Organometallics 1995, 14, 1901-1910
1901
Synthesis and Dynamic Behavior of (Pentamethylcyclopentadieny1)azatantalacyclopropane Complexes. Crystal Structures of TaCp*C14[C(Me)(NHR)] and TaCp*Me2(q2-Me2CNR) Mikhail V. Galakhov, Manuel Gbmez, Gerard0 J i m h e z , and Pascual Royo* Departamento de Quimica Inorganica, Universidad de Alcala de Henares, Campus Universitario, E-28871 Alcala de Henares, Spain
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 Diffrattometrica del CNR, Viale delle Scienze 78, I-43100 Parma, Italy Received June 24, 1994@ The amino carbene adducts TaCp*C14[C(Me)NHR)l(R = 2,6-Me&H3, la; 2,4,6-Me3CeHz, lb) have been prepared by reaction with HC1 of solutions containing the acylimidoyl complexes TaCp*C13(y2-MeC=NR)prepared by addition of isocyanides CNR to TaCp"Cl3Me. Solutions of pure acylimidoyl derivatives can be prepared and characterized in sealed tubes or in a drybox, as they are very easily hydrolyzed in the presence of traces of water. Reaction of TaCp*ClzMe2 with 1 equiv of isocyanides takes place with double migration of methyl, leading to the formation of azatantalacyclopropane complexes TaCp*C12(y2-Me2CNR)(R = 2,6-Me&H3, 2a; 2,4,6-Me&&, 2b). Complexes 2 are easily protonated by HC1 to give aryl isopropyl amido derivatives TaCp*C13(NiPrR) (R = 2,6-Me&&, 3a; 2,4,6-Me&H2, 3b), which decompose a t 120 "C with evolution of isopropyl chloride to give the imido complexes TaCp*C12(NR)(R = 2,6-Me2C&, 4a;2,4,6-Me3C&, 4b). Methylation of 2a with 2 equiv of LiMe gives TaCp*Me2[y2-Me2CN(2,6-Me2C6Ha)l (5a), which alternatively can be obtained by reaction of 3a with 3 equiv of MgClMe with evolution of methane. All the complexes isolated were studied by IR and lH, 13CNMR spectroscopy. The dynamic behavior of 2a and 5a was studied in solution between 203 and 303 K, and kinetic parameters were determined. The crystal structures of la and 5a were determined by X-ray diffraction methods. Crystals of the benzene solvate of l a are triclinic, space grou P-1 with 2 = 2 in a unit cell of dimensions a = 8.381(4) A,b = 8.977(4) c = 18.316(9) , a = 100.17(2)", = 97.83(2)", and y = 105.04(2)". Crystals of 5a are monoclinic, space group P21/n with 2 = 4 in a unit cell of dimensions a = 10.515(6) A, b = 14.615(9) c = 14.594(8) A, and p = 100.66(2)". Both structures were solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares fit on the basis of 3218 (laJ/2C6H6) and 3786 (5a)observed reflections to R and Rw values of 0.0432 and 0.0534 (laJ/2C6H6) and 0.0299 and 0.0316 (5a),respectively.
1
A,
A,
Introduction Migratory insertion of carbon monoxide into metalalkyl bonds and the reactivity of the resulting metalacyl function is one of the most important organometallic reactions, leading to different products through stoichiometric or catalytic pr0cesses.l The isoelectronic isocyanide ligands can be attacked at the nucleophilic nitrogen atom by hard electrophiles to give aminocarbyne complexes2or can be transformed into formimidoyl and acylimidoyl functions by migratory insertion of hydride3and alkyl group^.^ In comparison with the acyl ligands, the reactivity of these iminoacyl groups is even ~~
@Abstractpublished in Aduance ACS Abstracts, March 15, 1995. (1)Wolczanski, P.T.;Bercaw, J. E. Acc. Chem. Res. 1980,13,121. (2)(a)Filippou, A. C.; Fischer, E. 0.;Griinleitner, W. J. Organomet. Chem. 1990,386,333.(b) Filippou, A. C.; Griinleitner, W. J. Organomet. Chem. 1990,398,99;1991,407,61. ( c )Filippou, A. C.; Grunleitner, W.; Fischer, E. 0.;Imhof, W.; Huttner, G. J. Organomet. Chem. 1991,413,165.
more versatile. They can participate in reactions such as the following: (a) isomerization to the vinylamide5 and y3-l-azaally16complexes; (b) alkyl migration to the carbon atom to give coordinated imine^;^ (c) deprotonation followed by C=C coupling;8 (d) coupling with coordinated alkyne^;^ (e) insertion of a second isocyanide leading to dihapto-coordinated 1,4-diaza-3-alkylbutadien-2-yl heterometallacycles;6 (0 multiple insertion.1° The chemistry of related amido and imido derivatives is receiving increasing interest, but to date these types of complexes have not proved readily available for group (3)(a) Wolczanski, P.T.; Bercaw, J. E. J.Am. Chem. SOC.1979,101,
6450. (b) Evans, W. J.; Meadows, J. H.; Hunter, W. E.; Atwood, J. L.
Organometallics 1983, 2, 1252. (c) Evans, W. J.; Hanusa, T. P.; Meadows, J. H.; Hunter, W. E.; Atwood, J. L. Organometallics 1987, 6 , 295. (4) Durfee, L. D.; Rothwell, I. P. Chem. Reu. 1988,88, 1059. (5) Beshouri, S.M.; Fanwick, P. E.; Rothwell, I. P.; Huffman, J. C. Organometallics 1987,6, 891. (6) (a) Filippou, A. C.; Grunleitner, W.; Volkl, C.; Kiprof, P. J. Organomet. Chem. 1991,413,181.(b) Filippou, A. C.; Volkl, C.; Kiprof, P. J. Organomet. Chem. 1991,415,375.
0276-733319512314-1901$09.00/0 0 1995 American Chemical Society
Galakhov et al.
1902 Organometallics, Vol. 14,No. 4,1995 Scheme 1
HCI
// CI
CI
Ta\\ CI
R R = 2 , 6 - M e 2 C 6 H 3 , la 2,4,6-Me,C6H2, l b
5 and the chemistry of their isocyanide derivatives has not been particularly well deWe report herein the insertion and intramolecular rearrangement processes13aobserved when isocyanides, 2,4,6-Me3CsH2), are reacted CNR (R = 2,6-Me$&, with chloromethyl(pentamethylcyclopentadieny1)tantalum complexes, of the type TaCp*Cl,Me4-, (Cp* = q5-C5Me5, n = 2, 3).13b All compounds were fully characterized. In addition, some of the complexes were studied by X-ray diffraction methods.
