. This graphical method revealed an acceptable linear correlation between α(11B) or α(13C) shifts and those induced by substituents in unsubstituted (u) positions of the carborane cluster. The linearity holds for all nuclei involved in skeletal bonding: Δδ(N)u = g × α (where N = 11B, 13C, and 1H). The factor g (slope of the correlation line × 102) becomes an important measure of sensitivity of a given cage position to substituent changes. The β, γ, and δ = A (= antipodal) shifts can be therefore derived from the α-shift, are linearly proportional, and reflect additive character in double substitution. The ASC method appears to be an important tool for quantitative assessment of substituent NMR effects in all exo-substituted boron-cluster systems.

Initial studies on electrophilic halogenation of the dicarbaborane closo-1,2-C2B8H10 (1) have been carried out to reveal that the substitution takes place at B7 and B10 vertexes, which are the most removed from the CH positions. The course of the halogenation is strongly dependent on the nature of the halogenation agent and reaction conditions. Individual reactions led to the isolation of the monosubstituted compounds 1,2-C2B8H9-10-X (2) (where X = F, I) and 1,2-C2B8H9-7-X (3) (where X = Cl, I). Disubstituted carboranes 1,2-C2B8H8-7,10-X2 (4) (where X = Cl, Br, I) were obtained under more forcing conditions. Individual halo derivatives were characterized by mass spectrometry and high-field NMR (11B, 1H,13C) spectroscopy combined with two-dimensional [11B–11B]-COSY, 1H{11B(selective)}, and [11B–1H]-correlation NMR techniques. All of the derivatives bearing a halogen substituent in the B10 position exhibit a remarkable antipodal 13C and 1H NMR shielding at the CH1 vertex, increasing in the order H < I < Br ...

The discovery of systems that interact with small molecules plays a vital facilitating role in the development of devices that show sensitivity to their surroundings and an ability to quickly relay chemical and physical information. Herein, we report on the reaction of [NiCl2(dppe)] with decaborane that produces in usable yield a new 11-vertex nickelaborane, [7,7-(dppe)-nido-7-NiB10H12] (1), which shows interesting reactivity and functionality toward carbon monoxide and ethylisonitrile. This contribution describes the synthesis and full structural characterization of 1 and its small-molecule EtNC and CO adducts, 2 and 3, and delineates the dynamic molecular behavior of all of these species in solution. This information sets a foundation from which more advanced work on this and related metallaborane systems can be conceived and provides a more general reference to how NMR spectroscopy, combined with DFT calculations, can be used to analyze the precise locomotion of labile ligands around a metal center held within a borane cluster, The authors gratefully acknowledge the support of the Spanish Ministerio de Ciencia, Innovación y Universidades under reference no. PGC2018-099383-B-I00. We acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza. J.B. and M.G.S.L. also acknowledge support from the Czech Science Foundation and project no. 18-20286S.

Methyl-camouflaged dicarbaboranes closo-1,2- and 1,10-H

Sequential methylation of the 8-R-nido-7,8,9-C3B8H11 tricarbollides (R = Ph, p-tol and 2-naphthyl (2-naph)) in the presence of NaH in THF proceeds on the open-face B(10,11) positions to generate mono and dimethyl derivatives, 8-R-nido-7,8,9-C3B8H10-10-Me and 8-R-nido-7,8,9-C3B8H9-10,11-Me2. To demonstrate the general character of the alkylation procedure, B-dialkyl derivatives 8-Ph-nido-7,8,9-C3B8H9-10,11-R12 (R1 = C3H5 (All) and CH2Ph) were prepared via analogous alkylation of 8-Ph-nido-7,8,9-C3B8H11 with allyl and benzyl bromides. The structures were substantiated by multinuclear (11B, 1H and 13C) NMR spectroscopy and that of 8-Ph-nido-7,8,9-C3B8H9-10,11-Me2 was determined by an X-ray diffraction analysis.

Electrophilic methylation of the

Reported are procedures leading to the first types of methyl camouflaged dicarbadecaboranes with fewer than eleven vertices. The compounds contain the closo-1,6-C2B8 scaffolding inside the egg-shaped hepta - decamethyl sheath, which imparts unusually high air and solvolytic stability to all of these compounds.

Reported is an unusual tautomeric behavior within the [nido-5,6-C2B8H11]− (1a–) cage that has no precedence in the whole area of carborane chemistry. Isolated were two skeletal tautomers, anions [6-Ph-nido-5,6-C2B8H10-μ8,9]− (2d–) and [5,6-Me2-nido-5,6-C2B8H9-μ9,10]− (3b–), which differ in the positioning of the open-face hydrogen bridge. Their structures have been determined by X-ray diffraction analyses. The 3b–structure is stabilized by intermolecular interaction involving Et3NH+ and B8–B9 and H8 atoms in the solid phase; however, its dissolution in CD3CN causes instant conversion to the more stable [5,6-Me2-nido-5,6-C2B8H9-μ8,9]− (2b–) tautomer. The dynamic electron-correlation-based MP2/6-31G* computations suggest that the parent [nido-5,6-C2B8H11-μ8,9]− (2a–) tautomer is 3.9 kcal·mol–1 more stable than the [nido-5,6-C2B8H11-μ9,10]− (3a–) counterpart and the μ8,9 structure 2– is therefore the most stable tautomeric form in the solution, as was also demonstrated by multinuclear (1H, 11B, and 13C) NMR ...

