Iron complex crystallographic study

A ferric NHase from Rhodococcus sp. N-771 [54], which is probably the same as that from Rhodococcus sp. N-774 because of the coincidence in amino acid sequences, shows a photosensitive phenomenon both in vivo and in vitro [55,56], Its NHase activity is increased by exposure to near ultraviolet light. Absorption and fluorescence spectra indicated that the chromophore involved in the photoactivation is the iron complex. Crystallographic parameters of the Rhodococcus sp. N-771 NHase have been determined by precision X-ray diffraction studies [57]. 

Compounds 139 are tris(oximehydrazone) derivatives with an iron(ll) ion in the center of the cavity [230]. Compound 140 (Fig. 38) has been known for 30 years [231, 232] and was prepared from a tris(2-aldoximo-6-pyridyl)phos-phine that is capped by a BF unit to encapsulate cobalt(ll), zinc(ll), nickel(ll), and iron(II). All four macrocyclic complexes were characterized later by a comparative X-ray crystallographic study [233-236]. 

The iron complexes 35 (78) and 36(79) have been reported. Crystallographic studies on 35 indicate that the (> 4-diene)metal interaction is best represented by the valence bond description shown, in which the perfluorodiene acts as a... 

The anaerobic addition of catechol to catechol 2,3-dioxygenase (2,3-CTD) results in the formation of an ES complex that retains the Fe(II) oxidation state of the as-isolated enzyme as indicated by a number of spectroscopic (Mossbauer [162,163], XAS [158], near IR CD and MCD [157]) methods. These methods also indicate that the iron center remains 5-coordinate. Crystallographic studies... 

A report of the X-ray crystallographic studies of enan-tiopure ( -allyl)Fe(CO)2(NO) complex (170) has appeared, though httle detail was provided. The same report described the CD spectrum of this complex in more detail the negative band at ca. 350 mn and the positive band at ca. 450 nm can be used to assign the configuration of the complex. Diastere-omeric complexes exhibit the opposite Cotton effect. The crystal structures of corresponding monophosphine complexes (145) have been determined. ft is possible to consider these complexes as either trigonal bipyramidal (bidentate allyl) or tetrahedral see Tetrahedral) (monodentate allyl), with the central carbon of the allyl closer to the iron atom (2.084 A) than the terminal carbon atoms (2.117 and 2.142 A). These complexes are chiral at the iron atom, and it has proved possible to separate the diastereomeric complexes formed by enantiomerically pure aminophosphines. 

The preparation of some (polyfluorocyclohepta-l,3-diene)iron tricarbonyl complexes [104] is reported, and parameters are given in Table IV. (55) The appearance of the geminal fluorines at C5 and C 7 as an AB quartet when the adjacent carbon (C4 or Cl) carries a fluorine, but as a singlet when the vinylic neighbour is hydrogen is noteworthy. Since a crystallographic study shows that the ring is puckered across the line C1-C4, (56) this must be due to accidental equivalence. 

---