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Thiolate-bridged dinuclear iron(tris-carbonyl)-nickel complexes relevant to the active site of [NiFe] hydrogenase.

ABSTRACT: The reaction of NiBr(2)(EtOH)(4) with a 1:2-3 mixture of FeBr(2)(CO)(4) and Na(SPh) generated a linear trinuclear Fe-Ni-Fe cluster (CO)(3)Fe(mu-SPh)(3)Ni(mu-SPh)(3)Fe(CO)(3), 1, whereas the analogous reaction system FeBr(2)(CO)(4)/Na(S(t)Bu)/NiBr(2)(EtOH)(4) (1:2-3:1) gave rise to a linear tetranuclear Fe-Ni-Ni-Fe cluster [(CO)(3)Fe(mu-S(t)Bu)(3)Ni(mu-Br)](2), 2. By using this tetranuclear cluster 2 as the precursor, we have developed a new synthetic route to a series of thiolate-bridged dinuclear Fe(CO)(3)-Ni complexes, the structures of which mimic [NiFe] hydrogenase active sites. The reactions of 2 with SC(NMe(2))(2) (tmtu), Na{S(CH(2))(2)SMe} and ortho-NaS(C(6)H(4))SR (R = Me, (t)Bu) led to isolation of (CO)(3)Fe(mu-S(t)Bu)(3)NiBr(tmtu), 3, (CO)(3)Fe(S(t)Bu)(mu-S(t)Bu)(2)Ni{S(CH(2))(2)SMe}, 4, and (CO)(3)Fe(S(t)Bu)(mu-S(t)Bu)(2)Ni{S(C(6)H(4))SR}, 5a (R = Me) and 5b (R = (t)Bu), respectively. On the other hand, treatment of 2 with 2-methylthio-phenolate (ortho-O(C(6)H(4))SMe) in methanol resulted in (CO)(3)Fe(mu-S(t)Bu)(3)Ni(MeOH){O(C(6)H(4))SMe}, 6a. The methanol molecule bound to Ni is labile and is readily released under reduced pressure to afford (CO)(3)Fe(S(t)Bu)(mu-S(t)Bu)(2)Ni{O(C(6)H(4))SMe}, 6b, and the coordination geometry of nickel changes from octahedral to square planar. Likewise, the reaction of 2 with NaOAc in methanol followed by crystallization from THF gave (CO)(3)Fe(mu-S(t)Bu)(3)Ni(THF)(OAc), 7. The dinuclear complexes, 3-7, are thermally unstable, and a key to their successful isolation is to carry out the reactions and manipulations at -40 degrees C.

SUBMITTER: Ohki Y

PROVIDER: S-EPMC2409409 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Thiolate-bridged dinuclear iron(tris-carbonyl)-nickel complexes relevant to the active site of [NiFe] hydrogenase.

Ohki Yasuhiro Y Yasumura Kazunari K Kuge Katsuaki K Tanino Soichiro S Ando Masaru M Li Zilong Z Tatsumi Kazuyuki K

Proceedings of the National Academy of Sciences of the United States of America 20080529 22

The reaction of NiBr(2)(EtOH)(4) with a 1:2-3 mixture of FeBr(2)(CO)(4) and Na(SPh) generated a linear trinuclear Fe-Ni-Fe cluster (CO)(3)Fe(mu-SPh)(3)Ni(mu-SPh)(3)Fe(CO)(3), 1, whereas the analogous reaction system FeBr(2)(CO)(4)/Na(S(t)Bu)/NiBr(2)(EtOH)(4) (1:2-3:1) gave rise to a linear tetranuclear Fe-Ni-Ni-Fe cluster [(CO)(3)Fe(mu-S(t)Bu)(3)Ni(mu-Br)](2), 2. By using this tetranuclear cluster 2 as the precursor, we have developed a new synthetic route to a series of thiolate-bridged dinucle ...[more]

PMID: 18511566

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Project description:A series of mixed-valence nickel-iron dithiolates is described. Oxidation of (diphosphine)Ni(dithiolate)Fe(CO)(3) complexes 1, 2, and 3 with ferrocenium salts affords the corresponding tricarbonyl cations [(dppe)Ni(pdt)Fe(CO)(3)](+) ([1](+)), [(dppe)Ni(edt)Fe(CO)(3)](+) ([2](+)) and [(dcpe)Ni(pdt)Fe(CO)(3)](+) ([3](+)), respectively, where dppe = Ph(2)PCH(2)CH(2)PPh(2), dcpe = Cy(2)PCH(2)CH(2)PCy(2), (Cy = cyclohexyl), pdtH(2) = HSCH(2)CH(2)CH(2)SH, and edtH(2) = HSCH(2)CH(2)SH. The cation [2](+) proved unstable, but the propanedithiolates are robust. IR and EPR spectroscopic measurements indicate that these species exist as C(s)-symmetric species. Crystallographic characterization of [3]BF(4) shows that Ni is square planar. Interaction of [1]BF(4) with P-donor ligands (L) afforded a series of substituted derivatives of type [(dppe)Ni(pdt)Fe(CO)(2)L]BF(4) for L = P(OPh)(3) ([4a]BF(4)), P(p-C(6)H(4)Cl)(3) ([4b]BF(4)), PPh(2)(2-py) ([4c]BF(4)), PPh(2)(OEt) ([4d]BF(4)), PPh(3) ([4e]BF(4)), PPh(2)(o-C(6)H(4)OMe) ([4f]BF(4)), PPh(2)(o-C(6)H(4)OCH(2)OMe) ([4g]BF(4)), P(p-tol)(3) ([4h]BF(4)), P(p-C(6)H(4)OMe)(3) ([4i]BF(4)), and PMePh(2) ([4j]BF(4)). EPR analysis indicates that ethanedithiolate [2](+) exists as a single species at 110 K, whereas the propanedithiolate cations exist as a mixture of two conformers, which are proposed to be related through a flip of the chelate ring. Mössbauer spectra of 1 and oxidized S = 1/2 [4e]BF(4) are both consistent with a low-spin Fe(I) state. The hyperfine coupling tensor of [4e]BF(4) has a small isotropic component and significant anisotropy. DFT calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the SOMOs in complexes of the present type are localized in an Fe(I)-centered d(z(2)) orbital. The DFT calculations allow an assignment of oxidation states of the metals and rationalization of the conformers detected by EPR spectroscopy. Treatment of [1](+) with CN(-) and compact basic phosphines results in complex reactions. With dppe, [1](+) undergoes quasi-disproportionation to give 1 and the diamagnetic complex [(dppe)Ni(pdt)Fe(CO)(2)(dppe)](2+) ([5](2+)), which features square-planar Ni linked to an octahedral Fe center.

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Thiolate-bridged dinuclear iron(tris-carbonyl)-nickel complexes relevant to the active site of [NiFe] hydrogenase.

Publications

Thiolate-bridged dinuclear iron(tris-carbonyl)-nickel complexes relevant to the active site of [NiFe] hydrogenase.

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