heterodi- and heterotrimetallic compounds containing five-membered rings and σ(Pd-Csp2, ferrocene) bonds. X-ray crystal structure of the meso-form of [Pd2{Fe[(η5-C5H3)-C(CH 3)=N-C6</su

Article abstract of DOI:10.1021/om980834e

The syntheses and characterization of heterodi- and heterotrimetallic complexes of general formulas [Pd{[(η⁵-C₅H ₃)-C(R)=N-R′]Fe[(η⁵-C₅H ₄)-C(R)=N-R′]}Cl(PPh₃)] [Pd{[(η⁵

Full text of DOI:10.1021/om980834e

Organometallics 1999, 18, 1267-1274
1267
Heter od i- a n d Heter otr im eta llic Com p ou n d s Con ta in in g
2
F ive-Mem ber ed Rin gs a n d σ(P d -Csp , fer r ocen e) Bon d s.
X-r a y Cr ysta l Str u ctu r e of th e m eso-F or m of
[P d 2{F e[(η5-C5H3)-C(CH3)dN-C6H5]}2Cl2(P P h 3)2]
Ramon Bosque,† Concepcio´n Lo´pez,*,† Xavier Solans,‡ and Merce` Font-Bardia‡
Departament de Quı´mica Inorga`nica, Facultat de Qu´ımica, Universitat de Barcelona,
Martı´ Franque`s 1-11, 08028-Barcelona, Spain, and Departament de Cristal.lografia,
Mineralogia i Dipo`sits Minerals, Facultat de Geologia, Universitat de Barcelona,
Marti Franque`s s/ n, 08028-Barcelona, Spain
Received October 6, 1998
The syntheses and characterization of heterodi- and heterotrimetallic complexes of general
formulas [Pd{[(η5-C5H3)-C(R)dN-R′]Fe[(η5-C5H4)-C(R)dN-R′]}Cl(PPh3)], [Pd{[(η5-C5H3)-
C(C6H5)dN-C6H5]Fe[(η5-C5H4)-C(O)dN-C6H5]}Cl(PPh3)], and [Pd2{Fe[(η5-C5H3)-C(R)d
N-R′]2}Cl2(PPh3)2] {with R ) H, CH3, or C6H5 and R′) phenyl or benzyl groups} are reported.
The X-ray crystal structure of the meso-form of [Pd2{Fe[(η5-C5H3)-C(CH3)dN-C6H5]2}Cl2-
(PPh3)2] (2b) is also described.
The study of heteropolynuclear organometallic com-
pounds has attracted great interest during the past
decade, mainly due to their applications in several
areas. One of the methods used to prepare heteropoly-
nuclear compounds is based on the use of ferrocenyl
substrates containing heteroatoms {mainly nitrogen,
sulfur, phosphorus, or oxygen} and/or unsaturated
groups with good donor abilities, which may allow the
coordination of one or more metal ions.1,2 Among the
procedures described so far for the preparation of this
dated and cycloplatinated complexes containing N-donor
ferrocenyl ligands and a σ(M-Csp ,ferrocene) bond have
2
been studied extensively in the past decade. However,
doubly cyclometalated derivatives are scarce.8-10 To our
knowledge four articles have been published in this
field. Robinson et al.8 reported the bis(cycloplatination)
of the 1,1′-ferrocenyldiamine [Fe{(η5-C5H4)-CH2-
N(CH3)2}2]. The three remaining articles deal with bis-
(cyclopalladated) compounds, two of which (Figure 1, A
and B) arise from the orthopalladation of two different
ferrocenyl moieties.9 However, only one example of 1,1′-
bis(cyclopalladation) of the ferrocenyl fragment has been
reported (Figure 1, C).10
sort of compound, those involving the coordination of
2
the heteroatom and the activation of a σ(Csp ,ferrocene
-
H) bond are especially important since they produce
cyclometalated derivatives,3-6 which have been found
to be useful substrates in different areas.7 Cyclopalla-
Recent studies on cyclopalladation of monoferroce-
nylimines of general formula [(η5-C5H5)Fe{(η5-C5H4)-
C(R)dN-R′}] have shown that the palladacycles form
under mild experimental conditions.6 On this basis, we
attemped to prepare 1,1′-ferrocenyldiimines and to
study their proclivity to undergo mono- or biscyclopal-
ladation. In this paper we present the synthesis of the
1,1′-diimines [Fe{(η5-C5H4)-C(R)dN-R′}2] with R ) H,
R′ ) CH2-C6H5 (1a ); R ) CH3, R′ ) C6H5 (1b), C6H4-
4-CH3 (1c), and R ) R′ ) C6H5 (1d ) (Figure 1, D) and
their cyclopalladated complexes containing one or two
† Departament de Qu´ımica Inorga`nica.
‡ Departament de Cristal.lografia, Mineralogia i Dipo`sits Minerals.
(1) Togni, A.; Hayashi, T. In Ferrocenes. Homogeneous Catalysis.
Organic Synthesis and Materials Science; VCH: Weinheim, Germany,
1995.
(2) For recent publications involving heteropolynuclear compounds
containing ferrocenyl units see also: Whittall, I. R.; McDonagh, A. M.;
Humphrey, M. G.; Samoc, M. In Advances in Organometallic Chem-
istry; Stone, F. G. A., West, R., Eds.; Academic Press: San Diego, CA,
1998; Vol. 42, p 291. Crespo, O.; Gimeno, M. C.; J ones, P. G.; Laguna,
A.; Sarroca, C. Chem. Commun. 1998, 1481. Severin, K.; Bergs, R.;
Beck, W. Angew. Chem., Int. Ed., Engl. 1998, 37, 1635. Zhuravel, M.
A.; Glueck, D. S.; Liable-Sands, L. M.; Rheingold, A. L. Organometallics
1998, 17, 574.
(3) Ryabov, A. D.; Panyashkina, I. M.; Polyakov, V. A.; Howard, J .
A. K.; Kuz’mina, L. G.; Daft, M. S.; Sacht, B. Organometallics 1998,
17, 3615. Ryabov, A. D.; Kazankov, G. M.; Panyashkina, I. M.;
Grozovsky, O. V.; Dyachenko, O. G.; Polyakov, V. A.; Kuz’mina, L. G.
J . Chem. Soc., Dalton Trans. 1997, 4385.
2
σ(Pd-Csp ,ferrocene) bonds.
The diimine [Fe{(η5-C5H4)-C(H)dN-CH2-C6H5}2]
(1a ) was prepared by condensation of 1,1′-diformylfer-
rocene11 and benzylamine in a 1:2 molar ratio, using
the procedure described before for [(η5-C5H5)Fe{(η5-
(4) Crawford, S. S.; Kaesz, H. D. Inorg. Chem. 1977, 16, 3193.
