4576
Organometallics 1996, 14, 4576-4584
Analysis of Spectroscopic, Reactivity, and Structural Differences Originating Uniquely from Differing Modes of mFacial Complexation. The Three Possible Stereoisomeric Bis(isodicyclopentadieny1)titanium Combinations Florence Zaege1,t Judith C. Gallucci,e Philippe Meunier,? Bernard Gautheron,*st Eugene I. Bzowej,SJ and Leo A. Paquette*J Laboratoire de Synthbe et d'Electrosynth8se Organomdtalliques Associd au CNRS (URA1685), Universitd de Bourgogne, BP 138,21004 DGon, Cddex, France, and the Evans Chemical Laboratories, The Ohio State University, Columbus, Ohio 43210 Received May 9, 1995@ The three diastereomeric (isodiCp)zTiClzcomplexes have been prepared in stereocontrolled fashion. The exo,exo isomer, on reaction with boron tribromide or with ethereal methyllithium, gives rise to the dibromo and dimethyl analogues which show reasonable stability. I n contrast, the endo,endo and endo,exo dichlorides do not lead to stable products under analogous conditions. All three (isodiCp)zTiClz isomers do react well with pentafluorophenyllithium, leading to the air stable, crystalline (isodiCp)~Ti(CsF5)Cltriad, whose members are readily distinguished by their NMR spectra. An analysis of the notable trends reflected in these spectra is reported. X-ray crystallographic analysis of the three diastereomers reveals the three pentafluorophenyl complexes to have in common a solid-state spatial arrangement which differs notably from that adopted by the exo,exo dichloride and dimethyl derivatives. In recent years, considerable attention has been accorded to the complexation of cyclopentadienyl ligands endowed with diastereotopic faces to group 4 transition metals. h early example is the bis(~5-tricyclo[5.2.1.02~61deca-2,5-dienyl) or isodicyclopentadienyl anion ( 1h2 A wide variety of optically active anions of this generic class has subsequently been d e ~ e l o p e d . ~As - ~ a direct consequence of the inherent structural features of 1 and its congeners, the faces of these ligands feature distinctively different chemical environments. Their involvement in metalation reactions can lead to mixtures of metallocenes but often does not if proper controls are Universite de Bourgogne.
* The Ohio State University. +
Abstract published in Advance ACS Abstracts, September 1, 1995. (1)NSERC (Canada) Postdoctoral Fellow, 1994-1995. (2)Gallucci, J. C.; Gautheron, B.; Gugelchuk, M.; Meunier, P.; Paquette, L. A. Organometallics 1987,6, 15. (3)(a) McLaughlin, M. L.; McKinney, J. A.; Paquette, L. A. Tetrahedron Lett. 1986,27, 5595. (b) Paquette, L. A.; McKinney, J. A.; McLaughlin, M. L.; Rheingold, A. L. Tetrahedron Lett. 1986,27,5599. ( c ) Paquette, L. A,; Gugelchuk, M.; McLaughlin, M. L. J . Org. Chem. 1987,52,4732. (d) Paquette, L. A.; McLaughlin, M. L. Org. Synth. 1989,68,220. (e) Paquette, L. A,; Moriarty, K. J.; McKinney, J. A,; Rogers, R. D. Organometallics 1989,8, 1707. (0 Paquette, L. A.; Moriarty, K. J.; Rogers, R. D. Organometallics 1989,8, 1506. (g) Moriarty, K.J.; Rogers, R. D.; Paquette, L. A.Organometallics 1989, 8,1512. (4)(a)Halterman, R.L.; Vollhardt, K. P. C. Tetrahedron Lett. 1986, 27, 1461.(b) Halterman, R. L.; Vollhardt, K. P. C. Organometallics 1988,7,883.(c)Chen, 2.;Halterman, R. L. J . Am. Chem. SOC.1992, 114,2276.(d)Halterman, R. L.; Ramsey, T. M. Organometallics 1993, 12,2879.(e) Chen, Z.;Eriks, K.; Halterman, R. L. Organometallics 1991,10,3449. (5) (a)Burger, P.; Hund, H.-U.; Evertz, K.; Brintzinger, H.-H. J . Organomet. Chem. 1989,378,153. (b)Bhaduri, D.; Nelson, J. H.; Wang, T.; Jacobson, R. A. Organometallics 1994,13,2291.( c ) Burk, M. J.; Colletti, S. L.; Halterman, R. L. Organometallics 1991, 10,2998. (d) Hollis, T.K.; Rheingold, A. L.; Robinson, N. P.; Whelan, J.; Bosnich, B. Organometallics 1992 11, 2812.(e) Rheingold, A.L.; Robinson, N. P.; Whelan, J.; Bosnich, B. Organometallics 1992 11, 1869.(0 Bandy, J. A.; Green, M. L. H.; Gardner, I. M.; Prout, K. J . Chem. SOC.,Dalton Trans. 1991,2207. @
exercised. The engagement of a single face is presently recognized to be subject to reasonable modulation by several factors, including nonbonded steric interactions: monomer-dimer preequilibrium complexation to lithium counter ion^,^ reaction temperature: and con~entration.~ Since each ligand can in principle serve as precursor to three diastereomeric metallocenes, we have been led to investigate those features that distinguish such a subset of closely related complexes. To our knowledge, no investigation of this type has previously been undertaken. The one potential limitation of this study, ready access to the stereoisomerically pure diastereomers without the need t o accomplish difficult separations, was lifted by our earlier discovery that structurally defined trimethylsilyl-substituted ligands undergo complexation exclusively via net inversion of configuration.1° Results and Discussion Synthesis and Spectroscopic Analysis of the Diastereomeric (IsodiCp)2TiCL Complexes. The (6)(a) Sivik, M. R.; Rogers, R. D.; Paquette, L. A. J. Organomet. Chem. 1990,397,177.(b) Rogers, R. D.; Sivik, M. R.; Paquette, L. A. J . Organomet. Chem. 1993,450,125. (7)(a) Paquette, L. A.; Bauer, W.; Sivik, M. R.; Biihl, M.; Feigel, M.; Schleyer, P. von R. J.Am. Chem. SOC.1990,112,8776.(b) Bauer, W.; ODoherty, G. A.; Schleyer, P. von R.; Paquette, L. A. J.Am. Chem. (c) Bauer, W.; Sivik, M. R.; Friedrich, D.; Schleyer, SOC.1991,113,7093. P. von R.; Paquette, L. A. Organometallics 1992,11,4178.(d) Zaegel, F.; Gallucci, J. C.; Meunier, P.; Gautheron, B.; Sivik, M. R.; Paquette, L. A. J . Am. Chem. SOC.1994,116,6466. (8)(a)Paquette, L. A,; Moriarty, K. J.; Meunier, P.; Gautheron, B.; Crocq, V. Organometallics 1988,7,1873.(b)Paquette, L. A,; Moriarty, K. J.; Meunier, P.; Gautheron, B.; Sornay, C.; Rogers, R. D.; Rheingold, A. L. Organometallics 1989,8,2159. (9)Bhide, V. V.; Rinaldi, P. L.; Farona, M. F. Organometallics 1990, 9, 123 and the discussion in ref 11. (10)Paquette, L. A.;Sivik, M. R. Organometallics 1992,11, 3503.
Q276-7333l95I2314-4576$09.QQlQ 0 1995 American Chemical Society
Differing Mocks of n-Facial Complexation
Organometallics, Vol. 14, No. 10, 1995 4577
Table 1. 400 M H z 'H NMR Spectra of the (1sodiCp)aTiCla Diastereomers and Related ComplexeP cyclopentadienyl compd
central
peripheral
bridgehead
exo ethano
endo ethano
2b 3b
6.27 (t/2) 5.84 (t/2) 6.09 (ffl), exo 5.86 (ffl),endo 6.43 (t/l) 6.51 (U2) 6.07 (t/2)
6.08 (d4) 6.33 ( d 4 ) 6.17 (d/2), exo 6.29 (d2),endo 5.60 (d2) 6.19 (d4) 5.58 (d4)
3.32 (d4) 3.34 (d4) 3.34 (s/2), endo 3.29 (d2), exo 3.01 (d2) 3.38 (d4) 2.75 (d4)
1.86 (U4) 1.85( d 4 ) 1.85(m/4), exo endo 1.25 (d/2) 1.87 (d/4) 1.53 (d4)
1.11(d4) 1.73 (d4) 1.76 (d2), endo 1.09 (d/2), exo 0.49 (dd2) 1.14 (d4) 1.22 (d4)
6b
5c 7b 8c a
syn methano anti methano methyl 1.38 (d2) 1.22 (d/2) 1.91(ni2) 1.85 (d/2) endo 1.94 (nil),endo 1.85 (dl), 1.18 (dl),exo 1.32 ( d l ) , exo 1.94 (d/l) 1.02 (dl) 1.32 (d2) 1.02 (d2) 0.85 (d4) 0.25 (d6)
Chemical shift in 6, multiplicity, relative integration. In CDC13 solution. In C& as solvent.
