An unexpected transmetalation intermediate: isolation and structural characterization of a solely CH₃ bridged di-copper(i) complex

Abstract

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Dicopper Alkyl Complexes: Synthesis, Structure, and Unexpected Persistence

“… This 13 C resonance is upfield of both [AlMe 3 ] 2 resonances (bridge −5.34 ppm, terminal −8.03 ppm; at −78 °C in toluene- d 8 ) as well as the methyl resonances in a range of cuprates, CH 3 CuPCy 3 , and the aforementioned dinuclear gold complex (−0.1 ppm) . The shift observed for 1 is also upfield of the range of solid-state 13 C chemical shifts reported for Molteni and co-workers’ donor–acceptor complex (+1 to −16 ppm) and the solution-state shift reported for Ma and co-workers’ hexanuclear cluster (−18.99 ppm) …”

“…41 These frequencies are also similar to some of those reported for [Cu(PPh3)2(μ-CH3)CuCH3] (specifically 2852 and 2781 cm -1 ). 29 To bolster the assignment, the IR spectrum of the cation of 1 was calculated employing the ωB97X-D functional 42 and the def2-TZVP basis set.…”

“…In addition, 1 is significantly more thermally stable than the aforementioned dicopper μ-methyl complex, [Cu(PPh3)2(μ-CH3)CuCH3], which is reported to decompose rapidly in solution at room temperature. 29 Considering the relative stability of the bridging-methyl copper(I) complex in solution, installation of a significantly bulkier alkyl group was attempted. Treatment of [Cu2(μ-η 1 :η 1 -NCCH3)DPFN](NTf2)2 in THF at -30 °C with neopentyllithium (1.07 equiv) in pentane provided [Cu2(μ-η 1 :η 1 -CH2C(CH3)3)DPFN]NTf2 (eq 3), which was isolated in 50% yield.…”

“…Recently Molteni and co-workers reported the structure of another methyl-bridged dicopper complex, [Cu­(PPh 3 ) 2 (μ-CH 3 )­CuCH 3 ], which is described as the coordination of a Cu­(PPh 3 ) 2 + unit to a nearly linear CuMe 2 – . In comparison to this donor–acceptor complex, 1 exhibits a shorter Cu···Cu distance (for the donor–acceptor complex Cu···Cu 2.4121(4) Å) and a more symmetrical methyl-binding mode (for the donor–acceptor complex Cu−μ-CH 3 distances are 2.011(2) and 2.137(2) Å).…”

Metal–metal cooperative bond activation by heterobimetallic alkyl, aryl, and acetylide PtII/CuIcomplexes

“…However, it resembles the binding interaction in the unsymmetrical donor-acceptor-type Me-bridged [Cu(PPh 3 ) 2 (m-Me)CuMe] dicopper complex reported by Steffen and co-workers that is also stabilized by metal-metal interactions. 23 Compared to 3, NBO analysis shows that complex 4 exhibits only moderate donation from a Pt-Me A fragment to Cu [E (2) ¼ 44.23 kcal mol À1 ] and similar metal-metal interactions manifest in the donation from a d-type orbital on Pt to an s-orbital of Cu [E (2) ¼ 32.13 kcal mol À1 ] (Table S13 and Fig. S155 †).…”