Synthesis and Characterization of Homo- and Heterodinuclear Complexes Containing the N₃M(μ₂-SR)₃MN₃ Core (M = Fe, Co, Ni)

Abstract

A novel amine-thiolate ligand, H 3 3‚6HCl (N,N′,N′′-tris-[2-thio-3-aminomethyl-5-tert-butylbenzyl]-1,1,1-tris-(aminomethyl)ethane), has been synthesized and used in the preparation of dinuclear complexes of Fe, Co, and Ni. The nonadentate N 6 S 3 ligand H 3 3 is formally derived from the symmetric tridentate N 2 S ligand H 1 1 (2,6-bis(aminomethyl)-4-tert-butylthiophenol). It provides two dissimilar octahedral N 3 S 3 and N′ 3 S 3 coordination sites to give complexes with a central N 3 M(µ 2 -SR) 3 MN′ 3 core structure (N and N′ denote primary and secondary amine nitrogen atoms, respectively). The complexes of H 3 3 exist as dinuclear [M II 2 (3)] + , [M III M II (3)] 2+ , or [M III 2 -(3)] 3+ species which are all accessible by chemical or electrochemical reduction/oxidation. The following complexes were isolated as microcrystalline solids: [Co III 2 (3)][ClO 4 ] 3 (4b), [Ni III Ni II (3)][BPh 4 ] 2 (5b), and [Fe III Fe II (3)][BPh 4 ] 2 (6b). The chemical and physicochemical properties of the respective species are very similar to those of Fe, Co, and Ni complexes of H 1, and support the formulation of 4b-6b as discrete dinuclear species with a central N 3 M(µ 2 -SR) 3 MN′ 3 core. NMR spectra of diamagnetic cobalt complexes 4a and 4b reveal the complexes to be C 3h and C 3 symmetric, respectively, in the solution state. The crystal structure determination of [Co III 2 (1) 3 ][Fe(CN) 6 ]‚7MeOH‚3H 2 O (4c) (monoclinic, space group C2/c, a ) 28.037(2) Å, b ) 17.861(1) Å, c ) 25.727(2) Å, ) 90.24(1)°, and Z ) 8) reveals 4c to consist of dinuclear [Co III 2 (1) 3 ] 3+ trications featuring two fac-octahedral N 3 Co III (SR) 3 units bridged at the thiolate sulfur atoms. Compound 4c represents the first structurally characterized M III 2 complex of H 1 1. The ability of H 3 3 to form heterodinuclear complexes is demonstrated with the synthesis of [Co III Ni II (3)][BPh 4 ] 2 (7) and its linkage isomer [Ni II Co III (3)][BPh 4 ] 2 (8). All complexes undergo two electrochemically and chemically reversible one-electron-transfer reactions which convert the respective [M 2 (3)] n+ species. For M III 2 /M III M II (E 1 1/2 ) and M III M II / M II 2 (E 2 1/2 ): -0.40 V, -0.84 V (M ) Co), +0.49 V, +0.05 V (M ) Ni), +0.21 V, -0.33 V (M ) Fe) vs SCE.Heterodinuclear complexes 7 and 8 also give rise to two consecutive one-electron-transfer processes at E 1 1/2 (Ni III/II ) and E 2 1/2 (Co III/II ): +0.55 V, -0.71 V (for 7) and +0.60 V, -0.86 V (for 8), respectively. Comparison of the electrochemical properties of [Co III Ni II (3)] 2+ and [Ni III Ni II (3)] 2+ reveals the Ni III/II redox potential in the dinuclear complexes to be influenced by the oxidation state of the adjacent metal ion. At 77 K the mixed-valent Ni III Ni II (S ) 3 / 2 spin ground states) and Fe III Fe II complexes (S ) 1 / 2 spin ground states) exhibit localized and delocalized valencies, respectively, as indicated by UV-vis, EPR, and 57 Fe Mössbauer spectroscopy. IntroductionFace-sharing bioctahedral complexes of the type Y 3 M(µ 2 -X) 3 MY 3 (Chart 1), where ...

Mononuclear, Dinuclear, and Pentanuclear [{N,S(thiolate)}Iron(II)] Complexes: Nuclearity Control, Incorporation of Hydroxide Bridging Ligands, and Magnetic Behavior

“…Face-sharing biooctahedral complexes of the type L 3 M(m-X) 3 ML 3 form a large and well-studied group of molecules. [56][57][58] However, to our knowledge there are no examples of complexes in which two iron atoms share one O and two S bridging atoms. The Fe 2 (RS) 2 (O) core also reveals a striking asymmetry in the Fe II À OH bond lengths.…”

Tetranuclear complexes in molecular magnetism: Targeted synthesis, high-field EPR and pulsed-field magnetization

“…Reaction of 11 with 1,3-diaminopropane in a 2:1 molar ratio followed by subsequent reductions with NaBH 4 and Na/NH 3 then provided H 2 L 2 in good yields. The other polyamine-dithiophenolate ligands H 2 L 3 and H 3 L 4 were also prepared by this route and underline the broad scope of this reaction sequence [35,37,46]. When stored as their hydrochloride salts both HL 1 and H 2 L 2 are air-stable and could be directly used for metal complex synthesis.…”

“…The ligands HL 1 [33,34], H 2 L 2 [35], H 2 L 3 [36], H 3 L 4 [37] and H 2 L 5 [38] represent typical examples (Scheme 4). This section will focus specifically on the synthesis and coordination chemistry of the open chain ligands H 2 L 1 -H 2 L 4 .…”

“…The ligands HL 1 and H 3 L 4 were found to support homo-(12 [47], 13 [34], 14 [37], 15 [48]) as well as heterodinuclear complexes (16 [49], 17, 18 [37]) with a range of di-and trivalent metal ions (M = Cr, Fe, Co, and Ni). All complexes 12-18 have a face-sharing bioctahedral N 3 M(-S) 3 MN 3 core structure as illustrated in Scheme 6 and were found to undergo two reversible one-electron transfer reactions.…”

Solvothermal synthesis, structure and Mössbauer spectroscopy of a new mixed-valence iron aluminophosphate [FeII(H2O)2 Fe0.8IIIAl1.2(PO4)3]·H3O

“…57 Fe Mössbauer spectroscopy can help to determine whether iron atoms are Fe(II), Fe(III) [22][23][24][25] or mixedvalence [26][27][28][29][30][31][32][33][34][35]. The room-temperature Mössbauer powder spectrum of the sample (Fig.…”