Organometallics 1983,2, 251-257
251
Synthesis, NMR Studies, and Catalytic Activity of Cationic and Neutral Olefin Complexes of Platinum( I I ) Containing the $-Allyl Ligand Hideo Kurosawa" and Naonori Asada Department of Petroleum Chemistfy, Faculty of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565, Japan Received June 16, 1982
Cationic Ptn complexes containing terminal olefin ligands [Pt(s3-CH2CMeCH2)(PPh3)(CH2=CHR)]C104 (2, R = CH,Ph, Et, Me) were prepared. Formation of the neutral analogues of 2, i.e., Pt(s3CH2CMeCH2)C1(CH2=CHR)(3, R = CH2Ph,Et, Me, C6H4Y-p;Y = NMe2, OMe, Me, H, C1, NO2),from [Pt(s3-CH2CMeCHz)C1lz and the olefin in solution was confirmed by 'H and 13CNMR spectra. Comparison of the 13C NMR data and the stability trends in 2 and 3 indicated a much greater electrophilic activation of the olefin in 2 than in 3. All complexes of type 2 showed high catalytic activity in the double-bond migration of olefins under mild conditions, with catalysts recovered from the reaction mixture having been confvmed to almost completely retain the s3-methallyland the PPh3 ligands. Deuterium-labeling experiments employing CH2=CDCH3 suggested a key intermediate to be a Pt-H species. In contrast, complexes of type 3 were totally inactive in catalyzing the same transformations. A possible relevance of the different nature of the metal-olefin bond in 2 and 3 to the different catalytic activity was discussed.
Introduction
fin)]+ (2, olefin = CH2=CHC6H4Y-p) consistently supported the electrophilic nature of Pt" toward the coordinated olefin. Very few reports, however, paid attention to a comparison of both bonding modes and catalytic activities between neutral and cationic olefin complexes possessing closely related structures.
Activity of some transition-metal catalysts in transformations of olefinic substrates is remarkably enhanced by the use of cationic complexes or cocatalysts that are capable of producing cationic olefin complexes.'+ The central role of these complexes in catalysis appears to be c the electrophilic activation of the coordinated olefin. More characteristic of the cationic olefin complex would be the formation of incipient carbonium ions (1)that has recently been proposed"' to play a vital role in double-bond migration, oligomerization, and polymerization of olefins 1 catalyzed by [Pd(MeCN)4]2+. We have now found that a series of the neutral analogues Evidence supporting the significance of the electrophilic of 2, namely, 3, can be formed readily in solution (eq 1) activation of olefins or the bonding mode 1 in the olefin and fully characterized by NMR spectroscopy, although complexes of Pd" and Pt" was presented by X-ray crysthey cannot be isolated. We thought 2 and 3 to be partallographic,8 ~ t a b i l i t y , ~ and . ' ~ 13C NMR" studies of square-planar,12 substituted styrene complexes of these metals. In the earlier studies, there was some discrepancy between the 13C NMR and stability trends of the Pt" 3a-i complexes,ll but our recent studylo on the 13C NMR spectra and stabilities of [Pt(s3-CH,CMeCH2)(PPh3)(ole3a, olefin = CH,=CHCH,Ph b, olefin= CH,=CHCH,CH, c, olefin = CH,=CHCH, d, olefin = CH,=CHC,H,NMe,-p (1) Bogdanovic, B. Adv. Organomet. Chem. 1979,17, 105. (2) Pardy, R. B. A; Tkatchenko, I. J. Chem. SOC.Chem. Commun. e, olefin = CH,=CHC,H,OMe-p 1981. 49.