(5) Wu, Y. J .; Huo, S. Q.; Yang, L.; Du, C. X. J . Organomet. Chem.
1995, 490, 249. Huo, S. Q.; Zhu, Y.; Wu, Y. J . J . Organomet. Chem.
1995, 490, 243. Wu, Y. J .; Huo, S. Q.; Zhu, Y.; Yang, L. J . Organomet.
Chem. 1994, 481, 235. Zhao, G.; Wang, Q. G.; Mak, T. C. W.
Organometallics 1998, 17, 3437.
(6) (a) Lo´pez, C.; Sales, J .; Solans, X.; Zquiak, R. J . Chem. Soc.,
Dalton Trans. 1992, 2321. (b) Bosque, R.; Lo´pez, C.; Sales, J .; Solans,
X.; Font-Bardia, M., J . Chem. Soc., Dalton Trans. 1994, 735. (c) Bosque,
R.; Lo´pez, C.; Sales, J .; Solans, X. J . Organomet. Chem. 1994, 483, 61.
(d) Wu, Y. J .; Liu, Y. H.; Ding, K. L.; Yuan, H. Z.; Mao, X. A. J .
Organomet. Chem. 1995, 505, 37.
(7) Zhao, G.; Xue, F.; Zhang, Z. Y.; Mak, T. C. W. Organometallics
1997, 16, 4023. Lo´pez, C.; Bosque, R.; Sainz, D.; Solans, X.; Font-
Bard´ıa, M. Organometallics 1997, 16, 3261.
(8) Ranatunge-Bandarage, P. R. R.; Duffy, N. W.; J ohnson, S. M.;
Robinson, B. H.; Simpson, J . Organometallics 1994, 13, 511.
(9) Lo´pez, C.; Bosque, R. J . Organomet. Chem. 1996, 524, 247.
Bosque, R.; Lo´pez, C.; Sales, J .; Solans, X.; Silver, J . J . Chem. Soc.,
Dalton Trans. 1996, 3195.
(10) Sugimoto, M.; Nonoyama, M. Inorg., Nucl. Chem. Lett. 1979,
405.
(11) Balavoine, G. G. A.; Doisneau, G.; Fillebeen-Khan, T. J .
Organomet. Chem. 1991, 412, 381.
10.1021/om980834e CCC: $18.00 © 1999 American Chemical Society
Publication on Web 03/11/1999

1268 Organometallics, Vol. 18, No. 7, 1999
Bosque et al.
Sch em e 1a
a
(i) Na2[PdCl4], Na(CH3COO)‚3H2O, in MeOH at room temperature. (ii) PPh3, in benzene at room temperature. (iii) SiO2 column
chromatography, CH2Cl2 as eluant. (iv) Small amounts of [PdCl2(PPh3)2] were also formed in these reactions (see text). (v) Traces
of the monocyclopalladated complexes 3a and 3c were also obtained when the reactions were carried out using the ferrocenylimines
1a or 1c as starting materials (see text).
finding is consistent with the results reported for [(η5-
C5H5)Fe{(η5-C5H4)-C(R)dN-R′}] {with R′ ) H or
CH3}.6a,b However, 1b and 1c were prepared success-
fully by reaction of 1,1′-diacetylferrocene and the amines
in refluxing toluene and in the presence of freshly
activated alumina.12 In these reactions large excesses
of the amines were needed to force the displacement of
the equilibria. Ligand 1d 13 was prepared in a similar
way, but using 1,1′-dibenzoylferrocene as starting mate-
rial. For 1d , the reaction requires longer times, ca. 2
weeks, and larger excesses of aniline. The difficulties
of preparing ligands 1 increase according to the se-
quence 1a , 1b ≈ 1c < 1d ; this variation might be
attributed to the larger bulk of the substituent on the
>C(O) group {CH3 or C6H5} versus hydrogen.14
Compounds 1 are orange (1b, 1c) or red solids (1a ,
1d ) at room temperature and have been characterized
by elemental analyses and infrared and NMR spec-
troscopies. The NMR studies of these compounds sug-
gested that only one isomer (anti) was present in
solution.
The reaction of ligand 1a with Na2[PdCl4] and Na(CH3-
COO)‚3H2O (in a 1:2:2 molar ratio) in methanol at room
temperature for 2 days produced a red solid. Subsequent
treatment of this material with PPh3 in benzene for 3
h and concentration of the solution to dryness gave a
deep red solid (Scheme 1), and three complexes could
F igu r e 1. Schematic view of the bis(cyclopalladated)
(12) The success of the syntheses of compounds 1b and 1c is strongly
dependent on the proper activation of the alumina. In our case the
activation was carried out by heating Al2O3 in a hood at 250 °C for 24
h. After this period the alumina was transferred to an oven at 130 °C
to avoid rehydration.
2
complexes containing σ(Pd-Csp ,ferrocene) bonds described so
far and of the 1,1′-ferrocenyldiimines of general formula
[Fe{(η5-C5H4)-C(R)dN-R′}2)] (1a -1d ) under study.
(13) This complex can also be synthesized using the procedure
described by Cais, M.; Ashkenazi, P.; Dani, S.; Gottlieb, J . In J .
Organomet. Chem. 1977, 124, 49, which requires the use of TiCl4 and
the aniline 1,1′-dibenzoylferrocene, molar ratio equal to 44:1, and
benzene as solvent. In addition, this procedure produces a mixture of
several compounds, and ligand 1d was separated (also in a low yield:
35%) by column chromatography.
(14) Hansch, C.; Leo, A.; Koekman, D. Exploring QSAR, Hydropho-
bic, Electronic and Steric Constants; ACS, Prof. Reference Book:
Washington, DC, 1995.
C5H4)-C(H)dN-R′}], with R′ ) phenyl or benzyl
groups,6a,b which consists of the reaction of the starting
materials in benzene using a Dean-Stark apparatus to
remove the azeotrope (benzene/water) formed in the
course of the reaction.6a,b This method failed for the
syntheses of the 1,1′-diimines [Fe{(η5-C5H4)-C(CH3)d
N-C6H4-4-R}2] {with R ) H (1b) or CH3 (1c)}.This

Heterodi- and Heterotrimetallic Compounds
Organometallics, Vol. 18, No. 7, 1999 1269
be isolated by column chromatography: [PdCl2(PPh3)2],
[Pd2{Fe[(η5-C5H3)-C(H)dN-CH2-C6H5]2}Cl2(PPh3)2]
(2a ), and small amounts (ca. 7-8%) of [Pd{[(η5-C5H3)-
C(H)dN-CH2-C6H5]Fe[(η5-C5H4)-C(H))N-CH2-
C6H5]}Cl(PPh3)] (3a ). Compounds 3a and 2a arise from
the mono- and 1,1′-bis(metalation) of the ligand, respec-
tively.
