Conjugated pyridines with an end-capping ferrocene

Article abstract of DOI:10.1021/om960607h

This study reports the synthesis of new pyridyl ligands incorporating an alkyne entity with an end-capping ferrocenyl moiety: 1-(ferrocenylethynyl)-4-((4-pyridyl)ethynyl)benzene (FEPEB), 1-ferrocenyl-6-(4-pyridyl)hexatriyne (FPHT), and 1-ferrocenyl-4-(4-pyridyl)-butadiyne (FPBD). The complexes W(CO)₄(L)(FEPEB) (L = CO, PPh₃, P(OMe)₃, PMe₃), W(CO)₄(L)(FPHT) (L = CO, PPh₃, P(OMe)₃, PMe₃), and W(CO)₅(FPBD) are obtained by ligating FEPEB, FPHT, and FPBD to W(CO)₄(L)(THF). The energy of tungsten metal to pyridyl π* charge transfer (MLCT) depends on both the pyridyl ligand and the ancillary ligand, L. Treating FPHT and FPBD with MeI causes N-methylpyridinium derivatives to form, which exhibit a strong low-lying charge-transfer band. As a comparative study, the complexes 1-(ferrocenylethynyl)-4-((4-nitrophenyl)ethynyl)-benzene (FENEB) and 1-(ferrocenylethynyl)-4-((4-aminophenyl)ethynyl)benzene (FEAEB) have also been synthesized. X-ray analysis has been employed to examine the structures of 1-(ferrocenylethynyl)-4-ethynylbenzene, W(CO)₄(PPh₃)(FEPEB), W(CO)₅(FPHT), and 1,8-diferrocenyloctatetrayne.

Full text of DOI:10.1021/om960607h

5028
Organometallics 1996, 15, 5028-5034
Con ju ga ted P yr id in es w ith a n En d -Ca p p in g F er r ocen e
J iann T. Lin,* J iann J ung Wu, Chyi-Shiun Li, Yuh S. Wen, and Kuan-J iuh Lin
Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China
Received J uly 22, 1996X
This study reports the synthesis of new pyridyl ligands incorporating an alkyne entity
with an end-capping ferrocenyl moiety: 1-(ferrocenylethynyl)-4-((4-pyridyl)ethynyl)benzene
(FEPEB), 1-ferrocenyl-6-(4-pyridyl)hexatriyne (FPHT), and 1-ferrocenyl-4-(4-pyridyl)-
butadiyne (FPBD). The complexes W(CO)4(L)(FEPEB) (L ) CO, PPh3, P(OMe)3, PMe3),
W(CO)4(L)(FPHT) (L ) CO, PPh3, P(OMe)3, PMe3), and W(CO)5(FPBD) are obtained by
ligating FEPEB, FPHT, and FPBD to W(CO)4(L)(THF). The energy of tungsten metal to
pyridyl π* charge transfer (MLCT) depends on both the pyridyl ligand and the ancillary
ligand, L. Treating FPHT and FPBD with MeI causes N-methylpyridinium derivatives to
form, which exhibit a strong low-lying charge-transfer band. As a comparative study, the
complexes 1-(ferrocenylethynyl)-4-((4-nitrophenyl)ethynyl)-benzene (FENEB) and 1-(ferro-
cenylethynyl)-4-((4-aminophenyl)ethynyl)benzene (FEAEB) have also been synthesized.
X-ray analysis has been employed to examine the structures of 1-(ferrocenylethynyl)-4-
ethynylbenzene, W(CO)4(PPh3)(FEPEB), W(CO)5(FPHT), and 1,8-diferrocenyloctatetrayne.
In tr od u ction
Our previous papers reported dinuclear tungsten
carbonyl and rhenium carbonyl complexes with a pyr-
idyl bridge incorporating an alkyne entity.2 Our con-
tinuing inquiries now turn to how the metal moieties
as well as the bridges in these systems may be varied.
In view of the high stability and redox-active properties
of ferrocene,10 this study extends the interest to the
analogous pyridyl ligand bridged complexes in which an
electron-releasing ferrocenyl group11 is one of the ter-
minal subunits. This following work investigates the
syntheses and certain physical properties of these new
complexes.
The study of dinuclear complexes linked by conju-
gated pyridyl ligands is an intriguing area of research,
not least for the possibilities they offer of electronic
communication between terminal subunits.1 Our inter-
est in di- and polynuclear metal complexes bridged by
pyridyl ligands incorporating an alkyne entity2 has
focused on several potential aspects of application: (a)
the complexes may exhibit nonlinear optical phenom-
ena3 because the metal fragment can function either as
an electron donor,4 due to strong metal to ligand charge
transfer (MLCT),5 or as an electron acceptor, on the
basis of the σ-donation from the nitrogen atom to the
metal center;6 (b) a molecule can retain two or more
metal centers,7 providing a cooperative effect in cataly-
sis; (c) metal organic polymers can be derived from these
organometallic complexes;8 (d) bridged dinuclear com-
plexes may serve as models for investigating metal-
metal interaction.9
Exp er im en ta l Section
The general procedures and physical measurements re-
semble those described in an earlier report.2 4-Ethynylpyri-
dine,12 1,4-diethynylbenzene,13 1-iodoferrocene,14 ferrocen-
* To whom correspondence should be addressed. E-mail:
jtlin@chem.sinica.edu.tw.
X Abstract published in Advance ACS Abstracts, October 15, 1996.
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S0276-7333(96)00607-3 CCC: $12.00 © 1996 American Chemical Society

Conjugated Pyridines with an End-Capping Ferrocene
Organometallics, Vol. 15, No. 23, 1996 5029
ylacetylene,15 and ferrocenylbutadiyne16 have been prepared
as described previously.
W(CO)4(L)(F P HT) (8, L ) CO; 9, L ) P P h 3; 10, L )
P (OMe)3; 11, L ) P Me3). Again, the same procedures were
followed for synthesizing 8-11, and therefore, only the prepa-
ration of 9 is described. A THF solution of W(CO)4(PPh3)(THF)
prepared in situ from W(CO)6 (0.50 g, 1.42 mmol) and PPh3
(0.38 g, 1.42 mmol) was reduced in volume and transferred to
a flask containing FPHT (0.48 g, 1.42 mmol). The solution
was stirred for 18 h, and solvent was removed under vacuum.
