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A new homogeneous platinum containing catalyst for the hydrolysis of nitriles
A \\lew
Homogeneous for
the
Platinum H>drolgsis
Containing of
Catalyst
Nitriles.
The hycirol>zih ot nltrlic\ !o .umtlc\ 15 t~hu;iili ~JITUI ,)uI in the I&oratory usmg acid or base catalysis. A problem ahsoclated ~\lth thlh re,Lc‘uon I\ t!1ar It I\ illtell not possible to stop a[ the amide stage and further hytirolyw\ to the acid I)ccurs ’ I- nz> me\ : c‘,in nt’ LIVZOIc) give amides exclusively, and heterogeneous metal catalysts are used ~ndustrlali~, Inr example 111the manufacture of acryiamide.3 We report here the use of phobphimto complcxe\ ot plulrlurn ;I> nomo:cnrnu\ ..-,~:a:~st\for the selective hydrolysis of nitriles to amides. We discovered the <.a[.II! I1c ,ir’[l\ll\ c~f phc)\rhinltt, complexes u hlle jtudyng the reactions of secondary pho@unr complex?\ VV~ undenooi, the stud\ ixx.luw <>trhe interesrtn, 0 reactions of secondary phosphines in the co-ordmation
\pherc $I< n~r.ii\.
\c hlc!) h.:\t, herrl ,ummansed
by Wolfsberger.J
In common with other
In~extl&ato’“. 3.6 ‘i&II rollrlii tha: Iunder QV~V Lon,ilnons ~nvolvlng air or hydroxylic solvents, secondary phohphmeb form J \I\ trwmherd hqtirogrn tvndtrd whelm of the type xhown m I. Compounds of this type have been known ior rn,~n! >UI-S. and ha\c‘ ht~n in\ e\tlgated as hydroformylation catalysts by van Leeuwen ;md co-workers.” F:, ~.drllr.r work ha\ ieen rr\l:.\%~d h\ Koundhlll L’IO/ q We decided to investigate these Lomplese> as hSdrarl<)n <..lt,lly\t\
I
11.1.Ii: I I Ill?. s=c !
III
We t‘ind [hat thr pho\phrnlto L.<)rnpieu 11,1 i’,!t.ii!\c, the h)drolycls of nltriles to amides, with no detectable further hydrolyslh io the .KI~ Th15 \clectl\ r h\ droll ,15 ib very useful synthetically, as generally the rates of hydrolysis of amide\ to thr c,trboxyi,lte ion. are peatrr than the rateb of hydrolysis of niuiles to amides.10 The hydrolyvs 1scarr~cti out h! boiling rhe nllrlle ‘~.lrh eater under retlux. or if the nitrile is not soluble in water, in queous trtrah\tiroturan or ethanol. I‘hr rrio\t .lc’[lve catalyst we have found so far is derived from
8658
dimethylphosphme
oxide. and the most convenient precursor IS the hydride complex IIa. Generally 0.01-0.1
mole% of catalyst is sufficient to carry out the hydrolysis. which suggests possible industrial applications.’ ’ A comparison of the effectiveness of the new catalyst for the hydration of acetonittile relative to some of those already reported is given in Table 1. Table
1. Comparison of Catalytic rZctivities for the Hydration of Acetonitrile
-
[PtH(PMeflH)(PMep)zH] [PtH(HzO)(PMe3bl[OHl IP~H(HzO)(PE~~~][OH] [PcKXOH)(bipy)(HP)j wRcwl lhl2 Pt(PEt& c232
9 N402.5
-
tmp , Turnover Frequency mol/(mol of cat. h) “0 - .-
Catalyst
90 78 78 76 x0 x0 x0 78
P&
NaOH
to Acetamide
_-
1rumover Tnol/(mol
Number of cat.)
