Mono- and dinuclear five-coordinate cyclometalated palladium(II) compounds

Article abstract of DOI:10.1021/ic001094g

Reaction of cyclometalated halide-bridged Pd(II) complexes 1-4 with the tertiary triphosphine ligand (Ph₂PCH₂CH₂)₂PPh (triphos) yielded complexes [{(Ph₂PCH₂CH₂)₂PPh- P,P,P}Pd{N(Cy)=(H)C}C₆H₂{C(H)=N(Cy)}Pd{(Ph ₂PCH₂CH₂)₂PPh-P,P,P}][ClO ₄]₂5, [Pd{C₆H₄-N=NC₆H₅}{(Ph ₂PCH₂CH₂)₂PPh-P,P,P}][ClO ₄] 6, and [Pd{R-C₆H₃C(H)=NCy}{(Ph₂PCH₂CH ₂)₂PPh-P,P,P}][ClO₄] (7; R = 4-CHO, 8; 3-CHO). Spectroscopic and analytic data suggest five-coordination on the palladium atom, which, for complexes 5, 6, and 7, was confirmed by X-ray crystallography. The geometry around palladium may be view as a distorted trigonal bipyramid, with the palladium, nitrogen, and terminal phosphorus atoms in the equatorial plane. Compound 5 is the first doubly cyclometalated palladium(II) compound with two pentacoordinated metal centers. The structure of 6 comprises two discrete cations with slightly different geometries, showing the importance of crystal packing forces in order to determine the coordination arrangement.

