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Jourruxl of lkfolecular Catalysis, 63 (1990) 14

Hydr oformylat ion of propylene to but yra ldehyde u singdichloro-bis(salicylaldehyde)-o-phenylenediiminatoruthenate(II1)M. M. Taq u i Kha n *, N. Su m ita R ae a n d S . B. Hal l igud iDiscip l in e o f Coord in a t ion Chem is t ry an d Hom ogen eom Cata l@s , Cat ra l S a l t an dM a r i n e C h e m i c a l s R e s ea r c h I n s t i t u t e , B h a m a g a r 3 64 0 02 c l n d i a )(Received J an ua ry 12, 1990; accept ed J un e 2, 1990)

Abs t r ac tBut yraldehyde is obtain ed by th e hydroformylation of propylene in aqueous mediumcat alysed by Ru*-saloph -CO comp lex at 27 aim CO + Ha (1:l) syn gas with CSHB:syngas rat io 1:5 an d 120 C with a tu rn over ra te of 17 mol product per mol catalyst perhour.

Synt hesis of aldeh ydes by th e hydr oformylat ion of ole6ns un der milder conditionshas been of great interest in recent year s [l-5]. The usua l cat alysts involve th e meta lcomp lexes of cobalt su ch as cobalt carbonyl [6, 71 an d ph osphin e-coord ina ted cobaltcarbonyl[8], which act at - 130-160 C an d 100-200 at m CO+H, (1:l). The commercialprepa ra tion of but yraldehyde by th e hydroformylatlon of propylene uses rhodium complexesas catalysts [9, 10 J . The advanta ges [lo] of th e rh odium complex ar e low tem pera tu re(SO-120 C), low pres su re of CO + Ha (7-30 at m) an d th e high er selectivity for th e m orevaluable hydroform ylation product butyr aldehyde.

There ar e reports in th e literat ur e ln which hydroformylation of propylene tobut yraldehyde was achieved u sing ru th enium complexes as cat alysts at 150 C an d 150a&n CO + H, (1: 1) [ 111. In th e presen t p aper we report t he hydroform ylation of propyleneto but yra ldehyde usin g [Ru(saloph )CO] comp lex at 120 C an d 27 atm CO+Ha (1:l).

E x p e r i m e n t a l m e t h o d a n d r e s u l t sThe complex [Ru(saloph)CO)] was pr epa red by th e report ed met hod

[ 121. The hydroform ylat ion of propylene was stu died in aqu eous medium ina 300 ml pr essu re reactor u sing [Ru(saloph)CO] comp lex. The bomb, cont ai-ning C3H6 at 4 at m, was pressu rized by CO + Hz (1:l) to th e desir ed valuewhen th e desired t emperat ur e was at ta ined. The reaction was cont inued for4 h; liquid sam ples were with dra wn from t he rea ctor at specified tim e int ervalsand analysed by GLC (Shimadzu GC - 9A) using a 10% Carbowax column.It was observed th at up t o 4 h only but yraldehyde wa s form ed, after whichmin or a moun ts of isobulyraldehyde began to form . Th e n:i ra tio was foun dto be 10: 1. On cont inu ing th e rea ct ion for a longer conta ct tim e ( > 6 h)th e forma tion of th e corr esponding alcohols of but yra ldehyde an d isobu-

*Author to whom correspondence should be addressed.

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2

tyra ldehyde was also observed. The product but yraldehyde was fur th er confir-med by ta king 13C NMR spectr a of et her extr act of th e reaction mixtu re.The spectr um of th e rea ction mixtu re showed pea ks corr espondin g to n-but yra ldehyde (13C 6 206 ppm for C=O) an d some un reacted pr opylene (13C6 115 and 136 ppm for alkene carbons and 18.7 ppm for CH, protons).The conver sion of propylene to but yra ldehyde a fter a cont act t ime of 4 hwas foun d to be 60%, an d th e tu rn over ra te for but yraldehyde form at ion is17 mol product per mol catalyst per hour. The reaction was also conductedat a tm osph eric pr essur e of CO + Ha (1:l) with C3HG:syn gas ra tio 1:5 an d50 C. The yields of butyraldehyde were reduced to half as compared toth e yields obta ined at 120 C an d 27 at m CO + Ha (1: 1).