5,700 S,OOO-6,000 not reported not reported 405 54 4,000
3x0 178 70 29 27 3
not reported 0.3
-
Reference this work 12 12 13 14 14 15 12
-
We have carried out hydrolyses with a range of nitriles. some of which are listed in Table 2 Table
Z.Yields and Turnover Frequencies Using IIa
.Nitrile
Isolated yield
Reaction medium at reflux temperature
.Acetonittile Acnylonitrile Benzonitrile 2,6-difluorobenzonitrile 3-cyanopyndine
Turnover Frequency mol/(mol of cat.h)
,of amide (%)
Water Aqueous Ethanol Aqueous Ethanol Aqueous tetrahydrofuran Water
--I 91 93 86 7x
380 1485 518 220
‘)I
450
Interestingly. although the catalyst IS a co-ordmation compound of platinum, the catalysis is not inhibited by co-ordination of the pyridine nitrogen in 3-cyanopyndine. The catalyst is especially active for the hydrolysisof acrylonitrile: 0.004 mol% of catalyst is sufficient. and the turnover number exceeds 50,000. The hydrolysis of acrylonitrile also provides a test of selectivity. as usually hydration of the carbon-carbon double bond competes wtth amide formation. 12 GLC analvcis of the reaction mixture selectivity to acrylamide of >99%
using IIa as catalyst shows a
The active catalyst appears to be cationic as, although Ilb is not active. it becomes so on reaction with Ag+. The cationic nature of the catalytic species is also supported by the fact that the catalysis can be stopped by adding halide ion. McKenzie and Robson Is attribute their comparatively high turnover number to an intramolecular attack by OH on a co-ordinated nitrile. In our system we find that the catalytic activity is
8659
RCONHz
-v
Figure.
J ‘:
Suggested Mechanism for the Hydolysis of Nittiles by Phosphinito Complexes.
lowered when one ot the phosph!)rus donors does not have a hydroxy substituent. Thus the catalyst derived from I[1 and AgBF, has less than h.llf the turnover rate of the catalyst derived from IIb and AgBF,. This leads u to huggrst attack by the hydroxhphosphine on the co-ordmated nitrile as shown in the catalytic cycle in the Figure. We have not found condltlons under wtuch free phosphine oxides catalyse the hydration of nitriles. Other authors have noted subxtantul rate Increases on comparing intramolecular and intermolecular reactions, and iritramolccullu
reactIon\ are important in enzyme rnimics.lh.!?
Expertmental Procedure The catal! st Ila was prepared ils ‘,u,,cycrcstedbv other uorkers X I8 by the reaction of (Ph,P),Pt of dimethylphosphme oxtde In tolucne
with an excess
Prrpnruric~r[ (q llu- Dimeth! iphosphlne aside (0 1tl~. 2.05 mmol) was added to a stirred suspension of Ptt PPh,), I().$. 0.107 mmol) in dp toluene ( 10 m:l ,~troom temperature under nitrogen. Almost immediately a coiourless solution uja> obtatncd. \+ htch was >tlrrcu for 1h. during which time the product begins to przclpitate. Preqitatlon waj completed h!, ad&tlon ot ðyl ether (30 ml) and after stirring for a further hour the product was filtered off. ua\hed with dtcthyl ctller and hexane and dried in vucuo. Yield: 0.13g, 7.i%.M.p.
131-7.3?“C. vIPtmfir 1’140 i‘m 1 t-ound (‘. I’.? H.;l 8. C,H2,qP,Pt
requires C.16.8; H,4.Y%.
Hxdrurii)r~ ii!‘.~-(.‘tltli,~?.riifllli’. .4 \ Igc)rou’\ly btirrcd nilxture of lla 15.0 mg. 0.01 17 mmol), .Qyanopyrldinz tj.Og. O.O?Y mo11 ,md w:tti’r (51nl. 0 277 mol) was heated under reflux for 5 hours. After cooilng the esces:, of water \v‘is remo\cd under rctiuc ret prcjsure to s’ve nicotinamide (3.2g. 91%). X1.p. 12% 130, Lltt. ” I ‘Y- ! .{(I”(‘ ti~drdrion ~)j~zc.r\loriitniL :\ L ~gori~ii\l! ,tt:-r?d m:\tl,rc of lla 16.8 mg, (!.0158 mmol). acrylonitrile (20.15g. 0.3X rnol). ethanol (15 ml) ‘111~1,~,itr~ j 1’ II:! 0 X? m01 I was heated undrr retlux for 15h. After cooling, the
\olvcnts \scrc e\ aporatcd io glvc .~~r~Imi~dc (2.5 032. ‘1 ;Cr I uhlch
was dned in IJQCUO.M.p. 83-85. Litt.”
PYY .-\c,kr~l,l~letfr~mcr;r. Vve th,mh the E.Ps.R C t<>r rhr ,ir\ard ot a pobtgradute studentship Xlutthey pit for c~loan 01 p!,mnum \alt\. Jnd Dr (‘ \L 131rd for useful discussions.
