Teng-Yuan Dong

Physical properties of interannular bridged ferrocenophanium salts: structural, NMR, EPR and Mössbauer studies

Abstract The X-ray structure of 1,1′-(propane-1,3-diyl) ferrocenium iodide has been determined at 298 K: monoclinic, C 2/ c , a = 15.986(3), b = 15.125(3), c = 21.793(3) A, and β = 93.555(11)°; Z = 8, D calcd = 2.597 g cm - 3 , R F = 0.044, and R WF = 0.050. The compound 1,1′-(pentane-1,5-diyl) ferrocenium triiodide cyrstallizes in the triclinic space group P1ovbr: with four molecules in a unit cell with dimensions a = 9.5435(14), b = 13.1195(22), c = 15.2591(23) A, α = 106.317(13), β = 85.978(12), γ = 90.872(13)°. The final discrepancy factors are R F = 0.062 and R WF = 0.063. The physical properties of ferrocenophanium salts are reported. The EPR and Mossbauer results suggest that the electronic ground state of the interannular bridged ferrocenophanium cations is 2 E 2g . The changes of quadrupole splittings, proton chemical shifts, and low-symmetry parameters can be explained in terms of tilting of the Cp ring from parallel geometry.

The effect of interannular bridge on electron-transfer rate in mixed-valence biferrocenium triiodide salts

Abstract The physical properties of the new mixed-valence 1′,3:1‴,3″-bis(propane-1,3-diyl)-1,1″-biferrocenium triiodide ( 1 ) and 1′,3:1‴,3″-bis(pentane-l,5-diyl)-1,1″-biferrocenium triiodide ( 2 ) are reported. Compound 1 gives a Mossbauer spectrum with a single “average-valence” doublet at 77 K. On the other hand, compound 2 gives a Mossbauer spectrum with two quadrupole-split doublets at 300 K. Furthermore, compound 1 shows relatively EPR isotropic g tensors compared to compound 2 . Therefore, compound 1 is judged to have an electron-transfer rate in excess of ~ 10 10 s −1 , whereas the electron-transfer rate for 2 is slower than ~ 10 7 s −1 . Both compounds are localized on the IR timescale. Thus, the change of interannufar bridge in biferrocenium cations leads to a dramatic influence on the rate of electron transfer. It is concluded that compound 1 has a higher degree of electronic coupling between two iron ions than compound 2 . This difference in rate possibly originates in a structural difference in the interannular bridge in 1 and 2 .

Structures and Mössbauer spectra of phosphido-bridged heterobimetallic complexes CpFe(CO)2(μ-PPh2)W(CO)5 and CpFe(CO)(μ-CO)(μ-PPh2)W(CO)4

Abstract Structures of non metal-metal bonded phosphido-bridged heterobimetallic complexes, including CpFe(CO) 2 (μ-PPh 2 )W(CO) 5 ( 1 -W) and metal-metal bonded CpFe(CO)(μ-CO)(μ-PPh 2 )W(CO) 4 ( 2 ), were determined by a single crystal X-ray diffraction study. In 1 -W, the long distance between Fe and W indicates no metal-metal bond to exist. In 2 , a FeW bond with bond length 2.851 A and a semibridging carbonyl with WCO angle 153° were observed. Mossbauer spectra of 1 -W and 2 were taken at 77 K. Isomer shifts of 1 -W and 2 were − 0.0203 mm s −1 and 0. 1917 mm s −1 respectively.

