Organometallics 1996,14,2961-2968
2961
Heterobimetallic a,mAcetylide-Bridged Complexes from Disubstituted 1,3-Butadiynes Uwe Rosenthal,” Siegmar Pulst, Perdita Arndt, Andreas Ohff, Annegret Tillack, Wolfgang Baumann, Rhett Kempe, and Vladimir V. Burlakovf Max-Planck-Gesellschaft, Arbeitsgruppe “Komplexkatalyse”an der Universitat Rostock, Buchbinderstrasse 5-6, 0-18055 Rostock, Germany Received December 12, 1994@
It has been shown that a nickel(0) complex of bis(trimethylsilyl)butadiyne, (Ph3P)zNi(r2Me3SiC=CC=CSiMe3), readily reacts with the titanocene CpzTi(MesSiC=CSiMes) and zirconocene CpzZr(THF)(Me3SiC=CSiMed complexes t o form the heterobimetallic, doubly (M = Ti acetylide bridged complexes Cp2MCU-r1:r2-C=CSiMe3)Ni(PPh3)CU-y1:r2-C~CSiMe3) (l),M = Zr (2)). The structures of these complexes have been established by X-ray crystal structure analysis. Two o,n-bridging acetylide units are o-bonded to different metals and n-bonded to the second metal. Compound 1 in solution at 303 K is highly fluxional. An NMR study showed that at 190 K a n equilibrium exists between one isomer with two nonequivalent and another isomer with two equivalent acetylide units. The cleavage of the central C-C single bond of the butadiyne was not observed in the reaction of the unsymmetrically substituted butadiyne PhC=CC=CSiMe3 with titanocene “CpzTi”generator CpzTi(Me3SiCsCSiMe3). The product is a bridging tetradehydro-(l-3-q):(2-4-y)-trans,transbutadiene unit (zigzag butadiyne) between two titanium centers in CpzTi{p-(1-3-~):(2-4r)-trans,tran~-PhC~CC~CSiMe3}TiCpz (5). If the phenyl(trimethylsily1)butadiyne is complexed by nickel(O),the reaction with the titanocene generated from CpzTi(MesSiC=CSiMes) yields the heterobimetallic complex Cp2Ti@-y1:1;12-C=CSiMe3)01-);l’:y2-CWPh)Ni(PPh3) (6). Both acetylide units are a-bonded to the titanium atom and n-bonded to the nickel atom, giving a “tweezerlike” structure. Introduction
Interestingly, in the reaction of CpzZr(py)(MesSiCzCSiMe3) and tBuC+K+CtBu cleavage was not observed but 1:l complexation gave the smallest known the reactions of LzNi cyclocumulene ~ o m p l e x .Also, ~ fragments with 1,4-disubstituted 1,3-butadiynes gave no cleavage product but 1:l or 2:l n-complexe~.~ In the series of binuclear complexes LnM1(p-C=CR1)(p-CWR2)M2L, the bonding of the p-CrCR ligand can be widely varied, depending on different metals, ligands, and substituents.6 In the literature, complexes with R1 = R2 usually were synthesized by reacting two alkali-metal acetylides with one LnM1C12 compound and subsequently adding the second metal fragment L,M2.6 More re-
Recently we have reported the reaction of the titanocene complex CpaTi(MesSiCWSiMe3)with the disubstituted butadiyne MesSiCzCCWSiMe3, in which the starting butadiyne is cleaved by the generated “titanocene” to yield the dinuclear complex [CpzTi(p-r1:q2-CWSiMe3)lz(31.l Later we could show that the reaction products of disubstituted butadiynes R1C=CCWR2 and titanocene “CpzTi” strongly depend on the nature of the substituents R1 and R2. For R1 = R2 = Ph, t-Bu and R1 = SiMe3, R2 = Ph, t-Bu binuclear complexes with intact 1,4-disubstituted tetradehydrop-( 1-3-r):(2-4-~)-trans,trans-butadiene units between two titanium centers are formed.2 The reason for the different reactions is the decrease of electron density (4)Rosenthal, U.;Ohff, A,; Baumann, W.; Kempe, R.; Tillack, A,; Burlakov, V. V. Angew. Chem. 1994,106,1678. in the central C-C bond caused by two SiMe3 substit(5)(a) Rosenthal, U.; Pulst, S.; Arndt, P.; Baumann, W.; Tillack, uents.2 A.; Kempe, R. 2.Naturforsch. 1995,50b,368. (b) Rosenthal, U.;Pulst, On the other hand, with CpzZr(THF’XMe3SiCWSiMe3) S. Arndt, P.; Baumann, W.; Tillack, A.; Kempe, R. Z. Naturforsch. 1995, 50b,377. the cleavage reaction is favored in all cases, yielding (6)(a) Erker, G.; Fromberg, W.; Mynott, R.; Gabor, B.; Kriiger, C. the symmetrically and unsymmetrically substituted u,nAngew. Chem. 1986,98,456. (b) Erker, G.; Fromberg, W.; Benn, R.; Mynott, R.; Angermund, K.; Kriiger, C.Organometallics 1989,8,911. acetylide-bridged complexes Cp2ZrOL-)71:172-C~CR1)CU-rl: (c) Erker, G.; Albrecht, M.; Kriiger, C.; Nolte, M.; Werner, S. Organoy2-C=CR2)ZrCp2.3This result is explained by the larger metallics 1993,12,4979. (d) Kumar, P. N. V. P.; Jemmis, E. D. J . size of Zr and longer Zr-C bond lengths which for Zr A m . Chem. SOC.1988,110,125.(e)Yasufuku, K.; Yamazaki, H. Bull. Chem. SOC.Jpn. 1972,45,2664. (fl Lang, H.; Zsolnai, L. J . Organomake the type of structure without a central C-C bond met. Chem. 1991,406,C5. (g) Lang, H.; Herres, M.; Zsolnai, L.; Imhof, more stable compared to Ti.6d W. J . Organomet. Chem. 1991, 409, C7. (h) Lang, H.;Imhof, W. ~~
Permanent address: Institute of Organoelement Compounds of the Russian Academy of Sciences, Moscow, Russia. Abstract published in Advance ACS Abstracts, May 15,1995. (1)Rosenthal, U.;Gorls, H. J . Organomet. Chem. 1992,439,C36. (2) (a) Rosenthal, U.; Ohff, A.; Tillack, A.; Baumann, W.; Gorls, H. J . Organomet. Chem. 1994,468,C4. (b) Sekutowski, D. G.; Stucky, +