The hydr oformylat ion of pr opylene to but yra ldehyde was also car r iedou t us ing [Ru(EDTA)CO] complex at 120 C an d 27 a tm CO + Ha (1: 1) withC,H,:syn gas ra tio 1:5. It was observed th at along with butyra ldehyde,isobutyraldehyde also formed from the second hour onwards. The yield ofbutyraldehyde was found to be about 15 times less as compared to the[Ru(saloph)CO] complex. The n :i r a t io for [Ru(EDTA)CO] complex was foun dto be 3.0, a nd the overall tu rn over r at e in ter ms of form at ion of both norm alan d isobut yraldehyde was 16 mol products per m ol cat alyst per hour .Discussion

The mecha nism for t he [Ru(sa loph )CO] complex cat alysed hydr ofor-myla tion of propylene to but yra ldehyde is sh own in Schem e 1.

In th e proposed mechan ism, in the pr esence of CO + Ha th e Ru(III) Schiffba se complex [LRuUIC1,]- is redu ced to LRu(C0) species 1, which is theactual catalyst in the reaction. Complex 1 reacts with Hz with a heterolyticcleavage of th e lat ter to form th e monohydrido species 2 in a pre-equihbr iumstep. In a second pre-equilibriu m st ep Ka, th e hydr ido complex 2 form s anint erm ediate mixed ligan d olefln complex 3 with a ra te-determ ining tr an sferof H to the olefin to form th e alkyl complex 4. F ast insert ing CO in 4 resu ltsin th e format ion of acyl comp lex 5, which un dergoes hydr ogenolysis in th epr esence of CO in a fast step t o form th e hydr ide 2 a nd the pr oductbut yraldehyde. Tr an sfer of the hydride in step 4 to the P-car bon at om resu ltsin th e forma tion of isobutyra ldehyde. In th e cat alysis by complex 1, Mar-kownikoff s addition of the hydride to the c+carbon atom is however favouredover th e tr an sfer to P-car bon at om; the lat ter however picks up slight ly withthe progress of the reaction. The formation of carbonyl complex 1 is supportedby th e IR spectr um of the complex in solut ion, wh ich shows a peak at 1970cm- an d also a LMCT ban d in th e electr onic s pectr um of th e complex at370 nm [ 13-l 51. The pr oton NMR of th e hydr ide 2 gives a mu ltiplet in th eregion -20.0 to -30.0 ppm . The inser t ion of CO in th e all@ int erm ediat ean d th e hydr ogenolysis of th e acyl int erm ediate ar e th e usua l fast st eps inth e hydr oform ylat ion cat alysed by cobalt an d rh odium complexes [ 16-181.The values of equilibrium constants K1 and Ka and the rate constant kobtained at 120 C are:

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2LR u C12 + 2C0 + Hz 0 fast- 2LRu (CO) + COz + 2HClI

LRu n CO + Hz & [LRu (CO)H]- + H*1 2

CH H (332[ LR u - CO (H )]- + ;H , &% Lk u n ---;H

AH , A0

AH ,

2 3H

LIAl(332

-__;H kA A

LRu -( CH,),CH,H ? A

3 4

LRju ( CH2)2CH, fast- LR u -CO-( CH 2),CH 35

CO + H2LR u -CO-( CH 2)2CH 3 p fast LRu CO( H) + CHO ( CH,),CH 35L = bis(salicylaldehyde)o-phenylenediimineScheme 1.

Kl = 18.0 M-&=27.0 M-k=8.3 min-The t u r n o v e r r a t e fo r t h e r e a c t i o n i s 1 7 m o l b u t y r a l d e h y d e p e r m o l c a t a l ys tp e r h o u r .

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4References

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