Stable palladium(0), palladium(II), and platinum(II) complexes containing a new, multifunctional and hemilabile phosphino-imino-pyridyl ligand: Synthesis, characterization, and reactivity

Article abstract of DOI:10.1021/om9509047

The new, multifunctional, hemilabile phosphorus-bis(nitrogen) ligand N-(2-(diphenylphosphino)benzylidene)(2-(2-pyridyl)ethyl)amine, PNN, containing phosphine, imine, and pyridyl donor groups and alkyl-, allyl-, and acylpalladium complexes, methylplatinum complexes, and a zerovalent palladium complex containing PNN have been synthesized and characterized with ¹H-, ¹³C-, ³¹P-, and ¹⁵N-NMR. PNN commonly coordinates in a terdentate fashion, resulting in ionic complexes of the type [(PNN)M^II(R)]Y (M = Pd, Pt, R = CH₃, Y - Cl, CF₃SO₃; M = Pd, R = C(O)CH₃, Y = CF₃SO₃; M = Pd, R = η¹-CH₂C(H)=CH₂, Y = Cl, CF₃-SO₃). Bidentate coordination of PNN is observed for [(PNN)Pd^II(η³-(CH₃)₂CC(CH ₃)C(CH₃)₂)]-Cl and surprisingly also for neutral (PNN)Pd^II(C(O)CH₃)(Cl). An unprecedented zerovalent palladium complex (PNN)Pd⁰ has been isolated, which is stabilized by PNN only. Preliminary results show that palladium complexes of PNN are very active in allylic alkylation reactions.

Full text of DOI:10.1021/om9509047

3022
Organometallics 1996, 15, 3022-3031
Sta ble P a lla d iu m (0), P a lla d iu m (II), a n d P la tin u m (II)
Com p lexes Con ta in in g a New , Mu ltifu n ction a l a n d
Hem ila bile P h osp h in o-Im in o-P yr id yl Liga n d :
Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity
Richard E. Ru¨lke, Vincent E. Kaasjager, Petra Wehman, Cornelis J . Elsevier,
Piet W. N. M. van Leeuwen, and Kees Vrieze*
Anorganisch Chemisch Laboratorium, J . H. van ’t Hoff Research Institute, Universiteit van
Amsterdam, Nieuwe Achtergracht 166, NL 1018 WV Amsterdam, The Netherlands
J an Fraanje and Kees Goubitz
Laboratorium voor Kristallografie, Amsterdam Institute for Molecular Studies, Universiteit
van Amsterdam, Nieuwe Achtergracht 166, NL 1018 WV Amsterdam, The Netherlands
Anthony L. Spek
Bijvoet Center for Biomolecular Research, Rijks Universiteit Utrecht, Padualaan 8,
NL 3584 CH Utrecht, The Netherlands
Received November 22, 1995X
The new, multifunctional, hemilabile phosphorus-bis(nitrogen) ligand N-(2-(diphenylphos-
phino)benzylidene)(2-(2-pyridyl)ethyl)amine, PNN, containing phosphine, imine, and pyridyl
donor groups and alkyl-, allyl-, and acylpalladium complexes, methylplatinum complexes,
and a zerovalent palladium complex containing PNN have been synthesized and character-
1
ized with H-, 13C-, 31P-, and 15N-NMR. PNN commonly coordinates in a terdentate fashion,
resulting in ionic complexes of the type [(PNN)MII(R)]Y (M ) Pd, Pt, R ) CH3, Y ) Cl,
CF3SO3; M ) Pd, R ) C(O)CH3, Y ) CF3SO3; M ) Pd, R ) η1-CH2C(H)dCH2, Y ) Cl, CF3-
SO3). Bidentate coordination of PNN is observed for [(PNN)PdII(η3-(CH3)2CC(CH3)C(CH3)2)]-
Cl and surprisingly also for neutral (PNN)PdII(C(O)CH3)(Cl). An unprecedented zerovalent
palladium complex (PNN)Pd0 has been isolated, which is stabilized by PNN only. Preliminary
results show that palladium complexes of PNN are very active in allylic alkylation reactions.
As part of our ongoing research on palladium com-
tion3,4 and cross-coupling reactions,5a,b although other
mixed-donor ligands, such as ones with a N-S donor
set, may also be very active.6
We thus designed the multifunctional phosphorus-
bis(nitrogen) ligand N-(2-(diphenylphosphino)benzyli-
plexes in stoichiometric1 and catalytic reactions,2 it was
our goal to design a multifunctional, hemilabile ligand
that would stabilize both Pd(0) and Pd(II) under reac-
tion conditions. Such a ligand may facilitate a catalytic
reaction involving a Pd(0)-Pd(II) cycle, like the C-C
cross-coupling reaction, without the aid of additional
stabilizing ligands. This may be achieved by a ligand
that is able to act as a bidentate as well as a terdentate
ligand and that has variable chelate angles. It has
recently been found that P-N ligands in particular are
suitable ligands for palladium-catalyzed allylic alkyla-
(3) (a) Frost, C. G.; Howarth, J .; Williams, J . M. J . Tetrahedron
Asymm. 1992, 3, 1089. (b) Trost, B. M.; Verhoeven, T. R. J . Am. Chem.
Soc. 1978, 100, 3435.
(4) (a) Hayashi, T.; Konishi, M.; Fukushima, M.; Mise, T.; Kagotani,
M.; Tajika, M.; Kumada, M. J . Am. Chem. Soc. 1982, 104, 180. (b)
Hayashi, T.; Kumada, M. Acc. Chem. Res. 1982, 15, 395. (c) Hayashi,
T.; Hagihara, T.; Katsuro, Y.; Kumada, M. Bull. Chem. Soc. J pn. 1983,
56, 363. (d) Hayashi, T.; Ito, Y.; Yamamoto, A. J . Chem. Soc., Chem.
Commun. 1986, 1090. (e) Hayashi, T.; Yamamoto, A.; Hagihara, T.;
Ito, Y. Tetrahedron Lett. 1986, 27, 191. (f) Hayashi, T.; Kanehira, K.;
Hagihara, T.; Kumada, M. J . Org. Chem. 1988, 53, 113. (g) von Matt,
P.; Pfaltz, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 566. (h) Sprinz,
J .; Helmchen, G. Tetrahedron Lett. 1993, 34, 1769. (i) von Matt, P.;
Loiseleur, O.; Koch, G.; Pfaltz, A.; Lefeber, C.; Feucht, T.; Helmchen,
G. Tetrahedron Asymm. 1994, 5, 573. (j) Sennhenn, P.; Gabler, B.;
Helmchen, G. Tetrahedron Lett. 1994, 35, 8595. (k) Sprinz, J .; Kiefer,
M.; Helmchen, G.; Reggelin, M.; Huttner, G.; Walter, O.; Zsolnai, L.
Tetrahedron Lett. 1994, 35, 1523. (l) Brown, J . M.; Hulmes, D. I.;
Guiry, P. J . Tetrahedron 1994, 50, 4493. (m) Dawson, G. J .; Williams,
J . M. J .; Coote, S. J . Tetrahedron Lett. 1995, 36, 461.
(5) (a) J edlicka, B.; Kratky, C.; Weissensteiner, W.; Widhalm, M. J .
Chem. Soc., Chem. Commun. 1993, 1329. (b) J edlicka, B.; Weissen-
steiner, W.; Zsolnai, L.; Huttner, G. Organometallics, in preparation.
(c) J edlicka, B.; Ru¨lke, R. E.; Weissensteiner, W.; Gala´n, R. F.; J alo´n,
F. A.; Manzano, B. M.; Robr´ıguez-de la Fuente, J .; Veldman, N.; Spek,
A. L. J . Organomet. Chem., in press. (d) J edlicka, B.; Weissensteiner,
W.; Veldman, N.; Spek, A. L.; Vrieze, K. Organometallics, submitted
for publication.
* To whom correspondence should be addressed.
X Abstract published in Advance ACS Abstracts, J une 1, 1996.
(1) (a) van Asselt, R.; Gielens, E. E. C. G.; Ru¨lke, R. E.; Elsevier, C.
J . J . Chem. Soc., Chem. Commun. 1993, 1203. (b) van Asselt, R.;
Gielens, E. E. C. G.; Ru¨lke, R. E.; Vrieze, K.; Elsevier, C. J . J . Am.
Chem. Soc. 1994, 116, 977. (c) Dekker, G. P. C. M.; Elsevier, C. J .;
van Leeuwen, P. W. N. M.; Vrieze, K. J . Organomet. Chem. 1992, 430,
357. (d) To´th, I.; Elsevier, C. J . J . Am. Chem. Soc. 1993, 115, 10388.
(e) Ru¨lke, R. E.; Kliphuis, D.; Elsevier, C. J .; Fraanje, J .; Goubitz, K.;
van Leeuwen, P. W. N. M.; Vrieze, K. J . Chem. Soc., Chem. Commun.
1994, 1817.
(2) (a) van Asselt, R.; Elsevier, C. J . Organometallics 1992, 11, 1999.
(b) van Asselt, R.; Elsevier, C. J . Tetrahedron 1994, 50, 323. (c)
Wehman, P.; Dol, G. C.; Moorman, E. R.; Kamer, P. C. J .; van Leeuwen,
P. W. N. M.; Fraanje, J .; Goubitz, K. Organometallics 1994, 13, 4856.
(d) Wehman, P.; Kaasjager, V. E.; de Lange, W. G. J .; Hartl, F.; Kamer,
P. C. J .; van Leeuwen, P. W. N. M.; Fraanje, J .; Goubitz, K. Organo-
metallics 1995, 14, 3751. (e) Wehman, P.; Borst, L.; Kamer, P. C. J .;
van Leeuwen, P. W. N. M. J . Chem. Soc., Chem. Commun. 1996, 217.
(6) Allen, J . V.; Bower, J . F.; Williams, J . M. J . Tetrahedron Asymm.
1994, 5, 1895. Other S-N ligands are reported in ref 4k.