Table 2. 50 MHz lSC NMR Spectra of the (IsodiCphTiClz Diastereomers and Related Complexee compd
central
2b
128.4 121.3 125.5 123.1 125.8 129.1 118.8
3b
6b 5c
76 8c a
cyclopentadienyl peripheral quaternary 106.8 111.6 107.2 110.7 113.7 107.6 103.7
ethano bridge
bridgehead
methano bridge
methyl
28.0 27.2 28.0 27.2 28.6 28.4 29.4
41.4 42.8 41.4 42.8 42.3 42.2 40.6
47.7 59.1 47.5 59.3 50.2 47.5 47.1
46.1
144.8 154.3 145.4 153.8 149.8 145.0 136.1
Chemical shifts in 6. In CDCl3 solution. In C6Ds as solvent.
Scheme 1
2
3
\
Tc13.3 THF, THF, 25 "C
THF, -64"C
1
THF, A
Tic14
s ~ ~toluene, , 20 "C 4
6
exo,exo-bis(isodicyclopentadieny1)titanium dichloride 2 was obtained stereoselectively by reacting 1 with TiC13.3THF in tetrahydrofuran solution at 25 "C followed by 'ICidation WithHC1 (Scheme In admixing of 1 with TiCL.3THF in THF at -64 " c for 5 h followed by the introduction of cold CC4 prior to workup afforded 3 as an equally dark red crystalline solid (49%).11 We attribute the resultant stereochemical
crossover to the high levels of dimeric lithium isodicyclopentadienide present in solution below -60 oC.7a3d Arrival at endo,exo isomer 6 was accomplished somewhat less directly12J3by treatment of the known silane 414 with Tic14 in toluene at 20 "C to produce initially exo-(isodiCp)TiCl3(51, followed by the dropwise introduction of 5 to 1 equiv of 1 also dissolved in THF at -78 "C. All three diastereomers are configurationally stable and exhibit no tendency to interconvert when heated in solution. The fully assigned IH and 13CNMR data for 2,3,and 6 are compiled in Tables 1and 2 along with those for 5 and two other derivatives t o which attention will be drawn subsequently. A striking feature of these data is the very telltale response of the central and peripheral protons positioned on the cyclopentadienyl ring to the particular face being utilized for coordination to the titanium atom. Thus, exo,exo bonding as in 2 has the effect of deshielding the central proton (6 6.27) while simultaneously shiRing the peripheral protons somewhat t o higher field (6 6.08). In contrast, these same protons are strongly influenced in the opposite sense (6 5.84,6.33) when endo,endo complexation prevails as in 3. A similar trend is apparent in the stereochemically mixed complex 6, although the chemical shiR differences exhibited by the exo ligand (6 6.09, 6.17) reflect the actual state of affairs at a more accentuated level than those of the endo isodiCp component (6 5.86, 6.29). The electronegativity of the titanium center exerts an obvious influence on the norbornyl protons to which it is most closely positioned. In exo titanocenes, the anisochronous characteristics of the metal operate on the syn methano proton and shield it extensively (ca 0.6 ppm). On the other hand, an endo orientation positions the Ti proximal to the two magnetically Paquette, (11)Sornay, L. A. Oganometallics C.; Meunier, P.;1991, Gautheron, 2082, B.; O'Doherty, G . A,; (12) Cardoso, A. M.; Clark, R. J. H.; Moorhouse, S. J. Chem. SOC., Dalton Trans. 1980, 1156. (13)For more recent examples of this chemistry, consult (a)Llinas, G. H.; Mena, M.; Palacios, F.; Royo, P.; Serrano, R. J. Organomet. Ckm. 1988,340,37.(b)Lund, E. C.; Livinghouse, T.Organometallics 1990,9,2426. (c) Winter, C. H.; Zhou, X.-X.; Dobbs, D. A.; Hew, M. J. Organometallics 1991, 10, 210. (14) Paquette, L. A.; Charumilind, P.; Gallucci, J. C. J.Am. Chem. SOC.1983,105, 7364.
Zaegel et al.
4578 Organometallics, Vol. 14, No. 10,1995
Table 3. Ultraviolet Absorption Maxima of Representative Dichlorotitanium Complexes (CH&12 Solution) ligand 1 CP t-BuCp CP CP t-BuCp t-BuCp exo-isodiCp exo-isodiCp endo-isodiCp
A,,
ligand 2
(nm) 255.5 264 257 263 264 268 264 268 268
CP t-BuCp exo-isodiCp endo-isodiCp exo-isodiCp endo-isodiCp exo-isodiCp endo-isodiCp endo-isodiCp
equivalent endo ethano hydrogens with closely comparable consequences (TabIe 1). The bridgehead norbornyl protons are not sensitive to stereochemistry, appear consistently at 6 3.3, and serve as a useful internal point of reference.14-16 The ultraviolet absorption maxima of the (isodiCp)zTic12 isomers in CH2C12 solution have been compiled alongside those of simpler related systems in Table 3. Consequences of Chlorine Substitution. The availability of the three possible stereoisomeric (isodiCp)zTiClz complexes has prompted an investigation of their effective involvement in representative transformations and a comparative analysis of product stability. Treatment of 2 with boron tribromide in dry dichloromethane at 20 "C for 2 h according to Druce et al.17 gave rise t o the black, crystalline 7 in 86% yield after one recrystallization. Comparison of its lH NMR spectrum with that of 2 reveals a downward drift of those signals due to the central and peripheral cyclopentadienyl protons in addition to the anti methano hydrogen (Table 1). These effects are reasonable in light of the increased length of the Ti-Br bond, the change in electronegativity of the halogen, and the resultant response of Ti to these modifications. No loss of stereochemical integrity was seen. Comparable processing of 3 and 6 resulted in decomposition even at a temperature of -80 "C. Evidently, the highly reactive nature of BBr3 suffices to destroy the diastereomers of 7.
7
8
An analogous situation developed during the attempted preparation of the dimethyl derivatives. Whereas the exo,exo dichloride 2 reacted smoothly with >2 equiv of ethereal methyl1ithi~m'~J~ to give the orange crystalline 8 (68%),the other two isomers proved to be very unstable and were not characterized. Although the spectral properties of 8 are in fidl agreement with its assigned structure, the replacement of elec(15)Gallucci, J. C.; Kravetz, T.M.; Green, K E.; Paquette, L. A. J . Am. Chem. SOC.1985,107,6592. (16)Brown, F.R;H o d , K N. J . Am. Chem. SOC.1985,107,1971 and relevant references cited therein. (17)Druce, P. M.; Kingston, B. M.; Lappert, M. F.; Spalding, T.R.; Srivastava, R. C. J . Chem. Soc. (A) 1969,2106. (18)Samuel, E.;Rausch, M. D. J . Am. Chem. SOC.1973,95,6263. (19)Mach, K.;Varga, V.; Hanus, V.; Sedmera, P. J . Organomet. Chem. 1991,415,87.
