Synthesis and Characterization of a Stable Organolead(II) Compound: Bis[2-(N,N-dimethylaminomethyl)ferrocenyl]lead

Article abstract of DOI:10.1021/om990614g

The reaction of {C,N-[Fe(η⁵-C₅H₅)(η⁵-C ₅H₃-(CH₂NMe₂)-2)]}Li, [FcN]Li, with PbCl₂ yields the new stable tetracoordinated diorganolead(II) compound [FcN]₂Pb, 1, as a mixture of two diastereomers. In the solid state only the meso-diastereomer exists, which crystallizes in two polymorphs, P2₁/c and C2/c. The ratio of meso / rac-diastereomers in solution is solvent- and temperature-dependent, consistent with an intermolecular exchange between diastereomers. This is the very first observation of such an exchange for lead(II) compounds. An intramolecular exchange process is responsible for equivalency of both FcNgroups in solution. The NMR measurements of 1 revealed the authentic spectroscopical data: ¹³C-²⁰⁷Pb coupling constants in solid-state ¹³C NMR spectra.

Full text of DOI:10.1021/om990614g

1438
Organometallics 2000, 19, 1438-1441
Syn th esis a n d Ch a r a cter iza tion of a Sta ble
Or ga n olea d (II) Com p ou n d :
Bis[2-(N,N-d im eth yla m in om eth yl)fer r ocen yl]lea d †
Naka Seidel,‡ Klaus J acob,*,‡ Adolphus A. H. van der Zeijden,‡ Heike Menge,§
Kurt Merzweiler,‡ and Christoph Wagner‡
Institut fu¨r Anorganische Chemie, Martin-Luther-Universita¨t Halle-Wittenberg,
D-06099 Halle/ Saale, Germany, and Fachbereich Physik der Martin-Luther-Universita¨t
Halle-Wittenberg, Fachgruppe NMR, Friedemann-Bach-Platz 6,
D-06108 Halle/ Saale, Germany
Received August 2, 1999
Summary: The reaction of {C,N-[Fe(η5-C5H5)(η5-C5H3-
(CH2NMe2)-2)]}Li, [FcN]Li, with PbCl2 yields the new
stable tetracoordinated diorganolead(II) compound
[FcN]2Pb, 1, as a mixture of two diastereomers. In the
solid state only the meso-diastereomer exists, which
crystallizes in two polymorphs, P21/ c and C2/ c. The
ratio of meso/ rac-diastereomers in solution is solvent-
and temperature-dependent, consistent with an inter-
molecular exchange between diastereomers. This is the
very first observation of such an exchange for lead(II)
compounds. An intramolecular exchange process is
responsible for equivalency of both FcN groups in solu-
tion. The NMR measurements of 1 revealed the authentic
spectroscopical data: 13C-207Pb coupling constants in
solid-state 13C NMR spectra.
Sch em e 1
In tr od u ction
The chemistry of divalent organolead compounds, in
which the organic groups are σ-bonded to the metal, was
until recently very poorly investigated in comparison
to lead(IV) organometallic chemistry. Although Lappert
et al.1 reported the isolation of the very first plumbylene
Pb[CH(SiMe3)3]2 already in 1973, its structure has not
been determined yet.2,3 The difficulty in isolating these
compounds is their facile disproportionation to elemen-
tal lead and hexaorganodilead compounds. The few
plumbylenes that could be isolated owe their stability
to either steric shielding by voluminous alkyl4 or aryl2,5,6
groups, intramolecular stabilization,2,7,8 or formation of
diplumbenes.7,9 We now report on the formation and
characteristics of a new stable diorganolead(II) com-
pound, {C,N-[Fe(η5-C5H5)(η5-C5H3(CH2NMe2)-2)]}2Pb,
[FcN]2Pb, 1, which is stabilized by intramolecular Pb-N
interactions.
