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Separation of Steric and Electronic Effects in the Reaction Enthalpies of Association of Phosphorus Ligands.

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every subsequent ligand association leads to a reversal of the product
ratio of ( 4 ) and ( 5 ) .
[S] J . Kluth, Dissertation, Universitat Essen (GHS), planned for 1979.
[9] H . Schenkluhn, W Scheidt, B. Weimann, M . Ziihres. Angew. Chem. 91,
429 (1979); Angew. Chem. Int. Ed. Engl. 18, 401 (1979).
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1
Separation of Steric and Electronic Effects in the Reaction Enthalpies of Association of Phosphorus Ligands[**l
lll-/Jl
e
2
By Hartmut Schenkluhn, Walter Scheidt, Bruno Weimann, and
Manfred Ziiltres[*]
In homogeneous transition-metal catalysis the addition of
Lewis bases (e.g. phosphanes and phosphites) plays an important role, since the catalytic reactions can then be varied
within wide limits. Hence, data for characterization of the
metal-ligand bonding are of special interest for gaining an
insight into the directing influence of such ligands.
Only very few quantitative results have so far been reported
in this connection. An attempt has been made to describe
the bonding character in rhodium(1) complexes by resolution
into predominant covalent and electrostatic components"].
Fig. 3. Partial control maps (a) for the distribution of oiigomers: product
distribution in mol- % referred to converted butadiene; (b) the distribution
of dimers. sum of dimers equals 100%.
Figure 3 b shows the ratio of the dimers ( 4 ) - ( 6 ) as a
function of Ig[L],/[Ni],.
Several association processes are
recognizable. The controlling first association of the ligand
occurs at different ligand/metal ratios depending upon the
product. Consequently, the respective intermediary complexes
should be kinetically separated according to Figure I c . It
is interesting, moreover, that in the case of ( 4 ) and ( 5 ) there
are two different association processes['1 (cf. Fig. 1a). Thus,
for interpretation of this finding it is necessary to postulate
multiple associations of the controlling ligand and several
partially kinetically separated intermediary complexes for
which the range of existence can be given[81.
In the case of homogeneous metal-catalyzed reactions the
concentration-control maps can be used not only for the
analysis of the mechanisms (minimum number of intermediary
complexes and their coupling) but also for the following:
1) optimization of the catalyzed processes, 2) comparison of
catalysts, 3) determination of the limitingconditions for separation of the thermodynamic and kinetic selectivity as prerequisite for recognition of property-specific control and thus e. g.
separation of the steric and electronic influence of ligands['I.
(21
(1)
Table 1 . Reaction enthalpies of association of phosphorus ligands to ( 1 )
(corrected for tlic lie;it\ (11 inlying o f the ligands): enperimcnt:il conditions:
T = 273 K ; ( 1 ) 0.05 bl in tetralin, L : addltion of 1 bl tetralin solution.
'
~-
~
-.
~~
x,
No. Ligand L
0,
[cm-'1
["I
0.2
12.6
2.0
3.1
10.6
4.8
4.2
7.9
10.3
9.2
5.6
16.8
8.0
18.9
18.9
28.0
28.9
20.2
19.5
23.7
15.5
29.2
171
145
167
160
__
A H , , , [a]
[kJ/mol]
AHC8ic
[kJ/mol]
~
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Received: January 8, 1979 [Z 204a IE]
German version: Angew. Chem. 91. 428 (1979)
19
20
21
22
CAS Registry numbers:
( I ) , 676-22-2; ( 2 ) , 706-31-0; ( 3 ) . 2765-29-9; (41, 1552-12-1; (S), 100-40-3;
(61, 22038-68-2: butadiene, 106-99-0; Ni, 7440-02-0
P ( ~ - C ~ H ~ ) ( C - IC) Z ~ H I
P(C6Hs)3 [b]
P(t-C4H9)(i-C3H,)*
P(i-C3H7)3
P ( C ~ H S ) Z ( C ~ [bl
HS)
P(n-C3H7)3
P(n-C4H9)3
P(C~HS)(CZHS)Z
~ ( C ~ H J C H[b]
Z)~
P(C~H~)(CH~)Z
P(CZH,)~
P(C6HS(O-CIOHI9)2 [c]
P(CH,)3
P ( O - C I O H I ~ )[c]
~
P(O -i-C3H7)3
P(O-O-C~H~CH~)~
P(O - ~ I - C ~ H A C ~ H ~ ) ~
P(0-CrHs)z
P(O-II-C,H~)~
P(C6Hs)(O--Cc,Cl -12
P(ChH5)2(O-CZHsI [h]
P(O-ChHsJ3
-_
_
~
.
