Iron-molybdenum charge-transfer hybrids containing organometallic and inorganic fragments bridged by aryldiazenido ligands in a μ- η6:η1 coordination mode: Syntheses, characterization, X-ray structures, electrochemistry, and theoretical investigation

Article abstract of DOI:10.1021/ic0613098

Representative members of a new family of covalently bonded charge-transfer molecular hybrids, of general formula [(η⁵-C₅H ₅)Fe(μ,η⁶:η¹-p-RC₆H ₄NN)Mo(η²-S₂CNEt₂)₃] ⁺PF₆^- (R: H, 5⁺PF₆ ^-; Me, 6⁺PF₆^-; MeO, 7 ⁺PF₆^-) and [(η⁵-C ₅-Me₅)Fe(μ,η⁶:η¹-C ₆H₅NN)Mo(η²-S₂CNEt ₂)₃]⁺PF₆^-, 8 ⁺PF₆^-, have been synthesized by reaction of the corresponding mixed-sandwich organometallic hydrazines [(η⁶- C₅H₅)Fe(η⁶-p-RC₆H ₄NHNH₂)]⁺PF₆^- (R: H, 1⁺PF₆^-; Me, 2⁺PF₆ ^-; MeO, 3⁺PF₆^-) and [(η⁵-C₅Me₅)Fe(η⁶-C ₆H⁵NHNH₂)]⁺PF₆ ^-, 4⁺PF₆^-, with cis- dioxomolybdenum(VI) bis(diethyldithiocarbamato) complex, [MoO₂(S ₂CNEt₂)₂], in the presence of sodium diethyldithiocarbamato trihydrate, NaSC(=S)-NEt₂·3H ₂O, in refluxing methanol. These iron-molybdenum complexes consist of organometallic and inorganic fragments linked each other through a π-conjugated aryldiazenido bridge coordinated in η⁶ and ??¹ modes, respectively. These complexes were fully characterized by FT-IR, UV-visible, and ¹H NMR spectroscopies and, in the case of complex 7⁺PF₆^-, by single-crystal X-ray diffraction analysis. Likewise, the electrochemical and solvatochromic properties were studied by cyclic voltammetry and UV-visible spectroscopy, respectively. The electronic spectra of these hybrids show an absorption band in the 462-489 and 447-470 nm regions in CH₂Cl₂ and DMSO, respectively, indicating the existence of a charge-transfer transition from the inorganic donor to the organometallic acceptor fragments through the aryldiazenido spacer. A rationalization of the properties of 5 ⁺PF₆^--8⁺PF₆^- is provided through DFT calculations on a simplified model of 7 ⁺PF₆^-. Besides the heterodinuclear complexes 5⁺PF₆^--8⁺PF₆ ^-, the mononuclear molybdenum diazenido derivatives, [(η¹-p-RC₆H₄NN)Mo(η²-S ₂CNEt₂)₃] (R: H, 9; Me, 10; MeO, 11), resulting from the decoordination of the [(η⁵-C₅H ₅)Fe]⁺ moiety of complexes 5⁺PF ₆^--7⁺PF₆^-, were also isolated. For comparative studies, the crystalline and molecular structure of complex 10·Et₂O was also determined by X-ray diffraction analysis and its electronic structure computed.

Full text of DOI:10.1021/ic0613098

Inorg. Chem. 2007, 46, 1123−1134
Iron
−Molybdenum Charge-Transfer Hybrids Containing Organometallic
and Inorganic Fragments Bridged by Aryldiazenido Ligands in a
µ- :
η6 η1
Coordination Mode: Syntheses, Characterization, X-ray Structures,
Electrochemistry, and Theoretical Investigation†
Carolina Manzur,‡ Lorena Milla´n,‡ Mauricio Fuentealba,‡ Jean-Rene´ Hamon,§ Lo
1
ıc Toupet,|
Samia Kahlal,§ Jean-Yves Saillard,*,§ and David Carrillo*,‡
Laboratorio de Qu´ımica Inorga´nica, Instituto de Qu´ımica, Pontificia UniVersidad Cato´lica de
Valpara´ıso, AVenida Brasil 2950, Valpara´ıso, Chile, UMR 6226 “Sciences Chimiques de Rennes”,
CNRS-UniVersite´ de Rennes 1, Campus de Beaulieu, 35042 Rennes-Cedex, France, and UMR
6626 Groupe Matie`re Condense´e et Mate´riau, CNRS-UniVersite´ de Rennes 1, Campus de
Beaulieu, 35042 Rennes Cedex, France
Received July 14, 2006
Representative members of a new family of covalently bonded charge-transfer molecular hybrids, of general formula
-
[(
Me5)Fe(
mixed-sandwich organometallic hydrazines [(
MeO, 3+PF6-) and [( 5-C5Me5)Fe( 6-C6H5NHNH2)]+PF6-, 4+PF6-, with cis-dioxomolybdenum(VI) bis(diethyldithio-
carbamato) complex, [MoO2(S2CNEt2)2], in the presence of sodium diethyldithiocarbamato trihydrate, NaSC( S)-
NEt2 3H2O, in refluxing methanol. These iron molybdenum complexes consist of organometallic and inorganic
fragments linked each other through a -conjugated aryldiazenido bridge coordinated in
6 and 1 modes, respectively.
These complexes were fully characterized by FT-IR, UV
visible, and 1H NMR spectroscopies and, in the case of
complex 7+PF6-, by single-crystal X-ray diffraction analysis. Likewise, the electrochemical and solvatochromic
properties were studied by cyclic voltammetry and UV visible spectroscopy, respectively. The electronic spectra of
these hybrids show an absorption band in the 462 489 and 447 470 nm regions in CH2Cl2 and DMSO, respectively,
η
5-C5H5)Fe(
µ
,
η6
:
η
1-p-RC6H4NN)Mo(
η
2-S2CNEt2)3] +PF6 (R: H, 5+PF6-; Me, 6+PF6-; MeO, 7+PF6-) and [(
η
5-C5-
µ
,
η6
:
η
1-C6H5NN)Mo(
η
2-S2CNEt2)3]+PF6-, 8+PF6-, have been synthesized by reaction of the corresponding
-
-
η
5-C5H5)Fe( 6-p-RC6H4NHNH2)]+PF6 (R: H, 1+PF6-; Me, 2+PF6
η ;
η
η
d
‚
−
π
η
η
−
−
−
−
indicating the existence of a charge-transfer transition from the inorganic donor to the organometallic acceptor
-
fragments through the aryldiazenido spacer. A rationalization of the properties of 5+PF6
−
8+PF6- is provided through
DFT calculations on a simplified model of 7+PF6-. Besides the heterodinuclear complexes 5+PF6
−
8+PF6-, the
-
mononuclear molybdenum diazenido derivatives, [(
η
1-p-RC6H4NN)Mo(
η
2-S2CNEt2)3] (R: H, 9; Me, 10; MeO, 11),
-
resulting from the decoordination of the [(
η
5-C5H5)Fe]+ moiety of complexes 5+PF6
−
7+PF6-, were also isolated.
For comparative studies, the crystalline and molecular structure of complex 10‚Et2O was also determined by X-ray
diffraction analysis and its electronic structure computed.
Introduction
complex,1 the syntheses of a considerable amount of orga-
nodiazenido compounds have been reported2,3 and a great
variety of X-ray diffraction structures has been revealed.4
Much of the interest in transition metal complexes containing
organodiazenido ligands, R-NâdNR, arises from their
potential applications as models5 for intermediates in biologi-
cal6 and industrial7 dinitrogen to ammonia conversion. The
exceptional electronic structure of such ligands allows
In the last four decades and since the pioneering paper of
King and Bisnette describing the first (aryldiazenido)metal
* To whom correspondence should be addressed. E-mail: david.carrillo@
ucv.cl (D.C.), saillard@univ-rennes1.fr (J.-Y.S.).
† This article is dedicated to our friend Professor Didier Astruc on the
occasion of his 60th birthday.
‡ Pontificia Universidad Cato´lica de Valpara´ıso.
§ UMR 6226, Universite´ de Rennes 1.
| UMR6626, Universite´ de Rennes 1.
(1) King, R. B.; Bisnette, M. B. J. Am. Chem. Soc. 1964, 86, 5694.
Inorganic Chemistry, Vol. 46, No. 4, 2007 1123
10.1021/ic0613098 CCC: $37.00
Published on Web 01/20/2007
© 2007 American Chemical Society

