Paul Hamon

Redox-active organometallics: magnetic and electronic couplings through carbon-silicon hybrid molecular connectors.

Treatment of the triflate complex Cp*(dppe)FeOTf [12; Cp* = eta(5)-C(5)(CH(3))(5), dppe = 1,2-bis(diphenylphosphino)ethane, OTf = CF(3)SO(3)] with an excess of HC[triple bond]C-(Si(CH(3))(2))(x)-C[triple bond]CH (x = 2-4) in diethyl ether provides the binuclear bis(vinylidene) derivatives [Cp*(dppe)Fe=C=CH(Si(CH(3))(2))(x)CH=C=Fe(dppe)Cp*][OTf](2) (x = 2, 13; x = 3, 14; x = 4, 15), which were isolated as ochre solids and rapidly characterized by FT-IR, (1)H, (31)P, and (13)C NMR spectroscopies. The complexes 13-15 were reacted with potassium tert-butoxide to afford the bis(alkynediyl) complexes [Cp*(dppe)Fe-C[triple bond]C(Si(CH(3))(2))(x)C[triple bond]C-Fe(dppe)Cp*] (x = 2, 1; x = 3, 2; x = 4, 3), which were isolated as orange powders in yields ranging from 76 to 91%. The IR, cyclic voltammetry, and UV-vis data obtained for 1-3 and the X-ray crystal structures determined for 1 and 3 reveal the importance of the sigma-pi conjugation (hyperconjugation) between the Si-Si sigma bond and the adjacent C[triple bond]C pi-symmetric orbitals in the description of the electronic structure of the ground state of these complexes. When reacted at low temperature with 2 equiv of [(C(5)H(5))(2)Fe]X or AgX [X = BPh(4), B(3,5-(CF(3))(2)C(6)H(3))(4))], compounds 1-3 provide 1[X](2), 2[X](2), and 3[X](2), which can be isolated and stored below -20 degrees C. EPR spectroscopy and magnetization measurements established that the superexchange interaction propagates through the Si-Si bonds (J = -0.97(2) cm(-1) for 3[X](2)). UV-vis-near-IR spectra were obtained with an optically transparent thin-layer electrosynthetic (OTTLE) cell for 1-3[OTf](n) (n = 0-2). A band with a maximum that increases from 6400 cm(-1) (1[OTf]) to 8500 cm(-1) (3[OTf]) observed for the mixed-valence species was ascribed to intervalence charge transfer evidencing photodriven electron transfer through the carbon-silicon hybrid connectors with H(ab) parameters ranging from 64 to 285 cm(-1).

Organometallic iron (II) hydrazines and hydrazones — syntheses, characterisations and the X-ray crystal structures of [Fe(η5-Cp)(η6-C6H5NHNH2)]+PF6− and [Fe(η5-Cp)(η6-p-MeC6H4NHNCMe2)]+PF6−

The three new organometallic hydrazines [Fe(η 5 -Cp)(η 6 -RC 6 H 4 NHNH 2 )] + PF 6 − , CpC 5 H 5 , RH, [ 1 ] + PF 6 − ; m -Me, [ 2 ] + PF 6 − ; p -MeO, [ 3 ] + PF 6 − , were synthesised and characterised. They were obtained in CH 2 Cl 2 by reaction of the hydrazine monohydrate, NH 2 NH 2 ·H 2 O, with the corresponding precursors [Fe(η 5 -Cp)(η 6 -RC 6 H 4 Cl)] + PF 6 − . Similarly to free conventional organic hydrazines, the organometallic hydrazines [ 1 ] + PF 6 − and [ 3 ] + PF 6 − react with acetone affording hydrazones formulated as [Fe(η 5 -Cp)(η 6 -RC 6 H 4 NHNCMe 2 )] + PF 6 − , RH, [ 6 ] + PF 6 − ; p -MeO, [ 7 ] + PF 6 − . Likewise, the two other organometallic hydrazones containing the substituent groups R o -Cl, [ 8 ] + PF 6 − and p -Me, [ 9 ] + PF 6 − were also obtained from their parent hydrazine precursors [ 4 ] + PF 6 − and [ 5 ] + PF 6 − , respectively. All the new compounds were characterised by elemental analysis and IR, UV–vis, 1 H- and 13 C-NMR spectroscopy. The crystalline and molecular structures of [ 1 ] + PF 6 − and [ 9 ] + PF 6 − were determined by single crystal X-ray crystallographic analysis. Both structures show a cyclohexadienyl-like character at the coordinated C 6 ring of the phenylhydrazine and the p -methylphenylhydrazone with a folding angle of 6.0(5) and 7.1(6)°, respectively.

