Conversion of diamino-substituted carbene complexes into the isocyanide by acylation

Article abstract of DOI:10.1021/om970500+

Treatment of cyclic diaminocarbene complexes (CO)₅M=CNH(CH₂)_mNH (1) (M = Cr, Mo, W; m = 2, 3) with acylating agents resulted in the formation of the corresponding isocyanide complexes (CO)₅MCN(CH₂)

Full text of DOI:10.1021/om970500+

Organometallics 1998, 17, 1937-1940
1937
Articles
Con ver sion of Dia m in o-Su bstitu ted Ca r ben e Com p lexes
in to th e Isocya n id e by Acyla tion
Chi-Li Chen, Hung-Hui Lee, Tung-Ying Hsieh, Gene-Hsiang Lee,
Shie-Ming Peng, and Shiuh-Tzung Liu*
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
Received J une 12, 1997
Treatment of cyclic diaminocarbene complexes (CO)5M)CNH(CH2)m NH (1) (M ) Cr, Mo,
W; m ) 2, 3) with acylating agents resulted in the formation of the corresponding isocyanide
complexes (CO)5MCN(CH2)m NH2-n (COR)n (M ) Cr, Mo, W; m ) 2, 3; n ) 1, 2; R ) Ph CH3)
in high yields. It appears that the N-acyl group destabilizes the diaminocarbene complexes
and causes the cleavage of the C-N bond to form the isocyanide product. The reaction path-
way leading to the isocyanide complexes is discussed. The crystal structure of (CO)5WCt
N(CH2)2N(COPh)2 has been determined.
In tr od u ction
the donor nitrogen, the stronger the metal-carbon bond
in the related metal complexes. Thus, electronic modi-
fication of the donor character of the nitrogen substi-
tutents in order to weaken the metal-carbon bonds
becomes an interesting prospect. It has been reported
by Do¨tz and co-workers that the N-acylated products
of (CO)5CrdC(NHR)R′ have better reactivities toward
alkynes in annelation reactions.10 As part of our studies
on the properties of metal carbene complexes, we have
prepared the cyclic diamino-substituted carbene com-
plex 1 which holds secondary amine moieties.11 In view
of the modification of the secondary amine functionality,
we report that isocyanide complexes are formed instead
of N-acylated carbene species when diaminocarbene 1
is reacted with acylating agents.
Diamino-substituted carbene complexes have received
much attention recently due to the discovery that nitro-
gen atoms direct carbene ligands to be good σ-donors,
similar to phosphines.1- 8 Such carbene ligands are able
to incorporate with various metal ions to form stable
complexes.1-8 Indeed, the unusually stable palladium
complex [MeNCHdCHN(Me)C]2PdI2 was found by Herr-
mann and co-workers to be a useful catalyst for the
Heck reaction.3d However, the nitrogen-substituted car-
benes of these studies are typically tertiary amines, few
are secondary amine moiety.9 As mentioned, the better
(1) Regitz, M. Angew. Chem., Int. Ed. Engl. 1996, 35, 725 and
references therein.
(2) (a) Arduengo, A., J . III; Goerlich, J . R.; Marshall, W. J . J . Am.
Chem. Soc. 1995, 117, 7, 11027. (b) Alder, R. W.; Allen, P. R.; Murray,
M.; Orpen, A. G. Angew. Chem., Int. Ed. Engl. 1996, 35, 5, 1121. (c)
Enders, D.; Breuer, K.; Raabe, G.; Runsink, J .; Teles, J . H.; Melder,
J .-P.; Ebel, K.; Brode, S. Angew. Chem., Int. Ed. Engl. 1995, 34, 4,
1021 and references therein.
Resu lts a n d Discu ssion
(3) (a) Herrmann, W. A.; Elison, M.; Fischer, J .; Ko¨cher, C.; Artus,
G. R. Chem. Eur. J . 1996, 2, 772. (b) O¨ fele, K.; Herrmann, W. A.;
Mihalios, D.; Elison, M.; Herdtweck, E.; Scherer, W.; Mink, J . J .
Organomet. Chem. 1993, 459, 177. (c) Herrmann, W. A.; Gerstberger,
G.; Spiegler, M. Organometallics 1997, 16, 2209. (d) Herrmann, W.
A.; Elison, M.; Fischer, J .; Ko¨cher, C.; Artus, G. R. J . Angew. Chem.,
Int. Ed. Engl. 1995, 34, 4, 2371 and references therein.
