4-Iodobenzylidyne as a precursor ligand for extended unsaturated alkylidyne ligands

Article abstract of DOI:10.1039/a801556b

The synthesis of the 4-iodobenzylidyne and 4-bromobenzylidyne tungsten complexes [W(CC₆H₄Z-4)X(CO)₂-(pic)₂] [Z = I; X = Cl, (3a), Z = I, X = Br (3b); Z = Br, X = Cl (4a)] was achieved by sequential reaction of [W(CO)₆] with Li[C₆H₄I-4] or Li[C₆H₄Br-4] in diethyl ether and C₂O₂Cl₂ or C₂O₂Br₂ and 4-picoline (pic, 4-methylpyridine) in CH₂Cl₂. The chloro ligand in 3a could be replaced by the iodo ligand to give 3c (X = I) by reaction with NaI in THF. Substitution of the picoline ligands by N,N,N′,N′-tetramethylethylenediamine (tmeda) and dppe afforded the complexes [W(CC₆H₄Z-4)X(CO)₂(L₂)] [Z = I, L₂ = tmeda, X = Cl (5a), X = Br (5b), X = I (5c); Z = Br, L₂ = tmeda, X = Cl (6a); Z = I, L₂ = dppe, X = Cl (7a), X = Br (7b), X = I (7c)]. The iodo group of the new alkylidyne complexes underwent Pd^II catalyzed cross-coupling reactions effectively. Thus coupling of complexes 5a with trimethylsilylacetylene, followed by hydrolysis, afforded the acetylide derivative [W{CC₆H₄(CCH-4)}-Cl(CO)₂(tmeda)], 8. The alkynyl derivatives [W {CC₆H₄(CCC₆H₄Y)-4}Cl(CO) ₂(tmeda)] (Y = H 9, CHO 10 or CN 11) were obtained by reactions of complex 5a with the respective aromatic acetylenes. The molecular structures of complexes 5a and 10 have been determined by X-ray crystallography.

Full text of DOI:10.1039/a801556b

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4-Iodobenzylidyne as a precursor ligand for extended unsaturated
alkylidyne ligands
Marie Pui Yin Yu, Kung-Kai Cheung* and Andreas Mayr*,†
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
The synthesis of the 4-iodobenzylidyne and 4-bromobenzylidyne tungsten complexes [W(CC6H4Z-4)X(CO)2-
(pic)2] [Z = I; X = Cl, (3a), Z = I, X = Br (3b); Z = Br, X = Cl (4a)] was achieved by sequential reaction of [W(CO)6]
with Li[C6H4I-4] or Li[C6H4Br-4] in diethyl ether and C2O2Cl2 or C2O2Br2 and 4-picoline (pic, 4-methylpyridine)
in CH2Cl2. The chloro ligand in 3a could be replaced by the iodo ligand to give 3c (X = I) by reaction with NaI in
THF. Substitution of the picoline ligands by N,N,NЈ,NЈ-tetramethylethylenediamine (tmeda) and dppe afforded
the complexes [W(CC6H4Z-4)X(CO)2(L2)] [Z = I, L2 = tmeda, X = Cl (5a), X = Br (5b), X = I (5c); Z = Br,
L2 = tmeda, X = Cl (6a); Z = I, L2 = dppe, X = Cl (7a), X = Br (7b), X = I (7c)]. The iodo group of the new
alkylidyne complexes underwent PdII catalyzed cross-coupling reactions effectively. Thus coupling of complexes
5a with trimethylsilylacetylene, followed by hydrolysis, afforded the acetylide derivative [W{CC6H4(CCH-4)}-
Cl(CO)2(tmeda)], 8. The alkynyl derivatives [W{CC6H4(CCC6H4Y)-4}Cl(CO)2(tmeda)] (Y = H 9, CHO 10 or CN
11) were obtained by reactions of complex 5a with the respective aromatic acetylenes. The molecular structures of
complexes 5a and 10 have been determined by X-ray crystallography.
Molecular systems featuring strong electronic coupling between
transition-metal centers and unsaturated organic systems are
attracting increasing interest as potential components for
molecular materials.1 In this context, metal alkylidyne com-
plexes2 are of particular interest3 since they contain one of the
strongest metal–ligand π interactions, the metal–carbon triple
bond. The development of metal alkylidyne complexes as func-
tional components in molecular materials requires procedures
for the synthesis of extended unsaturated alkylidyne ligands.4
Currently available methods for the synthesis of alkylidyne
metal complexes2 are efficient as far as the synthesis of the
metal–carbon triple bond5 and the modification of the ancil-
lary ligands are concerned,6 but provide only limited direct
access to functionalized unsaturated alkylidyne ligands, since
they involve highly reactive intermediates or reagents which
would interfere with the presence of a variety of functional
groups.7 It is therefore necessary to devise procedures which
allow the elaboration of unsaturated alkylidyne ligands after
formation of the metal–carbon triple bond. In pursuit of this
goal, we have recently developed a route to tungsten complexes
of the 4-aminobenzylidyne ligand, a versatile precursor for
extended unsaturated alkylidyne ligands.8 In a continuation of
this effort, we present here tungsten complexes of the 4-iodo-
benzylidyne and 4-bromobenzylidyne ligands and demonstrate
the convenient replacement of the iodo substituent by alkynyl
groups via palladium-catalyzed cross-coupling reactions.
