Structures of the cis and trans isomers of the bis(1-thia-4,7-diazacyclononane)cobalt(III) cation

Hambley, T. W.; Gahan, Lawrence R.; Searle, G. H.

doi:10.1107/s010827018801399x

Cited by 10 publications

(5 citation statements)

References 17 publications

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“…This evidence from the crystallographic data base suggests an electronic reason, perhaps involving π-bonding between the first-row transition metal and the sulfur atoms, which causes cis-S-M-S bonds to be somewhat shorter than trans-S-M-S bonds. This effect has been noted before for cobalt-(III) complexes and ascribed to a weak trans effect of sulfur ligands (Hambley, 1988;Hambley et al, 1989). The available structures of FeS 2 (N or O) 4 complexes (discussed above) indicate that this trend holds, and is perhaps accentuated, for low-spin ferric complexes.…”

Section: First-sphere Exafs Analysissupporting

confidence: 64%

“…Further evidence for a tendency for pairs of M-S bonds to be shorter when they are cis is provided by cases where different stereoisomers have been crystallized. Defining ∆r S av ≡ r S av (trans-S isomer)r S av (cis-S isomer) (and averaging the values of r S av where there is more than one trans-S or cis-S structure), ∆r S av ) 0.04 Å for [Co(L-Met) 2 ] + (Hambley, 1988), ∆r S av ) 0.02 Å for bis-(1-thia-4,7-diazacyclononane)cobalt(3+) (Hambley et al, 1989;Hambley & Gahan, 1986), ∆r S av ) 0.05 Å for [Co(en) 2 (SO 3 ) 2 ] - (Raston et al, 1979;Fallon et al, 1980), ∆r S av ) 0.02 Å for bis(thiosemicarbazide)nickel(2+) (Gronbaek & Rasmussen, 1962;Hazell, 1968Hazell, , 1972, and ∆r S av ) 0.04 Å for bis(thioacetohydroxamato)nickel (Sato et al, 1968(Sato et al, , 1969.…”

Section: First-sphere Exafs Analysismentioning

confidence: 99%

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X-ray Spectroscopy of Nitrile Hydratase at pH 7 and 9

et al. 1996

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The iron K-edge X-ray absorption spectrum of Rhodococcus sp. R312 (formerly Brevibacterium sp. R312) nitrile hydratase in frozen solutions at pH 7 and 9 has been analyzed to determine details of the iron coordination. EXAFS analysis implies two or three sulfur ligands per iron and overall six coordination; together with previous EPR and ENDOR results, this implies an N3S2O ligation sphere. The bond lengths from EXAFS analysis [rav(Fe-S) = 2.21 A at pH 7.3; rav(Fe-N/O) = 1.99 A] support cis coordination of two cysteine ligands and conclusively rule out nitric oxide coordination to the iron, a possibility proposed on the basis of an FTIR difference experiment [Noguchi, T., Honda, J., Nagamune, T., Sasabe, H., Inoue, Y., & Endo, I. (1995) FEBS Lett. 358, 9-12]. The higher-frequency EXAFS can be simulated well by inclusion of multiple scattering from two or three imidazole ligands; the fit to the data is improved if first-sphere multiple scattering pathways are also included. A slight shortening (by 0.02 +/- 0.01 A) of one or both Fe-S bonds when the pH is raised from 7.3 to 9.0 is consistent with shifts observed in the Raman spectrum [Brennan et al. (1996) Biochemistry 35, 10068-10077].

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Section: First-sphere Exafs Analysissupporting

confidence: 64%

Section: First-sphere Exafs Analysismentioning

confidence: 99%

X-ray Spectroscopy of Nitrile Hydratase at pH 7 and 9

et al. 1996

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“…30 K during data collection. This effect is probably due to an electronic trans influence which lengthens bonds trans to the Co-S bond 24 and appears to be general for square planar and pseudo-octahedral first row transition metal complexes. R312 enzyme 16 except that E0 was shifted by 598 eV and we applied a central atom phase shift that was taken as the difference between scattering phases for Co(im)6 2+ and Fe(im)6 2+ as calculated by FEFF 5.05 (Mustre de Leon, J.; Rehr, J. J.; Zabinsky, S. I.; Albers, R. C. Phys.…”

