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Carboxylic Esters Produced by Low-Pressure Hydroformylation of Olefins in Benzil.

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shows the decrease in basal spacings between 30 and 90°C
in three sharp steps corresponding to the cooperative introduction of kinks into the alkyl chains; curve b) shows the
specific heat per mol of the tetradecanol complex of tetra-
value appears somewhat lower than the other two is probably due to looser packing of the chains in our model
system.
Reccivcd: June 29. 1973 [Z X X 7 II-]
German version: Angew. Chem. Ki. 915 (1973)
[I] S. Blosaiihrc.! and W Pcdiirolrl. Rheol Act;! 6. 174 11967): W f'ec hlrold.
Kolloid 2. Z. Polym 22N. I (1968)
[ 2 ] H A . Srrrurr, Ber. Bunsenges. I'hys. Chem. 74, 739 (1970): R. ffmc,iiiunir, ihirl. 7 4 , 756 (1970): W P i d i h o l d , E . Lrskrr, and A . B[rirniqurrwr.
Kolloid 2. 2. Polym. 250, 1017 (1972).
[3] W B<,ih/iold and B Stoll, Ber. Bunsengcs. Phys. C'hem. 74. XXX
(1970): B. Sroll, W Prcliliold. and S Bloseiihrn~.Kolloid 2. 2. Polym.
250. I I I I 1 1972).
[4] G. Lu~quly and A . Weiss. Kolloid 2. 2. Polym. 24X. 979 (19711.
Angew. Chem. 83, 580 (1971); Angcw. Chem internat. E d t 10. 558
( 197 I). 1 Wc.i.\.s. J Spits.\, E. Sfrikr. and G . L N ~ u /2.
Y .Natcirforsch.
276.31 7 ( 1972).
30
10
50
1188721
T
60
i"C1-
70
80
90
[5] G Wihsrr. and P. C. H i r g r k . Ber. Bunsenges. Phys. Chem. 74. X96
(1970). S. Blusrithri,i. and W Prdrhold. ihirl. 74. 784 ( 1970): P. C . f l r i g d r ~
and W Prdihold, Kolloid 2 2. Polym. 2 4 1 . 977 11970).
Fig. 2 Change of basal spacing d, (a) and specific heat cD(b) of n-tetradecylammoniurn-beidellite.'n-tetradccanol with temperature (the cp values
are referred t o 1 mol of n-tetradecylammonium-beidellite).
Carboxylic Esters Produced by Low-Pressure
Hydroformylation of Olefins in Benzil
decylammonium-beidellite. c,does not change continuously, but shows three distinctly marked transitions similar to
h-transitions occurring at the same temperatures as the
steps in the basal spacing.
Tahle I . Transition enthalptcs and entropies in the system ii-tctradecylamrnonium-beidellite, ii-tetradecanol.
Transition
temp. [ C]
AH
[kcal moll
[a1
50
60
72
0 73
0 72
0.68
AS
[cal deg moll
[a1
By Kuspar Bott[*l
Hydrogenation (a)and hydroformylation (b)of olefins catalyzed by transition-metal carbonyl complexes differ in that
in the latter reaction the addition of hydrogen is coupled
with insertion of carbon monoxide. We now report a new
variant (c)of hydroformylation in which hydrogen, carbon
monoxide, and benzil react with the olefinic double bond
in a definite order.
I
I
I
I
H-C-C-H
I
I
I
I
H-C-C-CHO
23
2.3
(1)
2.3
[a] Per mol of betdcllite.
From the c, values the transition enthalpies can be determined by graphical integration and the transition entropies
from the c,/T-values (Table 1). Each set of values is of the
same order of magnitude for each transition. Per formula
unit of the layer silicate, 0.43 alkylammonium ion and ca.
1.58 alkanol molecules are bonded so that a total of two
alkyl chains is present.
Since these chains are arranged as a bimolecular film, there
are two alkyl chains per formula unit of silicate standing
upon each other. Therefore: each step with a shortening of
basal spacings by 1.2-1.3 A corresponds to the formation
of one 2gl kink in one of the two chains only. The enthalpy
and entropy changes shown in Table 1 thus refer to formation of one isolated kink in one of the two alkyl chains.
