Bimetallic complexes with conjugated C4, C6, C10, and C14 bridges: Synthetic routes to alkynediyl-bridged bis(carbene) complexes

Article abstract of DOI:10.1021/om990145i

The reaction of [(CO)₅W=C(Ph)H] with Me₂NC≡CNMe₂ affords two complexes: the binuclear complex [(CO)₅W=C(NMe₂)(Me₂N)C=W(CO)₅] (2) and the insertion product [(CO)₅W=C(NMe₂)C(NMe₂)=C(Ph)H] (3). Sequential reaction of the (dimethylamino)-ethynylcarbene complex [(CO)₅W=C(NMe₂)C≡CH] (4a) with nBuLi, W(CO)₆, and F₃CSO₃-Me yields the new ethynediyl-bridged binuclear alkoxycarbene-aminocarbene complex [(CO)₅W=C(NMe₂)C≡C(MeO)C=W(CO)₅] (5). Treatment of 4a and of [(CO)₅Cr=C(NMe₂)C≡ CH] (4b) with nBuLi and iodine gives the new iodine-substituted complexes [(CO)₅M= C(NMe₂)C≡CI] (M = W (6a), M = Cr (6b)). By Pd-catalyzed coupling of 6a,b with the C-stannylated ethynylcarbene complexes [(CO)₅M=C(NMe₂)C≡CSn(nBu)₃] (7a,b) the butadiynediyl-bridged bis(carbene) complexes [(CO)₅M=C(NMe₂)(C≡C)₂(Me ₂N)C=M(CO)₅] (8a,b) are obtained. Analogously, from [(CO)₅W=C(NMe₂)(C≡C)_xH] (x = 2, 3) and nBuLi/I₂ amino(iodobutadiynyl)carbene and amino(iodohexatriynyl)carbene complexes [(CO)₅W= C(NMe₂)(C≡C)_xI] (x = 2 (10), 3 (14)) are obtained. Pd-catalyzed coupling with the corresponding C-stannylated alkynylcarbene complexes finally affords the binuclear C₁₀-(NMe₂)₂- and C₁₄(NMe₂)₂-bridged complexes [(CO)₅W=C(NMe₂)(C≡C)_x(Me ₂N)C=W(CO)₅] (x = 4 (12), 6 (16)). All alkynediyl-bridged bis(carbene) complexes are stable at room temperature. The spectroscopic data of 5 indicate that it is best described as a hybrid of a dipolar allenyl-type compound and an alkynylcarbene complex. In contrast, the C≡C units in the binuclear complexes 8a,b, 12, and 16 are essentially localized.

Full text of DOI:10.1021/om990145i

Organometallics 1999, 18, 2619-2627
2619
Bim eta llic Com p lexes w ith Con ju ga ted C4, C6, C10, a n d
C14 Br id ges: Syn th etic Rou tes to Alk yn ed iyl-Br id ged
Bis(ca r ben e) Com p lexes†
Cornelia Hartbaum, Elvira Mauz, Gerhard Roth, Kerstin Weissenbach, and
Helmut Fischer*
Fakulta¨t fu¨r Chemie, Universita¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Received March 1, 1999
The reaction of [(CO)5WdC(Ph)H] with Me2NCtCNMe2 affords two complexes: the
binuclear complex [(CO)5WdC(NMe2)(Me2N)CdW(CO)5] (2) and the insertion product
[(CO)5WdC(NMe2)C(NMe2)dC(Ph)H] (3). Sequential reaction of the (dimethylamino)-
ethynylcarbene complex [(CO)5WdC(NMe2)CtCH] (4a ) with nBuLi, W(CO)6, and F3CSO3-
Me yields the new ethynediyl-bridged binuclear alkoxycarbene-aminocarbene complex
[(CO)5WdC(NMe2)CtC(MeO)CdW(CO)5] (5). Treatment of 4a and of [(CO)5CrdC(NMe2)Ct
CH] (4b) with nBuLi and iodine gives the new iodine-substituted complexes [(CO)5Md
C(NMe2)CtCI] (M ) W (6a ), M ) Cr (6b)). By Pd-catalyzed coupling of 6a ,b with the
C-stannylated ethynylcarbene complexes [(CO)5MdC(NMe2)CtCSn(nBu)3] (7a ,b ) the
butadiynediyl-bridged bis(carbene) complexes [(CO)5MdC(NMe2)(CtC)2(Me2N)CdM(CO)5]
(8a ,b) are obtained. Analogously, from [(CO)5WdC(NMe2)(CtC)xH] (x ) 2, 3) and nBuLi/I2
amino(iodobutadiynyl)carbene and amino(iodohexatriynyl)carbene complexes [(CO)5Wd
C(NMe2)(CtC)xI] (x ) 2 (10), 3 (14)) are obtained. Pd-catalyzed coupling with the
corresponding C-stannylated alkynylcarbene complexes finally affords the binuclear C10-
(NMe2)2- and C14(NMe2)2-bridged complexes [(CO)5WdC(NMe2)(CtC)x(Me2N)CdW(CO)5] (x
) 4 (12), 6 (16)). All alkynediyl-bridged bis(carbene) complexes are stable at room
temperature. The spectroscopic data of 5 indicate that it is best described as a hybrid of a
dipolar allenyl-type compound and an alkynylcarbene complex. In contrast, the CtC units
in the binuclear complexes 8a ,b, 12, and 16 are essentially localized.
In tr od u ction
have been prepared.2 In addition, linear polynuclear
complexes with all-carbon units linking the metals6
as well as linear7 and L-shaped trinuclear8 and cyclic
tetra- and octanuclear butadiynediyl complexes9 have
been reported. Rigid-rod organometallic polymers
(-LnMCx-)y have also been studied theoretically by
extended-Hu¨ckel MO calculations.10 Only very few
complexes of structural type D are known. Schrock et
al. reported on [(tBuO)3WtCCtW(OtBu)3],11 and Tem-
pleton et al. recently synthesized [Tp′(CO)2MtC-Ct
W(CO)(PhCtCPh)Tp] (M ) Mo, W).12
Electronic communication between metal centers in
bi- and polynuclear complexes can be mediated in
different ways.1 Various types of bridging ligands have
been proposed. In recent years attention has focused on
carbon-rich bridges.2 Bi- and polynuclear transition-
metal complexes containing unsaturated conjugated
carbon bridges are expected to exhibit potentially useful
physical and chemical properties such as liquid crystal-
line properties3 and second-order or third-order nonlin-
ear optical properties.4
For Cn (carbon-only) bridges several structural motifs
are conceivable and have been realized (Chart 1, A-D).
Binuclear complexes of types A and B/C with vari-
ous lengths of the carbon chain Cx (x up to 20)5
(4) See e.g.: (a) Bruce, D. W., O’Hare, D., Eds. Inorganic Materials;
Wiley: Chichester, U.K., 1992. (b) Wisian-Neilson, P., Allcock, H. R.,
Wynne, K. J ., Eds. Inorganic and Organometallic Polymers II: Ad-
vanced Materials and Intermediates; ACS Symp. Ser. 572; American
Chemical Society: Washington, DC, 1994. (c) Whittall, I. R.; McDon-
agh, A. M.; Humphrey, M. G.; Samoc, M. Adv. Organomet. Chem. 1998,
42, 291. (d) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc,
M. Adv. Organomet. Chem. 1999, 43, 349.
* To whom correspondence should be addressed. Tel: +7531-882783.
Fax: +7531-883136. E-mail: hfischer@dg6.chemie.uni-konstanz.de.
† Dedicated to Prof. Helmut Werner on the occasion of his 65th
birthday.
(5) Bartik, T.; Bartik, B.; Brady, M.; Dembinski, R.; Gladysz, J . A.
Angew. Chem. 1996, 108, 467; Angew. Chem., Int. Ed. Engl. 1996, 35,
414.
