Reaction of [Fe2(CO)8(μ-CF2)] with AsMe3 and other Lewis bases: Syntheses, crystal structures of [Fe(CO)6(AsMe3)2(μ-CF2)] and [Fe(CO)5(AsMe3)3(μ-CF2)], and theoretical considerations

Article abstract of DOI:10.1021/ic0604011

The difluorcarbene complex [Fe₂(CO)₈(μ-CF ₂)] (2) reacts with AsMe₃ under CO substitution to give the μ-CF₂ containing complexes [Fe₂(CO) ₆(AsMe₃)₂(μ-CF₂)] (4) and [Fe₂(CO)₅(AsMe₃)₃(μ-CF ₂)] (5) which have an [Fe₂(CO)₉]-like structure as shown by X-ray analyses. In the solid state, 4 forms two isomers, 4a and 4b, in a 3 to 1 ratio, which differ in the position of the μ-CF₂ ligand; 4a has a local C₂ axis and 4b has C₁ symmetry. The Fe-Fe distances in 4 and 5 are 2.47 A and are the shortest ones found in [Fe₂(CO)₉]-like compounds. Efforts were also undertaken to replace one or more CO groups in 2 by other ligands, such as N (bpy, phen, pzy, etc.) or P donors (dppe, dppm). With dppm, only the CF₂ free complex, [Fe₂(CO)₄(μ-Ph₂PCH ₂PPh₂)₂(μ-CO)] (6), could be detected and characterized by X-ray analysis. Most of the reactions resulted in the formation of red-brown materials which were insoluble in the usual solvents and which could not be characterized. The use of CH₂Cl₂ during the attempts to crystallize a product from the reaction of 2 and phen gave [Fe(phen)₃]Cl₂ (7) in low yields. For 4 and 5, the electronic structures were analyzed using the atoms in molecules (AIM) theory. No electron density was found between the two iron atoms, and the short contacts can be interpreted in terms of a π-interaction.

Full text of DOI:10.1021/ic0604011

Inorg. Chem. 2006, 45, 9053−9063
Reaction of [Fe2(CO)8(
Syntheses, Crystal Structures of [Fe(CO)6(AsMe3)2(
[Fe(CO)5(AsMe3)3( -CF2)], and Theoretical Considerations
µ-CF2)] with AsMe3 and Other Lewis Bases:
µ
-CF2)] and
µ
Meritxell DelaVarga,† Wolfgang Petz,*,‡ Bernhard Neumuller,‡ and Ramon Costa*,†
1
Departament de Qu´ımica Inorga`nica, UniVersitat de Barcelona, Mart´ı i Franque`s 1-11, E-08028
Barcelona, Spain, and Fachbereich Chemie der Philipps-UniVersita¨t Marburg,
Hans-Meerwein-Strasse, D-35032 Marburg, Germany
Received March 9, 2006
The difluorcarbene complex [Fe2(CO)8(
containing complexes [Fe2(CO)6(AsMe3)2(
like structure as shown by X-ray analyses. In the solid state, 4 forms two isomers, 4a and 4b, in a 3 to 1 ratio,
which differ in the position of the -CF2 ligand; 4a has a local C2 axis and 4b has C1 symmetry. The Fe Fe
µ
-CF2)] (2) reacts with AsMe3 under CO substitution to give the
µ-CF2
µ
-CF2)] (4) and [Fe2(CO)5(AsMe3)3( -CF2)] (5) which have an [Fe2(CO)9]-
µ
µ
−
distances in 4 and 5 are 2.47 Å and are the shortest ones found in [Fe2(CO)9]-like compounds. Efforts were also
undertaken to replace one or more CO groups in 2 by other ligands, such as N (bpy, phen, pzy, etc.) or P donors
(dppe, dppm). With dppm, only the CF2 free complex, [Fe2(CO)4(µ-Ph2PCH2PPh2)2(µ-CO)] (6), could be detected
and characterized by X-ray analysis. Most of the reactions resulted in the formation of red-brown materials which
were insoluble in the usual solvents and which could not be characterized. The use of CH2Cl2 during the attempts
to crystallize a product from the reaction of 2 and phen gave [Fe(phen)3]Cl2 (7) in low yields. For 4 and 5, the
electronic structures were analyzed using the atoms in molecules (AIM) theory. No electron density was found
between the two iron atoms, and the short contacts can be interpreted in terms of a
π-interaction.
Introduction
as the ability to act as the source for the highly reactive 16-
electron fragment (CO)4Fe, the compound has gained the
interest of generations of chemists.
[Fe2(CO)9] is an unique and fascinating molecule in
organometallic chemistry containing six terminal and three
bridging carbonyl groups.1 The question of a direct Fe-Fe
interaction is a controversial issue with answers ranging from
yes2 to no,3 and the membership of publishers to one of the
groups is expressed in drawing or omitting a line between
the two metal atoms. However, it is commonly accepted that
a subtle balance between the metal to carbonyl bridge
bonding, metal-metal bonding, and intermetallic repulsion
is operative.3 Because of the high symmetric structure, the
golden color, and the insolubility in organic solvents, as well
The idea of substituting one or more carbonyl groups in
[Fe2(CO)9] by other isolobal 2-electron σ-donor/π-acceptor
systems, D, and of exploring the structural changes occuring
upon variation of D is very old and has inspired many
chemists. However, no simple series of [Fe2(CO)9-x(D)x]
compounds could be prepared. If one or more terminal or
bridging CO groups are replaced, the series of compounds
A-C (A has terminal D units, B has bridging D units, and
C has terminal and bridging D units) should be obtained,
and the structural options in the solid state are either an [Fe2-
(CO)9]-like structure (I) or an [Os2(CO)9]-like structure (II)
as depicted in Chart 1.4 For the type A compounds, a series
of chelating phosphine ligands, such as R2PCH2PR2,5,6 R2-
POPR2,7 R2PNHPR2,8 F2PNMePF2,9 and 1,2-diazine,10 bridge
the two Fe atoms to give [Fe2(CO)7(D-D)] or [Fe2(CO)5-
* To whom correspondence should be addressed: E-mail: petz@staff.uni-
marburg.de (W.P.); rcosta@ub.edu (R.C.).
† Universitat de Barcelona.
‡ Fachbereich Chemie der Philipps-Universita¨t Marburg.
(1) Cotton, F. A.; Troup, J. M. J. Chem. Soc., Dalton Trans. 1974, 800.
(2) (a) Mealli, C.; Proserpio D. M. J. Organomet. Chem. 1990, 386, 203.
(b) Reinhold, J.; Hunstock, E.; Mealli, C. New. J. Chem. 1994, 18,
465.
(4) Moss, J. R.; Graham, W. A. G. Chem. Commun. 1970, 835.
(5) Cotton, F. A.; Troup, J. M. J. Am. Chem. Soc. 1974, 96, 4422.
(6) Wong, W. K.; Chiu, K. W.; Wilkinson, G.; Motevalli, M.; Hursthouse,
M. B. Polyhedron 1985, 4, 1231.
(3) (a) Summerville, R. H.; Hoffmann, R. J. Am. Chem. Soc. 1979, 101,
3821. (b) Bauschlicher, C. W. J. Chem. Phys. 1986, 84, 872. (c) Rosa,
A.; Baerends, E. New. J. Chem. 1991, 15, 815.
10.1021/ic0604011 CCC: $33.50
Published on Web 09/27/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 22, 2006 9053

DelaVarga et al.
a
Chart 1. Derivatives of Fe2(CO)9
Chart 2. Bonding Situation in 2 with Two Semibridging CO Groups.
D ) CH2, while larger ligands prefer the structure type II.
The Fe-Fe distances in the type I complexes range from
2.47 to 3.00 Å depending on the nature of the bridging ligand.
With two15 or three20,23 µ-D ligands, a type I structure is
formed. However, to our knowledge, no [Fe2(CO)6-y(D′)y-
(CO)3-x(µ-D)x] complex of type C-I has been known up to
now, with the exception of CO-free [Fe2(CNEt)6(µ-CNEt)3].24
In all cases, the Fe-Fe distances in type II species are
appreciably longer than those in type I compounds.
Recently, we have described the syntheses and crystal
structures of compounds with the bridging difluorocarbene
ligand.15 While the structure of [Fe2(CO)7(µ-CF2)2] (1) is
closely related to that of [Fe2(CO)9] (B-I), with a very short
Fe-Fe distance of 2.47 Å, the complex [Fe2(CO)8(µ-CF2)]
(2) exhibits no bridging CO groups according to the IR
spectrum in either the solid state or solution down to -123
C°.25 The crystal structure of 2, which shows the presence
of two semibridging CO groups, was interpreted in terms of
being located between B-I and B-II, as shown in Chart 2.
The CF2 ligand is a better acceptor than CO;15,26 this is
indicated by a shift of the ν(CO) vibrations to higher wave-
numbers relative to those in [Fe2(CO)9]. It is therefore
expected that the introduction of a better σ-donor in a
terminal position should have a stabilizing effect.
a A : One or more D ligands in terminal positions. B: One or more D
ligands in bridging positions. C: D ligands in bridging and terminal
positions. I: Fe2(CO)9-like structure. II: Os2(CO)9-like structure.
(D-D)2] compounds which exhibit structure type II. How-
ever, aromatic chelating amine ligands, such as bpy,11,12
phen,12 or a chelating diarsine,13 are attached at one iron atom
generating two electronically different atoms, and the charge
is balanced by the formation of asymmetrically bridging or
semibridging CO groups; structures closely related to type
A-I are observed.