The residue was chromatographed under nitrogen. Elution
by CH2Cl2/hexane (1:3) provided a red band from which the
powdery 9 was isolated in 32% yield (400 mg). MS (FAB): m/e
893 (M+, 184W). Anal. Calcd for C43H28NO4PFeW: C, 57.81;
H, 3.16; N, 1.57. Found: C, 57.62; H, 3.01; N, 1.30.
The light red complex 8 was eluted by CH2Cl2/hexane (1:4)
and isolated in 54% yield. Anal. Calcd for C26H13NO5FeW:
C, 47.38; H, 1.99; N, 2.13. Found: C, 47.32; H, 1.93; N, 2.07.
The deep red complex 10 was eluted by CH2Cl2/hexane (1:
4) and isolated in 29% yield. Anal. Calcd for C28H22NO7-
PFeW: C, 44.53; H, 2.94; N, 1.85. Found: C, 44.35; H, 2.86;
N, 1.80.
The purple complex 11 was eluted by CH2Cl2/hexane (1:4)
and isolated in 31% yield. Anal. Calcd for C28H22NO4PFeW:
C, 47.56; H, 3.14; N, 1.98. Found: C, 47.50; H, 3.01; N, 1.83.
1-F er r ocen yl-4-(4-p yr id yl)bu ta d iyn e (12; F P BD). Com-
pound 12 was synthesized in the same manner employed for
7, except that ferrocenylacetylene was used instead of ferro-
cenylbutadiyne. The first band was identified as 1,4-bis-
(ferrocenyl)butadiyne (15%). The red powdery 12 was isolated
in 15% yield from the second band. MS (FAB): m/e 311 (M+).
Anal. Calcd for C19H13NFe: C, 73.34; H, 4.21; N, 4.50.
Found: C, 73.42; H, 4.38; N, 4.79.
1-(F er r ocen yleth yn yl)-4-eth yn ylben zen e (1). A 14.9 mL
amount of n-BuLi (1.6 M in hexane, 23.8 mmol) was added
over a 20 min period to a THF solution of 1,4-diethynylbenzene
(3.0 g, 23.8 mmol) prechilled to -70 °C. After 1 h, a THF
solution of ZnCl2 (3.24 g, 23.8 mmol) was added; the mixture
was warmed to room temperature and stirred for a further 1
h. The solution was then added to a mixture of iodoferrocene
(7.40 g, 23.8 mmol) and Pd(PPh3)4 (820 mg, 0.71 mmol); after
24 h, this mixture was pumped dry and the residue extracted
with Et2O/H2O. Then, the ether layer was pumped dry and
the residue chromatographed. Elution by CH2Cl2/hexane (1:
3) caused two bands to appear. The first was unreacted
iodoferrocene, and from the second, pale red-orange powdery
1 was obtained in 37% yield (2.70 g). MS (FAB): m/e 310 (M+).
Anal. Calcd for C20H14Fe: C, 77.45; H, 4.55. Found: C, 77.21;
H, 4.28.
1-(F er r ocen yleth yn yl)-4-((4-p yr id yl)eth yn yl)ben zen e
(2; F EP EB). Et2NH (100 mL) was added to a flask containing
a mixture of 4-bromopyridine hydrochloride (1.88 g, 9.8 mmol),
1 (2.50 g, 8.1 mmol), Pd(PPh3)2Cl2 (270 mg, 0.24 mmol), and
CuI (45 mg, 0.24 mmol). The resulting mixture was heated
to 60-65 °C for 24 h. The solvent was removed in vacuo and
the residue extracted with Et2O/H2O. The ether layer was
transferred to a flask containing MgSO4 to remove H2O and
filtered. The filtrate was pumped dry and the residue chro-
matographed. Elution by THF/hexane (1:5) provided the
yellow-orange powdery 2 in 46% yield (1.44 g). MS (FAB): m/e
387 (M+). Anal. Calcd for C25H17NFe: C, 77.52; H, 4.43; N,
3.62. Found: C, 77.42; H, 4.18; N, 3.45.
W(CO)5(F P BD) (13). Complex 13 was synthesized by the
same procedures employed for 8-11 except that FPBD served
instead of FPHT. A reddish brown complex 13 was eluted by
CH2Cl2/hexane (1:5) and isolated in 26% yield. Anal. Calcd
for C24H13NO5FeW: C, 45.39; H, 2.06; N, 2.21. Found: C,
45.32; H, 2.10; N, 2.16.
W(CO)4(L)(F EP EB) (3, L ) CO; 4, L ) P P h 3; 5, L )
P (OMe)3; 6, L ) P Me3). Essentially the same procedures
were applied to synthesize 3-6; consequently, only the prepa-
ration of 4 is described in detail. A THF solution of W(CO)4-
(PPh3)(THF) prepared in situ from W(CO)6 (600 mg, 1.70
mmol) and PPh3 (446 mg, 1.70 mmol) was reduced in volume
and transferred to a flask containing FEPEB. The solution
was stirred for 18 h, and the solvent was removed under a
vacuum. The residue was chromatographed under nitrogen.
Elution by CH2Cl2/hexane (1:3) caused a red band to appear,
from which a deep red powdery 4 was isolated in 28% yield
(450 mg). MS (FAB): m/e 946 ((M + 1)+, 184W). Anal. Calcd
for C47H32NO4PFeW: C, 59.71; H, 3.41; N, 1.48. Found: C,
59.84; H, 3.55; N, 1.32.
1-Fer r ocen yl-6-(1-m eth yl-4-pyr idin iu m yl)h exatr iyn e Io-
d id e (14; F P HTI). To a CH2Cl2 solution (50 mL) of 7 (100
mg, 0.299 mmol) was added a 10-fold excess of MeI. The
solution was then stirred at room temperature for 16 h. After
the solvent was removed, the residue was washed with hexane
and dried in vacuo to provide a brown powdery 14 in 56% yield
(81 mg). MS (FAB): m/e 350 ((M - I)+). Anal. Calcd for
C
22H16NIFe: C, 55.38; H, 3.38; N, 2.94. Found: C, 55.30; H,
3.22; N, 2.80.
The yellow complex 3 was eluted by CH2Cl2/hexane (1:6) in
a yield of 53%. Anal. Calcd for C30H17NO5FeW: C, 50.67; H,
2.41; N, 1.97. Found: C, 50.65; H, 2.38; N, 1.81.
