Organometallics 1995, 14, 848-854
Low Oxidation Dinuclear Titanium Complexes with the Bridging p (Dimethylsilyl)biscyclopentadienyl Ligand. Crystal Structure of [{Ti(~5-CsH5)}2(Cr-C1)Z(C1-Me2Si(C5H4)2)l
-
Tomas Cuenca, Ana Padilla, and Pascual Royo* Departamento de Quimica Inorganica, Universidad de Alcalb, Campus Universitario, E-28871 Alcala de Henares, Spain
Miguel Parra-Hake Centro de Graduados e Investigaci6n, Instituto Tecnolbgico de Tijuana, Apdo. Postal 1166,22000 Tijuana, Mixico
Maria Angela Pellinghelli and Antonio Tiripicchio Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universita di Parma, Centro di Studio per la Strutturistica Difrattometrica del CNR, Viale delle Scienze 78, I-43100 Parma, Italy Received August 9, 1994@ The chlorotitanium(II1) derivative [{Ti(y5-C5Hs)}201-C1)2~-Me2Si(C5H4)2}l(2) was synthesized in 85% yield by reduction of the titanium(rV) derivative {[Ti(y5-C5Hs)C12121U-Me2Si(C5H4)21} (1)with 2 equiv of sodium amalgam. The structure of 2 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/n, with 2 = 8, in a unit cell of dimensions a = 28.262(10), b = 8.089(5), and c = 18.446(9) p = 91.06(2)". The structure has been solved from difiactometer data by direct and Fourier methods and refined by blocked full-matrix least-squares methods on the basis of 3200 observed reflections to R and R, values of 0.0568 and 0.0727, respectively. The [Me2Si(CsH4)2I2-ligand, through the two cyclopentadienyl rings, acts as a bridge between the two Ti atoms, which are also involved in a double C1 bridge. Moreover, each Ti atom y5-interacts with a cyclopentadienyl ring. If the cyclopentadienyl centroids are considered as coordination sites, then the coordination geometry around each titanium is distorted tetrahedral. In the presence of oxygen, 2 is immediately transformed into the p-oxo compound { [Ti(y5-CsH5)C11201-0)CU-Me~Si(CgHq)21}. Reduction of 1 with sodium amalgam or HgCl2-activated magnesium in THF at room temperature in the presence of a stoichiometric amount of the appropriate ligand (L) gave [L = CO (3);CN(2,6-C&Me2) (511. the titanium(I1) adducts {Ti(y5-C5H5)L2}21U-Me2Si(C5H4)21 The same reduction of 1 with sodium amalgam or HgCl2-activated magnesium in THF, in the presence of PMezPh, resulted in the loss of hydrogen and formation of the diamagnetic (6). The dicarbonyl derivative 3 was complex [{Ti(PMe2Ph)}2~-y1-y5-C5H4)2~-MezSi(C5H4)2}l with CO. This reaction also obtained by reaction of [{Ti(y5-C5H5)Me2}2{p-Me2Si(C5H4)2}1 enables us to identify the formation of the acetone-coordinated titanium compound 4 as a n intermediate species.
A,
Introduction The (dimethylsily1)biscyclopentadienyl anion, [Measi(C5H4)2I2-, is capable of being coordinated to metallic centers as a chelating group (type I) or as a bridging group (type 11) (Figure 1). This ligand has been successfully used t o stabilize both high and low oxidation group 4d metal complexes. The chemistry of mononuclear compounds, type I, with symmetric and asymmetric rings bridged by a SiR2 fragment and their potential applications as catalysts in stereo- and enantioselective hydrogenation and polymerization of olefins have been extensively studied.l Recently we reported the synthesis of similar halo- and alkyltitanium(n7) derivatives,2 as well as new titanium(II1) and 41) metallocene complexes3 containing this ligand as a @
Abstract published in Advance ACSAbstracts, December 1,1994.
MLn I
/
\
MLn
MLn I1
Figure 1. Coordination modes of the (dimethylsily1)biscyclopentadienyl ligand.
chelating system (type I), and some aspects of their chemical behavior. Dinuclear compounds, type 11, are also well repre~ented,~ although they are less wellknown for group 4d metals5 and few dinuclear derivatives of these metals are known in low oxidation states. It has been demonstrated that the access to dinuclear titanium(II1) and zirconium(II1) complexes can be fa-
Q276-7333/95/2314-Q848$Q9.QQ/Q 0 1995 American Chemical Society
Organometallics, Vol. 14, No. 2, 1995 849
Scheme 1
2
L = co (3) CN(2,6-C6H,Me,) (5)
1 air
PM%Ph
or MgRIgCI,
.HZ
I
'
PMqPh
6
cilitated by using the fulvalene ligand, which is capable of being coordinated to two metal centers, and its inherent rotational flexibility can lead to trans or cis configurations of the coordinated metal fragments.6 Furthermore, this ligand is capable of undergoing carbon-hydrogen bond cleavage, leading t o the formation of dinuclear complexes containing v1-q5-C5H4bridg(1)(a) Kopf, H.; Kahl, W. J. Organomet. Chem. 1974,64,C37. (b) Fendrick, C. M.; Mintz, E. A.; Schertz, L. D.; Marks, T. J.; Day, V. W. organometallics, 1984,3,819. (c) Yasuda, H.; Nagasuna, K; Akita, M.; Lee, K; Nakamura, A. Organometallics l884,3,1470. (d) Bajgur, C. S.; Tikkanen, W. R.; Petersen, J. L. Znorg. Chem. 1985,24,2539. (e) Jeske, G.; Schock, L. E.; Swepston, P. N.; Schumann, H.; Marks, T. J. J. Am. Chem. SOC. 1985,107,8103.(0Jutzi, P.; Dickbreder, R. D. Chem. Ber. 1986,119,1750.