Low-coordinate tin and lead cations

Article abstract of DOI:10.1021/om100712a

A series of low-coordinate tin and lead cationic complexes have been synthesized using the bulky β-diketiminate ligand [{N(2,6- ⁱPr₂C₆H₃)C(Me)}₂CH] ^- (BDI) to stabilize the metal center. Two different routes to [(BDI)Sn]⁺[X]^- and [(BDI)Pb]⁺[X]^- were explored (X = B(C₆F₅)₄, AlCl₄, MeB(C₆F₅)₃): abstraction of the chloride with a Lewis acid from (BDI)SnCl and (BDI)PbCl and abstraction of a methyl group with a borane from (BDI)SnMe and (BDI)PbMe. The crystal structures of the tin and lead cations were determined; in both, solvent molecules were found to coordinate to the metal center. In the case of [(BDI)Pb]⁺[B(C ₆F₅)₄]^-, a dichloromethane molecule was found. Density functional theory (DFT) calculations showed that this could be due to crystal packing. In the case of [(BDI)Sn]⁺[MeB(C ₆F₅)₃]^-, an ether molecule was coordinated to the tin metal center. DFT calculations revealed a significant energy gain for the coordinated ether as opposed to the free molecules.

Full text of DOI:10.1021/om100712a

ARTICLE
pubs.acs.org/Organometallics
Low-Coordinate Tin and Lead Cations
Morgan J. Taylor, Amy J. Saunders, Martyn P. Coles, and J. Robin Fulton*
Department of Chemistry, University of Sussex, Falmer, Brighton BN1 9QJ, U.K.
S Supporting Information
b
ABSTRACT: A series of low-coordinate tin and lead cationic
complexes have been synthesized using the bulky β-diketimi-
nate ligand [{N(2,6-iPr2C6H3)C(Me)}2CH]- (BDI) to sta-
bilize the metal center. Two different routes to [(BDI)Sn]þ-
[X]- and [(BDI)Pb]þ[X]- were explored (X = B(C6F5)4,
AlCl4, MeB(C6F5)3): abstraction of the chloride with a Lewis
acid from (BDI)SnCl and (BDI)PbCl and abstraction of a
methyl group with a borane from (BDI)SnMe and
(BDI)PbMe. The crystal structures of the tin and lead cations
were determined; in both, solvent molecules were found to
coordinate to the metal center. In the case of [(BDI)Pb]þ-
[B(C6F5)4]-, a dichloromethane molecule was found. Density
functional theory (DFT) calculations showed that this could be
due to crystal packing. In the case of [(BDI)Sn]þ[MeB-
(C6F5)3]-, an ether molecule was coordinated to the tin metal
center. DFT calculations revealed a significant energy gain for the coordinated ether as opposed to the free molecules.
’ INTRODUCTION
bulky β-diketiminate ligand [{N(2,6-iPr2C6H3)C(Me)}2CH]-
(BDI) has been shown to be able to stabilize several unusual
complexes of germanium, tin, and lead. In this work, we have
expanded the chemistry of these systems and have generated
formally two-coordinate lead and tin cations using the bulky BDI
ligand to stabilize the metal center. Two different routes were
utilized for these group 14 metal cations: abstraction of chloride
from the corresponding BDI-metal chloride complexes, ((BDI)-
PbCl (1) and (BDI)SnCl (2)) and abstraction of a methyl group
from the corresponding BDI-metal alkyl complexes, ((BDI)Pb-
Me (3) and (BDI)SnMe (4)).
The coordination chemistry of the heavier group 14 metals is
diverse, with coordination numbers from 2 to 11 and even 12
reported for lead compounds.1-7 With regard to the lower
coordinate complexes of tin and lead, bulky terphenyl groups
have been successfully utilized to generate several two-coordi-
nate complexes,2,8 as well as a “quasi-one-coordinate” lead
cation.9 However, it should be noted that, in the solid state of
this lead cation complex, a nearby toluene molecule interacts
with the lead center in an η2 fashion. This result reflects the
difficulty of isolating low-coordinate lead complexes. Outside of
the growing number of diaryllead complexes, many of the
formally two-coordinate lead complexes are rarely two-coordi-
nate in the solid state,10 with Pb(N(SiMe3)2)2 a very rare
example of a PbN2 two-coordinate lead compound.1 The
solid-state structure of most other “two-coordinate” PbN2
complexes show inter- and intramolecular interactions be-
tween the metal center and nearby lone pairs,10,11 agostic
interactions between Pb and a hydrogen atom (C-H or B-
H),8,12 or the complex exists as a dimer in which the metal center
interacts intermolecularly with another ligand.13,14 Two-coordi-
nate tin complexes are much more common than two-coordinate
lead complexes,1,2,15-17 and there are many examples of stable
two-coordinate tin complexes in the solid state.18-21 However,
low-coordinate Sn(II) cations are rare, with only one two-coordi-
nate tin cation reported, albeit stabilized by long-distance interac-
tions with a triflate anion.22
’ RESULTS AND DISCUSSION
Treatment of lead chloride 1 with Li[B(C6F5)4] results in
immediate formation of [(BDI)Pb][B(C6F5)4] (5; eq 1). The
1H NMR spectrum of 5 in CD2Cl2 reveals one environment for
the N-aryl substituents, including a septet integrating to 4 protons
at δ 2.74 ppm and two doublets integrating to 12 protons each at
δ 1.26 and 1.21 ppm. These data indicate a symmetrically
substituted, possibly two-coordinate, metal center. The 19F
NMR spectrum shows three fluorine resonances, indicative of a
noncoordinating [B(C6F5)4]- anion. A 207Pb NMR spectro-
scopic signal for this complex was not found, presumably due to
fast relaxation of the lead nucleus. Complex 5 is not soluble
in aliphatic or aromatic solvents such as hexane, toluene, and
benzene; however, it is soluble in more polar solvents such as
The chemistry of group 14 β-diketiminate complexes has
Received: July 20, 2010
Published: February 22, 2011
recently been investigated by our group and others,23-30 and the
r
2011 American Chemical Society
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|

Organometallics
ARTICLE
dichloromethane and will decompose in ethereal solvents such as
diethyl ether and THF.
