Synthesis and Reactivity of Copper(I) Complexes Based on C₃‐Symmetric Tripodal HTIM(PR₂)₃ Ligands

Abstract

We present the first example of non-classical hydrogen bonding in Cu I complexes. To this end, we have studied the coordination capacity of the tripodal phosphine ligands HTIM(PR 2 ) 3 {tris[1-(di-R-phosphanyl)-3-methyl-1H-indol-2-yl]methane, R = Ph, iPr} towards copper, leading to a series of eight Cu I complexes [{HTIM(PR 2 ) 3 }CuX] [R = Ph (1-4), iPr (5-8); X = Cl -, I -, OTf -, BF 4 -]. An anagostic interaction in the Cu I complexes has been proposed based on the results of 1 H NMR, ultrahigh-resolution X-ray diffraction, and theoretical [atoms-inmolecules (AIM) and natural bonding orbital (NBO)] analyses of [a] 2612 Of the synthesized complexes, [{HTIM(PPh 2 ) 3 }CuOTf ] (2) has allowed the first study of a non-classical (X-H)···M hydrogenbonding interaction in Cu I complexes. We have characterized and further clarified the (C-H)···Cu interaction through a combination of experimental electron density map studies obtained by X-ray diffraction and atoms-in-molecules (AIM) and natural bonding orbital (NBO) analyses. This experimental and theoretical combination has allowed us to pinpoint the geometrical and electronic features of the (C-H)···Cu interaction in the C 3symmetric phosphorus-based tripodal system described herein. Results and Discussion Synthesis of HTIM(PR 2 ) 3 (R = Ph, iPr) Ligands and their Reactivity with First-Row Transition MetalsThe modular HTIM(PPh 2 ) 3 ligand was synthesized by the reported procedure in 75 % yield. [8] We also developed the syn-Eur.

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyDMe)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

“…1,10 For the M(I) complexes with M = Au, Ag, Cu, all d-orbitals are filled, precluding strong agostic interactions and leaving anagostic interactions as the main choice. 11 The question of Au×××H interactions has fascinated many, and the Au×××H-C H-bonding has been discussed and proposed. 12 However, the exact nature of the interaction is still under debate, and only recently, a genuine H-bonding was evidenced but for the strongly polarized N-H bond in an R3N + -H×××Au complex, 13 or for interactions between water and the AuMe2-anion.…”

“…The agostic and anagostic interactions have been well‐studied for d 8 metal complexes (Scheme 1), but “anagostic” interactions were also invoked for the low oxidation state metal complexes with at least partially filled d ‐shell ( e. g ., d 6 , d 8 , d 10 ) [1,21] . For the M(I) complexes with M=Au, Ag, Cu, all d ‐orbitals are filled, precluding strong agostic interactions and leaving anagostic interactions as the main choice [22] . The question of Au⋅⋅⋅H interactions has fascinated many, and the Au⋅⋅⋅H−C H‐bonding has been discussed and proposed [23–27] .…”

Well‐defined Nickel P3C Complexes as Hydrogenation Catalysts of N‐Heteroarenes Under Mild Conditions

“…As previously reported NiX 2 salts (X=Cl, Br, I, OTf), Ni(glyme)X 2 (X=Cl, Br) or bis(1,5-cyclooctadiene)nickel(0) do not directly react with the HTIM(PPh 2 ) 3 ligand even at elevated temperatures (150 °C). [19] However, the CÀ H activation of the ligand can be accomplished in good yield (93 %) if NEt 3 is present in the reaction mixture (Scheme 1). Under the same conditions, the reaction did not proceed in the absence of the base.…”

The transition metal-catalysed hydroboration reaction

“…More recently, copper(I) systems based on tripodal phosphine ligands have been employed in the catalytic hydroboration of CO 2 using 9-BBN giving mixtures of CH 2 (O-BBN) 2 , MeO-BBN, and HCO 2 BBN in varying selectivity. 531,532 A heterobimetallic copper/gold system was also found capable of reducing CO 2 using 9-BBN, with good selectivity for the boryl formate derivative, but relatively low turnover numbers. 533 Ruthenium complexes have also shown catalytic activity in the reduction of carbon dioxide.…”