Initial studies on electrophilic halogenation of the dicarbaborane closo-1,2-C

The reaction of di(alkyn-1-yl)vinylsilanes R1(H2C═CH)Si(C≡C―R)2 (R1 = Me (1), Ph (2); R = Bu (a), Ph (b), Me2HSi (c)) at 25°C with 1 equiv. of 9-borabicyclo[3.3.1]nonane (9-BBN) affords 1-silacyclopent-2-ene derivatives (3a, 3b, 3c, 4a, 4b), bearing one Si―C≡C―R function readily available for further transformations. These compounds are formed by consecutive 1,2-hydroboration followed by intramolecular 1,1-carboboration. Treated with a further equivalent of 9-BBN in benzene they are converted at relatively high temperature (80–100°C) into 1-alkenyl-1-silacyclopent-2-ene derivatives ( 5a, 5b 6a, 6b) as a result of 1,2-hydroboration of the Si―C≡C―R function. Protodeborylation of the 9-BBN-substituted 1-silacyclopent-2-ene derivatives 3, 4, 5, 6, using acetic acid in excess, proceeds smoothly to give the novel 1-silacyclopent-2-ene (7, 8, 9, 10). The solution-state structural assignment of all new compounds, i.e. di(alkyn-1-yl)vinylsilanes and 1-silacyclopent-2-ene derivatives, was carried out using multinuclear magnetic resonance techniques (1H, 13C, 11B, 29Si NMR). The gas phase structures of some examples were calculated and optimized by density functional theory methods (B3LYP/6-311+G/(d,p) level of theory), and 29Si NMR parameters were calculated (chemical shifts δ29Si and coupling constants nJ(29Si,13C)). Copyright © 2014 John Wiley & Sons, Ltd.

Reported is an unusual tautomeric behavior within the [nido-5,6-C

Sequential methylation of arachno-6,9-C2B8H14 (1) led to a series of methyl derivatives and finally to the camouflaging of all boron positions by mixed persubstitution. Thus, deprotonation of 1 produced the [arachno-6,9-C2B8H13] anion (1(-)), the methylation of which with MeI in tetrahydrofuran proceeded on the open-face boron vertexes with the formation of 5-Me-arachno-6,9-C2B8H13 (2; yield 28%) and 5,8-Me2-arachno-6,9-C2B8H12 (3; yield 36%). Observed in this reaction was also a side formation of 2-Me-closo-1,6-C2B8H9 (4; yield 6%).The electrophilic AlCl3-catalyzed CH3(+) attack of the neutral 1 in neat MeI at ambient temperature afforded 1,3-Me2-arachno-6,9-C2B8H12 (5), while a 76-h heating at 120 °C generated a mixture of the di- and triiodo derivatives 1,2,3,4,8,10-Me6-5,7-I2-arachno-6,9-C2B8H6 (6) and 1,2,3,4,7-Me5-5,7,10-I3-arachno-6,9-C2B8H6 (7). On the other hand, a HOTf-catalyzed reaction between 1 and MeOTf at reflux resulted in the isolation of 2-TfO-1,3.4,5,7,8,10-Me7-arachno-6,9-C2B8H6 (8; Tf = CF3SO2; yield 65%). The compounds were characterized by multinuclear ((11)B, (1)H, (13)C, and (19)F) NMR spectroscopy, mass spectrometry, and elemental analysis, and the structures of compounds 1, 1(-), 5, and 6 were established by X-ray diffraction analysis.

N-Methyl-anilinoborane exists as a dimer in the solid state, shown by X-ray structural analysis, whereas in solution, a monomer–dimer equilibrium is present (1H, 11B and 13C NMR spectroscopy). The phenyl groups are in trans positions in the crystalline dimer. In solution, both possible isomers of the dimer exist in a trans/cis ratio of 3:2, in agreement with the energies for calculated optimized geometries [B3LYP/6-311+G(d,p) level of theory]. In solution, the monomer is rather reactive and disproportionates completely after several days to give a 1:1 mixture of bis(N-methyl-anilino)borane and μ-(N-methyl-anilino)diborane(6). This observation led to a convenient high yield synthesis of μ-(amino)diborane(6) derivatives, starting from bis(amino)boranes and borane/THF.

The reaction of various alkynyl(vinyl)silanes containing two alkynyl groups with 9-borabicyclo[3.3.1]nonane (9-BBN) proceeds by regioselective 1,2-hydroboration of the vinyl group in the first step, followed by two intramolecular 1,1-organoboration reactions to afford 1,6-disilapentalene derivatives, fused silacarbacycles with a silole unit. Similarly, the analogous reaction of an alkynyl(allyl)silane gives a 1,7-disilaindene derivative. The products were characterized by multinuclear magnetic resonance (1H, 11B, 13C and 29Si NMR) in solution and in two cases by X-ray structural analysis in the solid state.

