Ambiphilic Al-Cu Bonding

Abstract

Copper-alumanyl complexes, [LCu-Al(SiN^Dipp )], where L=carbene=NHC^iPr (N,N'-diisopropyl-4,5-dimethyl-2-ylidene) and ^Me2 CAAC (1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) and featuring unsupported Al-Cu bonds, have been prepared. Divergent reactivity observed with carbodiimides and CO₂ implies an ambiphilicity in the Cu-Al interaction that is dependent on the identity of the carbene co-ligand.

Keywords: aluminum; coordination modes; copper; ligand effects; metal-metal interactions.

Scheme 1

Examples of nucleophilic gold molecules.

Scheme 2

Catalytic reduction of CO₂ by [(IPr)CuBpin] (VII) and the structure of X.

Scheme 3

Syntheses of carbene‐stabilized copper‐alumanyl complexes 1 and 2.

Figure 1

Displacement ellipsoid plot of a) compound 1 and b) compound 2 (30 % probability ellipsoids). Dipp substituents are shown as wireframe and hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]; 1: Cu1‐Al1 2.3449(4), Cu1‐C31 1.9529(12), Al1‐N1 1.8455(10), Al1‐N2 1.8473(10), C31‐Cu1‐Al1 178.85(4), N1‐Al1‐N2 112.05(5), N1‐Al1‐Cu1 123.41(4), N2‐Al1‐Cu1 124.54(3); 2: Cu1‐Al1 2.4028(7), Cu1‐C31 1.964(2), Al1‐N1 1.8668(18), Al1‐N2 1.8546(18), C31‐Cu1‐Al1 173.42(6), N1‐Al1‐N2 110.96(8).

Scheme 4

Reaction of copper‐alumanyl complexes 1 and 2 with N,N′‐diisopropylcarbodiimide and ¹³CO₂.

Figure 2

Displacement ellipsoid plot of a) compound 3 and b) compound 4 (30 % probability ellipsoids). Dipp substituents are shown as wireframe and hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]; 3: Cu1‐N6 1.8846(15), Cu1‐C31 1.8959(18), Al1‐N1 1.8425(14), Al1−N2 1.8411(14), Al1‐N5 1.8693(14), Al1‐C42 1.9554(17), N6‐Cu1‐C31 174.70(7), N1‐Al1‐N5 115.08(6); 4: Cu1‐C31 1.919(3), Cu1‐C51 1.960(3), Al1‐N1 1.860(2), Al1‐N2 1.862(2), Al1‐N4 1.908(2), Al1‐N5 1.923(2), C31‐Cu1‐C51 173.82(13).

Figure 3

Displacement ellipsoid plot of compound 6 (30 % probability ellipsoids). Dipp substituents are shown as wireframe and hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]; Cu1‐C31 1.894(2), Cu1‐C51 1.902(2), Al1‐O1 1.8563(16), Al1‐O2 1.8405(17), Al1‐N1 1.8096(19), Al1‐N2 1.8125(18), C31‐Cu1‐C51 171.16(10), O2‐Al1‐O1 71.34(7).