(3) Iehimura, Y.; Maruya, K.; Nakamura, Y.; Mizoroki, T.; Ozaki, A. Chem. Lett. 1981, 657. (4) de Renzi, A.; Panunzi, A.; Vitagliano, A.; Paiaro, G . J. Chem. Soc., Chem. Commun. 1976.47. (5) Sen, A.; Lai, T. W. J. Am. Chem. SOC.1981,103,4627. (6) Sen, A.; Lai, T. W. Organometallics 1982, 1, 415. (7) Sen, A.; Lai, T. W. Inorg. Chem. 1981,20, 4036. (8) Nyburg, S. C.; Simpson, K.; Wong-Ng, W. J. Chem. SOC.Dalton Trans. 1976, 1865. (9) Ban, E.; Hughes, R. P.; Powell, J. J. Organomet. Chem. 1974,69, 455. (10) Kurosawa, H.; Asada, N. J . Organomet. Chem. 1981, 217, 259. (11) Cooper, D. G.; Powell, J. Inorg. Chem. 1976, 15, 1959. (12) The nature of the olefin-metal bond in the 18-electron complex13
[Pd($-C,H,) (P&)(CH,==CHC,H,Y-p)]+ is somewhat different from that in the square-planar ~ o m p l e x e s . ~ * - ~ ~ (13) Kurosawa, H.; Majima, T.; Asada, N. J. Am. Chem. SOC.1980, 702. 6996. (14) Harley, F. R. J . Organomet. Chem. 1981, 216, 277. (15) Albright, T. A.; Hoffmann, R.; Thibeault, J. C.; Thorn, D. L. J. Am. Chem. SOC.1979,101, 3801. (16) Miki, K.; Shiotani, 0.;Kai, Y.; Kasai, N.; Kanatani, H.; Kurosawa, ---I
H. Organometallics, in press.
0276-733318312302-0251$01,50/0
f, olefin = CH,=CHC,H,Me-p g, olefin = CH,=CHC,H, h, olefin = CH,=CHC,H,Cl-I, i, olefin = CH,=CHC,H,NO,-p
2a, olefin = CH,=CHCH,Ph b, olefin = CH,=CHCH,CH, c , olefin = CH,=CHCH, ticularly suited for a comparative 13CNMR study, because both contain the same trans group with regard to the olefii ligand. We describe here the remarkably different 13C NMR and stability trends of 3, compared with those of 2. We further describe the far greater catalytic activity of 2 than 3 in the double-bond migration of olefins and the possible relevance of this difference to the difference in the nature of the olefin-Pt" bond. 0 1983 American Chemical Society
252 Organometallics, Vol. 2, No. 2, 1983
Kurosawa and Asada
determining K was essentially the same as that employed before ' except that sufficiently excess amounts of styrenes were for 2O used to compel eq 1to proceed almost completely. However, since the ratio of the two stereoisomers in each of 3d-i is not constant (e.g., major/minor = 1.3 for Y = NMe2, 1.4 for Y = H, and 2.5
for Y = NO2) and since some resonances of the minor isomers could not be separated well from those of the major isomers, the K values were calculated from the combined concentrations of the two isomers in each styrene complex. The K values thus obtained are 3.5 f 0.5 (Y= NMe2),1.5 f 0.3 (Y = Me), and 0.25 f 0.05 (Y = NO2). 'H and 13CNMR spectral data of 2 and 3 are shown in Tables I and 11. Double-Bond Migration of Olefins. In a typical catalysis reaction, to a CH2C12solution of l-butene (0.5-1.0 mol/L) was added 2b (0.005-0.015 mol/L) and the solution kept at 25 "C. The progress of the reaction was followed by GLC (Sebacconitrile, 3 mm X 10 m, 40 "C). The percent yield of 2-butenes ( Z / E = 1/3) increased almost linearly with time up to ca. 60% conversion. The slopes of these time-conversion plots were almost linearly dependent on the initial concentrations of 2b. GLC analysis (PEG-1000, 3 mm X 2 m, 70 "C) of the isomerization of allylbenzene showed that P-methylstyrene produced has predominantly the