Tungsten-lead triple bonds: Syntheses, structures, and coordination chemistry of the plumbylidyne complexes trans-[X(PMe3) 4W≡Pb(2,6-Trip2C6H3)]

Article abstract of DOI:10.1002/anie.200461725

Plumb line: A series of compounds trans-[L(PMe₃) ₄W≡Pb(2,6-Trip₂C₆H₃)] ⁿ⁺ (n = 0: L = Br, I; n = 1: L = PhCN, PMe₃; Trip = 2,4,6-iPr₃C₆H₂; see structure of L = PMe ₃ derivative) containing W-Pb triple bonds is reported. Quantum-chemical analyses of the W≡Pb bond in the plumbylidyne complex [(PMe₃)₅W≡Pb-(2,6-Trip₂C ₆H₃)]⁺ confirm the electronic analogy with Fischer-type carbyne complexes. (Chemical equation presented).

Full text of DOI:10.1002/anie.200461725

Communications
Lead Complexes
Tungsten–Lead Triple Bonds: Syntheses,
Structures, and Coordination Chemistry
of the Plumbylidyne Complexes
ꢀ
trans-[X(PMe3)4W Pb(2,6-Trip2C6H3)]**
Alexander C. Filippou,* Nils Weidemann,
Gregor Schnakenburg, Holger Rohde, and
Athanassios I. Philippopoulos
Compounds containing a multiple bond between lead and
another main-group element are very rare.[1] In fact, only a
few diplumbenes, [Pb2R4] (R = aryl, silyl),[2] have been
isolated to date,[3,4] whereas alkenes are ubiquitous in organic
chemistry. Similarly, very few transition-metal plumbanediyl
(plumbylene) complexes have been reported,[5] whereas
carbene complexes are a common class of organometallic
compounds.[6] Other prominent examples of compounds
containing transition-metal–lead multiple bonds are the
5
5
= =
heterocumulenes
[(h -C5H4R)(CO)2Mn Pb Mn(CO)2(h -
C5H4R)] (R = H, Me).[7] Two major reasons have emerged
from quantum chemical studies for the distinct reluctance of
lead to participate in multiple bonding. These are the
comparatively low bond energies[8] and the reduced hybrid-
ization of its 6s and 6p valence orbitals.[9,10] However, these are
not inherent properties of lead, as recently demonstrated by
our synthesis of the plumbylidyne complex trans-
ꢀ
[Br(PMe3)4Mo Pb(2,6-Trip2C6H3)], which features a triply
bonded, linear-coordinated lead atom.[11] We have now char-
acterized compounds with tungsten–lead triple bonds. First
results of the coordination chemistry of these compounds are
also presented, providing experimental evidence for their
electronic analogy with Fischer-type carbyne complexes.[12]
Starting materials were the dinitrogen complexes cis-
[W(N2)2(PMe3)4] and [W(N2)(PMe3)5][13] and the aryllead(ii)
halides [{Pb(2,6-Trip2C6H3)X}2] (X = Br (1-Br), I (1-I)).
Compound 1-I was prepared by metathetical exchange of 1-
[*] Prof. Dr. A. C. Filippou, Dipl.-Chem. N. Weidemann,
Dipl.-Chem. G. Schnakenburg, Dipl.-Chem. H. Rohde
Institut für Chemie
Humboldt-Universität zu Berlin
Brook-Taylor Strasse 2, 12489 Berlin (Germany)
Fax: (+49)30-2093-6939
E-mail: filippou@chemie.hu-berlin.de
Dr. A. I. Philippopoulos
Institute of Physical Chemistry, NCSR Demokritos
Ag. Paraskevi Attikis, 15310 Athens (Greece)
[**] We are grateful to the Humboldt-Universität zu Berlin and the
Deutsche Forschungsgemeinschaft (project FI445/6-1) for the
generous financial support of this work, Dr. B. Ziemer and P.
Neubauer for the X-ray diffraction studies, Dr. U. Hartmann and U.
Kätel for the elemental analyses, and W.-D. Bloedorn and A. Thiesies
for the 2D NMR spectra. N. Weidemann thanks the Fonds der
Chemischen Industrie for a fellowship. X=Br, I; Trip=2,4,6-
iPr3C6H2.
Supportinginformation for this article is available on the WWW
under http://www.angewandte.org or from the author.
