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Metallation of aliphatic carbon atoms
c51 Journal of Organometallic Chemistry, 280 (1985) C51-_C53 Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands
Preliminary
communication
METALLATION
OF ALIPHATIC
CARBON ATOMS
II*, SYNTHESES AND CHARACTERIZATION OF THE CYCLOPALLADATED COMPLEXES OFN,N-DIMETHYLNEOPENTYLAMINE
YOSHIO FUCHITA, KATSUMA HIRAKI* and YASUHIRO MATSUMOTO Department of Industrial Chemistry, Faculty of Engineering, Bunkyo-machi, Nagasaki 852 (Japan)
Nagasaki University,
(Received August 18th, 1984)
Summary N,N-Dimethylneopentylamine reacts with Pd(MeCO,), to give a novel trinuclear cyclopalladated complex [Me,NCH,CMe,CH,Pd(~-MeCO,),Pd(~-MeCOz),PdCH,CMe,CH,NMe,] a0.5C6H6 (I). The reaction of I with PPh, affords both truns-[Pd(MeCOz), (PPh,),] (II) and [Pd(CH,CMezCH,NMe,)(MeCO,)(PPh,)] (III). The reaction of III with LiCl yields a mononuclear cyclopalladated complex, [Pd(CH2CMezCH2NMe,)C1(PPh,)] (IV).
Metallation of an aliphatic carbon atom has been one of the current topics in organometallic chemistry in association with the activation of C-H bonds by transition metals [l] . Recently, we [ 21 reported the syntheses of the sixmembered cyclopalladated complexes of 2-neopentylpyridine through direct metallation of the aliphatic carbon atom by use of Pd(MeCOz),. This communication deals with the cyclopalladation of N,N-dimethylneopentylamine by Pd(MeCOz )*, resulting in the formation of a novel trinuclear cyclopalladated complex. NJ-Dimethylneopentylamine (5.5 mmol) reacted with Pd(MeCOz)z (4.45 mmol) in benzene (20 ml) at 50-55°C for 1.5 h. After the mixture was filtered to remove the precipitated palladium black, the filtrate was concentrated under reduced pressure and diluted with hexane to give a novel trinuclear cyclopalladated complex, [Me,NCH,CMe,CH2Pd(p-MeC02)zPd(p-MeCO,),PdCH,CMe,CH,NMe,] .0.5CsHb * (I) in 36% yield (Scheme 1). *Satisfactory
elemental
0022-328X/85/$03.30
analysis and ‘I-I NMR data were obtained.
0 1985 Elsevier Sequoia S.A.
C52
Complex I was not isolated from the reaction mixture either in acetic acid at 70°C or in methanol at 60°C. When NJ-dimethylneopentylamine was treated with Pd(MeCOz )Z in a molar ratio of 2/3 or l/l in CDC& at 19°C it was observed by ‘H NMR spectroscopy that I was formed smoothly. As for the reaction in the molar ratio of 2/l, I was produced in lower yield (about 10% after 4 h), and a large amount of palladium black was formed. In no case was any other cyclopalladated complex, such as a binuclear one, detected. Complex I reacted with PPh, to produce truns-[Pd(MeC0, )* (PPh3)2 ] (II) in 56% yield, as well as an oily product, Pd(CH,CMe, CH,NMe,)(MeCO,)(PPh,)* (III). The IR spectrum of II coincided quite well with that of the authentic sample [ 31. The oily product III was uncrystallizable and was converted into Pd(CH2CRfe,CH,NMe,)C1(PPh,) (IV) in 55% yield (based on I) by reaction with LiCI. The IR spectrum of I exhibited v(COO- ) frequencies due to bridging acetato groups at 1610(s), 1570(s), 1405(s), 1380(s), and 1335(s) cm-‘, which were very similar to those of the trimeric palladium(I1) acetate [ 31. The ‘H NMR spectrum of IV in CDCl, exhibited two methylene proton signals at 6 1.34 (d, 3J(HP) 4.5 Hz; Pd-CH,) and 2.50 ppm (s, N-(X2) and two methyl proton signals at 6 1.02 (s, CMe,) and 2.89 ppm (d, 4J(HP) 2.5 Hz; N&fez). The resonance at 6 1.34 ppm was assigned to the protons of the palladium-bonded methylene group which was produced by the cyclopalladation of N,N-dimethylneopentylamine. The coupling of the protons of both Pd-CHt and NMe, with the 31Pnucleus confirmed strongly the presence of a CHz ....NMe. chelate structure. The small coupling constant 3J(HP) for Pd-CH2 suggests that PPh3 is situated in a cis position to the palladated methylene carbon. These facts indicate unambiguously that I contains both the Pd(CH2CMezCH,NMe,)(MeC0,) and Pd(MeCO,), moieties. On the basis of these discussions, the elemental analysis, and the molecular weight (745.1 in benzene, calcd. 