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Precursors for MOCVD and ALD of Rare Earth Oxides−Complexes of the Early Lanthanides with a Donor-Functionalized Alkoxide Ligand

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posted on 23.07.2007, 00:00 by Helen C. Aspinall, Jamie F. Bickley, Jeffrey M. Gaskell, Anthony C. Jones, Gael Labat, Paul R. Chalker, Paul A. Williams
Complexes of the early lanthanides with the donor-functionalized alkoxide ligand mmp (Hmmp = HOCMe2CH2OMe, 1-methoxy-2-methylpropan-2-ol) are excellent precursors for Metal Organic Chemical Vapor Deposition (MOCVD) and Atomic Layer Deposition (ALD) of lanthanide oxides; however, their coordination chemistry, which is the subject of this paper, is rather complex. Precursors for MOCVD and ALD of lanthanide oxides are prepared by the reaction of [Ln{N(SiMe3)2}3] with 3 equiv of the alcohol Hmmp in toluene in the presence of 1 equiv of tetraglyme and are indefinitely stable in solution. Reaction of [Ln{N(SiMe3)2}3] with 3 equiv of Hmmp in the absence of stabilizing Lewis bases gives complex condensed products with empirical formula [{Ln(mmp)3-n}2On]. These condensed products show poor volatility and are unsatisfactory precursors for MOCVD or ALD of oxides. The cluster complex [La332-mmp)222-mmp)3(mmp)4] has been prepared by careful reaction of [La{N(SiMe3)2}3] with 4 equiv of Hmmp and has been characterized by single-crystal X-ray diffraction. Salt metathesis reactions using M(mmp) (M = Li or Na) are unreliable routes to [Ln(mmp)3]. Crystals of the heterometallic cluster complex [NaLa33-OH)(μ32-mmp)222-mmp)4(mmp)3] were isolated from the reaction of [La(NO3)3(tetraglyme)] with 3 equiv of Na(mmp), and crystals of [Li(κ2-Hmmp)Pr(μ22-mmp)4)LiCl] were isolated from the reaction of PrCl3 with 3 equiv of Li(mmp); both of these complexes have been characterized by single-crystal X-ray diffraction.

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