2
The activation of two ortho σ(Csp , ferrocene-H) bonds
in N-donor ferrocenyl ligands introduces planar chiral-
ity,2,15 and consequently, two stereoisomers {meso- and
d,l-forms} could be expected in the double cyclopalla-
dation of 1 (Scheme 1). Attempts to separate the two
isomers of 2a by either column chromatography or
fractional crystallization failed. However, the assign-
1
ment of the signals observed in the H NMR for each of
the isomers was carried out by comparison with the
results obtained for compounds [Pd2{Fe[(η5-C5H3)-
C(CH3)dN-R′]2)}Cl2(PPh3)2] (2b, 2c) (vide infra), and
the integration of the signals due to protons of the
>CHdN- group and the C5H3 ring revealed that the
two isomers coexisted in the molar ratio meso/d,l ) 1.2.
When the reaction was carried out using 1b or 1c and
identical experimental conditions, the coordination com-
plex [PdCl2(PPh3)2] and the two stereoisomers {meso-
and d,l-forms} of compounds [Pd2{Fe[(η5-C5H3)-C(CH3)d
N-R′]2}Cl2(PPh3)2] {with R′ ) C6H5 (2b), C6H4-4-CH3
(2c)} were isolated. The ratio between the two stereoi-
somers {meso-form/d,l-form ) 3.2 for 2b and 2.9 for 2c}
was clearly greater than for 2a (1.2). When the reaction
was performed using ligand 1c, a small amount (ca. 8%)
of [Pd{[(η5-C5H3)-C(CH3)dN-CH2-C6H5]}Fe[(η5-C5H4)-
C(CH3)dN-CH2-C6H5]}Cl(PPh3)] (3c) was also ob-
tained. In contrast, no evidence of the presence of
[Pd{[(η5-C5H3)-C(CH3)dN-(C6H4-4-CH3)]Fe[(η5-C5H4)-
C(CH3)dN-C6H5]}Cl(PPh3)] (3b) was detected when
the reaction was carried out with 1b.
Although these reactions were performed in identical
experimental conditions, compounds 2b and 2c were
obtained with a higher yield (52 and 46%) than 2a
(32%). This fact is consistent with previous studies on
the cyclopalladation of the ferrocenylimines [(η5-C5H5)-
Fe{(η5-C5H4)-C(R)dN-R′}] (with R ) H or CH3), since
for ligands with R ) CH3 the formation of the pallada-
cycle is achieved faster than for those with R ) H.6b
The two isomers of compounds 2b and 2c were charac-
terized by 1H, 13C, and 31P NMR spectroscopies (see
Experimental Section).
A perspective drawing of the molecular structure of
the meso-form of 2b is depicted in Figure 2. A selection
of bond lengths and angles is presented in Table 1. The
structure consists of discrete molecules of [Pd2{Fe[(η5-
C5H3)-C(CH3)dN-C6H5]2}Cl2(PPh3)2] separated by van
der Waals contacts. Each molecule has two “[Pd{(η5-
C5H3)-C(CH3)dN-C6H5}Cl(PPh3)]” fragments, which
contain a five-membered metallacycle formed by the
palladium, the nitrogen, and carbon atoms involved in
the imine bond and two carbon atoms of the C5H3 ring
{C(1) and C(5)}, thus confirming that cyclometalation
had taken place on the ferrocenyl unit. The bicyclic
system formed by the metallacycle and the C5H3 moiety
is practically planar, and their planes form an angle of
5.5°.
F igu r e 2. View of the molecular structure together with
the atom-numbering scheme for the meso-form of [Pd2{Fe-
[(η5-C5H3)-C(CH3)dN-C6H5]2}Cl2(PPh3)2] (2b).
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e m eso-F or m of Com p ou n d
[P d 2{F e[(η5-C5H3)-C(CH3)dN-C6H5]2}Cl2(P P h 3)2]
(2b) w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th eses
(A) Bond Lengths
Pd-P
2.333(10)
2.128(3)
1.421(6)
1.305(5)
1.506(6)
1.42(12)
Pd-Cl
2.3519(12)
2.006(4)
1.346(7)
1.422(5)
2.04(2)
Pd-N
Pd-C(1)
C(5)-C(6)
N-C(8)
Fe-Ca
C(1)-C(5)
N-C(6)
C(6)-C(7)
C-Ca
(B) Bond Angles
P-Pd-Cl
93.37(4)
80.3(2)
111.0(3)
114.3(4)
121.3(4)
126.8(3)
Cl-Pd-N
93.65(10)
92.78(12)
119.1(4)
114.2(3)
124.3(4)
N-Pd-C(1)
Pd-C(1)-C(5)
C(5)-C(6)-N
C(5)-C(6)-C(7)
Pd-N-C(8)
C(1)-Pd-P
C(1)-C(5)-C(6)
C(6)-N-Pd
C(7)-C(6)-N
a
Average value for the C5H3 units.
The palladium atom is tetracoordinated, since it is
bound to a chloride, the phosphorus atom of the PPh3,
the imine nitrogen, and the C(1) carbon atom of the
ferrocenyl fragment, giving a slightly distorted square-
planar environment around the palladium.16 The Pd-
ligand bond lengths (Table 1) as well as bond angles
between adjacent atoms in the coordination sphere of
the palladium are similar to those obtained in five-
2
membered palladacycles containing a σ(Pd-Csp ,ferrocene
)
bond.6
In complex 2b the two imine groups have an anti-
conformation, as reflected in the torsion angle C(5)-
C(6)-N-C(8) ) 173.9(4)°}. The >CdN- bond length
[1.305(5) Å] is similar to those reported for the related
ferrocenyl Schiff bases17 and their monocyclopalladated
(16) The least-squares equation of the plane defined by the atoms
Pd, P, N, Cl, and C(1) is (0.7958)XO + (-0.1388)YO + (0.5895)ZO )
5.4698. The deviations from the plane are Pd, -0.011; P, +0.036; Cl,
-0.034; N, 0.043 and C(1), -0.005 Å.
(15) Sokolov, V. I. Chirality and Optical Activity in Organometallic
Chemistry; Gordon and Breach: London, 1991.

1270 Organometallics, Vol. 18, No. 7, 1999
Bosque et al.