tronegative chlorine atoms by methyl groups does have its consequences. Relative to 2, all of the isodiCp protons are more shielded in 8 with the exception of the endo ethano protons located on the surface away from the metal. An exactly parallel trend is reflected in its 13C NMR spectrum (Table 2). Success in engaging all three diastereomers in conversion to stable products was realized upon exposure of the dichlorides to pentafluorophenyllithium in ether solution at 0 0C.20,21The resultant products 9-11 are
9
10
11
air-stable crystalline compounds differing in the color which they exhibit. As before, these diastereomeric complexes can readily be distinguished by their NMR spectra (Table 4). The trends in chemical shift are the same as those discussed above. However, the obvious reduction in symmetry causes several of the norbornyl proton pairs to be diastereotopic. This is most evident in the case of the peripheral cyclopentadienyl and bridgehead hydrogen atoms. Interestingly, the Ad in chemical shift is most dramatic for the bridgehead protons. Exo bonding to the titanium as in 9 and the upper half of 11 gives rise t o signals that are characteristically widely divergent (0.38 and 0.58 ppm, respectively). In contrast, endo complexation leads to less dramatic disparities (0.16 ppm for 10,0.15for the lower half of 11) as a consequence of the increased distance to the pentafluorophenyl substituent in this stereochemical arrangement. The 13C NMR spectrum of 9 features a methano bridge carbon at 47.7 ppm and two well-separated quaternary cyclopentadienyl carbons at 149.3 and 142.7 ppm. In endo,endo isomer 10, shielding of the methano bridge center by the metal no longer operates (now at 59.1 ppm) and the quaternary centers appear at 158.2 and 152.6 ppm, keeping with precedent. X-ray Crystallographic Analyses of 8-11. The molecular structures of (isodiCp)zTiMez (8) and the three pentafluorophenyl derivatives 9- 11 are shown in Figures 1-4, respectively. The numbering schemes used for 9-11 are identical, with the exception that 10 has additional letters (A and B) t o distinguish between the two molecules in the asymmetric unit. A summary of crystallographic data is given in Table 5. Selected bond lengths and angles are listed in Tables 6-9. Final positional parameters appear in Tables 10-13. The data set for 10 was weak, and, with two molecules in the asymmetric unit, this structure is not as well determined as the other three. Nevertheless, it remains possible to compare various features for all four structures. For all three diastereomers of (isodiCp)z"i(C~F~)Cl, the geometry about the Ti atom is pseudotetrahedral where the tetrahedron is defined by the chlorine atom, ~~
(20)Chaudhari, M. A.;Treichel, P. M.; Stone, F. G. A. J . Organomet. Chem. 1964,2,206. (21)(a) Moi'se, C.; Leblanc, J. C.; Tirouflet, J. J. Am. Chem. SOC. 1975,97,6272. (b) Leblanc, J.C; Moi'se,C.; Tirouflet,J.Nouu. J. Chim. 1977,1, 211.
Organometallics, Vol. 14,No. 10, 1995 4579
Differing Modes of n-Facial Complexation
Table 4. 500 MHz 'H,125 M H z W , and 188 M H z 19F NMR Spectra of the Diastereomeric (IsodiCp)zTiC1(CsFdComplexesa A. lH NMR Data cyclopentadienyl central peripheral 6.29 (ff2) 5.77 ( d 2 ) 5.61 ( d 2 ) 5.85 ( d 2 ) 6.02 (ff2) 5.75 ( d 2 ) 6.03 (dl), endo 6.21 (ffl), exo 6.10 (ffl), endo 5.72 (&I), exo 5.69 (dl), endo 5.61 (dl), exo
compd 9
10 11
bridgehead 3.38 (d2) 3.00 (d2) 3.41 (d2) 3.25 (d2) 3.42 ( d l ) endo , 3.40 (dl),exo 3.27 (dl),endo 2.82 ( d l ) exo ,
exo ethano 1.90 ( d 2 ) 1.84 ( d 2 ) 1.93 ( d 2 ) 1.84 ( d 2 ) 2.00 ( d l ) , endo 1.89 (&I),exo 1.81 (dl), exo 1.81 ("11, endo
endo ethano 1.12 ( d 4 )
syn methano 1.47 ( d 2 )
anti methano 1.32 ( d 2 )
1.69 ( d 4 )
1.93 ( d 2 )
1.84 ( d 2 )
1.09 ( d 2 ) , exo 1.81 W 2 ) , endo
1.42 ( d l ) , exo 2.00 W U , endo
1.26 ( d l ) , g x o 1.89 W U ,endo
B. 13CNMR DataQ compd
central
9
119.9
10
113.6
11
117.4 116.1
cyclopentadienyl peripheral quaternary 105.0 104.4 108.2 107.9 109.8 107.3 106.8 103.1
ethano bridge
bridgehead
methano bridge
28.9 28.4 27.6 26.8 29.0 28.7 28.5 27.6
41.8 41.2 43.4 42.6 43.4 42.9 42.3 41.3
47.7
149.3 142.7 158.2 152.6 158.9 149.1
59.1 59.9 47.9
C. I9FNMR Data compd 9
10 11
ortho -105.54 -114.26 -105.54 -114.49 -105.48 -114.51
(dl), J = 30.5 HZ ( d l ) , J = 31.9 HZ (dl) (dl) (dl), J = 27.7 HZ (dl),J = 30.5 HZ
para -159.17 (ffl), J = 20.8 HZ -159.98 (ffl),J = 19.9 HZ -159.14 (ffl), J = 19.4 HZ
meta -161.45 (dl) -164.19 (dl) -161.47 (dl) -164.11 (dl) -161.38 (dl) -164.20 (dl)
6 vs. Me&i or CFCl3, CDC13 solution. * The quaternary carbons of the CsFs rings were not detectable because of extensive C/F coupling.
P
Figure 1. ORTEP representation of 8; atoms drawn with 50% probability thermal ellipsoids. Hydrogen atoms are drawn with artificial radii.
C(21) (the carbon atom of the C6F5 group bonded to Ti), and the ring centroids of the approximately planar fivemembered rings of the isodiCp ligands. This pseudotetrahedral arrangement about the Ti atom is shared by the dimethyl derivative 8. When each of the pentafluorophenyl structures is viewed in projection onto the C1-Ti-C(21) plane, the
norbornane portion of one isodiCp ligand falls within the Cl-Ti-C(21) angle. The norbornane portion of the second isodiCp ligand always lies on the opposite side of the Ti atom from the C6F5 group. For the exo,exo (9) and endo,endo (10) isomers, the exo and endo isodiCp subunits, respectively, project within the Cl-Ti-C(B1) angle. For the exo,endo isomer 11 (where there is a choice), the exo ligand projects within this angle. One of these projected views is shown in Figure 2 for structure 9. These spatial arrangements contrast to that present in 8, which, when viewed in projection onto the Ti(CH3)2 plane, shows the norbornane subunits oriented away from each other and projecting well outside of the CH3-Ti-CH3 angle. exo,exo-(IsodiCp)2Tic12 (2) shows the same structure in projection as 8.2 For 9-11 the dihedral angle between the leastsquares plane through the C6F5 group and the plane defined by Cl-Ti-C(B1) is rather small: 5.7" for 11, 18.4" for 9, 18.8" for 10B, and 23.2" for 1OA. The fact that the C6F5 group lies almost in the plane defined by C1-Ti-C(21) is most likely the result of the aforementioned arrangement of the isodiCp ligands. The Ti t o Cp ring-carbon distances span a wide range, which is indicative of an asymmetric Ti-Cp ring interaction. These ranges are 2.379-2.446 A for 8, 2.354-2.440 A for 9, 2.316-2.573 A for lOA, 2.2982.515 A for lOB, and 2.352-2.463 A for 11. The largest range is for the endo,endo isomer 10. As seen in various (q5-RCp)2MC12structures,2,22the metal-to-ring carbon distance is expected to be greatest for the carbon atom (22) Howie, R. A.; McQuillan, G . P.;Thompson, D.W.; Lock, G. A. J. Orgunomet. Chem. 1986,303,213.
Zaegel et al.
4580 Organometallics, Vol. 14, No. 10,1995
F3
C17
Figure 4. ORTEP representation of 11;atoms drawn with 50% probability thermal ellipsoids. Hydrogen atoms drawn with artificial radii.
c20
Figure 2. Two ORTEP representations of 9; atoms drawn with 50% probability thermal ellipsoids. The labeling scheme on the upper drawing includes hydrogen atoms drawn with artificial radii. The view on the lower drawing is a projection of the structure onto the Cl-Ti-C(21) plane with hydrogen atoms omitted for clarity.