(1) For recent reviews see, e.g.: (a) Ward, M. D. Chem. Soc. Rev.
1995, 121. (b) Paul, F.; Lapinte, C. Coord. Chem. Rev. 1998, 178-180,
431.
(2) Recent reviews: (a) Beck, W.; Niemer, B.; Wieser, M. Angew.
Chem. 1993, 105, 969; Angew. Chem., Int. Ed. Engl. 1993, 32, 923. (b)
Lang, H. Angew. Chem. 1994, 106, 569; Angew. Chem., Int. Ed. Engl.
1994, 33, 547. (c) Bunz, U. H. F. Angew. Chem. 1996, 108, 1047; Angew.
Chem., Int. Ed. Engl. 1996, 35, 969. (d) Bartik, T.; Weng, W.; Ramsden,
J . A.; Szafert, S.; Falloon, S. B.; Arif, A. M.; Gladysz, J . A. J . Am. Chem.
Soc. 1998, 120, 11071 and literature cited therein.
(6) See e.g.: (a) Fujikura, Y.; Sonogashira, K.; Hagihara, N. Chem.
Lett. 1975, 1067. (b) Sonogashira, K.; Ohga, K.; Takahashi, S.;
Hagihara, N. J . Organomet. Chem. 1980, 188, 237.
(7) Weng, W.; Bartik, T.; Brady, M.; Bartik, B.; Ramsden, J . A.; Arif,
A. M.; Gladysz, J . A. J . Am. Chem. Soc. 1995, 117, 11922.
(8) See e.g.: (a) Bruce, M. I.; Ke, M.; Low, P. J . Chem. Commun.
1996, 2405. (b) Back, S.; Pritzkow, H.; Lang, H. Organometallics 1998,
17, 41.
(9) ALQuaisi, S. M.; Galat, K. J .; Chai, M.; Ray, D. G., III; Rinaldi,
P. L.; Tessier, C. A.; Youngs, W. J . J . Am. Chem. Soc. 1998, 120, 12149.
(10) Re, N.; Sgamellotti, A.; Floriani, C. J . Chem. Soc., Dalton Trans.
1998, 2521.
(3) Giroud-Godquin, A.-M.; Maitlis, P. M. Angew. Chem. 1991, 103,
370; Angew. Chem., Int. Ed. Engl. 1991, 30, 375.
10.1021/om990145i CCC: $18.00 © 1999 American Chemical Society
Publication on Web 06/15/1999

2620 Organometallics, Vol. 18, No. 14, 1999
Hartbaum et al.
Ch a r t 1
A feature common to all of these complexes is the
M-C(sp) linkage of the bridge to both LnM fragments.
Binuclear complexes with an M-C(sp2) and an M-C(sp)
linkage are likewise known. Several structural alterna-
tives are possible (Chart 1, E-G). Three different routes
to complexes of type E have been developed recently.
Gladysz et al. synthesized several heterobimetallic
complexes by reaction of [Cp*(NO)(PPh3)Re(CtC)x]-
with [Mn(CO)3Cp], [Fe(CO)5], [W(CO)6], or [Re2(CO)10]
and subsequent alkylation of the resulting metalate
with [Me3O]BF4.2d,13 Other approaches are the substitu-
tion of alkynylcarbene anions for the halide in metal
halides and the Pd-catalyzed coupling of C-stannylated
carbene complexes with [XMLn]. Recently, we reported
the synthesis of a series of heterobinuclear complexes
were obtained by reductive dimerization of the cationic
carbyne complexes [(CO)5ΜtCNEt2]BF4. However, sev-
eral complexes with unsaturated cyclic π-conjugated
carbon bridges linking two metal-carbene fragments
LnMdC(R) are known. These include phenyl-,21,22 bi-
phenyl-,23 binaphthyl-,22 anthracenyl-,24 or 1.6-methanol-
[10]annulen-2,7-diyl-bridged25 symmetrical bis(carbene)
complexes as well as derivatives with an ammonium
pentadienide bridge.26 Symmetrical bis(carbene) com-
plexes with a noncyclic alkenyl bridge are scarce.27
Carbon-only bridged bis(carbene) complexes are un-
known.
We now report on a new route to binuclear bis-
(carbene) complexes, on the synthesis of the first amino-
(iodoalkynyl)carbene complexes, and on the synthesis
and properties of the first series of homobinuclear bis-
(carbene) complexes of the type [(CO)5WdC(NMe2)(Ct
C)x(Me2N)CdW(CO)5] (x ) 0, 2, 4, 6).
[(CO)5MdC(NR2)(CtC)xM′L′n] (M ) Cr, W; NR2
)
NMe2, NHMe; x ) 1-3; M′ ) Sn, Mn, Re, Fe, Ru, Rh,
Ni, Pd) by the latter methods.14,15 “Linear” trinuclear
(M′ ) Fe, Ni, Pd, Pt, Hg),15,16 L-shaped (M′ ) Ti)
trinuclear,16 and star-shaped tetra- (M′ ) B, P)16 and
pentanuclear complexes (M′ ) Ge, Sn)16 were also
accessible. Complexes of type F (R ) H; x ) 1) have
also been studied.17 For LnM ) M′L′n () Fe(CO)2Cp*) a
dynamic process was observed which equilibrates the
two metal centers. To the best of our knowledge,
complexes of type G are unknown.
Resu lts a n d Discu ssion
The first member of the series (x ) 0), [(CO)5Wd
C(NMe2)(Me2N)CdW(CO)5] (2), was obtained as a
byproduct from the reaction of [(CO)5WdC(Ph)H] (1)28,29
with Me2NCtCNMe2. When the alkyne was added at
-50 °C to a solution of 1 in dichloromethane, the
solution immediately changed from red to orange.
Chromatographic workup afforded two fractions. The
first fraction contained the binuclear complex 2 and the
second fraction the mononuclear complex 3 (Scheme 1).
Two types of homo- and heterobinuclear complexes
with a C(R)(C)xC(R) bridge (two terminal M-C(sp2)
bonds) are conceivable (Chart 1, H and I). Complexes
of type H have been known for a long time. The first
one (x ) 0), [(CN)5CoC(COOMe)dC(COOMe)Co(CN)5],6-
was already prepared in 1967.18 Since then several
others have been synthesized.1b,2a Only two complexes
of type I have been reported until now. Both compounds,
[(CO)5MdC(NEt2)(Et2N)CdM(CO)5] (M ) Cr,19 W20),
(19) Fischer, E. O.; Wittmann, D.; Himmelreich, D.; Neugebauer,
D. Angew. Chem. 1982, 94, 451; Angew. Chem., Int. Ed. Engl. 1982,
21, 444; Angew. Chem. Suppl. 1982, 1036.
(20) Fischer, E. O.; Reitmeier, R. Z. Naturforsch. 1983, 38B, 582.
(21) Fischer, E. O.; Ro¨ll, W.; Huy, N. H. T.; Ackermann, K. Chem.
Ber. 1982, 115, 2951.
(22) Havra´nek, M.; Husˇa´k, M.; Dvorˇa´k, D. Organometallics 1995,
14, 5024.
(11) Listemann, M. L.; Schrock, R. R. Organometallics 1985, 4, 74.
(12) Woodworth, B. E.; White, P. S.; Templeton, J . L. J . Am. Chem.
Soc. 1998, 120, 9028.
(13) (a) Weng, W.; Ramsden, J . A.; Arif, A. M.; Gladysz, J . A. J . Am.
Chem. Soc. 1993, 115, 3824. (b) Weng, W.; Arif, A. M.; Gladysz, J . A.
Angew. Chem. 1993, 105, 937; Angew. Chem., Int. Ed. Engl. 1993, 32,
891. (c) Weng, W.; Bartik, T.; Gladysz, J . A. Angew. Chem. 1994, 106,
2269; Angew. Chem., Int. Ed. Engl. 1994, 33, 2199.
