Reactions of a gallium-bridged duron complex with alkyl lithium, HCl, and phosphines

Article abstract of DOI:10.1021/om800310h

Gallium-bridged diiron complex Cp*(dppe)FeGaFe(CO)₄ (2, Cp* = η-C₅Me₅, dppe = Ph₂CH ₂CH₂PPh₂) did not react with [PPN]Cl, DMAP (4-N,N-dimethylaminopyridine), and bpy (2,2′-bipyridine); however, reaction of 2 with HCl caused Ga-Fe(CO)₄ bond fission to give Cp*(dppe)FeGaCl₂ (4). The Ga-Fe(CO)₄ bond cleavage also occurred by the reaction of 2 with RLi (R = Me, ⁿBu) to afford Cp*(dppe)FeGaR₂ (R = Me (5a), ⁿBu (5b)). Irradiation of 2 in the presence of phosphine PR₃ (R = OPh, Me, and OMe) gave Cp*(dppe)FeGaFe(CO)₃L (L = P(OPh)₃ (6a), PMe ₃ (6b), and P(OMe)₃ (6c)) and Cp*(dppe)-FeGaFe(CO) ₂L₂ (L = PMe₃ (7b) and P(OMe)₃ (7c)) depending on the reaction conditions. Cleavage of the Cp*(dppe)Fe - Ga bond occurred by irradiation of 2 in the absence of PR₃ to give hydridoiron complex Cp*(dppe)FeH (8) via abstraction of hydrogen from solvent. Structural investigation of 6a and 6b revealed that substitution of CO with an electron-releasing ligand PR₃ caused shortening of the Ga - Fe(CO)₃L bond and elongation of the Cp*(dppe)Fe-Ga bond.

Full text of DOI:10.1021/om800310h

3918
Organometallics 2008, 27, 3918–3923
Reactions of a Gallium-Bridged Diiron Complex with Alkyl
Lithium, HCl, and Phosphines
Takako Muraoka, Hideaki Motohashi, Masakazu Hirotsu,† and Keiji Ueno*
Department of Chemistry and Biochemistry, Graduate School of Engineering, Gunma UniVersity,
Kiryu 376-8515, Japan
ReceiVed April 7, 2008
Gallium-bridged diiron complex Cp*(dppe)FeGaFe(CO)4 (2, Cp* ) η-C5Me5, dppe ) Ph2CH2CH2PPh2)
did not react with [PPN]Cl, DMAP (4-N,N-dimethylaminopyridine), and bpy (2,2′-bipyridine); however,
reaction of 2 with HCl caused Ga-Fe(CO)4 bond fission to give Cp*(dppe)FeGaCl2 (4). The Ga-Fe(CO)4
n
bond cleavage also occurred by the reaction of 2 with RLi (R ) Me, Bu) to afford Cp*(dppe)FeGaR2
n
(R ) Me (5a), Bu (5b)). Irradiation of 2 in the presence of phosphine PR3 (R ) OPh, Me, and OMe)
gave Cp*(dppe)FeGaFe(CO)3L (L ) P(OPh)3 (6a), PMe3 (6b), and P(OMe)3 (6c)) and Cp*(dppe)-
FeGaFe(CO)2L2 (L ) PMe3 (7b) and P(OMe)3 (7c)) depending on the reaction conditions. Cleavage of
the Cp*(dppe)Fe-Ga bond occurred by irradiation of 2 in the absence of PR3 to give hydridoiron complex
Cp*(dppe)FeH (8) via abstraction of hydrogen from solvent. Structural investigation of 6a and 6b revealed
that substitution of CO with an electron-releasing ligand PR3 caused shortening of the Ga-Fe(CO)3L
bond and elongation of the Cp*(dppe)Fe-Ga bond.
Ni{InC(SiMe3)3}45a inspired the discussion regarding the bond-
Introduction
ing between the transition metal and the ER ligand.2–5 Espe-
Much attention has recently been concentrated on the
compounds with multiple bonding between transition metals and
group 13 elements E.1 Isolation of terminal diyl complexes such
as boranediyl (OC)nMBR (M ) Fe (n ) 4), R ) Cp* (Cp* )
η5-C5Me5);2a M ) Cr and W (n ) 5), R ) N(SiMe3)22d),
alanediyl (OC)4FeAlCp*,3a gallanediyl (OC)4FeGaAr* (1, Ar*
cially, Robinson’s complex 1 triggered extensive discussion on
the contribution of π-back-bonding from iron to gallium atom.
Though the nature of M-E bonding is still under investigation,
recent theoretical studies demonstrated that the transition
metal-E bonding is dominated by electrostatic interaction
between a transition metal and group 13 elements E, but covalent
contributions composed of σ-donation and π-back-donation are
still important.3b,6,7 The degree of σ-donation and π-back-
donation depends on the π-basicity of both the transition metal
fragment and the R substituent on E. Thus, essentially 5e donor
ligand Cp* sufficiently filled the empty p-orbital of E to suppress
the π-back-donation from the metal to E, while a weak π-donor
)
2,6-(2,4,6-iPr3C6H2)2C6H3),4a and indanediyl complex
* To whom correspondence should be addressed. Tel & Fax: +81-277-
30-1260. E-mail: ueno@chem-bio.gunma-u.ac.jp.
† Present address: Department of Material Science, Graduate School of
Science, Osaka City University, Osaka 558-8585, Japan.
(1) (a) Braunschewig, H. Angew. Chem., Int. Ed. 1998, 37, 1786. (b)
Fischer, R. A.; Weiss, J. Angew. Chem., Int. Ed. 1999, 38, 2830. (c) Linti,
G.; Schno¨ckel, H. Coord. Chem. ReV. 2000, 206-207, 285. (d) Braunsch-
weig, H.; Colling, M. Eur. J. Inorg. Chem. 2003, 393. (e) Aldridge, S.;
Coombs, D. L. Coord. Chem. ReV. 2004, 248, 535. (f) Braunschweig, H.
AdV. Organomet. Chem. 2004, 51, 163. (g) Gemel, C.; Steinke, T.; Cokoja,
M.; Kempter, A.; Fischer, R. A. Eur. J. Inorg. Chem. 2004, 4161. (h)
Braunschweig, H.; Kollann, C.; Rais, D. Angew. Chem., Int. Ed. 2006, 45,
5254. (i) Ueno, K.; Muraoka, T. Bull. Jpn. Soc. Coord. Chem. 2007, 50,
18.
(2) (a) Cowley, A. H.; Lomelı´, V.; Voigt, A. J. Am. Chem. Soc. 1998,
120, 6401. (b) Coombs, D. L.; Aldridge, S.; Jones, C.; Willock, D. J. J. Am.