@
G. D. J . A m . Chem. SOC.1976,98,1376.
(3)Rosenthal, U.;Ohff, A.; Baumann, W.; Kempe, R.; Tillack, A.; Burlakov, V. V. Organometallics 1994,13,2903.
~
~~
~
Chem. Ber. 1992,125,1307. (i)Lang, H.; Herres, M.; Zsolnai, L. Bull. Chem. SOC.Jpn. 1993, 66, 429. (i) Ciriano, M.; Howard, J. A. K.; Spencer, J. L.; Stone, F. G. A,; Wadepohl, H. J . Chem. SOC.,Dalton Trans. 1979,1749. (k) Fornies, J.;Gbmez-Saso, M. A.; Lalinde, E.; Martinez, F.; Moreno, M. T. Organometallics 1992, 11, 2873. (1) Berenguer, J. R.; Falvello, L. R.; Fornices, J.; Lalinde, E.; Tomas, M. Organometallics 1993,12,6.(m) Berenguer, J. R.; Fornies, J.; Lalinde, E.; Martin, A. Angew. Chem. 1994,106,2196.(n)Lotz, S.; Van Rooyen, P. H.; Meyer, R. Adu. Organomet. Chem. 1995,37,219 and references
therein.
0276-733319512314-2961$09.0010 0 1995 American Chemical Society
Rosenthal et al.
2962 Organometallics, Vol. 14, No. 6, 1995 Scheme 1 MesSi,
,SiMe3
'SiMe3
Ib
cently, the reaction of CpsTiClz, magnesium, and Me3SiC=CCWSiMes was reported t o form a Ti-Mg bis(acetylide) complex in 40% yield.7 Here we describe further results of our method to cleave butadiynes by homo- or heterobimetallic systems and demonstrate the preparation of all possible combinations of such types of bis(acety1ide)-bridgeddinuclear complexes with (a) M1 = M2 and R1 = R2,1j3(b) M1 = M2 and R1 t R2,3(c) M1 t M2 and R1 = R2, and (d) M' t M2 and R1 t R2.
present. The 'H NMR spectrum shows two signals of the same intensity for the SiMes groups, in agreement with the unsymmetrical structure la,together with one smaller signal, indicating a second isomer in solution have the symmetrical structure lb. Correspondingly, for the Cp rings two resonances of different intensity are observed as well. The ratio of the unsymmetrical isomer t o the symmetrical one is about 5 1 . The 13C NMR resonances of the acetylide carbon atoms could not be detected. At 303 K the 31PNMR shows only one signal. The 'H NMR spectrum exhibits one signal for the SiMe3 groups and one signal for the Cp rings. The spectra at 303 K can be explained by a rapid exchange between a symmetrical and an unsymmetrical structure. A similar observation had been made in the case of the complex (C5H4tB~)2ZrOL-C=CR)Z~p2~-C~CR) and was taken as evidence that the acetylide ligands rapidly change places between the two Zr centers.6b The reaction of the nickel(0) complex (Ph3P)2Ni(y2MesSiC=CC=CSiMes) with the zirconocene alkyne complex CpzZr(THF)(MeaSiC=CSiMes) in THF at 20 "C yields the heterobimetallic doubly acetylide bridged complex Cp2Zr(p+:v2-C=CSiMe3)Ni(PPh3)@-v1:v2-C=CSiMe3)(2), the zirconocene analogue of 1.
Results and Discussion We found that a nickel(0) complex of bidtrimethylsilyl)butadiyne, (Ph3P)2Ni(y2-Me3SiC+X=CSiMe3),5 readily reacts in toluene at 50 "C with the titanocene generator CpzTi(Me3SiC=CSiMe3)to form the heterobimetallic, doubly acetylide bridged complex CpzTi@v1:v2-C=CSiMe3)Ni(PPh3)01-yl:y2-CWSiMe3) (1).
$,
(Ph3P)zNi
SiMe3
'
SiMe3 cpzTi4sik3
-P PPh3
D
- Me3SiCzSiMe3 SiMe3
-THF
1
I
-
Me3SiCfiiMe3
SiMe3
~e~si7' 1
Complex 1 is a red-brown, crystalline solid (mp 127133 "C under argon) which is soluble in THF and toluene and insoluble in n-hexane and was characterized by IR and NMR spectroscopy and X-ray crystallography. The infrared absorptions of the C=C bond in 1 are in the region characteristic of up-acetylide-bridged complexes. The assignment of the different metal n-complexed triple bonds was made in view of the fact that a more extended decrease in VC-C is observed in titanocene alkyne complexes in comparison to nickel(0)complexes.8 Therefore, the band at 1780 cm-l is assigned to the Tin-complexed and the band at 1911 cm-l to the Ni-ncomplexed acetylide unit. At 190 K the 31PNMR spectrum of 1 displays two signals, indicating that two isomers (Scheme 1) are (7) Troyanov, S. I.; Varga, V.; Mach, K. Organometallics 1993, 12, 2820. ( 8 ) Rosenthal, U.;Oehme, G.; Burlakov, V. V.; Petrovskii, P. V.; Shur, V. B.; Vol'pin, M. E. J. Organomet. Chem. 1990, 391, 119.