Section: Received June 7 1996mentioning

confidence: 89%

Nitrile Hydratase from Rhodococcus rhodochrous J1 Contains a Non-Corrin Cobalt Ion with Two Sulfur Ligands

et al. 1996

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We present spectroscopic data that show that a nitrile hydratase from Rhodococcus rhodochrous J1 is the first reported example of a native protein that contains a non-corrin Co 3+ ion with a mixed S and N(O) ligand field. Nitrile hydratases catalyze the addition of water to nitriles, yielding amides as the exclusive product, 3 and are used as industrial catalysts for the production of acrylamide. 4 The most thoroughly characterized nitrile hydratase is from Rhodococcus sp. R312 5 and is a (R ) 2 tetramer that contains two low-spin non-heme ferric ions of unknown function. These metal ions exist in a tetragonally distorted octahedral ligand field of three histidine imidazoles, two cysteine thiolates, and a hydroxide. 6-8 Two cobaltcontaining nitrile hydratases have been identified in R. rhodochrous J1. 9 We purified one of those enzymes 10,11 a multimer of R heterodimers totaling approximately 500 000 Da and containing non-corrin Co 3+ . 10 We measured the cobalt 12 and the protein 13 concentrations of samples of purified enzyme and found one cobalt ion per (R ). The same experiment yielded an unusually high 280 (2.7 (mg/mL) -1 cm -1 ), consistent with an earlier report. 10 EPR spectra of concentrated samples (0.3 mM cobalt) showed no signals attributable to the protein from 4 to 77 K, consistent with the presence of Co 3+ . When treated with sodium dithionite and methyl viologen, the samples developed an EPR spectrum characteristic of low-spin Co 2+ (Figure 1; g 1,2,3 ) 2.378, 2.206, 1.998; A Co 1,2,3 ) 58, 11, 97 G). 14 The cobalt K-edge X-ray absorbance spectrum of this nitrile hydratase (in the presumed Co 3+ form) is very similar to the Fe 3+ K-edge spectrum of the Rhodococcus sp. R312 enzyme 15,16 (Figure 2a,b). Using the method of Roe et al., 17 the area (in units of eV (% edge height)) of the lowest energy pre-edge peak in the cobalt spectrum (assigned to a 1s f 3d transition) is 6.3, slightly larger than areas we obtained for six-coordinate Co-(S 2 CNEt 2 ) 3 (3.6), Co(acac) 3 (3.9), and [Co(en) 3 ]Cl 3 (4.6), but much smaller than that found for the four-coordinate Co(im) 2 -Cl 2 (16.8). The size of the pre-edge peak is consistent with six-or possibly five-coordinate cobalt in nitrile hydratase, with distortions from octahedral symmetry that increase the peak area by approximately 50% compared to those of symmetrical sixcoordinate models. The pre-edge peak for the six-coordinate 7,8,16 iron in Rhodococcus sp. R312 nitrile hydratase is also approximately 50% larger than those of symmetrical six-coordinate Fe 3+ model complexes. 16 The best fits of the first sphere Fourier-filtered EXAFS are shown in Figure 2c and assume two sulfur scatterers at 2.20 Å and three ( ν 2 ) 1.3) 18 or four ( ν 2 ) 1.5) nitrogen scatterers at 1.95 Å. Any other integer values of n S or n N in two-shell fits gave ν 2 g 3.0 and were rejected on the basis of the criterion that ν 2 for a correct model is expected to be within one unit of the minimum ν 2 obtained. 19 The value of ν 2 increased by only 0.2-0.3 for each nitrogen ...

