Insertion of Isocyanides into Tantalum-Carbon Bonds of

Organometallics 1996,14,2843-2854

2843

Insertion of Isocyanides into Tantalum-Carbon Bonds of Azatantalacyclopropane Complexes. Crystal Structures of TaCp*C13(g2-NRCMe2CNHR), TaCp*Me(NR)(NRCMe=CMe2), and TaCp*Me(NR)(q2-NR=CCMe2CMe=NR) (R= 2,6-Me&&) Mikhail V. Galakhov, Manuel Gbmez, Gerard0 JimBnez, and Pascual Royo* Departamento de Quimica Inorganica, Uniuersidad de Alcalh 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 January 6, 1995@ Reaction of TaCp*ClzMea with 2 equiv of isocyanides or addition of 1equiv of isocyanides to azatantalacyclopropane complexes TaCp*C12(q2-NRCMe2)(R = 2,6-Me&H3, la, 2,4,6MesCeH2, lb) a t room temperature afforded new imido derivatives TaCp*C12(NR)(R = 2,6Me2CsH3, 2a, 2,4,6-Me&&, 2b) in almost quantitative yields, with simultaneous elimination of the imino ketene, RN=C=CMe2. When the same reactions were carried out in the presence of traces of water, small amounts of cyclic q2-amido-carbene species TaCp*C13(q2-NRCMe2CNHR) (R = R = 2,6-Me2C&, 3a, R = 2,6-Me2C&, R' = 2,4,6-Me&&, 3b) were simultaneously obtained. Complexes 3 can also be prepared by heating the corresponding trichloro-isopropylamido complexes TaCp*C13(NRiPr),4, at 90 "C in the presence of isocyanide and decompose by further heating a t 120 "C to give the imido compounds 2. A similar reaction of TaCp*Cl,Med-, (n = 0, 1)with 1 equiv of CN(2,6-Me2CsH3) afforded mono- and dimethylated azatantalacyclopropane derivatives TaCp*C1,Me2-,[q2-N(2,6-Me2C6H3)CMe21 (n = 1,5a; n = 0,5b),which react with one additional equivalent of isocyanide to give imido alkenylamido species TaCp*X[N(2,6-Me2C6H3)1(NRCMe=CMez) (X = C1, R = 2,6-Me2C&, 6a, and 2,4,6-Me&sH2, 6b;X = Me, R = 2,6-Me&&, 6c, and 2,4,6-Me3C&, 6d). Reaction of complexes 6a,c with a third 1 equiv of isocyanide afforded new y2-imino acyl compounds TaCp*X[N(2,6-Me&6H3)1(q2-NR"=CCMe2CMe=NR) (X = C1, R' = R" = 2,6-Me&H3, 7a; X = Me, R = R" = 2,6-Me&&, 7b, R = 2,6-Me&sH3, R" = 2,4,6-MesCsHz, 7c, and R = 2,6-Me&&, R" = tBu, 7d. All compounds were characterized by IR and lH and 13C NMR measurements, and the activation barrier t o rotation around the C=C double bond of the alkenyl group of 6a,c was determined in solution. Molecular structures of 3a, 6c, and 7b were studied by X-ray diffraction methods. Crystals of 3a are monoclinic, space group P21/ n, with 2 = 4 in a unit cell of dimensions a = 8.774(4) 8,b = 18.338(8) A, c = 18.470(7) A, and ,8 = 91.62(2)". Crystals of 6c are monoclinic, space grou P21/c, with 2 = 4 in a unit cell of dimensions a = 8.635(4) A, b = 34.156(9) A, c = 10.090(4) , and p = 105.94(2)". Crystals of 7b are orthorhombic, space group P212121, with 2 = 4 in a unit cell of dimensions a = 11.622(3) A, b = 14.141(5) .$, and c = 22.755(9) A. All three structures were solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix leastsquares on the basis of 6620 (3a),3442 (6c),and 3667 (7b)observed reflections to R and R, values of 0.0271 and 0.0394 (3a), 0.0272 and 0.0336 (6c), and 0.0450 and 0.0419 (7b), respectively.

1

Introduction We have reported1 recently the isolation of azatantalacyclopropane complexes by insertion of isocyanides into tantalum-methyl bonds of TaCp"ClzMe2 (Cp" = q5-C5Me5)with migration of two methyl groups. Similar compounds have also been reported for other transition Abstract published in Advance ACS Abstracts, May 1, 1995. (1) Galakhov, M. V.; Gbmez, M.; Jimenez, G.; Pellinghelli, M. A.;

@

Royo, P.; Tiripicchio, A. Organometallics 1995,14,1901.

metals.2 Further insertion of isocyanide is known3 to occur when more than two alkyl groups are bound to the metal, leading to imido alkenylamido complexes (2) (a) Takahashi, Y.; Onoyama, N.; Ishikawa, Y.; Motojima, S.; Sugiyama, K. Chem. Lett. 1978,525. (b) Wolczanski, P. T.; Bercaw, J. E. J . Am. Chem. Soc. 1979,101,6450. (c) Mayer, J. M.; Curtis, C. J.; Bercaw, J . E. J . Am. Chem. Soc. 1983,105,2651. (d) Nugent, W. A.; Overall, D. W.; Holmes, S. J. Organometallics 1983,2, 161. (e) Sielisch, T.; Behrens, U. J. Organomet. Chem. 1986,310, 179. (0 Brunner, H.; Wachter, J.; Schmidbauer, J. Organometallics 1986,5, 2212. (g)Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P. J.A m . Chem. SOC.1987,109,4720. (h) Durfee, L. D.; Hill, J. E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1990,9,75.

0276-7333/95/2314-2843$09.0Q/O 0 1995 American Chemical Society

Galakhov et al.

2844 Organometallics, Vol. 14, No. 6, 1995 Scheme 1

A

\

J \

4

CHMeZ

R=2.6-M&&. 4a 2 , 4 , 6 - . U e 3 v z , 4b

C

N

\

CHM

R'

which are analogous t o the oxido enolate derivatives isolated4 when the same reaction is carried out by using CO. The interest of this type of compounds in relation with many synthetic applications moved us to extend the study t o other (pentamethylcyclopentadieny1)tantalum chloro methyl complexes and t o investigate the reactivity of the azatantalacyclopropane derivatives. Here we describe the results found when 1 equiv of isocyanide is inserted in tri- and tetramethyltantalum complexes TaCp*Cl,Mer-, ( n = 0, 1)and the behavior of the resulting azatantalacyclopropane complexes in further insertions of isocyanides. The X-ray structures of the three most significant complexes and the dynamical behavior of the alkenylamido derivatives in solution are also described.

Results and Discussion Reactions of TaCp"ClzMe2 with Isocyanides. Reaction of TaCp*ClzMez with 1 equiv of isocyanide allowed us1 to isolate dichloroazatantalacyclopropane complexes 1. When the same reaction is repeated at room temperature by using 2 equiv of isocyanides under a rigorously dry inert atmosphere or in a sealed NMR tube, a different sequence of reactions takes place leading finally to the dichloro imido derivatives 2 as the unique reaction products in an almost quantitative yield. As shown in Scheme 1, exactly the same imido compounds are obtained when 1 equiv of the corresponding isocyanide is added a t room temperature to toluene solutions of the azatantalacyclopropane com(3j(aj Chiu, K. W.; Jones, R. A,; Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B. J . Am. Chem. SOC.1980,102,7978. (bj Chiu, K. W.; Jones, R. A.; Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B. J. Chem. SOC.,Dalton Trans. 1981, 2088. (c) Chamberlain, L. R.; Rothwell, I. P.; Huffman, J. C. J . Chem. SOC.,Chem. Commun. 1986, 1203. (d)Chamberlain, L. R.; Steffey, B. D.; Rothwell, I. P.; Huffman, J. D. Polyhedron 1989,8, 341. (4)Wood, C. D.; Schrock, R. R. J . A m . Chem. SOC.1979,101,5421.

plexes 1. However, when the same reaction is carried out in the presence of traces of water, the same imido complexes 2 are formed as the main products, but a small amount of air-stable q2-amido-carbene complexes 3 are simultaneously obtained. This behavior can be explained assuming that the azatantalacyclopropane complexes coordinate the isocyanide, which is inserted into the Ta-C bond by migration of the alkyl group of the metallacycle, to give the intermediate azatantalacyclobutane species A. Spontaneous thermal decomposition of this species at room temperature is so fast that A cannot be either isolated or observed by NMR spectroscopy. The decomposition takes place with elimination of the arylimine ketene. The imine ketene formed from l a in a sealed NMR tube was identified by its I3C spectrum, which shows the characteristic resonances of this species5 at 6 52:9 and 193.3,and its IR spectrum,6which shows 4CN) a t 2015 cm-l . In the presence of traces of water, hydrolysis of A or its precursor complex 1 takes place with evolution of HC1, which further reacts at room temperature to give complexes 3. Formation of complex A is required for 2 to be formed a t room temperature, because complexes 3 only decompose by heating at 120 "C in a sealed tube, being transformed into the same imido derivatives 2, with elimination of an unidentified organic residue. Complexes 3 can alternatively be obtained in an almost quantitative yield when a mixture of equimolar amounts of the already reported1 amido complexes 4, with the corresponding isocyanide, is heated at 90 "C. This reaction probably takes place by migration of the isopropyl hydrogen to the coordinated isocyanide, with simultaneous carbon-carbon bond formation. ( 5 ) Collier, C.; Webb, G. A. Org. Magn. Reson. 1979,12, 659. (6)Bestmann, H. J.;Lienert, J.; Mott, L. Liebigs Ann. Chem. 1968, 718, 24.

