Why are the {Cu₄N₄} rings in copper(i) phosphinimide clusters [Cu{μ-NPR₃}]₄(R = NMe₃or Ph) planar?

Abstract

The copper phosphinimide complexes [Cu{μ-N[double bond, length as m-dash]PR3}]4 (1, R = NMe2 and 2, R = Ph) were obtained in good yields from the reactions of Cu[Mes] (Mes = mesityl, C6H2Me3-2,4,6) with the corresponding iminophosphoranes, HNPR3. The molecular structures of 1 and 2 reveal the presence of planar eight-membered {Cu4N4} rings which contrasts with the saddle-shaped {M4N4} rings found in related metal phosphinimide complexes. According to computations, there is negligible aromaticity in the planar {Cu4N4} rings in 1 and 2 and the saddle shape observed in related {M4N4} rings is due to steric factors.

N–O Bond Activation and Cleavage Reactions of the Nitrosyl-Bridged Complexes [M2Cp2(μ-PCy2)(μ-NO)(NO)2] (M = Mo, W)

“…We should remark that 7 is the first structurally characterized complex with a X 3 PN – ligand bearing alkoxy substituents. The quite short P–N length of 1.515(3) Å in 7 can be viewed as indicative of a very strong double bond, actually being shorter than the reference P–N double-bond length of 1.57 Å, and in any case shorter than the values of 1.54–1.65 Å measured in all previous complexes having μ-NPX 3 ligands bearing alkyl, aryl, or even NR 2 substituentes …”

Metal exchange in lithiocuprates: implications for our understanding of structure and reactivity

“… 23 This has reinvigorated interest in the properties of lithium amidocuprates and it has been noted that the ability of bimetallics of the type (R 2 N) 2 CuLi to dimerize, coupled with the acknowledged issue of metal exchange between Li and Cu, as elucidated by van Koten and co-workers, 16a , b , 24 means that the field of Gilman cuprate chemistry is closely interwoven with that of copper–nitrogen metallacycles. These have been observed to constitute tetrameric ketimides, 25 hydrazides, 25 phosphinimides 26 mixed amides/guanidinates 27 and amides 9 with the last of these ligand-types also supporting 3D clusters. 28 Copper amides, first prepared a century ago 29 and more recently the focus of intense study, 11a , 30 have proven to be synthetically important, with solid state tetramers shown to deaggregate and participate in modified Ullmann amination 31 with arenes in the presence of 1,10-phenanthroline.…”

Computational Investigation of the Metal and Ligand Substitution Effects on the Structure and Electronic States of the Phosphoranimide Tetramer Complexes of Cu(I), Ni(I), Co(I), and Fe(I)

“…The additional insights could help improve the understanding of the spin multiplicity and spin pairing in these tetrametallic complexes and the effect in terms of electronic density repartition and configuration. The computational results are validated with respect to the available experimental magnetic moment and X-ray diffraction (XRD) measurements. , …”

“…Earth-abundant first-row transition-metal complexes containing ligands with highly tunable electron-donating capability that could effectively enable spatial and electronic control have been proposed as advanced and highly selective catalysts. − Among these, the tetrametallic complexes of Co and Ni stabilized in the unusual oxidation state of +1 by trialkylphosphoranimide (or −aryl−) ligands synthesized by Camacho-Bunquin and Stryker appear to be particularly attractive as catalyst precursors for heterogeneous hydrogenation and the hydrotreatment of heavy petroleum under mild reaction conditions. ,, Robinson and co-workers reported the Cu­(I) analogue that features a coplanar {M 4 N 4 } moiety, distinct from the bent {M 4 N 4 } moiety in Co­(I) and Ni­(I) complexes . These isostructural complexes consist of four coplanar metal centers, mutually bridged to phosphoranimide ligands via the N atom.…”

“…For example, depending on the oxidation state of the metal, ligand sphere, and electronic properties of substituents at the P atom, the complex can adopt either a linear configuration along the metal–N–P axis, or a bent geometry, or a μ 2 -N-bridge forming symmetrical or unsymmetrical four-membered M 2 N 2 rings, or a heterocubane {M 4 N 4 } structure . The M–N–P atoms’ arrangement may be affected by sterically bulky substituents. ,, Kuppuswamy et al have shown notably the effect of steric and electronic properties of the phosphoranimide ligand on the structure of complexes …”