38117-54-3

The compound (CO)2WC-SMe (1) reacts with two equivalents of (In)Rh(CO)2, where In = η5-indenyl, C9H7, in refluxing THF to give the brown-black crystalline μ3-carbyne > (2) containing a Rh2W triang

[Ti(NMe2)4] reacts with [FeH(CO)2(Cp)] to form [(NMe2)3 TiFe(CO)2(Cp)] (1), by the elimination of 1 equiv of HNMe2. This compound was spectroscopically characterized, and its structure was determined by single-crystal X-ray diffraction (R = 4.0%, Rw = 4.4%). There is a direct, unsupported bond between iron and titanium in 1, with bond lengths of 2.567 (1) and 2.569 (1) ? in two independent molecules. The relative orientation of the ligands on iron and titanium suggests that there may be a π-component of the metal-metal bond. Amide methyl groups distal to iron show unusually obtuse Ti-N-C angles of about 130°. Analogous complexes with alkoxide ligands on titanium are more labile than 1.

The polycarbon metal cluster [Fe6(CO)18C4]2- is formed by the reaction of CF3SO3SO2CF3 with [Fe3(CO)9(CCO)]2-. Apparently, the SO2CF3 moiety abstracts an oxygen from the ketenylidene (CCO) ligand and C - C coupling occurs to form the C4 ligand. A single-crystal X-ray structure determination reveals that the pattern of C-C bond lengths of the C4 ligand in [Fe6(CO)18C4]2- mimic those in free butadiene.

Reaction of the molybdenum alkyne complex [Mo-(P{OMe}3) 2(η2{4e}-PhC2Ph)(η5-C 5H5)][BF4] with K[Fe(CO)2- (η5-C5H5)] results in the formation of the η2(3e)-vinyl complex [Mo(P{OMe}3)2(η 2{3e}=CPh-CHPh)(η5-C5H5)] and [Fe-(CO)2(η5-C5H5)] 2. A study of the reaction by EPR spectroscopy implies that the reaction proceeds via [Mo(P{OMe}3)2(η2{4e}- PhC2Ph)(η5-C5H5)], which is then thought to undergo a hydrogen-abstraction reaction to give the observed product. The same radical was observed in the reaction of [Mo(P{OMe} 3)2-(η2{4e}-PhC2Ph) (η5-C5H5)][BF4] with LiBEt 3H, implying the presence of an alternative mechanistic pathway to the direct addition of hydride to the molybdenum alkyne complex.

Exchange etherification of dicarbonylcyclopentadienyl(η2-ethyl vinyl ether)iron tetrafluoroborate (4) with optically active primary and secondary alcohols yields a mixture of diastereomeric cations.These isomers are in rapid equilibrium at room

The compound (μ-Se)(η5-CpercentH5)Fe(CO)2>2 (1) has labile metal-selenium bonds and therefore undergoes insertion and metathesis reactions.Thus, reaction with elemental selenium gives the novel FeSeSeFe chain-type complex (μ,η1:η1-Se2)5-CpercentHpercent)Fe(CO)2>2 (2).Both compounds 1 and 2 react with the homodinuclear chromium complex 5-C5H5)Cr(CO)3>2 with formation of the heterodinuclear derivatives of composition (η5-C5H5)2CrFe(CO)5 (3; single-crystal X-ray structure: d(Cr-Fe) 290.1(1) pm) and (μ-Se2)5-C5H5)2CrFe(CO)4> (4).The latter compound exhibits a diselenido bridge ligand in η1:η2-coordination (single-crystal X-ray structure: d(Cr-Se) 249.5(2) and 255.5(2) pm, d(Fe-Se) 238.9(2), d(Se-Se) 229.7(1) pm) and can also be obtained by treatment of the chromium complex 3 with elemental selenium.

The hydrocarbon products of the thermal and photochemical decompositions of the complexes 1M2(CO)2(η-C5H5)> (M1=M2=Fe, n=3-5; M1=M2=Ru, n=3 or 4; M1=Fe, M2=Ru, n=3) have been determined and the results interpreted in terms of a transient dimetallacycle which undergoes decomposition via β-elimination and reductive elimination processes.Decomposition of the compounds containing three-carbon bridges yields cyclopropane and propene in a ratio strongly dependent upon the identity of the metal atoms and the conditions, factors which are rationalised by the proposed mechanism.But-1-ene, and cis- and trans-but-2-ene are obtained from the decomposition of complexes containing four-carbon chains, but only but-1-ene and trans-but-2-ene are produced from the thermolysis of Fe(CO)2(η-C5H5)>.This is attributed to a methyl-substituted dimetallacyclopentane intermediate adopting for steric reasons a conformation which does not allow the formation of cis-but-2-ene.The low proportion of but-1-ene can also be traced to crowding in the dimetallacyle.Pentane is preferetially evolved from Fe(CO)2(η-C5H5)>, with smaller amounts of pent-1-ene, and cis- and trans-pent-2-ene, interpreted as due to a predominantly radical mechanism for the decomposition of this compound.The organometallic products of the decompositions are the dimers (M=Fe or Ru) and, where appropriate, those of the subsequent photolysis of .Carbon-carbon bond fission occurs on heating Ru(CO)2(η-C5H5)> with Me3NO in tetrahydrofuran, giving a low yield of .

Photolysis of 5-C5H5)Fe(CO)2>2> in CH4 (12 K) and polyvinyl chloride film (12-77 K) matrices leads to the formation of a novel species proposed, on the basis of i.r. evidence including 13CO enrichment and u.v.-visible spectra, to be the CO-bridged dimer 5-C5H5)Fe>2>.

The iron-ruthenium complex is obtained in 60 percent yield from the reaction of Na with .In the solid state a trans- structure has been established by X-ray diffraction.Crystals are monoclinic, space group P21/c (no. 14), with Z=2 in a unit cell for which a=7.064(2), b=12.518(3), c=8.011(2) Angstroem, and β=106.23(2) deg.The structure was solved by heavy-atom methods and refined to R 0.0275 (R' 0.0313) for 1532 independent intensities.The molecule is disordered about a centre of inversion at the mid-point of the metal-metal bond, each metal site being occupied by half an iron and half a ruthenium atom, with an iron-ruthenium bond length of 2.626(1) Angstroem.In solution the cis- isomer is dominant, and shown by 13C n.m.r. to be undergoing cis trans isomerisation with bridge terminal carbonyl exchange at room temperature, but to be static at -80 deg C.The complex is an excellent precursor of organo-iron-ruthenium chemistry.Treatment with alkynes R1C2R2 (R1 = R2 = H, Me, or Ph, R2 = H) under u.v. irradiation gives complexes 1CR2>(η-C5H5)2> in 20-65 percent yield as a result of alkyne-CO linkage.This link in the complexes derived from ethyne, propyne, and but-2-yne is broken upon protonation, generating μ-vinyl cations 1=CHR2)(η-C5H5)2>+ (R1 = R2 H or Me; R1 = H, R2 = Me).These are attacked by hydride at the β carbon of the μ-vinyl to give μ-alkylidene complexes 1R2)(μ-C5H5)2> (R1 = H, R2 = Me, Et; R1 = Me, R2 = Et).Reaction of (η-C5H5)2> with Ph3P=CHR or CH(CO2Et)N2 in boiling toluene also gives μ-alkylidene complexes (R = H, Me, or CO2Et) in good yield, through ready displacement of diphenylacetylene.The μ-CH2 complex is best obtained (75 percent) by trating with LiBHEt3 then water, and in a related manner sequential addition of methyl-lithium, HBF4*OEt2, and NaBH4 affords .Under u.v. irradiation alkynes react with μ-alkylidene complexes 1)(η-C5H5)2> to give products of alkyne-alkylidene linking 3CR2CR1)(η-C5H5)2> (R1 = H or Me, R2 = R3 = H, Me, Ph, or CO2Me; R1 = H or Me, R2 = Me or Ph, R3 = H).These exist as non-interconverting isomers in which the new C3 ligand is either bound ? to iron and and ?, η2 to ruthenium or vice versa.The scope of organo-iron-ruthenium chemistry closely resembles that of the di-iron system but it is apparent that in reactivity terms there is an order: FeRu > Fe2 > Ru2.

The steric pressure introduced by the 2,4,6-C6H2 tBu3 group (R*) in the complex [Fe 2Cp2(μ-PR*)(μ-CO)(CO)2] (Cp = η5-C5H5) has pronounced effects

The reaction of diphenylacetylene with (η5-C5H5)Fe(CO)2Ar (3) affords the indenones (4) and/or (5); a cyclohexadienyliron derivative (10) is obtained when the acetylene is 2-ethynylpyridine, the structure of which was determined by X-ray crystallography.

The reactions of the sulfonium salts [Fe2(CO)2(cp)2(μ-CO){μ-C(X)SMe 2}]SO3CF3 [X = CN (1a), H (1b)] with a variety of amines are presented. 1a yields ammonium cations [Fe2-(CO)2(cp)2(μM-CO){μ-C(CN)NR 3}] [R = Me (2), Dabco (3) (Dabco = 1,4-diazabicyclo[2.2.2]-octane)], aminoalkylidene [Fe2(CO)2(cp)2(μ-CO){μ-C(CN)NR 2}] (4), isocyanide [Fe2(CO)2(cp)2(μ-CO)(μ-CNR)] (7), or diaminoalkylidene [Fe2{CN(H)(CH2)2N(H)}(CO)(cp) 2(μ-CO)2] (11) complexes by reacting with tertiary amines, secondary amines, primary amines, or ethylenediamine, respectively. 1b and secondary amines yield [Fe2(CO){C(H)NR2}(cp)2(μ-CO)2] (6). The formation of type 4 bridging and 6 terminal aminoalkylidene derivatives also via μ-C addition of CN- or H- to aminoalkylidyne [Fe2(CO)2(cp)2(μ-CO)(μ-CNR 2)]+, respectively, as well as the preparation of the terminal [Fe2{C(CN)NPri2}(CO)(cp) 2(μ-CO)2] (5) from 1a and NHPri2, allows to clarify the role of electronic and steric effects in determining the position of the aminoalkylidene ligands. The X-ray structure of 5 has been determined. The crystal contains two independent molecules of the trans-isomer. The terminally bonded aminoalkylidene ligand exhibits weaker Fe-C(carbene) (Fe-C 1.915(3) A?) and stronger C(carbene)-N(amine) π bonds (C-N 1.320(4) A?) with respect to the bridging coordination. Electrochemistry shows that 5 undergoes a chemically reversible one electron oxidation to the corresponding monocation [5]+, which has been characterized by X-band EPR spectroscopy. All the complexes have been spectroscopically characterized, and a variable-temperature NMR on [Fe2(CO){C(H)NMe2}(cp)2(μ-CO)2] (6a) indicates exchange of the aminoalkylidene ligand between the two Fe atoms.

