Angelika Sebald

Organoboration of cis-diethynylplatinum(II) complexes with R2P(CH2)2PR2 ligands: platinacyclopentadienes and their behaviour in solution

Organoboration of dppePt(Cue5fcCH)2 (1a) and depePt(Cue5fcCH)2 (1b) with BR13 (2) (R1 ue5fb Me (a), Et2 (b), or Pri (c)) gives the platinacyclopentadienes, 3a–c and 4c, respectively, in high yield. The stability of 3 in solution increases with the size of R1. In addition to slow decomposition of 3a (R1 ue5fb Me) in solution rearrangement into a platinum-borol complex was observed 4a (R1 ue5fb Me) decomposes at room temperature, but 4b (R1 ue5fb Et2) reacts readily with an excess of triethylborane to give a new type of platinum-borol complex with exocyclic BEt2 group and Pt coordination to only one half of the borol π-system. Variable-temperature 31P NMR shows that rotation of the Pt fragment about the axis linking it to the borol ring is rapid on the NMR time scale. The new compounds have been characterized by 1H, 11B, 13C, 31P and 195Pt NMR spectroscopy.

Darstellung und NMR-spektroskopie organometallisch substituierter dikobalthexacarbonyl-alkin-komplexe

Abstract Dicobalthexacarbonyl η2-alkyne complexes with organometallic substituents (silyl, stannyl, boryl) were prepared. The reactions of bis(alkynyl)-element compounds (element E ue5fb C, Si, Sn, B) with Co2(CO)8 were studied. In the case of E ue5fb B only one alkynyl group reacts, in the case of E ue5fb C or Sn the complexation of both alkynyl groups is preferred, whereas for E ue5fb Si one or both alkynyl groups react. Usually, the alkynylboranes are much less reactive than the organic silyl or stannyl alkynes. The complexes were studied by 1H, 13C, 59Co and 11B, 29Si, 119Sn NMR spectroscopy. The qualitative description of the bonding situation in the Co2C2 fragment derived from the discussion of the NMR parameters is in agreement with an MO analysis as reported in the literature.

Organoborierung von Alkinylstannanen. XV: Synthese von 1,2-Dihydro-1,2,5-Disilaborepinen

Abstract The reaction between 1,2-diethynyl-tetramethyldisilane ( 1 ) and two equivalents of diethylaminotrimethylstannane ( 2 ) leads to 1,2-bis(trimethylstannylethynyl)-tetramethyldisilane ( 3 ). The new alkyne derivative 3 reacts, already at room temperature, with trialkylboranes, R 3 B ( 5 ) (R = Me, Et), quantitatively to give 1,1,2,2-tetramethyl-3,7-bis(trimethylstannyl)-4,5,6-trialkyl-1,2-dihydro-1,2,5-disilaborepines ( 6 ). The reaction is much slower with R = Pr i which allows detection of intermediates by NMR spectroscopy. All products are characterized by 1 H, 11 B, 13 C, 29 Si and 119 Sn NMR data.

Organoborierung von alkinylstannanen: XVI. borol-synthese über die organoborierung von BIS(alknyl)Boranen

Abstract The organoboration of a new alkynylborane, diethylamino-bis(trimethylstannyl-ethynyl)borane gives 1-diethylamino-2,5-bis(trimethylstannyl)-3-diethylboryl-4-ethtylborol and 1-diethylamino-2-diethylboryl-3,5-bis(trimethylstannyl)-4-ethylborol. The stepwise reaction progress was monitored by NMR spectrocopy ( 1 H, 11 B, 13 C, 119 Sn) and the results were compared with those of the organoboration of bis(diethylamino)-trimethylstannylethynylborane.

13C and 199Hg nuclear magnetic resonance study of alkynyl mercury(II) compounds

Abstract Alkynyl mercury compounds of the type Hg(Cue5fcCue5f8R) 2 ( I ), R′ue5f8Hgue5f8Cue5fcCue5f8R ( II ) and R′ue5f8Hgue5f8Cue5fcCue5f8Hgue5f8R′ ( III ) have been studied by 1 H, 13 C and 199 Hg NMR. Chemical shifts (δ 1 H, δ 13 C, δ 199 Hg) and coupling constants J ( 199 Hg 1 H), J ( 199 Hg 13 C), J ( 13 C 1 H) and J ( 13 Cue5fc 13 C) (in natural abundance) are reported. The changes in magnitude of the coupling constants 1 J( 199 Hg 13 Cue5fc) and 1 J ( 13 Cue5fc 13 C) cannot be fully explained in terms of changes in the “ s -character” of the Hgue5f8Cue5fc bond and the Cue5fcC bond, respectively. The shielding of the alkynyl carbon linked to mercury in II is decreased by ca. 23 ppm as compared to the analogous carbon in I . This indicates a greatly different degree of polarization for the Hgue5f8Cue5fc bonds in I and II in agreement with the behaviour of 1 J ( 199 Hg 13 Cue5fc) and 1 J ( 13 Cue5fc 13 C). The solvent and temperature dependence of the 199 Hg chemical shift of I (R = C 6 H 5 , C 4 H 9 n ) and II (R = H, R′= CH 3 ) has been studied. The results indicate covalent interactions of I with amines, pyridine, dimethylsulphide and Br − , while the interaction with acetonitrile and oxygen donors (DMSO, DMF, dioxane, acetone) is of a different nature.

Indirect nuclear spin—spin coupling constants 1J(13C13C) in alkynes

Abstract Indirect nuclear spin—spin coupling constants 1 J( 13 Cue5fc 13 C) in alkynes Xue5f8Cue5fcCue5f8Y have been measured from natural abundance 13 C-NMR spectra. The influence of various substituents X, Y (H, alkyl, perfluoroalkyl, alkenyl, aryl, alkynyl, amino, phosphyl, alkoxy, silyl, stannyl, plumbyl) on the magnitude of 1 J(Cue5fcC) was studied. The large range of 1 J(Cue5fcC) (81–224.3 Hz) is explained in terms of energy changes of the Cue5fcC, ue5fcCue5f8X and ue5fcCue5f8Y σ orbitals due to the polarity of the ue5fcCue5f8X and/or the ue5fcCue5f8Y bonds. The trends observed for 1 J(Cue5fcC) parallel those for n J(ue5fcCue5f8H) and n J(Mue5f8Cue5fc) ( n = 1, 2; M = 29 Si, 119 Sn, 207 Pb) and analogies to 1 J( 15 Nue5fc 13 C) in nitriles and nitrile oxides are found.

Carbon-13 NMR of bis(cyclopentadienyl)titanium and -zirconium acetylides

Abstract Changes in the electronic structure of the title compounds are reflected by 13 C chemical shifts. An extreme deshielding of 13 C nuclei in the alkynyl group indicates the origin of low energy ligand-to-metal charge-transfer (LMCT).