concentrated dichloromethane solution of 5 at -30 °C. Table 1
gives selected bond lengths and angles, and Table 2 gives data
collection parameters. The solid-state structure of 5 (Figure 1)
reveals a formally two-coordinate metal center; however, a
dichloromethane molecule was found with partial occupancy
(64%) to give a long-range lead-chlorine interaction (Pb-
Cl(1) = 3.213(4) Å). In addition, a long-range interaction
between lead and one fluorine from the [B(C6F5)4h] anion is
observed (Pb-F = 3.319(4) Å). The Pb-N bond distances of
Crystals suitable for analysis by single-crystal X-ray diffraction
experiments were obtained by slowly diffusing pentane into a
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
Lead Cation 5 and Tin Cation 9
5
9
M-N(1)
M-N(2)
2.242(4)
2.228(4)
3.213(4)
2.1346(17)
2.1479(17)
Pb Cl(1)
3 3 3
Sn-O
2.3872(17)
86.61(7)
94.50(7)
90.57(6)
108.3(3)
125.65(18)
123.6(2)
0.474(3)
N(1)-M-N(2)
N(1)-Sn-O
N(2)-Sn-O
C(30)-O-C(32)
C(30)-O-Sn
C(32)-O-Sn
M-NCCCN plane
84.24(15)
Figure 1. Lead cation 5 with H atoms omitted (except for those on the
dichloromethane molecule). BDI C atoms and three C6F5 rings are
minimized for clarity.
0.478(7)
Table 2. Crystallographic Data for Lead Cation 5 and Tin Cation 9
5a
9b
chem formula
C28H41Pb 0.64CH2Cl2, C24BF20 (C5H12 or CH2Cl2)
C52H54BF15N2OSn
1137.47
3
formula wt
temp (K)
wavelength (Å)
cryst size (mm3)
cryst syst
space group
a (Å)
1430.40
173(2)
173(2)
0.710 73
0.710 73
0.25 ꢀ 0.11 ꢀ 0.06
monoclinic
0.20 ꢀ 0.14 ꢀ 0.14
orthorhombic
P212121 (No.19)
14.4223(1)
18.4966(2)
19.3560(2)
90
P21/c (No. 14)
17.7961(4)
b (Å)
18.4707(3)
c (Å)
22.4317(4)
R (deg)
β (deg)
90
126.654(1)
90
γ (deg)
90
90
V (Å3)
5915.4(2)
5163.47(9)
4
Z
4
Fc (Mg m-3
)
1.53
1.46
abs coeff (mm-1
)
3.01
0.59
θ range for data collecn (deg)
no. of measd/indep rflns (R(int))
no. of rflns with I > 2σ(I)
no. of data/restraints/params
goodness of fit on F2
3.45-27.10
3.46-27.49
84 679/11 803 (0.059)
10 942
92 559/13 031 (0.077)
10 117
13 031/0/723
1.017
11 803/1/652
1.009
final R indices (I > 2σ(I))
R1 = 0.056, wR2 = 0.122
R1 = 0.081, wR2 = 0.132
1.64, -1.11 (close to CH2Cl2)
R1 = 0.029, wR2 = 0.062
R1 = 0.034, wR2 = 0.064
0.26, -0.41
R indices (all data)
largest diff peak, hole (e Å3)
a The site occupancy factors of the dichloromethane solvate was freely refined (giving a total occupancy of 64%). The unit cell contains a highly disordered
solvent molecule that was treated as a diffuse contribution to the overall scattering without specific atom positions by SQUEEZE/PLATON.32 b One of the C-
C bond lengths in the ether ligand was restrained to give a more chemically reasonable value; there is possible unresolved disorder in one of the C6F5 rings.