Azatantalacyclopropane Complexes

Organometallics, Vol. 14,No. 6, 1995 2845

Scheme 2

fP'

Me'+\ X S I . Me

fP' Me

L

R=2,6-MqC&

/

X-4.50;Me.5b

N. 'C-C=NRI Me2 Me R=R'=R=2,6-Me$&, 7s (X=Cl); 7b @=Me) (X=Me), R=R=2.6-Me&H3. R=2,4.6-Me&I-12. (7c); But (7d)

The IR spectra of complexes 3 show the v(N-H) and v(C=N) absorptions at 3112 and 1628 cm-l, respectively. Their formulation is based on the observed NMR behavior. The 13C(lH) NMR spectra of 3 show one singlet due to the carbene carbon a t 6 261.2. The lH NMR spectra of 3 exhibit one broad signal at 6 12.2 due to the aminocarbene proton, one singlet at 6 1.17 (3a), 6 1.23 (3b) for the two equivalent methyl-methylene protons, and two singlets at 6 2.23 (3a,b) and 6 2.43 (3a), 6 2.44 (3b) due to also equivalent ortho-methylphenyl protons of the amido and amino phenyl groups, respectively. The structure of complex 3a was fully elucidated by X-ray diffraction analysis. It shows the amido nitrogen directly bonded t o the tantalum atom occupying one equatorial position together with the three chlorine atoms, whereas the carbene end of the ligand occupies the axial position. Reactions of TaCp*ClMes and TaCp*Me4 with Isocyanides. When 1equiv of the isocyanide is added to a toluene solution of the chlorotrimethyltantalum complex, a red solution is obtained, which after manipulation affords the monomethylated azatantalacyclopropane complex 5a, as shown in Scheme 2. The addition of a second 1 equiv of isocyanide to solutions of this azatantalacyclopropane complex 5a produces a new insertion leading finally to the imido alkenylamido derivatives 6a,b. When 1 equiv of CN(2,6-MezCsH3) is added to the tetramethyltantalum complex in a sealed NMR tube, an intense red solution is obtained, which according t o its 'H NMR spectrum consists of a mixture of three different components. The main product is complex 6c, together with a small amount of the expected dimethylazatantalacyclopropane derivative 5b, recently1 isolated by methylation of la, and an amount of unreacted

2

R"

6

'C=CMel Me'

R=R'=2,6-h.leg&, 60 (X=Cl);6c (X=Me) R=2.6-MqCgH3; R'=2.4,6-M%C&, 6b (X=CI); 6d (X=Me)

starting material. This behavior means that the insertion of CNR is much more favorable for complex 5b than for the starting tetramethyl derivative. However, when 2 equiv of CN(2,6-MezCsH3)is added to the tetramethyltantalum complex in toluene, a yellow-green product characterized as complex 6c is obtained in almost quantitative yield. The still remaining methyl substituent does not migrate, probably because it would lead t o a much less favorable unsaturated electron deficient compound.3b Neither does such a migration take place for TaCp*Me(y2-ArCWAr)(~z-ButN=CMe)g in spite of containing a cis-methyl group. The first step in both reactions with the trimethyland tetramethyltantalum complexes consists in the insertion of the first coordinated isocyanide molecule, with migration of two methyl groups to give 5a,b, containing the same azatantalacyclopropane system already studied' for compounds 1 and analogousto other reported4s7j8"?,?-ketone" complexes. Coordination of a second isocyanide to the vacant position is followed by a double migration of one methyl group and the met(7)(a) Masai, H.;Sonogashira, K.; Hagihara, N. Bull. Chem. SOC. Jpn. 1968,41,750.(b)Fachinetti, G.; Floriani, C. J . Chem. Soc., Chem. Commun. 1979,654. (c) Girolami, G. S.; Mainz, V. V.; Andersen, R. A.; Vollmer, S. H.; Day, V. W. J . Am. Chem. SOC.1981,103,3953.(d) Hessen, B.; Teuben, J.; Lemmen, T. H.; Huffman, J. C.; Caulton, K. G. Organometallics 1985, 4 , 946. (e) Negishi, E.; Takahashi, T. Synthesis 1988,1. (8)(a) Rosenfeldt, F.; Erker, G. Tetrahedron Lett. 1980,21, 1637. (b)Waymonth, R.M.; Clauser, K. R.; Grubbs, R. H. J . Am. Chem. SOC. 1986, 108, 638. (c) Stella, S.; Floriani, C. J . Chem. SOC.,Chem. Commun. 1986,1053. (d) Erker, G.; Dorf, V.; Czisch, P.; Petersen, J. L. Organometallics 1986,5,668. (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. (c) Hirpo, W.; Curtis, M. D. Organometallics 1994,13, 2706.

Galakhov et al.

2846 Organometallics, Vol. 14, No. 6, 1995

?P*

Y

1 . U :.IO

1 . 7 1 1.70 1 . 6 1 1.68 L S S I . %

De*

2.5 2 . 4 2.3 2 . 2 2 . 1 2 . 0 1.9 1.8 i . ? 1.6

ppm

Figure 1. 'H NMR spectra at variable temperature for complex 6c in CD&. allacycle alkyl group to the electrophilic isocyanide carbon atom. As shown in Scheme 2, two different pathways may be proposed depending on which is the order of migration of both groups, leading in any case to the same unidentified intermediate species that spontaneously rearranges, breaking the Ta-C and C-N(amido) bonds with simultaneous C=C bond formation, to give the resultant products 6. This behavior is similar to that observed in the formation of complexes 2, for which the C-N bond breaking also takes place, but the coordinating capacity of the resulting imino ketene is low, resulting in its dissociation. However, when a third methyl group is present, its migration transforms the imino into an amido group, which remains occupying its coordination position. Complexes 6a-c are reasonably stable compounds that can be easily crystallized and characterized by NMR spectroscopy. In order to favor the migration of the methyl group by addition of bases, we studied the reaction of complexes 6a and 6c with an additional 1 equiv of the isocyanides. Addition of 1 equiv of CNR to a toluene solution of the previously isolated 6a,c produces a very slow reaction to give after 7 days a t room temperature (2-3 days a t 50-60 "C) pale yellow-green solutions, which &er evaporation render complexes 7a-d. Therefore, the still remaining methyl group does not migrate to the electrophilic carbon atom of the new isocyanide

ligand, which instead attacks the terminal olefinic carbon atom of the amido ligand, leading to the new r2acylimidoyl complexes 7a-d. The structures of the complexes 6c and 7b were determined by X-ray difiaction methods. Formulation of the complexes 6 and 7 is also in agreement with the NMR structural behavior described (see Experimental Section). Structural and Dynamic N M R Studies. The structural characterization of complexes 1,2,4, and 5b has already been rep0rted.l The NMR behavior of complexes 3 has been discussed above, and the structure of 3a was determined by X-ray diffraction methods (see below). Complex 5a shows the NMR behavior expected for a molecule which does not contain the plane of symmetry observed for 5b; therefore, the lH and 13C NMR spectra of 5a show two singlets for the pair of nonequivalent methyl groups bound to the carbon atom of the azatantalacyclopropane ring, along with the singlet due to the ortho-methylphenyl groups made equivalent by rotation and that due to the methyl group bound to the metal. The NMR spectra of complexes 6 show that one of the two phenyl rings is freely rotating whereas the other does not rotate in the NMR scale time. A comparison between the two lH NMR spectra of complexes 6a,b or 6c,d (Figure 1) shows that the phenyl ring of the imido substituent possesses Cpu s y " e try. Broad 'H and 13Csignals are always observed for the =CMe2 methyl groups (Me2", Me2b)in all complexes


Organometallics, Vol. 14, No. 6, 1995 2847

Scheme 3

r

TP*

* '*

Scheme 4

\ 3 Me

Anti-

Syn-

Table 1. Kinetic Parameters of Rotation around the C=C Double Bond of Complexes 6a,c AH+, As*, AG* 298K, kcal/mol eu kcal/mol 6a 10.0% 0.4 11.5 f 1.8 9.5 k0.4 -15.8 1.7 14.2 r = 0.998 r = 0.998 6~ 8.0 i 0.1 11.1 f 0.9 7.5 *0.1 -16.3j10.4 12.2 r = 0.999 r = 0.999

E,, kcaYmol

log A

*

6 a t 303 K and also for the 'H resonance due to the Me3 group that can be resolved as a septuplet by coupling with the protons of the two Mezaand Me2bgroups, which seem to be equivalent at higher temperatures. When a CDC13 solution of 6c is cooled from 303 K down t o 243 K, the Me2 signal broadens with a coalescence point at 263 K (AG* = 12.2 kcal mol-l), being split into two signals observed at 6 1.47 and 6 1.73 at 243 K. A similar behavior is observed for complex 6a with the coalescence point at 313 K (AG* = 14.2 kcal mol-l). Kinetic parameters calculated on the basis of lH DNMR data by NMR line shape analysisll (see Table 1 ) show that this transformation is an intramolecular process [logA = 11.5 (6a),11.1 (6c)l taking place with negative AS* values, due to solvation effects with a highly polar transition state. The values found for these parameters are consistent with a transition state A (Scheme 3 ) resulting from the heterolytic dissociation of the C=C n bond, similar to that reported12 for enamines, in this case, with electron delocalization of the nitrogen lone pair over the C-NTa system. This delocalization is affected by the X substituent, as found from a comparison between the kinetic parameters for both complexes 6a and 6c that allows to conclude that E,, Al?, and AG* values are (10)Weber, W. P.; Gokel, G. W.; Ugi,I. K. Angew. Chem., Int. Ed. Engl. 1972,11, 530. (11)(a)Abragam, S. The principles of nuclear magnetism; Clarendon Press: Oxford, U.K., 1961. (b) Jackman, K.M.; Cotton, F. A. DNMR Spectroscopy; Academic Press: New York, 1975.

lower for the less electronegative substituent X bound to the metal. Rotation around the C-C axis in species A renders the terminal methyl groups (Meza,Me2b)equivalent on the NMR time scale at higher temperatures. A transition n-azaallylic species, whose rapid u-n-u conversion would allow the exchange between the syn- and antimethyl groups at the Ta-C a-stage, cannot be considered because the presence of a chiral metal center would make both methyl groups diastereotopic and therefore not equivalent. When the solution of 6c in CD2C12 is cooled at decreasing temperatures to the coalescence point, the width and chemical shift of one of the two Me2 signals is unaffected, whereas the other broadens and shifts to lower field and simultaneously the resonances due to Me3 and one of the two Me1 groups are slightly broadened and shifted. It is well-knownll that spin-relaxation times depend on the number of adjacent protons and their distances. Spin-lattice relaxation times (TI) have been measured for 6c at different temperatures. The TI values at 193 K combined with X-ray data can be used t o assign the resonances a t 6 1.6 and 1.7 t o Meza(TI = 0.428 f 0.001 s) and Me2b(TI = 0.200 f 0.001 s) protons, respectively. The behavior of Me2, and Me3 signals between 233 and 183 K can be explained by exchange of these signals with upfield and downfield lines, respectively, of the signals of the other isomer present in ca. 10% amount. Several signals of the minor isomer of 6c can be detected in the l3C(lH} NMR spectrum at 173 K. We propose that the second process is an exchange between the anti (major) and syn (minor) isomers (Scheme 4 ) due t o rotation around the C-N bond as reported12for organic enamines. Finally at 193 K is possible to detect the coalescence of the 2,6-Me&H3 methyl proton resonances (AG* = 8.7 kcal mol-') corresponding to the rotation around the Cip0-N bond. (12) Bakmutov, V. I.; Fedin, E. I. Bull. Magn. Reson. 1984,6 , 142.