Photoejection of one CO ligand from isolated CpM(CO)n+1BR2 (n = 1: M = Fe, Ru; n = 2: M = Mo,W; R2 = catecholate or pinacolate) compounds produces a coordinatively unsaturated 16 e- intermediate, a cyclic dioxaboryl transition metal complex, that can efficiently and selectively initiate regioselective C-H bond activation and can be used in the functionalization of alkanes. This chemistry appears distinct from that reported previously for related CpM(CO)n complexes of alkyl and aryl ligands. We show here by a combination of experimental and theoretical studies that the unoccupied p orbital of dioxaboryl ligands are intimately involved in the C-H bond activation step and that this hydrogen transfer to boron occurs by a boron-assisted, metal-mediated σ-bond metathesis. The unoccupied p orbital of boron lowers the energy of the transition state and the intermediates by accepting electron density from the metal. The metal-bound borane then rotates, transfers back through a σ-bond metathesis to capture the alkyl, and leaves the metal hydride. Copyright

Dicarbonyl(η5-cyclopentadienyl)(trimethylsilyl)iron (1) was found to react with a 1 M solution of tetrabutylammonium fluoride (2) in tetrahydrofuran at 25 deg C to give dicarbonyl(η5-cyclopentadienyl)iron anion (5).The anion generated under these conditions was trapped with electrophiles (R-X) to give 45-89percent yields of neutral dicarbonyl(η5-cyclopentadienyl)-alkyl, -allyl, -acyl-iron compounds and the ethylene cation.Tetrabutylammonium hydroxide also can be used in this reaction.Evidence indicates that fluoride ion instead of hydroxide attacks the silicon when tetrabutylammonium fluoride is used since fluorotrimethylsilane can be detected in the reaction product.Tetrabutylammonium fluoride and hydroxide quantitatively liberate styrene from dicarbonyl(η5-cyclopentadienyl)(η2-styrene)iron tetrafluoroborate, producing bis2-cyclopentadienyl)iron>.

The reactions between terminal ethynylpyridines, (trimethylsilyl)ethynylpyridines and cyclopentadienyliron dicarbonyl iodide were studied under Pd/Cu-catalyzed conditions to develop a synthetic approach to the s-alkynyl iron complexes Cp(CO)2Fe-C?C-R (R =ortho-,meta-,para-pyridyl). Depending on the catalyst and reagents used, the yields of the desired s-pyridylethynyl complexes varied from 40 to 95%. In some cases the reactions withortho-ethynylpyridine gave as byproduct the unexpected binuclear FePd μ-pyridylvinylidene complex [Cp(CO)Fe{μ2-?1(Ca):?1(Ca)-?1(N)-Ca?C?(H)(o-C5H4N)}(μ-CO)PdI]. The conditions, catalysts, and reagents that provide the highest yields of the desired s-pyridylethynyl iron compounds were determined. The methods developed allowed the synthesis of the corresponding s-4-benzothiadiazolylethynyl complex Cp(CO)2Fe-C?C-(4-C6H3N2S) as well. Eventually, synthetic approaches to s-alkynyl iron complexes of the type Cp(CO)2Fe-C?C-R (R =ortho-,meta-,para-pyridyl, 4-benzothiadiazol-2,1,3-yl) based on the Pd/Cu-catalyzed cross-coupling reactions were elaborated.

In tetrahydrofuran AgNO3 acts as a two-electron oxidant and cleaves to give a mixture of and via a detectable adduct, but in acetonitrile it acts as a one-electron oxidant to give NO3 and the . radical which then dimerises or reacts with added radical traps.

The synthesis and characterization of iron and manganese complexes containing the tetrachlorocatecholboryl (BO2C6Cl4) ligand are reported. Crystallographic study of the methylcyclopentadienyl derivative and reveals that th

A new synthesis of CpFe(CO)(PPh3)COOH is described as is the preparation of a new metallocarboxylic acid, CpRu(CO)(PPh3)COOH. Upon heating, the iron acid provided Cp2Fe2(CO)3(PPh3), as the first isolable product, which resulted from reaction of the acid with its decarboxylation product CpFe(CO)(PPh3)H. The ruthenium acid decarboxylated to the hydride in acetone, but it was stable to thermolysis in benzene. The ruthenium acid is not reactive toward CpM(CO)(PPh3)H (M = Fe, Ru). Thermolyses in chlorinated solvents take place wholly (iron acid) or in part (ruthenium acid) by redox paths; both acids were also readily oxidized by Ag+.

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The hydrido-phosphido-bridged complex 5-C5H5)2Fe2(μ-H)(μ-PMen2)(CO)2> (3) is prepared from 5-C5H5)Fe(CO)2>2 (1) and dimenthylphosphine HPMen2 in boiling toluene.The reaction proceeds via the intermediate 5-C5H5)2Fe2(HPMen2)(CO)3> (2). 2 forms a pair of cis-trans isomers, whereas 3 consists of three isomers, the meso-isomer cis-3 and the two diastereomers trans-3a and trans-3b.In hot toluene, 2 gives 1 and 3.In solution 3 undergoes a photochemical cis-trans isomerization reaction. 3 is an enantioselective catalyst in the photochemical hydrosilylation of acetophenone with diphenylsilane to give 1-phenylethanol in up to 33percent ee.

The reaction of Na (R = H.Me) with R2'AsCl (R' = Me, t-Bu) yields the novel arsanes C5R5(OC)2Fe-AsR2' (1a-1c).The high Lewis basicity of 1a-1c is proved by treatment with MeI giving the complex salts I and oxidation with

Photoreaction of CpFe(CO)2Me with sterically congested R 2GeH2 [R = 2,4,6-C6H2 iPr3 (Tip), 2,4,6-C6H2Me3 (Mes)] afforded paramagnetic germylene-bridged diiron complexes having a triplet ground state, Cp2Fe2(μ-CO)2(μ,- GeR2) (3a, R = Tip; 3b, R = Mes), while the analogous reaction with R2SnH2 afforded diamagnetic complexes Cp 2Fe2(CO)2(μ-CO)(μ-SnR2) (trans-5a, R = Tip; trans-5b, R = Mes). The structure of 3a was determined by X-ray crystallography.

We have developed a simple and convenient method for the synthesis of the first H-cluster models in which a L-cysteinyl group is coordinated to one of the two iron atoms of the diiron subsite through its sulfur atom. This synthetic method includes (i) treatment of the Boc-protected L-cysteine ester Boc-NHCH(CH2SH)CO2Et (1, Boc = tert-butoxycarbonyl) with EtONa to give the L-cysteinyl mercaptide NaSCH2CH(NH-Boc)CO 2Et (2); (ii) further treatment of 2 with [Cp(CO)2FeI] to produce the metallothioether ligand Cp(CO)2FeSCH2CH(NH- Boc)CO2Et (3); and (iii) treatment of the parent diiron complex [Fe2(μ-SCH2)2CH2(CO) 6] (4), [Fe2(μ-SCH2)2N(tBu)(CO) 6] (5), or [Fe2(μ-SCH2)2N(C 6H4OMe-p)(CO)6] (6) with Me 3NO·2H2O followed by ligand 3 to afford the target model compounds [Fe2(μ-SCH2)2CH 2(CO)5(ligand 3)] (7), [Fe2(μ-SCH 2)2N(tBu)(CO)5(ligand 3)] (8), or [Fe 2(μ-SCH2)2N(C6H 4OMe-p)(CO)5(ligand 3)] (9), respectively. All the new compounds 2, 3, and 7-9 have been characterized by elemental analysis and various spectroscopic techniques. The X-ray diffraction analysis of 8 has confirmed that these models contain a cysteinyl sulfur atom not only coordinated to one Fe atom of the diiron subsite, but also to the Fe atom of the Cp(CO)2Fe moiety to form the linkage [FeCp-(μ- cysteinyl-S)-Fesubsite], which is similar to [Fecubane- (μ-cysteinyl-S)-Fesubsite] found in natural enzymes. In addition, spectroscopic and electrochemical measurements have further demonstrated that the linkage [FeCp-(μ-cysteinyl-S)-Fesubsite] can provide substantial electronic communication between the diiron subsite and the Cp(CO)2Fe moiety. Under electrochemical conditions, 8 has been shown to be a catalyst for HOAc proton reduction to dihydrogen, and a new type of E*2E2C mechanism for this catalytic reaction is suggested. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

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The reactivity of the anionic silyl complex Na (1) towards a number of transition metal halide complexes has been investigated.Reaction with Cp(CO)2FeI yields cis- and trans-MeCp(CO)(MePh2Si)Mn(μ-CO)2Fe(CO)Cp (2).With Ph3PAuCl or PhHgBr the very stable heterodinuclear complexes MeCp(CO)2(MePh2Si)MnAuPPh3 (3) or MeCp(CO)2(MePh2Si)MnHgPh (4) are obtained.