To our knowledge, no type A compounds [Fe2(CO)6-x
-
(D)x(µ-CO)3] with a single two-electron donor (NR3, PR3,
or related bases) are known, but several type B compounds
[Fe2(CO)6(µ-CO)3-x(µ-D)x] are known. Therefore, we con-
centrate on compounds containing the two-electron donor
14
molecules CR2, CF2,15 C(CF3)2, CdCF2,16 SiR2, SnR2,17
As reported earlier, the addition of PPh3 to 2 generates
the disubstituted complex [Fe2(PPh3)2(CO)6(µ-CF2)] (3) with
a type C-II structure, and the phosphine ligands at both iron
atoms are arranged in an asymmetrical form.15
GeMe2,18 SO2,19 and derivatives of low-valent group 13
compounds, such as InR,20,21 GaR,22 and TlR.23 If only one
µ-D ligand is present (x ) 1), structure type I is found with
The easy access to 3 prompted us to study the possibility
of replacing CO by other donor molecules in more detail
using various types of monodentate or chelating ligands. In
particular, we studied the reaction of 2 with AsMe3, AsiPr3,
dppe, dppm, and the R-diimines, bpy (2,2′-bipyridine), phen
(1,10-phenantroline); we also studied it with pyrazine (pyz)
and 4,4′-bpy. The results of our investigations are reported
here. The electronic structures of the AsMe3 derivatives
obtained were analyzed using the atoms in molecules (AIM)
theory.
(7) De Leeuw, G.; Field, J. S.; Haines, R. J.; McCulloch, B.; Meintjies,
E.; Monberg, C.; Oliver, G. M.; Ramdial, P.; Sampson, C. N.;
Sigwarth, B.; Stehen, N. D. J. Organomet. Chem. 1984, 275, 99.
(8) Ellermann, J.; Gabold, P.; Knoch, F. A.; Moll, M.; Pohl, D.; Sutter,
J.; Bauer, W. J. Organomet. Chem. 1996, 525, 89.
(9) (a) Newton, M. G.; King, R. B.; Chang, M.; Gimeno, J. J. Am. Chem.
Soc. 1977, 99, 2802. (b) Brown, G. M.; Finholt, J. E.; King, R. B.;
Bibber, J. W.; Kim, J. H. Inorg. Chem. 1982, 21, 3790.
(10) Cotton, F. A.; Hanson, B. E.; Jamerson, J. D.; Stults, B. R. J. Am.
Chem. Soc. 1977, 99, 3293.
(11) Cotton, F. A.; Troup, J. M. J. Am. Chem. Soc. 1974, 96, 1233.
(12) DelaVarga, M.; Costa, R.; Reina, R.; Nunez, A.; Maestro, M. A.;
Mahia, J. J. Organomet. Chem. 2003, 677, 101.
(13) Bailey, W. I.; Bino, A.; Cotton, F. A.; Kolthammer, W. S.; Lahuerta,
P.; Puebla, P.; Uson, R. Inorg. Chem. 1982, 21, 289.
(14) (a) Meyer, B. B.; Riley, P. E.; Davis, R. E. Inorg. Chem. 1981, 20,
3024. (b) Mills, O. S.; Redhouse, A. D. J. Chem. Soc. A 1968, 1282.
(15) Petz, W.; Weller, F.; Barthel, A.; Mealli, C.; Reinhold, J. Z. Anorg.
Allg. Chem. 2001, 627, 1859.
(16) (a) Wiederhold, M.; Behrens, U. J. Organomet. Chem. 1994, 476, 101.
(b) Schulze, W.; Seppelt, K. Inorg. Chem. 1988, 27, 3872.
(17) Cardin, C. J.; Cardin, D. J.; Convery, M. A.; Devereux, M. M.; Tamley,
B.; Silver, J. J. Chem. Soc., Dalton Trans. 1996, 1145.
(18) Simons, R. S.; Tessier, C. A. Acta Crystallogr., Sect. C 1995, 51,
1997 and references therein.
(19) Meunier-Piret, J.; Piret, P.; Van Meerssche, M. Bull. Soc. Chim. Belges
1967, 76, 374.
(20) (a) Uhl, W.; Keimling, S. U.; Pohlmann, M.; Pohl, S.; Saak, W.; Hiller,
W.; Neumeyer, M. Inorg. Chem. 1997, 36, 5478. (b) Uhl, W.;
Pohlmann, M. Organometallics 1997, 16, 2478.
Results and Discussion
In contrast to [Fe2(CO)9], complex 2 is very soluble in
the common solvents. Thus, in most cases, we used THF,
toluene, or both as the solvent at room temperature, or the
(22) (a) Jutzi, P.; Neumann, B.; Reumann, G.; Stammler, H.-G. Organo-
metallics 1998, 17, 1305. (b) Uhl, W.; El-Hamdan, A.; Petz, W.;
Geiseler, G.; Harms, K. Z. Naturforsch. 2004, 59b, 789. (c) Linti, G.;
Ko¨stler, W. Chem. Eur. J. 1998, 942. (d) Linti, G.; Li, G.; Pritzkow,
H. J. Organomet. Chem. 2001, 626, 82.
(23) Whitmire, K. H.; Guzman Jimenez, I. Y.; Saillard, J.-Y.; Kahlal, S. J.
Organomet. Chem. 2000, 614, 243.
(24) Bassett, J.-M.; Green, M.; Howard, J. A. K.; Stone, F. G. A. J. Chem.
Soc., Chem. Commun. 1978, 1000.
(21) Petz, W.; Esser, M.; Neumu¨ller, B. Z. Anorg. Allg. Chem. 2006, in
press.
(25) Grevels, F. W. Personal communication.
(26) Brothers, P. I.; Roper, W. R. Chem. ReV. 1988, 88, 1293.
9054 Inorganic Chemistry, Vol. 45, No. 22, 2006

Reaction of [Fe2(CO)8(µ-CF2)] with Lewis Bases
Table 1. IR Frequencies (in Nujol mull, cm-1) of 2, 4, and 5 in the
ν(CO) and ν(CF) Region
character. This is in accordance with the results of the crystal
structure analysis showing longer C-F distances.
compound
ν(CO)
ν(CF2)
We also tried to prepare complexes with the more bulky
AsPri3 ligand. The reaction proceeded in ether with the
formation of a red-brown precipitate; however, efforts to
redissolve the precipitate in an appropriate solvent for further
characterization were unsuccessful. The solid showed ν(CO)
frequencies at 2042 m, 2010 w, 1986 w, 1966 m, 1931 vs,
and 1862 s cm-1, and the remaining solution showed a signal
at 42 ppm in the 19F NMR spectrum. No crystals for struc-
tural characterization could be obtained.
[Fe2(µ-CF2)(CO)8] (2)
2066 s, 2039 s,
2016 s, 1950 s
1034 m, 997 s
[Fe2(µ-CF2)(CO)6(AsMe3)2] (4)
2038 m, 2004 s,
1971 s, 1940 vs,
1878 m, 1790 s
2036 w, 2000 m,
1982 s, 1944 vs,
1878 vw, 1818 w,
1786 m, 1766 m
1018 m, 902 s
[Fe2(µ-CF2)(CO)5(AsMe3)3] (5)
1016 m, 900 m
Similarly, chelating phosphine ligands such as Ph2PCH2-
PPh2 (dppm) or (Ph2PCH2)2 (dppe) react slowly with 2 in
toluene to produce brown to red-brown precipitates. How-
ever, attempts to recrystallize the materials by dissolving
them in various solvents have failed. Most of the material
was insoluble and probably consisted of a mixture of
products. In some cases, however, we could isolate few red
crystals which were identified as [Fe2(CO)4(µ-Ph2PCH2-
PPh2)2(µ-CO)] (6), but no crystalline compound containing
a CF2 group was identified, and the whereabouts of this group
is still unclear. The lack of any 19F NMR signal in some
solutions of the reaction products indicate that the CF2 ligand
must be incorporated in the insoluble parts. It seems that
the presence of the strongly bonded CF2 bridge prevents, in
most cases, the formation of a substituted [Fe2(CO)9]-like
complex. The 19F NMR of the solution of 2 with dppm
showed a peak at about 42 ppm; in the 31P NMR spectrum,
a main signal at 60 ppm and others at 85, 62, and 20 ppm
were found. Similarly, the remaining solutions (after removal
of the precipitate) of the reaction of 2 with dppe gave one
signal at 35 ppm in the 19F NMR spectrum, and in the 31P
NMR spectrum, a singlet at 96 ppm, together with multiplets
at 70, 52 and 28 ppm, was observed.
The use of CH2Cl2 as a solvent in the reaction of 2 with
phen gave a crystalline compound which, however, was
identified as the oxidation product [Fe(phen)3]Cl2 (7). It is
known that CH2Cl2 can act as an oxidation agent toward
low-valent carbonyl compounds.27 In one of the recrystal-
lization procedures, we have also obtained [Fe(CO)3(phen)].12
No reaction of 2 with acetonitrile and pyz was found.
When TMNO was added as initiator for CO activation,12
the known trinuclear complex [Fe3(CO)9(µ3-CF)2] was
obtained.28 This product was also formed if 2 was allowed
to react with TMNO alone, but when other ligands were
present (dppe, bpy, or phen), [Fe3(CO)9(µ3-CF)2] was not
detected.