E configuration. Experiments to recover the catalyst were carried out by allowing carbon monoxide to pass through the catalysis solution ([2bIfid = 0.015 mol/L, [ l-butene]i,ita = 0.5 mol/L, 24 h, 80% conversion) for 5 min, followed by evaporation of the solvent under vacuum. The residual solids had an IR band at 2120 cm-' (VCO). The solids were dissolved in CD2C12 completely, and this solution was examined by 'H NMR spectroscopy to show, within the 'H NMR detection limit, the presence the absorptions of only [Pt(q3-CH2CMeCH2)(PPh3)(CO)]C104, of which agreed with those of the PF6 salt.lo Particularly informative was the relative peak ratio of the phenyl region protons and the 2-methylallylligand protons (calcd, 2.14/1; found, 2.20/1). Deuterium scrambling experiments employing [Pt(q3CH2CMeCH2)(PPh3)(CH2=CDCH3)]C104 (2c-d)were performed by quenching with PPh3 a CDCl3 solution (0.2 mol/L) of 2c-d after it was allowed to stand at room temperature for 24 h. After this solution was examined by lH NMR spectroscopy, gaseous products were collected in a gas sampler for mass spectroscopy through trap-tu-traptechniques under vacuum. A CDCl, solution of CHyCDCH3 (0.35 mol/L) in the presence of 2c-d (0.02 mol/L) was examined similarly except that no quenching by PPh3 was necessary. Mass spectral analysis of propene recovered from a CH2C12solution (0.1 mol/L) containing CH30D(5 mol/L) (2 days) was carried out in a similar way to show less than 5% deuterium incorporation. Similarly, after a CH&12 solution of 2a (0.05 mol/L) containing CH30D (2 mol/L) was allowed to stand for 4 days (ca. 85% conversion),P-methylstyrene was liberated from the complex by adding PPh3and separated by preparative GLC. Mass spectral analysis indicated the presence of only a trace amount of the monodeuterated product. $-Allyl Olefin Complexes [Pt(q3-CH2CHCH2)(PPh3)(olefin)]C104 (5). 5a (olefin = CH2=CMe2) was prepared in a manner similar to that for 2 described above; mp 135-138 "C dec. Anal. Calcd for C25H2804PClPt:C, 45.91; H, 4.31. Found: C, 45.65; H, 4.35. 'H NMR (CD2C12)at -20 "C: olefin portion, 6 2.02 (d, Jp= 1,Jpt = 42 Hz) and 2.42 (d, Jp = 1.5, Jpt = 40 Hz) (Me), 3.13 (d, J p = 1.5 Hz) and 3.20 (d, Jp = 2.3 Hz) (=CH2; satellites due to lg5Ptnot identified); allyl portion (for proton numbering, see Table I), 6 2.75 (d, J H = 11.3, Jpt = 58 Hz) (H4), 3.47 (dd, JH = 8.0, J p = 4.5 Hz) (H7),3.83 (br s) (H5),4.78 (br m) (H6);the central proton multiplet overlapped with CH2C12peak contained in commercial CD2C12samples. Allowing the CD2C12 solution of 5a to stand at room temperature for 24 h resulted in the appearance of the resonances due to 2c with the ratio 2c/5a being approximately 85/15. 5b (olefin = CH,=CHMe) was prepared similarly; mp 143-148 "C dec. Anal. Calcd for C24H2s04PClPt:C, 45.04; H, 4.10. Found: C, 44.85; H, 4.10. 'H NMR (CD2C12):olefin portion, 6 1.56 (d, JH = 6.0, Jpt = 38 Hz) and 1.93 (d, JH = 6.0, Jpt = 39 Hz) (Me), 3.52 (dd, JH = 9.0, J p = 3 Hz) and 4.05 (dd, JH = 13.5, J p = 5, Jpt = 59 Hz) (=CH2), 5.8 (m) (CH=); allyl portion, 2.89 (d, JH = 11.3, Jpt = 59 Hz) (H4),3.90 (br m) (H5),5.0-5.4 (br m) (H6and the central proton); the peak of H7overlapped with that of the olefin proton at 6 3.52.
