Zinc Hydrazides and Alkoxyhydrazides: Organometallic Compounds with Novel Zn₄N₈, Zn₄N₆O and Zn₄N₄O₂ Cage Structures

Abstract

Tetrameric [{RZn(NHNMe2)}4] (R = Me, Et), the first organometallic zinc hydrazides to be described, have been prepared by alkane elimination from dialkylzinc solutions and N,N-dimethylhydrazine. They were characterised by 1H and 13C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography. The compounds form asymmetric aggregates containing the novel Zn4N8 core; tetrahedra of Zn atoms bear the alkyl groups at Zn, with the triangular faces bridged by NHNMe2 substituents. The NH groups are connected to two Zn atoms, and the NMe2 groups to one. Hydrolysis of the compounds with water gives [(RZn)4(OH)(NHNMe2)3] as products, which also were characterised as described above. Higher yields of these hydroxo clusters were achieved in one-pot syntheses by reaction of dialkylzinc solutions with mixtures of N,N-dimethylhydrazine and water. They contain Zn4N6O cages, in which one hydroxide in the tetrameric hydrazides described above replaces one NHNMe2 group. Similar products can be prepared with alkoxy instead of hydroxy groups, in analogous one-pot syntheses with alcohols. Alcoholysis of [EtZn(NHNMe2)]4 with methanol or ethanol gave zinc trishydrazide monoalkoxides, [(EtZn)4(OR)(NHNMe2)3] (R = Me, Et), which have constitutions analogous to the monohydroxides. The organozinc bishydrazide bisalkoxides [(MeZn)4(NHNMe2)2(OEt)2] and [(EtZn)4(NHNMe2)2(OEt)2] were obtained in one-pot reactions from dialkylzinc solutions with mixtures of the hydrazine and alcohol, and their crystal structures, confirmed by spectroscopic methods in solution, show an unsymmetrical aggregation with the novel Zn4N4O2 cage structure.

“Isomerism” of Coordination Modes and Numbers in Pentanuclear Organozinc Hydroxylamides: An Exercise in Subtle Substituent Size Effects

“…VT-NMR spectroscopy sheds some light onto this and onto the molecular dynamics of the aggregates. Between 300 and 200 K, the 1 H NMR spectra of 1 show some signal broadening but no substantial change to indicate structural variations; the 13 C NMR spectra give a similar picture. A drawback to these measurements is the limited solubility of 1 especially at low temperatures, which is most probably due to its minimal alkyl periphery.…”

“…This stands in contrast to the isoelectronically related organozinc hydrazides (N-N double-donor), where zinc is exclusively tetracoordinate. [13] Scheme 1.…”

“…Variable-temperature 13 C NMR experiments of all-ethyl cluster 3 reveal that the R 2 NO -ligands rapidly exchange between the RZn + and Zn 2+ cations. This process is rationalised by a plausible model which also points out that the core structure of 3 could be an intermediate motif in the observed heteroatom connectivity exchange.…”

Organozinc Siloxide-Hydrazide Aggregates [(RZn)4(NHNMe2)x(OSiMe3)(4 – x)]

“…This area has recently been reviewed [5] and finds its parallels in the chemistry of hydroxylamide anions in the coordination sphere of Al and Ga, which was investigated by our group [6]. The hydrazide chemistry of zinc, the neighbour element of gallium in the Periodic Table, was -apart experiments leading to the only known zinc hydrazide [Zn(N 2 H 3 ) 2 ] [7] -untouched, until our two recent studies of the compounds [(RZn) 4 (NHNMe 2 ) 4 ] [8,9]. These are the sole products of the reactions of dialkylzinc solutions (ZnR 2 , R = Me, Et, i Pr) with N,N-dimethylhydrazine.…”

“…These hydrazides adopt unsymmetrical cage structures. They react with water and alcohols, whereby the parent hydrazine is regenerated and aggregates with various compositions of the general formula [(RZn) 4 (NHNMe 2 ) 4−x -(OR') x ] are formed [8,9]. The common motif for all Scheme 1. compounds is always that of tetranuclear cage compounds.…”