Results and Discussion Reactions with Ta(gS-C&Ies)CWe.Ta(q5-C5Me5)easily reacts with isocyanides14 to give stable ad-
c4
(7)(a) Wilkins, J. D. J. Organomet. Chem. 1974, 67, 269. (b) Takahashi, Y.;Onoyama, N.; Ishikawa, Y.; Motojirna, S.; Sugiyama, K. Chem. Lett. 1978,525.(c) Chiu, W.K.; Jones, R. A.; Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B. J.Am. Chem. SOC.1980,102,7978. (d) Chiu, W. K.; Jones, R. A,; Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B. J . Chem. Soc., Dalton Trans. 1981,2088.(e) Mayer, J. M.; Curtis, C. J.; Bercaw, J. E. J . Am. Chem. SOC.1983,105,2651. (0 Chamberlain, L. R.; Rothwell, I. P.; Huffman, J . C. J. Chem. SOC., Chem. Commun. 1986,1203. (g) Brunner, H.; Wachter, J.; Schmidbauer, J. Organometallics 1986,5,2212.(h) Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P. J.Am. Chem. SOC.1987,109,472. (i) Chamberlain, L. R.; Steffey, B. D.; Rothwell, I. P.; Huffman, J. C. Polyhedron 1989,8,341.(i) Durfee, L. D.; Hill, J. E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1990,9,75. (8)Martin, A.;Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.; Tiripicchio, A. J . Chem. SOC.,Dalton Trans. 1993,2117. (9)(a) Curtis, M. D.; Real, J. J.Am. Chem. SOC.1986,108,4668. (b) Curtis, M. D.; Real, J.; Hirpo, W.; Butler, W. M. Organometallics 1990,9,66. (lO)Carmona, E.; Marin, J . M.; Palma, P.; Poveda, P. L. J. Organomet. Chem. 1989,377,157,and references therein. (11)(a)Nugent, W. A.; Haymore, B. L. Coord. Chem. Rev. 1980,31, 123. (b) Parkin, G.; van Asselt, A.; Leahy; D. J . ; Whinnery, LeRoy; Hua, N. G.; g u a n , R. W.; Henling, L. M.; Schaefer, W. P.; Santarsiero, B. D.; Bercaw, J. E. Inorg. Chem. 1992,31,82. (c) Rocklage, S. M.; Schrock, R. R. J . Am. Chem. SOC.1982,104,3077.(d) Bradley, D.C.; Hursthouse, M. B.; Abdul Malik, K. M.; Nielson, A. J.; Chota Vuru, G. B. J . Chem. SOC.,Dalton Trans. 1984, 1069. (e) Williams, D. N.; Mitchell, J. P.; Poole, A. D.; Siemeling, U.; Clegg, W.; Hockless, D. C. R.; O'Neil, P. A.; Gibson, V. N. J. Chem. SOC.,Dalton Trans. 1992, 739. (0 Bradley, D. C.; Hursthouse, M. B.; Howes, A. J.; N. de M. Jelfs, A.; Runnacles, J. D.; Thomton-Pett, M. J. Chem. SOC.,Dalton Trans. 1991, 841. (g) Cockroft, J. K.; Gibson, V. C.; Howard, J. A. K.; Poole, A. D.; Siemeling, U.; Wilson, C. J . Chem. SOC.,Chem. Commun. 1992, 1668. (h) Siemeling, U.;Gibson, V. C. J . Chem. SOC.,Chem. Commun. 1992,1670. (i) Poole, A. D.; Gibson, V. C.; Clegg, W. J. Chem. SOC., Chem. Commun. 1992, 237. (j) Siemeling, U.;Gibson, V. C. J . Organomet. Chem. 1992,426,C25. (k) Jolly, M.; Mitchell, J. P.; Gibson, V. C. J. Chem. SOC.,Dalton Trans. 1992,1331. (12)Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger, L.; Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.; Huffman, J. C.; Streib, W. E.; Wang, R. J.Am. Chem. SOC.1987,109, 390.
ducts of the type Ta(q5-C5Me5)C14(CNR), (R = tBu; 2,6MezCsHs)containing the isocyanide ligand trans to the cyclopentadienyl ring. In spite of the lower acidity of the chloromethyl derivatives, Ta(q5-CsMe&1,Me4-, ( n = 2, 31, whose isocyanide adducts cannot be isolated, the coordination of the isocyanide can be reasonably assumed as the first step in subsequent reactions. When isocyanides are added to toluene suspensions of yellow Ta(q5-C5Me5)C13Me,an instantaneous insertion reaction takes place to give the iminoacyl derivatives Ta(q5-C5Me5)C13(q2-MeC=NR) (Scheme 1). These compounds are extremely sensitive to moisture, evolving HC1 in the presence of water, which then reacts with the iminoacyl complexes to give the carbene complexes Ta(q5-C5Me5)C14[CMe=N(H)Rl(Scheme 1). The formation of the intermediate iminoacyl complexes is confirmed by lH NMR of the reaction solution, which along with the resonances due to the presence of a small amount of the carbene complex la show one singlet at 6 1.90 (6H, b!fe2Cs&), one singlet at 6 2.06 ( E H , CsMe5) and one singlet a t 6 2.55 (3H, RN=CMe) as for the iminoacyl complex Ta(q5-C&le5)C13[q2-MeC=N(2,6-Me2C&)I. Solutions containing only the iminoacyl complex can be prepared when the reaction is carried out in a sealed tube, but all attempts to recover the pure complex by working up the solution always resulted in its transformation into the aminocarbene complex. The latter is quantitatively formed when solutions of the iminoacyl complexes are treated with HC1. The resulting pseudooctahedral 16-electron species are air-stable and do not react with additional isocyanide. NMR data are in full agreement with the proposed structure for la and l b (see Experimental Section), the methyl protons being observed at 6 2.93 and 3.00, respectively, and the amino proton being observed as a broad signal at 6 12.20 for both complexes. In both complexes, the presence of the amino proton causes the lH methyl carbene signal to appear as a doublet ( 4 J ~ ( ~ , = ) -0.9 ~ (Hz). ~ ) This is also consistent with the spin-spin coupling between the methyl carbene carbon and the NH proton observed in the 13C NMR spectra ( 3 J ~=-9.1 ~ Hz)of these compounds. The (13)(a) Galakhov, M. V.; Gdmez, M.; J i m h e z , G.; Pellinghelli, M. A.; Royo, P.; Tiripicchio, A.Organometallics 1994,13,1564.(b) G6mez, M.; J i m h e z , G.; Royo, P.; Selas, J . M.; Raithby, P. R. J. Organomet. Chem. 1992,439,147. (14)G6mez, M.; G6mez-Sa1, P.; Royo, P.; Nicolas, P. J.Organomet. Chem., in press.