(14) Hartbaum, C.; Roth, G.; Fischer, H. Chem. Ber./ Recl. 1997, 130,
479.
(15) (a) Hartbaum, C.; Fischer, H. Chem. Ber./ Recl. 1997, 130, 1063.
(b) Hartbaum, C.; Fischer, H. J . Organomet. Chem., in press.
(16) Hartbaum, C.; Roth, G.; Fischer, H. Eur. J . Inorg. Chem. 1998,
191.
(17) See: Akita, M.; Moro-oka, Y. Bull. Chem. Soc. J pn. 1995, 68,
420.
(23) Huy, N. H. T.; Lefloch, P.; Robert, F.; J eannin, Y. J . Organomet.
Chem. 1987, 327, 211.
(24) Albrecht, T.; Sauer, J . Tetrahedron Lett. 1994, 35, 561.
(25) Neidlein, R.; Gu¨rtler, S. Helv. Chim. Acta 1994, 77, 2303.
(26) Aumann, R.; J asper, B.; Fro¨hlich, R.; Kotila, S. J . Organomet.
Chem. 1995, 502, 137.
(27) (a) Pe´ron, V.; Porhiel, E.; Ferrand, V.; Le Bozec, H. J . Orga-
nomet. Chem. 1997, 539, 201. (b) Geisbauer, A.; Mihan, S.; Beck, W.
J . Organomet. Chem. 1995, 501, 61. (c) Etzenhouser, B. A.; Chen, Q.;
Sponsler, M. B. Organometallics 1994, 13, 4176. (d) Rabier, A.; Lugan,
N.; Mathieu, R. Organometallics 1994, 13, 4676. (e) Fox, H. H.; Lee,
J .-K.; Park, L. Y.; Schrock, R. R. Organometallics 1993, 12, 759. (f)
Aumann, R.; Heinen, H. Chem. Ber. 1987, 120, 537.
(28) (a) Casey, C. P.; Polichnowski, S. W. J . Am. Chem. Soc. 1977,
99, 6097. (b) Casey, C. P.; Polichnowski, S. W.; Shusterman, A. J .;
J ones, C. R. J . Am. Chem. Soc. 1979, 101, 7282.
(18) Kimball, M. E.; Martella, J . P.; Kaska, W. C. Inorg. Chem. 1967,
6, 414.
(29) Fischer, H.; Zeuner, S.; Ackermann, K. J . Chem. Soc., Chem.
Commun. 1984, 684.

Alkynediyl-Bridged Bis(carbene) Complexes
Organometallics, Vol. 18, No. 14, 1999 2621
Ta ble 1. Selected Bon d Dista n ces, Bon d An gles,
a n d Tor sion An gles for Com p lex 2
Bond Distances (Å)
W(1)-C(6)
W(1)-C(5)
C(6)-N(1)
C(6)-C(6A)
2.295(7)
1.991(8)
1.310(8)
1.463(9)
W(1A)-C(6A)
W(1A)-C(5A)
C(6A)-N(1A)
2.281(7)
1.978(8)
1.314(9)
Bond Angles (deg)
W(1)-C(6)-N(1)
130.4(5) W(1A)-C(6A)-N(1A) 128.8(5)
W(1)-C(6)-C(6A) 112.7(4) W(1A)-C(6A)-C(6)
N(1)-C(6)-C(6A) 116.6(6) N(1A)-C(6A)-C(6)
114.5(5)
116.6(6)
Torsion Angles (deg)
N(1)-C(6)-C(6A)-N(1A)
W(1)-C(6)-C(6A)-W(1A)
-89.7
-93.9
unfavorable steric interactions, the WdC distances
(2.281(7) and 2.295(7) Å) are rather long and are
significantly longer than in typical aminocarbene com-
plexes such as [(CO)5WdC(NHMe)Ph] (2.186(22) Å)33
and [(CO)5WdC(NMe2)CtCSiMe3] (2.224 Å).34 Com-
pared to a C(sp2)-N(sp2) single bond,35 the C(car-
bene)-N bonds are rather short. This indicates consid-
erable double-bond character of the C(carbene)-N
bonds, which is consistent with the observation of two
distinct NMR resonances for the NMe2 groups in the
1H and 13C NMR spectra. Both carbene atoms are
planar coordinated (sums of angles 359.7 and 359.9°).
These carbene planes are almost orthogonal (torsion
angle W1-C6-C6A-W1A ) -93.9°), which excludes
the presence of a bridging delocalized π-system.
F igu r e 1. ORTEP plot of complex 2 (hydrogens omitted).
Sch em e 1
Complex 2 exhibits in the IR spectrum two distinct
sets of (CO)5W ν(CO) vibrations. This indicates that in
solution two conformers are present. Two sets of ν(CO)
vibrations have also been reported for the related
(diethylamino)carbene complexes, [(CO)5MdC(NEt2)-
(Et2N)CdM(CO)5] (M ) Cr, W), prepared earlier by
Fischer et al.9,20 The interconversion of the conformers
Complex 3 was the expected reaction product. It was
formed by insertion of the CtC bond of the alkyne into
the WdC bond of 1. The insertion of electron-rich
alkynes into the metal-carbene bond is a typical
reaction of electrophilic carbene complexes.30 Complex
2 presumably was either formed by addition of two
(CO)5W fragments to the alkyne or, more likely, by
substitution of the alkyne for the bridging carbene
ligand in [(CO)5W{µ-C(Ph)H}W(CO)5] and subsequent
rearrangement. [(CO)5W{µ-C(Ph)H}W(CO)5] usually is
formed in addition to stilbene on thermolysis of 1.29,31
Both complexes were characterized by spectroscopic
1
must be rapid on the NMR time scale, since the H and
13C NMR spectra show only two NMe signals as
expected on the basis of restricted rotation around the
C(carbene)-N bond.
The π-conjugated, ethyne-bridged bis(carbene) com-
plex was prepared via the classical route to Fischer
carbene complexes starting from the ethynylcarbene
complex [(CO)5WdC(NMe2)CtCH]34 (4a ). Addition of
nBuLi to 4a in Et2O at -80 °C afforded the lithiated
derivative [(CO)5WdC(NMe2)CtCLi],34 which was then
used as the nucleophile in the in situ reaction with
[W(CO)6]. The resulting [(CO)5WdC(NMe2)CtC(LiO)Cd
W(CO)5] was alkylated with F3CSO3Me to give the new
unsymmetrical C2-bridged alkoxycarbene-aminocar-
bene complex [(CO)5WdC(NMe2)-CtC(MeO)CdW(CO)5]
(5) in 31% yield, after chromatography and recrystalli-
zation (Scheme 2).
1
means. The H NMR spectrum of 2 exhibits only two
singlets for the two inequivalent N-Me groups; the 13C
NMR spectrum shows signals for the two N-Me groups,
signals at δ 198.3 and 201.0 for the CO substituents,
and the carbene resonance at δ 241.4 in the range
typical for aminocarbene complexes.32 Although this
complex could not be obtained in an analytically pure
form, it was possible to grow a few crystals of 2 suitable
for X-ray analysis (Figure 1 and Table 1).
As expected, complex 5 exhibits in the IR spectrum
two partly overlapping sets of (CO)5W ν(CO) absorptions
and two resonances each for the cis and the trans CO
ligands in the 13C NMR spectrum. However, the 13C
NMR spectrum shows some peculiarities. In comparison
with C-substituted alkynes and alkynylcarbene com-
The (CO)5W fragments are connected by a C2(NMe2)2
bridge. The central C-C distance (1.463(9) Å) corre-
sponds to a C(sp2)-C(sp2) single bond and agrees well
with that in the related chromium complex [(CO)5Crd
C(NEt2)(Et2N)CdCr(CO)5] (1.480(9) Å).19 To prevent
(30) (a) Do¨tz, K. H.; Kreiter, C. G. J . Organomet. Chem. 1975, 99,
309. (b) Do¨tz, K. H. Angew. Chem. 1984, 96, 573; Angew. Chem., Int.