to T.G., Johnson
Rcfercnces I B.(’ Challts. A.J. Chaill\ in ( ,,rril)rc,il~r!\il.r, (:r~ciri~: c i~~,ni.srri \;I/.? rEds.D.Barton, W.D. Ollis), Pergamon.Oxiord.lY7Y.p 96J 2. L.A. Thompson. C.J. Knowlrs. E A Llnron. .I \I LL\.ltt. (‘I~em.Br, 1988,23.90(~. 3. F. blatsuda, Chem.T~i~.. 1Y 7 7.7.306 1. W Wolfsberger. C’il~n. -Zra 1 Y 88, II,‘.? 1.i 5. T. Gebauer. G. Frenzen. K. Dehmcke. % ,2’ut1crror\t /I 1 Y Y 2.3711. I SO5. 6. f? Leom. F.Mrlrchettl. MPasquah. J I)r:rz,fi,mer.i’iicn: , 1 YY3.rl_FI.C25. 7. T Ghaffar. 4. Kieszktewtcz. S.C. Kyburg, A.W. Parkms. Acru Ctysral1o~r.Secr.C , 199430,697. X. P.W.Iu‘.ll. van Leeuwen. C.F. Roobeek. J.H.G f.rJnc. r\.G. Orpen. Or~anomrrallics, 1990,9,1211. 9. D.M. Roundhill. R.P. Sperhne. W B. Bc~ultru. i‘~~-~>rd. Chem.Rev., 197826,263. IO. J. Chin, J.H. Kim, ;\npr\i. Ciwm Inr. Ed Enqi lYYO,2Y.57!. I 1. L’ K.PL~renr
Appfir~uann
3.506389.
17. C.hl. Jensen. WC Trogler. .I :\m C‘l~jn; .,‘(Jl, IYX(,.IIJX.7?3 1.3. (; Vill.un, G. Constant. .A GJiset. P. K,llck. J tlof (‘dral.. 10X0.7.355. I?. TYoshida.T.~latsud~.T.Okano.T.Kitan~. S.Ot\uka. .I .-lm C‘i~rm Sot 1979.101.2027. 15 C.J. hlcKenzie. R.Robson. .i C/~ern..So~,C‘licm (‘~~rr~rn;tn 19X8.1 12. 16. FM. hlenger, .4<,r‘ Cl~!m. Rrs.. I9 85.18.12~ 17. :I.J. Kirby. Aq:ew. Cilrm I/u Ed EnxI., IYYd.:‘.:.551. IX. \V.B. Beaulieu. T.13. Rauchfu~s. D.M. RoundhIll. !r~or,q.Chem 1975.11,1732. 19 I~ic~rrouu-v ojOrqc~r~;~~ C~~m~o~nd.s 5th Edition. Chapman and Hall. London. 1982.
Homogeneous for
the
Platinum H>drolgsis
Containing of
Catalyst
Nitriles.
The hycirol>zih ot nltrlic\ !o .umtlc\ 15 t~hu;iili ~JITUI ,)uI in the I&oratory usmg acid or base catalysis. A problem ahsoclated ~\lth thlh re,Lc‘uon I\ t!1ar It I\ illtell not possible to stop a[ the amide stage and further hytirolyw\ to the acid I)ccurs ’ I- nz> me\ : c‘,in nt’ LIVZOIc) give amides exclusively, and heterogeneous metal catalysts are used ~ndustrlali~, Inr example 111the manufacture of acryiamide.3 We report here the use of phobphimto complcxe\ ot plulrlurn ;I> nomo:cnrnu\ ..-,~:a:~st\for the selective hydrolysis of nitriles to amides. We discovered the <.a[.II! I1c ,ir’[l\ll\ c~f phc)\rhinltt, complexes u hlle jtudyng the reactions of secondary pho@unr complex?\ VV~ undenooi, the stud\ ixx.luw <>trhe interesrtn, 0 reactions of secondary phosphines in the co-ordmation
\pherc $I< n~r.ii\.
\c hlc!) h.:\t, herrl ,ummansed
by Wolfsberger.J
In common with other
In~extl&ato’“. 3.6 ‘i&II rollrlii tha: Iunder QV~V Lon,ilnons ~nvolvlng air or hydroxylic solvents, secondary phohphmeb form J \I\ trwmherd hqtirogrn tvndtrd whelm of the type xhown m I. Compounds of this type have been known ior rn,~n! >UI-S. and ha\c‘ ht~n in\ e\tlgated as hydroformylation catalysts by van Leeuwen ;md co-workers.” F:, ~.drllr.r work ha\ ieen rr\l:.\%~d h\ Koundhlll L’IO/ q We decided to investigate these Lomplese> as hSdrarl<)n <..lt,lly\t\
I
11.1.Ii: I I Ill?. s=c !