1-Eth yn yl-4-((4-n itr op h en yl)eth yn yl)ben zen e (15). A
7.7 mL portion of n-BuLi (1.5 M in THF, 11.6 mmol) was added
over a 10 min period to a THF solution of 1,4-diethynylbenzene
(1.33 g, 10.6 mmol), prechilled to -70 °C. After 1 h, a THF
solution of ZnCl2 (1.44 g, 10.6 mmol) was added and the
mixturewarmed to room temperature. The solution was
stirred for a further 1 h and then added to a mixture of 4-iodo-
1-nitrobenzene (2.63 g, 10.6 mmol) and Pd(PPh3)4 (365 mg, 0.32
mmol). After 24 h, the solution was pumped dry and the
residue extracted with Et2O/H2O. After the solvent was
removed from the ether layer, the pale yellow powdery 15 was
isolated in 50% yield (1.30 g). MS (FAB): m/e 247 (M+). Anal.
Calcd for C16H9NO2: C, 77.72; H, 3.67; N, 5.66. Found: C,
77.49; H, 3.37; N, 5.60.
1-(F er r ocen yleth yn yl)-4-((4-n itr op h en yl)eth yn yl)ben -
zen e (16; F ENEB). Et2NH (100 mL) was added to a flask
containing a mixture of iodoferrocene (1.27 g, 2.02 mmol), 15
(0.50 g, 2.02 mmol), Pd(PPh3)2Cl2 (42.5 mg, 0.060 mmol), and
CuI (19.2 mg, 0.10 mmol). The solution was then heated to
55-60 °C for 24 h. The solvent was removed in vacuo and
the residue extracted with Et2O/H2O. To remove H2O, the
ether layer was transferred to a flask containing MgSO4 and
filtered. The filtrate was pumped dry, and the residue was
chromatographed. Elution by CH2Cl2/hexane (1:3) yielded two
bands. The first was the unreacted iodoferrocene, and from
the second band, after the solvent was removed, red powdery
The red-orange complex 5 was eluted by CH2Cl2/hexane (1:
2), giving a yield of 27%. Anal. Calcd for C32H26NO7PFeW:
C, 47.61; H, 3.25; N, 1.74. Found: C, 47.67; H, 3.31; N, 1.57.
The red complex 6 was eluted by CH2Cl2/hexane (1:2.5),
providing a yield of 25%. Anal. Calcd for C32H26NO4PFeW:
C, 50.62; H, 3.45; N, 1.84. Found: C, 50.52; H, 3.48; N, 1.73.
1-F er r ocen yl-6-(4-p yr id yl)h exa tr iyn e (7, F P HT). To a
mixture of ferrocenylbutadiyne (1.00 g, 4.27 mmol), ethynyl-
pyridine (0.53 g, 5.12 mmol), Cu(OAc)2‚H2O (46 mg, 0.13
mmol), and CuI (24 mg, 0.13 mmol) was added 80 mL of
pyridine, 50 mL of Et2O, and 30 mL of MeOH. The resulting
mixture was stirred in air for 18 h. The solvent was removed
under vacuum, and the residue was chromatographed under
nitrogen. Elution by THF/hexane (1:6) afforded two bands.
The first band was identified as 1,8-bis(ferrocenyl)octatetrayne
(20%). The pale red-orange powdery 7 was isolated in 35%
yield (500 mg) from the second band. MS (FAB): m/e 401 (M+).
Anal. Calcd for C21H13NFe: C, 75.25; H, 3.91; N, 4.18.
Found: C, 75.20; H, 3.90; N, 4.00.
(15) Rosenblum, M.; Brawn, N.; Papenmeier, J .; Applebaum, M. J .
Organomet. Chem. 1966, 6, 173.
(16) Yuan, Z.; Stringer, G.; J obe, I. R.; Kreller, D.; Scott, K.; Koch,
L.; Taylor, N. J .; Marder, T. B. J . Organomet. Chem. 1993, 452, 115.

5030 Organometallics, Vol. 15, No. 23, 1996
Ta ble 1. Cr ysta l Da ta for Com p ou n d s 1, 4, 8, a n d 19
Lin et al.
1
4
8
19
C14H9Fe
233.07
chem formula
fw
C20H14Fe
C47H31FeNO4PFeW
944.43
C26H13NO5FeW
659.09
310.17
cryst size, mm
space group
a, Å
b, Å
c, Å
0.25 × 0.09 × 0.06
0.34 × 0.13 × 0.25
0.25 × 0.25 × 0.06
0.25 × 0.25 × 0.25
P21/n
P1h
P21/m
C2/m
5.993(2)
19.912(3)
12.393(2)
12.208(2)
12.674(1)
13.934(1)
108.707(7)
100.63(1)
94.7339(9)
1983.7(4)
2
8.321(2)
10.106(2)
14.411(3)
11.980(2)
8.942(2)
10.018(4)
R, deg
â, deg
98.06(2)
95.06(2)
106.47(2)
γ, deg
V, Å3
1464.2(6)
4
1207.2(4)
4
1029.0(5)
4
Z
T, °C
+25
+25
+25
+25
λ(Mo KR), Å
0.7107
1.407
10.2
0.7107
0.7107
3.627
110.0
1.00-0.48
0.031
0.033
0.7107
1.504
28.4
F
calc, g cm-3
1.581
34.1
1.00-0.64
0.031
µ, cm-1
transmissn coeff
1.00-0.95
0.041
0.044
0.92-0.78
0.029
0.033
Ra
Rw
b
0.035
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2; w ) 1/[σ2(Fo) + kFo2]. For 1, k ) 0.0002; for 4, 8, and 19, k ) 0.0001.
ethynyl)-4-ethynylbenzene (1).19 A Sonogashira cou-
pling20 of 1 and 4-bromopyridine catalyzed by 3 mol %
of PdCl2(PPh3)2 and CuI in diethylamine yielded 1-(fer-
rocenylethynyl)-4-((4-pyridyl)ethynyl)benzene (FEPEB;
2). Coordinating the dangling pyridine of 2 with
W(CO)4(L)(THF), prepared in situ by photolyzing W(CO)5-
(L), led to the formation of heteronuclear dimers I,
W(CO)4(L)(FEPEB) (3, L ) CO; 4, L ) PPh3; 5, L )
P(OMe)3; 6, L ) PMe3) (eq 1). A combination of Cu(I)
16 was obtained in 69% yield (0.60 g). MS (FAB): m/e 431
((M+). Anal. Calcd for C26H27NO2Fe: C, 72.39; H, 3.98; N,
3.25. Found: C, 72.15; H, 3.90; N, 3.12.
1-Eth yn yl-4-((4-am in oph en yl)eth yn yl)ben zen e (17). The
same general procedures were followed for synthesizing 15,
except that 4-iodoaniline served instead of 4-iodo nitrobenzene.
