Reaction of benzyne with cycloheptatriene preparation and thermolysis of some benzo(C9H10) hydrocarbons

The title reaction gave a 2+2 cycloadduct, 8,9-benzo-cis-bicyclo[5.2.0]nona-2,4,8-triene 7, together with ene product, 7-phenylcycloheptatriene. The structure of 7 was confirmed by catalytic reduction to give 8,9-benzo-cis-bicyclo[5.2.0]non-8-ene, which was also obtained in the reaction of benzyne with cycloheptene, and by reduction of the known 8,9-benzobicyclo[5.2.0]nona-1,8-diene. Other benzo(C₉H₁₀) hydrocarbons which have been synthesised are 7,8-benzobicyclo[4.2.1]nona-2,4,7-triene 5, 2,3-benzobicyclo[6.1.0]nona-2,4,6-triene 28 and 4,5-benzobicyclo[6.1.0]nona-2,4,6-triene 29. The thermolysis of 7, 28, 29 and of 3,4-benzo-exo-endo-tetracyclo[4.3.1.0^3,4.0^7,9]dec-3-en-10-one, 25, is described.     

Stabilization of highly reactive cyclic polyolefins by coordination to iron carbonyls : Methylpentalenediiron pentacarbonyl

Thermolysis of (cis-bicyclo[6.1.0]nonatriene)diiron hexacarbonyl (FeFe) involves rearrangement of the starting organic moiety with formation of four iron carboyl complexes. The major product is the known cis-8,9-dihydroindeneiron tricarbonyl complex (VI). Two complexes have the same formula, C₉H₈Fe₂(CO)₅ (VII and VIII); VII can be also obtained by reaction of VI with Fe₂(CO)₉, while VIII is a methylpentalenediiron pentacarbonyl complex and represents a further example of stabilization of this reactive organic molecule by coordination; IX is probably a polycyclic cyclopentadienyl derivative [C₉H₉Fe(CO)₂]₂.Possible mechanisms for the formation of the four compounds are discussed.     

Zur reaktivität komplexgebundener carbocyclen : V. Synthese un thermisches verhalten neuartiger cyclooctatrien- und cyclononatrien-eisencarbonylkomplexe

The reaction of cycloocta-1,3,5-triene and cycloocta-1,3,6-triene with Fe₂(CO)₉ has been reinvestigated under mild conditions. Two stable complexes of cycloocta-1,3,6-triene have been obtained as well as the previously unknown 1,3,5-C₈H₁₀Fe₂(CO)₇. All three complexes rearrange at 65°C to the known 1,3,5-C₈H₁₀Fe₂(CO)₆. Cyclonona-1,3,6-triene reacts at room temperature with Fe₂(CO)₉ to form an unstable tetracarbonyl complex, whereas reaction at 70°C leads to the formation of 1,3,5-C₉H₁₂Fe(CO)₃, which itself can be converted at 100°C to (bicyclo[4.3.0]nona-2,4-diene)Fe(CO)₃. Treatment of bicyclo[6.1.0]nona-2,4,6-triene with Fe₂(CO)₉ in CH₃OH gives (bicyclononatriene)Fe₂(CO)₆, (bicyclononatriene)Fe(CO)₃ and the symmetrical (cyclononatetraene)Fe(CO)₃ exclusively. All compounds were characterised by ¹³C-NMR.     

Anomalous behaviour of an allyl alcohol in reaction with iron pentacarbonyl

[(6,7,8,9-η)-Bicyclo[3.2.2]nona-2,6,8-trien-4-ol]tricabonyliron (6) rearranges in the presence of Fe(CO)₅ to [(2,3,6,7-η)-bicyclo[3.2.2]nona-2,6,8-trien-4-one] tricarbonyliron (7); rather than [(6,7,8,9-η)-bicyclo-[3.2.2]nona-6,8-dien-2-one] tricarbonyliron (9), the product expected on the basis of known organoiron chemistry and previously proposed mechanisms. The starting material 6 is stable in the absence of Fe(CO)₅, which leads to the conclusion that some iron-containing species derived from fe(CO)₅ is responsible for bringing about rearrangement. Since the usual mechanism for iron carbonyl-induced rearrangement in olefins cannot be operating here, a mechanism involving an ion pair with [HFe(CO)₄]^- is suggested.     