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DOI: 10.1002/anie.200461725
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Chemie
Br[14] with NaI in diethyl ether. It was isolated in 82% yield as
an air-sensitive, bright orange solid, which melts at 2228C and
decomposes at 2358C to give an oily, red mass.[15] Compound
1-I is the first organolead(ii) iodide to be structurally
characterized.[16] It crystallizes as a centrosymmetric iodide-
bridged dimer, which features a Pb2I2 parallelogram with a
of [W(N2)(PMe3)5] with 0.5 equivalents of 1-Br in toluene at
1008C (Scheme 1).[15] This reaction provides another example
for the aptitude of electron-rich[19] Group 6 metal dinitrogen
complexes with a d6 electron configuration to form triple
bonds to lead. Compounds 2-Br and 2-I are essentially
isotypic (Figure 2).[15] The isostructural, trans-configured
[17]
Pb···Pb separation of 4.603(1) Š and two quite different
ꢁ
Pb I bond lengths (2.9499(7) and 3.2764(8) Š) and internal
ꢁ
bond angles (84.81(2) and 95.19(2)8; Figure 1). The Pb Caryl
bond length of 1-I at 2.326(6) Š compares well with those of
Figure 2. DIAMOND plot of the molecular structure of 2-I in the solid
state. Thermal ellipsoids are set at 30% probability. Hydrogen atoms
are omitted for clarity. Selected bond lengths [Š] and angles [8] of 2-I
and [2-Br]: W-Pb 2.5477(3) [2.5464(5)], W-I 2.8656(4) [W-Br 2.6798(9)],
W-P1 2.4776(9) [2.474(2)], W-P2 2.481(1) [2.484(2)], W-P3 2.4663(9)
[2.461(2)], W-P4 2.486(1) [2.485(2)], Pb-C1 2.258(3) [2.254(6)]; W-Pb-
C1 175.79(8) [177.5(2)], I-W-Pb 177.857(8) [Br-W-Pb 179.05(3)], Pb-W-
P1 90.00(2) [90.17(5)], Pb-W-P2 98.17(2) [100.88(5)], Pb-W-P3 89.01(2)
[89.17(4)], Pb-W-P4 102.45(3) [102.84(6)].
Figure 1. DIAMOND plot of the molecular structure of 1-I in the solid
state. Thermal ellipsoids are set at 30% probability. Hydrogen atoms
are omitted for clarity. Selected bond lengths [Š] and angles [8]: Pb-I
2.9499(7), Pb-I# 3.2764(8), Pb-C1 2.326(6); C1-Pb-I 97.3(2), C1-Pb-I#
115.1(2), I-Pb-I# 84.81(2), Pb-I-Pb# 95.19(2).
octahedral complexes have approximate C2 point group
1-Br (2.306(13) and 2.329(11) Š).[14] Heating a solution of cis-
[W(N2)2(PMe3)4] with a stoichiometric amount of 1-Br or 1-I
in toluene at 1008C was accompanied by a rapid color change
from orange to red-brown to afford the plumbylidyne
complex 2-Br and 2-I, respectively (Scheme 1).[15,18] Com-
pounds 2-Br and 2-I were purified by crystallization from
pentane and isolated as red-brown, air-sensitive, microcrystal-
line solids in 66 (2-Br) and 58% (2-I) yields. Both complexes
are very soluble in pentane and decompose upon melting at
195 and 1928C, respectively. The plumbylidyne complex 2-Br
was also obtained in a straightforward manner by the reaction
symmetry,[20] and display almost linear W-Pb-Caryl linkages
ꢁ
(2-Br, 177.5(2)8; 2-I, 175.79(8)8) and the shortest W Pb bonds
(2-Br, 2.5464(5) Š; 2-I, 2.5477(3) Š) reported to date.[21] In
ꢁ
fact, the W Pb bond lengths of 2-Br and 2-I are 0.20 Š
shorter than those of the bridged plumbylidyne complex
[{W(CO)4}2(m-Br){m-Pb(2,6-Trip2C6H3)}]
(2.7423(3)
and
2.7517(3) Š), which contains a three-coordinate lead center
with trigonal-planar geometry,[14] and approximately 0.45 Š
ꢁ
shorter than the W Pb single bonds of the V-shaped
tungstenoplumbylene [Pb(2,6-Trip2C6H3){W(h5-C5H5)(CO)3}]
(2.9809(10) and 3.0055(6) Š).[21d] The Pb Caryl bonds of 2-Br
ꢁ
(2.254(6) Š) and 2-I (2.258(3) Š) are shorter than those of 1-
Br and 1-I (Figure 1), or those reported for the plumbylenes
ꢁ
[Pb(2,6-Trip2C6H3)R] (R = Me, tBu, Ph: Pb Caryl 2.272(9)–
2.321(3) Š)[14]
and
metalloplumbylenes
[Pb(2,6-
ꢁ
5
Trip2C6H3){M(h -C5H5)(CO)3}] (M = Cr, Mo, W: Pb Caryl
2.278(9)–2.294(4) Š),[21d] and indicate that the triply bonded
lead atom uses sp-hybrid orbitals for s bonding. The compo-
sition of 2-Br and 2-I was confirmed by elemental analyses
and IR, H, 31P{1H} and 13C{1H} NMRspectroscopy.