(17) Strasaburg, R. W.; Gregg, R. A.; Walling, C. J. Am. Chem. SOC. 1947,69,2141. (18) (a) Mabbott, D. J.; Mann, B. E.; Maitlis, P. M. J. Chem. SOC., Dalton Trans. 1977,294. (b) Lukas,J. Inorg. Synth. 1974,15,79.
Results and Discussion Preparation and NMR Studies of the Olefin Complexes. The cationic complexes 2a-c can be isolated as
,I I
Figure 1. 13C NMR spectrum of 3c in CD2C12 at -10 "C. X denotes the solvent peaks and Y the peaks due to 4.
Experimental Section Instruments. 'H and 13C NMR spectra were obtained on JEOL PS-100 and JEOL FX-60 spectrometers,respectively, both with tetramethylsilaneas internal standard. Mass spectra were obtained on a Hitachi RMU-6E spectrometer. GLC analyses were carried out on Hitachi 163 (FID) and 164 (TCD) chromatographs. Materials. p-Nitro and p-(dimethy1amino)styrenewere prepared by the reported methods." 2-Deuteriopropene was prepared from 2-propenylmagnesium bromide and D20 (299%) in EhO. The mass spectrum indicated 199% deuterium content, and the 'H NMR spectrum (CDCl3) exhibited only the methyl and the methylene proton signals with the peak ratio 3/2. The and used other olefins were purchased from Tokyo Kasei Co. La., without further purifications. The complexes [Pt(CH2CRCH&l], (R = H, Me) were prepared by the reported methods.18 Cationic Olefin Complexes. 2a was prepared in a manner similar to that for the styrene complexes described before.1° The method of preparation of 2b,c employing gaseous olefins was similar to that of the carbonyl complex [Pt(q3-CH2CMeCH2)(PPh3)(CO)]PF6 described before.1° All manipulations were carried out at below 5 "C. 2a: mp 138-140 "C dec. Anal. Calcd for C31H3204PC1Pt:C, 51.00; H, 4.42. Found C, 50.72; H, 4.54. 2 b mp 116119 "C dec. Anal. Calcd for C&HN04PClPtC, 46.75; H, 4.53. Found C, 46.52; H, 4.52. 2c: mp 100-102 "C dec. Anal. Calcd for C~B04PClPtC&: C, 50.50,H, 4.64. Found C, 50.86, H, 4.68 (benzene from crystallization confirmed by 'H NMR spectrum). Neutral Olefin Complexes. Compounds 3a-i were formed by adding to [Pt(q3-CH2CMeCH&l]2(4,0.1-0.6 mol/L) in CD2C12 or CDC13an equimolar or 2-3-fold excess of the olefin, and the solution was examined by 13Cand 'H NMR spectra at -10 "C. Typical spectra are shown in Figures 1and 2. 'H NMR spectra were somewhat complex owing to the presence of two stereoisomers in comparable concentrations, unlike the isomer ratio in 2,1° and thus not all of the proton resonances could be assigned unambiguously. However, the 13C spectra were much more straightforward to confirm the formation of 3 unambiguously. Attempts to isolate 3 either by removing the solvent under vacuum or by allowing CH2C12-n-hexanesolutions to stand in the refrigerator resulted in almost quantitative precipitation of 4. The equilibrium constant of eq 2 was determined in CDC13at -10 "C by means of 'H and 13CNMR spectroscopy. The procedure of
Olefin Complexes of Pt Containing the q3-Allyl Ligand
-
Organometallics, Vol. 2, No. 2, 1983 253
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254 Organometallics, Vol. 2. No. 2, 1983
Kurosawa and Asada
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Olefin Complexes of Pt Containing the q3-Allyl Ligand Table 111. Correlation (X= u d + b ) between
Organometallics, Vol. 2, No. 2, 1983 255
NMR Data of the Styrene Complexes and Hammett O+ Constants= 2 (olefin = CH,=CHC,H,Y-p)C
3d-i 6 cl(m?j) 6 &(mm) 6 c'(maj) 6 C2(min) Jptd
maj 1
Jptcl(min1 Jptd
maj 1
J,cz( min)
r
u , ppm or Hz
-3.47 -6.98 0.74 1.43
95.0 104.4 68.8 70.8
0.965 0.946 0.713 0.862
-6.04 -9.51 2.72 3.31
89.6 94.9 66.5 67.3
0.994 0.992 0.987 0.981
7.09 9.26 2.06 -3.18
89.7 93.8 117.2
0.991 0.980 0.715 0.791
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By linear regression analyses.