Linkage isomerism in 5-exo thiocyanate and isothiocyanate substituted tricarbonyl(η-cyclohexa-1,3-diene)iron and tricarbonyl(η-cyclohepta-1,3-diene)iron

Nucleophilic addition to the tricarbonyl(η-cyclohexadienyl)iron cation and the tricarbonyl(η-cycloheptadienyl)iron cation by the thiocyanate ion forms initially the 5-exo-isothiocyanate (NCS) isomers, C₆H₇NCSFe(CO)₃ and C₇H₉NCSFe(CO)₃, both of which isomerise to the corresponding 5-exo thiocyanate isomers C₆H₇SCNFe(CO)₃ and C₇H₉SCNFe(CO)₃ on exposure to air.     

Stereospecific incorporation of 13CO into olefinic substituted metal carbonyl compounds

The triene complex, (bicyclo[6.1.0] nona-2,4,6-triene)molybdenum tricarbonyl, has been observed to react with ¹³CO in solution to afford stereospecifically the axially labelled ¹³CO tetracarbonyl derivative. Further reactions of this ¹³CO derivative with triphenylphosphine or bis(1,2-diphenylphosphino)ethane resulted in formation of the cis disubstituted phosphine derivatives with retention of the ¹³CO label.     

Bicyclo[4.2.0]octa-1,3,5-triene: 2-Mono- and 2,5-Disubstituted Derivatives via Highly Regioselective Lithiation of Its Cr(CO)3 Complex and via Reductive Silylation/Oxidation

Treatment of [η⁶-(bicyclo[4.2.0]octa-1,3–5 triene)]tricarbonylchromium(0) ( 2 ) with BuLi or lithium 2,2,6,6-tetramethylpiperidinide (TMPLi) gives rise to a highly regioselective deprotonation at C(2). Subsequent reaction with electrophiles (6 examples) gives [η⁶-(2-R-bicyclo[4.2.0]octa-1,3,5-triene)]tricarbonylchromiurn complexes 3 and 5 – 9 in moderate (R?I, 50%; R?CHO, 67%) to good (R?Me, D, SiMe₃, CO₂Me, > 80%) yield (Scheme 1). Analogous reactions with tricarbonyl (η⁶-indane)chromium ( 10 ) give mixtures of complexes substituted at C(4) and C(5) (Scheme 2). In 10 , deprotonation β to the ring junction is strongly favoured with the bulky base TMPLi. Double lithiation/electrophile additions to 2 give access to [η⁶-(2-R′-5-R″-bicyclo[4.2.0]octa-1,3,5-triene)]tri-carbonylchromium complexes (e.g. 13 (R′?R″?Me₃Si) and 14 (R′?Me₃Si, R″?CHO)) as single products. The Cr(CO)³ group can be easily removed by oxidation (I₂, Ce(IV), O₂/light; 2 examples each) to give the free arenes. Base-catalyzed (C_sF, DMF/D₂O) deuterodesilylation of 13 yields the [(2,5-²H₂)bicyclo[4.2.0]octa-1,3,5-triene]chromium complex 15 , and treatment of 2,5-bis(trimethylsilyl) compound 16 with CF₃COOD gives the 2,4-dideuterated 17 . Compound 16 is also accessible more directly via reductive silylation/oxidation of bicyclo[4.2.0]octa-1,3,5-triene ( 1 ). Stereoselective base-catalyzed (t-BuOK.) H/D exchange of the benzylic H-atoms. opposite to the Cr(CO)₃ moiety in 2 takes place rapidly in (D₆)DMSO, but benzylic functionalization via this route remains elusive.     