783.9), complex I was assigned to have trinuclear structure, which involves four acetato bridges and two Me, NCH, CMe, CH2-C’,N chelates. It is noteworthy that N,iV-dimethylneopentylamine reacted with Pd(MeCO,), in hot benzene to afford directly the trinuclear cyclopahadated complex, I. Ukhin et al. [4] reported that Pd(MeCO,), reacted with 2,6-disubstituted pyrylium salts to afford trinuclear bis(l-3-v-1,3-diacylallyl)tripalladium(II) complexes having four p-acetato ligands. As for the ‘H NMR spectrum of I in CDCI, at 14°C the acetate-methyl protons appeared as four singlets at 6 1.78 (2,4H), 1.80 (2.4H), 1.82 (3.6H), and 1.84 ppm (3.6H), indicating that I contains both an (a-C’&&)(h-C’J-N)-type (&type) isomer and an (a-C’,b-N)-(h-N, Z-C’ )-type (al-type) isomer (Scheme 1) in a ratio of about 2/3. In addition, I exhibited two sets of signals corresponding to the two isomers. At 14°C one set consisted of six signals at 6 1.33 (s, H3CCCH3), 1.36 (s, H3CCCH3), 2.40 (q, A6 0.29 ppm, *J(HH) 8 Hz, Pd-CH2), 2.45 (q, A6 0.29 ppm, *J(HH) 9 Hz, N--(X2), 2.88 *The ‘H NMR spectrum of III was very similar to that of IV, except for the acetate-methyl proton reScmance at 6 1.54 ppm.
c53
Ph3P,
,02CMe Pd
MeC02/
t
‘PPh3 II
1
Me MeH
H
(ii) J
Me
Me4
PPh3
CH2,
Pd
N/
‘Cl
Me2 m
SCHEME 1. Reagents: i. PPh,
; ii,
LiCl.
(s, H3CNCH3), and 3.01 ppm (s, HBCNCH3) and was temperature-dependent. At 43°C the two C-methyl proton signals united to give one singlet at 6 1.34 ppm, whereas the two N-methyl proton signals coalesced into one singlet at 6 2.98 ppm; then, the two quartets changed into broad signals. The other set involved four singlets at 6 1.27 [C(CH,),], 2.73 (Pd-CH,), 2.93 (N-CH,), and 3.01 ppm [N(CH,),] * and virtually did not change in the range -35-43°C. The temperature-dependency of the ‘H NMR spectra of I was associated with the inversion of the acetato bridges, as observed for the other binuclear acetate-bridged complexes [ 5,6] . The inversion corresponding to the former set was actually quenched below 20°C whereas that corresponding to the latter set was not quenched even at -35°C. The “C-{‘H} NMR data of I in CDC13 at 24°C are quite consistent with the presence of the two isomers, showing four carboxylato carbon signals at S 181.6,181.9,183.4, and 183.5 ppm, two acetate-methyl carbon signals at 6 22.4 and 23.4 ppm, and two C-methyl carbon signals at 6 28.3 and 28.6 ppm. In addition, I exhibited four singlets at 6 35.9 (Pd--CH2), 43.8 (CMe,), 54.3 [N(CH,),l, and 80.3 (NCH2). The stability of I, III, and IV is associated with both the chelate structure of the PdCHzCMe,CH,NMe, moiety and the lack of P-hydrogen in the 3-(dimethylamino)-2,2_dimethylpropyl group. Acknowledgements. The present work was partially supported by a Grantin-Aid for Scientific Research from the Ministry of Education.
*The singlet at 6 3.01 ppm WASascribed to protons of one of two N-methyl BrouPs of the former set and those of two N-methyl groups of the latter set.
c54
References 1
D.E.
2
Y.
3
T.A.
Webster.
Fuchita,
Adv. K.
Organomet.
Hiraki
Stephenson,
and
S.M.
T.
Chem.,
15
Uchiyama,
Morehouse,
A.R.
(1977)
147.
J. Chem.
SIX.,
Powell,
Dalton
J.P.
Heffer
and
Yu.T.
Trans.,
and
(1983)
897.
G. Wilkmson,
J. Chem.
Sot..
(1965)
3652. 4
L.Yu.
Ukhin.
(1981)
263.
5
j.
6
A.J.
Powell,
N.A.
J. Am.
Deeming
and
Dolgopolova, Chem.