Organometallics, Vol. 14, No. 4,1995 1903
TaCp*Cl$C(Me)(NHR)l and TaCp *Medrf-MezCNR) Scheme 2
& I
CI-ya--Me
CI-Ta-Me
C1
/ \Me
c1/ l>-R L
C
Me'
Me'
'Me
R = 2,6-Me2C611,, Zn 2,4,6-Me,C6H *,Zb
Scheme 3
or an azatantalacyclopropane structure (C) with the plane of the metallacycle being perpendicular to the Cp* ring plane. Unfortunately, we were not able to obtain crystals adequate for X-ray diffraction,but the structure must be presumably the same as that described below for the analogous dimethyl derivative. Similar azatantalacyclopropane species have been proposed7f as intermediates in the transformation of alkyl bis(iminoacyl) complexes into imidoamidotantalum derivatives A B C and their structures confirmed by X-ray diffraction in CH~Ph)2](py-4the case of Ti(OAr-2,6-'Pr2)2[~~-~BuNC( chemical shifts observed in the lH spectra for the amino PhY and two tungsten derivative^.^^,^ More recently, NH proton and in the 13C spectra for the carbene carbon new azazirconacyclopropane derivatives have been iso~ ~ J ~ lated16 by orthometalation of 2,6-diethylpyridine with atom (6 -261) are consistent with those r e p ~ r t e d for other aminocarbene ligands. The IR spectra show a the cationic complex [ZrCpzMe(THF)l+. characteristic v(N-H) absorption at -3240 cm-'. When the same reactions are carried out in the The X-ray crystal structure of complex l a confirms presence of traces of water (under not rigorously dry the location of the carbene ligand in the axial position argon), hydrolysis takes place and the evolved HC1 trans to the Cp* ligand. This suggests that the reaction reacts with the metallacycles to give, after protonation leading to l a and lb involves the coordination of of the carbon atom, the dialkylamido derivatives 3a isocyanide a t the axial position, followed by migration and 3b, in 50% yield. However, complexes 3a and 3b of the equatorial methyl group to the isocyanide carbon are obtained in almost quantitative yield when 2a and with coordination of the resulting iminoacyl nitrogen to 2b are treated with a stoichiometric amount of HC1. the tantalum center, and finally protonation of the r2Their formulation as dialkylamide complexes is consisiminoacyl ligand with HC1. tent with the IR spectra showing an absorption at 599 Reactions with Ta(qe-CsMes)C12Me2. When the cm-l, which is tentatively assigned to the 4Ta-N) dimethyl complex is used, the sequence of reactions stretching frequencyiid,fand a characteristic isopropyl represented in Scheme 2 is observed. By addition of 1 absorption at 1168 and 1112 cm-' [y(CH3)1. The lH equiv of the isocyanides to toluene solutions of the NMR spectra show characteristic resonances for the dimethyl derivative under rigorously anhydrous condiisopropyl group and one singlet at 6 2.26 (3a) and 2.20 tions (drybox or sealed NMR tube), red solutions are (3b) for the equivalent methyl substituents of the phenyl obtained, which after evaporation of the solvent afford group. This behavior is also consistent with the obcomplexes 2 as red crystals (Scheme 2). served 13C{lH} spectra (see Experimental Section). Formation of these compounds can be explained as Complexes 3 are very soluble in aromatic hydrocarbons the result of two consecutive steps. The first step and moderately soluble in hexane. Their toluene soluinvolves migration of one methyl group t o the electrotions are slowly hydrolyzed in air to give, after eliminaphilic isocyanide carbon atom, giving an iminoacyl tion of the appropriate arylisopropyl ammonium chlointermediate. Although many stable alkyl iminoacyl ride, the reported17 p-oxohydroxo dimer [TaCp*C12complexes have been i~olated,3",~~-~-j,'~ in the present (OH)12@-0). case, further reaction takes place in the presence of the The amido complexes 3 are transformed by heating second methyl group, which easily migrates to the at 120 "C into the imido derivatives 4a and 4b. These iminoacyl carbon atom t o give an $-imine ligand. Three reactions are accompanied by the evolution of 2-chlorolimiting structures have been p r ~ p o s e d ~to ~ -describe j propane, as proved by the lH NMR spectrum of the the bonding of this ligand as represented in Scheme 3. resulting reaction solutions.18 The same compounds can At room temperature, the equivalency of both methyl of the be also obtained by thermal decomp~sition~~ groups, as evidenced by the lH and l3C(lH} NMR azatantalacyclopropane complexes, 2a and 2b, in respectra of 2a and 2b, argue against an yl-imine (A) binding mode, suggesting either an y2-iminegroup (B) (16)Guram, A. S.; Swenson, D. C.; Jordan, R. F. J.Am. Chem. Soc. ~
(15) Filippou, A. C.; Fischer, E. 0.J.Organomet. Chem. 1990,382, 143;1990,383,179.
~~~~
1992,114, 8991. (17) Jemakoff, P.;de Meric de Bellefon, C.; GeoEroy, G. L.; Rheingold,
A. L.; Geib, S. J . Organometallics 1987,6,1362.
Galakhov et al.
1904 Organometallics, Vol. 14, No. 4, 1995 Scheme 4 A
I
-
vN-R A
Ioluene rutlux
Me.CH=CH,
/ Me2CH
Me
Me
R=2,6.Me2C6H,,3n 2,4,6-Me3C6Hz,3b
2u,b
Scheme 5
fluxing toluene. Propene is liberated in these reactions. The two new imido complexes show a v(Ta=N)lle~fIR absorption at -1323 cm-l. In addition, one singlet is observed for the equivalent o-methyl(pheny1)protons and carbons in the 'H and 13C NMR spectra (see Experimental Section). The X-ray crystal structure of complex 4a13a confirms a pseudotetrahedral structure. Similar imidotantalum complexes have been obtained1lC by reacting alkylidene derivatives with RN=CHR in a metathesis-like reaction or by reacting the tetrachloro complexes Ta(y5-C5Rs)C14 (R = H or Me) with trimethylsilylamines.lle The dimethylazatantalacyclopropane complex 5 can be obtained by two alternative methods, as shown in Scheme 5. Addition of 2 equiv of MeLi to a toluene solution of 2a leads t o an orange solution from which pure 5a can (18)'H NMR spectrum of 2-chloropropane: 6 1.13 (d, 'JH-H = 6.5 Hz, 6H, Me), 3.67 (sept, VH-H = 6.5 Hz, lH,CHCl).
be isolated as an orange oil after extraction with pentane and evaporation of the solvent. Similarly, alkylation of the amido derivative 3a with 3 equiv of MgClMe takes place with evolution of methane to give Sa. This behavior can be explained as the result of the j?-hydrogenelimination in the intermediate trimethylamido complex. Dynamic Behavior of Azatantalacyclopropane Complexes. The 13CCP MAS NMR spectra of 2a and 5a (see Table 1)show the presence of only one isomer with inequivalent pairs of methyl groups. Both complexes show inequivalent methyl groups bound t o tantalum (Ta-Me2, 5a), t o the metallacycle carbon (CMez),and to the phenyl ring (NCsH3Me2). The ortho and meta phenyl ring carbon atoms are also inequivalent, as shown in Figures 3 and 4. The resonance corresponding to the ipso carbon atom appears as a doublet due to interaction with the 14N quadrupolar moment, with coupling constants that increase for decreasing positive charge on the nitrogen atom [J = 68 (Sa), 50 Hz (2a)l. Broad signals are observed for metal-bonded methyl groups and for the metallacycle carbon atom, probably due to the interaction with tantalum and nitrogen quadrupolar moments. However, at room temperature, in CDCL solution, complex Sa shows pairs of equivalent methyl groups, in agreement with the existence of a plane of symmetry defined by the tantalum, nitrogen, and carbon atoms, which is perpendicular to the C5Mes ring plane. Solutions of 5a show a dynamic behavior at variable temperature, as shown in Figure 1. At 293 K, a broad signal (AAv = 1.2 Hz) is observed for the methyl groups bonded to the tantalacycle carbon, which broadens and shiRs to high field (2a) as the temperature decreases. The other signal, 2b, is accidentally coincident with resonance due to the Cp* ligand. At temperatures lower than 213 K, two new signals are observed, which narrow and appear at 203 K as two new resonances, l b and 3b, at 8 -0.02 and 1.8. The values of spin-lattice relaxation times (2'1) measured at 203 K and the results of saturation transfer at 213 K show that the two new resonances correspond to methyl tantalum and Cp*, respectively. When the solution is diluted 10 times, the ratio does not change, indicating that the transformation is an intramolecular
TaCp "Cl$C(MeXNHR)l and TaCp*Medd-MezCNR)
Organometallics, Vol. 14, No. 4, 1995 1905
Table 1. 13C Chemical Shifts for Complexes 2a and 5a in Solution at Variable Temperature and in Solid chemical shifts, ppm complex CP* CI, I
I
CI ,Ta,
conditions 293 K, CDCls 208 K, CDCls solid, 293 K
CP* 10.8, 122.1 10.8, 121.6 10.6, 115.5
Me-Ta
C-Me2 93.5 94.4 95.6 (br)
C-Me2 28.8 28.7 29.6, 27.1
Clpso 150.5 149.9 150.6"
Conho 133.5 132.8 134.1, 133.2
CIW,, 128.9 128.7 129.0
Cpara 125.3 125.2 127
Me 20.5 20.3 22.0, 21.5
293 K, CDCls 203 K, CDCls
10.6, 115.5 10.9, 114.8 10.2, 115.2 11.5, 115.7
52.9 50.0 55.8 53.5
82.9 81.4 87.2 86.7 (br)
27.6 26.8 28.5 29.7,27.6
152.3 152.4 152.0 152.1b
134.4 135.5 132.8 135.3, 134.3
128.4 127.8
123.4 123.3
20.4 20.3
129.7, 129.4
125.6
22.4.21.5
MeYC,Me
2a CP* Me. I Me,Ta,I/N-Ar
solid, 293 K Me/',Me
5a a
J = 50 Hz. J = 68 Hz.