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2.242(4) and 2.228(4) Å (average 2.24 Å) are slightly shorter
than those reported for (BDI)PbOTf (average 2.27 Å)31 and
significantly shorter than for (BDI)PbCl (average 2.29 Å),24
indicating a more electropositive metal center. The N(1)-Pb-
N(2) bond angle of 84.24(15)° is wider than that reported for
other (BDI)Pb complexes.23-25,31 Interestingly, the lead is
displaced from the N(1)-C(1)-C(2)-C(3)-N(2) plane by
0.478(7) Å. Although this deviation is significantly less than
those for three-coordinate (BDI)Pb complexes such as
(BDI)PbCl and (BDI)PbOTf (0.683 and 0.964 Å, respectively),
it is similar to that for the carbonate complex (BDI)PbOCO2iPr
(0.420 Å), in which the metal center is coordinated to two or
more oxygen atoms in addition to the BDI ligand.25
functional theory (DFT) calculations on the lead cation. Geo-
metry optimization and frequency calculations were performed
on both the free cation (BDI)Pbþ as well as the dichloromethane
solvated cation (BDI)Pbþ DCM; however, the anion was
3
omitted from all calculations. In both cases, the experimental
solid-state geometric coordinates were used as the initial geo-
metry. All calculations were implemented in Gaussian 03.36 Two
different levels of theory were used: B3LYP DFT and LanL2DZ
pseudopotentials (and basis set) on all atoms as well as B3LYP
DFT and LanL2DZ pseudopotentials on Pb with 6-31G* on the
other atoms. The former level of theory was performed in order
to make comparisons with our previously published results on
other “(BDI)Pb” compounds.24 Both levels of calculations
showed that the optimized geometry for the metal center lies
in the N(1)-C(1)-C(2)-C(3)-N(2) plane (Figure 2). In
addition, although the experimental solid-state geometry was
used as the starting geometry in these calculations, the dichlor-
omethane solvate changed its position relative to the lead center
in the optimized geometry of the solvated molecule,
The asymmetric environment in the solid state is in
contrast to what is observed in the solution phase. This
could either be due to a true planar environment around the
Pb-N(1)-C(1)-C(2)-C(3)-N(2) ring in solution or a
rapid inversion in which the lead center essentially flips from
one side of the N(1)-C(1)-C(2)-C(3)-N(2) plane to the
other; thus, we are observing average spectra in solution.
This latter type of structure could be caused by coordination
to dichloromethane; however, we were not able to gain any
further spectroscopic evidence for this hypothesis. Although
dichloromethane complexes are known,33,34 including those
of heavier elements,35 the solution-state behavior of these
complexes is variable and the coordinated dichloromethane
(BDI)Pbþ DCM, resulting in the dichloromethane molecule
3
lying outside the Pb-Cl van der Waals radii. This result indicates
that the metal center is indeed two-coordinate in the gas phase.
Although there is a slight stabilization of -3 kcal mol-1 for a lead
cation in close proximity to a dichloromethane molecule in
(BDI)Pbþ DCM,37 this stabilization is not due to any direct
3
bonding between the lead center and the solvent. The lone pair
resulting from these calculations is found at HOMO-11; it is
almost spherical and occupies the space opposite the β-diketi-
minate ligand (Figure 2). The s character in this lone pair is
94.09% (or 94.74% with the higher level of theory) and is greater
than that for the three-coordinate lead chloride complex 1
(91.79%) or (BDI)PbI (92.96%) with p orbital contribution
decreasing accordingly (Table 3).24 Although studies have
shown a correlation between increasing s orbital contribution
with the decreasing hardness of the coordinated ligand,38,39 our
results could be simply due to the change in coordination
number at the lead center.
1
molecule is not always observed by H NMR spectroscopy,
due to its lability. In addition, solid-state packing can also
contribute to the observation of a coordinated dichloro-
methane molecule in the solid state.
In order to ascertain whether interaction with the dichlor-
omethane was due to solid-phase packing, we performed density
Similar to the case for the lead system, treatment of tin
chloride 2 with Li[B(C6F5)4] results in the formation of
[(BDI)Sn][B(C6F5)4] (6; eq 1). This complex has solubility
properties similar to those of the lead system, with the added
benefit of being stable in ethereal solvents (diethyl ether and
THF). Although we were unable to obtain crystals suitable for an
1
X-ray diffraction study, the H NMR spectrum reveals one
environment for the N-aryl substituents, and thus is consistent
with a symmetrically substituted metal center. A 119Sn NMR
signal is observed at δ 197.0 ppm, which is significantly downfield
from that of tin chloride 2 (δ -224 ppm).40 Unfortunately,
despite repeated attempts, we were unable to obtain satisfactory
microanalysis for this compound. Addition of AlCl3 to tin
Figure 2. View of the optimized geometry for (BDI)Pbþ DCM and
3
the lead-centered lone pair (HOMO-11) for (BDI)Pbþ.