Ed. Engl. 1984, 23, 587.
(33) Guy, J . T., J r.; Bennett, D. W. Transition Met. Chem. 1984, 9,
43.
(34) Rahm, A.; Wulff, W. D.; Rheingold, A. L. Organometallics 1993,
12, 597.
(35) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.
(31) Fischer, H.; Zeuner, S.; Ackermann, K.; Schmid, J . Chem. Ber.
1986, 119, 1546.
(32) Mann, B. E.; Taylor, B. F. 13C NMR Data for Organometallic
Compounds; Academic Press: London, 1981.

2622 Organometallics, Vol. 18, No. 14, 1999
Hartbaum et al.
Sch em e 2
Deprotonation of the (dimethylamino)ethynylcarbene
complexes 4a ,b with nBuLi in Et2O at -78 °C followed
by in situ reaction with an equimolar amount of iodine
afforded the novel (dimethylamino)(iodoethynyl)carbene
complexes 6a ,b in ca. 50% yield (Scheme 4). Essentially
the same route was used for the preparation of organic
iodine-substituted alkynes RCtCI.39 The IR and NMR
spectra of 6a ,b are similar to those of the starting
complexes 4a ,b except for a considerable shift of the
CtC resonances to higher field. At room temperature
in solution 4a ,b decompose within several days.
The stannylated alkynylcarbene complexes 7a ,b were
obtained from 4a ,b, nBuLi and ClSnnBu3.14 Coupling
of 6a ,b with 7a ,b was achieved by stirring 1:1 mixtures
of these complexes in toluene for 1 day in the presence
of 10 mol % [PdCl2(NCMe)2]. The butadiynediyl-bridged
bis(aminocarbene) complexes 8a ,b were obtained after
purification by column chromatography and recrystal-
lization in approximately 40% yield (Scheme 4).
As expected and in contrast to 5, the IR spectra of
8a ,b show only one set of (CO)5M ν(CO) absorptions.
The 13C NMR spectra of 5 and 8a ,b also differ consider-
ably. The CtC resonances of 8a ,b (δ 100.3 and 109.4
(8a ); δ 100.1 and 113.3 (8b)) are shifted upfield by more
than 60 ppm compared to those of 5. For 8a ,b only one
carbene resonance each is observed which is in the
range characteristic for aminocarbene complexes. From
these spectroscopic data it follows that the bis(carbene)
form dominates and that dipolar allenylalkynylcarbene
and pentatetraenylcarbene resonance forms such as h
and i (Scheme 5) at best only slightly contribute to the
overall bonding description.
plexes, the resonances of the alkynediyl unit appear at
unusually low field (δ 169.2 and 174.3). In contrast, the
resonances of both carbene carbon atoms are observed
at unusually high field. The carbene resonance of
[(CO)5WdC(NR2)CtCR′] complexes is usually found
between δ 220 and 235 (e.g. δ 231.1 in 4a 34). In contrast,
that of 5 is at δ 181.7 (1J W,C ) 99.0 Hz). The WdC(OMe)
resonance is expected in the range δ 270 and 300 (e.g.
δ 290.8 in [(CO)5WdC(OMe)CtCSiMe3]); however, that
in 5 is at δ 235.9 (1J W,C ) 86.6 Hz). These data indicate
that there is considerable π delocalization in the bridge
and that 5 is best represented by several mesomeric
structures (Scheme 3, a -f). The dipolar allenyl-type
resonance forms b and c significantly contribute to the
overall bonding description.
Usually, the alkoxy group in alkoxycarbene complexes
can be replaced by NH2, N(R)H, or NR2 by aminolysis
with ammonia or primary or secondary amines.36 How-
ever, attempts to transform 5 into the symmetrical
CtC-bridged bis(aminocarbene) complex [(CO)5Wd
C(NMe2)CtC(Me2N)CdW(CO)5] failed. When HNMe2
was added to a solution of 5 in diethyl ether at -100
°C,37 a mixture of many compounds rapidly formed
which were inseparable by thin-layer chromatography.
Presumably, the first reaction step involves nucleophilic
attack of the amine at the CtC bond (see mesomeric
forms b and c) instead of addition to the carbene carbon
atom.38
Since 5 could not be transformed into a bis(aminocar-
bene) complex, attempts to synthesize a π-conjugated,
(-CtC-)x-bridged bis(aminocarbene) complex via the
classical Fischer route followed by aminolysis were
abandoned. Instead, a different approach to symmetrical
alkynediyl-linked bis(aminocarbene) complexes [(CO)5Md
C(NMe2)(CtC)x(Me2N)CdM(CO)5] was developed. Cou-
pling of two mononuclear alkynylcarbene complexes
should afford binuclear complexes in a straightforward
way. The coupling could be achieved by Pd-catalyzed
reaction of mononuclear stannylated alkynylcarbene
complexes with (iodoalkynyl)carbene complexes.
The coupling route could be extended to the synthesis
of the corresponding octatetraynediyl- and dodeca-
hexaynediyl-bridged complexes. Reaction of 915a with
nBuLi/I2 gave the new amino(iodobutadiynyl)carbene
complex 10. The Pd-catalyzed coupling of 10 with 1115a
afforded 12 with a naked C8 unit linking two (aminocar-
bene)pentacarbonyltungsten fragments (Scheme 6).
Analogously, the reaction of 1315b with nBuLi and I2
yielded the amino(iodohexatriynyl)carbene complex 14.
Subsequent coupling of 14 with 1515b gave the dodeca-
hexaynediyl-bridged bis(aminocarbene)tungsten com-
plex 16 (Scheme 7).
All new alkynediyl-bridged bis(carbene) complexes 5,
8a ,b, 12, and 16 are stable at room temperature in the
solid state and in solution. In contrast, the (iodobutadiy-
nyl)carbene complex 10 and the (iodohexatriynyl)car-
bene complex 14 slowly decompose in solution at room
temperature but are stable in the solid state below -30
°C.
(36) See e.g.: (a) Klabunde, U.; Fischer, E. O. J . Am. Chem. Soc.
1967, 89, 7141. (b) Do¨tz, K. H., Fischer, H., Hofmann, P., Kreissl, F.
R., Schubert, U., Weiss, K., Eds. Transition Metal Carbene Complexes;
Verlag Chemie: Weinheim, Germany, 1983.
(37) The aminolysis of the typical Fischer carbene complex with
primary amines was studied in detail by kinetic methods, and a fourth-
order rate law was observed. The activation entropy is strongly
negative, giving rise to a negative Arrhenius activation energy. As a
consequence the reaction rate increases with decreasing temperature.
See: Werner, H.; Fischer, E. O.; Heckl, B.; Kreiter, C. G. J . Organomet.
Chem. 1971, 28, 367.
(38) Michael addition of amines to the CtC bond competes with
aminolysis. Due to the large negative activation entropy37 aminolysis
is favored at low temperature. For instance, the reaction of [(CO)5Wd
C(OEt)CtCPh] with HNMe2 affords at -60 °C [(CO)5WdC(NMe2)Ct
CPh] and EtOH and at -20 °C the Michael adduct [(CO)5Wd
C(OEt)CHdC(NMe2)Ph]. In the temperature range -60 to -20 °C
mixtures of both complexes are obtained. See: (a) Fischer; E. O.;
Kalder, H. J . J . Organomet. Chem. 1977, 131, 57. (b) Aumann, R.;
Nienaber, H. Adv. Organomet. Chem. 1997, 41, 163.