Resu lts a n d Discu ssion
The reaction of PbCl2 with 2 equiv of [FcN]Li in
1
diethyl ether yields a solution of 1 (Scheme 1). The H
and 13C NMR data of 1 in C6D6 at 25 °C (after taking a
sample and removal of ether in vacuo) show that
[FcN]2Pb appears in solution as a mixture of diastere-
omers 1a and 1b, respectively, in the ratio of 7:1. After
cooling the solution, only the major diastereomer 1a
crystallizes in the form of large deep-red prisms in 75%
yield. The compound can be handled in air for a few
minutes, but in solution it decomposes immediately
when exposed to air. It is thermally stable to its melting
point (123 °C). The EI mass spectrum shows a molecular
peak at m/z 692 with 80% relative intensity. 1 is readily
soluble in both polar and nonpolar solvents.
* E-mail: jacob@chemie.uni-halle.de.
† Dedicated to Professor Karl-Heinz Thiele on the occasion of his
70th birthday.
‡ Institut fu¨r Anorganische Chemie.
§ Fachbereich Physik der Martin-Luther-Universita¨t Halle-Witten-
berg.
(1) Davidson, P. J .; Harris, D. H.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1976, 2268.
(2) Stu¨rmann, M.; Weidenbruch, M.; Klinkhammer, K. W.; Lissner,
F.; Marsmann, H. Organometallics 1998, 17, 4425.
(3) Reference 4c in ref 2: “The plumbylene has a Pb‚‚‚Pb separation
of 412.9 pm and a trans-bent angle of 34.2°: Klinkhamer, K. W.;
Schwarz, W. unpublished results.”
X-ray diffraction analysis revealed two monoclinic
polymorphs of 1a , with different space groups, P21/c
(Figure 1) and C2/c. Both polymorphs were obtained
from the same crystallization. The structures are virtu-
ally identical. In the discussion below, the data of the
(4) Eaborn, C.; Ganicz, T.; Hitchcock, P. B.; Smith, J . D.; So¨zerli, S.
E. Organometallics 1997, 16, 5621.
(5) Brooker, S.; Buijink, J .-K.; Edelmann, F. T. Organometallics
1991, 10, 25.
(6) Simons, R. S.; Pu, L.; Olmstead, M. M.; Power, P. P. Organo-
metallics 1997, 16, 1920.
(7) Eaborn, C.; Hitchcock, P. B.; Smith, J . D.; So¨zerli, S. E.
Organometallics 1997, 16, 5653.
(8) Hitchcock, P. B.; Lappert, M. F.; Wang, Z.-X. J . Chem. Soc.,
Chem. Commun. 1997, 1113.
(9) Stu¨rmann, M.; Saak, W.; Weidenbruch, M.; Klinkhammer, K.
W. Eur. J . Inorg. Chem. 1999, 579.
10.1021/om990614g CCC: $19.00 © 2000 American Chemical Society
Publication on Web 03/10/2000

Notes
Organometallics, Vol. 19, No. 7, 2000 1439
angle of 95.1(6)° [94.8(4)°]. The Pb-N bond lengths of
2.638(6) and 2.727(5) Å [2.660(5) and 2.707(5) Å] are
significantly longer than those in nitrogen-centered
12
lead(II) compounds, e.g., 2.24(2) Å in Pb[N(SiMe3)2]2
or 2.465 Å (av) in Pb[{N(SiMe3)2}PPh2]2,13 but may be
compared to those of 2.678 Å (av) in Pb[CH2PMe2d
NSiMe3]2.8 The Pb-C(sp2) bond lengths of 2.310(9) and
2.283(6) Å [2.301(2) and 2.298(1) Å] correspond well to
the Pb-C(sp2) distance of 2.336 Å in Pb[C6H2(CF3)3-
5
2,4,6]2 and that of 2.296(4) Å in {(2,4,6-iPr3C6H2)[(Si-
Me3)3Si]Pb}2.9 The small bite angle of the FcN ligand
(C-Pb-N is about 71°) causes distortion around the
R-carbon and nitrogen atoms. Whereas the C-N-C
angles have ideal values, the Pb-N1-C11 and Pb-N2-
C24 angles (103.6(6)° [103.9(4)°] and 99.2(2)° [103.6(5)°],
respectively) are smaller than the other Pb-N-C
angles. Similarly, the C2-C1-Pb and C15-C14-Pb
(115.3(1)° [116.0(7)°] and 114.7(6)° [115.1(2)°], respec-
tively) are smaller than the C5-C1-Pb and C18-C14-
Pb angles (136.3(8)° [138.2(4)°] and 139.1(7)° [137.1(1)°],
respectively).