The reaction of diiron nonacarbonyl with cis-bicyclo[6.2.0]deca-2,4,6-triene

The reaction of diiron nonacarbonyl with cis-bicyclo[6.2.0]deca-2,4,6-triene in ether at room temperature produces several products which are separable by chromatography on alumina. Compound (A), C₁₀H₁₂Fe₂(CO)₆, obtained in 23% yield, is shown by PMR and IR spectra to have the FeFe bonded Fe₂(CO)₆ group attached to the triene portion of the starting bicyclotriene. Compound (B), C₁₀H₁₂Fe(CO)₃, obtained both from the initial reaction and by heating (A) in refluxing toluene; is the Fe(CO)₃ adduct of tricyclo[4.4.0.0^2.5]deca-7,9-diene, a molecule which has not been isolated in the free state. Compound (C), also obtained on pyrolysis of (A) in minute yield, has not yet been characterized. Compound (D), C₁₀H₁₂Fe₂(CO)₆, from the original reaction, in small yield, appears to have separate Fe(CO)₃ groups bonded to the olefinic portions of a C₁₀H₁₂ monocycle, but spectral data alone do not allow a complete specification of the structure.     

邻异丙硫基苯甲酰基和苯硫甲基铁衍生物的合成与反应

利用异丙基苯硫醚与丁基锂反应后,再依次与羰基铁和碘反应制得了碘桥双核邻异丙硫基苯甲酰基铁配合物[（o-ⁱPrS） C₆H₄COFe（CO）₂I]₂,而苯甲硫醚类似的反应却仅得到单核苯硫甲基铁配合物C₆H₅SCH₂Fe（CO）₃I。当与亲核试剂作用时,这2个化合物表现出显著不同的反应活性。如双核配合物[（o-ⁱPrS） C₆H₄COFe（CO）₂I]₂与2-吡啶硫醇钠（PySNa）反应得到单核配合物（o-ⁱPrS） C₆H₄COFe（CO）₂（SPy）,但单核配合物C₆H₅SCH₂Fe（CO）₃I与PySNa反应导致其分解。另一方面,单核配合物C₆H₅SCH₂Fe（CO）₃I与三苯基膦（PPh₃）反应得到羰基取代配合物C₆H₅SCH₂Fe（CO）₂（PPh₃） I,但是双核配合物[（o-ⁱPrS） C₆H₄COFe（CO）₂I]₂类似的反应却导致其分解,没有获得可表征的化合物。所有新合成的化合物都通过了核磁与红外光谱的表征,它们的结构也获得了X射线单晶衍射的确证。     

邻异丙硫基苯甲酰基和苯硫甲基铁衍生物的合成与反应

利用异丙基苯硫醚与丁基锂反应后,再依次与羰基铁和碘反应制得了碘桥双核邻异丙硫基苯甲酰基铁配合物[（o-ⁱPrS）C₆H₄COFe（CO）₂I]2,而苯甲硫醚类似的反应却仅得到单核苯硫甲基铁配合物C₆H₅SCH₂Fe（CO）₃I。当与亲核试剂作用时,这2个化合物表现出显著不同的反应活性。如双核配合物[（o-ⁱPrS）C₆H₄COFe（CO）₂I]2与2-吡啶硫醇钠（PySNa）反应得到单核配合物（o-ⁱPrS）C₆H₄COFe（CO）₂（SPy）,但单核配合物C₆H₅SCH₂Fe（CO）₃I与PySNa反应导致其分解。另一方面,单核配合物C₆H₅SCH₂Fe（CO）₃I与三苯基膦（PPh₃）反应得到羰基取代配合物C₆H₅SCH₂Fe（CO）₂（PPh₃）I,但是双核配合物[（o-ⁱPrS）C₆H₄COFe（CO）₂I]2类似的反应却导致其分解,没有获得可表征的化合物。所有新合成的化合物都通过了核磁与红外光谱的表征,它们的结构也获得了X射线单晶衍射的确证。     