Manzur et al.
Scheme 1
reactions have been suggested to proceed by a direct
nucleophilic aromatic substitution mechanism.8 These het-
erobinuclear complexes9 were fully characterized by spec-
troscopic techniques and their molecular structures were
studied by single-crystal X-ray diffraction analysis, but their
charge-transfer properties were not investigated.
The versatile hapticity exhibited by the organodiazenido
ligands in transition metal complexes and, particularly, the
hapticity exhibited in this type of heterobinuclear complexes,
the increasing interest observed on the functionalization of
polyoxometalates to generate new hybrid materials10 contain-
ing inorganic and organic or organometallic fragments linked
covalently one another by an extended π-conjugated bridge,
and the electronic cooperativity we have observed in CpFe-
(arylhydrazones) of ferrocenyl and diferrocenyl aldehydes
and ketones11 prompted our investigations toward the
synthesis of new organometallic-inorganic charge-transfer
hybrids. These complexes of general formula [(η5-Cp′)Fe-
different coordination modes, and consequently, several types
of geometric structures have been observed and described
in the literature.2,3 However, in the majority of mononuclear
organodiazenido complexes, this ligand is bonded to transi-
tion metal centers through the terminal NR atom, using its
σn, πσ, and ππ frontier molecular orbitals in an η1 or end-on
coordination mode,2,4 giving a near linear RNâdNR<M
fragment (Scheme 1,a). In monoaryldiazenido complexes,
calculations of the frontier molecular orbitals occupations
suggest that the formal oxidation state of the RNN ligand is
-1.4 Surprisingly, novel structures, where the organodiaz-
enido ligand acts as a spacer bridging two different metal
centers through the terminal NR atom and through the
π-system of the aryl group in a η1- and η6-coordination
fashions, respectively (Scheme 1b), have recently been
reported by Hidai and co-workers.8 To the best of our
knowledge, this type of inorganic-organometallic hybrid is
the first example reported in the literature. The complexes
that contain the heterobimetallic {M(µ,η6:η1-p-RC6H4NN)W}
core (M ) Cr, Fe, Ru; R ) H, Me, OMe, COOMe)8,9 have
been synthesized by reaction of the anionic dinitrogen
complex [W(NCS)(N2)(dppe)2]- or the neutral diazenido
complex [WF(NNH)(dppe)2] with activated η6-fluoroarene
complexes of Cr, Fe, and Ru, under mild conditions. These
(µ,η6:η1-p-RC6H4NN)Mo(η2-S2CNEt2)3]+PF6 , 5+PF6 -8+-
PF6- (Cp′ ) C5H5, C5Me5), were prepared by reacting their
respective organometallic hydrazine precursors [(η5-Cp′)Fe-
(η6-p-RC6H4NHNH2)]+PF6-, 1+PF6--4+PF6-, with [MoO2(S2-
CNEt2)2] in the presence of NaSC(dS)NEt2. As a result, we
report herein (i) the synthesis and the full characterization
of a series of charge-transfer hybrids, containing the electron-
withdrawing fragment [(η5-Cp′)Fe]+ and the strong electron-
releasing fragment [Mo(η2-S2CNEt2)3]+, bridged one other
by an aryldiazenido ligand, [p-RC6H4NN]-, R ) H, Me, and
MeO, in a µ,η6:η1 coordination mode, (ii) the crystal and
molecular structure of complex 7+PF6- and the mononuclear
derivative [(η1-p-MeC6H4NN)Mo(η2-S2CNEt2)3], 10‚Et2O, by
X-ray diffraction analysis, (iii) the effect of the nature of
-
-
-
the Cp′ ligands on the redox properties of complexes 5+PF6
-
and 8+PF6 and the necessary comparison of the redox
properties of complex 5+PF6- and the known compound 9,12
(2) (a) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley-
Interscience: New York, 1988. (b) Sutton, D. Chem. ReV. 1993, 93,
995. (c) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239. (d) Hidai,
M.; Mizobe, Y. Chem. ReV. 1995, 95, 1115. (e) Hirsch-Kuchma, M.;
Nicholson, T.; Davidson, A.; Jones, A. G. J. Chem. Soc., Dalton Trans.
1997, 3189. (f) Carrillo, D. C. R. Chimie 2000, 3, 175. (g) Hidai, M.;
Mizobe, Y. Can. J. Chem. 2005, 83, 358.
(3) (a) Chatt, J.; Pearman, A.; Richards, R. L. J. Chem. Soc., Dalton Trans.
1976, 1520. (b) Butler, G.; Chatt, J.; Leigh, G. J. J. Chem. Soc., Chem.
Commun. 1978, 352. (c) Leigh, G. J. J. Organomet. Chem. 2004, 689,
3999 and references therein.
(10) (a) Judenstein, P. Chem. Mater. 1992, 4, 4. (b) Du, Y.; Rheingold, A.
L.; Maatta, E. A. J. Am. Chem. Soc. 1992, 114, 345. (c) Strong, J. B.;
Ostrander, R.; Rheingold, A. L.; Maatta, E. A. J. Am. Chem. Soc.
1994, 116, 3601. (d) Mohs, T. R.; Yap, G. P. A.; Rheingold, A. L.;
Maatta, E. A. Inorg. Chem. 1995, 34, 9. (e) Hill, P. L.; Yap, G. P. A.;
Rheingold, A. L.; Maatta, E. A. J. Chem. Soc., Chem. Commun. 1995,
737. (f) Stark, J. L.; Young, V. G.; Maatta, E. A. Angew. Chem., Int.
Ed. Engl. 1995, 34, 2547. (g) Judenstein, P.; Sanchez, C. J. Mater.
Chem. 1996, 6, 511. (h) Moore, A. R.; Kwen, H.; Beatty, A. M.;
Maatta, E. A. Chem. Commun. 2000, 1793. (i) Strong, J. B.; Yap, G.
P. A.; Ostrander, R.; Liable-Sands, L. M.; Rheingold, A. L.; Thou-
venot, R.; Gouzerh, P.; Maatta, E. A. J. Am. Chem. Soc. 2000, 122,
639. (j) Wei, Y.; Xu, B.; Barnes, C. L. J. Am. Chem. Soc. 2001, 123,
4083. (k) Wei, Y.; Lu, M.; Cheung, C. F.-C.; Barnes, C. L.; Peng, Z.
Inorg. Chem. 2001, 40, 5489. (l) Xu, B.; Wei, Y.; Barnes, C. L.; Peng,
Z. Angew. Chem., Int. Ed. 2001, 40, 2290. (m) Lu, M.; Wei, Y.; Xu,
B.; Cheung, C. F.-C.; Peng, Z.; Powell, D. R. Angew. Chem., Int. Ed.
2002, 41, 1566. (n) Xu, L.; Lu, M.; Xu, B.; Wei, Y.; Peng, Z.; Powell,
D. R. Angew. Chem., Int. Ed. 2002, 41, 4129. (o) Okabe, A.;
Fukushima, T.; Ariga, K.; Aida, T. Angew. Chem., Int. Ed. 2002, 41,
3414. (p) Bose, A.; He, P.; Liu, C.; Ellman, B. D.; Twieg, R. J.; Huang,
S. D. J. Am. Chem. Soc. 2002, 124, 4. (q) Roesner, R. A.; McGrath,
S. C.; Brockman, J. T.; Moll, J. D.; West, D. X.; Swearingen, J. K.;
Castineiras, A. Inorg. Chim. Acta 2003, 342, 37. (r) Bar-Nahum, I.;
Cohen, H.; Neumann, R. Inorg. Chem. 2003, 42, 3677. (s) Kang, J.;
Nelson, J. A.; Lu, M.; Xie, B.; Peng, Z.; Powell, D. R. Inorg. Chem.
2004, 43, 6408. (t) Wu, P.; Li, Q.; Ge, N.; Wei, Y.; Wang, Y.; Wang,
P.; Guo, H. Eur. J. Inorg. Chem. 2004, 2819. (u) Lu, M.; Xie, B.;
Kang, J.; Chen, F.-C.; Yang, Y.; Peng, Z. Chem. Mater. 2005, 17,
402. (v) Lu, M.; Kang, J.; Wang, D.; Peng, Z. Inorg. Chem. 2005, 44,
7711.
(4) More than 100 papers related to structurally characterized organodia-
zenido transition metal complexes are gathered in the following:
Kahlal, S.; Saillard, J.-Y.; Hamon, J.-R.; Manzur, C.; Carrillo, D. New
J. Chem. 2001, 25, 231.
(5) Schrock, R. R. Acc. Chem. Res. 2005, 38, 955.
(6) See for example: (a) Hardy, R. W. F.; Bottomley, F.; Burns, R. C. A.
Treatise on Dinitrogen Fixation; Wiley-Interscience: New York, 1979.
(b) Molybdenum and Molybdenum-Containing Enzymes; Coughlan,
M. P., Ed., Pergamon: New York, 1980. (c) Veeger, C.; Newton, W.
E. AdVances in Nitrogen Fixation Research; Dr. W. Junk/Martinus
Nijhoff: Boston, MA, 1984. (d) Burgess, B. K.; Lowe, D. J. Chem.
ReV. 1996, 96, 2983.
(7) Smil, V. Enriching the Earth: Fritz Haber, Carl Bosch, and
Transformation of World Food Production; MIT Press: Cambridge,
MA, 2004.
(8) Ishii, Y.; Kawaguchi, M.; Ishino, Y.; Aoki, T.; Hidai, M. Organo-
metallics 1994, 13, 5062.
(9) The formulas of the heterobinuclear aryldiazenido complexes described
by Hidai and co-workers8 are the following: [{(CO)3Cr(µ-η6:η1-p-
CO2MeC6H4)-NdN}W(NCS)(dppe)2]‚CH2Cl2; [{(CO)3Cr(µ-η6:η1-
p-CO2MeC6H4)-NdN}WF(dppe)2]‚2THF; [{CpRu(µ-η6:η1-C6H5)-
NdN}W(NCS)(dppe)2]+PF6-‚CH2Cl2; [{CpFe(µ-η6:η1-p-MeC6H4)-
NdN}WF (dppe)2]+PF6‚Me2CO.
1124 Inorganic Chemistry, Vol. 46, No. 4, 2007