F igu r e 1. Molecular structure of 1 (P21/c polymorph) with
thermal ellipsoids at 50% probability level. Hydrogen atoms
are omitted for clarity.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [F cN]2P b, 1a
P21/c
C2/c
Solid-state 13C MAS NMR measurements at 25 °C
confirmed the results of the X-ray diffraction analysis.
In the solid state only one diastereomer, meso-[FcN]2Pb,
1a , is present. Due to the unequivalency of the FcN
groups, there is one set of signals for each group. Four
slightly broadened signals for the methyl groups are
present. The signals of the R-carbon atoms appear at
Pb-C1
2.311(4)
2.284(4)
2.684(4)
2.728(4)
94.8(1)
158.6(1)
71.5(1)
71.3(1)
2.301(4)
2.298(5)
2.708(5)
2.661(4)
95.2(2)
157.7(1)
70.8(2)
71.8(2)
Pb-C14
Pb-N1
Pb-N2
C1-Pb-C14
N1-Pb-N2
C1-Pb-N1
C14-Pb-N2
C1-Pb-N2
C14-Pb-N1
Pb-N1-C11
Pb-N1-C12
Pb-N1-C13
Pb-N2-C24
Pb-N2-C25
Pb-N2-C26
Pb-C1-C2
Pb-C14-C15
Pb-C1-C5
Pb-C14-C18
C-N-C (mean)
96.5(1)
91.6(1)
96.9(2)
90.7(2)
1
148.8 and 157.1 ppm, with coupling constants J C,Pb of
1260 and 1340 Hz, respectively [207Pb has 22.7% abun-
dance]. This is a rare example of 13C,207Pb coupling
constants of plumbylene compounds determined in solid-
state NMR measurements.
103.7(3)
114.9(3)
106.4(3)
99.2(2)
115.4(3)
111.4(3)
115.3(3)
114.8(3)
136.4(3)
139.2(3)
110.4(3)
103.9(4)
115.9(3)
105.8(3)
103.6(6)
113.3(4)
107.9(4)
116.1(3)
115.1(3)
138.2(4)
137.1(4)
110.0(6)
The 1H and 13C NMR data in C6D6 at 25 °C show only
one set of signals for both FcN groups in each diaste-
reomer, indicating intramolecular dynamics. In the 13C-
{1H} NMR spectrum (C6D6, rt) several signals of both
diastereomers are attended by satellites, due to coupling
with 207Pb. The chemical shift of the R-carbon atom of
the main diastereomer 1a , which appears at 151.1 ppm,
centric monoclinic modification will be given in paren-
theses. Selected geometrical data of both polymorphs
are listed in Table 1. The crystal structure in both
polymorphs is built up from discrete monomers. The
FcN ligand is chiral; in 1a one of the ligands is in R-
and the other in S-configuration (meso-diastereomer),
and therefore it is assumed that the other, minor
diastereomer 1b possesses a set of R,R (or S,S)-configu-
rated FcN ligands (rac-diastereomer). The shortest Pb-
Pb separation is 6.74 Å, which is beyond bonding
distance. The Pb-Pb distance in the second polymorph
(5.54 Å) is significantly shorter and might indicate a
weak interaction in the solid state reminiscent of other
metal-metal bonded dimeric plumbylenes.2,10,11 The
lead atom is four-coordinated with two chelating C,N-
bonded FcN groups. The molecule has a distorted
trigonal bipyramidal geometry in which the localized
lone pair occupies one of the equatorial positions, and
the amino groups are axial. The N1-Pb-N2 angle is
157.6(1)° [157.7(1)°]. The distortion is mainly caused by
the lead electron lone pair, which is in agreement with
the VSEPR principle. It leads to an acute C1-Pb-C14
1
shows a coupling constant J C,Pb ) 1305 Hz. These data
correspond nicely with the solid-state NMR data (vide
supra). The only literature data are from Stu¨rmann et
al.,2 with a value of 1288 Hz in a diarylplumbylene.