Homodimetallic iron(II) hydrazones: syntheses, spectroscopic, electrochemical, and theoretical investigations. X-Ray crystal structure of both syn- and anti- rotamers of [(η5-Cp)Fe(η6-C6H5)–NHNC(Me)–(η5-C5H4) Fe(η5-Cp)]+PF6−

Two homogeneous series of homodimetallic iron(II) hydrazone complexes of general formula [CpFe(η6-p-RC6H4)–NHNCH–(η5-C5H4)FeCp]+PF6− (Cp=η5-C5H5): R=H, [5]+PF6−; Me, [6]+PF6−; MeO, [7]+PF6−; Cl, [8]+PF6−; and [CpFe(η6-p-RC6H4)–NHNCMe–(η5-C5H4)FeCp]+PF6−: R=H, [9]+PF6−; Me, [10]+PF6−; MeO, [11]+PF6−, have been prepared. These hydrazones were stereoselectively obtained as their trans isomers about the NC double bond, by reaction of the corresponding organometallic hydrazines [CpFe(η6-p-RC6H4NHNH2)]+PF6−, R=H, [1]+PF6−; Me, [2]+PF6−; MeO, [3]+PF6−; and Cl, [4]+PF6−, with formylferrocene, CpFe(η5-C5H4–CHO), and acetylferrocene, CpFe(η5-C5H4–CO-Me), respectively. All the new compounds were characterized by elemental analysis and IR, UV-Vis and 1H NMR spectroscopies. For compound [9]+PF6−, the activation energy ΔG# for the hindered rotations of the mixed sandwich [CpFe(η6-C6H5–)]+ (41.8±0.9 and 41.2±3.7 kJ mol−1) and the ferrocenyl unit (40.0±3.2 kJ mol−1) about the –NH–NCMe– hydrazone backbone have been determined by variable temperature 1H NMR spectroscopic studies. The electrochemical behavior of the dinuclear hydrazones was explored by cyclic voltammetry, and features the role of the cationic [CpFe(η6-arene)]+ moiety as an electron acceptor. The crystalline and molecular structure of [9]+PF6− was determined by single crystal X-ray crystallographic analysis. The structure shows the presence of both syn and anti rotamers in the asymmetric unit. The analysis of the electronic structure of [9]+ through DFT calculations indicate a strong perturbation of the metal centers by the hydrazone bridge as well as some metal-metal interaction through the bridge.

Synthesis, X-ray crystal structure and magnetic properties of the six-coordinated intermediate-spin iron(II) complex [Fe(η5-C5Me5)(η2-Ph2PCH2CH2PPh2)(σ-OCMe2]+CF3SO3–

The σ-acetone complex [Fe(η5-C5Me5)(η2-dppe)(σ-OCMe2)]+ OSO2CF3–, (2 dppe = Ph2PCH2CH2PPh2) is cleanly synthesised by treatment of the hydride compound [Fe(η5-C5Me5)(η2-dppe)H]1 with MeOSO2CF3 in Et2O followed by crystallization from acetone–pentane; this compound, characterized by a single crystal X-ray diffraction, exhibits unexpected paramagnetic behaviour for a six-coordinated 18-electron iron(II) organometallic species.

Syntheses of deuterated sandwich- and piano-stool organo-iron complexes and polyalkylbenzenes

Abstract Deuteration of cationic iron sandwich complexes of the FeCp(arene) + family has been achieved by use of 1 M NaOD in D 2 O. The deuterated complexes are the starting point for the syntheses of various organo-iron and aromatic compounds.