(4) Enders, D.; Gielen, H.; Raabe, G.; Runsink, J .; Teles, J . H. Chem.
Ber. 1996, 129, 1483.
(5) Kuhn, N.; Bohnen, H.; Fahl, J .; Bla¨ser, D.; Boese, R. Chem. Ber.
1996, 129, 1579.
(6) Kernbach, U.; Ramm, M.; Luger, P.; Fehlhammer, W. P. Angew.
Chem., Int. Ed. Engl. 1996, 35, 310.
(7) Taton, T. A.; Chen, P. Angew. Chem., Int. Ed. Engl. 1996, 35,
1011.
(8) Guerret, O.; Sole´, S.; Gornitzka, H.; Teichert, M.; Trinquier, G.;
Bertrand, G. J . Am. Chem. Soc. 1997, 119, 6668.
(9) (a) Michelin, R. A.; Zanotto, L.; Braga, D.; Sabatino, P.; Angelici,
R. J . Inorg. Chem. 1988, 27, 93. (b) Fehlhammer, W. P.; Zinner, G.;
Bakola-Christianopoulou, M. J . Organomet. Chem. 1987, 331, 193. (c)
Belluco, U.; Michelin, R. A.; Ros, R.; Bertani, R.; Facchin, G.; Mozzon,
M.; Zanotto, L. Inorg. Chim. Acta 1992, 200, 883. (d) Sabate´, R.; Schick,
U.; Moreto´, J . M.; Ricart, S. Organometallics 1996, 15, 3611 and
references therein.
The reaction of 1c with an excess of benzoyl chloride
in the presence of pyridine at 100 °C did not provide
the N-acylated carbene product as expected. Instead,
the isocyanide tungsten complex 2c was obtained in 92%
yield. The isocyanide complex was characterized by
both spectroscopic and elemental analyses. The infra-
red spectrum of 2c in dichloromethane clearly shows
the carbonyl and isocyanide functionalities of the mol-
ecule. Thus absorptions at 2174 (w), at 2068 (w) and
1948 (s), and at 1697 and 1660 (s) cm-1 are consistent
with the coordinated isocyanide, the pentacabonyltung-
1
sten and the amidocarbonyl moieties. Both the H and
13C NMR spectra are also in agreement with the
proposed structure. Finally, the composition of 2c is
confirmed by X-ray single-crystal determination (see
crystallography).
S0276-7333(97)00500-1 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 04/17/1998

1938 Organometallics, Vol. 17, No. 10, 1998
Chen et al.
Ta ble 1. Sp ectr a l Da ta of Isocya n id e Com p lexes
Sch em e 1. P ossible Mech a n ism for th e F or m a tion
of Isocya n id e Com p lexes
IR (cm-1
compd yield (%) sCtN MsCtO NsC(dO)R
)
isolated
13C NMR
δ
CN, (ppm)a
2a
2b
2c
2d
3a
3c
4a
4b
77
48
92
80
51b
33b
52
51
2169 2066, 1944 1700, 1658
2169 2070, 1959 1699, 1658
2174 2068, 1948 1697, 1660
2177 2070, 1945 1684, 1653
2171 2061, 1945 1646,
2177 2066, 1945 1640,
2165 2067, 1942 1720, 1708
2181 2071, 1936 1720, 1678
166.0
155.2
145.6
146.7
163.5
144.8
145.9
144.0
a
Due to the weak intensity and broadening of the peak, the
values of J W-C are not available. b Accompanied with the formation
of 2a (25%) or 2c (20%).
n -butyllithium in tetrahydrofuran at - 78 °C. Followed
by addition of an excess of acetyl chloride to the dianion
solution, the reaction mixture was allowed to warm to
room temperature slowly. Monitoring the acylation by
NMR spectroscopy reveals that the reaction took place
at - 20 °C, but the observed outcome is the isocyanide
product. None of the N-acylated carbene species 7 was
detected by NMR. As a control run, the reaction of 6
with methyl iodide was carried out under similar con-
ditions, which provided the methylated product 8 ex-
clusively. This indicates that the first N-acylation takes
Under the same conditions, both the chromium and
molybdenum carbene complexes (1b and 1c) yielded
their corresponding isocyanide complexes (eq 1). In
addition, cyclic diaminocarbene in different ring sizes,
such as 1d , proceeded under the same type of reaction
to yield 2d . We also tried to prepare the monoacylated
product, but we found that a mixture of monobenzoy-
lated amidoisocyanide complexes 3 and 2 (ca 2:1 ratio)
was obtained from the reaction of an equimolar amount
of carbene and acylating agent at the temperature of
refluxing a tetrahydrofuran solution. Other acylating
agents under various conditions also provide the corre-
sponding N-acylated isocyanide complexes. Treatment
of 1c and 1d with an excess of acetic anhydride in the
presence of sulfuric acid or acetyl chloride in the pres-
ence of pyridine produced 4a and 4b, respectively.
place prior to the cleavage of the C-N bond. Such an
acylation also results in the immediate cleavage of the
C-N bond to provide the isocyanide product.