The origin of broadening of 13C(carborane) NMR signals of 1,2-, 1,7- and 1,12-dicarba-closo-dodecaboranes(12) and several diphenylsilyl derivatives has been examined in detail and could be traced only partially to unresolved 13C–11B spin-spin coupling. Other contributions to the line widths arise from 13C–1H dipole-dipole interactions and, in particular, from isotope-induced chemical shifts 1Δ10/11B(13C), observed here for carboranes for the first time. In the case of 1-diphenylsilyl-1,2-dicarba-closo-dodecaborane(12), the coupling constant 1J(13C,13C) = 9.3 Hz was measured in natural abundance of 13C. The small value of this coupling constant and its negative sign is predicted by calculations based on optimised structures [B3LYP/6-311+G(d,p) level of theory] of the parent carboranes and 1-silyl-1,2-dicarba-closo-dodecaborane(12) as a model compound [calcd. 1J(13C,13C) = –10.5 Hz]. Calculated coupling constants 1J(13C,11B) are small (

Deprotonation of Ap*pyH {Ap*pyH = (6-methylpyridin-2-yl)-[6-(2,4,6-triisopropylphenyl)-pyridin-2-yl]-amine} using KH leads to Ap*pyK which undergoes a clean salt metathesis reaction with [YbI 2 (thf) 4 ] and [EuI 2 (thf) 4 ] in THF forming [Yb 2 (Ap*py) 3 I(thf)] and [Eu 2 (Ap*py) 3 I(thf)], respectively. The two Yb II centers in [Yb 2 (Ap*py) 3 I(thf)] are in close proximity and chemically different. Thus, an f-block-element-f-block-element coupling pattern was observed. The low-field 171 Yb signal consists of a central singlet and two satellites with integral intensities of about 7 % each. This 14 % approximately corresponds to the natural abundance of the 171 Yb isotope and was assigned as a doublet arising from 1 J( 171 Yb, 171 Yb) spin-spin coupling with a magnitude of 76.1 Hz. The 151 Eu Mossbauer spectrum of [Eu 2 (Ap*py) 3 I(thf)] recorded at 77 K shows an isomer shift (δ) of -11.9(1) mm/s with an experimental line width (Γ) of 6.9(1) mm/s. This line width is extremely large and results from an overlap of the signals from both crystallographically independent europium sites. The reaction of [Yb2(Ap*py) 3 I(thf)] with Ap*pyK leads to [Yb 2 (Ap*py) 4 -(thf) 2 ]. In the reactions of [Yb 2 (Ap*py) 3 I(thf)] with azidotri-methylsilane and sulfur the rearrangement products [Yb 2 -(Ap*py) 3 I 2 ] and [Yb 2 (Ap*py) 3 I 3 ] were obtained, respectively. Treating [Yb 2 (Ap*py) 3 I(thf)] with NaN(SiMe 3 ) 2 afforded homoleptic "ate" complex Na 2 [Yb(Ap*py) 4 ]. A mixed silyl-amide dipyridylamide complex was obtained in the reaction of NaYb[N(SiMe 3 ) 2 ] 3 with Ap*pyH. All complexes - three of which are paramagnetic - were characterized by X-ray crystal structure analysis.

Three series of ferrocenes, derived from aminoferrocene Fc-NH2 and 1,1′-diaminoferrocene fc(NH2)2, were studied by 57Fe NMR spectroscopy. A marked decrease in 57Fe magnetic nuclear shielding with respect to ferrocene is observed if the nitrogen atom becomes part of a π-acceptor linked to one or both cyclopentadienyl rings. In contrast, π-donor properties of the amino group(s) affect δ57Fe to a much smaller extent. In the case of the fairly rigid structures of 1,3-diaza-2-element-[3]ferrocenophanes, a significant increase of 57Fe nuclear magnetic shielding is observed, in contrast to the corresponding [n]ferrocenophanes with n > 3. Structures of numerous of the ferrocene derivatives have been optimized for the gas phase by calculations (B3LYP/6–311 + G(d,p) level of theory), and 57Fe nuclear magnetic shieldings were calculated using these geometries. There is reasonable agreement in the trends for experimental and calculated data. Copyright © 2008 John Wiley & Sons, Ltd.

Bernd Wrackmeyer, Oleg L. Tok, and Wolfgang Milius Laboratorium fur Anorganische Chemie, Universitat Bayreuth, D-95440 Bayreuth, Germany Reprint requests to Prof. Dr. B. Wrackmeyer. E-mail: b.wrack@uni-bayreuth.de Z. Naturforsch. 2007, 62b, 1509 – 1513; received August 22, 2007 The 1 : 1 reactions of triphenylborane 1 with monoalkyn-1-yltin compounds Me3Sn–C≡C–R 2 [R1 = tBu (a), Ph (b), ferrocenyl (c), Si(H)Me2 (d), SnMe3 (e)] afford mainly (> 80%) the corresponding alkene derivatives 3 by 1,1-phenylboration. Exchange B-Ph/Sn–C≡C–R1 takes place as a side reaction. The corresponding 1 : 2 reaction with 2b leads to the dialkenylborane 4b (R1 = Ph), of which the molecular structure could be determined by X-ray analysis. In contrast, the 1 : 2 reaction with 2e gave an allene derivative 5e. The solution-state structures of compounds 3 – 5 have been confirmed by 1H, 11B, 13C and 119Sn NMR spectroscopy.