In acetonitrile solution, [Et4N]F·2.5H2O acts as a convenient source of hydroxide ions for use in organometallic chemistry. Within 20 min, at room temperature, it converts [Fe(η-C5H5)(CO)2(L)]+ salts (molar ratio 1:1) to [Fe2(η-C5H5)2(CO) 3(L)] (L=CO, CNMe and PPh3) complexes in good yields with the evolution of CO2 and, when L=CO, CO. Under the same conditions it converts [Fe(η-C5H5)(CO)2Cl] (molar ratio 1:2 or, better, 1:3) to [Fe2(η-C5H5)2(CO) 3(NCMe)]. Other [Fe(η-C5H5)(CO)2X] (X=Br or I) react only slowly to give [Fe2(η-C5H5)2(CO)4]. Other routes to [Fe2(η-C5H5)2(CO) 3(PPh3)] and [Fe2(η-C5H5)2(CO) 3(NCMe)] involve prolonged photolysis and give impure or non-isolable products. This route gives them as analytically pure solids in high yields. It is proposed that in acetonitrile solutions, the F- ions react with H2O to give HF and OH- in a reaction driven by the strength of the H-F bond and the lack of anion solvation in acetonitrile. The OH- ions then attack the [Fe(η-C5H5)(CO)2(L)]+ cations at CO with the evolution of CO2 to give the [Fe(η-C5H5)(CO)(L)]- which subsequently displaces L from the cations.

The influence of molecular hydrogen on the title reactions has been studied; different products (and yields) are obtained when this gas is used, instead of nitrogen, as reaction atmosphere.From the reactions of with > the new heterometallic complex > is obtained, whose structure has been determined by X-ray methods.Crystals are triclinic, space group P1, with a unit cell of dimensions a = 8.881(7), b = 17.224(12), c = 7.912(7) Angstroem, α =78.87(4), β = 114.95(6), γ = 91.60(4) degree, and Z = 2.The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R = 0.046 for 2 965 observed reflections.The complex shows a 'spiked-triangular' metal atom frame and the alkyne ligand interacts with all four metals through both triple and double bonds.An isomeric complex has been also characterized and a square-planar structure has been assigned to it on the basis of spectroscopy and by comparison with known compounds.From the reactions of with the same alkyne, instead of the expected >, the already known > complex has been obtained, by consequence of the hydrogenation of the reactant double bond.

The diastereoselectivity of [3 + 2] cycloaddition of tricarbonyl[(4,5,6,7-η)-2-methyltropone]iron (2) with an E,Z isomeric mixture of η1-(crotyl)Fp (4E/4Z) [Fp: C5H5Fe(CO)2 or CpFe(CO)2] has been stud

Reactions of FpCS-2K+ (1) and FpCO2-Na+ (and Li+) (2) (Fp=(η5-C5H5)(CO)2Fe) with organoiron electrophiles FpX (X=I, OSO2CF3, HgCl), (η5-C5H5)L(CO)FeI (L=P(OPh3), PPh3)

Dicarbonylcyclopentadienyliron chloride oxidizes copper in dimethylformamide and dimethyl sulfoxide to give copper(II) chloride and dicarbonylcyclopentadienyliron dimer. The apparent kinetic characteristics of the process and the thermodynamic parameters

Treatment of a coordinatively saturated cationic η2-alkyne iron complex 5-C5H5)Fe(CO)2(Ph-CC-Ph)>BF4 with various nucleophiles (Nu: O-, S- and N-nucleophiles) does not afford a trans-alkenyl complex but alkenic products with cis-structure, i.e. a cis-alkenyl complex, cis-(η5-C5H5)(CO)2Fe-C(Ph)=C(Ph)-Nu and/or a metallacycle, (η5-C5H5)(OC))-Nu> or (η5-C5H5)(OC)>.

The 13C-labeled (95-99percent) acetyl complex (η5-In)(CO)3Fe13C(O)CH3 (8) (In = indenyl) has been prepared by acylating In(CO)2Fe- Na+ (1) with CH3-13C(O)Cl.All of the starting 1 must be consumed in this reactio

A cationic intramolecular base-stabilized silyleneiron complex, [(η-C5H5)Fe(CO)2=SiMe{2-(Me 2-NCH2)C6H4}]PF6, was synthesized by hydride abstraction from the (hydrosilyl)iron complex (η-C5H5)Fe-(CO)2SiHMe{2-(Me 2NCH2)C6H4} with Ph3CPF6. Reaction of the silylene complex with MeOH afforded the methoxysilyl complex [(η-C5H5)Fe(CO)2SiMeOMe{2-(Me 2N(H)CH2)C6H4}]PF6 in good yield. The molecular structures of the silylene and methoxysilyl complexes were determined by X-ray crystal structure analysis.

The trifunctional trisilylmethane-derived amine HC{SiMe2NH(2-FC6H4)}3 (1) has been prepared which contains fluorine atoms in the ligand periphery which may act as additional donor functions in its amido complex derivatives. Lithiation with n-BuLi and reaction with YCl3 yields the seven-coordinate yttrium complex HC{SiMe2N(2-FC6H4)}3Y(OEt2) (3) which has been structurally characterized by X-ray crystallography: triclinic, P1- (No. 2), a = 9.4244(2) ? b = 10.5951(3) ?, c = 16.6929 ?, α = 93.280(8)°, β = 91.918(7)°, γ = 93.465(8)°, Z = 2, V = 1659.9(1) ?**3, and R = 0.062. All three fluorine donor atoms are coordinated to the yttrium center ((1)J((89)Y-(19)F)= 5.3 Hz at 295 K). Rapid dynamic processes in solution which cannot befrozen out at 180 K confer an effective 3-fold symmetry upon the molecule at ambient temperature. Reaction of lithiated 1 with ZrCl4 in diethylether yields the (μ-Cl)2-bridged complex HC{SiMe2N(2-FC6H4)}3ZrCl2Li(OEt2)2 (4) which has one peripheral F-atom weakly coordinated to the Zr-center as established analytically and by an X-ray structure analysis: monoclinic, P21/a (No. 14), a = 13.4123(2) ?, b = 18.0086(3) ?, c = 17.3750(3) ?, β = 90.391(7)°, Z = 4, V = 4196.6(2) ?**3, and R = 0.048. Reaction of 4 with MeLi gives the methyl-zirconium compound HC{SiMe2N(2-FC6H4)}3ZrCH3 (5) while upon condensation with [CpFe(CO)2](1-) the dinuclear Zr-Fe-bonded complex HC{SiMe2N(2-FC6H4)}3ZrFe(CO)2Cp (6) is obtained. The spectroscopic data and structural considerations indicate that in 5 all three F-donors are bonded to Zr whereas in 6 all are uncoordinated, demonstrating the coordinative flexibility ofthe ancillary donor functions in the tripodal amido complexes derived from 1.

Reaction of Cp4Fe4(CO)4 (1) with RLi and HBF4 in sequence affords Cp3Fe4(CO)4(C5H4R) (R= Me, Bun, and Ph) in moderate yields. Further sequential PhLi/HBF4 treatment of Cp3Fe4(CO)4(C5H4Ph) produces Cp2Fe4(CO)4(C5H4Ph) 2. On the other hand, 1 reacts with lithium diisopropylamide (LDA) and bromoferrocene sequentially to produce a ferrocenylated cluster [Cp3Fe4(CO)4(C5H 4)][(C5H4)FeCp] (3) and a double cluster [Cp3Fe4(CO)4(C5H4)] 2 (2). A similar LDA/dibromoferrocene treatment with 1 leads to 2, [Cp3Fe4(CO)4(C5H 4)][(C5H4)(C5H4Br)Fe] (4), and a ferrocenyl-bridged double cluster [Cp3Fe4(CO)4(C5H4)] 2[(C5H4)2Fe] (5). The new compounds have been characterized by elemental analysis and IR, mass, and NMR spectroscopy.

A combination of flash photolysis with UV-visible and IR detection has been used to study the intermediates in the photochemical reactions of Cp2Fe2(CO)4. The reaction kinetics of the intermediates have been investigated using conventional and laser flash photolysis at room temperature. Flash photolyses at low temperatures in hydrocarbon solutions under Ar or CO or in the presence of a phosphorus ligand were carried out for spectral characterizations of the unstable species. A CO-loss intermediate, assigned to the structure CpFe(μ-CO)2(μ-η1,η2-CO)FeCp, contains a semibridging CO group. This species is formed in relatively small amounts but is more stable than its structural isomer CpFe(μ-CO)3FeCp, a well-established intermediate. A second new intermediate, assigned to (η5-Cp)(CO)2Fe-Fe(CO)3(η 3-Cp), decays (k = 5 × 103 s-1 at 22°C in hexane) to form a third species, assignable to (η5-Cp)(CO)Fe(μ-η1η2-CO) Fe(CO)2(η3-Cp), which in turn decays (k = 62.4 s-1 at 25°C in hexane) to form Cp2Fe2(CO)4. The second and third intermediates are formed more extensively under CO. These results provide new evidence for certain previously unexplained features observed on this system. Experiments involving the use of 13CO indicate that formation of the formally 19-electron radical Cp(CO)3Fe from the 17-electron radical Cp(CO)2Fe and CO and the subsequent reaction between the two radicals is a major pathway for formation of (η5-Cp)(CO)2Fe-Fe(CO)3(η 3-Cp) and thus (η5-Cp)(CO)Fe(μ-η1,η 2-CO)Fe(CO)2(η3-Cp). Evidence of formation of the two dimer species, even in photolysis under Ar, implies that photoinduced unsymmetrical cleavage of CO bridges in Cp(CO)Fe(μ-CO)2Fe(CO)Cp to afford Cp(CO)3Fe and Cp(CO)Fe also occurs, in addition to the well-established photoinduced symmetrical cleavage to give two Cp(CO)2Fe. At low temperature, flash photolysis of Cp2Fe2(CO)4 in the presence of a phosphorus ligand (L = P(i-Pr)3, P(O-i-Pr)3, P(OMe)3, P(C6F5)3) affords evidence of new transient species. The experimental results also support the existence of short-lived precursors to CpFe(μ-CO)3FeCp; the latter has previously been considered to be a primary photoproduct via loss of a CO group from Cp2Fe2(CO)4.

The complex t-Bu(η5-C5H5)Fe(CO)2 has been treated with triphenylphosphine in refluxing THF to produce t-BuCO(η5-C5H5)Fe(CO)(PPh3).The large steric bulk of the t-butyl group suggests that this reaction should be faster than the reaction involving the methyl group, and a kinetic investigation illustrates this to be the case.The same steric bulk predicts that the reaction with SO2 should be slow, and indeed we have been unable to effect the related SO2 insertion reaction.Attempts to prepare the corresponding t-Bu(η5-C5H5)W(CO)3 led to formation of the related isobutyl complex.