7 5
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complexes is compared in Table 111. I t is clear that the change of both 6 and Jptxvalues in 2 (olefin = CHz= CHC6H4Y-p)as a function of the Hammett u+ constant of the para substituent is greater and more regular than the change of these values in 3d-i. The particularly poor correlation of the data of the C2 resonances in the latter with u+ is noteworthy. These observations, together with the signs of the slopes shown in Table 111, all are consistent" with the degree of the contribution of 1 (M = Pt, R = C6H4Y-p)to the overall bonding being greater in 2 than in 3. The relative magnitude of the JPt4 values of the two olefin carbons in the allylbenzene, 1-butene, and propene complexes (Table 11) is of further comment. In 2a-12,JRxz is considerably greater than Jpt-c~,while the reversed trend is seen with 3a,b. Two JPtxvalues in 3c are almost the same. These results are again consistent with the greater contribution of 1 (M = Pt, R = CHzC6H5,CH2CH3,CH3) in 2 than in 3. The relative stability of 3d,f,g,i was roughly evaluated by 'H and 13C NMR spectra from equilibrium 2. We could not separate the equilibrium constants ( K ) for the two stereoisomeric series (see Experimental Section). Therefore, a Hammett equation, i.e., log K = pa, derived from the overall K values does not correspond to, in a rigorous sense, the relationship within a series of the complexes possessing closely related structures. Nevertheless, such an apparent equation would not deviate too much from the respective, real equations in view of the relatively narrow range of the isomer ratio in each of 3d-i. The apparent p value for 3 thus estimated a t -10 "C (-0.73, r = 0.990) is considerably less negative than that for 2 (olefin = CHz=CHC6H4Y-p;p = -1.45, r = 0.997) determined in CDC13 a t the same temperature. This is again in accord with the less electrophilic nature of the Pt(q3CHzCMeCHz)Clthan the [Pt(q3-CHzCMeCHz)(PPh3)]+ moiety toward the coordinated olefin.
Catalytic Double-Bond Migration with the Cationic Olefin Complexes. All the cationic complexes 2 were found to catalyze the double-bond migration of allylbenzene and 1-butene under mild conditions. These two olefins isomerized at comparable rates with the initial rate equal to k[2lZ0(k = 1.5-2.0 h-' a t 25 "C in CHZClz),although the isomerization of allylbenzene exhibited slight induction periods. In marked contrast to 2, the cationic complex [Pt(q3-CHzCMeCHz)(PPh3)z]C104(6)21and the (7)22were totally neutral one Pt(q3-CH2CMeCHz)C1(PPh3) inactive in the double-bond migration under the similar
(19) The equilibrium concentration of 3a at [PtIba = [allylb e n ~ e n e =] ~0.2 ~ mol/L in CD2C12at -10 "C waa ca. 90% of the total platinum species. Similarly, ca. 80% of 4 was converted to 3g (Figure 2) from 0.4 mol/L of 4 and styrene.
(20) The olefii exchange in 2 is fast compared to the rate of the olefin isomerization, and thus at the mole ratio of [olefin]/[%]employed the identical complex is assumed to be formed at the initial stage of the isomerization whichever 2 is used as the catalyst. (21) Clark, H. C.; Kurosawa, H. Inorg. Chem. 1973, 12, 357. (22) Mann, B. E.; Shaw, B. L.; Shaw, G. J Chem. SOC.A 1971,3536.