Chem. Soc. 2003, 125, 6356. (c) Coombs, D. L.; Aldridge, S.; Rossin, A.;
Jones, C.; Willock, D. J. Organometallics 2004, 23, 2911. (d) Braunschweig,
H.; Kollann, C.; Englert, U. Angew. Chem., Int. Ed. 1998, 37, 3179. (e)
Braunschweig, H.; Colling, M.; Kollann, C.; Stammler, H. G.; Neumann,
B. Angew. Chem., Int. Ed. 2001, 40, 2298. (f) Braunschweig, H.; Colling,
M.; Kollann, C.; Merz, K.; Radacki, K. Angew. Chem., Int. Ed. 2001, 40,
4198. (g) Braunschweig, H.; Colling, M.; Hu, C.; Radacki, K. Angew. Chem.,
Int. Ed. 2003, 42, 205. (h) Kays, D. L.; Day, J. K.; Ooi, L.-L.; Aldridge, S.
Angew. Chem., Int. Ed. 2005, 44, 7457. (i) Aldridge, S.; Jones, C.; Gans-
Eichler, T.; Stasch, A.; Kays, D. L.; Coombs, N. D.; Willock, D. J. Angew.
Chem., Int. Ed. 2006, 45, 6118.
(4) (a) Su, J.; Li, X.-W.; Crittendon, R. C.; Campana, C. F.; Robinson,
G. H. Organometallics 1997, 16, 4511. (b) Jutzi, P.; Neumann, B.; Reumann,
G.; Stammler, H.-G. Organometallics 1998, 17, 1305. (c) Uhl, W.; Benter,
M.; Melle, S.; Saak, W.; Frenking, G.; Uddin, J. Organometallics 1999,
18, 3778. (d) Jutzi, P.; Neumann, B.; Schebaum, L. O.; Stammler, A.;
Stammler, H.-G. Organometallics 1999, 18, 4462. (e) Leiner, E.; Scheer,
M. J. Organomet. Chem. 2002, 646, 247. (f) Weiss, D.; Winter, M.; Merz,
K.; Knu¨fer, A.; Fischer, R. A.; Fro¨hlich, N.; Frenking, G. Polyhedron 2002,
21, 535. (g) Cokoja, M.; Steinke, T.; Gemel, C.; Welzel, T.; Winter, M.;
Merz, K.; Fischer, R. A. J. Organomet. Chem. 2003, 684, 277. (h)
Cadenbach, T.; Gemel, C.; Schmid, R.; Block, S.; Fischer, R. A. Dalton
Trans. 2004, 3171. (i) Yang, X.-J.; Quillian, B.; Wang, Y.; Wei, P.;
Robinson, G. H. Organometallics 2004, 23, 5119. (j) Cokoja, M.; Gemel,
C.; Steinke, T.; Schro¨der, F.; Fischer, R. A. Dalton Trans. 2005, 44. (k)
Steinke, T.; Gemel, C.; Cokoja, M.; Winter, M.; Fischer, R. A. Dalton Trans.
2005, 55. (l) Yang, X.-J.; Wang, Y.; Quillian, B.; Wei, P.; Chen, Z.;
Schleyer, P. v. R.; Robinson, G. H. Organometallics 2006, 25, 925.
(5) (a) Uhl, W.; Pohlmann, M.; Wartchow, R. Angew. Chem., Int. Ed.
1998, 37, 961. (b) Haubrich, S. T.; Power, P. P. J. Am. Chem. Soc. 1998,
120, 2202. (c) Jutzi, P.; Neumann, B.; Reumann, G.; Schebaum, L. O.;
Stammler, H.-G. Organometallics 1999, 18, 2550. (d) Uhl, W.; Melle, S.
Z. Anorg. Allg. Chem. 2000, 626, 2043. (e) Steinke, T.; Gemel, C.; Cokoja,
M.; Winter, M.; Fischer, R. A. Chem. Commun. 2003, 1066.
(3) (a) Weiss, J.; Stetzkamp, D.; Nuber, B.; Fischer, R. A.; Boehme,
C.; Frenking, G. Angew. Chem., Int. Ed. Engl. 1997, 36, 70. (b) Yu, Q.;
Purath, A.; Donchev, A.; Schno¨ckel, H. J. Organomet. Chem. 1999, 584,
94. (c) Weiss, D.; Steinke, T.; Winter, M.; Fischer, R. A.; Fro¨hlich, N.;
Uddin, J.; Frenking, G. Organometallics 2000, 19, 4583. (d) Steinke, T.;
Gemel, C.; Cokoja, M.; Winter, M.; Fischer, R. A. Angew. Chem., Int. Ed.
2004, 43, 2299. (e) Steinke, T.; Cokoja, M.; Gemel, C.; Kempter, A.; Krapp,
A.; Frenking, G.; Zenneck, U.; Fischer, R. A. Angew. Chem., Int. Ed. 2005,
44, 2943.
(6) (a) Bickelhaupt, F. M.; Radius, U.; Ehlers, A. W.; Hoffmann, R.;
Baerends, E. J. New J. Chem. 1998, 1. (b) Cotton, F. A.; Feng, X.
Organometallics 1998, 17, 128. (c) Ehlers, A. W.; Baerends, E. J.;
Bickelhaupt, F. M.; Radius, U. Chem.-Eur. J. 1998, 4, 210. (d) Boehme,
C.; Frenking, G. Chem.-Eur. J. 1999, 5, 2184. (e) Chen, Y.; Frenking, G.
J. Chem. Soc., Dalton Trans. 2001, 434.
10.1021/om800310h CCC: $40.75
2008 American Chemical Society
Publication on Web 06/28/2008

Reactions of a Gallium-Bridged Diiron Complex
Organometallics, Vol. 27, No. 15, 2008 3919
phile to the unsaturated E.8g,h In this paper, we report the
reaction of 2 with Lewis base, [PPN]Cl, RLi, and HCl, as well
as photolysis of 2 in the presence and absence of PR3. We also
show the electronic effect of metal fragments on the Fe-Ga
bonds in Cp*(P2)FeGaFe(CO)3L complexes (P2 ) dppe, dmpe;
L ) CO, P(OPh)3, and PMe3).
Scheme 1
Results and Discussion
substituent such as Ph cannot compensate for the π-acidity of
E to cause significant π-back-donation from the metal fragment.
Dinuclear complexes bridged by a naked E atom (LnM1(µ2-
E)M2Lm; M1, M2 ) Cr, Fe, Ru, Pt; E ) B, Ga, In, Tl) are also
particularly interesting since this type of complexes contains
an sp-hybridized, two-coordinate E atom and unsaturated M-E
bonds.8 We recently reported the first dimetal complex bridged
by a gallium atom, Cp*(dppe)FeGaFe(CO)4 (2; dppe )
Ph2PCH2CH2PPh2).8d The bonding in 2 is formally depicted as
Cp*(dppe)Fe-GadFe(CO)4, i.e., a single bond between
Cp*(dppe)Fe and Ga and a double bond between Ga and
Fe(CO)4 based on the 18-electron rule (Scheme 1A). However,
both Fe-Ga bonds are significantly shorter than the usual
Fe-Ga single bonds (2.36-2.46 Å).1a Furthermore, the former
(2.2479(10) Å) is even shorter than the latter (2.2931(10) Å).
