Anthony R. Manning

A reinvestigation of the reaction of [Fe2(η-C5H5)2(CO)4-n(CNR)n] (n = 1 or 2) with strong alkylating agents

Abstract The reaction of [Fe 2 (η-C 5 H 5 ) 2 (CO) 3 (CNR)] with R′OSO 2 CF 3 (R,R′  Me or Et) gives a mixture of cis and trans -[Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (μ-CO)μ-CN(R′)R]SO 3 CF 3 . When R  R′  Me the isomer ratio is variable, but the cis always predominates and is the only product when R ≠ R′. The complexes [Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (CNR) 2 ] react with R′OSO 2 CF 3 and the more reactive alkyl halides R′X to give a mixture of cis - [Fe 2 (η-C 5 H 5 ) 2 (CO)(CNR)(μ-CO)ν-CN(R′)R]X and cis -[Fe 2 (η-C 5 H 5 ) 2 (CO) 2 μ-CN(R′)R 2 ][X] 2 . In both series of cations the presence of μ-CN(R′)R ligands give rise to isomers that differ in respect of orientation about the CN bond. The cations are not fluxional and do not undergo cis - trans interconversion, bridge-terminal ligand exchange, or rotation about the μ-CN(R′)R double bond. The structure of the cations in the [Fe 2 (η-C 5 H 5 ) 2 (CO)(CNMe)(μ-CO)(μ-CNMe 2 )]BPh 4 and [Fe 2 (η-C 5 H 4 Me) 2 (CO) 2 (μ-CNMe 2 ) 2 ][SO 3 CF 3 ] 2 salts were confirmed as cis by X-ray diffraction studies. Their dimensions are similar to those previously found in cis - [Fe 2 (η-C 5 H 4 Me) 2 (CO) 2 (μ-CO)(μ-CNMe 2 )]I, but with variations due to the differing acceptor and donor abilities of the various ligands. Infrared and NMR spectra of the complexes are reported and discussed.

A new type of isomerism in some phosphine and phosphite derivatives of the metal carbonyls

Abstract A new type of isomerism is reported for a wide variety of transition metal carbonyl complexes of the general type (π-Ring)M(CO)(L)X where L is a tertiary phosphine or phosphite ligand. The effects of solvent and temperature upon this isomerism are described, and possible reasons for it are discussed.

The linear and nonlinear optical properties of organometallic chromophores derived from ferrocene, [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-CCH3)]+[BF4]− and terthienyl spacers. Crystal structure of 2-[(E)-2-ferrocenylethenyl]-5-(2-thienyl)thiophene

Several chromophores based on ferrocene, [Fe2( 5 -C5H5)2(CO)2(-CO)(-CCH3)] + and terthiophene or dithienylbenzo[c]thiophene have been synthesized. Both thienyls have been shown to act as good donor end groups in their own right but contrary to our expectations the benzo[c]thiophene merocyanine has a lower hyperpolarizablity (344 × 10 − 30 esu) than its thienyl congener (650 ×10 −30 esu). The structure of 2-[(E)-2-ferrocenylethenyl]-5-(2-thienyl)thiophene has been determined by single crystal X-ray diffraction. The terminal thienyl (thp) group is disordered over two orientations about the bithienyl C(sp 2 )C(sp 2 ) bond such that the two sulfur atoms in either thp ring are positioned trans/cis in the ratio 0.628(4):0.372(4). The integrity of the alkenyl CC remains with a bond length of 1.332(2) A and the CC lengths adjacent are 1.453(4)/1.441(4) A . Twisting of the rings from planarity occurs along the Fc–CC–(thp)–(thp) axis: the angle which the ethenylthiophene CCC4H2S moiety makes with the C5H4 is 11.2(2)°, and with the major orientation of the disordered terminal thienyl group, 16(1)°.