Kurosawa and Asada
256 Organometallics, Vol. 2, No. 2, 1983 conditions. We have no 'H NMR spectral evidence to indicate complex formation between 6 or 7 and the olefins. Somewhat surprisingly, 3, or actually 4,was also inactive in the double-bond migration. Thus, the olefin coordination is a requisite, but not necessarily an adequate factor to the catalytic activity. Instead, treatment of 3 with an equimolar quantity of AgC10, to create the cationic center in the presence of an excess of allylbenzene led to the very facile double-bond migration. Notably, more than 95% of the catalyst recovered from the catalysis mixture (80% completion: initial condition, [ 2 b ] = 0.015 mol/L, [1-butene] = 0.5 mol/L) retained the v3-methylallyl framework. This was confirmed by quenching the reaction mixture by adding CO, followed by 'H NMR characterization of the metallic residue as [ Pt(q3-CH2CMeCH2) (PPh,) (CO)]C10,. Allowing a CH2C12solution of 2a or 2b to stand a t room temperature for long periods also gave a mixture of complexes containing allylbenzene and P-methylstyrene or isomeric butenes, respectively. This was confirmed by GLC analyses of the solution after being quenched by adding benzonitrile, and, notably again, the complex was recovered as the known complex [Pt(v3-CH2CMeCH,)(PPh3)(C6H5CN)]C104'0 almost quantitatively. In order to gain insight into an active species, we have examined stoichiometric and catalytic deuterium scrambling of [Pt($-CH,CMeCH,) (PPh3)(CH2=CDCH3) ]C104 (212-4and CH2=CDCH3,respectively. 'H NMR and mass spectral analyses of the propene recovered after a CDC13 solution of 2c-d was allowed to stand a t room temperature for 20 hZ3revealed that intermolecular deuterium scrambling had occurred in a statistical fashion (eq 3); the ratio
-+
CH2=CDCH3 CHz=CHCH2D
CHD-CHCH, CD,=CHCH,
(5)
Finally, the way to the Pt-H intermediate is a matter of great speculation. No Pt-H intermediates nor precursors to Pt-H other than 2c could be detected by 'H NMR spectra during both the catalytic and the stoichiometric deuterium scrambling of CH,=CDCH,. Modification of eq 4 to include the formation of the Pt-H bond, instead of the liberation of the proton:' (e.g., eq. 5 ) , is not an unreasonable postulate in view of the greater contribution of the form 1 in 2 than in 3 and the greater activity of the former than the latter. The similar facile formation of the Pd-H bond as a result of the electrophilic activation of the olefin has been suggested, without firm evidence, during the formation of the (~3-allyl)palladium(II) complexes from olefins and Pd(00CCFg)2.28It is feasible that the allylic C-H bond activation, as in eq 5, is also involved in the facile allyl-olefin ligand exchange shown in eq 6,29 although eq 6 does not necessarily require the intermediate formation of the Pt-H bond. For a possibility of intramolecular C-H bond activation assisted by coexisting ligands without M-H bond formation, see ref 30.
+ CH,=CDCH3 + + CHD-CDCHB + ... (3)
of the lH NMR peak areas corresponding to the methyl, methylene, and methine protons of propene was nearly 31211, and the relative amounts of the multiple-deuterium-containing propenes ( d 4 / d 3 / d 2 / d l / d 0 )were 1/8/18/ 37/36 that can be compared to the statistical calculation value of 0.1/5.4/20.1/40.2/33.5. Similarly, the deuterium distribution pattern in the propene recovered after CH2=CDCH3 (0.35 mol/L) was allowed to contact 2c-d (6 mol % ) was found to be 1/7/18/40/34. No appreciable loss of the total deuterium content was apparent during the isomerization. The occurrence of eq 3 suggests that a platinum-hydrido species is present as a chain-carrying catalyst in both the stoichiometric and the catalytic transformation^.^^ The addition-elimination sequence involving metal hydrides and the free olefins is well recognized to accompany the 1,2 shift of hydrogen (or d e ~ t e r i u m ) . ' ~The alternative mechanisms involving the v3-allyl hydrido intermediatez6 and the deprotonation-protolysis sequence (eq 4)7are incompatible with the 1,2 shift of deuterium shown above. (23) That no appreciable decomposition products were present was confirmed by the 'H NMR spectra. GLC analyses of gaseous products after being quenched by PPh3 revealed the presence of only propene except for a very small amount of isobutene. (24) (a) The rate of stoichiometric isomerization was very slow, possibly because an extemely low concentration of the free olefins is liberated under the reaction conditions. (b) Although the solutions remained clear and no bulk metal was precipitated during the isomerization, a possibility that unperceived colloidal metal catalyzed the isomerization cannot be excluded at the moment. (25) Clark, H. C.; Kurosawa, H. Inorg. Chem. 1973, 12, 1566, and references therein. (26) Tulip, T.,H.; Ibers, J. A. J . Am. Chem. SOC.,1979, 101,4201, and references therein.
