1098
Organometallics 1995, 14, 1098-1100
A Stable Bimetallic Copper(1) Titanium Acetylide
Maurits D. Janssen,? Mathias Herres,S LaszM Zsolnai,*David M. Grove,?
and Gerard van Koten*>t
Anthony L. Spek,s Heinrich Lang,*>*
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8,
3584 CH Utrecht, The Netherlands, Ruprecht-Karls Universitat Heidelberg,
Anorganisch-Chemisches Institut, I m Neuenheimer Feld 270, 69120 Heidelberg, Germany, and
BGvoet Center for Biomolecular Research, Laboratory of Crystal and Structural Chemistry,
Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Received November 16, 1994@
Summary: The reaction of [(q5-Ca4SiMe3)2Ti(C=CSiMed&uCl (4) with 1 equiv of L i C s C R (R =
SiMes (5a), t-Bu (5b),Ph ( 5 ~ )affords
)
the monomeric
complexes [(r15-CgH4SiMe~zTi(C=CSiMed27CuC=CR(R
= SiMe3 (3a), t-Bu (3b), Ph ( 3 ~ ) )Complexes
.
3 were
independently prepared by starting from (r/5-Cd&S'iMe&Ti(CECSiMed2 (1) and 1 In [CuC=CRl,, (R = SiMe3
(2a), t-Bu (2b), Ph (2c)) and are the first examples of
stable monomeric bis(r/2-alkyne)(V1-alkynyl)coppercompounds. Reaction of 1 with 1 I4 [CuO-t-BuI4 (6) results
in the formation of the remarkably stable bimetallic
acetylide complex [(r5-Ca4SiMe3)zTi(C=CSiMe~(C=CCu)lz (7) (mp 157 "C dec) by nucleophilic substitution of one of the alkynyl-SiMe3 groups in 1, whereby
t-BuOSiMe3 is eliminated. Other nucleophiles (e.g. Fand EtO-) show a similar reactivity, although in this
case the substitution is much slower and less selective.
Alkynylcopper(1) compounds are generally encountered as polynuclear species which exist either as
discrete aggregates or as o1igomers.l In these species
the alkynyl ligands are 0-and nbonded to copper(1)
centers. Recently we showed that bis(alkyny1)titanocenes
are very useful chelating ligands for the stabilization
of mononuclear bis(q2-alkyne)(v1-aryl)copperand -silver
compounds, where aryl is for example CsH~Me3-2,4,6.~
In order to study intramolecular us intermolecular
alkyne to copper coordination, we are interested in the
isolation of mononuclear bis(y2-alkyne)(l11-alkynyl)copper(1) compounds, using the chelate effect of the
alkynyl units in the bis(alkyny1)titanocene (q5-C5H4SiMe3)2Ti(CWSiMe& (lL3
Addition of (v5-C5H4SiMe3)2Ti(C=CSiMe3)2
(l)3f
to
solutions or suspensions of alkynylcopper(1)compounds,
[CUCECR], (R = SiMes (2a),t-Bu (2b), Ph (2c)),lin a
1:l molar ratio leads to the quantitative formation of
the monomeric complexes [(v5-C5H4SiMe3)2Ti(C=CSiMes)2lCuC=CR (R = SiMe3 (3a), t-Bu (3b), Ph
( 3 ~ ) ) An
. alternative preparative route is the transmetalation of [(y5-C5H4SiMe3)2Ti(C=CSiMe3)21CUC1
(4)
with the corresponding alkynyllithium compounds
LiCECR (R = SiMe3 (5a), t-Bu Gb), Ph ( 5 ~ )(see
)
Scheme 1). Complexes 3 are stable in solution and in
the solid state and can be isolated as orange crystalline
solids by cooling their diethyl ether solutions to -30 "C.
They are soluble in most organic solvents, and solutions
of 3 can be handled safely in air for short periods of time.
Crystals of 3 are stable to air for a few weeks.
The presence of two different C z C stretching frequencies in the IR spectra of 3 indicates that besides
an +bonded alkynylcopper unit, CUCGCR,y2-bonded
disubstituted alkyne ligands are present. Through the
q2-coordination of these alkyne moieties t o the copper
atom in 3, the v(CeC) vibration is shifted from 2012
to 1896 in 3a, 1902 in
cm-l in the parent compound 13f
3b, and 1941 cm-l in 3c. The +bonded alkynyl group,
CzCR, is found at v(C=C) 2035 in 3a, 2095 in 3b, and
2094 cm-l in 3c.