This is a report on the synthesis and structure of novel dinuclear YbII complexes. In one of the described compounds, the two YbII centres are in close proximity and chemically different. Thus, an f-block-element–f-block-element coupling pattern was observed. The low-field 171Yb signal consists of a central singlet and two satellites with integral intensities of about 7 % each. This 14 % approximately corresponds to the natural abundance of the 171Yb isotope and was assigned as a doublet arising from 1J(171Yb, 171Yb) spin–spin coupling with a magnitude of 76.1 Hz. Furthermore, the relevance of such studies in understanding dimer equilibria and the rearrangement chemistry of rather bulky structural ensembles is discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Alkenes bearing a chlorosilyl and a diethylboryl group in cis-positions at the CC bond together with a dimethylaminomethyl group in geminal position to the silyl group were subjected to hydrolysis (a) and alcoholysis [ROH: R = Me (b), Et (c), iPr (d)]. In the case of the alkene 1 containing a chloro(dimethyl)silyl group, novel ammonium salts 3a–d were isolated as 2,5-dihydro-1,2,5-oxoniaboratole derivatives. In contrast, the alkene 2, containing a chloro(methyl)silyl group, did not give defined products under the same reaction conditions. In the presence of traces of water in diethylamine, 2 reacted at the SiH and SiCl bonds to give a zwitterionic disiloxane 4, a 2,5-dihydro-1,2,5-oxasilaboratole derivative. The new compounds were characterized in solution by 1H, 11B, 13C and 29Si NMR spectroscopy, and for two examples (3a and 4) by X-ray structure analysis in the solid state. Copyright © 2007 John Wiley & Sons, Ltd.

Boron-nitrogen compounds were studied with respect to indirect nuclear 15N-11B spin-spin coupling (1J(15N,11B)). Some new experimental data were determined for aminoboranes and tetra-Npyrrolylborate, and a variety of compounds with B-N single, double and triple bonds were examined using DFT methods for the calculation of 1J(15N,11B) at the B3LYP/6-311+G(d,p) level of theory. The calculations predict magnitude and sign of 1J(15N,11B) reasonably well, and the Fermi contact term was found to be dominant. A positive sign of 1J(15N,11B) was calculated in the case of 1-azacloso- dodecaborane(12), in contrast to all other compounds studied.

Dimethyl(divinyl)tin 1 reacts with triethylborane, BEt32a, triallylborane, BAll32b, tribenzylborane, BBz32c, trivinylborane, BVin32d, triphenylborane, BPh32e, and 1-boraadamantane 2f by intermolecular 1,1-organoboration via cleavage of the Snvinyl bond, followed by ring closure via intramolecular 1,1-organoboration (cleavage of the second Snvinyl bond) to give the boryl-substituted stannolanes 3a–e, and 7 and 8. The heterocycles 3a–e can undergo dehydroboration, hydroboration, and/or further reactions. If dialkylboranes such as 9-borabicylo[3.3.1]nonane 11 (9-BBN) or diethylborane (Et2BH) 12 are used, the first expected step is the hydroboration of one of the vinyl groups in 1, and the second step is the ring closure to boryl-substituted stannolanes 13 and 6a, respectively, by intramolecular 1,1-organoboration. The mechanism of the second step, in contrast to the literature, was confirmed by the reaction of dimethyl- (9) and diphenyl(di-2-propenyl)tin (10) with the boron hydrides 11 and 12. In the resulting stannolanes 14 and 15, the 3,5-positions of the methyl groups support the mechanism of 1,1-organoboration. The structures of the new cyclic organotin compounds are assigned on the basis of consistent one- and two-dimensional 1H, 11B, 13C and 119Sn NMR spectroscopic data sets. Copyright © 2007 John Wiley & Sons, Ltd.

