Bridged diiron complexes

The first example of iron-catalyzed asymmetric oxidation of sulfides was described by Fontecave and coworkers in 1997 [163]. An oxo-bridged diiron complex, which contained (—)-4,5-pinenebipyridine as chiral ligand, was reported to catalyze sulfide oxidations with H202 in acetonitrile, having the potential to transfer an oxygen atom directly to the substrates. However, the enantioselectivity of this process remained rather low (<40% ee, Scheme 3.53). 

Scheme 3.53 Oxo-bridged diiron complex for sulfide oxidations.

Reaction of a doubly silylene-bridged diiron complex with a silyliron complex gives a triply silylene-bridged dinuclear complex in a low yield, perhaps through the displacement of carbonyl ligands by a silylene unit [Eq. (32)]m... 

The mechanism for the formation of singly germylene-bridged complexes is considered to be identical with that for the formation of analogous silylene-bridged complexes shown in Scheme 3. On the other hand, the doubly germylene-bridged diiron complexes in Eqs. (42) and (43) are likely to form via the intermediate formation of K-type complexes. 

The molecular structures of some B-type silylene- and silylyne-bridged diiron complexes are shown in Fig. 1. All of (a), (b), and (c) have a bridging... 

For the silylene-bridged diiron complexes of the type Cp2Fe2(CO)2 (iu-CO)( U-SiRX), three geometric isomers are possible, as illustrated in Scheme 30. Malisch and Ries reported that the NMR spectra immediately after dissolution of crystalline Cp2Fe2(CO)2(/u.-CO)(/u,-SiMeH) show only the signals of two cis isomers, whereas the equilibrium containing all three... 

Other Fe complexes are known to epoxidize olefins with peracetic acid [244]. For example, Jacobson and coworkers report a Fe(mep) complex (mep=N,N -dimethyl-N,N -bis(2-pyridylmethyl)-ethane) (Fig. 1.3c) which self-assembles under reaction conditions to form a /z-oxo, carboxylate-bridged diiron complex similar to that found in the core of the hydroxylase active site of oxidized methane monooxygenase (MMO) [236]. 

Kurtz DM (1990) Oxo- and hydroxo-bridged diiron complexes a chemical perspective on a biological unit. Chem Rev 90 585-606... 

Structural and Magnetic Properties of Oxo-Bridged Diiron Complexes... 

The Mossbauer spectra of RRB2 at 4.2 K in large applied fields are indicative of a diamagnetic ground state. This result implies that the two iron centers in the dinuclear unit are coupled antiferromagnetically. Variable temperature magnetic susceptibility measurements yield a / of (-108 20) cm as expected for an oxo bridged diiron complex (24). 

Iron, substituted alkylidene-bridged diiron complexes 442... 

The insertion of CS2 occurs at the Fe-C bond of the tetramethylfulvene-bridged diiron complex 36, producing the triiron complex 37 and the monoiron complex 38 (Scheme 9) [82]. A dithiocarboxylato ligand in 37 bridges three iron fragments in a novel coordination mode. One iron atom adopts the distorted-piano-stool geometry, while the other two iron atoms are distorted octahedral. 

Figure 9.12 Selected examples of drthiolate-bridged diiron complexes efficient in light-driven H2 evolution.

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