Substitution of the dppe ligand with a more electron-releasing
ligand, dmpe (dmpe ) Me2PCH2CH2PMe2), causes shortening
of the Cp*(dmpe)Fe-Ga bond (2.2409(5) Å) and elongation
of Ga-Fe(CO)4 bond (2.3205(5) Å) in complex Cp*(dmpe)-
FeGaFe(CO)4 (3) compared to the corresponding bonds in 2.8j
This implies that the π-back-donations from both Fe fragments
to the Ga center compete with each other and the intensity of
π-back-donation depends on the π-basicity of the Fe fragments.
On the basis of these insights, contribution of canonical form
B (Scheme 1) is proposed as the major one for complexes 2
and 3.
Reaction of 2 with Lewis Base, [PPN]Cl, and HCl.
Complex 2 contains a coordinatively unsaturated electron-
deficient gallium center. Thus it seems feasible to bind a donor
molecule on the Ga center. Indeed, we have reported the
formation of base adduct complex Cp*(OC)2FeGa(2,2′-bpy)-
Fe(CO)4 by the reaction of anionic chlorogallylene-bridged
diiron complex K[Cp*(OC)2FeGa(Cl)Fe(CO)4] with bpy (2,2′-
bipyridine) (eq 1).8d Aldridge also reported that the reaction of
cationic Ga-bridged diiron complex [{Cp*(OC)2Fe}2Ga]+ with
[PPN]Cl ([PPN]+ ) [Ph3PdNdPPh3]+) and 4-picoline gave
[Cp*(OC)2Fe]2GaCl and [{Cp*(OC)2Fe}2Ga(4-picoline)]+,
respectively.8g,h Contrary to our expectation, no reaction oc-
curred in the treatment of 2 with [PPN]Cl, DMAP (4-N,N-
dimethylaminopyridine), and bpy. The low reactivity of 2 toward
the donor reagents is attributable to the steric protection of the
Ga center by Ph groups of the dppe ligand as well as the
electron-donating nature of the dppe ligand. The latter enhances
π-back-donation from the Cp*Fe fragment to the Ga center to
decrease the electrophilicity of Ga.
Several types of E atom-bridged complexes M1-E-M2 as
well as terminal group 13 diyl complexes M-ER have been
synthesized so far; however, their reactivity remains largely
unexplored. Cationic terminal borylene complexes are rare
examples whose reactivity has been investigated extensively,
which includes reactions with nucleophiles2c,i and unsaturated
metal fragments,9 borylene transfer reactions,2e,g,10 and MdB
metathesis reactions.2h For bimetallic complexes bridged by an
E atom, reported reactions are limited to addition of a nucleo-
In contrast to [PPN]Cl, DMAP, and bpy, complex 2 reacted
with 2 equiv of HCl to give Cp*(dppe)FeGaCl2 (4) in 66% yield
(eq 2). During the reaction, a resonance at -9.71 ppm was
transiently observed in the 1H NMR spectrum, which is
assignable to the hydride resonance of H2Fe(CO)4.11 This result
suggests that the reaction proceeds via the preceding protonation
on the Fe(CO)4 fragment, which decreases π-back-donation from
the metal fragment and consequently enhances electrophilicity
of the Ga center, addition of Cl- on Ga, and subsequent cleavage
of the FedGa bond. Protonation of the iron center in neutral
iron complexes has been reported previously with strong protic
acids such as HCl,12 CF3SO3H,13 and HBF4.14
(7) (a) Frenking, G.; Fro¨hlich, N. Chem. ReV. 2000, 100, 717. (b)
Cundari, T. R. Chem. ReV. 2000, 100, 807. (c) Boehme, C.; Uddin, J.;
Frenking, G. Coord. Chem. ReV. 2000, 197, 249. (d) Frenking, G.;
Wichmann, K.; Fro¨hlich, N.; Loschen, C.; Lein, M.; Frunzke, J.; Rayo´n,
V. M. Coord. Chem. ReV. 2003, 238-239, 55. (e) Macdonald, C. L. B.;
Cowley, A. H. J. Am. Chem. Soc. 1999, 121, 12113. (f) Uddin, J.; Boehme,
C.; Frenking, G. Organometallics 2000, 19, 571. (g) Uddin, J.; Frenking,
G. J. Am. Chem. Soc. 2001, 123, 1683. (h) Aldridge, S.; Rossin, A.; Coombs,
D. L.; Willock, D. J. Dalton Trans. 2004, 2649. (i) Coombs, N. D.; Clegg,
W.; Thompson, A. L.; Willock, D. J.; Aldridge, S. J. Am. Chem. Soc. 2008,
130, 5449.
(9) (a) Braunschweig, H.; Rais, D.; Uttinger, K. Angew. Chem., Int. Ed.
2005, 44, 3763. (b) Braunschweig, H.; Radacki, K.; Rais, D.; Uttinger, K.
Organometallics 2006, 25, 5159.
(10) (a) Braunschweig, H.; Herbst, T.; Rais, D.; Seeler, F. Angew. Chem.,
Int. Ed. 2005, 44, 7461. (b) Braunschweig, H.; Forster, M.; Radacki, K.
Angew. Chem., Int. Ed. 2006, 45, 2132.
(8) (a) Schiemenz, B.; Huttner, G. Angew. Chem., Int. Ed. Engl. 1993,
32, 1772. (b) Uso´n, R.; Fornie´s, J.; Toma´s, M.; Garde, R. J. Am. Chem.
Soc. 1995, 117, 1837. (c) Jeffery, J. C.; Jelliss, P. A.; Liao, Y.-H.; Stone,
F. G. A. J. Organomet. Chem. 1998, 551, 27. (d) Ueno, K.; Watanabe, T.;
Tobita, H.; Ogino, H. Organometallics 2003, 22, 4375. (e) Bunn, N. R.;
Aldridge, S.; Coombs, D. L.; Rossin, A.; Willock, D. J.; Jones, C.; Ooi, L.
Chem. Commun. 2004, 1732. (f) Braunschweig, H.; Radacki, K.; Schesch-
kewitz, D.; Whittell, G. R. Angew. Chem., Int. Ed. 2005, 44, 1658. (g)
Bunn, N. R.; Aldridge, S.; Kays, D. L.; Coombs, N. D.; Rossin, A.; Willock,
D. J.; Day, J. K.; Jones, C.; Ooi, L. Organometallics 2005, 24, 5891. (h)
Coombs, N. D.; Bunn, N. R.; Kays, D. L.; Day, J. K.; Ooi, L.; Aldridge, S.
