Photochemical reaction of W(CO)6 with GeCl4 as a source of germyl and germylene compounds acting as initiators for ring-opening metathesis polymerization of norbornene

Article abstract of DOI:10.1016/j.jorganchem.2006.05.031

Photolysis of W(CO)₆ in a solution of n-heptane containing GeCl₄ leads to the formation of two seven-coordinate compounds with direct W{single bond}Ge bonds: [(CO)₄W(μ-Cl)₃W(GeCl₃)(CO)₃] (1

Full text of DOI:10.1016/j.jorganchem.2006.05.031

Journal of Organometallic Chemistry 691 (2006) 3708–3714
www.elsevier.com/locate/jorganchem
Photochemical reaction of W(CO)6 with GeCl4 as a source
of germyl and germylene compounds acting as initiators
for ring-opening metathesis polymerization of norbornene
*
´
´
Marcin Gorski, Andrzej Kochel, Teresa Szymanska-Buzar
Faculty of Chemistry, University of Wrocław, ul. F. Joliot-Curie 14, 50-383 Wrocław, Poland
Received 1 March 2006; received in revised form 10 May 2006; accepted 16 May 2006
Available online 27 May 2006
Abstract
Photolysis of W(CO)6 in a solution of n-heptane containing GeCl4 leads to the formation of two seven-coordinate compounds with
direct WAGe bonds: [(CO)4W(l-Cl)3W(GeCl3)(CO)3] (1) and [(l-GeCl2){W(CO)5}2] (2). The molecular structures of these two tung-
sten–germanium compounds have been established by single-crystal X-ray diffraction studies. The germyl compound 1 is a previously
synthesized binuclear complex of tungsten(II) with a d 4 electronic configuration, while in the new germylene compound 2 the tungsten
atom is formally in the zero oxidation state with a d 6 electronic configuration and a direct WAW bond. In an attempt to establish
whether compounds 1 and 2 could be used as precatalysts for the ring-opening metathesis polymerization (ROMP) of cyclic olefins, their
reactivity towards norbornene has been studied. In chloroform-d1 solution the ROMP reaction is accompanied by the formation of a new
olefin, 2,20-binorbornylidene (bi-(NBE)), as a result of carbene–carbene coupling. In reaction of norbornene carried out in benzene solu-
tion the ROMP reaction is accompanied by the formation of 2-phenylnorbornane (hydroarylation product) and small amounts of bi-
(NBE). In general, in the presence of olefin, compound 2 undergoes rearrangement to give an olefin compound of the type
[(WCO)5(g2-olefin)].
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Tungsten; Germanium; Photochemistry; X-ray structure; Metathesis polymerization; Hydroarylation; Germyl; Germylene complex
1. Introduction
dative addition reaction of M(CO)6 M = W, Mo, and tin
or germanium tetrachloride [25], have emerged as versatile
initiators for synthetically important transformations such
as metathesis polymerization of alkynes, ring-opening
metathesis polymerization (ROMP), dimerization, and
hydroarylation of cyclic olefin [7,25].
The earlier-reported photochemical reaction of W(CO)6
with GeCl4 has been reinvestigated and found to give the
previously synthesized trichloro-bridged dinuclear tung-
sten(II) compound [(CO)4W(l-Cl)3W(GeCl3)(CO)3] (1)
and a previously unknown germylene-bridged tungsten(0)
dimer [(l-GeCl2){W(CO)5}2] (2) (Scheme 1). We have iso-
lated a ditungsten complex bridged by a germanium center
substituted with two chlorides. Here, we report the results
of our studies on the crystal structure of both compounds,
1 and 2, and on their reactivity towards olefin.
Heterobimetallic complexes with a direct metalAmetal
bond have attracted particular interest owing to their strik-
ingly different activity relative to the separate metal com-
plex, possible as a result of the cooperative effects of two
metals. Thus, a great number of group 6 metal complexes
containing germyl [1–14] or germylene ligands [15–24] have
been synthesized and characterized, and some of them have
proved to be very active and selective initiators for many
catalytic and stoichiometric processes [25]. Heterobimetal-
lic complexes of the type [(CO)4M(l-Cl)3M(M0Cl3)(CO)3]
M = W, Mo; M0 = Sn, Ge, prepared in photochemical oxi-
*
Corresponding author. Tel.: +48 71 375 7221; fax: +48 71 328 23 48.