Full text of DOI:10.1021/ic001094g

Inorg. Chem. 2001, 40, 4583-4587
4583
Mono- and Dinuclear Five-coordinate Cyclometalated Palladium(II) Compounds
Margarita Lo´pez-Torres,† Alberto Ferna´ndez,† Jesu´s J. Ferna´ndez,† Antonio Sua´rez,†
Ma Teresa Pereira,‡ Juan M. Ortigueira,‡ Jose´ M. Vila,*,‡ and H. Adams§
Departamento de Qu´ımica Fundamental, Universidad de La Corun˜a, E-15071 La Corun˜a, Spain,
Departamento de Qu´ımica Inorga´nica, Universidad de Santiago de Compostela, E-15782 Santiago de
Compostela, Spain, and Department of Chemistry, The University, Sheffield S3 7HF, U.K.
ReceiVed October 3, 2000
Reaction of cyclometalated halide-bridged Pd(II) complexes 1-4 with the tertiary triphosphine ligand (Ph2PCH2-
CH2)2PPh (triphos) yielded complexes [{(Ph2PCH2CH2)2PPh-P,P,P}Pd{N(Cy))(H)C}C6H2{C(H)dN(Cy)}Pd{(Ph2-
PCH2CH2)2PPh-P,P,P}][ClO4]25, [Pd{C6H4-NdNC6H5}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4] 6, and [Pd{R-
C6H3C(H)dNCy}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4] (7; R ) 4-CHO, 8; 3-CHO). Spectroscopic and analytic
data suggest five-coordination on the palladium atom, which, for complexes 5, 6, and 7, was confirmed by X-ray
crystallography. The geometry around palladium may be view as a distorted trigonal bipyramid, with the palladium,
nitrogen, and terminal phosphorus atoms in the equatorial plane. Compound 5 is the first doubly cyclometalated
palladium(II) compound with two pentacoordinated metal centers. The structure of 6 comprises two discrete
cations with slightly different geometries, showing the importance of crystal packing forces in order to determine
the coordination arrangement.
Introduction
pounds, with very short Pd-N distances, we have extended our
previous studies to ligands with different steric and electronic
Palladium(II) coordination and organometallic compounds
usually show square planar environments at the metal center;
five- and six-coordinate species being less common.1 In the past
few years we have studied the reactivity of cyclometalated
palladium(II) complexes with nucleophiles such as tertiary
mono- and diphosphine ligands; the reactions invariably yielded
square planar complexes.2 We then became interested in tri-
and tetradentate polyphosphine ligands which are known to
promote the formation of stable complexes of transition metals
with uncommon coordination numbers and geometries.3 Con-
sequently, we have reported the synthesis of the first pentaco-
ordinated cyclometalated palladium(II) complex by reaction of
a monodentate Schiff base cyclometalated derivative and the
triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine
(triphos),4 in which the coordination geometry of the palladium
atom is a distorted trigonal pyramid with a Pd-N bond slightly
longer than the value expected for a true Pd-N bond (2.359(4)
versus 2.23(2) Å). To ascertain that polyphosphine ligands, and
in particular triphos, are prone to induce a close to five-
coordination environment in palladium(II) cyclometalated com-
requirements, such as bidentate Schiff bases derived form
terephthalaldehyde or isophthalaldehyde, and azobenzene. We
are also aware of the importance of a systematic route to
synthesize five-coordinate palladium(II) species, regardless of
the specific characteristics of the ligands, in order to study the
accessibility of the fifth position at the palladium center and to
clarify the kinetic properties for substitution and exchange
reactions in solution and in biological systems.5 In addition,
the synthesis of transition metal complexes with polydentate
phosphine ligands is potentially interesting due to their applica-
tions in homogeneous and heterogeneous catalysis.6
In the present communication, we report the reaction of the
cyclometalated complexes [(Cl)PdN(Cy)dC(H)C6H2C(H)d
N(Cy)Pd(Cl)]n 1, [Pd{C6H4NdNC6H5}(µ-Cl)]2 2, [{Pd[4-(CHO)-
C6H3C(H)dNCy](Cl)}2] 3, and [{Pd[3-(CHO)C6H3C(H)dNCy]-
(Cl)}2] 4 with triphos to give the new pentacoordinated species
5, 6, 7, and 8, respectively, which have been fully characterized
by elemental analysis (C, H, N), conductivity measurements,
IR, 1H, and 31P-{1H} NMR spectroscopy, and, in part
(complexes 5, 6, and 7), by X-ray crystallography.
* To whom correspondence should be addressed. E-mail: qideport@usc.es.
† Departamento de Qu´ımica Fundamental, Universidad de La Corun˜a.
‡ Departamento de Qu´ımica Inorga´nica, Universidad de Santiago de
Compostela.
Experimental Section
Safety Note: CAUTION. Perchlorate salts of metal complexes with
organic ligands are potentially explosive. Only small amounts of these
materials should be prepared and handled with great caution.
Solvents were purified by standard methods.7 Chemicals were reagent
grade. The triphosphine (Ph2PCH2CH2)2PPh (triphos) was purchased
§ Department of Chemistry, The University.
(1) Abel, E. W.; Stone, F. G. A.; Wilkinson, G. ComprehesiVe Organo-
metallic Chemistry II: a reView of the literature 1982-1994;
Pergmon: Oxford, 1995; p 9.
(2) Vila, J. M.; Gayoso, M.; Pereira, M. T.; Sua´rez, A.; Ferna´ndez, J. J.;
Ortigueira, J. M.; Ferna´ndez, A.; Lo´pez-Torres, M. Trends Organomet.
Chem. 1997, 2, 21.
(3) (a)Levason, W. The Chemistry of Organo Phosphorus Compounds;
Hartley, F. R., Ed.; John Wiley and Sons: New York, 1990; p 617.
(b) Mayer, H. A.; Kaska, W. C. Chem. ReV. 1994, 94, 1239. (c) Cotton,
F. A.; Hong, B. Prog. Inorg. Chem. 1992, 40, 179.
(4) Vila, J. M.; Pereira, M. T.; Ortigueira, J. M.; Ferna´ndez, J. J.;
Ferna´ndez, A.; Lo´pez-Torres, M.; Adams, H. Organometallics 1999,
18, 5484.
(5) Wilkins, R. G. Kinetics and Mechanism of Reactions of Transition
Metals, 2nd ed.; VCH: Weinheim, 1991; Chapter 4.
(6) (a) Bianchini, C.; Graziani, M.; Kaspar, J.; Meli, A.; Vizza, F.
Organometallics 1994, 13, 1165. (b) Bianchini, C.; Marchi, A.;
Marvelli, L.; Peruzzini, M.; Romerosa, A.; Rossi, R.; Vacca, A.
Organometallics 1995, 14, 3203. (c) Seebach, D.; Sommerfeld, T. L.;
Jiang, Q. M.; Venanzi, L. HelV. Chim. Acta 1994, 77, 1313.
10.1021/ic001094g CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/27/2001

4584 Inorganic Chemistry, Vol. 40, No. 18, 2001
Lo´pez-Torres et al.
from Aldrich-Chemie. The synthesis of the cyclometalated complexes
1,8 2,9 3,10 and 411 has been reported previously. Microanalyses were
carried out using a Carlo-Erba Elemental Analyzer, Model 1108. IR
spectra were recorded as Nujol mulls or KBr disks. NMR spectra were
obtained as CDCl3 solutions, referenced to SiMe4 (1H and 13C) or 85%
H3PO4 (31P-{1H}), and recorded on a Bruker AC-2005 spectrometer
(200 MHz for 1H, 81.0 MHz for 31P). All chemical shifts are reported
downfield from standards.
Scheme 1
Syntheses. [{(Ph2PCH2CH2)2PPh-P,P,P}Pd{N(Cy)d(H)C}C6H2-
{C(H)dN(Cy)}Pd{(Ph2PCH2CH2)2-PPh-P,P,P}][ClO4]2 5. To a sus-
pension of 1 (0.026 g, 0.045 mmol) in acetone (ca. 15 cm3),
(Ph2PCH2CH2)2PPh (0.048 g, 0.090 mmol) was added. The resulting
mixture was stirred at room temperature for 24 h, after which an excess
of sodium perchlorate was added, and the mixture was stirred for a
further 2 h. The complex was then precipitated out by addition of water,
filtered off, dried in vacuo, and recrystallized from dichloromethane/
n-hexane. (Yield: 0.07 g, 88%.) Anal. