Water- and oxygen-sensitive compounds R*EHal2•D, R*EHal2 and R*2EHal (R* = SitBu3; E = B, Al, Ga, In, TI; Hal = F, Cl, Br, I; D = OR2, NR3) have been synthesized by reaction of EHal3 with NaR* in the absence or presence of donors as well as by substitution of D, Hal or R* by other substituents, or by reaction of R*2E-ER*2 (E = Al, In) with I2, H2, AgF2 or HBr. Thermal decomposition of the compounds in solution or in the gas phase leads to elimination of D from R*EHal2•D, or of R*Hal from R*EHal2 and R*2EHal, respectively. The dihalides R*EHal2 act as Lewis acids with respect to donors OR2 or NR3 (formation of adducts R*EHal2•D), the monohalides R*2EHal as Lewis bases with respect to acceptors EHal3 (formation of R*2E+ EHal4-). Dehalogenations of R*2EHal and R*EHal2 with alkali metals or NaR* leads to compounds R*4E2 (E = AI, In, Tl), R*3E2• (E = AI, Ga), R*4E3• (E = Al, Ga), R*4E4 (E = AI, Ga), R*6Ga8, R*8In12, (R*2B- ), R*2A- , R*3Ga2-, R*4Ga3-, R*4Ga42-, R*4Tl3Cl, or R*6Tl6Cl2. The structures of R*BBr2•Py, R*AlBr2•NEtMe2, (R*AlClOBu)2, R*2BF as well as R*2ECl (E = B, Al, Ga, Tl) have been determined by X-ray structure analyses.

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.

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Keywords: Borazines / Ring distortionThe solid-state structure of (HN=BF) 3 has been redetermined. It is characterised by a stacking of the molecules, similar to hexagonal boron nitride. In contrast, (F 3 CH 2 N=BF) 3 shows no intermolecular interactions between the planar borazine rings. In (Cl 2 BN=BCl) 3 , the Cl 2 B groups are almost perpendicularly oriented to the planar borazine ring and its B-Cl bonds are shorter than the Cl-B bonds to the ring boron atoms. Reactions of (Cl 2 BN=BCl) 3 with Me 3 SiNMe 2 allows a successive Cl/Me 2 N exchange. Depending on the molar ratio, the compounds [Cl

2,2,6,6‐Tetramethylpiperidine (tmpH) reacts smoothly with aluminum trihalides AlX3 (X = Cl, Br, I) and monochloroalane AlH2Cl · 2 thf to give the addition compounds tmpH · AlX3 (X = Cl, Br, I) and tmpH · AlH2Cl, respectively. These adducts of the secondary amine tmpH are stable and do not undergo intramolecular elimination of HX or H2 with formation of the aminoalanes tmpAlX2 or tmpAl(H)Cl. In the solid state, tmpH · AlX3 (X = Cl, Br, I) and tmpH · AlH2Cl are tetracoordinated molecular adducts. While this is also true for solutions of tmpH · AlX3 (X = Br, I) and tmpH · AlH2Cl, the compound tmpH · AlCl3 dissolves in CH2Cl2 as the salt [tmpAlCl3]tmpH2 and the adduct tmpH · Al2Cl6, as is evident from its NMR spectra and from conductivity measurements. This behavior is supported by a semiempirical AM1 calculation.

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