Table 3. NBO Analysis of Lead Cations (BDI)Pbþ and (BDI)Pbþ DCM
3
compound
natural electron configuration
lone pair NBO on M
lone pair occupancy
LanL2DZ on Every Atom
(BDI)Pbþ
(BDI)Pbþ (DCM)
Pb: 6s (1.87), 6p (0.64)
Pb: 6s (1.87), 6p (0.65)
s [94.09%], p 0.06 [5.91%]
s [94.00%], p 0.06 [6.00%]
1.979
1.979
3
LanL2DZ on Pb, 6-31G* on N, C, H
(BDI)Pbþ
(BDI)Pbþ (DCM)
Pb: 6s (1.89, 6p (0.69), 7p (0.01)
Pb: 6s (1.91), 6p (0.66), 7p (0.01)
s [94.74%], p 0.06 [5.26%]
s [95.57%], p 0.05 [4.43%]
1.986
1.986
3
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chloride 2 also results in the abstraction of chloride from the tin
(eq 2); similar to the case for 6, only one environment for the
1
N-aryl substituents is observed by H NMR spectroscopy. In
addition, one sharp 27Al resonance was observed at δ 99.7 ppm,
and a 119Sn NMR resonance was observed at δ -626.7 ppm.
This chemical shift is significantly more upfield from other
reported (BDI)Sn signals and could potentially indicate that
the AlCl4 anion is coordinated to the metal center. However, we
have been unable to gain any further evidence for this
hypothesis.40 As with 6, we were unable to grow X-ray-quality
crystals of complex 7; however, in this case, the composition was
confirmed by combustion analysis.
Figure 3. Tin cation 9 with H atoms omitted, BDI C atoms minimized,
and [MeB(C6F5)]- omitted for clarity.
The second route utilized to generate group 14 cations was
abstraction of a methyl group from (BDI)PbMe or (BDI)SnMe
using B(C6F5)3 (eq 3). This proved successful with both the lead
and tin systems, with complete conversion observed when the
reactions were monitored by 1H NMR spectroscopy. Although
we were unable to obtain X-ray-quality crystals for
1
[(BDI)Pb][MeB(C6F5)3] (8), the H and 13C NMR spectra
are almost identical with those obtained for 5, with only one
environment observed for the isopropyl groups on the N-aryl
substituent. The 1H NMR spectrum also revealed a resonance at
δ 0.45 ppm, corresponding to the CH3 protons on the borate
anion, and the 19F NMR spectrum revealed only three fluorine
environments, with a Δδ(m,p) value of 2.6, which is indicative of
a noncoordinating anion.41
Figure 4. View of the tin-centered lone pair (HOMO-9) for (BDI)Snþ
(left) and (BDI)Snþ OEt2 (right).
3
1
The H NMR spectrum of the etherate crystals revealed a
significant shift in the resonances corresponding to the ether
molecule as well as the BDI ligand, indicating that diethyl ether is
indeed coordinated to the tin metal center in solution; however,
only one N-aryl environment is observed. This is presumably due
to the lability of the coordinated ether; thus, an average structure
is observed by 1H NMR spectroscopy. DFT was used to calculate
the ground-state energies of both the solvated tin cation and
Addition of B(C6F5)3 to (BDI)SnMe results in immediate
abstraction of the methyl group to form [(BDI)Sn][MeB(C6F5)3]
(9; eq 3). Similar to the case for the other Sn cations, this
compound is soluble and stable in polar solvents such as
dichloromethane, diethyl ether, and THF. As with the other
cationic complexes, only one N-aryl environment is observed in
the 1H NMR spectrum. A resonance corresponding to the CH3
protons on the borate anion was observed at δ 0.46 ppm.
Attempts at growing X-ray-quality crystals in noncoordinating
solvent systems were unsuccessful. However, crystals suitable for
an X-ray diffraction study were grown by slowly cooling a
concentrated diethyl ether solution to -30 °C (Figure 3). The
solid-state structure has a diethyl ether molecule bound to the tin
metal center (Sn-O = 2.3872(17) Å). The tin center is displaced
from the N(1)-C(1)-C(2)-C(3)-N(2) plane by 0.473 Å,
which is smaller than that of (BDI)SnCl (0.658 Å)40 and
(BDI)SnMe (0.807 Å)42 as well as (BDI)SnOTf (0.605 Å),40
but larger than that of (BDI)SnN(SiMe3)2 (0.361 Å).42 The Sn-
N bond distances of 2.1342(17) and 2.1480(17) Å are shorter
than those of (BDI)SnCl (2.185 and 2.180 Å) and (BDI)SnMe
(2.209 and 2.218 Å) but very similar to those of (BDI)SnOTf
(2.139 and 2.142 Å), therefore indicating a more electropositive
metal center. The 119Sn NMR resonance of this etherate complex
was found at δ -139.50 ppm.