1,1′-Diaminoferrocene (2) and 1,1′-bis(trimethylsilylamino)ferrocene (3) have been converted into sulfinylamines by treatment with thionyl chloride in the presence of triethylamine. In the case of 2 the 1:2 reaction affords 1,1′-bis(sulfinylamino)ferrocene (5) and the 1:1 reaction gives 6-amino-1-sulfinylaminoferrocene (6). Bis(trimethylsilylamino)ferrocene reacts with thionyl chloride in a 1:1 molar ratio to give 1-sulfinylamino-6-(trimethylsilylamino)ferrocene (8). In contrast, the reaction of N,N′-dilithiobis(trimethylsilylamino)ferrocene (4) with thionyl chloride gives the [3]ferrocenophane 9, which contains an N–S(O)–N bridge, rather than sulfinylamines or a sulfur diimide. The molecular structures of 5 and 8 were determined by X-ray analysis. The 57Fe NMR chemical shift (δ = +2597.0 ppm) for 5 indicates the strong π-acceptor properties of the NSO groups. Dynamic 1H and 13C NMR spectra prove the hindered rotation of the NSO group about the C–N bonds in 5, 6 and 8. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Coupling constants 1J(17O,11B) of borates, borane adducts and boranes with boron-oxygen bonds have been calculated on the basis of optimised molecular structures using the B3LYP/6-311+G(d,p) level of theory. This indicates that such coupling constants can be of either sign and that their magnitudes can be rather small. Since both 11B and 17O are quadrupole nuclei, it is therefore difficult to measure representative data. In the cases of trimethoxyborane and tetraethyldiboroxanes, it proved possible to obtain experimental data 1J(17O,11B) (22 and 18 Hz) by measurement of 17O NMR spectra at high temperature (120 °C and 160 °C) respectively. The magnitude of these coupling constants is in reasonable agreement with calculated data. In the case of the diboroxane, this points towards a bond angle B-O-B more close to 180◦ than to 140°

The reactions of n-hexyn-1-ylsilanes or arylethyn-1-ylsilanes, bearing methyl groups and one (2), two (3) or three hydride functions (4) at the silicon atom, with triallylborane 1 lead primarily to products of 1,1- or 1,2-allylboration. In the alkenes (5, 9, 13) formed by stereoselective 1,1-allylboration, with the silyl and the diallylboryl groups in cis-positions at the C=C bond an electron-deficient Si-H-B bridge is present. The activation of the Si-H bond in these alkenes induces intramolecular hydrosilylation under very mild reaction conditions to give 1,4-silabora-cyclohept-2-enes (7 and 11). The products of 1,2-allylboration (6, 10, 14) are further transformed into 1-boracyclohex-2-enes (8, 12, 15) and 7-borabicyclo[3.3.1]non-2-enes (16, 17) by intramolecular 1,2-allylboration reactions. The proposed structures are based on consistent sets of 1H, 11B, 13C and 29Si NMR data.

Ferrocenylethynyl(trimethyl)tin (1), bis(ferrocenylethynyl)dimethyltin (2), tetrakis(ferrocenylethynyl)tin (3), and chloro(ferrocenylethynyl)dimethyltin (4) have been prepared and characterized in solution by 1H, 13C, and 119Sn NMR spectroscopy. Solid-state MAS 13C and 119Sn NMR spectra were measured for 2 and 3, and the molecular structure of one of the modifications of 2 was determined by X-ray analysis. The reactivity of 1–4 towards triethylborane has been explored. 1,1-Organoboration takes place in all cases, and the reactions are stereoselective for 1 and 4 to give the alkenes 5 and 6, respectively, in which the stannyl and the boryl groups are in cis-positions at the C=C bond. In the case of 2, the final products are the 1-stannacyclopenta-2,4-diene 7a and the 1-stanna-4-boracyclohexa-2,5-diene 8a, whereas the reaction of 2 with triisopropylborane leads selectively to the six-membered ring 8b. Zwitterionic intermediates 9a,b, in which the tin atom is coordinated side-on to the C≡C bond of an alkynylborate, have been detected by NMR spectroscopy. Compound 3 reacts with triethylborane to give a mixture of three spirotin compounds 10–12 as the final products, where the tin atom connects five- and six-membered rings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

1,1-Organoboration, using triethyl-, triallyl- and triphenyl-borane (BEt3, BAll3, BPh3), of dimethysilylethynyl(trimethyl)stannane, Me3SnCCSi(H)Me2 (1), affords alkenes bearing three different organometallic groups at the CC bond. For BEt3 and BPh3, the first products are the alkenes 4 with boryl and stannyl groups in cis-positions. These rearrange by consecutive 1,1-deorganoboration and 1,1-organoboration into the isomers 5 as the final products, where boryl and silyl groups are in cis-positions linked by an electron-deficient SiHB bridge. 1,1-Ethylboration of bis(dimethylsilylethynyl)dimethylstannane, Me2Sn[CCSi(H)Me2]2 (2), leads to the stannacyclopentadiene 6 along with non-cyclic di(alkenyl)tin compounds 7 and 8. 1,1-Ethylboration of ethynyl(trimethylstannylethynyl)methylsilane, Me(H)Si(CCSnMe3)CCH (3), leads selectively to a new silacyclopentadiene 13 as the final product. The reactions were monitored and the products were characterized by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 29Si and 119Sn NMR). Copyright © 2005 John Wiley & Sons, Ltd.