A possible mechanism for the formation of isocyanide
complexes from the carbenes is illustrated in Scheme
1. The carbenes undergo N-acylation first to yield the
intermediate 7. The amido group decreases the stability
of the aminocarbene dramatically, which causes the
ring-opening reaction that leads to the isocyanide com-
plex. It is noted by Aumann and co-workers that reac-
tion of aminocarbene (CO)5CrdC(NH2)R with R′CHO in
the presence of base yields a mixture of a 2-azaallenyl
complex and an isocyanide complex (CO)5CrCN-R 10.12
The formation of 10 is clearly involved in the migration
of the substituent. In our investigation, the isocyanide
complexes are simply created via the cleavage of C-N
bonds and the driving force is presumably due to the
electronic destabilization of the amido group toward the
carbene functionality and the relief of the steric interac-
tion between the substituted cyclic carbene constituent
and the carbonyl ligands.
Some of the spectral data of these complexes are sum-
marized in Table 1.
It is reported by Do¨tz and co-workers that aminocar-
bene chromium complexes [(CO)5CrdC(R)NHR] readily
underwent acylation with acetic anhydride or di-ter t-
butyl dicarbonate in the presence of 4-(N,N-dimethyl-
amino)pyridine at 25 °C.10 Diamino-substituted car-
benes, however, do not react with acyl chloride under
mild conditions, which is attributed to the high stability
of such complexes. But at elevated temperatures, the
acylation proceeds, followed by the cleavage of the C-N
bond to form the isocyanide complex.
Cr ysta llogr a p h y
In our previous investigation, we were able to obtain
the N-alkylated products 5 by the deprotonation of 1
with NaH followed by treatment with various alkyl
iodides.11 By adopting a similar strategy, the dianion
6 was prepared by the treatment of 1d with 2 equiv of
The data for the crystal of complex 2c is summarized
in Table 2, and the ORTEP plot of 2c is depicted in
Figure 1. As expected, the tungsten metal ion displays
a typical octahedral geometry with the isocyanide donor
and five carbonyl ligands. All bond distances and angles
lie within normal ranges, as given in Table 3. The
distance of the metal to isocyanide ligand (W-C6 2.10-
(10) (a) Do¨tz, K. H.; Grotjahn, D.; Harms, K. Angew. Chem., Int.
Ed. Engl. 1989, 28, 1384. (b) Grotjahn, D. B.; Kroll, F. E. K.; Scha¨fer,
T.; Harms, K.; Do¨tz, K. H. Organometallics 1992, 11, 298.
(11) Liu, C.-Y.; Chen, D.-Y.; Cheng, M.-C.; Peng, S.-M.; Liu, S.-T.
Organometallics 1996, 15, 1055.
(12) Aumann, R.; Althaus, S.; Kru¨ger, C.; Betz, P. Chem. Ber. 1989,
122, 357.

Diamino-Substituted Carbene Complexes
Organometallics, Vol. 17, No. 10, 1998 1939
Ta ble 2. Cr ysta l Da ta , Collection , a n d Refin em en t
Deta ils for Com p lex 2c
formation of the N-acylated diaminocarbene complexes
is a challenge. We are currently working on developing
the synethetic approach to the N-acylated diaminocar-
bene complexes.
formula
cryst size, mm
cryst syst
space group
a, Å
C22H14N2O7W
0.30 × 0.50 × 0.50
monoclinic
P21/c
11.591(3)
25.520(5)
7.701(5)
Exp er im en ta l Section
b, Å
c, Å
Gen er a l In for m a tion . Nuclear magnetic resonance spec-
tra were recorded in CDCl3 on either a Bruker AC-E 200 or
AM-300 spectrometer. Infrared spectra were measured on a
Biorad FT-30 instrument in CH2Cl2 solution, unless otherwise
stated.