dynamic process. This behavior indicates the existence of two stereoisomers in an approximate ratio 311, the major component corresponding to that observed in the solid. Both isomers contain the N and C azatantalacyclopropane atoms interchanging their mutual positions. The 13C{lH) spectrum a t 203 K (Table 1)also shows two groups of signals belonging to two different isomers. Complex 2a also shows the same dynamic behavior, but the ratio of the two isomers is -711. So, from these results is possible t o conclude that an intramolecular isomerization process takes place. Kinetic parameters were evaluated (see Table 2) by using lH D NMR data.19 Values of log A confirm the intramolecular nature of the process, and the negative values of AS* suggest that the transition state is characterized by a high polarization. Two different activated species could be proposed, as shown in Scheme 6. The transition state species A is a tantalum(II1) complex containing the alkylideneamine group coordinated by a metal-olefin-type bond, whereas B is the result of the Ta-C bond breaking t o give a tantalum(V1 amido complex. Formulation of species B would be in good agreement with the chemical behavior described above, which reveals the nucleophilic character of the carbon atom, whereas A seems t o fit better the low values found for the free activation energy and the displacement by ligands of the alkylideneamine reported7j for similar titanium derivatives. The isomerization activation energy E , depends on the charge separation in the ground state, as observed in Table 2 for relative values measured for chloro (2a)and methyl (5a)derivatives and is also in agreement with relative values of the quadrupole coupling constants between 14Nand the ipso phenyl carbon, observed in the 13C CP MAS spectra. X-ray Crystal Structures of la.'/zC@~and 5a. In the crystals of TaCp*C4[C(Me)(NHR)I(R= 2,6-Me&&) (la),0.5 mol of CsH6 solvate is present. A view of the complex la is shown in Figure 2 together with the atom numbering scheme. Selected bond distances and angles are given in Table 3. The pentamethylcyclopentadienyl ring is bound t o the Ta atom in a nearly symmetric v5fashion [the Ta-C distances range from 2.466(14) to 2.527(10) A] with the distance between the metal and the centroid of the ring being 2.184(13) The Ta atom is bound also to four C1 atoms with the Ta-CI bond
A.
(19) Jackman, L.M.; Cotton, F. A. DNMR Spectroscopy; Academic Press, Inc.: New York, 1975; p 45.
lengths ranging from 2.384(4) to 2.418(4) A. The coordination around the Ta atom is completed by the carbenic C(11)atom from the aminocarbene ligand [TaC(11) = 2.321(12)AI. The complex can be described as pseudooctahedral if the centroid of the Cp* ring is considered as occupying one coordination site. The Ta atom is displaced by 0.551(1) A from the equatorial plane containing the four C1 atoms toward the Cp* ring and the carbenic atom C(11) is positioned trans to the Cp* ring. The NC(ll)C(12)C(13) moiety of the aminocarbene ligand is perfectly planar, the aminocarbene plane including the Ta atom and being perpendicular to the phenyl ring [dihedral. angle 89.2(6)"1. The N-C(ll), N-C(13), and C(ll)-C(12) bond distances, 1.279(15), 1.468(15),and 1.512(17)A,respectively, agree with the following bonding system H+,
..
N
I
.,c;
CH3
confirming the carbenic nature of the C(11) atom. Also, the Ta-C(l1) bond length of 2 . 3 2 ~ 1 2A ) is comparable to those found in TaCp*Clr[CHzPMePhsl [2.35(3) and in TaCp*C13[(CH~)zPPh21 [2.347(12) in which the carbon atom is also in the trans position with respect to the Cp* centroid and is bound to the Ta atom through a u bond. The N-bound hydrogen of the carbene ligand is involved in an intramolecular bifurcated hydrogen bond with two of the coordinated C1 atoms. The N-..C1(1) and Ne **C1(2) distances of 3.036(9) and 3.105(11) as well as the H..*Cl(l) and H- *.C1(2)distances of 2.63(12)and 2.45(14) A, respectively, suggest such an interaction. A view of the complex TaCp*Me2(v2-MezCNR)(R = 2,6-Me&H3, 5a) is shown in Figure 3 together with the atom numbering scheme. Selected bond distances and angles are given in Table 4. The pentamethylcyclopentadienyl ring is bound to the Ta atom in a nearly symmetric v5-fashion [the Ta-C distances range from 2.451(5) to 2.525(6) AI, with the distance between the metal and the centroid of the ring being 2.172(5)A.This distance is only slightly shorter than that of la. The Ta atom is also bound to two C atoms of the methyl
A,
(20) Fandos, R.; Gdmez, M.; Royo, P.; Garcia-Blanco, S.; MartinezCarrera, S.; Sanz-Aparicio, J. Organometallics 1987,6, 1581. (21)Gdmez, M.; Jimenez, G.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A.J. Organomet. Chem. 1992, 439, 309.
Galakhov et al.
1906 Organometallics, Vol. 14, No. 4, 1995
the Ta-N bond length, 1.930(4)A, is comparable t o those found in tantalum dialkylamido derivative^^^ and denotes a certain degree of double-bond character. Finally, the value of the N-C(l3) bond length, 1.467(7) A, is consistent w i t h a single bond. The azatantalacyclopropane ring is perpendicular t o the cyclopentadienyl ring, to the T a C ( l l ) C ( 1 2 ) plane, and to the aryl group, the dihedral angles being 89.7(3)",89.5(2)", and 89.6(2)", respectively. It bisects the C(ll)-Ta-C(12) angle and is simultaneously the pseudomirror plane of the molecule (Figure 4). The coordination of the Ta a t o m can be therefore considered as a distorted trigonal bipyramid [ t h e distortion being mainly d u e to the very narrow N-Ta-C(13) angle], w i t h the C(11), (3121, and N a t o m s occupying t h e equatorial positions and the centroid of the Cp* ring and the C(13) a t o m the apical sites.
Experimental Section
293U
243a
21%
1
II
rl-
20%
la
I ' . " I " " l " " l " " I ' " ' i " " " '
2.5
2.0
1.5
1.0
0.5
0.0
pp.
Figure 1. lH NMR variable-temperature spectra of 5aCDzClz: Tl(4) = 0.439 s; T1(3) = 0.604 s (3a), 0.614 s (3b); TI(2a) = 0.133 s; Tl(1) = 0.410 s (la), 0.411 s (lb). oups [Ta-C(11) = 2.179(7) A, Ta-C(l2) = 2.178(7) E. The CMeZNR ligand is coordinated t o the Ta a t o m in a v2-fashion with the N and C( 13) a t o m s forming an azatantalacyclopro ane system. The Ta-C(l3) bond distance, 2.209(6) , is only slightly longer than those of the tantalum-bonded methyl groups and is comparable t o those found for other Ta alkyls.22 The value of
K
(22) Churchill, M. R.; Youngs, W. J. J.Am. Chem. SOC.1979, 101, 6462.