(g) Muller, J.; Ludemann, F.; Kopf, H. J. Organomet. Chem. 1986,303,167.(h)Herrmann, W. A.; Rohrmann, J.; Herdtweck, E.; Spaleck, W.; Winter, A. Angew. Chem., Znt. Ed. Engl. 1989,28, 1511. (i) Kabi-Satpathy, A.; Bajgur, C. S.; Reddy, K. P.; Petersen, J. L. J. Organomet. Chem. 1989,363, 105. (j) Roll, W.; Brintzinger, H. H.; Rieger, B.; Zolf, R. Angew. Chem., Int. Ed. Engl. 1990,29,279. (k) Conticello, V. P.; Brard, L.; Giardello, M. A.; Tsuji, 1992,114, Y.; Sabat, M.; Stern, C. L.; Marks, T. J. J. Am. Chem. SOC. 2761. (2)(a)G6mez, R.;Cuenca, T.; Royo, P.; Herrmann, W. A.; Herdweck, E. J. Organomet. Chem. 1990,382,103. (b) Gbmez, R.; Cuenca, T.; Royo, P.; Hovestreydt, E. Organometallics 1991,10, 2516. (3)(a) G6mez, R.; Cuenca, T.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A. Organometallics 1991, 10, 1505. (b) Cuenca, T.; G6mez, R.; G6mez-Sal, P.; Royo, P. J. Organomet. Chen. 1993,454,105. (4)(a) Weaver, J.; Woodward, P. J. Chem. SOC.,Dalton Trans. 1973, 1439. (b) Wegner, P. A.; Uski, V. A.; Kiester, R. P.; Dabestani, S.; Day, V. W. J.Am. Chem. SOC. 1977,99,4846.(c) Wright, M. E.; Mezza, T. Amstrong, N. R. Organometallics 1983,2,1711.(d) M.; Nelson, G. 0.; Abrieland W., Heck, J. J. Organomet. Chem. 1986,302,363.(e) Hock, N.;Oroschin, W.; Paolucci, G.; Fischer, R. D. Angew. Chem., Int. Ed. Engl. 1986,25,738. (0 Qiao, K.;Fischer, R. D.; Paolucci, G.; Traldi, P.; Celon, E. Organometallics 1990,9,1361. (5)(a) Reddy, K.P.; Petersen, J. L. Organometallics 1989,8,547. (b) Reddy, K P.; Petersen, J. L. Organometallics 1989,8, 2107. (c) Cacciola, J.; Reddy, K. P.; Petersen, J. L. Organometallics 1992,11, 665. (d) Ciruelos, S.;Cuenca, T.; Flores, J. C.; G6mez, R.; G6mez-Sa1, P.; royo, P. Organometallics 1993,12,944. (e) Cuenca, T.; Flores, J. C.; G m e z , R.; G6mez-Sa1, P.; Parra-Hake, M.; Royo, P. Inorg. Chem. 1993,32,3608. (6)(a) Ashworth, T. V.; Cuenca, T.; Herdtweck, E.; Herrmann, W. A. Angew. Chem., Int. Ed. Engl. 1986, 25, 289. (b) Cuenca, T.; Herrmann, W. A.; Ashworth, T. V. Organometallics 1986,5,2514.(c) Herrmann, W. A.; Cuenca, T.; Kiisthardt, U. J. Organomet. Chem. 1986, 309, C15. (d) Herrmann, W. A,; Cuenca, T.; Menj6n, B.; Herdtweck, E. Angew. Chem., Int. Ed. Engl. 1987,26,697.(e) Cuenca, T.; G6mez, R.; mmez-Sal, P.; Rodriguez, G.; Royo, P. Organometallics 1992,11, 1229. (0 Gambarotta, S.;Chiang, M. Y. Organometallics 1987,6,897. (g) Wielstra, Y.; Gambarotta, S.; Meetsma, A.; de Boer, J. L. Organometallics 1989,8,250. (h) Wielstra, Y.; Gambarotta, S.; Meetsma, A,; Spek, A. L. Organometallics 1989,8,2948. (i)Wielstra, Y.; Meetsma, A.; Gambarotta, S.; Khan, S. Organometallics 1990,9, 876. (j) Wielstra, Y.; Gambarotta, S.; Spek, A. L.; Smeets, W. J. J. Organometallics 19w),9,2142.
ing gr~ups.~g-'t~ The use of the (dimethylsily1)biscyclopentadienyl anion, [MezSi(C5H4)2I2-, as a bridging ligand is an alternative system to prepare this type of dinuclear complexes, but only one dinuclear zirconium(111)compound, [{Z~q5-C5H5)}~01-C1)aCU-Me~Si(C5H4)a}1, with this bridging ligand has been reported.5c We describe below the synthesis and characterization of new dinuclear titanium(II1) and 411) complexes [{Ti(v5C5H5)}~01-C1)~01-Me~Si(C5)~}1(2), [{Ti(q5-C5H5)LzI~CUMezSi(CsH4)a)I[L = CO (3),CN(2,6-C6H3Med(5)1,and [{Ti(PMezPh))z01-v1-q5-C5H4)~01-Me2Si(C5~)~}1 (6).All these compounds were characterized by analytical and spectroscopic methods, and the X-ray structure of 2 was fully elucidated by an X-ray diffraction study.
Results and Discussion Reduction of a toluene solution of the titanium(IV) (1)with derivative [{Ti(q5-C5H5)C12}2CU-Me~Si(C5H4)2)l 2 equiv of sodium amalgam gave the chlorotitanium(111)complex [{Ti(q5-C5H5)}~CU-Cl)a~-Me~Si(C5H4)a}1 (2) (Scheme 1) as a dark amber crystalline solid in 85% yield. Complex 2 is scarcely soluble in THF and more soluble in dichloromethane, from which it can be recrystallized t o give single crystals suitable for an X-ray study. Complex 2 is very oxygen and moisture sensitive but can be stored unchanged under argon or nitrogen for months. In the presence of oxygen, 2 is immediately transformed into the pox0 compound [{Ti(~5-C5H5)C1}~~-O)~-Me~Si(CgHq)2)l.5e Magnetic susceptibility measurements at room temperature gave a magnetic moment 01,s) of 1.423 k 0.66 pB, similar to values previously observed for other phalotitanium(II1) derivatives.* When the reduction of 1 was carried out with sodium amalgam or HgCla-activated magnesium in THF at room temperature (Scheme 1) in the presence of the stoichiometric amount of the appropriate ligand L, the titanium(I1) adducts [{Ti(~5-C5H5)L~)~CU-Me~Si(C5H4)2)l [L = CO (3);CN(2,6-C&Me2), (5)lwere isolated in high (7)(a) Berry, M.; Cooper, N. J.; Green M. L. H.; Simpson, S. J. J. Chem. Soc., Dalton Trans. 1980,29.(b) Erker, G.; Schlund, R.; Kriiger, C. Organometallics 1989,8,2349. (8)Wailes, P. C.; Coutts, R. S. P.; Weigold, H. Organometallic Chemistry of Titanium, Zirconium and Hafnium; Academic Press: New York 1974.