S0276-7333(95)00904-6 CCC: $12.00 © 1996 American Chemical Society
+
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Stable Pd(0), Pd(II), and Pt(II) Complexes
Organometallics, Vol. 15, No. 13, 1996 3023
group. The resonances of the ethylpyridyl moiety have
no visible phosphorus couplings (J (P-H) < 1 Hz). Table
3 shows the 31P- and 15N-NMR and IR data. The two
nitrogen nuclei of 1 shift -45.2 and -68.3 ppm relative
to nitromethane, which are expected values for imino
and pyridyl nitrogens, respectively.11,12 The imino
nitrogen shows a small 3.0 Hz phosphorus coupling. The
phosphorus atom in 1 has a chemical shift of -13.6 ppm,
which is in agreement with similar triarylphosphine
ligands, e.g. triphenylphosphine. The IR shows the
F igu r e 1. Structure and adopted numbering scheme of
PNN, 1.
dene)(2-(2-pyridyl)ethyl)amine (PNN, 1); see Figure 1.
The new potentially terdentate ligand 1 contains three
donor atoms, a diphenylphosphino, an imino, and a
pyridyl group. The latter two were chosen in an effort
to enhance the π-accepting capacity of the system. Such
π-accepting abilities are a prerequisite for the stabiliza-
tion of zerovalent palladium complexes. The intrinsic
flexibility of the ligand facilitates the adaptation of the
bite angles between the metal and the donor atoms, as
needed for the different oxidation states of palladium.
Because of its flexible structure, 1 can act either as a
monodentate P ligand, as a bidentate P-N one, or as a
terdentate P-N-N one. Upon coordination both the
P-N and the N-N sets will form six-membered chelate
rings. Preliminary results of the coordination chemistry
of ligand 1 in palladium complexes have been reported
recently,7 and Mo(CO)4 complexes containing related
ligands have been reported briefly by Rauchfuss.8
expected resonance of the CdN group at 1635 cm-1 8
.
Meth ylp a lla d iu m Com p ou n d s. Methylpalladium
compound [(PNN)Pd(CH3)]Cl, 2, was synthesized from
(η2,η2-1,5-cyclooctadiene)Pd(CH3)(Cl) in chloroform or
dichloromethane at room temperature as published
recently; see Figure 2.7 The isostructural complex
[(PNN)Pd(CH3)]CF3SO3, 3, has been synthesized from
2 upon metathesis with silver trifluoromethanesulfonate
at room temperature in acetonitrile. The platinum ana-
logues of 2 and 3, [(PNN)Pt(CH3)]Cl, 9, and [(PNN)Pt-
(CH3)]CF3SO3, 10, have been obtained via the same
procedures, starting with (COD)Pt(CH3)(Cl).
Whereas compounds 2 and 3 readily dissolve in
solvents such as chloroform, dichloromethane, acetoni-
trile, and DMSO and are moderately soluble in less
polar solvents like benzene and toluene, 9 and 10 are
only moderately soluble in dichloromethane and chlo-
roform and poorly soluble in benzene and toluene. In
the solid state as well as in solution 2, 3, 9, and 10 are
stable in solution at ambient temperature for several
months.
Resu lts
Th e P NN Liga n d , 1. The orange, potentially ter-
dentate ligand 1 has been synthesized in 81% yield from
the Schiff’s base condensation reaction of 2-(diphen-
ylphosphino)benzaldehyde and 2-(2-aminoethyl)pyridine
according to the method of Lavery and Nelson.9 1 was
In 2, 3, 9, and 10, PNN coordinates in a static
terdentate fashion as can be concluded from (i) the
presence of small phosphorus couplings on the 13C-NMR
resonances of the pyridyl ring, (ii) a very characteristic
set of multiplets for H8 and H9, (iii) a 45 Hz phosphorus
coupling on the resonance of the pyridyl N in the 15N-
NMR in combination with a coordination induced shift
(CIS) of ca. -50 ppm, and (iv) conductometric experi-
ments, since terdentate coordination of PNN in divalent
palladium complexes results in ionic compounds.
1
characterized by H-, 13C-, 31P-, and 15N-NMR, IR, and
mass spectroscopy (Figure 1). The ligand proved to be
fairly insensitive toward oxidation. In the solid state
the ligand is stable for months, and in solution, no
significant amounts of the oxidation product were
observed within 4 weeks.
1
The 1H-NMR spectrum of 1, see Table 1, shows a
phosphorus coupling constant of 4.7 Hz on H7, which is
absent in the spectra of its palladium and platinum
complexes 2-11. Presumably this is a through-space
coupling, indicating a conformation of free 1 in which
the imino-hydrogen atom points toward the phosphorus
lone pair.10 This feature was also reported by Rauchfuss
for the related ligands (C5H6)2P-2-C6H4C(H)dNR (R )
p-C6H4OCH3, CH2C(H)dCH2, CH2-2-C5H4N, and CH2-
CH2SCH3).8 Phosphorus couplings of 3.9 and 4.7 Hz are
found on H2 and H4 of the benzaldimino group, respec-
tively, which are also present in the palladium com-
plexes of 1. The 13C-NMR spectrum of 1, see Table 2,
shows phosphorus couplings on the resonances of the
two phenyl groups and on C2 and C7 of the benzaldimino
Additionally, 195Pt couplings are present in the H-,
13C-, and 31P-NMR spectra of the platinum compounds
9 and 10 (Tables 1-3); large Pt-P coupling constants
of 4101 and 4078 Hz, Pt-H coupling constants of 70
Hz on the methyl ligand and 36 and 32 Hz on H14, and
Pt-C coupling constants of 659 and 668 Hz on the
methyl ligand of 9 and 10, respectively, indicate that
the methyl resides cis with respect to the phosphorus.13
Unlike the coordination behavior of nonsymmetric ter-
dentate nitrogen ligands,11,14 of which the flexible eth-
ylpyridyl moiety easily dissociates, PNN coordinates to
2, 3, 9, and 10 in a static terdentate fashion at the NMR
time scale, as concluded from the lack of fluxionality in
the NMR spectra recorded between 223 and 323 K.
Cr ysta l Str u ctu r e Deter m in a tion of [N-(2-(d i-
p h en ylp h osp h in o)ben zylid en e)(-(2-(2-p yr id yl)eth -
yl)a m in e]m eth ylp a lla d iu m (II) Tr iflu or om eth a n e-
su lfon a te, 3. The precise arrangement of the ligands
in complexes 27 and 3 has been determined by X-ray
studies of their colorless crystals. The structural data
(7) Wehman, P.; Ru¨lke, R. E.; Kaasjager, V. E.; Elsevier, C. J .;
Kooijman, H.; Spek, A. L.; Vrieze, K.; van Leeuwen, P. W. N. M. J .
Chem. Soc., Chem. Commun. 1995, 331.
(8) (a) Rauchfuss, T. B. J . Organomet. Chem. 1978, 162, C19. (b)
J effery, J . C.; Rauchfuss, T. B.; Tucker, P. A. Inorg. Chem. 1980, 19,
3306.
(9) Lavery, A.; Nelson, S. M. J . Chem. Soc., Dalton Trans. 1984,
615.
(10) See for example: (a) Contreras, R. H.; Facelli, J . C. In Annual
Reports in NMR Spectroscopy; Webb, G. A., Ed.; Academic Press Ltd.:
London, England, 1993. (b) J ameson, C. J . In Phosphorus-31 NMR
Spectroscopy in Stereochemical Analysis; Verkade, J . G., Quin, L. D.,
Eds.; VHC: Deerfield Beach, FL, 1987.
(11) Ru¨lke, R. E.; Ernsting, J . M.; Spek, A. L.; Elsevier, C. J .; van
Leeuwen, P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769.
(12) (a) Buchanan, G. W. Tetrahedron 1985, 45, 581. (b) von
Philipsborn, W.; Mu¨ler, R. Angew. Chem., Int. Ed. Engl. 1986, 25, 383.
(c) Pregosin, P. S.; Ruedi, R.; Anklin, C. Magn. Reson. Chem. 1986,
24, 255.
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3024 Organometallics, Vol. 15, No. 13, 1996
Ta ble 1. Selected 1H-NMR Da ta for th e Com p ou n d s 1-11
Ru¨lke et al.
1H-NMR (ppm)
compd (solvent
M-R
H2
H5
7.03
H7
H8
H9
H14
1 (CDCl3)
2 (CDCl3)
3 (CDCl3)
4 (CDCl3)
5 (CDCl3)
6 (CDCl3)
7 (CD2Cl2)
8 (CD2Cl2)
9 (CDCl3)
10 (CDCl3)
11 (CDCl3)
7.93 [3.9]
8.15 [4.3]
7.90 [4.3]
obscured
7.91b
8.85 [4.7]
9.47
8.80
8.51
8.50
9.43
8.63
8.14
3.89
4.22
4.00
4.25
4.24
4.03
3.86
4.41
4.35
4.23
4.11
2.97
3.48
3.49
3.38
3.42
3.54
3.41
3.34
3.40
3.48
3.56
8.49
8.41
8.42
8.45
8.44
8.59
8.63
8.36
0.36 [2.7]
0.35 [2.7]
2.19 [1]
2.13
7.07 [11]
7.16 [10]
7.14a
7.11a
2.19c
8.08 [4.3]
7.11 [10]
7.20 [10]
6.77 [10]
7.09 [11]
7.15 [11]
7.09 [11]
2.27c
7.91b
obscured
8.21 [4.2]
8.02b
0.34 [3] {70}
0.44 [3] {70}
9.85 {44}
9.26 {41}
10.00
8.45 {36}
8.46 {32}
8.87
8.49b
a
b
Phosphorus couplings could not be determined since H5 has coincided with H4. J (P-H) could not be determined. c H1′ of the η1-allyl
moiety.