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“…A more valid comparison involves thioether donors in the middle of a polymethylene unit that is anchored at each end by other thioether or amine groups. In this case, the Co−S bond lengths found in [Co(Me 2 -N 3 S 3 sar)] 3+ (2.235 Å), in particular, fall in the middle of a relatively narrow range observed for such systems (2.217 Å for cis -[Co([9]ane-N 2 S) 2 ] 3+ to 2.256 Å for [Co([18]ane-N 2 S 4 )] 3+ ). The Co−S bond length is the same within experimental error as that found in the structure of the related homoleptic thioether cage [Co(Me 2 -S 6 sar)] 3+ (2.237(7) Å) .…”

Section: Resultsmentioning

confidence: 81%

Cobalt Cage Complexes with N₃S₃ Donor Sets and Differing Cavity Sizes: A Novel Macrobicyclic Cage with a Contracted Cap

et al. 1999

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Treatment of the cobalt(III) complex of the hexadentate tripodal N(3)S(3) ligand ten (4,4',4' '-ethylidynetris(3-thiabutan-1-amine) with propanal and paraformaldehyde under basic conditions, followed by borohydride reduction and reoxidation of the metal center, leads largely to the encapsulated (red) metal complex cation [Co(Me(2)-N(3)S(3)sar)](3+) (Me(2)-N(3)S(3)sar = 1,8-dimethyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6]icosane). Unexpectedly, significant amounts of the homologous (yellow) complex cation [Co(Me(2)-N(3)S(3)absar)](3+) (Me(2)-N(3)S(3)absar = 1,8-dimethyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.5]nonadecane) were also obtained. This macrobicyclic complex has a contracted cavity resulting from a cap containing one fewer methylene units than Me(2)-N(3)S(3)sar. The structures of both cobalt(III) complexes have been determined by X-ray crystallography. [Co(Me(2)-N(3)S(3)sar)]Cl.ZnCl(4).H(2)O crystallizes in the cubic space group P2(1)3 with Z = 4, a = 13.9683(11) Å. [Co(Me(2)-N(3)S(3)absar)](ClO(4))(3).0.5CH(3)CN.0.5H(2)O crystallizes in the triclinic space group P&onemacr; with Z = 4, a = 12.036(4) Å, b = 15.932(9) Å, c = 17.212(14) Å, alpha = 64.93(7) degrees, beta = 72.77(5) degrees, gamma = 88.91(7) degrees. The surprising structural rearrangement is examined, along with the spectral and redox properties of both cobalt complexes. The influence of the reduced cavity size in the absar type cage is reflected in a shift of the bands in the electronic spectrum of both the cobalt(II) and cobalt(III) complexes to higher energy, and a more negative value for the Co(III/II) redox potential. The demetalation of the complexes is also described.

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Structures of the cis and trans isomers of the bis(1-thia-4,7-diazacyclononane)cobalt(III) cation

Abstract: Abstract.trans-Bis(1-thia-4,7-diazacyclononane)-cobalt(III) trifluoromethanesulfonate, (I), trans- [Co-

Cited by 10 publications

References 17 publications

X-ray Spectroscopy of Nitrile Hydratase at pH 7 and 9

X-ray Spectroscopy of Nitrile Hydratase at pH 7 and 9

Nitrile Hydratase from Rhodococcus rhodochrous J1 Contains a Non-Corrin Cobalt Ion with Two Sulfur Ligands

Cobalt Cage Complexes with N₃S₃ Donor Sets and Differing Cavity Sizes: A Novel Macrobicyclic Cage with a Contracted Cap

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Structures of the cis and trans isomers of the bis(1-thia-4,7-diazacyclononane)cobalt(III) cation

Abstract: Abstract.trans-Bis(1-thia-4,7-diazacyclononane)-cobalt(III) trifluoromethanesulfonate, (I), trans- [Co-

Cited by 10 publications

References 17 publications

X-ray Spectroscopy of Nitrile Hydratase at pH 7 and 9

X-ray Spectroscopy of Nitrile Hydratase at pH 7 and 9

Nitrile Hydratase from Rhodococcus rhodochrous J1 Contains a Non-Corrin Cobalt Ion with Two Sulfur Ligands

Cobalt Cage Complexes with N3S3 Donor Sets and Differing Cavity Sizes: A Novel Macrobicyclic Cage with a Contracted Cap

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Cobalt Cage Complexes with N₃S₃ Donor Sets and Differing Cavity Sizes: A Novel Macrobicyclic Cage with a Contracted Cap