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Reaction of the tri(μ-sulfido)triiron(III) tris(β-diketiminate) cyclophane complex, Fe3S3LEt/Me (1), or of the di(μ-sulfido)diiron(III) complex Fe2S2HLEt/Me (5), with the related tri(bromide)triiron(II) complex Fe3Br3LEt/Me (2) results in electron and ligand redistribution to yield the mixed-ligand multiiron complexes, including Fe3Br2SLEt/Me (3) and Fe2Br2SHLEt/Me (4). The cleavage and redistribution observed in these complexes is reminiscent of necessary Fe–S bond cleavage for substrate activation in nitrogenase enzymes, and provides a new perspective on the lability of Fe–S bonds in FeS clusters. [ABSTRACT FROM AUTHOR]

A cyclophane ligand (H6L) bearing three β-oxo-δ-diimine arms and the corresponding tri-iron and -zinc complexes in which the metal ions are bridged by either chlorides, viz. Fe3Cl3(H3L) (1) and Zn3Cl3(H3L) (2), or hydrides, viz. Fe3H3(H3L) (3), Zn3H3(H3L) (4), were synthesized and characterized. 1 adopts a chair-shaped C3v-symmetric [Fe3(μ-Cl)3]3+ cluster wherein only one hemisphere of the ligand is metallated and the other three ketoimine sites remain protonated as evidenced by single crystal X-ray diffraction and vibrational and NMR spectroscopic analyses. 3 and 4 were synthesized by substitution of the bridging chlorides in 1 and 2 using KBEt3H and are accessed with retention of the three protonated ketoimine sites. [ABSTRACT FROM AUTHOR]

The rational design of trimetallic transition metal clusters supported by a trinucleating cyclophane ligand, L3−, and the reactivities of these complexes with dinitrogen and carbon dioxide are discussed. Emphasis is placed on the differences in the observed reactivity between these trimetallic cyclophane complexes and that of the mono- and dinuclear transition metal compounds. [ABSTRACT FROM AUTHOR]

A μ3-sulfide bridged triiron cluster(ii,ii,iii) supported by a cyclophane ligand undergoes metal-based reduction to yield an all-ferrous species. The latter complex incorporates a three-coordinate iron center that provides an accessible coordination site to a solvent molecule. [ABSTRACT FROM AUTHOR]

A [3Fe–3(μ-S)]3+ cluster is reported in which each ferric center has a distorted trigonal pyramidal geometry, with an S = 1/2 ground state for the cluster and unusually anisotropic hyperfine coupling constants as determined by variable temperature magnetometry and Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

A trinucleating cyclophane bearing three β-diketimine arms, and the corresponding iron(ii) and manganese(ii) complexes have been synthesized and characterized. The three metal ions are oriented towards the internal void space, and are coordinated by a N2Br2 donor set, in which a unique combination of μ3, μ, and terminal coordination modes are observed for the halide donors. [ABSTRACT FROM AUTHOR]

Reaction of the tri(μ-sulfido)triiron(iii) tris(β-diketiminate) cyclophane complex, Fe 3 S 3 L Et/Me (1), or of the di(μ-sulfido)diiron(iii) complex Fe 2 S 2 HL Et/Me (5), with the related tri(bromide)triiron(ii) complex Fe 3 Br 3 L Et/Me (2) results in electron and ligand redistribution to yield the mixed-ligand multiiron complexes, including Fe 3 Br 2 SL Et/Me (3) and Fe 2 Br 2 SHL Et/Me (4). The cleavage and redistribution observed in these complexes is reminiscent of necessary Fe-S bond cleavage for substrate activation in nitrogenase enzymes, and provides a new perspective on the lability of Fe-S bonds in FeS clusters.

A cyclophane ligand (H6L) bearing three β-oxo-δ-diimine arms and the corresponding tri-iron and -zinc complexes in which the metal ions are bridged by either chlorides, viz. Fe3Cl3(H3L) (1) and Zn3Cl3(H3L) (2), or hydrides, viz. Fe3H3(H3L) (3), Zn3H3(H3L) (4), were synthesized and characterized. 1 adopts a chair-shaped C3v-symmetric [Fe3(μ-Cl)3]3+ cluster wherein only one hemisphere of the ligand is metallated and the other three ketoimine sites remain protonated as evidenced by single crystal X-ray diffraction and vibrational and NMR spectroscopic analyses. 3 and 4 were synthesized by substitution of the bridging chlorides in 1 and 2 using KBEt3H and are accessed with retention of the three protonated ketoimine sites.

The triiron trihydride complex Fe 3 H 3 L ( 1 ) [where L 3- is a tris(β-diketiminate)cyclophanate] reacts with CO and with BF 3 ·OEt 2 to afford (Fe I CO) 2 Fe II (μ 3 -H) L ( 2 ) and Fe 3 F 3 L ( 3 ), respectively. Variable-temperature and applied-field Mössbauer spectroscopy support the assignment of two high-spin (HS) iron(i) centers and one HS iron(ii) ion in 2 . Preliminary studies support a CO-induced reductive elimination of H 2 from 1 , rather than CO trapping a species from an equilibrium mixture. This complex reacts with H 2 to regenerate 1 under a dihydrogen atmosphere, which represents a rare example of reversible CO/H 2 exchange and the first to occur at high-spin metal centers, as well as the first example of a reversible multielectron redox reaction at a designed high-spin metal cluster. The formation of 3 proceeds through a previously unreported net fluoride-for-hydride substitution, and 3 is surprisingly chemically inert to Si-H bonds and points to an unexpectedly large difference between the Fe-F and Fe-H bonds in this high-spin system.

A μ3-sulfide bridged triiron cluster(ii,ii,iii) supported by a cyclophane ligand undergoes metal-based reduction to yield an all-ferrous species. The latter complex incorporates a three-coordinate iron center that provides an accessible coordination site to a solvent molecule.

A [3Fe-3(μ-S)](3+) cluster is reported in which each ferric center has a distorted trigonal pyramidal geometry, with an S = 1/2 ground state for the cluster and unusually anisotropic hyperfine coupling constants as determined by variable temperature magnetometry and Mössbauer spectroscopy.

Reaction of tris(5-amino-2-ethoxy-3-isopropylphenyl)methane and pyridine-2,6-dicarbonyl-dichloride affords a multi-dentate cryptand in 48% yield. Metallation with iron(III) chloride results in a substantial conformational change of this ligand to give a trianionic triiron(III) complex. Ferric cations line the periphery of the internal cavity with each adopting a square pyramidal N(3)Cl(2) coordination environment.

The hydrogen storage properties of Fe(2)(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) and an oxidized analog, Fe(2)(O(2))(dobdc), have been examined using several complementary techniques, including low-pressure gas adsorption, neutron powder diffraction, and inelastic neutron scattering. These two metal-organic frameworks, which possess one-dimensional hexagonal channels decorated with unsaturated iron coordination sites, exhibit high initial isosteric heats of adsorption of -9.7(1) and -10.0(1) kJ mol(-1), respectively. Neutron powder diffraction has allowed the identification of three D(2) binding sites within the two frameworks, with the closest contacts corresponding to Fe-D(2) separations of 2.47(3) and 2.53(5) Å, respectively. Inelastic neutron scattering spectra, obtained from p-H(2) (para-H(2)) and D(2)-p-H(2) mixtures adsorbed in Fe(2)(dobdc), reveal weak interactions between two neighboring adsorption sites, a finding that is in opposition to a previous report of possible 'pairing' between neighboring H(2) molecules.