Other routes to the Pt-H intermediate include the allyl olefin insertion, as in the Ni(q3-allyl)(X) (olefin) catalysts,' and the Wacker-type attack by a trace of water a t the olefin ligand.31 Both processes would give alkylplatinum intermediates that would lead, via P elimination, to the Pt-H bond and some byproducts. In fact, however, no such byproducts could be detected3' during the catalyses except for isobutene, the formation of which is consistent with eq 5 . Further work is in progress to clarify more (27) Allowing a CH2C12solution of 2a or 2c to stand in the presence of MeOD ([MeOD]/[Z] 2 40) for more than 2 days resulted in no s i g nificant deuterium incorporation into b-methylstyrene or propene. (28) (a) Trost, B. M. Acc. Chem. Res. 1980,13,385. (b) Trost, B. M.; Metzner, P. J. J. Am. Chem. SOC. 1980, 102, 3572. (29) Though eq 6 may well be reversible (cf. ref 23), the equilibrium concentration of 5a seems extremely low so that the initial deuterium content in 2c-d was almost retained in the propene ligand under the scrambling experimental conditions. In contrast, there was observed fast deuterium shift from the olefin to the q3-allyl ligand in 5b containing CD2=CDCD3 or CH,=CDCH,. (30) Tulip, T. H.; Thorn, D. L. J . Am. Chem. Soc. 1981, 103, 2448. (31) The stoichiometric isomerization in CHzC12that either gets saturated with H 2 0 or contains 5 vol % MeOH was somewhat slower than in dry CH2C1,. (32) We cannot exclude the possibility that extremely low concentrations of the byproducts provide the real catalyst of sufficiently high activity. Also, a reviewer suggested that ortho metalation involving PPh, is consistent with all the isomerization data. We presume this possibility to be less likely because (1) keeping a solution containing [Pt(q3CH,CMeCH2)1P(CGD6)3)(olefin)]C10* and an excess of the olefin under the isomerization conditions did not cause the 'H NMR peaks due to the phosphine phenyls to appear and (2) the catalyst containing no PPh3 (3 + AgC104) was as active as 2.
Organometallics 1983, 2, 257-263 detailed mechanisms of the double-bond migration catalyzed by the cationic complexes.
Acknowledgment. Valuable discussions with Prof. N.
K d and Dr. K. Miki are gratefully acknowledged.
This work W ~ Spartly supported by a Grant-in-kd for Scientific Research from the Ministry of Education, Japan (No.
57550539). Registry No. 2a, 83947-72-2;2b, 83947-74-4;2c, 83947-76-6;
257
3a, 83947-77-7; 3b, 83947-78-8;3c, 83947-79-9;3a, 83947-80-2;3e, 83947-81-3; 3f, 83947-82-4; 3g, 83947-83-5; 3h, 83947-84-6; 3i, 83947-85-7;4,35770-44-6;5a, 83947-87-9;5b, 83947-89-1;CH2= CDCH3,1184-59-4;CHflHCHZPh, 300-57-2;CHflHCH2CH3, 106-98-9; CHdHCH3,115-07-1; CH2
