Heidi E. Maisel

Ein- und zwei-dimensionale Multikern NMR-Spektroskopie an den isomeren Halbsandwich-Komplexen cis- und trans-[(η5-C5H5)W(CO)2(H)PMe3]

Abstract The 1:1 mixture of the complexes cis and trans -[(η 5 -C 5 H 5 )W(CO) 2 (H)PMe 3 ] ( 1a.b ) has been studied by multinuclear magnetic resonance ( 1 H, 13 C, 31 P, 183 W) at variable temperature, with one- and two-dimensional (2d) NMR techniques. This has led to the unambiguous assignment of the 1 H(WH), 13 C(CO) and all other 13 C resonances as well as of the 31 P and 183 W resonance signals. The sign of the coupling constants 1 J ( 183 W 13 C), 1 J 183 W 1 H) and 1 J ( 183 W 31 P) was shown to be positive by the consistent results of various 2D X/ 1 H- and inverse 2D 1 H{ 183 W} heteronuclear shift correlations. In contrast, a negative sign of 2 J ( 31 PW 1 H) cis/trans and 2 J ( 31 PW 13 C) cis emerged from these experiments. The 13 C(CO) resonance signals of the cis -isomer 1a are broadened, even at −40°C, indicating that the cis — cis rearrangement occurs more readily than the cis — trans rearrangement.

1,3,2-Diazastanna-[3]ferrocenophanes bearing alkyn-1-yl groups at tin and their 1,1-organoboration with triethylborane—molecular structure of a novel spirotin compound

Abstract 2,2-Dichloro-1,3-bis(trimethylsilyl)-1,3,2-diazastanna-[3]ferrocenophane (3) reacts with lithium alkynides LiCCR1 to give the corresponding di(alkyn-1-yl)tin derivatives 4a (R1=tBu) and 4b (R1=SiMe3). 1,1-Organoboration of 4 with triethylborane affords the spirotin compounds 5 which contain both a ferrocenophane and a stannacyclopentadiene ring. The crystal structure of 5b was determined by X-ray analysis. The compounds 4 and 5 were characterised in solution by multinuclear magnetic resonance (1H-, 11B-, 13C-, 15N-, 29Si-, 119Sn-NMR), using pulsed field gradients in HMBC experiments for the 1H detected 15N- and 119Sn-NMR signals. The compound 5b was also studied by solid-state 13C, 29Si and 119Sn MAS NMR in order to correlate liquid and solid-state NMR data with the structural evidence.

New zwitterionic heterocycles derived from 1-chloro(dimethyl)silyl-1-borylalkenes and 2-lithio-1-methylimidazole and 1-lithio-indazole

Abstract The 1-alkynyl(chloro)dimethylsilane tBuC CSiMe2Cl (1) reacts with tetraethyl-diborane(6) or 9-borabicyclo[3.3.1]nonane dimer, (9-BBN)2, to give the (Z)-1-chloro-dimethylsilyl-1-diethylboryl-alkenes 2 and 3. These alkenes react with 2-lithio-1-methylimidazole or 1-lithio-indazole by formation of LiCl and of 4, 5 and 9 together with small amounts of 6, 7 or 8 as minor products. In 4 and 5, a zwitterionic structure is present which can be alternatively described as a borane adduct of a carbene. All new compounds were characterised by 1H-, 11B-, 13C-, 15N- and 29Si-NMR spectroscopy, and the molecular structure of 5 was determined by X-ray structural analysis.

57Fe-NMR spectroscopy revisited: ferrocene derivatives containing heterosubstituents

Abstract 57 Fe-NMR spectra (16.1 MHz; natural abundance) of mono- and 1,1′-disubstituted ferrocene derivatives ( 1 – 15 ), including two ferrocenophanes ( 14 , 15 ), could be measured in a much shorter time than expected according to previous reports (500 MHz spectrometer, standard equipment; solutions in 5-mm tubes). Substituents were t Bu, alkynyl, silyl, germyl, stannyl and boryl groups, and the bridges in the ferrocenophanes were SiMe 2 ( 14 ) and Me 2 SiSiMe 2 units ( 15 ). The δ 57 Fe values cover a fairly large range of >450 ppm. There is a large difference (365 ppm) in 57 Fe nuclear shielding for the two ferrocenophanes, with the higher 57 Fe shielding in the [1]ferrocenophane 14 . Parallel trends were observed between δ 57 Fe of ferrocene derivatives and δ 55 Mn of comparable sandwich complexes derived from [(η 5 -C 5 H 5 )Mn(η 6 -C 6 H 6 )].

Hydroboration of alkyn-1-yl(methyl)silanes bearing functional substituents at silicon

Abstract Alkyn-1-yl(methyl)silanes Me2(H)Si–CC–R (1), Me(H)(Cl)Si–CC–R (2) and Me2(Cl)Si–CC–R (3) [R=Bu (a), tBu (b), Ph (c), SiMe3 (d)] react with 9-borabicyclo[3.3.1]nonane (9-BBN) by 1,2-cis-hydroboration to give selectively (except of 3d) the alkenylsilanes 4 (from 1), 5 (from 2), and 6 (from 3), in which the boryl group has become attached to the carbon atom adjacent to the silyl group bearing functional substituents. In the case of 3d, a mixture consisting of the alkenes 6d and the isomers 7d, 8d and 9d is obtained. All products were characterised by NMR spectra (1H-, 11B-, 13C- and 29Si-NMR) in solution, and in the cases of 5c and 6c, the molecular structures in the solid state were determined by X-ray analysis.