Complex 2 is a red-brown, crystalline solid (mp 145150 "C under argon) which is soluble in THF and toluene and insoluble in n-hexane and was characterized by IR and NMR spectroscopy and X-ray crystallography. The spectral data for the zirconocene complex 2 are very similar to those for the analogous titanocene complex 1. On the basis of the same considerations, the absorption at 1876 cm-l in the IR spectrum of 2 is assigned to the nickel and that at 1771 cm-l to the zirconium n-complexed CsCSiMes group. In the lH NMR spectrum of 2 at 303 K one signal due to the Cp rings and two signals due to the SiMe3 groups are observed. The I3C NMR spectrum displays one Cp-ring signal and four signals due t o the acetylide carbon atoms. In contrast t o compound 1,the bridging acetylide units in 2 are nonequivalent at room temperature. The structures of 1 (Figure 1) and 2 (Figure 2) have been established by X-ray diffraction. Table 1 lists crystallographic data. Positional parameters and selected bond lengths and angles of 1 are given in Tables 2 and 3 and those of 2 in Tables 4 and 5. Table 6 lists selected structural data for 1 and 2 in comparison with those for the isostructural homobimetallic complexes [CpzTi@-);11:172-C'CSiMe3)12 (3)lJ2and CCp2Zr@-v':v2-C=CSiMe3)12 (4h3J3
Heterobimetallic a,n-Acetylide-BridgedComplexes
Organometallics, Vol. 14,No. 6, 1995 2963
CpzTi(PhCWSiMe3) (1.289(4), 1.279(4) CpzZr(THF)(Me3SiC=CSiMes)(1.302(9) A).lib In both complexes 1 and 2 the Ni-C(l) a-bond (1.828(5) and 1.835(8)A) is shorter than the Ti-C(3) (2.067(4) A) and Zr-C(3) a-bonds (2.178(9)A). The latter are very similar t o the a-bonds in the corresponding complexes 3 (2.069(1)A) and 4 (2.191(5) A). The angle C(3)-C(4)-Si(2) of the Ni(PPh3)-complexed triple bond in 1 (145.8(4)") and 2 (141.7(7)")is about 20" smaller than the angle C(l)-C(2)-Si(l) of the titanocene- or zirconocene-complexed triple bond in 1 (164.4(4)") or 2 (159.2(7)"). The distances Ti-C(l) (2.331(4) A) and Zr-C(l) (2.385(7) A) are between 0.2 and 0.3 A shorter than the Ti-C(2) (2.628 A) and the Zr-C(2) (2.557 A) distances. This might explain the large angles for the titanocene- or zirconocene-complexed triple bond in 1 and 2. Comparable angles C-C-Si are found in the complexes 3 (141.5(2)"), 4 (142.5(4)"), CpzZr(THF)(Me3SiC=CSiMes)(143.5(6)",llb Figure 1. Molecular structure of complex 1, shown by an (Ph3P)zNi(MesSiC=CSiMes) (143.3(1)"),9aCpz134.4(6)"), ORTEP plot at the 40% probability level. Ti(PhCWSiMe3) (148.2(2)", 151.9(2)"),11a and (Ph3P)zNi(PhCWSiMe3) (138.7(5)").9b The distance M(l)-M(2) of 2.728(1)A in 1 and 2.830(1) A in 2 cannot be considered as a direct bonding interaction between the nickel atom and the metallocene center. Bonding interactions can be excluded for the bis(metal1ocene) species 3 (3.550(3) A) and 4 (3.522(2) A). Complex 1 is formally a Ti(III)/Ni(I)and complex 2 a Zr(III)/Ni(I) species and should therefore exhibit paramagnetism. However, both compounds are diamagnetic. The reason could be an antiferromagnetic coupling between the metal centers or an electronic coupling between the metals via the bridging alkynyl groups. Because of the long metal-metal distances in 1 and 2, we favor an electronic coupling via the unsaturated bridging groups as in 3 and 4.3,6b The relatively short Ti-C(3) and Zr-C(3) bond lengths in 1 and 2 are good arguments for a considerable n-interaction between the metal centers and the organic Figure 2. Molecular structure of complex 2, shown by an n-system across the a-bonds (Chart l), as found for [CpzORTEP plot at the 40% probability level. ZrOl-q1:y2-C~CR)12-type complexes.6b In contrast, the Ni-C(l) distances (1, 1.828(5) A; 2, The most interesting feature of the structures of 1 and 1.835(8) A) justify the description as single bonds which 2 is that they differ from the "tweezerlike" structure, in NiBr(C=CSiMes)are slightly longer than those found e.g., in the titanium-nickel complex (q5-CsH&iMe3)2Ti(PMe3)z (1.773(23) and 1.818(25)).10 @M,J:~~-C=CR)~N~(CO).