The synthesis of mono‐NHC alane adducts of the type (NHC)⋅AlH3 (NHC=Me2Im (1), Me2ImMe (2), iPr2Im (3 and [D3]‐3), iPr2ImMe (4), Dipp2Im (10); Im=imidazolin‐2‐ylidene, Dipp=2,6‐diisopropylphenyl) and (NHC)⋅AliBu2H (NHC=iPr2Im (11), Dipp2Im (12)) as well as their reactivity towards different types of carbenes is presented. Although the mono‐NHC adducts remained stable at elevated temperatures, ring expansion occurred when (iPr2Im)⋅AlH3 (3) was treated with a second equivalent of the carbene iPr2Im to give (iPr2Im)⋅AlH(RER‐iPr2ImH2) (6). In 6, {(iPr2Im}AlH} is inserted into the NHC ring. In contrast, ring opening was observed with the sterically more demanding Dipp2Im with the formation of (iPr2Im)⋅AlH2(ROR‐Dipp2ImH2)H2Al⋅(iPr2Im) (9). In 9, two {(iPr2Im)⋅AlH2} moieties stabilize the ring‐opened Dipp2Im. If two hydridic sites are blocked, the adducts are stable with respect to further ring expansion or ring opening, as exemplified by the adducts (iPr2Im)⋅AliBu2H (11) and (Dipp2Im)⋅AliBu2H (12). The adducts (NHC)⋅AlH3 and (iPr2Im)⋅AliBu2H reacted with cAACMe by insertion of the carbene carbon atom into the Al−H bond to give (NHC)⋅AlH2/iBu2(cAACMeH) (13–18) instead of ligand substitution, ring‐expansion, or ring‐opened products.

The synthesis and characterization of N-Heterocyclic carbene (NHC) and cyclic (alkyl)(amino)carbene (cAAC) gallane and chlorogallane adducts of the type (NHC)∙GaH3 (NHC = Me2ImMe 1, iPr2Im 2 and Dipp2ImH 3; Me2ImMe...

The NHC alane and gallane adducts (NHC)•AlH 2 I (NHC = Me 2 Im Me 7, iPr 2 Im 8, iPr 2 Im Me 9) and (NHC)•GaH 2 I (NHC = Me 2 Im Me 10, iPr 2 Im Me 11, Dipp 2 Im 12; R 2 Im = 1,3-diorganyl-imidazolin-2-ylidene; Dipp = 2,6-diisopropylphenyl; iPr = isopropyl; Me 2 Im Me = 1,3,4,5-tetra-methyl-imidazolin-2-ylidene) were prepared either by the simple yet efficient reaction of the NHC adduct (NHC)•AlH 3 with elemental iodine or by the treatment of (NHC)•GaH 3 with an excess of methyl iodide at room temperature. The reaction of one equivalent of the group [a] A

The structure of the complex MeCi CMe.H2Fe~(CO)8, isolated from the reaction of but-2-yne with alkaline solutions of iron hydrocarbonyl, has been determined by three-dimensional Fourier methods and refined by least-squares methods. The compound crystallizes in the monoclinic system, space group P2t/c, with four molecules in a unit cell of dimensions a=12.26, b=7.47, c=15-7 A, fl=97.5 °.The structure exhibits a number of novel features which include (i) a four-carbon chain chelated on to one of the iron atoms with which it forms single metal-carbon bonds, (ii) :~-bonds between this four-carbon chain and the second iron atom, (iii) the probability that one of the six Fe-C~O linkages is non-linear (168°). The metal-carbon separations can be classified into three groups of average length 2-13, 1-95 and 1-78 A. The latter is significantly shorter than the single-bond distance (1.95 A) and provides confirmation for the shortening of the metal-CO distance as a result of partial double-bond character. Carbon-oxygen separations correspond either to normal triple-bond carbonyl links (1.14 A) or to phenolic C-OH lengths (1-37 A) in agreement with chemical and spectroscopic evidence. The metal atoms are bonded together with a normal covalent Fe-Fe separation of 2.49 A.