The following compounds were prepared and their pyrolysis in a stream of argon was studied: 5-C5H5)(CO)2>2 (1), 5-C5H5)(CO)3>2 (2, M=Mo; 3, M=W), 5-C5H5)(CO)2(CCSiMe3)> (4), 5-C5H5)(CO)3(CCSiMe3)> (5 M = Mo; 6, M=W), 5-C5H5)3(CO)7(μ-η2:2:1-CCSiMe3)> (7), 5-C5H5)2(CO)4(μ-η2:2-HCCC6H5)> (8), 5-C5H5)2(CO)4(μ-η2:2-RCC-SiR'R''-CCR> (9a, R=H, R'=R''=CH3; 9b, R=C6H5, R'=H, R''=CH3; 9c, R=C6H5, R'=CH=CH2, R''=CCC6H5), 5-C5H5)2(CO)4(μ-η2:2-Me3SiCC-CCSiMe3)> (10), 5-C5H5)4(CO)8(μ4-η2:2:2:2-Me3SiCC-CCSiMe3)> (11).The products of bulk pyrolysis of selected compounds are formed in 20percent-60percent yield, based on the charged sample weight.The ceramic materials obtained consist of metal carbides (MC, M2C) together with small amounts of metal(0) (M=Mo, W) and amorphous carbon.Keywords: Pyrolysis; Preceramics; Ceramics; Iron; Molybdenum; Tungsten

The reactions of several carbonyl cations with bis(triphenylphosphine)imminium nitrite under aprotic conditions have been studied using acetone as solvent.The trigonal-bipyramidal iron(0) and colbalt(I) cations +, +, + and + yielded four-coordinate iron(-II) and cobalt(-I) nitrosyl complexes Fe(NO)(N2C6H4COCH3-p)(CO)(PPh3), Fe(NO)2(CO)(PPh3), Fe(NO)2(PPh3)2, Co(NO)(CO)2(PPh3) and Co(NO)(CO)2(P(Bu-n)3) via a procedure which is much simpler than previous methods.The reaction involves an atom-transfer redox between nitrite and coordinated CO to yield the coordinated nitrosyl ligand and CO2.The related cation + did not react.The other cations investigated underwent decomposition and/or gave non-nitrosyl products with the exception of + which yielded an unstable blue nitrosyl which could not be characterised.A modification of the procedure employing Na(15)NO2 in the presence of a catalytic amount of crown ether was shown to be a very simple method for the preparation of 15N-labelled nitrosyls.The analogues reaction with arenediazotate anion did not lead to arenediazo complexes.

Oxidation of magnesium with dicarbonyl(cyclopentadienyl)iron(II) chloride in dimethylformamide gives rise to η5-C5H 5Fe(CO)2MgCl. Kinetic regularities of the process were determined. Thermodynamic parameters of

The rate constant for the methyl abstraction reaction of CpFe(CO) 2Me has been measured with the benzyl radical clock as (1.1 ± 0.2) × 105 M-1 s-1 at room temperature. Time-resolved Fourier-transform Infrared (FTIR) absorption spectroscopy pointed towards the formation of the CpFe(CO)2 radical upon benzyl abstraction. The main stable product has been established by a linear scan of the reaction mixture as Cp2Fe2(CO)4 produced by the dimerization of the CpFe(CO)2 radicals. The transition state structure for the abstraction process was also found at UB3LYP/6-311+G* level of theory to contain a planar CH3 group.

Addition of BH3·thf to 1-alkylimidazoles (alkyl=methyl, butyl) and 1-methylbenzimidazole leads to BH3 adducts, which are deprotonated by BuLi to yield the organolithium compounds (L)Li+(1b-d)-. In the solid stat

Azaferrocene, (η5-C5H5)(η5-C4H4N)Fe, undergoes a η5→η1 haptotropic shift of the pyrrolyl ligand upon long-wavelength photolysis (λexc>495 nm) both in alkane solvents at room temperature and in frozen matrixes at 12 K. Room-temperature photolysis (λexc>495 nm) in CO-saturated cyclohexane solution generated (η5-C5H5) (η1-N-C4H4N)Fe(CO)2. Irradiation with λexc = 532 nm also produced an allyl monocarbonyl species, exo-(η5-C5H5)(η3-C-C4H4N)Fe(CO), identified by IR spectroscopy. In CO-doped matrixes at 12 K both (η5-C5H5)(η1-N-C4H4N)Fe(CO) and (η5-C5H5)(η1-N-C4H4N)Fe(CO)2 are formed following broad-band irradiation (λexc>495 nm) of (η5-C5H5)(η5-C4H4N)Fe, in a ratio dependent on the concentration of CO in the matrix. Initial irradiation with λexc = 538 nm followed by broad-band photolysis (λexc>495 nm) in CO-doped matrixes formed additional monocarbonyl species, exo-(η5-C5H5) (η3-C-C4H4N)Fe(CO), and a species absorbing at 1962 cm-1, which is either the appropriate endo-isomer or aza-allyl species. Laser flash photolysis experiments of (η5-C5H5)(η1-N-C4H4N)Fe(CO)2 in either CO-saturated cyclohexane or toluene produced (η5-C5H5)(η1-N-C4H4N)Fe(CO), which reacted with CO with rate constants measured at 298 K of (3.0±0.3)×108 and (3.3±0.3)×108 M-1 s-1, respectively, regenerating (η5-C5H5)(η1-N-C4H4N)Fe(CO)2.

A series of first row transition metal complexes with unsupported M-Fe bonds, (3,5-iPr2-Ar*)MFe(η5-C 5H5)(CO)2 (M = Fe (1), Mn (2), Cr (3), 3,5-iPr2-Ar* = -C6H-2,6-(C 6H2-2,4,6-iPr3)2-3,5- iPr2), was synthesized by salt metathesis. They were characterized by 1H NMR, UV-vis spectroscopy, X-ray crystallography, and SQUID magnetic measurements. Two distinct Fe atoms in 1 were confirmed by Moessbauer spectroscopy. All three compounds feature short metal-metal bond distances (Fe-Fe, 2.3931(8) A (1); Mn-Fe, 2.4512(5) A (2); Cr-Fe, 2.4887(5) A (3)). Their DFT computed structures were in excellent agreement with the experimental data and revealed a dative bonding interaction between the metals.

The syntheses and properties of 2,4-dimethylpentadienyl (2,4-C7H11) analogues of (C5H5)Fe(CO)2X (Fp) complexes have been investigated. Thus, reaction of (2,4-C7H11)Fe(CO)3+ with KI in acetone leads to Fe(2,4-C7H11)(CO)2I, for which NMR spectroscopy indicates an unsymmetric structure (ΔG? = 11.45 kcal/mol). Reduction with sodium amalgam leads to the dimer [(2,4-C7H11)Fe(CO)2]2, for which an ESR signal can be observed in solution. An unsymmetric dimer, [(C5H5)Fe(CO)2][(2,4-C7H 11)Fe(CO)2], can be prepared from the iodide on reaction with (C5H5)Fe(CO)2-. Treatment of the iodide complex with an excess of sodium amalgam leads to the apparent formation of (2,4-C7H11)Fe(CO)2-, which can be converted to the thermally unstable liquid (2,4-C7H11)Fe(CO)2(CH3) with CH3I. Like the analogous iodide complex, this species also exists in an unsymmetric configuration, as indicated by NMR spectroscopy (ΔG? = 12.75 kcal/mol). The methyl compound reacts with P(CH3)2(C6H5) to yield a solid η1-acyl complex, which is itself thermally converted to at least two other products, which appear to involve acyl-pentadienyl coupling. A single-crystal X-ray diffraction study on (2,4-C7H11)Fe(CO)2I has confirmed the unsymmetric coordination environment, in which the iodide and one carbonyl ligand reside under the C(2) and C(4) positions, with the second carbonyl under the open edge of the pentadienyl ligand. The average Fe-CO and Fe-I bond distances are 1.780 (5) and 2.645 (1) A?, while the Fe-C(pentadienyl) bond distances range from 2.100 (6) to 2.158 (8) A?, averaging 2.133 A?. The space group is C2h5 - P21/n (No. 14), with a = 8.034 (2) A?, b = 16.589 (4) A?, c = 8.485 (2) A?, β = 91.24 (2)°, and V = 1130.7 (4) A?3, for Z = 4 and Dcalcd = 1.96 g/cm3. The final agreement indices are R = 0.037 and Rw = 0.031 for the 1595 independent observed reflections.

Based on iron(II) piano-stool complexes, five compounds were synthesized by varying the organo-heteroatom ligands in their structure. Two different heteroatoms were considered, namely, nitrogen and sulfur, as constituents of the ligands on the complexes.

A rhodium(II) dibenzotetramethylaza[14]annulene dimer ([(tmtaa)Rh]2) undergoes metathesis reactions with [CpCr(CO)3]2, [CpMo(CO)3]2, [CpFe(CO)2]2, [Co(CO)4]2, and [Mn(CO)5]2 to form (tmtaa)Rh-M complexes (M = CrCp(CO)3, MoCp(CO)3, FeCp(CO)2, Co(CO)4, or Mn(CO)5). Molecular structures were determined for (tmtaa)Rh-FeCp(CO)2, (tmtaa)Rh-Co(μ-CO)(CO)3, and (tmtaa)Rh-Mn(CO)5 by X-ray diffraction. Equilibrium constants measured for the metathesis reactions permit the estimation of several (tmtaa)Rh-M bond dissociation enthalpies (Rh-Cr = 19 kcal mol-1, Rh-Mo = 25 kcal mol-1, and Rh-Fe = 27 kcal mol-1). Reactivities of the bimetallic complexes with synthesis gas to form (tmtaa)Rh-C(O)H and M-H are surveyed.