A pale yellow powdery 17 was isolated in 45% yield (1.50 g).
MS (FAB): m/e 218 (M+). Anal. Calcd for C16H11N: C, 88.13;
H, 5.44; N, 6.43. Found: C, 87.95; H, 5.21; N, 6.25.
1-(Fer r ocen yleth yn yl)-4-((4-am in oph en yl)eth yn yl)ben -
zen e (18; F EAEB). Pale yellow 18 was synthesized by the
same procedures as employed for 16, except that 17 was
utilized instead of 15. Complex 18 was eluted by THF/hexane
(1:5), providing a yield of 55%. Anal. Calcd for C26H29NFe:
C, 77.82; H, 4.77; N, 3.49. Found: C, 77.68; H, 4.70; N, 3.39.
Cr ysta llogr a p h ic Stu d ies. Crystals of 1, 4, 8, and 1,8-
bis(ferrocenyl)octatetrayne (19) were grown by slowly diffusing
hexane into a concentrated solution of relevant complexes in
CH2Cl2. Crystals were mounted in thin-walled glass capillar-
ies. Diffraction was measured by an Enraf-Nonius CAD4
diffractometer with an θ-2θ scan mode. Unit cells were
determined by centering 25 reflections in the appropriate 2θ
range. Other relevant experimental details are listed in Table
1. All data reduction and refinements were performed on a
MicroVax 3800 computer employing NRCVAX17 programs.
Intensities were collected and corrected for decay, absorption
(empirical, ψ-scan), and Lp effects. The structures were solved
by a combination of direct methods18 and difference Fourier
methods and further refined by full-matrix least-squares
techniques. All non-hydrogen atoms were refined anisotropi-
cally, and all hydrogen atoms were included in the structure
factor calculation in idealized positions with dC-H ) 0.95 Å.
Because of disorder, atoms C13-C16 and C21-C25 in complex
8 have only 50% occupancy.
and Cu(II) from various sources, with or without the
presence of O2, was observed to effect the oxidative
coupling of terminal alkynes.21 It was found that
combining Cu(OAc)2 and CuI in oxygen caused the
coupling of ferrocenylbutadiyne (or ferrocenylacetylene)
and ethynylpyridine to form 1-ferrocenyl-6-(4-pyridyl)-
hexatriyne (7; FPHT) or 1-ferrocenyl-4-(4-pyridyl)-
butadiyne (12; FPBD), although the homocoupling
products 1,8-bis(ferrocenyl)octatetrayne16 (or 1,4-difer-
rocenylbutadiyne16) and 1,4-bis(4-pyridylbutadiyne
(DPB)12, were also obtained. Complexes of series II,
W(CO)4(L)(FPHT) (8, L ) CO; 9, L ) PPh3; 10, L )
Resu lts a n d Discu ssion
In this study, three series of complexes, I, II, and III,
containing an end-capping ferrocenyl moiety, were
synthesized. A palladium(0)-catalyzed coupling of or-
ganozinc with iodoferrocene provided 1-(ferrocenyl-
(19) Compound 1 was reported in the literature recently: Hsung,
R. P.; Chidsey, S. E. D.; Sita, L. R. Organometallics 1995, 14, 4808.
(20) Campbell, I. B. In Organocopper Reagents; Taylor, R. J . K., Ed.;
Oxford University Press: Oxford, U.K., 1994; Chapter 10.
(21) (a) Kozhushkov, S.; Haumann, T.; Boese, R.; Knieriem, B.;
Scheib, S.; Bauerle, P.; de Meijere, A. Angew. Chem., Int. Ed. Engl.
1995, 34, 781. (b) Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis,
2nd ed.; Wiley: New York, 1992; pp 194-195. (c) Tabushi, I.; Yuan,
L. C.; Shimokawa, K.; Mizutani, T.; Kuroda, Y. Tetrahedron Lett. 1981,
22, 2273. (d) Hay, A. S. J . Org. Chem. 1962, 27, 3320.
(17) Gabe, E. J .; LePage, Y.; Charland, J . P.; Lee, F. L.; White, P.
S. J . Appl. Crystallogr. 1989, 22, 384.
(18) Main, P.; Fiske, S. J .; Hull, S. E.; Lessinger, L.; Germain, G.;
Declercq, J . P.; Woolfson, M. M. Multan80: A System of Computer
Programs for the Automatic Solution of Crystal Structures from X-ray
Diffraction Data; Universities of York, U.K., and Louvain, Belgium,
1980.

Conjugated Pyridines with an End-Capping Ferrocene
Organometallics, Vol. 15, No. 23, 1996 5031
Ta ble 2. IR Sp ectr a in th e ν(CO) Region a n d 1H a n d 31P {1H} NMR Sp ectr a
ν(CO), ν(CtC),a
compd
cm-1
δ, ppmb,c (J , Hz)
δ, ppmb,d (J , Hz)
1
8.91(d, 2 H, J H-H ) 6.8, NCH), 8.68 (d, 2 H, J H-H ) 6.0, NCH), 7.72 (d, 2 H, J H-H ) 6.8,
NCHCH), 7.54 (d, 2 H, J H-H ) 6.0, NCHCH)
2
3
4
5
6
8.57 (d, 2 H, J H-H ) 5.9, NCH), 7.53 (d, 2 H, J H-H ) 8.5, Ph), 7.47 (d, 2 H, J H-H ) 8.5, Ph),
7.38 (d, 2 H, J H-H ) 5.9, NCHCH), 4.50 (t, 2 H, J H-H ) 1.8, C5H4),
