Synthesis and Structure of Tetrameric Gallium(I) Amides

Abstract

The amino substituted gallatetrahedranes described herein, Ga4(tmp)4 [tmp = 2,2,6,6‐(tetramethylpiperidino)] and Ga4[N(SiMe3)dipp]4 (dipp = 2,6‐diisopropylphenyl), are the first oligomeric gallium(I) amides to be reported. These compounds are formed in a facile manner from “GaI”. A new hexagallane with an unusual structure is also described. The clusters were characterized by NMR and UV/Vis spectroscopy, single‐crystal X‐ray crystallography, and DFT calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Oxidative Addition Reactions of Element–Hydrogen Bonds with Different Polarities to a Gallium(I) Compound

“…[2][3][4][5] Depending on the substituent R, these clusters can monomerize in solution. This was reported for [GaCp*] (Cp* = pentamethylcyclopentadiene), [6] [GaCA C H T U N G T R E N N U N G (SiMe 3 ) 3 ] 4 , [7] [Ga 4 -A C H T U N G T R E N N U N G (tmp) 4 ] (tmp = 2,2,6,6-tetramethylpiperidine), [8] and [Ga-A C H T U N G T R E N N U N G (aryl)] 2 (aryl = 2,6-(2,6-iPr 2 C 6 H 3 ) 2 C 6 H 3 ), [9] for example. By using the bidentate b-diketoiminate [{NA C H T U N G T R E N N U N G (dipp)CMe} 2 CH] (dipp = 2,6-diisopropylphenyl) as a ligand, it was possible to isolate the stable gallium(I) compound [Ga({N-A C H T U N G T R E N N U N G (dipp)CMe} 2 CH)] (1).…”

“…This has been discussed already for other monomer gallium(I) derivatives and their oligomers or oxidation products. [2,3,8,39] With an increase in the electronegativity of the oxidatively added element, the absolute charge of the gallium decreases. The elements phosphorus and tin cause the gallium to take on a negative charge (Table 4).…”

“…Upon tetramerization, shorter gallium-nitrogen bonds are observed in, for example, [Ga 4 A C H T U N G T R E N N U N G (tmp) 4 ] (tmp = 2,2,6,6-tetramethylpiperidine). [8] This has been discussed as a consequence of the lone pair in gallium(I) species, GaR, which has predominantly s character and is slightly antibonding in regard to a GaR bond. [40] If the lone pair is used for bonding-that means an increased oxidation state for gallium, as in 2-the gallium-nitrogen bonds are shortened.…”

The role of the bis-trimethylsilylamido ligand, [N{SiMe3}2]−, in main group chemistry. Part 2: Structural chemistry of the metallic p-block elements

“…It was assumed that the intermediate three-coordinate iminogallane, "Ga(BDI Ar )(=NSiMe 3 )", formed although once again this was not observed. The reaction of "GaI" with LiN{SiMe 3 } 2 did not proceed to give the tetrameric Ga(I) compound, as noted for the other bulky amides [N(Ar)SiMe 3 ] − and tmp [34]. Instead the product of a disproportion reaction was isolated containing the hexa-gallanate anion, [Ga 6 I(O)(N{SiMe 3 } 2 ) 6 ] − ( [30]), with an 'adventitious' oxygen atom from either hydrolysis or cleavage of the ether solvent [34].…”

“…When 4 equiv. of NaN{SiMe 3 } 2 were used, the coupled diradical product (34) was formed, believed to be a result of Si C bond scission and methyl migration.…”