Reactions of metallated nucleophiles MIY [Y = OR, SR, NR2, PR2, AsR2, CR3, Si(SiMe3)3, R = organyl, H] with bis(2,2,6,6‐tetramethylpiperidino)aluminum halides [tmp2AlX, (X = Cl, Br, I)] offer facile access to a variety of bis(amino)alanes of the type tmp2AlY. As indicated by 27Al‐NMR spectroscopy, mass spectrometry and X‐ray crystal structure determina‐tions, all of these compounds are monomeric in the solid state, in solution, and in the gas phase. Even Al–E single bonds (E = Si, P, As etc.) that are not commonly encountered are stabilized by the supporting tmp fragments. The results of a systematic analysis of the bonding parameters determined for the tmp2AlY compounds, combined with a quantum mechanical study on model compounds (H2N)2AlY, not only reveal the presence of a highly polar Al–N bond, but at the same time rule out AlN‐pp(π) bonding, in contrast to the situation in the analogous tmp2BY compounds. It is shown that the Al–N bond length depends on the acidic character of the protic species HY: the shorter d(Al–N), the less basic is Y.

Keywords:1,3-Di(tert-butyl)-2,4-bis(2,2,6,6-tetramethylpiperidino)-1,3,2,4-diphosphadiboretane / 1-tert-Butyl-2,4-bis(2,2,6,6-tetramethylpiperidino)-1,3-diphospha-2,4-diborabicyclo[1.1.0]butane cation / 2,2,6,6-Tetramethylpiperidino-tert-butylphosphinideneborane-AlBr 3 adduct / X-ray structures / ab initio calculations Depending on reaction conditions the 1,3,2,4-diphosphadiboretane 1 reacts with AlBr 3 to give the unstable adduct tmp=B=P(tBu)AlBr 3 , 3, and/or the somewhat more stable salt [(tmpB) 2 (PtBu)P] + [AlBr 4 ], 2. The X-ray structure determination of 3 shows an almost linear NBP array with BN and BP double bonds resembling an allene type structure. NBO analysis shows the presence of BN-and BP-π-bonds. On the other hand, the cation of compound 2 has a bicyclic structure

The reaction of LiGePh3 with Me2AlCl in ether yields the trisgermylaluminate Li(OEt2)n[(Ph3Ge)3AlMe]. The Ge−Al bond length is 2.520 Å and the geometry around the Al center almost tetrahedral.

tmpAlBr2 (tmp = 2,2,6,6-tetramethylpiperidino) was prepared from AlBr3 and tmp2AlBr at 90 °C in the absence of a solvent, but could not be crystallised from toluene or hexane because it reacted with the solvents to form tmpH·AlBr3 in high yield. tmpH·AlMeCl2, obtained from the components, decomposes at elevated temperatures but no tmpAlCl2 could be isolated. Attempts to generate the cation [tmp-Al-tmp]+ from tmp2AlBr or tmp2AlCl by halide abstraction with B(C6F5)3, Ph3C(SnCl5) or SbCl5 or from tmp2AlR (R = Me, Ph) and B(C6F5)3 have failed. An unexpected reaction occurred on treatment of tmp-B=P(tBu)AlBr3 with BH3 in THF which led to the formation of [AlBr2(thf)4][AlBr4]. The attempted synthesis of tBu2Al(tmp) from tBu2AlBr and Li(tmp) gave a product which, on exposure to CO2 at dry ice temperature, yielded the salt [(tBuAl)2(O2C(tmp))3][tBu3Al-Br-AltBu3] in low yield. All isolated products were characterized by NMR spectroscopy and by X-ray determination of their molecular structures.

The reactions of bis(2,2,6,6-tetramethylpiperidino)aluminum bromide (tmp2AlBr) with Me3SiN3 or Me3SiCN lead to trimeric tmp2AlN3 and tmp2AlCN, respectively, while the reaction with Me3SiOCN produces the bicyclic compound [tmpCON(SiMe3)2]2′ , 3. Similarly, di(tertbutyl) aluminum bromide reacts with Me3SiCN to give tetrameric (Me3C)2AlCN, 4. The compounds (Me3C)2AlN3 and (Me3C)2AlOCN, obtained as oily products, have tetracoordinated Al atoms as shown by NMR spectroscopy, but the degree of oligomerization has not been determined.