Aryl Group Transfer from Tetraarylborato Anions to an Electrophilic Dicopper(I) Center and Mixed-Valence μ-Aryl Dicopper(I,II) Complexes

Abstract

The synthesis of discrete, cationic binuclear μ-aryl dicopper complexes [Cu2(μ-η(1):η(1)-Ar)DPFN]X (Ar = C6H5, 3,5-(CF3)2C6H3, and C6F5; DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine; X = BAr4(-) and NTf2(-); Tf = SO2CF3) was achieved by treatment of a dicopper complex [Cu2(μ-η(1):η(1)-NCCH3)DPFN]X2 (X = PF6(-) and NTf2(-)) with tetraarylborates. Structural characterization revealed symmetrically bridging aryl groups, and (1)H NMR spectroscopy evidenced the same structure in solution at 24 °C. Electrochemical investigation of the resulting arylcopper complexes uncovered reversible redox events that led to the synthesis and isolation of a rare mixed-valence organocopper complex [Cu2(μ-η(1):η(1)-Ph)DPFN](NTf2)2 in high yield. The solid-state structure of the mixed-valence μ-phenyl complex exhibits inequivalent copper centers, despite a short Cu···Cu distance. Electronic and variable-temperature electron paramagnetic resonance spectroscopy of the mixed-valence μ-phenyl complex suggest that the degree of spin localization is temperature-dependent, with a high degree of spin localization observed at lower temperatures. Electronic structure calculations agree with the experimental results and suggest that the spin is localized almost entirely on one metal center.

Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex

“…Initial synthetic efforts focused on displacement of the bridging acetonitrile ligand in [Cu 2 (m-h 1 :h 1 -MeCN)DPFN](NTf 2 ) 2 (1) with methylphosphaalkyne (MeCP). 24,25 Addition of 3 equivalents of MeCP to a solution of 1 in THF quantitatively afforded the corresponding [Cu 2 (m-h 2 :h 2 -MeCP)DPFN](NTf 2 ) 2 complex 2, isolated in high yield by removing volatile compounds in vacuo and triturating the resulting powder with diethyl ether to afford an analytically pure yellow powder (Scheme 1).…”

“…2 and SC1), resulting in an expanded dicopper core with a Cu1/Cu2 distance of 2.6548(5)Å compared to that of 2.4781(6) in 1. 25 This complex has a lower symmetry than 1, since m-h 2 :h 2 binding disrupts the mirror plane containing the ligand's naphthyridine core. However, the mirror plane perpendicular to the naphthyridine is preserved, and MeCP binds symmetrically to both copper centers; the two Cu-P1 distances are equivalent, as are the Cu-C31 distances.…”

“…[21][22][23] One system that notably exhibits a high tendency toward symmetrical m-h 1 :h 1 binding is the naphthyridine-supported dicopper (I) core reported by this laboratory, which binds nitriles, isonitriles, carbon monoxide, as well as phenyl and terminal alkynyl anions exclusively in a symmetrical m-h 1 :h 1 fashion. [24][25][26] However, these earlier studies primarily focused on the coordination of C-and N-donating unsaturated bridging fragments, and reactions with heavier, soer donors like phosphorus-based ones have not been investigated. Here we describe the coordination of phosphaalkynes, a relatively understudied class of reactive compounds that are useful building blocks for complex phosphorus-containing assemblies.…”

Selective Synthesis of a Series of Isostructural MIICuI Heterobimetallic Complexes Spontaneously Assembled by an Unsymmetrical Naphthyridine‐Based Ligand

“…[11] Theu se of bifunctionall igandsw ith hard and soft binding sites, including those based on different P, Nand N,N-chelation, [12,13] has been as uccessful strategy in this regard; [14][15][16][17][18] however,t his approach often resultsi ns tructures that do not allow ready access to bridging coordination sites, [16][17][18][19][20] or is specific to certainm etal-metal combinations. [23][24][25] Moreover,n aphthyridine-based bimetallicc omplexes have been shown to catalyzearange of reactions. [22] The rigid naphthyridine core promotes ac lose interaction between two transition metals, and additional donor groups mayb ei ncorporated to enforce open binding sites for exploration of metal-metalc ooperativity in reactionc hemistry.…”

“…[22] The rigid naphthyridine core promotes ac lose interaction between two transition metals, and additional donor groups mayb ei ncorporated to enforce open binding sites for exploration of metal-metalc ooperativity in reactionc hemistry. [23][24][25] Moreover,n aphthyridine-based bimetallicc omplexes have been shown to catalyzearange of reactions. [26][27][28][29][30][31] However, these mostly symmetrical systems have so far been used to study homobimetallic complexes.…”