The molecular structure of 3a was determined by a
single-crystal X-ray diffraction a n a l y ~ i s . ~
The molecular structure of 3a (see Figure 1)shows
that [(v5-C5H4SiMe3)2Ti(C4XiMe3)21CuC=CSiMe3 is
monomeric. Both alkyne groups from the bis(alkyny1)titanocene are y2-coordinated to the copper atom C u l ,
(3)(a) Lang, H.; Herres, M.; Zsolnai, L.; Imhof, W. J . Organomet.
Chem. 1991, 409, C7-Cll. (b) Lang, H.; Herres, M.; Zsolnai, L.
Organometallics 1993,12,5008-5011. (c) Lang, H.; Imhof, W. Chem.
Debye Institute, Utrecht University.
Ber. 1992, 125, 1307-1311. (d) Lang, H.; Zsolnai, L. J . Organomet.
1: Universitat Heidelberg.
Bijvoet Center for Biomolecular Research, Utrecht University.
Chem. 1991, 406, C5-C8. (e) Lang, H.; Herres, M.; Zsolnai, L. Bull.
Abstract published in Advance ACS Abstracts, February 1, 1995.
Chem. SOC.Jpn. 1993, 66, 429-431. (f) Lang, H.; Seyferth, D. 2.
Naturforsch. 1990,45B, 212-220.
(1)(a) For a review on metal alkynyls: Nast, R. Coord. Chem. Reu.
1982, 47, 89-124. (b) [Cu(C=CPh)(PMea)ld: Corfield, P. W. R.;
(4) Single crystals of 3a were grown by cooling a saturated Et20
solution to -20 "C. Crystal data for 3a: C31H53CuSibTi, red crystal
Shearer, H. M. M. Acta Crystallogr. 1966, 21, 957-965. (c)
[Ag(C=CPh)(PMea)]: Corfield, P. W. R.; Shearer, H. M. M. Acta
(0.38 x 0.38 x 0.63 mm), monoclinic, space group P21/c, with a =
Crystallogr. 1966,20, 502-508. (d) [Cu3013-rl1-C~CPh)*(dppm)31BF~ 20.9981(9) A b = 12.0851(9)A, c = 15.2434(10)A, /3 = 100.146(4)", V
and [Cu3013-r11-C~CPh)(dppm)31(BF4)2:
Diez, J.; Gamasa, M. P.; Gi= 3807.7(4)A3, 2 = 4, dcalcd= 1.182 g ~ m -F(000)
~ , = 1440, p(Mo Ka)
= 9.4 cm-l. A total of 9267 (8447 unique) reflections (0.99 < 0 < 27.50";
meno, J.; Lastra, E.; Aguirre, A.; Garcia-Granda, S. Organometallics
1993, 12, 2213-2220. (e) [Cu3013-r11-C~C-t-Bu)~3-Cl)(dppm)3]PF~: w/20 scan; T = 150 K) were measured on an Enraf-Nonius CAD-4T
Yam, V. W.-W.; Lee, W.-IC; Lai, T.-F. Organometallics 1993,12,2383rotating anode diffractometer using graphite-monochromated Mo K a
2387. (f) [Cu3(SAr)zC=C-t-BuIn: Knotter, D. M.; Spek, A. L.; van
radiation (1 = 0.710 73 A). Data were corrected for Lorentz polarizaKoten, G. J . Chem. SOC.,Chem. Commun. 1989,1738-1739. Knotter,
tion effects and absorption (DIFABS minimum and maximum correcD. M.; Spek, A. L.; Grove, D. M.; van Koten, G. organometallics 1992,
tion: 0.826/1.103). The structure was solved by direct methods
11, 4083-4090. (g) [CuC=CPhl,: Corfield, P. W. R.; Shearer, H. M.
(SHELXS86) and difference Fourier techniques and refined on F by
M. In Organometallic Compounds; Coates, G. E., Green, M. L. H.;
full-matrix least squares (SHELXL93) to an R1 value of 0.055 for 5854
Wade, K., Eds.; Chapman and Hall: London, 1977; Vol. 2. (h)
reflections with F,,> 4 d F J and 343 parameters, wR2 = 0.151, S =
[CUCEC-t-Buls: Coates, G. E.; Parkin, C. J.Inorg. Nucl. Chem. 1961,
1.024, and w-l = (02(Fo2) (0.0826P)2),whereP = (max(FO2,0) 2FC2)/
22, 59. (i) [MCSCCF~I, (M = Cu, Ag): Haszeldine, R. N. J. Chem.
3. Hydrogen atoms were introduced on calculated positions and refined
SOC.1961, 588-591.
riding on their carrier atoms. All non-H atoms were refined with
(2) Janssen, M. D.; Herres, M.; Spek, A. L.; Grove, D. M.; Lang, H.;
anisotropic thermal parameters. A final Fourier map showed no
van Koten, G. To be submitted for publication.
residual density outside -0.43 and 0.58 e/A3 (near Cul).
