Reactions of the Aluminum(<scp>I</scp>) Monomer LAl [L = HC{(CMe)(NAr)}₂; Ar = 2,6‐<i>i</i>Pr₂C₆H₃] with Imidazol‐2‐ylidene and Diphenyldiazomethane. A Hydrogen Transfer from the L Ligand to the Central Aluminum Atom and Formation of the Diiminylaluminum Compound LAl(N=CPh₂)₂

Abstract

Abstract The solid‐state reaction of LAl and imidazol‐2‐ylidene at elevated temperature (120 °C) yielded the aluminum monohydride N ‐heterocyclic carbene adduct [{HC[C(CH 2 )NAr] (CMeNAr)}AlH‐{CN(R)C 2 Me 2 N(R)}] [R = i Pr ( 1 ), Me ( 2 )]. Compounds 1 and 2 have been characterized by spectroscopic (IR, and 1 H and 13 C NMR), mass spectrometric, and elemental analyses, and 1 was further characterized by X‐ray structural analysis. These experimental data indicate that the Al−H bond is formed by hydrogen migration from one of the methyl groups of the β‐diketiminato ligand backbone. The reaction of LAl with two equivalents of diphenyldiazomethane afforded the diiminylaluminum compound LAl(N=CPh 2 ) 2 ( 3 ), while an excess of diphenyldiazomethane resulted in the formation of Ph 2 C=N−N=CPh 2 . This suggests that Ph 2 C=N−N=CPh 2 is initially generated and then reacts further by oxidative addition to yield 3 . The X‐ray structural analysis reveals that compound 3 contains the shortest Al−N iminyl bond among those with a four‐coordinate aluminum center. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)