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Chlorocarbon Activation Catalytic Carbonylation of Dichloromethane and Chlorobenzene.

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yield phenyl complexes of type 6. Further, 6a, can be rapidly
carbonylated (25 "C, 30 bar CO) to yield 7a; the reaction is
reversible at 60 "C under argon.
[Pd(PR,),(dba)] 1, PR, = PCy, (la), PCy,Ph, P(CH,Ph),, PiPr,
trrms-[Pd(PR,),(C,H,)CI] 6, PR, = PCy, (6a)
trans-[Pd(PR,),(COC,H,)Cl]7, PR, = PCy, (7a)
The substituted chlorobenzenes,p-RC,H,Cl (R = OCH,,
NO,, COOEt) also react to form complexes analogous to
7a, the rate of reaction decreasing in the order R =
NO, > COOEt $ H > OCH,. The X-ray structure analysis
of the adduct, 6a,['01confirms the trans arrangement of the
phenyl- and chloro-ligands (Fig. 2).
Fig. 2. Structure (ORTEP) ofcomplex 6a. Principal bond distances [A]: Pd-PI
2.343(1). Pd-P2 2.347(1), Pd-CI 2.403(1), Pd-Cl 2.004(6); selected bond angles
['I: PI-Pd-P2 173.9815). Cl-Pd-C1 177.5(2), Cl-Pd-PI 90.07(5), CI-Pd-P2
90.05(5). C1-Pd-PI 90.4(1), CI-Pd-P2 89.8(1).
Under suitable conditions, the activation and functionalization of these chlorocarbons can be carried out catalytically with 1 a. Thus, the carbonylation of CH,CI, to ketene
(or its derivatives) is possible if the complex 3 formed
from l a can be reduced to regenerate the active species
Pd(PCy,), . This has been carried out using H, and a base B
to trap the HC1 formed as BHeCI'. However, B must be a)
a poor nucleophile (e.g. sterically hindered) to minimize
chloride displacement in 2a and quaternization of CH,Cl,,
but b) more basic than PCy, to prevent protonation of the
phosphane. Excess PCy, is used to maintain Pd(PCy,), as
the predominant species of Pdo even under CO pressure. To
illustrate the catalytic formation of ketene, NCy,H was used
as base so as to trap ketene by its reaction with the N-H
function to form CH,CONCy,, which is stable under the
reaction conditions and readily quantified. Hence, using 1 a/
PCy, (1 :3), CH,CI, (25 equiv.) and NCy,H (50 equiv.) in
toluene at 280 "C under CO/H, (30 bar, l / l ) a 40% yield of
CH,CONCy, and CH,NCy, ( l / l ) is formed over 2.5 hours.
Using NEtiPr, as base under the same conditions, both
CH,CONiPr, and CH,CONEtiPr were produced at a turnover rate of 5 (mol Pd)-' h - ' .
With chlorobenzene, two catalytic reactions were studied:
alkoxycarbonylation and hydrocarbonylation with 1 or 6 as
catalyst. The equations (a) and (b) show examples.
Angeu. Chrm. In(. Ed. Engl. 2R (1989)
No. 10
+ CO + ROH + B + C,H,COOR + BHeCle
+ CO + H, + B +C,H,CHO + BH@Cle
B = base
Typical conditions for these reactions are presented in the
Experimental Section, but we note:
1) Significant catalytic activity is found only with phosphanes which are both strongly basic (pK, > 6.5'"') and with
well defined steric volume, i.e. the cone angle 0"21must exceed ca. 160" but be less than 180". Hence in alkoxycarbonylation [Eq. (a)], only PCy, (pK, 9.7,O = 179")and PiPr, (pK,
8.7, 0 = 160") gave active catalysts, complexes involving
smaller (PEt,, pK, 8.7, 0 = 130"), larger (PtBu,, pK, 10.3,
0 = 182") or less basic phosphanes (P(CH,Ph),, pK, 6.0,
0 = 165"; PPh,, pK, 2.9, 0 = 145") being totally inactive.
