Amine‐stabilized cyclopentadienyl diisobutyl aluminum complexes as new kinds of precursors for the deposition of thin aluminum films by CVD

Abstract

Ab initio calculations (up to MP4SDQ/6‐31+G*//MP2(FU)/6‐31+G* + δZPVE) on several model nitroaldol (Henry) reactions have been performed. It is found that the free nitronate anions react with aldehydes via transition states in which the nitro and carbonyl dipoles are antiperiplanar to each other. This kind of reaction yields anti (erythro) nitroalcohols as major products. The Henry reaction between lithium nitronates and aldehydes is predicted to occur via cyclic transition structures yielding syn nitroalcohols as major products. The stereocontrol in these model reactions is low. The factors affecting the stereoselectivity in the reaction between dilithiated nitronates and aldehydes are also discussed.

Synthesis of Silyl Aluminum Reagents: Relevance Toward Atomic Layer Deposition of Metal Silicides and the Serendipitous Synthesis of a Novel Al-Hydride Cluster

“…In the solid state 5-Br exhibits a dimeric structure, in which the bromine atoms bridge two aluminum atoms to form a planar four-membered ring. This structural motif has been reported previously for analogous organo-aluminum halides. − Complexes 4-Cl and 5-Br sublime under reduced pressure (0.2 Torr) at 140 °C with no detectable decomposition. By analogy, 2 equiv of Et 3 SiLi reacts with AlBr 3 to yield, similarly to t BuMe 2 SiLi, the corresponding di-silyl-substituted aluminum complex 6-Br (Scheme ) as assayed by 1 H and 13 C­{ 1 H} NMR spectroscopy (see Supporting Information), and upon workup it yields a low-melting point semi-solid material.…”

“…Complex 1-NMe 3 was separated from the reaction mixture by sublimation (100 °C, 0.2 Torr) or by crystallization from a saturated solution of hexane, which yielded crystals that were not, however, suitable for X-ray crystallography analysis (see the Supporting Information). Although, amine coordination tends to increase the thermal stability of aluminum complexes , (see also below), a neat sample of 1-NMe 3 exhibits low thermal stability with complete decomposition to an insoluble white powder after 24 h at 120 °C.…”

“…Attempts to completely remove the coordinated Et 2 O molecule from complex 12-Et 2 O by applying low pressure (0.2 Torr) and heating (80 °C) were unsuccessful and about 20% (relative to Al) of coordinated Et 2 O molecules remained, as assayed by 1 H NMR spectroscopy. In targeting diethyl ether-free reagents, NMe 3 has been previously utilized to displace Et 2 O from organo-aluminum species. ,, Furthermore, DFT calculations on the model systems of 12-Et 2 O and 16-NMe 3 with the smaller Me 3 Si groups show that the Me 3 N–Al­(SiMe 3 ) 3 binding energy (Δ H = 35.9 kcal/mol) is stronger by 9.8 kcal/mol than the Et 2 O–Al­(SiMe 3 ) 3 binding energy (Δ H = 26.1 kcal/mol) (see the Supporting Information for details). With this knowledge in hand, addition of excess NMe 3 (∼10 equiv) to complexes 4-Cl or 5-Br followed by removal of all volatiles under low pressure (0.2 Torr) results in the clean formation of a white powder identified as the NMe 3 -coordinated bis­(silyl)aluminum chloride or bromide, i.e., 2-NMe 3 and 15-NMe 3 , respectively (Scheme ).…”

Synthesis, Structure, and Significance for MOCVD of Intramolecularly Base-Stabilized Monomeric Cyclopentadienylaluminum and -gallium Dihydrides

“…Compounds of the type [(Me 2 NCH 2 CH 2 )C 5 R 4 ]MR‘ 2 , with M = Al, Ga, R= H, Me and R‘ = H, i- Bu, have a sufficient volatility and a well-understood fragmentation behavior in thermolysis experiments. Therefore, they are useful precursors for the deposition of Al and Ga, respectively, in the MOCVD process. − , We carried out MOCVD experiments using 5 and 8 as precursor molecules in a hot-wall reactor and observed the formation of highly reflective metal films. The films of aluminum were deposited at substrate temperatures between 580 and 620 °C.…”

Strategies in the cyclopentadienyl chemistry of p-block elements

“…In the case of the pentamethylcyclopentadienyl-substituted substrates, the compounds pentamethylcyclopentadiene and tetramethylfulvene are the sole organic decomposition products. Dimethylaminoethyl-cyclopentadienyl compounds of aluminum and gallium have been used as precursors for the deposition of thin films of Al and Ga, respectively (Scheme 13) [46,47]. The dimethylamino group prevents oligomerization by an intramolecular coordination to the group 13 element.…”