the solvent-free molecule. In contrast to (BDI)Pbþ DCM, the
3
diethyl ether molecule remains coordinated to the metal center
in (BDI)Snþ OEt2, and the calculated bond lengths and bond
3
angles are generally within 4% of those in the solid-state structure
of 9. The only significant difference is a slight elongation of the
Sn-O bond by 4.1%, and the Sn metal center only deviates from
the N(1)-C(1)-C(2)-C(3)-N(2) plane by 0.376 Å. The
etherate complex (BDI)Snþ OEt2 is 6.1 kcal mol-1 more stable
3
than the free cation (BDI)Snþ and ether alone.37 When the
unsolvated cation (BDI)Snþ was considered, the lone pair was
observed in the HOMO-9 molecular orbital; the lone pair of the
tin etherate complex (BDI)Snþ OEt2 was also found at
3
HOMO-9 (Figure 4). The amount of s character in the lone
pair for (BDI)Snþ is 90.52% and for (BDI)Snþ OEt2 is 88.64%,
3
whereas the amount of s character for (BDI)SnCl is 86.09%
(Table 4).24 The decrease in s character corresponds with a
decrease in the population of the 5s orbital (1.81, 1.79, and 1.75,
respectively). These trends are potentially consistent with the
strength of the metal-ligand interaction—the stronger the interac-
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Table 4. NBO Analysis of Tin Cations (BDI)Snþ and (BDI)Snþ OEt2
3
compound
natural electron configuration
lone pair NBO on M
lone pair occupancy
LanL2DZ on Every Atom
(BDI)Snþ
(BDI)Snþ OEt2
Sn: 5s (1.81), 5p (0.72)
s [90.52%], p 0.10 [9.48%]
s [88.64%], p 0.13 [11.36%]
1.973
1.963
Sn: 5s (1.77), 5p (0.72), 6p (0.01)
3
LanL2DZ on Sn, 6-31G* on N, C, H
(BDI)Snþ
(BDI)Snþ OEt2
Sn: 5s (1.83), 5p (0.76)
s [91.32%], p 0.10 [8.68%]
s [90.10%], p 0.11 [9.90%]
1.981
1.978
Sn: 5s (1.81), 5p (0.76), 6p (0.01)
3
tion, the more s/p mixing is observed in the lone pair. Thus, as
two-coordinate (BDI)Snþ does not possess any additional
metal-ligand interaction, its lone pair has the highest relative
percentage of s character.
[CH{(CH3)2CN-2,6-iPr2C6H3}2Sn]þ[B(C6F5)4]- (6). Compound
2 (100 mg, 0.17 mmol) was dissolved in ∼10 mL of dichloromethane in a
Schlenk tube and cooled to -78 °C. Li[B(C6F5)4] (117 mg, 0.17 mmol)
was mixed with 10 mL of dichloromethane in another Schlenk tube and
added dropwise to the cold solution of compound 2. The mixture was
stirred for 2 h before it was warmed to room temperature. The pale yellow
solution was filtered and then concentrated to encourage crystallization.
Yield: 87 mg (42.0%). 1H NMR (500 MHz, CD2Cl2, 30 °C): δ7.36 (m, 6H,
Haryl), 5.88 (s, 1H, CH), 2.97 (sept, 4H, J = 6.7 Hz, CHMe2), 2.03 (s, 6H,
NCMe), 1.25 (d, 12H, J = 6.8 Hz, CHMe2), 1.23 (d, 12H, J = 6.8 Hz,
CHMe2). 13C NMR (100.5 MHz, CD2Cl2, 30 °C): δ 168.5 (NCMe), 143.5,
138.2, 128.9, 125.0 (Caryl), 105.7 (middle CH), 28.6 (CHMe2), 26.1, 24.1
(CHMe2), 23.5 (NCMe). 119Sn NMR (223.6 MHz, CD2Cl2, 30 °C): δ
197.0. IR (KBr, Nujol): 1642.05 (s), 1511.13 (s), 1259.16 (m), 1167.82 (m),
’ CONCLUSIONS
We have synthesized a series of rare low-coordinate lead and
tin cations. In solution, most of the cations appear as symme-
trical, potentially two-coordinate species; however, in the solid
state, both tin and lead are coordinated to solvent molecules.
DFT calculations have revealed that the solvated complexes
(BDI)Pbþ DCM and (BDI)Snþ OEt2 are slightly more stable
3
3
than the free cations (BDI)Pbþ and (BDI)Snþ; however, in the
978.33 (m), 798.67 (s), 773.24 (s), 755.10 (s), 694.10 (s), 659.01 (s) cm-1
.
case of (BDI)Pbþ DCM, the stabilization observed is minimal
and is not due to a Cl-Pb interaction.
3
[CH{(CH3)2CN-2,6-iPr2C6H3}2Sn]þ[AlCl4]- (7). A 10 mL dichloro-
methane solution of AlCl3 (47 mg, 0.35 mmol) was added dropwise to a
10 mL dichloromethane solution of compound 2 (200 mg, 0.35 mmol)
at -78 °C. The mixture was stirred for 2 h before it was warmed to room
temperature. The pale yellow solution was filtered and then concen-
trated to encourage crystallization. Yield: 82 mg (33%). 1H NMR (500
MHz, CD2Cl2, 30 °C): δ 7.43 (m, 6H, Haryl), 5.95 (s, 1H, CH), 2.83
(sept, 4H, J = 6.5 Hz, CHMe2), 2.21 (s, 6H, NCMe), 1.30 (d, 12H, J =
6.7 Hz, CHMe2), 1.28 (d, 12H, J = 6.7 Hz, CHMe2). 13C NMR (100.5
MHz, CD2Cl2, 30 °C): δ 159.3 (NCMe), 140.6, 139.0, 123.6, 121.3
(Caryl), 92.1 (middle CH), 26.4 (CHMe2), 22.3, 21.2 (CHMe2), 18.5
(NCMe). 119Sn NMR (149.0 MHz, C6D6, 20 °C): δ -626.7. 27Al NMR
(104.1 MHz, C6D6, 20 °C): δ 99.69 ppm. Anal. Calcd for
C29H41N2Cl4AlSn: C, 49.24; H, 5.80; N, 3.96. Found: C, 49.35; H,
5.96; N, 3.92.