Iron-Molybdenum Charge-Transfer Hybrids
the precursor where the CpFe+ group is absent, (iv) the effect
Elemental analysis were conducted on a Thermo-FINNIGAN Flash
EA 1112 CHNS/O analyzer by the Microanalytical Service of the
CRMPO at the University of Rennes 1 (Rennes, France).
of the solvent polarity, CH2Cl2 (µ ) 8.90) and DMSO (µ )
-
47.6) on the electronic transitions of complexes 5+PF6 -
Synthesis of [(η5-C5H5)Fe(µ,η6:η1-C6H5NN)Mo(η2-S2CN-
Et2)3]+PF6-, 5+PF6-. A solution of 100 mg (0.267 mmol) of [(η5-
Cp)Fe(η6-C6H5NHNH2)]+PF6-, 1+PF6-, in dry MeOH (5 mL) was
added dropwise to a Schlenk tube containing 5 mL of an orange
suspension of 57.0 mg (0.134 mmol) of [MoO2(S2CNEt2)2] and
30.0 mg (0.133 mmol) of NaSC(dS)NEt2‚3H2O. The solution was
vigorously stirred and refluxed for 5 h under dry N2. It was then
cooled to room temperature and concentrated under vacuum until
a solid was formed. The crude solid was filtered out and then
dissolved in 1.0 mL of CH2Cl2. The solution was percolated through
a column containing silica gel (grade 60) suspended in hexane. First,
the use of pure Et2O as eluant produced the release of a green band.
Removal of the solvent under vacuum gave a green solid identified
as [(η1-C6H5NN)Mo(η2-S2CNEt2)3], 9, by comparison of its spec-
troscopic data with those of the literature.12 A green-brownish band
was then eluted with a Et2O/CH2Cl2 (1:1) mixture. Evaporation of
the solution to dryness afforded a dark solid, composed of a mixture
of the green complex 9 and of the desired heterobinuclear
-
8+PF6 , particularly on the charge-transfer transitions, and
(v) a DFT calculation which provides a rationalization of
the electrochemical and spectroscopic properties and analyses
the electronic communication between the metal centers in
complex 7+.
Experimental Section
Materials and Physical Measurements. All manipulations were
carried out under a dinitrogen atmosphere using standard Schlenk
techniques and chromatographic columns with protection from light
to avoid decomplexation of the CpFe+ fragment. Solvents were
dried by common procedures and distilled under dinitrogen before
use. Reagents were purchased from commercial sources and used
as received. The organometallic hydrazines [(η5-Cp′)Fe(η6-p-RC6H4-
-
NHNH2)]+PF6-, 1+PF6--4+PF6 (Cp′ ) C5H5,13 C5Me514), and
[MoO2(S2CNEt2)2]15 were synthesized according to published
procedures. Solid IR spectra were recorded from KBr disks on a
Perkin-Elmer, model Spectrum One, FT-IR spectrophotometer.
Electronic spectra were obtained in CH2Cl2 and DMSO solutions
-
1
compounds 5+PF6 (IR and H NMR spectroscopy). In the three
experiments below, this fraction was immediately discarded. Finally,
elution with pure CH2Cl2 produced the release of the desired dark
red band, which was collected. After the solvent was removed in
vacuo, a reddish brown microcrystalline solid was isolated. Yield:
28 mg (23%). Mp: 202 °C (dec). Anal. Calcd for C26H40F6FeMoN5-
PS6 (Mr ) 911.77 g mol-1): C, 34.25; H, 4.42; N, 7.68. Found:
C, 33.70; H, 3.87, N, 7.50. UV-vis [(λmax, nm (log ꢀ)] (CH2Cl2):
271 (4.63); 310 (4.47); 382 (3.87); 485 (3.76). UV-vis [(λmax, nm
(log ꢀ)] (DMSO): 275 (4.57); 319 (3.56); 385 (3.83); 469 (3.82).
IR (KBr, cm-1): 3116 (vw); 3087 (vw); 3068 (w); 2977 (w); 2933
(w); 2870 (vw), ν(C-H); 1511 (s), 1463 (sh); 1440 (vs), ν(NdN),
1
on a Spectronic, Genesys 2, spectrophotometer. The H and 13C
NMR spectra were recorded on a multinuclear Bruker Advance
400 Digital and Advance 500 Instruments. All NMR spectra are
reported in ppm (δ) relative to tetramethylsilane (Me4Si), with the
residual solvent proton resonance and carbon resonances used as
internal standards. Coupling constants (J) are reported in Hertz (Hz),
and integrations are reported as number of protons. High-resolution
electrospray ionization mass spectra (ESI-MS) were obtained at
the Centre Re´gional de Mesures Physiques de l’Ouest (CRMPO,
Rennes, France) on a MS/MS ZabSpec TOF Micromass spectrom-
eter (4 kV). Cyclic voltammetry experiments were performed at
room temperature with a Radiometer PGZ100 potentiostat, using
a standard three-electrode setup with a platinum working and
platinum wire auxiliary electrodes and a Ag/AgCl electrode as the
reference. Dichloromethane solutions were 1.0 mM in the com-
pound under study and 0.1 M in the supporting electrolyte n-Bu4N+-
PF6- with a voltage scan rate ) 0.1 V s-1. The potentials are given
against E1/2 of the Cp2Fe/Cp2Fe+ couple. Melting points were
determined in evacuated capillaries and were not corrected.
1
ν(C-C), and/or ν(C-N); 841 (vs), ν(PF6); 558 (m), δ(P-F). H
NMR (400 MHz, CD3CN): δ 1.15 (t, 3H, CH2CH3, JH-H ) 7.1
Hz); 1.20-1.30 (m, 15H, CH2CH3); 3.70-3.87 (m, 12H, CH2CH3);
4.80 (s, 5H, Cp); 5.85-5.96 (m, 3H, Ph); 6.06 (pseudo t, 2H, Ph).
Synthesis of [(η5-C5H5)Fe(µ,η6:η1-p-MeC6H4NN)Mo(η2-S2CN-
Et2)3]+PF6-, 6+PF6-. The procedure adopted was similar to that
described for the preparation of complex 5+PF6-, using in this case
-
133 mg (0.340 mmol) of [(η5-Cp)Fe(η6-p-MeC6H4NHNH2)]+PF6
,
2+PF6-, 73.4 mg (0.172 mmol) of [MoO2(S2CNEt2)2], and 38.9
mg (0.173 mmol) of NaSC(dS)NEt2‚3H2O. Workup and chro-
matographic separation as described above gave the green complex
10 (see below) and 6+PF6- as a reddish brown powder. Yield: 54
mg (34%). Mp: 166 °C (dec). Anal. Calcd for C27H42F6FeN5MoPS6
(Mr ) 925.80 g mol-1): C, 35.03; H, 4.57; N, 7.56. Found: C,
34.71; H, 4.39; N, 7.43. UV-vis [λmax, nm (log ꢀ)] (CH2Cl2): 244
(4.57); 295 sh (3.84); 388 (3.77); 489 (3.79). UV-vis [(λmax, nm
(log ꢀ)] (DMSO): 264 (4.53); 309 sh (4.07); 381 (3.77); 463 (3.73).
IR (KBr, cm-1): 3123 (vw); 3072 (vw); 2975 (w); 2930 (w); 2920
(w); 2874 (w); 2850 (w), ν(C-H); 1508 (s); 1447 (sh), 1433 (vs),
ν(NdN), ν(C-C) and/or ν(C-N); 839 (vs), ν(PF6); 558 (m), δ-
(11) (a) Manzur, C.; Milla´n, L.; Fuentealba, M.; Hamon, J.-R.; Carrillo,
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D.; Mata, J. A.; Sinbandhit, S.; Hamon, P.; Hamon, J.-R.; Kahlal, S.;
Saillard, J.-Y. New J. Chem. 2002, 26, 213. (d) Manzur, C.; Fuentealba,
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Trujillo, A.; Fuentealba, M.; Manzur, C.; Carrillo, D.; Hamon, J.-R.
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M.; Mata, J. A.; Carrillo, D.; Hamon, J.-R. J. Organomet. Chem. 2005,
690, 1265. (h) Figueroa, W.; Fuentealba, M.; Manzur, C.; Vega, A.
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2859.
(13) (a) Neto, A. F.; Miller, J. An. Acad. Bras. Cienc. 1982, 54, 331. (b)
Pio´rko, A.; Sutherland, R. G.; Vessie`res-Jaouen, A.; Jaouen, G. J.
Organomet. Chem. 1996, 512, 79. (c) Manzur, C.; Baeza, E.; Milla´n,
L.; Fuentealba, M.; Hamon, P.; Hamon, J.-R.; Boys, D.; Carrillo, D.
J. Organomet. Chem. 2000, 608, 126.
1
(P-F). H NMR (400 MHz, CD3CN): δ 1.22 (t, 3H, CH2CH3,
JH-H ) 7.1 Hz); 1.26-1.31 (m, 15H, CH2CH3); 2.16 (s, 3H, Ph-
CH3); 3.75-3.92 (m, 12H, CH2CH3); 4.75 (s, 5H, Cp); 5.85 (pseudo
t, 1H, Ph); 5.97 (d, 1H, Ph, JH-H ) 5.9 Hz); 6.01 (pseudo t, 1H,
Ph); 6.51 (d, 1H, Ph, JH-H ) 6.4 Hz).
Synthesis of [(η5-C5H5)Fe(µ,η6:η1-p-MeOC6H4NN)Mo(η2-
S2CNEt2)3]+PF6-, 7+PF6-. This compound was prepared following
-
a procedure similar to that described above for complex 5+PF6
(14) Fuentealba, M.; Toupet, L.; Manzur, C.; Carrillo, D.; Hamon, J.-R. J.
Organomet. Chem. 2006, doi:10.1016/j.jorganchem.2006.11.008.
(15) Moore, F. W.; Larson, M. L. Inorg. Chem. 1967, 6, 998.
using in this case 160 mg (0.396 mmol) of [(η5-Cp)Fe(η6-p-
MeOC6H4NHNH2)]+PF6-, 3+PF6-, 84.0 mg (0.198 mmol) of
Inorganic Chemistry, Vol. 46, No. 4, 2007 1125

