An Aluminum Hydride That Functions like a Transition‐Metal Catalyst

Abstract

Scheme 1. Synthesis of aluminummonohydride complex 1. Ar = 2,6-iPr 2 C 6 H 3 ,T f= SO 2 CF 3 .

Aluminum Hydrides Stabilized by N‐Heterocyclic Imines as Catalysts for Hydroborations with Pinacolborane

“…of HBpin with 1 equiv. of carbonyl‐functionalized substrate with the addition of 4 mol % of 2 in C 6 D 6 (Table ) . For aldehydes, the O‐borylated products of type B formed in high yield within 1 d at room temperature as concluded from 1 H NMR spectroscopic analysis.…”

“…Very recently, Roesky and co‐workers have demonstrated the catalytic activity of 1,3‐diketimino‐bonded aluminum hydrides ( IV , V , Figure ) in the hydroboration of terminal alkynes, as well as of carbonyl groups with pinacolborane (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane, HBpin). [11c], Until the upcoming of these most remarkable results the field of catalytic hydroboration with dioxaborolanes (e.g. HBpin, catecholborane) had mostly been limited to transition‐metal complexes , .…”

“…Inspired by the outstanding findings of Roesky and co‐workers, we set out to test our NHI‐substituted aluminum hydrides for activity in catalytic hydroborations using HBpin. [11c], Herein, we report the synthesis of the novel dimeric aluminum hydride {L Mes NAl(H)OTf} 2 ( 2a ) and its application in catalytic hydroboration of selected aldehydes and ketones (L Mes N = 1,3‐dimesityl‐imidazolin‐2‐imino, Mes = 2,4,6‐trimethylphenyl, Tf = triflyl). Moreover, the earlier reported aluminum hydrides {L Mes NAlH 2 } 2 ( 1a ), {L Dip NAlH 2 } 2 ( 1b ), and {L Dip NAl(H)OTf} 2 ( 2b ) were also examined with regard to their use as a catalyst in the hydroboration of alkynes and carbonyl compounds, respectively (L Dip N = 1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐imino).…”

Recent Developments on the Use of Group 13 Metal Complexes in Catalysis

“…Not too surprisingly,t he potentialo fs everal well-defineda luminum-based Lewis acids has been investigated, though studies in the area remainl imited. The compound [Al(H)OTf(nacnac)] (5,S cheme 5) was shown to be an active catalyst for the hydrosilylation and hydroboration of aldehydes and ketones, [38] whereas the strong Lewis acid Al(C 6 F 5 ) 3 was significantly less active than its boron congener B(C 6 F 5 ) 3 (Scheme 5, top). [22] This was attributed to the formation of the more stable Al···O = CR 2 adduct preventing the necessary Si-H activation for the reduction.…”

Synthesis and Characterization of a Tripodal Tris(nitroxide) Aluminum Complex and Its Catalytic Activity toward Carbonyl Hydroboration

“…The application of aluminum complexes as catalysts for the reduction of organic substrates has gained traction in recent years, 11 including systems for the hydroboration of carbonyls. 12,13 In comparison to those systems, our catalyst is less active and higher catalyst loadings are required to obtain similar yields. We attribute this at least partially to a different mechanism for our catalyst.…”