’ EXPERIMENTAL SECTION
All manipulations were carried out under an atmosphere of dry nitrogen
or argon using standard Schlenk techniques or in an inert-atmosphere
glovebox. Solvents were dried from the appropriate drying agent, distilled,
degassed, and stored over 4 Å sieves. The 1H, 13C, 19F, 27Al, 119Sn, and
207Pb NMR spectra were recorded on Varian 400, 500, and 600 MHz
spectrometers which were equipped with X{1H} broadband-observe
1
probes. The H and 13C NMR spectroscopy chemical shifts are given
relative to residual solvent peaks, the 19F signals wereexternallyreferenced
to CFCl3, the 27Al signals were externally referenced to aqueous Al-
(NO3)3, the 119Sn signals were externally referenced to SnMe4, and the
207Pb signals were externally referenced to PbMe4. The data for the
X-ray structures were collected at 173 K on a Nonius Kappa CCD
diffractometer (λ(Mo KR) = 0.710 73 Å) and refined using the
SHELXL-97 software package.43 (BDI)PbCl, (BDI)SnCl, (BDI)PbMe,
and (BDI)SnMe were prepared via known literature procedures.24,31,40,42
[CH{(CH3)2CN-2,6-iPr2C6H3}2Pb]þ[B(C6F5)4]- (5). Compound
1 (150 mg, 0.22 mmol) was dissolved in ∼10 mL of toluene and cooled
to -78 °C. To this solution was added 10 mL of a toluene solution of
Li[B(C6F5)4] (200 mg, 0.29 mmol), dropwise. The mixture was stirred for
30 min and warmed to room temperature, after which the toluene was
removed in vacuo and dichloromethane was added. The bright red-orange
solution was filtered and then concentrated. Crystals were grown at -30 °C
by slow diffusion of pentane into a concentrated dichloromethane solution
of the compound. Yield: 95 mg (33.1%). 1H NMR (500 MHz, CD2Cl2,
30 °C): δ 7.42 (m, 6H, Haryl), 5.46 (s, 1H, middle CH), 2.74 (sept, 4H, J =
6.9 Hz, CHMe2), 2.00 (s, 6H, NCMe), 1.26 (d, 12H, J = 6.8 Hz, CHMe2),
1.21 (d, 12H, J = 6.8 Hz, CHMe2). 13C NMR (100.5 MHz, CD2Cl2,
30 °C): δ 171.7 (NCMe), 144.2, 142.2, 130.0, 128.8, 123.9, 114.5 (Caryl),
91.8 (middle CH), 27.9, 27.4 (CHMe2), 23.3, 22.4 (CHMe2), 21.5
(NCMe). 19F NMR (375.9 MHz, CD2Cl2, 30 °C): δ -133.1 (d, 6F, o-
F), -163.8 (t, 3F, p-F), -167.7 (td, 6F, m-F). IR (KBr, Nujol): 1644.57
[CH{(CH3)2CN-2,6-iPr2C6H3}2Pb]þ[B(Me)(C6F5)3]- (8). B(C6F5)3
(80 mg, 0.15 mmol) was mixed with 10 mL of dichloromethane and
added dropwise to a -10 °C dichloromethane solution of compound
3 (100 mg, 0.15 mmol). The bright orange-red solution was stirred for
30 min; then the dichloromethane was removed in vacuo and the
compound dissolved in the minimum amount of diethyl ether at -30 °C
1
to encourage crystallization. Yield: 120 mg (66.7%). H NMR (400
MHz, CD2Cl2, 30 °C): δ 7.43 (m, 6H, Haryl), 5.50 (s, 1H, CH), 2.77
(sept, 4H, J = 6.8 Hz, CHMe2), 2.02 (s, 6H, NCMe), 1.27 (d, 12H, J =
6.8 Hz, CHMe2), 1.22 (d, 12H, J = 6.9 Hz, CHMe2), 0.45 (s, 1H, Me).
13C NMR (100.5 MHz, CD2Cl2, 30 °C): δ 167.5 (NCMe), 142.9, 137.4,
129.5, 125.1 (Caryl), 115.9 (middle CH), 28.0 (CHMe2), 26.6 (CHMe2),
26.3 (NCMe), 23.0 (Ar3BMe). 19F NMR (375.9 MHz, CD2Cl2, 30 °C):
δ -132.9 (d, 6F, o-F), -165.2 (t, 3F, p-F), -167.8 (td, 6F, m-F). IR
(KBr, Nujol): 1641.18 (s), 1510.62 (s), 1261.00 (s), 1087.11 (br),
1019.90 (br), 799.79 (s) cm-1. Anal. Calcd for C48H44N2F15BPb: C,
50.04; H, 3.82; N, 2.43. Found: C, 50.13; H, 3.77; N, 2.36.