RCiO,
0 Figure 3. ORTEP representation of 1 0 atoms drawn with 50% probability thermal ellipsoids. Hydrogen atoms are drawn with artificial radii. bonded to a substituent group. In 9-11, the carbon atoms C(l), C(5), C(11), and C(15) are bonded to a
norbornyl fragment, and it is always one of these atoms out of each Cp which is the farthest distance from the Ti atom. In 8, C(3) is farthest from the Ti atom for one Cp ring, while C(16) is farthest for the other ring. For all four structures, the isodiCp ligands are bent about the bond common to the Cp ring and the norbornane fragment, and this bending is always in a direction away from the Ti atom. For example, in 9-11 the C(6) and C(9) atoms lie significantly out of the best plane through the five-membered ring C(l)-C(5) and are on the opposite side of this plane from the Ti atom. A measure of bending in these complexes is described by the dihedral angle between the least-squares planes through C(l)-C(2)-C(3)-C(4)-C(5) and C(6)-C(5)C(l)-C(9) and, for the other isodiCp ligand, the dihedral angle between the C(ll)-C(12)-C(13)-C(l4)-C(15) best plane and the C(16)-C(15)-C(ll)-C(19) best plane. The dihedral angles are identically identified for 8. The dihedral angles for the endo-oriented isodiCp ligands are slightly larger than those for the exo ligands: 11.3 and 12.0" for 8, 11.7 and 12.6" for 9, 15.8 and 16.6" for lOA, 15.7 and 16.4" for 10B, and 16.8 (endo) and 12.4" (exo) for 11. We again emphasize that coordination of the isodiCp ligand from the exo surface bends the Cp ring in the preferred endo direction.16sz3 For the two structures reported here having coordination from the endo surface, the modestly exaggerated bending in the less preferred exo direction arises because the metal center and its substituents experience greater nonbonded steric compression when located on this n-surface. The C1-Ti-C(21) bond angle is slightly larger for 9-11 (at 102.0, 100.7, 97.6, and 100.9") than the C1Ti-C1 angle observed for various (q5-RCp)zMC12structures (92.5-96.1") and the CH3-Ti-CH3 angle of 92.4" in 8. It is also larger than the C-Ti-C1 angle observed at 93.6(2Y and Cpzin Cp2TiC10L-)71:)761-Fc6~)cr(C0)3 TiC10L-)71:)76-p-CH3CsHq)Cr(C0)3 at 94.8(2)0.24 These ~~
(23)See the many references in: (a) Paquette, L. A,; Kiinzer, H.; Green, K. E.; DeLucchi, 0.; Licini, G.; Pasquato, L.; Valle, G. J.Am. Chem. SOC.1986, 108, 3453. (b) Paquette, L. A.; Shen, C . 4 . J. Am. Chem. SOC.1990,112, 1159. (c) Irngartinger, H.; Deuter, 3.; Charumilind, P.; Paquette, L. A. J. Am. Chem. SOC.1989, 111, 9236. (24)van Rooyen, P. H.; Schindehutte, M.; Lotz, S. Organometallics 1992,11, 1104.
Differing Modes of n-Facial Complexation
Organometallics, Vol. 14, No. 10,1995 4581
Table 5. Experimental Crystallographic Data for 8-11 8 formula space group a,A b, A C,
9
CzzHzaTi m2121 7.792(2) 14.174(8) 16.012(4)
A
a, deg
A deg Y,deg
v, A3
1768 4 340.35 1.28 0.18 x 0.30 x 0.33 5.01
Z mol wt Dcalcd, g C m 3 cryst size, mm3 p, cm-l transmissn factors" temp, "C 20 limitsb scan range, deg in w data collcd scan type no. of unique data no. of obsd dataC final no. of variables Rod Rw(FF goodness-of-fit max peak in final diff map, e/A3
18 2 i 20 5 50" 0.80 0.35 tan 0 +h, +k, +1 w-20 1814 1433 214 0.037 0.054 0.44 0.3
+
7.150(1) 12.187(1) 12.678(1) 93.835(8) 90.187(8) 94.81l(7) 1098 2 512.80 1.55 0.16 x 0.30 x 0.37 5.60 0.85-0.92 22 4 5 20 5 55" 1.30 0.35 tan 0 +h, fk,fl w-20 5077 3993 299 0.038 0.032 1.96 0.29
+
10
11
C~6HzzClF5Ti P 2 Iln 14.826(3) 13.887(2) 21.572(3)
CzsHzzClF5Ti p211c
7.518(2) 18.064(3) 16.093(2)
93.95(1)
90.93(2)
4431 8 512.80 1.54 0.04 x 0.23 x 0.27 5.55 22 4 5 20 5 50" 1.20 +h, +k, 51
2185 4 512.80 1.56 0.05 x 0.11 x 0.35 5.63 0.94-0.97 22 4 i 20 i 50" 1.20 fh,f k , f l
0
w
8214 2930 590 0.102 0.054 1.50 0.68
4005 2004 298 0.069 0.039 1.35 0.41
a An analytical absorption correction was applied to the data for 9 and 11. Data were measured with a Rigaku AFC5S diffractometer using graphite-monochromatedMo Ka radiation for 9-11 and with an Enraf-Nonius CAD-4 diffractometer with graphite-monochromated Mo Ka radiation for 8. Observed data used in the least-squares refinements are defined as Z z 41)for 9-11 and Foz 5 4 F 0 )for 8. R(F) = CllFol - lFcllEIFol.e R,(F) = [Zw(IF,I - ~Fc~)2Ew~Fo~211'2, with w = l/uz(Fo)for 9-11 and w = l/(u2(Fo) 0.0O42Fo2)for 8.