All manipulations were performed under an inert atmosphere of argon using standard Schlenk techniques or a glovebox. Solvents used were previously dried and freshly distilled from n-hexane (Na/K alloy) and toluene (sodium). Reagent grade HCl(1 M in OEtz), LiMe (1.6 M in OEtz), and MgClMe (3 M in THF) were purchased from Aldrich Chemical Co. and were used without further purification. I s ~ c y a n i d e s ~ ~ RNC (R = 2,6-MezC& 2,4,6-Me&,&) and the starting materials TaCp*ClnMe4-, (n. = 2, 3)11 were prepared as described previously. Infrared spectra were recorded on a Perkin-Elmer 583 spectrophotometer (4000-200 cm-l) as Nujol mulls between CsI or as polyethylene pellets. lH and 13CNMR spectra were recorded on a Varian VXR-300 Unity instrument. 'H and 13C NMR shifts were measured relative to residual 'H and 13C resonances in the deuterated solvents: CsDs (6 7.15), CDCl3 (6 7.24) and CsDs (6 1281, CDC13 (6 77), respectively. CsDs and CDC13 were purchased from Fluorochem Limited. A DNMR5 programz5 was used for evaluation of kinetic parameters. Mass spectra were recorded on a HP 5988A instrument. C, H, and N analyses were carried out with a Perkin-Elmer 240 C microanalyzer. TaCpCC4(C(Me)(NHR)}(la,b). A solution of CNR (1.44 mmol) in 10 mL of toluene was slowly added at room temperature to a stirred freshly prepared suspension of TaCp*Cl3Me (0.63 g, 1.44 mmol) in 50 mL of toluene. The reaction mixture was treated with ethyl ether solution of HC1 (1.44 mmol) and stirred for 2 h. The solvent was evaporated to dryness and the residue extracted with n-hexane (3 x 15 mL). The resulting yellow solution was concentrated to -30 mL and subsequently cooled at -40 "C to give la (R = 2,6-MezC&) or l b (R = 2,4,6-Me&&) as yellow crystals. The data for la follows. Yield: 0.37 g (85%). IR (Nujol mull, Y cm-l): 3242 (m), 1555 (SI, 1020 (m) 778 (s), 354 (SI, 323 (s), 300 (s). lH NMR (6 ppm, in CsD6): 12.20 [br, l H , CMe(NHR)], 6.75 (t, IH, 3 5 H - H = 7.3 HZ,p-H3C&fez),6.60 (d, 2H, 3 J ~ = 7.3 - ~HZ, m-H&&fez), 2.93 [d, 3H, 4 J ~ =0.9~Hz, CMe(NHR)I, 2.35 (s, 15H, C f i e ~ ) ,2.05 (s, 6H, 2,6-&fezcsH3). 13C NMR (6 ppm, ~ Hz, CMe(NHR)I, 138.2 (m, in CsDs): 261.1 [q, 2 J ~ =- 6.1 z-C&Mez), 133.8 (m, o-CsH&fez),131.5 (m, C5Mes), 129.0 (d, VC-H= 158.7 Hz, p-C&€jMez),128.9 (d, ~Jc-H = 159.1 Hz, ~ 4.9 Hz, 2,6m-C&IsMez), 29.6 (qd, 'Jc-H= 129.3 Hz,3 J c - = Me&&), 17.8 [qd, 'Jc-H= 127.6 Hz, 3 J c - ~= 9.1 Hz, CMe(NHR)], 12.8 (9, ~ J c - H= 128.1 Hz,C a e 5 ) . MS (EI, 70 eV): mle 470 (lo),323 (31,288 (4), 147 (861,135 (451,132 (loo), (23) Profilet, R. D.; Fanwick, P. E.; Rothwell, I. P. Polyhedron 1992, 12, 1559. (24) Weber, A. P.; Gokel, G. W.; Ugi,I. K. Angew. Chem., Int. Ed. Engl. 1972,11, 530. (25) Stephenson, D. S.; Binsch, G. QCPE 1978,11,365.
OrganometaZZics, VoZ. 14, No. 4, 1995 1907
TaCp*CZdC(Me)(NHR)l a n d TaCp*Mez(q-Me&NR)
Table 2. Kinetic Parameters for Isomerization of Complexes 2a Z= 2b and Sa Z= 5b Obtained from '€ DNMR I Data by Using Arrhenius and Evring Equations Earkcal/mol log A 9.2 f 0.15 11.3 f 0.4 r = 0.9984 5" 203-253 0.00060-0.025 7.6 f 0.15 11.5 f 1.0 r = 0.9986 For seven experimental points and 0.95 confidence limit. 2"
temp range, K
lifetime range t. s
208 -273
0.00017-0.0020
A P , kcal/mol
AP, eu
AGmsSK,kcdmol
7.6 f 0.3 -13.2 f 1.2 r = 0.9988 7.1 f 0.7 -15.1 f 1.4 r = 0.999 1
11.5 11.6
Scheme 6
L
A
I
he
J
I
I< X= CI. 2 ~ Me. : Sa
XI
Major isomer
CI.2h: Me, Fib
Minor isomer
I L
1h
M(.
I e
I
1
B 105 (48). Anal. Calcd for CzoH2aClNa: C, 39.70; H, 4.66; N, 2.31. Found: C, 39.68; H, 4.62; N, 2.27. The data for lb follow. Yield: 0.27 g (80%). IR (Nujol mull, v cm-l): 3235 (m), 1550 (s), 1025 (m), 780 (s), 354 (s), 321 (s), 305 (m). lH NMR (6 ppm, in C6D6): 12.20 [br, 1H, CMe(NHR)], 6.42 (s, 2H, m-HzCsMes), 3.00 [(a, 3H, 4JH-H = 0.9 Hz, CMe(NHR)I, 2.36 (s, 15H, C5Me5), 2.05 (s,6H, 2,4,6-Me&&), 1.94 (s,3H, 2,4,6-Me&Hd. 13C{lH) NMR (6 ppm, in C&3): 261.3 [S, CMe(NHR)I, 138.6 (s), 136.0 (s), 133.7 (SI, 129.7 (s,Cj, C,, C,, c,, C&Med, 131.5 (s, CsMes), 29.6 [s, CMe(NHRl1, 20.8 (5, 2,4,6-Me&Hd, 17.7 (s,2,4,6-Me&H2), 12.8 (s,c a e 5 ) . Anal. Calcd for C21H30ClNa: C, 40.79; H, 4.88; N, 2.26. Found: C, 40.36; H, 4.77; N, 2.30. TaCp*C12(q2-Me2CNR)(2a,b). A stirred yellow-green solution of TaCp*C12Mez (0.97 g, 2.32 mmol) in toluene (60 mL) was treated with CNR (2.32 mmol) under rigorously anhydrous conditions for 30 min. During this time, the color of the mixture changed to dark red. Subsequently,the solution was concentrated to -10 mL, n-hexane (15 mL) was added, and the mixture cooled to -40 "C to give 2a (R = 2,6-Me&&) or 2b (R = 2,4,6-Me&sH2). The data for 2a follow. Yield: 1.16 g (91%). IR (Nujol mull, v cm-l): 1259 (m), 1105 (w), 1024 (m),803 (m), 768 (m), 347 ( 5 ) . lH NMR (Qppm, in C6D6): 7.02 (t, 1H, 35H-H = 7.5 HZ, p-&C&fez), 6.94 (d, 2H, 3JH-H = 7.5 Hz, m-&C6Me2), 2.44 ( 8 , 6H, 2,6-Me&&), 2.11 (s, 6H, MenCNR), 1.74 (s, 15H, C5Med. 13C NMR (6 ppm, in C6D6): 150.5 (m, i-C6H3Me2), 133.5 (m, o-C&Mez), 128.9 (dm, 'Jc-H = 157.8 HZ, m-C&Med, 125.3 (d, 'Jc-H = 159.8 Hz, P-CsHa-
Figure 2. ORTEP view of the molecular structure of TaCp*C14[C(Me)(NHR)] (R = 2,6-Me&H3, la) with the atom numbering scheme. The thermal ellipsoids are drawn at the 30% probability level. Table 3. Selected Bond Distances (A) and Angles (deg) with ESDs in Parentheses for la*1/zCaH6u Ta-CE(1) Ta-CI( 1) Ta-Cl(2)
Bond Distances 2.184(13) Ta-Cl(3) 2.384(4) N-C(I 1) 2.417(3) Ta-Cl(4) 2.393(3) N-C( 13) 2.418(4) Ta-C(1I) 2.321(12) C(Il)-C(12)
CE( I)-Ta-CI( 1) CE( I)-Ta-C1(2) CE( l)-Ta-C1(3) CE( I)-Ta-Cl(4) CE( 1)-Ta-C( 11) C1( I)-Ta-C1(2) CI( 1)-Ta-Cl(3) CI( l)-Ta-C1(4) C1( 1)-Ta-C( 1 I ) C1(2)-Ta-C1(3)
Bond Angles 102.7(3) C1(2)-Ta-C1(4) 103.7(3) C1(2)-Ta-C( 11) 103.2(3) C1(3)-Ta-C1(4) 103.5(3) C1(3)-Ta-C( 1 1 ) 178.1(4) C1(4)-Ta-C( 11) 84.6(1) C(Il)-N-C(13) 87.7( 1) Ta-C( 1 I)-N 153.5(1) Ta-C(I I)-C(12) 78.3(3) N-C(I 1)-C(12) 153.0(1)
1.279(15) 1.468(15) 1.512(17) 85.3( 1) 77.9(3) 90.3( 1) 75.2(3) 75.6(3) 130.2(9) 123.0(8) 125.9(9) 1 1 1.1( 10)
CE(1) is the centroid of the C( 1P*C(5) cyclopentadienyl ring.