Galakhou et al.


C(26

Figure 2. ORTEP view of the molecular structure of TaCp*Cl&$NRCMezCNHR) (R = 2,6-MezCcH3)(3a)with the atom-numbering scheme. The thermal ellipsoids are drawn at the 30% probability level. Table 2. Selected Bond Distances (A) and Angles (deg) with Esd's in Parentheses for Compound 3a Ta-CE(1)" Ta-Cl(1) Ta-Cl(2) Ta-Cl(3) Ta-N(l) Ta-C(12) CE(l)-Ta-Cl( 1) CE(l)-Ta-C1(2) CE(l)-Ta-C1(3) CE(l)-Ta-N(l) CE(lI-Ta-C(l2) Cl(l)-Ta-C1(2) Cl(l)-Ta-C1(3) Cl(l)-Ta-N(l) Cl(l)-Ta-C(12) C1(2)-Ta-C1(3) C1(2)-Ta-N(1) C1(2)-Ta-C(12) a

2.199(4) 2.452(1) 2.526(1) 2.450(1) 2.029(3) 2.195(3) 103.9(1) 104.6(1) 104.5(1) 112.4(1) 175.9(1) 78.7(1) 148.1(1) 90.4(1) 76.7(1) 80.2(1) 142.9(1) 79.5(1)

N(l)-C(ll) N(1)- C(15) C(ll)-C(12) N(2)-C(12) N(2)-C(23) C1(3)-Ta-N(1) C1(3)-Ta-C(12) N(l)-Ta-C(12) Ta-N(l)-C(ll) Ta-N(l)-C(lS) C(ll)-N(l)-C(E) C(12)-N(2)-C(23) N(l)--C(ll)-C(12) Ta-C(12)-N(2) Ta-C(12)-C(11) N(2)-C(l2)-C(ll)

1.527(4) 1.439(4) 1.505(5) 1.289(4) 1.454(4) 92.2(1) 76.1(1) 63.5(1) 104.2(2) 139.6(2) 116.3(3) 129.9(3) 94.6(3) 132.8(3) 97.7(2) 129.5(3)

CE(1) is the centroid of the C(1) ..C(5) cyclopentadienyl ring.

X-ray Crystal Structures of 3a, Bc, and 7b. A view of the complex TaCp*C13(y2-NRCMe2CNHR)(R = 2,6Me2CsHs) (3a) is shown in Figure 2 together with the atom-numbering scheme. Selected bond distances and angles are given in Table 2. The pentamethylcyclopentadienyl ring is bound to the Ta atom in a nearly symmetric v5-fashion (the Ta-C distances range from 2.472(4) to 2.562(4) A), with the distance between the metal and the centroid of the ring being 2.199(4) A. The Ta atom is bound to the N(1) and C(12) atoms of the chelating amido carbene ligand. The Ta atom is bound also to three C1 atoms with Ta-C1 bond lengths of 2.450(11, 2.452(1), and 2.526(1) A, the longest one involving the C1 atom trans to the amido N(1) atom. 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 0.621(1) A from the equatorial plane, containing the three C1 atoms and the

N(1) atom, toward the Cp* ring, and the carbene C(12) atom is positioned trans to the Cp* ring. The Ta-N(l) and Ta-C(12) bond distances involving the chelating atoms are 2.029(3) and 2.195(3) A, respectively. The Ta-N(l) distance shows a double bond character similar to that found in the complex TaCp*Me2(y2-Me2CNR), where the value of this distance has been found much shorter, 1.930(4) 8.l Also the value of the Ta-C(12) bond distance is much shorter than that found, 2.321(12) A, with the carbene carbon atom in the complex TaCp*C14[C(Me)NHR)].l This remarkable shortening could be due to the steric effect of the narrow bite of the chelating ligand, as shown by the very different angles at the carbene C(12) atom [the C(ll)-C(12)-Ta angle is 97.7(2)' against 125.9(9)', the N(2)-C(12)-Ta one is 132.8(3)' against 123.0(8)', and the N(2)-C(12)C(11) one is 129.5(3)' against 111.1(10)"1. The fourmembered ring containing the Ta, N(l), C(11), and C(12) atoms is planar with the C(ll)-C(12) and N(lI-C(l1) bond distances being consistent with single bonds. This plane forms a dihedral angle of 89.5(2)' with the mean plane passing through the cyclopentadienyl ring. The N(2)-C(12) bond length of the aminocarbene moiety is 1.289(4) A, corresponding t o a localized double bond. Also the C(ll)C(12)N(2)C(23)moiety is perfectly planar with the Ta and N(1) atoms deviating by 0.132(1) and 0.056(1) A from this plane. The N(2)-bound hydrogen is involved in an intramolecular hydrogen bond with the coordinated Cl(2) atom. The N(2). *C1(2)and H. Cl(2) distances of 3.029(3) and 2.34(6) A, respectively, as well as the N(2)-Ha * Cl(2) angle of 132(5)' are in agreement with this bonding. It is noteworthy the very large TaN(l)-C(15) angle, 139.6(2)', is probably due to steric hindrance of the C(9) atom from the methyl group with the C(15) and C(16) atoms. The C(9>*.C(15) and C(9).**C(16)contacts are of 3.112(7) and 3.210(7) A, respectively, and the C(9) atom is displaced from the mean plane of the cyclopentadienyl ring plane by 0.401(5)A, much more then the other methyl carbon atoms deviate (in the range 0.132(5)-0.210(6) A). A view of the complex TaCp*Me(NR)(NRCMe=CMe2) (R=2,6-Me&~H3)(6c) is shown in Figure 3 together with the atom-numbering scheme. Selected bond distances and angles are given in Table 3. The pentamethylcyclopentadienyl ring is bound to the Ta atom in a slightly asymmetric y5-fashion (the Ta-C distances range from 2.392(8) t o 2.564(6) A), with the distance between the metal and the centroid of the ring being 2.179(7)A. The Ta atom is also bound to the C(32) atom of a methyl group and to the two N(1) and N(2) atoms from the phenylimido and alkenylamido ligands. The complex, which can be described as pseudotetrahedral if the centroid of the Cp* ring is considered as occupying one coordination site, is chiral, and both enantiomers are present in the crystal. The Ta-C(32) bond distance [Ta-C(32) = 2.181(7) AI is quite normal and can be compared with those found, 2.178(7) and 2.179(7) A, in TaCp*Mez(y2-Me2CNR).l The values of the Ta-N( 1) bond length, 1.784(4) A, consistent with a triple bond character, and the nearly linear Ta-N(l)-C(ll) angle of 168.0(4)' are expected for an imido ligand and are strictly comparable with those found for the same ligand in complex 7b (see below). The Ta-N(2) bond length, 2.050(5) A, involving the alkenylamido ligand, is consistent with a double bond character and is comparable

-



Figure 3. ORTEP view of the molecular structure of TaCp*Me(NR)(NRCMe=CMez)(6c)with the atom-numberingscheme. The thermal ellipsoids are drawn at the 30% probability level. Table 3. Selected Bond Distances (A>and Angles (deg) with Esd's in Parentheses for Compound 6c Ta-CE(1)" Ta-N(l) Ta-N(2) Ta-C(32) N(l)-C(ll) N(2)-C(19) CE(l)-Ta-N(l) CE(l)-Ta-N(2) CE(l)-Ta-C(32) N(l)-Ta-N(Z) N( 1)-Ta-C(32) N(2)-Ta-C(32) Ta-N(l)-C(ll) Ta-N(2)-C(19) a

2.179(7) 1.784(4) 2.050(5) 2.181(7) 1.382(7) 1.453(6) 114.7(2) 133.2(2) 106.3(3) 99.4(2) 100.9(2) 96.9(2) 168.0(4) 117.9(3)

N(2)-C(27) C(27)-C(28) C(27)-C(29) C(28)-C(30) C(28)-C(31) Ta-N(2)-C(27) C(l9)-N(Z)-C(27) N(2)-C(27)-C(29) N(2)-C(27)-C(28) C(28)-C(27)-C(29) C(27)-C(28)-C(31) C(27)-C(28)-C(30) C(3O)-C(28)-C(31)

1.431(7) 1.354(10) 1.507(8) 1.504(9) 1.512(9) 125.9(4) 116.1(4) 112.6(5) 128.3(5) 119.2(6) 128.9(6) 120.2(6) 110.9(6)

CE(1)is the centroid of the C(1)..*C(5)cyclopentadienyl ring.

to that found for the Ta-N(l) bond length involving the nitrogen atom of the amido group in 3a. In the alkenylamido ligand the C(27)-C(28) bond distance, 1.354(10) A, agrees with a double bond character. The alkenylamido and phenyl groups are almost perpendicular one to another, the dihedral angle between them being 85.0(1)'. Also in 6c the Ta-N(2)-C(27) angle, 125.9(4)",is large probably due to steric hindrance of the C(8) atom from the methyl group with the C(29) atom [the C(8) **C(29)contact is of 3.349(14) A and moreover the C(8) atom is that which deviates more remarkably from the cyclopentadienyl ring plane]. A view of the structure of TaCp*Me(NR)(y2NR=CCMe2CMe=NR) (R = 2,6-MezC&) (7b)is shown in Figure 4 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 y5-fashion (the Ta-C distances range from 2.432(11)to 2.508(11)A), with the distance between the metal and the centroid of the ring being 2.155(11) A. The Ta atom is also bound t o the C(11) atom of a methyl group, to the N(1) atom from the phenylimido ligand, and to N(2) and C(28) from the y2-coordinated NR=CCMezCMe=NR ligand. The coordination geometry is a distorted square pyramid if the