_
71
75
86
91
141 99
132 103
132 108
136 110
165 113
127 113
132 113
142 117
118 120
140 121
77
(112)
82
88
(111)
I06
I05
109
(97)
I I6
108
121
I20
I25
131
I40
135
I44
142
130 131
_
~
141 134
152 140
110 142
112 143
134 144
133 147
128 148
_
_
136
~
~
(123)
I49
_
~
_
~
[a] k 4 kJjmol. [b] These ligands were not taken into account in the determination of the functional relationship. [c] (OC,,H,,)= 0-menthyl.
[I]
121
[S]
[4]
[5]
161
171
a) P. Heimbach, Angew. Chem. 85, 1035 (1973); Angew. Chem. Int.
Ed. Engl. 12,975 (1973); b) P. W Jolly, G. Wilkr: The Organic Chemistry
of Nickel. Vol. 2. Academic Press, New York 1975.
P. W Jolly, G. Willie: The Organic Chemistry of Nickel. Vol. 1. Academic
Press, New York 1974.
B. Barnrft, B. Bussemeyer, P. Heimboch, P. W. Jolly, C . Kriiger, 1. R a t chenko, G. Wilke, Tetrahedron Lett. 1972, 1457.
It should be noted that Figure 1 considers the actual equilibrium concentration. In the ligdnd-concentration control maps (Fig. 2 and 3) the
chosen reference to the external amounts of L and M (as well as for
ligand-dependent inhibition- and activation phenomena) yields characteristic changes in the shape and position of the curves.
The cyclodimer divinylcyclobutane [I a] which is also formed rearranges
into ( 4 ) and ( 5 ) during the catalysis and no longer can be detected
after the long reaction time chosen by us (complete conversion of butadiene).
F. Brille, J . Klurk, H . Schenkluhn, J. Mol. Catal. S, 27 (1979).
For ligands such as triphenyl phosphite and phenyldiphenoxyphosphane
even a stepwise threefold association can be detected"'. Interestingly,
Anyew.
Clieiii.
lilt. Ed. Enyl. 18 ( 1 9 7 9 ) Nu. 5
~
[*I Dr. H. Schenkluhn ['I, Ing. (grad.) M. Zahres
Universitat Essen-Gesamthochschule. Fachbereich S---Chemie
Postfach 6843, D-4300 Essen (Germany)
and Max-Planck-Institut fur Kohlenforschung
D-4330 Miilheim/Rnhr (Germany)
Ing. (grad.) W. Scheidt, Dr. 6. Weimann
Max-Planck-Institut fur Kohlenforschung
D-4330 Mulheim/Ruhr (Germany)
[**I Organometallic Complex Compounds, Part 4. This work was supported
by the Deutsche Forschungsgemeinschaft. We thank Dr. E . KO& lnstitut
fur Strahlenchemie im MPI fur Kohlenforschung, for help with the construction of the DTA apparatus.-Part 3: P. Heinibuck, M. M o l i n , J. Organomet.
Chern. 49,483 ( 1 9 7 3 b P a r t 2: P. Hriinbach, M Molin. ibrd. 49. 477 (1973).Part 3 : P. Hermhacli. Angew. Chem. 76, 586 (1964); Angea. Chem. Int. Ed.