Manzur et al.
-
Table 1. Crystallographic Data Collection and Structure Refinement Parameters for Complexes 7+PF6 and 10‚OEt2
-
param
empirical formula
7+PF6
10‚OEt2
C27H42F6FeMoN5OPS6
941.77
C26H47MoN5OS6
733.99
formula mass, g mol-1
collcn T, K
cryst system
space group
a (Å)
120(1)
triclinic
P1h
130(1)
triclinic
P1h
10.0854(3)
16.2396(7)
25.2360(9)
92.994(3)
10.5071(7)
13.0548(7)
13.1799(9)
85.927(5)
85.955(4)
75.668(4)
1744.55(19)
2
b (Å)
c (Å)
R (deg)
â (deg)
93.952(3)
γ (deg)
107.908(3)
3911.9(2)
V (Å3)
Z
D
4
calcd (g cm-3
)
1.599
1.397
cryst size (mm)
F(000)
0.22 × 0.18 × 0.08
0.12 × 0.12 × 0.03
1920
768
abs coeff (mm-1
θ range (deg)
range h, k, l
)
1.111
0.762
2.35-27.53
0/13, -21/20, -32/32
17 367
3.10-27.26
0/13, -15/16, -16/16
no. of indepdt reflcns
no. unique reflcns (>2σ)
data/restraints/params
final R indices [I > 2σ(I)]
R indices (all data)
7688
5197
10 662
17 367/0/865
R1 ) 0.0776; wR2 ) 0.1578
R1 ) 0.1732; wR2 ) 0.1942
1.119
7688/0/353
R1 ) 0.0555; wR2 ) 0.1069
R1 ) 0.1015; wR2 ) 0.1266
1.033
goodness of fit/F2
largest diff peak and hole (e·A-3
)
1.051 and -0.672
0.844 and -0.613
[MoO2(S2CNEt2)2], and 44.0 mg (0.195 mmol) of NaSC(dS)NEt2‚
3H2O. The solution was refluxed for 1 h. Workup and chromato-
graphic separation as described above gave the green complex 11
(see below) and 7+PF6- as a reddish brown powder. Single crystals
Ph, JH-H ) 6.4 Hz); 5.52 (t, 1H, Ph, JH-H ) 5.9 Hz); 5.62 (t, 2H,
Ph, JH-H ) 6.4 Hz).
Characterization of [(η1-p-MeC6H4NN)Mo(η2-S2CNEt2)3]‚
Et2O, 10‚Et2O. Crystals of 10‚Et2O suitable for X-ray structure
determination were grown by slow evaporation of a concentrated
diethyl ether solution at room temperature. Mp: 158 °C. Anal. Calcd
for C26H47MoON5S6 (Mr ) 734.02 g mol-1): C, 42.54; H, 6.45;
N, 9.54. Found: C, 42.36; H, 6.36; N, 9.44. UV-vis [λmax, nm
(log ꢀ)] (CH2Cl2): 253 (4.57); 305 sh (4.08); 412 (3.98); 537 (2.78).
UV-vis [(λmax, nm (log ꢀ)] (DMSO): 247 (4.55); 304 sh (3.99);
414 (3.90); 512 (2.77). IR (KBr, cm-1): 2972 (w); 2928 (w); 2845
(vw); 2868 (vw), ν(C-H); 1532 (m); 1532 (s), 1505(s), 1487 (s),
1454 (m), 1430(s), ν(NdN) and ν(C-C) and/or ν(C-N). 1H NMR
-
of 7+PF6 suitable for X-ray diffraction studies were obtained by
slow diffusion of diethyl ether into a concentrated dichloromethane
solution, at room temperature. Yield: 60 mg (33%). Mp: 169 °C
(dec). Anal. Calcd for C27H42F6FeMoN5OPS6 (Mr ) 941.80 g
mol-1): C, 34.43; H, 4.49; N, 7.44. Found: C, 34.22; H, 4.40; N,
7.36. UV-vis [λmax, nm (log ꢀ)] (CH2Cl2): 256 (4.56); 304 sh
(4.11); 365 (3.80); 478 (3.71). UV-vis [(λmax, nm (log ꢀ)]
(DMSO): 274 (4.57); 305 sh (3.11); 382 (3.74); 470 (3.83). IR
(KBr, cm-1): 2964 (w); 2920 (w); 2870 (w); 2853(w), ν(C-H);
1506 (s); 1436 (vs), ν(NdN), ν(C-C) and/or ν(C-N); 1256 (m),
ν(C-O); 840 (vs), ν(PF6); 558 (m), δ(P-F). 1H NMR (400 MHz,
CD3CN): δ 1.22 (t, 3H, CH2CH3, JH-H ) 7.1 Hz); 1.26-1.32 (m,
15H, CH2CH3); 3.76-3.86 (m, 12H, CH2CH3); 3.88 (s, 3H, OCH3);
4.83 (s, 5H, Cp); 5.88 (d, 2H, Ph, JH-H ) 6.9 Hz); 5.98 (d, 2H,
Ph, JH-H ) 6.9 Hz).
(500 MHz, CD3COCD3): δ 1.13 (t, 6H, O-CH2-CH3, JH-H
)
7.0 Hz); 1.22 (t, 3H, N-CH2-CH3, JH-H ) 6.8 Hz); 1.30 (pseudo
q, 15H, N-CH2-CH3); 2.35 (br s, 3H, p-CH3C6H4); 3.44 (q, 4H,
O-CH2-CH3, JH-H ) 7.0 Hz); 3.81-3.87 (m, 12H, N-CH2-
CH3); 7.02 (br s, 4H, C6H4). 13C NMR (125 MHz, CD3COCD3):
11.56, 11.94 (2 × 1CH3, NEt2); 11.85, 12.09 (2 × 2CH3, NEt2);
14.76 (CH3, OEt2); 19.91 (p-CH3C6H4); 43.38, 43.57 (2 × 2CH2,
NEt2); 44.90, 45.50 (2 × 1CH2, NEt2); 65.26 (CH2, OEt2); 120.4
(N-o-C6H4); 121.9 (Me-Cipso); 129.0 (N-m-C6H4); 132.9 (N-
Synthesis of [(η5-C5Me5)Fe(µ,η6:η1-C6H5NN)Mo(η2-S2CN-
Et2)3]+PF6-, 8+PF6-. This compound was synthesized following
-
a procedure similar to that described above for complex 5+PF6
,
using in this case 100 mg (0.225 mmol) of [(η5-C5Me5)Fe(η6-C6H5-
NHNH2)]+PF6-, 4+PF6-, 48.0 mg (0.113 mmol) of [MoO2(S2-
CNEt2)2], and 28.0 mg (0.124 mmol) of NaSC(dS)NEt2‚3H2O.
Workup and chromatographic separation as described above for
Cipso); 199.14 (S2CNEt2). HRMS (positive ESI, methanol, [M -
H]+, m/z): calcd for C22H3898MoN5S6, 662.0506; found, 662.0480.
Characterization of [(η1-p-MeOC6H4NN)Mo(η2-S2CNEt2)3],
11. Only minute amounts of pure green powdered complex 11 were
isolated as a side product of the preparation of 7+PF6- (see above).
Mp: 186 °C. IR (KBr, cm-1): 2972 (w); 2928 (w); 2862 (vw),
ν(C-H); 1538 (sh); 1498 (sh), 1490 (vs), 1459 (m), 1431 (s), ν-
(NdN) or ν(C-N); 1268 (s), ν(C-O). HRMS (positive ESI,
methylene chloride, [M]+, m/z): calcd for C22H3798MoN5OS6,
677.0373; found, 677.0370.
-
the Cp counterparts gave the green complex 912 and 8+PF6 as a
reddish brown powder. Yield: 91 mg (82%). Mp: 200 °C. Anal.
Calcd for C31H50F6FeMoN5PS6 (Mr ) 981.91 g mol-1): C, 37.92;
H, 5.13; N, 7.13. Found: C, 37.44; H, 5.22; N, 6.83%. UV-vis
[λmax, nm (log ꢀ)] (CH2Cl2): 261 (4.71); 321 sh (4.02); 382 (3.78);
462 (3.90). UV-vis [(λmax, nm (log ꢀ)] (DMSO): 257 (4.53); 294
sh (4.41); 386 (3.53); 447 (3.92). IR (KBr, cm-1): 3073 (vw); 2978
(w); 2920 (w); 2870 (vw), 2850 (vw), ν(C-H); 1512 (s); 1500 (s),
1445 (vs); 1436 (vs), ν(NdN), ν(C-C) and/or ν(C-N); 839 (vs),
ν(PF6); 558 (s), δ(P-F). 1H NMR (400 MHz, CD3CN): δ 1.20 (t,
3H, CH2CH3, JH-H ) 7.1 Hz); 1.22-1.38 (m, 15H, CH2CH3); 1.83
(s, 15H, C5-CH3); 3.72-3.90 (m, 12H, CH2CH3); 5.42 (d, 2H,
Crystallographic Data Collection and Structure Determina-
-
tions for 7+PF6 and 10‚Et2O. Suitable crystals of complexes
7+PF6- and 10‚Et2O for data collection were selected and mounted
with epoxy cement on the tip of a glass fiber. Crystal data collection
-
and refinement parameters are given in Table 1. Compounds 7+PF6
and 10‚Et2O were studied on a Kappa-CCD Enraf-Nonius diffrac-
1126 Inorganic Chemistry, Vol. 46, No. 4, 2007