´
E-mail address: tsz@wchuwr.chem.uni.wroc.pl (T. Szymanska-Buzar).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.031

M. Go´rski et al. / Journal of Organometallic Chemistry 691 (2006) 3708–3714
3709
hν
n-heptane
4W(CO)6 + 2GeCl4
[(CO)4W(μ-Cl)3W(GeCl3)(CO)3] (1) + [(μ-GeCl2){W(CO)5}2] (2) + 7CO
Scheme 1. Photochemical synthesis of WAGe compounds 1 and 2.
2019
2. Results and discussion
2.1. Synthesis and spectroscopic characteristic
1942
1990
As was observed using IR and NMR spectroscopy sev-
eral years ago, the photochemical reaction of tungsten
hexacarbonyl with GeCl4 in cyclohexane solution leads to
the formation of two compounds, the dimeric tungsten(II)
compound (1), an analogue of [(CO)4W(l-Cl)3W-
(SnCl3)(CO)3], and a not-fully characterized pentacarbon-
yltungsten–dichlorogermylene adduct [7]. Reinvestigation
of this reaction and change of the reaction solvent from
cyclohexane to n-heptane, in which all compounds are
more soluble, allowed us to isolate two compounds, the
germyl 1 and the germylene compound 2 in pure crystalline
form and characterize both by spectroscopic methods in
solution and by X-ray diffraction studies in the solid state.
The IR spectrum of compound 1 is typical for dimeric
halocarbonyls of group 6 metals containing mutually cis
four and three carbonyl groups (Fig. 1A) [25]. The penta-
carbonyl moiety of compound 2, instead of the typical
three-band pattern commonly observed in the IR spectra
of complexes of the type [M(CO)5L] with a local C4v sym-
metry, gives at least five m(C„O) bands in the IR spectrum
(Fig. 1B), indicating a substantial lowering of the local C4v
symmetry arising from the presence of seven atoms around
the central tungsten atom. In the 13C NMR spectrum of
compound 2 the carbonyl ligands give two resonances in
the intensity ratio 1:4 at d = 194.5 and 192.9, respectively,
differing very greatly in the tungsten–carbon coupling con-
1912
A
2097
1969
A
B
S
O
R
B
A
N
C
E
1943
1993
2071
B
2112
2042
1934
C
2077
1
1
stant: JW–C = 147 Hz, (1CO), JW–C = 120 Hz (4CO).
This indicates a stronger interaction of one of the five car-
bonyl groups with the tungsten atom than the other four
carbonyl groups and suggests this unique CO group is trans
to the germylene ligand, which is a poorer p-acceptor than
the CO ligand. In the 13C NMR spectrum of the tung-
sten(II) compound 1, three resonances in the intensity ratio
2:1:4 at d = 217.3, 212.1 and 204.5, respectively, were
observed [7], i.e. at lower field than for the tungsten(0)
compound 2. The lowest-field resonance of CO ligands at
d = 217.3 differs from the highest-field resonance at d =
2200
2100
2000
1900
1800
Wavenumbers (cm-1)
Fig. 1. Comparison of the m(C„O) region of IR spectra in KBr pellets of
compounds 1 (A) and 2 (B), and an insoluble product formed in reaction
of 2 with olefin (C).
(Fig. 2, Table 1). Selected bond lengths and angles are
listed in Table 2. The geometry of the coordination sphere
of the tungsten atom in 1 approximates that of the 4:3
piano stool structure identified in analogous WASn and
MoASn complexes [25]. The angles between the plane
defined by three chlorine atoms and the tetragonal base
defined by four carbon atoms and the other plane defined
by the germanium atom and three carbon atoms are
3.6(1)ꢁ and 3.7(8)ꢁ, respectively. Four carbonyl carbon
atoms are at a slightly longer distance from the tungsten
204.5 in the tungsten–carbon coupling constant (1JW–C
=
1
136 Hz, (2CO), JW–C = 111 Hz (4CO)), indicating a
stronger interaction of two of the seven CO ligands with
the tungsten atoms.