Sot.,
I.P.
Rothwell,
L.G. 91
(1969)
Kuz’mina
Struchkov,
J. Organomet.
Chem..
210
4311.
J. Organomet.
JOURNAL OF ORGANOMETALLIC
Chem.,
205
(1981)
CHEMISTRY,
117.
VOL. 280,
NO. 2
AUTHOR INDEX
Arad-Yellin, Assadourian,
R., 197 L., 153
Baccar, B., 165 Bellassoued, M., 165 Bin Shawkataly, O., 289 Black, P., 159 Bruce, M.I., 289 Butler, I.R., C47 Bywater, S., 159 Cullen,
W.R.,
C47
Del Vecchio, A.L., DSppert, K., 203 Doyle, G., 253 DrZiger, M., 183 Dyk, M. Van, 241 El Borgi, A., 165 Engen, D. Van, 253
173
Haaland, A., C43 Hgberle, K., 183 Harris, R.K., 281 Hiraki, K., C51 Horn, E., 289 Hudson, A., 173 Jackson,
R.A.,
173
Klein, H.-P., 203 Klein, S.I., 281 Klement, II., 215 Kreiter, C.G., 225 Kroto, H.W., 281 Kruger, G.J., 241 Lachance, P., 159 Lappert, M.F., C43 Leyendecker, M., 225 Linford, L., 241 Lotz, S., 241
Faure, R., 153 Fiorenza, M., 177 Fjeldberg, T., C43 Fuchita, Y., C51
Mann, B.E., C47 Matsumoto, Y., C51 Meidine, M.F., 281 Mordini, A., 177 Muzart, J., 269
Gau, G., 153 Gaudemar, M., 165
Nixon, J.F., 281 Nurse, C.R., C47
Oro, L.A., Packer,
261
K.J., 281
Pete, J.P., 269 Pinillos, M.T., 261 Raubenheimer, H.G., Reams, P., 281 Rhodes, C.J., 173 Riahi, A., 269 Ricci, A., 177 Riess, J.G., 215
241
Schilling, B.E.R., C43 Shawkataly, O.bin, 289 Snow, M.R., 289 Tejel, C., 261 Thewalt, U., 203 Thorne, A.J., C43 Van Dyk, M., 241 Van Engen, D., 253 Volden, H.V., C43 Wachter, J., 215 Wudl, F., 197
Preliminary
communication
METALLATION
OF ALIPHATIC
CARBON ATOMS
II*, SYNTHESES AND CHARACTERIZATION OF THE CYCLOPALLADATED COMPLEXES OFN,N-DIMETHYLNEOPENTYLAMINE
YOSHIO FUCHITA, KATSUMA HIRAKI* and YASUHIRO MATSUMOTO Department of Industrial Chemistry, Faculty of Engineering, Bunkyo-machi, Nagasaki 852 (Japan)
Nagasaki University,
(Received August 18th, 1984)
Summary N,N-Dimethylneopentylamine reacts with Pd(MeCO,), to give a novel trinuclear cyclopalladated complex [Me,NCH,CMe,CH,Pd(~-MeCO,),Pd(~-MeCOz),PdCH,CMe,CH,NMe,] a0.5C6H6 (I). The reaction of I with PPh, affords both truns-[Pd(MeCOz), (PPh,),] (II) and [Pd(CH,CMezCH,NMe,)(MeCO,)(PPh,)] (III). The reaction of III with LiCl yields a mononuclear cyclopalladated complex, [Pd(CH2CMezCH2NMe,)C1(PPh,)] (IV).
Metallation of an aliphatic carbon atom has been one of the current topics in organometallic chemistry in association with the activation of C-H bonds by transition metals [l] . Recently, we [ 21 reported the syntheses of the sixmembered cyclopalladated complexes of 2-neopentylpyridine through direct metallation of the aliphatic carbon atom by use of Pd(MeCOz),. This communication deals with the cyclopalladation of N,N-dimethylneopentylamine by Pd(MeCOz )*, resulting in the formation of a novel trinuclear cyclopalladated complex. NJ-Dimethylneopentylamine (5.5 mmol) reacted with Pd(MeCOz)z (4.45 mmol) in benzene (20 ml) at 50-55°C for 1.5 h. After the mixture was filtered to remove the precipitated palladium black, the filtrate was concentrated under reduced pressure and diluted with hexane to give a novel trinuclear cyclopalladated complex, [Me,NCH,CMe,CH2Pd(p-MeC02)zPd(p-MeCO,),PdCH,CMe,CH,NMe,] .0.5CsHb * (I) in 36% yield (Scheme 1). *Satisfactory
elemental
0022-328X/85/$03.30
analysis and ‘I-I NMR data were obtained.
