Iron complex isoelectronic

Chiral rhenium complexes, such as 1 and 4, are isoelectronic to the a-alkoxy vinyl-iron complexes discussed above and they exhibit analogous chemistry in many respects. Like the iron complexes, they are prepared as the Z-isomer and are readily alkylated by primary iodoalkanes and (bromomethyl)benzene with efficient 1,3-asymmetric induction97. Subsequent, spontaneous loss of halomethane produces the elaborated rhenium-acyl complexes. Two examples of the stereocontrolled preparation of diastereomeric rhenium-acyl complexes via this methodology are illustrated. 

In metallic complexes, the bridged and non-bridged structures are often very close in energy, and small changes can favour one geometry or the other. Thus, in the trimetallic complex [Os3(CO)i2], which is analogous to cyclopropane (5-21a), all the carbonyl ligands are terminal. However, in the isoelectronic iron complex, two carbonyl... 

Unstable (C6H6)aRu has been prepared from Ru vapour and benzene n.m.r. spectra confirm the l-4-i l-6-j co-ordination of the benzene ligands. Reaction of [RuCl2(arene)]a complexes with cod, chd, or ethylene in the presence of base (NaaCOs) or zinc dust yields (arene) RuLa complexes (La=cod or chd L=Ca-Hi) under similar conditions, chpt yields the protonation product [(arene)Ru-(cycloheptadienyl)]+. Some of the analogous iron complexes have also been prepared, and the reactivity of the Ru complexes towards electrophiles resembles closely that of the isoelectronic CpRh(diene) series. 

Dihydro-lH-l,2-azaboroles derive from cyclopentadiene by the isoelectronic replacement of a C=C group by a BN moiety ". The neutral rings react in xs boiling Fe(CO)j without any other solvent to form red-brown iron-dihydro-1,2-azaborolyldi-carbonyl dimers as their cis and transisomers in 56% yield, or with CojfCOg in petroleum ether at 60-80°C to the half-sandwich complex (dihydro-1,2-azaborolyl)Co(CO)2 (40%). The CO group can easily be substituted by olefins ... 

With the iron atom in its most negative oxidation state of —2 this complex possesses nucleophilic properties and thus can be used in nucleophilic substitution reactions. As the iron atom in this complex formally has ten valence electrons, it is isoelectronic with Pd(0), which is a well-known catalyst in allylic substitution reactions [49]. 

The Fe(II)-NO complexes of porphyrins 66-68) and heme proteins 24, 49, 53, 69-76) have been studied in detail by EPR spectroscopy, which allows facile differentiation between five-coordinate heme—NO and six-coordinate heme—NO(L) centers. However, only a few reports of the Mossbauer spectra of such complexes have been published 68, 77-82), and the only Fe(III)-NO species that have been studied by Mossbauer spectroscopy include the isoelectronic nitroprusside ion, [FeCCNlsCNO)] (7S), the five-coordinate complexes [TPPFe(NO)]+ 68) and [OEPFe(NO)]+ 82), and two reports of the nitro, nitrosyl complexes of iron(III) tetraphenylporphjrrins, where the ligand L is NO2 82, 83). 

Rhenium-acyl complexes, such as 1, are isoelectronic with the iron-acyl complexes discussed above and many reactivity patterns are common to the two groups of compounds. Treatment of complex 1 with strong bases, such as butyllithium or lithium diisopropylamide, results in abstraction of a cyclopentadienyl proton which is followed by rapid migration of the acyl ligand to the cyclopentadienyl ring to produce the metal-centered anion 384. Alkylation of 3generates a metal-alkyl species, such as 4. 

Fe (Por)] is formed when Feni(Por) or Feu(Por) is electrochemically reduced or treated with a stoichiometric amount of sodium anthracenide in THF.89 [Fe TTP]" (Na-18-crown-6)+ (THF)2 is a tow-spin square planar complex jitK 2.5 BM, g x 2.1, 1.9, Fe—Npor 2.023(5) A), and shows a similar visible spectrum to that of Fe (TPP) but with a much lower intensity. This species is isoelectronic to Co (Por), the anionic charge, in addition to an odd electron to the dzl orbital, diminishes the ligand affinity of the iron atom. Further reduction generates an Fe"-porphyrin dianion. 

There are a sufficiently large number of complexes, mainly of germanium, containing more than one type of transition metal, to warrant a separate discussion some examples have already been mentioned (viz. 38 and 57). Mackay and Nicholson (89,91) have described the reaction between [Fe2-(CO)8(//-GeH2)2] and [Co2(CO)8], which affords the mixed cobalt-iron clusters [Fe2(CO)8 /i-Ge(Co2(CO)7) 2], 82, and [Fe2(CO)7 /i-Ge(Co2-(CO)7) 2], 83, the latter having been characterized by X-ray diffraction. This is isoelectronic with the iron-germanium cluster, 63, and both adopt very similar structures. 

Mn(diene)(CO>3] complexes are isoelectronic with [Fe(diene)(CO>3] complexes but owing to their anionic character are much more reactive toward electrophiles than the neutral iron analogs. The first examples of these species to be reported were [Mn(cyclohexadiene)(CO>3] complexes prepared via... 

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