The increase in entropy by a constant amount probably
indicates that the transition between individual phases is
caused by introduction of one further 2gl kink into the
alkyl chains and not (or very rarely) by rearrangement of
2gl kinks into kinks of higher order as ...tttgtgttt ... ( = 2gl)
+ ... ttgtttgtt ... (= 2g2) + ...tgtttttgt ... ( = 2g3).
A transition enthalpy of 0.7 kcal/mol is evaluated from the
experimental data. This is of the same order as the values
calculated for kink formation in an isolated n-alkyl chain
(1.2 kcal/mol) and in a bundle of parallel polyethylene mol~ . fact that the experimental
ecules (0.95 k ~ a l / m o l ) [ ~The
The x-benzoylbenzyl carboxylates (3) formed in this way
can be regarded formally as the result of a TishchenkoClaisen reaction between the aldehyde ( 1 ) (formed by
hydroformylation, i. e. an 0x0 synthesis) and benzil ( 2 ) .
This synthesis requires low pressures of synthesis gas and
presence of a rhodium catalyst. The determining intermediate appears to be an acylrhodium compound ( 5 ) containing a benzil ligand in addition to carbon monoxide; this
complex either reacts with hydrogen to give an aldehyde
( 1 ) or undergoes insertion of (2) to yield the ester precursor ( 8 ) . Finally the rhodium-carbon bond of ( 8 ) suffers
fission by hydrogen.
As the first three examples in Table 1 show, benzil ( 2 )
can be converted into the ester ( 3 ) in 80-87% yield
[*] Dr. K. Bott
Forschungslahoratorien der Chemischc Werke Hiils A G
437 Marl (Germany)
851
\
,c=C
/
\
+H2+cO+L
I
I
I
I
H-C-C-
+Rh,Ol
+ co
I
H-7-7-
1
I
I
I
I
H-C-C-
+
c =O
Rh(CO),L
1.
+ Hz
I
+ RhH(CO),L
CHO
t(2)
2 . t El2
I
H-7-7-
I
Benzil
L = (2)
I
P
66
O=C-CH
-
I
H-C-k-
c=o
I
P ?
+ (6)
I
p
=
(8)
gas pressure (molar ratio CO/H2 = 1 : 1) is increased to
120-140 atmospheres, the yield of x-benzoylbenzyl cyclohexanecarboxylate is then only I6 %.
The efficient catalysis of double bond migration by the
rhodium-benzil system is surprising; this is shown convincingly by the equality of the isomer ratio of Cs aldehydes
obtained from both 1-butene and 2-butene (Table 2)[11.
Analogously, the hydroformylation of 1-hexene and 1octene gives rise to formation of branched aldehydes, which
must be attributed to the presence of olefins with double
bonds in the “interior” of the chain. The 0x0 synthesis
with I-octene afforded, after 62 % conversion, a residual
olefin containing less than 4% of “x-isomer”.
Table 2 also presents the isomer distribution of the esters
(3) It turns out that approximately the same proportions
of unbranched aldehydes and unbranched carboxylic esters
are formed from 1. and 2-butene and propene. with higher
olefins the proportion of unbranched carboxylic acid in
(3) is very little changed but that of branched aldehyde
is increased.
If the phosphane-containing complex RhH[P(C6H5)3]zC0
is used instead of rhodium oxide as catalyst for the Iowpressure hydroformylation of propene in benzil, the n/iso
ratio rises to 69: 3 1 for hutyraldehyde and to 68: 32 for
the butyric ester.
Table 1. 9-Benzoylbenzyl carboxylates ( 3 ) from benzil ( 2 ) , olefins, and
synthesis gas [a]
I-Butene
Isobutene
Cyclohexene
1 -Hexene
I-Octene
Cvclododecene
Pressure of
synthesis gas [atm]
(H2/CO=I:1)
(3),
yield
25-35
35-45
25-30
30-35
30-40
50
87
80
80
65
18 [el
25 m
[el
~~
[YO] [b]
L
s
+ 16)
131
when the reaction is carried out with lower olefins, but
the yields decrease considerably with I-octene and cyclododecene owing to the lower molar olefii conversions.