~~ In this complex both acetylide Complexes 1 and 2 are stable at room temperature. groups are a-bonded to the titanium atom and n-coorCompound 1 reacts with an excess of CO to give a dinated to the Ni(C0) fragment. The structures of 1 mixture of the "tweezerlike" titanium-nickel complex and 2 are unsymmetrical and display the two acetylide CpzTi(p-q1:q2-C=CSiMe3)2Ni(C0),6h (PhaP)Ni(CO)3,and groups a-bonded to different metals and q2-bonded on PPh3, as shown by comparison of IR and NMR spectra. n-coordination t o the other metal, as in the recently Under analogous conditions for complex 2 mainly the published example CpzTiOL-ql:q2-C~CtBu)~(PPh3)CU-?7l: unchanged starting material was obtained. Both comV~-C=C~BU).~~ plexes on reaction with an excess of PhCECCECPh and In the complexes 1 and 2 the Ni-n-complexed triple Me&iC=CC%CSiMes even at 90 "C in toluene gave only bond C(3)=C(4) (1.261(7) A in 1 and 1.284(13) in 2) trimerization products of PhCECCECPh and not the is slightly longer than the Ti- or Zr-n-complexed triple unsymmetrically substituted diyne PhC=CC=CSiMea bond C(l)=C!(2) (1.233(7) A in 1 and 1.236(12)A in 2). as a result of disproportionation in a "C-C a-bond The latter is almost identical with the distances in the metathesis". homobimetallic complexes 3 (1.244(3) A) and 4 (1.249(10)Klein, H.-F.; Zwiener, M.; Petermann, A.; Jung, T.; Cordier, G.; (7) A). Comparable monometallic alkyne complex CzC Hammerschmitt, B.; Florke, U.; Haupt, H.-J.; Dartiguenave, Y. Chem. bond lengths are as follows: (PhP)zNi(Me3SiC4SiMed Ber. 1994,127, 1569. (11) (a) Burlakov, V. V.; Polyakov, A. V.; Yanovsky, A. I.; Struchkov, (1.256(2) A);ga(PhaP)zNi(PhC=CSiMes)(1.273(8) (9) (a) Rosenthal, U.; Schulz, W.; Gorls, H. 2. Anorg. Allg. Chem. 1987,550, 169. (b) Bartik, T.; Happ, B.; Iglewsky, M.; Bandmann, H.; Boese, R.; Heimbach, P.; Hoffmann, T.; Wenschuh, E. Organometallics 1992,11, 1235.
Y. T.; Shur, V. B.; Vol'pin, M. E.; Rosenthal, U.; e r l s , H. J . Orgunomet. Chem. 1994,476,197. (b) Rosenthal, U.; Ohff, A,; Michalik, M.; Gorls, H.; Burlakov, V. V.; Shur, V. B. Angew. Chem. 1993,105,1228. (12) Wood, G. L.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem. 1989,28,382. (13) Metzler, N.; Noth, H. J . Organomet. Chem. 1993,454,C5.
2964 Organometallics, Vol. 14,No.6,1995
Rosenthal et al.
Table 1. Crystallographic Data compd chem formula lattice constants a (A) b (A) c (A) P (deg) temp (K) space group cryst dimens (mm) cryst color p (mm-’) abs cor 8 range (deg) no. of rflns (measd) no. of rflns (indep) R(int) no. of rflns (obsd),I > 2 d I ) R1 (I> 2u(I)) wR2 (all data) non-H atoms refined treatment of H atoms
1.0.5THF C40.sH43NiPSizTi
2.0.5THF C40H43Ni00,~PSiZr
3 C33H34SiTi~
4
22.389(1) 9.4295(3) 36.182(3) 90.516(5) 293 c2tc 0.5 x 0.4 x 0.3 red-brown 0.833 no 2.13-24.10 12 297 6049 0.049 4882 0.078 0.210 anisotropic (except solvent) geom riding
22.537(2) 9.4457(7) 36.568(3) 90.390(8) 293 c2tc 0.5 x 0.4 x 0.4 red-brown 0.881 Y-scan 2.40-24.99 7684 6847 0.088 4937 0.057 0.232 anisotropic (except solvent) geom riding
8.2232(6) 32.86(1) 10.479(1) 102.77(1) 293 P2da 0.6 x 0.2 x 0.1 green 0.642 Y-scan 2.61-24.97 5198 4843 0.045 3045 0.066 0.245 anisotropic geom riding
12.981(1) 13.052(1) 21.288(2) 95.008(7) 293 P21ta 0.6 x 0.5 x 0.3 red-brown 0.851 Y-scan 2.36-24.98 6618 6322 0.038 4642 0.040 0.123 anisotropic geom riding
As previously reported, “CpzTi”alone does not cleave disubstituted butadiynes R1C=CC=CR2 with R1 = R2 = Ph, t-Bu and R1 = SiMes, R2 = Ph, t-Bu. The reaction products are binuclear complexes with intact 1,Cdisubstituted tetradehydro-p-(l-3-v):(2-4-v)-trans,transbutadiene units between two titanium centers.2 Preparation and some properties of 5 were reported in a preliminary communication.2 SiMe3
Ph
toluene at 90 “C only decomposition occurs and no symmetrically substituted diynes PhC=CC=CPh and MesSiCzCCsCSiMes were obtained as a result of a “C-C a-bond metathesis”. Surprisingly, the cleavage reaction of PhC=CC=CSiMes, which does not occur with “CpzTi” alone (see above), succeeded when a bimetallic Ni-Ti system was used. The reaction of nickel(0) complex ( P ~ ~ P ) z N ~ ( ~ ~ - P ~ C = C with C = the C S ~ti-M ~ ~ ) ~ ~ tanocene alkyne complex CpzTi(MesSiCWSiMe3) in toluene at 80 “C yields the heterobimetallic, doubly acetylide bridged complex CpzTi01-v1:v2-C~CPh)01-v1: v2-C=CSiMe3)Ni(PPhs)(61, which has a structure different from those of 1 and 2.