Cp* is considered as occupying the apical coordination site with the Ta atom deviating 0.984(1) A from the mean plane passing through atoms C(11), N(l), N(2), and C(28) toward the Cp* ring. The complex is chiral, and in the crystals only one of the two enantiomers is present. The values of the Ta-N(l) bond length, 1.812(8) A, and of the Ta-N(U-C(l2) angle, 171.1(8)", are comparable with those found for the same phenylimido ligand in complex 6c. The value of the Ta-C(l1) bond distance [Ta-C(11) = 2.203(11)AI is very similar to that found in 6c. The imino acyl NR=CCMezCMe=NR ligand is dihapto coordinated to the Ta atom through the N(2) and C(28)atoms. The Ta-C(28) bond distance, 2.188(9) A, is comparable to that involving the methyl group and also t o that found, 2.209(6) A, for the azatantalacyclopropane ligand in TaCp*Mez(y2-Me2CNR1.l The value of the Ta-N(2) bond length, 2.148(7) A, is much longer than that found, 1.930(4) A, for the azatantalacyclopropane ligand in TaCp*Me2(v2-Me2CNR),' denoting a single bond character instead of the double bond character evidenced in the azatantalacyclopropane ligand. Both imino acyl and isopropylidenamine ligands show a clearly different behavior as illustrated by the following observations. The values of the N(2)-C(28) and N(3)-C(30) bond lengths, 1.294(13) and 1.271(13)A, are consistent with a double bond character. The TaN(2)C(28)plane forms dihedral angles of 131.8(4)"with the cyclopentadienyl ring, of 104.6(4)" with the TaC(ll)N(l)plane, and of 83.1(4)"with the aryl group, whereas in TaCp*Mez(y2-MezCNR)the azatantalacyclopropane ring was almost perpendicular t o the cyclopentadienyl ring.l Moreover, in this last complex the centroid of the cyclopentadienyl ring was coplanar with the triatomic ring, whereas in 7b the centroid is out of the plane of the triatomic ring by 1.49(1) A.

Conclusions With this and a previously reported work1 we have completed a systematic study of the isocyanide insertion reactions into tantalum-methyl bonds of different ha-

Galakhov et al.


Figure 4. ORTEP view of the molecular structure of TaCp*Me(NR)(y2-NR=CCMe2CMe=NR) (7b)with the atom-numbering scheme. The thermal ellipsoids are drawn at the 30% probability level. Table 4. Selected Bond Distances (A) and Angles (deg) with Esd’s in Parentheses for Compound 7b Ta-CE(1)” Ta-N(l) Ta-N(2) Ta-C(11) Ta-C(28) Ta-CE(2) N(l)-C(12)

2.155(11) 1.812(8) 2.148(7) 2.203(11) 2.188(9) 2.069(8) 1.380(14) 118.6(4) CE(l)-Ta-N(l) CE(l)-Ta-N(2) 134.5(4) 104.3(4) CE(l)-Ta-C(ll) 118.5(4) CE(l)-Ta-C(28) N(l)-Ta-N(2) 105.2(3) N(l)-Ta-C(ll) 99.7(4) 101.3(4) N(l)-Ta-C(28) N(2)-Ta-C(11) 78.6(4) N(2)-Ta-C(28) 34.7(3) C(ll)-Ta-C(28) 113.2(4) CE(l)-Ta-CE(2) 128.0(4) CE(2)-Ta-N(1) 103.9(3)

N(2)-C(20) N(2)-C(28) N(3)-C(30) N(3)-C(31) C(28)-C(29) C(29)-C(30) CE(2)-Ta-C(11) Ta-N(1)-C(12) Ta-N(2)-C(28) Ta-N(2)-C(20) C(20)-N(2)-C(28) C(30)-N(3)-C(31) Ta-C(28)-N(2) Ta-C(28)-C(29) N(2)-C(28)-C(29) N(3)-C(30)-C(29) N(3)-C(30)-C(41) C(29)-C(3O)-C(41)

1.435(14) 1.294(13) 1.271(13) 1.419(13) 1.548(14) 1.564(14) 96.1(4) 171.1(8) 74.3(5) 148.4(7) 137.2(9) 120.9(8) 71.0(5) 161.2(7) 127.6(9) 117.3(8) 126.2(9) 116.5(8)

CE(1)is the centroid of the C(1) .-C(5)cyclopentadienyl ring, and CE(2) the midpoint of the N(2)-C(28) bond. Q

lomethyl(pentamethylcyclopentadieny1)tantalum complexes TaCp*CLnMen. Whereas the monomethyl complex ( n = 1)leads t o the formation of the q2-coordinated imino acyl compound, the dimethyl derivative ( n = 2) gives the dichloroazatantalacyclopropane complex by double migration of two m e t h y l groups. Similar chloromethyl- and dimethylazatantalacyclopropane complexes are also obtained b y insertion into tri- and t e t r a m e t h y l (n = 3,4)complexes, respectively, but these compounds take p a r t in a simultaneous further insertion of isocyanide leading to the chloro- and methylimido alkenylamido complexes, which are almost quantitatively obtained when an additional 1equiv of isocyanide is used. Attack of the isocyanide to the terminal olefinic carbon of the alkenyl moiety in these complexes converts the amido into an imino acyl ligand containing a terminal ketimine function. Activation barriers for the

intramolecular isomerization of the azatantalacyclopropane complexes (AG* = 11.5-11.6 kcal mol-l) and for the rotation around the C=C double bond of the alkenyl group in imido alkenyl complexes (AG* = 12.2-14.2 kcal mol-l) were determined by dynamic NMR measurements. Carbene, amido, and imido derivatives can be easily obtained b y protonation, rearrangement, or thermal transformation of these imino acyl and azatantalacyclopropane compounds. Experimental Section General Procedures. All manipulations were carried out under a n atmosphere of argon using conventional Schlenktube and glovebox techniques. Solvents were purified by distillation from a n appropriate drying agent n-hexane ( N a K alloy) and toluene (sodium). NCtBu was purchased from Fluka and used without further purification. Isocyanides’O CNR (R = 2,6-MezCsH~,2,4,6-Me&&) and starting materials TaCp*C1,Me4-, ( n = 0,4J31,14215)and TaCp*Clz(qZ-RN-CMez)’ were synthesized according to literature procedures. Infrared spectra were recorded on a Perkin-Elmer 583 spectrophotometer (4000-200 cm-l) as Nujol mulls between CsI pellets or polyethylene films. ‘H and I3C NMR spectra were recorded on a Varian Unity-300 MHz spectrometer, and DNMR studies were carried out on a Varian Unity-500 MHz spectrometer. Chemical shifts are reported in d units, CDC13 or C& being used as the reference signal. C, H, and N analyses were carried out with a Perkin-Elmer 240C microanalyzer. Reaction of TaCp*ClzMeZwith CNR. CNR (1.06 mmol) was added under rigorously anhydrous conditions to a solution of TaCp*ClzMez (0.22 g, 0.53 mmol) in toluene (20 mL), and the reaction mixture was stirred for 24 h. The red solution obtained was evaporated to dryness and the residue washed (13)Sanner, R. D.; Carter, S. T.; Bruton, W., Jr. J . Organomet. Chem. 1982,240, 157. (14) McLain, S . L.; Wood, C. D.; Schrock, R. R. J . Am. Chem. SOC. 1979, 101, 4558. (15) Gbmez, M.; Jimenez, G.; Royo, P.; Selas, J. M.; Raithby, P. R. J . Organomet. Chem. 1992, 439, 147.



