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

Abstract

The (N,N-dialkylaminoethyl)cyclopentadienyl group 13 element dichlorides 3 and 4 of the typewith the respective group 13 element trichlorides. The reaction of 3 with LiAlH 4 afforded the cyclopentadienylaluminum dihydride [(Me 2 NCH 2 CH 2 )C 5 H 4 ]AlH 2 (5) in nearly quantitative yield. Treatment of the organogallium dichlorides [ 5), i-Pr (7)} in good yields. The reaction of 6 with LiGaH 4 resulted in the formation of the organogallium dihydride [(Me 2 NCH 2 CH 2 )C 5 H 4 ]GaH 2 (8). The novel compounds 3-5, 7, and 8 were characterized by elemental analysis, NMR spectroscopy, mass spectrometry, and X-ray crystallography. In the solid state and also in solution, all compounds feature a monomeric structure with an intramolecularly coordinated dialkylamino group. The coordinative and electronic saturation of the metal center in these compounds leads to a drastically decreased reactivity toward moisture and air in comparison to nondonorstabilized Cp-group 13 element compounds. The dynamic behavior observed in solution is based on fast haptotropic shifts in a "windshield-wiper" type process. Sufficient volatility makes the organodihydrido compounds 5 and 8 suitable precursors for the deposition of aluminum and gallium, respectively, in the MOCVD process. Ex-situ characterization with sputter auger electron spectroscopy (SAES) provides information about the chemical composition of the aluminum and gallium layers. Irradiation of 5 and 8 in solution is followed by decomposition into the respective metal and into the hydrogen-functionalized ligand [C 5 H 5 (CH 2 CH 2 NMe 2 )].

Organometallic compounds of Group 13 elements containing the ligand C(SiMe3)2(SiMe2C5H4N-2)

“…In the compounds LL′GaCl 2 , Ga-N bonds are usually longer than Ga-C bonds (for an exception see [22]). The Ga-N [2.047(5) Å ] and Ga-C bond lengths [2.008(5) Å ] in 3 are within the reported ranges [Ga-N 2.013(2)-2.092(5) Å and Ga-C 1.936(6)-2.013(7) Å [15,16,23]] and close to the values [Ga-N 2.057(4), Ga-C 2.000(4) Å ] found for the compound GaCl 2 C(SiMe 3 ) 2 (SiMe 2 NMe 2 ) (5c) [13]. The Ga-O distance in 3 [2.099(4) Å ] is a little longer than the sum of the covalent radii (1.93 Å ) and at the upper end of the range found in organogallium hydroxides [1.892(5)-2.033(5) Å ] [11,21,24].…”

“…AlCl 2 C(SiMe 3 ) 2 (SiMe 2 NMe 2 ) (5a) [12] or AlCl 2 C(SiMe 2 NMe 2 ) 2 (SiMe 2 NMe 2 ) (5b) [13] have dative Al-N bond lengths in the range 1.968(4)-1.975(2) Å . The bonds in compounds with five-or six-membered rings are usually (but not always [14]) longer [1.960(2)-2.085(4) Å ] [14][15][16][17]. The dative Al-N bond length from the pyridyl nitrogen in 2a [1.9383(16) Å ] is shorter than any of these and similar to those in amine adducts of AlCl 3 [18].…”

Strategies in the cyclopentadienyl chemistry of p-block elements

“…Interestingly, the protonated Cp-substituent is the main organic product regained after the thermal decomposition process. The lability of the El-C(Cp) bond is nicely demonstrated by the photochemical decomposition of the dihydrido gallium species (Me 2 NCH 2 CH 2 )H 4 C 5 GaH 2 in benzene solution [47].…”

“…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.…”

Synthesis and protonolysis of neutral aluminum dihydride compounds stabilized by tridentate-substituted pyrrolyl ligands: Synthesis, structural characterization and ring-opening polymerization of ɛ-caprolactone

“…Moreover, the bond angle of Al(1)eN(4)eC(11) is even larger than that of Al(1)eS(1)eC(11) in 5, probably because of the bulky 2,6-diisopropylphenyl group pushing the aryl ring away from the aluminum atom.In compound 10 (Fig. 5), the geometry around the aluminum atom is similar to that of 4 showing a distorted trigonal bipyramidal.…”