Using methanol, both C,H,COOMe and C,H,COOEt were
observed, the latter resulting from metathetical alkyl exchange with the base NEt,. No double carbonylation products were
In hydrocarbonylation [Eq. (b)], the
use of PCy, and PiPr, again gave the highest activity, other
phosphanes studied giving either inactive (PPh,, P(m-tol), ,
PPh,Bu, P(CH,Ph),) or poorly active (PEt,, PnBu,, PtBu,)
catalyst systems. The only products detected were
C,H,CHO (ca. 90%) and C,H, (ca. loo/,).
2) On addition of excess phosphane to the catalyst system
a) the Pd catalyst is more stable to decomposition and b) the
rate of catalysis increases until a certain phosphane concentration is reached. Further addition of phosphane beyond
this optimum value causes a decrease in the reaction rate.
Thus, on using 6 a as catalyst, addition of 3 equiv. of PCy,
increased the rate of hydrocarbonylation fourfold. However,
if a further 5 equiv. of PCy, are added, the rate now observed
is only twice that found initially. The optimum concentration of phosphane depends on the conditions used and, in
general, increases with increasing CO pressure.
3) The nature and concentralion of the base B are both
important. The base must have a pKa higher than that of the
phosphane used if the phosphane is not to serve as proton
acceptor. Further, the rate of hydrocarbonylation increases
with increasing concentration of base used. Hence on doubling the base concentration under standard conditions, the
catalytic rate increases from I .9 to 3.4 (mol Pd)- ' h ', the
selectivity for C,H,CHO remaining constant.
The observation that a maximum rate occurs for a certain
phosphane concentration can be related to two opposing
effects. Firstly, an increase in phosphane concentration will
increase the concentration of the C-C1 activating species,
Pd(PR,), , with a concomitant decrease in inactive carbonylcontaining species. A rate increase is thus expected but will
only occur if the phosphane is sufficiently bulky to prevent
further formation of less reactive Pd(PR,), (n = 3,4) species.
Secondly, the rate limiting step in such reactions is the baseassisted alcoholysisr'31or hydrogenolysis of 7 which is inhibited by phosphane, addition of which will thereby cause a
decrease in rate.
In conclusion, although the catalytic reactions of bromoand iodo-aromatics are weJl known," 3l the analogous
chloro-derivatives have resisted functionalization except
when coactivated by coordination to a tricarbonylchromium
moiety.['41 The molecular Pd complexes reported here show
a well defined window of reactivity imposed by the electronic
and steric properties of the phosphane ligands. Further, despite our preconceptions, the C-CI activation of CH,C1, and
C,H,CI is not rate limiting in the catalytic process and, unexpectedly, is comparatively facile.
VCH Verlugsgesellsrhafi mbH. 0.6940 Weinheim, 1989
Experimental Procedure.
Synthesis of 2a: 186 mg (0.2 mmol) of I a were dissolved in CH,CI, (10 mL).
After 15 min, the red solution had turned yellow. The solvent was removed, and
the recovered solid washed with 2 x 10 mL Et,O and recrystallized from 1 : 1
(CH,),CO/Et,O to yield colorless microcrystals. Yield 95 mg (65 %). 'H NMR
'J(P-H) = 8 Hz, 2 H , Pd-CH,CI). 1.20-2.66
(200 MHz, C6D& 6 = 3.92 (I.
(m, 66H, C,H,,P); " P ( ' H } N M R (80 MHz, C,D,): b = 24.0(s); IR (nujol)
S[cm-'] = 650 (C-CI); MS: mi: = 715 (Me-C1), 701 (Me-CH,CI).
Synthesis of 6 a : 1.3 g (1.44 mmol) l a were dissolved in C,H,CI (100mL) and
the solution heated at 60 "C for 2 h and filtered to remove traces of metallic Pd.
After evaporation of the filtrate, the resultant colorless solid was washed with
ether (50 mL) to extract free dha. Yield 850 mg (76%). Crystals suitable for an
X-ray structure determination were obtained from toluene solutions. 'H NMR
(200 MHz, C,D,): 6 = 7.74(d, 2 H , H ortho), 7.13 (t. 2 H . H meta), 7.00(t. 1 H.
H para), 1.2- 2.35 (m, 66H. C,H,,, P); "P('H) NMR (80MHz. C,D,):
6 = 22.9(s). Satisfactory inicroanalyses (C,H.P.CI) were obtained. Similar procedures were used for other phosphane complexes 6. and substituted chlorobenzenes.