The
1
[15]
1
number and relative intensity of the H NMRspectroscopy
signals of the m-terphenyl substituent and the PMe3 ligands
suggest an averaged C2v symmetry of the plumbylidyne
complexes 2-Br and 2-I in solution, and their 31P{1H} NMR
spectra in C6D6 showed a singlet for the four chemically
equivalent PMe3 ligands, which appears up field (2-Br, d =
Scheme 1. Syntheses of the plumbylidyne complexes 2-X (X=Br, I).
Angew. Chem. Int. Ed. 2004, 43, 6512 –6516
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Communications
ꢁ43.6 ppm; 2-I, d = ꢁ53.9 ppm) of those of the lighter
ꢀ
Group 14 element analogues trans-[Cl(PMe3)4W E-R] (E =
C, R = Me: dP = ꢁ20.8 ppm, 1J(W,P) = 285 Hz;[22] E = Ge,
R = C6H3-2,6-Dipp2 (Dipp = 2,6-iPr2C6H3): dP = ꢁ31.1 ppm,
1J(W,P) = 258 Hz;
E = Sn,
R = 2,6-Dipp2C6H3:
dP =
ꢁ30.8 ppm, 1J(W,P) = 256 Hz).[23] The 31P NMRsignals are
flanked by one pair of satellites arising from coupling with the
183W nucleus,[24] the 1J(W,P) coupling constants (2-Br, 257 Hz;
2-I, 258 Hz) comparing well with those of the ylidyne
ꢀ
complexes trans-[Cl(PMe3)4W E-R] (E = Ge, Sn; R = aryl,
see above). The 13C{1H} NMRspectra of the plumbylidyne
complexes 2-Br and 2-I display a characteristic downfield-
shifted signal for the lead-bonded Cipso atom at d = 270.2 (2-
Br) and 267.9 ppm (2-I), as do those of the aryllead(ii) halides
1-Br (dC = 287.9 ppm)[14] and 1-I (dC = 276.7 ppm).[15]
Electrophile-induced halide abstraction was shown to be a
very efficient method for the preparation of cationic Fischer-
type carbyne complexes from neutral precursors.[25] Applica-
tion of this method to 2-Br and 2-I was envisaged as an
approach to cationic plumbylidyne complexes, given the
electronic analogy of 2-Br and 2-I with Fischer-type carbyne
complexes.[12] In fact, treatment of 2-Br with Na[B{3,5-
(CF3)2C6H3}4][26] and PhCN in toluene afforded the brown
benzonitrile complex salt 3, and bromide abstraction from 2-
Br by Li[B(C6F5)4]·2.5Et2O[27] in fluorobenzene gave in the
presence of PMe3 the olive-green to brown plumbylidyne
complex salt 4 [Eq. (1)].[15] Both salts are soluble in THF, and
decompose upon melting at 181–182 (3) and 149–1508C (4).
Figure 3. DIAMOND plot of the structure of the complex cation in 3.
Thermal ellipsoids are set at 30% probability. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Š] and angles [8]: W-Pb
2.5520(6), W-N 2.099(4), W-P1 2.469(1), W-P2 2.472(2), W-P3
2.493(2), W-P4 2.496(2), Pb-C1 2.228(5), C49-N 1.137(7); W-Pb-C1
171.7(1), N-W-Pb 174.9(1), Pb-W-P1 90.28(4), Pb-W-P2 95.69(4), Pb-W-
P3 91.56(4), Pb-W-P4 104.96(4), W-N-C49 179.1(5).