Complexes 1 and 2 are then treated sequentially in methylene
chloride with oxalyl halide (either the chloride or bromide)
and 4-picoline (4-methylpyridine, pic) to give the 4-picoline-
stabilized trans-chloro- or trans-bromo-tungsten alkylidyne
complexes 3a, 3b and 4a, respectively5 [equation (2)]. The trans-
CO
CO
1. C2O2X2, CH2Cl2
1, 2
(2)
Z
X
pic
W
C
2. pic
pic
3a: Z = I, X = Cl
3b: Z = I, X = Br
4a: Z = Br, X = Cl
iodo-substituted analogue 3c can be obtained from 3a by
treatment with NaI in THF10 [equation (3)]. The 4-picoline
CO
CO
NaI, THF
(3)
3a
I
W
C
I
pic
pic
3c
ligands are easily replaced by the chelating ligands N,N,NЈ,NЈ-
tetramethylethylenediamine (tmeda) and 1,2-bis(diphenyl-
phosphino)ethane (dppe) to give the complexes 5, 6 and 7,
respectively [equation (4)]. Palladium-catalyzed cross-coupling
CO
CO
Results and Discussion
L
THF
L
3, 4
(4)
X
L
W
C
Z
The synthesis of the 4-iodobenzylidyne and 4-bromobenzyl-
idyne ligands follows established procedures.5 In the first step,
tungsten hexacarbonyl is allowed to react with (4-iodophenyl)-
lithium and (4-bromophenyl)lithium in diethyl ether to afford
the anionic acyl complexes 1 and 2, respectively, which are
isolated as the tetramethylammonium salt9 [equation (1)].
L
5a: Z = I, X = Cl, L2 = tmeda
5b: Z = I, X = Br, L2 = tmeda
5c: Z = I, X = I, L2 = tmeda
6a: Z = Br, X = Cl, L2 = tmeda
7a: Z = I, X = Cl, L2 = dppe
7b: Z = I, X = Br, L2 = dppe
7c: Z = I, X = I, L2 = dppe
1. LiC6H4Z-4, Et2O
W(CO)6
[NMe4][W{C(O)C6H4Z-4}(CO)5]
(1)
2. NMe4Br, H2O
reactions11 of the 4-iodobenzylidyne ligand were demonstrated
for complex 5a, but have not been successful for the bromo
derivative 6a. Thus the 4-ethynylbenzylidyne complex 8 can be
obtained by cross-coupling of 5a with trimethylsilylacetylene,
followed by hydrolysis [equation (5)]. Cross-coupling of 5a with
1: Z = I
2: Z = Br
† On leave from the Department of Chemistry, State University of
New York at Stony Brook, Stony Brook, NY 11794–3400.
J. Chem. Soc., Dalton Trans., 1998, Pages 2373–2378
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Table 1 Crystal data and collection parameters for complexes 5a and
10
Complex
5a
10
Molecular formula
M
WIClO2N2C15H20
606.54
WClO3N2C24H25ؒ¹CH2Cl2
651.24
¯
²
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
β/Њ
Triclinic
P1 (no. 2)
Monoclinic
C2/c (no. 15)
38.685(4)
8.229(2)
¯
12.89(1)
14.11(2)
12.358(4)
90.46(7)
109.19(4)
68.0(1)
1951(3)
4
17.228(2)
106.43(2)
γ/Њ
U/Å3
5260(1)
8
46.27
301
Z
µ/cmϪ1
76.54
301
T/K
Crystal color
Crystal dimensions/
mm
Total reflections
measured
Orange
Orange
0.15 × 0.10 × 0.25 0.35 × 0.15 × 0.10
7992
5057
Unique reflections
Reflections > 3σ(I)
used in analysis
R
7632
5541
4987
2768
Fig. 1 (a) Molecular structure of complex 5a. (b) Pairwise arrange-
ment of two molecules 1 in the crystal structure of 5a
0.035
0.041
0.028
0.034
RЈ
CO
W
CO
1. HCCSiMe3, THF
5a
Cl
C
C
CH
(5)
2. NEt3, PdII,CuI
L
L
3. KOH, THF
8: L2 = tmeda
phenylacetylene as well as 4-ethynylbenzonitrile and 4-ethynyl-
benzaldehyde affords the complexes 9–11 containing function-
alized extended unsaturated alkylidyne ligands [equation (6)].
5a
1. YC6H4(CCH-4), THF
2. NEt3, PdII, CuI
CO
CO
(6)
Y
Cl
W
C
C
C
L
L
9: Y = H, L2 = tmeda
10: Y = CHO, L2 = tmeda
11: Y = CN, L2 = tmeda
The new alkylidyne tungsten complexes 3–11 exhibit two IR
absorptions for the two carbonyl ligands. The carbonyl stretch-
ing frequencies of complexes 3 and 4 shift to slightly lower
energies upon substitution of the 4-picoline ligands by tmeda
and to higher energies by about 30 cmϪ1 upon substitution by
dppe. A weak absorption at 2214 cmϪ1 was observed for the
alkynyl group of complexes 10 and 11. The substitution of the
4-iodo substituent of the benzylidyne ligand by the alkynyl
groups has virtually no discernible influence on the stretching
frequencies of the carbonyl ligands. The introduction of the
alkynyl groups also exerts very little influence on the 13C NMR
resonance of the alkylidyne carbon atoms. The alkynyl groups
of complexes 8–11 give rise to two characteristic 13C NMR
resonances in the range δ 79–94.
