Room-temperature oxidation of 2-aminobenzoyl- To 2-aminobenzoato-palladium(II) complexes and of coordinated PPh3 by atmospheric oxygen; X-ray crystal structure of [(PPh3)2Pd(NH2C6H4CO 2-2)Pd{C(O)C6H4NH2-2} (PPh3)]O3SCF3

Article abstract of DOI:10.1039/a701552f

trans-[Pd(C₆H₄NH₂-2)I(PPh ₃)₂] reacts with CO to give the insertion product trans-[Pd{C(O)C₆H₄NH₂-2)](PPh₃) ₂]-O₃SCF₃ or, in the presence of atmospheric oxygen, [(PPh₃)₂-Pd(NH₂C₆H ₄CO₂-2)Pd{C(O)C₆H₄NH ₂-2}(PPh₃)]O₃SCF₃, whose crystal structure is solved.

Full text of DOI:10.1039/a701552f

View Article Online / Journal Homepage / Table of Contents for this issue
Room-temperature oxidation of 2-aminobenzoyl- to
2-aminobenzoato-palladium(ii) complexes and of coordinated PPh3 by
atmospheric oxygen; X-ray crystal structure of
[(PPh3)2Pd(NH2C6H4CO2-2)Pd{C(O)C6H4NH2-2}(PPh3)]O3SCF3
Jose´ Vicente,*† Jose´-Antonio Abad,*‡ Andrew D. Frankland and M.-Carmen Ram´ırez de Arellano
Grupo de Qu´ımica Organometa´lica,§ Departamento de Qu´ımica Inorga´nica, Facultad de Qu´ımica, Universidad de Murcia, Aptdo.
4021, E-30071 Murcia, Spain
trans-[Pd(C6H4NH2-2)I(PPh3)2] reacts with CO to give the
insertion product trans-[Pd{C(O)(C6H4NH2-2)}(PPh3)2]-
O3SCF3 or, in the presence of atmospheric oxygen, [(PPh3)2-
Pd(NH2C6H4CO2-2)Pd{C(O)C6H4NH2-2}(PPh3)]O3SCF3,
whose crystal structure is solved.
The formation of organoperoxometal, ROO[M], complexes
by insertion of O2 into a R–[M] bond has been described.8
However, we are not aware of such a process with an acyl
transition–metal complex such as 3. Di(acyl)nickel(ii) com-
plexes are proposed to be intermediates in reactions of benzyne
Ni0 complexes with CO in the presence of traces of air giving
phthalatonickel(ii) complexes.9 Photolysis of Me3SiC(O)R
(R = H, Me, Ph) in O2-doped argon matrices gives mainly
Me3SiOOC(O)R.10 Both these results are in accordance with
our proposal for the intermediate 6 in Scheme 1. With a less
oxophilic metal ion like PdII, the insertion of oxygen into the
metal–carbon bond requires stronger oxidizing agents.11 In
addition, peroxo-palladium(ii) and platinum(ii) complexes
[M(R)(OORA)L2] (M = Pd, Pt; R = activated alkyl; RA = H,
But; L = phosphine),12 or [Pt{OOC(O)Ph}Cl(PPh3)2],13 have
2-Aminophenylpalladium complexes appear to be interme-
diates in the palladium-catalysed formation of nitrogen-
containing heterocycles from o-iodo- or o-bromo-anilines and,
for example, alkynes,1 dienes,2 or vinyl cyclopropanes and
cyclobutanes,3 as well as in intramolecular cascade cyclisa-
tions.4 Recently, a one-pot palladium catalysed synthesis of
2-aryl and 2-vinyl-4H-3,1-benzoxazin-4-ones from 2-iodoani-
line, carbon monoxide and unsaturated halides or triflates has
been reported.5 These results have prompted us to try to isolate
intermediates in such carbonylation reactions and to study their
reactivity in order to gain more insight into the mechanism of
the palladium-catalysed carbon–carbon bond formation.6 Palla-
dium-catalysed carbonylation of aryl halides and allylic com-
pounds has been shown to occur through (acyl)palladium
complexes.7
L
Pd
L
O
i
2
2
I
L
Pd
L
NH2
2
I
NH2
1
o-Iodoaniline reacts with Pd(dba)2 in the presence of 2 equiv.