1+ Ph
SiMe3
(PhaPhNi Qi~e3 5
The structure of 5 has now been determined by X-ray diffraction (Figure 3). Table 1 lists crystallographic data. Positional parameters and selected bond distances and angles of 5 are given in Tables 7 and 8. Structures with intact 1,4-disubstituted tetradehydro-p-(l-3-v):(2-4-v)-trans,trans-butadiene units between two titanocene centers are well-known.2 They differ markedly from the type discussed above with upbridging acetylide units. The structure displays the intact Cq chain (“zigzag butadiyne”) between two titanium atoms. The titanium atoms and the diyne ligand are coplanar to within 0.017(5) A with titanium-carbon a-bond distances of 2.083(7) and 2.337(7) A in the Ph-substituted part and 2.164(7) and 2.114(7) A in the SiMes-substituted part. The alternatin C-C bond lengths of 1.327(9), 1.511(9), and 1.317(9)if are close to those expected for a diolefin with the central C-C bond in the region typical of C-C single bonds. Also, the angles C(l)-C(2)-C(3) (126.6(6)”)and C(2)C(3)-C(4) (128.4(6)”)approach those observed in butadienes. Complex 5 is very stable and does not react with water, carbon dioxide, carbon monoxide, or triphenylphospine. With an excess of PhC=CCzCSiMes in
C41H39NiPSiTi
Cp2Ti
-PPh3 - Me$iCsiMe3
’SiMe3 Ph
‘SiMe3 6
Complex 6 is a deep red, crystalline substance which is readily soluble in benzene and THF and melts at 184-185 “C under argon. The C s C triple bond absorptions for 6 (1846, 1797 cm-l) are both in the region of a,n-acetylide-bridged complexes. In order to assign the IR bands to the different acetylide groups, we note that a decrease in vclc is observed upon substitution with SiMe3.* Therefore, the absorption at 1797 cm-l should be assigned t o the SiMe3-substituted and the other at 1846 cm-l to the Ph-substituted triple bond. At ambient temperature the SiMes group and the Cp rings each exhibit a single resonance in the lH NMR spectrum. In the 13CNMR spectrum four resonances for the acetylide carbon atoms were detected. The structure of 6 has been determined by X-ray diffraction (Figure 4). Table 1 lists crystallographic data. Positional parameters and selected bond distances and angles of 6 are given in Tables 9 and 10.
Heterobimetallic 0,mAcetylide-BridgedComplexes
Organometallics, Vol. 14, No. 6, 1995 2965
Table 2. Atomic Coordinates ( x lo4) and Equivalent Isotropic Displacement Parameters (A2 x 103) for 1" atom
z
Y
X
8304(1) 7472(1) 8864(1) 6861(1) 9174(1) 7753(2) 7359(2) 8157(2) 8609(2) 6463(3) 7316(4) 6299(4) 9920(3) 8988(6) 9188(4) 7548(3) 8120(3) 8252(3) 7768(3) 7320(3) 6871(2) 7003(3) 6733(3) 6425(2) 6508(3) 9548(2) 9883(2) 10395(3) 10582(3) 10250(3) 9739(3) 9109(2) 8688(3) 8827(4) 9402(4) 9825(3) 9685(2) 8520(2) 8484(3) 8188(3) 7950(3) 7990(3) 8270(2) 0 68(9) 177(9)
2630(1) 2062(1) 2689(1) -1203(2) 5522(2) 1210(5) 300(5) 3511(5) 4183(6) -1801(8) -2700(7) -719(9) 4998(11) 7274(9) 5714(13) 1458(7) 1683(7) 621(7) -249(6) 261(6) 3683(6) 4336(6) 3568(8) 2443(7) 2516(6) 1634(5) 1296(6) 505(6) 13(7) 327(8) 1127(7) 4455(5) 5507(6) 6859(7) 7217(7) 6206(7) 4807(6) 2002(5) 2762(6) 2214(7) 895(7) 106(7) 660(5) - 1938(42) 352(22) -1102(25)
U,,
Table 3. Selected Bond Distances (deg) for 1
C(l)-C(S)-Si(l) C(3)-C(4)-Si(2)
1.233(7) 1.261(7) 1.832(5) 1.835(5) 1.828(5) 1.909(5) 164.4(4) 145.8(4)
atom