Iron-Molybdenum Charge-Transfer Hybrids
Scheme 2
tometer equipped with a bidimensional CCD detector employing
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å). The
cell parameters were obtained with Denzo and Scalepack with 10
frames (ψ rotation: 1°/frame).16 The data collection17 (2θmax ) 54°,
1491 frames via 0.3° ω rotation and 30 s/frame; 2θmax ) 54°, 160
frames via 2.0° ω rotation and 300 s/frame) provided reflections
for 7+PF6 and 10‚Et2O, respectively. Subsequent data reduction
-
with Denso and Scalepack16 gave the independent reflections (Table
1). The two structures were solved with SIR 97 which revealed
the non-hydrogen atoms.18 After anisotropic refinement, the remain-
ing atoms were found in Fourier difference maps. The complete
structures were then refined with SHELX97 by full-matrix least-
squares procedures on reflection intensities (F2).19 The absorption
was not corrected. In both cases the non-hydrogen atoms were
refined with anisotropic displacement coefficients, and all hydrogen
atoms were treated as idealized contributions. There are two
chemically equivalent but crystallographically independent mol-
ecules in the asymmetric unit of 7+PF6-. The relatively high R value
for 7+PF6 is due to a rather large mosaicity (1.63°). Atomic
-
scattering factors were taken from the literature.20 ORTEP views
-
of 7+PF6 and 10‚Et2O were generated with ORTEP3 for Win-
dows.21 Compounds 7+PF6- and 10‚Et2O are CCDC reference nos.
253301 and 261935, respectively. See http://www.ccdc.cam.ac.uk.
Computational Details. Density functional theory (DFT) cal-
culations were carried out on the model compounds 7′2+/+/0 and
10′+/0/- using the Amsterdam Density Functional (ADF) program,22
developed by Baerends and co-workers.23 Electron correlation was
treated within the local density approximation (LDA) in the Vosko-
Wilk-Nusair parametrization.24 The nonlocal corrections of Becke
and Perdew were added to the exchange and correlation energies,
respectively.25,26 The numerical integration procedure applied for
the calculations was developed by te Velde et al.23e Spin-unrestricted
calculations were carried out on all the odd-electrons systems. The
atom electronic configurations were described by a triple-ú Slater-
type orbital (STO) basis set for H 1s, C 2s and 2p, N 2s and 2p, O
2s and 2p, and S 3s and 3p augmented with a 3d single-ú
polarization for C, N, O, and S atoms and with a 2p single-ú
polarization for H atoms. A triple-ú STO basis set was used for Fe
3d and 4s and for Mo 4d and 5s augmented with a single-ú 4p
polarization function for Fe and a single-ú 5p polarization function
Mo. A frozen-core approximation was used to treat the core shells
up to 1s for C, N, and O, 2p for S, 3p for Fe, and 4p for Mo atoms.23
Full geometry optimizations were carried out using the analytical
gradient method implemented by Verluis and Ziegler.27 The LB94
potential,28 which provides a correct Coulombic asymptotic behavior
in the inner atomic region, was used for the TD-DFT excited-state
calculations (atomic basis set unchanged). The Kohn-Sham MOs
were obtained using the LB94 method. The excitation energies and
oscillator strengths were calculated by following the procedure
described by van Gisbergen and co-workers.29 Representation of
the orbitals were done using MOLEKEL4.3.30
Results and Discussion
Syntheses. As shown in Scheme 2, the heterodimetallic
-
organodiazenido complexes 5+PF6 -7+PF6- were prepared
(16) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected In Oscillation Mode. In Methods in Enzymology, Vol. 276,
Macromolecular Crystallography; Carter, C. W., Sweet, R. M. Eds.;
Academic Press: London, 1997; Part A, p 307.
(17) Nonius Kappa CCD Software; Nonius BV: Delft, The Netherlands,
1999.
(18) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(19) Sheldrick, G. M. SHELX97. Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(20) International Tables for X-ray Crystallography; Wilson, A. J. C., Ed.;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C.
(21) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(22) ADF2002.01, Theoretical Chemistry; Vrije Universiteit: Amsterdam,
The Netherlands, 2002.
(23) (a) Baerends, E. J.; Ellis, D. E.; Ros, P. Chem. Phys. 1973, 2, 41. (b)
te Velde, G.; Baerends, E. J. J. Comput. Phys. 1992, 99, 84. (c) Fonseca
Guerra, C.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor. Chem.
Acc. 1998, 99, 391. (d) Bickelhaupt, F. M.; Baerends, E. J. ReV.
Comput. Chem. 2000, 15, 1. (e) te Velde, G.; Bickelhaupt, F. M.;
Fonseca Guerra, C.; van Gisbergen, S. J. A.; Baerends, E. J.; Snijders,
J. G.; Ziegler, T. J. Comput. Chem. 2001, 22, 931.
-
in 23-34% yield, while complex 8+PF6 , which contains
-
the C5Me5 ligand, was isolated in 82% yield, by reaction
-
-
of organometallic hydrazines 1+PF6 -4+PF6 , respectively,
with [MoO2(S2CNEt2)2] in the presence of sodium dieth-
yldithiocarbamato trihydrate, NaSC(dS)NEt2‚3H2O (2:1:1),
in refluxing methanol. This synthetic strategy is analogous
to that reported for classic organodiazenido derivatives [(η1-
ArNN)Mo(η2-S2CNR2)3] (R) alkyl, aryl).31,32 The known
complex 9,12 and the two new mononuclear diazenido
molybdenum compounds [(η1-p-MeC6H4NN)Mo(η2-S2-
CNEt2)3], 10, and [(η1-p-MeOC6H4NN)Mo(η2-S2CNEt2)3],
11, were also isolated as green microcrystalline powder after
chromatographic workup.
(27) Verluis, L.; Ziegler, T. J. Chem. Phys. 1988, 88, 322.
(28) van Leeuwen, R.; Baerends, E. J. Phys. ReV. A 1994, 49, 2421.
(29) van Gisbergen, S. J. A.; Snijders, J. G.; Baerends, E. J. Comput. Phys.
Commun. 1999, 118, 119.
(24) Vosko, S. D.; Wilk, L.; Nusair, M. Can. J. Chem. 1990, 58, 1200.
(25) (a) Becke, A. D. J. Chem. Phys. 1986, 84, 4524. (b) Becke, A. D.
Phys. ReV. A 1988, 38, 3098.
(26) (a) Perdew, J. P. Phys. ReV. B 1986, 33, 8822. (b) Perdew, J. P. Phys.
ReV. B 1986, 34, 7406.
(30) Flu¨kiger, P.; Lu¨thi, H. P.; Portmann, S.; Weber, J. Swiss Center for
Scientific Computing (CSCS), Switzerland, 2000-2002.
(31) Bishop, M. W.; Butler, G.; Chatt, J.; Dilworth, J. R.; Leigh, G. J. J.
Chem. Soc., Dalton Trans. 1979, 1843.
(32) Dilworth, J. R.; Miller, J. R. J. Chem. Educ. 1991, 68, 788.
Inorganic Chemistry, Vol. 46, No. 4, 2007 1127

Manzur et al.
The low yields obtained for the cyclopentadienyl deriva-
hydroxyl group in this intermediate by the free dithiocar-
bamate ligand, present in the reaction mixture, could lead
to the formation of the heptacoordinate molybdenum com-
plex. The presence of NaSC(dS)NEt2 is an important factor
to increase the yield of this class of coordination compounds.
Spectroscopy and Electrochemistry. The most remark-
able features observed in the IR spectra of complexes 5+-
-
-
tives 5+PF6 -7+PF6 are presumably due to partial deco-
ordination of the CpFe+ moiety at an early stage of the
reaction. In contrast, the bulky and electron-releasing C5-
Me5 ligand should play an important role in stabilizing a
common key intermediate, thus leading to the isolation of
-
-
8+PF6 in high yield. Once formed, compounds 5+PF6 -
-
-
-
7+PF6 are thermally stable (mp > 165 °C). They are light
PF6 -7+PF6 is the presence of (i) two characteristic and
prominent absorption bands in the 1506-1511 and 1433-
1463 cm-1 regions, attributed to the ν(NdN) mode of the
aryldiazenido or the ν(C-N) mode of the diethyldithiocar-
bamato ligands,31,32 and (ii) two typical bands, one, very
strong, in the 839-841 cm-1 region and the other one, of
medium intensity, at 558 cm-1, which correspond to the ν-
(PF6) and δ(P-F) modes,10 respectively. The spectrum of
sensitive in solution, while, as expected, the pentamethyl
-
analogue 8+PF6 is stable under the same conditions.33
-
However, complexes 5+PF6 -7+PF6- can be stored as solids
in the dark for several months. Despite the fact that the
-
-
bimetallic complexes 5+PF6 -8+PF6 are ionic and the
mononuclear species 9-11 are neutral, they cannot be cleanly
separated by dissolution/precipitation sequences. This also
renders their chromatographic separation difficult (see Ex-
perimental Section) and, consequently, reduces the yields of
the heterobinuclear complexes.
-
complex 8+PF6 is quite similar to those of complexes 5+-
-
-
PF6 -7+PF6 , except the band attributed to the ν(NdN)
mode which splits yielding two identical strong and sharp
bands at 1512 and 1500 cm-1. On the other hand, the neutral
molybdenum complex 10‚Et2O and 11 display a character-
istic pattern in the 1550-1400 cm-1 range, quite similar to
that showed for the reported complexes [(η1- C6H5NN)Mo-
(η2-S2CNMe2)3].32
These iron-molybdenum complexes were isolated as
reddish brown microcrystalline diamagnetic solids, soluble
in CH2Cl2, Me2CO, MeCN, and DMSO, slightly soluble in
-
MeOH, and insoluble in hexane. Complexes 5+PF6 -8+-
-
PF6 , 10, and 11 were fully characterized by FT-IR, UV-
visible, and 1H NMR spectroscopies and elemental analysis;
complex 10‚Et2O was also characterized by 13C NMR
spectroscopy and high-resolution electro spray ionization
mass spectrometry (ESI-MS). Some analytical data exhibit
some minor deviations which are presumably due to the
presence of minute amounts of solvated diethyl ether (beyond
the accuracy of the NMR detection) that could not be
removed by vacuum drying. However, they are consistent
The UV-visible spectral data for the iron-molybdenum
-
-
complexes 5+PF6 -8+PF6 have been recorded in CH2Cl2
and DMSO (see Experimental Section). The four complexes
exhibit similar spectra, indicating similar structural features.
They exhibit two overlapped absorption bands attributed to
intraligand charge-transfer excitations placed, the more
intense band, in the 244-271 nm range and the other one,
much less intense, in the 295-321 nm range. Additionally,
two less intense visible bands are observed in the 350-700
nm region: (i) a band at 382-386 nm which is not solvent-
dependent and (ii) a lower energy band in the 462-489 nm
region attributed to a MoIV f FeII charge-transfer excitation
through the aryldiazenido spacer, which exhibits a negative
solvatochromism36 by 8-26 nm with increasing solvent
polarity, i.e., on moving from CH2Cl2 (µ ) 8.90) to DMSO
(µ ) 47.6) (Figure 1). This indicates a change in the dipole
moment upon excitation from a more charge-localized
ground state, with a high dipole moment, to an excited state
where the positive charge is more delocalized throughout
the entire molecule and the dipole moment is lower.37 This
band assignment has been supported by our TD-DFT
calculations (vide infra).
-
-
with the proposed structures. Complexes 5+PF6 -8+PF6
consist of organometallic and inorganic fragments bridged
by an aryldiazenido ligand in a µ,η6:η1 fashion, the molyb-
denum center adopting a pentagonal bipyramidal geometry.
On the other hand, the crystal and molecular structures of
complexes 7+PF6- and 10‚Et2O were solved by single-crystal
X-ray diffraction analysis (vide infra).
The classic reaction of monosubstituted hydrazines with
transition metal coordination compounds containing cis-(Od
MdO) moieties, M ) Mo, W, and Re coordinated by
different types of ancillary ligands, has demonstrated to be
an effective one-pot experimental procedure for the synthesis
of a great variety of mono- and cis-bis(organodiazenido)
complexes.34 Nevertheless, the mechanisms of this well-
known reaction is far from being well understood at present
or, at least, remains unclear. However, it seems admissible
to take into account, although from a speculative point of
view, that the reaction may be viewed formally as a simple
condensation reaction of the cis-MoO2 group with the
organohydrazine, RNHNH2, R ) alkyl and aryl, to afford
H2O and the probable OdModN-NHR intermediate. The
removal of the remaining NH hydrogen atom can be carried
out through the formation of the HO-Mo species involving
some internal redox step.35 A further substitution of the
1
-
-
The H NMR spectra of complexes 5+PF6 -8+PF6 are
consistent with the proposed formulas. The sandwich moiety
[CpFe(η6-p-RC6H4-)]+ is clearly identified by a single
resonance at ca. 4.8 ppm attributable to the Cp moiety and
two to four resolved signals of cumulative relative intensity
(35) (a) Hsieh, T.-C.; Zubieta, J. A. Polyhedron 1986, 5, 305. (b) Hsieh,
T.-C.; Shaikh, S. N.; Zubieta, J. Inorg. Chem. 1987, 26, 4079.
(36) (a) Lever, A. B. P. Inorganic Electronic Spectroscopy, 2nd ed.;
Elsevier: Amsterdam, 1984; pp 208-212. (b) Reichardt, C. Chem.
ReV. 1994, 94, 2319.
(37) Dodsworth, E. S.; Hasegawa, M.; Bridge, M.; Linert, W. Fundamen-
tals: Physical Methods, Theoretical Analysis, and Case Studies. In
ComprehensiVe Coordination Chemistry II; From Biology to Nano-
technology; Lever, A. B. P., Ed.; Elsevier: New York, 2003; Vol. 2,
pp 351-365.
(33) Hamon, J.-R.; Astruc, D.; Michaud, P. J. Am. Chem. Soc. 1981, 103,
758.
(34) Gouzerh, P.; Proust, A. Chem. ReV. 1998, 98, 77 and references therein.
1128 Inorganic Chemistry, Vol. 46, No. 4, 2007