0 1985 Elsevier Sequoia S.A.
C52
Complex I was not isolated from the reaction mixture either in acetic acid at 70°C or in methanol at 60°C. When NJ-dimethylneopentylamine was treated with Pd(MeCOz )Z in a molar ratio of 2/3 or l/l in CDC& at 19°C it was observed by ‘H NMR spectroscopy that I was formed smoothly. As for the reaction in the molar ratio of 2/l, I was produced in lower yield (about 10% after 4 h), and a large amount of palladium black was formed. In no case was any other cyclopalladated complex, such as a binuclear one, detected. Complex I reacted with PPh, to produce truns-[Pd(MeC0, )* (PPh3)2 ] (II) in 56% yield, as well as an oily product, Pd(CH,CMe, CH,NMe,)(MeCO,)(PPh,)* (III). The IR spectrum of II coincided quite well with that of the authentic sample [ 31. The oily product III was uncrystallizable and was converted into Pd(CH2CRfe,CH,NMe,)C1(PPh,) (IV) in 55% yield (based on I) by reaction with LiCI. The IR spectrum of I exhibited v(COO- ) frequencies due to bridging acetato groups at 1610(s), 1570(s), 1405(s), 1380(s), and 1335(s) cm-‘, which were very similar to those of the trimeric palladium(I1) acetate [ 31. The ‘H NMR spectrum of IV in CDCl, exhibited two methylene proton signals at 6 1.34 (d, 3J(HP) 4.5 Hz; Pd-CH,) and 2.50 ppm (s, N-(X2) and two methyl proton signals at 6 1.02 (s, CMe,) and 2.89 ppm (d, 4J(HP) 2.5 Hz; N&fez). The resonance at 6 1.34 ppm was assigned to the protons of the palladium-bonded methylene group which was produced by the cyclopalladation of N,N-dimethylneopentylamine. The coupling of the protons of both Pd-CHt and NMe, with the 31Pnucleus confirmed strongly the presence of a CHz ....NMe. chelate structure. The small coupling constant 3J(HP) for Pd-CH2 suggests that PPh3 is situated in a cis position to the palladated methylene carbon. These facts indicate unambiguously that I contains both the Pd(CH2CMezCH,NMe,)(MeC0,) and Pd(MeCO,), moieties. On the basis of these discussions, the elemental analysis, and the molecular weight (745.1 in benzene, calcd. 783.9), complex I was assigned to have trinuclear structure, which involves four acetato bridges and two Me, NCH, CMe, CH2-C’,N chelates. It is noteworthy that N,iV-dimethylneopentylamine reacted with Pd(MeCO,), in hot benzene to afford directly the trinuclear cyclopahadated complex, I. Ukhin et al. [4] reported that Pd(MeCO,), reacted with 2,6-disubstituted pyrylium salts to afford trinuclear bis(l-3-v-1,3-diacylallyl)tripalladium(II) complexes having four p-acetato ligands. As for the ‘H NMR spectrum of I in CDCI, at 14°C the acetate-methyl protons appeared as four singlets at 6 1.78 (2,4H), 1.80 (2.4H), 1.82 (3.6H), and 1.84 ppm (3.6H), indicating that I contains both an (a-C’&&)(h-C’J-N)-type (&type) isomer and an (a-C’,b-N)-(h-N, Z-C’ )-type (al-type) isomer (Scheme 1) in a ratio of about 2/3. In addition, I exhibited two sets of signals corresponding to the two isomers. At 14°C one set consisted of six signals at 6 1.33 (s, H3CCCH3), 1.36 (s, H3CCCH3), 2.40 (q, A6 0.29 ppm, *J(HH) 8 Hz, Pd-CH2), 2.45 (q, A6 0.29 ppm, *J(HH) 9 Hz, N--(X2), 2.88 *The ‘H NMR spectrum of III was very similar to that of IV, except for the acetate-methyl proton reScmance at 6 1.54 ppm.
c53
Ph3P,
,02CMe Pd
MeC02/
t
‘PPh3 II
1
Me MeH
H
(ii) J
Me
Me4
PPh3
CH2,
Pd
N/
‘Cl
Me2 m
SCHEME 1. Reagents: i. PPh,
; ii,
LiCl.