Ta ble 2. Selected 13C-NMR Da ta for th e Com p ou n d s 1-11
13C-NMR (ppm)
compd (solvent)
M-R
5.0 [4]
Ci
C1
C2
C6
C7
C8
C9
1 (CDCl3)
2 (CDCl3)
3 (CDCl3)
6 (CDCl3)
8 (CD2Cl2)
9 (CDCl3)
10 (CDCl3)
11 (CDCl3)
137.1 [10]
123.8 [45]
123.8 [45]
124.4 [45]
128.0 [43]
122.1 [57]
125.6 [56]
120.4
140.1 [17]
128.0 [56]
127.9 [56]
127.2 [52]
125.8 [34]
126.7 [66]
129.2 [78]
125.5 [55]
128.4 [4.5]
138.6 [9]
138.3 [9]
134.6 [12]
ca. 133
137.6 [9]
139.3 [9]
139.4 [8]
137.2 [20]
137.5 [14]
137.2 [14]
137.2 [14]
136.5 [15]
137.0 [13]
139.1 [13]
137.3 [16]
160.7 [21]
168.2 [6.8]
167.4 [6.8]
169.4 [5]
61.6
56.2
56.1
54.4
66.0
54.8
55.3
58.9
40.1
39.1
38.9
39.3
41.6
38.3
38.8
37.9
5.2 [3.8]
31.9a
170.9 [-]
-8.5 [6.2] {659}
-8.1 [6.8] {668}
165.7 [5.3]
167.0 [5.3]
159.9 [6]
a
C1′ of the η1-allyl moiety.
Ta ble 3. 31P - a n d 15N-NMR, a n d IR Da ta for th e Com p ou n d s 1-11
15N-NMR
compd (solvent)
31P-NMR: δ (ppm)
δ(imine) (ppm)
δ(pyridyl) (ppm)
IR:c ν (cm-1
)
1 (CDCl3)
2 (CDCl3)
3 (CDCl3)
4 (CDCl3)
5 (CDCl3)
6 (CDCl3)
6a (CDCl3)
7 (CD2Cl2)
8 (CD2Cl2)
9 (CDCl3)
10 (CDCl3)
11 (CDCl3)
-13.6
37.0
37.2
20.9
24.9
33.1
22.9
33.3
24.9
-45.2 [3]
-123 [3]
-121 [3]
-68.3
1635 (m), CdN
-122 [45]
-123 [45]
1686 (m), CdO
1680 (m), CdO
-119a
-119a
12.2 {4101}
12.3 {4078}
30.9
-131 [3] {210}
-133 [72]b
a
b
Only one, broad signal has been observed. No platinum satelites have been observed because of a poor S/N ratio. c In KBr.
Ta ble 4. Selected Bon d Len gth s (Å) for th e
Non -Hyd r ogen Atom s of th e Tw o In d ep en d en t
Molecu les of (P NN)m eth ylp a lla d iu m (II)
Tr iflu or om eth a n esu lfon a te, 3 (w ith Esd ’s betw een
P a r en th eses)
F igu r e 2. Structure of the methylpalladium and methyl-
platinum complexes 2, 3, 9, and 10.
n ) 1
n ) 2
Pd(n)-N(n01)
Pd(n)-N(n02)
Pd(n)-C(n27)
Pd(n)-P(n)
P(n)-C(n14)
C(n08)-C(n9)
N(n02)-C(n08)
C(n14)-C(n09)
P(n)-C(n15)
P(n)-C(n21)
2.106(5)
2.125(5)
2.084(8)
2.1986(17)
1.821(5)
1.475(7)
1.269(8)
1.402(7)
1.816(6)
1.814(5)
2.107(5)
2.120(4)
2.066(8)
2.1998(15)
1.818(5)
1.461(7)
1.276(7)
1.398(7)
1.806(5)
1.803(5)
are listed in Tables 4-6 and 8. The asymmetric unit
contains two crystallographically independent molecules
3 and two molecules of chloroform. The molecular
structure of {(PNN)Pd(CH3)}CF3SO3, 3, comprises the
expected square planar arrangement of the three donor
atoms of PNN and the methyl ligand around the
palladium atom (Figure 3), analogous to 2.7
phosphino-amino chelates.5c,13,15 The Pd-C(27) dis-
tances of 2.084(8) Å [2.066(8) Å] are relatively short
compared to those of known (P-N)Pd(CH3)(Cl) com-
The bond angles between Pd and two neighboring
donor atoms are between 87.2(2)° [87.0(2)°] and 91.87-
(13)° [91.67(17)°]. Values so close to the ideal 90° must
be attributed to the flexibility of the ligand even when
it acts as a terdentate ligand. The ligand-palladium
distances are close to those of the analogous chloride
complex 27 and other palladium complexes containing
five-membered and six-membered phosphino-imino or
(13) Dekker, G. P. C. M.; Buijs, A.; Elsevier, C. J .; Vrieze, K.; van
Leeuwen, P. W. N. M.; Smeets, W. J . J .; Spek, A. L.; Wang, Y.-F.; Stam,
C. H. Organometallics 1992, 11, 1937.
(14) Ru¨lke, R. E.; Kaasjager, V. E.; Kliphuis, D.; Elsevier, C. J .;
Goubitz, K.; van Leeuwen, P. W. N. M.; Vrieze, K. Organometallics
1996, 15, 668.
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Stable Pd(0), Pd(II), and Pt(II) Complexes
Organometallics, Vol. 15, No. 13, 1996 3025
Ta ble 5. Selected Bon d An gles (d eg) for th e
Non -Hyd r ogen Atom s of th e Tw o In d ep en d en t
Molecu les of (P NN)m eth ylp a lla d iu m (II)
Tr iflu or om eth a n esu lfon a te, 3 (w ith Esd ’s betw een
P a r en th eses)
n ) 1
n ) 2
P(n)-Pd(n)-N(n02)
91.87(13)
91.01(13)
89.8(3)
91.49(12)
91.67(17)
89.6(3)
N(n02)-Pd(n)-N(n01)
N(n01)-Pd(n)-C(n27)
C(n27)-Pd(n)-P(n)
87.2(2)
87.0(2)
P(n)-Pd(n)-N(n01)
N(n02)-Pd(n)-C(n27)
Pd(n)-P(n)-C(n14)
176.51(12)
174.4(2)
111.33(17)
122.0(4)
114.5(5)
126.3(5)
128.5(5)
128.9(3)
115.2(4)
115.7(5)
118.1(5)
116.8(5)
175.84(13)
174.2(2)
111.63(16)
121.5(4)
115.1(5)
126.2(5)
129.4(5)
128.4(3)
115.7(3)
115.6(4)
118.5(5)
116.7(5)
P(n)-C(n14)-C(n09)
C(n10)-C(n09)-C(n08)
C(n14)-C(n09)-C(n08)
C(n09)-C(n08)-N(n02)
C(n08)-N(n02)-Pd(n)
C(n07)-N(n02)-Pd(n)
C(n07)-N(n02)-C(n08)
C(n01)-N(n01)-C(n05)
N(n01)-C(n05)-C(n06)
F igu r e 3. ORTEP (drawn at the 50% probability level) of
3. Only one of the crystallographically independent cations
is shown.
Ta ble 6. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for th e Non -Hyd r ogen Atom s of
(N-(2-(Dip h en ylp h osp h in o)ben zylid en e)-
Sch em e 1. Str u ctu r es of Neu tr a l
(P NN)P d (C(O)CH3)(Cl), 4, a n d Ion ic
[(P NN)P d (C(O)CH3)]OTf, 5
(2-(2-p yr id yl)eth yl)a m in e)ch lor oa cetylp a lla d iu m (II),
4 (w ith Esd ’s betw een P a r en th eses)
Bond Distances
Pd-C(1)
Pd-P(1)
Pd-N(1)
C(1)-O(1)
C(1)-C(2)
2.379(4)
2.232(3)
2.19(1)
1.18(2)
1.51(2)
C(16)-C(11)
C(16)-C(10)
C(10)-N(1)
P(1)-C(21)
P(1)-C(31)
1.39(2)
1.48(2)
1.29(2)
1.83(1)
1.832(9)
Bond Angles
P(1)-Pd-N(1)
P(1)-Pd-C(1)
C(1)-Pd-Cl(1)
N(1)-Pd-Cl(1)
Pd-P(1)-C(11)
Pd-C(1)-C(2)
Pd-C(1)-O(1)
Pd-N(1)-C(3)
90.0(3)
90.8(4)
84.3(4)
95.0(3)
111.1(4)
117(1)
Pd-N(1)-C(10)
127.3(8)
174.8(1)
178.9(4)
122(1)
128(1)
115(1)
P(1)-Pd-Cl(1)
N(1)-Pd-C(1)
C(2)-C(1)-O(1)
N(1)-C(10)-C(16)
C(3)-N(1)-C(10)
P(1)-C(11)-C(16)
C(11)-C(16)-C(10)
121.4(8)
117.3(8)
123.6(8)
127(1)
pounds,5c,13 probably due to the better π-accepting
capacity of the trans-situated imino nitrogen N(1) in the
case of 3. The double six-membered ring chelate of the
PNN ligand causes a twisted conformation of the ligand
around the palladium atom. The pyridyl group is
rotated 43.7(2)° [42.1(3)°], the imino group C(n07)-
N(n02)-C(n08)-C(n09) 22.2(5)° [21.8(5)°] with regard
to the palladium coordination plane (P(n), N(n01),
N(n02), and C(n27)).
For the carbonylation of 2, a vanishing Pd-CH3
resonance of 2 at 0.36 ppm and a growing Pd-C(O)-
1
CH3 resonance of 4 at 2.19 ppm are observed in the H-
NMR, while in the 31P-NMR the resonance of 2 at 37.0
ppm vanished with simultaneous formation of the
resonance of 4 at 20.9 ppm. In the IR the carbonyl
resonance at 1661 cm-1 typical for the acetyl group has
been observed for 4. Similar results have been obtained
for the carbonylation of 3 (Tables 1 and 3).
Ca r bon yla tion Rea ction s w ith Meth ylp a lla d iu m
Com p lexes of P NN. Carbonylation of 2 and 3 at room
temperature under atmospheric CO pressure proceeds
very slowly.5d,13 However, under 25 bar of CO at 50 °C
quantitative carbonylation was achieved within 2 days.
When the reaction was followed with 31P-NMR, using
a single-crystal sapphire high-pressure NMR tube, CO
insertion half-lives of 20 h have been determined for 2
and 3.16 Unfortunately, the methylplatinum compounds
9 and 10 failed to react with CO, even under these
reaction conditions.