Cuenca et al.
850 Organometallics, Vol. 14,No. 2, 1995 Table 1. 13C NMR Data for Titanium and Zircodum Complexes with the Ligand [Me2Si(Cs&)2I2complex
c1
106.7 TiC12[SiMe2(q5-C5H&1 81.3 Ti(PMezPh)z[SiMez($-CsH&] 76.9 Ti(CO)z[SiMez(rl5-CsH4)21 T ~ [ C N ( ~ , ~ - C ~ H ~ M ~ Z ) ~ ~ [ S ~ M ~ Z ( ~ ~ ~ - C S80.9 ~)~I 109.2 ZrC12[SiMe2(r15-CsH4)zl 135.5 [TiCpC1~1~lu-SiMez(r~-CsH4)21 124.6 [ZrCpCl2lz~-SiMe~(~~-CsH4)21 128.2 [ZrCp*Cl~lz~-SiMe?(0~-CsH4)21 [~poL-C1)1~~-SiMe2(r15-C5H4)z1 114.3 97.4 (TiCp[CN(2,6-CsH~Mez)z}2lu-SiMe2(rl5-CsH)21 [Ti(lc-rl1-rlS-C5H4)(PMe~Ph)]2lu-SiMe2(r)21 87.6
c2
c3
135.5 102.4 103.1 106.2 128.6 129.1 125.3 125.5 112.4 103.6
118.8 90.4 90.8 92.3 114.3 120.8 117.2 115.3 104.2 97.6
ab
ref Id 3b 3b 3b Id 5e 5b 5b
5c this work this work
Chemical shifts in ppm reference to TMS. Cp = C5H5; Cp* = C5Me5.
yield after evaporation of the solvent and extraction of the crude residue with hexane. The solubility and air sensitivity of these dinuclear compounds are similar to those reported3b for the mononuclear complexes containing the same (dimethylsily1)biscycyclopentadienylgroup as a chelating ligand. The IR spectra of all these complexes show the characteristic absorptions reportedg for compounds containing this silyl-bridged biscyclopentadienyl ligand. Two IR absorption bands are observed for v(C0) (1870 and 1960 cm-l) and v(CN) (1932 and 2033 cm-l) stretching frequencies for complexes 3 and 5, respectively, which are lower than those observed for the corresponding mononuclear derivatives [Ti(CO)zl[MezSi(C5H4121[v(CO),1905 and 1980 cm-'I and [Ti{CN(2,6C ~ H ~ M ~ ~ ) } ~ I [ M ~ ~[v(CN), S ~ ( C E1938 , H ~and ~ I 2044 ~ m - l ] .This ~ ~ effect reveals an enhanced TiCX (X = 0, NR) back-donation due to the increase of electron density a t the metal center, provided by the presence of one C5H5 ring instead of a silyl-substituted cyclopentadienyl group. The 'H NMR spectra for 3 and 5 show the expected two pseudotriplets for the silylcyclopentadienyl ring protons of an AA'BB' spin system, one singlet for the protons for both equivalent methylsilyl groups of the bridging ligand and one singlet for the unsubstituted cyclopentadienyl ring protons. All the resonances are displaced to higher fields, particularly those observed for the dicarbonyl compound 3, as expected for lower valent metal compounds. The same reduction of 1 with sodium amalgam or HgCl2-activated magnesium in THF in the presence of PMeaPh resulted in the loss of hydrogen and formation of the diamagnetic complex [{Ti(PMe2Ph)}2@-v1-r5C5H4)2@-Me2Si(C5H4)2}1(6)as a crystalline dark violet solid (Scheme 1). A similar r1-r5-C5H4disposition has been reportedlo by Rausch and co-workers for other group 4 metal derivatives, and the X-ray structure of [Ti(175-C5H5)(PMe3)12~-171-r5-C5H4)2 has been determined.loc It has been reportedlocthat this p-~$l7~-C5H4bridged compound results only when the reduction of Ti(r-C5H&C12 is carried out in the presence of 2 equiv of PMe3, whereas the same reaction in the presence of an excess of PMe3 gives the titanium(I1) complex Ti@ C5H5)2(PMe&. We have observed a different behavior for the (dimethylsily1)biscyclopentadienylderivatives. (9) (a)Burger, H.Organomet. Chem. Rev. 1968,3,425. (b) Cotton, F.A.; Marks, T.J. J. Am. Chem. SOC.1969,91, 7281.
(10)(a) Gell, K. I.; Harris, T. V.; Schwartz, J. Inorg. Chem. 1981, 20,481. (b) Gell, K.I.; Schwartz, J. J. A m . Chem. SOC.1981,103, 2687. (c) Kool, L. B.; Rausch, M. D.; Alt, H. G.; Herberhold, M.; Thewalt, U.; Honold, B. J. Organomet. Chem. 1986,310, 27.