The effect of different bithienyl spacers on the linear and non-linear optical properties of organometallic chromophores derived from [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-C–CH3)]+ [BF4]−: Crystal structure of [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-(E)-C–CHCH-7-(thieno[3,2-e][1]benzothiophene))]+ [BF4]−

Abstract Two series of organometallic merocyanines incorporating a variety of bithienyl moieties both as spacers and end groups were synthesised. In the first series the bithienyls function as end groups and were appended to an acceptor derived from [Fe 2 (η 5 -C 5 H 5 ) 2 (CO) 2 (μ-CO)(μ-C–CH 3 )] + [BF 4 ] − . In the second series, ferrocene acting as an organometallic donor was incorporated into the chromophores at the far terminus of the bithienyl spacers. The molecular first hyperpolarisabilities β of the second series were determined by hyper-Rayleigh scattering and the values range from 429×10 −30 esu to 867×10 −30 esu in dichloromethane. A single crystal X-ray study of [Fe 2 (η 5 -C 5 H 5 ) 2 (CO) 2 (μ-CO)(μ-( E )-C–CHCH-7-(thieno[3,2- e ][1]benzothiophene))] + [BF 4 ] − ·CH 2 Cl 2 is reported.

Preparation, spectra and structure of [Fe2(η-C5H5) 2(L)(CN)(μ-CO){μ-CN(R′)R}], [Fe2(η-C5H5) 2(CO)(CN) {μ-CNMe2}2]+ and [Fe2(η-C5H5) 2(CN) 2{μ-CNMe2}2] zwitterions (L = CO or organoisocyanide) and their reactions with alkyl and protic electrophiles

Abstract The thermal, photolytic or chemical activation of [Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (μ-CO)(μ-CNMe 2 )]X and cis -[Fe 2 ( η -C 5 H 5 ) 2 (CO)(CNMe)( μ -CO)( μ -CNMe)]X and related salts (X − = I − or [SO 3 CF 3 ] − ) allows replacement of one t -CO ligand by L = CN − , CNMe or CNC 6 H 3 Et 2 -2,6 to give respectively [Fe 2 (η-C 5 H 5 ) 2 (CO)(L)(μ-CNMe 2 )] + and [Fe 2 (η-C 5 H 5 ) 2 (L)(CNMe)(μ-CO)(μ-CNMe 2 )] + derivatives. Similar reactions of cis -[Fe 2 ( η -C 5 H 5 ) 2 (CO) 2 ( μ -CNMe 2 ) 2 ][SO 3 CF 3 ] 2 allows the replacement of one or both t -CO groups in turn by L = CN − , CNMe or CNC 6 H 11 to give respectively [Fe 2 (η-C 5 H 5 ) 2 (CO)(L)(μ-CNMe 2 ) 2 ] 2+ and [Fe 2 (η-C 5 H 5 ) 2 (L) 2 (μ-CNMe 2 ) 2 ] 2+ derivatives. Some of these substitution reactions take place with isomerism of the Fe 2 (L) 2 (μ-L′) 2 framework cis 〈−〉 trans , but the cis isomers always predominate no matter what precursor. However, alkylation of the t -CN ligand by ROSO 2 CF 3 , but not RI, proceeds without any such isomerism, which allows correlation of spectra with structure for a number of different types of compound. Protonation of the t -CN ligands of [Fe 2 (η-C 5 H 5 ) 5 (CO)(CN)(μ-CNMe 2 ) 2 ] + and [Fe 2 (η-C 5 H 5 ) 2 (CN) 2 (μ-CNMe 2 ) 2 ] to give complexes containing t -CNH ligands may be effected by HOSO 2 CF 3 , but this straight-forward approach does not work for [Fe 2 (η-C 5 H 5 ) 2 (CO)(CNH)(μ-CO)(μ-CNMe 2 )] + which is best prepared by the reaction of [Fe 2 (η-C 5 H 5 ) 5 (CO)(CN)(μ-CO)(μ-CNMe 2 )] with EtOSO 2 CF 3 in wet chloroform. The spectra of the various compounds are reported and discussed. There is no exchange between cis and trans isomers or bridging and terminal ligands, or rotation about the CN bonds of the μ -C=NR 2 ligands in any of the complexes reported below 80°C.