+
Table 6. Selected Bond Distances (A)and Angles (deg) for 8 Ti-C(l) Ti-C(3) Ti-C(5) Ti-C(7) Ti-C(14) Ti-C(16) Centl-Ti C(l)-Ti-C(B) Centl-Ti-C(l) Cent2-Ti-C(l)
2.171(5) 2.431(4) 2.381(5) 2.406(4) 2.389(4) 2.446(4) 2.094 92.4(2) 105.0 105.8
Ti-C(2) Ti-C(4) Ti-C(6) Ti-C(l3) Ti-C(15) Ti-C(17) Cent2-Ti Centl-Ti-Cent2 Centl-Ti-C(2) Cent2-Ti-C(2)
2.175(5) 2.421(4) 2.385(5) 2.403(4) 2.379(4) 2.437(4) 2.086 134.3 106.4 105.3
Table 7. Selected Bond Distances (A)and Angles (deg) for 9 Ti-Cl Ti-C(l) Ti-C(2) Ti-C(3) Ti-C(4) Ti-C(B) Ti-C(11)
2.3453(7) 2.429(2) 2.378(2) 2.354(2) 2.403(2) 2.440(2) 2.427(2)
Ti-C(12) Ti-C(13) Ti-C(14) Ti-C(15) Ti-C(21) Ti-RC(1Ia Ti -RC(2)
Cl-Ti-C(21) Cl-Ti-RC(1) Cl-Ti-RC(2)
101.99(6) 104.28(7) 106.24(6)
C(Sl)-Ti-RC(l) C(21)-Ti-RC(2) RC(l)-Ti-RC(P)
2.402(2) 2.372(2) 2.370(2) 2.383(2) 2.273(2) 2.082(2) 2.071(2) 106.57(8) 101.52(8) 132.6(1)
latter two structures both contain a small endocyclic C-C-C bond angle for the derivatized phenyl ring where the central carbon atom is (T bonded t o the Ti atom: This small endocyclic C-C-C angle is also observed in each of the three pentafluorophenyl derivatives: 111.7(2)' for 9,113(1) and 111(1)"for 10, and 111.5(6)"for 11. Conclusion
The charge density of the carbon atoms in the cyclopentadienyl sector of the isodiCp ligand gives evidence of being quite sensitive to the n surface involved in complexation. These unique observations may possibly be the result of several factors, including differing
Table 8. Selected Bond Distances (A)and Angles (de& for 10 Ti(l)-Cl(l) Ti(l)-C(lA) Ti(l)-C(2A) Ti(l)-C(3A) Ti(l)-C(4A) Ti(l)-C(5A) Ti(1)-C( 11A) Ti(l)-C(12A) Ti(l)-C(13A) Ti(l)-C(14A) Ti(1)-C( 15A) Ti(l)-C(21A) Ti(l)-RC(lAP Ti(l)-RC(2AP
2.316(4) 2.453(12) 2.378(13) 2.340(13) 2.418(13) 2.492(14) 2.508(13) 2.358(12) 2.316(12) 2.415(13) 2.573(14) 2.260(13) 2.102(13) 2.124(14)
Cl(l)-Ti(l)-C(2lA) Cl(l)-Ti(l)-RC(lA) Cl(l)-Ti(l)-RC(BA) C(21A)-Ti(l)-RC(lA) C(21A)-Ti(l)-RC(2A) RC(lA)-Ti(l)-RC(2A)
97.6(3) 108.4(4) 104.8(4) 101.66) 106.4(5) 132.6(6)
Ti(2)-C1(2) Ti(2)-C(lB) Ti(2)-C(2B) Ti(2)-C(3B) Ti(2)-C(4B) Ti(2)-C(5B) Ti(2)-C(llB) Ti(2)-C( 12B) Ti(2)-C(13B) Ti(2)-C( 14B) Ti(2)-C(15B) Ti(2)-C(21B) Ti(2)-RC(lBr Ti(2)-RC(2BP
2.333(4) 2.512(14) 2.419(13) 2.298(13) 2.370(13) 2.515(14) 2.498(15) 2.385(14) 2.336(15) 2.367(13) 2.451(15) 2.245(13) 2.109(14) 2.100(15)
C1(2)-Ti(2)-C(21B) C1(2)-Ti(2)-RC(lB) C1(2)-Ti(2)-RC(2B) C(2lB)-Ti(2)-RC(lB) C(21B)-Ti(2)-RC(2B) RC(lB)-Ti(2)-RC(2B)
100.7(4) 103.2(4) 108.5(5) 107.1(5) 100.1(5) 133.0(6)
a RC(1A) is the ring centroid for C(lA)-C(2A)-C(3A)-C(4A)C(5A). b RC(2A) is the ring centroid for C(llA)-C(12A)-C(13A)C(14A)-C(15A). RC(1B) is the ring centroid for C(lB)-C(BB)C(3B)-C(4B)-C(5B). RC(2B) is the ring centroid for C(11B)-
C(12B)-C(13B)-C(14B)-C(l5B).
electronic contributions from the fused norbornyl subunit and nonbonded steric interactions, and additional studies to shed light on these issues are in progress. Recently, Doman, Hollis, and Bosnich have deduced on the strength of molecular mechanics force field calculations that the conformation adopted by bent metallocenes of the generic formula Cp2MC12 in the crystal is not generally the most stable.25 Although the importance of crystal-packing forces always needs t o be reckoned with and the various possible conformations of 2,3,6,and 8-11 are quite probably close in energy, it is nonetheless remarkable that the three pentafluo(25) Doman,T. N.; Hollis, T. K.; Bosnich, B. J.Am. Chem. Soc. 1995,
117, 1352.
Zaegel et al.
4582 Organometallics, Vol. 14, No. 10, 1995
Table 9. Selected Bond Distances (A) and Angles (deg) for 11 Ti-Cl Ti-C(l) Ti-C(2) Ti-C(3) Ti-C(4) Ti-C(5) Ti-C(11) C1-Ti-C(21) C1-Ti-RC( 1) C1-Ti-RC(2) b
2.336(2) 2.452(7) 2.381(6) 2.352(7) 2.389(7) 2.463(6) 2.447(7)
Ti-C(12) Ti-C(13) Ti-C(14) Ti-C(15) Ti-C(21) Ti-RC(1P Ti-RC(2Ib
2.412(7) 2.359(7) 2.372(7) 2.419(7) 2.264(6) 2.092(7) 2.085(7)
100.9(2) 106.1(2) 106.0(2)
C(Pl)-Ti-RC(l) C(21)-Ti-RC(2) RC(l)-Ti-RC(B)
102.5(3) 104.0(3) 133.1(3)
a RC(1) is the ring centroid for C(l)-C(2)-C(3)-C(4)-C(5). RC(2) is the ring centroid for C(ll)-C(12)-C(13)-C(14)-C(15).
Table 10. Positional Parameters and B(eq) Values for 8 atom Ti C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22)
xlu
-0.13069(9) 0.0782(7) -0.3203(7) -0.0221(6) -0.1637(8) -0.3081(7) -0.2549(6) -0.0753(6) 0.0726(6) 0.0842(7) 0.1475(7) 0.1615(7) 0.2228(6) -0.1979(5) -0.0190(5) 0.0404(6) -0.0981(6) -0.2461(6) -0.4303(6) -0.4189(7) -0.3688(7) -0.3518(6) -0.4981(5)
Ylb -0.94792(5) -1.0491(3) -1.0542(4) -0.9432(4) -1.0028(4) -0.9472(5) -0.8532(4) -0.8521(3) -0.7860(3) -0.7826(5) -0.8828(4) -0.9342(3) -0.8512(4) -0.8066(3) -0.8097(3) -0.8893(3) -0.9320(3) -0.8818(3) -0.8637(3) -0.7779(4) -0.6950(3) -0.7427(3) -0.8148(4)
ZIC
-0.75728(4) -0.7623(3) -0.7902(4) -0.6150(3) -0.6150(3) -0.6362(3) -0.6501(3) -0.6362(3) -0.6189(3) -0.5219(3) -0.4984(3) -0.5840(3) -0.6381(3) -0.8336(2) -0.8231(3) -0.8689(3) -0.9085(3) -0.8861(2) -0.9122(3) -0.9723(3) -0.9132(3) -0.8266(3) -0.8325(3)
NeqP 1.81 3.22 3.32 2.51 3.48 3.53 2.81 2.13 2.32 3.49 3.46 2.76 2.51 1.75 1.92 2.27 2.45 1.93 2.37 2.77 2.68 2.32 2.67
+
a B(eq) = (8n2/3)[a2U~~(u*)2 b2Uzz(b*)2+ C ~ U ~ ~ +( C ub(cos *)~ y)UlN*b* ac(cos p)U13u*c* bc(cos a)U23b*c*l.
+
+
rophenyl complexes preferentially adopt a three-dimensional arrangement in which one isodiCp ligand falls within the C1-Ti-C(21) angle. (IsodiCp)(Cp)TiCl;!and (isodiCp)(Me&p)TiClzhave previously been recognized to have the exo portion of the isodiCp ligand similarly projected into the C1-Ti-C1 angle.8b Whatever the origins of this effect, they are not operational in 2 or in 8 , both of which have the norbornyl segments positioned as remotely from each other as possible. The spacefilling nature of the C6F5 substituent and its electronwithdrawing capabilities are very likely responsible for the different geometric features. It remains to demonstrate that rotameric conformations adopted by CpzM(CsF5)Cl complexes differ generically from those complexes lacking this particular aryl substituent. Experimental Section All manipulations were carried out under a n argon atmosphere. The solvents were distilled from sodium benzophenone ketyl prior to use. The E1 high-resolution mass spectra were recorded in the CSM at Dijon and at The Ohio State University Campus Chemical Instrumentation Center. Elemental analyses were performed by the "Service central de microanalyses du CNRS" (Lyon, France).