Inorg. Chim. Acta 2006, 359, 3693. (i) Buchin, B.; Gemel, C.; Cadenbach,
T.; Ferna´ndez, I.; Frenking, G.; Fischer, R. A. Angew. Chem., Int. Ed. 2006,
45, 5207. (j) Ueno, K.; Hirotsu, M.; Hatori, N. J. Organomet. Chem. 2007,
692, 88.
(11) Chemical shift of hydride resonance on H2Fe(CO)4 has never been
reported. (a) Blanchard, A. A.; Coleman, G. W. Inorg. Synth. 1946, 2, 243.
(b) Farmery, K.; Kilner, M. J. Chem. Soc. (A) 1970, 634. (c) Schroeder,
M. A.; Wrighton, M. S. J. Am. Chem. Soc. 1976, 98, 551. (d) Vancea, L.;
Graham, W. A. G. J. Organomet. Chem. 1977, 134, 219. (e) Nagorski, H.;
Mirbach, M. J. J. Organomet. Chem. 1985, 291, 199. (f) Zybill, C.; Mu¨ller,
G. Organometallics 1988, 7, 1368.
(12) (a) Rogers, W. N.; Baird, M. C. J. Organomet. Chem. 1979, 182,
C65. (b) Basallote, M. G.; Dura´n, J.; Ferna´ndez-Trujillo, J.; Ma´n˜ez, M. A.;
Torre, J. R. J. Chem. Soc., Dalton Trans. 1998, 745. (c) Basallote, M. G.;
Dura´n, J.; Ferna´ndez-Trujillo, J.; Ma´n˜ez, M. A. J. Chem. Soc., Dalton Trans.
1998, 2205.
(13) (a) Sowa, J. R., Jr.; Zanotti, V.; Facchin, G.; Angelici, R. J. J. Am.
Chem. Soc. 1991, 113, 9185. (b) Shima, T.; Hampel, F.; Gladysz, J. A.
Angew. Chem., Int. Ed. 2004, 43, 5537.

3920 Organometallics, Vol. 27, No. 15, 2008
Muraoka et al.
A strong Lewis base, alkyl lithium, also reacted with 2 to
cause the cleavage of the GadFe(CO)4 bond. Thus, reaction of
2 with 2 equiv of MeLi and nBuLi in C6D6 at ambient
temperature afforded dialkylgallyliron complex Cp*(dppe)-
n
FeGaR2 (R ) Me (5a) and Bu (5b)) in 8% and 39% yield,
respectively (eq 2). The reactions also formed a white precipi-
tate, which is tentatively assigned to Li2Fe(CO)4. Identification
of 5a and 5b was achieved by comparing their spectroscopic
data with those of the authentic samples prepared by the reaction
n
of 4 with 2 equiv of MeLi and BuLi, respectively.
Figure 1. ORTEP drawing of 6a (thermal ellipsoids at the 50%
Photolysis of 2. Irradiation of 2 in the presence of P(OPh)3,
PMe3, and P(OMe)3 resulted in the substitution of CO to give
monosubstituted complex Cp*(dppe)FeGaFe(CO)3L (L )
P(OPh)3 (6a), PMe3 (6b), and P(OMe)3 (6c)), disubstituted
complex Cp*(dppe)FeGaFe(CO)2L2 (L ) PMe3 (7b) and
P(OMe)3 (7c)), and hydride complex Cp*(dppe)FeH (8) de-
pending on reaction conditions (eq 3). For example, irradiation
of a THF solution containing 2 and 3 equiv of PMe3 for 12 h
gave a 87:13:0 mixture of 6b, 7b, and 8, respectively, while a
13:69:18 mixture was obtained after prolonged irradiation (250
h) with 10 equiv of PMe3. Complexes 6a-c and 7b,c were
isolated as red crystals in 40-62% yields and were characterized
by spectroscopic methods and elemental analysis. Complexes
6a and 6b were also investigated by X-ray crystal structure
analysis. Complexes 6 and 7 showed ν(CO) bands in the range
1872-1820 cm-1, which are significantly shifted to lower
frequencies compared to those of 2 (1998, 1923, 1890, and 1878
probability level).
trans to the gallium atom. Thus the phosphine ligands in 7 are
considered to be at the positions trans and cis to the gallium
atom, as depicted in eq 3. In contrast to our expectations, 31P
and 1H NMR showed only one signal for the two PR3 ligands.
Furthermore, 31P NMR signals for dppe and PR3 ligands
appeared as a singlet. Observation of only one signal for the
two PR3 ligands as well as disappearance of the JPP coupling
indicates the rapid scrambling of the two phosphines on the
NMR time scale.
Hydride complex 8 was formed upon prolonged irradiation
(eq 3). The same product was also formed by irradiation of 2
in toluene (by NMR) (eq 4). The 1H NMR spectrum of 8 showed
a characteristic triplet resonance at -16.8 ppm assignable to
the hydride ligand on iron (2JPH ) 68.0 Hz).15 The formation
mechanism of the hydride complex 8 is not clear at present,
but the hydride ligand was evidently abstracted from the solvent
molecules since deuteridoiron complex Cp*(dppe)FeD (8-D)15b
was exclusively obtained upon photolysis of 2 in C6D6.
4
cm-1), suggesting stronger π-basic character of the Fe(CO)4-n
-
(PR3)n fragment than that of Fe(CO)4.8d Phosphorus-31 NMR
of 6a showed a triplet and a doublet signal (4Jpp ) 7.8 Hz) at
192.2 and 92.6 ppm, which are assignable to P(OPh)3 and the
dppe ligand, respectively. Complexes 6b and 6c also showed
4
the corresponding two multiplet signals with Jpp ) 3.4 and
7.5 Hz, respectively.
Structures of 6a and 6b. ORTEP drawings of 6a and 6b
are shown in Figures 1 and 2, and selected bond distances and
angles are listed in Tables 2 and 3, respectively. The structures
of 6a and 6b are characteristics of the linear Fe1-Ga-Fe2
framework (176.430(12)° and 177.389(19)°, respectively),
indicating sp-hybridization of the gallium atom. The incorpo-
rated PR3 ligand is at the position trans to the gallium atom.
Both of the Fe-Ga bonds in 6a and 6b are significantly shorter
than the usual Fe-Ga single bond (2.36-2.46 Å), which
indicates multiple-bond character of the Fe-Ga bonding.1b The
Fe1-Ga bond of 6a (2.2844(8) Å) and 6b (2.2686(5) Å) is
shorter than the (OC)4Fe-Ga bond in 2 (2.2931(10) Å), while
the Fe2-Ga bond in 6a (2.2690(8) Å) and 6b (2.2769(5) Å) is
longer than the corresponding bond in 2 (2.2479(10) Å).
As described later, crystal structure analysis of 6a and 6b
revealed that the substituted PR3 ligand occupied the position
(14) (a) Morris, R. H.; Sawyer, J. F.; Shiralian, M.; Zubkowski, J. D.