Men), 122.1 (m, CsMes), 93.5 (spt, 2 J ~=- 8.6 ~ Hz, MezCNR), 28.8 (qq, 'Jc-H = 124.0 HZ, 3JC-H = 4.1 HZ, Me&NR), 20.5 (qd, 'Jc-H = 126.8 Hz, 3 J c - ~ = 5.1 Hz, 2,6-Me&&), 10.8 (q, 'Jc-H = 128.2 Hz, CsMe5). Anal. Calcd for C21H30C12NTa: C, 45.99; H, 5.51; N, 2.55. Found: C, 46.23; H, 5.62; N, 2.47. The data for 2b follow. Yield: 1.15 g (95%). IR (Nujol mull, v cm-'): 1259 (m), 1227 (m), 1102 (w), 1024 (m), 803 (m), 768 NMR (6 ppm, in CsDs): 6.80 (s, 2H, &c6' (m), 346 (6). Mea), 2.50 (s,6H, 2,4,6-Me&s&), 2.17 (s,3H, 2,4,6-Me3c&), 'H} NMR (6 ppm, 2.08 (s, 6H, Me2CNR),1.76 (s,C5Med. lac{
Galakhou et al.
1908 Organometallics, Vol. 14,No. 4,1995 n c ( l 0 )
C(9)
c (a
ci23;"v C(22)
Figure 3. ORTEP view of t h e molecular structure of TaCp*Mez($-MezCNR) (R = 2,6-MezCeH3, 5a) with t h e atom numbering scheme. The thermal ellipsoids are drawn at t h e 30% probability level. Table 4. Selected Bond Distances (A) and Angles (deg) with ESDs in Parentheses for 5aa Ta-CE(1) Ta-N Ta-C(l1)
Bond Distances 2.172(5) Ta-C(12) 2.178(7) N-C(14) 1.930(4) Ta-C(13) 2.209(6) C(13)-C(22) 2.179(7) N-C(13) 1.467(7) C(13)-C(23)
CE( 1)-Ta-N CE(l)-Ta-C(ll) CE( 1)-Ta-C( 12) CE(l)-Ta-C(13) N-Ta-C( 11) N-Ta-C( 12) N-Ta-C( 13) C(ll)-Ta-C(12) C(ll)-Ta-C(13) C(12)-Ta-C( 13)
Bond Angles 115.0(2) Ta-N-C(13) 107.3(2) Ta-N-C(14) 106.0(2) C( 13)-N-C( 14) 155.8(2) Ta-C(13)-N 112.1(2) Ta-C(13)-C(22) 111.9(2) Ta-C(13)-C(23) 40.8(2) N-C(13)-C(22) 103.8(3) N-C(13)-C(23) 87.4(2) C(22)-C(13)-C(23) 88.3(2)
1.426(7) 1.534(9) 1.530(9) 79.9(3) 154.3(3) 125.8(4) 59.3(3) 123.9(4) 124.2(4) 115.9(5) 114.8(5) 108.6(6)
CE(1) is the centroid of the C( 1). C(5)cyclopentadienyl ring.
C(16) Figure 4. Projection of the structure of 5a on the TaC(11)C(12) plane showing the pseudomirror (excepting for t h e Cp* ring) and t h e azatantalacyclopropane ring perpendicular to it. in C&): 147.8 (S), 134.4 (S), 133.1 (S), 129.7 (5,c,, c, c, c, C&&Me3), 122.1 (s, CsMed, 93.2 (5, Me&NR), 28.9 (8, Me2CNR), 20.7 (s, 2,4,6-Me&&), 20.4 (s, 2,4,6-Me&&), 10.8 (9, Cae5). Anal. Calcd for C~2H32C12NTa:C, 46.98; H, 5.73; N, 2.49. Found: C, 46.86; H, 5.68; N, 2.42. TaCp*Cls[N(CHMez)Rl(3a,b). A solution of HCl 1 M in OEtz (0.24 mL, 0.42 mmol) was added a t -78 "C to a solution
of 2a or 2b (0.42 mmol) in toluene (50 mL) and stirred for 5 min. The color of the mixture changed quickly from red to pale yellow. The mixture was then warmed to room temperature, the solvent evaporated to dryness, and the resulting pale yellow solid washed with cold n-hexane (2 x 5 mL) and dried in vacuo. The data for 3a follow. Yield: 0.23 g (92%). IR (Nujol mull, v cm-I): 1206 (m), 1168 (m), 1112 (m), 1091 (m), 1023 (m),804 (m), 787 (m),373 (m), 319 (m), 295 (m). 'H NMR (6 ppm, in CsD6): 6.80 (m, 3H, H&sMez), 4.57 (Spt, 1H, 3 5 H - H = 4.6 Hz, Me&H), 2.91 (s, 15H, C a e s ) , 2.26 (s, 6H, 2,6Me&,&), 1.12 (d, 6H, MeZCH). l3cNMR (6 ppm, in C&): 143.3 (m, Z-CsH&fez),139.9 (m, o-CsHsMez),129.3 (dm, 'Jc-H = 160.3 Hz, m-C&Mez), 126.8 (d, 'Jc-H= 160.2 Hz, pC6H3= 113 Hz, MezCH), 21.1 Mez), 126.0 (m, CsMes), 46.9 (d, VC-H (9, ~Jc-H = 125.7 Hz, 2,6-Me&&), 16.4 (qm, 'Jc-H = 134.5 Hz, MezCH), 12.6 (4, UC-H= 129.3 Hz, Cae5). MS (EI, 70 EV): mle 547 (3), 505 (loo), 386 (261,135(31), 119 (68). Anal. Calcd for CZ1H31C13NTa: C, 43.17; H, 5.35; N, 2.40. Found: C, 42.97; H, 5.28; N, 2.44. The data for 3b follow. Yield: 0.24 g (95%). IR (Nujol mull, Y cm-'1: 1225 (m), 1156 (m), 1089 (m), 1025 (m), 790 (m), 380 (m), 305 (m), 290 (m). 'H NMR (6 ppm, in C&): 6.60 (S,2H, m-HzCsHs), 4.60 (Spt, 1H, 3 J H - ~= 5.1 Hz, Me2CH), 2.20 (s, 6H, 2,4,6-Me&&), 2.10 (s, 3H, 2,4,6Me3C,&), 1.94 (s, 15H, Cae51, 1.12 (d, 6H, = 5.1 Hz, Me2CH). 13C{1H}NMR (6 ppm, in CsDs): 141.2 (SI, 139.1 (SI, 136.4 (s), 130.3 (s, C,, C,, C,, C,, CsHzMes), 126.3 (s, CsMed, 47.0 (s, MeZCH), 21.4 (s, 2,4,6-Me&sHz), 20.7 (s, 2,4,6Me&&), 16.8 (s, MeZCH), 12.9 (s, Cae5). Anal. Calcd for C~2H33C13NTa:C, 44.12; H, 5.55; N, 2.34. Found: C, 44.10; H, 5.45; N, 2.22. TaCp*Clz(NR) (4a,b). Method A. A CsDs solution of 3 (0.205 mmol) was heated a t 120 "C for 4-5 days in a sealed NMR tube. The reaction was monitored by 'H NMR spectroscopy until total conversion of 3 to 4 was observed with simultaneous appearance of isopropyl chloride. Method B. Toluene (50 mL) solutions of 2a,b (1.82 mmol) were heated under reflux for 4 days. The resulting red solutions were evaporated to dryness and the residues extracted with n-hexane (2 x 30 mL). The solutions were concentrated to -20 mL and cooled t o -40 "C to give microcrystalline red solids identified as 4a [R = 2,6-MezC&; yield 0.53 g (62%)]or 4b [(R = 2,4,6-Me&Hz; yield 0.49 g (56%)1. When the same reaction was carried out in a sealed NMR tube and monitored by lH NMR spectroscopy, the presence of free propene was detected. The data for 4a follow. IR (Nujol mull, v cm-l): 1323 (s), 1158 (w), 1095 (m), 1024 (m), 981 (w), 915 (w), 758 (SI, 395 (w), 348 (SI. 'H NMR (6 ppm, in CsDs): 6.96 (d, 2H, 3 J ~=- 7.5 ~ Hz, m-&C&fez), 6.66 (t, 1 H, 3 J ~=-7.5 ~ Hz,p-H3C&Iez), 2.45 (s, 6H, 2,6-Me&H3), 1.83 (s, 15H, c a e 5 ) . 