Monoanionic, Bis(pyrazolyl)methylborate [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]⁻ as a Supporting Ligand for Copper(I)-ethylene, cis-2-Butene, and Carbonyl Complexes

Abstract

The monoanionic bidentate ligand [(PhB)CH(3,5-(CH)Pz))] has been prepared from lithium bis(pyrazolyl)methanide and triphenylborane. This useful new ligand is closely related to the well-established bis(pyrazolyl)borate and bis(pyrazolyl)methane ligands but has key differences to both analogues as well. The ethylene, cis-2-butene, and carbon monoxide adducts [(PhB)CH(3,5-(CH)Pz)]Cu(L) (where L = CH, cis-CHHC═CHCH, and CO) have been prepared from [(PhB)CH(3,5-(CH)Pz))]Li(THF), copper(I) triflate, and the corresponding coligand. These complexes have been characterized by NMR spectroscopy and X-ray crystallography. In all cases the bis(pyrazolyl) moiety is bound in κN fashion with the BPh group rotated to sit over the metal center, sometimes coordinating to the metal via phenyl carbons as in [(PhB)CH(3,5-(CH)Pz))]Li(THF) and [(PhB)CH(3,5-(CH)Pz)]Cu(CO) or simply hovering above the metal site as in [(PhB)CH(3,5-(CH)Pz))]Cu(CH) and [(PhB)CH(3,5-(CH)Pz))]Cu(cis-CHHC═CHCH). The C andH resonances of the ethylene carbon and protons of [(PhB)CH(3,5-(CH)Pz))]Cu(CH) appear at δ 81.0 and 3.71 ppm in CDCl, respectively. The characteristic CO frequency for [(PhB)CH(3,5-(CH)Pz)]Cu(CO) has been observed at υ̅ 2092 cm by infrared spectroscopy and is lower than that of free CO suggesting moderate M → CO π-back-donation. A detailed analysis of these complexes has been presented herein.

Single-Crystal-to-Single-Crystal Transformations of Metal–Organic-Framework-Supported, Site-Isolated Trigonal-Planar Cu(I) Complexes with Labile Ligands

“…To elucidate the Cu­(I) coordination environment, SCXRD data were collected using synchrotron radiation. , Close inspection of the diffraction data revealed a trigonal planar Cu­(I) complex comprised of two N atoms from L and an ethylene ligand, MnMOF-1 ·[Cu­(C 2 H 4 )]­BF 4 . The Cu–C bond lengths of 2.125(16) and 2.036(15) Å are comparable with those of analogous molecular complexes. ,, Analogous to our previous studies, ,, the charge-balancing anion (BF 4 – ) occupies a pocket within the MOF pore adjacent to the N,N′-chelated Cu­(I) center. Numerous three-coordinate, N,N′-chelated copper­(I) ethylene complexes have been reported in the literature and structurally characterized, ,,, highlighting the relative stability of the Cu–ethylene bond when suitably protected.…”

“…59,60 Close inspection of the diffraction data revealed a trigonal 16) and 2.036(15) Å are comparable with those of analogous molecular complexes. 50,61,62 Analogous to our previous studies, 10,12,63 the charge-balancing anion (BF 4 − ) occupies a pocket within the MOF pore adjacent to the N,N′-chelated Cu(I) center. Numerous three-coordinate, N,N′-chelated copper(I) ethylene complexes have been reported in the literature and structurally characterized, 45,50,62,64 highlighting the relative stability of the Cu− ethylene bond when suitably protected.…”

When SF5 outplays CF3: effects of pentafluorosulfanyl decorated scorpionates on copper

“…The CO stretching frequencies of [Ph 2 B(3-(SF 5 )Pz) 2 ]Cu(CO) and [Ph 2 B(3-(CF 3 )Pz) 2 ]Cu(CO) were observed at 2121 and 2117 cm −1 , respectively. For comparison, the (CO) for the highly fluorinated [H 2 B(3,5-(CF 3 ) 2 Pz) 2 ]Cu(CO) 20 and relatively electron rich [(Ph 3 B)CH(3,5-(CH 3 ) 2 Pz) 2 ]Cu(CO) 21 appear at 2127 and 2092 cm −1 , respectively. These data indicate that [Ph 2 B(3-(SF 5 )Pz) 2 ]Cu(CO) has a notably Lewis acidic copper site, and a relatively weakly donating supporting scorpionate, consistent with the observed carbon chemical shifts and DFT analysis of the corresponding ethylene complex.…”

Syntheses and Reactivity of New Zwitterionic Imidazolium Trihydridoborate and Triphenylborate Species

“…B-NMR spectra showed a quartet at δ −19.38 and −19.21 ppm for Compounds 1 and 2, respectively, in CDCl 3 solution, indicating a coordination of the imidazole rings at the BH 3 group[62,90]. The single broad11 B resonances observed at δ −6.52 ppm for Compound 3 and at δ −6.37 ppm for Compound 4, in (CD 3 ) 2 CO and CDCl 3 solutions, respectively, are indicative of a four-coordinate boron center; they are in the range observed for analogously triphenylborate species[91], being considerably shifted in comparison with the triphenylborane one, which is observed at δ −60.2 ppm[92].Inthe ESI(+)-MS spectra of 1 and 2 we observed peaks at m/z 195 and 223, due to the molecular specie [(HIm Bn )BH 3 + Na] + and [(HIm Mes )BH 3 + Na] + , respectively. In addition the ESI(+)MS spectra displayed peaks due to the fragmentation species [HIm R + H] + and to the aggregates [(HIm R ) 2 BH 2 ] + (R = Bn or Mes).…”

“…The 11 B-NMR spectra showed a quartet at δ −19.38 and −19.21 ppm for Compounds 1 and 2 , respectively, in CDCl 3 solution, indicating a coordination of the imidazole rings at the BH 3 group [ 62 , 90 ]. The single broad 11 B resonances observed at δ −6.52 ppm for Compound 3 and at δ −6.37 ppm for Compound 4 , in (CD 3 ) 2 CO and CDCl 3 solutions, respectively, are indicative of a four-coordinate boron center; they are in the range observed for analogously triphenylborate species [ 91 ], being considerably shifted in comparison with the triphenylborane one, which is observed at δ −60.2 ppm [ 92 ].…”