The reaction of alkyn-1-yl(vinyl)silanes R2Si(C CR1)CH CH2 [R = Me (1), Ph (2); R1 = tBu (a), Ph (b), SiMe3 (c)] with 9-borabicyclo[3.3.1]nonane in a 1:1 ratio affords the 1-silacyclopent-2-ene derivatives 4a–c (R = Me) and 5a–c (R = Ph) as a result of selective intermolecular 1,2-hydroboration of the vinyl group, followed by intramolecular 1,1-organoboration of the alkynyl substituent. The analogous reaction sequence converts the alkyn-1-yl(allyl)dimethylsilanes 3a,c into the 1-silacyclohex-2-ene derivatives 7a,c. All reactions were monitored by 29Si NMR spectroscopy and the structural assignment of the final products was based on multinuclear magnetic resonance data (1H, 11B, 13C and 29Si NMR). The molecular structure of 6a was determined by X-ray analysis.

The reaction of the di(alkyn-1-yl)silanes Me2Si(C≡CSiMe2H)2 1a and Me(H)Si(C≡CSiMe2H)2 1b with triethylborane was studied. In the case of 1a, the 4-ethyl-3-diethylboryl-1,1-dimethyl-2,5- bis(dimethylsilyl)-1-sila-2,4-cyclop entadiene 2a was the sole product. In the case of 1b, the analogous silole 2b was formed along with two other products which were identified as di(alkenyl)silanes 3b and 4b, in which different types of electron-deficient Si-H-B bridges could be detected. All products were characterised by consistent sets of solution NMR data (1H, 11B, 13C and 29Si NMR). The coupling constants 1J(13C,13C) were measured for 2a and calculated by using DFT methods (B3LYP/6-311+G(d,p) level of theory)

N,N′-Dilithiated 1,1′-bis(trimethylsilylamino)ferrocene (2) reacts with boron halide adducts (HBBr2–SMe2; BF3–OEt2 and BBr3–SMe2), boron halides (BCl3, BBr3, BCl2(OPh) and BCl2(Ph)) and 1,1-bis(dimethylamino)dichlorodiborane(4) to give the corresponding 1,3-bis(trimethylsilyl)-1,3,2-diazabora-[3]ferrocenophanes (3)–(8) and the 2,3-bis(dimethylamino)-1,4-bis(trimethylsilyl)-1,4,2,3-diazadibora-[4]ferrocenophane (9). All new complexes were characterised by multinuclear magnetic resonance spectroscopy in solution, and the solid-state molecular structures of the hydride (3), fluoride, chloride (4, 5), and of the phenoxy and phenyl derivatives (7, 8) were determined by X-ray analysis.

Trimethylborane (1), triethylborane (2), 1,3-dimethyl-1-boracyclopentane (3), 1-methyl-1- boracyclohexane (4), 9-methyl- and 9-ethyl-9-borabicyclo[3.1.1]nonane [5(Me) and 5(Et)], and 1- boraadamantane (6) were studied by 11B and 13C NMR spectroscopy with respect to coupling constants 1J(13C,11B) and 1J(13C,13C). Results of DFT calculations at the B3LYP/6-311+g(d,p) level of theory show satisfactory agreement with the experimental data. Hyperconjugation arising from C-C σ bonds adjacent to the tricoordinate boron atom is indicated, in particular for 1-boraadamantane (6), by the optimised calculated structures, and by the experimental and calculated data 1J(13C,13C). The calculated magnitude of 1J(13C,1H) for carbon atoms adjacent to boron becomes significantly smaller if the optimised structures suggest hyperconjugative effects arising from these C-H bonds