6239(1) 6765(1) 5754(1) 6115(1) 6711(1) 6188(1) 6206(1) 6705(1) 6595(1) 6543(2) 5952(3) 5758(3) 6564(3) 6496(4) 7223(2) 7404(1) 7281(2) 7023(2) 6986(2) 7217(2) 6423(2) 6760(2) 7032(2) 6871(2) 6495(2) 5785(1) 5473(1) 5504(2) 5848(2) 6152(2) 6125(2) 5611(1) 5597(2) 5484(3) 5409(2) 5428(2) 5521(2) 5326(1) 4999(1) 4691(2) 4706(2) 5027(2) 5338(1) 2500 2295(4) 2203(6)
(A)and Angles
Ni-C(4) Ti-C(3) Ti-C(l) Ti-C(2) Ni-P Ni-Ti Ni-C(1)-C(2) Ti-C(3)-C(4)
2.061(5) 2.067(4) 2.331(4) 2.628 2.1674(13) 2.7277(10) 170.4(4) 164.5(4)
Heterobimetallic, tweezerlike complexes are wellknown,6 but compound 6 represents the first example of such a compound with different substituents a t the acetylide groups. The structure shows that both of the acetylide groups in 6 are coordinatively y2-side-onbonded to the Yi(PPh3) unit. There is no or only little influence of the different substituents at the C-C triple bond on the complexed C-C bond distances and on the Ni-C bond lengths t o the carbon atoms, which are also a-bonded to Ti. The other Ni-C bond distances to the carbon atoms not bonded to Ti are, as expected,gbshorter
.Y
z
2597(1) 1914(1) 2684(2) -1254(2) 5426(3) 1166(7) 277(8) 3448(8) 4108(9) -1813(12) -2753(12) -798(16) 4880(16) 7176(14) 5592(22) 1199(11) 1445(12) 425(11) -489(10) -10(10) 3652(10) 4259(9) 3414(11) 2301(11) 2429(10) 1615(8) 1304(9) 509(10) -20(11) 253(12) 1093(11) 4444(8) 5487(10) 6841(10) 7192(10) 6195(11) 48 13(10) 2020(8) 2805(9) 2250(11) 941(12) 149(10) 676(9) 463(37) -977(38) -1913(46)
6215(1) 6751(1) 5736(1) 6091(1) 6687(1) 6158(2) 6196(2) 6696(2) 6564(2) 6498(4) 5951(5) 5731(4) 6544(4) 6473(6) 7190(4) 7417(2) 7286(3) 7019(3) 6992(3) 7230(2) 6434(3) 6769(3) 7039(2) 6875(2) 6508(3) 5760(2) 5463(2) 5490(3) 5823(3) 6139(3) 6098(3) 5601(2) 5573(4) 5470(4) 5409(3) 5434(3) 5518(3) 5309(2) 4988(2) 4688(3) 4686(2) 5007(3) 5309(2) 2312(7) 2169(9) 2500
X
8290(1) 7436(1) 8850(1) 6867(1) 9 16%1) 7746(3) 7353(3) 8151(3) 8594(3) 6443(5) 7336(6) 6331(7) 9903(5) 8996(8) 9163(7) 7548(5) 8119(5) 8250(4) 7754(4) 7319(5) 6762(4) 6904(4) 6656(4) 6348(4) 6410(4) 9529(3) 9871(3) 10383(4) 10548(4) 10214(5) 9705(4) 9105(3) 8685(4) 8832(6) 9404(5) 9825(5) 9677(4) 8518(3) 8486(4) 8196(5) 7955(4) 7988(4) 8270(4) 29(16) 107(14) 263(18)
U,,is defined as one-third of the trace of the orthogonalized Ub tensor.
C(l)-C(2) C(3)-C(4) C(P)-Si(l) C(4)-Si(2) Ni-C(l) Ni-C(3)
Table 4. Atomic Coordinates ( x lo4) and Equivalent Isotropic Displacement Parameters (A2 x 103) for 2"
U,,
a U,,is defined as one-third of the trace of the orthogonalized U,j tensor.
Table 5. Selected Bond Distances (deg) for 2 C(l)-C(2) C(3)-C(4) C(B)-Si(l) C(4)-Si(2) Ni- C(1) Ni-C(3) C(l)-C(2)-Si(l) C(3)-C(4)-Si(2)
1.236(12) 1.284(13) 1.847(9) 1.835(9) 1.835(8) 1.961(8) 159.2(7) 141.7(7)
(A)and Angles
Ni-C(4) Zr-C(3) Zr-C(l) Zr-C(2) Ni-P Ni-Zr Ni-C(1)-C(2) Zr-C(3)-C(4)
2.035(9) 2.178(9) 2.385(7) 2.557 2.168(2) 2.829% 13) 166.4(7) 160.4(7)
for the Ph-substituted case (Ni-C(4) - 2.038(3)A) than for the Si-substituted part of the structure (Ni-C(B) 2.065(3) A). The unexpectedgb larger bending-back angle C(l)-C(Z)-Si of 134.1(3)" in comparison with C(l)-C(2)-C(5) of 148.4(4)"is explained by steric effects and the possibility for the phenyl ring of the acetylide of finding a nearly parallel arrangement to a phenyl ring of the phosphine. The Ti-C distances are somewhat shorter compared to those in complexes 1 and 3, indicating also the n-interaction discussed above (cf.
2966 Organometallics, Vol. 14, No. 6, 1995
Rosenthal et al.