Fig. 2 (a) Molecular structure of complex 10. (b) Pairwise arrange-
ment of two molecules in the crystal structure of 10
lar structures of 5a and 10 are shown in Fig. 1(a) and 2(a). The
molecules of 5a and 10 differ only in the respective substituents
at the 4 position of the benzylidyne ligands. The tungsten–
carbon triple bond distance in both structures is about 1.80 Å,
which is normal for tungsten alkylidyne complexes.2 Thus
neither the iodo nor the alkynyl substituent in the 4 position of
the benzylidyne ligand exerts any discernible influence on
the length of the metal–carbon triple bond. This result was
expected, since several electronically more consequential trans-
formations of the amino group in 4-aminobenzylidyne tungsten
The molecular structures of complexes 5a and 10 were
determined by X-ray crystallography. The crystallographic
information is summarized in Table 1. Selected bond distances
and bond angles are listed in Table 2. Drawings of the molecu-
2374
J. Chem. Soc., Dalton Trans., 1998, Pages 2373–2378

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Table 2 Selected bond lengths (Å) and angles (Њ) for complexes 5a and 10
5a
Molecule 1
Molecule 2
10
W(1)᎐Cl(1)
W(1)᎐N(2)
W(1)᎐C(2)
W(1)᎐N(1)
W(1)᎐C(1)
W(1)᎐C(3)
I(1)᎐C(7)
C(3)᎐C(4)
C(4)᎐C(5)
C(4)᎐C(9)
C(5)᎐C(6)
C(6)᎐C(7)
C(7)᎐C(8)
C(8)᎐C(9)
2.536(2)
2.312(7)
1.94(1)
2.317(7)
1.990(10)
1.807(8)
2.088(7)
1.46(1)
1.38(1)
1.40(1)
1.39(1)
1.36(1)
1.38(1)
1.39(1)
W(2)᎐Cl(2)
W(2)᎐N(4)
W(2)᎐C(17)
W(2)᎐N(3)
W(2)᎐C(16)
W(2)᎐C(18)
I(2)᎐C(22)
C(18)᎐C(19)
C(19)᎐C(20)
C(19)᎐C(24)
C(20)᎐C(21)
C(21)᎐C(22)
C(22)᎐C(23)
C(23)᎐C(24)
2.534(2)
2.300(7)
1.958(10)
2.320(7)
1.98(1)
1.818(8)
2.082(8)
1.45(1)
1.39(1)
1.39(1)
1.38(1)
1.38(1)
1.36(1)
1.38(1)
W(1)᎐Cl(1)
W(1)᎐N(2)
W(1)᎐C(2)
W(1)᎐N(1)
W(1)᎐C(1)
W(1)᎐C(3)
Cl(2)᎐C(25)
O(3)᎐C(18)
C(3)᎐C(4)
C(4)᎐C(5)
C(4)᎐C(9)
C(5)᎐C(6)
C(6)᎐C(7)
2.583(2)
2.294(6)
1.982(9)
2.320(6)
1.994(8)
1.800(7)
1.64(1)
1.175(10)
1.454(9)
1.380(9)
1.400(10)
1.395(10)
1.38(1)
C(7)᎐C(8)
1.38(1)
C(7)᎐C(10)
C(8)᎐C(9)
1.440(10)
1.364(10)
1.171(9)
1.451(9)
1.38(1)
1.37(1)
1.37(1)
1.36(1)
1.38(1)
1.49(1)
1.38(1)
C(10)᎐C(11)
C(11)᎐C(12)
C(12)᎐C(13)
C(12)᎐C(17)
C(13)᎐C(14)
C(14)᎐C(15)
C(15)᎐C(16)
C(15)᎐C(18)
C(16)᎐C(17)
Cl(1)᎐W(1)᎐N(1)
Cl(1)᎐W(1)᎐N(2)
Cl(1)᎐W(1)᎐C(1)
Cl(1)᎐W(1)᎐C(2)
88.9(2)
87.0(2)
88.3(3)
85.7(3)
Cl(2)᎐W(2)᎐N(3)
Cl(2)᎐W(2)᎐N(4)
Cl(2)᎐W(2)᎐C(16)
Cl(2)᎐W(2)᎐C(17)
Cl(2)᎐W(2)᎐C(18)
N(3)᎐W(2)᎐N(4)
N(3)᎐W(2)᎐C(16)
N(3)᎐W(2)᎐C(17)
N(3)᎐W(2)᎐C(18)
N(4)᎐W(2)᎐C(16)
N(4)᎐W(2)᎐C(17)
N(4)᎐W(2)᎐C(18)
C(16)᎐W(2)᎐C(17)
C(16)᎐W(2)᎐C(18)
C(17)᎐W(2)᎐C(18)
88.0(2)
89.0(2)
85.9(3)
86.4(3)
167.9(2)
78.1(3)
172.1(3)
96.9(4)
99.5(3)
96.7(3)
173.3(4)
101.8(3)
87.8(4)
87.3(4)
83.3(4)
Cl(1)᎐W(1)᎐N(1)
Cl(1)᎐W(1)᎐N(2)
Cl(1)᎐W(1)᎐C(1)
Cl(1)᎐W(1)᎐C(2)
Cl(1)᎐W(1)᎐C(3)
N(1)᎐W(1)᎐N(2)
N(1)᎐W(1)᎐C(1)
N(1)᎐W(1)᎐C(2)
N(1)᎐W(1)᎐C(3)
N(2)᎐W(1)᎐C(1)
N(2)᎐W(1)᎐C(2)
N(2)᎐W(1)᎐C(3)
C(1)᎐W(1)᎐C(2)
C(1)᎐W(1)᎐C(3)
C(2)᎐W(1)᎐C(3)
W(1)᎐C(3)᎐C(4)
C(7)᎐C(10)᎐C(11)
C(10)᎐C(11)᎐C(12)
O(3)᎐C(18)᎐C(15)
88.3(2)
88.2(2)
89.5(2)
87.1(2)
169.6(2)
78.5(3)
176.4(3)
97.3(3)
98.4(3)
98.7(3)
173.8(3)
100.9(3)
85.3(3)
84.3(3)
84.1(3)
171.0(6)
179.9(9)
177.1(9)
125.6(9)
Cl(1)᎐W(1)᎐C(3) 168.7(3)