1
The ν(CO) spectra and the H and 13C NMR spectra
of the (CO)5WdC(NMe2) part of 8a , 12, and 16 are
almost identical. This indicates that the σ-donor/π-
acceptor properties of the bridging alkynylaminocarbene
ligand in the ground state is nearly independent of the
number of (CtC) units forming the chain. Obviously,
insertion of a C2 or a C4 unit into the (Me2N)CCtCCt
CC(NMe2) fragment does not significantly modify the
bonding situation. The spectra of 8a , 12, and 16 also
differ only slightly from those of 4a , 9, and 13 and of 6,
(39) (a) de Graaf, W.; Smits, A.; Boersma, J .; van Koten, G.;
Hoekstra, W. P. M. Tetrahedron 1988, 44, 6699. (b) Kloster-J enson,
E. Tetrahedron 1971, 27, 33.

Alkynediyl-Bridged Bis(carbene) Complexes
Organometallics, Vol. 18, No. 14, 1999 2623
Sch em e 3
Sch em e 4
Sch em e 5
10, and 14. An alternation of the 13C NMR resonances
along the (CtC)x chain is observed. The alternation
decreases along the chain with increasing distance from
the carbene carbon atom: ∆δ(Câ-CR) > ∆δ(Cδ-Cγ) >
∆δ(Cê-Cꢀ). In general, the alternation is less pro-
nounced than in the corresponding unsubstituted, π-ac-
ceptor-substituted (SiMe3, Sn(nBu)3), and π-donor-sub-
stituted (I) mononuclear alkynylaminocarbene com-
plexes. This may be interpreted as a sign for a weak
interaction of both (CO)5W groups.
In the series 8a , 12, and 16 the absorption at lowest
energy in the UV/vis spectra is shifted toward longer
wavelengths (Figure 2). The absorption is assigned to
a MLCT transition. The HOMO in these complexes is
essentially metal d in character. Conversely, the LUMO
is predominantly localized at the bridging ligand. From

2624 Organometallics, Vol. 18, No. 14, 1999
Hartbaum et al.
Sch em e 6
Sch em e 7
the IR and NMR spectra it follows that the energy of
the HOMO is only marginally influenced by the length
of the bridge. Therefore, the bathochromic shift reflects
the decreasing energy of the LUMO. The insertion of a
(CtCCtC) fragment lowers the energy of the LUMO
by about 15-20 kJ /mol. Although 8a , 12, and 16 are
symmetric, the MLCT transition is solvent-dependent
and is shifted toward shorter wavelengths when non-
polar solvents are replaced by polar ones. However, the
solvatochromic effect is small and decreases with in-
creasing length of the chain (ν˜(pentane-CH2Cl2) 2830
(8a ), 1240 (12), 900 (16) cm-1).
are accessible by two different CC-coupling routes. The
reaction of the lithiated (dimethylamino)ethynylcar-
bene complex [(CO)5WdC(NMe2)CtCLi] with [W(CO)6]
followed by alkylation with methyl triflate affords the
unsymmetrically bridged alkoxycarbene-aminocar-
bene complex [(CO)5WdC(NMe2)CtC(MeO)CdW(CO)5]
(5). This route should also be applicable to other
“electron-poor” metal carbonyls such as [Cr(CO)6] and
[Mo(CO)6]. Presumably, the method can also be ex-
tended to the synthesis of binuclear complexes with
longer alkynediyl linking groups such as [(CO)5Md
C(NR2)(CtC)x(R′O)CdM(CO)5] (x ) 2, 3, ...). However,
the yields are expected to be much lower due to the
reduced nucleophilicity of the lithiated alkynylcarbene
complexes [(CO)5WdC(NMe2)(CtC)xLi] required as the
starting compounds.
Con clu sion s
Novel binuclear bis(carbene) complexes with an
alkynediyl fragment linking two (CO)5MdC(R) units

Alkynediyl-Bridged Bis(carbene) Complexes
Organometallics, Vol. 18, No. 14, 1999 2625
bathochromic shift of the MLCT absorption in the series
8, 12, and 16 a decreasing energy of the LUMO with
increasing chain length can be deduced. In contrast to
8, 12, and 16, the considerable high-field shift of both
carbene resonances and the low-field shift of both CtC
resonances of the unsymmetrical alkoxycarbene-ami-
nocarbene complex 5 indicate significant π-interaction
between both carbene units.
Exp er im en ta l Section
All operations were performed under argon by using stan-
dard Schlenk techniques. Solvents were dried by refluxing
from CaH2 (CH2Cl2) and sodium benzophenone ketyl (pentane,
Et2O, THF) and were freshly distilled prior to use. The yields
refer to analytically pure compounds and were not optimized.
Silica used for column chromatography (Fa. J . T. Baker, silica
for flash chromatography) was argon-saturated. The complexes
1,28,29 4a ,b ,16 7a ,b ,3 9,4 11,4 13,5 15,5 NEt4[(CO)5WCPh-
(OMe)H],40 and [PdCl2(MeCN)2]23 were prepared according to
literature procedures. NMR spectra were determined on
Bruker AC 250, Bruker DRX 600, and J EOL J NX 400
instruments; chemical shifts are reported relative to internal
TMS (1H and 13C). Unless mentioned otherwise, all NMR
spectra were recorded in CDCl3 at room temperature. The
labeling scheme for atoms in the chain is as follows: [(CO)5Md
C(NMe2)CRtCâCγtCδCꢀtCêR]. IR spectra were measured on
Biorad FTS 60 and Perkin-Elmer 983G instruments and UV/
vis spectra on a Hewlett-Packard 8452A diode-array spectro-
photometer. IR and UV/vis spectra were analyzed using the
program Peakfit (SPSS Inc.). For UV/vis spectra only the
absorption at lowest energy is given. MS determinations were
carried out on a Finnigan MAT 312 instrument and elemental
analyses on a Heraeus CHN-O-RAPID.
µ-B i s [p e n t a c a r b o n y l((d i m e t h y la m i n o )c a r b e n e )-
tu n gsten ] (2) a n d P en ta ca r bon yl[(d im eth yla m in o)(1-
(d im eth yla m in o)-2-p h en yleth en yl)ca r ben e]tu n gsten (3).
A 1.0 mL (7.3 mmol) portion of bis(dimethylamino)ethyne was
added at -50 °C to a solution of [(CO)5WdC(Ph)H] (1) in 10
mL of CH2Cl2 freshly prepared from 0.90 g (1.6 mmol) of
NEt4[(CO)5WCH(OMe)Ph] and 0.44 mL (3.2 mmol) of HBF4
(54% in Et2O). The initially red solution immediately changed
to orange. The solvent was removed in vacuo and the residue
dissolved in CH2Cl2 and chromatographed at -50 °C on silica.
The first yellow zone was eluted with hexane/CH2Cl2 (1:1).
Subsequently, an orange fraction was eluted with hexane/CH2-
Cl2 (ratio gradually changing from 1:1 to 0:1). The solvents of
both fractions were removed in vacuo. When the residue of
the first fraction was dissolved at 0 °C in the least amount of
hexane/CH2C12 (1:1) possible and the temperature slowly
reduced to -30 °C, fine orange-brown needles of 2 formed.
Similarly, the residue of the second fraction was dissolved in
hexane/CH2C12 (1:1) at ambient temperature and the temper-
ature was reduced to -30 °C to give yellow crystals of 3.
2: yield 0.10 g (8% based on NEt4[(CO)5WCH(OMe)Ph]);
F igu r e 2. UV/vis spectra of [(CO)5WdC(NMe2)(CtC)x-
(Me2N)CdW(CO)5] in dichloromethane at room tempera-
ture: (s) n ) 2; (‚‚‚) n ) 4; (---) n ) 6.