Chart 3. Position of the AsMe3 Ligands in 4a, 4b, and 5 with
Terminal and Bridging CO Groups
reaction was started at low temperature. With the majority
of bases we introduced, red-brown precipitates formed, and
the remaining red-brown solutions showed more than one
signal in the 19F NMR spectra (and in the 31P NMR spectra
in the case of P donors). From the intensities of the signals,
it was clear that nearly all the reaction products were
concentrated in the precipitates which were insoluble in the
usual organic solvents; in some cases, no NMR signals could
be obtained from these solutions. No reaction of 2 with
acetonitrile and pyz was found. However, in the case of
AsMe3, we could isolate and characterize substituted com-
pounds still containing the bridging CF2 ligand. New
complexes [Fe2(CO)6(AsMe3)2(µ-CF2)] (4) and [Fe2(CO)5-
(AsMe3)3(µ-CF2)] (5) were obtained in low yields and are
the first examples of substituted [Fe2(CO)9] derivatives in
which structure type C-I is achieved (Chart 3). Complex 4
turned out to be a mixture of the isomers 4a and 4b in the
solid state.
While the presence of the CF2 groups in 1 and 2 causes a
shift of the ν(CO) vibrations to higher frequencies with
respect to [Fe2(CO)9], according to the better π-acceptor
properties of CF2,15 the introduction of the AsMe3 ligands
causes a shift in the reverse direction, and the frequencies
are now located below those of [Fe2(CO)9]. The three ligands
in 5 are more effective than the two ligands in 4. Thus, the
better σ-donor/π-acceptor relation of AsMe3 overcompen-
sates for the low σ-donor/π-acceptor relation of CF2 with
more electron density moving into π*-orbitals of the CO
groups. In Table 1, the ν(CO) and ν(CF2) frequencies of 4
and 5 are compared with those of 2. The introduction of the
AsMe3 ligands causes also the ν(CF2) bands in 4 and 5 to
shift to lower frequencies, according to the enhanced electron
density in the complexes and the decreasing CF double bond
During our studies of the chemistry of 2, it turned out
that CO groups cannot simply be replaced by other donor
ligands. Thus, as yet, the earlier reported complex 3 and the
compounds 4 and 5 in this contribution are the only known
substitution products of 2 established by X-ray analyses.
Crystal Structures. General Remarks. To obtain more
insight into the properties of the compounds, the structures
(27) Petz, W.; Weller, F. Z. Naturforsch. 1991, 46b, 297.
(28) Lentz, D.; Bru¨dggam, I.; Hartl, H. Angew. Chem., Int. Ed. Engl. 1985,
24, 119.
Inorganic Chemistry, Vol. 45, No. 22, 2006 9055

DelaVarga et al.
Figure 1. Projection view of 4a with the labeling scheme (30% ellipsoids).
The hydrogen atoms have been omitted for clarity.
Figure 3. Projection view of 5 with the labeling scheme (30% ellipsoids).
The hydrogen atoms have been omitted for clarity.
Figure 2. Projection view of 4b with the labeling scheme (30% ellipsoids).
The hydrogen atoms have been omitted for clarity.
of 4, 5, and 6 have been determined by single-crystal X-ray
diffraction measurements. The synthesis of 6 was described
earlier,7 and the crystal structures of the solvates 6‚OC-
29
30
(Me)2 and 6‚2MeC6H5 were obtained. In our case, 6
crystallizes as a toluene solvate but with only one solvent
molecule. We also present the crystal structure of [Fe(phen)3]-
Cl2 (7) which we obtained during the attempts to recrystallize
the red material from the reaction of 2 with phen in CH2Cl2.
ORTEP views of molecules 4a, 4b, and 5 are depicted in
Figures 1-3, respectively; Figure 4 shows the crystal struc-
ture of the cation of 7. Details of the structure determinations
are collected in Table 2, and the bond distances and angles
are summarized in Table 3.
Crystal Structure of [Fe2(CO)6(µ-CF2)(AsMe3)2] (4a
and 4b). In contrast to 3, where a C-II structure type is
found, the presence of two AsMe3 ligands allows the isolation
of the first compounds of type C-I. In the solid state, 4 was
found to be a superposition of the chiral isomers 4a and 4b
with 75 and 25% distributions, and the molecular structures
are depicted in Figures 1 and 2, respectively. The disorder
of the methyl groups at As(2) probably coincides with the
disorder of the CF2 position. The major isomer 4a has
approximately a local molecular C2 axis through C(1) of the
CF2 group and the middle of the Fe-Fe bond; 4b has C1
symmetry. The Fe-Fe distance in 4 amounts to 2.47 Å and
Figure 4. Projection view of the cation of 7 with the labeling scheme
(40% ellipsoids). The hydrogen atoms have been omitted for clarity.
is the shortest one found in the related type I complexes; a
similar short distance is also found in 1.15 It is the same in
5 and apparently not influenced by the number and nature
of the terminal non-CO ligands. When the predominate
isomer, 4a, is considered, the bridging CO(3) ligand, which
is not involved in the disorder, and the other bridging CO-
(2) group form asymmetric bonds to the iron atoms. Both
CO groups have one AsMe3 ligand and one terminal CO in
the trans position. The short Fe-CO distances (1.90 Å) are
directed toward the trans-AsMe3 groups, while the longer
ones (2.04 Å) are opposite to the CO groups. The Fe-As
distances are nearly equal at 2.371 and 2.378 Å, but they
are about 0.07 Å longer than in the mononuclear arsine
complex [(CO)4FeAsMe3].31 The F-C-F angles of 4a and
4b are equal (101°) and identical with that of the starting
complex 2. Along the Fe(1)-Fe(2) connection, the ligands
form approximately three planes. The terminal and bridging
ligands are staggered as in [Fe2(CO)9], and the ligand
(29) Moodley, K. G.; Engel, D. W.; Field, J. S.; Haines, R. J. Polyhedron
1993, 12, 533.
(30) Hitchcock, P. B.; Madden, T. J.; Nixon, J. F. J. Organomet. Chem.
1993, 463, 155.
(31) Legendre, J.-J.; Girard, C.; Huber, M. Bull. Soc. Chim. Fr. 1971, 1998.
9056 Inorganic Chemistry, Vol. 45, No. 22, 2006

Reaction of [Fe2(CO)8(µ-CF2)] with Lewis Bases
Table 2. Experimental Data for the X-ray Diffraction Studies of Complexes 4, 5, 6‚MeC6H5, and 7
4
5
6‚MeC6H5
7
formula
mol wt
cryst syst
space group
a (Å)
C13H18As2F2Fe2O6
569.81
C15H27As3F2Fe2O5
661.83
C62H52Fe2O5P4
1112.68
triclinic
P1h (No. 2)
12.173(2)
12.587(2)
19.775(3)
70.96(1)
71.88(1)
70.66(1)
2631.7(1)
2
C38H28Cl6N6Fe
837.25
orthorhombic
Pbca (No. 61)
14.411(1)
11.368(1)
24.717(1)
90
90
90
4049.2(6)
8
1.869
orthorhombic
Pna21 (No. 33)
14.213(1)
16.597(2)
10.070(1)
90
90
90
2375.4(4)
4
1.851
monoclinic
I2/a (No. 15)
19.185(2)
10.781(1)
18.466(1)
90
103.69(1)
90
3710.9(6)
4
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
vol (×106 pm3)
Z
d
calcd (g/cm3)
1.404
1.499
temp (K)
193
47.2
0.0251
0.0320
193
54.0
0.0479
0.1176
193
7.2
0.0692
0.1496
193
µ(Mo KR) (cm-1
R1 (F0 > 4σF0)a
R2 (all data)
)
0.0419
0.1222
a refinement: SHELXL-97,32 structure solution, direct methods, SHELXS-97.33
arrangements in 4a and 4b are sketched in Charts 4 and 5,
respectively. Each Fe atom is in an approximately octahedral
environment.
carbonyl groups. The As(1)-Fe(1)-As(2) angle is about 11°
larger than that in [(diars)Fe2(CO)7],8 where the five-
membered ring forces the As atoms closer together. Both
the bridging carbonyl groups, CO(1) and CO(2), show
tendencies to form pairwise asymmetric bridges, especially
CO(2), which is located opposite of the long As(2), and tends
nearly toward a semibridging CO group at Fe(1) forming a
long C(2)-Fe(2) distance of 2.161 Å. This is supported by
the different Fe(1)-C(2)-O(2) and Fe(2)-C(2)-O(2) angles
of 152 and 131°, respectively. The geometrical classifications
made earlier11,33,34 coincide with consideration of the CO(1)
ligand as an asymmetric bridging carbonyl group and CO-
(2) as a semibridging one.
Crystal Structure of [Fe2(CO)5(µ-CF2)(AsMe3)3] (5).