The isostructural compounds 2 and 3 and also 9 and
10 have almost identical NMR spectra. However, 4 and
5 have quite different NMR and IR spectra, most
prominently in the 31P-NMR spectra, suggesting that 4
and 5 have different structures. Whereas in 5 PNN
coordinates in the terdentate fashion, and hence is
isostructural with ionic 2 and 3, in 4 PNN coordinates
in a bidentate fashion as a phosphino-imino chelate
with the chloride ligand coordinating; see Scheme 1. For
1
example, in the H-NMR spectra of 4 the resonances of
the bridging region (-CH2CH2-) have two sharp trip-
lets which are also present in the free ligand and in
analogous palladium complexes with a free ethylpyridyl
group11,14 but not in 2, 3, 5, 9, and 10. Crystals of 4
suitable for X-ray analysis were obtained, and a crystal
structure determination has been carried out, vide infra,
which confirms the proposed structure of 4.
During the formation of 4, weak signals belonging to
the acetyl(carbonyl)palladium intermediate [(PNN)Pd-
(C(O)CH3)(CO)]Cl, 4a , have been observed with reso-
(15) (a) Sacco, A.; Vasopollo, G.; Nobile, C. F.; Piergiovanni, A.;
Pellinghelli, M.; A.; Lanfranchi, M. J . Organomet. Chem. 1988, 356,
397 (with Pd-P ) 2.290(3) Å, Pd-N ) 2.073(8) Å, Pd-C ) 1.991(10)
Å, and P-Pd-N ) 83.6(2)° (five-membered ring)). (b) Cecconi, F.;
Ghilardi, C. A.; Midollini, S.; Monetti, S.; Orlandini, A.; Scapacci, G.
J . Chem. Soc., Dalton Trans. 1989, 211 (with Pd-P ) 2.357(4) Å, Pd-N
) 2.23(2) Å, and P-Pd-N ) 84.6(1)° (five-membered ring)). (c) Clark,
G. R.; Palenik, G. J . Inorg. Chem. 1970, 9, 274 (with Pd-P ) 2.243 Å,
Pd-N ) 2.148 Å, and P-Pd-N ) 92.4° (six-membered ring)).
(16) (a) Roe, D. C. J . Magn. Reson. 1985, 63, 388. (b) For applica-
tions in palladium chemistry, see: Elsevier, C. J . J . Mol. Catal. 1994,
92, 285.
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3026 Organometallics, Vol. 15, No. 13, 1996
Ru¨lke et al.
The Pd-N(1) distance of 2.19(1) Å is longer than in 27
and 3, which can be attributed to the higher trans-
influence of the acetyl group trans to N(1), when
compared to the lower trans-influence of the methyl
group in 2 and 3.17 However, we have recently observed
shorter Pd-N distances of the trans nitrogen for acetyl
groups than for methyl groups in the case of palladium
complexes with R-diimine ligands, which is in contrast
with the trend observed here. For these compounds,
the shorter Pd-N(trans) bond has been attributed to
an electronic push-pull effect, in which the higher trans
influence of the acetyl increases the back-donation of
charge from the palladium to the nitrogen. In 4, both
the imino group C(3)-N(1)-C(10) and the acetyl group
C(2)-C(1)-O are rotated (63.9(6) and 77.2(8)°, respec-
tively) with respect to their ideal coplanar and perpen-
dicular positions, while these groups make an angle of
104.9(7)° with each other. Such deformations from the
ideal values may prevent suitable overlap of the rel-
evant orbitals and diminish the push-pull effect, re-
sulting in a longer Pd-N(1) distance for 4 than for 2
and 3.
F igu r e 4. ORTEP (drawn at the 50% probability level) of
(PNN)Pd(C(O)CH3)(Cl), 4.
1
nances at 2.15 ppm (C(O)CH3) in the H- and at 31.7
ppm in the 31P-NMR, beside the growing signals of the
acylpalladium compound 4. Experiments performed
under 7 bar of 13CO failed to show the carbonyl
resonance in the 13C-NMR because of the low concentra-
tion of 4a , although in the IR a carbonyl 13CdO
vibration at 2099 cm-1 and an acetyl 13CdO vibration
at 1686 cm-1 were observed. A similar intermediate
[(PAN)Pd(C(O)CH3)(CO)]Cl (PAN ) 1-(diphenylphos-
phino)-8-(dimethylamino)naphthyl) was observed by us
in the past.13
Acetylpalladium compounds 4 and 5 are stable as
solids for weeks but dissolved in CDCl3 only for a few
hours. In CDCl3, resonances in the 31P-NMR belonging
to the degradation products [(PNN)Pd(Cl)]Y (Y ) Cl,
OTf)7 at 31.1 ppm become visible. For example, after
the formation of the acetylpalladium compounds 4 was
completed, ca. 15% of the dichloropalladium compound
was already formed and upon standing 4 is completely
converted into [(PNN)PdCl]Cl without the formation of
Pd-black.
The bite angle of the P-N(1) chelate has the ideal
value of 90.0(3)°, which must be attributed to the
flexibility of the six-membered chelate ring. However,
the Cl-Pd-C(1) angle of 84.3° is small whereas the Cl-
Pd-N(1) angle is large. Such deviations from the ideal
values are not commonly observed for palladium com-
pounds with very flexible ligands. Its origin may be the
pendant ethylpyridyl group, forcing the chloride ligand
toward the acetyl group.
Allylp a lla d iu m Com p lexes of P NN. In order to
prepare a precursor for the zerovalent PNN palladium
compound 11, we have synthesized allylpalladium com-
plexes of PNN, since allylpalladium complexes can be
reduced to zerovalent palladium complexes by soft
carbanions or amines.3,4 When PNN is reacted with 0.5
20
equiv of [(C3H5)Pd(µ-Cl)]2 in chloroform at room tem-
perature, a 1:1 mixture of ionic [(PNN)Pd(η1-C3H5)]Cl,
6, and neutral (PNN)Pd(η3-C3H5)(Cl), 6a , are initially
formed, as concluded from the two sets of resonances
1
present in the H- and 31P-NMR spectra. Heating the
mixture of 6 and 6a in chloroform at 65 °C for 2 h
resulted in 6 exclusively.
Cr ysta l Str u ctu r e Deter m in a tion of [N-(2-(d i-
p h en ylp h osp h in o)b en zylid en e)(2-(2-p yr id yl)et h -
yl)a m in e]ch lor oa cetylp a lla d iu m (II), 4. A small crop
of white crystals of 4 could be isolated after release of
the CO pressure, filtration of the solution, and slow
diffusion of diethyl ether into the solution. The molec-
ular structure of (PNN)Pd(C(O)CH3)(Cl), 4, is presented
in Figure 4. The positional data are listed in the
Supporting Information, selected bond distances and
bond angles are in Table 6, and the crystal and refine-
ment data are in Table 8.
In 4 PNN is coordinating in a bidentate fashion as a
P-N chelate with a pendant ethylpyridyl group. As
expected, the acetyl group and the phosphorus atom,
being the strongest donors,17 are situated in a cis
position. The palladium ligand distances Pd-P )
2.232(3) Å, Pd-N(1) ) 2.19(1) Å, Pd-Cl ) 2.379(4) Å,
and Pd-C(1) ) 2.00(1) Å of 4 are in agreement with
those of similar structures found in the literature.5c,13,15
The short Pd-C(1) distance of 2.00(1) Å, although ca.
0.10 Å shorter than in analogous methylpalladium
compounds, is normal for an acetylpalladium bond.18,19
The terdentate coordination fashion of the PNN
ligand in 6 was easily determined, via a procedure
analogous to the one used for the methylpalladium
compounds 2 and 3; vide supra. In addition, the η1-
allyl moiety shows the characteristic resonances of 2.19
(d, 2H, H1′), 4.50 (d, H3′), 4.62 (d, H3′), and 5.52 ppm
1
(m, H2′) in the H-NMR and of 31.9 (C1′) and 110.7 ppm
(C3′) in the 13C-NMR.4,21 The 13C-NMR resonances are
slightly broadened, while C2′ is concealed by resonances
of 1. In the 31P-NMR a sharp resonance at 33.1 ppm is
observed, a value typical for compounds of the type (P-
N)Pd(alkyl)(Y) and close to 2 and 3.
(18) Ru¨lke, R. E.; Delis, J . G. P.; Groot, A. M.; Elsevier, C. J .; van
Leeuwen, P. W. N. M.; Vrieze, K.; Goubitz, K.; Schenk, H. J .
Organomet. Chem. 1996, 508, 109.
(19) (a) Bardi, R.; del Pra, A.; Piazzesi, A. M.; Toniolo, L. Inorg.
Chim. Acta 1979, 35, L345. (b) Bardi, R.; Piazzesi, A. M.; Cavinato,
G.; Cavoli, P.; Toniolo, L. J . Organomet. Chem. 1982, 224, 407. (c)
Bardi, R.; Piazzesi, A. M.; del Pra, A.; Cavinato, G.; Toniolo, L. Inorg.
Chim. Acta 1985, 102, 99. (d) Markies, B. A.; Wijkens, P.; Boersma,
J .; Spek, A. L.; van Koten, G. Recl. Trav. Chim. Pays-Bas 1991, 110,
133.
(20) Dent, W. T.; Long, R.; Wilkinson, A. J . J . Chem. Soc. 1964, 1585.
(21) Numata, S.; Okawara, R.; Kurosawa, H. Inorg. Chem. 1977,
16, 1737.
(17) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.
