Bernd Wrackmeyer

119Sn-NMR Parameters

Publisher Summary Tin (Sn) compounds are well-recognized both in basic research and in industrial applications. Tin NMR spectroscopy includes three magnetically active tin isotopes namely, 115Sn, 117Sn , and l19Sn. However, most tin NMR parameters refer to the 119Sn nucleus owing to its properties such as abundance, magnetic moment, and NMR frequency. This chapter describes: (1) the compilation and updation of 119Sn chemical shifts (δ 119Sn) from studies on organotin compound and inorganic tin compounds, (2) indirect nuclear spin-spin couplings, (3) relaxation mechanisms concerning the 119Sn nucleus, and (4) experimental details for 1I9Sn-NMR measurements. It is observed that with modem equipment there are, in principle, no serious experimental difficulties in observing 119Sn resonances either directly or by heteronuclear double resonance. δ 119Sn data, available for all kinds of tin compounds, significantly allows using this parameter in an empirical way in order to find models for the qualitative interpretation of δ 119Sn. This also applies to couplings involving the l19Sn nucleus, which serve as a sensitive tool in the discussion of structure and bonding. All 119Sn-NMR parameters of tin compounds largely concern measurements in the liquid state.

New bicyclic organylboronic esters derived from iminodiacetic acids

Abstract The reactions of phenylboronic acid or dinethylthexyboronic ester with iminodiacetic- or N -methyliminodiacetic acids lead to high yield to the air-stable bicyclic esters (N-B)phenyl[iminodiacete- O , N ]borane ( 1 ), (N-B)phenyl[ N -methyliminodiacetate- O , N ]borane ( 2 ), (N-B)thexy[iminodiacetate[ O , N ]borane ( 3 ) and (N-B)thexyl[ N -methyliminodiacetate- O , N ]borane ( 4 ). These are shown by 1 H, 11 B and 13 C NMR spectroscopy to have rigid bicyclic structures of strong intramolecular N-B coordination.

Organoborierung von alkinylstannanen : II. Zur reaktion von triorganylboranen mit dialkyldiethinylstannanen☆

Abstract Dialkyldiethinylstannanes of the type R 2 Sn(CCH) 2 (R = CH 3 , C 2 H 5 ) smoothly react with trialkylboranes BR′ 3 (R′ = C 2 H 5 ; i-C 3 H 7 , n-C 4 H 9 ) to give substituted 1-stannacyclopentadienes (stannoles). The products were identified by means of 1 H, 11 B, 13 C and 119 Sn NMR spectroscopy. A possible mechanism for the formation of the heterocycles is discussed.

Organoborierung von alkinylstannanen : IV. Zur darstellung verschiedenartig substituierter 1-stannacyclopentadiene

Abstract The preparation of 1-stannacyclopentadienes via organoboration reactions of dialkynyldimethylstannanes (CH 3 ) 2 Sn(CCR′) 2 (R′= t-C 4 H 9 , Si(CH 3 ) 3 ) with BR 3 (R = CH 3 , C 2 H 5 ) is reported. A stepwise synthesis also leads to the title compounds. Reaction of 1-stannacyclopentadienes with BCl 3 yields 1-boracyclopentadienes. The structures of the new compounds are discussed by means of 1 H, 11 B, 13 C and 119 Sn NMR spectroscopy.

The NB coordination in hindered cyclic thexylboronic esters derived from diethanolamines

Abstract The reaction between thexylborane and diethanolamines in THF leads to cyclic thexylboronic esters. The intramolecular NB coordination was demonstraated by dynamic 1 H and 11 B NMR spectroscopy. The existence of steric interactions between the N-substituents of the B -thexyl group was indicated by the 1 H and 11 B NMR data.