Further couplings are found for the signal at 46.3 ppm
attributed to the NMe2 group (2J C,Pb ) 21 Hz) and for
the signals of the substituted Cp ring at 70.1 ppm (J )
33 Hz), 70.2 ppm (J ) 47 Hz), and 78.2 ppm (J ) 58
Hz). Due to its low abundance, satellites for the minor
diastereomer 1b were only observed for the signal of
the methyl groups at 46.7 ppm (2J C,Pb ) 19 Hz) and for
the R-carbon atom at 148.4 ppm (1J C,Pb ) 1272 Hz). The
coupling constants are very similar to those of 1a . By
comparing the chemical shifts in the solution NMR
spectra with those in the solid-state NMR spectrum, it
is concluded that meso-[FcN]2Pb is the main diastereo-
mer 1a .
At -50 °C in toluene-d8 the signals of methyl and
methylene groups of 1a are slightly broadened. At -80
°C there are two signals for the methyl groups of 1a in
a ratio of 1:3 at 1.94 and 2.25 ppm, respectively. As one
(10) Klinkhammer, K. W.; Fa¨ssler, F. T.; Gru¨tzmacher, H. Angew.
Chem. 1998, 111, 145; Angew. Chem., Int. Ed. 1998, 37, 124.
(11) Stu¨rman, M.; Saak, W.; Marsmann, H.; Weidenbruch, M.
Angew. Chem. 1999, 111, 145; Angew. Chem., Int. Ed. 1999, 38, 187.
(12) Fjeldberg, T.; Hope, H.; Lappert, M. F.; Power, P. P.; Thorne,
A. J . J . Chem. Soc., Chem. Commun. 1983, 639.
(13) Kiliman, U.; Noltemeyer, M.; Edelmann, F. T. J . Organomet.
Chem. 1993, 443, 35.

1440 Organometallics, Vol. 19, No. 7, 2000
Notes
Sch em e 2
expects four signals for these groups, the chemical shifts
of three methyl groups probably coincide. The signals
of the methylene groups are split into four doublets. The
signal of the C5H5 group is also split into two signals at
3.91 and 4.21 ppm. We could not observe the decoales-
cence of the methyl signals of 1b, because of overlap
with signals of the meso-diastereomer. Due to C2 sym-
metry, only two signals for the methyl groups should
be seen. The temperature-dependent NMR data can be
explained by a rapid dissociation of one of the Pb-N
bonds and recoordination (Scheme 2).
As mentioned before, solution NMR data show the
presence of both diastereomers, in contrast to the solid-
state NMR data. Their ratio measured in different
solvents (C6D6, toluene-d8, CDCl3, THF-d8) at 25 °C was
within the range 6:1 to 8:1. The ratio is temperature-
dependent as well and suggests an intermolecular
exchange between diastereomers. The proportion of 1a
is higher at lower temperatures. To our knowledge, this
is the first observation of such a process for plumbylene
compounds. The equilibrium constant K (1a /1b) gradu-
ally changes from 4.8 at +90 °C to 22.2 at -80 °C in
toluene-d8. Plotting ln K against 1/T gives a straight
line (r ) 0.998) from which the thermodynamical
parameters ∆H ) 5.1 kJ mol-1 and ∆S ) 0.99 J K-1
mol-1 were obtained.
ferrocene, FcND. [FcN]2Pb can also act as an organyl-
ating reagent: reaction with HgCl2 afforded [FcN]2Hg15
as a 1:1 mixture of diastereomers.