All of the reaction, manipulation, and purification steps were
performed under a dry nitrogen atmosphere. Tetrahydrofuran
was distilled under nitrogen from sodium benzophenone ketyl.
Dichloromethane was dried by CaH2 and then distilled under
nitrogen. Pyridine was dried over sodium hydroxide and
distilled before use. Other chemicals and solvents were used
from commercial sources without further purification. Com-
plexes 1a -d were prepared by the method previously re-
ported.11
Gen er a l P r oced u r e of th e Acyla tion of 1a -c. A mixture
of 1 (0.1 mmol), benzoyl chloride (0.3 mmol), and pyridine (5
mL) was heated at 100 °C for 8-10 h. After the reaction
mixture was cooled to room temperature, it was poured into
water (20 mL) and extracted with dichloromethane. The
organic portion was separated, washed with water, dried over
MgSO4, and concentrated. The residue was chromatographed
on silica gel with ethyl acetate/hexane (1:4) as the eluent. After
concentration of the elute, the isocyanide complex was ob-
tained.
â, deg
96.21(5)
4
2264.5 (16)
1.766
52.513
Z
V, Å3
D
calcd, gcm-3
µ, cm-1
radiation
Mo KR (0.7107 Å)
298
temp, K
F(000)
1156
diffractometer
scan type
scan width, deg
hkl ranges
Enraf-Nonius CAD 4
θ-2θ
2(0.70 + 0.35 tan θ)
-13 to 13, 0-30, 0-9
2.75-8.24
3871
2768
290
NRCVAX
0.056; 0.064
2.15
scan speed (deg/min)
no. of reflns measd
no. of reflns obsd (I > 2.0 σ(I))
no. of params refined
refinement program
a
Rf, Rw
GOF
resid in final D-map, e Å-3
-2.620 and 2.110
a Rf ) ∑(Fo - Fc)/∑(Fo); Rw ) [∑(w(Fo - Fc))2/∑(wFo2)]1/2. GOF
) [∑(w(Fo - Fc))2/(no. of reflns - no. of params)]1/2
.
(CO)5WCN(CH2)2N(COP h )2 (2c). Into a flask equipped
with a refluxing condenser were placed 1c (1.0 g, 2.54 mmol),
benzoyl chloride (0.9 mL, 7.81 mmol), and pyridine (5 mL).
The resulting mixture was heated at 100 °C for 8 h. Water
(20 mL) followed by dichloromethane (25 mL) were added to
the reaction mixture. The organic layer was separated, dried,
and concentrated. The residue was chromatographed on silica
gel (60 g) with ethyl acetate/hexane (1:4) as the eluent.
Complex 2c was obtained as a white solid (1.16 g, 92%).
Recrystallization from a solution of dichloromethane and
hexane gave 2c as a clear, colorless crystalline solid that is
suitable for X-ray crystal determination. Complex 2c: white
solid; mp 142-144 °C (dec); IR 2174 (υCtN), 2068, 1948 (υCO),
1697, 1660 cm-1 (υN-CO); 1H NMR (200 MHz) δ 7.4-7.0 (m, 10
H, Ar-H), 4.44 (t, J ) 6 Hz, 2 H), 4.16 (t, J ) 6.0 Hz, 2 H);
13C NMR (CDCl3, 50 MHz) δ 195.8, 194.0 (J W-C ) 60 Hz),
173.7, 145.6 (-CtN-), 135.8, 132.3, 128.9, 128.3, 45.0, 43.2.
Anal. Calcd for C22H14N2O7W: C, 43.88; H, 2.34; N, 4.65.
Found: C, 44.14; H, 2.33; N, 4.60.
F igu r e 1. ORTEP plot of 2c.
(2) Å) is identical to that of the species CH3C[CH2NCW-
(CO)5]3 (9; 2.08(2) Å) reported by Hahn and co-workers.13
Due to the isoelectronic nature of the isocyanide and
carbonyl ligands, the distances between the metal and
carbonyl ligands either cis or trans to the isocyanide are
essentially indistinguishable, which is similar in the
structure of 9. Apparently, there is not much of a trans
influence in this kind of structure. The bond length of
C6-N1 (1.17(2) Å) is typical for CtN in the coordinated
isocyanide ligand, which is consistent with the spectral
data for this functionality.
