Isolable Copper(I) η²-Cyclopropene Complexes

Abstract

Treatment of bis­(pyrazolyl)­borate ligand supported [(CF3)2Bp]­Cu­(NCMe) with 1,2,3-trisubstituted cyclopropenes produced thermally stable copper­(I) η2-cyclopropene complexes amenable to detailed solution and solid-state analysis. The [(CF3)2Bp]­Cu­(NCMe) also catalyzed [2 + 1]-cycloaddition chemistry of terminal and internal alkynes with ethyl diazoacetate affording cyclopropenes, including those used as ligands in this work. The tris­(pyrazolyl)­borate [(CF3)2Tp]­Cu­(NCMe) is a competent catalyst for this process as well. The treatment of [(CF3)2Tp]Cu with ethyl 2,3-diethylcycloprop-2-enecarboxylate substrate gave an O-bonded rather than a η2-cyclopropene copper complex.

Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate

“…The remaining hydrogen atoms were included in their calculated positions and refined as riding on the atoms to which they are joined. X-ray structural figures were generated using Olex2 [96] (6) [6]. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html (accessed on 7 December 2021) or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge, CB2 1EZ, UK).…”

“…We also discovered that the mononuclear, bis(pyrazolyl)borate [H 2 B(3,5-(CF 3 ) 2 Pz) 2 ]Cu(NCMe) (1, Pz = pyrazolyl; Figure 1) is an excellent mediator of cyclopropenation chemistry of alkynes with ethyl diazoacetate. [6] Molecules 2021, 26, x FOR PEER REVIEW 2 of 16 complexes of copper pyrazolates show interesting luminescence [46]. We also discovered that the mononuclear, bis(pyrazolyl)borate [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) (1, Pz = pyrazolyl; Figure 1) is an excellent mediator of cyclopropenation chemistry of alkynes with ethyl diazoacetate.…”

“…Over the past few years, we have been working on the coordination chemistry [42][43][44][45][46][47] and transformations [6,[47][48][49] of alkynes involving copper. For example, we demonstrated that the trinuclear copper(I) pyrazolate {µ-[3,5-(CF 3 ) 2 Pz]Cu} 3 [50] is an effective catalyst for facile azide-alkyne cycloaddition leading to 1,2,3-triazoles, alkyne C(sp)-H bond carboxylation with CO 2 , and S-H addition to alkyne moiety [47].…”

“…We also discovered that the mononuclear, bis(pyrazolyl)borate [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) (1, Pz = pyrazolyl; Figure 1) is an excellent mediator of cyclopropenation chemistry of alkynes with ethyl diazoacetate. [6] Figure In this work, we describe the use of [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) as a catalyst in azide-alkyne cycloaddition chemistry between p-tolylazide and several alkynes including acetylene and trimethylsilylacetylene. We also describe the isolation of an acetylene complex as well as larger alkyne complexes involving the copper bis(pyrazolyl)borate moiety [H2B(3,5-(CF3)2Pz)2]Cu.…”

“…Copper is an important metal in alkyne chemistry. It mediates a number of transformations of acetylene as well as larger alkynes including cycloaddition chemistry [ 1 , 2 , 3 , 4 , 5 ], cyclopropenation [ 6 , 7 , 8 ]. Terminal and Internal Alkyne Complexes and Azide-alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate partial hydrogenation, [ 9 , 10 ] hetero atom-hydrogen bond additions [ 11 , 12 , 13 , 14 , 15 , 16 ], C sp -H bond functionalizations, and alkyne coupling processes [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”