Using cyclic voltammetry [FcN]2Pb in CH2Cl2 under-
goes a single-stepped two-electron oxidation at E°′ )
+0.40 V (accompanied by yellow-to-blue color change)
having features of chemical reversibility (at 0.05 V s-1
∆ep ) 80 mV, blue-to-yellow change accompanies reduc-
tion). The redox process takes place on the FcN ligand
of [FcN]2Pb and not on the Pb center of the molecule.
The oxidation potential may be compared with that of
free FcNH, which oxidizes reversibly at E°′ ) +0.38 V;
in addition, the blue color is typical for the formation
of ferricinium cation. After several cycles of exhaustive
oxidation/reductions the compound decomposes.
As 1 is a nonreducing reagent, it might be a promising
starting material for the synthesis of early transition
metal complexes bearing the FcN ligand.
Exp er im en ta l P a r t
Gen er a l Com m en ts. All operations were carried out under
a purified argon atmosphere in Schlenk tubes. Solvents used
in reactions were distilled under argon and carefully dried over
conventional drying agents.
The 1H and 13C{1H} NMR spectra were obtained on a Varian
1
GEMINI XL-300 spectrometer, the H low-temperature NMR
Two mechanistic pathways can be considered for the
observed intermolecular exchange. Both of them invoke
at first the interaction of two [FcN]2Pb units. In the first
one, this is followed by a concerted intramolecular
migration of two σ-bonded FcN groups. That is, a
dyotropic rearrangement of two FcN groups, as consid-
ered probable for a similar exchange of aryl groups in
tetraaryldisilenes.14 In the second one, the migration
of only one FcN group generates a zwitterionic form,
followed by the shift of a second FcN group back to the
incipient lead atom. The unimolecular mechanism of the
interconversion is considered to be highly unlikely,
because it should involve a 1,3-exchange along the Cp
ring of a C-Pb bond against a C-H bond, to convert
one enantiomer of the FcN ligand into the other.
In corroborating the stabilizing effect of the CH2NMe2
side chain in 1, we reacted 2 equiv of ferrocenyllithium,
FcLi, with PbCl2 in ether. No Fc2Pb is formed; instead
decomposition took place with formation of ferrocene
(FcH), elemental lead, and LiCl. In the presence of
triethylborane [FcN]2Pb decomposed after a few hours
at room temperature. The weak BfN coordination is
obviously strong enough to decompose the compound 1
completely. With methanol-d4 1 reacted immediately,
giving a white precipitate of Pb(II) methanolate and a
solution of (1-deuterio)(2-N,N-dimethylaminomethyl)-
spectra on a Varian Unity 500. 13C MAS NMR spectra were
recorded on a Varian INOVA 400 MHz. Mass spectra were
recorded on a AMD 402 by EI at 70 eV. Materials and
apparatus for electrochemistry have been described else-
where;16 all potential values are referenced to the saturated
calomel electrode.
The organolithium reagents FcNLi17 and FcLi18 were pre-
pared as solids as previously described.
Bis[2-(N,N-d im eth yla m in om eth yl)fer r ocen yl]lea d (1).