2.2. X-ray crystal structure
Although the structure of compound 1 has been pro-
posed earlier based on the results of IR and NMR spectro-
scopic investigations, here we report the single crystal
structure of 1 determined by X-ray diffraction studies
˚
atom W(1) (W(1)ACO = 2.03 A av.) than three carbonyl
carbon atoms from the tungsten atom W(2)
(W(2)ACO = 1.99 A av.). In contrast to carbonyl groups,
˚

3710
M. Go´rski et al. / Journal of Organometallic Chemistry 691 (2006) 3708–3714
Table 2
O(3)
O(5)
C(5)
˚
Selected bond lengths (A) and angles (ꢁ) for 1
Atoms
Distance
Atoms
Angle
C(3)
Cl(3)
Cl(1)
W(1)AC(4)
W(1)AC(6)
W(1)AC(5)
W(1)AC(7)
W(1)ACl(1)
W(1)ACl(2)
W(1)ACl(3)
W(2)AC(1)
W(2)AC(3)
W(2)AC(2)
W(2)ACl(3)
W(2)ACl(2)
W(2)ACl(1)
W(2)AGe
GeACl(4)
GeACl(6)
GeACl(5)
C(1)AO(1)
C(2)AO(2)
C(3)AO(3)
C(4)AO(4)
C(5)AO(5)
C(6)AO(6)
C(7)AO(7)
2.01(2)
2.02(2)
2.04(2)
2.04(2)
2.475(5)
2.506(5)
2.515(5)
1.95(2)
1.99(2)
2.03(2)
2.487(5)
2.553(5)
2.553(5)
2.551(2)
2.162(5)
2.167(6)
2.178(5)
1.17(2)
1.10(2)
1.11(2)
1.13(3)
1.11(2)
1.15(2)
1.10(3)
C(4)AW(1)AC(6)
C(4)AW(1)AC(5)
C(6)AW(1)AC(5)
C(4)AW(1)AC(7)
C(6)AW(1)AC(7)
C(5)AW(1)AC(7)
C(4)AW(1)ACl(1)
C(5)AW(1)ACl(2)
C(6)AW(1)ACl(3)
Cl(1)AW(1)ACl(2)
C(1)AW(2)AC(3)
C(1)AW(2)AC(2)
C(1)AW(2)ACl(3)
C(1)AW(2)AGe
114.8(9)
73.9(8)
75.5(8)
72.2(9)
72.7(8)
116.6(8)
145.2(6)
165.6(6)
164.9(6)
77.1(2)
73.4(7)
111.2(8)
148.0(5)
67.8(5)
114.9(6)
71.7(5)
143.8(1)
165.8(6)
166.2(6)
76.6(2)
76.2(2)
75.2(2)
89.3(1)
88.0(2)
89.3(1)
O(4)
O(1)
C(1)
W(2)
W(1)
C(4)
C(7)
O(7)
C(2)
O(2)
Cl(6)
Ge
C(6)
O(6)
Cl(2)
Cl(4)
Cl(5)
Fig. 2. Crystal structure of 1.
C(3)AW(2)AGe
C(2)AW(2)AGe
Cl(3)AW(2)AGe
C(3)AW(2)ACl(2)
C(2)AW(2)ACl(1)
Cl(3)AW(2)ACl(2)
Cl(3)AW(2)ACl(1)
Cl(2)AW(2)ACl(1)
W(2)ACl(3)AW(1)
W(2)ACl(2)AW(1)
W(2)ACl(1)AW(1)
Table 1
Crystal data and structure refinement parameters for [(CO)4W(l-
Cl)3W(GeCl3)(CO)3] (1) and [(l-GeCl2){W(CO)5}2] (2)
1
2
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
Unit cell dimensions
C7Cl6GeO7W2
849.06
0.07 · 0.05 · 0.03
Orthorombic
Pbca (No. 61)
C10Cl2GeO10W2
791.29
0.12 · 0.10 · 0.08
Monoclinic
P21/c (No. 14)
˚
˚
the Wꢀ ꢀ ꢀW contact distance of 3.514(1) A was found. The
a (A)
15.578(3)
13.646(3)
17.258(3)
90.0
3668.7(12)
8
9.236(2)
12.762(3)
16.833(2)
119.16(2)
1732.6(8)
4
˚
˚
b (A)
WAGe distance of 2.551(2) A in 1 is comparable with those
˚
c (A)
reported for other germyl compounds of tungsten [1–14],
and is very close to that found in the germylene compound
2 (2.561(1) and 2.569(1) A) (Fig. 3, Table 3). The structure
of compound 2 is very similar to that found for l-(dibrom-
ogermylene)-bis(pentacarbonyltungsten) [3], and to other
structurally characterized binuclear carbonyl complexes
of tungsten containing bridging silylene or carbene ligands
[26,27]. However, as can be expected, the WAW bond
b (ꢁ)
3
˚
V (A )
˚
Z
Dcalc (g/cm3)
Diffractometer
Radiation
3.074
3.033
Kuma KM4CCD
Kuma KM4CCD
˚
˚
Mo Ka (k = 0.71073 A) Mo Ka (k = 0.71073 A)
Temperature (K)
100(2)
15.037
3040
100(2)
15.324
1416
l (mmꢁ1
F(000)
)
˚
length of 3.360(1) A in 2 is longer than in analogous silyl-
ene (3.265(2) A in [(l-SiPh2){W(CO)5}2] [26]) and carbene
(3.118(1) A in [(l-CHPh){W(CO)5}2] [27]) compounds.