Nuclear magnetic resonance studies of boron compounds : XVI. Carbon-13 studies of organoboranes: Phenylboranes and boron-substituted aromatic heterocycles☆

Abstract 13C and 11B NMR data of 29 phenylboranes and 9 boron-substituted aromatic heterocycles (thiophene, N-methylpyrrole and furan) are discussed. The observed 13C chemical shifts of the para-carbon atoms in phenylboranes and the corresponding carbon atoms in the aromatic heterocycles are consistent with mesomeric interactions of the boryl group with the aromatic system. The trend of δ(13C(para)) in phenylboranes corresponds to that observed for isoelectronic phenylcarbocations. Low temperature 13C NMR and/or 13C {11B, 1H} heterocuclear triple resonance experiments were employed to obtain the 13C chemical shifts of the boron-bonded carbon atoms.

NMR-Untersuchungen al alkinylstannanen

Abstract 13 C, 29 Si, 119 Sn, 207 Pb NMR data (chemical shifts δ and coupling constants J ( 13 C 13 C), J ( 29 Si 13 C), J ( 119 Sn 13 C), J ( 207 Pb 13 C), J ( 119 Sn 29 Si), J ( 119 Sn 119 Sn), J ( 207 Pb 119 Sn)) of alkynylstannanes (CH 3 ) 3 SnCCX and R 2 Sn(CCX) 2 (X  H, alkyl, C 6 H 5 , Si(CH 3 ) 3 , Ge(CH 3 ) 3 , Sn(CH 3 ) 3 , Pb(CH 3 ) 3 , OC 2 H 5 ; R  CH 3 , C 2 H 5 ) are reported together with some data of other alkynes for comparison. The nature of the bonding is discussed on the basis of the various coupling constants and chemical shifts.

Organoborierung von alkinylstannanen : V. Zur reaktion von dialkyldi-1-propinylstannanen mit trialkylboranen

Abstract Treatment of R′ 2 Sn(CCCH 3 ) 2 (R′ = CH 3 , C 2 H 5 ) with BR 3 (R = CH 3 , C 2 H 5 , i-C 3 H 7 ) gives 1-bora-4stannacyclohexadienes and 2,5-bis(dialkylboryl)-1-stannacyclopent-3-enes. The formation of the heterocycles depends in a complex manner upon the ratio of the starting compounds, upon the nature of groups R and R′ and also upon the solvent. The proposed structures are discussed on the basis of 1 H, 11 B, 13 C and 119 Sn NMR data.

Carbon-tin and carbon-lead indirect nuclear spin-spin coupling constants in alkynyl tin(IV) and alkynyl lead(IV) compounds

Abstract The signs of the reduced indirect nuclear spin-spin coupling constants n K ( 119 Sn 13 C ) and n K ( 207 Pb 13 C ) (n = 1, 2) were determined by heteronuclear double-resonance experiments 1H{119Sn}(Et3SnlCCH,Et2Sn(CCH)2) and 1H{207Pb}(Et3PbCCH). n K( 119 Sn 13 C ) (n = 1, 2) was found to be positive, relative to 2 K( 13 C  1 H ) and 1K(13C1H) while n K( 207 Pb 13 C ) is negative in Et3PbCCH. A representative series of alkynyl tin(IV) and lead(IV) compounds was studied by 13C NMR and anomalies in the trend of n K( 207 Pb 13 C ) can be explained by assuming a negative sign for some of these coupling constants in analogy to the findings for Et3PbCCH.

Organoborierung von alkinylstannanen: XVII. Synthese von neuen sila- und germacyclopentadienderivaten und IHRE umwandlung in sila- und germacyclopent-3-ene☆

Abstract The organoboration of the new alkynylsilane and alkynylgermane, bis(trimethylstannylethynyl)dimethylsilane and bis(trimethylstannylethynyl)dimethylgermane leads to the 1,1-dimethyl-2,5-bis(trimethylstannyl)-3-dialkylboryl-4-alkyl-sila- and germacyclopentadienes, respectively, in quantitative yield. These compounds react in an unprecedented way with 2 equivalents of ethanol or methanol to give quantitatively 1,1-dimethyl-3,4-dialkyl-1-sila- and 1-germacyclopent-3-enes, respectively. All compounds are characterized by NMR spectroscopy (1H, 11B, 13C, 29Si and 119Sn NMR).