New ferrocenyl amine derivatives: N-silyl, N-stannyl and N-boryl ferrocenyl amines

Abstract N-Ferrocenyl amine, Fc-NH2 (1), reacts with chlorosilanes in the presence of Et3N to give N-silylated derivatives such as Fc-NH-SiMe3 (2), Fc-NH-SiMe2H (3) and (Fc-NH)2SiMe2 (6). N-Lithiation of 1, followed by reaction with Me3SnCl, gives Fc-NH-SnMe3 (4) which is in equilibrium with Fc-N(SnMe3)2 (5). Lithiated 1, Fc-NH-Li, reacts with Me2SnCl2 (1:1) to give the trimer (Fc-N-SnMe2)3 (7). The tin analogue of 6 was not found. Lithiation of 2, followed by reaction with Me3SnCl, affords Fc-N(SiMe3)-SnMe3 (8). The silylamine 2 reacts with the 9-borabicyclo[3.3.1]nonane dimer (H-9-BBN)2 and with tetraethyldiborane(6), either by elimination of H2 to give Fc-N(SiMe3)-(9-BBN) (9) and Fc-N(SiMe3)-BEt2 (10), or by elimination of Me3SiH to give Fc-NH-(9-BBN) (11) and Fc-NH-BEt2 (12), respectively, depending on the reaction conditions.

1,1-ORGANOBORATION OF MONO-1-ALKYNYLTIN COMPOUNDS USING DIALKYL(N-AZOLYL) BORANES-STEPWISE RING ENLARGEMENT OF BORON HETEROCYCLES

Abstract Mono-1-alkynyltin compounds 1–4 (Me3Sn-C ≡ CR1; R1 = H (1), Me (2), Ph (3), SnMe3 (4)) react with various dialkyl(N-azolyl)boranes 5–9 (azolyl = pyrrolyl (a), 2,5-dimethylpyrrolyl (b), indolyl (c), carbazolyl (d)) stereospecifically by 1,1-organoboration to give organometallic-substituted alkenes 10–20, 22–25, with the trimethylstannyl and the boryl group in cis-positions at the C=C bond. These reactions proceed via an alkynylborate-like zwitterionic intermediate ZI, and exchange of the azolyl against the 1-alkynyl group may compete (Eq. (1)(b)) with the 1,1-organoboration (Eq. (1)(a)), depending on the reactivity of the boron carbon bonds and the steric requirements. It is also shown that in addition to the products formed in the reactions with 1:1 stoichiometry other products result from the reaction of two equivalents of 1 with one equivalent of the borane. These products may be either 1,3-butadiene derivatives or allenes formed by allylic rearrangement. All products were characterized by 1H, 11B, 13C and 119Sn NMR. The molecular structure of the allene 24a was determined by X-ray structural analysis.

Organometallic-substituted allenes - determination of coupling signs and molecular structures of two stannylated allenes

Abstract The stannylated allenes1 and2 were prepared by 1,1-organoboration of two equivalents of bis(trimethylstannyl)ethyne (4) with one equivalent of triethylborane or ferrocenyl-dimethylborane. The organometallic-substituted alkenes5 and6 could be obtained from1:1 reactions. 4-(9-Borabicyclo[3.3.1]non-9-yl)-1,1,4,4-tetrakis(trimethylstannyl)-1,2-butadiene (3) was obtained from the reaction of4 with dimeric 9-borabicyclo[3.3.1]nonane. The molecular structures of the allenes1 and3 were determined by X-ray analysis. In both cases, the structural parameters of the (Me3Sn)2C BR2 unit indicate Sn C hyperconjugation, and this model is supported by the small magnitude of the coupling constants1J(119Sn,13C), by the increased11B nuclear shielding as well as by the unusual changes in the δ119Sn values in going from the solution to the solid state. A fairly complete set of signs of coupling constantsnJ(119Sn,1H)nJ(119Sn,13C)andnJ(Sn, Sn) was derived for the allene3 using 2D13C/1H and119Sn/1H heteronuclear shift correlations.

57Fe NMR spectroscopy of ferrocenes derived from aminoferrocene and 1,1′‐diaminoferrocene

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

Darstellung, Charakterisierung und Reaktivität der Komplexe (η5-C5H4CMe2C13H9)M(CO)3X (M = Cr, Mo, W; X = H, Me)

Abstract The reaction of cyclopentadienylpropylidenefluorene, C5H5CMe2C13H9, with stoichiometric amounts of butyllithium gives the anion [C5H4CMe2C13H9]− (1). The thermal reaction of 1 with the complexes M(CO)5(thf) (M = Cr, Mo, W) and the subsequent alkylation with CH3I leads to the alkyl complexes (η5-C5H4Me2C13H9)M(CO)3Me (3). The protonation of the anions [(η5-C5H4CMe2C13H9)M(CO)3]− (2) with acetic acid affords the hydrido complexes (η5-C5H4CMe2C13H9)M(CO)3H (4). The photolysis of complexes 3 results in the elimination of methane and formation of the complexes (η5:η1-C5H4CMe2 C13H8)M(CO)3 (5). The thermal reaction of the hydrido complexes 4b,c (M = Mo, W) and PMe3 gives cis- and trans-(η5-C5H4CMe2C13H9)M(CO)2(PMe3)H (6b,c), and the photo-induced reaction between 4b and PMe3 yields the disubstitution product trans-(η5-C5H4CMe2C13H9)Mo(CO)(PMe3)2H (7b).