Sch em e 2a
a
(i) Monometalation. (ii) Metalation. (iii) Rotation around the C1′-C1′ bond.
complexes [Pd{[(η5-C5H3)-C(R)dN-R′]Fe(η5-C5H5)}Cl-
(PPh3)] {with R ) H, CH3, or Ph, and R′ ) phenyl or
benzyl groups}.6
The phosphorus and the imine nitrogen are in trans-
arrangement {P-Pd-N bond angle ) 172.49(10)°}, thus
consistent with the results obtained from 31P NMR. The
phenyl rings are planar and geometry of the ferrocenyl
moiety has average Fe-Cring and C-Cring bond lengths,
in good agreement with data reported for other ferrocene
derivatives.18
According to the general mechanism proposed for
cyclopalladation, the reaction proceeds in two steps: the
binding of the palladium to the nitrogen and the
subsequent electrophilic attack.19 When N-donor ferro-
cenyl ligands such as [(η5-C5H5)Fe{(η5-C5H4)-C(R)dN-
R′}] are used as starting materials, the reaction pro-
duces di-µ-chloro-bridged cyclopalladated derivatives,
i.e., [Pd{[(η5-C5H3)-C(R)dN-R′]Fe(η5-C5H5)}(µ-Cl)]2,
which are highly insoluble and difficult to characterize.
These polynuclear complexes react with Lewis bases,
L, giving [Pd{[(η5-C5H3)-C(R)dN-R′]Fe(η5-C5H5)}Cl-
(L)]. On these bases, the formation of the two stereoi-
somers (meso- and d,l-forms) of compounds 2a -2c can
be easily explained since once the first metallacycle is
formed (Scheme 2), the orientation of the other cyclo-
pentadienyl ring during the subsequent metalation
determines the stereochemistry of the reaction. That is
to say, if the electrophilic attack of the palladium takes
place on the C2′, site the meso-isomer would be formed.
The formation of the other stereoisomer (d,l-form)
requires (a) the rotation around the C1′-C6′ bond and
(b) the subsequent electrophilic attack of the palladium
to the C5′. It is worth noting that the interconversion of
the two stereoisomers (d,l-form T meso-form) would
require the cleavage of the σ(Pd-C) bond.
In addition, it is well-known that the reaction of the
di-µ-chloro-bridged complexes with Lewis bases, such
PPh3, does not involve cleavage of the Pd-N bond. Thus,
the differences in the relative proportion of the two
stereoisomers (meso-/d,l-form) in 2a (1.2), 2b (3.2), and
2c (2.9) might be related to the ease with which the
rotation around the C1′-C6′ bond occurs. A similar
argument has been used to explain the stereoselectivity
of the bis(cycloplatination) of [Fe{(η5-C5H4)-CH2-N-
(CH3)2}2].8
The presence of bulky substituents on the imine group
would hinder the free rotation around the C1′-C6′ bond.
Thus, an increase in the ratio meso-/d,l-form would be
expected. Since the substituents R and R′ in imines 1b
and 1c are bulkier14 than in 1a , the free rotation around
the C1′-C6′ bond would be more difficult and the
formation of the d,l-form of 2b and 2c would be less
favored.
More interesting are the results obtained when the
reaction was carried out using ligand 1d and identical
1
experimental conditions. The H and 13C NMR spectra
of the final product were more complex than expected.
Seven signals (of identical intensity) in the range 3.20-
1
5.20 ppm were observed in the H NMR spectrum. The
2D heteronuclear {1H-13C} correlation showed seven
cross-peaks in the range 3.0-5.2 ppm (Figure 3).
(17) Lo´pez, C.; Bosque, R.; Solans, X.; Font-Bard´ıa, M. New J . Chem.
1996, 20, 1295.
(18) Allen, T. H.; Kennard, O. Chem. Des. Automat. News 1993, 8,
146.
(19) Ryabov, A. D.; Sakodinskaya, I. K.; Yatsimirski, A. K. J . Chem.
Soc., Dalton Trans. 1985, 2629. Ryabov, A. D.; Yatsimirski, A. K. Inorg.
Chem. 1984, 23, 789. Ryabov, A. D. Inorg. Chem. 1987, 26, 1252.
Go´mez, M.; Granell, J .; Martinez, M. Organometallics 1997, 16, 2539.
Go´mez, M.; Granell, J .; Martinez, M. J . Chem. Soc., Dalton Trans.
1998, 37.
The 13C NMR spectra showed 10 signals in the range
105.0-70.0 ppm and two low-intensity signals at ca.
182.85 and 197.98 ppm, respectively. Comparison of the
position of these signals with 13C NMR data of 2a -2c
and of the monometalated derivative [Pd{[(η5-C5H3)-
C(C6H5)dN-C6H5]Fe(η5-C5H5)}Cl(PPh3)] (3e) {δ13C
(>CdN-) ) 183.44 ppm6c} allowed us to assign the

Heterodi- and Heterotrimetallic Compounds
Organometallics, Vol. 18, No. 7, 1999 1271
F igu r e 4. Plots of the variation of the formation enthalpy,
∆H (in kcal/mol), for the meso-forms of 2b (filled circles)
and 2d (filled squares) versus the torsion angle Φ (in
degrees). The variation of the formation enthalpy, ∆H, was
calculated according to the expression ∆H ) ∆Hform (for a
Φ value) - ∆Hform (for a Φ ) 180°).
F igu r e 3. Partial view of the 2D heteronuclear {1H-13C}
correlation (500 MHz) of the solid isolated in the reaction
of 1d . The numbers 3, 4, and 5 correspond to the protons
or carbons of the metalated C5H3 ring, and the numbers
2′, 3′, 4′, and 5′ refer to the nonmetalated C5H4 ring.
oisomers complex 2d were built. Their manipulation
showed that the phenyl rings bound to the imine carbon
cannot be coplanar with the C5H3 unit. This is consistent
with the arrangement of rings found in the crystal
structures of the imines [(η5-C5H5)Fe{(η5-C5H4)-C(R)d
N-R′}].17
signal at ca. 182.85 ppm to the >CdN- group. The
position of the singlet at 197.97 ppm was similar to that
observed in the 13C NMR spectrum of 1,1′-dibenzoyl-
ferrocene [198.46 ppm]20 and could be ascribed to the
>C(O) group. In addition, two bands [at 1628 and 1637
cm-1] were detected in the infrared spectrum. These
absorptions are ascribed to the stretching of the >Cd
N- and >C(O) groups, {ν{>C(O)}20 ) 1637 cm-1 for
1,1′-dibenzoylferrocene20}. The elemental analyses agreed
with those expected for [Pd{[(η5-C5H3)-C(C6H5)dN-
C6H5]Fe[(η5-C5H4)-C(O)dN-C6H5]}Cl(PPh3)] (4d), which
arises from the monocyclopalladation of the ligand and
the hydrolysis of one of the two >CdN- groups of ligand
1d . The IR spectrum of the crude solid isolated after
the reaction also showed a band at 1637 cm-1. This
suggested that the hydrolysis took place before the
chromatography. No evidence of the formation of any
other cyclopalladated complex was detected in this case.
