Bis(imidazolium)‐1,3‐diphosphete‐diide: A Building Block for FeC₂P₂ Complexes and Clusters

Abstract

Reaction of the 6π-electron aromatic fourmembered heterocycle (IPr) 2 C 2 P 2 (1) (IPr = 1,3-bis(2,6diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) with [Fe 2 CO 9 ] gives the neutral iron tricarbonyl complex [Fe(CO) 3 -η 3 -{(IPr) 2 C 2 P 2 }] (2). Oxidation with two equivalents of the ferrocenium salt, [Fe(Cp) 2 ](BArF 24 ), affords the dicationic tricarbonyl complex [Fe(CO) 3 -η 4 -{(IPr) 2 C 2 P 2 }](BArF 24 ) 2 (4). The one-electron oxidation proceeds under concomitant loss of one CO ligand to give the paramagnetic dicarbonyl radical cation complex [Fe(CO) 2 -η 4 -{(IPr) 2 C 2 P 2 }](BArF 24 ) (5). Reduction of 5 allows the preparation of the neutral dicarbonyl complex [Fe(CO) 2 -η 4 -{(IPr) 2 C 2 P 2 }] ( 6). An analysis by various spectroscopic techniques ( 57 Fe Mössbauer, EPR) combined with DFT calculations gives insight into differences of the electronic structure within the members of this unique series of iron carbonyl complexes, which can be either described as electron precise or Wade-Mingos clusters.

From the Iron Pentacarbonyl Cation to Heteroleptic η6‐arene Carbonyls and bis‐η6‐arene Cations

“…In the last year, two reports on heterocyclic half‐sandwich iron carbonyl complexes have been published, underlining the current and rising interest: Grützmacher et al. reported the synthesis of bis(imidazolium)‐1,3‐diphosphete‐diide bound to an iron carbonyl moiety in multiple oxidation states [18] . One month earlier Braunschweig et al.…”

“…[17] In the last year, two reports on heterocyclic half-sandwich iron carbonyl complexes have been published, underlining the current and rising interest: Grützmacher et al reported the synthesis of bis(imidazolium)-1,3-diphosphetediide bound to an iron carbonyl moiety in multiple oxidation states. [18] One month earlier Braunschweig et al described the synthesis of a two-legged piano stool of Fe(0) using a cyclic carbene stabilized 1,4-diborabenzene. [19] When focusing on η 6coordinating benzene derivatives, the literature is scarce.…”