Noninnocent Behavior of Bidentate Amidophosphido [NP]^2– Ligands upon Coordination to Copper

Abstract

The synthesis and preliminary coordination chemistry of two new redox-active bidentate ligands containing amido and phosphido donors are described. Treatment of the [(R)NP](2-) (R = Ph, 2,4,6-trimethylphenyl) ligands with CuCl2 and PMe3 results in a dimeric copper(I) P-P coupled product via ligand oxidation. The intermediate of this reaction is proposed to involve a ligand radical generated via oxidation of the [(R)NP](2-) ligand by copper(II), and the existence of such an intermediate is probed using computational methods. Significant radical character on the phosphorus atoms of the alleged [(R)NP](•-)/copper(I) intermediate leads to P-P radical coupling.

Redox‐Active Ligand‐Induced Homolytic Bond Activation

“…In contrast and at odds with the relevance of phosphorus ligands in homogeneous catalysis, few phosphine‐containing redox‐active ligands exist 6. 7 Thomas and co‐workers recently described an ( o ‐anilino)phenylphosphine ligand that is susceptible to oxidation in the coordination sphere of Cu I , but radical P–P coupling precluded the use of this scaffold as a reversible redox‐active ligand 8. Installment as a redox‐innocent entity adjacent to a redox‐active framework is less likely to affect the coordinative properties at phosphorus, but relatively few of these ligands have been developed 9.…”

“…[5] In contrast and at odds with the relevance of phosphorus ligands in homogeneous catalysis, few phosphine-containing redox-active ligands exist. [8] Installment as a redox-innocent entity adjacent to a redox-active framework is less likely to affect the coordinative properties at phosphorus, but relatively few of these ligands have been developed. [8] Installment as a redox-innocent entity adjacent to a redox-active framework is less likely to affect the coordinative properties at phosphorus, but relatively few of these ligands have been developed.…”

“…[6,7] Thomas and co-workers recently described an (o-anilino)phenylphosphine ligand that is susceptible to oxidation in the coordination sphere of Cu I , but radical P-P coupling precluded the use of this scaffold as a reversible redox-active ligand. [8] Installment as a redox-innocent entity adjacent to a redox-active framework is less likely to affect the coordinative properties at phosphorus, but relatively few of these ligands have been developed. [9,10] Bond homolysis is a very useful reaction to probe for accessible ligand-based reactivity.…”

Redox-ligand sustains controlled generation of CF3 radicals by well-defined copper complex

“…These systems are now being developed in broader (catalytic) contexts 10 with several metals including iridium, 11 cobalt, 12 , 13 palladium 14 , 15 and copper. 16 , 17 Previous work allowed us to establish that the interaction of complex 1 [Cu( ii )(L SQ ) 2 ] with an electrophilic source of CF 3 triggers CF 3 uptake by the complex through ligand-based bis-electronic redox participation while preserving the metal Cu( ii ) oxidation state. 18 The resulting [Cu( ii )(L BQ ) 2 CF 3 ] + complex 2 exhibits a nucleophilic intramolecular CF 3 reactivity, thus suggesting that redox involvement of ligands can sustain formal umpolung of the CF 3 moiety ( Fig.…”

Synthesis of N,P‐Disecondary o‐Arylphosphanylanilines via o‐R1NHC6H4P(R)O2Et Precursors and Preliminary Study of Cyclocondensations with (EtO)3CH/NH4PF6

“…Syntheses of N ‐methyl‐ o ‐phenylphosphanylaniline, and two N‐aryl o ‐phenylphosphanylanilines are known but are methodically limited by the final cleavage of a P ‐phenyl group from the corresponding o ‐diphenylphosphanylaniline precursors by Na or Li. This prompted us to re‐examine our earlier reported synthetic route to N ‐secondary alkyl‐ and aryl‐substituted o ‐phosphanylanilines for the preparation of N , P ‐disecondary representatives.…”