= 157.5 Hz, m-CsH$dez), 124.7 (d, 'Jc-H= 159.3 Hz, p-CsH3twice with n-hexane (2 x 5 mL) t o give microcrystalline red Med, 118.6 (m, CjMes), 89.3 (m, MezCNR), 52.5 (q, VC-H= solids identified as 2 a (R = 2,6-MezC&; yield 0.21 g, 78%) or 120.8 Hz, Ta-Me), 29.8 qq, 27.9 qq ('Jc-H= 124.5 Hz, 3 J C - H 2 b (R = 2,4,6-Me&&; yield 0.19 g, 70%). Analytical and = 3.7 Hz, MezCNR), 20.7 (qm, ~Jc-H = 129.1 Hz, 2,6-MezCsH3), structural data for 2a,b are coincidental with those previously 10.5 (q, VC-H= 128.2 Hz, C5Me5). Anal. Calcd for TaC1rep0rted.l C22H33N: C, 50.05; H, 6.30; N, 2.65. Found: C, 50.15; H, 6.28; Reaction of TaCp*C12(q2-RNCMe2) (la,b) with CNR'. N, 2.69. Toluene solutions (50 mL) of la or l b (1.20 mmol) were treated Reaction between TaCp*Mer and CNR in Molar Ratio with CNR (1.20 mmol) under rigorously anhydrous conditions 1:l. A C6D6 solution of TaCp*Me4 (0.10 g, 0.27 mmol) was (drybox) and stirred for 24 h. Solutions were concentrated to placed into a NMR tube, and under rigorously anhydrous dryness and the residues extracted with n-hexane (3 x 20 mL). conditions, CNR (0.035 g, 0.27 mmol) was added and the tube Solutions were concentrated to ca. 20 mL and cooled to -40 sealed under vacuum. The reaction was monitorized by 'H "C to yield red microcrystalline solids identified' as 2 a (yield: NMR spectroscopy until no further change was observed. The 0.44 g, 80%) or 2 b (yield: 0.44 g, 76%). spectrum showed the presence of a mixture of the three Preparation of TaCp*C13(q2-NR-CMez-CNHR) ( R = R' following components: a new complex 6c as the major product, = 2,6-MezCeHs, 3a; R = 2,6-MezCeHs, R' = 2,4,6-MesCsHz, 5b, and a small amount of unreacted starting material 3b). Method A. In a standard vacuum line, CN(2,6-MezC&) TaCp*Me4. (0.18 g, 1.44 mmol) was added t o a toluene (30 mL) solution Preparation of TaCp*X(NR)(NR'CMe=CMed (X = C1, of TaCp*ClzMez (0.30 g, 0.72 mmol) under not rigorously dry R = R = 2,6-MezC&, 6a; X = c1, R = 2,6-MezCeHs, R' = argon and the reaction mixture stirred for 12 h. The resulting 2,4,6-Me3C6Hz, 6b;X = Me, R = R = 2,6-Me&H~, 6c; X = red solution was filtered, the solvent evaporated t o dryness, Me, R = 2,6-Me2C&, R = 2,4,6-MesC,&, 6d). 6a. To a and the residue extracted with n-hexane (2 x 25 mL). The toluene (60 mL) solution of TaCp*ClMe3 (1.07 g, 2.71 mmol) solution was cooled to -40 "C t o give 3a as yellow crystals, was added CNR (0.71 g, 5.42 mmol). After being stirred a t which were filtered out and dried under vacuum. Yield: 0.05 room temperature for 12 h, the resulting solution was evapog (10%). The residual solution containing a mixture of red 2 a rated t o dryness in vacuo, the resulting yellow residue was as the main product and still a small amount of 3a was not extracted with n-hexane (2 x 25 mL), and the solution was further worked. cooled t o -30 "C to afford 6a (Yield: 0.99 g, 56%). The same Method B. A mixture of equimolar amounts of the amido compound can also be prepared by addition of 1 equiv of complex 4a and isocyanide CNR in benzene was heated at 90 isocyanide t o 5a. The data for 6 a follow. IR (Nujol mull, v , "C for 1 week in a sealed tube. After the tube was opened, cm-l): 1625 (w), 1575 (w), 1315 (SI, 1252 (m), 1189 (m), 1155 the solution was evaporated t o dryness and the residue (m), 1095 (m), 1022 (m), 937 (m), 875 (m), 805 (m), 765 (m), recrystallized from toluenehexane t o give yellow crystals of 350 (m),335 (m). 'H NMR (6 ppm, in CsDs): 6.92 (d, 2H, 3 J ~ - ~ 3a or 3b. Yield: 90%. The data for 3a follow. IR (Nujol mulls, = 7.5 Hz, m-H&&fez, R), 6.7 (m, 3H, HsCsMez, R ) , 6.55 (t, v, cm-I): 3112 (w), 1628 (m), 1252 (w), 1230 (w), 1198 (w), l H , 3 J ~ - H= 7.5 Hz, p-H&sMez, R), 2.61 (S, 3H, 2,6-MezCsH3, 1138 (m), 1022 (w), 910 (w), 834 (w), 790 (m), 350 (m), 290 R), 2.27 (s, 6H, 2,6-Me&H3, R ) , 2.25 (s, 3H, 2,6-MezCsH3, (m). 'H NMR (6 ppm, in CsDs): 12.20 (br, l H , TaCNHR), 6.85 m, 6.51 d ( 3 5 ~ = -7.5 ~ HZ, m-HaCsMez), 6.85 m, 6.71 t ( 3 5 ~ - ~R), 1.89 (S, 15H, CSMes), 1.86 [Spt, 3H, 'JH-H = 0.93 Hz, C(Me)-CMez], 1.6 br, 1.3br [MezC=C(Me)l. I3C NMR (6 ppm, = 7.5 Hz, p-H&sMez), 2.43 s, 2.23 s (2,6-MezC&), 2.00 (s, in C&): 154.5 (m, i-CsH&fez, R ) , 151.3 (m, i-CsHsMez, R), 15H, CsMes), 1.17 (s, 6H, CMe2). l3cNMR (6 ppm, in CsD6): 135.2 (m, o-C&Mez, R), 135.1 m, 132.9 m (o-CsHsMe2, R ) , 261.2 (m, TaCNHR), 145.0 m, 138.4 m (i-CsHsMez),140.2 m, 128.6 d, 127.6 d ('Jc-H= 157.0 Hz, m-CsH~Mep,R),126.5 (dm, 135.5 m (o-C&,Mez),129.3 d, 129.2 d ('Jc-H= 158.2 Hz, 'Jc-H ~Jc-H = 157.5 Hz, m-c&Me2, R), 124.2 (d, 'Jc-H= 161.2 Hz, = 157.9 Hz, m-C&Mez), 128.0, 126.2 d ('Jc-H = 159.2 Hz, p-CsH3Me2, R ) , 122.1 (d, 'Jc-H= 161.2 Hz, p-CsH3Me2, R), = 75 Hz, CMed, p-CsH&fez), 125.7 (m, C5Me5), 87.4 (spt, 'Jc-H 135.1 [m, C(Me)=CMe2], 119.3 (m, CjMej), 112.4 [m, 22.1 (qd, 'Jc-H= 127.1 Hz, 3 J c - = ~ 4.9 Hz, 2,6-MezC&), 21.9 C(Me)=CMez], 23.1 [q, 'Jc-H= 125.5 Hz, C(Me)=CMed, 22.0 (qd, 'Jc-H= 126.3 Hz, 3 J ~=-5.1 ~ Hz, 2,6-MezCsH3), 18.7 (qq, [v br, C(Me)-CMez], 20.3 (qd, 'Jc-H= 126.8 Hz, 3JC-H = 4.5 'Jc-H= 128.1 Hz, 3 J c -=~ 4.6 Hz, CMez), 11.7 (q, 'Jc-H= 128.2 = 125.9 Hz, 3 J c - = ~ 5.1 Hz, 2,6-Me&H3, R), 20.1 (qd, 'Jc-H Hz, C a e 5 ) . Anal. Calcd for TaC13C30H40N2: C, 50.33; H, 5.63; Hz, 2,6-Mezc,& R ) , 19.4 (qd, 'Jc-H = 126.4 Hz, 3 J c - ~ = 5.5 N, 3.90. Found: C, 50.23; H, 5.68; N, 3.86. The data for 3b = 127.4 Hz, CjMe5). Anal. Hz, 2,6-Me2CsH3,R), 11.6 (9, ~Jc-H follow. 'H (6 ppm, in CsDs): 12.20 (br, l H , TaCNHR), 6.85 Calcd for TaC1C31H42N2: C, 56.49; H, 6.42; N, 4.25. Found: (m, 3H, H&Me2), 6.33 (s, 2H, HzCsMea), 2.44 (s, 6H, 2,4,6C, 56.37; H, 6.40; N, 4.23. Me&&), 2.23,(s, 6H, 2,6-Me2C&), 2.01 (s, 15H, CsMed, 1.86 (s, 3H, 2,4,6-Me3C6H2),1.23 (s, 6H, CMe2). 13C(1H}NMR (6 6b. C6Ds (0.6 mL) was added t o a mixture of complex 5a (0.13 g, 0.25 mmol) and CN(2,4,6-Me&sHz) (0.036 g, 0.25 ppm, in CsDs): 261.2 (s, TaCNHR), 144.7 s, 139.8 s, 129.3 s, mmol) in a NMR tube. The reaction was monitored by 'H 135.6 s (ci,C,, C,, C,, CsHsMez), 138.7 s, 134.8 s, 128.0 s, NMR until complete reaction. Formation of 6b was confirmed 125.8 s (Ci, C,, C,, C,, CsH2Me3),125.7 (s, CsMes), 87.1 (s, by its lH and I3C NMR spectra and the data follow. lH NMR CMez), 21.8 (s, 2,6-Me2CsH3),21.6 (s, 2,4,6-Me&&), 20.7 (s, (6 ppm, in CDC13): 6.76 (d, 2H, 3 J ~=- 7.5 ~ Hz, m-HsCsMez, 2,4,6-Me&&), 18.3 (s, CMez), 11.8 (s, CjMe5). R), 6.61 d, 6.58 d ( 4 J ~ = 1.9 - ~Hz, m-HzCsMe3, R ) , 6.50 (t, Preparation of TaCp*ClMe(q2-NRCMez) (R = 2,6IH, 3 J ~ - H = 7.5 HZ, p-H&Mez, R), 2.31 S, 2.25 S (2,4,6Me&&, 5a). To a green solution of TaCp*ClMe3 (1.06 g, Me&&, R ) , 2.12 (s, 3H, 2,4,6-Me3CsHd, 2.09 (s, 15H, 2.67 mmol) in toluene (50 mL) was added CNR (0.35 g, 2.67 CjMej), 2.05 (s, 6H, 2,6-Me&&, R), 1.86 [spt, 3H, 'JH-H = mmol) at room temperature. The color quickly changed to 0.87 Hz, C(Me)=CMez], 1.7 vbr, 1.3 vbr [C(Me)=CMezI. 13C dark red, and after 20 min the solution was evaporated to NMR (6 ppm, in CDC13): 151.8 (m, i-CsHzMe3, R ) , 151.4 (m, dryness and the residue extracted with n-hexane (3 x 15 mL). i-CsHsMez, R), 135.3[m, C(Me)=CMe21, 135.1(m, o-C&Mez, The suspension was filtered and the solution concentrated to R), 134.6 (t,2 J ~=-5.5 ~ Hz, p-CsHzMe3, R ) , 133.4 m, 132.5 m ca. 20 mL and cooled to -40 "C to give a red microcrystalline (o-CsHzMe3,R ) , 129.2 (dm, VC-H = 153.9 Hz, m-CsHzMea, R ) , solid identified as 5a. Yield: 0.85 g (60%). The data for 5a 128.1 (dm, 'Jc-H= 154.4 Hz, m-CsHzMe3, R ) , 126.4 (dm, 'Jc-H follow. IR (Nujol mull, v , cm-I): 1259 (m), 1229 (m), 1105 (w), = 157.2 Hz, m-C,&Mez, R), 122.0 (d, 'Jc-H = 160.3 Hz, 1025 (w), 782 (w), 764 (m), 485 (m), 341 (m). 'H NMR (6 ppm, p-CsHsMez,R), 119.1 (m, CjMes), 112.6 [m, C(Me)=CMed, 22.8 in CsDs): 7.06 (d, 2H, 3 J ~= -7.2~HZ, m-H&~Mez),6.94 (t, [q, ~Jc-H = 125.5 Hz, C(Me)=CMe21,22.0 [vbr, C(Me)=CMe21, l H , 3 J ~=-7.2 ~ Hz, p-H&&kz), 2.28 (S, 3H, MezCNR), 2.22 20.5 (qt, 'Jc-H= 125.9 Hz, 3 J C - H = 4.6 Hz, 2,4,6-Me&&, (s, 3H, MeZCNR), 2.11 (s, 6H, 2,6-MezCsH3), 1.66 (s, 15H, R ) , 20.2 (qd, *Jc-H= 126.9 Hz, = 5.5 Hz, 2,4,6-Me3CsHz, CsMes), 0.60 (s, 3H, Ta-Me). l3C NMR (6 ppm, in CsD6): R ) , 20.0 (qd, 'Jc-H= 125.9 Hz, 3 J c - ~= 5.05 Hz, 2,4,6151.7 (m, i-C&Mez), 133.7 (m, o-CsHsMez), 128.9 (dm, 'Jc-H

2852

Galakhov et al.