Iron-Molybdenum Charge-Transfer Hybrids
and its pentamethylated analogue [(η5-C5Me5)Fe(µ,η6:η1-
-
-
C6H5NN)Mo(η2-S2CNEt2)3]+PF6 , 8+PF6 , were chosen for
this aim. The voltammograms of both complexes, recorded
at room temperature, display three major features:
(i) There is an irreversible cathodic process at -1.89 and
-2.12 V, respectively, which one is tempted to assign to
the single-electron reduction of the 3d6 Fe(II), 18-electron
complexes, to the 3d7 Fe(I), 19-electron species, at the mixed-
sandwich fragment.33,38 Instead, it turned out that this
irreversible wave is attributable to the reduction of the
molybdenum center followed by a Mo-S bond cleavage,
as found by DFT calculations (vide infra).
(ii) A primary reversible one-electron oxidation wave at
E1/2 ) 0.41 V (∆E ) 100 mV) and E1/2 ) 0.37 V (∆E )
110 mV), respectively, is confidently assigned to a single-
electron oxidation of the 4d2 Mo(IV), 18-electron complexes,
to the 4d1 Mo(V), 17-electron species, at the [MoIV(η2-S2-
CNEt2)3]+ fragment (vide infra). According to the ESR inves-
tigations of the electro-oxidized complex [(η1-PhNN)Mo(S2-
CNMe2)3]+, the unpaired electron is essentially located on
the molybdenum center.39 On the other hand, the absence
of the [(η5-C5H5)Fe]+/[(η5-C5Me5)Fe]+ electron-attracting
groups is dramatically evidenced by the 380/340 mV cathodic
shift observed for the oxidation wave of the parent complex
[(η1-C6H5NN)Mo(η2-S2CNEt2)3], 9 (E1/2 ) 0.031 V, ∆E )
102 mV),12 thus nicely illustrating the strong electronic
cooperativity between the two metal centers. These conclu-
sions are fully consistent with our DFT results (vide infra).
(iii) There is a secondary ill-resolved irreversible oxidation
wave at ca. 1.12 and 1.15 V, respectively, similar to that
observed for the reported mononuclear complexes [(η1-
ArNN)Mo(η2-S2CNMe2)3].39 The irreversibility of this oxida-
tion wave is probably due to the fast follow up chemical
reaction of the unstable electrode generated trication [(η5-
Cp′)Fe(µ,η6:η1-C6H5NN)Mo(η2-S2CNEt2)3]3+.
-
Figure 1. Visible bands in the electronic spectrum of complex 5+PF6
.
5H (5+) or 4H (6+, 7+, and 8+) that correspond to the upfield
π-coordinated aromatic protons. Singlet resonances were also
observed at δ ) 2.16 (p-Me) and 3.88 (p-MeO), for 6+ and
7+, respectively, whereas the C5Me5 ligand of compound 8+
exhibited its characteristic sharp peak integrating for 15
protons at δ ) 1.83 ppm. In addition, for the four bimetallic
compounds, the [Mo(η2-S2CNEt2)3]+ fragment gave rise to
a triplet at ca. 1.20 ppm and a multiplet centered at ca. 1.25-
1.30 ppm, attributable to the methyl protons of the NEt2
groups, and a second multiplet at ca. 3.85 ppm assigned to
the methylene protons of the NEt2 groups, with the 3:15:12
relative intensity. 1H NMR spectrum of crystals of 10‚Et2O,
from which a well-shaped one was selected for the X-ray
analysis (vide infra), clearly showed the presence of both
the neutral molybdenum complex and the solvated diethyl
ether in the ratio 1:1. Accordingly, the triplet and quartet
attributed to the solvate molecule were seen at 1.13 and 3.44
ppm, respectively, while the signal pattern of 10 is quite
similar to that of 6+ with the exception of the Cp resonance
and the downfield shift of the aromatic protons to 7.02 ppm.
With the aid of 2-D homo- and heteronuclear NMR
spectroscopy it was possible to distinguish signals corre-
sponding to four types of ethyl groups in the room-
temperature 13C NMR spectrum of 10‚Et2O. This is in
accordance with a stereochemically rigid molecule bearing
a plane of symmetry containing the molybdenum center, the
diazenido fragment, and one dithiocarbamate ligand with a
sulfur atom in the equatorial plane and the other one in the
apical position.
These electrochemical data indicate unambiguously that
the electron-withdrawing property of the [(η5-C5H5)Fe]+
-
group of complex 5+PF6 is stronger than that of [(η5-C5-
-
Me5)Fe]+ group of complex 8+PF6 and, therefore, the
-
reduction and oxidation potentials of complex 5+PF6 are
- 33
more anodic than those of complex 8+PF6 . On the other
hand, it is clear (and confirmed by DFT calculations; vide
-
-
infra) that in complexes 5+PF6 and 8+PF6 the character
of the LUMO is determined by the cationic mixed sandwich,
[(η5-Cp′)Fe(η6-aryl)]+, whereas the nature of the HOMO is
centered in the [Mo(η2-S2CNEt2)3]+ moiety. This is consistent
with the electronic spectral data. In fact, the visible spectra
of complexes 5+PF6- and 8+PF6- exhibit in CH2Cl2 a band
at 485 nm (log ꢀ ) 3.76) and 462 nm (log ꢀ ) 3.90),
respectively, which can be reasonably attributed to a charge-
transfer transition from the MoIV f FeII through the
phenyldiazenido ligand.
The mixed-sandwich [(η5-Cp′)Fe(η6-arene)]+ complexes
are well-known for their interesting redox behavior.33,38 For
this reason, it was of interest to explore by cyclic voltam-
metry the electronic influence of the acceptor [Cp′Fe]+
groups through the aryldiazenido linker on the donor
[MoIV(η2-S2CNEt2)3]+ group. In particular, two complexes,
[(η5-C5H5)Fe(µ,η6:η1-C6H5NN)Mo(η2-S2CNEt2)3]+PF6-,5+PF6-,
X-ray Crystallographic Studies. The detailed crystalline
and molecular structures of the ionic heterobimetallic
complex 7+PF6 and the neutral complex 10‚Et2O were
-
(38) (a) Astruc, D. In Electron Transfer and Radical Reactions in
Transition-Metal Chemistry; VCH: New York, 1995; Chapter 2, pp
147-149. (b) Astruc, D. Chem. ReV. 1988, 88, 1189.
(39) Butler, G.; Chatt, J.; Leigh, G. J.; Pickett, C. J. J. Chem. Soc., Dalton
Trans. 1979, 113.
Inorganic Chemistry, Vol. 46, No. 4, 2007 1129