Reaction of (Ar′NacNac)ZnI with potassium/mercury amalgam gave the trimetallic compound {(Ar′NacNac)Zn}2Hg (1) containing a Zn-Hg-Zn unit and the first example of a bond between two different Group 12 metals; DFT and QTAIM analyses suggest that 1 is best described as two formally Zn(i) atoms with a Hg(0) atom positioned between them; reactions of 1 with stoichiometric I2, FpI or Fp2 gave addition products of the type (Ar′NacNac)ZnX (X = I, Fp) and Hg. Ar′NacNac = HC{C(Me)N(2,6-C6H3iPr2)}2; Fp = CpFe(CO)2. This journal is

The propen-2-yl-dimetallacyclopentenone complex [Fe2Cp 2(CO)(μ-CO){μ-η1:η3-C α(H)Cβ(Cγ(CH 3)CH2)C(O)}] (1) underwent electrophilic additions at the propenyl moiety to afford the μ-allenyl complexes [Fe2Cp 2(CO)2(μ-CO){μ-η1: η2α,β-CαHC βCγ(CH3)(CH2E)}][BF 4] (E = CPh3, [2][BF4]; E = H, [3][BF 4]), in ca. 85% yield. The molecular structure of ([2][BF 4]) was ascertained by X-ray diffractometry; X-ray, NMR and DFT results agreed in that one single isomer formed, bearing the [CH 2CPh3] group pointing far from the Fe-Fe axis. The reaction of [3][BF4] with NHEt2 in the presence of PhSSPh resulted in the prevalent formation of [FeCp(CO)2SPh] (7).

The dimeric iron carbonyl [CpFe(CO)2]2 and the iodosilanes tBu2RSiI were obtained from the reaction of [CpFe(CO)2]I with the silanides Na[SiRtBu2] (R = Me, tBu) in THF. By the reactions of [CpFe(CO)2]I and Na[SiRtBu2] (R = Me, tBu) the disilanes tBu2RSiSiRtBu2 (R = Me, tBu) were additionally formed using more than one equivalent of the silanide. In this context it should be noted that reduction of [CpFe(CO)2]2 with Na[SitBu3] gives the disilanes tBu3SiSitBu 3 along with the sodium ferrate [(Na(18-crown-6))2Cp] [CpFe(CO)2]. The potassium analogue [(K(18-crown-6)) 2Cp][CpFe(CO)2] (orthorhombic, space group Pmc2 1), however, could be isolated as a minor product from the reaction of [CpFe(CO)2]I with [K(18-crown-6)][PtBu2BH3]. The reaction of [CpFe(CO)2]2 with the potassium benzophenone ketyl radical and subsequent treatment with 18-crown-6 yielded the ferrate [K(18-crown-6)][CpFe(CO)2] in THF at room temperature. The crown ether complex [K(18-crown-6)][CpFe(CO)2] was analyzed using X-ray crystallography (orthorhombic, space group Pna21) and its thermal behaviour was investigated.

The complex [Fe2Cp2(μ-PMes*)(μ-CO)(CO) 2] (Mes* = 2,4,6-C6H2tBu 3), which in the solid state displays a pyramidal phosphinidene bridge, reacted at room temperature with H2 (ca. 4 atm) to give the known phosphine complex [Fe2Cp2(μ-CO) 2(CO)(PH2Mes*)] as the major product, along with small amounts of other byproducts arising from the thermal degradation of the starting material, such as the phosphindole complex [Fe2Cp 2(μ-CO)2(CO){PH(CH2CMe2)C 6H2tBu2}], the dimer [Fe 2Cp2(CO)4], and free phosphine PH 2Mes*. During the course of the reaction, trace amounts of the mononuclear phosphide complex [FeCp(CO)2(PHMes*)] were also detected, a compound later found to be the major product in the carbonylation of the parent phosphinidene complex, with this reaction also yielding the dimer [Fe2Cp2(CO)4] and the known diphosphene Mes*P=PMes*. The outcome of the carbonylation reactions of the title complex could be rationalized by assuming the formation of an unstable tetracarbonyl intermediate [Fe2Cp2(μ-PMes*)(CO) 4] (undetected) that would undergo a fast homolytic cleavage of a Fe-P bond, this being followed by subsequent evolution of the radical species so generated through either dimerization or reaction with trace amounts of water present in the reaction media. A more rational synthetic procedure for the phosphide complex was accomplished through deprotonation of the phosphine compound [FeCp(CO)2(PH2Mes*)](BF4) with Na(OH), the latter in turn being prepared via oxidation of [Fe 2Cp2(CO)4] with [FeCp2](BF 4) in the presence of PH2Mes*. To account for the hydrogenation of the parent phosphinidene complex it was assumed that, in solution, small amounts of an isomer displaying a terminal phosphinidene ligand would coexist with the more stable bridged form, a proposal supported by density functional theory (DFT) calculations of both isomers, with the latter also revealing that the frontier orbitals of the terminal isomer (only 5.7 kJ mol-1 above of the bridged isomer, in toluene solution) have the right shapes to interact with the H2 molecule. In contrast to the above behavior, the cyclohexylphosphinidene complex [Fe2Cp 2(μ-PCy)(μ-CO)(CO)2] failed to react with H 2 under conditions comparable to those of its PMes* analogue. Instead, it slowly reacted with HOR (R = H, Et) to give the corresponding phosphinous acid (or ethyl phosphinite) complexes [Fe2Cp 2(μ-CO)2(CO){PH(OR)Mes*}], a behavior not observed for the PMes* complex. The presence of BEt3 increased significantly the rate of the above reaction, thus pointing to a pathway initiated with deprotonation of an O-H bond of the reagent by the basic P center of the phosphinidene complex, this being followed by the nucleophilic attack of the OR- anion at the P site of the transient cationic phosphide thus formed. The solid-state structure of the cis isomer of the ethanol derivative was determined through a single crystal X-ray diffraction study (Fe-Fe = 2.5112(8) A, Fe-P = 2.149(1) A).

The dimetallacyclopentenone complexes [Fe2Cp2(CO) (μ-CO){μ-η1:η3-CαHC β(R)C(O)} (R = CH2OH, 1a; R = CMe2OH, 1b; R = Ph, 1c) were prepared by photolytic reaction of [Fe2Cp 2(CO)4 with alkyne according to the literature procedure. The X-ray and the electrochemical characterization of 1c are presented. The μ-allenyl compound [Fe2Cp2(CO)2(μ-CO) {μ-η1:η2α,β-C αHCβCMe2[BF4 ([2[BF 4), obtained by reaction of 1b with HBF4, underwent monoelectron reduction to give a radical species which was detected by EPR at room temperature. The EPR signal has been assigned to [Fe2Cp 2(CO)2(μ-CO){μ-η1: η2α,β-CαHC βCMe2}, [2?. The molecular structures of [2+ and [2? were optimized by DFT calculations. The unpaired electron in [2? is localized mainly at the metal centers and, coherently, [2? does not undergo carbon-carbon dimerization, by contrast with what previously observed for the μ-vinyl radical complex [Fe2Cp2(CO)2(μ-CO){μ- η1:η2-CHCH(Ph)}?, [3 ?. Electron spin density distributions similar to the one of [2? were found for the μ-allenyl radical complexes [Fe 2Cp2(CO)2(μ-CO){μ-η1: η2α,β-CαHC βC(R1)(R2)}? (R 1 = R2 = H, [4?; R1 = H, R 2 = Ph, [5?; R1 = R2 = Ph, [6?).

The phosphinidene complexes [Fe2Cp2(μ-PR)(μ-CO) (CO)2] (Cp = η5-C5H5; R=Cy, Ph, Mes, Mes* Mes = 2,4,6-C6H2Me3, Mes* = 2,4,6-C6H2tBu3) were readily prepared in high yields through a two-step procedure starting from the corresponding phosphine complexes [Fe2Cp2(μ-CO) 2(CO)(PH2R)]. When R = Cy, Ph, Mes, the first step required the oxidation of the phosphine complex with 1 equiv of [FeCp 2]BF4, this being followed by spontaneous dehydrogenation to yield the cationic phosphide complexes [Fe2Cp2(μ- PHR)(μ-CO)(CO)2]BF4, while the formation of the related PMes*H-bridged complex required a double oxidation of the corresponding neutral precursor in the presence of a deprotonating agent. In all cases the final step involved the deprotonation of the above cations with strong bases such as M(OH) (M = Na, K). Attempts to decarbonylate the above phosphinidene complexes by either thermolysis or photolysis in solution gave results strongly dependent on the nature of R. Thus, the photolysis of the cyclohexylphosphinidene complex gave a mixture of the clusters [Fe 4Cp4(μ3-PCy)2(μ3- CO)(μ-CO)(CO)] (Fe-Fe distances 2.6115(7) and 2.5332(8) A) and [Fe 3Cp3(μ3-PCy)(μ-PCyH)(μ-CO) 2], while the thermal decarbonylation of the mesitylphosphinidene complex in refluxing toluene gave the trinuclear derivative [Fe 3Cp3(μ-PMes)(μ-PMesH)(μ-CO)2(CO)], having a trigonal phosphinidene ligand bridging two iron atoms (Fe-P = 2.161(8), 2.165(8) A). The formation of all these compounds presumably involves the participation of the corresponding intermediate complex [Fe2Cp 2(μ-PR)(μ-CO)2], a species likely to contain a trigonal (four-electron-donor) phosphinidene ligand, not detected. In contrast, the supermesitylphosphinidene complex undergoes a C(tBu)-H oxidative addition to the P atom under mild thermal conditions to give the phosphine derivative [Fe2Cp2(μ-CO)2(CO){PH(CH 2CMe2)C6H2tBu 2}], while its photolysis gave a mixture of the above phosphine complex and the phosphide-hydride derivatives cis- and trans-[Fe 2Cp2(μ-H){μ-P(CH2CMe2)C 6H2tBu2}(CO)2], the latter resulting from the oxidative addition of a P-H bond to the dimetal center.