(s, H3CNCH3), and 3.01 ppm (s, HBCNCH3) and was temperature-dependent. At 43°C the two C-methyl proton signals united to give one singlet at 6 1.34 ppm, whereas the two N-methyl proton signals coalesced into one singlet at 6 2.98 ppm; then, the two quartets changed into broad signals. The other set involved four singlets at 6 1.27 [C(CH,),], 2.73 (Pd-CH,), 2.93 (N-CH,), and 3.01 ppm [N(CH,),] * and virtually did not change in the range -35-43°C. The temperature-dependency of the ‘H NMR spectra of I was associated with the inversion of the acetato bridges, as observed for the other binuclear acetate-bridged complexes [ 5,6] . The inversion corresponding to the former set was actually quenched below 20°C whereas that corresponding to the latter set was not quenched even at -35°C. The “C-{‘H} NMR data of I in CDC13 at 24°C are quite consistent with the presence of the two isomers, showing four carboxylato carbon signals at S 181.6,181.9,183.4, and 183.5 ppm, two acetate-methyl carbon signals at 6 22.4 and 23.4 ppm, and two C-methyl carbon signals at 6 28.3 and 28.6 ppm. In addition, I exhibited four singlets at 6 35.9 (Pd--CH2), 43.8 (CMe,), 54.3 [N(CH,),l, and 80.3 (NCH2). The stability of I, III, and IV is associated with both the chelate structure of the PdCHzCMe,CH,NMe, moiety and the lack of P-hydrogen in the 3-(dimethylamino)-2,2_dimethylpropyl group. Acknowledgements. The present work was partially supported by a Grantin-Aid for Scientific Research from the Ministry of Education.
*The singlet at 6 3.01 ppm WASascribed to protons of one of two N-methyl BrouPs of the former set and those of two N-methyl groups of the latter set.
c54
References 1
D.E.
2
Y.
3
T.A.
Webster.
Fuchita,
Adv. K.
Organomet.
Hiraki
Stephenson,
and
S.M.
T.
Chem.,
15
Uchiyama,
Morehouse,
A.R.
(1977)
147.
J. Chem.
SIX.,
Powell,
Dalton
J.P.
Heffer
and
Yu.T.
Trans.,
and
(1983)
897.
G. Wilkmson,
J. Chem.
Sot..
(1965)
3652. 4
L.Yu.
Ukhin.
(1981)
263.
5
j.
6
A.J.
Powell,
N.A.
J. Am.
Deeming
and
Dolgopolova, Chem.
Sot.,
I.P.
Rothwell,
L.G. 91
(1969)
Kuz’mina
Struchkov,
J. Organomet.
Chem..
210
4311.
J. Organomet.
JOURNAL OF ORGANOMETALLIC
Chem.,
205
(1981)
CHEMISTRY,
117.
VOL. 280,
NO. 2
AUTHOR INDEX
Arad-Yellin, Assadourian,
R., 197 L., 153
Baccar, B., 165 Bellassoued, M., 165 Bin Shawkataly, O., 289 Black, P., 159 Bruce, M.I., 289 Butler, I.R., C47 Bywater, S., 159 Cullen,
W.R.,
C47
Del Vecchio, A.L., DSppert, K., 203 Doyle, G., 253 DrZiger, M., 183 Dyk, M. Van, 241 El Borgi, A., 165 Engen, D. Van, 253
173
Haaland, A., C43 Hgberle, K., 183 Harris, R.K., 281 Hiraki, K., C51 Horn, E., 289 Hudson, A., 173 Jackson,
R.A.,
173
Klein, H.-P., 203 Klein, S.I., 281 Klement, II., 215 Kreiter, C.G., 225 Kroto, H.W., 281 Kruger, G.J., 241 Lachance, P., 159 Lappert, M.F., C43 Leyendecker, M., 225 Linford, L., 241 Lotz, S., 241
Faure, R., 153 Fiorenza, M., 177 Fjeldberg, T., C43 Fuchita, Y., C51
Mann, B.E., C47 Matsumoto, Y., C51 Meidine, M.F., 281 Mordini, A., 177 Muzart, J., 269
Gau, G., 153 Gaudemar, M., 165
Nixon, J.F., 281 Nurse, C.R., C47
Oro, L.A., Packer,
261
K.J., 281
Pete, J.P., 269 Pinillos, M.T., 261 Raubenheimer, H.G., Reams, P., 281 Rhodes, C.J., 173 Riahi, A., 269 Ricci, A., 177 Riess, J.G., 215
241
Schilling, B.E.R., C43 Shawkataly, O.bin, 289 Snow, M.R., 289 Tejel, C., 261 Thewalt, U., 203 Thorne, A.J., C43 Van Dyk, M., 241 Van Engen, D., 253 Volden, H.V., C43 Wachter, J., 215 Wudl, F., 197