Ironcarbonyl Complexes of 5,6-Dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene Derivatives. Synthesis of Substituted Tricarbonyl(ortho-quinodimethane)iron Complexes and 2-Indanones

The l-dimethoxymethyl-5,6-dimethyldene-7-oxabicyclo[2.2.1]hept-2-ene ( 9 ) has been prepared. On treatment with Fe₂(CO)₉, the endocyclic double bond C(2)?C(3) was coordinated first giving the corresponding exo-Fe(CO)₄ complex 10 . The latter reacted with Fe₂(CO)₉ and afforded cis-heptacarbonyl-μ-[1RS,2SR,3RS,4SR,5RS,6SR-2,3-η: C5,6,C-η-(1-(dimethoxymethyl)-5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]diiron ( 11 ) as a major product. On heating, 11 underwent deoxygenation of the 7-oxabicyclo[2.2.1]heptene moiety yielding tricarbonyl[C,5,6,C-η-(1-(dimethoxymethyl)-5,6-dimethylidenecyclohexa-1,3-diene)]iron ( 13 ). In MeOH, a concurrent, regioselective methoxycarbonylation was observed giving tricarbonyl[C,3,4,C-η-(methyl 5-(dimethoxymethyl)-3,4-dimethylidenecyclohexa-1,5-diene-1-carboxylate)]iron ( 14 ). Oxidative removal of the Fe(CO)₃ moiety in 13 and 14 did not afford the expected ortho-quinodimethane derivatives but led to CO insertions giving 2,3-dihydro-2-oxo-1Hindene-4-carbaldehyde ( 20 ) and methyl 7-formyl-2-3-dihydro-2-oxo-lH-indene-5-carboxylate ( 21 ), respectively.     

Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]iron

The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept–2-ene-l-methanol ( 7 ) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe₂(CO)⁹] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene ( 8 ) led to the formation of a 1.7:1 mixture of ‘trans’ ( 19, 21, 22 ) vs. ‘cis’ ( 20, 23, 24 ) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron ( 25 ) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron ( 26 ). The structures of products 19 and of its exo ( 21 ) and endo ( 22 ) [Fe(CO)₃(1,3-diene)]complexes) and 20 (and of its exo ( 23 ) and endo (24) (Fe(CO)₃(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron ( 21 ). In the latter, the Fe(CO)₃(1,3-diene) moiety deviates significantly from the usual local C_s symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η³-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).     

Indenyl and fluorenyl transition metal complexes : VII. Innersphere “ricochet” rearrangements on alkylation of η5-indenyl- and η5-fluorenyltricarbonylchromate anions

Alkylation of K[η⁵-C₉H₇Cr(CO)₃] (Xa) with CH₃I and C₆H₅CH₂Br leads to σ-alkyl derivatives of η⁵-C₉H₇Cr(CO)₃Alk type. These complexes undergo innersphere “ricochet” rearrangement, with the alkyl group being shifted to the endo position at C(1) and the chromium tricarbonyl group shifted to the benzene nucleus. The structure of the product of such a rearrangement in the case of η⁵-C₉H₇(CO)₃CrCH₂C₆H₅, i.e. (1-benzyl-3a,4-7,7a-η⁶-indene)chromium tricarbonyl (XVIII), is established by a low temperature X-ray study, indicating an endo position for the benzyl radical.On alkylation of equilibrium tautomeric mixtures of η⁵- and η⁶-fluorenylchromium tricarbonyl anions XIa ? XIb under similar conditions, the η⁵-anion (Xa) yields a σ-alkyl derivative, which is rearranged to (9-endo-alkyl-1-4,4a,9a-η⁶-fluorene)chromium tricarbonyl. Electrophilic attack of the η⁶-anion (XIb) takes place on the outer side at C(9) and leads to a corresponding 9-exo-alkyl derivative.     

