Gallanes formation

Treatment of GaH3(quin) (quin = quinuclidine) with 1 equivalent of the sterically bulky formamidine as shown in Scheme 40 resulted in formation of a monomeric amido-gallane complex containing a monodentate amidinate ligand. Reaction of this species with a second equivalent of the amidine led to displacement of the quinuclidine ligand and formation of a five-coordinate monohydride complex, which could also be prepared directly by a one-pot reaction of GaHsfquin) with the free amidine in a molar ratio of 1 2 ... 

The reaction between a Lewis acid R3M and a Lewis base ER3, usually resulting in the formation of a Lewis acid-base adduct R3M—ER3, is of fundamental interest in main group chemistry. Numerous experiments, in particular reactions of alane and gallane MH3 with amines and phosphines ER3, have been performed [14]. Several general coordination modes, as summarized in Fig. 2, have been identified by X-ray diffraction. 

These particular properties of chloroalanes favor the formation of simple Lewis acid-base adducts, as was observed for the reaction of R2AICI with Sb(Tms)3 (R = Et, f-Bu). In contrast, reactions of the analogous gallanes and indanes yielded the desired heterocycles. The same tendencies were observed in reactions of R2MCI (M = Al, Ga, In R = Et, i-Bu) with P(Tms)3 and As(Tms)3. The gallane and indane react under formation of the expected M—E heterocycles [71], while the corresponding alanes yield the simple adducts... 

Single crystal X-ray analyses clearly reveal the formation of monomeric, dmap-stabilized compounds. The most important bonding parameters of the alane and gallane derivatives are given in Table XXIII. 

Wells et al. reported almost twenty years ago on the reactions of chloro-gallanes and trimethylsilyl-substituted arsanes R 2AsSiMe3, which occurred under elimination of MesSiCl and subsequent formation of arsinogallanes of the types [Cl2GaAsR 2]%> RGa(AsR2)2 and Ga(AsR2)3 [23]. In 1988, Cowley et al. extended this reaction type to the synthesis of heterocyclic stibinogal-lanes and -indanes [21]. 

Donor adducts of aluminum and gallium trihydride were the subject of considerable interest in the late 1960s and early 1970s.1 Thin-film deposition and microelectronic device fabrication has been the driving force for the recent resurgence of synthetic and theoretical interest in these adducts of alane and gallane.24 This is directly attributable to their utility as low-temperature, relatively stable precursors for both conventional and laser-assisted CVD,59 and has resulted in the commercial availability of at least one adduct of alane. The absence of direct metal-carbon bonds in adducts of metal hydrides can minimize the formation of deleterious carbonaceous material during applications of CVD techniques, in contrast to some metal alkyl species.10, 11... 

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