N(1)᎐W(1)᎐N(2)
N(1)᎐W(1)᎐C(1)
N(1)᎐W(1)᎐C(2)
N(1)᎐W(1)᎐C(3)
N(2)᎐W(1)᎐C(1)
N(2)᎐W(1)᎐C(2)
N(2)᎐W(1)᎐C(3)
C(1)᎐W(1)᎐C(2)
C(1)᎐W(1)᎐C(3)
C(2)᎐W(1)᎐C(3)
W(1)᎐C(3)᎐C(4)
78.0(3)
174.9(3)
97.7(3)
99.1(3)
97.6(3)
171.6(3)
102.4(3)
86.4(4)
84.2(4)
85.3(4)
169.1(6)
W(2)᎐C(18)᎐C(19) 170.1(6)
complexes failed to significantly affect the bond distances
beyond the immediate vicinity of the amino group.8 The
structures of complexes 5a and 10 exhibit some noteworthy
deviations in the bond angles from the idealised geometry of
octahedral alkylidyne metal complexes. The Cl(1)᎐W(1)᎐C(3)
and the W(1)᎐C(3)᎐C(4) bond angles are smaller than 180Њ (by
9–12Њ) and the co-ordination angles between the carbonyl and
alkylidyne ligands are, in part, significantly smaller than 90Њ (by
up to 6Њ). These structural features are presumably the con-
sequence of crystal packing forces. As special intermolecular
interactions which may, at least in part, be responsible for these
features, we were able to identify a short iodine–oxygen con-
tact12 in 5a, [I(1) ؒ ؒ ؒ O(1Ј) of molecule 1 3.381(8) Å] [no corre-
sponding short contacts were found for I(2) of molecule 2]
and short π–π contacts13 in 10 [C(10) ؒ ؒ ؒ C(11Ј) 3.67(1),
C(10) ؒ ؒ ؒ C(12Ј) 3.53(1), C(11) ؒ ؒ ؒ C(11Ј) 3.47(1) Å]. These
short intermolecular contacts are illustrated in Figs. 1(b) and
2(b).
conveniently accessible. In conjunction with facile ligand sub-
stitution reactions on pyridine- and tmeda-substituted metal
alkylidyne complexes, the present work provides a versatile
basis for the design of functionalized unsaturated alkylidyne
metal complexes.
Experimental
General
Standard inert atmosphere techniques were used throughout.
Diethyl ether, hexane and tetrahydrofuran were purified by
reflux over sodium and distilled under nitrogen. Methylene
chloride was heated to reflux over calcium hydride and distilled
under nitrogen. Tungsten hexacarbonyl, oxalyl chloride, oxalyl
bromide, 4-picoline, tmeda, dppe, p-diiodobenzene, p-dibromo-
benzene, trimethylsilylacetylene and phenylacetylene were
obtained from commercial sources and used as received. 4-
Ethynylbenzaldehyde and 4-ethynylbenzonitrile were syn-
thesized according to the reported procedure.11d
The present work establishes the 4-iodobenzylidyne ligand as
a precursor ligand for extended unsaturated alkylidyne ligands.
The 4-iodobenzylidyne ligand performs well in palladium-
catalyzed cross-coupling reactions with unsaturated organic
substrates, making extended unsaturated alkylidyne ligands
Proton, 13C and 31P NMR spectra were recorded on 270 MHz
JEOL JNMGSX270 FT-NMR, 300 MHz BRUKER DPX300
FT-NMR and 500 MHz BRUKER DRX500 FT-NMR spec-
1
trometers. Chemical shifts of H and 13C spectra are given in
J. Chem. Soc., Dalton Trans., 1998, Pages 2373–2378
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parts per million (δ) relative to tetramethylsilane, 31P NMR
spectra are referenced to 85% H3PO4 and are proton decoupled.
Infrared spectra were recorded on a Shimadzu FTIR-8201PC
spectrometer, melting points on a Stuart Scientific SMP1
instrument under nitrogen. Elemental analysis were performed
by Butterworth Laboratories Ltd.