* To whom correspondence should be addressed.
+
@
+
0276-733319512314-1098$09.00/0 0 1995 American Chemical Society
+
Organometallics, Vol. 14,No. 3, 1995 1099
Communications
Scheme 1
1
'SiMe3
Me3Si
2
1
3a: R = SiMe3
3b: R='Bu
3 ~ R: = P h
Me&
I
%Me3
4
5
Figure 1. Molecular structure of 3a (ORTEP, thermal
ellipsoids at 50%probability). Selected bond distances (A)
and bond angles (deg): Til-Cul, 2.9665(8); Cul-C11,
1.898(3); Cul-C1, 2.074(4); Cul-C2, 2.112(4); Cul-C6,
2.069(4); Cul-C7, 2.111(4); C1-C2, 1.236(5); C6-C7,
1.240(5); Cll-C12, 1.215(6); Til-C1, 2.081(4); Til-C6,
2.095(4); Til-Cl-C2,165.0(3); C1-C2-Sil, 162.8(3);TilC6-C7, 165.4(4); C6-C7-Si2, 162.9(4); Cul-C11-C12,
175.6(3);Cll-C12-Si3, 171.4(4).
while the alkynyl ligand from the starting alkynylcopper(1) compound is exclusively +coordinated. The
C=C bond lengths of the Ti(C=CSiMe& unit are
lengthened from a n average of 1.208 8, in 13bto 1.236( 5 ) 8, (Cl-C2) and 1.240(5) A (C6-C7) in 3a. The
copper atom possesses a trigonal-planar geometry and
is surrounded by the two +bonded alkynyl ligands from
1 and by one +bonded alkynyl ligand and represents
the first example in organocopper chemistry for which
the monomeric structure is brought about by q2-bonded
alkyne ligands. The Ti-CW-Si units are significantly
bent (Til-C1-C2 = 165.0(3)", Til-C6-C7 = 165.4(4)",
C1-C2-Si1 = 162.8(3)", C6-C7-Si2 = 162.9(4)"; see
Figure 1) due to the q2-coordination of the
Ti-C=C-SiMes ligands to the copper atom. The same
behavior is observed in similar bis(q2-alkyne)CuXcomplexes (X = singly bonded organic or inorganic ligand).2,3
The Vl-bonded (trimethylsily1)ethynylunit, CuC=CSiMes,
has a geometry typical for a noncoordinating alkynyl
ligand (Cll-C12 = 1.215(6) A, Cul-C11-Cl2 =
175.6(3)", Cll-C12-Si3 = 171.4(4)"; see Figure 1).
Surprisingly, complex 1 reacts selectively with 1/4
[CuO-t-Bul4(6)5in Et20 at ambient temperature to yield
quantitatively the dimeric complex [(y5-C5H4SiMe3)2Ti(C=CSiMe3)(C=CCu)l2 (7). The intermediate formation
of the bis(y2-alkyne) coordination complex [(v5-C5H4SiMe3)2Ti(C~CSiMe3)21CuO-t-B~
( 8 ) is not observed;
elimination of t-BuOSiMe3 (as detected with GC-MS)
and the formation of 7 is instantaneous and quantitative. Other nucleophiles ( e g . F- and EtO-) show a
similar reactivity toward complexes 3, although the
reaction is much slower and less selective due to
competitive cleavage of the Ti-C=C bond (see Scheme
2).
Complex 7 is a dark red solid which melts with
decomposition at 157 "C; it is air-stable and is soluble
in most organic solvents. The thermal and kinetic
stability of 7 is remarkable, since bimetallic acetylide
species of copper(1)(CuCgCM) are usually very reactive
and can be explosive.lg
A cryoscopic molecular weight determination of 7 in
benzene indicates that it is dimeric in solution. Variable-temperature lH NMR experiments indicate that 7
maintains this aggregation state in solution; in the
temperature range 207-353 K the lH spectra remain
essentially identical.
The molecular structure of 7 (see Figure 216 comprises
(5) Lemmen, T. H.; Goeden, G. V.; H u f h a n , J. C.; Geerts, R. L.;
Caulton, K. G. Inorg. Chem. 1990,29,3680-3685.