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Stable Pd(0), Pd(II), and Pt(II) Complexes
Organometallics, Vol. 15, No. 13, 1996 3027
Sch em e 2. F or m a tion of (η1-Allyl)p a lla d iu m
Com p ou n d s 6 a n d 7 fr om th e Allylch lor op a lla d iu m
Dim er
Sch em e 3. F or m a tion of Zer ova len t 11 a n d 11a by
Rea ction of 6 w ith P yr r olid in e
1
6a shows strongly broadened resonances in both H-
3), along with a small amount of a second product, 11a ,
which we tentatively formulate as the η2-N-allylpyrro-
lidinium chloride stabilized zerovalent palladium com-
pound {(PNN)Pd0[η2-H2CdC(H)CH2N(H)C4H8]}Cl. Dis-
solved in chloroform, this mixture of 11 and 11a proved
to be stable only for a few hours. Yet, we were able to
characterize 11 by 1H-, 31P-, and 13C-NMR spectroscopy,
but due to the small amount present, 11a could not be
characterized. In the 31P-NMR spectrum, resonances
at 30.9 ppm for 11 and at 35.1 ppm for 11a have been
found. The first resonance was found before when
synthesizing 11 from Pd2(DBA)4 (DBA ) bis(benzylide-
ne)acetone), although we were not able to isolate the
zerovalent compound from this reaction mixture. Col-
umn chromatography of the mixture of 11 and 11a
resulted in almost pure 11 with traces of 6. Zerovalent
11 is soluble in dichloromethane and chloroform and
only moderately soluble in toluene and benzene. As a
solid, 11 is stable for a few weeks.
Compound 11 was further characterized by mass
spectroscopy using the Europium plasma desorption
ionization technique. Besides small impurities at m/z
536.3 and m/z 541 belonging to [(PNN)Pd(Cl)]+ and
[(PNN)Pd(C3H5)]+, 6, respectively, a signal at m/z 500.7
is present which is clearly due to 11. Europium plasma
desorption is a very soft ionization technique, and the
presence of a stabilizing molecule (solvent, alkene)
should have been detected.
C-C Bon d F or m a tion s Ca ta lyzed by P a lla d iu m
Com p lexes of P NN. In order to test the catalytic
activity of palladium complexes of PNN, some allylic
alkylation reactions have been performed starting with
6 as the precursor.3,4 The results are listed in Table 7.
The catalytic reactions were carried out on a 1 mmol
(allylic substrate) scale in THF at room temperature
with 1 mol % of 6 (entries 1-3). In the case of 3-acetoxy-
1,3-diphenylpropene (entry 4 in Table 7), a typical
substrate for studies on enantioselective allylic alkyla-
tion reactions, 3 mol % of the catalyst precursor 6 and
3 mmol of sodium diethylmalonate were used in order
to compare the performance of PNN with ligands in the
literature.4 Samples were taken at 0.5, 1, 4, and 24 h
of reaction time, although most reactions were com-
pleted within 0.5 h. These rates are much higher than
those reported for enantioselective allylic alkylations
catalyzed by palladium complexes with amino-phos-
phine, sulfido-phosphine, and amino-sulfide ligands.4,6
Furthermore, no significant formation of Pd-black was
and 31P-NMR at room temperature. When the mixture
of 6 and 6a is cooled to 223 K, these signals sharpen
up. Although in the 1H-NMR some resonances of 6a
are concealed by signals belonging to 6, the presence of
an η3-allyl group in 6a was easily determined. The
proposed structure is confirmed by the resonance at 22.9
ppm in the 31P-NMR spectrum, a typical value for
complexes of the type (PR3)Pd(η3-allyl)(Cl) (Rdaryl).22
In 6a , PPN is coordinating in a monodentate fashion
and not as a P-N chelate (6b in Scheme 2), since 6a is
not observed when the reaction is carried out in the
presence of AgOTf. In this experiment, [(PNN)Pd(η1-
allyl)]OTf, 7, is formed instantaneously, without a sign
of other isomeric compounds (Scheme 2).
When PNN is added to in situ formed (pentamethy-
lallyl)palladium chloro dimer1a,23 in dichloromethane in
the presence of silver triflate, [(PNN)Pd(η3-C8H15)]OTf,
8, is readily formed as concluded from the 1H-, 13C-, and
31P-NMR data. The allylic carbons and the five methyl
substituents have the chemical shifts and the phospho-
rus couplings characteristic of complexes of the type
[(P-N)Pd(allyl)]Y.24 Unfortunately, additional charac-
terization of 8 by elemental analysis was not possible
since it is not very well possible to synthesize [(η3-
C8H15)Pd(Cl)]2 quantitatively from (COD)Pd(CH3)(Cl):
due to the very slow insertion of TMA,1a,23 the reaction
cannot be completed in order to prevent degradation
reactions. A small amount of the starting material
therefore cannot be avoided. Thus, after reaction with
PNN, 8 always contains a certain amount of simulta-
neously generated 2, which, however, does not seem to
affect the structural integrety of 8 nor complicates its
NMR characterization.
Zer ova len t P a lla d iu m Com p lexes of P NN. Syn-
thesis of the zerovalent compound (PNN)Pd, 11, which
is stabilized only by PNN without the aid of additional
stabilizing ligands such as alkenes, was achieved by in
situ reduction of the allylpalladium complexes 6 or 7
with pyrrolidine, as outlined in Scheme 3.
In doing so, a mixture of (PNN)Pd0, 11, was obtained
as concluded from the spectroscopic data (see Scheme
(22) (a) Cotton, F. A.; Faller, J . W.; Musco, A. Inorg. Chem. 1967, 6,
179. (b) Powell, J .; Shaw, B. L. J . Chem. Soc. A 1967, 1839. (c)
Kurosawa, H.; Kajimaru, H.; Ogoshi, S.; Yoneda, H.; Miki, K.; Kasai,
N.; Murai, S.; Ikeda, I. J . Am. Chem. Soc. 1992, 114, 8417.
(23) Ankersmit, H. A.; Veldman, N.; Spek, A. L.; Eriksen, K.;
Goubitz, K.; Vrieze, K.; van Koten, G. Inorg. Chim. Acta, in press.
(24) A° kermark, B.; Krakenberger, B.; Hansson, S.; Vitagliano, A.
Organometallics 1987, 6, 620.
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3028 Organometallics, Vol. 15, No. 13, 1996
Ru¨lke et al.
Sch em e 4. CO In ser tion in to Meth ylp a lla d iu m
Com p lexes of P NN
the case for complexes containing symmetric bidentate
ligands for which much shorter CO insertion half-lives
(minutes) have been found.1c,14,18
The observation that 2 and 3 have CO insertion half-
lives even longer (t1/2 ) 20 h) than methylpalladium
complexes of the above mentioned bidentate P-N
ligands may have two origins. First, the Pd-N(pyridyl)
bond in 2 and 3 may be stronger than the Pd-Cl bond
in complexes (P-N)Pd(CH3)(Cl), due to π-back-donation.
Second, the methyl group in 2 and 3 is stabilized by the
π-accepting imino nitrogen in the trans position. This
stabilizing push-pull effect is not present in the three
above mentioned compounds, since these have amine
nitrogens, which have no relevant π-accepting proper-
ties.
observed during and after the catalytic reaction, and no
change in the product distribution in the case of 3-chlo-
robutene (entry 2 in Table 7) due to palladium-catalyzed
isomerization reactions was observed within 24 h.
Although the allylic alkylation reactions catalyzed by
6 have not been studied in full detail, the results show
that catalytic system performs very well and with very
high rates compared with other palladium complexes
Discu ssion
4
6
containing P-N and N-S ligands used in (enanti-
oselective) allylic alkylation reactions. It is not very
probable that this remarkable performance can be
attributed to the interaction of the pendant ethylpyridyl
group with sodium diethyl malonate, similar to P-P-
N-OH ligands reported by Hayashi. Palladium com-
plexes with such bifunctional ligand systems did not
show a significant accelerating effect and only enhance
the stereoselectivity of the reaction.4a-f Alternatively,
the observed high rates might be cause by the presence
of the imino nitrogen in the P-N chelate of PNN. In
this scenario, the electrophilicity of the η3-allyl
ligandsproviding the reactive species contains a η3-allyl
groupsis increased by the π-accepting properties of the
imino group, thus increasing its succeptibility for nu-
cleophilic attack. Indeed, Helmchen and co-workers
also observed a very fast reaction for the similar ligand
2-[2-(diphenylphosphino)phenyl)]-4-(2-propyl)-4,5-dihy-
drooxazole, but surprisingly, this rate enhancing effect
was not observed for analogous phosphino-oxazole
ligands.4k As yet, the exact mechanistic implications
of both the ethylpyridyl group and the presence of an
imino nitrogen remain unclear.
The structural characterization of the complexes 2,
3, 5, 6, 9, and 10 and also of [(PNN)Pd(Cl)]Cl and of
[(PNN)Pd(solvent)[OTf2, which were published re-
cently,7 shows that 1 has a very strong tendency to
coordinate in a terdentate fashion. Such a strong
tendency has not been observed for ligands with a
N-N-N donor set unless steric constraints are impos-
ing terdentate coordination, such as palladium com-
plexes of terpyridine.1e,11,14,25
The strong tendency of 1 to maintain coordination in
the terdentate fashion is particularly remarkable in
allylpalladium compound 6. Whereas the isomer in
which PNN coordinates in a monodentate fashion 6a
has been observed for a few hours, no sign of the
expected P-N-coordinating isomer 6b has been ob-
served; see Scheme 2. Only when η1-coordination of the
allyl moiety is unfavorable, as in (pentamethylallyl)-
palladium compound 8, is a P-N chelate observed.
The reason for the surprising bidentate coordination
fashion in the acetylpalladium complex 4 is not well
understood, although a similar behavior was observed
recently for palladium complexes containing the trini-
trogen ligand 2-((2-(2′-methylidene-6′-methylpyridyl)-
amino)ethyl)pyridine.14 Apparently, the Pd-Cl bond is
stronger in 4 than the one in 2. Perhaps the Coulombic
interaction Pd+Cl- is relatively strong in 4 (and in
acetylpalladium complexes in general) due to a higher
positive charge on Pd+, caused by the more electrone-
gative acetyl group.
The low reactivity of the methylpalladium compounds
2, 3, 9, and 10 toward insertion of CO is not unexpected.