As mentioned above, the reaction of 1a , 1b, or 1c, with
Na2[PdCl4] and Na(CH3COO)‚3H2O, produced the bis-
(cyclopalladated) compounds 2a -2c. For 1a and 1c,
small amounts of the monometalated derivatives (3a ,
3c) were also isolated. However, in none of these
reactions was there any evidence of the hydrolysis of
either of the two >CdN- bonds. In contrast, when 1d
was used, complex [Pd{[(η5-C5H3)-C(C6H5)dN-C6H5]-
Fe[(η5-C5H4)-C(O)dN-C6H5]}Cl(PPh3)] (4d ) (which re-
quires the hydrolysis of the imine group) was formed
instead of the bis(cyclopalladated) derivative [Pd2{Fe-
[(η5-C5H3)-C(C6H5)dN-C6H5]2}Cl2(PPh3)2] (2d ) (which
is formally analogous to 2a -2c), and the monometa-
lated derivative [Pd{[(η5-C5H3)-C(C6H5)dN-C6H5]Fe-
[(η5-C5H4)-C(C6H5)dN-C6H5]}Cl(PPh3)] (3d ) was not
detected.
In compounds 2, the relative orientation of the two
palladacycles can be described by the torsion angle
defined by C6, ø, ø′, and C6′ (hereafter referred to as Φ),
where C6 and C6′ are the imine carbon atoms of the two
C5H3 rings and ø, ø′ represent the centroids of these
rings. The use of molecular models for 2 suggests that
a parallel orientation of the two metallacycles (Φ ) 0°)
is not possible due to strong steric hindrance produced
by short contacts between the phenyl rings of the two
PPh3 {for the meso-form} or between the phenyl rings
of the PPh3 ligand in one moiety and the substituents
on the imine carbon {in the d,l-form}. For the meso-
form of 2, the less hindered orientation corresponds to
Φ ≈ 180° (which agrees with the X-ray data of 2b). The
use of the Spartan 4.1 program21 has allowed us to
compare the formation enthalpy for the different ar-
rangements of the two metallacycles in the meso-form
of 2b. Figure 4 shows the variation of the formation
enthalpy {∆H} for a wide variety of orientations {Φ from
130° to 230°}. For Φ values larger than 230° (or smaller
than 130°) the system collapses due to short contacts
between the CH3 group in one of the moieties and the
aryl rings of the PPh3 group in the other fragment. Data
shown in Figure 4 indicate that the rotation is resticted
to a narrow interval of Φ.
In complex 3d , which can be visualized as derived
from 2b by replacement of the two methyl groups by
phenyl rings, the distribution of the substituents in each
one of the moieties is more crowded, leading to an
increase of the steric hindrance, which would destabilize
the molecule. In fact, even for the less hindered ar-
rangement of the metallacycles in the meso-form of 3d
(Φ ) 180°) short contacts between the hydrogen atoms
on the meta-sites of the phenyl rings of the PPh3 ligand
(in one of the moieties) and two carbon atoms of the
imine C6H5 ring of the other half appeared (Hmeta‚‚‚Cmeta
0.85 Å and Hmeta‚‚‚Cpara 0.85 Å). Besides that, it is
To elucidate whether the differences observed in the
nature of the final products isolated in the cyclopalla-
dation of 1d , when compared with those of 1a -1c, could
be related to the steric hindrance introduced by the
bulky phenyl rings bound to the >CdN- groups in 1c,
molecular models for the ligand and for the two stere-
(20) Gmelins Handbuch der Anorganische Chemie: Ferrocen; Spring-
er-Verlag: Heidelberg, Germany, 1977; Vol. A3, p 181.
(21) SPARTAN 4.0; Wavefunction Inc.: 18401 Von Karman Ave
3370, Irvine, CA 92715, 1995.

1272 Organometallics, Vol. 18, No. 7, 1999
Bosque et al.
by filtration and air-dried {yields: 903 mg, (58%) for 1b and
764 mg (46%) for 1c}.
noteworthy to remark that in 3d tiny modifications of
the Φ angle (i.e. Φ ) 180 ( 5°) produce a significant
increase of the formation enthalpy (Figure 4). These
facts could be related with the ease with which the
hydrolysis of one of the two >CdN- groups takes place.
This process would significatly reduce the steric hin-
drance around the coordinative nitrogen and the pal-
ladium.
Ch a r a ct er iza t ion Da t a for 1b . Anal. (%) Calcd for
C26H24N2Fe (found): C, 74.29 (74.0); H, 5.75 (5.7); N, 6.66 (6.6).
IR: ν(>CdN-) ) 1618 cm-1.1H NMR (in ppm):21 ferrocenyl
moiety, 4.85 [4 H, H2 and H5], 4.50 [4 H, H3 and H4]; 2.15 [6
H, -C(CH3)dN-] and aromatic protons, 7.39 [4 H, HR], 7.09
[4H, Hâ] and 6.81 [2 H, Hγ]. 13C NMR (in ppm):22 ferrocenyl
moiety, 85.56 [C1], 72.39 [C2 and C5], 70.56 [C3 and C4]; 18.46
[CH3], 167.34 [>CdN-], and 152.01, 129.36, 123.56, and
120.15 [aromatic].
Exp er im en ta l Section
1c. Anal. (%) Calcd for C28H28N2Fe (found): C, 75.03 (74.9);
H, 6.25 (6.1); N, 6.30 (6.2). IR: ν(>CdN-) ) 1623 cm-1.1H
NMR (in ppm):22 ferrocenyl moiety, 4.80 [4 H, H2 and H5], 4.48
[4 H, H3 and H4]; 2.15 [6 H, -C(CH3)dN-]; 2.32 [6 H, CH3]
and aromatic protons, 7.10 [4 H, HR] and 6.64 [4 H, Hâ]. 13C
NMR (in ppm):22 ferrocenyl moiety: 85.70 [C1], 72.31 [C2 and
C5], 69.98 [C3 and C4]; 18.59 [CH3], 167.34 [>CdN-], 17.6
[CH3], 149.45, 132.91, and 122.54 [aromatic].
[F e{(η5-C5H4)-C(C6H5)dN-C6H5}2] (1d ). This compound
was prepared using the same procedure as for 1b and 1c; in
this case the progress of the reaction was monitored by IR
spectroscopy (yield: 38%).
Elemental analyses (C, H, and N) were carried out at the
Serveis Cientifico-Te`cnics de la Universitat de Barcelona.