No. of data/
restraints/
parameters
Index ranges
4479/0/209
4157/0/226
˚
˚
ꢁ20 6 h 6 20;
ꢁ17 6 k 6 17;
ꢁ22 6 l 6 22
40,214
ꢁ12 6 h 6 12;
ꢁ13 6 k 6 17;
ꢁ21 6 l 6 21
22,756
No. of reflections
collected
Cl(2)
Cl(1)
Data collected,
h minimum/
maximum (ꢁ)
Rint
3.01/28.58
3.13/28.54
O(6)
O(2)
C(2)
Ge
0.1412
1.577
0.0729
1.239
C(6)
S
O(1)
Final residuals:
R1, wR2 (I > 2r(I))
Tmin, Tmax
0.1024, 0.1634
0.0343, 0.0598
O(10)
C(10)
C(1)
W(1)
W(2)
C(7)
0.137, 0.608
1.970/ꢁ2.028
0.260, 0.373
0.961/ꢁ1.802
ꢁ3
˚
Dqmax/Dqmin (e A
)
C(8)
C(3)
O(8)
O(3)
C(4)
O(4)
O(7)
the bridging Cl atoms are slightly closer to W(1) than to
C(5)
O(5)
C(9)
O(9)
˚
W(2) (average W(1)ACl = 2.499 A and W(2)ACl =
˚
2.531 A). The average angles, ClAW(1)ACl = 77.1ꢁ,
ClAW(2)ACl = 76.0ꢁ,
and
W(1)AClAW(2) = 88.6ꢁ,
ensure that there is no metalAmetal bonding in 1, in which
Fig. 3. Crystal structure of 2.

M. Go´rski et al. / Journal of Organometallic Chemistry 691 (2006) 3708–3714
3711
Table 3
Selected bond lengths (A) and angles (ꢁ) for 2
˚
1
Atoms
Distance
Atoms
Angle
C6H6
n
W(1)AC(3)
W(1)AC(2)
W(1)AC(1)
W(1)AC(4)
W(1)AC(5)
W(1)AGe(1)
W(1)AW(2)
W(2)AC(8)
W(2)AC(6)
W(2)AC(7)
W(2)AC(10)
W(2)AC(9)
W(2)AGe(1)
Ge(1)ACl(1)
Ge(1)ACl(2)
C(1)AO(1)
C(2)AO(2)
C(3)AO(3)
C(4)AO(4)
C(5)AO(5)
C(6)AO(6)
C(7)AO(7)
C(8)AO(8)
C(9)AO(9)
C(10)AO(10)
2.022(6)
2.037(7)
2.046(6)
2.060(6)
2.070(6)
2.561(1)
3.360(1)
2.006(7)
2.031(7)
2.050(6)
2.058(6)
2.076(6)
2.569(1)
2.155(2)
2.170(2)
1.133(7)
1.136(8)
1.128(8)
1.124(7)
1.132(8)
1.140(8)
1.131(8)
1.142(8)
1.137(8)
1.126(8)
C(3)AW(1)AC(2)
C(3)AW(1)AC(1)
C(2)AW(1)AC(1)
C(3)AW(1)AC(4)
C(2)AW(1)AC(4)
C(1)AW(1)AC(4)
C(3)AW(1)AC(5)
C(2)AW(1)AC(5)
C(3)AW(1)AGe(1)
C(6)AW(2)AC(8)
C(8)AW(2)AC(7)
C(6)AW(2)AC(7)
C(7)AW(2)AC(10)
C(6)AW(2)AC(9)
C(8)AW(2)AC(9)
C(7)AW(2)AGe(1)
C(6)AW(2)AGe(1)
C(8)AW(2)AGe(1)
C(9)AW(2)AGe(1)
C(10)AW(2)AGe(1)
Cl(1)AGe(1)ACl(2)
Cl(1)AGe(1)AW(1)
Cl(2)AGe(1)AW(1)
Cl(1)AGe(1)AW(2)
Cl(2)AGe(1)AW(2)
W(1)AGe(1)AW(2)
80.4(3)
90.1(2)
90.4(2)
91.2(2)
89.5(2)
178.6(2)
84.3(3)
164.3(2)
154.1(2)
81.9(2)
91.7(3)
91.5(3)
175.6(3)
163.9(2)
82.5(2)
43 %
7 %
50 %
Scheme 2. Transformation of NBE in reaction carried out in benzene
solution in the presence of 1.