Engl. 3, 648 (1964).
[+]Author to whom correspondence should he addressed
401
A parametrization of the “electronic” and “steric” ligand
influences has been described by T o l m ~ n [Using
~ ~ . this method
the first examples for the dominance of steric ligand influences
could be found in calorimetric investigations on platinum(r~)[~”]
and nickel(0) complexes13b1.We have now established that
these ligand parameters are suitable not only for the qualitative
estimation but also for the quantitative determination of the
“steric” and “electronic” ligand influences. This is illustrated
here for the reaction enthalpy of the association of Lewis
bases to di-p-methylbis[l -methyl-1-3-q-(2-butenyl)]dinickel
(Table 1).
A slightly modified calorimeter for differential thermal analyses in solution151was used for the determination of the
enthalpy of reaction. The values were determined at 0°C
in a 0.05 M solution of ( I ) in tetralin and the data thus
obtained were corrected for the heat of mixing of the ligands,
since ligand addition was carried out from 1 M solution.
A plot of the measured values z j against the electronic
ligand parameter xj and against the steric ligand parameter
Oj gave no definite indication of a functional relationship.
We therefore attempted a separation of the electronic and
steric components by regression analysis.
There already is a good approximation for the polynomial
~(xj,Oj)=172.0+1.65x,-0.56Oj
since the quotient of the variance of fit (S2= 18) and the
variance of the measured data (oz=16) is approximately
unityL6].In Figure 1 17] each ligand L (xj, Oj) is characterized
ingly covalent bondingLs1.A still undefined “mesomeric effect”
may have to be taken into consideration, corresponding to
the parameterization of the substituent effects in organic
chemistry.
Received: July 12. 1978 [ Z 204b IE]
revised: February 23. 1979
German version: Angew. Chem. 91. 429 (1979)
CAS Registry numbers:
( 1 1.68472-10-6: ( 2 1 , L = P ( ~ - C ~ H ~ ) ( C -1)2,69991-16-X;
C~HI
( 2 ) . L = P(C,H j)~,
69991-17-9: / 2 ) . L=P(~-C,H,)I~-C,H-)L.
69991-IX-0: ( 2 ) . L=P(i-C3H-)3,
69991-19-1; ( 2 ) , L = P ( C , H S ) Z ( C ~ H ~69991-20-4:
).
( 2 1 , L=P(n-C,H,),,
69991-21 -5 ; (2), L = P(li-CjH9)3, 69991 -22-6; ( 2 ,I, L = P(C6H 5)(C2H5)zI
70006-11-0; f 2 ) , L = P(C6HsCHz)a. 69991 -23-7; (2), L = P ( C B H ~ ) ( C H ~ ) , ,
69991-24-8 : ( 2 ) . L = P(C,H,),, 69991-25-9: ( 2), L = P(C,H,)(O-C, oH19)2,
69991-26-0; ( 2 ) , L=P(CH3)3, 69991-27-1: (2), L=P(O-CloH19),,
70006-00-7; f 2), L = P(O-i-C3H7)3,69991-28-2; ( 2 ) , L = P(O-o-C,H,CH
3)3,
69991-29-3 ; ( 2 ) ,L = P ( O - O - C ~ H ~ C ~ H S69991-30-6;
)~.
( 2 ) , L = P(O-CzHs),,
69991-31-7; ( 2 ) , L=P(O-n-C4H9),, 69991-32-8; ( 2 ) ,
L = P(CbHs)(O-C6H s)2, 69991-33-9: / 2 ) . L = P(C,H5)2( O-C2H5), 6999134-0; ( 2 ) , L = P ( O -CbH5)3. 69991-35-1
___
[ I ] M . P. Li, R. S. Drago, J. Am. Chem. SOC.98. 5129 (1976).