of PPh3 to give trans-[Pd(C6H4NH2-2)I(PPh3)2] 1. When
carbon monoxide is bubbled through dichloromethane solutions
of 1, the insertion product trans-[Pd{C(O)(C6H4NH2-
2)}I(PPh3)2] 2 is formed and isolated as a moisture-stable
solid (Scheme 1, step i). When complex 2 was reacted
ii
iii
O
L
+
Pd
NH2
O
+
L
2
iv
O
L
O
with TlO3SCF3, the dimer [(PPh3)2Pd(NH2C6H4CO2-
C
+
Pd
Pd
2)Pd{C(O)C6H4NH2-2}(PPh3)]O3SCF3 4 was isolated instead
L
NH2
L
NH2
3
v
of the expected [Pd{C(O)C6H4NH2-2}(PPh3)2]O3SCF3
3
(Scheme 1, step ii). This product can be viewed as resulting
O
–OL
4
from the replacement of the PPh3 ligand trans to the carbonyl
+O2
2
C
O
L
vi
+
group in 3, for the complex [Pd{OC(O)C6H4NH2-
2}(PPh3)2]O3SCF3 5. The displaced PPh3 appears in solution as
OPPh3 (31P NMR).
Both 3 and 5 can be independently isolated. Thus, if 1 is
reacted with TlO3SCF3 under an atmosphere of CO the
expected complex 3 is isolated (Scheme 1, step iii). It is
reasonable to assume that 3 is an intermediate in the formation
of 4. In fact, when a solution of 3 is stirred in the open air it
transforms into 4 (Scheme 1, step iv).
Pd
H2N
L
NH2
L
+
Pd
L
5
O
O
O
L
+
O
Pd
3
L
NH2
6
3
O2
5
Contrary to the above mentioned relationship between
complexes 3, 4 and 5, complexes 3 and 5 do not react with each
other. This observation, and the formation of OPPh3, can be
interpreted assuming that the oxidation occurs not only on the
benzoyl group but also on PPh3 while it is still coordinated. We
assume that this process occurs by formation of a peroxoben-
zoyl complex 6 which interacts with the phosphine trans to the
carbonyl group in 3, as depicted in Scheme 1. By reacting 3 or
4 with PPh3 in the presence of oxygen, complex 5 can be
isolated. These results can be explained by the cyclic process
shown in Scheme 1.
Ph3P
4
6
3
OPPh3
Scheme 1 L = PPh3. Reagents and conditions: i, + 2 CO (1 atm.); ii, + 2
TlO3SCF3 + O2 2 2 TlI 2 OPPh3; iii, + 2 TlO3SCF3 + 2 CO (1 atm.) 2 2
TlI; iv, + O2 2 OPPh3; v, + O2 + PPh3 2 OPPh3; vi + O2 + 2 PPh3
2
OPPh3
Chem. Commun., 1997
959

View Article Online
(aP)2 = bP], P = (2Fc2 + Fo2)/3]; residual electron density 1.660 (20.901)
e Å23, three of the dichloromethane molecules are disordered over two
sites.
Atomic coordinates, bond lengths and angles, and thermal parameters
have been deposited at the Cambridge Crystallographic Data Centre
(CCDC). See Information for Authors, Issue No. 1. Any request to the
CCDC for this material should quote the full literature citation and the
reference number 182/430.
C(31)
C(41)
C(91)
C(16)
C(21)
C(13)
C(15)
C(14)
O(3)
C(17)
C(11)
P(1)
P(3)
C(61)
C(81)
N(2)
Pd(2)
C(71)
C(12)
C(101)
Pd(1)
O(1)
P(2)
References
O(2)
C(7)
1 R. C. Larock and E. K. Yum, J. Am. Chem. Soc., 1991, 113, 6689.
2 R. C. Larock and L. Q. Guo, Synlett, 1995, 465.
C(1)
C(51)
C(2)
N(1)
3 R. C. Larock and E. K. Yum, Tetrahedron, 1996, 52, 2743.
4 R. Grigg, P. Fretwell, C. Meerholtz and V. Sridharan, Tetrahedron,
1994, 50, 359; C. C. Yang, P. J. Sun and J. M. Fang, J. Chem. Soc.,
Chem. Commun., 1994, 2629; S. Brown, S. Clarkson, R. Grigg and
V. Sridharan, J. Chem. Soc., Chem. Commun., 1995, 1135.
5 S. Cacchi, G. Fabrizi and F. Marinelli, Synlett, 1996, 997.
6 J. Tsuji, Palladium Reagents and Catalysts, Wiley, Chichester, 1995;
R. F. Heck, Palladium Reagents in Organic Synthesis, Academic Press,
New York, 1985.
