Bis(σ-B–H) complexes of copper(i): precursors to a heterogeneous amine–borane dehydrogenation catalyst

Abstract

A series of bis(σ-B-H) complexes of copper(i) have been prepared by displacement of arene solvent from a β-diketiminate copper(i) complex by four-coordinate boranes, H3B-L (L = NMe3, lutidine). In the presence of the same copper arene complex, the secondary amine-borane H3B-NMe2H undergoes dehydrogenation. We provide evidence for formation of a heterogengous catalyst from decomposition of the solution species.

Selective Reduction of CO2 to a Formate Equivalent with Heterobimetallic Gold‐ ‐ ‐Copper Hydride Complexes

“…[21,44,45] Ther eversible dissociation of 2·Au was confirmed by reaction with PCy 3 ,which resulted in the trapping of the copper(I) fragment as 2·PCy 3 (see the Supporting Information, Figure S4). Va riable temperature (VT) NMR analysis of 1·Au and 2·Au resulted in the observation of both sides of the equilibrium at low temperature (1·Au:2 13 K; 2·Au:2 53 K), and allowed vantH off analysis with 2·Au to give the thermodynamic parameters DH8 8 = À0.1 kcal mol À1 , DS8 8 = À9.3 cal K À1 mol À1 , and DG8 8 298 =+2.7 kcal mol À1 .T hese values are consistent with the weak and reversible binding previously reported for s-complexes of copper(I).…”

Design, Synthesis, and Chemistry of Bis(σ)borate and Agostic Complexes of Group 7 Metals

“…These results circuitously specify some "bending" of the s(BÀH) bond critical paths toward Mn. This is av ery similare nvironment to that of the [30] (L = lutidine), and is consistent with two 3c-2e interactions (1:F igure3; 3:F igure S4 in the Supporting Information). The electron density,L aplacian of the electron density,a nd ellipticity values at the bcps of selected bonds are listed in Table S6 in the Supporting Information.…”

Experimental and Theoretical Evidence for an Agostic Interaction in a Gold(III) Complex

“…Compared to other transition metals,c omplexes containing coinage metals tend to behave singularly,t hat is,t he formation of s bonds within their complexes remains extremely rare.Afew s complexes of Cu have been recently characterized (Figure 1), [4][5][6][7] but the question of whether or not s complexes with gold can exist remains an open question. [8] Thep resence of short Au···H(C) contacts has been identified in af ew gold(I) and gold(III) complexes,a nd the possible existence of agostic interactions in gold complexes has been speculated upon.…”

“…[2,3] Over the years,the presence of agostic interactions has been documented in numerous complexes.Alarge body of experimental and theoretical data has been progressively collected providing in-depth understanding of the scope, nature,a nd characteristics of this weak metal-ligand interaction. Agostic interactions are not only of fundamental interest, but they have also been found to play amajor role in the reactivity of many organometallic species.They have been found to be ubiquitous in all C À Ha ctivation processes, regardless of the associated mechanism (for example oxidative addition, s-metathesis,orb À He limination).Compared to other transition metals,c omplexes containing coinage metals tend to behave singularly,t hat is,t he formation of s bonds within their complexes remains extremely rare.Afew s complexes of Cu have been recently characterized (Figure 1), [4][5][6][7] but the question of whether or not s complexes with gold can exist remains an open question. [8]…”