[CH{(CH3)2CN-2,6-iPr2C6H3}2Sn]þ[B(Me)(C6F5)3]- (9). A10mL
dichloromethane solution of B(C6F5)3 (186 mg, 0.35 mmol) was added
dropwise to a 10 mL dichloromethane solution of compound 4 (200 mg,
0.35 mmol) at -10 °C. The solution was stirred for 2 h; then the mixture
was filtered and the dichloromethane removed in vacuo. A pale yellow
solid was isolated. Yield: 130 mg (37.5%). 1H NMR (500 MHz, CD2Cl2,
(s), 1261.30 (s), 1089.65 (br), 1021.09 (br), 800.81 (s), 722.87 (s) cm-1
.
Anal. Calcd for C53H41N2F20BPb: C, 48.81; H, 3.15; N, 2.15. Found: C,
49.30; H, 3.47; N, 1.92.
1338
dx.doi.org/10.1021/om100712a |Organometallics 2011, 30, 1334–1339

Organometallics
ARTICLE
20 °C): δ 7.38 (m, 6H, Haryl), 6.16 (s, 1H, CH), 2.71 (sept, 4H, J = 6.8
Hz, CHMe2), 2.12 (s, 6H, NCMe), 1.31 (d, 12H, J = 6.8 Hz, CHMe2),
1.15 (d, 12H, J = 6.9 Hz, CHMe2), 0.46 (s, 3H, Me). 13C NMR (100.5
MHz, CD2Cl2, 20 °C): δ 170.1 (NCMe), 142.9, 136.8, 129.9, 128.9,
125.3 (Caryl), 108.9 (middle CH), 28.6 (CHMe2), 26.1, 24.1 (CHMe2),
23.0 (NCMe), 21.1 (Ar3BMe). 19F NMR (375.9 MHz, CD2Cl2, 30 °C):
δ -133.05, -165.32, -167.90. 119Sn NMR (223.6 MHz, CD2Cl2,
30 °C): δ -139.50. IR (KBr, Nujol): 1957.41 (s), 1642.55 (m), 1595.40
(m), 1510.57 (s), 1268.11 (m), 1168.34 (br), 1022.08 (m), 952.04 (br),
848.95 (br), 801.10 (s), 753.43 (s), 694.09 (s) cm-1. Anal. Calcd for
C48H44N2F15BSn: C, 54.21; H, 4.14; N, 2.64. Found: C, 54.30; H, 4.23;
N, 2.56.
(16) Weidenbruch,M.;Schlaefke,J.;Schafer, A.;Peters,K.;Vonschnering
H. G.; Marsmann, H. Angew. Chem., Int. Ed. Engl. 1994, 33, 1846–1848.
(17) Kira, M.; Yauchibara, R.; Hirano, R.; Kabuto, C.; Sakurai, H.
J. Am. Chem. Soc. 1991, 113, 7785–7787.
(18) Jimenez-Perez, V. M.; Munoz-Flores, B. M.; Roesky, H. W.;
Schulz, T.; Pal, A.; Beck, T.; Yang, Z.; Stalke, D.; Santillan, R.; Witt, M.
Eur. J. Inorg. Chem. 2008, 2238–2243.
(19) Westerhausen, M.; Gruel, J.; Hausen, H. D.; Schwarz, W. Z.
Anorg. Allg. Chem. 1996, 622, 1295–1305.
(20) Braunschweig, H.; Hitchcock, P. B.; Lappert, M. F.; Pierssens,
L. J. M. Angew. Chem., Int. Ed. Engl. 1994, 33, 1156–1158.
(21) Chorley, R. W.; Hitchcock, P. B.; Lappert, M. F.; Leung, W. P.;
Power, P. P.; Olmstead, M. M. Inorg. Chim. Acta 1992, 198, 203–209.
(22) Ayers, A. E.; Dias, H. V. R. Inorg. Chem. 2002, 41, 3259–3268.
(23) Fulton, J. R.; Hitchcock, P. B.; Johnstone, N. C.; Tam, E. C. Y.
Dalton Trans. 2007, 3360–3362.
(24) Chen, M.; Fulton, J. R.; Hitchcock, P. B.; Johnstone, N. C.;
Lappert, M. F.; Protchenko, A. V. Dalton Trans. 2007, 2770–2778.
(25) Tam, E. C. Y.; Johnstone, N. C.; Ferro, L.; Hitchcock, P. B.;
Fulton, J. R. Inorg. Chem. 2009, 48, 8971–8976.
(26) Yao, S. L.; Brym, M.; Merz, K.; Driess, M. Organometallics 2008,
27, 3601–3607.
(27) Jana, A.; Sarish, S. P.; Roesky, H. W.; Schulzke, C.; Samuel, P. P.
Chem. Commun. 2010, 46, 707–709.
(28) Wang, W. Y.; Inoue, S.; Yao, S. L.; Driess, M. Chem. Commun.
2009, 2661–2663.