Carhonylation of 2a: a solution of 400 ing 2a in C,D, (10 mL) was stirred at
room temperature under CO (30 bar). Sample were analyzed periodically by 'H
and 3 i P ( ' H } NMR. The reaction wascompleteafter48 h, giving3and diketene
4 quantitatively.
Catalytic experiments werecarried out in a 125 mL autoclave (Hastelloy HB2):
A typical experiment used: Pd complex (1 mmol), PCy, (total 5 mmol). CO
(15 bar), C,H,CI (SO mmol), NEt, (55 mmol), in toluene (total volume 30 mL).
180 'C. In reaction a) CH,OH ( S O mmol) was added: in reaction h) HL(15 bar)
was used. The Pd catalysts originally used were 1 or 6 with 3 equiv. of PR, in
addition. hut their generation in situ under the appropriate conditions by use of
Pd(CH,COO), with 5 equiv. of phosphane was found to give similar behavior.
Products from a) were C,H,COOR where R = CH, or C,H, with turnover
rates of ca. 1.2 (mol Pd)-' h - I . Products from h) were C,H,CHO and C,H,
(selectivityca.9:l) witha turnoverrateof1.9 (mol Pd)-' hK1.Usingnoexcess
PCy,. a r a t e o f O S ( r n o l P d ) - ' h - ' w'as observed. Using 110 mmol NEt,, the
rate of 3.4 (mol Pd)-' hY' was measured.
Received: May 8, 1989
revised: July 19. 1989 [Z332613327 IE]
German version: Angex. Chem. 101 (1989) 1427
CAS Registry numbers:
l a , 122744-44-9; 2a. 122700-57-6; Zb,122700-59-8; 3,78655-99-9; 4,674-82-8;
6a, 122700-58-7; 7a, 122700-60-1 ; CH,CI,. 75-09-2; C,H,CI, 108-90-7;
CH,Br,, 74-95-3; NCy,H. 101-83-7; CH,CONCy,. 1563-91-3; CH,NCy,,
[l] a ) Y. C. Lin. J. C. Calabrese, S. S. Wreford, J. Ani. Chem. Soc. 105 (1983)
1679; h) M. J. Krause. R. G. Bergman, ihid. 107 (1985) 2972.
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Angeir. Chem. 94 (1982) 74; Angex. Chem. hit. Ed. Engl. 21 (1982) 73;
Angex.. Chem. Suppl. 1982, 1; c) H. H. Murray, J. P. Fackler, A. M. Mazani, Orgunometullics3 (1984) 1310; d) B. Kellenherger, S. J. Young. J. K.
Stille, J. Am. Chem. Soc. 107 (1985) 6105; e)T. Yoshida, T. Ueda, T.
Adachi. K. Yamamoto, T. Higuchi, J. Chem. Soc. Chem. Cornmun. 1985,
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[3] a) W L. Olson, D. A. Nagaki, L. F. Dahl, Organome/a/lics5 (1986) 630;
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A. von Zelewsky, Nelv. Chim. Acta 6Y (1986) 1855.
[4] M. Huser, .I.A. Oshorn. unpublished results.
[5] For path A see: S. I. Hommeltoft, M. C. Baird, Organometallicr 5 (1986)
161 For path B see: a) A. Miyashita, R. H. Gruhhs, Tetruhedron Lett. 22
(1981) 1255; h) A. Miyashita, H. Shitara, H. Nohird, J. Chem. Soc. Chem.
Commun. 19R5.850; c) 0rganometuNL.s4 (19x5) 1463; d) B. Cetinkaya, P.
Dixneuf, M. F. Lappert, J. Chcm. Soc. Chem. Commun. 1973,206; e) T. W.
Bodnar, E. J. Crawford, A. R. Cutler, 0rganonietuIlic.s 5 (1986) 947;
f) C. A. Ghilardi, S. Midollini, S. Moneti, A. Orlandini, J. A. Ramirez, J.
Cheni. Soc. Chem. Commun. 1985, 304.
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(1971) 279; h) M. Hidai, Y. Uchida, I. Ogato, Urgunotranszrion MEI.Chem.