Table 11. Positional Parameters and B(eq) Values for 9 atom
X
0.22302(5) -0.06995(8) -0.1695(2) -0.2697(2) -0.0215(3) 0.3361(3) 0.4421(2) 0.3015(3) 0.4686(3) 0.4606(3) 0.2908(4) 0.1939(3) 0.0359(4) 0.1325(5) 0.2554(5) 0.2128(4) 0.0051(4) 0.2194(3) 0.1726(3) 0.3316(3) 0.4733(3) 0.4020(3) 0.4625(3) 0.4870(4) 0.2849(4) 0.1645(3) 0.2728(4) 0.1402(3) -0.0363(3) -0.0946(4) 0.0314(4) 0.2099(4) 0.2596(3)
Y
z
0.28049(3) 0.30130(5) 0.1577(1) 0.0849(1) 0.0957(1) 0.1832(2) 0.2560(1) 0.4417(2) 0.4049(2) 0.4194(2) 0.4636(2) 0.4772(2) 0.5355(2) 0.6462(2) 0.6098(2) 0.4817(2) 0.4726(2) 0.1461(2) 0.0892(2) 0.1025(2) 0.1690(2) 0.1973(2) 0.2368(2) 0.1289(2) 0.0744(2) 0.1555(2) 0.2660(2) 0.2184(2) 0.1707(2) 0.1305(2) 0.1356(2) 0.1792(2) 0.2181(2)
0.31537(3) 0.39343(5) 0.1955(1) 0.0012(1) -0.1596(1) -0.1186(1) 0.0742(1) 0.2164(2) 0.2563(2) 0.3671(2) 0.3960(2) 0.3020(2) 0.2597(2) 0.2254(2) 0.1313(2) 0.1194(2) 0.1506(2) 0.4484(2) 0.3510(2) 0.2862(2) 0.3411(2) 0.4424(2) 0.5539(2) 0.6098(2) 0.6162(2) 0.5632(2) 0.5997(2) 0.1473(2) 0.1203(2) 0.0194(2) -0.0609(2) -0.0402(2) 0.0613(2)
B(echa Az 2.18(1) 3.71(3) 5.94(8) 6.44(9) 6.48(9) 7.7(1) 5.68(8) 3.2(1) 3.6(1) 3.8(1) 3.6(1) 3.3(1) 4.4(1) 6.1(2) 6.2(2) 4.3(1) 4.7(1) 2.60(8) 2.97(9) 3.0(1) 2.73(9) 2.40(8) 3.3(1) 3.7(1) 3.7(1) 3.541) 4.1(1) 2.70(9) 3.3(1) 3.9(1) 4.2(1) 4.4(1) 3.5(1)
The form of the equivalent isotropic displacement parameter is B(eq) = ( 8 n 2 / 3 ) ~ : i ~ , U ~ * ~ u * ~ a ~ . a , . "C in a CHCl3-liquid Nz bath and added quickly to a solution of TiC13.3THF (550 mg, 1.35mmol) in THF (40 mL) at the same temperature. The reaction mixture was stirred a t -64 "C for 5 h. Freshly distilled and previously cooled cc14 (20 mL) was introduced, and the solution developed a dark red coloration. After 15 min of stirring, the reaction mixture was poured into 10 mL of concentrated hydrochloric acid and ice. The aqueous phase was extracted with CHC13, and the combined organic layers were washed with water, dried, and evaporated. Recrystallization of the residue from CHzClz-hexanes afforded 3 (243 mg, 49%) as a dark red solid, mp 208-210 "C; 'H and 13C NMR (see Tables); MS m l z (relative intensity): 380 (M+, 13), 345 (M+ - C1, 171, 249 (M+ - isodiCp, 46), 131 (CloH11, 84) 103 (CeH7, 100). Anal. Calcd for C2oH2ZClzTi: C, 63.02; H, 5.77. Found: C, 62.93; H, 5.76. exo-(q6-Isodicyclopentadienyl)titaniu Trichloride (5). (1sodicyclopentadienyl)lithium (799 mg, 5.79 mmol) was dissolved in dry THF (30 mL), and freshly distilled trimethylsilyl chloride (7.5 mL, 59.1 mmol) was introduced dropwise. The reaction mixture was refluxed for 1 h, returned to room temperature, and stirred for a n additional 2 h. Following solvent removal in vacuo, the product was extracted into pentane (3 x 8 mL), and the combined yellowish extracts were concentrated to leave the oily silane 4,14which was directly dissolved in toluene (2 mL). In a second flask, Tic14 (0.7 mL, 6.38 mmol) was diluted with dry toluene (5 mL). The solution of 4 was slowly transferred into the Tic14 solution via cannula, and the mixture was stirred at room temperature for 15 h. The solvent was removed in vacuo, and the dark green residue was triturated with pentane (3 x 10 mL). The pentane extracts were dried and concentrated to give 5 (1.337 g, 85%) as greenish crystals, mp 140-142 "C; lH and 13C NMR (see Tables). Anal. Calcd for C10H11C13Ti: C, 42.08; H, 3.88. Found: C, 42.36; H, 4.00.
Dichloride (3). A solution of (isodicyclopentadienyl)lithium2
endo,exo-Bis(qs-isodicyclopentadienyl)ti~~ Dichloride (6). A solution of 5 (264 mg, 0.93 mmol) in dry THF (17
(360 mg, 2.61 mmol) in dry THF (46 mL) was cooled to -64
mL) a t -78 "C was treated gradually with a solution of
endo,endo-Bis(qS-isodicyclopentadienyl)titanium
DifferingModes of n-Facial Complexation
Organometallics, Vol. 14, No. 10, 1995 4583
Table 12. Positional Parameters for 10 atom
X
Y
z
B(eq)" or B, A2
Ti(1) Cl(1) F(1A) F(2A) F(3A) F(4A) F(5A) C(1A) C(2A) C(3A) C(4A) C(5A) C(6A) C(7A) C(8A) C(9A) C(1OA) C(11A) C(12A) C(13A) C(14A) C(15A) C(16A) C(17A) C(18A) C(19A) C(20A) C(21A) C(22A) C(23A) C(24A) C(25A) C(26A) Ti(2) Cl(2) F(1B) F(2B) F(3B) F(4B) F(5B) C(1B) C(2B) C(3B) C(4B) C(5B) C(6B) C(7B) C(8B) C(9B) C(1OB) C(11B) C(12B) C(13B) C(14B) C(15B) C(16B) C(17B) C(18B) C(19B) C(20B) C(21B) C(22B) C(23B) C(24B) C(25B) C(26B)
0.7980(2) 0.8567(2) 0.6657(5) 0.5438(6) 0.4839(6) 0.5513(5) 0.6767(5) 0.790(1) 0.728(1) 0.6639(9) 0.6828(9) 0.759(1) 0.806(1) 0.907(1) 0.944(1) 0.858(1) 0.810(1) 0.8591(8) 0.8407(9) 0.9024(9) 0.9534(9) 0.929(1) 0.964(1) 0.892(1) 0.820(1) 0.853(1) 0.958(1) 0.6858(9) 0.643(1) 0.579(1) 0.547(1) 0.5833(9) 0.649(1) 0.2959(2) 0.2093(2) 0.3733(6) 0.4924(6) 0.5901(6) 0.5680(6) 0.4450(5) 0.166(1) 0.146(1) 0.212(1) 0.269(1) 0.242(1) 0.239(1) 0.255(1) 0.176(1) 0.120(1) 0.134(1) 0.341(1) 0.406(1) 0.440(1) 0.389(1) 0.323(1) 0.267(1) 0.173(1) 0.190(1) 0.291(1) 0.311(1) 0.3977(9) 0.417(1) 0.481(1) 0.528(1) 0.517(1) 0.454(1)