Complex 5 represents a further example of the C-I type and
contains three terminal AsMe3 groups making the two Fe
atoms electronically different. The Fe-Fe distance is (2.471
Å) as short as in 4. The Fe atoms and the CF2 group form
a slightly asymmetric triangle with Fe-C bond lengths of
1.978 (Fe(1)) and 1.930 Å (Fe(2)), respectively. The dihedral
angle between the planes Fe2C(1) and Fe2C(3) is 125°; the
other dihedral angles are nearly equal with values of 118
and 117°, respectively. Two Fe-As distances are equal
(2.364 Å), but one of the two Fe-As distances at the same
side (As(2)) is about 0.05 Å longer which may be the result
of packing effects; related Fe-As distances of 2.36 and 2.34
Å were also measured in the [(diars)Fe2(CO)7] complex in
which the chelating ligand, o-phenylenebis(dimethylarsine),
is coordinated at one Fe atom.8 The mean C-F distance of
1.39 Å is appreciably longer than the related distance in 2
(1.36 Å); the same trend that was observed for the CO ligands
is observed here. All Fe-As distances in 5 are about 0.06-
0.11 Å longer than in the mononuclear arsine complex
[(CO)4FeAsMe3] (2.30(3) Å),31 indicating less back-bonding
into the As atoms in the dinuclear complex; a similar trend
is observed with the Fe-P distances in comparing the
[(CO)4FePPh3]32 compounds with 3.15 Along the Fe(1)-Fe-
(2) connection, three planes perpendicular to this can be
defined with terminal, bridging, and terminal ligands, as
depicted in Chart 6 (superposition of the planes 1, 2, and
3); two AsMe3 groups are arranged cis to the CF2 ligand
(plane 1), and the unique AsMe3 group (plane 3) is trans to
the CF2 group and trans to the middle of the other AsMe3
groups in plane 1. The As(1)-Fe(1)-Fe(2) and As(2)-Fe-
(1)-Fe(2) angles are different with values of 125.8 and
115.6°, respectively. The Fe2C(CF2) containing triangle, one
terminal CO group at Fe(1), and the As(3) atom are located
within the non-crystallographic symmetry plane. At Fe(1),
the two AsMe3 groups are located trans to the bridging
The F(1)-C(3)-F(2) angle is more acute than in the
starting complex 2. If the Fe-Fe-interaction is ignored, the
coordination at each Fe atom is nearly octahedral with two
octahedrons sharing one face.
Crystal Structure of [Fe2(µ-dppm)2(CO)5]‚MeC6H5 (6‚
MeC6H5). For the type [Fe2(CO)5(D-D)2] compounds,
crystal structures have been published from compounds with
D-D ) R2P-Y-PR2, where R ) Me, Y ) CH2;6 R ) OEt
Y ) O;35 R ) F, Y ) NEt;9 and R ) Ph, Y ) NH,8 CH2.29,30
From compounds with R ) Ph, Y ) CH2 (as in 6), the
30
solvates 6‚2Me2CO29 and 6‚2MeC6H5 were described,
whereas in our case, the monotoluene solvate 6‚MeC6H5 has
formed. The different numbers and types of solvent mol-
ecules incorporated have some influence on the parameters
of the molecule. Whereas for 6‚2MeC6H5, a crystallographic
mirror plane and an Fe-Fe separation of 2.711 Å were
found,30 no mirror plane and a long Fe-Fe distance of 2.740
Å were measured in 6‚MeC6H5; the other distances and
angles are nearly identical. The 6‚2Me2CO derivative has
the same Fe-Fe separation29 as our results, but all distances
are about 0.03 to 0.06 Å longer, and most of the bond angles
are far from those in 6‚MeC6H5. Within the series of [Fe2-
(CO)5(D-D)2] compounds for 6‚MeC6H5 the largest Fe-
Fe distance is recorded. The structure is also closely related
(33) Colton, R.; McCormick, M. J. Coord. Chem. ReV. 1980, 31, 1.
(34) Cotton, F. A. Prog. Inorg. Chem. 1976, 21, 1.
(35) Cotton, F. A.; Haines, R. J.; Hanson, B. E.; Sekutowski, J. C. Inorg.
Chem. 1978, 17, 2010.
(32) Riley, P. E.; Davis, R. E. Inorg. Chem. 1980, 18, 159.
Inorganic Chemistry, Vol. 45, No. 22, 2006 9057

DelaVarga et al.
Table 3. Selected Bond Distances (Å) and Angles (deg) in 4, 5, 6‚MeC6H5, and 7
4a and 4b
As(1)-Fe(1)
As(1)-C(9)
As(2)-Fe(2)
As(2)-C(121)
As(2)-C(112)
As(2)-C(132)
Fe(1)-C(1)
Fe(1)-C(3)
O(1)-C(1)
2.3782(6)
1.932(3)
2.3713(5)
1.904(5)
1.83(2)
As(1)-C(8)
As(1)-C(10)
As(2)-C(111)
As(2)-C(131)
As(2)-C(122)
Fe(1)-Fe(2)
Fe(1)-C(2)
1.930(3)
1.923(3)
1.950(6)
1.908(6)
1.86(2)
2.4705(6)
1.900(4)
1.798(4)
Fe(1)-C(5)
Fe(2)-C(2)
Fe(2)-C(6)
F(11)-C(1)
O(2)-C(2)
O(4)-C(4)
O(6)-C(6)
F(12)-C(2)
1.775(4)
2.036(3)
1.807(4)
1.375(4)
1.187(5)
1.141(4)
1.140(3)
1.40(1)
Fe(2)-C(1)
2.002(3)
1.903(4)
1.769(4)
1.382(4)
1.175(4)
1.143(4)
1.153(4)
1.30(1)
Fe(2)-C(3)
Fe(2)-C(7)
F(21)-C(1)
O(3)-C(3)
O(5)-C(5)
O(7)-C(7)
F(22)-C(2)
1.96(2)
1.978(3)
2.044(3)
1.18(1)
Fe(1)-C(4)
Fe(1)-As(1)-C(8)
Fe(1)-As(1)-C(10)
C(8)-As(1)-C(10)
Fe(2)-As(2)-C(111)
Fe(2)-As(2)-C(131)
Fe(2)-As(2)-C(122)
C(111)-As(2)-C(121)
C(121)-As(2)-C(131)
C(112)-As(2)-C(132)
As(1)-Fe(1)-Fe(2)
As(1)-Fe(1)-C(2)
As(1)-Fe(1)-C(4)
Fe(2)-Fe(1)-C(1)
Fe(2)-Fe(1)-C(3)
Fe(2)-Fe(1)-C(5)
C(1)-Fe(1)-C(3)
115.86(9)
114.4(1)
102.4(1)
122.1(2)
116.1(2)
114.1(7)
99.9(2)
Fe(1)-As(1)-C(9)
C(8)-As(1)-C(9)
C(9)-As(1)-C(10)
Fe(2)-As(2)-C(121)
Fe(2)-As(2)-C(112)
Fe(2)-As(2)-C(132)
C(111)-As(2)-C(131)
C(112)-As(2)-C(122)
C(122)-As(2)-C(132)
As(1)-Fe(1)-C(1)
As(1)-Fe(1)-C(3)
As(1)-Fe(1)-C(5)
Fe(2)-Fe(1)-C(2)
Fe(2)-Fe(1)-C(4)
C(1)-Fe(1)-C(2)
C(1)-Fe(1)-C(4)
C(2)-Fe(1)-C(3)
C(2)-Fe(1)-C(5)
C(3)-Fe(1)-C(5)
As(2)-Fe(2)-Fe(1)
119.4(1)
101.6(1)
100.4(1)
115.7(2)
121.8(7)
109.4(5)
100.0(3)
103.0(1)
101.1(7)
90.7(1)
85.9(1)
95.3(1)
53.6(1)
121.0(1)
86.2(1)
As(2)-Fe(2)-C(1)
As(2)-Fe(2)-C(3)
As(2)-Fe(2)-C(7)
Fe(1)-Fe(2)-C(2)
Fe(1)-Fe(2)-C(6)
C(1)-Fe(2)-C(2)
C(1)-Fe(2)-C(6)
C(2)-Fe(2)-C(3)
C(2)-Fe(2)-C(7)
C(3)-Fe(2)-C(7)
Fe(1)-C(1)-Fe(2)
Fe(1)-C(1)-F(21)