(CO)5Cr CN(CH2)2N(COP h )2 (2a ): white solid (77%), mp
150-151 °C (dec); IR 2169 (υCtN), 2066, 1944 (υCO), 1700, 1658
1
cm-1 (υN-CO); H NMR (200 MHz) δ 7.40-7.11 (m, 10 H, Ar-
H), 4.40 (t, J ) 6.0 Hz, 2 H), 4.07 (t, J ) 6.0 Hz, 2 H); 13C
NMR δ 216.6, 214.5 (Cr-CO), 173.7, 166.0 (-CtN-), 135.8,
132.2, 128.8, 128.3, 45.0, 43.4. Anal. Calcd for C22H14N2O7-
Cr: C, 56.18; H, 3.00; N, 5.96. Found: C, 55.92; H, 2.94; N,
5.88.
(CO)5MoCN(CH2)2N(COP h )2 (2b): white solid (48%), mp
133-134 °C (dec); IR 2169 (υCtN), 2070, 1959 (υCO), 1699, 1658
Su m m a r y
1
cm1 (υN-CO); H NMR (200 MHz) δ 7.41-7.09 (m, 10 H, Ar-
H), 4.41 (t, J ) 6.0 Hz, 2 H), 4.09 (t, J ) 6.0 Hz, 2 H); 13C
NMR δ 206.4, 203.5 (Mo-CO), 173.7, 155.2 (-CtN-), 135.8,
132.2, 128.8, 128.2, 45.0, 43.0. Anal. Calcd for C22H14N2O7-
Mo: C, 51.38; H, 2.74; N, 5.45. Found: C, 50.86; H, 2.75; N,
5.31.
It has been demonstrated in this report that the stable
diaminocarbene ligand can be converted into the iso-
cyanide complex via the cleavage of the C-N bond.
Along with this, it is also found that the mono-N-al-
kylated diaminocarbene (CO)5WCN(Et)CH2CH2NH does
not react with benzoyl chloride in the presence of pyri-
dine in refluxing tetrahydrofuran. This appears that
(CO)5WCN(CH2)3N(COP h )2 (2d ): white solid (80%), IR
2177 (υCtN), 2070, 1945 (υCO), 1684, 1653 cm-1 (υN-CO); 1H NMR
(300 MHz) δ 7.41-7.11 (m, 10 H, Ar-H), 4.18 (t, J ) 6.6 Hz,
2 H), 3.84 (t, J ) 6.6 Hz, 2 H), 2.26 (pent, J ) 6.6 Hz, 2 H);
13C NMR δ 196.2, 194.3 (J W-C ) 62 Hz), 174.0, 146.7
(13) Hahn, F. E.; Tamm, M. J . Organomet. Chem. 1991, 410, C9.

1940 Organometallics, Vol. 17, No. 10, 1998
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles (d eg)
Chen et al.
W-C1
W-C2
W-C3
W-C4
1.93(2)
2.06(2)
1.97(2)
1.97(2)
C1-O1
C2-O2
C3-O3
C4-O4
1.22(3)
1.12(3)
1.16(2)
1.18(2)
W-C5
W-C6
N1-C7
2.08(2)
2.10(2)
1.42(2)
C5-O5
C6-N1
1.08(3)
1.17(2)
C6-W-C1
C6-W-C2
88.5(7)
91.6(6)
C6-W-C3
C6-W-C4
177.1(8)
89.1(6)
C6-W-C5
W-C6-N1
89.0(6)
178(2)
C6-N1-C7
176(2)
(-CtN-), 136.0, 132.1, 128.8, 128.3, 43.8, 42.2, 28.9. Anal.
Calcd for C23H16N2O7W: C, 44.83; H, 2.62; N, 4.55. Found:
C, 44.44; H, 2.72; N, 4.42.
complex 4a was obtained as a light yellow solid (1.26 g, 52%):
mp 60-62 °C (dec); IR 2165 (υCtN), 2067, 1943 (υCO), 1720,
1
1708 cm-1 (υN-CO); H NMR (200 MHz) δ 4.04-3.98 (m, 4 H),
(CO)5Cr CN(CH2)2NH(COP h ) (3a ). To a flask was added
1a (0.2 g, 0.76 mmol), C6H5COCl (0.22 mL, 1.9 mmol), and
pyridine (0.15 mL, 2.48 mmol) in tetrahydrofuran (5 mL). The
mixture was heated to reflux for 30 h. After the reaction
mixture was cooled to room temperature, it was washed with
water and the organic layer was separated. The organic
extract was dried and concentrated. The residue was chro-
matographed on silica gel with ethyl acetate/hexane (1:4) as
the eluent. Two fractions were collected and concentrated,
which were identified as 2a (25%) and 3a (51%). Complex 3a
2.47 (s, 6 H); 13C NMR (CDCl3, 50 MHz) δ 195.4, 193.8 (J W-C
) 63 Hz), 172.5 (Me-CO-), 145.9 (-CtN), 43.4, 42.9, 26.4.