Symmetrically substituted alkynediylbis(aminocar-
bene) complexes are obtained by Pd-catalyzed coupling
of two (CO)5MdC(NR2)(CtC)x units. Thus, C(NMe2)(Ct
C)x(Me2N)C-bridged binuclear complexes with x ) 2, 4,
and 6 are readily accessible. This route is not restricted
to the synthesis of complexes with an even number of
CtC units. Since two different precursors, [(CO)5Md
C(NR2)(CtC)xI] and [(CO)5MdC(NR2)(CtC)ySnR3], are
involved, complexes with an odd number of CtC linking
units can likewise be prepared. The same applies to
binuclear complexes with an even larger number of
bridging CtC units. In the series 8, 12, 16 the thermal
stability of the complexes is not significantly reduced
by elongation of the bridging ligand. Therefore, com-
plexes with even longer bridging chains should also be
stable. Limitations may arise from the availability of
the unsubstituted alkynylcarbene complexes [(CO)5Md
C(NR2)(CtC)xH], which are the precursors for both the
iodo- and the SnR3-substituted complexes. Until now,
two different routes to alkynylcarbene complexes
[(CO)5MdC(NR2)(CtC)xH] (x > 1) have been devel-
oped: (a) Cu-catalyzed coupling of [(CO)5WdC(NMe2)Ct
CLi] with I(CtC)xSiMe3 followed by desilylation of the
resulting product with KF in MeOH/THF and (b) Pd-
catalyzed coupling of [(CO)5WdC(NMe2)CtCSn(nBu)3]
with I(CtC)xSiMe3 and subsequent desilylation. Both
routes suffer from rather poor yields.15
Crucial intermediates in these syntheses are unsub-
stituted alkynylcarbene complexes [(CO)5MdC(R)(Ct
C)xH]. For R ) NR2 these compounds are stable at
room temperature. However, the corresponding alkoxy-
alkynylcarbene complexes are very labile. [(CO)5Wd
C(OMe)CtCH] has been shown to decompose rapidly
even at -78 °C.34 Therefore, until now it was not
possible to synthesize binuclear alkynediyl-bridged bis-
(alkoxycarbene) complexes related to 5, 8, 12, and 16
(OR instead of NMe2).
From a comparison of the IR and NMR spectra of the
symmetrically substituted alkynediyl-bridged complexes
8, 12, and 16 with those of 2 it follows that in the ground
state there is only weak π-interaction between the
(CO)5WdC(NMe2) fragments through the bridge. In
complex 2 π-interaction is prevented by the orthogonal
arrangement of both carbene planes. However, from the
C
16H12N2O10W2 (759.96). It was not possible to completely
separate 2 from 3 and bis(dimethylamino)ethyne. The sample
still contained about 16% of 3 and 9% of bis(dimethylamino)-
1
ethyne, as determined by H NMR spectroscopy. IR (hexane):
ν(CO) 2071 w, 2064 w, 2009 sh, 1956 s, 1937 sh, 1933 sh, 1925
vs cm-1. 1H NMR (-50 °C): δ 3.21 (s, 6 H, NMe), 3.83 (s, 6 H,
NMe). 13C NMR (-50 °C): δ 51.2, 46.0 (NMe), 198.3 (1J W,C
)
128 Hz, cis-CO), 201.0 (trans-CO), 241.4 (WdC). EI-MS, m/z
(%): 760 (7) [M+], 732 (17), 704 (3), 676 (3), 648 (7), 620 (16)
[M+ - n CO, n ) 1-5], 592 (34), 564 (18), 536 (27), 504 (18),
480 (18) [M+ - 10 CO], 380 (18), 352 (58) [W(CO)6+], 73 (100).
3: yield 0.21 g (25% based on NEt4[(CO)5WCH(OMe)Ph]);
mp 79-80 °C; C18H18N2O5W (526.18). It was impossible to
(40) Casey, C. P.; Polichnowski, S. W.; Tuinstra, H. E.; Albin, L. D.;
Calabrese, J . C. Inorg. Chem. 1978, 17, 3045.

2626 Organometallics, Vol. 18, No. 14, 1999
Hartbaum et al.
completely separate 3 from bis(dimethylamino)ethyne, which
was used in about 7-fold excess. The sample of 3 still contained
about 20% of bis(dimethylamino)ethyne, as determined by H
(100) [M+ - n CO, n ) 2-5], 244 (83) [M+ - CO - I]. Anal.
Calcd for C10H6CrINO5 (399.1): C, 30.10; H, 1.52; N, 3.51.
Found: C, 29.98; H, 1.67; N, 3.32.
1
NMR spectroscopy. IR (hexane): ν(CO) 2064 w, 1975 vw, 1949
1,4-B is [p e n t a c a r b o n y l((d im e t h y la m in o )c a r b e n e )-
tu n gsten ]-1,3-bu ta d iyn e (8a ) a n d 1,4-Bis[p en ta ca r bon yl-
((dim eth ylam in o)car ben e)ch r om iu m ]-1,3-bu tadiyn e (8b).
A 1.59 or 1.20 g portion of 6a ,b, respectively (3.00 mmol), and
2.08 or 1.69 g of 7a ,b (3.00 mmol), respectively, along with
0.08 g (0.30 mmol) of [PdCl2(MeCN)2] were dissolved in 15 mL
of toluene. The solution was stirred for 1 day at room
temperature. The color of the solution changed from yellow to
dark brown. Removal of the solvent in vacuo afforded a dark
brown residue which was dissolved in 6 mL of CH2Cl2 and
chromatographed at -40 °C on silica. With pentane/CH2Cl2
(3:1) the red fraction containing 8 was eluted. Evaporation of
the solvent in vacuo afforded 8a ,b as a red solid. 8a : yield
0.96 g (40% based on 7a ); mp 89 °C dec. IR (Et2O): ν(CtCCt
1
vw, 1938 s, 1925 vs cm-1. H NMR (-30 °C): δ 2.75 (s, 6 H,
NMe), 3.21 (s, 3 H, WdCNMe), 3.86 (s, 3 H, WdCNMe), 4.88
(s, 1 H, dC(Ph)H), 7.2-6.9 (m, 5 H, Ph). 13C NMR (-30 °C):
δ 39.4 (Me), 44.4 (Me), 52.9 (Me), 93.2 (dC), 123.5, 126.3, 128.4,
137.1, 155.9 (Ph), 198.2 (1J W,C ) 128 Hz, cis-CO), 203.3 (trans-
CO), 254.6 (WdC). EI-MS, m/z (%): 526 (18) [M+], 498 (29),
470 (37), 442 (64), 414 (62), 386 (100) [M+ - n CO, n ) 1-5].
1-[P en ta ca r bon yl((d im eth yla m in o)ca r ben e)tu n gsten ]-
2-[p en ta ca r bon yl(m eth oxyca r ben e)tu n gsten ]eth yn e (5).
A 3.13 mL portion of a 1.6 M solution of nBuLi in hexane (5.00
mmol) was added at -78 °C to a solution of 2.03 g (5.00 mmol)
of 4a in 30 mL of Et2O. When the yellow solution was stirred
for 30 min at -78 °C, a white precipitate formed. A 1.76 g
(5.00 mmol) portion of [W(CO)6] and 10 mL of THF were added,
and the mixture was stirred at 0 °C for 1 h. At -30 °C 1.23 g
(7.50 mmol) of F3CSO3Me was added and the solution was
stirred for another 30 min. A 150 mL amount of Et2O was
added, and the yellow solution was extracted three times with
50 mL of a saturated aqueous NaHCO3 solution. The yellow
organic layers were combined, and the solvent was evaporated
in vacuo. The yellow residue was dissolved in 10 mL of CH2-
Cl2 and chromatographed at -40 °C on silica with pentane/
CH2Cl2 (2:1). First a light yellow fraction containing unreacted
[W(CO)6] was eluted. The second yellow fraction contained
complex 5. Removal of the solvent in vacuo gave 5 as a
analytically pure yellow powder: yield 1.20 g (31% based on
4a ); mp 147 °C dec. IR (Et2O): ν(CO) 2072 w, 2063 w, 1982 w,
C) 2066 w; ν(CO) 2061 m, 1977 w, 1936 vs, 1925 m, sh cm-1
.