0.2063(2) 0.3597(2) 0.0497(5) 0.0700(6) 0.2458(6) 0.4037(6) 0.3905(5) 0.178(1) 0.115(1) 0.174(1) 0.272(1) 0.272(1) 0.330(1) 0.337(1) 0.234(1) 0.178(1) 0.253(1) 0.105(1) 0.0511(9) 0.084(1) 0.157(1) 0.171(1) 0.208(1) 0.268(1) 0.192(1) 0.097(1) 0.111(1) 0.218(1) 0.141(1) 0.149(1) 0.237(1) 0.315(1) 0.306(1) 0.0365(2) 0.1753(2) 0.2540(5) 0.3169(6) 0.1939(7) 0.0024(7) -0.0660(6) 0.003(1) -0.031(1) -0.103(1) -0.110(1) -0.044(1) -0.023(1) 0.083(1) 0.136(1) 0.054(1) -0.024(1) 0.072(1) 0.099(1) 0.013(1) -0.061(1) -0.027(1) -0.058(1) -0.010(2) 0.097(2) 0.105(1) 0.015(2) 0.089(1) 0.186(1) 0.223(1) 0.161(1) 0.064(1) 0.032(1)
0.7631(1) 0.7781(2) 0.8406(4) 0.9230(4) 0.9542(4) 0.8990(4) 0.8200(4) 0.6507(6) 0.6797(6) 0.7030(6) 0.6903(6) 0.6571(6) 0.6100(7) 0.6291(7) 0.6224(7) 0.6023(7) 0.5571(6) 0.8525(6) 0.7984(7) 0.7549(6) 0.7838(7) 0.8445(7) 0.9067(7) 0.9337(7) 0.9507(6) 0.9239(6) 0.9420(7) 0.8285(6) 0.8546(7) 0.8978(8) 0.9120(7) 0.8862(7) 0.8443(6) 0.7182(1) 0.7277(2) 0.6769(4) 0.6021(4) 0.5361(4) 0.5510(4) 0.6227(4) 0.6401(7) 0.6986(7) 0.7132(6) 0.6641(7) 0.6179(7) 0.5493(6) 0.5331(6) 0.5625(7) 0.5863(7) 0.5360(6) 0.8294(7) 0.7933(7) 0.7668(7) 0.7862(7) 0.8238(7) 0.8766(8) 0.8680(7) 0.8758(8) 0.8853(9) 0.9269(7) 0.6535(6) 0.6465(7) 0.6070(7) 0.5743(7) 0.5805(7) 0.6199(7)
2.7(1) 3.8(2) 5.6(5) 6.6(5) 6.9(5) 6.4(5) 5.5(5) 3.2(7) 3.8(8) 3.3(7) 3.5(8) 3.1(7) 4.1(8) 5(1) 5(1) 5(1) 5(1) 3.2(7) 3.4(7) 3.3(7) 3.7(8) 3.4(8) 4.9(9) 5(1) 4.6(8) 4.1(8) 6(1) 2.7(7) 3.5(8) 5(1) 5(1) 4.3(9) 3.5(8) 3.2(1) 4.2(2) 5.6(5) 6.3(6) 8.2(6) 7.2(6) 5.8(5) 3.2(7) 4.0(8) 3.9(8) 4.2(8) 3.8(8) 3.9(8) 4.5(8) 5.1(9) 4.2(8) 4.7(8) 4(1) 5(1) 5(1) 4.4(9) 5(1) 6(1) "(1) 8(1)
6(1) 7(1) 3.2(7) 3.8(8) 4.4(9) 4.4(4)b 4.4(9) 4.3(9)
a The form of the equivalent isotropic displacement parameter Refined isotropically. is B(eq) = (8xz/3)ClC~U,a*la*Ja;a,. (isodicyclopentadieny1)lithium(130 mg, 0.94 "01) in THF (32 mL) a t the same temperature. After 5 h of stirring at -78 "C, the reaction mixture was treated with concentrated HC1 (5 mL) and ice, then extracted with CHC13 (20 mL and then 2 x 10 mL). The combined organic layers were washed with water, dried, and evaporated. The residue was recrystallized once from CHzClz-hexanes to give 194 mg (55%) of 6 as dark red crystals, mp 196-198 "C; 'H and 13C NMR (see Tables); MS m l z (relative intensity): 380 (M+, 22), 345 (M+ - C1, 29),
Table 13. Positional Parameters and B(eq) Values for 11 atom X Y 2 B(eq),oAz 0.44416(7) 0.71997(7) Ti 0.2442(1) 2.92(6) -0.0383(2) 0.4214(1) 0.6629(1) 4.2(1) c1 0.8740(2) 0.4779(5) 0.5268(2) 4.6(2) F(1) 0.6125(2) 1.0022(2) 5.1(2) F(2) 0.4053(5) 0.6399(2) 1.0437(2) 5.3(2) F(3) 0.0631(5) 0.5785(2) 0.9532(2) 4.9(2) F(4) -0.2046(5) 0.8226(2) 4.5(2) -0.1404(5) 0.4950(2) F(5) 0.3310(4) 0.7124(4) 3.6(4) C(1) 0.4232(9) 0.7829(4) 4.0(4) 0.4748(9) 0.3721(4) C(2) 0.8358(4) 3.9(4) C(3) 0.3288(10) 0.3722(4) 0.3344(4) 0.7976(4) 3.8(4) C(4) 0.1851(9) 0.7221(5) 3.4(3) 0.2474(9) 0.3078(3) C(5) 0.6585(5) 0.2122(10) 0.2476(4) 4.6(4) C(6) 0.5705(5) 5.5(5) C(7) 0.2224(11) 0.2787(4) 0.5602(5) 5.9(5) C(8) 0.4188(12) 0.2990(4) 0.6446(5) 5.0(4) 0.5015(9) 0.2822(5) C(9) 0.6649(5) 5.3(5) C(10) 0.3983(11) 0.2098(4) 0.6154(4) 3.4(4) 0.2223(8) 0.5422(4) C(11) 0.4853(4) 0.5829(4) 4.1(4) C(12) 0.3238(9) 0.6331(4) 3.9(4) 0.4795(9) 0.4791(4) C(13) 0.5321(4) 0.6960(4) 3.8(4) C(14) 0.4720(9) 0.6853(4) 0.3111(8) 0.5713(4) 3.3(3) C(15) 0.7068(4) 4.2(4) C(16) 0.2173(10) 0.6422(4) 0.6377(5) 5.5(5) (317) 0.2695(10) 0.6956(4) 0.5592(5) 5.7(5) 0.1727(11) 0.6644(4) C(18) 0.5960(4) 0.5930(5) 4.6(4) C(19) 0.0731(9) 0.6800(5) 5.0(4) C(20) 0.0255(10) 0.6248(4) 0.8347(4) 2.9(3) 0.1737(9) 0.5097(3) C(21) 0.5409(4) 0.8867(4) 3.0(3) C(22) 0.3027(8) 0.9559(4) 3.3(4) 0.2698(9) 0.5844(4) C(23) 0.9764(4) 3.4(4) C(24) 0.1009(10) 0.5981(4) 0.9312(4) 3.1(3) 0.5679(4) C(25) -0.0351(8) 0.5241(3) 0.8626(4) 3.0(3) C(26) 0.0044(9) a The form of the equivalent isotropi.c displacemen.t parameter is B(eq) = (8x2/3)Ci~jU"u*iu*jai.aj. 249 (M+ - isodicp, 181,131(CloH11,58),103 (CEH,, 100). Anal. Calcd for C2oH22ClzTi: C, 63.02; H, 5.77. Found: C, 62.73, H,
5.91. exo,exo-Bis(~6-isodicyclopentadienyl)titanium Dibromide (7). Boron tribromide (465 mg, 1.84 mmol) was diluted with dry CHzClz (3 mL) and slowly added to a solution of 2 (475 mg, 1.25 mmol) in CHzClz (18 mL). The mixture was stirred at room temperature for 2 h before the volatiles were removed in vacuo. The residue was recrystallized from CH2Clz-hexanes to furnish 506 mg (86%) of 7 as black crystals, mp 238-240 "C; lH and 13C NMR (see Tables); MS m l z (relative intensity): 470 (M+, 50), 389 (M+ - Br, 52), 339 (M+ - isodicp, 311, 131 (isodiCp, 31). Anal. Calcd for C Z O H Z Z B ~ ~ T ~ . ~ /C,~ 48.04; C H ~ CH,~ 4.52. ~: Found: C, 48.88; H, 4.60.
