Synthesis of Open-Shell, Bimetallic Mn/Fe Trinuclear Clusters

Abstract

Concomitant deprotonation and metallation of hexadentate ligand platform tbsLH6 (tbsLH6 = 1,3,5-C6H9(NHC6H4-o-NHSiMe2 tBu)3) with divalent transition metal starting materials Fe2(Mes)4 (Mes = mesityl) or Mn3(Mes)6 in the presence of tetrahydrofuran (THF) resulted in isolation of homotrinuclear complexes (tbsL)Fe3(THF) and (tbsL)Mn3(THF) respectively. In the absence of coordinating solvent (THF) the deprotonation and metallation exclusively afforded dinuclear complexes of the type (tbsLH2)M2 (M = Fe or Mn). The resulting dinuclear species were utilized as synthons to prepare bimetallic trinuclear clusters. Treatment of (tbsLH2)Fe2 complex with divalent Mn source (Mn2(N(SiMe3)2)4) afforded the bimetallic complex (tbsL)Fe2Mn(THF) which established the ability of hexamine ligand tbsLH6 to support mixed metal clusters. The substitutional homogeneity of (tbsL)Fe2Mn(THF) was determined by 1H NMR, 57Fe Mössbauer, and X-ray fluorescence. Anomalous scattering measurements were critical for the unambiguous assignment of the trinuclear core composition. Heating a solution of (tbsLH2)Mn2 with a stoichiometric amount of Fe2(Mes)4 (0.5 mol equiv) affords a mixture of both (tbsL)Mn2Fe(THF) and (tbsL)Fe2Mn(THF) as a result of the thermodynamic preference for heavier metal substitution within the hexa-anilido ligand framework. These results demonstrate for the first time the assembly of mixed metal cluster synthesis in an unbiased ligand platform.

Ligand‐Based Control of Single‐Site vs. Multi‐Site Reactivity by a Trichromium Cluster

“…Metalation of tbs LH 6 with three equivalents of Cr(NTMS 2 ) 2 (thf) 2 (TMS=trimethylsilyl) at 120 °C yielded the trinuclear cluster ( tbs L)Cr 3 (thf) ( 1 , Figure ). At lower temperatures, metalation arrested at a dinuclear form similar to those previously reported on this platform . Crystals suitable for single‐crystal X‐ray diffraction (SC‐XRD) were grown from a concentrated diethyl ether solution of 1 at −35 °C.…”

Linear, Trinuclear Cobalt Complexes with o‐Phenylene‐bis‐Silylamido Ligands

“…In the parent L5 , different redox states have been assigned by structural and spectroscopic techniques . Furthermore, pre‐organized ligand scaffolds comprising o ‐phenylene‐ N ‐alkyl‐ N ′‐(trialkylsilyl)amides have been used for the stabilization of homo‐ and hetero‐metallic 3d metal clusters …”

Determination of the electronic and structural configuration of coordination compounds by synchrotron-radiation techniques

“…Applications span a variety of research areas in solid state chemistry [138,[228][229][230]564], including the discrimination of Zn and Ga in microporous materials [565] or of Pb and Bi in minerals [566], the investigation of the distribution of cations in multi-cationic zeolites [229,567,568], substitution of Cu by Fe, Co, Ni, and Zn in high-critical-temperature superconductor cuprates [556]. A few recent applications of contrast-mode anomalous X-ray diffraction specifically deal with the structural determination of coordination compounds, including multinuclear metal complexes [569][570][571] and MOFs [572]. A representative example is the study of Co−Co and Fe−Co bonds in a series of coordination complexes with formally mixed-valent [M2] 3+ cores (where M = Fe, Z= 26; Co, Z = 27), by Zall et al [570].…”

“…The refinement demonstrated that only a minor amount of metal-site mixing occurs in the heteronuclear complex: this compound is precisely described by the structure formula (Fe0.94(1)Co0.06(1))(Co0.95(1)Fe0.05(1))LPh, where L Ph = phenyl-substituted tris(amidinato)amine, as depicted by the pie charts in Figure 8a. [571]. Finally, a relevant example of the use of anomalous XRD in the structural characterization of MOFs is provided by Brozek et al [572].…”