Proc. Jpn-An?. Semin. ls/ (1974) 265; Cliem. Abstr. X6 (1977) 42 729; c ) S.
Otsuka, K. Tani, I. Kato. 0. Teranaka. J. Chem. Sor. Dnlron Trans. 1574,
2216; d ) M. Uchino, K. Asagi, A. Yamamoto, S. Ikeda, J Orgunornet
Chem. R4 (1975) 93; M. Uchino. A. Yamamoto, S. Ikeda, ihid. 24 (1970)
C63; e) M . Foa, L. Cassar, J. Chem. SOC.Dalton Trans. IY75.2572; 0 P. E.
Garrou, R. F. Heck. J. Am. Chem. Soc. 5R (1976) 4115; g) M. Troupel, Y.
Rollin, S. Sibille, J. F. Fauvarque, J. Perichon, J. Chem. Res. Synop. 1980,
24. 147; h) T. T. Tsou, J. K. Kochi. J. Am. Chcm. Sac. 101 (1979) 6319;
i) D. R. Fahey, J. E. Mahan. ihid. Y9(1977) 2501 ;j) A. Morvillo. A. Turco.
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(> VCH Ycrlagsgesell.srhufimbH. 0-6940 Weinheim. 19x5
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P2,;c; a = 17.686(6),
[lo] Crystal structure analysis of 6 a : C,,H,,P,CIPd;
h = 9.656(4), c = 27.845(9) A, = 101.04(2)-, V = 4667.3 A' and Z = 4.
p,,,, = 1.241 g ~ m - ~(CU,,)
~ ,
= 4 . 7 c m - ' . Philips PW 1100j16 diffractometer; 173K; 5312 measured reflections, averaged to 5195. of which
3827 observed ( I 2 3411; R = 0.054, R, = 0.075).
[ I l l W A. Henderson, Jr.. C. A. Streuli, J. Am. Chrm. Soc. R2 (1960) 5791.
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1141 R. Mutin, C. Lucds, J. Thivolle-Carat, V. Dufaud, F. Dany, J. M. Basset.
J. Chem. Sol,. Chrm. Commun. 1988. 896.
Pronounced Anion Dependence
of Valence Detrapping Temperature in
Mixed-Valence l',l"'-Disubstituted
Biferrocenium Salts **
By Robert J. Webb, Arnold L. Rheingold, Steven J. Geib,
Donna L. Staley. and David N . Hendrickson *
The study of intramolecular electron-transfer events in
mixed-valence metal complexes [ I 1 in the solid state has given
fundamental information about environmental effects on
rates of electron transfer. The lowest-energy electronic states
are vibronict2]and as a result mixed-valence complexes are
very sensitive to their environments. The sensitivity to solvate molecules (S) has been demonstrated for mixed-valence
p-0x0-centered [Fe,O(O,CCH,),(py),] . S complexes.[31
However, little is known of what effect a change in counterion has on the rate of intramolecular electron transfer in
binuclear o r trinuclear mixed-valence complexes. In this paper we report dramatic changes in the temperature of valence
detrapping which occur for the mixed-valence l',l"'-diiodobiferrocenium and related cations as the anion is changed
(see 1).
X = I , Br. CI. CH2C,H,
Y = I,.SbF,,PF,
Detailed physical data have been presentedr4] for the I,"
and Br-I-Br' salts of various 1',1"'-disubstituted biferrocenium cations. The I," salts of the l',l"'-dibromo- and l',l"'diiodobiferrocenium cations are valence detrapped (one
[*] Prof. Dr. D. N. Hendrickson
Department of Chemistry, D-006
University of California at San Diego
La Jolla, CA 92093 (USA)
Prof. Dr. A. L. Rheingold, S. J. Geih. D. L. Staley
Department of Chemistry, University of Delaware
Newark, DE 19716 (USA)
R. J. Webb
School of Chemical Sciences. University of Illinois
Urbana. IL 61801 (USA)
This work was supported by the U.S. National Institutes of Health
(HL 13652).
A n p r . Chem. Inz. Ed. EngI. 2R (1989) No. 10
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carbonylation, chlorobenzene, catalytic, activation, dichloromethane, chlorocarbon
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