CO insertion half-lives between 0.5 and 3 h at 25 bar of
CO and at room temperature have been found for
complexes of the type (P-N)Pd(CH3)(Y) (P-N ) 1-(di-
methylamino)-8-(diphenylphosphino)naphthalene,13
1-(dimethylamino)-3-(diphenylphophino)propane, and13
cyclopentadienyl(7-(dimethylamino)-1-(diphenylphos-
phino)-4,5,6,7-tetrahydroindenyl)iron;5d Y ) Cl, OTf). In
order to insert CO into the Pd-C bond of a methylpal-
ladium compound containing a P-N ligand, the reaction
has to pass either via a large kinetic barrier in the
migration step (route A in Scheme 4) or via a prear-
rangement equilibrium reaction with an unfavorable
equilibrium constant (route B in Scheme 4). This is not
Con clu sion s
We have shown that the potentially terdentate ligand
1 can coordinate to palladium in mono-, bi-, and ter-
dentate coordination fashions. 1 stabilizes a series of
organopalladium(II) and -platinum(II) complexes, with
a strong tendency to terdentate coordination. Bidentate
coordination is preferred in the acetylchloropalladium
complex 4 and in (pentamethylallyl)palladium com-
pound 8. Interestingly, the Pd(0) compound 11 meets
the stability we aimed for. It is stable in the solid state
for weeks as well as in solution in benzene or toluene
for hours. The stability of both the zerovalent and
divalent palladium complexes and the proven multi-
functional coordination behavior of 1 now open a way
to catalytic applications through a Pd(0)-Pd(II) cycle
without additional stabilizing ligands. Indeed, our
preliminary results of allylic alkylation reactions show
that palladium complexes of PNN are very active.
Exp er im en ta l Section
(25) Ru¨lke, R. E.; Han, I. M.; Elsevier, C. J .; Vrieze, K.; van
Leeuwen, P. W. N. M.; Roobeek, C. F.; Zoutberg, M. C.; Wang, Y.-F.;
Stam, C. H. Inorg. Chim. Acta 1990, 169, 5.
Ma ter ia ls a n d Ap p a r a tu s. All manipulations were car-
ried out in an atmosphere of purified, dry nitrogen by using
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Stable Pd(0), Pd(II), and Pt(II) Complexes
Organometallics, Vol. 15, No. 13, 1996 3029
standard Schlenk techniques. Solvents were dried and stored
under nitrogen, with acetonitrile also stored over 3 Å molecular
sieves. Starting compounds (COD)Pd(CH3)(Cl),11 (COD)Pt-
(C11), 130.8 (C3), 134.0 (C4), 134.7 ([20], Co), 136.7 (C12), 137.1
([10], Ci), 137.2 ([20], C6), 140.1 ([17], C1), 149.81 (C14), 160.3
(C10), 160.7 ([21], C7). 31P-NMR (CDCl3): -13.6. 15N-NMR
(CDCl3): -45 ([3], imine N), -68 (pyridyl N).
20
(CH3)(Cl),13,26 and [(C3H5)Pd(Cl)]2 have been synthesized
according to the literature. [(η3-C8H15)Pd(Cl)]2 was synthesized
from (COD)Pd(CH3)(Cl) by insertion of tetramethylallene into
the Pd-C bond.23 Other starting chemicals are commercially
available and were used without further purification except
where mentioned explicitly. Carbon monoxide (2.5 grade) was
obtained from HoekLoos and 13CO from Campro. Silver
trifluoromethanesulfonate was stored under nitrogen and in
the dark.
Syn th esis of Meth ylp a lla d iu m a n d Meth ylp la tin u m
Com p ou n d s of P NN. The syntheses of the methylpalladium
complexes 2, 3, 9, and 10 have been carried out according to
published methods, starting with (COD)Pd(CH3)(Cl)11 or (COD)-
Pt(CH3)(Cl).13,26
2: Colorless crystals; yield 78%. 1H-NMR (CDCl3): 0.36
([2.7], CH3), 3.48 (H9), 4.22 (H8), 7.07 ([11], H5), 7.48 (13H, Ho,
Hm, Hp, H4, H11, and H13), 7.66 (H3), 7.88 (H12), 8.15 ([4.3], H2),
8.41 (H14), 9.47 (H7). 13C-NMR (CDCl3): 5.0 [4.0], Pd-Me, 39.1
(C9), 56.2 (C8), 123.8 ([45], Ci), 124.3 ([<1], C13), 125.6 ([2.3],
C5), 128.0 ([56], C1), 129.8 ([12], Cm), 132.4 ([2.3], Cp), 133.1
([<1], C11), 133.3 ([7.5], C3), 134.4 ([12], Co), 134.4 (C4), 137.5
([14], C6), 138.6 ([9], C2), 140.4 (C12), 150.4 (C14), 160.9 (C10),
168.2 ([6.8], C7). 31P-NMR (CDCl3): 37.0. 15N-NMR (CDCl3):
-122 ([45], pyridyl N), -123 ([3], imine N). Anal. Found for
[(PNN)Pd(CH3)]Cl‚H2O: C, 57.06; H, 5.23; N, 4.99. Calcd: C,
56.96; H, 4.96; N, 4.92.
3: Colorless crystals; yield 70%. 1H-NMR (CDCl3): 0.35
([2.7], CH3), 3.49 (H9), 4.00 (H8), 7.16 ([10], H5), 7.50 (13H, Ho,
Hm, Hp, H4, H11, and H13), 7.68 (H3), 7.90 ([4.3], H2), 7.96 (H12),
8.42 (H14), 8.80 (H7). 13C-NMR (CDCl3): 5.2 ([3.8], Pd-Me),
38.9 (C9), 56.1 (C8), 123.8 ([45], Ci), 124.6 ([<1], C13), 125.7
([2.3], C5), 127.9 ([56], C1), 129.8 ([11], Cm), 132.5 ([2.3], Cp),
133.2 ([<1], C11), 133.5 ([7.5], C3), 134.4 ([12], Co), 134.5 (C4),
137.2 ([14], C6), 138.3 ([9.0], C2), 140.7 (C12), 150.5 (C14), 160.9
(C10), 167.4 ([6.8], C7). 31P-NMR (CDCl3): 37.2. 15N-NMR
(CDCl3): -121 ([3], imine N), -123 ([45], pyridyl N).
9: Pale yellow microcrystals; yield 73%. 1H-NMR (CDCl3):
0.34 ([3.0], {70}, CH3), 3.40 (H9), 4.35 (H8), 7.09 ([11], H5), 7.46
(13H: Ho, Hp, Hm, H11, H13, H4), 7.66 (H3), 8.00 (H12), 8.21 ([4.2],
H2), 8.45 ({36}, H14), 9.85 ({44}, H7). 13C-NMR (CDCl3): -8.5
([6.2], {659}, Pt-Me), 38.3 (C9), 54.8 (C8), 122.1 ([57], Ci), 124.2
({36}, C13), 125.1 ([<1], C5), 126.7 ([66], {43}, C1), 128.8 ([11],
Cm), 131.8 ([2.3], Cp), 132.5 ([<1], C4), 132.7 ([8.0], C3), 132.9
([<1], C11), 133.7 ([11], {45}, Co), 137.0 ([13], C6), 137.6 ([9.1],
C2), 141.0 (C12), 149.9 (C14), 160.0 (C10), 165.7 ([5.3], C7). 31P-
NMR (CDCl3): 12.2 {4101}. 15N-NMR (CDCl3): -131.5 ([3],
{210}, imine N), -132.6 ([72], pyridyl N, platinum satellites
not visible due to the low signal to noise ratio). Anal. Found
for [(PNN)Pt(CH3)[Cl‚H2O: C, 52.16; H, 4.65; N, 4.24. Calcd:
C, 54.40; H, 4.57; N, 4.23.
Elemental analyses have been carried out by Dornis and
Kolbe Mikroanalytisches Laboratorium, Mu¨hlheim a.d. Ruhr,
Germany, and by Mikroanalytisches Laboratorium (J . Thei-
ner), Universita¨t Wien, Wien, Austria. 1H-, 13C-{1H}-, 31P-
{1H}-, and 15N-INEPT-NMR spectra were recorded on a Bruker
AMX 300 spectrometer, and the HP-NMR experiments, on a
Bruker AC 100 spectrometer. Mass spectra were acquired
using a Bio-Ion desorption time-of-flight mass spectrometer
with a 15 cm flight tube (ABI Sweden, Uppsala, Sweden). The
acceleration voltage was 18 kV. Samples were deposited from
an acetonitrile solution of the complex on a nitrocellulose-
coated target. GC-FID spectra were recorded on a Hewlett-
Packard HP5790 gas chromatograph, the GC-MS spectra on
a Hewlett-Packard HP5790 gas chromatograph equipped with
a HP 5971A mass selective detector in the EI mode, and
infrared spectra on a BioRad FTS-7 spectrophotometer.
NMR spectra have been obtained from CDCl3 solutions,
unless noted otherwise. Chemical shifts are relative to TMS
(1H- and 13C-{1H}-NMR), H3PO4 (31P-{1H}-NMR) and CH3NO2
(15N-{1H}-NMR).27 Coupling constants J (H-H) are listed
between J (P-H) and J (P-C) between parentheses, and J (Pt-
H) and J (Pt-C) between braces. INEPT measurements were
performed using the standard INEPT pulse sequence27 with
an evolution time τ set at 22.7 ms.
In order to save space, the homonuclear coupling constants
of the ligand are not listed individually. The values for
compounds 1-11 are as follows: H2 dd (7.7, 1.3), H3 t (7.7),
H4 dd (7.7, 1.0), H5 d (7.7), H7 s, H8 t (7.4), H9 t (7.4), H11
d
(7.7), H12 dt (7.7, 1.2), H13 dd (7.7, 5.5), and H14 d (5.5). Ho,
Hm, and Hp generally coincide and often conceal the resonances
of H3, H5, H11, and H13. Numbering of the allyl moiety in 6
1′
2′
3′
and 7: PdC1′C2′dC3′; in 6a and 8: ) trans P, ) central,
a
s
) cis P, ) anti, ) syn.