J. Am. Chem. Soc. 1985, 107, 5581. (b) Bautista, M. T.; Earl, K. A.; Maltby,
P. A.; Morris, R. H. J. Am. Chem. Soc. 1988, 110, 4056. (c) Bautista, M. T.;
Cappellani, E. P.; Drouin, S. D.; Morris, R. H.; Schweitzer, C. T.; Sella,
A.; Zubkowski, J. J. Am. Chem. Soc. 1991, 113, 4876. (d) Hamon, J.-R.;
Hamon, P.; Toupet, L.; Costuas, K.; Saillard, J.-Y. C. R. Chim. 2002, 5,
89.
(15) (a) Roger, C.; Marseille, P.; Salus, C.; Hamon, J.-R.; Lapinte, C.
J. Organomet. Chem. 1987, 336, C13. (b) Roger, C.; Hamon, P.; Toupet,
L.; Rabaaˆ, H.; Saillard, J.-Y.; Hamon, J.-R.; Lapinte, C. Organometallics
1991, 10, 1045. See also: (c) Hamon, P.; Toupet, L.; Hamon, J.-R.; Lapinte,
C. Organometallics 1992, 11, 1429. (d) Hamon, P.; Hamon, J.-R.; Lapinte,
C. J. Chem. Soc., Chem. Commun. 1992, 1602. (e) Hamon, P.; Toupet, L.;
Hamon, J.-R.; Lapinte, C. J. Chem. Soc., Chem. Commun. 1994, 931.

Reactions of a Gallium-Bridged Diiron Complex
Organometallics, Vol. 27, No. 15, 2008 3921
by the fact that substitution of P(OPh)3 in 6a by the more
electron-releasing ligand PMe3 in 6b further shortens the
Ga-Fe(CO)3L bond and elongates the Cp*(dppe)Fe-Ga bond.
Substitution of dppe in 2 by the more electron-releasing ligand
dmpe in 3, in contrast, shortens the Cp*(P2)Fe-Ga bond and
elongates the Ga-Fe(CO)4 bond, which is also rationalized by
the changes of the π-basicity of the metal fragment. These results
indicate that the contributions of π-back-donation from two iron
fragments toward Ga compete with each other; in other words,
the electronic effect of a metal fragment affects another metal
fragment via the gallium-metal unsaturated bonding.
Figure 2. ORTEP drawing of 6b (thermal ellipsoids at the 50%
probability level).
Experimental Section
General Procedures. All manipulations were performed using
either standard Schlenk tube techniques under nitrogen, vacuum
line techniques, or a drybox under nitrogen. The syntheses of
Cp*(dppe)FeGaFe(CO)4 (2) and Cp*(dppe)FeGaCl2 (4) were
reported previously.8d Toluene, THF, and hexane were dried by
refluxing over sodium benzophenone ketyl followed by distillation
under a nitrogen atmosphere before use. Dichloromethane was dried
by refluxing over CaH2 and distilled under nitrogen before use.
Benzene-d6 was distilled from a potassium mirror under vacuum
and stored on 4 Å molecular sieves. Dichloromethane-d2 was used
as received. [PPN]Cl was recrystallized from dichloromethane/
hexane. 4,4-Dimethylaminopyridine (DMAP) and 2,2′-bipyridine
(2,2′-bpy) were purified according to standard methods.16 The
Table 1. Selected Bond Lengths [Å] and Angles [deg] for
Cp*(dppe)FeGaFe(CO)3{P(OPh)3} (6a)
Fe1-Ga
Fe1-P1
Fe2-P3
Fe1-C2
Fe2-C22
Fe2-C24
Fe2-C26
O2-C2
2.2845(3)
2.1104(5)
2.1940(5)
1.764(2)
2.152(2)
2.126(2)
2.154(2)
1.160(2)
Fe2-Ga
Fe2-P2
Fe1-C1
Fe1-C3
Fe2-C23
Fe2-C25
O1-C1
2.2691(3)
2.1908(5)
1.778(2)
1.773(2)
2.122(2)
2.129(2)
1.157(2)
1.158(2)
O3-C3
Fe1-Ga-Fe2
P1-Fe1-C1
P1-Fe1-C3
C2-Fe1-C3
Fe1-C1-O1
Fe1-C3-O3
P3-Fe2-Ga
176.430(12)
92.89(6)
96.57(6)
117.16(9)
177.4(2)
179.0(2)
91.06(2)
P1-Fe1-Ga
P1-Fe1-C2
C1-Fe1-C2
C3-Fe1-C1
Fe1-C2-O2
P2-Fe2-Ga
P2-Fe2-P3
176.993(17)
95.03(6)
118.09(9)
122.65(9)
176.9(2)
n
concentrations of MeLi in Et2O (1.20 M), BuLi in hexane (1.01
M), and HCl in Et2O (0.92 M) were determined by standard titration
techniques. P(OPh)3 and PMe3 were used as received. P(OMe)3
was dried over 4 Å molecular sieves.
85.05(1)
86.10(2)
NMR spectra were recorded on a JEOL JNM-AL300 or a JEOL
JNM-AL500 Fourier transform spectrometer at room temperature.
IR spectra were recorded on a JASCO FT/IR-600 Plus spectrometer
at room temperature. Elemental analyses were performed by the
Microanalytical Center, Gunma University. Photolysis was carried
out using an Ushio UV-452 450W medium-pressure Hg lamp placed
in a water-cooled quartz jacket immersed in a water bath (4 °C)
and a Pyrex reaction vessel.
Table 2. Selected Bond Lengths [Å] and Angles [deg] for
Cp*(dppe)FeGaFe(CO)3(PMe3) (6b)
Fe1-Ga
Fe1-P1
Fe2-P3
Fe1-C2
Fe2-C33
Fe2-C35
Fe2-C37
O2-C2
2.2686(5)
2.1805(8)
2.1695(7)
1.764(3)
2.113(3)
2.148(3)
2.123(3)
1.165(4)
Fe2-Ga
Fe2-P2
Fe1-C1
Fe1-C3
Fe2-C34
Fe2-C36
O1-C1
2.2769(5)
2.1735(8)
1.768(3)
1.760(3)
2.141(3)
2.129(3)
1.159(4)
1.167(4)
Reaction of 2 with Alkyl Lithium. An ether solution of MeLi
(2.6 µL, 3.2 × 10-3 mmol) was added to a C6D6 solution (0.5
mL) of Cp*(dppe)FeGaFe(CO)4 (2) (1.3 mg, 1.6 × 10-3 mmol) in
a NMR sample tube with a Teflon vacuum valve. The color of the
reaction mixture immediately changed from orange to red-purple
with formation of white precipitates. The precipitates were removed
from the reaction mixture by decantation. Volatiles were evaporated
from the solution under reduced pressure. The residue was dissolved
in C6D6 (0.5 mL) and subjected to NMR measurements. Reaction
of 2 with nBuLi is also performed in a similar manner using 2 (1.6
O3-C3
Fe1-Ga-Fe2
P1-Fe1-C1
P1-Fe1-C3
C2-Fe1-C3
Fe1-C1-O1
Fe1-C3-O3
P3-Fe2-Ga
177.389(19)
92.48(10)
92.48(9)
124.35(15)
176.7(3)
P1-Fe1-Ga
P1-Fe1-C2
C1-Fe1-C2
C3-Fe1-C1
Fe1-C2-O2
P2-Fe2-Ga
P2-Fe2-P3
176.26(3)
90.70(9)
117.93(16)
117.40(10)
177.7(3)
177.9(3)
89.36(2)
87.99(2)
85.65(3)
n
mg, 1.9 × 10-3 mmol) and a hexane solution of BuLi (1.9 µL,
Interestingly, the Fe2-Ga bond in 6a is shorter than the Fe1-Ga
bond in the same molecule, while the former in 6b is longer
than the latter. Thus, the strong electron-releasing ligand PMe3
significantly shortens the Fe1-Ga bond and elongates the
Fe2-Ga bond.