Starting
olefin
p
63
& g ( c o ) &
( 7)
I
H-C-CI I
C=O
I
+ Ii2
1
(31,
m. p. [ C] or
b.p. [ C/torr]
150- 153/0.1 [d]
56 57
100-101
163-16710
175-180/0
100-101
Y
1 [d]
I [d]
-
.
[a] General conditions of the synthesis are described in the example.
[b] Olefin and b e n d ( 2 ) were used in equal amounts by weight: the
yields refer to benzil.
[c] Total pressure of CO, H 2 . and isobutene.
rdl Mixture of isomers shown in Table 2.
[el Conversion of olefin = 62%.
[fl Conversion of olefin = 76 %.
__
As required by the mechanism proposed, the proportion
of benzil incorporated into the ester (3) increases with
Table 2. Isomer distribution of the hydroformylation products ( I i and (3) from ti-olefins.
Olefin
Aldehyde I J
Rel.
yield
Carboxylic acid in ( 3 )
[“/.I
[“’OI
_ _ _ _ ~ ~ _ _ ~ _
Propene
_____._.
2-methyl propionic
Butyric
49
51
61-58
39- 42
2-Methylbutyric
Pentanoic
57--58
43- 42
2-ethyl pentanal
2-Methylhexdnal
Heptdnal
17
48
35
2-Ethylpentanoic
2-Methylhexanoic
Heptanoic
13
41
46
2- Propylhexanal
2-Ethylheptanal
2-Methyloctanal
Nonanal
13
17
41
29
2- Propylhexanoic
2-Ethylheptanoic
2-Methyloctanoic
Nonanoic
9
I2
33
46
~
2-Butene
50
50
2-Methylpropanal
Butanal
Rel.
yield
~
~
_
2-M et hyl butanal
Pentanal
_
_
~
~~
I-Hexene
~~~
I-Octene
increasing concentration of benzil in the reaction solution
and with decreasing partial pressure of carbon monoxide
because the rhodium complexes ( 4 ) - ( 6 ) and ( 8 )
exchange the benzil ligand in a reversible reaction for
carbon monoxide. If, in the example below, the synthesis
852
The selectivity for conversion of the olefins into aldehydes
(1) and esters (3) exceeds 90%[41. Reaction of the alkene
with benzil ( 2 ) and hydrogen, which would lead to the
ether (7), could not be detected even in absence of carbon
monoxide.
Anyru,. Chem. internar. Edit.
1 Yo/. 12 ( 1 9 7 3 ) N o . 1 0
C~~~Iolir.~trrircarbaldehpdc
atid cw-bmzoylbeiizyl cjriohrxat~ecurbos~~latr
Cyclohexene (250g, 3.05mol), benzil (250g, 1.19mol), and
R h 2 0 3(0.10g) are placed in a 2-1 steel autoclave previously
purged with nitrogen and are heated at 120 C with synthesis gas (20atm cold pressure). The synthesis gas pressure
is raised from 25 to 30 atm during the reaction. After 11
hours' reaction, distillation of the autoclave content affords
cyclohexanecarbaldehyde (146 g) boiling at 5&56 "C/17
torr and a-benzoylbenzyl cyclohexanecarboxylate (308 g,
80% yield based on benzil), boiling at 175-177"C/0.2 torr,
m.p. 100-101 "C (from light petroleum).
Received. May 23. 1973, revised: July 10, 1973 [Z 890 IE]
German version: Angew. Chem Xi. 911 (1973)
'H-NMR (ext.TMS,otherconditionsasabove)["I: I C H ~ P A
8.82ppm, d, J(HCPA) 8.1 Hz; sCHJPF~8.10, d, J(HCPs)
13.4; ICH~PC8.02, d, J(HCPc) 13.5; sCH~PB9.60, dd
(broad), J(HCP,) 16.1, J(HCPA) 2 13: rCH2Pc 9.48. dd
(broad), J(HCPc) 16.2, J(HCPA) -6.