The structures of the complex cations in 3 and 4 (Figures 3
and 4) reveal the same bonding features of the plumbylidyne
ligand as observed in 2-Br and 2-I. These are the almost linear
coordination geometry at lead (W-Pb-Caryl = 171.7(1) (3),
Figure 4. DIAMOND plot of the structure of the complex cation in 4.
Thermal ellipsoids are set at 30% probability. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Š] and angles [8]: W-Pb
2.5744(2), W-P1 2.500(1), W-P2 2.490(1), W-P3 2.513(1), W-P4
2.495(1), W-P5 2.565(1), Pb-C1 2.289(4); W-Pb-C1 177.5(1), Pb-W-P1
87.10(3), Pb-W-P2 93.90(3), Pb-W-P3 88.93 (3), Pb-W-P4 92.93(3),
Pb-W-P5 174.87(3).
ꢁ
177.5(1)8 (4)), the short W Pb triple bonds (2.5520(6) (3),
ꢁ
2.5744(2) Š (4)), and the comparatively short Pb Caryl bonds
ꢁ
of 2.228(5) Š (3) and 2.289(4) Š (4). The W P bond of the
trans-disposed PMe3 ligand in 4 is longer (2.565(1) Š) than
those of the cis-coordinated PMe3 ligands (2.490(1)–
2.513(1) Š), reflecting the trans-influence of the plumbyli-
dyne ligand.[28] 1H, 31P{1H}, 19F{1H}, and 13C{1H} NMR
spectroscopic studies corroborated the X-ray structures of 3
and 4.[15] Thus, the IRspectrum of 3 in nujol displays a
comparison, the 31P{1H} NMRspectrum of 4 reveals the signal
pattern expected for
a nonfluxional, square-pyramidal
W(PMe3)5 fragment, that is, one doublet at d = ꢁ52.1 ppm
(2J(P,P) = 31 Hz, 1J(W,P) = 249 Hz) and one quintet at d =
ꢁ65.6 ppm (2J(P,P) = 31 Hz) in the intensity ratio of 4:1.[15]
The structures of 3 and 4 are also confirmed by the Pb-Cipso
resonance signal in the 13C{1H} NMRspectra at d = 278.7 (3)
and 279.1 ppm (4). The Cipso signal of 4 is split into a doublet as
a result of coupling with the trans-disposed PMe3 ligand
(3J(P,C) = 22 Hz).
ꢀ
characteristic n(C N) band of the benzonitrile ligand at
2171 cmꢁ1, which is at lower wavenumbers than that of free
ꢁ1
ꢀ
PhCN (n(C N) in nujol = 2230 cm ) and indicates some
tungsten–nitrile back-bonding.[29] In addition, the 31P{1H}
NMRspectrum of 3 shows a singlet resonance at d =
ꢁ36.8 ppm (1J(W,P) = 262 Hz) for the PMe3 ligands, which
confirms the trans-configuration of the complex cation in 3. In
ꢀ
The similarity of the plumbylidyne complex [(PMe3)5W
Pb(2,6-Trip2C6H3)]+ with the Fischer-type carbyne complexes
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Angew. Chem. Int. Ed. 2004, 43, 6512 –6516

Angewandte
Chemie
Table 1: Results of the bondinganalyses of the cation of 4.
NBO analysis[a]
BDE[c]
EDA[d] [kJmolꢁ1
]
center
NPA[b] charges
occupancy
%(W)
hybrid.
%(Pb)
hybrid.
WBI
1.42
[kJmolꢁ1
]
DEPauli
DEelstat
DEorb
DEint
W
Pb
ꢁ1.58
+1.21
s: 1.71
p1:1.85
p2: 1.83
41.1
81.0
81.0
sd1.54
d
d
58.9
19.0
19.0
sp0.77
p
p
149.7
+472.0
ꢁ352.0
ꢁ530.9
ꢁ410.9
ꢁ
[a] BP86/LANL2DZ; Natural bond orbital analysis of the W Pb bond: NBO occupancies, bond polarization in%Wand%Pb, orbital hydridization, and
ꢁ
Wibergbond index. [b] Natural population analysis. [c] Gibbs free dissociation energy (298.15 K, 1 atm) of the W Pb bond to the fragments in their
relaxed geometries and electronic ground states (zero point energy (ZPE) corrected). [d] Energy decomposition analysis (BP86/TZ2P for Pb, W, and P,
and DZP for C and H): Pauli repulsion (DEPauli), electrostatic interaction (DEelstat), orbital interaction (DEorb), and total interaction energy DEint between
the fragments [W(PMe3)5] and [Pb(2,6-Trip2C6H3)]+ at their frozen geometries in the complex cation.