New tricarbonyl(amido-substituted-1,3-diene)iron complexes

X-substituded benzamides (X = H; 2-OH; 4-MeO; 3-MeO; 3,5-(MeO)₂; 4-Cl and 2,4-Cl₂) have been shown to add reversibly to the dienyl rings of the organometallic compounds [(dienyl)Fe(CO)₃]BF₄ (dienyl = C₆H₇, 2-MeOC₆H₆ or C₇H₉) to give the corresponding cationic tricarbonyl(substituted-diene)iron complexes.     

Iron pyrrole‐based PNP pincer ligand complexes as catalyst precursors

The structure of a pincer ligand consists of a backbone and two `arms' which typically contain a P or N atom. They are tridentate ligands that coordinate to a metal center in a meridional configuration. A series of three iron complexes containing the pyrrole‐based PNP pincer ligand 2,5‐bis[(diisopropylphosphanyl)methyl]pyrrolide (PN^pyrP) has been synthesized. These complexes are possible precursors to new iron catalysts. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}carbonylchlorido(trimethylphosphane‐κP )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₃H₉P)(CO)] or [Fe(PN^pyrP)Cl(PMe₃)(CO)], (I), has a slightly distorted octahedral geometry, with the Cl and CO ligands occupying the apical positions. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}chlorido(pyridine‐κN )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₅H₅N)] or [Fe(PN^pyrP)Cl(py)] (py is pyridine), (II), is a five‐coordinate square‐pyramidal complex, with the pyridine ligand in the apical position. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}dicarbonylchloridoiron(II), [Fe(C₁₈H₃₄NP₂)Cl(CO)₂] or [Fe(PN^pyrP)Cl(CO)₂], (III), is structurally similar to (I), but with the PMe₃ ligand replaced by a second carbonyl ligand from the reaction of (II) with CO. The two carbonyl ligands are in a cis configuration, and there is positional disorder of the chloride and trans carbonyl ligands.     

Platinum Indolylphosphine Fluorido and Polyfluorido Complexes: An Interplay between Cyclometallation,Fluoride Migration,and Hydrogen Bonding

The reaction of [PtCl₂(COD)] (COD=1,5-cyclooctadiene) with diisopropyl-2-(3-methyl)indolylphosphine (iPr₂P(C₉H₈N)) led to the formation of the platinum(ii ) chlorido complexes, cis-[PtCl₂{iPr₂P(C₉H₈N)}₂] ( 1 ) and trans-[PtCl₂{iPr₂P(C₉H₈N)}₂] ( 2 ). The cis-complex 1 reacted with NEt₃ yielding the complex cis-[PtCl{κ²-(P,N)-iPr₂P(C₉H₇N)}{iPr₂P(C₉H₈N)}] ( 3 ) bearing a cyclometalated κ²-(P,N)-phosphine ligand, while the isomer 2 with a trans-configuration did not show any reactivity towards NEt₃. Treatment of 1 or 3 with (CH₃)₄NF (TMAF) resulted in the formation of the twofold cyclometalated complex cis-[Pt{κ²-(P,N)-iPr₂P(C₉H₇N)}₂] ( 4 ). The molecular structures of the complexes 1–4 were determined by single-crystal X-ray diffraction. The fluorido complex cis-[PtF{κ²-(P,N)-iPr₂P(C₉H₇N)}{iPr₂P(C₉H₈N)}] ⋅ (HF)₄ ( 5 ⋅ (HF)₄) was formed when complex 4 was treated with different hydrogen fluoride sources. The Pt(ii ) fluorido complex 5 ⋅ (HF)₄ exhibits intramolecular hydrogen bonding in its outer coordination sphere between the fluorido ligand and the NH group of the 3-methylindolyl moiety. In contrast to its chlorido analogue 3 , complex 5 ⋅ (HF)₄ reacted with CO or the ynamide 1-(2-phenylethynyl)-2-pyrrolidinone to yield the complexes trans-[Pt(CO){κ²-(P,C)-iPr₂P(C₉H₇NCO)}{iPr₂P(C₉H₈N)}][F(HF)₄] ( 7 ) and a complex, which we suggest to be cis-[Pt{C=C(Ph)OCN(C₃H₆)}{κ²-(P,N)-iPr₂P(C₉H₇N)}{iPr₂P(C₉H₈N)}][F(HF)₄] ( 9 ), respectively. The structure of 9 was assigned on the basis of DFT calculations as well as NMR and IR data. Hydrogen bonding of HF and NH to fluoride was proven to be crucial for the existence of 7 and 9 .     

