A series of C3-symmetric heterobimetallic Cr–M (M = Fe, Co and Cu) complexes

Abstract

A series of tris(phosphinoamide) heterobimetallic Cr-M (M ¼ Fe, Co and Cu) complexes has been investigated in an effort to probe and contribute to the understanding of the electronic structure and metal-metal bonding in heterobimetallic complexes of the first row transition metals. The chromium tris(phosphinoamide), [Cr( i PrNPPh 2 ) 3 ] (1), is a useful isolable precursor and can be treated with MI 2 under reducing conditions to form [Cr( i PrNPPh 2 ) 3 M-I] (M ¼ Fe (2), Co (3)). Both of these complexes can be reduced by one electron to generate [Cr( i PrNPPh 2 ) 3 M-PMe 3 ] (M ¼ Fe (4), Co ( 5)). The Cr-Cu complex [Cr( i PrNPPh 2 ) 3 Cu-I] (6) has also been synthesized for comparison. The solid state structures of 2-6 have been determined crystallographically, revealing relatively short metal-metal interatomic distances. M össbauer spectroscopy, cyclic voltammetry, and computational methods have been used to evaluate the electronic structure and metal-metal interactions in these unique bimetallic complexes in an effort to uncover the underlying factors that affect metal-metal bonding between elements of the first row transition series.

Ligand Field Strength Mediates Electron Delocalization in Octahedral [(HL)2Fe6(L′)m]n+ Clusters

“…To best describe the magnetic data presented in the previous section, two models were employed: (1) a single spin (SS) model that considers the six-metal-atom cluster to behave as a single-spin entity, as has been done previously, 11a,45 and (2) a coupled spins (CS) model that assumes the spins of metal sites within the cluster to be coupled. In the latter model, the iron sites are coupled through exchange interactions between adjacent ( J cis ) and trans-located ( J trans ) metal sites.…”

Bi- and trimetallic rare-earth–palladium complexes ligated by phosphinoamides

“…Kempe et al reported a few Nd-Rh and Nd-Pd complexes about 15 years ago. Co-Ti, 11 Co-Zr, 10,12 Co-Hf, 3 Pt-Zr, 13 V-Fe, 14 Nb-Co, 5b Ta-Co, 5b and Co-U. Hou et al recently published rare-earth-platinum heterobinuclear half-sandwich rare-earthmetal alkyl complexes bearing Cp ligands with a phosphine side arm.…”

Synthesis and investigation of the metal–metal interactions in heterobimetallic Cr/Rh and Cr/Ir complexes

“…Cr/Ir complexes from treatment of the previously reported Cr tris(phosphinoamide) complex Cr( i PrNPPh 2 ) 3 [10] with [MCl(COD)] 2 precursors have proven unsuccessful thus far. Therefore, we turned our attention to a more electron-rich chromium variant, namely Cr( i PrNP i Pr 2 ) 3 (1).…”

“…In recent years, heterobimetallic complexes have seen a resurgence in the literature, with the emergence of chelating ligand platforms carefully designed to hold two different metal centers in close proximity. The Thomas and Lu groups, in particular have utilized C 3 -symmetric ligand platforms with the appropriate combination of hard and soft donor ligands to support both early/late heterobimetallic complexes and homobimetallic complexes with coordination site differentiation [7][8][9][10][11][12][13][14]. By targeting complexes featuring first row metals, the systematic variation of metal-metal combination, redox state, and ligand environment has provided a better understanding of the metal-metal bonding in heterobimetallic complexes [15].…”

“…The tris(phosphinoamide) ligand platform was also used to assemble diiron complexes in which the two iron centers occupy different coordination sites, allowing the isolation of homobimetallic complexes featuring two metals in different oxidation and spin states by differentiating the ligand field [8,28,29]. This family of complexes was recently expanded to combinations of first row metals, including multiply bonded V/Fe and Cr/M (M = Fe, Co and Cu) complexes [9,10]. With a better understanding of the metal-metal bonding properties of first row metals in hand, we sought to explore complexes featuring first row early transition metals…”