The monomeric aluminium hydrazide H10 C5 NN(AltBu2 )Ad (4; Ad=adamantyl, NC5 H10 =piperidinyl) was obtained in high yield by hydroalumination of the corresponding hydrazone derivative 1. Compound 4 has a strained AlN2 heterocycle formed by a donor-acceptor bond between the β-nitrogen atom of the hydrazide group and the aluminium atom. Opening of this bond resulted in the formation of an active Lewis pair that was able to cooperatively activate carbon dioxide or isocyanates. Insertion of the heterocumulenes into the AlN bond selectively afforded a carbamate and two urea derivatives in high yield. In the first step, phenyl isocyanate gave the adduct 6, which has the oxygen atom coordinated to the aluminium atom and its central carbon atom bound to the nitrogen atom of the piperidine moiety. Adduct 6 represents a reasonable intermediate state for these activation processes. The applicability of hydroaluminated compounds, such as 4, in organic synthesis was demonstrated by the reaction with an imidoyl chloride, which gave the corresponding amidrazone derivative 9.

The two new heterometallic cobalt(II)/titanium oxo cages octanuclear [Ti(7)O(5)(OEt)(19)(CoCl)] (1) and pentanuclear [Ti(4)O(OEt)(15)(CoCl)] (2) have been obtained via condensation reactions of Ti(OEt)(4) in the presence of CoCl(2). This simple methodology gives access to key well-defined molecular building blocks for Co-doped hybrid materials.

Hydroalumination or hydrogallation of a sterically encumbered hydrazone, H10C5N–NC­(C9H14) (NC5H10 = piperidine, C­(C9H14) = 2-adamantdiyl), afforded hydrazides that, depending on the steric shielding by the substituents at the metal atoms, had different molecular structures. While both di­(tert-butyl)metal derivatives (1a, 1b) are monomeric in the solid state with highly strained MN2 heterocycles (M = Al, Ga), the dimethylmetal compounds (1c, 1d) are dimeric with M2N2 heterocycles and exocyclic N–N bonds. The latter compounds are highly dynamic in solution. 1d crystallized as a mixture of cis- and trans-isomers as detected by crystal structure determinations. These compounds react as active Lewis pairs by their specific donor–acceptor functionality and are able to activate C–H bonds of moderately acidic substrates. Reaction of 1a (M = Al) with H–CC–C6H5 afforded by C–H bond activation and release of H–CMe3 trialkynyl compound 4, in which three alkynyl groups and a neutral hydrazine ligand are bound to Al. 1b (M = Ga) gave only the known dimeric monoalkynyl derivative [(Me3C)2Ga–CC–C6H5]2 (5b). The sterically less shielded dimethyl compounds 1c and 1d similarly yielded trialkynylmetal compounds by methane and hydrogen elimination. In this case a hydrazone ligand is coordinated to the metal atoms. 1d reacted with pentafluorobenzene in an unprecedented reaction to yield a diaryl-methylgallium compound with the metal atom bound to two electron-withdrawing groups and a hydrazone ligand completing the coordination sphere of Ga.

Hydrogallation of Me 3 Si-CϵC-NR' 2 with R 2