1
monitored by H NMR spectroscopy (Fig. 4). It should
be noted that poly-(NBE) is poorly soluble in benzene
and for that reason its characteristic olefinic proton signals
at d = 5.53 for trans and d = 5.39 for cis (ACH@CHA)
units are of low intensity [28]. The most intense signals in
the spectrum are due to protons of exo-2-phenyl-d5-3-d1-
norbornane d: 2.64 (t, JHH = 7.2 Hz, 1H, C2H), 2.31 (s,
1H, C1H), 2.23 (s, 1H, C4H), 1.64 (d, JHH = 7.2, 1H;
C3HD), 1.49 (m, 3H; C6,5,7H2), 1.23 (m, 1H; C6H2), 1.18
(m, 1H, C5H2), 1.08 (d, JHH = 9.6, 1H; C7H2) [29]. The
simultaneous formation of four stereoisomers (anti–cis,
syn–cis, anti–trans, and syn–trans) of bi-(NBE) is indicated
by signals characteristic for their methine protons (HC1) at
d = 2.93, 2.88, 2.78, and 2.75 [30,31]. During the conver-
91.4(2)
70.7(2)
152.5(2)
124.6(2)
84.8(2)
99.64(8)
121.44(6)
119.31(5)
117.83(6)
118.04(6)
81.82(3)
1
sion of NBE in the presence of 1 monitored by H NMR
spectroscopy in chloroform-d1 solution, the decay of
NBE and the appearance of poly-(NBE) as well as bi-
(NBE) are nicely detected (Fig. 5). The formation of small
amounts of exo and endo-2-chloronorbornane in this sol-
vent is indicated by signals characteristic for the methine
proton (HC2) at d 3.8 and 4.2, respectively [29]. Although
the reaction was performed under anhydrous conditions,
we could not exclude the presence of traces of water leading
The WACO bond length in 2 falls in the range 2.006(7)–
˚
2.070(6) A. The shortest WACO bond distance is observed
for CO in the cis position to the remaining four carbonyl
ligands, which are at an average distance of 2.053 A from
˚
the tungsten atom.
In 1 and 2, the germanium atom is four-coordinate with
a geometry that is best described as distorted tetrahedral.
The average bond angle at the germanium atom is 109ꢁ
in 1 and 109.5ꢁ in 2. However, in 1 the WAGeACl average
angle (115.9ꢁ) is larger than the ClAGeACl average angle
(102.1ꢁ), whereas in 2 the WAGeAW angle (81.82(3)ꢁ) is
noticeably smaller than other tetrahedral angles
(ClAGeACl = 99.64(8)ꢁ and WAGeACl = 119.1ꢁ av.).
s
a
2.3. Reactivity of compound 1 towards norbornene
In our previous investigations, we have shown that com-
pound 1 reacts rapidly at room temperature with phenyl-
acetylene to give red poly(phenylacetylene) in high yield
[7,25]. Here we tested the reactivity of 1 and 2 towards
bicyclic olefins – norbornene (NBE).
In reaction of NBE carried out in C6H6 solution at
70 ꢁC in the presence of 1, the yield of ROMP polymer
(poly-1,3-cyclopentylenevinylene, poly-NBE) reached ca.
50% (by mass), but the rest of NBE transforms to 2,20-
binorbornylidene (bi-(NBE)), and to the hydroarylation
product (2-phenylnorbornane) in a 1:6 molar ratio, respec-
tively (Scheme 2). An identical distribution of products was
detected during the reaction carried out in C6D6 solution,
n
n
b
b
pc
pt
c
*
7.0
6.0
5.0
4.0
3.0
2.0
1.0
(ppm)
Fig. 4. The 1H NMR spectrum (500 MHz, C6D6 (s)) obtained during
reaction of 1 with NBE (n) showing the formation of poly-(NBE) (p) and
bi-(NBE) (b). Signals characteristic for exo-2-phenyl-d5-3-d1-norbornane
are denoted by (a), those characteristic for chloronorbornane by (c), and
signals of [W(CO)5(g2-C7H10)] are labeled by an asterisk ( ).
