Iron complexes trimethylenemethane

Phenyl-substituted trimethylenemethane iron complexes can be obtained from the methylenecyclopropanes, XLVIIa and b, when reacted with Fe(CO)j [alternatively. 

A tricarbonyl(trimethylenemethane)iron complex containing a cyclopropane subunit 5 was converted photochemically with an acid to give chrysanthemic acid. °... 

Oxidation of tricarbonyl(trimethylenemethane)iron complexes 25 containing an olefinic side chain, with Me3NO in boiling benzene, affords dibridged dicarbonyl (bis-7r-allyl)iron complexes. 

Alternatively, (trimethylenemethane)iron complexes can be synthesized by disproportionation of tricarbonyl(2-methallyl)ironJ Enantiomerically pure tricarbonyl-(trimethylenemethane)iron complexes can be obtained by resolution of the racemic mixture via diastereomeric esters or amides. (5)-(-)-Ethyl lactate and (/ I)-(+)-a-methyl-benzylamine are employed as resolving reagents for this piupose. The chiral auxiliaries can be removed by a variety of reagents leaving the (trimethylenemethane)iron fragment unaffected. Treatment of both the corresponding Boc-protected amides and the chiral esters with diisobutylaluminum hydride (DIBAL) or methyllithium provides the primary or tertiary alcohols, respectively. Saponification of the ester with lithium hydroxide in methanol and subsequent acidification of the mixture affords the methyl ester. Treatment of the ester with triethylsilane leads to complete reduction of the functionality to leave a methyl group (Scheme 4—85). ... 

Scheme 4-85. Resolution of chiral tricarbonyl(trimethylenemethane)iron complexes.

Scheme 4-99. Reaction of (trimethylenemethane)iron complexes with a,P unsaturated ketones.

Cyclization of an (T -trimethylenemethane)iron complex with a double bond of a diene in an appropriate distance leads to bis(T -allyl)iron complexes (Scheme 4—100), which are presumably also intermediates in the reactions presented in Scheme 4—99. ... 

For cyclobutadiene complexes, the energy of activation of rotation of ligands about the M-C4R4 axis is very small, while for the trimethylenemethane iron derivative the AG of rotation of trimethylenemethane is high, equaling 71-75 kJ mol (Table 8.4). 

The complex [Fe C(CH2)3 (CO)3] reacts with bromine to afford a 2-bromo-methylallyl iron complex [equation (8.88)]. The addition of HCl may also take place [equation (8.89)]. Some other trimethylenemethane complexes may also react in a similar manner " [equation (8.90)]. 

Similar to the first syntheses of cyclobutadiene complexes [2, 9], the first synthesis of a trimethylenemethane complex started from dichloride 2, which was treated with diironenneacarbonyl to give tricarbonyl(trimethylenemethane) iron(O) (3) in 30% yield In addition to iron(II) chloride (Scheme 10.1) [10]. The r -coordination has been confirmed by crystal structure analyses [11, 12]. Very recently, Frenking et al. published a detailed theoretical bonding analysis of some late transition metal sandwich trimethylenemethane complexes [13]. 

Mitsudo reported the synthesis of the fluoro-substituted trimethylenemethane complex 28 by treatment of the trifluoromethyl-substituted vinylcarbene iron complex 27 with K[B(sec-Bu)3H] in 34% yield (Scheme 10.10) [28]. 

While the q -bonding mode in the iron complex 3 has earlier been established crystallographically [11, 12], it is remarkable that this coordination mode is observed in a 17 electron iron(III) complex as well. Dixneuf et al. treated iron(III) chloride with magnesium and dichloride 2 in the presence of phosphane ligands and obtained the respective trimethylenemethane iron(II) complexes, which were then oxidized with silver triflate resulting in the formation of cationic trimethylenemethane complexes with the ligand still being q -coordinated [30]. Bazan et al. reported a distorted coordination to zirconium [31], and... 

Kerber et al. succeeded in the synthesis of the first iron complexes of isobenzo-fulvene. Reaction of the dibromide 89 with Collman s reagent (disodiumtetracar-bonylferrate) afforded isobenzofulvene complexes 90 and 91 in 4 and 2% yield, respectively. 90 is a trimethylenemethane system anellated to an intact benzene ring (Scheme 10.31) [83]. 

Methoxybutadiene has been complexed photochemically using Fe2(CO)9, instead of the more conventional thermal conditions. Complexation of acyclic dienes with Fe2(CO)9 constituted the first step toward trimethylenemethane complexes. All details concerning the preparation and spectral properties of tricarbonyl(butadiene)iron complexes are gathered in recent reviews. ... 

Reaction with Electrophilic AUenes. Formation of tricarbonyl(l,3-butadiene)iron(0) complexes from allenes (e.g. 57) is possible via tricarbonyl(trimethylenemethane)iron(0) intermediates (eq 35 ). ... 

Substituted methylenecyclopropanes react with diiron nonacarbonyl to give trimethylenemethane and 1,3-diene iron tricarbonyl complexes . Theoretical analysis of the former... 

First, cis- and trans-2-phenylmethylenecyclopropanes-3-d were shown to give trimethyl-enemethane complexes with the deuterium at a location consistent only with disrotatory ring-opening (Figure 41). Second, reaction of 2,2-diphenylmethylenecyclopropane with a variety of iron carbonyl reagents allowed isolation of the methylenecyclopropane iron tetracarbonyl complex. This compound could be shown to give the trimethylenemethane complex on reaction with trimethylamine-N-oxide or diiron nonacarbonyl, both of which... 

JOM(322)103>. Other more exotic addition reactions of (55) have also appeared including reactions with allenes <90OM289> and phosphinimines <89JA7279,920M2613). The former reaction is an efficient method for the preparation of iron trimethylenemethane complexes. 

In contrast, isolable t/ -transition-metal complexes of trimethylenemethanes, e.g. the iron compounds 8 or 9, usually exhibit almost no tendency to undergo cycloadditions due to their extraordinary stability. Only low yields of cycloaddition products are obtained, even at elevated temperatures and prolonged reaction times, and with highly reactive alkenes such as tetracyanoethene. As in all of these cases, the complexes have to be oxidatively destroyed in order to accomplish any cycloaddition, so that catalytic pathways cannot be generated using these reactants. 

Farmgia LJ, Camtaxrn E, Tegel M (2006) Chemical bonds without chemical bonding a combined expraimental and theoretical charge density study on an iron trimethylenemethane complex. J Phys Chem A 110 7952—7961... 

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