The reduction of the mononuclear ansa-[TiCl2l[Me2Si(C5&)21 complex in the presence of any amount of PMe2comPh gives the ansa-[Ti(PMe~Ph)2I[Me~Si(C~H4)~1 whereas the same reaction with the dinuclear derivative 1 aways leads to the p-~7'-7,7~-C5H4 complex 6,even when the Ti/PMezPh molar ratio is 1/14. The 'H NMR spectrum of complex 6 reveals that all the protons from the 171-q5-C5H4bridging groups and from the cyclopentadienyl rings of the pU-[Me2Si(C5H4)21 ligand are magnetically not equivalent and appear as eight multiplets (6 4.36-5.88), corresponding to an ABCD spin system for each ring. The methyl groups of the PMezPh ligand give two doublets, corresponding to two diastereotopic methyl groups, as a result of the chirality of the metal center, with 2 J p - ~= 4.5 Hz. The I3C NMR spectrum of 6 shows the resonance due t o the metal a-bonded C1 of the bridging p-r1-r5-CsH4unit (6 190.81, significantly shifted to lower field in comparison with the proximal and distal C2 and C3 resonances. The 2 J p - ~coupling constant for this C1 resonance is high (15.1 Hz), whereas those for C2 and C3 are not detectable. These data are in agreement with a direct Ti-C1 a-bond and are consistent with the a-n bridging arrangement of the 171-q5-C5H4 unit, as reportedlo for similar compounds. The 13Cresonance due to the cyclopentadienyl bridgehead ipso-carbon C1 atom of the [Me2Si(C5H4)2l2-anion appears to be sensitive t o the mode of coordination of the ligand. For most dinuclear titanium and zirconium derivatives containing this group as a bridging ligand, the C1 resonance is typically found downfield from the proximal and distal C2 and C1 resonances, which are less sensitive to the mode of coordination, as shown in Table 1,whereas the opposite behavior is observed for similar ansa-mononuclear complexes. This spectral feature has been used to distinguish both possible coordination modes of the ligand. However, the behavior observed for compound 5 and 6 is the reverse, as the bridgehead C1 13C resonance is shown shifted downfield (6 97.39 and 87.6, respectively) with respect to the C2 and C3 resonances, thus proving that this spectral behavior cannot be used as a general rule to predict the bridging or chelating disposition of the (dimethylsily1)biscyclopentadienylligand in this type of group 4 metal derivatives. The reaction of 6 with HC1 was studied in order to gain further support for its formulation. The reaction of a toluene solution of 6 with a 1 M diethyl ether solution of HCl (Ti/HCl molar ratio 1/2>proceeds with formation of the known titanium(II1) compound 2. When the same reaction was carried out using a TYHC1
Structure of [{ Ti(r5C a d I.&- Clh@-Me~Si(CdiSzI1
Organometallics, Vol. 14, No. 2, 1995 851
Scheme 2
1
Me M e A
molar ratio of 1/4, the reported5etitanium(IV) derivative [{Ti(r5-C5H5>Cl~}~CU-Me~Si(C5H4)2)l was isolated. These reactions demonstrate that the first step consists of the addition of HC1 to the a-Ti-C bond of the bridging Ti77l-r5-C5H4group, regenerating the r5-C5H5disposition with simultaneous substitution and formation of one Ti-C1 bond to give 2. The second equivalent of HC1 reacts with 2 to give the titanium(IV) complex with evolution of hydrogen by an oxidative addition process. The dicarbonyl derivative 3 was also obtained by with reaction of [{Ti(~5-C5H5)Me~}~~-Me~Si(C5H4)~}15e CO (Scheme 2). When CO was bubbled through a toluene solution of the dimethyl compound and the reaction mixture was stirred overnight, a reddish brown solution was obtained. Subsequent workup of the resulting solution showed the presence of acetone and afforded a dark red crystalline compound which was characterized as 3.The reaction between dimethyl group 4 metal derivatives with CO is known to give the reduced titanium(I1) dicarbonyl compounds with elimination of acetone,8 probably through the formation of an intermediate acetone-coordinated species, although few early transition metal-acetone complexes have been isolated." When the reaction of [{Ti(r5-C5H5)Me~}~{~-MezSi(C&I&}] with CO was monitored by lH NMR spectroscopy, the formation of an intermediate species was detected. Its lH NMR spectrum showed two signals for the cyclopentadienyl ring protons a t 6 5.78 and 5.81, indicative of the presence of two nonequivalent titanium atoms and two singlets at 6 0.88 and 0.89, due to the methyl protons of an acetone ligand bridging both titanium atoms, along with other methyl resonances due to the methyl groups bonded to the silicon and the titanium atoms. This behavior suggests the intermediate formation of the acetone-coordinated titanium compound 4 (Scheme 21, which could not be isolated. In the (11)(a) Wood, C. D.; Schrock, R. R. J. Am. Chem. SOC.1979,101, 5421. (b)Martin, B. D.; Mactchett, S. A.; Norton, J. R.; Anderson, 0. P. J.Am. Chem. Soc. 1986,107,7952. (c) Stella, S.;Floriani. C. J. Chem. SOC.,Chem. Commun. 1986, 1053. (d) Erker, G.; Czisch, P.; Schlund, R.; Angermund, K; Kruper, C. Angew. Chem., Int. Ed. Engl. 1986,25, 364. (e) Erker, G.; Dorf,U.;Czisch, P.; Petersen, J. L. Organometallics 1986,5 , 668. (0Bemo, P.;Stella, 5.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J.Chem. SOC.,Dalton n u n s . 1990,2669. ( g ) Bryan,J. C.; Mayer, J. M. J.Am. Chem. Soc. 1987,109,7213.(h) Flores, J. C.; Mena, M.; &yo, P.; Serrano, R. J. Chem. SOC.,Chem. Commun. 1989,617.
PC(12)
C(17) C(13
C(14)
C(18)
Figure 2. Perspective view of the molecular structure of one of the two independent complexes [{Ti(75-C5H5)}&4C ~ ) ~ @ - M ~ Z S ~ ( C(2) ~H ~ ) Zthe } Iatomic labeling scheme. with presence of an excess of CO, 4 evolves acetone, and new lH resonances appear, corresponding to the dicarbonyl compound 3. The dimeric nature of the starting compounds {[Ti(~5-C~H~)X~l~~-Me~Si(C5H4)~l} (X= C1, Me) is responsible for the different behavior observed in the reduction of the chloro derivative in the presence of PMezPh and favors the formation of the intermediate acetonecoordinated complex in the reaction of the dimethyl derivative with CO with respect to the reported reactions with mononuclear derivatives. Description of the Crystal Structure of [{Ti(q6C 6 H 6 ) } 2 ~ - C l ) 2 { ~ - M e 2 s i ( c ~ ~(2). ) 2 } ]In the crystals of 2, two crystallographically independent but essentially identical molecules are present. The structure of one of them is depicted in Figure 2, together with the atomic numbering scheme; the most important bond distances and angles are given in Table 2. The [Me~Si(C5&)zl~ligand acts as a bridge between the two Ti atoms through the two cyclopentadienyl rings interacting, in a nearly symmetrical r5-fashion. The two metals (at a separation distance of 3.8 A) are symmetrically bridged also by two C1 atoms, the Ti-C1 bond distances ran 'ng from 2.507(3) to 2.536(33) A r2.515(4)to 2.534(3) ;heretoatter, the values in brackets refer to the second independent moleculel. Each Ti atom is
x
Cuenca et al.
