Diethylmagnesium Mg(C2H5)2 (MgEt2)
Diethylmagnesium Mg(C2H5)2 (MgEt2)
Diethylmagnesium Mg(C2H5)2 (MgEt2) is a liquid at room temperature and atmospheric pressure. It has been tested as Mg precursor for ALD and CVI.
MgEt2 for MgO by ALD
MgEt2 was applied for the growth of high quality MgO thin films on Si(111) substrates by atomic layer growth (ALG) (based on surface hydrolysis reaction of MgEt2 and H2O). The growth orientation of MgO changed from (111) to (100) when increasing substrate temperature rom 600 to 900 °C. The growth orientation difference of MgO grown by ALG was explained in terms of the surface diffusion coefficients on MgO.[115]
MgEt2 for Mg metal growth by CVI
MgEt2 was attempted to grow Mg metal by chemical vapor infiltration (CVI) on the carbon foam by connecting a heated flask with material to a vacuumed deposition chamber, using Ar carrier gas. However the attempt failed because of precursor premature decomposition during evaporation (before and during boiling). In an additional test, a piece of carbon foam was placed in the flask with MgEt2 and was inductively heated by a high-frequency generator, however this resulted an a coating that contained a considerable amount of organic material. It was concluded that while MgEt2 is volatile, it is not suitable for vapor transport and therefore for Mg deposition on the foams by CVD. [116]
Di-tert-butylmagnesium (MgtBu2)
Di-tert-butylmagnesium (MgtBu2)
Di-tert-butylmagnesium (MgtBu2) was proposed as potential precursior for the MOCVD of Mg-containing compounds: [[i]]
The synthesis and structural characterization of di-tert-butylmagnesium tBu2Mg has been reported [[ii]]. The complex is dimeric three-coordinate [ t Bu 2 Mg] 2 with a folded CMg(μ-C)2MgC skeleton both in solid state and solution, as determined by the single-crystal XRD and variable-temperature 1H and 13C NMR spectroscopy, as well as by the molecular weight measurements. The crystal structures of [tBu2Mg]2 contains intra- and intermolecular CH3···Mg agostic interactions playing a significant role in the molecular assembly.
The thermolysis of bis(tert-butylmagnesium) MgtBu2 in the deuterated hydrocarbon solvents was studied by Pulsed Fourier transform NMR. The decomposition of MgtBu2 leads to metal, to the polarized disproportionation products isobutane and isobutene (rate constant kd), as well as to the unpolarized combination product 2,2,3,3-tetramethylbutane (rate constant kc). A radical mechanism for the main decomposition process has been proposed based on the analysis of the ratio kd/kc as well as the activation entropies for the decomposition. In the decomposition of MgtBu2 an A/E multiplet polarization was observe, which is opposite to the E/A polarization of these products arising during the thermolysis of di-t-butylmercury (for comprarison). Thus, dialkylmagnesium, decomposes in a free-radical reaction of uncorrelated t-butyl pairs. [[iii]]
[i] K.B.Starowieyski, J.Lewinski, R.Wozniak, J. Lipkowski, A.Chrost, Organometallics, 2003, 22 (12), pp 2458–2463.
[ii] K.B. Starowieyski, J. Lewinski, R. Wozniak, J. Lipkowski, A. Chrost, Organometallics, 2003, 22 (12), pp 2458–2463.
[iii] R. Benn, Chemical Physics, Volume 15, Issue 3, 15 July 1976, Pages 369–376, Chemically induced dynamic nuclear polarizations (CIDNP) and kinetic studies of the decomposition of di-t-butylmagnesium, -zinc, and -mercury
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