’ ASSOCIATED CONTENT
S
Supporting Information. Tables giving Cartesian coor-
b
dinates of the optimized structures of (BDI)Pbþ, (BDI)Pbþ
3
DCM, (BDI)Snþ, (BDI)Snþ OEt2, text giving the complete ref
3
35, and CIF files and figures giving crystallographic data and
ORTEP diagrams for complexes 5 and 9. This material is
available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*To whom correspondence should be addressed. E-mail:
j.r.fulton@sussex.ac.uk.
(29) Pineda, L. W.; Jancik, V.; Colunga-Valladares, J. F.; Roesky,
H. W.; Hofmeister, A.; Magull, J. Organometallics 2006, 25, 2381–2383.
(30) Pineda, L. W.; Jancik, V.; Starke, K.; Oswald, R. B.; Roesky,
H. W. Angew. Chem., Int. Ed. 2006, 45, 2602–2605.
(31) Jana, A.; Sarish, S. P.; Roesky, H. W.; Schulzke, C.; Doring, A.;
John, M. Organometallics 2009, 28, 2563–2567.
’ ACKNOWLEDGMENT
(32) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
(33) Burger, P.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 10462–
10463.
We are grateful for financial support from the EPSRC (M.J.T.,
Grant No. EP/E032575/1).
(34) Taw, F. L.; Mellows, H.; White, P. S.; Hollander, F. J.; Bergman,
R. G.; Brookhart, M.; Heinekey, D. M. J. Am. Chem. Soc. 2002, 124,
5100–5108.
(35) Bryan, J. C.; Kavallieratos, K.; Sachleben, R. A. Inorg. Chem.
2000, 39, 1568–1572.
’ REFERENCES
(1) Fjeldberg, T.; Hope, H.; Lappert, M. F.; Power, P. P.; Thorne,
A. J. J. Chem. Soc., Chem. Commun. 1983, 639–641.
(2) Simons, R. S.; Pu, L. H.; Olmstead, M. M.; Power, P. P.
Organometallics 1997, 16, 1920–1925.
(3) Cramer, R. E.; Mitchell, K. A.; Hirazumi, A. Y.; Smith, S. L.
J. Chem. Soc., Dalton Trans. 1994, 563–569.
(4) Tsubomura, T.; Ito, M.; Sakai, K. Inorg. Chim. Acta 1999, 284,
149–157.
(5) Liu, L. K.; Lin, C. S.; Young, D. S.; Shyu, W. J.; Ueng, C. H. Chem.
Commun. 1996, 1255–1256.
(36) Frisch, M. J., et al. Gaussian 03, Revision C.02; Gaussian, Inc.,
Wallingford, CT, 2004.
(37) This value has not been corrected for basis set superposition error.
(38) Akibo-Betts, G.; Barran, P. E.; Puskar, L.; Duncombe, B.; Cox,
H.; Stace, A. J. J. Am. Chem. Soc. 2002, 124, 9257–9264.
(39) Shimoni-Livny, L.; Glusker, J. P.; Bock, C. W. Inorg. Chem.
1998, 37, 1853–1857.
(40) Ding, Y.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.;
Power, P. P. Organometallics 2001, 20, 1190–1194.
(41) Horton, A. D.; DeWith, J.; vanderLinden, A. J.; vandeWeg, H.
Organometallics 1996, 15, 2672–2674.
(6) Pu, L.; Twamley, B.; Power, P. P. Organometallics 2000, 19,
2874–2881.
(7) Hino, S.; Olmstead, M. M.; Phillips, A. D.; Wright, R. J.; Power,
P. P. Inorg. Chem. 2004, 43, 7346–7352.
(42) Jana, A.; Roesky, H. W.; Schulzke, C.; Doring, A.; Back, T.; Pal,
A.; Herbst-Irmer, R. Inorg. Chem. 2009, 48, 193–197.
(43) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.
(8) Sturmann, M.; Weidenbruch, M.; Klinkhammer, K. W.; Lissner,
F.; Marsmann, H. Organometallics 1998, 17, 4425–4428.
(9) Hino, S.; Brynda, M.; Phillips, A. D.; Power, P. P. Angew. Chem.,
Int. Ed. 2004, 43, 2655–2658.
(10) Brooker, S.; Buijink, J. K.; Edelmann, F. T. Organometallics
1991, 10, 25–26.
(11) Sturmann, M.; Saak, W.; Weidenbruch, M. Z. Anorg. Allg. Chem.
1999, 625, 705–706.
(12) Izod, K.; McFarlane, W.; Wills, C.; Clegg, W.; Harrington, R. W.
Organometallics 2008, 27, 4386–4394.
(13) Charmant, J. P. H.; Haddow, M. F.; Hahn, F. E.; Heitmann, D.;
Frohlich, R.; Mansell, S. M.; Russell, C. A.; Wass, D. F. Dalton Trans.
2008, 6055–6059.
(14) Hahn, F. E.; Heitmann, D.; Pape, T. Eur. J. Inorg. Chem. 2008,
1039–1041.
(15) Zhong, H.; Zeng, X. R.; Yang, X. M.; Luo, Q. Y. Acta Crystallogr.,
Sect. E 2007, 63, M1566–U1169.
1339
dx.doi.org/10.1021/om100712a |Organometallics 2011, 30, 1334–1339