Organometallics, Vol. 14, No. 6, 1995

Table 5. Experimental Data for the X-ray = 126.8 Hz, 3 J c - = ~ 5.5 Hz, 2,6Me3C&12, R ) , 19.5 (qd, 'Jc-H Diffraction Studies MezCsHa, R), 11.6 (q, I J C - H = 127.7 Hz, CsMed. 3a 6c 7b 6c. A sample of TaCp*Me4 (1.769 g, 4.70 mmol) was dissolved in 30 mL of toluene in a Schlenk tube in the glovebox. mol formula C3oH4oC13N2Ta C32N45N2Ta CaH54N3Ta After the addition of a toluene (10 mL) solution of CNR (1.23 715.97 638.67 769.85 mol wt monoclinic monoclinic orthorhombic g, 9.40 mmol), the color of the solution changed quickly from cryst system space group P2 lln P21lc P212121 green to red. The reaction mixture was stirred for 1h at room graphite-monochromated (A = 0.710 73 A) radiatn (Mo Ka) temperature and then evaporated to dryness. The oily residue 8.774(4) 8.635(4) 11.622(3) a, A was extracted with n-hexane (2 x 10 mL) and cooled to -40 18.338(8) 34.156(9) 14.141(5) b, A "C to give 6c as yellow crystals. Yield: 2.75 g (92%). The 18.470(7) 10.090(4) 22.755(9) C, A same compound can also be prepared by addition of 1equiv of 91.62(2) 105.94(2) deg isocyanide to 5b. The data for 6c follow. IR (Nujol mull, Y , 2971(2) 2861(2) 3740(2) v, A3 cm-I): 1612 (w), 1585 (w), 1320 (s), 1254 (m), 1192 (m), 1154 4 4 4 z (m), 1095 (m), 1025 (m), 939 (m), 879 (m), 800 (m), 763 (m), 1.601 1.482 1.367 1432 1296 1576 383 (m), 338 (m). 'H NMR (6 ppm, in CsDs): 6.9 (d, 2H, 3 J ~ - ~ 0.25 x 0.30 x 0.27 x 0.32 x 0.23 x 0.27 x cryst dimens, = 7.5 Hz, m-H&Mez, R), 6.7 (m, HsCsMe2, R), 6.6 (t, l H , 0.35 0.40 0.30 mm 3 J ~=- 7.5 ~ Hz, p-H&Me2, R),2.48 S, 2.35 S (2,6-MezCsH3, 29.70 38.63 39.92 p(Mo Ka), cm-' R ) , 2.24 (s, 2,6-Me&&, R), 1.77 (s, 15H, C5Med, 1.64 [spt, Siemens AED Phillips PW Siemens AED diffractometer 3H, 5 J H - ~= 0.95 Hz, C(Me)=CMe21, 1.5 [br, 6H, C(Me)-CMezI, 1100 0.87 (s, 3H, Ta-Me). 13C NMR (6 ppm, in CsDs): 153.4 (m, 6-54 6-60 6-60 28 range, deg i-CsH3Me2, R'), 152.7 (m, i-CsHaMe2, R), 135.7 [m, ih,k,l rth,k,l kh,k,l reflcns measd C(Me)=CMe2], 133.7 (qd, 2 J ~=-3 J ~ c -= ~ 6.5 Hz, o-CsHaMez, 5994 6223 no. of unique tot. 8712 R ) , 134.6 (qd, 2 J ~ =-3~J c - ~= 5.9 Hz, o-CsHsMe2, R ) , 134.2 data 6620 3442 3667 no. of unique (qd, 2 J ~=-3 ~J c - ~ = 5.8 Hz, o-CsHaMez, R), 128.4 (dm, 'Jc-H [I > 2 m 1 [I ' 2 d ) l [I > 2a(Z)I obsd data = 157.4 Hz, m-CsH3Me2, R ) , 127.6 (dm, 'Jc-H= 156.6 Hz, 0.0450 0.0271 0.0272 R m-CsHsMe2, R ) , 126.4 (dm, 'Jc-H = 155.7 Hz, m-CsHsMez, 0.0336 0.0419 0.0394 RW R), 123.3 (d, 'Jc-H= 159.3 Hz, p-CsHaMez, R ) , 120.6 (d, 'Jc-H 1.06 1.02 0.96 goodness of fit = 160.3 Hz, p-CsHsMez, R), 116.2 (m, CsMed, 111.3 [m, = 102.9 Hz, Ta-Me), 21.6 [br, C(Me)=CMe21, 33.4 (9, 'Jc-H (s, NCCMezCMeN), 171.0 (s, NCCMeZCMeN), 150.8 s, 149.8 C(Me)=CMe21, 21.4 [q, ~Jc-H = 125.2 Hz, C(Me)=CMez], 20.8 s, 141.7 s(i-CsH3Me2, R, R , R"), 136.1 s, 130.5 s, 128.9 s, 128.3 (qd, 'Jc-H= 125.8 Hz, 3 J C - H = 5.9 Hz, 2,6-MezCsH3,E),20.4 S, 128.2 9, 125.7 s (o-CsHaMez,R, R , R"), 128.0 S, 127.9 S, 127.5 (qd, 'Jc-H = 128.1 Hz, 3 J c - = ~ 5.2 Hz, 2,6-MezC&, R ) , 19.4 s, 127.2 s, 126.7 s, 126.4 s (m-CsHsMe2, R, R , R"), 126.2 s, (qd, *Jc-H= 125.6 Hz, 3 J C - H = 5.25 Hz, 2,6-MezCsH3,R), 11.3 122.9 s, 120.6 s (p-csH3Me2, R, R , R ) , 116.8 (s, CsMes), 55.5 (9, lJc-H = 127.5 Hz, CsMe5). Anal. Calcd for TaC32H45N.z (5, NCCMeZCMeN), 26.2 s, 26.0 s (NCCMezCMeN), 20.7 (s, C, 60.18; H, 7.10; N, 4.39. Found: C, 60.38; H, 7.00; N, 4.35. NCCMezCMeN), 20.1 s, 19.4 s, 19.3 s, 19.0 s, 18.1 s, 17.6 s 6d. Complex 5b (0.12 g, 0.236 mmol), CNR (0.034 g, 0.236 (2,6-Me2CsH3,R, R , R ) , 11.9 (s, C5Me5). Anal. Calcd for mmol), and CsD6 (0.6 mL) were placed in a NMR tube. The TaClC4oH51N3: C, 60.78: H, 6.51; N, 5.31. Found: C, 60.92; reaction was instantaneous and checked by NMR confirmed H, 6.25; N, 5.25. the formation of 6d in quantitative yield. The data for 6d 7b. C N R (0.11 g, 0.83 mmol) was added to a solution of ~ follow. 'H NMR (6 ppm, in C&): 6.91 (d, 2H, 3 J ~=- 7.5 6c (0.53 g, 0.83 mmol) in toluene (30 mL). The reaction Hz, m-H&Mez, R), 6.68 d, 6.57 d (45H-H = 2 Hz, m-HzCsMe3, mixture was heated for 2 days at 50-60 "C. The resulting R ) , 6.21 (t, l H , 3 J ~=- 7.5 ~ Hz, p-HsCsMez, R), 2.46 S, 2.33 S yellow-green solution was evaporated to dryness. Recrystal(2,4,6-Me&sHz, R ) , 2.25 (s, 6H, 2,6-MeGH3, R), 2.06 (s, 3H, lization from n-hexane a t -40 "C afforded 7b as yellow crystals 2,4,6-MeaC&, E),1.78 (s, 15H, CsMed, 1.66 [spt, 3H, 't7H-H in 92% yield (0.59 g). The data for 7b follow. IR (Nujol mull, = 1.2 Hz, C(Me)=CMe2], 1.5 [vbr, 6H, C(Me)=CMezI, 0.86 (s, v , cm-'1: 1652 (SI, 1599 (SI, 1325 (SI, 1210 (m), 1153 (m), 1123 3H, Ta-Me). 13C11H}NMR (6 ppm, in CsDs): 152.7 (5,i-CsH2(m), 1090 (m), 1019 (m), 976 (m), 759 (m), 515 (w), 487 (m), Mea, R ) , 150.8 (s, i-CsHsMe2,R), 135.5 [s, C(Me)=CMez], 133.7 343 (m). 'H NMR (6 ppm, in C&): 6.9 (m, HsCsMez, R,R', (s, o-CsH3Me2,R), 134.2 s, 132.9 s (o-CsHzMe3, R ) , 132.8 (s, R ) , 2.52 s, 2.44 s, 2.08 s, 1.93 s, 1.72 s, 1.68 s (2,6-Me&Ha, p-CsHzMe3, R ) , 129.3 s, 128.1 s (m-CsHzMea, R ) , 127.6 (s, R, R , R ) , 1.89 (s, 15H, CsMes), 1.66 (s, 3H, NCCMe2CMeN1, m-CsHaMe2, R), 121.0 (s, p-C6H3Me2, R), 115.5 (s, CsMed, 1.52 (s, 3H, NCCMezCMeN), 1.31 (s, 3H, NCCMe2CMeN),O.43 109.6 [s, C(Me)=CMe21, 32.2 (s, Ta-Me), 21.43 [s, (s, 3H, Ta-Me). 13C NMR (6 ppm, in CsDs): 241.2 (s, C(Me)=CMe2], 21.0 [br, C(Me)=CMed, 20.1 s, 20.0 s (2,4,6NCCMezCMeN), 171.9 (9, 2 J ~=- 2.8 ~ Hz, NCCMe&MeN), Me3CsH2,R ) , 19.8 (s, 2,4,6-Me3CsH2,R ) , 19.3 (s, 2,6-MezCsH3, 154.3 m, 147.1 m, 142.0 m (i-CsH3Me2, R, R , R ) , 134.2 qd, R), 11.2 (s, CsMe5). Preparation of TaCp*X(NR){q2-N(R')=CCMe2- 130.0 qd, 130.0 qd, 129.0 qd, 127.8 qd, 126.3 qd ( 2 J ~=-3~J c - ~ = 7.0 Hz, o-CsH3Me2, R, R , R')), 128.6 dd, 128.0 dd, 127.9 dd, CMe=NR'} (X = C1, R = R = R = 2,6-MezCsHs, 7a; X = 127.6 dd, 126.8 dd, 126.4 dd ('Jc-H= 158.2 Hz, 3JC-H = 5 Hz, Me, R = R = R = 2,6-MezCeHs, 7b;X = Me, R = R = 2,6m-C6HBMep,R, R , R ) , 125.6 d, 122.7 d, 118.9 d ('Jc-H = 157.8 M e z C a 3 , R = 2,4,6-Me&Hz, 7 c ; X = Me, R = R' = 2,6Hz, p-C&Mez, R, R , R"), 113.4 (m, CsMes), 57.4 (spt, 2 J ~ - ~ MezCeH3, R = But, 7d). 7a. C N R (0.09 g, 0.69 mmol) was = 3.4Hz,NCCMe2CMeN),25.8 qq, 25.5 qq ( ~ J c - H128.3 = Hz, added to a solution of 6a (0.45 g, 0.69 mmol) in toluene (30 2 J ~ = 4.6 ~ Hz, NCCMezCMeN), 21.6 (q, 'Jc-H = 118.1 Hz, mL) and the reaction mixture heated for 3 days a t 60 "C. The Ta-Me), 20.3 (4, 'Jc-H= 127.4 Hz, NCCMenCMeN), 20.1 qd, resulting yellow-green solution was evaporated to dryness. The 19.5 qd, 19.0 qd, 18.8 qd, 18.1 qd, 17.7 qd ('Jc-H= 126.4 Hz, residue was extracted with n-hexane (3 x 15 mL) and the 3JC-H = 4.5 Hz, 2,6-MezCsH3, R, R , R"), 11.5 (q, 'Jc-H= 125.9 solution filtered, concentrated to ca. 15 mL, and cooled to -40 Hz, C5Me~). Anal. Calcd for TaC41H54N3: C, 63.97; H, 7.07; "C t o give 7 a as yellow crystals. Yield: 0.46 g (85%). The N, 5.46. Found: C, 63.66; H, 6.99; N, 5.43. data for 7 a follow. IR (Nujol mull, v , cm-'1: 1655 (s), 1600 7c. To a solution of 6c (0.13 g, 0.20 mmol) in CsDs (0.6 mL) (s), 1326 (s), 1209 (m), 1165 (m), 1122 (m), 1080 (m), 1020 (m), was added CNR' (0.03 g, 0.20 mmol) a t room temperature in 978 (m), 746 (m), 343 (m), 339 (m). IH NMR (6 ppm, in CsDs): a NMR tube. The reaction mixture was heated to 50 "C during 6.8 (m, 9H, H3CsMe2, R, R , R"), 2.68 s, 2.44 s, 2.02 s, 2.00 s, 3 days and then was checked by 'H NMR showing 7c as the 1.59 s, 1.45 s (2,6-MezC& R, R , R'), 1.99 (s, 15H, C5Me51, unique product. The data for 7c follow. 'H NMR (6 ppm, in 1.79 (s, 3H, NCCMe2CMeN1, 1.68 (s, 3H, NCCMe&MeN), 1.35 CsDs): 6.8 (m, HsCsMez, R, R'; HzCsMe3, R"), 2.54 s, 2.45 s, (s, 3H, NCCMe2CMeN). 13C{lH}NMR (6 ppm, in CsDs): 240.0 ~~~