*

3712
M. Go´rski et al. / Journal of Organometallic Chemistry 691 (2006) 3708–3714
and tungsten(0) pentacarbonylcarbene complexes [33–35]
and detected by Schrock et al. in reaction of alkylidene
complexes of tantalum, molybdenum, and tungsten [36–
38]. For the first time the carbene–carbene coupling reac-
tion was applied in synthesis of bi-(NBE) from NBE in
reaction catalyzed by a WASn compound [30]. Previously,
the McMurry and Fleming procedure for reductive dimer-
ization of ketones had been applied for the synthesis of
compounds of that type [31,39]. As shown here, compound
1 can also be used as a catalyst in synthesis of bi-(NBE),
which is formed as a mixture of four stereoisomers. It is
worth pointing out that the detection of bi-(NBE) provides
direct evidence for tungsten(II)-promoted transformation
of olefin to metallacarbene, which is able to initiate the
ROMP of NBE or to disproportionate giving a new olefin
as the carbene–carbene coupling product.
s
b
b
b
b
b
n
n
c
p
tpc
c
*
7.0
6.0
5.0
4.0
3.0
2.0
1.0
2.4. Reactivity of compound 2
(ppm)
Fig. 5. The 1H NMR spectrum (500 MHz, CDCl3) obtained during
reaction of 1 with NBE showing the formation of poly-(NBE) (p) and bi-
(NBE) (b). Signals characteristic for chloronorbornane are denoted by (c)
To investigate the reactivity of a new analogue of the
bridging carbene compound 2, its reactions with various
olefins were examined. Thus, reaction of 2 in n-heptane
solution with ethene at room temperature cleanly yields
two tungsten carbonyl compounds: an g2-ethene com-
plex soluble in n-heptane, [W(CO)5(g2-C2H4)], [40,41]
and a compound insoluble in n-heptane, with an IR
spectrum characteristic for a pentacarbonyl moiety with
a local C4v symmetry, containing one weak and one
and those characteristic for [W(CO)5(g2-C7H10)] labeled by an asterisk ( ).
*
to the formation of 3-hydroxyl-2,20-binorbornyl, observed
in the latter spectrum due to a characteristic signal at
d = 3.35 and subsequently identified by GC–MS analysis
(Mr = 206.32). The g2-coordination of NBE to the tung-
sten atom is indicated by a proton signal at d = 4.8 [29].
The NMR experiment provides very important informa-
tion about the initiation of ROMP reaction by 1. The
mechanism for the formation of poly-(NBE) as well as
bi-(NBE) involves the coordination of NBE to the tungsten
atom and its transformation to a tungstanorbornylidene
species as a result of 1,2-hydride shift (Scheme 3). A similar
g2-olefin-to-alkylidene rearrangement has been proposed
by others for catalytic systems where an olefin ligand is
the only source of an alkylidene species [28]. The first direct
evidence for an alkene-to-alkylidene rearrangement was
obtained by Wolczanski et al. [32]. In our study it was
observed that a bimolecular coupling of the tungstanor-
bornylidene intermediate species led to the formation of
bi-(NBE) and regenerated the binuclear compound 1. A
similar bimolecular coupling of two carbene ligands has
been observed during mild thermolysis of chromium(0)
strong band at 2077 and 1934 cmꢁ1
,
respectively
(Fig. 1C). The very poorly soluble solid studied by 13C
NMR spectroscopy in CDCl3 solution has shown only
a low-intensity broad signal at d = 194.99. In a similar
reaction of 2 with NBE the formation of [W(CO)5(g2-
C7H10)] [29] and the initiation of ROMP reaction were
observed by 1H NMR spectroscopy in benzene-d6 and
chloroform-d1 solutions. Similarly as for compound 1,
ROMP reaction initiated by 2 in benzene solution was
accompanied by the formation of bi-(NBE) and 2-
phenylnorbornane.
2.5. Conclusions
In photochemical reaction of W(CO)6 and GeCl4, tri-
chlorogermyl and dichlorogermylene species are formed
which bind to the tungsten atom to give compounds 1
and 2, respectively. Compound 1 is a binuclear complex
of tungsten(II) with a d4 electronic configuration, while in
compound 2, which has a direct WAW bond, the tungsten
atom is formally in the zero oxidation state with a d6 elec-
tronic configuration.
[W]
Investigation of the reactivity of compounds 1 and 2
revealed that both compounds can be used as precatalysts
for the ROMP of NBE. In reaction of complexes 1 and 2
with NBE the initiation of ROMP reaction as well as the
formation of bi-(NBE) were observed. This experiment
provided direct evidence that the mechanism for the forma-
tion of poly-(NBE) as well as bi-(NBE) must involve the
[W]
[W2]
= 1
[W2]
[W2]
+
Scheme 3. Initiation of ROMP of NBE and formation of 2,20-binor-
bornylidene in reaction carried out in CDCl3 solution in the presence of 1.