4.28 (t, 2 H, J H-H ) 1.8, C5H4), 4.23 (s, 5 H, C5H5)
2072 m, 1972 vw, 9.10 (d, 2 H, J H-H ) 6.9, NCH), 7.62 (d, 2 H, J H-H ) 8.3, Ph), 7.56 (d, 2 H, J H-H ) 8.3, Ph),
1929 s, 1890 sh
7.50 (d, 2 H, J H-H ) 6.9, NCHCH), 4.54 (t, 2 H, J H-H ) 1.8, C5H4),
4.33 (t, 2 H, J H-H ) 1.8, C5H4), 4.26 (s, 5 H, C5H5)
8.54 (d, 2 H, J H-H ) 6.7, NCH), 7.60 (d, 2 H, J H-H ) 8.6, Ph), 7.54 (d, 2 H, J H-H ) 8.6, Ph),
7.45-7.38 (m, 15 H, PPh3), 7.14 (d, 2 H, J H-H ) 6.7, NCHCH), 4.54 (t, 2 H, J H-H ) 1.8,
C5H4), 4.33 (t, 2 H, J H-H ) 1.8, C5H4), 4.26 (s, 5 H, C5H5)
8.97 (d, 2 H, J H-H ) 6.5, NCH), 7.63 (d, 2 H, J H-H ) 8.6, Ph), 7.55 (d, 2 H, J H-H ) 8.6, Ph),
7.51 (d, 2 H, J H-H ) 6.5, NCHCH), 4.54 (t, 2 H, J H-H ) 1.8, C5H4), 4.33 (t, 2 H,
J H-H ) 1.8, C5H4), 4.26 (s, 5 H, C5H5), 3.59 (d, 9 H, OMe)
2026 vs, 1925 s,
1891 m
36.7 (s, J P-W ) 241)
152 (s, J P-W ) 341)
-21.5 (s, J P-W ) 226)
2019 m, 1893 vs,
1853 s, 2217 w
2007 m, 1874 vs,
1845 s, 2214 w
9.00 (d, 2 H, J H-H ) 6.6, NCH), 7.62 (d, 2 H, J H-H ) 8.5, Ph), 7.55 (d, 2 H, J H-H ) 8.5, Ph),
7.52 (d, 2 H, J H-H ) 6.5, NCHCH), 4.54 (t, 2 H, J H-H ) 1.8, C5H4),4.33 (t, 2 H,
J H-H ) 1.8, C5H4), 4.26 (s, 5 H, C5H5), 3.59 (d, 9 H, OMe)
7
8
8.64 (d, 2 H, J H-H ) 5.7, NCH), 7.50 (d, 2 H, J H-H ) 5.7, NCHCH), 4.66 (t, 2 H, J H-H ) 1.8,
C5H4), 4.43 (t, 2 H, J H-H ) 1.8, C5H4), 4.30 (s, 5 H, C5H5)
2071 m, 1965 vw, 9.07 (d, 2 H, J H-H ) 6.4, NCH), 7.61 (d, 2 H, J H-H ) 6.4, NCHCH), 4.66 (t, 2 H, J H-H ) 1.8,
1927 s, 1890 sh,
2167 w
2011 m, 1885 vs,
1849 s, 2166 w
C5H4), 4.45 (t, 2 H, J H-H ) 1.8, C5H4), 4.31 (s, 5 H, C5H5)
9e
8.56 (d, 2 H, J H-H ) 6.8, NCH), 7.46-7.38 (m, 15 H, PPh3), 7.14 (d, 2 H, J H-H ) 6.8, NCHCH), 37.0 (s, J P-W ) 241)
4.67 (t, 2 H, J H-H ) 1.8, C5H4), 4.45 (t, 2 H, J H-H ) 1.8, C5H4), 4.31 (s, 5 H, C5H5)
10e 2019 m, 1903 vs,
1850 s, 2168 w
11e 2007 m, 1874 vs,
1846 s, 2165 w
12
8.99 (d, 2 H, J H-H ) 6.7, NCH), 7.52 (d, 2 H, J H-H ) 6.7, NCHCH), 4.67 (t, 2 H, J H-H ) 1.8,
C5H4), 4.44 (t, 2 H, J H-H ) 1.8, C5H4), 4.31 (s, 5 H, C5H5), 3.61 (d, 9 H, J P-H ) 11.0, OMe)
9.03 (d, 2 H, J H-H ) 6.6, NCH), 7.51 (d, 2 H, J H-H ) 6.6, NCHCH), 4.67 (t, 2 H, J H-H ) 1.8,
C5H4), 4.44 (t, 2 H, J H-H ) 1.8, C5H4), 4.29 (s, 5 H, C5H5), 1.50 (d, 9 H, J P-H ) 7.5, Me)
8.61 (d, 2 H, J H-H ) 5.1, NCH), 7.46 (d, 2 H, J H-H ) 5.1, NCHCH), 4.62 (t, 2 H, J H-H ) 1.8,
C5H4), 4.40 (t, 2 H, J H-H ) 1.8, C5H4), 4.29 (s, 5 H, C5H5)
9.04 (d, 2 H, J H-H ) 5.1, NCH), 7.56 (d, 2 H, J H-H ) 5.1, NCHCH), 4.65 (t, 2 H, J H-H ) 1.8,
C5H4), 4.43 (t, 2 H, J H-H ) 1.8, C5H4), 4.30 (s, 5 H, C5H5)
9.24 (d, 2 H, J H-H ) 6.4, NCH), 8.33 (d, 2 H, J H-H ) 6.6, NCHCH), 4.70 t, 2 H, J H-H ) 1.8,
C5H4), 4.64 (s, 3 H, NCH3), 4.49 (t, 2 H, J H-H ) 1.8, C5H4), 4.33 (s, 5 H, C5H5)
8.29 (d, 2 H, J H-H ) 8.4, CHCNO2), 7.84 (d, 2 H, J H-H ) 8.4, CHCHCNO2), 7.66 (d, 2 H,
J H-H ) 8.7, C6H4), 7.58 (d, 2 H, J H-H ) 8.7, C6H4), 3.82 (s, 1 H, tCH)
8.31 (d, 2 H, J H-H ) 8.8, CHCNO2), 7.96 (d, 2 H, J H-H ) 8.8, CHCHCNO2), 7.60 (d, 2 H,
J H-H ) 8.3, C6H4), 7.54 (d, 2 H, J H-H ) 8.3, C6H4), 4.56 (t, 2 H, J H-H ) 1.8, C5H4),
4.33 (t, 2 H, J H-H ) 1.8, C5H4), 4.29 (s, 5 H, C5H5)
7.47 (s, 4 H, Ph), 7.24 (d , 2 H, J H-H ) 6.6, CHCHNH2), 6.66 (d, 2 H, J H-H ) 6.6, CHNH2),
5.05 (br s, 2 H, NH2)
7.45 (d, 2 H, J H-H ) 8.7, C6H4), 7.42 (d, 2 H, J H-H ) 8.7, C6H4), 7.20 (d, 2 H, J H-H ) 8.4,
CHCHCNH2), 6.55 (d, 2 H, J H-H ) 8.4, CHCNO2), 5.61 (s, 2 H, NH2),
4.57 (t, 2 H, J H-H ) 1.8, C5H4), 4.34 (t, 2 H, J H-H ) 1.8, C5H4), 4.26 (s, 5 H, C5H5)
153 (s, J P-W ) 384)
-21.8 (s, J P-W ) 233)
13
14
15
16e
2070 m, 1932 s,
1897 m
17
18e
a
b
Measured in CH2Cl2 solution. Measured in acetone-d6 except for 2, 3, and 5, which were measured in CDCl3. c Reported in ppm
relative to δ(Me4Si) at 0 ppm. Reported in ppm relative to δ(85% H3PO4) at 0 ppm. e The signals due to the AA′MM′ spin system in
symmetrical Cp ligands are, due to their simple appearance, reported as triplets with coupling constants equal to half of the separation
d
between the two outer lines. Abbreviations: s ) singlet, d ) doublet, t ) triplet, m ) multiplet.