Table 6. Selected Bond Distances and Angles for 1-4 L,M( 1 )-C(1)=C(P)-SI(l )Me3
4
t
M~~S~(~)-C(~)SC(~)-MM(~)CP~
1
2
Atoms Ni Zr PPh3 Distances (A) 1.233(7) 1.236(12) 1.261(7) 1.284(13) 1.828(5) 1.835(8) 1.909(5) 1.961(8) 2.061(5) 2.035(9) 2.067(4) 2.178(9) 2.331(4) 2.385(7) 2.628 2.557 2.7277(10) 2.8295(13) Angles (deg) 164.4(4) 159.2(7) 145.8(4) 141.7(7) 170.4(4) 166.4(7) 164.5(4) 160.4(7)
Ni Ti PPh3
C(l)-C(B)-Si(l) C(3)-C(4)-Si(2) M(l)-C(l)-C(2) M(2)-C(3)-C(4)
3
413
Ti Ti CP2
Zr
1.244(3) 1.244(3)
1.249(7) 1.260(7)
2.069(1) 2.393(1) 2.318(2) 3.550(3)[121
2.191(5) 2.426(5) 2.407(5) 3.522(2)
141.5(2)
142.5(4)
176.4(1)
172.7(4)
Zr CPZ
Figure 3. Molecular structure of complex 5, shown by an ORTEP plot at the 40%probability level. Table 7. Atomic Coordinates ( x lo4) and Equivalent Isotropic Displacement Parameters (k x 10s) for 5” atom
Chart 1 SiMe3 i
Ld
Me& Chart 1). The long Ti-Ni distance suggests that there is little, if any, metal-metal interaction. The different reaction pathways of PhC=CC=CSiMes with “Cp2Ti”to 5 on the one hand and of (Ph3P)2Ni(v2PhCSCCECSiMes) with “Cp2Ti”to 6 on the other hand can be explained in general by Scheme 2. The first step is in all cases the formation of the cyclocumulene complex A, which is stable and was structurally characterized for R = R = t-Bu14and also the zirconocene a n a l ~ g u e .The ~ question is open as to whether such complexes A react (i) intramolecularly through bis(acetylide1 complexes B or (ii) directly and intermolecularly with “Cp2Ti”t o give 5 or with “(Ph3P12Ni” to give 6. Possibly, the nickel fragment is acting mainly as a trapping agent for an intermediate of the cleavage reaction. Conclusion Reactions of early-late transition-metal systems with 1,4-disubstituted 1,3-butadiynes proceed smoothly to give heterobimetallic complexes with o,n-bridging acetylide units. In solution, an equilibrium of different structures obtains. In the solid state, a well-defined energy minimum of the structure, influenced by small effects of the substituents, the metal, and the ligands, is reached. Phenyl substituents at the acetylide unit and small ligands a t the Ni center favor tweezerlike structures. In contrast, bulky t-Bu and SiMes groups in combination with larger ligands on the Ni atom ~~~~~
(14)Burlakov, V. V.; Ohff, A.; Lefeber, C.; Tillack, A.; Baumann, W.; Kempe, R.; Rosenthal, U. Chem. Ber., submitted for publication.
X
11625(2) 11148(2) 13996(3) 10142(8) 10798(8) 11992(8) 12640(8) 14434(14) 13532(20) 12902(14) 13453(15) 14369(12) 8885(11) 9755(15) 10950(15) 11016(16) 9751(20) 11763(14) 13093(13) 13847(10) 12936(13) 11662(12) 9878(12) 9269(11) 8339(11) 8373(12) 9321(14) 15629(11) 12742(13) 15068(15) 8849(8) 8125(9) 6872(11) 6331(11) 7067(11) 8300(10) a
Y
2
3983(1) 3431(1) 4337(1) 3485(2) 3539(2) 3873(2) 3942(2) 4065(4) 4025(6) 3646(6) 3453(4) 3703(4) 4267(3) 4383(3) 4616(4) 4679(3) 4479(4) 2734(3) 2952(3) 3123(2) 3009(3) 2755(3) 3793(3) 3969(3) 3680(4) 3320(3) 3385(4) 4103(3) 4698(3) 4632(4) 3205(2) 2925(2) 2669(3) 2693(3) 2962(3) 3224(2)
3549(1) 7062(1) 7793(2) 3768(6) 5031(6) 5630(7) 6876(7) 3396(18) 2148(17) 2026(12) 3 148(15) 4014(10) 2907(15) 1984(10) 2487(15) 3729(15) 4075(11) 6685(11) 6529(9) 7677(11) 8617(8) 7949(11) 8567(9) 7389(10) 6581(10) 7303(13) 8536(10) 9108(9) 8569(11) 6712(11) 3104(7) 3781(8) 3117(9) 1769(9) 1104(8) 1744(7)
U,“
U,, is defined as one-third of the trace of the orthogonalized
Ut,tensor.
prevent this structure and 1 and 2 are formed. For example, the acetylide phenyl group in 6 is almost parallel to one phenyl group of the triphenylphosphane. By this, the triphenylphosphane is put into a staggered position towards the trimethylsilyl group and a tweezer like structure results. For two trimethylsilyl groups as acetylide substituents this orientation would be more sterically hindered. This might explain the different
Heterobimetallic a,n-Acetylide-Bridged Complexes
Organometallics, Vol. 14, No. 6, 1995 2967
Table 9. Atomic Coordinates ( x lo4) and Equivalent Isotropic Displacement Parameters (k x lo3)for 6" atom
Figure 4. Molecular s t r u c t u r e of complex 6, shown by an ORTEP plot at t h e 40%probability level. Table 8. Selected Bond Distances (deg) for 5
(A) and Angles
1.327(9) 1.511(9) 1.317(9) 1.838(7) 2.083(7) 126.6(6) 128.4(6) 156.4(6)
2.337(7) 2.164(7) 2.114(7) 2.302(7) 2.115(7) 154.9(6) 130.8(7) 135.0(6).