+
[(CO)5M C-NEt2] (M = Cr, Mo, W) is noticeable.[30] This
ꢀ
1986, 25, 1; c) R. West, Angew. Chem. 1987, 99, 1231; Angew.
Chem. Int. Ed. Engl. 1987, 26, 1201; d) J. Barrau, J. EscudiØ, J.
SatgØ, Chem. Rev. 1990, 90, 283; e) T. Tsumuraya, S. A.
Batcheller, S. Masamune, Angew. Chem. 1991, 103, 916;
Angew. Chem. Int. Ed. Engl. 1991, 30, 902; f) R. S. Grev, Adv.
Organomet. Chem. 1991, 33, 125; g) M. Weidenbruch, Coord.
Chem. Rev. 1994, 130, 275; h) J. EscudiØ, C. Couret, H.
Ranaivonjatovo, J. SatgØ, Coord. Chem. Rev. 1994, 130, 427;
i) R. Okazaki, R. West, Adv. Organomet. Chem. 1996, 39, 231;
j) M. Driess, H. Grützmacher, Angew. Chem. 1996, 108, 900;
Angew. Chem. Int. Ed. Engl. 1996, 35, 828; k) K. M. Baines,
W. G. Stibbs, Adv. Organomet. Chem. 1996, 39, 275; l) J. EscudiØ,
C. Couret, H. Ranaivonjatovo, Coord. Chem. Rev. 1998, 178,
565; m) J. EscudiØ, H. Ranaivonjatovo, Adv. Organomet. Chem.
1999, 44, 113; n) M. Weidenbruch, Eur. J. Inorg. Chem. 1999,
373; o) P. P. Power, Chem. Rev. 1999, 99, 3463; p) M. Weiden-
bruch, J. Organomet. Chem. 2002, 646, 39.
ꢁ
fact prompted us to study the nature of the W Pb bond in 4 by
various quantum chemical methods. Optimization of the
structure of the complex cation at the BP86/LANL2DZ level
ꢁ
of theory led to a minimum structure with a W Pb separation
of 2.609 Š and a bond angle at the lead atom of 174.98 in good
agreement with the experimental values (Figure 4). Analysis
of the electronic charge distribution by the natural bond
orbital (NBO) method[31] gives an optimal Lewis structure
with a W Pb triple bond. The W Pb bond is composed of a
s component that is polarized towards the lead atom, and two
nearly degenerate p bonds, which are strongly polarized
towards the tungsten center (Table 1). The high polarity of the
ꢁ
ꢁ
ꢁ
W Pb bond is further reflected in the natural population
analysis (NPA) partial charges of the Pb (+ 1.21) and W atom
(ꢁ1.58) and the Wiberg bond index (WBI) of 1.42 (Table 1),
which is slightly lower than that of the model compound trans-
[2] The name diplumbene underlines the similar composition of
[Pb2R4] and alkenes, and is used herein instead of the term
bis(plumbanediyl) which is more appropriate to describe the
physical properties, structures, and chemical behavior of these
compounds, which bear little resemblance to those of alkenes.
[3] a) K. W. Klinkhammer, T. F. Fässler, H. Grützmacher, Angew.
Chem. 1998, 110, 114; Angew. Chem. Int. Ed. 1998, 37, 124; b) M.
Stürmann, M. Weidenbruch, K. W. Klinkhammer, F. Lissner, H.
Marsmann, Organometallics 1998, 17, 4425; c) M. Stürmann, W.
Saak, H. Marsmann, M. Weidenbruch, Angew. Chem. 1999, 111,
145; Angew. Chem. Int. Ed. 1999, 38, 187; d) M. Stürmann, W.
Saak, M. Weidenbruch, K. W. Klinkhammer, Eur. J. Inorg.
Chem. 1999, 579.
[11]
ꢀ
[Br(PH3)4Mo Pb-Ph] (WBI = 1.51).