C(6)
C(3)
C(4)
C(5)
Fig. 1 Structure of complex 3. Hydrogen atoms have been omitted for
clarity. Selected bond lengths (Å) and angles (°): Pd(1)–O(1) 2.074(2),
Pd(1)–N(1) 2.116(3), Pd(2)–C(17) 1.959(3), Pd(2)–N(2) 2.129(3), Pd(2)–
O(2) 2.165(2), O(1)–C(7) 1.284(4), O(2)–C(7) 1.247(4), O(3)–C(17)
1.209(4); O(1)–Pd(1)–N(1) 81.35(10), N(1)–Pd(1)–P(2) 96.96(8),
O(1)–Pd(1)–P(1) 84.59(7), P(2)–Pd(1)–P(1) 97.45(3), C(17)–Pd(2)–N(2)
83.22(13), N(2)–Pd(2)–O(2) 93.14(10), C(17)–Pd(2)–P(3) 90.83(11),
O(2)–Pd(2)–P(3) 92.71(7), O(2)–C(7)–O(1) 122.0(3).
7 Y. Yamamoto, Bull. Chem. Soc. Jpn., 1995, 68, 433.
8 M. J. Kendrick and W. Al-Akhdar, Inorg. Chem., 1987, 26, 3971;
R. D. Arasasingham, A. L. Balch and L. Latos-Grazynski, J. Am. Chem.
Soc., 1987, 109, 5846; R. D. Arasasingham, A. L. Balch, and
C. R. Cornman, J. Am. Chem. Soc., 1989, 111, 4357; R. D. Arasasing-
hamn, A. L. Balch, R. L. Hart and L. Latos-Grazynski, J. Am. Chem.
Soc., 1990, 112, 7566; G. Ferguson, P. K. Monagham, M. Parvez and
R. J. Puddephatt, Organometallics, 1985, 4, 1669.
been shown to react with free PPh3 to give OPPh3 but not with
coordinated phosphines, as occurs in our case.
Acylpalladium(ii) complexes are obtained by reacting CO
with alkyl-,7,14–16 p-allyl,14 or arylpalladium(ii)17 complexes.
There are few reported palladium complexes with a phosphine
trans to an acyl group, however, they are too unstable to be
isolated as pure compounds.16,18 Therefore, as far as we are
aware, complex 3 is the first isolated complex containing such
ligands in trans positions. We believe that the mutual
destabilizing effect of carbon and phosphorus ligands in trans
positions is responsible for the instability of these complexes,
the facile oxygen insertion in complex 3, and the oxidation of
the phosphine trans to the carbonyl group. We have found that
such transphobia19 leads to C–P bond coupling processes,20 and
believe it is also responsible for other important C–C and C–N
coupling reactions.
9 M. A. Bennett, D. C. R. Hockless, M. G. Humphrey, M. Schultz and
E. Wenger, Organometallics, 1996, 15, 928.
10 M. Trommer and W. Sander, Organometallics, 1996, 15, 189.
11 C. Sinha, Transition Met. Chem., 1994, 19, 41; S. Chattopadhyay,
C. Sinha, S. B. Choudhury and A. Chakravorty, J. Organomet. Chem.,
1992, 427, 111; P. K. Sinha, J. Chakravarty and S. Bhattacharya,
Polyhedron, 1996, 15, 2931; A. K. Mahapatra, D. Bandyopadhyay,
P. Bandyopadhyay and A. Chakravorty, Inorg. Chem., 1986, 25, 2214;
P. L. Alsters, H. T. Teunissen, J. Boersma, A. L. Spek and G. van Koten,
Organometallics, 1993, 12, 4691; P. L. Alsters, J. Boersma and G. van
Koten, Organometallics, 1993, 12, 1629; J. M. Valk, R. Vanbelzen,
J. Boersma, A. L. Spek and G. van Koten, J. Chem. Soc., Dalton Trans.,
1994, 2293; R. Bhawmick, H. Biswas and P. Bandyopadhyay,
J. Organomet. Chem., 1995, 498, 81.
The isolated complexes 1–5 have been fully characterized by
12 G. Strukul, R. A. Michelin and R. Ros, Inorg. Chem., 1982, 21, 495.
13 M. J. Y. Chen and J. K. Kochi, J. Chem. Soc., Chem. Commun., 1977,
204.