III
We t‘ind [hat thr pho\phrnlto L.<)rnpieu 11,1 i’,!t.ii!\c, the h)drolycls of nltriles to amides, with no detectable further hydrolyslh io the .KI~ Th15 \clectl\ r h\ droll ,15 ib very useful synthetically, as generally the rates of hydrolysis of amide\ to thr c,trboxyi,lte ion. are peatrr than the rateb of hydrolysis of niuiles to amides.10 The hydrolyvs 1scarr~cti out h! boiling rhe nllrlle ‘~.lrh eater under retlux. or if the nitrile is not soluble in water, in queous trtrah\tiroturan or ethanol. I‘hr rrio\t .lc’[lve catalyst we have found so far is derived from
8658
dimethylphosphme
oxide. and the most convenient precursor IS the hydride complex IIa. Generally 0.01-0.1
mole% of catalyst is sufficient to carry out the hydrolysis. which suggests possible industrial applications.’ ’ A comparison of the effectiveness of the new catalyst for the hydration of acetonittile relative to some of those already reported is given in Table 1. Table
1. Comparison of Catalytic rZctivities for the Hydration of Acetonitrile
-
[PtH(PMeflH)(PMep)zH] [PtH(HzO)(PMe3bl[OHl IP~H(HzO)(PE~~~][OH] [PcKXOH)(bipy)(HP)j wRcwl lhl2 Pt(PEt& c232
9 N402.5
-
tmp , Turnover Frequency mol/(mol of cat. h) “0 - .-
Catalyst
90 78 78 76 x0 x0 x0 78
P&
NaOH
to Acetamide
_-
1rumover Tnol/(mol
Number of cat.)
5,700 S,OOO-6,000 not reported not reported 405 54 4,000
3x0 178 70 29 27 3
not reported 0.3
-
Reference this work 12 12 13 14 14 15 12
-
We have carried out hydrolyses with a range of nitriles. some of which are listed in Table 2 Table
Z.Yields and Turnover Frequencies Using IIa
.Nitrile
Isolated yield
Reaction medium at reflux temperature
.Acetonittile Acnylonitrile Benzonitrile 2,6-difluorobenzonitrile 3-cyanopyndine
Turnover Frequency mol/(mol of cat.h)
,of amide (%)
Water Aqueous Ethanol Aqueous Ethanol Aqueous tetrahydrofuran Water
--I 91 93 86 7x
380 1485 518 220
‘)I
450
Interestingly. although the catalyst IS a co-ordmation compound of platinum, the catalysis is not inhibited by co-ordination of the pyridine nitrogen in 3-cyanopyndine. The catalyst is especially active for the hydrolysisof acrylonitrile: 0.004 mol% of catalyst is sufficient. and the turnover number exceeds 50,000. The hydrolysis of acrylonitrile also provides a test of selectivity. as usually hydration of the carbon-carbon double bond competes wtth amide formation. 12 GLC analvcis of the reaction mixture selectivity to acrylamide of >99%
using IIa as catalyst shows a
The active catalyst appears to be cationic as, although Ilb is not active. it becomes so on reaction with Ag+. The cationic nature of the catalytic species is also supported by the fact that the catalysis can be stopped by adding halide ion. McKenzie and Robson Is attribute their comparatively high turnover number to an intramolecular attack by OH on a co-ordinated nitrile. In our system we find that the catalytic activity is
8659
RCONHz
-v
Figure.
J ‘:
Suggested Mechanism for the Hydolysis of Nittiles by Phosphinito Complexes.
lowered when one ot the phosph!)rus donors does not have a hydroxy substituent. Thus the catalyst derived from I[1 and AgBF, has less than h.llf the turnover rate of the catalyst derived from IIb and AgBF,. This leads u to huggrst attack by the hydroxhphosphine on the co-ordmated nitrile as shown in the catalytic cycle in the Figure. We have not found condltlons under wtuch free phosphine oxides catalyse the hydration of nitriles. Other authors have noted subxtantul rate Increases on comparing intramolecular and intermolecular reactions, and iritramolccullu
reactIon\ are important in enzyme rnimics.lh.!?
Expertmental Procedure The catal! st Ila was prepared ils ‘,u,,cycrcstedbv other uorkers X I8 by the reaction of (Ph,P),Pt of dimethylphosphme oxtde In tolucne
with an excess
Prrpnruric~r[ (q llu- Dimeth! iphosphlne aside (0 1tl~. 2.05 mmol) was added to a stirred suspension of Ptt PPh,), I().$. 0.107 mmol) in dp toluene ( 10 m:l ,~troom temperature under nitrogen. Almost immediately a coiourless solution uja> obtatncd. \+ htch was >tlrrcu for 1h. during which time the product begins to przclpitate. Preqitatlon waj completed h!, ad&tlon ot ðyl ether (30 ml) and after stirring for a further hour the product was filtered off. ua\hed with dtcthyl ctller and hexane and dried in vucuo. Yield: 0.13g, 7.i%.M.p.