Partitioning of the
total interaction energy DEint (ꢁ410.9 kJmolꢁ1) between the
frozen fragments [W(PMe3)5] and [Pb(2,6-Trip2C6H3)]+ into
the attractive Coulomb term DEelstat of ꢁ352.0 kJmolꢁ1, the
repulsive Pauli term DEPauli of + 472.0 kJmolꢁ1, and the
orbital interaction term DEorb of ꢁ530.9 kJmolꢁ1 affords a
[32]
ꢀ
covalent character of 60% for the W Pb bond. All these
ꢁ
results suggest that the W Pb triple bond of 4 can be
reasonably described with the Dewar–Chatt–Duncanson
model as a donor–acceptor interaction involving a [PbR]+!
[W(PMe3)5] s donation and two [W(PMe3)5]![PbR]+ p back-
donations.[33]
ꢁ
[4] A Pb Pb multiple bond has been also formulated in the complex
anion [{W(CO)5}4Pb2]2ꢁ: P. Rutsch, G. Huttner, Angew. Chem.
2000, 112, 3852; Angew. Chem. Int. Ed. 2000, 39, 3697.
Finally, the Gibbs free dissociation energy of 4 to give the
fragments [W(PMe3)5] and [Pb(2,6-Trip2C6H3)]+ in their
electronic ground states and minimum geometries[34,35] was
calculated to be only 149.7 kJmolꢁ1, which suggests that the
complex cation might be useful as a [Pb-R]+ transfer reagent.
Several applications of these compounds in stoichiometric
reactions might be envisaged given their structural and
electronic analogy with Fischer-type carbyne complexes.
[5] a) J. D. Cotton, P. J. Davidson, M. F. Lappert, J. Chem. Soc.
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Received: August 19, 2004
Keywords: density functional calculations · lead · plumbylidyne
.
ligands · triple bonds · tungsten
[1] Review articles on multiple bonds of the heavier group
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85, 419; b) A. G. Brook, K. M. Baines, Adv. Organomet. Chem.
Angew. Chem. Int. Ed. 2004, 43, 6512 –6516
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ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Communications
[8] a) M. J. S. Dewar, M. K. Holloway, G. L. Grady, J. J. P. Stewart,
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[23] A. C. Filippou, N. Weidemann, H. Rohde, unpublished results.
[24] No 207Pb satellites were observed in the 31P{1H} NMRspectra of
2-Br, 2-I, 3, and 4 at room temperature, and attempts to detect
the 207Pb NMRsignal of 2-Br in C6D6 at ambient temperature
were not successful to date.
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[28] For the trans-influence of carbyne and germylidyne ligands see:
a) ref. [12b]; b) E. Bannwart, H. Jacobsen, F. Furno, H. Berke,
Organometallics 2000, 19, 3605; c) F. Furno, T. Fox, H. W.
Schmalle, H. Berke, J. Organometallics 2000, 19, 3620; d) A. C.
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[14] L. Pu, B. Twamley, P. P. Power, Organometallics 2000, 19, 2874.
[15] The Supporting Information contains the experimental section
including the syntheses, spectroscopic, and crystallographic data
of 1-I and of the plumbylidyne complexes 2-Br, 2-I, 3, and 4. It
also contains IRand NMRspectroscopic data of the dinitrogen
complexes cis-[W(N2)2(PMe3)4] and [W(N2)(PMe3)5] and details
of the electronic structure calculations of the complex cation
+
ꢀ
[(PMe3)5W Pb(2,6-Trip2C6H3)] . CCDC-247928 (1-I·(n-C5H12)),
CCDC-247927 (2-Br), CCDC-247929 (2-I·0.5(n-C5H12)),
CCDC-247931 (3) and CCDC-247930 (4·0.705(C6H5F)) contains
the supplementary crystallographic data for this paper. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax:
(+ 44)1223-336-033; or deposit@ccdc.cam.ac.uk).
[29] For d6 tungsten nitrile complexes revealing dp(tungsten)!
p*(nitrile) back-bonding see: a) J. Chatt, G. J. Leigh, H.
Neukomm, C. J. Pickett, D. R. Stanley, J. Chem. Soc. Dalton
Trans. 1980, 121; b) B. J. Carter, J. E. Bercaw, H. B. Gray, J.
Organomet. Chem. 1979, 181, 105; c) H. Seino, Y. Tanabe, Y.
Ishii, M. Hidai, Inorg. Chim. Acta 1998, 280, 163; d) C. M.
Habeck, N. Lehnert, C. Näther, F. Tuczek, Inorg. Chim. Acta
2002, 337, 11.