M. Go´rski et al. / Journal of Organometallic Chemistry 691 (2006) 3708–3714
3713
coordination of NBE to the tungsten atom and its transfor-
mation to a tungstanorbornylidene species as a result of
1,2-hydride shift (the activation of the olefin CAH bond
by the tungsten atom). Tungstanorbornylidene species are
able to initiate the ROMP of NBE or, in carbene–carbene
coupling reaction, give a new olefin bi-(NBE). In that way
direct evidence was obtained for the transformation of a
cyclic olefin ligand to a carbene species as a result of the
activation of the olefin CAH bond by the tungsten atom
in a low oxidation state.
extracted with a few portions (5 cm3) of n-heptane to give,
after evaporation of the solvent, compound 2 (32 mg, 29%
yield). IR (KBr disc): m = 2112 (w), 2071 (s), 2042 (w), 1993
(s,sh), 1969 (vs), 1943 (s,sh), 577 (w), 557 (w) cmꢁ1 13C
.
NMR (125 MHz, CDCl3): d = 194.5 (1JW–C = 147 Hz,
1CO), 192.9 (1JW–C = 120 Hz, 4CO). Anal. Calc. for
C10Cl2GeO10W2: C, 15.18; Cl, 8.96. Found: C, 15.35; Cl,
9.09%. Compound 1, insoluble in n-heptane, was recovered
(40 mg, 33% yield) [7].
In benzene solution the ROMP reaction is accompanied
by the hydroarylation reaction of NBE, which indicates
that compounds 1 and 2 are also able to activate the C–
H bond of arene.
The very reactive germylene compound 2, in reaction
with olefin undergoes rearrangement to give an olefin and
bis(germylene) compounds. The pentacarbonylnorbornene
complex of tungsten(0) very easily transforms to a carbene
species initiating the ROMP reaction.
3.3. X-ray diffraction studies
Crystal data for a yellow plate of 1 with approximate
dimensions of 0.07 · 0.05 · 0.03 mm and a for red block
of
2
with approximate dimensions of 0.12 · 0.10 ·
0.08 mm were collected at 100 K, using a KM4-CCD dif-
fractometer and graphite-monochromated Mo Ka radia-
tion, generated from a diffraction X-ray tube operated at
50 kV and 35 mA. The images were indexed, integrated,
and scaled using the KUMA data reduction package Cry-
sAlis RED (Oxford Diffraction Poland Sp., CCD data col-
lection and reduction GUI, Version 1.173.13 beta, release
14.11.2003, Copyright 1995–2003). The structure was
solved by the heavy atom method using SHELXS97 (Program
for the Solution of Crystal Structure, University of Go¨et-
tingen, Go¨ettingen, Germany, 1997), and refined by the
full-matrix least-squares method on all F2 data (Program
for the Refinement of Crystal Structure, University of
Go¨ettingen, Go¨ettingen, Germany, 1997). All atoms were
included in the refinement, with anisotropic displacement
parameters. The data were corrected for absorption, min/
max absorption coefficients 0.137/0.608 for 1 and 0.260/
0.373 for 2.
Further efforts to explore these germyl and germylene
complexes of tungsten in ROMP reaction of different deriv-
atives of norbornene are in progress [43].
3. Experimental
3.1. General information
The synthesis and manipulation of all chemicals were
carried out under an atmosphere of nitrogen using stan-
dard Schlenk techniques. Solvents and liquid reagents were
pre-dried with CaH2 and vacuum transferred into small
storage flasks prior to use. IR spectra were measured with
a Nicolet-400 FT-IR instrument. 1H and 13C NMR spectra
were recorded with a Bruker AMX 300 or 500 MHz instru-
ment. All chemical shifts are referenced to residual solvent
protons for 1H NMR (d 7.24 CDCl3; 7.20 benzene-d6; 4.65
D2O) and to the chemical shift of the solvent for 13C NMR
(77.00 CDCl3; 128.00 benzene-d6). The photolysis source
was an HBO 200 W high-pressure Hg lamp. Analyses of
the catalytic reaction products were performed on a Hew-
lett–Packard GC–MS system. The average molecular
weights (Mn) of the polymers were determined by gel per-
meation chromatography (GPC) of the solution in CHCl3
on a Hewlett–Packard 1090II instrument equipped with a
refractive index detector HP 1047A and Plgel 10 l
MIXED-B or Plgel 5 l MIXED-C columns previously cal-
ibrated using commercially available polystyrene standards
in the molecular mass range 11.6 · 103 to 2.9 · 106.
3.4. Reaction of compound 2 with ethene
The ethene was bubbled into a freshly prepared solution
of 2 in n-heptane at room temperature. The decay of 2 was
complete after 60 min (IR spectroscopy). The clear, yellow
solution was then decanted and separated from an yellow
precipitate to give clean [W(CO)5(g2-C2H4)] [40,41]. The
compound, insoluble in n-heptane, was not fully identified.