and NaI (1 g) were added. The resulting mixture was stirred at
50 ЊC for 2 h. The solvent was then removed in vacuo. The
residue was dissolved in CH2Cl2 and filtered. After filtration,
hexane was added to the filtrate to afford red-orange micro-
1
crystals. Yield: 0.272 g, 71%, m.p. 138–140 ЊC (decomp.). H
NMR (CDCl3): δ 8.97 (d, J = 6.6, 2 H, C5H4N), 7.58 (d,
J = 8.30, 2 H, C6H4I), 7.11 (d, J = 6.35, 2 H, C5H4N), 7.06
(d, J = 8.30 Hz, 2 H, C6H4I), 2.39 (s, 6 H, NCH3). 13C NMR
Preparations
᎐
(CDCl ): δ 259.6 (W᎐C), 218.9 (CO), 154.0, 150.2, 147.5, 137.1,
᎐
3
[NMe4][W{C(O)C6H4I-4}(CO)5] 1. A solution of Li[C6H4I-4]
was prepared first by the addition of LiBun in hexane (0.95
equivalent, 1.6 , 8.9 ml) to p-diiodobenzene (15 mmol, 4.95 g)
in diethyl ether (50 ml) and stirred for 1 h at room temperature
(r.t.). The resulting solution was transferred to a suspension of
W(CO)6 (12.8 mmol, 4.52 g) in ether (30 ml) at r.t., the solvent
was removed in vacuo after stirring the mixture for 1 h. The
solid residue was redissolved in degassed deionized water (100
ml). After filtration, NMe4Br (2.8 g) in deionized water (20 ml)
was added. The mixture was stirred at 0 ЊC for 5 min and the
precipitate filtered off and dried in vacuo. The precipitate was
dissolved in CH2Cl2 and dried with magnesium sulfate. After
filtration hexane was added to the solution to afford red
crystals. Yield: 58%, m.p. 160–165 ЊC (decomp.). 1H NMR
(CD3CN): δ 7.70 (d, J = 8.54, 2 H, C6H4I), 7.17 (d, J = 8.30 Hz,
130.3, 126.0, 93.3 (C6H4I, C5H4N), 21.2 (CH3). IR (CH2Cl2,
cmϪ1): 1990s (νCO), 1904s (νCO) [Found (Calc.): C, 33.22 (32.84);
H, 2.18 (2.36); N, 3.76 (3.65)%].
[W(CC6H4Br-4)Cl(CO)2(pic)2] 4a. The synthesis for complex
4a followed the procedure described for 3a, whereby complex 2
was used. Orange-red crystals. Yield: 71%, m.p. 150–153 ЊC
(decomp.). 1H NMR (CDCl3): δ 8.87 (d, J = 6.59, 4 H, C5H4N),
7.38 (d, J = 8.54, 2 H, C6H4Br), 7.17 (d, J = 8.30, 2 H, C6H4Br),
7.11 (d, J = 6.59 Hz, 4 H, C5H4N), 2.38 (s, 6 H, CH3). 13C NMR
᎐
(CDCl ): δ 259.7 (W᎐C), 220.7 (CO), 152.3, 150.4, 148.2, 131.1,
᎐
3
130.6, 123.0, 121.4 (C6H4Br, C5H4N), 21.2 (CH3). IR (CH2Cl2,
cmϪ1): 1989s (νCO), 1902s (νCO) [Found (Calc.) (with 0.25 mol
hexane): C, 40.94 (41.60); H, 3.25 (3.03); N, 4.26 (4.32)%].
2 H, C6H4I), 3.07 (s, 12 H, NCH3). 13C NMR (CD3CN): δ 278.5
[W(CC6H4I-4)Cl(CO)2(tmeda)] 5a. Complex 3a (1 mmol,
0.677 g) was dissolved in THF (40 ml), and tmeda (1 ml) was
added. The resulting mixture was stirred at 50 ЊC for 2 h, the
solvent was then removed in vacuo. The residue was washed
with hexane, dried, and redissolved in CH2Cl2. After filtration,
hexane was added to the filtrate to afford orange crystals.
Yield: 85%, m.p. 170–175 ЊC (decomp.). 1H NMR (CDCl3):
δ 7.58 (d, J = 8.55, 2 H, C6H4I), 6.95 (d, J = 8.54, 2 H, C6H4I),
3.20 (s, 6 H, NCH3), 2.95–2.85 (br, 4 H, NCH2), 2.94 (s, 6 H,
᎐
(C᎐O), 208.6, 204.1 (C᎐O), 157.5, 137.5, 128.1, 94.9 (C H I),
᎐
᎐
6
4
56.2 (NCH3). IR (CH2Cl2, cmϪ1): 2046w (νCO), 1952 (sh) (νCO),
1904s (br) (νCO) [Found (Calc.): C, 30.46 (30.55); H, 2.50 (2.56);
N, 2.14 (2.23)%].
[NMe4][W{C(O)C6H4Br-4}(CO)5] 2. The synthesis for
complex 2 followed the procedure described for 1, whereby
p-dibromobenzene and 1.1 equivalent LiBun were used. Red
crystals. Yield: 73%, m.p. 140–143 ЊC (decomp.). 1H NMR
(CD3CN): δ 7.48 (d, J = 8.54, 2 H, C6H4Br), 7.32 (d, J = 8.54
NCH3). 13C NMR (CDCl ): δ 259.5 (W᎐C), 220.7 (CO), 148.2,
᎐
᎐
3
137.1, 130.7, 93.1 (C6H4I), 61.0, 58.2, 52.2 [CH2N(CH3)2]. IR
(CH2Cl2, cmϪ1): 1989s (νCO), 1898s (νCO) [Found (Calc.): C,
29.93 (29.70); H, 3.30 (3.32); N, 4.58 (4.62)%].
Hz, 2 H, C6H4Br), 3.07 (s, 12 H, NCH3). 13C NMR (CD3CN):
᎐
δ 278.2 (C᎐O), 208.6, 204.1 (C᎐O), 156.9, 132.3, 131.4, 128.0,
᎐
᎐
122.7 (C6H4Br). IR (CH2Cl2, cmϪ1): 2048w (νCO), 1952 (sh)
(νCO), 1904s (νCO) [Found (Calc.): C, 33.02 (33.02); H, 2.50
(2.77); N, 2.48 (2.41)%].
[W(CC6H4I-4)Br(CO)2(tmeda)] 5b. The synthesis of complex
5b used the procedure given for 5a but starting from 3b. Yellow-
orange microcrystals. Yield: 57%, m.p. 180–183 ЊC (decomp.).