13C{1H)NMR (6 ppm, in C&): 151.1 (s), 135.1 (s), 127.3 (s), 124.1 (s, C,, C,,, c, C,, C,&Mez), 121.3 (9, CsMed, 18.8 (9, 2,6-MezCsH3), 11.2 (s, C a e s ) . MS (EI, 70 eV): mle 505 (M', 7 9 , 386 (28), 351 (ll),135 (291, 119 (96). Anal. Calcd for ClsHz4C12NTa: C, 42.70; H, 4.28; N, 2.77. Found: C, 43.02, H, 4.31; N, 2.75. The data for 4b follow. IR (Nujol mull, v cm-l): 1320 (s), 1145 (w), 1022 (m), 965 (w), 775 (s), 375 (m). 'H NMR (6 ppm, in CsD6): 6.77 (s, 2H, m-HzCsMed, 2.47 (5, 6H, 2,4,6-Me&&), 2.25 ( 6 , 3H, 2,4,6-Me&Hz), 1.85 (s, C a e s ) . 'T{'H} NMR (6 ppm, in CsDs): 151.0 (SI, 134.8 (81, 132.3 (s), 129.8 (s, C,, C,, C,, C,, C&Med, 121.2 (s, CsMes), 20.7 (S,2,4,6-Me3C&), 18.8 (S,2,4,6-Me&jHz), 11.3 (S,C a e s ) . Anal. Calcd for C19H26C12NTa:C, 43.86; H, 5.04; N, 2.69. Found: C, 44.13; H, 5.02; N, 2.76. TaCp*Mez[q2-Me#N(Csmedl (Sa). Method A. 2a (0.41 g, 0.74 mmol) was dissolved in 40 mL of toluene, and 0.93 mL of a 1.6 M solution of LiMe (1.48 mmol) in OEt2 was added a t -78 "C. After 30 min, the reaction mixture was warmed to room temperature and stirred for a further 2-h period. The suspension was evaporated to dryness and the orange residue extracted with n-hexane (2 x 20 mL). The solution was filtered, concentrated to -10 mL, and cooled to -40 "C to give 5a as orange crystals. Yield 0.17 g (52%).
Ta Cp *Cl$C(Me)(NHR)l a n d TaCp*Mez($- MeZCNR)
Organometallics, Vol. 14, No. 4, 1995 1909
Table 5. Experimental Data for the X-ray Diffraction Studies
Table 6. Atomic Coordinates ( x 104) and Isotropic Thermal Parameters (A2x lo4) with ESDs in Parentheses for the Non-Hydrogen Atoms of 1w1/2C6H6
~
la.'l2CsHs mol formula mol wt cryst system space group radiatn a,
A
b, A c, A
a,deg
B. deg Y deg 3
v,A3
Z Dcalcd,
g/cm'
F(000) cryst dimens, mm p(Mo Ka),cm-l diffractometer 20 range, deg reflctns measd no. of unique total reflctns no. of unique obsd reflctns R RW
Sa
C Z O H Z B C ~ ~ N T ~ " /C23H3dTa ~C~-I~, 644.26 507.49 triclinic monoclinic pi P2Iln Nb-filtered graphitemonochromated (MoKa,2 = 0.710 73 A) 8.381(4) 10.515(6) 8.977(4) 14.615(9) 18.316(9) 14.594(8) 100.17(2) 97.83(2) 100.66(2) 105.04(2) 1286(1) 2204(2) 2 4 1.664 1.529 634 1016 0.24 x 0.30 x 0.35 0.22 x 0.27 x 0.38 47.00 49.92 Siemens AED Phillips PW 1100 6-50 6-60 h,fk,fl fh,k,l 4531 6419 3218 [ I 2 2o(T)] 3786 [ I 2 2o(T)] 0.0432 0.0299 0.0534 0.03 16
Method B. A sample of 3a (0.17 g, 0.294 mmol) was dissolved in toluene (15 mL), and 0.3 mL of a 3 M solution of MgClMe (0.88 mmol) in THF was added at -78 "C. After 30 min, the reaction mixture was allowed t o warm to room temperature and stirred for a further 4-h period. Evolution of methane was observed. The orange suspension was evaporated to dryness and the residue extracted with n-hexane (2 x 15 mL). After removal of the solvent, 0.08 g of an orange solid identified as Sa was obtained. Yield 50%. The data for Sa follow. IR (Nujol mull, v cm-'1: 1262 (s), 1231 ( s ) , 1105 (m), 1025 (m), 973 (w), 789 (m), 767 (s), 424 (m). 'H NMR (6 ppm, in C6D6): 7.21 (d, 2H,3 J ~=-7.5 ~ HZ, ?n-H&sMez), 7.05 (t, 1H, 3 J ~=-7.5 ~ Hz,p-H&sMez), 2.31 ( s , 6H, 2,6-MezCsH3), 1.98 (s, 6H, CMeZ), 1.72 (s, 15H, C&feS), -0.17 (s, 6H, MezTa). l3C NMR (6 ppm, in C6D6): 152.3 (m, i-Cs&Mez), 134.4 (qd, 2 J ~=- 3~J c - ~= 5.4 Hz, o-C&Mez), 128.4 (dm, 'Jc-H = 157 = 159.4 Hz,p-C&Mez), 115.5 Hz, m-C6H&fez),123.4 (d, ~Jc-H (m, C5Me51, 82.9 (spt, VC-H= 7.8 Hz, CMez), 52.9 (9, 'Jc-H= 118.9 Hz, MezTa), 27.6 (qq, 'Jc-H= 123.6 Hz, 3 J c - = ~ 4.5 Hz, CMeZ), 18.8 (qd, 'Jc-H = 126.3 Hz, 3 J c - ~= 5.05 Hz, 2,6Me&&), 10.6 (9, 'Jc-H= 127.3 Hz, c&fe5). Anal. Calcd for Cz3H36NTa: C, 54.43; H, 7.15; N, 2.76. Found: C, 54.33; H, 7.22; N, 2.80. X-ray Data Collection,Structure Determination, and Refinement for Compounds la+&& and Sa. Crystals suitable for the X-ray analyses were obtained by recrystallization from benzene solutions. The crystallographic data for both compounds are summarized in Table 5. Data were collected at room temperature (22 "C) on a Siemens AED diffractometer (lw1/zC6H6,using the niobium-filtered Mo Ka radiation) and on a Phillips PW 1100 (Sa,using the graphitemonochromated Mo K a radiation) and the 8/28 scan type. The reflections for both compounds were collected with a variablescan speed of 3-12" min-' and a scan width (deg) of 1.20 0.346 tan 0. One standard reflection was monitored every 100 measurements; no significant decay was noticed over the time of data collection. The individual profiles have been analyzed following Lehmann and Larsenz6 Intensities were corrected for Lorentz and polarization effects. A correction for absorption was applied (maximum and minimum values for the transmission factors were 1.235 and 1.051 (laJ/zC~H6)and
atom
~~
ylb
7Jc
U
2403 1) 723(4) 4 169(4) 1335(4) 4887(4) 4 149(10) 117(15) -271( 12) 103%13) 2189(14) 1663(15) -1 107(21) - 1908(18) 984(24) 3741(20) 2286(24) 3949(13) 4833(2) 5076(13) 67 16(13) 7519(17) 6716( 18) 5046(21) 4175(15) 7582( 16) 24 lO(20) -32(42) 1467(42) 2099(42) 123l(42) -268(42) -900(42)
3940(1) 3217(4) 2511(4) 6 159(4) 534 l(4) 5419(11) 3 158( 14) 1928(13) 1213(13) 1962(16) 3 168(14) 4023( 19) 1313(19) -227( 18) 1438(21) 4147(25) 5767(13) 7490( 18) 6410(12) 6459( 13) 7339( 16) 8094(15) 7967( 14) 7134( 13) 5624( 19) 7000(21) -932(39) -1018(39) - 119(39) 865(39) 951(39) 52(39)