(6) Single crystals of 7 were grown from a saturated diethyl ether
solution at -30 "C. 7 contains one molecule of Et20 in the unit cell:
C46H70Cu2Si6Ti2.Et201dark orange crystal (0.30 x 0.20 x 0.40 mm),
secured in a glass capillary and sealed under nitrogen, triclinic, space
group Pi, with u = 11.714(3)A,b = 12.190(4)A,c = 12.581(3)A, a =
101.12(2)",j3 = 117.39(2)", y = 90.54(2)", V = 1555.2(8) A3, 2 = 1, dcdd
= 1.241 g cm-3, F(OO0)= 616, p(Mo Ka)= 10.7cm-'. Diffraction data
were collected on a Siemens (Nicolet Syntex) R3mN difiactometer by using the 8-20 technique (28 limits 2 5 20 5 47", scan range
0.75", scan speed 3 5 w 5 29.3" min-' and Mo Ka radiation (1 =
0.710 79 A). The structure was solved by direct methods (SHELXTLPLUS) on 4240 unique reflections with F > 4dF.l. Non-hydrogen atoms
were refined anisotropically, and hydrogen atoms were fixed at
calculated positions (number of variables 284). An empirical absorption correction was applied. Final discrepancy indices: R = 0.030 and
wR = 0.031.
1100 Organometallics, Vol. 14,No.3, 1995
Communications
Scheme 2
MegSi
1
Me3Si’
I
SiMe3
7
I
Me3Si
‘SiMe3
c12a
Figure 2. Molecular structure of 7 (ORTEP, thermal
ellipsoids at 50% probability). Selected bond distances (A)
and bond angles (deg): Til-Cul, 2.911(1); Cul-Cula,
2.998(1); Cul-C22, 2.107(2); Cul-C23, 2.161(3); CulC23a, 1.920(3); Cul-C17, 2.030(3); Cul-C18, 2.086(3);
C17-C18,1.234(3); C22-C23,1.243(4); Til-C17,2.097(3);
Til-C22,2.079(3); Til-C17-C18,164.6(2); C17-Cl8-Si3,
165.0(2);Til-C22-C23,163.4(2); C22-C23-Cula, 165.0(2);
C17-Til-C22, 90.5(1);Cul-C23-Cula, 94.4(1).
a dimer of the bimetallic acetylide (y5-CsH4SiMe&Ti(CzCSiMes)(C=CCu) in which the alkynyl ligand within
the Ti-CEC-Cu entity is also +bonded to a second
copper atom, thus forming an alkyne-bridged dimer. The
C s C bond lengths of the alkyne ligands within this
building block are lengthened from 1.208 A in 1 to
1.234(3) A (TiCZCSi) and 1.243(4) A (TiCSCCu) in 7.
Each copper atom exhibits a somewhat distorted trigonal planar geometry with two r2-and one rl-bonded
alkynyl ligands. The Ti-CW-Cu
moiety deviates
from linearity upon its r2-coordination to a second
copper atom (Cull (Til-C22-C23 = 163.4(2)”,CulaC23-C22 = 165.0(2)”). The central Cuz(r$C=C)z core
of 7 has a structural arrangement which corresponds
t o that observed in most polynuclear alkynylcopper(1)
compounds, in which the alkynyl ligands are rl- as well
as +bonded to copper atoms, thus forming an infinite
zigzag chain.lg
In the IR spectrum of 7 two distinct v(C=C) vibrations
at 1896 cm-’ (TiCZCSi) and 1844 cm-l (TiCZCCu) are
observed. These IR data are in agreement with the v2coordination of both TiCWSi and TiC=CCu entities to
the copper atom. Note that the C=C vibration frequency for the TiCGCSi unit in 7 is the same as that
found in complex 3a.
The bis(172-alkyne)(771-alkynyl)complexes 3 and 7 are
surprisingly stable. They are selectively formed by selfassembly from alkynylcopper or copper alkoxide aggregates and the bis(alkyny1)titanocene 1. Moreover,
dimeric 7 can be formed from monomeric 3, when
nucleophiles are present in solution (Scheme 2).
The coordination properties of the chelating bis(alkyne) ligand 1 are currently being investigated for
the synthesis and isolation of stabilized mononuclear
aryl-, alkenyl-, or alkylcopper(1)fragments out of heterocopper and cuprate reagents. As an example, the
isolation of C(r5-C5H4SiMe3)zTi(C”CSiMes)zICu{C6H4NMez-4) from in situ prepared c~(C6H4Nbfez-4)~
has
recently been achieved.2
Acknowledgment. This research was supported in
part by the Deutsche Forschungsgemeinschaft, the
Volkswagenstiftung, and the Fonds der Chemischen
Industrie (Germany) and also in part (A.L.S.) by the
Netherlands Foundation for Chemical Research (SON)
with financial aid from the Netherlands Organization
for Scientific Research (NWO).
Supplementary Material Available: Text giving synthetic procedures and analytical and spectroscopic data for 3
and 7 and tables of all atom parameters for 3a and 7 (27
pages). Ordering information is given on any current mast-
head page.
OM940874S
(7) van Koten, G.;Leusink, A. J.;Noltes, J. G. J.Organomet. Chem.
1976,85,105-114.