structures of complex 1and 2, where one acetylide g r o u p is 0-bonded to the nickel. Experimental Section
X
6853(1) 8070(1) 8813(1) 5900(1) 6635(3) 6737(3) 8346(3) 9201(3) 10315(3) 10969(3) 12028(3) 12449(4) 11819(4) 10758(3) 5663(7) 4672(4) 6400(4) 6076(4) 6502(4) 7570(4) 7796(4) 6863(5) 6788(4) 6460(4) 5530(3) 5296(4) 6053(5) 10119(3) 10269(3) 11246(3) 12076(3) 11930(3) 10958(3) 8125(3) 8587(3) 8061(4) 7074(4) 6612(4) 7129(3) 8956(3) 9076(3) 9181(4) 9170(4) 9068(4) 8951(3)
Y
1854(1) 3291(1) 4574(1) 3804(1) 2770(3) 3395(3) 2370(3) 2745(3) 2749(3) 2722(3) 2653(4) 2629(5) 2664(5) 2728(4) 2627(6) 4260(8) 4842(4) 269(3) 632(4) 655(4) 288(4) 52(3) 2579(4) 3345(3) 3024(4) 2072(4) 1795(4) 4967(2) 5183(3) 5419(3) 5436(3) 5247(3) 5010(3) 5799(3) 6726(3) 7641(3) 7629(4) 6724(4) 5810(3) 4381(3) 5168(3) 4966(3) 3973(4) 3182(3) 3385(3)
z
567(1) 1308(1) 1809(1) 2384(1) 1321(2) 1766(2) 588(2) 792(2) 784(2) 1334(2) 1317(3) 75x41 198(3) 210(2) 2851(3) 1964(3) 2927(2) 781(3) 1352(3) 1318(3) 739(3) 411(3) -460(2) -67(2) 158(2) -89(2) -477(2) 1630(2) 1012(2) 835(2) 1286(2) 1905(2) 2076(2) 1673(2) 1823(2) 1715(2) 1434(2) 1265(2) 1383(2) 2667(2) 3107(2) 3747(2) 3953(2) 3525(2) 2887(2)
General Considerations. All operations were carried out under a n inert atmosphere (argon) with standard Schlenk techniques. Solvents were freshly distilled from sodium tetraethylaluminate under argon prior t o use. Deuterated solvents were treated with sodium or sodium tetraethylalua U,, is defined as one-third of the trace of the orthogonalized minate, distilled, and stored under argon. The following Uij tensor. spectrometers were used: NMR, Bruker ARX 400; IR, Nicolet Table 10. Selected Bond Distances (A) and Angles Magna 550 (Nujol mulls using KBr plates); MS, AMD 402. (deg) for 6 Melting points were measured in sealed capillaries on a Buchi 535 apparatus. C(l)-C(2) 1.250(5) Ni-C(l) 1.986(3) Diffraction data were collected on a CAD4 diffractometer C(3)-C(4) 1.256(5) Ni-C(3) 2.005(3) C(2)-Si 1.855(4) Ni-C(2) 2.065(3) using M o Ka radiation. The structure was solved by direct C(4)-C(5) 1.447(5) Ni-C(4) 2.038(3) m e t h o d P a and refined by full-matrix least-squares techniques Ti-C(l) 2.040(4) Ni-P 2.1659(9) against F.16b Structural representation was obtained by using Ti-C(3) 2.048(4) Ti-Ni 2.840 ORTEP. C(l)-Ti-C(3) 134.1(3) C~ZT~(I~-~~:?~-C~CS~M~~)N~( (1). PP~S) ( I ~ - ~ ~ : ~89.25(13) ~ - C ~ S ~ C(l)-C(S)-Si M~~) Ti-C(l)-C(Z) 165.2(3) C(3)-C(4)-C(5) 148.4(4) To a solution of 2.10 g (2.70 mmol) of (Ph3P)2Ni(y2-Me3Ti-C(3)-C(4) 160.4(3) SiC=CC=CSiMe3) in 20 mL of toluene was added 0.98 g (2.81 mmol) of CpzTi(Me3SiC~CSiMe3)in 1 5 mL of toluene. As the H, SiMes), 5.63 (s, 10 H, Cp); 190 K, symmetrical form, d -0.43 yellowish brown reaction mixture was stirred for 4 h a t 50 "C, (s, 18 H, SiMes), 5.47 (s, 10 H, Cp) (ratio unsymmetrical to the color changed to red-brown. The solvent was evaporated symmetrical form -5:l). 13C NMR (THF-d8): 303 K, d 1.1(s, in vacuo, and the residue crystallized by diffusion of n-hexane SiMea), 105.9 (s, Cp), 128.9 (d, 3J(C,P) = 9 Hz, P h (meta)), into a THF solution. After 2 days, filtration left dark red129.4 (5, Ph (para)), 135.2 (d, 2J(C,P) = 13 Hz, Ph (ortho)), brown crystals, which were washed twice with n-hexane and 137.0 (d, 'J(C,P) = 35 Hz, Ph (ipso)). Anal. Calcd for C38H43dried in vacuo. 729.5);15C, 65.85; H, 6.51; Ni, 8.05; Ti, NiPSi2Ti-0.5C4H80(M, Yield: 1.39 g (70%) of 1. Mp: 127-133 "C. MS: m l z 692 6.56. Found: C, 65.91; H, 6.73; Ni, 8.24; Ti, 6.61. (M+). IR (Nujol mull): 1780, 1911 cm-I (vc..~). 31P NMR CpzZrOl-t11:92-C=CSiMes)Ni(PPh3)Ol-9 ':p2-C=CSiMe3) (THF-&): 303 K, 6 43.1; 190 K, 6 41.4, 42.7 (ratio -5:l). 'H (2). A solution of 1.40 g (1.80 mmol) of (Ph3P)2Ni(q2NMR (THF-d8): 303 K, 6 -0.11 (s, 18 H, SiMes), 5.53 (s, 10 Me3SiC=CC=CSiMe3) in 10 mL of THF was added to 0.89 H, C5H5), 7.31-7.36 (m, 10 H, Ph), 7.56-7.60 (m, 5 H, Ph); g (1.92 mmol) of CpzZr(THF)(Me3SiC=CSiMe3) in 10 mL 190 K, unsymmetrical form, d -0.35 (9, 9 H, SiMes), 0.25 (s, 9
Rosenthal et al.
2968 Organometallics, Vol. 14, No. 6, 1995
Scheme 2 R'
Cp2T()j
-
R
R
- "Ni(PPh&'
I +
(Ph3P)zNi
cP2T\/R'
"Cp,Ti"
CpzTi