However, when the above-mentioned reactants are mixed,
not in ti-pentane, but in tetrahydrofuran at 0 C, or when
the product (2) is treated in that solvent with an excess
of the ylide, a colorless precipitate of tetramethylphosphonium chloride is formed together with a yellow product
(3) that is soluble in ether, benzene or toluene and is
volatilc in a vacuum (sublimes at 45 Ci0.I torr. dec. 87 C;
yield 23%); at the same time a second molecule of trimethylphosphane is liberated [eq. (Ib)].
[ I ] In contrast t o hydroformylation with cobalt catalysts, olefin isomerization duc to rhodium catalysis I S completely suppresscd by complexing
agents such as phosphanes [2. 33.
[2] B. F r l l . M! Riipi1fii.s. and F . A.siiiyer. Tetrahedron Lett. 1'368, 3261.
[3] J . H . Croddock. A . Hcrslrmuri, F . E. Prriilib, and J . F. Roih, Ind.
Eng. Chem Prod. Rcs. Develop. X , 291 (1969).
[4] K. B o i f . DOS 2306405 (1973), Chemischc Werke Huls.
Tetrakis(dimethy1phosphoniumbismethylide)dinickel, a New Type of Cage Compound
By Hans Heinz Karsch and Hubert Schmidbaur"'
It was shown recently that metal-carbon o-bonds of ylide
complcxcs itre appreciably more stable than those of simple
alkyl derivatives. The effect of introducing of an "onium
center" on otherwise unstable M-C structural units is
exemplified by the unusual properties of the copper compound ( I ) and its homologsf'.21.
We now report the synthesis of an analogous nickel compound that has a binuclear structure with no less than
four Ni-C 0-bonds attached to each of the two d8-nickel
atoms.
Reaction of dichlorobis(trimethy1phosphane)nickel with
trimethylmethyleneph~sphorane[~~
in n-pentane at room
temperature affords a golden-yellow product (dec. 125 C;
yield 93 YO),
whose composition is almost independent of
the molar ratio of the reactants and which is insoluble
in that solvent or in diethyl ether but soluble in methylene
chloride. From the analytical data and particularly from
'H- and 3'P-NMR findings it is concluded that it has
the salt-like onium structure ( 2 ) , formed as shown in
eq. ( I a).
3'P-NMR (CH,Cl,, 85% H,PO,,H-decoupled, -40"C)f41:
6PA +19.9ppm, d, J(P,NiCP,) 15.2Hz; 6P, -23.6, dd,
J(P,CNiP,) 3.4; 6Pc -24.5, d, J(PANiCPc)0.
[*] Prof. Dr. H Schmidbaur and Dipl.-Chcin H. H. Karsch
lnstitut liir Anorganische Chemte der Universitiit
X7 Wiirzburg, Am Hubland (Germany)
The complex ( 3 ) formed by two-fold metalation of the
ylide is shown by cryoscopic determination of its molecular
weight to be a dimerc5]. The molecular ion of the dimer
appeared in the mass spectrum only at low ionization
energies and high target temperature ( I 8 eV, 85 C), but
then had the expected isotope distribution. Spectra measured at 70eV and 30 C, however, show only the ions
of the monomer f4)f61.
The 'H-NMR spc'c'tra of toluene solutions show only two
I : 1 doublets u i t h ;I 3 . 2 ratio of areas in the temperature
range +80 to -80°C: rCH,P 8.77 ppm, J(H,CP)
- 11.9Hz; rCH,P 11.9, J(H,CP) -4.8. P-Decoupling leads
to singlets. Double-resonance experiments prove that
J(H2CP) and J(H3CP) have the same sign. In the Hdecoupled "P-NMR spectrum 6P. at 1.7 ppm. appears
in the region for tetracoordinated onium centers['! The
IR and Raman absorptions correspond largely to those
of ( I ) and its homologs: strong bands at 665, 638 and
467cm-' can be assigned to vibrations of the skeleton
of heavy atoms.
Taking our results as a whole we propose for (3) a structure
in which two parallel square-planar Ni(CH2)" units''] are
bonded together by four dimethylphosphonium groups.
Models indicate that such a type of bonding can be strainfree. In this structure the eight-membered ring unit of
( 1 ) is present twice, as in the string by which a parcel
is tied up. It is conceivable that the monomer ( 4 ) is
in equilibrium with (3) under the conditions of the mass
853
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