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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. +
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0276-733319512314-1098$09.00/0 0 1995 American Chemical Society
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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.