To a suspension of FcNLi (5.48 g, 22.0 mmol) in 250 mL of
diethyl ether cooled at -50 °C was slowly added a suspension
of PbCl2 (2.79 g, 10.0 mmol) in 100 mL of diethyl ether with
vigorous stirring. The reddish reaction mixture was stirred
overnight, being allowed to warm to room temperature. LiCl
was filtered off and the filtrate stripped to dryness. The deep-
red solid was isolated by exhaustive extraction of the residue
with pentane. Yield: 80%. Anal. Calcd for C26H32N2Fe2Pb: C,
45.18; H, 4.63; N, 4.05. Found: C, 45.21; H, 4.76; N, 3.90. NMR
data for 1a (1b in brackets): 1H NMR (C6D6, 25 °C): δ 2.22
1
[2.29] (12H, NMe2), 2.86 [2.80] (d, 2H, CH2N, J C,H ) 13 Hz
[14 Hz]), 3.93 [3.71] (d, 2H, CH2N, 1J C,H ) 13 Hz [14 Hz]), 3.91
[4.31] (2H, C5H3), 3.95 [4.32] (2H, C5H3), 4.02 (10H, C5H5), 4.12
[4.33] (2H, C5H3). 13C{1H} NMR (C6D6, 25 °C): δ 46.3 [46.7]
(NMe2, 2J C,Pb ) 21 Hz [19 Hz]), 63.5 [62.8] (-CH2N), 69.0 [68.8]
(15) Seidel, N.; J acob, K. Unpublished results.
(16) Togni, A.; Hobi, M.; Rihs, G.; Rist, G.; Albinati, A.; Zanello, P.;
Zech, D.; Keller, H. Organometallics 1994, 13, 1224.
(17) Rausch, M. D.; Moser, G. A.; Maede, C. F. J . Organomet. Chem.
1973, 51, 1.
(14) Yokelson, H. B.; Maxka, J .; Siegel, D. A.; West, R. J . Am. Chem.
Soc. 1986, 108, 4239.
(18) Rebiere, F.; Samuel, O.; Kagan, H. B. Tetrahedron Lett. 1990,
31, 3121.

Notes
Organometallics, Vol. 19, No. 7, 2000 1441
(C5H5), 70.1 [70.4] (C5H3, J C,Pb ) 33 Hz), 70.2 [70.4] (C5H3,
J C,Pb ) 47 Hz), 78.2 [78.1] (C5H3, J C,Pb ) 58 Hz), 97.8 [98.2]
Cr ysta l Str u ctu r e Deter m in a tion . Data were collected
a STOE IPDS diffractometer using Mo KR radiation
on
1
(C5H3-CH2NMe2), 152.1 [147.3] (Pb-C5H3, J C,Pb ) 1305 Hz
(0.71073 Å) and corrected for Lorentz, polarization, and
absorption effects. The structures were solved by direct phase
determination with SHELXS-9719 and refined by a full-matrix
least-squares refinement on F2 with anisotropic temperature
factors for all non-hydrogen atoms and isotropic factors for all
hydrogen atoms using SHELXL-97.20 All hydrogen atoms were
found in the difference Fourier map.
[1276 Hz]). Solid-state 13C MAS NMR: δ 44.7/48.4 (NMe2),
62.6/63.7 (CH2N), 68.9/69.3 (C5H5), 70.0/77.2 (C5H3), 79.1
(C5H3), 97.1/100.1 (C5H3-CH2NMe2), 148.8 (1J C,Pb ) 1260 Hz)/
1
1
157.1 (Pb-C5H3, J C,Pb ) 1340 Hz). H NMR (toluene-d8, -80
°C): 1.94 (9H, NMe2) 2.17 (3H, NMe2) [2.25 (12H, NMe2)], 2.63
1
1
(d, 1H, CH2N, J C,H ) 13 Hz) 2.86 (d, 1H, CH2N, J C,H ) 13
1
Hz) [2.72 (d, 2H, CH2N, J C,H ) 14 Hz)], 3.82 (d, 1H, CH2N,
Crystal data for meso-bis[2-(N,N-dimethylaminomethyl)-
ferrocenyl]lead (the data for the other polymorph are given in
brackets): C26H32N2Fe2Pb, 1a , M ) 691.43, monoclinic, P21/c
[C2/c], a ) 11.643(4) [19.239(5)] Å, b ) 10.994(3) [19.628(2)]
Å, c ) 20.086(6) [24.756(6)] Å, â ) 104.54(4) [103.95(3)]°, Z )
4 [8], V ) 2488.1(13) [4913(2)] Å3, T ) 193 K, µ ) 7.916 [8.018]
mm-1, specimen 0.3 × 0.6 × 0.8 [0.1 × 0.3 × 0.4] mm, 22 778
[16 388] collected reflections, R1 ) 0.0268 [0.0290] for 4664
[4773] [I > 2σ(I)], wR2 ) 0.0676 (for all data) [0.0723].