1H NMR (CDCl3): δ 7.58 (d, J = 8.35, 2 H, C6H4I), 6.97 (d,
J = 8.35 Hz, 2 H, C6H4I), 3.24 (d, 6 H, NCH3), 3.04 (s, 6 H,
[W(CC6H4I-4)Cl(CO)2(pic)2] 3a. Complex 1 (2 mmol, 1.258
g) was dissolved in CH2Cl2 (60 ml) and the solution was cooled
to Ϫ78 ЊC. Oxalyl chloride (2.02 mmol, 0.18 ml) in CH2Cl2
(10 ml) was added. The resulting solution was allowed to warm
up to Ϫ20 ЊC and 4-picoline (2 ml) was added. The mixture
was stirred at r.t. for 2 h, the solvent was then removed in vacuo.
The residue was washed with hexane, dried, and redissolved
in CH2Cl2. After filtration, hexane was added to the solution
to afford orange-red crystals. Yield: 58%, m.p. 153–155 ЊC
(decomp.). 1H NMR (CDCl3): δ 8.86 (d, J = 6.59, 4 H, C5H4N),
7.59 (d, J = 8.54, 2 H, C6H4I), 7.11 (d, J = 6.47, 4 H, C5H4N),
NCH3), 2.96–2.92 (m, 4 H, NCH2). 13C NMR (CDCl3): δ 259.4
᎐
(W᎐C), 220.0 (CO), 147.6, 137.1, 130.5, 93.3 (C H I), 61.2,
᎐
6
4
58.5, 53.6 [CH2N(CH3)2]. IR (CH2Cl2, cmϪ1): 1990s (νCO), 1900s
(νCO) [Found (Calc.): C, 27.98 (27.68); H, 3.03 (3.10); N, 4.27
(4.30)%].
[W(CC6H4I-4)I(CO)2(tmeda)] 5c. The synthesis of complex
5c used the procedure given for 5a but starting from 3c. Orange-
yellow microcrystals. Yield: 70%, m.p. 190–193 ЊC (decomp.).
1H NMR (CDCl3): δ 7.57 (d, J = 8.55, 2 H, C6H4I), 7.00 (d,
J = 8.55 Hz, 2 H, C6H4I), 3.29 (s, 6 H, NCH3), 3.22 (s, 6 H,
NCH3), 2.98–2.97 (br, 4 H, NCH2). 13C NMR (CDCl3): δ 259.5
7.03 (d, J = 8.55 Hz, 2 H, C6H4I), 2.38 (s, 6 H, CH3). 13C NMR
᎐
(CDCl ): δ 259.7 (W᎐C), 220.7 (CO), 152.3, 150.4, 148.7, 137.0,
᎐
3
130.7, 126.0 (C6H4I, C5H4N), 21.2 (CH3). IR (CH2Cl2, cmϪ1):
1989s (νCO), 1902s (νCO) [Found (Calc.): C, 37.34 (37.28); H,
2.85 (2.68); N, 4.17 (4.14)%].
᎐
(W᎐C), 218.8 (CO), 146.8, 137.3, 130.3, 93.5 (C H I), 61.5,
᎐
6
4
58.8, 56.4 [CH2N(CH3)2]. IR (CH2Cl2, cmϪ1): 1989s (νCO), 1902s
(νCO) [Found (Calc.): C, 25.90 (25.81); H, 2.64 (2.89); N, 3.99
(4.01)%].
[W(CC6H4I-4)Br(CO)2(pic)2] 3b. The synthesis for complex
3b followed the procedure described for 3a, whereby C2O2Br2
was used instead of C2O2Cl2. Red-orange crystals. Yield: 43%,
m.p. 144–147 ЊC (decomp.). 1H NMR (CDCl3): δ 8.90 (d,
J = 6.59, 4 H, C5H4N), 7.59 (d, J = 8.30, 2 H, C6H4I), 7.11
(d, J = 6.59, 4 H, C5H4N), 7.04 (d, J = 8.30 Hz, 2 H, C6H4I), 2.39
[W(CC6H4Br-4)Cl(CO)2(tmeda)] 6a. Red-orange crystals.
Yield: 82%, m.p. 198–201 ЊC (decomp.). 1H NMR (CDCl3):
δ 7.36 (d, J = 8.30, 2 H, C6H4Br), 7.08 (d, J = 8.30 Hz, 2 H,
C6H4Br), 3.20 (s, 6 H, NCH3), 2.96–2.87 (br, 4 H, NCH2), 2.94
13
(s, 6 H, NCH3). 13C NMR (CDCl ): δ 259.4 (W᎐C), 220.7 (CO),
᎐
᎐
(s, 6 H, CH3). C NMR (CDCl ): δ 259.7 (W᎐C), 220.0 (CO),
᎐
3
᎐
3
152.9, 150.3, 137.1, 130.5, 126.0, 93.1 (C6H4I, C5H4N), 21.2
(CH3). IR (CH2Cl2, cmϪ1): 1990s (νCO), 1904s (νCO) [Found
(Calc.): C, 35.01 (34.89); H, 2.50 (2.52); N, 3.64 (3.89)%].
147.7, 131.2, 130.6, 121.5 (C6H4Br), 61.0, 58.2, 52.2
[CH2N(CH3)2]. IR (CH2Cl2, cmϪ1): 1989s (νCO), 1898s (νCO
)
[Found (Calc.): C, 32.53 (32.20); H, 3.23 (3.60); N, 5.18
(5.01)%].