Table 3 summarizes the Fe-Ga bond lengths and ν(CO)
frequencies of Ga-bridged diiron complexes 6a-c and 7b,c as
well as those of previously reported complexes 2 and 3.
Substitution of one carbonyl ligand of 2 by the more electron-
releasing ligand P(OPh)3 elongates the Cp*(dppe)Fe-Ga bond
and shortens the Ga-Fe(CO)3L bond (complex 6a). This is
attributable to the fact that the increased electron density on
the Fe(CO)3L fragment enhances the π-back-donation from the
Fe(CO)3L fragment to the Ga center and, consequently, sup-
presses that from the Cp*(dppe)Fe fragment. The red shift of
the ν(CO) frequencies also suggests the increase of π-basicity
in the Fe(CO)4-nLn fragment. This explanation is also supported
1.9 × 10-3 mmol).
n
Preparation of Cp*(dppe)FeGaR2 (R ) Me (5a), Bu (5b)).
Complex 5a was prepared according to the following procedure:
To a toluene solution (20 mL) of Cp*(dppe)FeGaCl2 (4) (90 mg,
1.2 × 10-4 mol) in a 50 mL round-bottomed flask was added a
Et2O solution of MeLi (200 µL, 2.4 × 10-4 mol) with vigorous
stirring. The resultant mixture was stirred for 1 h at 25 °C and then
filtered through a glass filter. After removal of volatiles from the
filtrate in vacuo, the residue was extracted with toluene (10 mL).
The extract was allowed to stand at -30 °C to give red-orange
crystals of Cp*(dppe)FeGaMe2 (5a) in 63% yield (52 mg, 7.5 ×
10-5 mol). 1H NMR (300 MHz, C6D6): δ/ppm 7.51-7.06 (m, 20H,
PPh), 2.56 (m, 2H, PCH2CH2P), 2.28 (m, 2H, PCH2CH2P), 1.58
(s, 15H, C5Me5), -0.04 (s, 6H, GaMe2). 13C{1H} NMR (125.7
(16) (a) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.

3922 Organometallics, Vol. 27, No. 15, 2008
Muraoka et al.
Table 3. Fe-Ga Bond Lengths and ν(CO) Frequencies of Cp*(P2)Fe-Ga-Fe(CO)4-nLn
a
complex
P2
L
n
Cp*(P2)Fe-Gaa
Ga-Fe(CO)4-nLn
ν(CO)b
3
2
6a
6b
6c
7b
7c
dmpe
dppe
dppe
dppe
dppe
dppe
dppe
CO
CO
P(OPh)3
PMe3
P(OMe)3
PMe3
P(OMe)3
1
1
1
1
1
2
2
2.2410(3)
2.2479(10)
2.2690(8)
2.2769(5)
2.3204(3)
2.2931(10)
2.2844(8)
2.2686(5)
1991, 1917, 1882, 1869
1998, 1923, 1890, 1878
1872, 1851
1831
1853, 1837
1837, 1782
1872, 1820
a Å. b cm-1
.
Table 4. Crystal Data and Structure Refinement for Complexes 6a and 6b · 2THF
6a
6b · 2THF
C50H64Fe2GaO5P3
1019.34
150(2)
empirical formula
fw
temp (K)
C57H54Fe2GaO6P3
1109.33
150(2)
wavelength (Å)
cryst syst
space group
unit cell dimens
a (Å)
0.71073
triclinic
P1
0.71073
monoclinic
C2/c
11.3945(8)
14.6164(10)
17.6617(11)
25.3048(11)
21.5508(10)
18.0423(9)
b (Å)
c (Å)
R (deg)
108.5590(10)
99.294(2)
110.135(2)
2493.7(3)
2
1.477
1.259
1144
ꢀ (deg)
92.599(2)
γ (deg)
volume (Å3)
Z
9829.0(8)
8
1.378
1.269
Dcalc (Mg/m3)
absorp coeff (mm-1
F(000)
)
4256
cryst size (mm3)
0.2 × 0.2 × 0.2
0.2 × 0.2 × 0.2
θ range for data collection (deg)
index ranges
1.28-32.05
1.65-32.03
-14 e h e 14
-21 e k e 21
-23 e l e 23
24 989
-33 e h e 34
-31 e k e 29
-26 e l e 20
35 211
no. of reflns collected
no. of indep reflns [R(int)]
absorp corr
maximum and minimum transmn
refinement method
12 727 [0.0177]
semiempirical from equivalents
1.000 and 0.811
full-matrix least-squares on F2
12 727/0/627
1.136
14 107 [0.0205]
semiempirical from equivalents
1.0000 and 0.6049
full-matrix least-squares on F2
14 107/0/577
no. of data/restraints/params
goodness-of-fit on F2
1.213
final R indices [I > 2σ(I)]
R indices (all data)
R1 ) 0.0370, wR2 ) 0.0908
R1 ) 0.0382, wR2 ) 0.0918
0.490 and -0.822
R1 ) 0.0618, wR2 ) 0.1729
R1 ) 0.0710, wR2 ) 0.2141
1.677 and -3.199
largest diff in peak and hole (e Å-3
)
MHz, C6D6): δ/ppm 133.2-127.3 (m, PPh), 86.1 (s, C5Me5), 33.4
formation of precipitates. The reaction was monitored by 31P{1H}
1
2
3
1
(dd, JPC ) 32 Hz, JPC ) 14 Hz, PCH2), 11.9 (t, JPC ) 3.6 Hz,
GaMe), 11.6 (s, C5Me5). 31P{1H} NMR (121.5 MHz, C6D6): δ/ppm
106.9 (s, dppe). Anal. Calc for C38H45FeGaP2: C, 66.22; H, 6.58.
Found: C, 65.12; H, 6.54. Although attempted extensively, agreeable
elemental analysis data were not obtained probably due to its
instability toward moisture and air.
and H NMR. Yield of Cp*(dppe)FeGaCl2 (4)8d was determined
1
from the H NMR spectrum (66%).