[2] a) The electronic parameter x, of ligand L j is determined 1R spectroscopically uiu the induced shift of the vco(Al) band of the L,Ni(C0)3 complex,
with respect to the reference ligand tri(tert-buty1)phosphane with
v~~(A1)=2056.1
c m - ’ [ ~ , = v , , c ~ ( A I ) - 2 0 5 6 .cm-’1.
1
The steric parameter is obtained as conic angle 0, of the corresponding atomic space
filling model; b) Review: C. A . Tolman, Chem. Rev. 77, 313 (1977).
[3] a) L. E. ManzPr, C. A . Tolman, J. Am. Chem. Soc. 97, 1955 (1975):
b) C . A . Tolmun, D. W Reutter. W C. Seidef, J. Organomet. Chem.
1f 7, C 30 ( 1 976).
[4] For the synthesis of ( I ) and ( 2 ) see H. Schenkluhn, Dissertation, Universitat Bochum 1971.
[S] E . Koch, Chem.-1ng;Tech. 37, 1004 (1965).
161 For the regression. the polynomial expression
with the variance of fit
was chosen; m, n were optimized with the quotient Sk,,/02 and a Chi2
test ( 0 2=variance of measured value).
171 This plot is related to Tolman’s “steric and electronic box” [Zb].
[ S ] Similar observations were made in the analysis of a series of catalytic
experiments on nickel ligand catalysts ( P . Heimbach. J. Kluth, H. Schenkfuhn, unpublished), The fact that we could, on the other hand, satisfactorily
resolve e. g. the results on platinum(I1) complexes [3a] into the electronic
and steric ligand influence with incorporation of P(henzyl), and
P(phenyl), is due t o the extremely small electronic influence (20% with
respect to the total ligand property control. 26 ligands, polynomial
degree m, n = 3, 3).
I
-
160
1LO
8j“l
120
Fig. 1.Threedimensional representation of the reaction enthalpies of association
of phosphorus ligands to the nickel complex ( I j as a function of the electronic
xj and steric 0 ligdnd parameters [la].
by a point in the x.y-plane: the respective measured value
zj is given in the :-direction. An intersection vertical to the
abscissa corresponds to the separated steric influence, while
an intersection vertical to the ordinate corresponds to the
separated electronic influence; surprisingly, in the former case
there is a simple linear relationship for both parameters. Collectively, the calculated enthalpies of association span a range
of 82 kJ/mol, of which 48 kJ/mol is ascribed to the electronic
influence and 34 kJ/mol to the steric influence (electronic
to steric ratio of 60: 40). In the regression analysis the phosphorus ligands PPh3, PPh20Et, PPh2Et, and P(benzyl), show
the worst approximation. This would indicate that a description of the bonding character with the aid of the two chosen
ligand parameters does not suffice in the case of overwhelm402
Regiospecific Synthesis of Disubstituted Benzene
Derivatives[**]
By Guy F d i x , Jacques Dunogub, and Raymond Calm[‘]
We have been able to extend application of the “organosilicon method”[’], which had previously been employed only
in individual casesc2]for the regiospecific synthesis of benzene
derivatives, to the synthesis of numerous disubstituted benzene
derivatives. The method proposed by us is based on the stepwise exchange of the trimethylsilyl groups of the readily accessibler3] 0-,m-, or p-bis(trimethylsily1)benzenes ( I o), ( I m),
and ( I p ) , respectively (see reaction scheme and Table 1).
[*I Prof. Dr. R. Calas, Dr. G. Felix, Dr. J. Dunoguks
Laboratoire de Cbimie Organique et Laboratoire de Chimie des Composes Organiques du Silicium et de I’Etain associe au CNRS (no 35)
Universite de Bordeaux I
351, Cours de la Liberation, F-33405 Talence Cedex (France)
[**I We wish to thank Frunpise Pisciottz for her valuable experimental
assistance.
Angew. Chem. I n t . Ed. Eriyl. 18 (1979) No.
0 Verlag C’hrmir, GmhH, 6940 Weinheim, I979
0570-OH33!7Y:Oj0?-0402
S
S 02.50:O
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