Syn th esis of (N-(2-(Dip h en ylp h osp h in o)ben zylid en e)-
(2-(2-p yr id yl)eth yl)a m in e), 1. To a solution of 1.58 g (5.45
mmol) of 2-(diphenylphosphino)benzaldehyde28 in 50 mL of
benzene was added 699.2 mg (5.72 mmol) of 2-(2-aminoethyl)-
pyridine, and the solution was refluxed for 1 h. The solution
was dried on MgSO4 and the solvent removed in vacuo to yield
a pale yellow oil. The oil was dissolved in hot hexane and
subsequently cooled in an ice bath. An orange precipitate is
formed slowly. After decanting of the hexane and removal of
the volatiles in vacuo, 1 was obtained purely.
10: Pale yellow microcrystals; yield 86%. 1H-NMR
(CDCl3): 0.44 ([3.0] {70}, Pt-Me), 3.48 (H9), 4.23 (H8), 7.15
([11], H5), 7.47 (13H, Ho, Hp, Hm, H111, H13, and H5), 7.65 (H3),
8.02 (m, H2 and H12), 8.46 ({32}, H14), 9.26 ({41}, H7). 13C-
NMR (CDCl3): -8.1 ([6.8], {668}, Pt-Me), 38.8 (C9), 55.3 (C8),
125.6 ([56], Ci), 127.2 [<1], C13), 127.7 ([4.0], C5), 129.2 ([78],
{43}, C1), 131.4 ([11], Cm), 134.4 ([2.3], Cp), 135.1 (C4), 136.0
([8.0], C3), 136.2 (C11), 136.4 ([12], Co), 139.1 ([13], C6), 139.3
([9.0], C2), 143.0 C12), 152.7 (C14), 162.2 (C10), 167.0 ([5.3], C7).
31P-NMR (CDCl3): 12.3 {4078}.
1: Orange microcrystals; yield 81%, mp 75 °C (from hexane).
Anal. Found: C, 78.9; H, 6.0; N, 7.2; P, 7.7. Calcd: C, 79.2;
H, 5.9; N, 7.1; P, 7.9. 1H-NMR (CDCl3): 2.97 (H9), 3.89 (H8),
Syn th esis of (P NN)P d (C3H5)]Cl, 6. To a stirred solution
20
of 9.8 mg (0.054 mmol of “Pd”) of [(C3H5)Pd(µ-Cl)]2 in 5 mL
6.86 ([4.7], H4), 7.03 (H5), 7.05 (H13), 7.30 (11H: Ho + Hm
+
of chloroform was added 21.1 mg (0.054 mmol, 1.0 equiv) of 1.
In order to obtain 6 purely, the solution was refluxed for 2 h
and the solvent removed in vacuo to give pure 6. Similarly, 6
can also be prepared in dichloromethane.
Hp + H11), 7.38 (H3), 7.50 (H12), 7.93 ([3.9], H2), 8.49 (H14), 8.85
([4.7], H7). 13C-NMR (CDCl3): 40.1 (C9), 61.6 (C8), 121.7 (C13),
124.1 (C5), 128.4 ([4.5], C2), 129.1 ([7.5], Cm), 129.3 (Cp), 129.4
6: Yellow microcrystals. 1H-NMR (CDCl3, 223 K): 2.19 (dd,
H1′), 3.54 (H9), 4.03 (H8), 4.50 (H3′), 4.62 (d, H3′), 5.52 (ddt, H2′),
7.11 ([10], H5), 7.40 (m, 14H, Ho, Hm, Hp, H3, H4, H11, H13),
7.94 (H12), 8.08 ([4.3], H2), 8.59 (H14), 9.43 (H7). 13C-NMR
(CDCl3): 31.9 (C1′), 39.3 (C9), 54.4 (C8), 110.7 (C3′), 124.4 ([45],
Ci), 124.8 (C13), 126.1 ([2], C5), 127.2 ([52], C1), 130.1 ([11], Cm),
132.7 ([2], Cp), 133.1 ([2], C11), 133.4 ([8], C3), 133.6 ([2], C4),
134.6 ([12], Co), 137.2 ([14], C6), 138.5 ([9], C2), 140.8 (C12),
149.9 (C14), 159.8 (C10), 169.4 ([5], C7). 31P-NMR (CDCl3,
223K): 33.1. 15N-NMR (CDCl3, 223 K): -119 (broad, imine
(26) (a) Yoshida, G.; Numata, S.; Kurosawa, H. Chem. Lett. 1976,
705. (b) Kurosawa, H.; Yoshida, G. J . Organomet. Chem. 1976, 120,
297.
(27) Nitromethane is preferred by us as internal standard instead
of the recommended standard liquid, anhydrous ammonia, because of
the relative temperature independence of the first and its widespread
use in articles about organic and organometallic compounds. Conver-
sion to the recommended ammonia standard by adding 380 ppm to
the nitromethane standard, for this reason, only gives
a rough
indication. For theoretical aspects of 15N-INEPT-NMR spectroscopy,
see: Benn, R.; Gu¨nther, H. Angew. Chem. 1983, 95, 381.
(28) Rauchfuss, T. B.; Wrobleski, D. A. Inorg. Synth. 1982, 21, 175.
+
+

3030 Organometallics, Vol. 15, No. 13, 1996
Ta ble 7. Resu lts fr om Selected Allylic Alk yla tion Rea ction s Ca ta lyzed by 6
Ru¨lke et al.
entry
electrophile
time (h)
yield (%)
product (ratio)
1
2
ClCH2CHdCH2
ClCH(CH3)CHdCH2
0.5
0.5
1
>99a
50a
H2CdCHCH2CH(COOEt)2
86a
24
>99a
H2CdCHCH(CH3)CH(COOEt)2 (38%)
E-H3CCHdCHCH2CH(COOEt)2 (54%)
Z-H3CCHdCHCH2CH(COOEt)2 (8%)
E-PhCHdCHCH2CH(COOEt)2
3
4
BrCH2CHdCHPh
AcOCH(Ph)CHdCH(Ph)
0.5
1
>99a
>99b
E-PhCHdCHCH(Ph)CH(COOEt)2
According to GC. According to 1H-NMR.
a
b
N and pyridyl N). Anal. Found for [(PNN)Pd(C3H5)]Cl‚CH2-
Cl2: C, 48.52; H, 4.22; N, 4.18. Calcd: C, 49.28; H, 4.29; N,
4.26.
6a : 1H-NMR (CDCl3, 223 K): 2.73 (d, (11.7), H3′a), 2.89 (t,
[12.9], H1′a), 3.17 (H8), 3.94 (dd, [7], [15], H3′s), 4.18 (dd, [9],
[12], H1′s), 4.87 (H9), 6.06 (m, H2′), 8.76 (H14), 8.90 (H7), other
signals concealed by signals of 6. 31P-NMR (CDCl3, 223 K):
22.9.
or immersing it into the NMR probe. To this end we have
conveniently employed an explosion-proof tube holder. Details
may be obtained from one of the authors (C.J .E.).16b
4: White crystals. 1H-NMR (CDCl3): 2.19 ([1], C(O)CH3),
3.38 (H9), 4.25 (H8), 7.14 (m, 2H, H4 and H5), 7.50 (15H, Ho,
Hm, Hp, H2, H3, H11, H12, and H13), 8.45 (H14), 8.51 (H7). 31P-
NMR (CDCl3, 223 K): 20.9.
5: Off-white microcrystals. 1H-NMR (CDCl3): 2.13 (C(O)-
CH3), 3.42 (H9), 4.24 (H8), 7.11 (m, 2H, H4 and H5), 7.50 (m,
14H, Ho, Hm, Hp, H3, H11, H12, and H13), 7.91 (H2), 8.44 (H14),
8.50 (H7). 31P-NMR (CDCl3, 223 K): 24.9.
Syn th esis of [(P NN)P d (C3H5)]OTf, 7, a n d (P NN)P d -
(C8H15)]OTf, 8. To a stirred solution of 15.3 mg (0.084 mmol
20
of “Pd”) of [(C3H5)Pd(µ-Cl)]2 in 3.0 mL of dichloromethane
were added 33.0 mg (0.084 mmol, 1.0 equiv) of 1 and 16.3 mg
(0.084 mmol, 1.0 equiv) AgOTf. The instantaneously formed
white precipitate was filtered off and the solvent removed in
vacuo, yielding pure 7. The pentamethylallyl analogue 8 was
obtained via the same procedure, starting from [(C8H15)Pd(µ-
Cl)]2,23 and was used for NMR characterization without
isolation.
P a lla d iu m -Ca ta lyzed Allylic Alk yla tion Rea ction . To
a stirred solution of 100 mg (1.0 mmol) of sodium diethyl
malonate in 3.9 mL of THF at room temperature were
subsequently added a solution of 5.8 mg (0.01 mmol) of 6 in
0.9 mL of THF, 10 mL of THF, and 1 mmol of allyl electrophile.
Samples (1 mL) of the reaction mixture were taken at 0.5, 1,
and 4 h reaction times and the remaining reaction mixture
after 24 h. The samples were worked up by quenching with
aqueous ammonium chloride, extracting the organic com-
pounds with diethyl ether and drying with magnesium sulfate.
Qualitative analysis of the products was carried out by GC-
MS, and quantitative analysis, by GC.
7: Yellow microcrystals. 1H-NMR (CD2Cl2, 223 K): 2.27
(d, H1′), 3.41 (t, H9), 3.86 (H8), 4.52 (d, H3′), 4.65 (d, H3′), 5.57
(ddt, H2′), 7.20 (H5), 7.40-7.65 (14H, Ho, Hm, Hp, H3, H4, H11
,
H13), 7.91 (H12), 7.91 (H2), 8.37 (H7), 8.63 (H14). 31P-NMR (CD2-
Cl2, 223 K): 33.3.
8: Yellow microcrystals. 1H-NMR (CD2Cl2, 293 K): 0.99
([10], H1′a), 1.23 ([6], H3′a), 1.91 ([5], H3′s), 1.94 ([9], H1′s), 2.06
(H2′), 3.34 (H9), 4.41 (H8), 6.11 (H11), 6.77 ([10], H5), 7.50 (15H,
Ho, Hm, Hp, H2, H3, H4, H12 and H13), 8.14 (H7), 8.36 (H14). 13C-
NMR (CDCl3): 20.2 (Me3′a), 26.7 (Me2′), 27.0 ([5] Me1′s), 28.3
([2] Me1′a), 29.1 (Me3′s), 41.6 (C9), 66.0 (C8), 76.4 ([7] C3′), 109.1
([26]), 121.6 ([5] C2′), 125.8 (C13), 125.8 ([34] C1), 126.1 (C5),
128.0 ([43] Ci), 128.4 ([43] C1′), 129.9 ([9] Cm), 130.6 ([10] Co),
132-135 (complex pattern of C11, C2, C3, C4, and Cp signals),
136.5 ([15] C6), 139.6 (C12), 153.7 (C14), 157.0 (C10), 170.9 (C7).