P(OMe)3; 11, L ) PMe3) and W(CO)5(FPBD) (13), were
synthesized from the reactions of W(CO)4(L) with 7 and
12, respectively (eq 2). 1-Ethynyl-4-((4-nitrophenyl)-
ethynyl)benzene (18; FEAEB), were obtained from a
subsequent Sonogashira coupling reaction between io-
doferrocene and 15 (or 17) (eq 3).
The spectroscopic properties (Table 2) of these new
complexes correlate with their formulations. Three
moderate/strong carbonyl stretching bands for 4-6 and
9-11 in the infrared spectra require that the phospho-
rus donor ligand and pyridine be mutual by cis at the
tungsten center. Except for 4 and 9, the R-ring protons
of pyridines for the complexes have the chemical shifts
appearing at lower field than those of free ligands in
ethynyl)benzene (15) and 1-ethynyl-4-((4-aminophenyl)-
ethynyl)benzene (17) were synthesized from a palla-
dium(0)-catalyzed coupling of organozinc derived from
1,4-diethylbenzene with 4-iodo-1-nitrobenzene and 4-io-
doaniline, respectively. The complexes of series III,
1-(ferrocenylethynyl)-4-((4-nitrophenyl)ethynyl)ben-
zene (16; FENEB) and 1-ferrocenyl-4-((4-aminophenyl)-
1
the H NMR spectra. The lower δ values for the R-ring
protons of pyridine in 4 and 9 probably arise from the
ring current shielding caused by the phenyl ligand of

5032 Organometallics, Vol. 15, No. 23, 1996
Lin et al.
Ta ble 3. UV Sp ectr a a n d Assign m en ts in CH2Cl2
Ta ble 4. Red ox P oten tia ls for Com p lexes in
CH2Cl2/CH3CN (1:1) a t 298 Ka
λ
max, nm
Eox (∆Ep)/Fe(2+/3+);
Ered (∆Ep)/
(PY(0/1-)
compd
π-π*
MLCT
complex
W(1+/2+)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
18
310
316
330
330
330
330
318, 340, 365
330, 358
325, 348, 370
325, 348
1, EFEB
2, FEPEB
+0.19 (77)
+0.18 (80)
-2.00 (i)
-2.02 (i)
-2.04 (i)
-2.05 (i)
-2.06 (i)
-2.14 (i)
395
437
404
454
3, W(CO)5(FEPEB)
4, W(CO)4(PPh3)(FEPEB)
5, W(CO)4(P(OMe)3)(FEPEB) +0.20 (76); +0.46 (i)
6, W(CO)4(PMe3)(FEPEB)
7, FPHT
8, W(CO)5(FPHT)
+0.14 (80); +0.70 (i)
+0.15 (86); +0.36 (i)
+0.23 (overlapping)
+0.22 (90)
+0.22 (110); +0.70 (i) -1.78 (130);
425
487
460
505
-2.22 (140)
9, W(CO)4(PPh3)(FPHT)
+0.26 (overlapping)
-1.79 (110);
-2.26 (110)
-1.82 (105);
<-2.50
10, W(CO)4(P(OMe)3)(FPHT) +0.24 (80); +0.39 (i)
315, 335, 370
305, 325, 335
315, 350, 375
348
402
558
11, W(CO)4(PMe3)(FPHT)
+0.20 (91, overlapping) -1.78 (i);
<-2.50
-2.10 (i)
-1.60 (i)
-2.07 (i)
12, FPBD
13, W(CO)5(FPBD)
14, FPHTI
+0.20 (94)
+0.22 (92)
+0.25 (80)
335
16, FENEB
+0.14 (78), +0.28 (60) -1.44 (120),
the triphenylphosphine. A singlet accompanied by a
pair of tungsten satellites with J P-W ) 226-384 Hz is
-2.30 (130)
<-2.50
1
18, FEAEB
+0.18 (i), +0.68 (i)
observed in the 31P NMR spectra for all complexes
containing a coordinated phosphine or phosphite.
Table 3 illustrates the electronic spectra of the new
complexes in CH2Cl2 at room temperature. The π f
π* transition bands were assigned according to the
various ferrocenyl complexes22 and the tungsten to
pyridine charge-transfer (MLCT) transition bands as-
signed according to the relevant tungsten carbonyl
pyridyl complexes.23 In accordance with what previous
literature has reported, these MLCT bands fall in the
range of 390-490 nm24 and exhibit a hypsochromic shift
as the solvent polarity increases.25 The ancillary ligands
strongly influence the MLCT energies of the complexes,
and the MLCT energies in turn are ordered in ac-
cordance with the π-accepting ability of the ligands; L
) CO > P(OMe)3 > PPh3 > PMe3. The much weaker
d-d transition substantially overlap the MLCT bands
and are not assigned. The intense π f π* transition
associated with conjugated alkynyl ligands for 1 (λ )
310 nm) and 2 (λ ) 316 nm) is not observed in
ferrocenylacetylene in the same region, possibly because
elongating the conjugation length lowers the energy of
the π* orbital. The extra pyridine moiety in 2 increases
the λmax value by 6 nm compared to the value for 1.
Coordinating the dangling pyridine of 2 with W(CO)4(L),
an inductive acceptor,6a further increases the λmax value
by 14 nm. The spectra of compounds 7 and 12 are more
complicated than that of ferrocenyl-4-pyridylacetylene
a
Analyses performed in 10-3 M deoxygenated CH2Cl2/CH3CN
(1:1) solutions containing 0.1 M TBAP; the scan rate is 100 mV.
All potentials in volts vs ferrocene (0.00 V with peak separation
of 81 mV in CH2Cl2/CH3CN (1:1)); scan range +1.5 to -2.5 V; i )
irreversible process; ∆Ep ) Epa - Epc (mV).
