Dialumination of unsaturated species with a reactive bis(cyclopentadienyl) dialane

Abstract

A new bis(cyclopentadienyl) dialane is prepared, which shows controlled, selective dialumination reactions with a conventional alkyne, an electron-rich alkyne, and an azide. The reactions provide structurally diverse products, featuring a range of aluminium coordination numbers, cyclopentadienyl binding modes, and cyclic motifs. The variable nature of the bonding in the Cp*Al units allows a range of binding modes depending on the electronic requirements of the Al atom and provides new possibilities to the chemistry of dialanes, as demonstrated by the isolation of a double internal Lewis adduct with "ring-slipped" Cp* rings in this work.

Lewis‐Base‐Induced Disproportionation of a Dialane

“…Interestingly, the unit cell of 3 contains four independent molecules, one bindingi nah 1 mode (3a)a nd three with the Cp* ligand adopting an h 5 binding mode (3b). The individual AlÀC Cp* bond lengths in the h 5 system differ from around2 .21 to 2.36 .T he distances between Al and the Cp* centroids (1.928 )a re, as expected, slightly shorter than the AlÀCd istance of the h 1 -coordinated species (1.996 (10) ). The latterv alue is similar to that reported for [Cp*AlI 2 ](OEt 2 )( 1.99 (3) ).…”

“…The Cp* units both exhibit an η 1 coordination mode, whereas the Al−C Cp* distance (2.102(5) Å) is significantly longer than that of 11 (2.006(4) Å). In the initial report, the Br‐Al‐Al‐Br torsion angle of 1 (102.04(5)°) was found to deviate greatly from the expected angle (180°), and an even greater deviation was observed for [Cp*AlI] 2 (91.14(3)°) . In contrast, the torsion angles X‐Al‐Al‐X (X=Br, N, C) around the Al−Al bond in 12 are exactly 180°.…”

“…All syntheses were carried out in an Argon‐filled glovebox or with standard Schlenk techniques unless otherwise stated. [Cp*AlBr 2 ], [AlBr(η 5 ‐Cp*)] 2 , and [RhPMe 3 Cl] were prepared as described previously . All solvents were dried by distillation over appropriate drying agents and stored over molecular sieves.…”

“…However, to the best of our knowledge, the reverse reaction has never been observed, that is, the controlled disproportionation of an Al II species into Al I and Al III products. We recently reported the synthesis of a new Cp*‐based dialane, [Cp*AlBr] 2 ( 1 ), and demonstrated its insertion reactivity with organic compounds . Herein, we present the reaction of 1 towards several Lewis bases, leading to a Lewis‐base‐induced disproportionation of a dialane into Al I and Al III species.…”

“…We recently reported the synthesis of a new Cp*-based dialane, [Cp*AlBr] 2 (1), and demonstrated its insertionr eactivity with organic compounds. [10] Herein, we present the reactiono f1 towards several Lewis bases,l eadingt oa Lewis-base-induced disproportionation of ad ialane into Al I and Al III species. Furthermore, we present the formation of several new Cp*-containing Lewis base adducts, aR h ÀAl metalonly Lewispair (MOLP), asw ellasadialane bis-adduct.…”