Reactivity of molybdenum complexes containing both NHNPhR and NNPhR ligands (R = Ph, Me) toward hydridotris(pyrazolyl)borate, Tp and hydridotris(3,5-dimethylpyrazolyl0borate, Tp*, ligands. X-ray crystal structure of [TpMo(NNMePh)2Cl]

Abstract Molybdenum complexes containing mixed disubstituted organohydrazido(1−) and organohydrazido(2−) ligands, [Mo(NHNPhR)(NNPhR)(acac)Cl 2 ], R = Ph ( I ), R = Me ( II ), react in acetonitrile with sodium hydridotris(pyrazolyl)borate, NaTp, or in toluene with potassium hydridotris (3,5-dimethylpyrazolyl) borate, KTp * , to afford the neutral six-coordinated species formulated as [TpMo(NNPhR) 2 Cl], R = Ph ( III ), R = Me ( IV ) and [Tp*Mo(NNPhR) 2 Cl], R = Ph ( V ), R = Me ( VI ). These compounds have been characterized by elemental analysis, by IR, UV-visible, 1 H and 13 C NMR spectroscopy, and by mass spectrometry. The electrochemical behavior of complexes III–VI has also been studied by cyclic voltammetry. The X-ray crystal structure of IV has been determined. Crystals are parallelepiped, space group Pbnm , with a = 7.468(2), b = 18.483(3), c = 19.052(3) A, α = β = γ = 90° and Z = 4. The structure was solved and refined by full-matrix, least-squares methods to R and R w , values of 0.038 and 0.049, respectively. The complex displays a distorted octahedral geometry with symmetrical organohydrazido(2−) ligands adopting the nearly linear mode (Mo-N-N = 169.4(3)°). This linearity and the short bond distances (Mo-N = 1.771(4), N-N = 1.308(5) A) indicate an extensive π -electronic delocalization throughout the Mo-N-N fragment.

Relative M–X bond dissociation energies in 16-, 17- and 18-electron organotransition-metal complexes (X = halide, H)

The Fe–halide bonds in Cp*Fe(dppe)X (X = F, Cl, Br, I) complexes are weakened as a consequence of one and two-electron oxidations; the bond weakening decreases in the order F << Cl < Br < I and is much less pronounced for F than the other halides, indicating a pronounced effect of apparent fluoride-to-metal backbonding as a consequence of the removal of electrons.

Isolation and characterization of a cationic 19-electron iron(III) hydride complex; electron transfer induced hydride migration by carbon monoxide at an iron(III) centre

The first hypervalent 19-electron metal hydride complex [Fe(C5Me5)(dppe)(CO)H]PF63, synthesized from the 17-electron iron(III) hydride complex [Fe(C5Me5)(dppe)H]PF62, is isolated and its structure is established by IR, Mossbauer and ESR data; reaction of the iron(III) complex 2 with carbon monoxide causes hydride transfer to the C5Me5 ligand through an electrochemical chemical electrochemical (ECE)-like pathway [dppe = ethylenebis-(diphenylphosphine)].

Correction to Theoretical and Experimental Investigations on Hypoelectronic Heterodimetallaboranes of Group 6 Transition Metals

Density functional theory (DFT) has been used to probe the bonding and electronic properties of dimolybdaborane [(Cp*Mo)(2)B(5)H(9)], 1 (Cp* = η(5)-C(5)Me(5)), and several other heterodimolybdaborane clusters, such as [(Cp*Mo)(2)B(5)(μ(3)-OEt)H(7)] (2), [(Cp*Mo)(2)B(5)(μ(3)-OEt)(n-BuO)H(6)] (3), [(η(5)-C(5)H(5)W)(2)B(4)H(4)S(2)] (4), and [(Cp*Mo)(2)B(4)H(4)E(2)] (5-7, where, for 5, E = S, for 6, E = Se, and for 7, E = Te). The DFT results were also used to address some key points such as (i) the metal-metal bond length, (ii) the location and number of bridging and terminal hydrogen atoms, (iii) the molecular orbital analysis, and (iv) the assignment of (11)B and (1)H NMR chemical shifts. These studies further provide meticulous insight into similarities and differences between various dimetallaborane clusters 1-7. In addition, the crystal structures of 5 and 7 are reported, which come on top of the already existing literature of dimetallaboranes and support the theoretical findings.