s‐Block Metal–Metal Bonds

Facile Benzene Reduction by a Ca2+/AlI Lewis Acid/Base Combination

“…[9] Since the C-Al-C angle is also unusually small (77.2(1)8 8 vs.1 17.4(1)8 8 in (BDI)AlMe 2 ), [13] the long AlÀCb onds are likely caused by ring strain and/or steric repulsion with the bulky BDI ligand. [17] Thec oordination sphere of the significantly larger Ca 2+ ion is completed by aC 6 19 FNMR spectra are as expected, an 27 Al NMR signal could not be detected. It is clear from the CÀ Cbond distances in the C 6 H 6 2À ring that both negative charges are located at the opposing flagpole carbon centers C1 and C4.…”

“…[1] Thev ery potent Lewis acidity of these cationic complexes is most convincingly illustrated by the synthesis of aMg-silyl ether complex (IV) [2] with the simple silyl ether (Me 3 Si) 2 O, and on account of negative hyperconjugation of its Olone pairs,itisnotoriously inert to metal bonding. [5] These adducts have been shown to exist in solution as well but are generally in at emperatureand concentration-dependent equilibrium with the naked cationic species I.T oa ssess the limits of the coordination chemistry of these highly Lewis acidic Ae cations,w e ventured into the highly topical area of metal-metal bonding, [6] aiming to prepare ac ationic heterobimetallic Ae-Al complex (V)b yc omplexation of (BDI)Ae + with the stable well-known Al I complex (BDI)Al I . [7] Since directly bound Ca-Al complexes are hitherto unknown we directed our research activities especially towards the synthesis of the (BDI)Ca + -Al I (BDI) cation.…”

“…[1][2][3] In contrast to previous work on (BDI)Ae + · (pyridine) 3 complexes, [4] our (BDI)Ae + complexes are completely free of additional Lewis bases.T hese naked cations show an extraordinary Lewis acidity that exceeds that of the benchmark Lewis acid B(C 6 F 5 ) 3 .T his acidity has been demonstrated by the syntheses of as et of robust (BDI)Ae + · (arene) complexes (II) [1,3] and the isolation of the first unsupported Mg-alkyne complex (III). [5] These adducts have been shown to exist in solution as well but are generally in at emperatureand concentration-dependent equilibrium with the naked cationic species I.T oa ssess the limits of the coordination chemistry of these highly Lewis acidic Ae cations,w e ventured into the highly topical area of metal-metal bonding, [6] aiming to prepare ac ationic heterobimetallic Ae-Al complex (V)b yc omplexation of (BDI)Ae + with the stable well-known Al I complex (BDI)Al I . [5] These adducts have been shown to exist in solution as well but are generally in at emperatureand concentration-dependent equilibrium with the naked cationic species I.T oa ssess the limits of the coordination chemistry of these highly Lewis acidic Ae cations,w e ventured into the highly topical area of metal-metal bonding, [6] aiming to prepare ac ationic heterobimetallic Ae-Al complex (V)b yc omplexation of (BDI)Ae + with the stable well-known Al I complex (BDI)Al I .…”

Topological analysis of the metal-metal bond: A tutorial review

“…All the combinations of alkali metal diatomic molecules have been observed either in the gas phase or at very low temperature in solids. Although no stable complex involving two bonded group 1 elements have been reported so far [15], neutral and charged clusters, M n or M a+ n have been studied by quantum chemical techniques. QTAIM studies have been reported for Li 2 [105][106][107], Na 2 and Na 4 [105], Li n planar clusters (n = 4, 5, 6) [106].…”

“…It opened the way of a rich chemistry of multiple M-M bonding in bimetallic complexes [8][9][10] as illustrated by the Cr-Cr distances ranging from 1.7056 Å [11] to 2.498 Å in the bulk metal and even to 2.612 Å [12]. The wealth and diversity of M-M bonding across the transition element series has no equivalent in rare-earth metals, but recent compounds involving heavy main group elements such as Sn, Pb, Sb or Bi complexes [13][14][15] challenges the long-held assumption that multiple bonds are stable only between first-row elements.…”