(FPA) due to the conjugated system located on the
polyyne fragment.26 Notably, a strong low-lying band,
attributable to charge-transfer transition, is observed
for derivatives of 7 (λ ) 558 nm) and 12 (λ ) 554 nm) if
the pendant pyridine is converted to N-methylpyri-
dinium, which is a good electron acceptor.27 Replacing
the amino group in 18 (λ ) 335 nm) by a strong π
acceptor causes only a slight increase in λ (348 nm, 16).
The λmax values of several ferrocene-termi-
nated phenylethynyl oligomers, Cp2Fes[CtCsC6H4]nsX,
were also observed to be rather insensitive to variations
of X.19
The oxidation potentials (Table 4) of tungsten atoms
in the complexes W(CO)4(L)(FEPEB) and W(CO)4(L)-
(FPHT) share certain common features with complexes
W(CO)4(L)(PY) (PY ) conjugated pyridines), as has been
previously reported:2b (1) the oxidation process is ir-
reversible; (2) the oxidation potentials in the same series
of complexes are ordered L ) CO > P(OR)3 > PPh3
>
PMe3; (3) within the same series of complexes, a complex
with L ) CO exhibits a significantly higher oxidation
potential than any with an L ) phosphorus donor
ligand. Except for complex 18, the iron atoms in all the
complexes were found to possess a reversible oxidation
potential, which appeared at more positive values
(0.15-0.25 eV) than ferrocene. This phenomenon re-
sembles that observed for the complexes Cp2Fes
[CtCsC6H4]nsX19 and may be attributable to the
presence of a somewhat electron withdrawing alkyne
unit in the cyclopentadienyl ligand.
(22) (a) Alain, V.; Fort, A.; Barzoukas, M.; Chen, C. T. Inorg. Chim.
Acta 1996, 242, 43. (b) Calabrese, J . C.; Cheng, L. T.; Green, J . C.;
Marder, S. R.; Tam, W. J . Am. Chem. Soc. 1991, 113, 7227. (c) Toma,
S.; Gaplovsky, A.; Elecko, P. Chem. Pap. 1985, 39, 115. (d) Sohn, Y.
S.; Hendrickson, D. N.; Gray, H. B. J . Am. Chem. Soc. 1971, 93, 3603.
(e) Rosenblum, M.; Brawn, N.; Papenmeier, J .; Applebaum, M. J .
Organomet. Chem. 1966, 6, 173.
(23) (a) Zulu, M. M.; Lees, A. J . Inorg. Chem. 1988, 27, 1139. (b)
Lees, A. J .; Fobare, J . M.; Mattimore, E. F. Inorg. Chem. 1984, 23,
2709. (c) Gaus, P. J .; Boncella, J . M.; Rosengren, K. S.; Funk, M. O.
Inorg. Chem. 1982, 21, 2174. (d) Pannel, K. H.; Gonzalez, M. G. d. l.
P. S.; Leano, H.; Iglesias, R. Inorg. Chem. 1978, 17, 1093. (e) Wrighton,
M. S.; Abrahamson, H. B.; Morse, D. L. J . Am. Chem. Soc. 1976, 98,
4105.
The reduction potentials for PY π* levels of the
complexes are consistent with the energy stabilization
obtained by the π* acceptor orbital upon ligation of PY.
(24) (a) Zulu, M. M.; Lees, A. J . Inorg. Chem. 1988, 27, 1139. (b)
Lees, A. J .; Fobare, J . M.; Mattimore, E. F. Inorg. Chem. 1984, 23,
2709. (c) Gaus, P. L.; Boncella, J . M.; Rosengren, K. S.; Funk, M. O.
Inorg. Chem. 1982, 21, 2174. (d) Pannel, K. H.; Gonzalez, M. G. d. l.
P. S.; Leano, H.; Iglesias, R. Inorg. Chem. 1978, 17, 1093. (e) Wrighton,
M. S.; Abrahamson, H. B.; Morse, D. L. J . Am. Chem. Soc. 1976, 98,
4105.
(26) (a) Hoshi, T.; Okubo, J .; Kobayashi, M.; Tanizaki, Y. J . Am.
Chem. Soc. 1986, 108, 3867. (b) Steigman, A. E.; Miskowski, V. M.;
Perry, J . W. J . Am. Chem. Soc. 1987, 109, 5884. (c) Kobayashi, M.;
Hoshi, T.; Okubo, J .; Hiratsuka, H.; Harazono, T.; Nakagawa, M.;
Tanizaki, Y. Bull. Chem. Soc. J pn. 1984, 108, 3867.
(27) (a) Marder, S. R.; Perry, J . W.; Yakymyshyn, C. P. Chem. Mater.
1994, 6, 1137. (b) Marder, S. R.; Perry, J . W.; Tiemann, B. G.; Schaefer,
W. P. Organometallics 1991, 10, 1896.
(25) Kaim, W.; Kuhlmann, S.; Olbrich-Deussner, B.; Bessen-bacher,
C.; Schulz, A. J . Organomet. Chem. 1987, 321, 215.

Conjugated Pyridines with an End-Capping Ferrocene
Organometallics, Vol. 15, No. 23, 1996 5033
Ta ble 5. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lexes 1, 4, 8, a n d 19
1
4
8
19
Distances
W-P
2.560(2)
W-N
2.268(5)
1.960(8)
2.032(8)
1.954(8)
2.008(8)
2.277(8)
2.02(1)
2.03(1)
1.98(1)
W-C1
W-C2
W-C3
W-C4
Fe-C1
Fe-C2
Fe-C3
Fe-C4
Fe-C5
Fe-C6
Fe-C7
Fe-C8
Fe-C9
Fe-C10
Fe-C20
Fe-C21
Fe-C22
Fe-C23
Fe-C24
Fe-C25
Fe-C26
Fe-C27
Fe-C28
Fe-C29
C1-O1
C2-O2
C3-O3
C4-O4
N-C5
2.040(5)
2.027(6)
2.011(7)
2.020(7)
2.017(5)
2.039(5)
2.032(5)
2.036(5)
2.036(5)
2.043(5)
2.032(5)
2.024(4)
2.032(4)
2.00297)
2.001(5)
1.990(5)
F igu r e 1. ORTEP diagram of complex 1. Thermal el-
lipsoids are drawn with 30% probability boundaries.
2.030(7)
2.048(8)
2.028(8)
2.031(9)
2.033(8)
2.035(8)
2.044(9)
2.033(8)
2.037(8)
2.046(8)
1.15(1)
2.01(1)
2.02(1)
2.02(1)
2.02(1)
2.00(1)
F igu r e 2. ORTEP diagram of complex 4. Thermal el-
lipsoids are drawn with 30% probability boundaries.