Anal. Calcd for C12H10N2O7W: C, 36.17; H, 2.62; N, 5.62.
Found: C, 35.92 H; 2.14; N, 5.53.
(CO)5WCN(CH2)3N(COCH3)2 (4b). This compound was
prepared similarly to 4a and isolated as a white solid (51%):
1
IR 2181 (υCtN), 2071, 1936 (υCO), 1720, 1678 cm-1 (υN-CO); H
NMR (300 MHz) δ 3.81 (t, J ) 7 Hz, 2 H), 3.74 (t, J ) 7 Hz,
2 H), 2.42 (s, 6 H), 2.03 (m, 2 H); 13C NMR δ 195.8, 194.1 (J W-C
) 63 Hz), 172.8, 144.0 (-CtN-), 42.1, 42.0, 28.8, 26.3. Anal.
Calcd for C13H12N2O7W: C, 31.73; H, 2.46; N, 5.69. Found:
C, 32.44; H, 2.42; N, 5.44.
Cr ysta llogr a p h y. Cell parameters were determined on a
CAD-4 diffractometer at 298 K by a least-squares treatment.
Atomic scattering factors were taken from ref 14. Calculations
were performed using the NRCC SDP VAX package.15 The
crystal data is listed in Table 2, and selected bond distances
and angles are summarized in Table 3. The atomic coordinates
as well as other crystal data are collected as Supporting
Information.
o
was obtained as a white solid: mp 112-113 C (dec); IR 3358
(υN-H) 2171 (υCtN); 2061, 1945 (υCO) 1646 cm1 (υN-CO); 1H NMR
(200 MHz) δ 7.79-7.76 (m, 2 H, Ar-H), 7.57-7.40 (m, 3 H,
Ar-H), 6.5 (br, 1H, N-H), 3.89 (t, J ) 6 Hz, 2 H), 3.76 (t, J )
6.0 Hz, 2 H); 13C NMR δ 216.6, 214.7 (Cr-CO), 168.2, 163.5
(-CtN-), 133.3, 132.0, 128.7, 126.9, 44.1, 39.3. Anal. Calcd
for C15H10N2O6Cr: C, 49.19; H, 2.75; N, 7.65. Found: C, 49.21;
H, 2.92; N. 7.59.
(CO)5WCN(CH2)2NH(COP h ) (3c). The preparation of 3c
was similar to the procedure described for 3a . Complex 3c is
a light-yellow solid (33%); mp: 131-132 °C (dec); IR 3363
(υN-H), 2177 (υCtN), 2066, 1945 (υCO), 1640 cm1 (υN-CO);1H NMR
(CDCl3, 200 MHz) δ 7.76 (m, 2 H), 7.54-7.40 (m, 3 H), 6.74
(br, 1 H), 3.93 (m, 2 H), 3.74 (m, 2 H); 13C NMR (CDCl3, 50
MHz) δ 195.8, 194.2 (J W-C ) 62 Hz), 168.1, 144.8 (-CtN-),
133.2, 132.2, 128.8, 129.9, 44.0, 39.3. Anal. Calcd for
Ack n ow led gm en t. We thank the National Science
Council (Grant No. NSC86-2113-M002-21) for financial
support.
Su ppor tin g In for m ation Available: Tables listing atomic
coordinates, anisotropic thermal parameters, and complete
bond distances and bond angles for 2c (3 pages). Ordering
information is given on any current masthead page.
C
15H10N2O6W: C, 36.17; H, 2.62; N, 5.62. Found: C, 35.92 H,
2.14; N, 5.53.
(CO)5WCN(CH2)2N(COCH3)2 (4a ). To a mixture of com-
plex 1c (2.0 g, 5.07 mmol) and acetic anhydride (10 g, 98 mmol)
was added a few drops of concentrated sulfuric acid. The
resulting mixture was heated at reflux for 12 h. After concen-
tration under vacuum, the residue was chromatographed on
silica gel (ethyl acetate/hexane, 1:4). Upon concentration,
OM970500+
(14) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974; Vol. IV.
(15) Gabe, E. J .; Lee, F. L. Acta Crystallogr., Sect. A 1981, 37, S339.