Fe(2)-C(1)-F(11)
Fe(2)-C(1)-O(1)
Fe(1)-C(2)-Fe(2)
Fe(1)-C(2)-F(12)
Fe(2)-C(2)-O(2)
Fe(2)-C(2)-F(22)
Fe(1)-C(3)-Fe(2)
Fe(2)-C(3)-O(3)
90.74(9)
As(2)-Fe(2)-C(2)
As(2)-Fe(2)-C(6)
Fe(1)-Fe(2)-C(1)
Fe(1)-Fe(2)-C(3)
Fe(1)-Fe(2)-C(7)
C(1)-Fe(2)-C(3)
C(1)-Fe(2)-C(7)
C(2)-Fe(2)-C(6)
C(3)-Fe(2)-C(6)
C(6)-Fe(2)-C(7)
Fe(1)-C(1)-F(11)
Fe(1)-C(1)-O(1)
Fe(2)-C(1)-F(21)
F(11)-C(1)-F(21)
Fe(1)-C(2)-O(2)
Fe(1)-C(2)-F(22)
Fe(2)-C(2)-F(12)
F(12)-C(2)-F(22)
Fe(1)-C(3)-O(3)
87.30(9)
173.5(1)
95.1(1)
48.7(1)
120.4(1)
82.0(1)
171.0(1)
86.4(1)
171.8(2)
90.8(2)
76.7(1)
119.4(2)
118.4(2)
140.9(6)
77.7(1)
116.0(6)
136.2(3)
122.4(6)
77.4(1)
144.9(3)
91.8(1)
51.19(9)
53.8(1)
123.9(1)
86.5(1)
90.1(2)
89.5(1)
90.1(1)
98.3(2)
122.1(2)
142.2(6)
118.8(2)
101.6(3)
146.1(3)
121.5(6)
118.2(5)
101.4(9)
137.7(3)
99.4(3)
105.0(9)
118.8(4)
171.9(1)
92.0(1)
52.1(1)
48.75(9)
125.5(1)
83.4(1)
89.8(2)
90.3(1)
172.8(1)
86.3(1)
92.2(2)
173.2(2)
120.07(2)
C(1)-Fe(1)-C(5)
C(2)-Fe(1)-C(4)
C(3)-Fe(1)-C(4)
90.1(1)
96.6(2)
C(4)-Fe(1)-C(5)
5
As(1)-Fe(1)
As(1)-C(8)
As(2)-Fe(1)
As(2)-C(11)
As(3)-Fe(2)
As(3)-C(14)
Fe(1)-Fe(2)
Fe(1)-C(2)
2.363(1)
1.93(1)
2.413(1)
1.95(1)
2.364(1)
1.93(1)
2.471(2)
1.83(1)
As(1)-C(7)
As(1)-C(9)
As(2)-C(10)
As(2)-C(12)
As(3)-C(13)
As(3)-C(15)
Fe(1)-C(1)
Fe(1)-C(3)
1.92(1)
1.92(1)
1.94(1)
1.93(1)
1.936(8)
1.936(9)
2.005(9)
1.978(8)
Fe(1)-C(4)
Fe(2)-C(2)
Fe(2)-C(5)
F(1)-C(3)
O(1)-C(1)
O(4)-C(4)
O(6)-C(6)
1.79(1)
Fe(2)-C(1)
Fe(2)-C(3)
Fe(2)-C(6)
F(2)-C(3)
O(2)-C(2)
O(5)-C(5)
1.938(9)
1.930(8)
1.73(1)
1.391(9)
1.19(1)
1.17(1)
2.161(9)
1.753(8)
1.388(8)
1.18(1)
1.14(1)
1.20(1)
Fe(1)-As(1)-C(7)
Fe(1)-As(1)-C(9)
C(7)-As(1)-C(9)
Fe(1)-As(2)-C(10)
Fe(1)-As(2)-C(12)
C(10)-As(2)-C(12)
Fe(2)-As(3)-C(13)
Fe(2)-As(3)-C(15)
C(13)-As(3)-C(15)
As(1)-Fe(1)-As(2)
As(1)-Fe(1)-C(1)
As(1)-Fe(1)-C(3)
As(2)-Fe(1)-Fe(2)
As(2)-Fe(1)-C(2)
As(2)-Fe(1)-C(4)
Fe(2)-Fe(1)-C(2)
Fe(2)-Fe(1)-C(4)
C(1)-Fe(1)-C(3)
116.9(4)
120.3(3)
101.3(6)
118.3(4)
122.8(4)
96.7(6)
114.8(2)
117.6(3)
102.6(4)
96.75(5)
174.5(3)
89.3(2)
115.58(5)
172.8(3)
91.6(3)
58.1(3)
123.5(3)
85.2(3)
Fe(1)-As(1)-C(8)
C(7)-As(1)-C(8)
C(8)-As(1)-C(9)
Fe(1)-As(2)-C(11)
C(10)-As(2)-C(11)
C(11)-As(2)-C(12)
Fe(2)-As(3)-C(14)
C(13)-As(3)-C(14)
C(14)-As(3)-C(15)
As(1)-Fe(1)-Fe(2)
As(1)-Fe(1)-C(2)
As(1)-Fe(1)-C(4)
As(2)-Fe(1)-C(1)
As(2)-Fe(1)-C(3)
Fe(2)-Fe(1)-C(1)
Fe(2)-Fe(1)-C(3)
C(1)-Fe(1)-C(2)
C(1)-Fe(1)-C(4)
115.9(3)
99.8(5)
99.2(5)
112.6(4)
99.9(5)
103.0(7)
117.6(3)
100.9(4)
100.7(4)
125.8(4)
90.2(3)
95.8(3)
83.2(2)
91.9(2)
50.0(3)
49.9(2)
89.7(4)
89.6(4)
C(2)-Fe(1)-C(3)
C(3)-Fe(1)-C(4)
As(3)-Fe(2)-C(1)
As(3)-Fe(2)-C(3)
As(3)-Fe(2)-C(6)
Fe(1)-Fe(2)-C(2)
Fe(1)-Fe(2)-C(5)
C(1)-Fe(2)-C(2)
C(1)-Fe(2)-C(5)
C(2)-Fe(2)-C(3)
C(2)-Fe(2)-C(6)
C(3)-Fe(2)-C(6)
Fe(1)-C(1)-Fe(2)
Fe(2)-C(1)-O(1)
Fe(1)-C(2)-O(2)
Fe(1)-C(3)-Fe(2)
Fe(1)-C(3)-F(2)
Fe(2)-C(3)-F(2)
86.1(4)
173.4(4)
85.0(3)
166.6(2)
92.3(3)
45.9(3)
125.5(3)
82.5(3)
92.4(4)
78.8(3)
86.9(4)
92.1(4)
77.6(3)
143.7(8)
152.3(9)
78.4(3)
120.6(5)
118.2(5)
C(2)-Fe(1)-C(4)
As(3)-Fe(2)-Fe(1)
As(3)-Fe(2)-C(2)
As(3)-Fe(2)-C(5)
Fe(1)-Fe(2)-C(1)
Fe(1)-Fe(2)-C(3)
Fe(1)-Fe(2)-C(6)
C(1)-Fe(2)-C(3)
C(1)-Fe(2)-C(6)
C(2)-Fe(2)-C(5)
C(3)-Fe(2)-C(5)
C(5)-Fe(2)-C(6)
Fe(1)-C(1)-O(1)
Fe(1)-C(2)-Fe(2)
Fe(2)-C(2)-O(2)
Fe(1)-C(3)-F(1)
Fe(2)-C(3)-F(1)
F(1)-C(3)-F(2)
89.8(4)
115.57(6)
88.8(3)
97.8(3)
52.4(3)
51.7(2)
120.4(4)
88.4(4)
169.1(4)
171.3(4)
94.1(4)
98.5(5)
138.6(8)
76.0(2)
131.1(8)
119.8(5)
121.1(5)
99.9(6)
6‚MeC6H5
Fe(1)-Fe(2)
Fe(1)-P(1)
Fe(1)-C(1)
Fe(1)-C(3)
2.740(1)
2.197(2)
1.972(7)
1.784(8)
Fe(1)-P(3)
Fe(1)-C(2)
Fe(2)-P(2)
Fe(2)-C(1)
2.218(2)
1.723(7)
2.227(2)
1.957(6)
Fe(2)-P(4)
Fe(2)-C(4)
O(1)-C(1)
2.223(2)
1.714(7)
1.218(7)
Fe(2)-C(5)
P(4)-C(31)
P(3)-C(31)
1.783(7)
1.833(7)
1.831(7)
P(1)-Fe(1)-P(3)
P(1)-Fe(1)-C(2)
P(3)-Fe(1)-C(1)
P(3)-Fe(1)-C(3)
C(1)-Fe(1)-C(3)
P(2)-Fe(2)-P(4)
P(2)-Fe(2)-C(4)
P(4)-Fe(2)-C(1)
170.3(6)
86.8(3)
96.6(2)
88.7(3)
140.1(3)
170.89(9)
85.2(3)
90.8(2)
P(1)-Fe(1)-C(1)
P(1)-Fe(1)-C(3)
P(3)-Fe(1)-C(2)
C(1)-Fe(1)-C(2)
C(2)-Fe(1)-C(3)
P(2)-Fe(2)-C(1)
P(2)-Fe(2)-C(5)
P(4)-Fe(2)-C(4)
91.4(3)
88.5(3)
86.0(3)
105.5(3)
114.3(4)
88.2(2)
95.2(2)
86.6(3)
P(4)-Fe(2)-C(5)
C(1)-Fe(2)-C(5)
Fe(1)-P(1)-C(6)
Fe(2)-P(2)-C(6)
Fe(1)-C(1)-Fe(2)
Fe(2)-C(1)-O(1)
P(3)-C(31)-P(4)
91.8(2)
136.2(3)
113.7(2)
113.8(2)
88.4(3)
C(1)-Fe(2)-C(4)
C(4)-Fe(2)-C(5)
Fe(1)-P(3)-C(31)
Fe(2)-P(4)-C(31)
Fe(1)-C(1)-O(1)
P(1)-C(6)-P(2)
109.8(3)
114.0(4)
112.6(2)
111.0(2)
136.3(5)
114.4(3)
135.2(6)
109.0(4)
9058 Inorganic Chemistry, Vol. 45, No. 22, 2006

Reaction of [Fe2(CO)8(µ-CF2)] with Lewis Bases
Table 3. Continued
7
Fe(1)-N(1)
Fe(1)-N(3)
1.979(2)
1.972(2)
Fe(1)-N(2)
N(2)-C(11)
1.987(2)
1.365(3)
N(1)-C(12)
C(11)-C(12)
1.366(3)
1.423(3)
N(3)-C(18)
1.366(3)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-N(1a)
N(1)-Fe(1)-N(1a)
N(2)-Fe(1)-N(1a)
82.45(7)
N(1)-Fe(1)-N(3)
N(1)-Fe(1)-N(2a)
N(2)-Fe(1)-N(3)
N(2)-Fe(1)-N(2a)
92.24(7)
N(2)-Fe(1)-N(3a)
Fe(1)-N(1)-C(12)
Fe(1)-N(2)-C(10)
Fe(1)-N(3)-C(18)
93.77(7)
112.6(1)
130.4(2)
113.2(1)
N(3)-Fe(1)-N(3a)
Fe(1)-N(1)-C(1)
Fe(1)-N(2)-C(11)
82.60(7)
130.4(2)
112.5(1)
172.65(8)
93.28(7)
92.35(7)
92.35(7)
173.41(7)
90.37(7)
Chart 4. Arrangement of the Two AsMe3 Ligands (As) in 4a Looking
down the Fe(1)-Fe(2) Connection (dotted line)
dication lies on a C2 axis and is shown in Figure 4. The
planar rings Fe(1)-N(1)-C(12)-C(11)-N(2) and Fe(1)-
N(3)-C(18)-C(18a)-N(3a) form an dihedral angle of 84°,
and the N-Fe-N angles within the rings are 82.5°. The
mean Fe(1)-N distance is 1.979(2) Å and is in a normal
range.