852 Organometallics, Vol. 14, No. 2, 1995 Table 2.
Selected Bond Distances (A) and Angles (deg) with Esd Values in Parentheses for Compound 2" molecule 1
molecule 2
Ti( 1)-Cl( 1) Ti( 1)-C1(2) Ti(2)-C1( 1) Ti(2)-C1(2) Ti( 1)-CE( 1) Ti(2)-CE(2) Ti( 1)-CE(3) Ti(2)-CE(4) Si-C(l) Si-C(6) Si-C( 11) Si-C(12)
2.535(3) 2.5 19(3) 2.536(3) 2.507(3) 2.054(11) 2.055(9) 2.069(10) 2.089( 12) 1.888(10) 1.846(11) 1.863(12) 1.858(12)
2.519(3) 2.534(3) 2.515(4) 2.531(3) 2.056(11) 2.061(11) 2.070( 15) 2.065( 14) 1.852(10) 1.865(10) 1.836(13) 1.836(12)
C1(1)-Ti( 1)-C1(2) C1(1)-Ti( 1)-CE( 1) C1(1)-Ti( 1)-CE(3) C1(2)-Ti( 1)-CE( 1) C1(2)-Ti( 1)-CE(3) CE( 1)-Ti( 1)-CE(3) Cl(l)-Ti(2)-Cl(2) C1( 1)-Ti(2) -CE(2) C1(l)-Ti(2)-CE(4) C1(2)-Ti(2)-CE(2) C1(2)-Ti(2)-CE(4) CE(2)-Ti(2)-CE(4) Ti( 1)-Cl( 1)-Ti(2) Ti( 1)-Cl( 2)-Ti( 2) C(1)-Si-C(6) C( 1)-Si-C(l1) C( l)-Si-C(12) C(6)-Si-C(11) C(6)-Si-C(12) C(ll)-Si-C(12) Si-C( 1)-C(2) Si-C( 1)-C(5) C(2)-C(l)-C(5) Si-C(6)-C(7) Si-C(6)-C(lO) C(7)-C(6)-C( 10)
8 1.9(1) 108.9(3) 107.5(4) 108.5(3) 106.8(4) 131.9(5) 82.1(1) 107.9(3) 109.4(3) 107.0(3) 108.6(3) 13 LO(5) 97.4(1) 98.6(1) 118.9(4) 106.6(5) 105.8(5) 107.5(5) 105.7(5) 112.4(5) 126.4(8) 125.9(8) 106.7(9) 125.4(8) 128.3(8) 105.3(9)
82.6(1) 108.3(4) 107.5(4) 107.5(3) 107.0(4) 132.6(6) 82.8(1) 107.0(3) 109.4(5) 109.O( 3) 108.3(5) 130.2(6) 97.7(1) 96.9(1) 117.6(4) 106.3(5) 107.3(5) 109.3(5) 106.8(5) 109.5(5) 124.1(8) 128.0(8) 106.6(9) 125.8(7) 128.3(8) 105.3(9)
CE(l), CE(2), CE(3), and CE(4) are the centroids of the C(l)..C(5), C(6).*C(10), C(13)..C(17), and C(lQ*C(22) Cp rings, respectively.
also involved in a nearly symmetrical v5 interaction with a cyclopentadienyl ring. If the cyclopentadienyl centroids (CE) are considered as coordination sites, the coordination geometry around titanium is a distorted tetrahedron, the other two coordination sites being occupied by the two chlorine atoms. The angles are in agreement with those expected for this coordination, except the C1-Ti-C1 ones, which are narrower, and the CE-Ti-CE, which are much larger. This geometry is very similar to that observed for titanocene derivatives of this type.ld The distances between the metal and the centroids of the cyclopentadienyl rings of the [MeaSi(C5H4)2I2-ligand are 2.054(11) and 2.055(9) A L2.056(11)and 2.061(11) AI, and those with the other cyclopentadienyl rings are 2.069(10) and 2.089(12) A [2.070(15) and 2.065(14) A]. All four cyclopentadienyl rings are planar, but in those of the [Me2Si(C5H4)212-ligand, the Si atoms deviate from the mean plane by 0.234(3) and 0.279(3) A [0.287(3) and 0.196(3) A]because of the strain due to the interannular bridge. The dihedral angle between the mean planes of the these rings, 44.9(4)" [45.3(4)"1,is related to the degree of canting of the rings. It can be interesting to compare some structural features of this ligand when it is acting as bridge (as in 2) and when it is acting as a chelating ligand (as in the mononuclear complex {TiCKPMezPh)[MezSi(C5H&l}.3a As a consequence of the rather narrow bite of this ligand when it is chelating, the dihedral angle between the
mean planes of the rings, 53(2)",is larger than in 2, the C(l)-Si-C(G) angle much narrower [93.3(3)"]than in 2, ll8.9(4)' [117.6(4)"1,and the separation between the bridgehead C(1) and C ( 6 ) atoms much closer [2.705(6) AI than in 2, 3.215(14) A [3.179(14) AI.