The novel cationic diiron μ-allenyl complexes [Fe2Cp 2(CO)2(μ-CO){μ-η1: η2α,β-Cα(H)C βCγ(R)2}]+ (R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from [Fe2Cp2(CO)4]. The solid state structures of [4a][CF3SO3] and of the diruthenium analogues [Ru 2Cp2(CO)2(μ-CO){μ-η1: η2α,β-Cα(H)C βCγ(R)2}][BPh4] (R = Me, [2a][BPh4]; R = Ph, [2c][BPh4]) have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Bronsted bases result in formation of the μ-allenylidene compound [Ru2Cp 2(CO)2(μ-CO){μ-η1:η1- CαCβCγ(Ph)2}] (5) and of the dimetallacyclopentenone [Fe2Cp2(CO)(μ-CO) {μ-η1:η3-Cα(H)C β(Cγ(Me)CH2)C(O)}] (6), respectively. The nitrile adducts [Ru2Cp2(CO)(NCMe)(μ- CO){μ-η1:η2-Cα(H)C βCγ(R)2}]+ (R = Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me3NO, react with N2CHCO2Et/NEt3 at room temperature, affording the butenolide-substituted carbene complexes [Ru2Cp 2(CO)(μ-CO){μ-η1:η3-C α(H)CβCγ(R) 2OC(O)C(H)] (R = Me, 10a; R = Ph, 10b). The intermediate cationic compound [Ru2Cp2(CO)(μ-CO){μ-η1: η3-Cα(H)CβC γ(Me)2OC(OEt)C(H)]+ (9) has been detected in the course of the reaction leading to 10a. The addition of N 2CHCO2Et/NHEt2 to 7a gives the 2-furaniminium-carbene [Ru2Cp2(CO)(μ-CO){μ- η1:η3-Cα(H)C βCγ(Me)2OC(OEt)C(H)]+ (11). The X-ray structures of 10a, 10b and [11][BF4] have been determined. The reactions of 4a,b with MeCN/Me3NO result in prevalent decomposition to mononuclear iron species. The Royal Society of Chemistry 2010.

1,3-Dipoles of the type metallo nitrile ylide and metallo nitrile imine were prepared by mono-a-deprotonation of CH-acidic {[W(CO)5CHCH 2PPh3]PF6, M(CO)5CNCH 2CO2A (M = Cr, W; R = Me, Et), [Pt(Cl)(CNCH 2CO2Et)(PPh3)2]BF4} and NH-acidic isocyanide complexes (Cr(CO)5CNNH2) and were stabilized by coordination to a second transition metal complex fragment (Cr(CO)5, [M(CO)5]+ (M= Mn, Re), [FeCp(CO) 2]+, [Pt(Cl)(PR3)2]+ (R = Et, Ph)}. All dinuclear products 1-7, 10, and 11 are neutral species except [(Ph3P)2(Cl)Pt{μ2-CNCH(CO 2Et)}Pt(Cl)(PPh3)2]BF4 (8). Complex (OC)5W{μ2-CNCH(CO2Et)}Pt(Cl)(PEt 3)2 (5b) was characterized by X-ray diffraction. Twofold deprotonation/platination to give (OC)5Cr(μ3-CNC(Ph)} [Pt(Cl)(PPh3)2]2 (9) was achieved, in the case of Cr(CO)5CNCH2Ph.

The phosphinidene complexes [Fe2Cp2(μ-PR)(μ-CO) (CO)2] (Cp = η5-C5H5; R = Cy, Ph, Mes*; Mes* = 2,4,6-C6H2tBu 3) react readily with diazoalkanes N2CR′R″ (R′ = H, R″ = H, CO2Et, SiMe3; R′ = R″ = Ph) in dichloromethane solution at room temperature or below to give the corresponding P:P-bridged phosphadiazadiene derivatives [Fe 2Cp2(μ-RPN2CR′R″)(μ-CO)(CO) 2] (2) with high yield. The diazomethane derivative (Fe-Fe = 2.6198(6) A) is protonated selectively with HBF4· OEt2 at the P-bound nitrogen atom to yield the aminophosphide derivative [Fe2Cp2(μ-CyPNHNCH2)(μ-CO)(CO) 2](BF4) (Fe-Fe = 2.6126(5) A). Compounds 2 decompose upon heating in toluene solution at 363 K to give the dimer [Fe 2Cp2(CO)4] as the only organometallic product. The same result was obtained when irradiating with visible-UV light toluene solutions of the phenylphosphinidene-derived compounds. In contrast, relatively selective decarbonylations could be induced photochemically when R = Cy, Mes*. The reaction products, however, were strongly dependent on the nature of all substituents present in compounds 2. The diazomethane derivative yielded a mixture of the P:N-bound phosphadiazadiene complex [Fe 2Cp2(μ-CyPN2CH2)(μ-CO) 2] (major) and the phosphaalkene derivative [Fe2Cp 2(μ-CyPCH2)(μ-CO)(CO)] (minor). In contrast, the ethyldiazoacetate derivative gave the paramagnetic complex [Fe 2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO) (CO)], possibly containing a μ-P:P,C-phosphadiazadiene ligand, which upon chromatography fully rearranges into the aminophosphide-iminoacyl complex [Fe2Cp2{μ-CyPNHNC(CO2Et)}(μ-CO)(CO)] (Fe-Fe = 2.6261(8) A), possibly through a protonation/deprotonation sequence on the alumina surface. The trimethylsilyldiazomethane derivative instead gave directly the analogous aminophosphide-iminoacyl complex [Fe 2Cp2{μ-CyPN(SiMe3)NCH}(μ-CO)(CO)], now resulting from an unusual 1,3-shift of the SiMe3 group along the ligand backbone. Finally the photochemical treatment of the ethyldiazoacetate derivative of the supermesithylphosphinidene substrate gave the complex [Fe 2Cp2{μ-Mes*PN2CH(CO 2Et)}(μ-CO)2] (Fe-Fe = 2.514(1) A), containing a P:N-bridged phosphadiazadiene ligand bound to the dimetal center in a novel coordination mode, this involving the P-bound nitrogen atom, instead of the C-bound nitrogen.

Photochemical irradiation of an equimolar mixture of (η5 -C5H5)Fe(CO)2SiR3, FpSiR 3, and FpMe leads to the efficient formation of the silicon-carbon-coupled product R3SiMe, R3 = Me 3, Me2Ph, MePh2, Ph3, ClMe 2, Cl2Me, Cl3, Me2Ar (Ar = C 6H4-p-X, X = F, OMe, CF3, NMe2). Similar chemistry occurs with related germyl and stannyl complexes at slower rates, Si > Ge Sn. Substitution of an aryl hydrogen to form FpSiMe2C6H4-p-X has little effect on the rate of the reaction, whereas progressive substitution of methyl groups on silicon by Cl slows the process. Also, changing FpMe to FpCH2SiMe3 dramatically slows the reaction as does the use of (η5-C 5Me5)Fe(CO)2 derivatives. A mechanism involving the initial formation of the 16e intermediate (η5-C 5H5)Fe(CO)Me followed by oxidative addition of the Fe-Si bond accounts for the experimental results obtained.

Two new compounds CpFeMn2(CO)7(μ3-S2)2 (2) and Cp3Fe3Mn(CO)4(μ3-S 2)2(μ3-S) (3) were obtained by the treatment of [CpFeMn(

The halogenoalkyl complexes [Cp(CO)2M{(CH2)nX}] (n = 3-10, 12, M = Fe; n = 5, 6, M = Ru, X = Br, I) react with Ph3CPF6 in dry CH2Cl2 to give the corresponding carbocation complex

Palladium-catalyzed transmetalation between [CpFe-(CO)2I] and aryl Grignard reagents emerges as a new method for the synthesis of [CpFe(CO)2Ar]. The aryliron complexes thus formed are useful arylmetal reagents that become active upon oxidation or UV irradiation.

Transmetalation between [CpFe(CO)2I] and arylzinc reagents or arylboronic acids under palladium catalysis yields the corresponding aryliron complexes [CpFe(CO)2Ar]. The reactions offer easy and reliable accesses to a variety of [CpFe(CO)2Ar] species bearing a functionalized aryl group.

The alkyl-bridged iron(II) complexes [{Cp(CO)2Fe}2{μ-(CnH2n)}] (n = 6-10, Cp = η5-C5H5) undergo both single and double hydride abstraction when reacted with one equivalent of Ph3CPF6 to give both the monocationic complexes, [{Cp(CO)2Fe}2{μ-(CnH2n-1)}]PF6, and the dicationic complexes, [{Cp(CO)2Fe}2{μ-(CnH2n-2)}](PF6)2. The ratios of monocationic to dicationic complexes decrease with the increase in the value of n. The complexes where n = 4 and 5 undergo only single hydride abstraction under similar conditions. When reacted with two equivalents of Ph3CPF6, the complexes where n = 6-10 undergo double hydride abstraction to give dicationic complexes only. In contrast, the complex where n = 5 gives equal amounts of the monocationic and the dicationic complexes, while the complex where n = 4 only gives the monocationic complex. 1H and 13C NMR data show that in the monocationic complexes one metal is σ-bonded to the carbenium ion moiety while the other is bonded in a η2-fashion forming a chiral metallacylopropane type structure. In the dicationic complexes both metals are bonded in the η2-fashion. The monocationic complexes where n = 4-6, react with methanol to give η1-alkenyl complexes[Cp(CO)2Fe(CH2)nCH{double bond, long}CH2] (n = 2-4) as the major products and σ-bonded ether products [{Cp(CO)2Fe}2{μ-(CH2)nCH(OCH3)CH2}] as the minor products. The complex where n = 8 reacted with iso-propanol to give the η1-alkenyl complex [Cp(CO)2Fe(CH2)6CH{double bond, long}CH2]. The dicationic complexes where n = 5, 8 and 9 were reacted with NaI to give the respective α, ω-dienes and [Cp(CO)2FeI].

