Fe carbonyl complexes

The project by Sun et al. has been extended to photochemical production of H2 by a Ru(II) photosensitizer covalently linked to a proton reduction catalyst of dinuclear Fe carbonyl complex [128,129] (Fig. 25, left). The researchers synthesized (but did not isolate) a Ru(II) terpy complex connected to an [Fe2( x - SCH2N(Ph)CH2S)(CO)6] complex by an acetylene spacer [129] (Fig. 25, right). However, the photoproduction of H2 has not yet been reported. 

Royo et al. prepared the NHC-Fe carbonyl complexes 183 by reaction of corresponding imidazolium salts with [Fe3(CO)j2] and tested them in the hydrosilylation of benzaldehyde and acetophenone (Figure 13.23). Related NHC-Fe carbonyl complexes were also tested in the selective hydrosilylation of esters to give aldehydes. With complex [(IMes)Fe(CO)4] in the presence of Et2SiH2 (1.1 equiv.), both activity and selectivity were enhanced, full conversion was observed after 3 h at room temperature, and only the aldehyde product was detected. 

Iron(II) alkyl anions fFe(Por)R (R = Me, t-Bu) do not insert CO directly, but do upon one-electron oxidation to Fe(Por)R to give the acyl species Fe(Por)C(0)R, which can in turn be reduced to the iron(II) acyl Fe(Por)C(0)R]. This process competes with homolysis of Fe(Por)R, and the resulting iron(II) porphyrin is stabilized by formation of the carbonyl complex Fe(Por)(CO). Benzyl and phenyl iron(III) complexes do not insert CO, with the former undergoing decomposition and the latter forming a six-coordinate adduct, [Fe(Por)(Ph)(CO) upon reduction to iron(ll). The failure of Fe(Por)Ph to insert CO was attributed to the stronger Fe—C bond in the aryl complexes. The electrochemistry of the iron(lll) acyl complexes Fe(Por)C(0)R was investigated as part of this study, and showed two reversible reductions (to Fe(ll) and Fe(l) acyl complexes, formally) and one irreversible oxidation process."" ... 

An iron-catalyzed carbonylation reaction of alkynes 120 forming succinimides 121 by the aid of Fe(CO)5 78 or [Fe3(CO)i2] 119 has been reported by Beller et al. (Scheme 31) [94]. This reaction seems interesting as iron-carbonyl complexes are kinetically relatively inert. As a model system 3-hexyne was reacted with excess ammonia under 20 bar CO pressure. Employing a higher pressure leads to... 

A half-metallocene iron iodide carbonyl complex Fe(Cp)I(CO)2 was found to induce the living radical polymerization of methyl acrylate and f-bulyl acrylate with an iodide initiator (CH3)2C(C02Et)I and Al(Oi- Pr)3 to provide controlled molecular weights and rather low molecular weight distributions (Mw/Mn < 1.2) [79]. The living character of the polymerization was further tested with the synthesis of the PMA-fc-PS and PtBuA-fi-PS block copolymers. The procedure efficiently provided the desired block copolymers, albeit with low molecular weights. 

Synergistic studies were carried out on mixed metal carbonyl and mixtures of metal carbonyl complexes by Pakkanen and coworkers.94 95 A largely applied research approach, results are reported below in Table 23 for Fe-Ru and Fe Os carbonyl catalysts. Also tested (not shown) were Fc -Co and Fe-Rh carbonyl catalysts, Ru-Co and Ru Rh carbonyl catalysts, and Co-Rh, Co-Ir, and Rh Ir carbonyl catalysts. Typical conditions T = 100 °C Pco = 0.42-0.60 atm pyridine = 2.0-4.0 ml H20 = 0.36 ml. Note that dppe = Ph2PCH2CH2PPh2. The data shown in Table 23 are representative of the TON for their catalysts. 

---