Theoretical Studies. The Bader’s atoms in molecules
(AIM)36-38 topological analysis of the molecular electronic
density (obtained from ab initio calculations) has been used
to study the bonding and structure properties of diiron
nonacarbonyl39 and some of its derivatives,12 especially
focusing on the Fe-Fe bond. The key point of Bader’s theory
is that a chemical bond must be characterized by the
existence of a point on the internuclear bondpath line where
the Hessian matrix of the total electronic density has one
positive and two negative eigenvalues: this point is called a
bond critical point (BCP), and we can imagine it as a
bottleneck of electron density between the two bonded atoms.
The values of the density, together with its Laplacian and
the bond ellipticity (F, 32F and ꢀ respectively) at these points,
give indications on how the bonding density is distributed
along the internuclear line and aids in the bond characteriza-
tion. Nevertheless, most works fail to find a BCP on the
central part of the line joining the two iron nuclei; on the
contrary, electronic density depletions corresponding to cage
critical points (CCP)39 or ring critical points (RCP)12 are
found at those regions. These findings suggest that the
existence of a direct iron-iron bond through overlap over
the internuclear line predicted by the 18-electron rule in this
kind of complex11 is doubtful and that dinuclear integrity is
kept exclusively by the bridging carbonyl ligands. From that
viewpoint, such dinuclear complexes consist of two iron
coordination polyhedra sharing one face or one edge (see
Chart 7).
Chart 5. Arrangement of the Two AsMe3 Ligands (As) in 4b Looking
down the Fe(1)-Fe(2) Connection (dotted line)
Chart 6. Arrangement of the Three AsMe3 Ligands (As) in 5 Looking
down the Fe(1)-Fe(2) Connection (dotted line)
to that with R ) Me (Y ) CH2),6 but the Fe-Fe distance is
0.02 Å longer than in the methyl derivative which causes
also elongation of the Fe(1)-C(1), Fe(2)-C(1), and C(1)-
O(1) bonds lengths at the single bridging carbonyl group;
similarly, this effect is observed concerning the Fe-P
distances.
If only one chelating ligand is present, as in [Fe2(CO)7(Ph2-
PCH2PPh2)],5 the Fe-Fe distance is about 0.03 Å shorter,
although no further bridging ligand forces the atoms together.
Compared to this, the mean Fe-CO(terminal) distances in
6‚MeC6H5 are shorter, indicating enhanced π-back-bonding
to the remaining CO groups in the presence of four weaker
acceptor atoms. If the terminal carbonyl groups are consid-
ered to be inline with the Fe-Fe bond, they are more
involved in back-bonding (Fe-C ) 1.72 Å, C-O ) 1.20
Å) than those perpendicular to the Fe-Fe bond (Fe-C )
1.78 Å, C-O ) 1.18 Å).
Electron localization function analysis of the complete
wave functions on [Fe2(CO)9] supports this interpretation.40
Nevertheless, MO studies are not conclusive in this
aspect,2a,3a,41-43 and an interesting controversy arises about
whether the Fe-Fe bond exists. The new compounds 4 and
(36) Bader, R. F. W. Atoms in MoleculessA Quantum Theory; Oxford
University Press: London, 1990.
(37) Bader, R. F. W.; Johnson, S.; Tang, T. H.; Popelier, P. L. A. J. Phys.
Chem. 1996, 100, 15398.
(38) Bader, R. F. W. Coord. Chem. ReV. 2000, 197, 71.
(39) Bo, C.; Sarasa, J. P.; Poblet, J. M. J. Phys. Chem. 1993, 97, 6362.
(40) Kraupp, M. Chem. Ber. 1996, 129, 527.
(41) Jang, J. H.; Lee, J. G.; Lee, H.; Xie, Y.; Schaeffer, H. F. J. Phys.
Chem. A 1998, 102, 5298.
(42) Salzmann, R.; Kraupp, M.; McMahon, M. T.; Oldfield, E. J. J. Am.
Chem. Soc. 1998, 120, 4771.
(43) Hunstock, E.; Mealli, C.; Calahorda, M. J.; Reinhold, J. Inorg. Chem.
1999, 38, 5053.
Crystal Structure of [Fe(phen)3]Cl2 (7). The red com-
pound crystallizes with two molecules of CH2Cl2. These and
the Cl- ions are connected via very weak hydrogen bonds
with a Cl‚‚‚C contact of 3.437(4) Å. No further contacts exist
between the cation and the two anions. Complex 7 crystal-
lizes in the centrosymmetric space group I2/a, and the
Inorganic Chemistry, Vol. 45, No. 22, 2006 9059

DelaVarga et al.
Table 4. Ranges of Values of the Electronic Density (eÅ-3), Laplacian
and Ellipticity at the BCPs for Non-bridging Ligands' bonds in
Compounds 4a and 5
Table 5. Values of the Electronic Density (e Å-3), Laplacian, and
Ellipticity at the BCPs for Bridging Ligand Bonds in Compounds 4a
and 5
2
F
∇ F
ꢀ
4a
5
C-H
0.304 ( 0.003 -1.36 ( 0.02
0.237 ( 0.005 -0.07 ( 0.03
0.141 ( 0.004 -0.08 ( 0.01
0.068 ( 0.004 +0.13 ( 0.01
<0.01
0.24 ( 0.01
bonda
Fe(X)-CF2
CF2-Fe(Y)
Fe(X)-CO(A)
F
32F
ꢀ
F
32F
ꢀ
C-F
0.113 +0.237 0.035 0.127 +0.238 0.031
0.109 +0.214 0.043 0.114 +0.237 0.024
0.123 +0.305 0.070 0.113 +0.288 0.053
C-As
Fe-As
<0.03
0.05 ( 0.02
0.08 ( 0.003
Fe-CO (terminal)
0.15 ( 0.02
0.47 ( 0.01
+0.63 ( 0.03
+0.46 ( 0.07 e 0.03
CO(A)-Fe(Y) 0.094 +0.205 0.029 0.100 +0.223 0.051
C-O (terminal)a
Fe(X)-CO(B)
0.092 +0.205 0.033 0.073 +0.150 0.029
a Because of their special characteristics, terminal carbonyls CO(5) and
CO(6) belonging to 5 have been moved to Table 5 and are not considered
in the intervals.
CO(B)-Fe(Y) 0.122 +0.302 0.068 0.141 +0.397 0.102
C-O (A)
C-O (B)
C(5)-O(5) (terminal)
C(6)-O(6) (terminal)
0.425 +0.198 0.022 0.428 +0.240 0.029
0.436 +0.288 0.020 0.419 +0.120 0.018
0.439 +0.206 0.003
0.413 -0.028 0.002
a X ) 1 for 4a and 2 for 5. Y ) 2 for 4a and 1 for 5. A ) 2 for 4a and
1 for 5. B ) 3 for 4a and 2 for 5.
Chart 7. Bonding Schemes for Diiron Carbonyl Complexes Arising
from the 18-Electron Rule and AIM Calculations
depletion of the electronic density on the internuclear line
where BCPs are placed.
As can be seen in Tables 4 and 5, C-O BCPs in carbonyl
ligands show the highest-electronic density values, which
are indicative of the strength of the triple bonds. Density
and Laplacian values corresponding to the bridging BCPs
(see Table 5) are less intense than those of the terminal ones
(see Table 4). This bond weakening is attributable to both
the loss of internal bond density to establish two σ-donations
toward the bridged iron atoms, and the double back-donations
from the two metals to the CO antibonding orbitals. For the
ellipticity, terminal CO BCPs have values below 0.003,
indicating a cylindrical distribution of the electronic density
around the bondpath (the addition of one σ- and two
perpendicular π-bond densities). For the bridging carbonyls,
ellipticity raises 1 order of magnitude, thus indicating a
dominant double-bond character caused by the preferential
back-donation to the antibonding orbital inside the Fe-CO-
Fe plane.
As noted before, terminal CO(6) and CO(5) carbonyls
belonging to 5 do not follow the preceding trends: although
their BCPs have extremely low ellipticities, the small elec-
tronic density, Laplacian values, and crystallographic bond
distances are comparable to those of bridging carbonyls, so
they have been included with them in Table 5. CO(6) has
the most anomalous triple-bond distances, which could be
related to its involvement in an intermolecular O(6)‚‚‚H(73)-
C(7) weak hydrogen bond (2.377 Å, 147.4(7)°) with the (x,
y, z - 1) neighboring moiety. Because electronic density
calculations have been performed on isolated molecules, they
cannot properly account for the effect of this intermolecular
interaction.