Cp*(dppe)FeGaFe(CO)3{P(OPh)3} (6a). A degassed THF solu-
tion (30 mL) of Cp*(dppe)FeGaFe(CO)4 (2) (83 mg, 0.10 mmol)
and P(OPh)3 (26.2 µL, 0.100 mmol) was placed in a Pyrex sample
tube with a Teflon vacuum valve and irradiated with a medium-
pressure Hg lamp. During the photolysis, the solution color changed
from orange to red-orange. After 15 h irradiation, volatiles were
removed from the reaction mixture. The residue was washed with
toluene (5 mL) to give orange crystals of Cp*(dppe)FeGa-
Cp*(dppe)FeGanBu2 (5b) was prepared in a similar manner using
Cp*(dppe)FeGaCl2 (4) (100 mg, 1.4 × 10-4 mol) and a hexane
solution of nBuLi (170 µL, 2.7 × 10-4 mol) as red-orange crystals
in 77% yield (82 mg, 1.1 × 10-4 mol). 1H NMR (300 MHz, C6D6):
δ/ppm 7.07-7.57 (m, 20H, PPh), 2.67 (m, 2H, PCH2CH2P), 2.46
(m, 2H, PCH2CH2P), 1.59 (s, 15H, C5Me5), 1.33 (m, 4H, nBu),
1.13 (m, 4H, nBu), 0.95 (t, 6H, nBu), 0.60 (m, 4H, nBu). 13C{1H}
NMR (125.7 MHz, C6D6): δ/ppm 127.2-145.8 (m, PPh), 86.4 (s,
C5Me5), 34.0 (dd, 1JPC ) 29.4 Hz, 2JPC ) 14.7 Hz, PCH2), 29.6 (s,
1
Fe(CO)3{P(OPh)3} (6a) in 50% yield (56 mg, 0.050 mmol). H
NMR (300 MHz, CD2Cl2): δ/ppm 7.63-7.15 (m, 35H, Ph), 2.22
(m, 4H, PCH2), 1.46 (s, 15H, C5Me5). 13C{1H} NMR (125.7 MHz,
2
CD2Cl2): δ/ppm 216.4 (d, JPC ) 26 Hz, CO), 152.4-122.5 (m,
Ph), 86.4 (s, C5Me5), 32.7 (m, PCH2), 10.5 (s, C5Me5). 31P{1H}
n
n
n
4
nBu), 29.1 (s, Bu), 27.5 (s, Bu), 14.2 (s, Bu), 11.7 (s, C5Me5).
31P{1H} NMR (121.5 MHz, C6D6): δ/ppm 108.7 (s, dppe). Anal.
Calc for C44H57FeGaP2: C, 68.33; H, 7.43. Found: C, 67.41; H,
7.32.
NMR (121.5 MHz, CD2Cl2): δ/ppm 192.2 (t, JPP ) 7.8 Hz,
4
P(OPh)3), 92.6 (d, JPP ) 7.8 Hz, dppe). IR (KBr): ν/cm-1 1872
(vs, CdO), 1851 (vs, CdO). Anal. Calc for C57H54Fe2GaO6P3: C,
61.71; H, 4.91. Found: C, 61.22; H, 4.85.
Reaction of 2 with HCl. To a C6D6 solution (0.5 mL) of
Cp*(dppe)FeGaFe(CO)4 (2) (3.5 mg, 4.2 × 10-3 mmol) in a NMR
sample tube with a Teflon vacuum valve was added a Et2O solution
of HCl (9.0 µL, 8.4 × 10-3 mmol). The color of the reaction
mixture immediately changed from orange to red-purple with
Cp*(dppe)FeGaFe(CO)3(PMe3) (6b). A THF solution (20 mL)
of Cp*(dppe)FeGaFe(CO)4 (2) (103 mg, 0.124 mmol) and PMe3
(38.5 µL, 0.372 mmol) was irradiated in a manner similar to that
for 6a for 12 h. After removal of the volatiles from the reaction
mixture, the residue was extracted with toluene (10 mL). Cooling

Reactions of a Gallium-Bridged Diiron Complex
Organometallics, Vol. 27, No. 15, 2008 3923
the extract to -35 °C gave orange crystals of Cp*(dppe)FeGa-
Fe(CO)3(PMe3) (6b) in 65% yield (71 mg, 0.081 mmol). 1H NMR
(300 MHz, C6D6): δ/ppm 8.04-6.99 (m, 20H, Ph), 2.62 (m, 2H,
PCH2CH2P), 2.20 (m, 2H, PCH2CH2P), 1.58 (s, 15H, C5Me5), 1.28
31P{1H} NMR (121.5 MHz, C6D6): δ/ppm 197.3 (s, P(OMe)3), 95.9
(s, dppe). IR (KBr): ν/cm-1 1872 (s, CdO), 1820 (vs, CdO). Anal.
Calc for C44H57Fe2GaO8P4: C, 51.85; H, 5.64. Found: C, 51.90; H,
5.64.
2
(d, JPH ) 9 Hz, 9H, PMe3). 13C{1H} NMR (125.7 MHz, C6D6):
Photolysis of 2. A degassed toluene solution (15 mL) of
Cp*(dppe)FeGaFe(CO)4 (2) (50 mg, 0.060 mmol) in a Pyrex sample
tube with a Teflon vacuum valve was irradiated with a medium-
pressure Hg lamp. The color changed from orange to red with
formation of black precipitates during the photolysis. After 150 h
irradiation, the reaction mixture was filtered through a glass filter.
After removal of volatiles from the filtrate, the residue was extracted
with hexane (30 mL). Cooling the extract at -30 °C gave a small
amount of red crystals of Cp*(dppe)FeH (8).15 1H NMR (300 MHz,
C6D6): δ/ppm 7.82-7.12 (m, 20H, PPh), 1.74 (m, 2H, PCH2CH2P),
2
δ/ppm 220.7 (d, JPC ) 22 Hz, CO), 140.5-127.5 (m, PPh), 86.3
1
2
(s, C5Me5), 33.2 (dd, JPC ) 29 Hz, JPC ) 8.9 Hz, PCH2), 22.0
(d, JPC ) 29 Hz, PMe3), 10.8 (s, C5Me5). 31P{1H} NMR (121.5
1
MHz, C6D6): δ/ppm 94.7 (d, 4JPP ) 3.4 Hz, dppe), 36.4 (t, 4JPP
)
3.4 Hz, PMe3). IR (KBr): ν/cm-1 1831 (vs, CdO). Anal. Calc for
C42H48Fe2GaO3P3: C, 57.64; H, 5.53. Found: C, 57.38; H, 5.57.