1J C,H ) 13 Hz) [3.63 (d, 2H, CH2N, J C,H ) 14 Hz)], 3.91 (5H,
1
C5H5), 4.21 (5H, C5H5), 3.95 [4.10] (2H, C5H3), 4.18 [4.32] (2H,
C5H3), 4.44 [4.38] (2H, C5H3). MS (EI, 70 eV): m/z 692 (M+,
80), 484 ((FcN)2, 70), 450 (FcNPb, 100), 242.8 (FcN, 35).
Rea ction of [F cN]2P b w ith CD3OD. The [FcN]2Pb was
dissolved in CD3OD, and the white precipitate, presumably
1
(CD3O)2Pb, was filtered off. From the solution H and 13C NMR
spectra were taken, and the product was identified as (1-
deuterio)(2-N,N-dimethylaminomethyl)ferrocene, FcND. 1H
NMR (CD3OD, rt): 2.20 (6H, NMe2), 3.38 (2H, CH2N), 4.17
(5H, C5H5), 4.18 (2H, C5H3), 4.25 (1H, C5H3).
Ack n ow led gm en t. The authors thank Prof. Dr.
Piero Zanello from Dipartimento di Chimica, University
of Siena, Siena, Italy, for cyclovoltammetric measure-
ments. K.J . thanks the Deutsche Forschungsgemein-
schaft for financial support, N.S. thanks the DFG
program “Graduierten-Kolleg: Synthese und Reaktions-
verhalten von Organometallverbindungen und Met-
allkomplexen” for a fellowship.
Rea ction of P bCl2 w ith F cLi. To the suspension of PbCl2
(1.45 g, 5.2 mmol) in 50 mL of diethyl ether cooled at -50 °C
was slowly added a suspension of FcLi (2.00 g, 10.4 mmol) in
100 mL of diethyl ether with vigorous stirring. After stirring
the reaction mixture for 2 h and warming to room temperature,
a dark gray precipitate was formed. It was filtered off and
washed out with water to remove LiCl and dried in vacuo (0.85
g, 96% calcd on Pb). It was identified as elemental lead on the
basis of the following experiments: a sample was dissolved in
diluted HNO3 and neutralized with soda, and the following
reactions were done: with H2SO4 a white powder (PbSO4)
precipitated, with K2CrO4 a yellow one (PbCrO4), and by
adding of NaOH solution a white precipitate (Pb(OH)2) was
formed. The orange filtrate contained ferrocene, FcH. 1H NMR
(C6D6, rt): 4.16 (10H, C5H5).
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates for H atoms, bond lengths, bond
angles, anisotropic displacement coefficients, and crystal pack-
ing diagrams for the two polymorphs of 1a , as well as a figure
of a molecular structure of the C2/c polymorph. Ordering
information is given on any current masthead page.
R ea ct ion of [F cN]2P b w it h BE t 3. Triethylborane (0.21
mL, 1.4 mmol) was added to a solution of [FcN]2Pb (0.50 g,
0.7 mmol) in 3 mL of C6D6 with stirring at room temperature,
and the reaction followed by NMR. The orange color of the
solution was slightly discharged. After 2 h decomposition was
complete, and elemental lead and FcNH had formed.
OM990614G
(19) Sheldrick, G. M. SHELXS-97. Program for the Automatic
Solution of Crystal Structures; University of Go¨ttingen, Germany, 1997.
(20) Sheldrick, G. M. SHELXL-97. Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Germany, 1997.