Diagonally Related s‐ and p‐Block Metals Join Forces: Synthesis and Characterization of Complexes with Covalent Beryllium–Aluminum Bonds

Abstract

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(DipNacnac)] (DipNacnac=[(DipNCMe)2CH]−, Dip=2,6‐diisopropylphenyl), have yielded the first examples of compounds with beryllium–aluminum bonds, [(DipNacnac)(X)Al‐Be(X)(tmeda)]. For sake of comparison, isostructural Mg–Al and Zn–Al analogues of these complexes, viz. [(DipNacnac)(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 [(DipNacnac)(Br)Al‐Be(Br)(tmeda)] are reported.

The unique β-diketiminate ligand in aluminum(i) and gallium(i) chemistry

“…The isostructural Mg-Al (19) and Zn-Al (20) analogues of these complexes have been isolated in the 1 : 1 reaction of Dipp NacNacAl(I) (1) with [MgI 2 (tmeda)] and [ZnBr 2 (tmeda)], respectively (Scheme 5). 25 The composition of compound 20 was confirmed by means of single-crystal X-ray structural analysis ( Fig. 3).…”

Hydrostibination

“…Diagonal relationships between elements based on valency,e lectronegativity,c harge/volume ratio,o rf rontier orbital similarity (isolobality) are ap owerful organizing concept for predicting structure,b onding,a nd reactivity in the main group elements.T his notion is usually applied for element pairs from adjacent periodic groups with principle quantum numbers n/n + 1, as shown by the comparative chemistry of the Li/Mg, Be/Al, B/Si, and C/P element pairs. [1] Recently we reported bismuth and antimony triamides whose molecular and electronic structures were strongly reminiscent of boranes because each featured an eutral, planar, trivalent p-block atom expressing av acant p-orbital perpendicular to the molecular plane (compare Figure 1aand b). [2] Given that the Pauling electronegativities of boron (2.04), bismuth (2.02), and antimony (2.05) are also similar, we were interested in exploring the nonintuitive diagonal relationship between the lightest p-block element and the heaviest Group 15 elements.I nt his context it is also noteworthy that the LUMO of binary halides SbX 3 and BiX 3 (X = F, Cl, Br,I)under the C 3v point group is an equal sum of two E À X s*o rbitals and bears as triking resemblance to the vacant p-orbital of boranes ( Figure 1c).…”

A Stable Calcium Alumanyl

“…Both the Mg1 and Al1 centers of compound 15 are unambiguously three‐coordinate (closest Al−C separation 4.965 Å) and the two N ‐donor ligand systems are almost orthogonal (Figure a), such that the dihedral angle subtended by the N1−Al1−N2 and N3−Mg1−N4 mean planes is 84.1°. Although the Mg1‐Al1 bond in 15 [2.7980(6) Å] is longer than the comparable length in compound 8 [2.696(1) Å], it is commensurate with the corresponding distances observed in compounds 3 [2.7687(8) Å] and 4 [2.7687(5) Å], which also comprise magnesium coordinated by the Dipp BDI ligand, and in Jones’ derivative, [(TMEDA)(I)Mg‐Al(I)( Dipp BDI)] [2.727(2) Å] …”