Dinuclear molybdenum carbonyls bridged by hydride ligands

Abstract Complexes (μ-H)(μ-Ph2P(CH2)nPPh2)Mo2(CO)7(NO) (n = 1–4, designated, respectively, as 1, 2, 3, and 4), (μ-H)Mo2-(CO)8(L)(NO) (5, L = PPh3; 6, L = P(p-C6H4F)3; 7, L = P(p-C6H4Me)3; 8, L = P(p-C6H4OMe)3), and (μ-H)Mo2(CO)7-(L)2(NO) (9,L = P(OMe)3; 10, L = PMe2Ph) are synthesized from nitrosylation of (Et4N)((μ-H)(μ-Ph2P(CH2)PPh2)Mo2(CO)8) (n = 1–4), (Et4N)((μ-H)Mo2(CO)9(P(p- C6H4X)3)) (X = H, F, Me, OMe), and (Et4N)(μ-H)Mo2 (CO)8(L)2) (L=P(OMe)3, PMe2Ph) with one equivalent of NO+ BF4− in CH2Cl2 at −60°C. Treatment of 1–4 with Ph3P=NnPr provides (μ-H)(μ-Ph2P(CH2)nPPh 2)Mo2(CO)6(CNnPr)(NO) (11–14, n=1–4). X-ray crystal structure analyses for complexes 3, 12, and (μ-H) W2(CO)7(PMe2Ph)2(NO) (16) were carried out to give data as follows. 3: triclinic, P 1 , Z = 4, a 11.698 (2), b 13.926(2), c 21.605(4) A, α 93.72(2), β 92.89(3), γ 91.85(3)°, V 3505.5 A3, R = 0.034, Rw3= 0.036. 12: triclinic, P 1, Z = 2, a 10.100(3), b 12.982(4), c 15.453(4) A, α 102.60(2), β 83.29(2), γ 105.75(2)°, V 1899.6A3, R = 0.054, Rw = 0.055. 16: monoclinic, C2/c, Z 8, a 15.668(1), b 12.892(2), c 28.764(3)A, β 98.883(8)°, V 5740.4 A3, R = 0.032, Rw= 0.034.

Electron transfer in mixed-valence 1′,6′-bis(triphenylmethyl)biferrocenium triiodide

Abstract The 1′,6′-bis(triphenylmethyl)biferrocenium triiodide (6) was prepared. The intramolecular electron transfer rates in the solid state and in solution have been determined. Compound 6 gives a Mossbauer spectrum which reveals the presence of localized and delocalized species. An investigation of the energy and the line-shape of the intervalence transition band, permitted the calculation of the electron transfer rate in solution.

Electron transfer in mixed-valence 1′,1‴-bis(m-bromobenzyl)biferrocenium triiodide

Abstract The solid-state physical properties of the new mixed-valence 1′,1‴-bis( m -bromobenzyl)biferrocenium triiodide are reported. Mossbauer spectra of a microcrystalline sample indicated the presence of both delocalized and localized species. In the case of a recrystallized sample, below 200 K there are two doublets in the 57 Fe Mossbauer spectra which, on increasing the temperature, become a single “average-valence” doublet at ca. 250 K. The effects of the nature of the motion of charge in counterion and cation—anion interactions on solid-state electron transfer were investigated by studying intramolecular electron transfer for a series of 1′,1‴-bis(halobenzyl)biferrocenium salts in solution.

Micromodulation of electron-transfer rates in mixed-valence 1′,1″′-dibenzylbiferrocenium cations

Abstract X-Ray structures of 1′,1′″-disubstituted biferrocenium triiodide salts have been studied and the dramatic effects of substituents on the intramolecular electron-transfer rates are described.

Valence delocalization in mixed-valence 1',6'-bis(p-halobenzyl) biferrocenium salts. A new zigzag configuration for the polyiodide ion I5-

The results of an X-ray diffraction study of 1′,6′-bis(p-bromobenzyl)biferrocenium pentaiodide and those of Mossbauer spectroscopy indicate that the degree of delocalization of negative charge in the triiodide unit controls the intramolecular electron transfer in mixed-valence biferrocenes.

Pronounced effect of interannular trimethylene bridges on the rate of intramolecular electron-transfer in mixed-valence biferrocenium salts. A novel electronic ground state of ferrocenium cations

Abstract X-ray structure determinations of two new constitutional isomers of biferrocene, the effects of interannular trimethylene bridges on intramolecular electron-transfer rates in the solid state, and characterization of the electronic ground state of a series of ferrocenium cations are reported.