2626(1) 1366(2) 2059(2) 2858(2) 3555(2) 1362(5) 3365(7) 2704(7) 2725(7) 3414(7) 3797(6) 358% 11) 2144( 10) 2179(11) 3673(10) 4563(9) 2045(6) 2402(8) 910(6) 919(6) 462(7) 17(7) 11(8) 464(6) 1402(9) 459(9) 4468(13) 4870(13) 5606( 13) 5939(13) 5536( 13) 4801( 13)
365(2)" 570( 11)" 621( 13)" 652( 13)" 687(13)" 448(34)" 565(49)0 531(46)" 500(43)" 580(49)" 559(47Y 1066(87)' 981(77)0 1073(93)O 1052(90)" 1249(98)0 463(43)y 720(60)" 470(41)" 47 1(40)a 617(51)" 634(55)" 673(60)y 488(43)" 684(59)" 762(66)" 1186(215) 1323(139) 1010(102) 1273(136) 918( 178) 1264(134)
Equivalent isotropic U defined as one-third of the trace of the orthogonalized Ui, tensor.
Table 7. Atomic Coordinates ( x lo4) and Isotropic Thermal Parameters (A2x 104) with ESDs in Parentheses for the Non-Hydrogen Atoms of 5a atom
+
(26) Lehmann, M. S.; Larsen, F. K. Acta Crystallogr., Sect. A 1974, 30, 580.
xla
xla
Ylb
dC
Ud
453(1) -560(4) 455(5) 1752(5) 1824(5) 583(6) -276(5) 2(6) 2887(5) 3044(6) 219(8) - 1693(6) -454(7) 2323(6) -376(6) -1217(5) -2543(5) -3 15 l(7) -2476(8) -1200(8) -526(6) -3346(6) 904(6) 414(8) - 1622(7)
2377(1) 2297(3) 697(3) 961(3) 1371(3) 1375(4) 969(3) 99(3) 753(4) 1654(5) 1622(5) 756(4) 325 l(5) 3022(5) 3291(4) 1821(3) 1631(4) 1140(4) 845(4) 1027(4) 1525(3) 1905(6) 1668(4) 3725(4) 3842(4)
1899(1) 2872(3) 1924(3) 1937(4) 1063(4) 523(4) 1047(4) 2637(4) 2705(4) 731(5) -502(4) 689(5) 753(5) 2387(5) 2841(4) 3499(3) 3257(4) 3861(5) 4698(6) 4944(4) 4364(4) 2312(5) 4684(4) 3723(5) 2549(5)
333(1) 368(12) 374(14) 414(16) 478(19) 504(20) 446( 18) 592(22) 707(25) 792(29) 971(37) 829(29) 692(27) 684(26) 582(23) 397(16) 526(20) 729(29) 874(36) 734(29) 503(19) 920(33) 723(26) 898(33) 945(35)
Equivalent isotropic U defined as one-third of the trace of the orthogonalized U,,tensor. (i
1.103 and 0.887 (Sa).27 Only the observed reflections were used in the structure solutions and refinements. Both structures were solved by Patterson and Fourier methods and refined by full-matrix least-squares fits first with isotropic thermal parameters and then with anisotropic ther-
1910 Organometallics, Vol. 14,No. 4,1995 mal parameters for the non-hydrogen atoms, excepting the carbons of the solvent for la*'/zC6H6. All hydrogen atoms of lw1/zC6H6,except those of the methyl groups of the Cp* ring which were placed at their geometrically calculated positions (C-H = 0.96 A) and refined "riding" on the corresponding carbon atoms (with isotropic thermal parameters) and those of the benzene molecule which were not calculated, were clearly localized in the final A F map and refined isotropically. All hydrogen atoms of 5a, except those of the methyl groups at C(11) and C(12) which were clearly localized in the final A F map and refined isotropically, were placed at their geometrically calculated positions (C-H = 0.96 A) and refined "riding" on the corresponding carbon atoms (with isotropic thermal parameters). The final cycles of refinement were carried out on the basis of 291 (la.VzCsH6) and 249 (Sa) variables; after the last cycles, no parameters shifted by more than 0.88 (la.VzC6H6) and 0.92 (5a) ESD. The highest remaining peak in the final difference map was equivalent t o 1.09 (la*'/zC~H6)and 0.75 (Sa) e/A3. In the final cycles of refinement a weighting scheme w = K[a2(Fa) + gFa21-'was used; at convergence, the K andg values were 0.638 and 0.0035 (laJ/zCsHs) and 1.137 and 0.0004 (5a), respectively. The analytical scattering factors, corrected for the real and imaginary parts of anomalous dispersion, were taken from ref 28. All calculations were carried out on the GOULD POWER(27) Walker, N.; Stuart, D. Acta Crystallogr., Sect A 1983,39, 158. Ugozzoli, F. Comput. Chem. 1987, 1 1 , 109.
Galakhov et al. NODE 6040 and ENCORE 91 computers of the "Centro di Studio per la Strutturistica Diffrattometrica" del CNR, Parma, using the SHELX-76 and SHELXS-86 systems of crystallographic computer programs.29 The final atomic coordinates for the non-hydrogen atoms are given in Table 6 (laJ/zC6H6) and Table 7 (Sa). The atomic coordinates of the hydrogen and SI1 (Sa), the atoms are given in Tables SI (la.1/zC6H~) thermal parameters in Tables SI11 (lw1/zC6H6)and SIV (5a) of the supplementary material.
Acknowledgment. We are grateful to DGICYT (Project PB-92-0178-C) and Consiglio Nazionale delle Ricerche, Rome, for financial supports. Supplementary Material Available: Tables of hydrogen atom coordinates (Tables SI, SII), thermal parameters (Tables SIII, SIV),and complete bond distances and angles (Tables SV, SVI),variable-temperature 'H NMR spectra of complexes 2 and 5, and Eyring plots of the kinetics of isomerization of 2a and 5a (27 pages). Ordering information is given on any current masthead page. OM9404975 (28) International Tables for X-Ray Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV. (29) Sheldrick, G. M. SHELX-76 Program for crystal structure determination, University of Cambridge, England, 1976; SHELXS-86 Program for the solution of crystal structures, University of Gottingen, 1986.