1.14(1)
1.13(1)
1.15(2)
1.14(1)
1.16(2)
1.14(1)
1.332(9)
N-C6
1.33(1)
1.32(1)
N-C9
1.36(1)
1.19(1)
N-C10
C7-C8
C9-C10
C10-C11
C11-C12
C13-C14
C15-C16
C19-C20
1.19(1)
1.188(9)
F igu r e 3. ORTEP diagram of complex 8. Thermal el-
lipsoids are drawn with 30% probability boundaries.
1.189(8)
1.170(8)
1.18(2)
1.21(2)
1.20(2)
Angles
C1-W-C2
C1-W-C3
C1-W-C4
C1-W-C1a
C2-W-C2a
C1-W-P
85.1(3)
86.1(3)
88.1(3)
87.9(4)
89.8(4)
91.7(4)
92.6(4)
175.4(2)
91.5(2)
87.8(3)
171.0(3)
99.4(2)
92.3(2)
C1-W-N
89.0(3)
90.8(4)
C2-W-C3
C2-W-C4
C2-W-P
C2-W-N
90.4(3)
C2-W-N1
C3-W-C4
C3-W-P
F igu r e 4. ORTEP diagram of complex 19. Thermal
ellipsoids are drawn with 30% probability boundaries.
85.8(3)
94.4(2)
177.6(3)
87.4(2)
93.8(2)
177.1(7)
175.2(6)
176.1(7)
174.9(7)
87.9(1)
C3-W-N
178.3(4)
Molecu la r Str u ctu r es of 1-(F er r ocen yleth yn yl)-
4-eth yn ylben zen e (1), W(CO)4(P P h 3)(F EP EB) (4),
W(CO)5(F P HT) (8), a n d 1,8-Bis(fer r ocen yl)octa tet-
r a yn e (19). The ORTEP drawings of 1, 4, 8, and 19
are displayed in Figures 1-4, respectively. Table 5 lists
selected bond distances and angles for the complexes.
The coordination core surrounding the tungsten atom
in 4 and 8 almost configures an octahedron, and in 4,
the pyridyl ligand is cis to the phosphine ligand. In
order for dxz and dyz orbitals to participate effectively
in the metal to pyridyl π* charge transfer (N-W-C3 is
assumed to be the z axis), the dihedral angle between
the pyridyl ring (plane A) and the best constituted plane
of W, N, C2, C3, and C4 (or W, N, C2a, C3, and C1)
(plane B) should be 0, 45, or 90°. Complex 4 signifi-
cantly deviates from these ideal angles (the largest
deviations of atoms from the least-squares planes A and
C4-W-P
C4-W-N
W-C1-O1
W-C2-O2
W-C3-O3
W-C4-O4
P-W-N
C1-C7-C8
C7-C8-C9
C8-C9-C10
C9-C10-C10b
C7-C10-C11
C8-C11-C12
C10-C11-C12
C11-C12-C13
C13-C14-C15
C14-C15-C16
C15-C16-C21
C15-C18-C19
C18-C19-C20
C16-C19-C20
177.9(8)
178.3(7)
177(1)
179.5(5)
177.9(6)
179.6(6)
179.6(6)
176.9(9)
178.0(9)
179(1)
175.8(6)
176.7(6)
155.9(7)
178(2)
177(2)
171(2)
174.4(9)
176.3(8)
179.8(7)

5034 Organometallics, Vol. 15, No. 23, 1996
Lin et al.
B are 0.075(4) and 0.01(1) Å, respectively; dihedral angle
21.7(3)°). The dihedral angle for 8 closely approximates
the ideal angle (the largest deviations of atoms from the
least-squares planes A and B are 0.00(1) and 0.03(1) Å,
respectively; dihedral angle 45.8(4)°). Retaining the
planarity of the backbone in the bridge is regarded as
crucial to the conjugation of π electrons through the
bridge. Only 16 has perfect coplanarity for the two Cp
rings. Other complexes appear to differ in the degree
that the aromatic rings deviate from planarity: for 1,
the dihedral angle of Cp/Ph is 8.6(2)°, and the largest
deviations of atoms from the least-squares planes are
0.002(7) and 0.007(7) Å for Cp and Ph, respectively; for
4, the dihedral angles of py/Ph and Ph/Cp are 2.5(3) and
17.8(4)°, and the largest deviations of atoms from the
least-squares planes are 0.00(1) and 0.01(1) Å for Ph
and Cp, respectively. Therefore, information regarding
just how effective the delocalization of the metal to
ligand charge transfer through the bridge proved to be
was not accessible from the solid-state structural data.
The WsCsO linkage (174.9(7)-178.3(7)°) does not
significantly deviate from linearity. The carbonyl WsC
distances range from 1.954(8) to 2.03(1) Å, and as
expected, the two mutual trans carbonyl ligands project
slightly longer WsC distances. Other relevant crystal
data also appear to be normal: the WsP distance is
2.560(2)°; the alkynyl CtC distances range from 1.170(8)
to 1.21(2) Å. A structural analysis of the series of
molecules NH2C6H4(CtC)nC6H4NO2 (n ) 0-3) con-
firmed that charge-transfer interactions through the
conjugated backbone gave rise to quinonoid distortions
of the nitrophenyl and aminophenyl functional groups,
but not of the acetylene bridges.28 No apparent bond
alternation in the pyridyl ring or acetylene linkers in 8
was observed. The WsN distances (2.268(5)-2.277(8)
Å) are also comparable to the values recorded in the
previous literature.29
Ack n ow led gm en t. We wish to thank Academia
Sinica and the National Science Foundation of the
Republic of China for financially supporting this re-
search under Grant no. NSC-85-2113-M-001-034.
Su p p or tin g In for m a tion Ava ila ble: Listings of all bond
distances and angles, positional parameters, anisotropic and
isotropic thermal parameters, and dihedral angles between the
least-squares planes and stereoviews for complexes 1, 4, 8, and
19 (29 pages). Ordering information is given on any current
masthead page.
OM960607H
(28) Graham, E. M.; Miskowski, V. M.; Perry, J . W.; Coulter, D. R.;
Stiegman, A. E.; Schaefer, W. P.; Marsh, R. E. J . Am. Chem. Soc. 1989,
111, 8772.
(29) Lin, J . T.; Huang, P. S.; Tsai, T. Y. R.; Liao, C. Y.; Tseng, L. H.;
Wen, Y. S.; Shi, F. K. Inorg. Chem. 1992, 31, 4444.