Synthesis and Characterization of Heterobimetallic Carbonyl Clusters with Direct Au‐Fe and Au···Au Interactions Supported byN‐Heterocyclic Carbene and Phosphine Ligands

Abstract

The reaction of Collman's reagent Na 2 [Fe(CO) 4 ]·2thf with one equivalent of Au(NHC)Cl (NHC = IMes, IPr; IMes = C 3 N 2 H 2 (C 6 H 2 Me 3 ) 2 ; IPr = C 3 N 2 H 2 (C 6 H 3 iPr 2 ) 2 ) in dmso resulted in the [Fe(CO) 4 (AuNHC)] -(NHC = IMes, 1; IPr, 2) mono-anions. 1-2 further reacted with Au(NHC)Cl or Au(PPh 3 )Cl affording the neutral complexes Fe(CO) 4 (AuNHC) 2 (NHC = IMes, 3; IPr, 4), Fe(CO) 4 (AuIMes)(AuIPr) (5) and Fe(CO) 4 (AuNHC)(AuPPh 3 ) (NHC = IMes, 6; IPr, 7). 1-7 have been spectroscopically characterized by IR, 1 H, 13 C{ 1 H} and 31 P{ 1 H} NMR techniques. Moreover, the molecular structures of 1, 2, 4, 6 and 7 have been determined through single-crystal X-ray diffraction as their [NMe 4 ][Fe(CO) 4 -[a] Dipartimento

A Comparative Experimental and Computational Study of Heterometallic Fe‐M (M = Cu, Ag, Au) Carbonyl Clusters Containing N‐Heterocyclic Carbene Ligands

“…The 1 H and 13 C{ 1 H} NMR data of 1 – 4 were in keeping with the proposed structures and similar to those previously reported for 5 and 6 . Compounds 1 – 4 displayed two ν CO bands in dmso solution, that is a sharp band at 1909–1913(s) and a broader band at 1796–1801(vs) cm –1 (Figures S39–S40 in the Supporting Information), significantly shifted towards lower wavenumbers compared to the Au‐congeners 5 and 6 ( ν CO 1924(s) and 1820(vs) cm –1 ).…”

“…2 adopted a trigonal bipyramidal structure, with the CuIPr fragment in an axial position. Similar structures were found for the gold related species 5 and 6 , and in the cobalt complexes Co(CO) 4 (AuPPh 3 ) and Co(CO) 4 (CuIPr) . The root mean square deviation (RMSD) between the experimental data for 2 and the computed geometry for 1 , once removed the N‐bonded substituents, was quite low (0.229 Å), supporting the quality of the geometries predicted by the PBEh‐3c method.…”

“…Isolation of 2 was possible because of the enhanced steric stability of IPr‐derivatives compared to IMes‐derivatives, as well as the (slightly) greater stability of Fe–Cu species compared to Fe–Ag, as pointed out by DFT calculations. Indeed, all attempts to isolate 1 , 3 and 4 following a similar procedure failed, leading to the formation of complex mixtures of decomposition products.…”

“…The reaction of Collman's reagent Na 2 [Fe(CO) 4 ] · 2thf with one equivalent of M(NHC)Cl (M = Cu, Ag; NHC = IMes, IPr) in dmso resulted in the [Fe(CO) 4 {M(NHC)}] – (M = Cu, NHC = IMes, 1 ; M = Cu, NHC = IPr, 2 ; M = Ag, NHC = IMes, 3 ; M = Ag, NHC = IPr, 4 ) mono‐anions in accord to Scheme . At difference with the related gold‐containing species [Fe(CO) 4 {Au(NHC)}] – (NHC = IMes, 5 ; IPr, 6 ), the copper and silver compounds 1 – 4 displayed a limited stability which, in most of the cases, prevented their isolation and crystallization. Thus, 1 – 4 were characterized directly in the crude reaction mixtures by means of IR, 1 H and 13 C{ 1 H} NMR spectroscopy (Figures S5–S12 in the Supporting Information.…”

“…The scope of this work was further widened, in the case of Au, to other ligands and stoichiometric combinations of Au and Fe. Thus, the syntheses and thermal reactions of [Fe(CO) 4 {Au(NHC)}] – (NHC = IMes; IPr = C 3 N 2 H 2 (C 6 H 3 i Pr 2 ) 2 ), Fe(CO) 4 {Au(NHC)} 2 (NHC = IMes, IPr), Fe(CO) 4 {Au(IMes)}{Au(IPr)} and Fe(CO) 4 {Au(NHC)}{Au(PPh 3 )} (NHC = IMes, IPr) were systematically investigated , . As a result, the higher nuclearity clusters [Fe 2 (CO) 8 {Au(NHC)}] – (NHC = IMes, IPr), [Au 3 Fe 2 (CO) 8 (IMes) 2 ] – , [Au 3 {Fe(CO) 4 } 2 (PPh 3 ) 2 ] – and [Au 16 S{Fe(CO) 4 } 4 (IPr) 4 ] n+ were obtained …”