This work describes a systematic experimental and theoretical study of the properties of two series of isoelectronic and largely isosteric ligands, namely PPh2Me, PPh2BH3-, and SiPh 2Me- and SPtBu3, SPrBu2BH 3-, and SSitBu3-. In addition, we have also investigated the oxo derivatives OPPh2BH3 - and OSiPh2Me-. Based on X-ray crystal structure determinations (Fe-CO and C-O bond lengths) as well as NMR [e.g. δ(13CO)] and IR [ν(CO)] spectroscopic investigations of the corresponding [CpFe(CO)2]+ complexes, we can conclude that, with respect to electron donor strength, phosphanyl borohydrides occupy an intermediate position between phosphanes (weakest donors) and silyl ligands (strongest donors). The same is true for the thio derivatives, although the differences are smaller. In the reaction with [CpFe(CO)2] +, the oxo derivative OPPh2BH3- transfers a hydride ion rather than forming a stable [CpFe(CO) 2(OPPh2BH3)] complex. The tendency to undergo hydride-transfer reactions was studied by density functional calculations for the series PtBu2BH3-, OPtBu2BH 3, and SPtBu2BH3-. The results reveal that OPtBu2BH3- is the strongest and SPtBu2BH3- the weakest hydride donor, in accordance with the experimental observations. Theoretical analysis indicates that the three derivatives PPh2Me, PPh2BH3 _, and SiPh2Me- are truly isolobal species despite variations in their charge distributions. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

The homodinuclear, bridged haloborylene transition metal complexes [(μ-BCl){(η5-C5H5)Fe(CO) 2}2] and [(μ-BX){Mn(CO)5}2] (X = Cl, Br) were prepared by salt elimination reactions a

Insertion reactions of dicyclohexylcarbodiimide with aminoboranes and with aminoboryl and -borylene transition metal complexes have been examined as potential routes to new boron-containing ligand systems. Reactions with systems containing two-coordinate

The thermal reaction between [CpFe(CO)2]2 and 1-tert-butyl-3,4-dimethylphosphole leading to phosphaferrocene has been studied with respect to its mechanistic characteristics. Isobutene was identified as the only product originating from the tBu group, suggesting a nonradical pathway which involves β-H elimination from the intermediately formed [CpFe(CO)2-tBu].

The mechanism of chloride substitution in CF2{double bond, long}CFCl with [Re(CO)5]- and [CpFe(CO)2]- anions is investigated experimentally and theoretically. The substitution reaction begins with the nucleophile addition to CF2{double bond, long}CFCl producing the carbenoid anion [MCF2CFCl]- (A) (M = Re(CO)5, CpFe(CO)2). This is shown by trapping the intermediate A with electrophiles - proton donor (t-BuOH) to give MCF2CFClH or with CF2{double bond, long}CFRe(CO)5 to give acylmetallate III, and by the formation of the substitution products CF2{double bond, long}CFM from the anion A, generated by the deprotonation of MCF2CFClH with t-BuOK. 1,2-Shift of metal carbonyl group concerted with the α-elimination of chloride anion is proposed as the transformation pathway of carbenoid A into CF2{double bond, long}CFM. A competing process of carbene insertion into Fe-C{triple bond, long}O bond is proposed to explain the formation of {A figure is presented} (XI). The feasibility of these two pathways is confirmed by DFT (B3LYP/SDD and 6-31G*) calculations of the carbenes [MCF2CF:] and carbenoid anions [MCF2CFCl]-. Transition states (TS) for 1,2-shift (+3.2 kcal/mol) and for nucleophilic addition at C{triple bond, long}O ligand (+5.4 kcal/mol) are located for [(CO)5ReCF2CFCl]-, but only one TS corresponding to carbene insertion into Fe-C{triple bond, long}O bond (+2.1 kcal/mol) is located for [(CO)2CpFeCF2CFCl]-. The formation of other newly observed products, F(CO)CHFRe(CO)5 (V) and Cp(CO)2FeC{triple bond, long}CFeCp(CO)2 (VIII) is also discussed.

The synthesis, spectroscopic and structural characterization of the aryloxy and amino functionalized chloroboryl complexes (η5-C 5R5)Fe(CO)2B(OMes)Cl (R = H, 2a; R = Me, 3a) and (η5-C5H5)Fe(CO)2B(N iPr2)Cl (7a) are reported. Compound 2a is shown to be a versatile substrate for further boron-centred substitution chemistry leading to the asymmetric boryl complexes (η5-C5H 5)Fe(CO)2B(OMes)ERn [ERn = OC 6H4tBu-4, 2c; ERn = SPh, 2d] with retention of the metal-boron bond. The reactivities of 2a, 3a and 7a towards the halide abstraction agent Na[BArf4] have also been examined, in order to investigate the potential for the generation of cationic heteroatom-stabilized terminal borylene complexes. The application of this methodology to the mesityloxy derivatives 2a and 3a gives rise to B-F containing products, presumably via fluoride abstraction from the [BArf 4]- counter-ion. By contrast, amino-functionalized complex 7a is more amenable to this approach, and the thermally robust terminal aminoborylene complex [(η5-C5H5)Fe(CO) 2B(NiPr2)][BArf4] (9) can be isolated in ca. 50% yield. The reactivity of 9 towards a range of nucleophilic and/or unsaturated reagents has been examined, with examples of addition, protonolysis and metathesis chemistries having been established. The Royal Society of Chemistry 2006.

The kinetic and activation parameters of oxidation of cadmium with dicarbonylcyclopentadienyliron chloride in dimethylformamide were determined. The apparent equilibrium constants, enthalpy, and entropy of adsorption of the reactants on the metal surface

Thermal decomposition of the iron-manganese methoxycarbyne Cp(CO)Fe(μ-CO)(μ-COCH3)Mn(CO)MeCp (1a) occurs to give MeCpMn(CO)3 and in low yield CpFe(CO)2CH3; in the presence of PPh3, CpFe(CO)(PPh3)CH3 (2a) forms in high yield. The reaction is first-order in carbyne, but a side reaction that is also first-order in phosphine occurs to give [Cp(CO)Fe(μ-CO)2Mn(CO)MeCp]-[CH3PPh 3]+ (3a) as a byproduct. Crossover experiments between la and its bis-MeCp, CD3 analogue 1b-d3 result in scrambling of the methoxycarbyne methyl label between the products 2a and the MeCp analogue 2b. No alkyl exchange is seen in recovered starting materials in the reaction between 1a and bis-MeCp analogue 3b or (except after prolonged reaction) between the products 2a and 2b-d3. Control crossover experiments between 1a and 2b-d3 give complete alkyl scrambling. The data prove that alkyl exchange occurs among products after carbyne decomposition and presumably is induced by an intermediate that is formed by carbyne decomposition. Previous results show that the 16-electron intermediate CpFe(CO)CH3 forms at essentially the same rate from 2a as from la, ruling it out as the exchange intermediate since 2a and 2b-d 3 undergo only very slow exchange. A speculative proposal for the reactive intermediate is that it is the isomeric terminal methoxycarbyne CpFe≡COCH3, and alkyl migration from oxygen to iron occurs after cluster cleavage. A detailed kinetic scheme for alkyl scrambling is proposed and tested by computer modeling: using an iterative procedure that couples numerical integration of the proposed rate equations with a simplex minimization algorithm designed to find the best rate constants, concentration data from several runs could be quantitatively fit to the proposed mechanism.

Thermal and photochemical reactions of the carbonylate salts A[(η5-C5H5)Fe(CO)2], A[(η5-C5H5)Mo(CO)3] and A[(η5-C5H5)W(CO)3] (A = Na, PPN) in THF with C60 result in all cases in electron transfer to give [C60]- and the transient 17-electron, metal-centered radicals CpFe(CO)2, CpMo(CO)3 and CpW(CO)3, respectively. Subsequent self-coupling of the three metal-centred radicals then results in the formation of the metal-metal bonded dimers [CpFe(CO)2]2, [CpMo(CO)3]2 and [CpW(CO)3]2. In contrast, while the mixture of Na[C60] and [CpFe(CO)2]2 does not react further under photochemical conditions, photolysis of mixtures of Na[C60] and both [CpMo(CO)3]2 and [CpW(CO)3]2 ultimately results in complete homolysis of the dimers and regeneration of the corresponding metal-centered radicals, which then combine with the [C60]- remaining in solution to form the η2-C60 complexes A[CpMo(CO)2(η2-C60] and A[CpW(CO)2(η2-C60]. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Reactions of polyfluorinated alkenyl halides Z-(CF3) 3CCF=6;CFHal (Hal=Cl,I-Cl, Hal=Br, I-Br) and CF2=CFBr (II-Br) with [CpFe(CO)2]K (FpK) and [Re(CO)5]Na proceed through the initial attack of metal carbonyl anion on halogen. Reaction with FpK gives minor amounts of σ-alkenyl complexes Z-RfCF=CFFe(CO)2Cp (I-Fe, II-Fe) (3-30%), but primarily leads to dimer [CpFe(CO)2] 2. Reaction with [Re(CO)5]Na produces anionic halo(acyl)rhenates cis-[Z-RfCF=CF(CO)Re(CO)4Hal]Na (V-Cl, V-Br, VI) (70-90%) which were isolated, and halo(acyl)rhenate VI (Rf=F) was characterized by X-ray structure analysis. Halo(acyl)rhenates result from the attack of the intermediate carbanion [RfCF=CF]- on the carbonyl ligand of Re(CO) 5Hal. The involvement of [RfCF=CF]- is demonstrated by their trapping with t-BuOH or CH-acid, which gives the protodehalogenated alkenes I-H and II-H, and suppresses the nucleophilic substitution reaction leading to I-Fe, II-Fe or V-Cl. Arguments against a radical/SET mechanism for the substitution reaction are also advanced.

The μ2-silylene-bridged iron complexes [Cp(OC)2Fe]2SiX2 (X = F (2), Br (4), I (5)) have been prepared from the μ2-SiH2 functional precursor [Cp(OC)2Fe]2SiH2 (1) by hydrogen/halogen exchange, using HBF4, CBr4, and CH2I2, respectively. The fluoro- and bromo-substituted derivatives 2 and 4 are converted upon UV irradiation to the carbonyl-and dihalosilylene-bridged dinuclear complexes [Cp(OC)Fe]2(μ2-CO)(μ2-SiX2) (X = F (6), Br (7)) via CO elimination. All new compounds have been characterized spectroscopically, and, in addition, the molecular structure of 2, 4, and the previously reported chloro derivative Cp(OC)2Fe]2SiCl2 (3) has been determined by single-crystal X-ray diffraction methods. For 1-5, the Fourier transform infrared and Raman spectra have been recorded and discussed, together with density functional theory calculations, which support the experimental results of the structural and vibrational analysis. The computed geometries, harmonic vibrational wavenumbers, and their corresponding Raman scattering activities are in good agreement with the experimental data. A significant dependence of the CO and Fe-Si stretching modes on the X substituents of the μ2-silylene bridge has been observed and discussed.

