Reactions of Amides with Organoaluminum Compounds:  Factors Affecting the Coordination Mode of Aluminum Amidates

Abstract

Factors affecting the coordination mode of an amidato group on aluminum will be presented. The reaction of N-tert-butylalkylacetamide ((t)BuNHCR([double bond]O)) with 1.1 molar equiv of Me(3)Al in refluxing hexane affords a pentacoordinated, dimeric compound [Me(2)Al[eta(2)-(t)BuNC(R)(mu(2)-O)]](2) (3, R = p-(t)Bu-C(6)H(4); 4, R = 2,6-F,F-C(6)H(3); 5, R = Me; 6, R = CF(3); 7, R = p-F(3)C-C(6)H(4)). However, in the presence of 2.2 molar equiv of Me(3)Al, N-tert-butyl-4-tert-butylbenzamide ((t)BuNHC(p-(t)Bu-C(6)H(4))([double bond]O in refluxing hexane gives [Me(2)Al[eta(2)-(t)BuNC(p-(t)Bu-C(6)H(4))(mu(2)-O)]AlMe(3)], 8. In contrast, the reaction of R'NHCR' '([double bond]O) with 1 molar equiv of R(3)Al at room temperature produces tetracoordinated, dimeric, eight-membered ring aluminum compounds [R(2)Al[mu,eta(2)-R'NC(R' ')O]](2) (9, R = Me, R' = 2,6-(i)Pr, (i)()Pr-C(6)H(3), R' ' = Ph; 10, R = Me, R' = (i)Bu, R' ' = Ph; 11, R = Et, R' = Bn, R' ' = Ph; 12, R = Me, R' = Ph, R' ' = CF(3); 13, R = Me, R' = Bn, R' ' = CF(3)). On the other hand, 4'-chlorobenzanilide ((p-Cl-C(6)H(4))NHCPh([double bond]O)) reacts with R(3)Al to produce trimeric, twelve-membered ring aluminum compounds [R(2)Al[mu, eta(2)-(p-Cl-C(6)H(4))NC(Ph)O]](3) (14, R = Me; 15, R = Et). Furthermore, the reaction of 2'-methoxybenzanilide with 1 molar equiv of Me(3)Al in hexane yields a dinuclear aluminum complex [Me(2)Al(o-OMe-Ph)NC(Ph)(O)AlMe(3)], 16.

Synthesis, structures and ε-caprolactone polymerization activity of aluminum N,N′-dimethyloxalamidates

“…Similarly to the dimeric and trimeric aluminum monoamidates {R 2 Al[l,g 2 -R'NC(R 00 )O]} n (n = 2, 3) [7,8], each of the aluminum atoms is bonded to two alkyl groups, and oxygen and nitrogen atoms originating from two different amidate groups which are a part of the same N,N 0 -dimethyloxalamidate unit. The geometry around the aluminum atoms is a distorted tetrahedron.…”

“…Recently tris-amidate aluminum complex was proposed as the catalyst resting state in a transamidation reaction between simple secondary carboxamides and primary amines [3]. According to literature data, the structure of alkyl aluminum amidates and coordination mode of amidato ligands on aluminum depend strongly on bulkiness of amidate units and alkyl groups bonded to aluminum atoms [4][5][6][7][8]. Electronic effects originating from aromatic substituents are also important.…”

“…Thermal ellipsoids are shown at the 50% level. Selected bond lengths (Å) and bond angles (°)109.92(8). (Bottom) View of the molecule showing that two fused central cycles and two N(1)-C(2) bonds are situated in one plane.…”

An Unusual N‐Bridged (Amido)(hydrido)(phenoxido)aluminium Dinuclear Compound – The Role of Nitrogen Substituents in Determining Nuclearity: A Combined Experimental and Theoretical Study

“…[37,51] Examples are known with both O and N atoms bridging in hydroxypyridine ligands (in an isolobal disposition to carboxylatebridged ligands) [25] or with an amidate group [52][53][54][55] between two aluminium atoms.…”

“…[25,60] In addition, a discussion of the factors affecting the coordination modes of amidate ligands to aluminium has been reported. [55] Thus, we started a computational study in order to clarify and rationalize the structural behaviour observed in the final products obtained in the treatment of AlH 3 ·NEtMe 2 with iminophenol and aminophenol compounds, depending on the nitrogen substituents.…”