1H NMR: δ 3.56 (s, 6 H, Me), 3.78 (s, 6 H, Me). 13C NMR: δ
47.7 (Me), 51.2 (Me), 100.3 (CR), 109.4 (Câ), 197.6 (1J W,C ) 127.1
Hz, cis-CO), 203.5 (trans-CO), 226.4 (WdC). UV/vis, λmax, nm
(log ꢀ): 492 (3.719) [pentane]; 454 (3.958) [CH2Cl2]. EI-MS,
m/z (%): 808 (2) [M+], 780 (4), 752 (1), 696 (3), 668 (5), 640
(11), 612 (5), 584 (8), 556 (6), [M+ - n CO, n ) 1, 2, 4-9], 352
(66) [W(CO)6+]. Anal. Calcd for C20H12N2O10W2 (808.0): C,
29.73; H, 1.50; N, 3.47. Found: C, 29.84; H, 1.50; N, 3.43. 8b:
yield 0.65 g (40% based on 7b); mp 74 °C dec. IR (Et2O): ν-
(CtCCtC) 2059 w; ν(CO) 2053 m, 1984 w, 1939 vs, 1925 m,
1
sh cm-1. H NMR: δ 3.61 (s, 6 H, Me), 3.90 (s, 6 H, Me). 13C
NMR: δ 49.1 (Me), 100.1 (CR), 113.3 (Câ), 216.5 (cis-CO), 223.8
(trans-CO), 246.4 (CrdC). UV/vis, λmax, nm (log ꢀ): 521 (3.872)
[pentane]; 477 (3.769) [CH2Cl2]. MS (FAB, 3-nitrobenzyl
alcohol), m/z (%): 544 (30) [M+], 488 (85), 460 (6), 432 (87),
376 (27), 348 (40), 320 (13) [M+ - n CO, n ) 2-7]. Anal. Calcd
for C20H12Cr2N2O10 (544.1): C, 44.13; H, 2.22; N, 5.15. Found:
C, 43.91; H, 2.31; N, 5.32.
1
1976 w, 1945 vs, 1927 s cm-1. H NMR: δ 3.40 (s, 3 H, NMe),
3.86 (s, 3 H, NMe), 4.54 (s, 3 H, OMe). 13C NMR: δ 48.4 (NMe),
51.9 (NMe), 63.2 (OMe), 169.2, 174.3 (CR, Câ), 181.7 [1J W,C
)
99.0 Hz, WdC(NMe2)], 196.3 (1J W,C ) 126.5 Hz), 197.0 (1J W,C
) 125.0 Hz, trans-CO), 201.5 (1J W,C ) 126.4 Hz), 202.4 (1J W,C
) 133.3 Hz, cis-CO), 235.9 [1J W,C ) 86.6 Hz, WdC(OMe)]. UV/
vis, λmax (nm) (log ꢀ): 396 (2.823) [pentane]; 389 (3.825) [CH2-
Cl2]. EI-MS, m/z (%): 771 (53) [M+], 743 (7), 687 (20), 659 (43),
631 (74), 603 (100), 575 (66), 547 (54), 519 (17), 491 (22) [M+
- n CO, n ) 1, 3-10]. Anal. Calcd for C17H9NO11W2 (771.0):
C, 26.48; H, 1.18; N, 1.82. Found: C, 26.37; H, 1.34; N, 1.82.
P e n t a c a r b o n y l(1-(d i m e t h y la m i n o )-3-i o d o p r o p y -
n ylid en e)tu n gsten (6a ) a n d -ch r om iu m (6b). A 3.13 mL
portion of a 1.6 M solution of nBuLi in hexane (5.00 mmol)
was added to a solution of 2.03 g of 4a or 1.37 g of 4b (5 mmol)
in 15 mL of Et2O. When the yellow solution was stirred for 30
min at -78 °C, a white precipitate formed. A 1.27 g (5.00
mmol) amount of I2 in 20 mL of THF was added, and the
mixture was stirred for 30 min at room temperature. The
solvent was removed in vacuo. The dark residue was dissolved
in 10 mL of CH2Cl2 and chromatographed at -40 °C on silica.
With pentane/CH2Cl2 (4:1) a yellow fraction containing 6 was
eluted. Removal of the solvent in vacuo afforded 6a or 6b as
a yellow powder.
P en tacar bon yl(1-(dim eth ylam in o)-3-iodo-2,4-pen tadiy-
n ylid en e)tu n gsten (10). A 1.25 mL portion of a 1.6 M
solution of nBuLi in hexane (2.00 mmol) was added to a
solution of 0.86 g (2.00 mmol) of 9 in 20 mL of Et2O. When
the yellow solution was stirred for 30 min at -78 °C, a white
precipitate formed. After 2.00 mmol (0.51 g) of I2 in 10 mL of
THF was added, the mixture was stirred for 30 min at room
temperature. The solvent was removed in vacuo. The dark
residue was dissolved in 5 mL of CH2Cl2 and chromatographed
at -40 °C on silica. With pentane/CH2Cl2 (5:1) a dark yellow
fraction containing 10 was eluted. Removal of the solvent in
vacuo afforded 10 as an orange powder: yield 0.14 g (13%
based on 9); mp 88 °C dec; C12H6INO5W (554.9). The sample
was contaminated with about 15% of the starting complex 9.
We refrained from a rigorous purification of 10 because
compound 9 did not significantly influence the reaction of 10
with 11 and because of the rather poor yield of 10. IR
1
(pentane): ν(CO) 2065 w, 1981 w, 1946 vs, 1937 vs cm-1. H
NMR (-40 °C): δ 3.60 (s, 3 H, Me), 3.77 (s, 3 H, Me). 13C NMR
(-40 °C): δ 27.1 (Cδ), 47.6 (Me), 51.6 (Me), 69.9 (Cγ), 76.0 (CR),
6a : yield 1.37 g (52% based on 4a ); mp 70 °C dec. IR
(pentane): ν(CtC) 2146 vw; ν(CO) 2065 m, 1978 w, 1943 s,
111.8 (Câ), 197.7 (1J W,C ) 128.2 Hz, cis-CO), 204.3 (1J W,C
)
1
1934 vs cm-1. H NMR (-40 °C): δ 3.62 (s, 3 H, Me), 3.74 (s,
130.1 Hz, trans-CO), 229.4 (WdC). EI-MS, m/z (%): 555 (39)
[M+], 527 (17), 499 (100), 471 (53), 443 (94), 415 (97) [M+ - n
CO, n ) 1-5], 400 (27), 372 (42), 344 (33), 316 (31), 288 (44)
[M+ - n CO - I, n ) 1-5].
1,8-B is [p e n t a c a r b o n y l((d im e t h y la m in o )c a r b e n e )-
tu n gsten ]-1,3,5,7-octa tetr a yn e (12). A 0.05 g (0.20 mmol)
portion of [PdCl2(MeCN)2] was added to a solution of 1.11 g
(2.00 mmol) of 10 and 1.44 g (2.00 mmol) of 11 in 10 mL of
toluene. The solution was stirred for 1 day at room tempera-
ture. The solvent was removed in vacuo. The dark brown
residue was dissolved in 5 mL of CH2Cl2 and chromatographed
at -40 °C on silica. The red fraction containing 12 was eluted
with pentane/CH2Cl2 (3:1). Evaporation of the solvent in vacuo
afforded 12 as a red powder: yield 0.61 g (36% based on 11);
3 H, Me). 13C NMR (-40 °C): δ 46.9 (Me), 50.8 (Câ), 51.4 (Me),
97.6 (CR), 197.9 (1J W,C ) 128.4 Hz, cis-CO), 204.5 (1J W,C ) 131.7
Hz, trans-CO), 229.9 (1J W,C ) 88.3 Hz, WdC). EI-MS, m/z
(%): 531 (39) [M+], 475 (55), 447 (40), 419 (100), 391 (87) [M+
- n CO, n ) 2-5], 376 (14), 348 (32), 320 (17) [M+ - n CO -
I, n ) 1-3]. Anal. Calcd for C10H6INO5W (530.9): C, 22.62;
H, 1.14; N, 2.64. Found C, 22.69; H, 1.08; N, 2.64.