Experimental Section All operations were performed under an inert atmosphere of dinitrogen or argon using Schlenk and vacuum-line techniques or a VAC glovebox Model HE-63-P. The following solvents were dried and purified by distillation under argon before use by employing the appropriate drying/deoxygenated agents: tetrahydrofuran (sodiumhenzophenone), toluene (sodium), hexane (sodiudpotassium alloy), and dichloromethane (phosphorus pentoxide). [Ti(i5-C5H5)Cl~l~Cu-Me~Si(C5H4)~1,5e [Ti(y5-C5H5)Mez]z[U-Me~Si(CgH4)~],5e and C N ( ~ , ~ - C ~ H ~ M ~ Z ) ' ~ were prepared according to literature procedures. Sodium (Panreac), magnesium (Merck), mercury dichloride (Panreac), dimethylphenylphosphine (Aldrich), carbon monoxide ( 99%, SEO), and 1 M HC1 in diethyl ether solution (Aldrich) were purchased from commercial sources and used without further purifications. lH, 13C,and 31P{1H}NMR spectra were recorded on a Varian FT-80 and Varian 300 Unity instruments. lH and 13C chemical shifts are reported in 6 units (positive chemical shifts to a higher frequency) relative to TMS standard, and 31P chemical shifts were referenced to H3P04 in DzO. The coupling constants reported correspond to Job. IR spectra were recorded on a Perkin-Elmer 883 spectrophotometer (4000-200 cm-') as Nujol mulls between CsI pellets. Mass spectra were recorded on a Hewlett-Packard 5890 spectrometer. Magnetic susceptibilities were measured according to the Faraday method using a Bruker B-E 15 magnetic balance with a temperature control unit. Elemental C, H, and N analyses were performed with a Perkin-Elmer 240B microanalyzer. Synthesis of [Ti(q5-CaHs)l~0I-C1)a[lr-Me~Si(C~~)~I (2). Toluene (50 mL) was added t o a mixture of [ T ~ ( T , - ~ - C ~ H ~ ) C ~ ~ I Z ~ MezSi(C5H4)zI (1)(0.31 g, 0.56 mmol) and 10% sodium (0.027 g, 1.17 mmol) amalgam and then stirred for 17 h. A dark brown solution was formed, which was filtered and evaporated to dryness in vacuum to give a dark solid, which was washed with cold toluene and hexane. Extraction with tetrahydrofuran gave a dark solution, from which a dark amber crystalline solid was obtained a&r cooling at -35 "C that was characterized as 2; yield, 0.23 g (85%). Suitable single crystals for X-ray studies were obtained from a saturated solution of 2 in dichloromethane at -35 "C. EI/MS (70 eV) mlz = 483.7 ([MI+). ,U,R = 1.423 f 0.66 ,UB at 298 K. Anal. Calcd for CzzH24Cl~SiTiz: C, 54.68; H, 5.00. Found: C, 54.54; H, 5.28. Synthesis of [n(qs-CaH~)(CO)zlz[CI-MezSi(CaH4)2] (3). Method a. Toluene (50 mL) was added to a mixture of [Ti(~5-C5H5)C1~l~~-Me~Si(C5H4)~l (1)(0.15 g, 0.27 mmol) and 10% sodium (0.026 g, 1.13 mmol) amalgam. The mixture was stirred under CO (1.0 kg ~ m - for ~ )48 h at room temperature to give a deep red solution. The solvent was removed by evaporation in vacuum to obtain a dark red oil. After extraction with hexane, the resulting solution was concentrated to ca. 15 mL and cooled to -35 "C to give dark red crystals characterized as 3;yield, 0.1 g (70.6%). Method b. A 250 mL Schlenk containing a toluene solution (50 mL) of [Ti(i5-C5H5)Mez1~[-Me~Si(C5H4)~1 (0.26 g, 0.55 mmol) was filled with CO (1.0 kg ~ m - ~ at ) , -78 "C. The reaction mixture was slowly warmed to room temperature and stirred overnight to give a red solution, which was worked up as described above; yield, 0.22 g (75%). IR (Nujol mull, cm-'1: v(C0) 1870 and 1960 cm-l. 'H NMR (300 MHz, CsD6, 25 "C): 6 0.28 (s, 6H, SiMes), 4.60 (8, 10H, C5H5), 4.66 (t, ~ H BJ , = 2.44 Hz, C&), 4.69 (t,4Ha, J = 2.44 Hz, C5H4). Anal. Calcd for C26H~Ti2Si04:C, 59.54; H, 4.58. Found: C, 59.43; H, 4.22. (12)Weber, W. P.; Gokel, G. W.; Ugi, I. K. Angew. Chem., Int. E d . Engl. 1972, 11, 530.