C, H, N analyses, IR spectroscopy and H, 31P and 13C NMR
1
(Supplementary material). The X-ray crystal structure of
complex 3 (the cation of which is shown in Fig. 1 and Scheme
1),¶ shows it to be dimeric with the o-aminobenzoato ligand
bridging, via the O atoms of the carboxylate group, the two
metal centres. The square-planar geometry of the palladium
atoms is fulfilled, in the case of Pd(1), by two phosphine ligands
and the N and O atoms of the o-aminobenzoato group, and for
Pd(2) the other O atom of this ligand, one phosphine and the
o-aminobenzoyl ligand. All bonding distances and angles are
unremarkable.
We thank Direccio´n General de Investigacio´n Cient´ıfica y
Te´cnica (PB92-0982-C) for financial support. A. D. F. and M.
C. R. A. are grateful to Ministerio de Educacio´n y Ciencia for a
Grant and a Contract, respectively.
14 A. Yamamoto, J. Organomet. Chem., 1995, 500, 337.
15 M. J. Green, G. J. P. Britovsek, K. J. Cavell, B. W. Skelton and
A. H. White, Chem. Commun., 1966, 1563; G. Dekker, A. Buijs,
C. J. Elsevier, K. Vrieze, P. Vanleeuwen, W. J. J. Smeets, A. L. Spek,
Y. F. Wang and C. H. Stam, Organometallics, 1992, 11, 1937; H. Jin,
K. J. Cavell, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton
Trans., 1995, 2159; D. L. Reger and D. G. Garza, Organometallics,
1993, 12, 554; B. A. Markies, D. Kruis, M. H. P. Rietveld,
K. A. N. Verkerk, J. Boersma, H. Kooijman, M. T. Larkin, A. L. Spek
and G. Vankoten, J. Am. Chem. Soc., 1995, 117, 5263; P. Wehman,
R. E. Rulke, V. E. Kaasjager, P. C. J. Kamer, H. Kooijman, A. L. Spek,
C. J. Elsevier, K. Vrieze and P. Vanleeuwen, J. Chem. Soc., Chem.
Commun., 1995, 331.
16 F. Ozawa, T. Hayashi, H. Koide and A. Yamamoto, J. Chem. Soc.,
Chem. Commun., 1991, 1469.
17 G. K. Anderson and R. J. Cross, Acc. Chem. Res., 1984, 17, 67;
V. V. Grushin and H. Alper, Organometallics, 1993, 12, 1890;
J. L. Hoare, K. J. Cavell, R. Hecker, B. W. Skelton and A. H. White,
J. Chem. Soc., Dalton Trans., 1996, 2197; P. E. Garrou and R. F. Heck,
J. Am. Chem. Soc., 1976, 98, 4115.
18 P. W. N. M. van Leeuwen, C. F. Roobeek and H. van der Heijden, J. Am.
Chem. Soc., 1994, 116, 12 117; C. G. Anklin and P. S. Pregosin,
J. Organomet. Chem., 1983, 243, 101.
19 J. Vicente, A. Arcas, D. Bautista and P. G. Jones, Organometallics, in
the press.
20 J. Vicente, A. Arcas, D. Bautista, A. Tiripicchio and M. Tiripicchio-
Camellini, New J. Chem., 1996, 20, 345.
Footnotes
† E-mail: jvs@fcu.um.es
‡ E-mail: jaab@fcu.um.es
§ WWW: http://www.scc.um.es/gi/gqo/
¶ Crystal data: 3·4CH2Cl2, C74H65Cl8F6N2O9P3Pd2S2, M
= 1893.71,
yellow prism of dimensions 0.62 3 0.60 3 0.28 mm, triclinic, space group
–
P1, a = 15.245(2), b = 16.005(2), c = 17.158(2) Å, a = 87.882(8),
b = 71.080(10), g = 86.266(8)°, U = 3951.3(9) Å3, Z = 2, Dc = 1.592 Mg
m23, 2qmax = 50°, Siemens P4 diffractometer, Mo-Ka (l = 0.71073 Å),
w-scan, T = 173 K, 18038 reflections collected of which 13857 were
independent,
y-scans
absorption
correction
(max.,
min.
21 G. M. Sheldrick, SHELXL 93, University of Go¨ttingen, 1993.
transmission = 0.267, 0.208), direct primary solution and refinement on F2
using Siemens-SHELXTL program,21 1009 refined parameters, riding
hydrogens, R1 = 0.0354 [I > 2s(I)], wR2 (all data) = 0.0955 [R1 = s∑Fo¡
Received in Cambridge, UK, 5th March 1997; Com.
7/01552F
2 ¡Fc∑/s¡Fo¡, wR2 = {s[w(Fo 2 Fc2)2]/s[w(Fo2)2]}0.5, w = 1/[s (F2) +
2
2
960
Chem. Commun., 1997