5 offer a good opportunity to investigate the bulk electronic
density of diiron carbonyl derivatives with similar external
structures but with one different bridging ligand in their core.
The AIM analyses of 4a and 5 show the common trends
found for diiron carbonyl derivatives.12 The BCP electronic
density parameters for the C-H, C-F, and C-As bonds
(see Table 4) are closely similar in both compounds and lie
inside the normal ranges described in the literature for
classical bonds. All of them show negative Laplacian values,
which indicate a local electronic density concentration at the
BCPs, as expected for bonds with a dominant σ-overlap. The
C-H BCPs are that of highest-electronic density values and
the most-negative Laplacians, whereas the C-As BCPs have
small values, corresponding to strong and weak bonds
respectively; their small ellipticities indicate a dominant
σ-overlap. Comparatively, the C-F BCPs of the bridging
difluoromethylenes show very high ellipticities, being indica-
tive of significant π-bond character: this confirms the good
efficiency of these heteroallylic bridges as π-acceptors, as
stated in previous works.15
If we focus on the iron atoms coordination environments,
the Fe-As BCPs have the weakest-electronic densities,
pointing to some lability of the arsine ligands. The Fe-C
BCPs have higher densities, similar to those found in related
complexes,12 and they decrease in the order Fe-CO (termi-
nal) > Fe-CF2 (bridging) ≈ Fe-CO (bridging). The latter
comparison confirms the good efficiency of the difluoro-
methylene fragment as a bridging ligand.15
With the only exception of the C(6)-O(6) bond in 5, all
of the Fe-As, Fe-C, and CO BCPs in both compounds
show positive Laplacian values (see Tables 4 and 5), indicat-
ing that they are placed in a local density depletion. This
distinctive characteristic was detected in a previous work12
for bonds involved in a π-back-bonding mechanism: the
non-negligible component of the orbital overlap that lies
outside of the internuclear line could explain the local
A more detailed inspection of the electronic density inside
the dinuclear cores in 4a and 5 requires the use of a common
9060 Inorganic Chemistry, Vol. 45, No. 22, 2006

Reaction of [Fe2(CO)8(µ-CF2)] with Lewis Bases
Chart 8. Alternative Views for Complexes 4a and 5 Where Strong
and Weak Bridging Bonds Are Equally Oriented, Leading to a Common
Labelling Scheme for Table 5
labeling scheme. For both complexes, each bridging ligand
is connected to the two iron atoms through nonequal bonds,
one shorter than the other. Consequently, molecules must
be reoriented in such a way that strong and weak bringing
branches coincide to compare them properly: this has been
done as indicated in Chart 8. This labeling scheme is used
in Table 5.
Figure 5. Contour plot for the electronic density of the CF2 bridge in
compound 4a across the Fe(1)-C(1)-Fe(2) plane. External lines step 0.01
e Å-3 and involve the weak bridging bonds. Internal lines step 0.10 e Å-3
and correspond to strong bonds and atomic cores. Terminal carbonyls are
not in-plane and may appear distorted.
The core of 4a contains the most-symmetrical bridging
ligand, the CF2 moiety. This group binds to both irons
through two BCPs which densities are less than 5% different.
On the contrary, their two bridging carbonyls are clearly
asymmetric, as the BCP densities at both sides differ more
than 30%. Each iron atom is connected to the two CO bridges
through one high-density and one low-density BCP. It is
worth noting that the arsine ligands are placed trans to the
strong bridging bonds (see Chart 4), so they receive little
back-bonding density as deduced from their BCP properties.
almost identical electronic properties (F ) 0.049 au, 32F )
+0.13 au), indicating low density and moderate charge
depletion. Although the relations between the number of
critical points computed for both molecules satisfy the Hopf-
Poincare´ rule, (n attractors) - (n + 1 BPCs) + 2 RCPs -
0 CCPs ) 1 (with n ) 43 for 4a and n ) 54 for 5), they are
not congruent with the bondpath topology, so a third RCP
and a CCP must be present in both.
The core of 5 is quite similar, although it has a less
symmetrical CF2 bridge (BCP densities differ by 11%) with
two different ligands in their trans positions. CO(1) is the
less asymmetrical bridging carbonyl, as its two BCP densities
differ only by 13%; the densest bondpath is connected to
Fe(2) and its trans position is occupied by the anomalous
terminal carbonyl CO(6). Conversely, the CO(2) ligand is
the most asymmetrical bridging carbonyl: the ratio between
its two BCP densities approaches 2:1, thus resulting in a
semibridging carbonyl. Fe(2)-CO(2) is the weakest bridging
bond, which has the second anomalous terminal carbonyl
CO(5) in a trans position (see Chart 6). It can be guessed
that Fe(2) spends little electronic density to establish the very
weak bridging bond with CO(2), so it can use the surplus to
reinforce the bonds with the terminal CO(5) ligand through
supplementary back-bonding donation. This would cause the
weakening of the internal C-O bonds with conservation of
the low ellipticity.
The contour maps of electronic density shown in Figures
5 and 6 for complex 4a (they are very similar for 5) illustrate
how the core center consists of a region with small and short-
ranged density values. The analysis of the Laplacian (see
Figure 7) shows continuously positive values across the Fe-
Fe line for the outer shell of the metals, reaching a (3, +3)
critical point (a minimum of charge depletion with 32F )
+0.121 au and F ) 0.049 au) close to the core center and
inside a region of highly uniform values. Consequently, it
is highly probable that both the missed third RCP and CCP
would be closely located, together with the two detected
RCPs, inside a zone of weak and homogeneous density and
Laplacian. As the four expected CPs would be feebly
distinguishable, it is reasonable that gradient search methods
fail to fix the two missing ones.
In summary, the AIM analysis of the complexes indicates
that there is no direct σ-bonding interaction between the two
iron atoms inside the dinuclear complexes. This supports the
leading rule of the CO and CF2 bridges in keeping the
dinuclear integrity found from MO analysis in similar
compounds.15 Nevertheless, this analysis does not exclude
the presence of a direct π-overlap between the two metals,
for which no density along the Fe-Fe line is necessary. As
its density would be superimposed to that of the bonds with
carbonyl and difluoromethylene bridges, its existence would
be very difficult to characterize from electronic density
analysis.
For both cores, six BCPs connecting the iron atoms and
the bridging ligands have been found. Their bondpath
connectivities clearly define a closed Fe2C3 structure and
three different Fe2C2 four-membered rings. This electronic
topology should imply the presence of one cage critical point
(CCP) and three ring critical points (RCPs) close to the
molecular center. Nevertheless, calculations are unable to
find all of them: only two very close ring critical points
(0.3 Å apart) are found in that region for 4a and 5, with
Inorganic Chemistry, Vol. 45, No. 22, 2006 9061

DelaVarga et al.
station. The 6-3111+G basis set was applied for the iron
centers, whereas for the rest of the atoms, the 6-311G* basis
set was used. Wave function files were treated with the
AIMPAC48 suite of programs, modified to account for the
input size. Electronic density and Laplacian values were
analyzed using the standard built-in parameters. Graphical
representations were performed by means of the MOLDEN
software.49
Conclusion
The replacement of one bridging CO ligand in [Fe2(CO)9]
by the CF2 ligand has not only a dramatic influence on the
structure but also on the reactivity of the resulting complex
2 toward the usual donor ligands. The mechanism of the
reaction of 2 with donor ligands is not yet understood and
seems to be very complicated. One reason for the different
manner of the reaction may be that [Fe2(CO)9] is easily
degraded in solution into [Fe(CO)4] and [Fe(CO)5] which
represent the real reaction partners in substitution processes.
Rapid reaction of the 16-electron fragment followed by
reaction with [Fe(CO)5] or a further [Fe(CO)4] species
probably is a key step for the formation of all [Fe2(CO)x-
(D)y] or [Fe2(CO)x(D-D)y] complexes or even cluster
compounds. A related splitting of 2 into [Fe(CO)4] and [Fe-
(CO)4CF2] is probably less favorable because of the stronger
bond of the CF2 ligand to both iron atoms and the tendency
of the latter fragment to dimerize with loss of CO to give
[Fe2(CO)7(CF2)2] (1). However, 1 could not be isolated in
any of the runs described here. This is a strong argument
against such a splitting. One strategy may be in stabilization
of a mononuclear CF2 containing fragment or a [Fe2(CO)x-
(CF2)(D)y] species by addition of stronger donor ligands
containing more bulky substituents at the donor atoms. The
reason that the disubstituted product in the case of AsMe3
forms a type C-I species (as in 4) and in the case of PPh3 a
type C-II species (as in 3) is as yet unclear: one explanation
may be that the bulkiness of the phenyl rings may cause the
iron atoms to separate more than with the smaller methyl
groups of AsMe3. However, electronic reasons cannot be
excluded, and further studies are to be done.
Figure 6. Contour plots for the electronic density of the carbonyl bridges
in compound 4a across the Fe(1)-C(2)-Fe(2) (upper half) and Fe(1)-
C(3)-Fe(2) (lower half) planes. External lines step 0.01 e Å-3 and involve
the weak bridging bonds. Internal lines step 0.10 e Å-3 and correspond to
strong bonds and atomic cores. Oxygen atoms are not in-plane and may
appear distorted.
Although we have found the shortest Fe-Fe distances of
2.47 Å in 4 and 5, which are derived from the [Fe2(CO)9]
structure by replacing bridging and terminal CO groups by
other two electron donors, a direct Fe-Fe σ-bond is not
Figure 7. Contour plot of the Laplacian of the electronic density (step
0.01 au) for the internuclear Fe-Fe line in compound 4a across the
Fe(1)-C(1)-Fe(2) plane. Continuous and dashed lines correspond to
positive and negative values, respectively. Terminal carbonyls are not in-
plane and may appear distorted.