Infrared spectra were obtained with a NICOLET-Impact 400
spectrophotometer using KBr pellets. 31P NMR spectra of 2,
3, and 4d were obtained with a Bruker-250-DRX instrument
using CDCl3 as solvent and P(OCH3)3 as reference [δ31P-
{P(OCH3)3} ) 140.17 ppm]. 13C{1H} NMR spectra were
obtained with a Varian-300 MHz instrument using CDCl3 as
solvent and TMS as internal standard. High-resolution 1H
NMR spectra and the heteronuclear {1H-13C} NMR experi-
ments were undertaken with a Bruker 500 MHz instrument
and using CDCl3 as solvent and TMS as internal standard.
Ch a r a ct er iza t ion Da t a for 1d . Anal. (%) Calcd for
Ma ter ia ls a n d Syn th eses. 1,1′-Diacetylferrocene, 1,1′-
dibenzoylferrocene, and the amines were obtained from com-
mercial sources and used as received. 1,1′-Diformylferrocene
was prepared as reported previously.12 The solvents except
benzene were distilled and dried before use (CH2Cl2 over CaO
and CH3OH over CaCl2).
C
36H28N2Fe (found): C, 79.41 (79.3); H, 5.18 (5.25); N, 5.14
(5.0). IR: 1602 cm-1 1H NMR data (in ppm):22 ferrocenyl
.
moiety, 4.87 [4 H, H2 and H5] and 4.53 [4 H, H3 and H4]; 6.9-
7.6 [20 H, aromatic].
[P d 2{F e[(η5-C5H3)-C(R)dN-R′]2}Cl2(P P h 3)2] {w ith R )
H, R′ ) CH2-C6H5 (2a ), R ) CH3, R′ ) C6H5 (2b), or C6H4-
4-CH3 (2c)}. The corresponding 1,1′-ferrocenyldiimine (1a -
1c) (0.720 mmol), Na2[PdCl4] (0.426 g, 1.45 mmol), and
Na(CH3COO)‚3H2O (0.197 g, 1.46 mmol) were suspended in
methanol (50 cm3). The reaction flask was protected from light
with aluminum foil and stirred at room temperature (ca. 20
°C) for 2 days. The dark red precipitate formed was collected
by vacuum filtration, washed with three portions (10 cm3) of
methanol, and air-dried. This material was then treated with
PPh3 (1.46 mmol) in 20 cm3 of benzene. The resulting mixture
was stirred at room temperature for 3 h. The undissolved
materials were removed by filtration, and the red filtrate was
concentrated to dryness on a rotary evaporator. The residue
was dissolved in CH2Cl2 (ca. 30 cm3) and filtered. The filtrate
was then passed through a SiO2 column (250 × 10 mm), using
CH2Cl2 as eluant. When the reaction was carried out using
ligand 1a , three different bands were collected. After concen-
tration to dryness of the first band eluted it gave complex
[PdCl2(PPh3)2]. A mixture of the two stereoisomers of 2a (meso-
and d,l-forms in a 1.2 molar ratio) was isolated after the
concentration to dryness of the second band and the subse-
quent treatment of the residue with 20 cm3 of n-hexane. The
reddish solid formed was collected by filtration and air-dried
(yield: 32%).
Some of the preparations described below require the use
of benzene, which should be handled with CAUTION.
[F e{(η5-C5H4)-CHdN-CH2-C6H4}2] (1a ). A 1.0 g amount
(4.14 mmol) of 1,1-[Fe{(η5-C5H4)-CH(O)]12 was suspended in
50 cm3 of benzene, stirred at room temperature for 30 min,
and filtered out. Then, the stoichiometric amount of benzy-
lamine (8.28 mmol) was added to the filtrate. The reaction
flask was then connected to a condenser equipped with a
Dean-Stark apparatus, and the reaction mixture was refluxed
until ca. 15 cm3 had condensed. The resulting solution was
filtered, and the filtrate was concentrated to dryness on a
rotary evaporator, giving a deep red solid, which was collected
and dried in vaccum (yield: 725 mg, 42%). Ch a r a cter iza tion
Da ta for 1a . Anal. (%) Calcd for C26H24N2Fe (found): C, 74.29
1
(74.5); H, 5.75 (5.9); N, 6.66 (6.5). IR: 1625 cm-1. H NMR (in
ppm):22 ferrocenyl moiety, 4.66 [4 H, H2 and H5] and 4.36 [ 4
H, H3 and H4]; 8.10 [2 H, -CHdN-]; 4.59 [2 H, -CH2-]; 7.2-
7.8 [10 H, aromatic]. 13C NMR (in ppm):22 ferrocenyl moiety,
81.96 [C1], 71.93 [C2, C5]; 70.19 [C3, C4]; 65.75 [-CH2-], 161.78
[-CHdN-] and 139.89, 129.01, 128.4, and 127.46 [aromatic].
[F e{(η5-C5H4)-C(CH3)dN-C6H4-4-R}2] {w ith R ) H (1b)
or CH3 (1c)}. 1,1′-Diacetylferrocene (1.0 g, 3.7 mmol), freshly
activated alumina (2.5 g), and 3.7 mmol of aniline (for 1b) or
4-methylaniline (for 1c) were suspended in dried toluene (50
cm3) and refluxed. To control the progress of the condensation
reaction, the infrared spectra of the solution were recorded.
Daily additions of small quantities of the amines (ca. 0.5 cm3)
and activated alumina (1.0 g) were needed to force the
displacement of the equilibria. This procedure was repeated
for 8-10 days until the infrared spectra did not exhibit the
band due to the asymmetric stretching of the >CdO group
[ν(CdO) ) 1665 cm-1].20 The undissolved materials were then
removed by filtration and washed with dried toluene until the
washings became colorless. The orange-red solution was
concentrated to dryness on a rotary evaporator, and the oil
formed was treated with n-hexane (ca. 30 cm3) and stirred at
room temperature for 30 min. The solids formed were collected
Three bands were collected when the reaction was per-
formed with ligand 1b or 1c; the first band contained the
coordination compound [PdCl2(PPh3)2]. The two stereoisomers
of compounds 2b and 2c were isolated from the two remaining
bands using the identical procedure as for 2a , yielding an
orange (meso-isomers) and a red solid (d,l-isomer). The molar
ratios (meso-form/d,l-form) were 3.2 and 2.9 for 2a and 2b,
respectively. The meso-forms exhibited in both cases higher
Rf values than the d,l-forms {yields: 460 mg (52%) for 2a and
402 mg (46%) for 2b}.