31P-NMR (CDCl3, 223 K): 24.9.
Syn th esis of (P NN)P d , 11. To an NMR tube containing
a solution of 14.2 mg (0.025 mmol) of 6, or an equimolar
amount of 7, in 0.5 mL of CDCl3 at room temperature was
added 2.0 mL (1.7 mg, 1.0 equiv of pyrrolidine, and the reaction
was monitored with 1H- and 31P-NMR. After 30 min, the
formed mixture of 11 and 11a was separated on a small
column of activated silica with ethyl acetate as the eluent.
11: Orange microcrystals. 1H-NMR (CDCl3): 3.56 (H9), 4.11
(H8), 7.09 ([11], H5), 7.50 (H, Ho, Hm, H3, H4, H11, H12 and H13),
7.90 (H12), 8.49 ([3.9], H2), 8.87 (H14), 10.00 (H7). 13C-NMR
(CDCl3): 37.9 (C9), 58.9 (C8), 120.4 (weak, probably Ci), 124.2
(C13), 125.5 ([55], C1), 125.6 (C5), 129.8 ([12], Cm), 133.3 (Cp),
133.6-134.1 (coinciding signals from C3, C4 and C11), 134.5
([11], Co), 137.3 [16], C6), 139.4 ([8], C2), 140.9 (C12), 151.8 (C14),
158.8 (C10), 159.9 ([6], C7). 31P-NMR (CDCl3): 30.9. MS
(plasma desorption): m/z 500.7.
Ca r bon yla tion Rea ction s. A 10 mm o.d. single-crystal
sapphire high-pressure NMR tube16 was filled with 30 mg of
2 or 3 in 1.5 mL of CDCl3 and pressurized with CO to 25 bar.
The carbonylation was then followed with 1H- and 31P-NMR
at 323 K for 72 h. Experiments with 13CO have been
performed in the same fashion, except that the HP-NMR tuve
was pressurized to 7 bar of 13CO.
Note: Although the above described high-pressure tubes have
been used safely in our institute for years in the pressure range
1-50 bar, it is absolutely recommended to avoid direct exposure
to a charged high-pressure tube while preparing, transporting,
In the case of 3-acetoxy-1,3-diphenylpropene, 300 mg (3.0
mmol) of sodium diethylmalonate in 4.0 mL of THF and 0.03
mmol of 6 were used. The workup was done in the same
fashion, except that the reaction mixture was purified over
silica with 95:5 hexane/ethyl acetate. The product was
analyzed with 1H-NMR.
X-r a y Da ta Collection a n d Str u ctu r e Refin em en t of
(N-(2-(Dip h en ylp h osp h in o)b en zylid en e)(2-(2-p yr id yl)-
eth yl)a m in e)m eth ylp a lla d iu m Tr iflu or om eth a n esu lfon -
a te, 3. X-ray data were collected on an Enraf Nonius CAD4T/
rotating anode diffractometer (Mo KR, graphite monochromator)
for a colorless crystal cut to size in oil and glued on top of a
glass fiber. Accurate unit-cell parameters were derived from
the SET4 setting angles of 25 reflections in the range 11° < θ
< 14°. Reflection data were corrected for Lp and absorption
(DIFABS)29 and averaged into a unique dataset (Rav ) 0.021).
The structure was solved with DIRDIF9230 and refined on F
with SHELX-76.31 Hydrogen atoms were located from a
difference density map. Their positions were refined with
individual isotropic atomic displacement parameters. A final
difference map showed no residual features (apart from
residual absorption artifacts near Pd). Neutral scattering
factors and anomalous dispersion corrections were taken from
Cromer and Mann and Cromer and Liberman, respectively.32
Geometrical calculations including the ORTEP illustration
were done with PLATON.33 All calculations were done on a
DEC5000 cluster. Numerical data have been collected in Table
8.
(29) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(30) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. D.; Smits, J . M. M.; Smykalla, C. The
DIRDIF program system; Technical report of the Crystallographic
Laboratory, Universiteit Nijmegen: Nijmegen, The Netherlands, 1992.
(31) Sheldrick, G. M. SHELX-76, Crystal Structure Analysis Pack-
age; University of Cambridge: Cambridge, England, 1976.
(32) (a) Cromer, D. T.; Mann, J . B. Acta Crystallogr., Sect. A 1968,
24, 321. (b) Cromer, D. T.; Liberman, D. J . Chem. Phys. 1970, 53,
1891.
(33) Spek, A. L. Acta Crystallogr., Sect. A 1990, 46, C34.
+
+

Stable Pd(0), Pd(II), and Pt(II) Complexes
Organometallics, Vol. 15, No. 13, 1996 3031
Ta ble 8. Cr ysta l a n d Refin em en t Da ta for 3 a n d 4
3
4
Unit Cell Data
chem formula
fw
C28H26F3N2O3PPdS‚CHCl3
784.36
C28H26ClN2OPPd
579.4
cryst system
space group
a, Å
b, Å
c, Å
monoclinic
P21/c
monoclinic
P21/c
25.945(2)
10.5396(3)
27.825(2)
120.66(1)
6545.1(10)
1.592
13.1382(9)
10.977(3)
18.776(2)
109.018(8)
2560.0
â, deg
V, Å3
dx, g‚cm-3
Z
1.50
4
8
F(000)
3152
9.6
1176
77.51
0.05 × 0.30 × 0.70
µ, cm-11
cryst size, mm
0.25 × 0.25 × 0.10
Data Collection
150
T, K
252
θ
min, θmax, deg
0.85, 27.5
0.710 73
0.59 + 0.35 tan θ
ω/2θ
2h33, 2h25, 2h34
-30:33, 0:13, 0:36
16 177
15 010
8887
3.5, 65
1.5418
1.2 + 0.15 tan θ
ω/2θ
1h02, 302
-15:14, 0:12, 0:22
4330
4330
2604
λ, Å
∆ω
scan mode
ref reflns
dataset (hkl)
tot. no. of data
tot. no. of unique reflns
no. of obsd data
DIFABS corr range
0.84:1.07
0.73:1.42
Refinement
no. of params
991
412
R
Rw
0.045
0.034
1.48
0.056
0.084
0.40
(7.3 + Fo + 0.0139Fo
0.51
-1.2, 0.6
S
w-1
σ2(F)
)
2
-1
∆/σ
0.04
-0.44, 1.24
∆l (min, max)
Ta ble 9. Con d u ctom etr ic Da ta Obta in ed fr om 2
a n d 3
Con d u ctom etr y. The conductometric experiments were
carried out with a Consort K720 conductometer equipped with
a Philips PW 9512/00 conductometric cell in a closed glass
vessel. For the experiments, ca. 20 mg of the complex was
dissolved in 5.0 mL of chloroform or acetonitrile. The conduc-
tivities were not corrected for the temperature. The results
are presented in Table 9.
compd (solvent)
specific conductivity, µS‚M-1 (T, K)
2 (CHCl3)
2 (CH3CN)
3 (CHCl3)
3 (CH3CN)
264 (233), 328 (293), 330 (319)
34 900 (233), 74 000 (293), 84 800 (318)
300 (233), 526 (293), 548 (318)
34 500 (233), 71 700 (293), 83 700 (318)
Ack n ow led gm en t. The Innovation Oriented Re-
search Programme (IOP-catalysis) is acknowledged
(P.W.) for their financial support. This work was also
supported in part (A.L.S) by the Netherlands Founda-
tion of Chemical Research (SON) with financial aid from
the Netherlands Foundation for Scientific Research
(NWO). Thanks are due to Dr. W. M. A. Niessen of the
Rijks Universiteit Leiden for the mass spectroscopy
measurements and to Dr. M. Widhalm of the University
of Vienna for very fruitful discussions.
X-r a y Da ta Collection a n d Str u ctu r e Refin em en t of
(N-(2-(Dip h en ylp h osp h in o)b en zylid en e)(2-(2-p yr id yl)-
eth yl)a m in e)ch lor oa cetylp a lla d iu m , 4. The crystal data
were collected (3.5° < θ < 65°, Cu KR radiation, graphite
monochromator) on an Enraf Nonius CAD-4 diffractometer.
A total of 4330 unique reflections with 2604 significant [Fo >
2.5σ(F)] have been obtained (Table 8). Data were corrected
for Lp and for a linear decay of 9% of the reference reflections
during 53 h of X-ray exposure time. An empirical absorption
correction was applied (DIFABS).29 The structure was solved
by direct methods. The hydrogens were calculated. Full-
matrix least-squares refinement on F, anisotropic for the non-
hydrogen atoms and isotropic for the hydrogen atoms, re-
straining the latter in such a way that the distance to their
carrier remained constant at approximately 1.09 Å, converged
Su p p or tin g In for m a tion Ava ila ble: Listings of atomic
coordinates and U values, anisotropic thermal parameters, and
complete bond distances and bond angles of 3 and 4 (26 pages).
Ordering information is given on any current masthead page.
OM9509047
to R ) 0.056, Rw ) 0.084, (∆/σ)max ) 0.51. A weighting scheme
2
-1 was used. Scattering factors were
(34) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, England, 1975; Vol. 4.
(35) XTAL 3.2 Reference Manual; Hall, S. R., Stewart, J . M., Eds.;
Universitites of Western Australia, Perth, Australia, and of Maryland,
College Park, MD, 1992.
w ) (7.3 + Fo + 0.0139Fo
)
taken from the literature.32a,34 The anomalous scattering of
Pd, Cl, and P was taken into account. All calculations were
performed with XTAL 3.0, unless stated otherwise.35
+
+