Synthesis and Structures of Copper(I) Complexes with Phosphino-Functionalized N-Heterocyclic Carbenes (NHCP) and Bis-N-Heterocyclic Carbenes (Bis-NHC)

Abstract

New copper(I) complexes bearing N-phosphino- and N-phosphinomethyl-functionalized NHC ligands (NHCP systems) were synthesized and fully characterized. Using halide-containing copper(I) precursors, strikingly different structural motifs were found, dependent on the substitution pattern of the NHCP moiety. An interesting tetranuclear μ4-bridged copper(I) cluster (4b) is formed when CuBr·SMe2 is reacted with the N-phosphino-substituted ligand 1a, whereas the dinuclear complex 4a is formed in an analogous reaction with 1b. Dinuclear metallacycles (2a,b) were isolated and characterized by X-ray diffraction when the halide-free copper(I) precursor [Cu(CH3CN)4]PF6 was reacted with NHCP ligands 1a,b using the N-phosphinomethyl-substituted NHCP ligands 5a,b, as well as employing the bis-NHC ligands BIM and BIM-BMe2 (10a,b), respectively. The observed copper(I)–copper(I) distances are directly correlated with the size of the metallacycle formed. An unexpected strong influence upon the metal–metal separation was found for the charged complexes in 10a,b. Using directly N-tBu-substituted NHCP ligands led to formation of an electronically less favorable trans-C,C coordination at the copper(I) centers (3 and 6a), which inhibited the formation of a dimeric species in the case of 3.

Regulatory factors and the nature of Cu⋯Cu interaction in copper(i) complexes with NHC and NHCP ligands: a theoretical assessment

“…That is, increasing the ring size of the dinuclear metallacycles results in increased metal-metal separation. This conclusion is identical to that drawn from the experimental results of Hofmann et al 25 Moreover, it is worthy to notice in P-deca-C, although the ligand is NHCP and the ring size is 10, there is still a short Cu-Cu distance of 2.62 Å. The short Cu-Cu distance may be caused by the shape of the ring.…”

“…Hofmann pointed out that theoretical treatment using quantum mechanics at the appropriate level of theory to gain a deep understanding of the Cu(I)Á Á ÁCu(I) interactions in these systems remains a challenging task. 25 To the best of our knowledge, there is no systematic theoretical study on the Cu(I)Á Á ÁCu(I) bonding in copper(I) complexes with the ligand NHCP or N-heterocyclic (NHC) (Scheme 1). Therefore, a detailed and systematic theoretical study on the nature of such bonding is desirable.…”

Di‐ and Trinuclear Gold Complexes of Diphenylphosphinoethyl‐Functionalised Imidazolium Salts and their N‐Heterocyclic Carbenes: Synthesis and Photophysical Properties

“…A downfield resonance is seen at 172.6 ppm, which is in the typical range of gold-carbene complexes. [67] Since no signal broadening is observed in the 31 P{ 1 H} NMR spectrum or for the ethylene bridge in 1 H NMR spectrum, a mixture of products or a dimeric complex, [(L1) 2 Au 2 ]Cl 2 , similar to those described by Hofmann [44] or Kostyuk, [40] can be excluded. The EI-MS spectrum of compound 1 exhibits an ion peak for the [MÀCl] + ion including the correct isotopic pattern.…”

Stable N‐Phosphanyl Acyclic Diaminocarbenes

“…Recently, we have designed and introduced into synthetic practice N ‐phosphanyl‐substituted N‐heterocyclic carbenes (NHCPs) A (Figure 1). These ligands bearing a second P‐based coordination site are stable and have already found some applications 4–9. Another type of carbene, the acyclic diaminocarbenes (ADCs), provide greater opportunity to fine‐tune their catalytic activities.…”