Dimethyl~exo,e~o-bis(qs-isodicyclopentadienyl)titanium (8). A suspension of 2 (145 mg, 0.38 mmol) in dry ether (6 mL) was cooled t o -80 "C, and methyllithium (0.45 mL of 2 M in ether, 0.90 mmol) was introduced dropwise. The reaction mixture was warmed to room temperature, stirred for 2 h, diluted with ether (6 mL), and filtered t o remove the LiC1. The solid was rinsed with ether (2 x 5 mL), and the combined filtrates were evaporated. The residue was recrystallized from hexanes at -20 "C to afford 8 (87 mg, 68%) as very air-sensitive orange crystals, mp 140-150 "C decomp; 'H and 13C NMR (see Tables); MS m l z (relative intensity): 340 (M+, 71, 325 (M+ - CH3, 43), 310 (M+ - 2CH3, 100). Anal. Calcd for C2zHz~Ti: C, 77.64; H, 8.23; Ti, 14.11. Found: C, 77.20; H, 8.43; Ti, 13.70. General Procedure for Preparation of the Pentafluo-
rophenyl Bis(q6-isodicyclopentadieny1)titaniumChlorides (9-11). Bromopentafluorobenzene(0.08 mL, 0.64 "01, previously distilled under argon) was diluted with ether (3 mL) and cooled to -78 "C. n-Butyllithium (0.43 mL of 1.49 M in hexanes, 0.64 mmol) was added dropwise during 20 min. After 10 min of stirring at room temperature, the reaction mixture was recooled to 0 "C and a suspension of 2 (124 mg, 0.32 mmol)
4584
Organometallics, Vol. 14, No. 10, 1995
in THF (5 mL) and ether (3mL) was introduced via a cannula. The reaction mixture was stirred overnight a t room temperature, filtered through Celite, and evaporated. Flash chromatography of the residue on silica gel (elution with hexanesCHzClZ, 7:3) afforded 64 mg (39%) of product. Analytically pure samples were obtained by crystallization from hexanesCHzC12. Data for the exo,exo isomer 9: orange-red crystals, mp 245-255 "C, decomp; MS m l z (M+) calcd 512.0810, obsd 512.0794. Anal. Calcd for C26HzzClF~,Ti: C, 60.90; H, 4.32. Found: C, 60.84; H, 4.16. For the endo,endo isomer 10: dark red crystals, mp 182-192 "C, decomp; MS m l z (M+) calcd 512.0810, obsd 512.0762. Anal. Calcd for C Z ~ H Z Z C ~ FC,~ T ~ : 60.90; H, 4.32. Found: C, 60.65; H, 4.47. For the endo,exo isomer 11: blood red crystals, mp 175-185 "C, decomp; MS m l z (M+) calcd 512.0810, obsd 512.0782. Anal. Calcd for Cz6Hz2ClF5Ti: C, 60.90; H, 4.32. Found: C, 60.17; H, 4.40. X-ray Crystallographic Analysis of 10. The data collection crystal was a red plate which was coated with epoxy as a precaution against air sensitivity. Examination of the diffraction pattern on a Rigaku AFC5S diffractometer indicated a monoclinic crystal system with systematic absences of OkO, k = 2n 1,and h01, h 1 = 2n 1. The space group is uniquely determined as P21ln. Unit cell constants were obtained by a symmetry-restricted least-squares fit of the diffractometer setting angles for 25 reflections in the 28 range 17-23" with Mo K a radiation (1(Kad = 0.709 30 A). Six standard reflections were measured after every 150 reflections during data collection and indicated a substantial amount of crystal decay had occurred. The average decrease in intensity was 18.7%. Data reduction included a linear decay correction and was done with the TEXSAN package.26 The structure was solved with the direct methods procedure of SHELXS-86.27There are two molecules in the asymmetric unit, and they are labeled as " A and "B". For the three structures 9-11, full-matrix least-squares refinements were performed in TEXSAN;26the function minimized was Ew(IFo[ - lFc1)2with w = l/uz(Fo). It was not possible to refine atom C(24B) anisotropically, so it was kept isotropic. All ofthe other non-hydrogen atoms were refined anisotropically. Hydrogen atoms are included in the model as fixed contributions at calculated positions with C-H = 0.98 A and BH = 1.B(attached carbon atom) for this structure and for 9 and 11. The final refinement cycle was based on the 2930 intensities with I > a(I) and 590 variables and resulted in agreement indices of R = 0.102 and R , = 0.054. A structure factor calculation for the 2003 intensities with I > 3 d I ) gives a n R value of 0.054. Scattering factors for all four structures are from the International Tables for X-ray Crystallography and include terms for anomalous dispersion.28 X-ray Crystallographic Analysis of 9. Crystals of 9 are clear, orange-red rectangular rods. One rod was cleanly cut to a suitable size and used for data collection. Examination of the diffraction pattern on a Rigaku AFC5S diffractometer indicated a triclinic crystal system. Unit cell constants were obtained by a least-squares fit of the diffractometer setting angles for 25 reflections in the 28 range 25-30" with Mo Ka radiation (I(Ka1) = 0.709 30 A). Six standard reflections were measured after every 150
+
+
+
(26) TEXSAN, Single Crystal Structure Analysis Software, Version 5.0; Molecular Structure Corporation: The Woodlands,TX 77381,1989. (27) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467. (28) Scattering factors for the non-hydrogen atoms, including terms for anomalous dispersion, are from the International Tables for X-ray Crystallography;Kynoch Press: Birmingham, England, 1974; Vol. IV, pp 71 and 148. The scattering factor for the hydrogen atom is from the following: Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J.Chem. Phys. 1966,42, 3175.
Zaegel et al. reflections during data collection and indicated that the crystal was stable. Data reduction was done with the TEXSAN package.26 An analytical absorption correction was applied to the data.29 The structure was solved in Pi by the Patterson method in SHELXS-86.27 A secondary extinction parameteso refined to a final value of 9.7(11) x The final refinement cycle was based on the 3993 intensities with I > o(I) and 299 variables and resulted in agreement indices ofR = 0.038 and R, = 0.032. X-ray Crystallographic Analysis for 11. Crystals of 11 are blood-red plates. Examination of the diffraction pattern on a Rigaku AFC5S diffractometer indicated a monoclinic crystal system with systematic absences of h01, 1 = 2n 1, and OkO, k = 2n 1. The space group was uniquely determined as P21lc. Unit cell constants were obtained by a symmetry-restricted least-squares fit of the diffractometer setting angles for 25 reflections in the 28 range 21-26" with Mo K a radiation (I(Ka1) = 0.709 30 A). Six standard reflections were measured after every 150 reflections during data collection and indicated a small amount of crystal decay. On average, the standards decreased in intensity by 1.6%. Data reduction included a linear decay correction which was done with the TEXSAN package.26 An analytical absorption correction was also applied to the data.29 The structure was solved by the direct methods procedure in SHELXS-86.27The final refinement cycle was based on the 2004 intensities with I > dI)and 298 variables and resulted in agreement indices of R = 0.069 and R, = 0.039. X-ray Crystallographic Analysis for 8. A transparent single crystal of 8 was mounted in a thin-walled glass capillary under Ar and transferred to the goniometer. The space group was determined to be P212121 from the systematic absences. The structure of 8 has a pseudo 2-fold axis which bisects the CH3-Ti-CH3 angle. Because of the arrangement of the isodiCp ligands, the molecule is chiral in the solid state. Only one enantiomer has crystallized here in P212121. Least-squares refinement with isotropic thermal parameters led t o R = 0.079. The geometrically constrained hydrogen atoms were placed in calculated positions 0.95 A from the bonded carbon atom and allowed to ride on that atom with B fixed a t 5.5 A2. The methyl hydrogen atoms were included as a rigid group with rotational freedom a t the bonded carbon atom (C-H = 0.95 A, B = 5.5 Az).31 Refinement of nonhydrogen atoms with anisotropic temperature factors led t o the final values of R = 0.037 and R, = 0.054.
+
+
Acknowledgment. The Ohio State group thanks the National Science Foundation for their financial support of this research program and Prof. Robin Rogers for the X-ray crystallographic analysis of 8. We are also grateful to Bruno Andrioletti and Dr. Bernard Boitrel (URA 1685, Dijon, France) for the 500 MHz NMR measurements. Supporting Information Available: Tables of leastsquares planes, bond lengths and angles, bond distances involving the hydrogen atoms, anisotropic displacement parameters, and calculated positional parameters for the hydrogen atoms of 8-11 (39 pages). Ordering information is given on any current masthead page. OM950337N (29) De Meulenaer, J.; Tompa, H. Acta Crystallogr. 1966,19, 1014. (30) Zachariasen, W. M. Acta Crystallogr. 1963, 16, 1139. (31) Sheldrick, G. M. SHELX76, A system of computer programs
for X-ray structure determination as locally modified, University of Cambridge: Cambridge, England, 1976.