The stereospecificity at the iron center of the decarbonylation of an ironacetyl complex

The dinuclear complex [(h⁵-1-CH₃-3-C₆H₅C₅H₃)Fe(CO)₂]₂ was synthesized by reaction of Fe₂(CO)9 with 1-methyl-3-phenylcyclopentadiene; it was converted to (h⁵-1-CH₃-3-C₆H₅C₅H₃)Fe(CO)₂CH₃ by reduction with sodium amalgam and addition of CH₃l, and thence to (h⁵-1-CH₃-3-C₆H₅C₅H₃)Fe(CO)[P(C₆H₅)₃] (COCH₃) (I) by reaction with P(C₆H₅)₃. The acetyl I was separated into two diastereomerically related pairs of enantiomers. Ia and Ib, by a combination of column chromatography on alumina and crystallization from benzene/pentane. The photochemical decarbonylation of Ia and Ib in benzene or THF solution was examined by ¹H NMR spectroscopy. This reaction proceeds with high stereospecificity (>84% retention or inversion) at the iron center to yield (h⁵-1-CH₃-3-C₆H₈C₅H₃)Fe(CO)[P(C₆H₅)₃]CH₃(II), enriched in the diastereomerically related pairs of enantiomers, IIa and IIb, respectively. Since IIa and IIb epimerize under the photolytic conditions of decarbonylation, the actual stereospecificity of the conversion of I to II is higher than 84%, and likely 100%. This is supported by the data from kinetic studies of the decarbonylation of I and the epimerization of II, carried out under identical photolytic conditions. The implications of the foregoing results to the mechanism of the decarbonylation are considered. Also described herein is the synthesis of other complexes with two asymmetric centers of the general formula (h⁵-cyclopentadienyl)Fe(CO)(L)(COR) and (h⁵-cyclopentadienyl)Fe(CO)(L)R that contain either an unsymmetrically substituted h⁵-cyclopentadienyl ring or a chiral tertiary phosphine.     

Synthesis of cationic indenyliron complexes: [η5-C9H7Fe(CO)2L]+ (L = phosphine,phosphite, CO)

Synthetic routes to the cationic complexes [η⁵-C₉H₇Fe(CO)[₂L]⁺, (L = CO, phosphine, phosphite, nitrile, pyridine) have been investigated. The most versatile method is oxidation of the dimer [η⁵-C₉h₇Fe(CO)₂]₂ with ferricinium ion. in the presence of the appropriate ligand. [η⁵-C₉H₇Fe(CO)₃]⁺ is best prepared by oxidation of the dimer with Ph₃CBF₄. This tricarbonyl cation readily loses one CO group on reactiom with phosphines and P(OCH₃). The acentonitrile ligand [η⁵-C₉H₇Fe(CO)₂CH₃CN]⁺ can also be replaced bny phosphines. Finally, reactions of η⁵-C₉H₇Fe(CO)₂X, (X = Br, I) with phosphines also yield cationic products isolatedas PF₆⁻ salts.     

