Iron alkynyls

Table 7. Molecular third-order NLO data for iron alkynyl and ferrocenyl complexes ...

Iron alkynyl complexes containing aromatic moieties are of particular interest as building blocks for molecular devices. Second-order non-linear optical properties have been investigated for various Fe(ii) and Fe(iii) complexes of the type [(dppe)Gp Fe(G=G-Ar)] where Ar = pyridine, GsH4N(GH3), or/>-G6H4X (X = NO2, GN, GF3, H, OMe, and NH2). These compounds have shown significant quadratic redox-switchable polarizabilities. Further examples of redox-active iron alkynyl synthons containing aromatic units have been reported, where the iron alkynyl unit is... 

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

The low spin aryliron complexes Fe(Por)Ar behave differently than their alkyl counterparts toward oxygen. In chloroform the products of the reaction of Fe(Por)Ar with O2 are the iron(IV) alkyl Fe(Por)Ar] and Fe(Por)Cl, while in toluene the aryloxide complexes Fe(Por)OAr are formed with no direct evidence for the formation of arylperoxo intermediates."" The high spin iron(lll) alkynyl complexes which have more ionic character in the Fe—C bond do not react with oxygen, and the order of reactivity of organoiron(lll) complexes toward O2 is given by Fe(Por)(alkyl) > Fe(Por)(aryl) > Fe(Por)(C=CR). ... 

With the successful chemistry of the cymantrenes and the (cyclobuta-diene)tricarbonyl iron, the quest for tetraethynylated cyclobutadienes based on CpCo-stabilized complexes arose. Why would they be interesting Whereas all derivatives of 63 and 68 exhibit reasonable stability when their alkynyl substituents are protected by either an alkyl or a trimethylsilyl group, the desilylated parents are isolated only with difficulty and are much more sensitive. 

Scheme 29 Iron-promoted cyclization/halogenation of alkynyl diethyl acetals...

Reactions of cyclopentadienyl- and (pentmethylcyclopentadienyl)iron dicarbonyl 2-alkynyl complexes as well as cyclopentadienylmolybdenum tricarbonyl 2-alkynyl complexes with 4,5-diphenyl-3,6-dihydro-l,2-dithiin 1-oxide 111 were shown to yield transition metal-substituted five-membered ring thiosulfinate esters 112 in moderate to excellent yields (Scheme 27) <19910M2936, 1989JA8268>. These reactions are formal [3-1-2] cycloadditions. When... 

Alkynyl ligands are only modest 7i-acids however, this can allow electronic communication between metal centres bound to bis(alkynyl)diyl bridging ligands, e.g. the diruthenium butadiyne-l,4-diyl complex shown (Figure 4.19) undergoes four single 1VE oxidations. If the metals were not in electronic communication, oxidation of one iron centre would not significantly affect the redox potential of the second, i.e. both would oxidize at the same potential. 

The chemistry of (l-alkynyl)carbene iron complexes is different from that of chromium and tungsten compounds. [4+2] cycloaddition of cyclopentadiene to a (l-alkynyl)carbene iron complex 11,m (R = SiMe3, r-Bu, c-QHn, n-Pr, Ph) affords (l-alkenyl)carbene Fe(CO)4 complexes 55, but these are readily isomerized at 50°C to Fe(CO)2 complexes 57 by insertion of carbon monoxide into the Fe = C bond of an intermediate Fe(CO)3... 

Scheme 78. Trinuclear iron derivative of an alkoxy(l-alkynyl)carbene complex.

Molecular wires, 208 211 in which two metal centers are connected by an unsupported C3 chain, as in compound 191, have been generated by addition of BF3 to binuclear bridged (l-alkynyl)carbene complex lw (Scheme 80).27 29,212 Similar compounds were derived from tungsten, rhenium, and iron moieties. A binuclear complex 192 containing a C5 bridge has been also obtained 27... 

Iron complexes with hydrated furane ligands are available from appropriate alkynyl- and alkenyl-substituted iron compounds as precursors 174). 

Ffe. 33. CpFe[C=C(Me)S(0)0CH2](C0)2. (Reprinted, with permission, from Characterization of r-C5H5Fe(CO)2C4H5S02. A Novel Compound from the Reaction of Sulfur Dioxide with a 2-Alkynyl Complex of Iron, Churchill, M. R. et al. J. Am. Chem. Soc. 92, 1975, copyright, 1970, by the American Chemical Society)... 

In the fields of organometallic polymer see Polymer) chemistry , in which complexes may have particularly interesting physical properties (liquid crystallinity, optical nonlinearity see Nonlinear Optical Materials), etc.), or of molecular electronics , metal alkynyl complexes play a significant role. These areas have been the subject of recent reviews, thus only a brief overview of methods to prepare iron alkynes will be given here. Liu has also recently reviewed the cyclization chemistry of alkynyl organometaUics, including those of iron. ... 

Transmetallation of iron hahdes with lithium acetylides or alkynyl Grignards affords a-alkynyl complexes in moderate... 

The chemistry of iron vinylidene complexes is dominated by the electrophilicity of the carbon atom adjacent to the iron organometallic unit. While addition of water leads to an acyl complex (i.e., the reverse of the dehydration shown in equation 10), addition of an alcohol leads to a vinyl ether complex. Similarly, other iron vinyl complexes can be prepared by the addition of thiolate, hydride, or an organocuprate (Scheme 33). " The nucleophilic addition of imines gave enaminoiron intermediates that could be further elaborated into cyclic aminocarbenes. This methodology has been used to provide access to /3-lactams and ultimately penicillin analogs, and good diastereoselectivities were observed (6 1-15 1) (Scheme 34). 04 Iso, vinylidene complexes are intermediates in cyclizations of alkynyl irons with substituted ketenes, acid chlorides, and related electrophiles an example is shown (equation 11). These cyclizations led to the formation of a series of isolable and characterizable cyclic vinyl iron complexes. 

Dimeric association (71) can be obtained by an acid-base reaction between alkyl zirconocene and a terminal alkynyl ruthenium complex (equation 32). Surprisingly, the same reaction was observed with an iron acetylide opposed to Schwartz s reagent see Schwartz s Reagent) (equation 33). ... 

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