Manzur et al.
-
Complex 7+PF6 crystallizes in the triclinic space group
P1h with 2 crystallographically inequivalent molecules/
asymmetric unit, the difference between the two molecules
being essentially due to very slight variations in the
conformation of the ethyl groups. The cationic entity 7+
consists of an organometallic moiety [(η5-Cp)Fe]+ and an
inorganic fragment [Mo(η2-S2CNEt2)3]+, both connected
through the π-conjugated aryldiazenido bridge, [p-MeOC6H4-
NdN]-, in η6 and η1 mode. The MoIV center possesses the
seven-coordinate pentagonal bipyramidal structure, with two
[Et2NCS2]- ligands in the equatorial plane in an η2 mode
and the third spanning an axial and an equatorial position.
The aryldiazenido ligand whose oxidation state is -1 4
occupies the remaining axial position through the terminal
NR atom in a η1 fashion. The aryl group is hexahapto
coordinated to the [(η5-Cp)Fe]+ moiety. In the mixed
sandwich fragment, the iron atom is coordinated to the
cyclopentadienyl ring at a ring centroid-iron distance of
1.664 Å and to the aryl ring at a ring centroid-iron distance
of 1.536 Å. A careful examination of Table 3 reveals some
interesting features provoked by the strong electron-
withdrawing CpFe+ moiety on the aryldiazenido ligand. In
fact, one of the most remarkable deviation observed in the
molecular parameters of this complex correspond to the Fe-
Cipso bond length, 2.140(7) Å, which is ca. 0.065 Å longer
than the mean of the other Fe-C (C6 ring) bond lengths.
Likewise, the Cipso-N bond length, 1.395(10) Å, is ca. 0.042
Å shorter than the mean reported for a C-N single bond.41
Such features had also been observed by Hidai et al. in
related heterobinuclear aryldiazenido complexes8,9 although
the elongation and shortening observed in the M-Cipso and
Cipso-N bonds, respectively, were much more dramatic than
that observed in 7+ (see Table 3). These observations were
rationalized by Hidai et al. assuming that the aryldiazenido
linker receives an important contribution of the zwitterionic
resonance structure as a consequence of the presence of both
the electron-rich WII(5d4) center and the (CO)3Cr, [(η5-Cp)-
Fe]+, or [(η5-Cp)Ru]+ electron-withdrawing groups.7,8 These
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for
-
Complexes 7+PF6 and 10‚OEt2
param
7+
10‚OEt2
Bond Distances
1.773(6)
2.534(2)
2.530(2)
2.514(2)
2.494(2)
2.575(2)
2.529(2)
1.276(9)
1.395(10)
1.411
Mo(1)-N(1)
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
Mo(1)-S(4)
Mo(1)-S(5)
Mo(1)-S(6)
N(1)-N(2)
1.782(4)
2.6039(13)
2.4865(11)
2.5397(12)
2.5206(12)
2.5283(12)
2.5319(12)
1.234(5)
N(2)-Ca
1.428(5)
1.391
CCb
Fe(1)-C(26)
Fe(1)-C(23)
Fe(1)-C(16-20)c
Fe(1)-C(21-26)c
2.140(7)
2.106(7)
2.046
2.085
Bond Angles
118.6(7)
171.5(6)
170.9(2)
96.0
C
a-N(2)-N(1)
N(2)-N(1)-Mo(1)
N(1)-Mo(1)-Sd
N(1)-Mo(1)-Se
119.7(4)
170.4(3)
165.73(11)
95.0
a C′ ) C(16) for 10‚OEt2 and C(26) for 7+. b Average C-C bond length
in the phenyl ring, C(16-21) for 10‚OEt2 and C(21-26) for 7+. c Average
Fe-C bond length. d S′ ) S(1) for 10‚OEt2 and S(5) for 7+. e Average bond
angle made by the apical nitrogen, the molybdenum, and the equatorial
sulfurs atoms, S(2-6) for 10‚OEt2 and S(1-4,6) for 7+.
observations lead us also to attribute to the species 7+
a
partial positive charge on the molybdenum center and,
consequently, a cyclohexadienyl-like character of the arene
ring with a partial negative charge and a dihedral folding
angle of 6.0(8)° (Chart 1). These findings are in accord with
previous structural data42 and theoretical work43 and more
recently in several diiron and triiron organometallic hydra-
zones.11 In the case of complex 7+, the presence of both a
MoIV(4d2) center and the electron-withdrawing [(η5-Cp)Fe]+
group must stabilize the charge-separated resonance structure
Figure 2. Molecular structure and atom numbering scheme for 7+.
Hydrogen atoms and the PF6 counterion have been omitted for clarity.
Displacement ellipsoids are shown at the 30% probability level.
-
unambiguously determined by X-ray diffraction studies as
outlined in the Experimental Section and Table 1. Key bond
lengths and angles are listed in Table 2. Drawings of the
cationic organometallic entity 7+ and the neutral species 10,
along with the atom-numbering scheme, are depicted in
Figures 2 and 3, respectively. Likewise, for the sake of
comparison, Table 3 contains the relevant bond lengths and
bond angles of the heterobinuclear aryldiazenido cores of
7+ and those of Cr-W, Ru+-W, and Fe+-W described by
Hidai et al.8 This table also includes the metrical parameters
of three classic aryldiazenido molybdenum cores of general
formula [(η1-RC6H4NN)Mo(S2CNMe2)3], R ) H and m-
NO2,40 and 10‚Et2O that do not contain the electron-attracting
CpFe+ fragment.
(40) Butler, G.; Chatt, J.; Leigh, G. J.; Smith, A. R. P.; Williams, G. A.
Inorg. Chim. Acta 1978, 28, L165.
(41) Orpen, A. G.; Bramer, L.; Allen, F. H.; Kennard, D.; Watson, D. G.;
Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1.
(42) (a) Saillard, J.-Y.; Grandjean, D.; Le Maux, P.; Jaouen, G. NouV. J.
Chim. 1981, 5, 153. (b) Hunter, A. D.; Shilliday, L.; Furey, W. S.;
Zaworotko, M. J. Organometallics 1992, 11, 1550. (c) Lambert, C.;
Gaschler, W.; Matschiner, R.; Wortmann, R. J. Organomet. Chem.
1999, 592, 109. (d) Djukic, J.-P.; Rose-Munch, F.; Rose, E.; Vais-
sermann, J. Eur. J. Inorg. Chem. 2000, 1295. (e) Moriuchi, A.; Uchida,
K.; Inagaki, A.; Akita, M. Organometallics 2005, 24, 6382.
(43) Ruiz, J.; Ogliaro, F.; Saillard, J.-Y.; Halet, J.-F.; Varret, F.; Astruc,
D. J. Am. Chem. Soc. 1998, 120, 11693.
1130 Inorganic Chemistry, Vol. 46, No. 4, 2007

Iron-Molybdenum Charge-Transfer Hybrids
Chart 1
Theoretical Investigations. To get a better understanding
of the properties of the title compound and on the iron-
molybdenum communication along the aryldiazenido bridge,
we have carried out DFT calculations on a simplified model
of 7+ in which the ethyl groups of the dithiocarbamato
ligands are replaced by hydrogen atoms. The monooxidized
and monoreduced states have been also computed. These
model complexes are labeled 7′+, 7′2+, and 7′, respectively.
The mononuclear species 10 has been modelized in the same
manner, and its monooxidized and monoreduced states were
also computed. These models are labeled 10′, 10′+, and 10′-,
respectively. Computational details are given in the Experi-
mental Section. Major optimized bond distances and angles
and other selected computed data are given in Table 4. The
MO diagrams of 10′ and 7′+ are shown in Figure 4.
The optimized geometries of 7′+ and 10′ are in good
agreement with the X-ray structures of 7+ and 10. As usually
found with this type of calculations, the computed metal-
ligand distances are slightly longer than the experimental
ones. The opposite trend is observed for the N-N distances.
The HOMO of 10′ lies somewhat isolated 0.78 eV above
the HOMO-1 (left-hand side of Figure 4). It can be described
as a Mo d-type lone-pair (48%) mixed in a bonding way
with the π*(NN) orbital (20%). This orbital can be consid-
ered as containing the two d electrons of the MoIV center,
since all the other occupied MOs have minor metal participa-
tion. The HOMO-1 can be associated with the N(2) lone
pair, mixed in an antibonding way with the π-bonding
Mo-N electron pair. It has N(1), N(2), and Mo participations
of 14%, 17%, and 25%, respectively. The lowest unoccupied
orbitals are Mo-S antibonding. The LUMO and LUMO+1
have similar localization on Mo (55% and 57%, respectively)
and on S (40% and 43%, respectively). Complexing the
phenyl ring by a CpFe+ moiety merely perturbs these
features, as it can be seen on the MO diagram of 7′+ (right-
hand side of Figure 4). The only important change is the
inclusion of five Fe(II) d-type levels in the diagram. The
occupied Fe “t2g” levels are associated with the HOMO-4,
HOMO-5, and HOMO-7. The two other Fe d-type AOs (the
so-called “eg*” set) correspond to the LUMO and LUMO+1.
They are largely Fe-Cp antibonding, with similar localiza-
tion on Fe (53% and 62%, respectively) and on Cp (19%
and 26%, respectively). The LUMO has some Mo participa-
Figure 3. Molecular structure and atom numbering scheme for 10.
Hydrogen atoms and the solvent molecule have been omitted for clarity.
Displacement ellipsoids are shown at the 30% probability level.
of the aryldiazenido ligand. In classic aryldiazenido molyb-
denum complexes, which do not contain electron-withdraw-
ing moieties, these structural changes are obviously not
observed and the Cipso-N bond lengths lie in the normal
range 1.41-1.43 Å (see Table 3). On the other hand, the
N-N bond length of 7+, 1.276(9) Å, compares well with
those reported by Hidai et al.8 (Table 3), but they are longer
than those measured in the classic (aryldiazenido)molybde-
num complexes, whose NdN bond lengths conserve the
double-bond character.2,40 Finally, the Mo<N bond length
determined in complex 7+, 1.773(6) Å, seems to be unex-
ceptional for a MoN double bond2 and too long for a triple
bond. This bond length cannot be compared with those
observed in the complexes reported by Hidai et al.8 due to
the different oxidation states of the involved metal centers,
MoIV and WII, giving rise to different external electronic
configurations, 4d2 and 5d4, respectively, and different ionic
radii.
Complex 10‚Et2O, of formula [(η1-p-MeC6H4NdN)Mo-
(η2-S2CNEt2)3]‚Et2O, also crystallizes in the triclinic space
group P1h as a diethyl ether solvate, with one independent
molecule/asymmetric unit (see Experimental Section and
Table 1). This complex is analogue to the classic com-
plexes reported by Chatt et al.40 and does not deserve further
discussion (see Table 3 for key bond lengths and angles).
Inorganic Chemistry, Vol. 46, No. 4, 2007 1131