Ch a r a ct er iza t ion Da t a for 2a . Anal. (%) Calcd for
C
62H52N2Cl2FeP2Pd2 (found): C, 59.14 (59.1); H, 4.18 (4.1); N,
2.23 (2.2). IR: ν(>CdN-) ) 1578 cm-1. (meso-form) 1H NMR
(in ppm):22 ferrocenyl moiety, 3.25 [2 H, H3], 3.60 [ 2 H, H4],
3.72 [2 H, H5]; 5.16 and 4.60 [4 H, -CH2-]; 8.10 [2 H, -CHd
(22) Selected data. Numbering of the atoms corresponds to that
shown in Scheme 1.

Heterodi- and Heterotrimetallic Compounds
Organometallics, Vol. 18, No. 7, 1999 1273
N-23]. 31P NMR (in ppm): 35.63. (d,l-form) 1H NMR (in ppm):
Ta ble 2. Cr ysta llogr a p h ic Da ta a n d Deta ils of th e
Refin em en t of th e Cr ysta l Str u ctu r e of th e
m eso-F or m of
22
ferrocenyl moiety, 2.87 [2 H, H3]; 4.11 [2 H, H4], 4.22 [2 H,
H5]; 4.88 and 4.48 [4 H, -CH2-]; 8.19 [2 H, -CHdN-23]. 31P
NMR (in ppm): 36.92. 13C NMR (in ppm):22 ferrocenyl moiety,
93.18 [C1], 101.52 [C2], 78.28 [C3], 78.19 [C4] and 71.56 [C5];
182.60 [>CdN-], 17.95 [CH3].
F or 2b. Anal. (%) Calcd for C62H52N2Cl2FeP2Pd2 (found): C,
60.71 (60.75); H, 4.27 (4.3); N, 2.28 (2.2). IR: ν(>CdN-) )
1590 cm-1. (meso-form) 1H NMR (in ppm):22 ferrocenyl moiety,
3.09 [2 H, H3]; 4.16 [2 H, H4], 4.19 [2 H, H5]; 1.54 [6 H,
-C(CH3)dN-]. 31P NMR (in ppm): 37.53. 13C NMR (in ppm):
[P d 2{F e[(η5-C5H3)-C(CH3)dN-C6H5]2}Cl2(P P h 3)2]
(2b)
empirical formula
M
C62H52Cl2FeN2P2Pd2
1226.55
cryst size/mm
crystallographic system
a/Å
b/Å
c/Å
R ) γ/deg
â/deg
0.1 × 0.1 × 0.2
monoclinic
9.8267(13)
14.3970(10)
20.126(3) Å
90.0
90.130(10)
P21/c
2
1.431
1.066
0.710 69
1240
22
ferrocenyl moiety, 89.36 [C1], 103.37 [C2], 73.74 [C3], 77.17
[C4] and 69.78 [C5]; 181.20 [>CdN-], 21.69 [CH3]. (d,l -
form): 1H NMR (in ppm):22 ferrocenyl moiety, 2.85 [2 H, H3];
space group
Z
3.98 [2 H, H4], 4.22 [2 H, H5]; 2.09 [6 H, -C(CH3)dN-].31
P
Dc/g cm-3
NMR (in ppm): 38.85. 13C NMR (in ppm):22 ferrocenyl moiety,
93.18 [C1], 101.52 [C2], 78.28 [C3], 78.19 [C4] and 71.56 [C5];
182.60 [>CdN-], 17.95 [CH3].
abs coeff/mm-1
λ (Mo KR)/Å
F(000)
F or 2c. Anal. (%) Calcd for C64H56N2Cl2FeP2Pd2 (found): C,
61.27 (61.0); H, 4.50 (4.55); N, 2.23 (2.25). IR: ν(>CdN-) )
1585 cm-1. (meso-form) 1H NMR (in ppm):22 ferrocenyl moiety,
3.09 [2 H, H3]; 4.11 [2 H, H4], 4.15 [2 H, H5]; 1.63 [6 H,
Θ range for data collection/deg
from 2.02 to 30.01
-13 e h e 13,
0 e k e 20,
0 e l e 28
6735
h, k, l ranges
-C(CH3)dN-]; 2.37 [6 H, CH3]. 31P NMR (in ppm): 36.01. 13
C
no. of reflns collected
no. of ind reflns
no. of data
NMR (in ppm):22 ferrocenyl moiety, 74.76 [C3], 75.90 [C4], 70.41
[C5]; 183.26 [>CdN-]. (d,l-form) 1H NMR (in ppm):22 ferro-
cenyl moiety, 2.86 [2 H, H3]; 3.85 [2 H, H4]; 4.10 [2 H, H5];
2.05 [6 H, -C(CH3)dN-]. 31P NMR (in ppm): 37.03. 13C NMR
(in ppm):22 ferrocenyl moiety, 73.53 [C3], 71.11 [C4]; 70.92 [C5]
and 184.51 [-CHdN-].
6498 [R(int) ) 0.0375]
6448
no. of params
416
1.050
goodness of fit on F2
final R indices [I >2 σ(I)]
R indices (all data)
extinction coeff
R1 ) 0.0548, wR2 ) 0.1374
R1 ) 0.0656, wR2 ) 0.1520
0.0003(2)
[P d{[(η5-C5H3)-C(R)dN-R′]Fe[(η5-C5H4)-C(R)dN-R′]}-
Cl(P P h 3)] {w ith R ) H, R′ ) CH2-C6H5 (3a ), R ) CH3, R′
) C6H5-4-CH3 (3c)}. These compounds were isolated in a low
yield as byproducts in the syntheses of 2a and 2b. The isolation
of small amounts (yields < 10%) of these complexes was carried
out according to the following procedure: once the bands
containing compounds 2 were collected, a mixture of CH2Cl2/
MeOH {100:1} was used as eluant. The red band was then
collected and concentrated to dryness on a rotary evaporator,
giving a deep red residue, which was collected and air-dried.
Ch a r a ct er iza t ion Da t a for 3a . Anal. (%) Calcd for
largest diff peak and hole/e Å-3
0.635 and -0.407
was collected and concentrated to dryness on a rotary evapora-
tor. Addition of n-hexane followed by stirring at room tem-
perature gave a bright red solid, which was collected and dried
in a vacuum (yield: 385 mg, 46%).