Mononuclear carbonylmetal complexes of chromium, molybdenum and tungsten containing the sulfane S(C7H7)2 (1) have been obtained starting from precursors such as the THF-stabilized pentacarbonylmetal fragments, [M(CO)5](thf), the acetonitrile intermediates M(CO)6-x(CH3CN)x (x = 1, 2, 3) (M = Cr, Mo, W) or the η4-norbornadiene complexes M(CO)4(C7H8) (M = Cr, Mo). In addition to the pentacarbonyls, M(CO)5[S(C7H7)2] (M = Cr (2a), Mo (2b), W (2c)) which contain 1 unchanged as a two-electron sulfane ligand with two pending cyclohepta-2, 4, 6-trienyl substituents, isomeric complexes M(CO)5[S(CH2Ph)(C7H7)] (M = Cr (3a), W (3c)) were obtained at higher temperatures (40-50 °C) in which one of the two organic groups has been transformed into a benzyl substituent. In the tetracarbonyls, cis-M(CO)4[S(C7H7)(η2-C7H7)] (M = Mo (4b), W (4c)), the ligand 1 serves as an olefinic sulfane four-electron chelate ligand. The reaction of either Mo(CO)6 or (mesitylene)Mo(CO)3 with S(C7H7)2 (1) in boiling THF leads to the sulfur-free ditropyl complex Mo(CO)3[(η6-C7H7)-C7H7] (5b, two isomers). The 1H and 13C NMR spectra of the new complexes 2-4 reveal various dynamic processes including pyramidal inversion of the sulfur atom and [1, 7]-sigmatropic shifts at the C7H7 ring. The molecular structures of 2c, 3a, 4b and 4c have been determined by X-ray crystallography. Umsetzungen von Di(1-cyclohepta-2, 4, 6-trienyl)sulfan, S(C7H7)2, mit Derivaten der Hexacarbonyle, M(CO)6 (M = Cr, Mo, W) Einkernige Carbonylmetall-Komplexe des Chroms, Molybdans und Wolframs mit dem Sulfan S(C7H7)2 (1) wurden ausgehend von Vorstufen wie den THF-stabilisierten Pentacarbonylmetall-Fragmenten, [M(CO)5](thf), den Acetonitril-Zwischenstufen, M(CO)6-x(CH3CN)x (x = 1, 2, 3) (M = Cr, Mo, W) oder den η4-Norbornadien-Komplexen, M(CO)4(C7H8) (M = Cr, Mo) dargestellt. Neben den Pentacarbonylen, M(CO)5[S(C7H7)2] (M = Cr (2a), Mo (2b), W (2c)), die 1 in unveranderter Form als Zweielektronen-Sulfanliganden mit zwei frei beweglichen Cyclohepta-2, 4, 6-trienyl-Substituenten enthalten, entstanden bei hoherer Temperatur (40-50 °C) isomere Komplexe M(CO)5[S(CH2Ph)(C7H7)] (M = Cr (3a), W (3c)), in denen eine der beiden Organylgruppen als Benzyl-Substituent vorliegt. In den Tetracarbonylen, cis-M(CO)4[S(C7H7)(η2-C7H7)] (M = Mo (4b), W (4c)) fungiert das olefinische Sulfan 1 als Vierelektronen-Chelatligand. Die Reaktion von Mo(CO)6 oder (mesitylen)Mo(CO)3 mit S(C7H7)2 (1) in siedendem THF fuhrte zum schwefelfreien Ditropyl-Komplex, Mo(CO)3[(η6-C7H7)-C7H7] (5b, zwei Isomere). Die 1H- und 13C-NMR-Spektren der neuen Komplexe 2-4 lassen verschiedene dynamische Prozesse erkennen, darunter pyramidale Inversion am Schwefelatom und [1, 7]-sigmatrope Verschiebungen am C7H7-Ring. Die Molekulstrukturen von 2c, 3a, 4b und 4c im Kristall wurden anhand von Rontgenstrukturanalysen bestimmt.

Isocyanoferrocene (1) and 1, 1′-diisocyanoferrocene (2) were prepared and studied by 1H, 13C, 14N and 57Fe NMR spectroscopy in order to gain a more complete data set. The NMR data of 1 (chemical shifts and coupling constants) were calculated by DFT methods [B3LYP/6-311+G(d, p)] and compare favourably with experimental data. The molecular structure of 1 was determined by X-ray structural analysis, and an almost undistorted ferrocene-like geometry was found. NMR-spektroskopische Charakterisierung von Isocyano- and 1, 1′-Diisocyanoferrocen. Die Molekulstruktur von Isocyanoferrocen Isocyanoferrocen (1) und 1, 1′-Diisocyanoferrocen (2) wurden hergestellt und mittels 1H-, 13C-, 14N- und 57Fe-NMR-Spectroskopie untersucht, um einen vollstandigeren Datensatz zu gewinnen. Die Geometrie und die NMR Parametere von 1 (Chemische Verschiebungen und Kopplungskonstanten) wurden mit DFT Methoden [B3LYP/6-311+G(d, p)] berechnet und stimmen gut mit den experimentellen Daten uberein. Die Molekulstruktur von 1 wurde mittels Rontgenstrukturanalyse bestimmt und zeigt eine fast ungestorte Ferrocen-analoge Geometrie.

Agostic (C−H···M) complexes [closo-3,3-(σ,η2-C8H13)-1,2-μ-(ortho-xylylene)-3,1,2-IrC2B9H9] (5) and [closo-3,3-(σ,η2-C8H13)-1,2-μ-(ortho-xylylene)-3,1,2-RhC2B9H9] (9), stable in the solid state, have been prepared via the reaction of [M(η4-COD)Cl]2 (M = Ir, Rh) with the K+ salt of the [nido-7,8-μ-(ortho-xylylene)-7,8-C2B9H10]- anion and characterized by a combination of analytical (in the case of 5) and multinuclear NMR data, including a single-crystal X-ray diffraction study of 5. The crystallographic study confirmed the agostic structure of 5 and revealed that the orientation of the σ,η2-cyclooctenyl moiety relative to the carborane ligand is substantially influenced by the specific intramolecular C−H···π interaction between the agostic hydrogen and the π-system of the cage aromatic substituent. In solution, 5 exhibited both “side-to-side” agostic hydrogen migration and reversible interconversion with [closo-3-(η3-C8H13)-1,2-μ-(ortho-xylylene)-3,1,2-IrC2B9H9] (8). The agostic rhodium complex (9), in cont...