The cleavage of coordinated heterocumulenes. The reactions of [Fe(CO)2(PPh3)2(η-SCY)] and their analogues with [Co(η-C5H5)(PPh3)2] to give heteronuclear [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S)(μ3-CY)] (Y=S or SR+) and related clusters

Abstract The reaction of [Fe(CO)2(PPh3)2(η2-CS2)] with two equivalents of [Co(η-C5H5)(PPh3)2] gives [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CS)] (L=PPh3) as the sole product in good yield. Under the same conditions, [Fe(CO)2(L)2(η2-CS2Me)][SO3CF3] gives [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CSMe)][SO3CF3]. The PPh3 ligand of [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CS)] (L=PPh3) may be replaced by P(OPh)3 and P(OMe)3 on UV photolysis to give the complexes where L=P(OPh)3 and P(OMe)3, but no isolable products were formed when L=CO, CNMe, PMe3 or PBu3n. The three clusters react with RI and ROSO2CF3 (R=Me, Et or allyl) to give [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CSR)]+ salts, and there is spectroscopic evidence for the formation of the [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S)(μ3-CSMe2)]2+ cation. The molecular structures of [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S)(μ3-CS)] and [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S){μ3-CSMe}][I] have been determined by X-ray diffraction methods, and shown to be based on a Co2Fe triangle capped on one face by a μ3-S ligand and on the other face by a μ3-CS or μ3-CSMe+ ligand acting as a two-electron donor to the cluster. In the salt there are two cations whose structures differ slightly. In general, bond lengths are normal, but those to iron are always longer than those to cobalt.

Structure−Property Dependence of the First Hyperpolarisabilities of Organometallic Merocyanines Based on the μ-Vinylcarbynediiron Acceptor and Ferrocene Donor

In order to investigate the structure−property relationship of nonlinear optical materials, a series of organometallic chromophores were synthesised utilising the [Fe2(η-C5H5)2(CO)2(μ-CO)(μ-C−)]+ electron-accepting moiety and the ferrocenyl group, Fc, as the electron donor. The π-linker between these two termini was systematically modified and the mutual electronic communication between them was determined using IR, NMR, and electronic absorption spectroscopy. An X-ray structure determination of [Fe2(η-C5H5)2(CO)2(μ-CO)(μ-C−CH=CH−CH=C(Cl)−Fc)][BF4] confirmed the strong electronic interaction between the donor and the acceptor with reduced π-bridge bond-length alternation. The nonlinear optical properties of these complexes were examined using the hyper Rayleigh scattering technique. The experimental first hyperpolarisabilities are some of the highest obtained for ferrocenyl chromophores and, significantly, no enhancement was found due to two-photon absorption fluorescence. When polyene linkers −(CH=CH)n− are used, the values for β0 increase with a ca. n1.5 dependence with no sign of saturation up to n = 4. However, the highest values for β and βo were obtained for linkers which contained an aromatic ring as opposed to pure polyenes and in this respect a benzene ring was more effective than a thiophene or furan. Consequently, the higher β and β0 are not exhibited by those merocyanines with the highest values for λmax. It is concluded for these compounds that a low excitation energy Eeg and a large transition moment M for the electronic excitation are less important than a large change in the dipole moment Δµeg. Furthermore, a chloro substituent on the olefinic double bond proximate to the ferrocenyl group has a dramatic effect on the β and β0 values.

Chiral organometallic chromophores for nonlinear optics derived from [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-CCH3)]+ [BF4]−

Abstract Two series of chiral organometallic Donor-π-Acceptor chromophores derived from [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-CCH3)]+ [BF4]− have been synthesised. In the first series (S)-(−)-2-methoxymethyl pyrrolidine acts as the chiral donor end group and in the second series 1,1′-binaphthyl acts as the chiral π-bridging unit. The nonlinear optical properties of these compounds were measured by the Kurtz powder technique and by hyper-Raleigh scattering. β-values of up to 964×10−30 esu were obtained for a member of the first series. Single crystal X-ray studies of [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-CCH3)]+ [BF4]−, [Fe2(η5-C5H4CH3)2(CO)2(μ-CO)(μ-(E)-CCHCH-2-(5-piperidin-1-yl-thiophene))]+ [BF4]− and [Fe2(η5-C5H4CH3)2(CO)2(μ-CO)(μ-(E)-CCHCH-2-(naphthalene))]+ [BF4]− are reported.