[30] a) U. Schubert, E. O. Fischer, D. Wittmann, Angew. Chem. 1980,
92, 662; Angew. Chem. Int. Ed. Engl. 1980, 19, 643; b) U.
Schubert, D. Neugebauer, P. Hofmann, B. E. R. Schilling, H.
Fischer, A. Motsch, Chem. Ber. 1981, 114, 3349; c) E. O. Fischer,
D. Wittmann, D. Himmelreich, U. Schubert, K. Ackermann,
Chem. Ber. 1982, 115, 3141; d) E. O. Fischer, D. Wittmann, D.
Himmelreich, R. Cai, K. Ackermann, D. Neugebauer, Chem.
Ber. 1982, 115, 3152.
[31] A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88, 899.
[32] The DEorb term could not be broken down into the s and p bond
energy contributions owing to the lack of symmetry. The
percentage contribution of DEorb to the total attractive inter-
actions (DEorb and DEelstat) reflects the covalent character of the
bond.
[33] G. Frenking, N. Fröhlich, Chem. Rev. 2000, 100, 717 and
references therein.
[34] [W(PMe3)5] has a singlet ground-state configuration and adopts
a distorted trigonal-bipyramidal minimum geometry, in which
[16] The only other known organolead(ii) iodide is [Pb(h-C5H5)I]:
A. K. Holliday, P. H. Makin, R. J. Puddephatt, J. Chem. Soc.
Dalton Trans. 1976, 435.
[17] The Pb···Pb separation of 1-I is much longer than the interatomic
distance in elementary lead (3.494 Š): a) H. P. Klug, J. Am.
Chem. Soc. 1946, 68, 1493; b) A. F. Wells, Structural Inorganic
Chemistry, 5th ed., Clarendon, Oxford, 1984, p. 1288.
[18] IRspectra of the reaction solutions and the 1H and 31P{1H} NMR
spectra of the crude products, that were isolated after comple-
tion of the reaction, revealed the concomitant formation of two
by-products. These were identified to be [W(N2)(PMe3)5] and
1,3-Trip2C6H4 by comparison with authentic samples (Support-
ing Information). A gray-green solid, which is soluble in THF,
but insoluble in pentane was also formed in these reactions. This
solid burned upon exposure to air in dried form and was not
further characterized.
[19] The term “electron-rich” is used herein to emphasize the strong
p-electron donating ability of the metal centers in these
complexes: a) A. J. L. Pombeiro, R. L. Richards, Coord. Chem.
Rev. 1990, 104, 13; b) A. J. L. Pombeiro, M. F. C. Guedes da -
Silva, R. A. Michelin, Coord. Chem. Rev. 2001, 218, 43.
[20] The orientation of the para-positioned isopropyl substituents
lowers the molecular symmetry of 2-Br and 2-I from roughly C2v
to C2. The terphenyl substituent adopts in both plumbylidyne
complexes an eclipsed conformation, as shown by the interplane
angle of 5.9(2) (2-Br) and 9.0(1)8 (2-I) between the central aryl
ring and the least-square plane through the atoms Br (I), W, P1,
and P3.
ꢁ
one of the equatorial PMe3 ligands displays a C H agostic
interaction with the metal center (see Supporting Information).
[W(PMe3)5] has been suggested as an intermediate in the
cyclometallation reaction of [W(PMe3)6] to afford
[W(PMe3)4(h2-CH2PMe2)H] and PMe3: D. Rabinovich, G.
Parkin, J. Am. Chem. Soc. 1990, 112, 5381.
[35] The ion [Pb(2,6-Trip2C6H3)]+ has a singlet ground state (see
Supporting Information). The toluene adduct of [Pb(2,6-
Trip2C6H3)]+ was isolated recently with the counterion
[B(Me)(C6F5)3]ꢁ: S. Hino, M. Brynda, A. D. Phillips, P. P.
Power, Angew. Chem. 2004, 116, 2709; Angew. Chem. Int. Ed.
2004, 43, 2655.
ꢁ
[21] Only a few compounds with W Pb bonds have been structurally
ꢁ
characterized. The W Pb bond lengths range in these com-
pounds from 2.7423(3) to 3.339(1) Š depending on the bond
order, the oxidation states, and the coordination numbers of lead
and tungsten: a) ref. [4]; b) ref. [14]; c) S. Seebald, G. Kickelbick,
F. Möller, U. Schubert, Chem. Ber. 1996, 129, 1131; d) L. Pu, P. P.
6516
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 6512 –6516