(Anal. Found C, 13.55). IR (KBr disc): m = 2077 (w), 1934
(vs), 595 (w), 571 (w) cmꢁ1 13C NMR (125 MHz, CDCl3):
.
d = 194.99 (broad).
3.5. Reaction of compound 2 with NBE in n-heptane
During the reaction of 2 with NBE in n-heptane at room
temperature the decay of m(C„ O) bands of germylene
compound of tungsten, and simultaneous appearance of
m(C„O) bands at 2078 (w) and 1951 (vs) cmꢁ1, character-
istic for a norbornene complex [W(CO)5(g2-C7H10)] [29],
were observed by IR spectroscopy. The reaction solution
changed from orange to yellow, and the light yellow precip-
itate was settled out, leaving the g2-norbornene complex in
the n-heptane solution.
3.2. Synthesis of WAGe complexes 1 and 2
A solution of W(CO)6 (100 mg, 0.28 mmol) and GeCl4
(0.3 cm3, 1.1 mmol) in n-heptane (30 cm3) was irradiated
through quartz at room temperature by ca. 1.5 h. The vol-
atile materials were then stripped off the reaction mixture
under reduced pressure at room temperature and the unre-
acted W(CO)6 sublimated off at ca. 320 K. The residue was

3714
M. Go´rski et al. / Journal of Organometallic Chemistry 691 (2006) 3708–3714
´
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solution
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NBE (ca. 0.3 g, 3.5 mmol) in solution of C6H6 (5 cm3)
was added to ca. 0.03 g (0.035 mmol) of compound 1 or
2 and stirred at 343 K until completion (ca. 6 h). The con-
´
´
[10] T. Szymanska-Buzar, T. Głowiak, I. Czelusniak, J. Organomet.
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1
version was determined by H NMR spectroscopy, with
D2O as the external standard. The polymer was then pre-
cipitated in methanol, isolated, and dried under vacuum
(ca. 0.15 g, 50%). The GC–MS analysis of the residue
obtained after separation of polymer revealed the forma-
tion of 2-phenylnorbornane (Mr = 172.27) [42] and 2,20-
binorbornylidene (Mr = 188.32) [30,31] in a molar ratio
of ca. 6:1. The average molecular weights Mn of poly-
(NBE) obtained in reaction initiated by 1 and 2 were
58,490 and 25,090, respectively.
´
´
´
[12] T. Szymanska-Buzar, T. Głowiak, I. Czelusniak, M. Gorski, Inorg.
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8 (2005) 500.
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3.7. General procedure for reaction of NBE in the NMR tube
Under a nitrogen atmosphere, complex 1 or 2 (ca.
0.03 g, 0.035 mmol) was weighed into an NMR tube. The
tube was then capped with a septum. A portion of NBE
(ca. 0.03 g, 0.32 mmol) in (0.7 cm3) appropriate solution
(CDCl3, C6D6) was then added to the NMR tube via a syr-
inge. The tube was shaken very briefly and transferred to
the NMR probe. The conversion of NBE was observed
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1
by H NMR spectroscopy at room temperature and the
desired time.
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(2003) 4869.
4. Supplementary material
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[28] K.J. Ivin, J.C. Mol, Olefin Metathesis and Metathesis Polymerization,
Academic Press, London, 1997.
The X-ray crystallographic data for compounds 1 and 2
have been deposited at the Cambridge Crystallographic
Data Centre with deposition Nos. CCDC 250426 (1) and
250427 (2). 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 CB2 1EZ, UK; fax: +44 1223 336 033; or e-
mail: deposit@ccdc.cam.ac.uk).
´
´
[29] M. Gorski, A. Kochel, T. Szymanska-Buzar, Organometallics 23
(2004) 3037.
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[30] A. Malinowska, I. Czelusniak, M. Gorski, T. Szymanska-Buzar, J.
Mol. Catal. A: Chem. 226 (2005) 259.
[31] S.F. Nelsen, L.A. Reinhardt, J. Phys. Org. Chem. 14 (2001) 847.
[32] A.S. Veige, P.T. Wolczanski, E.B. Lobkovsky, Angew. Chem., Int.
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R.R. Schrock, A.H. Hoveyda, J. Am. Chem. Soc. 125 (2003)
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Acknowledgments
This work was generously supported by the Polish State
Committee for Scientific Research (Grant No. 3 T09A 103
28). The authors thank Dr. M. Kowalska and S. Baczynski
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[37] W.C.P. Tsang, J.Y. Jamieson, S.L. Aeilts, K.C. Hultzsch, R.R.
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for the measurement of NMR spectra and M. Hojniak for
GC–MS analysis.
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