The photochemical reactions of [Fe2Cp2(CO) 4] (Cp = η5-C5H5) and the bidentate ligand Ph2PCH2PPh2 give a complex mixture of products. These include the known complexes [Fe2-Cp 2(μ-CO)2(μ-Ph2PCH2PPh 2)] and cis-[Fe2Cp2(μ-PPh2) 2(CO)2], as well as the new species [Fe 2Cp(μ-η5:κ1-C5H 4CH2PPh2)(μ-CO) 2(CO)],cis-[Fe2Cp2(μ-H)(μ-PPh 2)(CO)2], [Fe2Cp(μ-η 5:κ1-C5H4-CH 2PPh2)(μ-H)(μ-PPh2)(CO)], trans-[Fe 2Cp2(μ-H)(μ-PPh2)(CO)(PMePh 2)], and [Fe2Cp2(μ-PPh2) 2(μ-CO)]. An intermediate species, trans-[Fe2Cp 2(μ-CO)2(CO)(κ1-Ph2PCH 2PPh2)], having an intact diphosphine ligand coordinated through one of the P atoms, can be detected at the early stages of the reaction. Separate experiments indicate that the latter species is the precursor of the unique diphosphine-bridged complex, but of none of the other products. The above results indicate that different P-C (diphosphine) and C-H (cyclopentadienyl) bond cleavage processes are operative under the conditions examined, as well as novel C-C bond formations. The structures of the new complexes are analyzed on the basis of the corresponding IR and NMR ( 1H, 31P, and 13C) data, as well as a single-crystal X-ray study on the (diphenylphosphinomethyl)cyclopentadienyl complex [Fe2Cp(μ-η5:κ1-C 5H5CH2PPh2)-(μ-CO) 2(CO)]. A reassessment of the 31 P chemical shifts for cis- and trans[Fe2Cp2(μ-PPh2)2-(CO) 2 ] is also made.

The thermal and photochemical reactions of [Fe2Cp2(CO)4] and the bidentate ligand (EtO)2POP(OEt)2 (tedip) proceed with different P-O or C-O bond cleavages in the diphosphite ligand. Thus, boiling toluene solutions of the above species yield the known compound [FeCp(CO)2{P(O)(OEt)2}] and the new dicarbonyl complexes [Fe2Cp2{μ-(EtO)2POP(O)(OEt)}{μM-P(OEt) 2}(CO)2] (three isomers). The latter are slowly decarbonylated at room temperature by atmospheric oxygen to give the metal-metal-bonded complex [Fe2Cp2{μ(EtO)2POP(O)(OEt)}{μ-P(OEt) 2}(μ-CO)]. In contrast, the photochemical reaction between the iron dimer and the diphosphite ligand gives the phosphido-phosphonate complexes [Fe2Cp2{μ-OP(OEt)2}{μ-P(OEt)2} (CO)2], as a mixture of cis and trans isomers. The latter compounds experience a remarkable P-O bond reductive elimination in boiling xylenes under a CO atmosphere, whereby the diphosphite-bridged complex [Fe2Cp2(μ-CO)2(μ-tedip)] is formed in moderate yield. The structure of the latter was analyzed through an X-ray study. The related complexes [Fe2Cp2(μ-CO)2(CO)(κ1-tedip )] and [{Fe2Cp2(μ-CO)2(CO)}2(μ-tedip) ] were prepared from [Fe2Cp2(μ-CO)2(CO)(NCMe)] and the diphosphite ligand, and their role as potential precursors of the above dicarbonyl complexes was evaluated. The structures of the new complexes are analyzed on the basis of the corresponding IR and NMR (1H, 31P, 13C) data, and the reaction pathways operative in these complex reactions are discussed on the basis of the available data and some cross-experiments.

The synthesis of the new Fe(II) complex [CpFe(CO)2(N4C-C5H4N)] (2) is described. 1H- and 13C-NMR spectroscopy data of (2) indicate the presence of interannular conjugation in the pyridyl-tetrazolate ligand, implying coplanarity between the two rings. Addition of electrophiles to 2 resulted in the formation of cationic complexes such as [CpFe(CO)2(4-MeN4-C5H4N)] [O3SCF3] (3), [CpFe(CO)2 and of the doubly protonated complex [CpFe(CO)2 (4-HN4C-C5H4N-H)][O3SCF 3]2 (5). In all cases, the out-of-plane rotation of the pyridyl ring occurred as a consequence of the quaternization of the N-4 of tetrazole ring. X-ray structure of complex 5 indicates a torsion angle of 20.9(2)° between the aromatic rings. Protonation reactions were found to be reversible and complexes 4-5 were easily converted into the starting complex 2 by addition of a base.

Photolysis of FpCH2SiMe2SiMe2CH2Fp (1; Fp = (η5-C5H5)Fe(CO)2) for 4 h resulted in the quantitative formation of 1,3-tetramethyldisilacyclobutane (9) and Fp2. Similar irradiation of meso-FpCH2SiMePhSiMePhCH2Fp (2a) led to trans-1,3-dimethyl-1,3-diphenyl-1,3-disila-cyclobutane (10t), while photolysis of the racemic isomer (2b) afforded only cis-1,3-disilacyclobutane (10c) and Fp2. Photolysis of a mixture of 1 and 2a proved that the process was intramolecular. Irradiation for 35 h of FpCH2SiMe2CH2SiMe2Fp (3), an isomer of 1, led to clean conversion to 9 and Fp2 and irradiation of FpCH2SiMePhCH2SiMePhFp, a 1:1 mixture of the two diastereomers 6a and 6b, afforded a mixture of 10t and 10c (1:1). The third isomer of 1, FpSiMe2CH2CH2SiMe2Fp (7), is photochemically inert. Photolysis of the tungsten analogue of 1, WpCH2SiMe2SiMe2CH2Wp (8; Wp = (η5-C5H5)W(CO)3), produced a complex mixture of products.

The complexes [η5-C5H5)Fe(CO)2(SC≡CR)] (R = Bu, SiMe3) have been obtained by reaction of [(η5-C5H5)Fe(CO)2I] and the corresponding LiSC≡CR. These are the first examples of mononuclear iron compounds containing alkynethiolate ligands. The crystal structure of [(η5-C5H5)Fe(CO)2(SC≡CSiMe3)] has been determined by X-ray diffraction. The role of [(η5-C5H5)Fe(CO)2(SC≡CSiMe3)] as a metalloligand in its reactions with metal carbonyls has been explored.

The novel bis(ferrio)silanols [Cp(OC)2Fe]2Si(X)OH [X = H (2), OH (4), Cl (7)] are obtained via hydrolysis of [Cp(OC)2Fe]2Si(H)Cl (1) or via oxygenation of the bis(ferrio)hydridosilanes [Cp(OC)2Fe]sub

The synthesis, spectroscopic and structural characterization of the bromo-boryl complexes (η5-C5R4R′)Fe(CO)2- B(2,4,6-Me3C6H2)Br (R = R′ = H, 2; R = H, R′ = Me, 3; R = R′ = Me, 4) are reported. These are shown to be versatile substrates for the synthesis of both asymmetric boryl complexes [e.g. (η5-C5H5)Fe(CO)2B(2,4,6-Me 3C6H2)OC6H4 tBu-4, 6], and bridging borylene complexes {e.g. [η5-C5H4R)Fe(CO)2] 2B(2,4,6-Me3C6H2), R = H, 7; R = Me, 8} via substitution chemistry with retention of the metal-boron bond. Complexes 7 and 8 are thefirst reported examples of structurally characterized bridging borylene complexes without a supporting M-M bond. Photolytically induced CO loss from [η5-C5H5)Fe(CO)2] 2B(2,4,6-Me3C6H2) yields the complex [η5-C5H5)Fe(CO)]2(μ 2-CO)[μ2-B(2,4,6-Me3C6H 2)] (11), which features a supported bridging borylene ligand.

Reaction of various 1,2-dihalodiboranes(4) with Na[(η5-C5H4R)M(CO)3] yielded the diborane(4)yl complexes [X(Me2N)B-B(NMe2){η5-(C5H 4R)M(CO)3}] (5

Photolysis of FpCH2SiMe2SiMe2SiMe2CH2Fp (1), Fp = [(η5-C5H5)Fe(CO)2], resulted in almost quantitative formation of 1,1,2,2,4,4-hexamethyl-1,2,4-trisilacyclopentane (2) and Fp2. Similar treatment of FpCH2Me2SiMeSiEtSiMe2CH2Fp (6) afforded 1-ethyl-1,2,2,4,4-pentamethyl-1,2,4-trisilacyclopentane (7), indicating that the central silicon of the trisilane remains associated with the silicon-silicon bond of the product. Irradiation of FpCH2-PhMeSiSiMe2SiMe2CH2Fp (11) led to the formation of the two positional isomers (ratio 4:3), 1,1,2,2,4-heptamethyl-4-phenyl-1,2,4-trisilacyclopentane (12a) and 1,1,2,4,4-heptamethyl-2-phenyl-1,2,4-trisilacyclopentane (12b), indicating that either one of the two terminal silicon atoms of the trisilane remains in the Si-Si bond of the product while the other becomes the silicon atom of the product at 4-position. A mechanism for the formation of 1,2,4-trisilacyclopentane is suggested. Irradiation of 11 also produced a small amount the rearranged product FpPhMeSiCH2SiMe2CH2SiMe2Fp (13), whereas photochemical treatment of the tetrasilane analogue, FpCH2SiMe2SiMe2SiMe2SiMe2 CH2Fp (15), resulted in only the high-yield rearrangement product FpMe2SiCH2SiMe2SiMe2CH2Si Me2Fp (17) with an absence of elimination products.