Structure of [{ Ti($-CsHS, > 2 ( ~ - C l ) ~ C u - M e z S i ( C s H ~ ~ } l
Table 3. Summary of Crystallographic Data for Complex 2 mol formula mol wt cryst syst space group a, 8,
CzzH~ClzSiTiz 483.22 monoclinic
Organometallics, Vol. 14, No. 2, 1995 853
Table 4. Atomic Coordinates ( x 104) and Isotropic Thermal Parameters (Azx 104) with Esd Values in Parentheses for the Non-Hydrogen Atoms of Compound 2
P21h 28.262( 10) 8.089(5) 18.446(9) 91.06(2) 4216(4) 8 1.522 1984 10.73 0.0568 0.0727
Ti( 11) Ti(21) C1( 11) P, deg Cl(21) v, A3 Si(1) 2 C(11) Dcalcdr g C(21) F(W) C(31) ~ ( M Ka), o cm-' ~(41) R ~(51) R W C(61) ~(71) Synthesisof {Ti(l]s-CaHa)[CN(2,&CsHsMea)12}2~-M~Si. C(81) (C~.&)al (6). [Ti(r15-CsHs)C1~1~[u-MezSi(CsH4)21 (1)(0.4 g, 0.72 ~(91) C(101) mmol) was added under argon to a mixture of magnesium C(111) turnings (0.4 g, 16.45 mmol), HgClz (20 mg, 0.075 mmol), and C(121) CN(2,6-C&Me2) (0.38 g, 2.9 mmol) in tetrahydrofuran (60 C(131) mL). The reaction mixture was stirred for 12 h a t room C(141) temperature to give a red brown solution. The solvent was C(151) removed under vacuum and the residue extracted with hexane C(161) (100mL). The resulting solution was concentrated to ca. 30 C(171) mL and cooled to -30 "C t o give a red brown solid. RecrysC(181) tallization from cold hexane gave a crystalline red brown solid, C(191) C(201) which was characterized as 5; yield, 0.51 g (75%). IR (Nujol C(211) mull, cm-'): v(CN) 1932 and 2033 cm-l. lH NMR 300 C(221) MHz, 25 "0:6 0.45 (8, 6H, SiMez), 2.18 ( 8 , 24H, CeHaez), b, 8, c,
'4
(cas,
xla
396(1) -462(1) -459(1) 377(1) 355(1) 600(4) 1016(4) 1107(4) 747(5) 447(4) -127(4) -70(4) -516(5) -854(5) -621(4) 860(4) 105(4) 802(5) 447w 2~4) 103(5) 593(6) -573(4) -561(4) -964(5) -1206(4) -979(4)
Ylb
dc
Molecule 1 -2391(2) 770(2) -2248(3) 618(3) -1697(4) -2828( 12) -2453( 13) -3741(16) -4901(15) -4368( 12) -185(13) 156313) 2333( 15) 1076(16) -450( 15) -579( 16) -3317(14) -2224( 19) -1028( 17) -1843(17) -3540(17) -3757( 18) 1848(15) 3 173(14) 3062( 16) 1650(18) 929(15)
6763(1) 7526(1) 7155(1) 7113(1) 8790(1) 7985(5) 7626(5) 7144(6) 7 194(6) 7723(6) 8639(5) 86 16(5) 8628(6) 8649(5) 8663(5) 9228(6) 9386(6) 5643(6) 5605(5) 5625(5) 5672(5) 5665(5) 6324(5) 6808(6) 7223(6) 70 15(7) 6466(7)
U" 309W 295(6) 362(8)
350(8) 390(10) 369(34) 414(38) 555(47) 659(50) 430(38) 383(37) 409(38) 568(48) 582(49) 466(41) 677(50) 664(50) 652(52) 592(51) 553(49) 555(46) 7 17(62) 514(43) 532(45) 626(5 1) 646(52) 555(46)
5.20 (8, 10H, C5H5), 5.25 (t, 4Hp, J = 2.44 Hz, CsH4), 5.37 (t, Molecule 2 2969(1) -175(2) Ti(12) 5074(1) 341(6) 4H,, J = 2.44 Hz, C5H4), 6.61-6.71 (m, 12H, C&Me2). I3C 2113(1) 2955(2) Ti(22) 4263(1) 322(6) NMR (C6D6, 75.5 MHz, 25 "c): 6 1.0 (q, Jc-H= 119.05 Hz, 2 169(1) -119(3) Cl(12) 4451(1) 463(9) SiMez), 18.9 (4,Jc-H= 127.29 Hz, CsHdfez), 95.3 (d, Jc-H= 2928(1) 2915(3) Cl(22) 4856(1) 398(8) 173.08 Hz, CsHs), 97.4 [s, Ci(CsH4)1, 97.6 [d, Jc-H= 173.08 2136(1) 21 81(4) Si(2) 6299( 1) 363(9) Hz, C3 (Cs&)], 103.6 [d, Jc-H= 173.08 Hz, C2 (Cs&)], 123.12579(4) 6150(5) 374(35) 536(12) C(12) 130.0 (CsHaMez), 236.4 (9, CN). EVMS (70 eV) m/z = 936 3077(4) 721(14) 495(41) 6293(5) C(22) ([MI+). Anal. Calcd for CssH6oTizSiN4: c, 74.34; H, 6.45; N, 3285(5) -896(20) 6243(6) 717(57) ~(32) 5.98. Found: C, 73.46; H, 6.60; N, 5.81. 2929(6) -1988(19) 6090(7) 768(58) ~(42) 2495(4) 481(42) 6033(5) -1223(12) ~(52) Synthesis of [Ti(PMe2Ph)12((c-tl1-tl5-CaH4)2[lr-MezSi(C~1847(3) 5482(5) 3 128(13) 373(35) C(62) I-I4)2l (6). [Ti(~5-CsHs)Cl~lz[u-MezSi(CsH4)~l (1) (0.4 g, 0.72 1926(4) 485(41) 5220(5) 4761( 13) ~(72) mmol) was added under argon to a mixture of magnesium 1599(5) 5083( 17) 466 l(6) 64401) C(82) turnings (0.4 g, 16.45 mmol), HgCl2 (0.020 g, 0.075 mmol), and 1327(4) 3700(19) 4557(6) 667(53) CW) PMezPh (0.41 mL) in tetrahydrofuran (60 mL). The reaction 1467(3) 25 13(15) 5062(5) 470(40) C(102) mixture was stirred for 12 h at room temperature to give a 2439(5) 6828(6) 3799(16) 806(60) C(112) black violet solution. The solvent was removed in vacuum and 1661(4) 6839(6) 1279(16) 651(50) C(122) 3413(4) 19(16) 3985(7) 587(48) C(132) the residue extracted with 100 mL of toluene. The resulting 3145(5) -1320(18) 3910(7) 685(54) C(142) solution was concentrated to ca. 30 mL and cooled to -30 "C 3282(7) -2471(15) 4446(10) 970(78) C(152) to give a black violet solid. Recrystallization from toluene/ 3668(6) 4834(8) 920(76) C(162) -1701(23) hexane gave a crystalline violet solid, which was characterized 3725(4) 4548(7) 724(58) C(172) -148(20) as 6;yield, 0.39 g (79%). 'H NMR (C&, 300 MHz, 25 "C): 6 2560(5) 3300(7) 828(73) 3996(28) C( 182) 0.47 (s, 6H, SiMez), 1.16 (d, 6H, Jp-H = 4.5 Hz, PMezPh), 1.4 2166(8) 3288(7) 872(71) 4850(20) C( 192) (d, 6H, J p - H = 4.5 Hz, PMezPh), 4.36 (m, 2H, CsH4), 4.65 (m, 1811(6) 3128(7) 927(85) 3885(32) C(202) 2H, C5H4), 4.90 (m, 2H, C5H4), 5.14 (m, 2H, C5H4), 5.21 (m, 1948(9) 3036(7) 2327(25) 936(79) C(212) 2H, C5H4), 5.74 (m, 2H, C5H4), 5.88 (m, 4H, C5H4), 7.06 [6H, 245 l(8) 3 126(6) 907(76) 2369(23) C(222) m- and pC6H5 (PMezPh)], 7.48 [4H, o-C& (PMezPh)]. 