ChemInform Abstract: Neutral Complexes of Tungsten Oxotetrafluoride with Hydrazine Derivatives.

Abstract

A 13C and 19F NMR spectroscopic investigation of the complexes (I), obtained by the reaction of hydrazines and hydrazones with WOF4, shows the existence of isomerism which is due to different orientations of substituents of the coordinated hydrazine.

Organometallic precursors to aluminum nitride: synthesis and crystal structures of amidodimethylaluminum trimer and the planar species amidodi-tert-butylaluminum trimer

“…In connection with the application of the R3A1 + NH3 system as a source of AIN, it is noteworthy that the R2A1NH2 intermediate and the final AIN structure share a common feature, the existence of (A1N)3 rings. The relatively facile conversion of these intermediates to AIN on heating may (31) reflect the small amount of structural reorganization required for this conversion as well as the existence of a facile mechanism for the elimination of RH as a stable byproduct (Figure 3). A detailed study of the mechanism of this thermal decomposition process in the case of the trimethylaluminum-ammonia system is in progress.…”

Multinuclear NMR Study of the Structure and Intramolecular Dynamics of (η2-Acetone phenylhydrazonato)tetrafluorooxotungsten(VI)

“…On the other hand, we previously showed 27 that the deprotonated nitrogen atom of the η 2 -coordinated ligand in tungsten oxo fluoro hydrazido complexes is in close spatial proximity to whichever of the two equatorial fluorine atoms (F C or F M ) has a greater constant of spin−spin coupling with the third atom (F A ). This also seems to be valid for this tungsten oxo fluoro hydrazonato complex 3 Parts of the 19 F NMR spectra of the reaction mixture with the resonances of the [WOF 4 (aph)] - complex at low (−25 °C) and increased (+40 °C) temperatures.…”

“…When dissolved in acetonitrile, oxotungsten(VI) tetrafluoride forms an adduct (WOF 4 ·CD 3 CN) with the acetonitrile molecule in a trans position relative to the oxygen atom . The 13 C and 19 F NMR spectra indicate that increasing the H-aph concentration in the reaction mixture results in the formation of several types of mono- and binuclear complexes; specifically [WOF 4 (H-aph)], [WOF 3 (aph)·CD 3 CN], [W 2 O 2 F 9 ] - , [W 2 O 2 F 8 (aph)] - , and [W 2 O 2 F 7 (aph) 2 ] - were observed in the systems with oximes, amines, ketimines, and substituted hydrazines. − If WOF 4 , H-aph, and NEt 3 are combined in a 1:3:2 molar ratio, the complex anion [WOF 4 (aph)] - is the predominant product. In this paper, we aimed our structural study on just this latter complex species.…”

“…The asymmetry of the complex characterized by non equivalence of the fluoro ligands and a considerable change of δ( 15 N) of the imino nitrogen unambiguously demonstrate that aph - is incorporated in the tungsten complex as a η 2 ligand via the two hydrazone nitrogens. Taking into account the NMR data of analogous complexes with oximes, ,, hydrazones, and hydrazine derivatives, one can assign the signals at −14.6 and −108.2 ppm to fluorines in positions trans to aph - and oxygen, respectively. The increased values of spin-spin coupling between neighboring equatorial fluorine atoms is characteristic of complexes with η 2 ligands. ,, This increase is probably caused by a closer arrangement of fluorine ligands in the equatorial plane due to coordination of the two-center ligand.…”

“…Complexes of WOF 4 with two n-donor atoms in the equatorial plane are normally stable only at low temperatures. At elevated temperatures intramolecular dynamic processes involving two-center donors occur. , NMR spectroscopy, especially 19 F NMR, is a very efficient method for monitoring these processes. − …”