[W(CC6H4I-4)I(CO)2(pic)2] 3c. Complex 3a (0.5 mmol,
0.3383 g) was dissolved in THF (30 ml), a few drops of 4-picoline
[W(CC6H4I-4)Cl(CO)2(dppe)] 7a. Complex 3a (1 mmol,
2376
J. Chem. Soc., Dalton Trans., 1998, Pages 2373–2378

View Article Online
0.667 g) was dissolved in THF (40 ml) and dppe (1.05 mmol,
0.418 g) was added. The resulting mixture was stirred at 50 ЊC
for 2 h, the solvent was then removed in vacuo. The residue was
washed with hexane, dried, and redissolved in CH2Cl2. After
filtration, hexane was added to the filtrate to afford yellow crys-
C6H5), 7.38 (d, J = 8.19, 2 H, C6H4C), 7.36–7.25 (m, 3 H, C6H5),
7.20 (d, J = 8.15 Hz, 2 H, C6H4C), 3.22 (s, 6 H, NCH3), 2.95 (s,
6 H, NCH3), 2.94–2.89 (br, 4 H, NCH2). 13C NMR (CDCl3):
1
1
᎐
δ 260.7 (W᎐C, JWC = 199), 220.9 (CO, JWC = 174 Hz), 148.5,
᎐
131.5, 131.2, 129.2, 128.4, 123.1, 122.0 (C6H4C, C6H5), 91.6,
1
89.5 (C᎐C), 61.0, 58.2, 52.2 [CH N(CH ) ]. IR (CH Cl , cmϪ1):
᎐
tals. Yield: 0.59 g, 66%, m.p. 165–168 ЊC (decomp.). H NMR
᎐
2
3
2
2
2
(CDCl3): δ 7.74–7.19 (m, 22 H, PPh2, C6H4I), 6.17 (d, J = 8.37
1989s (νCO), 1898s (νCO) [Found (Calc.): C, 47.34 (47.57); H,
4.08 (4.34); N, 4.96 (4.82)%].
Hz, 2 H, C6H4I), 2.99–2.82 (m, 2 H, CH2PPh2), 2.73–2.56 (m,
2 H, CH2PPh2). 13C NMR (CDCl ): δ 264.1 (W᎐C), 212.2 (CO,
᎐
᎐
3
1JtransPC = 46 Hz), 148.3, 136.4, 135.89, 135.3, 133.0, 132.9,
[W{CC6H4(CCC6H4CHO-4}Cl(CO)2(tmeda)] 10. The syn-
thesis of complex 10 followed the procedure described for 9,
whereby 4-ethynylbenzaldehyde was used. Orange crystals.
Yield: 76%, m.p. 175–180 ЊC (decomp.). 1H NMR (CDCl3):
δ 10.02 (s, 1 H, CHO), 7.86 (d, J = 8.52, 2 H, C6H4CHO), 7.66
(d, J = 8.24, 2 H, C6H4CHO), 7.41 (d, J = 8.52, 2 H, C6H4C),
7.22 (d, J = 8.51 Hz, 2 H, C6H4C), 3.23 (s, 6 H, NCH3), 2.96 (s, 6
132.8, 132.6, 132.5, 132.1, 130.8, 130.3, 130.1, 128.6, 128.5,
128.4, 93.2 (PPh2, C6H4I), 27.5, 27.4, 27.2, 27.0 (CH2PPh2). 31
P
NMR (CDCl3): δ 38.5 (1JWP = 231 Hz). IR (CH2Cl2, cmϪ1):
2008s (νCO), 1940s (νCO) [Found (Calc.): C, 47.33 (47.30); H,
3.10 (3.18); N, <0.3 (0)%].
H, NCH3), 2.95–2.92 (br, 4 H, NCH2). 13C NMR (CDCl3):
[W(CC6H4I-4)Br(CO)2(dppe)] 7b. As for 7a but from 3b,
yellow microcrystals. Yield: 69%, m.p. 175–178 ЊC (decomp.).
1H NMR (CDCl3): δ 7.73–7.20 (22 H, PPh2, C6H4I), 6.32 (d,
᎐
δ 260.1 (W᎐C), 220.8 (CO), 191.4 (CHO), 149.1, 135.4, 132.0,
᎐
᎐
131.4, 129.6, 121.0 (C H C, C H CHO), 93.6, 90.6 (C᎐C), 61.1,
᎐
6
4
6
4
58.2, 52.2 [CH2N(CH3)2]. IR (CH2Cl2, cmϪ1): 2214w (νC᎐C),
J = 8.34 Hz, 2 H, C6H4I), 3.12–2.92 (m, 2 H, CH2PPh2), 2.73–
᎐
13
᎐
1989s (νCO), 1898s (νCO) [Found (Calc.) (with 0.25 mol CH2Cl2):
C, 45.76 (46.23); H, 3.66 (4.08); N, 4.29 (4.45)%].
2.54 (m, 2 H, CH2PPh2). C NMR (CDCl ): δ 263.6 (W᎐C),
᎐
3
211.0 (CO, 1JcisPC = 8, 1JtransPC = 44 Hz), 148.0, 136.5, 136.0,
135.3, 132.9, 132.8, 132.7, 132.6, 132.3, 130.7, 130.0, 128.6,
128.5, 128.4, 93.4 (PPh2, C6H4I), 27.5, 27.4, 27.1, 27.0
(CH2PPh2). 31P NMR (CDCl3): δ 35.9 (1JWP = 231 Hz). IR
(CH2Cl2, cmϪ1): 2010s (νCO), 1942s (νCO) [Found (Calc.): C,
45.49 (45.05); H, 2.89 (3.02); N, <0.3 (0)%].
[W{CC6H4(CCC6H4CN-4)}Cl(CO)2(tmeda)] 11. The syn-
thesis of complex 11 followed the procedure described for 9,
whereby 4-ethynylbenzonitrile was used. Red-orange crystals.