13C OEquivalent isotropic U defined as one-third of the trace of the NMR (C&, 75.5 MHz, 25 "c): 6 0.1 ( 8 , SiMez), 16.96 (d, Jp-c orthogonalized Uv tensor. = 11.31 Hz, PMezPh), 17.73 (d, Jp-c = 12.8 Hz, PMezPh), 87.6 [CI, (~$r~-CsH4)], 91.2,102.3,106.3, 109.4,110.6,110.7, 112.6, solution was concentrated and cooled to -35 "C, yielding brown 116.4 [CZand C3, (q1-q5-C5H4)and Si-(C5&)1,126-128 [nand green crystals of 2. pC6H5 (PMezPh)], 131.0 [O-C6Hs (PMezPhIl, 142.1 [P-C 6) TVHCl Molar Ratio 1/4. When the same reaction was (PMeSh)], 190.8 [d, J p - c = 15.08 Hz, a-Ti-C (r]1-~5-C~H4)1. carried out as described above using a double amount of the 1 31P{1H}" f R (C6D6, referenced to in DzO): 6 21.1 (8). M solution of HC1 in diethyl eter (1 mL, 1 mmol) and the Anal. Calcd for C36H~Ti2SiP~: C, 66.47; H, 6.46. Found: C, reaction mixture was stirred for 36 h, the color of the solution 65.36; H, 6.41 (extremely air sensitive). changed slowly from dark violet to orange with formation of a red brown precipitate. After removal of the solvent under Reactionof [Ti(PM%Ph)12~-81-85-C~)~~-M~i(Cs vacuum, the solid residue was recrystallized from toluene/ (6) with HC1. (a) TVHCl Molar Ratio 1/2. A 1 M solution hexane by cooling to -30 "C, giving orange crystals of the HC1 in diethyl ether (0.5 mL, 0.5 mmol) was added to a toluene reportedse compound {[Ti(~5-CsHs)Clzlz[u-MezSi(CsH4)~l}. solution (50 mL) containing CTi(PMezPh)1201-r11-r15-CsH4)2[uMezSi(C5H4)zl (6)(0.16 g, 0.24 mmol). The dark violet color X-ray Data Collection, Structure Determination, and of the solution changed immediately to amber, and the reaction Refinement for {[Ti(~5-CaHa)12((c-Cl)~[lr-Me~Si(C~I-14)21) (2). A single crystal of 2, having approximate dimensions ca. mixture was stirred for 2 h. After filtration, the resulting
854 Organometallics, Vol. 14, No. 2, 1995 0.18 x 0.23 x 0.30 mm3, was sealed in a Lindemann glass capillary under dry nitrogen and used for data collection. The crystallographic data are summarized in Table 3. Unit cell parameters were determined from the 8 values of 30 carefully centered reflections, having 10 < 8 < 18". Data were collected at room temperature (22 "C) on a Siemens AED diffractometer, using the niobium-filtered Mo Ka radiation (L = 0.710 73 A) and the 8/28 scan type. The reflections were collected with a variable scan speed of 3-12" min-l and a scan width from (8 - 0.6Y t o (8 0.6 0.346 tan 8)". Of 9240 unique reflections, with 8 in the range 3-27", 3200 with I > 2dI) were used for the analysis. One standard reflection was monitored every 50 measurements; no significant decay was noticed over the time of data collection. The individual profiles have been analyzed following Lehmann and Larsen.13 Intensities were corrected for Lorentz and polarization effects. No correction for absorption was applied. Only the observed reflections were used in the structure solution and refinement. The structure was solved by direct and Fourier methods and refined by blocked full-matrix least-squares methods, first with isotropic thermal parameters and then with anisotropic thermal parameters for all non-hydrogen atoms. All hydrogen atoms were placed at their geometrically calculated positions (C-H = 1.00 A) and refined "riding" on the corresponding carbon atoms. The final cycles of refinement were carried out on the basis of 497 variables; after the last cycles, no parameters shifted by more than 0.70 esd. The biggest remaining peak in the final difference maps was equivalent t o about 0.58 ,/A3. In the final cycles of refinement, a weighting scheme, w = K[a2(Fo) gFo21-lwas used; at
+ +
+
(13)Lehmann, M. S.; Larsen, F. K. Acta Crystallogr., Sect A 1974, 30, 580.
Cuenca et al. convergence the K and g values were 0.528 and 0.0051, respectively. The analytical scattering factors, corrected for the real and imaginary parts of anomalous dispersions, were taken from ref 14. All calculations were carried out on the GOULD POWERNODE 6040 and ENCORE 91 computers of the "Centro di Studio per la Strutturistica Diffrattometrica" del C.N.R., Parma, Italy, using the SHELX-76 and SHELXS86 systems of crystallographic computer programs.15 The final atomic coordinates for the nonhydrogen atoms are given in Table 4. The atomic coordinates of the hydrogen atoms are given in Table SI, the thermal parameters in Table SI1 of the supplementary material.
Acknowledgment. Financial support for this research by DGICYT (Project 92-0178-C) and Consiglio Nazionale delle Ricerche (Rome) is gratefully acknowledged. Supplementary Material Available: Tables of hydrogen atom coordinates (Table SI) and anisotropic thermal parameters for the non-hydrogen atoms (Table SII) and a complete list of bond distances and angles (Table SIII) (7 pages). Ordering information is given on any current masthead page. OM940634C (14) International Tables for X-Ray Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV. (15) Sheldrick, G. M. SHELX-76 Program for crystal structure determination; University of Cambridge, England, 1976. SHEIXS86 Program for the solution of crystal structures; University of Gdttingen, FRG, 1986.