Ch a r a cter iza tion Da ta for 4d . Anal. (%) Calcd for C48H38
ClFeNOPPd: C, 66.08 (65.95); H, 4.27 (4.3); N, 1.61 (1.6). IR:
ν(>CO) ) 1637 and ν(>CdN-) ) 1628 cm-1 1H NMR (in
-
.
ppm):22 ferrocenyl moiety, 3.54 [1 H, H3]; 4.18 [1 H, H4], 4.02
[1 H, H5]; 4.31 [1 H, H3′]; 4.48 [1 H, H4′], 4.62 [1 H, H2′] and
4.82 [1 H, H5′].13C NMR (in ppm):22 ferrocenyl moiety, meta-
lated ring, 102.76 [C1], 92.47 [C2], 78.26 [C3], 73.20 [C4] and
73.18 [C5]; nonmetalated ring, 78.71 [C1′], 73.18 [C2′], 71.90
[C3′], 75.62 [C4′] and 72.8 [C5′]; 182.84 [>CdN-] and 197.97
[>C(O)]. 31P NMR (in ppm): 36.70 ppm.
C
44H38N2ClFePPd (found): C, 64.58 (64.7); H, 4.65 (4.6); N,
3.40 (3.3). H NMR (in ppm):22 metalated ring, 3.40 [1 H, H3];
3.81 [1 H, H4], 3.98 [1 H, H4]; 7.90 [1 H, -CHdN-];23
nonmetalated ring, 4.33 [1 H, H2], 4.37 [1 H, H3]; 4.65 [1 H,
H4], 4.76 [1 H, H4] and 8.11 [1 H, -CHdN-]. 31P NMR (in
ppm): 38.40.
1
Cr ysta llogr a p h y. A summary of the crystal data for the
meso-form of 2b is given in Table 2. A prismatic red crystal
(0.1 mm × 0.1 mm × 0.2 mm) was selected and mounted on
an Enraf-Nonius CAD4 four-circle diffractometer. Unit cell
parameters were calculated from accurate settings of 25
automatically centered reflections in the range 12° e θ e 21°
and refined by the least-squares method. Intensities were
collected with graphite-monochromated Mo KR radiation,
using ω-2θ scans. The numbers of collected reflections in the
range 2.02° e θ e 30.01° and those assumed as observed [I >
2σ(I)] are given in Table 2. Three reflections were measured
every 2 h as orientation and intensity control, and no signifi-
cant intensity decay was observed. Lorentz-polarization cor-
rections were made but not for absorption.
F or 3c. Anal. (%) Calcd for C44H42N2ClFePPd (found): C,
1
64.88 (64.8); H, 4.97 (5.05); N, 3.29 (3.3). H NMR (in ppm):22
metalated ring, 3.37 [1 H, H3]; 4.06 [1 H, H4], 4.09 [1 H, H5];
2.07 [3 H, -C(CH3)dN-]; nonmetalated ring, 4.38 [1 H, H2],
4.22 [1 H, H3]; 4.48 [1 H, H4], 4.67 [1 H, H5]; 2.25 [3 H,
-C(CH3)dN-]. 31P NMR (in ppm): 38.40.
[P d {[(η5-C5H3)-C(C6H5)dN-C6H5]}F e[(η5-C5H4)-C(O)-
(C6H5)]}Cl (P P h 3)] (4d ). The diimine 1d (0.500 g, 0.92 mmol),
Na2[PdCl4] (0.541 g, 1.84 mmol), and NaCH3COO‚3H2O (0.251
g,1.84 mmol), were suspended in 50 cm3 of methanol. The
reaction flask was protected from light with aluminum foil and
stirred at ca. 20 °C for 2 days. The dark red solid formed was
filtered out, washed with methanol until colorless mother
liquors were obtained, and air-dried. This material was then
suspended in 50 cm3 of benzene and treated with 0.482 g (1.84
mmol) of PPh3. The reaction mixture was stirred at room
temperature (ca. 20 °C) for 3 h. After this period the undis-
solved materials were removed by filtration and discarded, and
the red filtrate was concentrated to dryness on a rotary
evaporator. The residue formed was dissolved in CH2Cl2 (15
cm3) and passed through an SiO2 column (15 × 1.5 mm).
Elution with CH2Cl2 produced the release of a red band, which
The structure was solved by direct methods using the
SHELXS computer program24 and refined by the full-matrix
least-squares method with the SHELX93 computer program,25
using 6448 reflections (very negative intensities were not
2
2 2
assumed). The function minimized was ∑w||Fo| - |Fc| | , where
2
2
w ) [σ2(I) + (0.0990P)2 + 0.1314P]-1, and P ) (|Fo| + 2|Fc| )/
3. Values of f, f ′, and f ′′ were taken from the literature.26
(24) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(25) Sheldrick, G. M. SHELX93. A computer program for determi-
nation of X-ray crystal structures; University of Go¨ttingen: Germany,
1990.
3
(23) Doublet due to phosphorus coupling J (P-H) (in Hz) ) 7.3 (2a )
and 7.1 (3a ).

1274 Organometallics, Vol. 18, No. 7, 1999
Bosque et al.
Twenty-three hydrogen atoms were located from a difference
synthesis and refined with an overall isotropic temperature
factor, and three hydrogen atoms were computed and refined
with an overal isotropic temperature factor using a riding
model. The number of refined parameters was 416. The final
R indices and further details concerning the refinement of the
crystal structure are summarized in Table 2.
the formation enthalpy for each one of the conformations
{defined by the Φ value}. For 2d , the calculations were
performed similarly, but replacing the two methyl groups of
2b by phenyl rings.
Ack n ow led gm en t. We are grateful to the Ministe-
rio de Educacio´n and to the Generalitat de Catalunya
for financial support (Grants PB96-0164 and 1997-SGR-
0044).
Com p u ta tion a l Deta ils. The SPARTAN 4.0 program21 was
used to calculate the formation enthalpy {∆Hform} of the meso-
forms of 2b and 2d for a wide variety of the torsion angle: Φ
defined by C6, ø, ø′, and C6′ , where C6 and C6′ are the imine
carbon atoms of the two C5H3 rings and ø, ø′ represent the
centroids of these rings. For 2b, the atomic coordinates of all
atoms obtained from the X-ray studies (Φ ) 180°) were used
as imput in the CERIUS2.0 program27 to generate the different
arrangements of the two halves of the molecule, and the atomic
coordinates obtained for each one of the Φ values were
transferred to the SPARTAN 4.0 program21 in order to obtain
Su p p or tin g In for m a tion Ava ila ble: Tables containing
final atomic coordinates for non-hydrogen atoms and equiva-
lent isotropic displacement parameters (S1), a complete list
of bond lengths and angles (S2), anisotropic displacement
parameters (S3), hydrogen coordinates (S4), and hydrogen
bond lengths and angles (S5) for the meso-form of 2b. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(26) International Tables of X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974, Vol. 4, pp 99, 100, and 149.
(27) CERIUS2.0, Modeling Environment; Molecular Simulation
Incorporated, San Diego, CA 92121-3742, 1994.
OM980834E