Yield: 56%, m.p. 160–163 ЊC (decomp.). 1H NMR (CDCl3):
δ 7.64 (d, J = 8.52, 2 H, C6H4CN), 7.59 (d, J = 8.51, 2 H,
C6H4CN), 7.40 (d, J = 8.52, 2 H, C6H4C), 7.21 (d, J = 8.52 Hz, 2
H, C6H4C), 3.23 (s, 6 H, NCH3), 2.96 (s, 6 H, NCH3), 2.95–2.91
[W(CC6H4I-4)I(CO)2(dppe)] 7c. As for 7a but from 3c, yellow
microcrystals. Yield: 89%, m.p. 185–188 ЊC (decomp.). 1H
NMR (CDCl3): δ 7.72–7.17 (m, 22 H, PPh2, C6H4I), 6.46 (d,
J = 8.30 Hz, 2 H, C6H4I), 3.16–2.99 (m, 2 H, CH2PPh2), 2.74–
13
᎐
(br, 4 H, NCH2). C NMR (CDCl ): δ 259.8 (W᎐C), 220.7
᎐
3
(CO), 149.3, 132.1, 131.4, 129.3, 128.1, 120.7, 118.5, 111.5
᎐
13
(C H C, C H CN), 93.9, 89.8 (C᎐C), 61.1, 58.2, 52.3 [CH N-
᎐
᎐
6
4
6
4
2
2.56 (m, 2 H, CH2PPh2). C NMR (CDCl ): δ 262.3 (W᎐C),
᎐
3
(CH3)2]. IR (CH2Cl2, cmϪ1): 2214w (νC᎐C), 1989s (νCO), 1898s
(νCO) [Found (Calc.) (with 0.25 mol CH᎐2Cl2): 46.03 (46.45); H,
3.62 (3.94); N, 6.43 (6.70)%].
208.9 (CO, 1JcisPC = 8, 1JtransPC = 41 Hz), 147.5, 136.7, 135.9,
135.3, 134.1, 133.4, 132.8, 132.7, 132.6, 132.5, 132.4, 130.5,
130.2, 128.5, 128.4, 128.3, 93.6 (PPh2, C6H4I), 27.8, 27.6, 27.4,
27.2 (CH2PPh2). 31P NMR (CDCl3): δ 30.0 (1JWP = 230 Hz). IR
(CH2Cl2, cmϪ1): 2006s (νCO), 1940s (νCO) [Found (Calc.): C,
43.16 (42.89); H, 2.51 (2.88); N, <0.3 (0)%].
Crystallography
Details of the structure analyses for complexes 5a and 10 are
given in Table 1. The thermal ellipsoids in the ORTEP14 draw-
ings of Figs. 1 and 2 are drawn at the 40% probability level.
CCDC reference number 186/1020.
See http://www.rsc.org/suppdata/dt/1998/2373/ for crystallo-
graphic files in .cif format.
[W{CC6H4(CCH-4)}Cl(CO)2(tmeda)] 8. Complex 5a (1
mmol, 0.607 g) was dissolved in THF (40 ml) and NEt3 (1 ml)
was added. To this solution HCCSiMe3 (40% excess, 0.2 ml),
cis-[PdCl2(PPh3)2] (10 mg) and CuI (20 mg) were added. The
resulting mixture was stirred at 50 ЊC for 3 h, the solvent was
then removed in vacuo. The residue was redissolved in THF (40
ml), KOH powder (0.4 g) was added and the solution stirred at
r.t. for 4 h. The solution was then filtered, and the solvent was
removed in vacuo. The residue was washed with hexane, dried,
and redissolved in CH2Cl2. After filtration, hexane was added
to the filtrate to afford red-orange crystals. Yield: 0.278 g, 55%,
m.p. 125–129 ЊC (decomp.). 1H NMR (CDCl3): δ 7.35 (d,
J = 8.30, 2 H, C6H4CCH), 7.16 (d, J = 8.55 Hz, 2 H, C6H4-
CCH), 3.21 (s, 6 H, NCH3), 3.19 (s, 1 H, CCH), 3.00–2.83 (br, 4
Acknowledgements
Support for this work by the Hong Kong Research Grants
Council and the Committee on Research and Conference
Grants of the University of Hong Kong is gratefully acknow-
ledged. M. P. Y. Y. acknowledges the receipt of a Postgraduate
Studentship, administered by The University of Hong Kong.
References
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᎐
(W᎐C), 220.8 (CO), 149.1, 131.8, 129.2, 120.8 (C H ), 83.7
᎐
6
4
1
1
(CCH, JCH = 49), 79.2 (CCH, JCH = 252 Hz), 61.6, 58.3, 52.3
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)
[Found (Calc.): C, 40.85 (40.46); H, 4.00 (4.19); N, 5.46
(5.55)%].
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mmol, 0.303 g) was dissolved in THF (30 ml) and NEt3 (1 ml)
was added. To this solution HCCC6H5 (20% excess, 78 mg), cis-
PdCl2(PPh3)2 (10 mg) and CuI (20 mg) were added. The result-
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removed in vacuo. The residue was washed with hexane, dried,
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to the filtrate to afford red-orange crystals. Yield: 76%, m.p.
165–168 ЊC (decomp.). 1H NMR (CDCl3): δ 7.53–7.51 (m, 2 H,
J. Chem. Soc., Dalton Trans., 1998, Pages 2373–2378
2377

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Received 24th February 1998; Paper 8/01556B
2378
J. Chem. Soc., Dalton Trans., 1998, Pages 2373–2378