Circular Dichroism of Tricarbonyl(diene)iron Complexes. The Octant Rule Applied to Ketones Perturbed by Remote Fe(CO)3 Groups. Crystal Structure of (±)-Tricarbonyl[(1RS,4RS,5RS,6SR)-C5,6,C-η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanone)]iron

The preparation and the CD spectra of optically pure (+)-trans-μ-[(1R,4S,5S,6R,7R,8S)-C,5,6,C -η : C,7,8,C-η-(5,6,7,8-tetramethylidene-2-bicyclo [2.2.2]octanone)]bis(tricarbonyliron) ((+)- 7 ) and (+)-tricarbonyl[(1S,4S,5S,6R)-C-5,6,C-η-(5,6,7,8,-tetramethylidene-2-bicyclo[2.2.2]octanone)]iron ((+)- 8 ), and of its 3-deuterated derivatives (+)-trans-μ-[(1R,3R,4S,5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C-η-5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]-(octanone)]bis(tricarbonyliron) ((+)- 11 ) and (+)-tricarbonyl[(1S,3R,4S,5S,6R)-C-5,6,C- η-(5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]octanone)]iron ((+)- 12 ) are reported. The chirality in (+)- 7 and (+)- 8 is due to the Fe(CO)₃ moieties uniquely. The signs of the Cotton effects observed for (+)- 7 and (+)- 8 obey the octant rule (ketone n→π*_CO transition). Optically pure (?)-3R-5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]octanone ((?)- 10 ) was prepared. Its CD spectrum showed an ‘anti-octant’ behaviour for the ketone n→π*_CO transition of the deuterium substituent. The CD spectra of the alcoholic derivatives (?)-trans-μ-[(1R,2R,4S, 5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C- η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanol)]bis(tricarbonyliron) ((?)- 2 ) and (?)-tricarbonyl- [(1S,2R,4S,5S,6R)- C,5,6,C- η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanol)]iron ((?)- 3 ) and of the 3-denterated derivatives (?)- 5 and (?)- 6 are also reported. The CD spectra of the complexes (?)- 2 , (?)- 3 , (+)- 7 , and (+)- 8 were solvent and temperature dependent. The ‘endo’-configuration of the Fe(CO)₃ moiety in (±)- 8 was established by single-crystal X-ray diffraction.     

Synthesis and structures of photoactive rhenium carbonyl complexes derived from 2‐(pyridin‐2‐yl)‐1,3‐benzothiazole, 2‐(quinolin‐2‐yl)‐1,3‐benzothiazole and 1,10‐phenanthroline

Carbon monoxide (CO) has recently been identified as a gaseous signaling molecule that exerts various salutary effects in mammalian pathophysiology. Photoactive metal carbonyl complexes (photoCORMs) are ideal exogenous candidates for more controllable and site‐specific CO delivery compared to gaseous CO. Along this line, our group has been engaged for the past few years in developing group‐7‐based photoCORMs towards the efficient eradication of various malignant cells. Moreover, several such complexes can be tracked within cancerous cells by virtue of their luminescence. The inherent luminecscent nature of some photoCORMs and the change in emission wavelength upon CO release also provide a covenient means to track the entry of the prodrug and, in some cases, both the entry and CO release from the prodrug. In continuation of the research circumscribing the development of trackable photoCORMs and also to graft such molecules covalently to conventional delivery vehicles, we report herein the synthesis and structures of three rhenium carbonyl complexes, namely, fac‐tricarbonyl[2‐(pyridin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₂H₈N₂S)(CO)₃](CF₃SO₃), ( 1 ), fac‐tricarbonyl[2‐(quinolin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₆H₁₀N₂S)(CO)₃](CF₃SO₃), ( 2 ), and fac‐tricarbonyl[1,10‐phenanthroline‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₂H₈N₂)(CO)₃](CF₃SO₃), ( 3 ). In all three complexes, the Re^I center resides in a distorted octahedral coordination environment. These complexes exhibit CO release upon exposure to low‐power UV light. The apparent CO release rates of the complexes have been measured to assess their comparative CO‐donating capacity. The three complexes are highly luminescent and this in turn provides a convenient way to track the entry of the prodrug molecules within biological targets.