P7

~



Table 6. Atomic Coordinates ( x lo4) and Isotropic Thermal Parameters (A2x lo4)with Esd's in Parentheses for the Non-HydrogenAtoms of ComDound 3a atom xla ylb 2IC U" 1997(1) -222(1) 2207(1) 4734(1) 2330(3) 3410(3) 1700(5) 233(4) -158(4) 1081(4) 2230(4) 2524(8) -851(6) -1710(5) 989(7) 3638(6) 3002(4) 2977(4) 4605(5) 2003(6) 2113(4) 3284(5) 3028(7) 1674(7) 570(6) 750(5) 4771(5) -579(5) 3946(4) 5499(5) 5948(6) 4901(7) 3389(7) 2880(5) 6680(5) 1212(6)

2871(1) 2233(1) 3194(1) 3129(1) 2050(2) 1668(2) 4210(2) 3923(2) 3524(2) 3588(2) 3995(2) 4720(3) 4061(3) 3220(3) 3449(3) 4290(3) 1433(2) 1859(2) 1220(3) 749(2) 1898(2) 2088(2) 1981(3) 1678(3) 1496(3) 1596(2) 2437(3) 1396(3) 965(2) 805(2) 127(3) -339(3) -144(2) 515(2) 1339(3) 713(3)

5251(1) 5721(1) 6579(1) 5362(1) 4536(2) 6341(2) 5176(2) 5248(2) 4604(2) 4130(2) 4481(2) 5689(4) 5855(3) 4407(4) 3334(2) 4141(4) 5000(2) 5696(2) 4772(2) 5010(3) 3776(2) 3290(2) 2543(2) 2285(2) 2760(3) 3503(2) 3521(2) 3964(3) 6611(2) 6602(2) 6883(2) 7176(3) 7208(3) 6928(2) 6352(3) 6979(3)

250(1) 422(3) 423(3) 416(3) 297(7) 325(8) 404(11) 383(10) 378(10) 398(10) 446( 12) 759(20) 626(17) 706(20) 690(19) 832(23) 341(9) 299(8) 488(12) 534(14) 352(9) 422(11) 558(15) 682(19) 596(16) 460(12) 542(14) 587(15) 354(10) 417(11) 582(15) 642(18) 578(16) 455(12) 593(16) 730(20)

Equivalent isotropic U defined as one-third of the trace of the orthogonalized U, tensor. a

2.10 S, 2.06 s, 1.92 s , 1.75 s, 1.69 s (2,6-Me&H3, R, R'; 2,4,6Me3CsHz, R"), 1.92 ( s , 15H, CsMes), 1.67 (s, 3H, NCCMe2CMeN), 1.52 (5, 3H, NCCMezCMeN), 1.37 ( s , 3H, NCCMezCMeN), 0.46 (s, Ta-Me). I3C NMR (6 ppm, in CsDs): 242.1 (s, NCCMe&MeN), 172.0 (9, 'Jc-H = 2.8 Hz, NCCMezCMeN), 154.4 m, 147.2 m, 139.2 m (i-CsHaMez, R, R'; i-C6H&fe3, R'), 135.1 m, 134.2 m, 129.8 m, 126.8 m, 126.3 m, 125.6 m ( o - c & , M e z ,R, R'; o-C&Mea, R"), 129.4 dm, 128.4 dm, 128.0 dm, 127.9 dm, 127.6 dm, 126.4 dm ('Jc-H = 158.2 Hz, m-C&Mez, R, R'; m-CsHzMe3, R"), 122.7 d, 118.9 d, 116.2 = 158.9 Hz, p-C&&fez, R, R'; p-CsHzMes, R"), 113.4 m ('Jc-H (m, CbMes), 54.6 (m, NCCMe2CMeN1, 25.8 qq, 25.6 qq ('Jc-H = 129.1 Hz, 3 J C - H = 4.6 Hz, NCCMeZCMeN),21.7 (9, 'Jc-H= 119.5 Hz, Ta-Me), 20.2 (9, 'Jc-H= 127.1Hz, NCCMeZCMeN), 20.7 qt, 19.4 qd, 18.9 qd, 18.8 qd, 18.7 qd, 18.1 qd, 17.6 qd (~Jc-H = 127.3 Hz, 3JC-H = 4.8 Hz, 2,6-MezC6H3,R, R'; 2,4,6Me3CsH2, R"), 11.5 (9, 'Jc-H= 127.3 Hz, C5Med. 7d. A sample of 6c (0.56 g, 0.87 mmol) was added at room temperature to a solution of CNtBu (0.1 mL, 0.88 mmol) in toluene (50 mL). The reaction mixture was heated a t 60 "C for 2 days, the resulting solution was concentrated to dryness, and the residue was extracted with n-hexane (3 x 10 mL). The solution was filtered, concentrated to ca. 15 mL, and cooled to -40 "C to give 7d as a yellow microcrystalline solid. Yield: 0.51 g (81%). The data for 7d follow. IR (Nujol mull, Y , cm-l): 1639 (s), 1606 (m), 1591 (m), 1326 (SI, 1208 (m), 1190 (m), 1113 (m), 1096 (m), 1023 (m), 954 (m), 765 (SI, 503 (w), 473 (m), ~ 7.5 HZ, 341 (m). 'H NMR (6 ppm, in CsDs): 7.0 (d, 3 J H - = 2H, m-H&&ez, R), 6.93 (m, 2H, m-H&sMez, R'), 6.93 (m, l H , p-H&&fez, R), 6.68 (t, 3 J ~ =7.5~HZ, 1H, p-HaCsMez, R), 2.54 s, 2.03 s, 1.95 s (2,6-Me&H3, R, R'), 1.88 ( s , 15H,

Table 7. Atomic Coordinates ( x lo4) and Isotropic Thermal Parameters (A2x lo4) with Esd's in Parentheses for the Non-HydrogenAtoms of Comnound 6c atom

xla

2163(1) 3721(6) 1769(5) 3440(8) 3550(8) 1991(10) 907(7) 1805(8) 4845(9) 5092(9) 1666(13) -850(9) 1172(11) 4995(7) 6553(7) 7769(8) 7518(9) 5999(9) 4743(8) 6884(8) 3089(8) 3041(7) 3985(7) 5175(8) 5457(9) 4536(9) 3294(8) 3712(8) 2195(9) 363(7) -152(7) -618(8) -1651(8) 547(9) 68(8)

Ylb

1118(1) 855(1) 1551(1) 885(2) 1299(2) 1456(2) 1144(2) 792(2) 607(3) 1533(3) 1876(3) 1163(3) 382(2) 620(2) 772(2) 525(2) 131(3) -21(2) 215(2) 1200(2) 39(2) 1635(2) 1974(2) 2058(2) 1821(2j 1491(2) 1395(2) 2240(2) 1049(2) 1793(2) 2010(2) 1787(2) 2255(2) 2039(2) 762(2)

2IC

1022(1) 2219(5) 2295(4) -743(6) -638(6) -1225(7) -1593(6) -1261(7) -402(8) -290(7) -1620(8) -2347(8) -1616(9) 2902(6) 3485(6) 4162(6) 4299(7) 3754(7) 3057(6) 3348(8) 2468(8) 3542(5) 3572(6) 4765(7) 5887(8) 5858(7) 4700(6) 2331(7) 4727(7) 2049(6) 2967(7) 562(7) 2493(8) 4512(7) 1028(7)

Ua 266(1) 310(17) 259(16) 470(27) 422(25) 459(27) 444(23) 469(27) 755(38) 708(37) 844(43) 780(37) 790(39) 328(21) 374(22) 465(25) 593(32) 522(29) 403(24) 547(30) 535(29) 292(19) 381(23) 510(27) 613(31) 549(29) 395(24) 509(28) 534(29) 3 16(21) 398(23) 581(30) 628(32) 618(32) 485(27)

a Equivalent isotropic U defined as one-third of the trace of the orthogonalized U, tensor.