131-7.3?“C. vIPtmfir 1’140 i‘m 1 t-ound (‘. I’.? H.;l 8. C,H2,qP,Pt
requires C.16.8; H,4.Y%.
Hxdrurii)r~ ii!‘.~-(.‘tltli,~?.riifllli’. .4 \ Igc)rou’\ly btirrcd nilxture of lla 15.0 mg. 0.01 17 mmol), .Qyanopyrldinz tj.Og. O.O?Y mo11 ,md w:tti’r (51nl. 0 277 mol) was heated under reflux for 5 hours. After cooilng the esces:, of water \v‘is remo\cd under rctiuc ret prcjsure to s’ve nicotinamide (3.2g. 91%). X1.p. 12% 130, Lltt. ” I ‘Y- ! .{(I”(‘ ti~drdrion ~)j~zc.r\loriitniL :\ L ~gori~ii\l! ,tt:-r?d m:\tl,rc of lla 16.8 mg, (!.0158 mmol). acrylonitrile (20.15g. 0.3X rnol). ethanol (15 ml) ‘111~1,~,itr~ j 1’ II:! 0 X? m01 I was heated undrr retlux for 15h. After cooling, the
\olvcnts \scrc e\ aporatcd io glvc .~~r~Imi~dc (2.5 032. ‘1 ;Cr I uhlch
was dned in IJQCUO.M.p. 83-85. Litt.”
PYY .-\c,kr~l,l~letfr~mcr;r. Vve th,mh the E.Ps.R C t<>r rhr ,ir\ard ot a pobtgradute studentship Xlutthey pit for c~loan 01 p!,mnum \alt\. Jnd Dr (‘ \L 131rd for useful discussions.
to T.G., Johnson
Rcfercnces I B.(’ Challts. A.J. Chaill\ in ( ,,rril)rc,il~r!\il.r, (:r~ciri~: c i~~,ni.srri \;I/.? rEds.D.Barton, W.D. Ollis), Pergamon.Oxiord.lY7Y.p 96J 2. L.A. Thompson. C.J. Knowlrs. E A Llnron. .I \I LL\.ltt. (‘I~em.Br, 1988,23.90(~. 3. F. blatsuda, Chem.T~i~.. 1Y 7 7.7.306 1. W Wolfsberger. C’il~n. -Zra 1 Y 88, II,‘.? 1.i 5. T. Gebauer. G. Frenzen. K. Dehmcke. % ,2’ut1crror\t /I 1 Y Y 2.3711. I SO5. 6. f? Leom. F.Mrlrchettl. MPasquah. J I)r:rz,fi,mer.i’iicn: , 1 YY3.rl_FI.C25. 7. T Ghaffar. 4. Kieszktewtcz. S.C. Kyburg, A.W. Parkms. Acru Ctysral1o~r.Secr.C , 199430,697. X. P.W.Iu‘.ll. van Leeuwen. C.F. Roobeek. J.H.G f.rJnc. r\.G. Orpen. Or~anomrrallics, 1990,9,1211. 9. D.M. Roundhill. R.P. Sperhne. W B. Bc~ultru. i‘~~-~>rd. Chem.Rev., 197826,263. IO. J. Chin, J.H. Kim, ;\npr\i. Ciwm Inr. Ed Enqi lYYO,2Y.57!. I 1. L’ K.PL~renr
Appfir~uann
3.506389.
17. C.hl. Jensen. WC Trogler. .I :\m C‘l~jn; .,‘(Jl, IYX(,.IIJX.7?3 1.3. (; Vill.un, G. Constant. .A GJiset. P. K,llck. J tlof (‘dral.. 10X0.7.355. I?. TYoshida.T.~latsud~.T.Okano.T.Kitan~. S.Ot\uka. .I .-lm C‘i~rm Sot 1979.101.2027. 15 C.J. hlcKenzie. R.Robson. .i C/~ern..So~,C‘licm (‘~~rr~rn;tn 19X8.1 12. 16. FM. hlenger, .4<,r‘ Cl~!m. Rrs.. I9 85.18.12~ 17. :I.J. Kirby. Aq:ew. Cilrm I/u Ed EnxI., IYYd.:‘.:.551. IX. \V.B. Beaulieu. T.13. Rauchfu~s. D.M. RoundhIll. !r~or,q.Chem 1975.11,1732. 19 I~ic~rrouu-v ojOrqc~r~;~~ C~~m~o~nd.s 5th Edition. Chapman and Hall. London. 1982.