Search

Reaction of a lithium boryl, [(THF)2 Li{B(DAB)}] (DAB=[(DipNCH)2 ]2- , Dip=2,6-diisopropylphenyl), with a dinuclear magnesium(I) compound [{(Mes Nacnac)Mg}2 ] (Mes Nacnac=[HC(MeCNMes)2 ]- , Mes=mesityl) unexpectedly afforded a rare example of a terminal magnesium boryl species, [(Mes Nacnac)(THF)Mg{B(DAB)}]. Attempts to prepare the magnesium boryl via a salt metathesis reaction between the lithium boryl and a β-diketiminato magnesium iodide compound, instead led to an intractable mixture of products. Similarly, reaction of the lithium boryl with a β-diketiminato beryllium bromide precursor, [(Dep Nacnac)BeBr] (Dep=2,6-diethylphenyl) did not give a beryllium boryl, but instead afforded an unprecedented example of a beryllium substituted diazaborole heterocycle, [{(Dep Nacnac)Be(4-DAB-H )}BBr]. For sake of comparison, the same group 2 halide precursor compounds were treated with a potassium gallyl analogue of the lithium boryl, viz. [(tmeda)K{:Ga(DAB)}] (tmeda=N,N,N',N'-tetramethylethylenediamine), but no reactions were observed.

Reactions of two magnesium(I) compounds, [{(Ar Nacnac)Mg}2 ] (Ar Nacnac=[HC(MeCNAr)2 ]- ; Ar=mesityl (Mes) or o-xylyl (Xyl)), with CO in the presence of [Mo(CO)6 ] lead to the reductive hexamerization of CO, and formation of magnesium benzenehexolate complexes, [{(Ar Nacnac)Mg}6 (C6 O6 )]. [Mo(CO)6 ] is not consumed in these reactions, but is apparently required to initiate (or catalyze) the CO hexamerizations. A range of studies were used to probe the mechanism of formation of the benzenehexolate complexes. The magnesium(I) reductive hexamerizations of CO are closely related to Liebig's reduction of CO with molten potassium (to give K6 C6 O6 , amongst other products), originally reported in 1834. As the mechanism of that reaction is still unknown, it seems reasonable that magnesium(I) reductions of CO could prove useful homogeneous models for its elucidation, and for the study of other C-C bond forming reactions that use CO as a C1 feedstock (e.g. the Fischer-Tropsch process).

Reactions of the beryllium dihalide complexes [BeX2 (OEt2 )2 ] (X=Br or I) with N,N,N',N'-tetramethylethylenediamine (TMEDA), a series of diazabutadienes, or bis(diphenylphosphino)methylene (DPPM) have yielded the chelated complexes, [BeX2 (TMEDA)], [BeX2 {(RN=CH)2 }] (R=tBu, mesityl (Mes), 2,6-diethylphenyl (Dep) or 2,6-diisopropylphenyl (Dip)), and the non-chelated system, [BeI2 (κ1 -P-DPPM)2 ]. Reactions of lithium or potassium salts of a variety of β-diketiminates have given both three-coordinate complexes, [{HC(RCNAr)2 }BeX] (R=H or Me; Ar=Mes, Dep or Dip; X=Br or I); and four-coordinate systems, [{HC(MeCNPh)2 }BeBr(OEt2 )] and [{HC(MeCNDip)(MeCNC2 H4 NMe2 }BeI]. Alkali metal salts of ketiminate, guanidinate, boryl/phosphinosilyl amide, or terphenyl ligands, lead to dimeric [{BeI{μ-[(OCMe)(DipNCMe)]CH}}2 ], and monomeric [{iPr2 NC(NMes)2 }BeI(OEt2 )], [κ2 -N,P-{(HCNDip)2 B}(PPh2 SiMe2 )NBeI(OEt2 )] and [{C6 H3 Ph2 -2,6}BeBr(OEt2 )], respectively. Compound [{HC(MeCNPh)2 }BeBr(OEt2 )] undergoes a Schlenk redistribution reaction in solution, affording the homoleptic complex, [{HC(MeCNPh)2 }2 Be]. The majority of the prepared complexes have been characterized by X-ray crystallography and multi-nuclear NMR spectroscopy. The structures and stability of the complexes are discussed, as is their potential for use as precursors in poorly developed low oxidation state beryllium chemistry.

Chemistry freshmen learn to distinguish between nitrate NO 3 − and nitrite NO 2 − or sulfate SO 4 2− and sulfite SO 3 2− , but how many would know about carbonite CO 2 2− in contrast to carbonate CO 3 2− ? This is not surprising for an anion that has never been observed in solution. However, it might be a crucial intermediate in the reductive activation of CO 2 . This review will track back carbonite and reflect on its relevance to carbon dioxide binding in metal complexes.

Additions of beryllium-halide bonds in the simple beryllium dihalide adducts, [BeX2 (tmeda)] (X=Br or I, tmeda=N,N,N',N'-tetramethylethylenediamine), across the metal center of a neutral aluminum(I) heterocycle, [:Al(Dip Nacnac)] (Dip Nacnac=[(DipNCMe)2 CH]- , Dip=2,6-diisopropylphenyl), have yielded the first examples of compounds with beryllium-aluminum bonds, [(Dip Nacnac)(X)Al-Be(X)(tmeda)]. For sake of comparison, isostructural Mg-Al and Zn-Al analogues of these complexes, viz. [(Dip Nacnac)(X)Al-M(X)(tmeda)] (M=Mg or Zn, X=I or Br) have been prepared and structurally characterized. DFT calculations reveal all compounds to have high s-character metal-metal bonds, the polarity of which is consistent with the electronegativities of the metals involved. Preliminary reactivity studies of [(Dip Nacnac)(Br)Al-Be(Br)(tmeda)] are reported.