We present herein the utilization of NHC-stabilized alane adducts of the type (NHC)·AlH 3 [NHC = Me 2 Im (1), Me 2 Im Me (2), iPr 2 Im (3), iPr 2 Im Me (4), Dipp 2 Im (5)] and (NHC)· AliBu 2 H [NHC = iPr 2 Im (6), Dipp 2 Im (7)] as novel hydride transfer reagents in the hydrodefluorination (HDF) of different fluoroaromatics and hexafluoropropene. Depending on the alane adduct used, HDF of pentafluoropyridine to 2,3,5,6-tetrafluoropyridine in yields of 15-99 % was observed. The adducts 1, 2, and 5 achieved a quantitative conversion into 2,3,5,6-tetrafluoropyridine at room temperature immediately after mixing the reactants. Studies on the HDF of fluorobenzenes with the (NHC)·AlH 3 adducts 1, 3, and 5 and (Dipp 2 Im)·AliBu 2 H (7) showed the decisive influence of the reaction temperature on [a] 4032 Scheme 3. Hydrodefluorination of hexafluorobenzene, pentafluorobenzene, and 1,2,4,5-tetrafluorobenzene using (NHC)·AlH 3 [NHC = Me 2 Im (1), iPr 2 Im (3), Dipp 2 Im (5)] and (Dipp 2 Im)·AliBu 2 H (7)..Eur. J. Inorg. Chem. 2018, 4031-4043 www.eurjic.org

The reaction of NHC alane adducts NHC·AlH3 (NHC = N‐Heterocyclic Carbene; NHC = iPr2Im, Dipp2Im; R2Im = 1,3‐di‐organyl‐imidazolin‐2‐ylidene; iPr = isopropyl; Dipp = 2,6‐diisopropylphenyl) with secondary amines HNR2 [R = iPr, Ph, Si(CH3)3] and the reaction of the trimethylamine alane adduct (NMe3)·AlH3 with secondary amines followed by the reaction with the NHC both lead to formation of the compounds NHC·AlH2(NR2) 1–6 [NHC = iPr2Im, Dipp2Im, R = iPr, Ph, Si(CH3)3]. These compounds are stable in solution up to temperatures of 90 °C. In contrast to the NHC alane adduct (iPr2Im)·AlH3 (I) and (Dipp2Im)·AlH3 (II), no ring expansion reaction to six‐membered heterocyclic rings or ring opening reaction were observed for the reaction of (iPr2Im)·AlH2(NR2) with another equivalent of the NHCs iPr2Im or Dipp2Im. Thus, amide substituted NHC alane adducts show a much high stability compared to the parent compounds NHC·AlH3. Furthermore, the reaction of NHC·AlH3 (NHC = iPr2Im, Dipp2Im) with 2,4,6‐trimethylphenol leads to the formation of the adducts NHC·AlH3–n(OMes)n 7–10 (n = 1, 2). The reaction with n ≥ 3 equivalent of 2,4,6‐trimethylphenol afforded the imidazolium salt [Dipp2ImH]+[Al(OMes)4]– (11). The compounds 7–11 are also stable with respect to ring expansion after addition of another equivalent NHC.

The cover picture for this issue in celebration of Werner Uhl's 65th birthday shows two of his favorites, aluminum compounds (from the professional side) and the mountains of the Alpes, which ask for a hike. In our article “Hydride Amide and Hydride Phenolate Complexes of NHC Coordinated Aluminum” we describe reactions of NHC alane adducts NHC∙AlH3 with some amines and phenolates, which lead with H2 elimination to the formation of complexes of the type NHC∙AlH2(NR2) and NHC∙AlH3-n(OAr)n (n = 1, 2). The crystal structures shown on the cover are those of the compounds Dipp2Im∙AlH2N{Si(CH3)3}2 3, Dipp2Im∙AlH2(OMes) 9 and Dipp2Im∙AlH2(OMes)2 10. More details can be found in the article by Andreas Hock, Heidi Schneider, Mirjam J. Krahfuß, and Udo Radius on page http://onlinelibrary.wiley.com/doi/10.1002/zaac.201800251/abstract.

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