6b: yield 0.96 g (48% based on 4b); mp 55 °C dec. IR
(pentane): ν(CtC) 2125 vw; ν(CO) 2058 m, 1983 w, 1946 s,
1
1938 vs cm-1. H NMR (-40 °C): δ 3.65 (s, 3 H, Me), 3.84 (s,
3 H, Me). 13C NMR (-40 °C): δ 48.2 (Me), 49.2 (Me), 54.2 (Câ),
95.8 (CR), 216.6 (cis-CO), 223.9 (trans-CO), 250.2 (CrdC). EI-
MS, m/z (%): 399 (16) [M+], 343 (14), 315 (39), 287 (24), 259

Alkynediyl-Bridged Bis(carbene) Complexes
Organometallics, Vol. 18, No. 14, 1999 2627
mp 97 °C dec. IR (Et2O): ν(CO) 2063 w, 1980 w, 1938 vs cm-1
.
on silica. The red fraction containing 16 was eluted with
pentane/CH2Cl2 (5:2). After evaporation of the solvent in vacuo
16 was obtained as a dark red powder (purity at least 95%):
yield 0.21 g (23% based on 15); mp 113 °C dec; C28H12N2O10W2
1H NMR: δ 3.56 (s, 6 H, Me), 3.76 (s, 6 H, Me). 13C NMR: δ
48.0 (Me), 51.5 (Me), 70.9 (Cγ), 76.8 (CR), 88.1 (Cδ), 112.0 (Câ),
197.6 (1J W,C ) 126.9 Hz, cis-CO), 203.5 (trans-CO), 229.5 (Wd
C). UV/vis, λmax, nm (log ꢀ): 538 (due to the poor solubility of
12 in pentane, log ꢀ could not exactly be determined) [pentane];
506 (3.759) [CH2Cl2]. MS (FAB, 3-nitrobenzyl alcohol), m/z
(%): 856 (17) [M+], 828 (38), 800 (19), 772 (31), 744 (47), 716
(13), 688 (19), 660 (11), 632 (9), 576 (12) [M+ - n CO, n )
1-8, 10]. Anal. Calcd for C24H12N2O10W2 (856.1): C, 33.67; H,
1.41; N, 3.27. Found: C, 33.75; H, 1.47; N, 3.44.
(904.1). IR (Et2O): ν(CO) 2062 w, 1979 w, 1939 vs cm-1 1H
.
NMR ([D8]THF): δ 3.94 (s, 6 H, Me), 4.12 (s, 6 H, Me). 13C
NMR ([D8]THF): δ 48.9 (Me), 52.1 (Me), 61.6 (Cγ), 72.3, 74.0
(CR, Cê), 87.3 (Cδ), 109.4 (Câ), 198.4 (cis-CO), 204.1 (trans-CO),
223.5 (WdC); the Cꢀ resonance is presumably obscured by the
solvent signal. UV/vis, λmax, nm (log ꢀ): 584 (due to the poor
solubility of 16 in pentane, log ꢀ could not exactly be deter-
mined) [pentane]; 565 (3.867) [CH2Cl2]. MS (FAB, 3-nitroben-
zyl alcohol), m/z (%): 904 (5) [M+], 876 (11), 848 (6), 820 (8),
792 (12) [M+ - n CO, n ) 1-4].
P en t a ca r b on yl(1-(d im et h yla m in o)-3-iod o-2,4,6-h ep -
ta tr iyn ylid en e)tu n gsten (14). A 1.25 mL portion of a 1.6 M
solution of nBuLi in hexane (2.00 mmol) was added to a
solution of 0.86 g (2.00 mmol) of 13 in 20 mL of Et2O. When it
was stirred for 30 min at -78 °C, the yellow solution turned
cloudy. Then 0.51 g (2.00 mmol) of I2 in 10 mL of THF was
added and the mixture was stirred for 30 min at room
temperature. The solvent was removed in vacuo. The dark
residue was dissolved in 5 mL of CH2Cl2 and chromatographed
at -40 °C on silica. With pentane/CH2Cl2 (5:1) an orange
fraction containing 14 was eluted. Removal of the solvent in
vacuo afforded 14 as an orange solid: yield 0.13 g (11% based
on 13); mp 97 °C dec; C14H6INO5W (579.0). The sample was
contaminated with about 5% of the starting complex 13. We
refrained from a rigorous purification of 14 because compound
13 did not significantly influence the reaction of 14 with 15
and because of the rather poor yield of 14. IR (pentane): ν-
X-r a y Str u ctu r a l An a lysis of 2. Crystal data: C16H12N2-
O
10W2, Mr ) 760.0, triclinic, space group P1h, a ) 8.530(2) Å, b
) 9.404(2) Å, c ) 15.188(4) Å, R ) 78.91(2)°, â ) 74.47(2)°, γ
) 64.48(2)°, V ) 1055.3(4) Å3, Z ) 2, dc ) 2.392 g cm-3, F(000)
) 700, µ ) 10.947 mm-1, R (Rw) ) 0.0331 (0.0746) for 3705
observed reflections (I > 2.0σ(I)]), largest difference peak/hole
+2.283/-1.160 e Å-3. A single crystal was grown from CH2-
Cl2/hexane (1:1) and mounted in a glass capillary. All data
were collected on a Siemens R3m/V diffractometer at -39 °C
(Wyckoff scan, 5° < 2θ < 54°) with a graphite monochromator
(Mo KR, λ ) 0.710 73 Å). The structure was solved with
Patterson methods and refined by full-matrix least-squares
techniques (Siemens SHELXTL PLUS). The positions of the
hydrogen atoms were calculated in ideal geometry (dCH ) 0.960
Å) and refined in the “riding model”. All other atoms were
refined anisotropically.
(CO) 2065 w, 1981 w, 1947 s, 1937 vs cm-1 1H NMR (-40
.
°C): δ 3.60 (s, 3 H, Me), 3.77 (s, 3 H, Me). 13C NMR (-40 °C):
δ 15.3 (Cê), 48.0 (Me), 51.6 (Me), 54.9 (Cγ), 70.1 (CR), 77.9 (Cꢀ),
88.9 (Cδ), 111.4 (Câ), 197.6 (1J W,C ) 128.5 Hz, cis-CO), 204.2
(trans-CO), 228.7 (WdC). EI-MS, m/z (%): 579 (35) [M+], 551
(9), 523 (59), 495 (35), 467 (41), 439 (32) [M+ - n CO, n )
1-5], 424 (20), 396 (18) [M+ - n CO - I, n ) 1, 2], 128 (100)
[HI+].
Ack n ow led gm en t. Support of this work by the
Fonds der Chemischen Industrie is gratefully acknowl-
edged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinement details, complete positional and thermal
parameters, and bond distances and angles for complex 5 and
NMR spectra of the complexes 2, 3, 10, 14, and 16. This
material is available free of charge via the Internet at
http://pubs.acs.org.
1,12-Bis[p e n t a ca r b on yl((d im e t h yla m in o)ca r b e n e )-
tu n gsten ]-1,3,5,7,9,11-d od eca h exa yn e (16). A 0.74 g (1
mmol) portion of 15, 0.58 g (1.00 mmol) of 14, and 0.03 g (0.10
mmol) of [PdCl2(MeCN)2] were dissolved in 10 mL of toluene.
The solution was stirred for 1 day at room temperature. The
solvent was removed in vacuo. The dark brown residue was
dissolved in 5 mL of CH2Cl2 and chromatographed at -40 °C
OM990145I