Cp*(dppe)FeGaFe(CO)3{P(OMe)3} (6c). Complex 6c was
obtained as orange crystals according to a procedure similar to that
for 6a using Cp*(dppe)FeGaFe(CO)4 (2) (100 mg, 0.121 mmol)
and P(OMe)3 (43.0 µL, 0.365 mmol) in 62% yield (69 mg, 0.075
1.69 (m, 2H, PCH2CH2P), 1.62 (s, 15H, C5Me5), -16.8 (t, 2JPH
)
1
mmol). H NMR (300 MHz, C6D6): δ/ppm 7.98-6.99 (m, 20H,
68. 0 Hz, 1H, FeH).
3
15b
Ph), 3.64 (d, JPH ) 12 Hz, 9H, P(OMe)3), 2.57 (m, 2H,
Cp*(dppe)FeD (8-D).
A degassed C6D6 solution (0.5 mL)
PCH2CH2P), 2.11 (m, 2H, PCH2CH2P), 1.57 (s, 15H, C5Me5).
of Cp*(dppe)FeGaFe(CO)4 (2) (1.3 mg, 1.6 × 10-3 mmol) was
irradiated in a NMR sample tube with a Teflon vacuum valve. The
reaction was monitored by 1H NMR. 1H NMR (300 MHz, C6D6):
δ/ppm 7.82-7.12 (m, 20H, PPh), 1.74 (m, 2H, PCH2CH2P), 1.69
(m, 2H, PCH2CH2P), 1.69 (s, 15H, C5Me5).
13C{1H} NMR (125.7 MHz, C6D6): δ/ppm 218.1 (d, JPC ) 26
2
Hz, CO), 139.8-127.5 (m, PPh), 86.1 (s, C5Me5), 51.7 (s,
P(OMe)3), 32.9 (m, PCH2), 10.7 (s, C5Me5). 31P{1H} NMR (202.5
4
MHz, C6D6): δ/ppm 204.3 (t, JPP ) 7.5 Hz, P(OMe)3), 93.9 (d,
4JPP ) 7.5 Hz, dppe). IR (KBr): ν/cm-1 1853 (vs, CdO), 1837
(vs, CdO). Anal. Calc for C42H48Fe2GaO6P3: C, 54.64; H, 5.24.
Found: C, 54.19; H, 5.41.
X-ray Crystal Structure Determination of Cp*(dppe)-
FeGaFe(CO)3{P(OPh)3}(6a)andCp*(dppe)FeGaFe(CO)3(PMe3) ·
2THF (6b · 2THF). A single crystal of 6a or 6b suitable for X-ray
crystal structure determination was obtained by recrystallization
from CH2Cl2 or THF, respectively. The intensity data were collected
on a Rigaku RAXIS-IV imaging plate diffractometer with graphite-
monochromated Mo KR radiation at 150 K. Readout was performed
in the 0.100 mm pixel mode. Empirical absorption corrections were
applied. Crystallographic data are summarized in Table 4. The
structure was solved by direct and Fourier transform methods using
the SHELX-97 systems.17 All non-hydrogen atoms were refined
by full-matrix least-squares techniques with anisotropic displace-
ment parameters based on F2 with all reflections. All hydrogen
atoms except for that of THF molecules in 6b · 2THF were placed
at their geometrically calculated positions and refined riding on the
corresponding carbon atoms with isotropic thermal parameters. The
hydrogen atoms of the THF molecule were not included in the
refinement. The final residue R1 and the weighted wR2 were 0.0370
and 0.0908 for 6a and 0.0618 and 0.1729 for 6b · 2THF, respectively.
Cp*(dppe)FeGaFe(CO)2(PMe3)2 (7b). A THF solution (15 mL)
of Cp*(dppe)FeGaFe(CO)4 (2) (150 mg, 0.181 mmol) and PMe3
(190 µL, 1.84 mmol) was irradiated for 350 h in a manner similar
to that for 6a. Volatiles were removed from the reaction mixture.
The residue was extracted with Et2O (10 mL). Cooling the extract
to -35 °C gave red-orange crystals of Cp*(dppe)FeGa-
Fe(CO)2(PMe3)2 (7b) in 40% yield (67 mg, 0.073 mmol). 1H NMR
(300 MHz, C6D6): δ/ppm 8.09-6.97 (m, 20H, Ph), 2.74 (m, 2H,
PCH2CH2P), 2.30 (m, 2H, PCH2CH2P), 1.67 (s, 15H, C5Me5), 1.25
(d, 2JPH ) 6.9 Hz, 18H, PMe3). 13C{1H} NMR (125.7 MHz, C6D6):
2
δ/ppm 226.4 (t, JPC ) 15 Hz, CO), 141.4-127.2 (m, PPh), 86.0
1
3
(s, C5Me5), 33.0 (m, PCH2), 25.6 (dd, JPC ) 15 Hz, JPC ) 7.3
Hz, PMe3), 10.9 (s, C5Me5). 31P{1H} NMR (121.5 MHz, C6D6):
δ/ppm 94.9 (s, dppe), 20.9 (s, PMe3). IR (KBr): ν/cm-1 1837 (vs,
CdO), 1782 (vs, CdO). Anal. Calc for C44H57Fe2GaO2P4: C:,
57.24; H, 6.22. Found: C, 53.28; H, 6.08. Although attempted
extensively, agreeable elemental analysis data were not obtained
probably due to its instability toward moisture and air.
Acknowledgment. This work was supported by a Grant-
in-Aid for Scientific Research on Priority Areas (Nos.
16033212 and 19027012) and for Scientific Research (No.
17655022) from the Ministry of Education, Culture, Sports,
Science and Technology of Japan.
Cp*(dppe)FeGaFe(CO)2{P(OMe)3}2 (7c). A THF solution (20
mL) of Cp*(dppe)FeGaFe(CO)4 (2) (100 mg, 0.121 mmol) and
P(OMe)3 (143 µL, 1.21 mmol) was irradiated for 140 h in a manner
similar to that of 6a. Volatiles were removed from the reaction
mixture. The residue was extracted with Et2O (10 mL). The extract
was concentrated to ca. 5 mL and cooled to -35 °C. Red-orange
crystals of Cp*(dppe)FeGaFe(CO)2{P(OMe)3}2 (7c) were obtained
Supporting Information Available: X-ray crystallographic data
are available as a CIF file. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
in 48% yield (59 mg, 0.058 mmol). H NMR (300 MHz, C6D6):
2
δ/ppm 8.01-7.02 (m, 20H, Ph), 3.48 (t, JPH ) 5.4 Hz, 18H,
OM800310H
P(OMe)3) 2.67 (m, 2H, PCH2CH2P), 2.22 (m, 2H, PCH2CH2P),
1.66 (s, 15H, C5Me5). 13C{1H} NMR (125.7 MHz, C6D6): δ/ppm
2
221.4 (t, JPC ) 11 Hz, CO), 141.5-127.4 (m, PPh), 86.7 (s,
(17) Sheldrick, G. M. SHELX-97, Program for Crystal Structure
Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
C5Me5), 50.6 (s, P(OMe)3), 33.2 (m, PCH2), 10.9 (s, C5Me5).