CsMes), 1.75 (s, 3H, NCCMe2CMeN1, 1.69 ( s , 3H, NCCMe2CMeN), 1.25 ( s , 9H, Me&, R"), 1.21 ( s , 3H, NCCMezCMeN), 0.88 ( s , 3H, Ta-Me). l3cNMR (6 ppm, in C&): 248.5 (s, NCCMeZCMeN), 174.7 (9, 2 J ~=- 2.6 ~ Hz, NCCMe&MeN), 155.4 m, 147.5 m (i-CsHsMe2,R, R"), 132.2 m, 132.2 m, 126.2 m, 125.7 m (o-C&Me2, R, R ) , 128.3 dm, 128.3 dm, 126.9 dm, 126.9 dm (~Jc-H = 155.5 Hz, m-C&Mez, R, R'), 122.8 d, 118.9 = 159.2 Hz, p-CsH3Me2,R, R ) , 113.8 (m, CsMes), 63.3 d (~Jc-H ~ Hz, CMe3, R"), 52.7 (m, NCCMeZCMeN),33.7 (m, 2 J ~=-3.7 qq, 24.8 qq (~Jc-H = 128.7 Hz, 2 J c - ~= 5.05 Hz, NCCMe2CMeN), 30.9 (qspt, 'Jc-H= 126.9 Hz, 3JC-H = 4.1 Hz, Me&, R"), 19.6 (9, 'Jc-H= 127.8 Hz, NCCMe&MeN), 19.5 (9, 'Jc-H = 119.5 Hz, Ta-Me), 20.2 qd, 20.2 qd, 19.6 qd, 18.5 qd ('Jc-H = 126.2 Hz, 3 J c - = ~ 5 Hz, 2,6-Me&H3, R, R'), 11.8 (q, 'Jc-H = 126.4 Hz, &Mes). Anal. Calcd for TaC37H54N3: C, 61.57; H, 7.54; N, 5.82. Found: C, 61.59; H, 7.53; N, 5.80. X-ray D a t a Collection, Structure Determination, and Refinement f o r C o m p o u n d s 3a, 6c, and 7b. The crystallographic data for the three compounds are summarized in Table 5. Data were collected at room temperature (22 "C) on a Siemens AED diffractometer (3a and 7b) and on a Phillips PW 1100 (6c), using graphite-monochromated Mo Ka radiation and the 8128 scan type. The reflections for both compounds were collected with a variable scan speed of 3-12" min-l and a scan width (deg) of 1.20 0.346 tan 8. 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.I6 Intensities were

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(16)Lehmann, M. S.; Larsen, F. K. Acta Crystallogr., Sect. A 1974, 30,580.

Galakhov et al.

2854 Organometallics, Vol. 14,No. 6, 1995

Table 8. Atomic Coordinates ( x 104) and Isotropic Thermal Parameters (k x 104) with Esd’s in Parentheses for the Non-HydrogenAtoms of ComDound 7b atom xla YJb zlc U“ 631(1) 927(7) 2213(6) 1507(8) -1210(10) -1437(8) -1192(9) -903(10) -918(10) -1493(12) -1895(11) - 1362(11) -769(13) -799(14) 1387(11) 976(7) 730(10) 851(10) 1208(11) 1439(11) 1317(10) 273(11) 1554(12) 3302(10) 4214(10) 5264(12) 5410(16) 4471(18) 3427(13) 4060(11) 2404(14) 1661(8) 2072(10) 2020(9) 1521(10) 511(11) 457(13) 1447(17) 2442(14) 2486(11) -576(12) 3559(12) 3353(9) 1306(11) 2640(10)

337(1) -471(7) 428(6) -2608(6) -5(8) 95(6) 1022(7) 1536(8) 893(9) -867(10) -632(9) 1458(9) 2610(7) 1134(11) 1640(8) - 1066(7) -2050(7) -2640( 10) -2272(11) -1325(11) -725(10) -2456(8) 336(11) 885(8) 650(9) 1105(13) 1722(14) 2024(11) 1580(8)

-50(8) 1896(8) -283(8) -964(7) -2006(7) -3585(7) -4010(8) -4970(8) -5525(10) -5110(9) -4131(9) -3446(9) -3700(10) -813(7) -810(8) -2210(7)

4441(2) 5040(3) 3956(3) 3152(4) 3975(5) 4590(5) 4747(4) 4228(5) 3760(5) 3615(7) 5007(6) 5348(5) 4 186(7) 3113(5) 4806(5) 5521(5) 5463(4) 5954(6) 6487(6) 6541(5) 6074(5) 4903(5) 6140(5) 3870(5) 4251(6) 4162(8) 3716(9) 3377(8) 3456(6) 4757(6) 3082(6) 373x41 3245(5) 3473(4) 3295(5) 3473(4) 3574(5) 3483(7) 3270(6) 3179(6) 3541(6) 2935(7) 3048(5) 2698(5) 4038(4)

345(1) 411(29) 360(25) 445(30) 507(41) 399(35) 417(33) 532(40) 530(43) 839(60) 697(52) 646(46) 811(54) 875(61) 533(40) 438(31) 467(34) 620(49) 691(53) 650(52) 488(41) 590(45) 795(54) 471(38) 642(46) 914(68) 1121(89) 983(70) 643(49) 680(49) 797(61) 379(28) 422(33) 376(31) 408(35) 516(38) 625(45) 890(70) 669(52) 574(46) 745(50) 921(67) 518(39) 576(44) 428(35)

a Equivalent isotropic U defined as one-third of the trace of the orthogonalized U, tensor.

corrected for Lorentz and polarization effects. A correction for absorption was applied (maximum and minimum values for and transmission factors were 1.092 and 0.939 (3a),1.098 and 0.905 (6c), and 1.109 and 0.836 (7b)).17 Only the observed reflections were used in the structure solutions and refinements. (17) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983,39,158. Ugozzoli, F. Comput. Chem. 1987, 11, 109.

The structures were solved by Patterson and Fourier methods and refined by full-matrix least-squares first with isotropic thermal parameters and then with anisotropic thermal parameters for the non-hydrogen atoms. In order to test the chirality of the complex 7b,a refinement of the nonhydrogen atoms with anisotropic thermal parameters was carried out using the coordinates -2, -y, - 2 ; a remarkable increase of the R and R, values was obtained [R(x,y, z ) = 0.0508, R,(x, y , Z ) = 0.0541; R(-x, -y, -z) = 0.0600, R,(-x, -y, - 2 ) = 0.07101. The former model was selected, and the reported data refer to this model. All hydrogen atoms, excepting for HN(2) of 3a, clearly localized in the final AF map and refined isotropically, were placed a t 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 338 (3a),325 (6c),and 412 (7b) variables; after the last cycles, no parameters shifted by more than 0.81 (3a), 0.92 (6c), and 0.31 (7b)esd. The highest remaining peak in the final difference ma was equivalent to about 0.70 (3a),0.69 (6c),and 0.66 (7b) 3.!./e In the final cycles of refinement a gFa21-’ was used; at weighting scheme w = K[a2(Fa) convergence the K and g values were 0.570 and 0.0047 (3a), 0.722 and 0.0044 (6~1, and 1.025 and 0.0002 (7b), respectively. The analytical scattering factors, corrected for the real and imaginary parts of anomalous dispersion, were taken from ref 18. All calculations were carried out on the Gould Powernode 6040 and Encore 91 computers of the “Centro di Studio per la Strutturistica Diffrattometrica” del CNR, Parma, Italy, using the SHELX-76 and SHELXS-86 systems of crystallographic computer programs.19 The final atomic coordinates for the non-hydrogen atoms are given in Table 6 (3a), Table 7 (6121, and Table 8 (7b).

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Acknowledgment. We are grateful to the DGICYT and the Consiglio Nazionale delle (Grant PB92-0178-C) Ricerche, Rome, for financial support. SupplementaryMaterial Available: Atomic coordinates and SI11 (7b), of the hydrogen atoms (Tables SI (3a)SI1 (6~1, thermal parameters (Tables S N (3a),SV (6c),and SVI (7b), complete bond distances and angles (Tables SVII (3a),SVIII (6c),and SIX (7b), chemical shifts for 6a and 6c a t variable temperature in solution (6a-CDC13, 6c-CDzClz) and in the solid (Table SX), spin-lattice relaxation times for 6c in CDzClz solution (Table SXI),‘H NMR spectra at variable temperature for complex 6c in CDZC12 solution (Figure SI), and a l3C[IH} NMR spectrum (6c) in CDzC12 solution (Figure SII) (18 pages). Ordering information is given on any current masthead page. OM950009N (18)International Tables for X-Ray Crystallography; Kynoch Press: Birmingham, England, 1974;Vol. IV. (19)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.

Insertion of Isocyanides into Tantalum-Carbon Bonds of

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