Manzur et al.
Table 3. Comparison of Selected Bond Lengths (Å) and Bond Angles (deg) of Heterobimetallic Aryldiazenido Cores and Mononuclear Related
Complexes
bond lengths (Å)/bond angles (deg)
compd
M-Cipso
Cipso-N
NN
N-M
M-NN
NN-C
ref
[{(CO)3Cr(µ-η6:η1-p-C6H4CO2Me)NdN}W(NCS)(dppe)2]a
[{(CO)3Cr(µ-η6:η1-p-C6H4CO2Me)NdN}WF(dppe)2]a
[{CpRu(µ-η6:η1-C6H5)NdN}W(NCS)(dppe)2]+ a
[{CpFe(µ-η6:η1p-C6H4Me)NdN}WF(dppe)2]a
[{CpFe(µ-η6:η1p-C6H4Me)NdN}Mo(Et2-dtc)3]+ b (7+)
[{(C6H5)NdN}Mo(Me2-dtc)3]b
2.431(5)
2.50(1)
2.39(2)
2.24(1)
2.140(7)
1.366(6)
1.30(2)
1.40(2)
1.314(5)
1.33(2)
1.28(1)
1.784(4)
1.80(1)
1.75(1)
1.778(8)
1.773(6)
1.781(4)
1.770(6)
1.782(4)
164.9(3)
161(1)
166(1)
164.0(7)
171.5(6)
171.5(4)
170.6(6)
170.4(3)
120.0(4)
117(1)
8
8
8
8
122(11)
120.6(8)
118.6(7)
120.5(5)
117.9(7)
118.6(7)
1.35(1)
1.32(1)
1.395(10)
1.417(7)
1.410(10)
1.428(5)
1.276(9)
1.233(6)
1.262(9)
1.234(5)
this work
40
40
[{(m-C6H4NO2)NdN}Mo(Me2-dtc)3]b
[{(p-C6H4Me)NdN}Mo(Et2-dtc)3]b (10)
this work
a dppe ) bis(diphenylphosphino)ethane. b dtc ) dithiocarbamate.
Table 4. Major Computed Data for 7′2+/+/0 and 10′+/0/-
param
7+2
7+
7
10+
10
10-
first ionization energy (eV)
electronic affinity (eV)
HOMO-LUMO gap (eV)
dipole moment (D)
bond dists (Å)
8.97
4.23
1.78
14.70
5.96
1.63
1.68
2.14
23.33
7.77
5.70
5.59
Mo(1)-N(1)
1.906
2.580
2.550
2.576
2.565
2.560
2.593
1.217
1.418
1.427
2.109
2.210
2.094
1.833
2.586
2.611
2.614
2.553
2.634
2.613
1.244
1.390
1.428
2.184
2.149
2.092
2.124
1.817
2.581
2.918
2.839
2.535
2.676
2.657
1.268
1.371
1.430
2.261
2.105
2.103
2.121
1.909
2.570
2.558
2.578
2.588
2.602
2.567
1.207
1.406
1.409
1.847
2.665
2.564
2.598
2.608
2.611
2.604
1.222
1.413
1.408
1.827
2.731
2.551
2.636
2.585
3.857
2.561
1.244
1.404
1.410
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
Mo(1)-S(4)
Mo(1)-S(5)
Mo(1)-S(6)
N(1)-N(2)
N(2)-Ca
C-Cb
Fe(1)-C(26)
Fe(1)-C(23)
Fe(1)-C(16-20)c
Fe(1)-C(21-26)c
bond angles (deg)
Ca-N(2)-N(1)
N(2)-N(1)-Mo(1)
N(1)-Mo(1)-Sd
N(1)-Mo(1)-Se
123.2
171.2
167.6
95.9
121.0
171.8
169.5
96.4
118.9
173.4
169.2
97.3
125.3
172.0
169.4
94.4
123.2
172.0
168.2
95.3
121.3
174.3
169.0
97.9
tion (12%). The Mo-S antibonding levels lie just above the
LUMO+1.
10′ or 7′+ leads in both cases to partial decoordination of
the dithiocarbamato ligands with the formation of a formally
MoIII metal center as exemplified by the spin density plots
of 10′- and 7′ shown in Figure 5. Thus, in the case of 7′,
sulfur decoordination provides more stabilization than creat-
ing a Fe(I) 19-electron center. It should be noted, however,
that, in this compound, small but significant spin density is
computed on Fe (0.11, vs 0.53 on Mo), indicative of the
electron-withdrawing effect of the CpFe+ moiety. Similarly
to their ionization potentials, the electronic affinities of 10′
and 7′+ are significantly different (Table 4), mainly because
of their different electric charges. Thus, it is easier to reduce
7′+ than 10′. This result is consistent with the electrochemical
experiments discussed above.
Oxidizing 10′ and 7′+ consists in removing one electron
from similar HOMOs. Since this orbital is NN antibonding
and Mo-N bonding (Figure 4), N-N shortening and Mo-N
lengthening result (Table 4). This oxidation can be described
as a MoIV to MoV oxidation change, as exemplified by the
spin density plots of 10′+ and 7′2+ shown in Figure 5.
Interestingly, the ionization potentials of 10′ and 7′+ are
different (Table 4). Due to its cationic charge, the oxidation
of 7′+ requires more energy than that of neutral 10′. This
result is in full agreement with the electrochemical experi-
ments discussed above.
At first sight, the monoelectronic reductions of 10′ and
7′+ might be expected to be different because of the different
nature of their LUMO’s. Indeed, reducing 7′+ may lead to
predict the formation of a CpFe(I)(η6-aryl) entity (vide supra).
Calculations actually show that this is not the case. Mo-S
decoordination is found for both 10′- and 7′. In the case of
10′-, the Mo-S(5) distance (3.86 Å) is definitely nonbond-
ing. In the case of 7′, Mo-S(2) (2.92 Å) and Mo-S(3) (2.84
Å) are also nonbonding or weakly bonding. Also one cannot
ascertain that we found the structure of lowest energy for
10′- and 7′, our calculations show clearly that reduction of
TD-DFT calculations have also been carried out on 7′ in
vacuum (see computational details) to ascertain the nature
of the more intense visible bands of Figure 1. The computed
wavelengths are much larger than their experimental coun-
terparts. This may be partly due to the ligand simplification
in the computed model but more likely because solvent
effects were not considered in the calculations. Nevertheless,
they are consistent with the two-band shape of the spectrum
shown in Figure 1. The less energetic computed transition
(736 nm) can be assigned to the band observed at ∼470 nm
1132 Inorganic Chemistry, Vol. 46, No. 4, 2007

Iron-Molybdenum Charge-Transfer Hybrids
Figure 4. Molecular Orbital diagrams of 7′+ and 10′.
component to this observed band is computed at 467 nm
and corresponds to mixed ligand/Mo charge transfer to
ligand.
Conclusions
As a result of this study, we have succeeded in the
synthesis of representative members of a new family of
covalently bonded charge-transfer molecular hybrids of
general formula [(η5-Cp)Fe(µ,η6:η1-p-RC6H4NN)Mo(η2-S2-
-
-
-
CNEt2)3]+PF6 , 5+PF6 -7+PF6 , and [(η5-C5Me5)Fe(µ,η6:
-
-
η1-C6H5NN)Mo(η2-S2CNEt2)3]+PF6 , 8+PF6 . These hybrid
complexes consist of organometallic and inorganic fragments,
[(η5-Cp)Fe]+ and [Mo(η2-S2CNEt2)3]+, respectively, which
are connected one other by an aryldiazenido spacer,
[RC6H4NdN]-, in a µ,η6:η1 mode through the π-system of
the aryl group and the σ-π orbitals of the diazenido group.
Moreover, electronic spectra and electrochemical and struc-
tural data in conjunction with theoretical investigations
clearly indicate the existence of a charge-transfer transition
from the inorganic donor to the organometallic acceptor
fragments through the aryldiazenido spacer. The readiness
with which the organometallic arylhydrazines form these new
molecular architectures with dioxomolybdenum complexes
represents an alternative strategy to those described by Hidai
et al.8 for the preparation of new charge-transfer hybrids and
could be extended to other transition metal complexes
containing oxometal functionalities, e.g., RedO and WdO.
Along this line, we are currently extending this new strategy
to Lindqvist hexamolybdate species to prepare new organo-
metallic-inorganic charge-transfer hybrids.
Figure 5. Plots of the computed spin densities of 10′+, 7′2+, 10′-, and 7′.
(Figure 1). It corresponds to transitions from the HOMO to
the LUMO and LUMO+1, confirming its Mo to Fe charge-
transfer nature. A nearby computed transition at 669 nm with
a 60% weaker oscillator strength corresponds to mixed
ligand/Mo charge transfer to Fe. This transition likely
contributes also somewhat to the band observed at ∼470 nm.
The next strong excitation is computed at 491 nm and can
be assigned to the band observed at ∼380 nm (Figure 1). It
corresponds to transitions from the HOMO to two antibond-
ing ligand-based MOs which are of dithiocarbamato and
aryldiazenido nature, respectively, confirming the Mo to
ligand charge-transfer nature of this band (vide supra).
Another transition which should contribute as a minor
Acknowledgment. Thanks are expressed to Drs. S.
Sinbandhit, P. Jehan, and P. Gue´not (CRMPO, Rennes,
France) for skillful assistance in recording high-field NMR
Inorganic Chemistry, Vol. 46, No. 4, 2007 1133

Manzur et al.
Supporting Information Available: Crystallographic files
in CIF format for the two reported X-ray crystal structures.
This material is available free of charge via the Internet at
http://pubs.acs.org.
and high-resolution mass spectrometry. Financial support
from the Fondo Nacional de Desarrollo Cient´ıfico y Tecno-
lo´gico, FONDECYT-Chile, Grant Nos. 1980433 and 1060490,
is gratefully acknowledged. Computing facilities were pro-
vided by the PCIO Center at the University of Rennes 1 and
the IDRIS-CNRS Center at Orsay, France.
IC0613098
1134 Inorganic Chemistry, Vol. 46, No. 4, 2007