Reactions of [Fe2(η-C5H5)2(CO)2(L)(CNMe)](L = CO or CNMe) with lewis acids resulting in adduct formation, dimer scission or both. Structure of[Fe(η-C5H5)(CO)(CNMe)2] [BF4]

Abstract [Fe2(η-C5H5)2(CO)2(L)(CNMe)] (L = CO or CNMe) react with Lewis Acids E = SnX2, Snx4, ZnX2, CdX2, AsCl3, NiCl2·6H2O and AgNO3 (X = F, Cl, Br or I) to form adducts of the type [Fe2(η-C5H5)2(CO)(L)(μ-CO){μ-CN(Me)E}] where there are N → E bonds between the μ-CNR ligand and the Lewis acid. The adducts have been identified by IR and, where possible, 1H NMR spectroscopy, but only a few could be isolated and analysed. Often they decomposed to mononuclear species e.g. the [Fe2-(η-C5H5)2(CO)2(CNMe)2]/AgNO3 adduct ultimately deposits silver metal and gives [Fe(η-C5H5)(CO)-(CNMe)NO3] as the sole product in high yields. Other Lewis acids e.g. CoI2, CuCl2·4H2O or BF3·OEt2 cleave the dimers, apparently without adduct formation, but only the principal cleavage product from the [Fe2(η-C5H5)2(CO)2(CNMe)2]/BF3·OEt2 reaction could be identified. It was [Fe(η-C5H5)(CO)(CNMe)2][BF4] and its structure has been determined using X-ray diffraction techniques. [Structure solved by the heavy-atom method from photographic data and refined by full-matrix least-squares to R = 0.071 for 370 non-zero unique reflexions. Crystals of this compound are orthorombic with space group Pca21, Z = 4, a = 12.998 ± 0.012, b = 6.305±0.006, and c = 16.603±0.015 A.] The cation has the usual ‘piano-stool’, half-sandwich ligand arrangement about the Fe atom.

Synthesis and Properties of a Novel Series of Organometallic Merocyanines Combining the Potent Electron‐Donating [(CpFeCO)2(μ‐CO)(μ‐C=CH−)] Fragment with Tropylium‐Type Acceptors

The potent electron-donating group [(CpFeCO)2(µ-CO)(µ-C=CH−)] was combined with different tropylium-based acceptors yielding the push-pull complexes [(CpFeCO)2(µ-CO)(µ-C=CH−CH=A)][BF4] where =A represents [=CH−(η7-C7H6)Cr(CO)3]+ (5), [={C10H7}]+ (azulenylium) (7) [={C10H4Me2iPr}]+ (guaiazulenylium) (8). Crystal structures of the precursor complexes [(CpFeCO)2(µ-CO)(µ-C=CH−CH=CH−C7H7)] (3), [(CpFeCO)2(µ-CO){µ-C=CH−CH=CH−(η6-C7H7)Cr(CO)3}] (4) and the push-pull derivative 5 are presented. Whereas complexes 3 and 4 demonstrate localised carbon−carbon double and single bonds in the π-bridge between the diiron moiety and the seven-membered ring a small but distinct π-bond delocalisation can be observed in the π-linker of the cationic derivative 5. From the NMR spectroscopic results a correlation between the 13C NMR shift of the bridging carbon atom µ-C of the diiron unit and the coupling constant J(1H-1H) of the β- and γ-protons of the π-bridge was found. This correlation indicates an increased π-bond delocalisation throughout the conjugated bridge with respect to the electron-accepting capability in the order tricarbonyl(η7-cycloheptatrienylium)chromium < guaiazulenylium < azulenylium implying a predominantly charge-delocalised form in the case of the azulenylium complex 7. Considerably large first hyperpolarisabilities β were determined for 5 and 8 by means of hyper-Rayleigh scattering. Based on the two-level model β0 values were calculated and related to the bond-length alternation in the π-linker. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)