(47) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R.
L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara,
A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B. G.;
Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.; Replogle,
E. S.; Pople, J. A. Gaussian 98, revision A.7; Gaussian, Inc.:
Pittsburgh, PA, 1998.
Computational Details. DFT-B3LYP44-46 single-point
calculations were run over the crystallographic geometry
(with no optimization) of the compounds 4a (atoms with
occupancy factor 0.25 or less were excluded) and 5 with
the Gaussian 98 code47 on an IBM RS/6000 3AT work-
(48) Biegler-Konig, F. W.; Bader, R. F. W.; Tang, T. J. Comput. Chem.
1982, 3, 317.
(49) Schaftenaar, G. MOLDEN, A package for displaying molecular density;
CMB1, University of Nijmegen: Nijmegen, The Netherlands, 1991.
(44) Kohn, W.; Sham, L. J. Phys. ReV. 1965, 140, A1133.
(45) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(46) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B 1982, 37, 785.
9062 Inorganic Chemistry, Vol. 45, No. 22, 2006

Reaction of [Fe2(CO)8(µ-CF2)] with Lewis Bases
as containing [Fe2(µ-CF2)(CO)6(AsMe3)2] (4) by its IR spectrum.
The solution was filtered, concentrated, and layered with n-pentane.
A mixture of [Fe2(µ-CF2)(CO)6(AsMe3)2] (4) and [Fe2(µ-CF2)(CO)5-
(AsMe3)3] (5) was obtained, and the crystals were separated
mechanically. Yield for 4: 80 mg (0.14 mmol, 16%). Analyses:
H, 2.89 (3.18); C, 26.11 (27.40)%. Yield for 5: 55 mg (0.08 mmol,
9%). Analyses: H, 4.30 (4.11); C, 26.38 (27.20)%. The IR spectra
(Nujol mull) of 4 and 5 are collected in Table 1. Further efforts to
manipulate the precipitate resulted in insoluble decomposition
products being obtained. The solubility of 4 and 5 is low in common
solvents.
operative as shown by AIM calculations; however, the
description of this bond with a π-interaction seems more
realistic and is supported by the calculations and the line
drawn between the two metals may be interpreted in this
sense.
Experimental Section
General Considerations. All operations were carried out under
an argon atmosphere in dried and degassed solvents using Schlenk
techniques. IR spectra were run on a Nicolet 510 spectrometer. 19
F
NMR and 31P NMR spectra were recorded on a Bruker AC 300
instrument using CFCl3 and H3PO4 (0.00 ppm) as the external
standard. Elemental analyses were performed by the analytical
service of the Fachbereich Chemie der Universita¨t Marburg
(Germany). Although crystalline samples packed under Ar were
provided, unsatisfactory results were obtained because of the
incomplete combustion despite the wide range of catalyzers assayed.
The starting complex 2 has been prepared according to a published
i
Reaction of 2 with AsPr3 . A solution of 2 (320 mg, 0.83 mmol)
i
in ether was layered with a solution of excess AsPr3 and allowed
to react for several hours until the signal at 49.8 ppm in the 19F
NMR of 2 disappeared and one signal at 42 ppm appeared. The
majority of the obtained product precipitates in the reaction mixture.
Further efforts to manipulate the solid resulted in insoluble decom-
position products being obtained. IR (Nujol mull) of the precipi-
tate: 2042 m, 2010 w, 1986 w, 1966 m, 1931 vs, 1862 s cm-1
.
i
procedure.15 AsMe3 and AsPr3 were prepared by known proce-
Reaction of 2 with Ph2PCH2PPh2 (dppm). An equimolar
mixture of 2 (320 mg, 0.84 mmol) and dppm (440 mg, 0.84 mmol)
in toluene was stirred for several hours at 50 °C. The mixture was
filtered off and evaporated to dryness. The residue was redissolved
with toluene and layered with n-pentane. After several recrystalli-
zations from THF/n-pentane, some red crystals of [Fe2(µ-dppm)2-
(CO)5]‚MeC6H5 (6‚MeC6H5) were isolated (yield below 5%). IR
(Nujol mull): 2025 w, 1987 w, 1923 m, 1901 s, 1873 s, 1854 s,
1682 s, 1603 w, 1588 w, 1574 w, 1495 w, 1485 m, 1435 s, 1366
m, 1333 w, 1310 w, 1277 w, 1190 w, 1161 w, 1127 w, 1094 s,
1082 w, 1001 w, 789 s, 764 m, 735 s, 692 s, 625 s, 592 m, 565 m,
515 s, 490 s cm-1. Analyses: H, 4.48 (4.71); C, 65.90 (66.92)%.
Reaction of 2 with Ph2PCH2CH2PPh2 (dppe). A solution of
dppe (460 mg, 0.85 mmol) in toluene and TMNO (1.70 mmol)
were added to a solution of 2 (330 mg, 0.85 mmol) in toluene. The
mixture was stirred at room temperature and allowed to react for
several hours until the 19F and 31P NMR remained unchanged. The
solution was filtered off and evaporated to dryness. Effort to
recrystallize the residue gave decomposition products. 19F NMR
(toluene): δ 35. 31P NMR: δ 96. IR (Nujol mull): 2046 m, 2005
dures,50 as were the chelating ligands Ph2PCH2PPh2 (dppm) and
Ph2P(CH2)2PPh2 (dppe).51 The ligands bpy and phen were com-
mercially available; anhydrous trimethylaminoxid (TMNO) was
obtained from Aldrich as the dihydrate and dehydrated by vacuum
sublimation.
Reaction of 2 with bpy. A solution of 2,2′-bpy (266 mg, 0.95
mmol) in THF and a suspension of TMNO (130 mg, 1.70 mmol)
were added to a precooled solution of 2 (330 mg, 0.84 mmol) in
THF at -25 °C. The mixture was stirred for several hours (until
the 19F NMR remained unchanged), during that time a red-brown
precipitate formed which then was filtered off and evaporated to
dryness. Although several routes to recrystallize the solid were tried
using THF, toluene, hexane, and n-pentane, no crystals suitable
for an X-ray analysis were obtained. IR (Nujol mull): 2060 m, sh
1971 vs, 1930 vs, 1911 vs, 1763 vw, 1089 vw, 1039 w cm-1. The
remaining solution showed a 19F NMR signal at 9.70 ppm.
Reaction of 2 with phen. A solution of phen (200 mg, 1.10
mmol) in THF and a suspension of TMNO (173 mg, 2.30 mmol)
were added to a precooled solution of 2 (440 mg, 1.15 mmol) in
THF at -25 °C. The mixture was stirred for several hours (until
the 19F NMR remained unchanged) and then filtered off and
evaporated to dryness. As with the bpy reaction product, no crystals
were obtained. For the solid, IR (KBr): 2021 s, 1971 vs, 1930 vs,
1905 vs, 1768 vw, 1038 m cm-1. For the solution, 19F NMR: 9.50
ppm. The recrystallization of the solid in CH2Cl2 resulted in red
crystals of [Fe(phen)3]Cl2 (7) being obtained in about a 2% yield.
IR (Nujol mull): 1599 w, 1574 w, 1512 w, 1425 m, 1343 w, 1289
s, 1975 vs, 1887 m, 1831 w, 1789 w, 1018 m, 952 m cm-1
.
Acknowledgment. We thank the Deutsche Forschungs-
gemeinschaft for financial support. We are also grateful to the
Fonds der Chemischen Industrie, Frankfurt/Main, Germany,
and the Max-Planck-Society, Munich, Germany, for financial
support. M.D.V. was partially funded by scholarship from
the Universitat de Barcelona. M.D.V. and R.C. thank the
Ministerio de Education y Ciencia for financial support
(Grants BQU2003/00539 and CTQ2005-08459-C02-01,
respectively).
w, 1223 w, 1138 m, 1094 m, 851 s, 804 w, 723 s, 692 w cm-1
.
During recrystallization of the solid in THF/n-pentane, the product
finally decomposes, and [Fe(CO)3(phen)] was obtained and identi-
fied by its IR spectrum.12
Reaction of 2 with AsMe3. A solution of 2 (345 mg, 0.87 mmol)
in ether was layered with a solution of excess AsMe3, and the
mixture was allowed to react for several hours until the signal at
49.8 ppm in the 19F NMR of 2 disappeared. Immediately the
formation of a precipitate was observed. The product was identified
Supporting Information Available: Tables of atomic positions,
equivalent isotropic thermal parameters, and anisotropic thermal
displacement coefficients. This material is available free of charge
via the Internet at http://pubs.acs.org. The crystallographic data have
been deposited as supplementary publications CCDC-292781 (4),
-292780 (5), -292782 (6), and -292783 (7) at the Cambridge
Crystallographic Data Center. Copies of the data can be ordered
from CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (e-mail:
deposit@ccdc.cam.ac.uk).
(50) Claeys, E. G. J. Organomet. Chem. 1966, 5, 446.
(51) Issleib, K.; Mu¨ller, D.-W. Chem. Ber. 1959, 92, 3175.
(52) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 1997.
(53) Sheldrick, G. M. SHELXS-97; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 1997.
IC0604011
Inorganic Chemistry, Vol. 45, No. 22, 2006 9063