The reaction of Grignard compounds of 1-bromo-2,4,6-diisopropylbenzene (1) or 1-bromo-2,6-dimethylbenzene (2), formed in situ, with 2,6-dibromopyridine in the presence of a catalytic amount of [(dme)NiBr2] (dme = 1,2-dimethoxyethane) and tricyclohexylphosphane (1:2 ratio) leads to the corresponding monoarylated bromopyridines. These bromopyridines undergo Pd-catalysed aryl amination (Buchwald−Hartwig amination) with 2,6-diisopropylaniline giving rise to (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine (Ap*H) and (2,6-diisopropylphenyl)[6-(2,6-dimethylphenyl)pyridin-2-yl]amine (Ap′H) (Ap = aminopyridinate). Deprotonation of Ap*H in diethyl ether using BuLi results (after workup in hexane) in a colourless crystalline material. X-ray structural analysis reveals it to be a monomeric three-coordinate lithium aminopyridinate. In toluene solution, an equilibrium between [(Ap*Li)2] (in excess at room temperature) and [Ap*Li(OEt2)] (prominent at low temperature) is observed. Reaction of Ap′H with BuLi in diethyl ether gives rise to [Ap*LiAp*Li(OEt2)]. Deprotonation of Ap*H and Ap′H using KH leads to [Ap*K]n and [Ap′K]∞, respectively. [Ap′K]∞ is a rare example of a crystalline organometallic polymer, as determined by X-ray analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Di(alkyn-1-yl)dimethylsilanes and –methylsilanes of the type Me2Si(C≡C–CH2NMe2)2 (1a), Me(H)Si(C≡C–CH2NMe2)2 (1b), Me2Si(C≡C–CH2NMe2)C≡C–R1 [R1=Bu (3a), SiMe3 (4a)], and Me(H)Si(C≡C–CH2NMe2)C≡C–R1 [R1=Bu (3b), SiMe3 (4b)] were prepared, and their reactivity towards triethylborane, BEt3, was studied. In all cases, the final products of 1,1-ethylboration were sila-2,4-cyclopentadienes (siloles) 7, 10–13, bearing a diethylboryl group in 3- or 4-position. If the CH2NMe2 and the boryl group are in neighboured positions, the Me2N group is always coordinated to the boron atom. Side products 9b and 16b containing an electron-deficient Si–H–B bridge could be detected by NMR spectroscopy. The proposed structures of the siloles follow from a consistent set of multinuclear magnetic resonance data (1H, 11B, 13C and 29Si NMR).

The reaction of bis(silyl)ethynes 2–4, bearing one, two and three hydrides at one of the silicon atoms, with triallylborane 1 leads primarily to alkenes 5, 8 and 11 respectively by 1,1-allylboration. In these alkenes, the diallylboryl and the silyl group bearing one or more SiH functions are in cis-positions at the CC bond, giving rise to the formation of an electron-deficient SiHB bridge. This follows unambiguously from the consistent set of NMR data, in particular from the observation of isotope-induced chemical shifts 2Δ10/11B(29Si). The activation of the SiH bond in 5, 8 and 11 induces intramolecular hydrosilylation under very mild reaction conditions to give 1,4-silabora-cyclo-2-heptenes 7, 10 and 13 respectively. Upon heating, these seven-membered heterocycles undergo ring contraction by 1,1-deallylboration to give the 1-sila-cyclo-2-hexenes 14–16, and bear an exocyclic diallylboryl group in 3-position. All proposed structures are based on consistent 1H, 11B, 13C and 29SiNMR data. Copyright © 2004 John Wiley & Sons, Ltd.

The crystal structure of tetra(propyn-1-yl)silane, Si(C≡CMe)4 1, has revealed a completely asymmetric molecule (point group C1). Since this finding concerns a single crystal, the bulk material of 1 was studied by solid-state 29Si and 13C MAS NMR. This confirmed the result of the X-ray analysis, and by comparison with previous NMR measurements of the tin analogue 1(Sn) it is concluded that 1 and 1(Sn) must have very similar solid-state structures which are in contrast to those known for other tetra(alkyn-1-yl)silicon and -tin compounds. The NMR data set of 1 in solution was completed by determination of the magnitude of coupling constants 1J(13C,13C).

Thermal isomerisation of the ferraphosphadicarbaborane [1-Cp-closo-1,2,4,5-FePC2B8H10] (1a; Cp = η5-C5H5−) at elevated temperatures (180−350 °C) leads to the formation of three new isomeric complexes. These were characterized by multinuclear (1H, 11B, 31P, and 13C) NMR spectroscopy and mass spectrometry as [1-Cp-closo-1,2,3,8-FePC2B8H10] (1b), [1-Cp-closo-1,10,2,4-FePC2B8H10] (1c), and closo-[1,2,4,10-FePC2B8H10] (1d). The formation of 1b is accompanied by an unusual agglomeration of the P and C heteroatoms. Complexes 1b and 1c have also been isolated as side products from the direct reaction between nido-[7,8,9-PC2B8H11] (2) and [CpFe(CO)2]2 in refluxing mesitylene, and 1a and 1b from the pyrolysis of [7-Fp-(η1-nido-7,9,10-PC2B8H10)] [3; Fp = CpFe(CO)2] at 350 °C. NMR intercomparisons of all five [1-Cp-closo-FePC2B8H10] isomers thus far isolated have been made. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)