Electronic Structures and Reactivity Profiles of Aryl Nitrenoid-Bridged Dicopper Complexes

Abstract

Dicopper complexes templated by dinucleating, pacman dipyrrin ligand scaffolds ( Mes dmx, tBu dmx: dimethylxan-thine-bridged, cofacial bis-dipyrrin) were synthesized by deprotonation/ metalation with mesitylcopper (CuMes; Mes: mesityl) or by transmetalation with cuprous precursors from the corresponding deprotonated ligand. Neutral imide complexes ( R dmx)Cu 2 (μ 2 -NAr) (R: Mes, t Bu; Ar: 4-MeOC 6 H 4 , 3,5-(F 3 C) 2 C 6 H 3 ) were synthesized by treatment of the corresponding dicuprous complexes with aryl azides. While one-electron reduction of

Syntheses and solid-state structures of two cofacial (bis)dipyrrin dichromium complexes in different charge states

“…Of note were subtle increases in bond length between dipyrrin N atoms (N1, N2, N3, and N4) and tBu-substituted C atoms (C5, C9, C37, and C41) from 1 to 2 (Table 2), consistent with partial reduction of the dipyrrin ligand. The C-N bond lengths are also elongated compared to the bond lengths between dipyrrin N atoms and tBu-substituted C atoms seen in previous diiron and dicopper Pacman dipyrrin complexes (Johnson et al, 2019;Carsch et al, 2020) and related mononuclear dipyrrin compounds (Dong et al, 2020;Carsch et al, 2019).…”

“…The observed CrÁ Á ÁCr separations in 1 and 2 are shorter than the Fe1Á Á ÁFe2 distances of 3.5616 (7) and 3.743 (1) Å observed in previously reported diiron Pacman compounds with Fe II ions bridged by a 2 -oxo bridging ligand (Johnson et al, 2019). For the dicopper core bridged by aryl nitrenes within the bis(dipyrrin) scaffold, a more pronounced metal-metal interaction is present, as indicated by Cu1Á Á ÁCu2 distances of 2.822 (1)-2.9448 (7) Å (Carsch et al, 2020).…”

“…Detailed synthetic protocols of the Pacman dipyrrin and its deprotonation are reported elsewhere (Johnson et al, 2019;Carsch et al, 2020).…”

“…For instance, whereas mononuclear copper-dipyrrin scaffolds with sterically unencumbered flanking units (e.g. mesityl, adamantyl, and tert-butyl) furnish azoarene upon treatment with aryl azides, the analogous dimethylxanthene-tethered bis(dipyrrin) scaffold allows for isolation of bridging di(copper) nitrenoid species that exhibit nitrene transfer to nucleophiles (Carsch et al, 2020). Additionally, a diiron bridging oxo has been prepared that exhibits drastic differences in the oxo basicity and the Fe-O-Fe bond angle as a function of Fe oxidation states (Johnson et al, 2019).…”

“…Whereas all equatorial metal coordination sites are occupied in porphyrin Pacman compounds, the related Pacman dipyrrin framework occupies two cis coordination sites per metal, potentially allowing for both axial and equatorial chemistry. Bis(dipyrrin) complexes with iron and copper have been prepared (Johnson et al, 2019;Carsch et al, 2020) and offer the possibility for co-operativity between the metals to effect novel reactivity. Potential applications of dipyrrin Pacman complexes include stabilization of a bimetallic center with a modular metal-metal distance based on the supporting linker, control over bimetallic center accessibility based on steric modification of the dipyrrin substituents, and promotion of group transfer catalysis from the bridging motifs to exogeneous substrate.…”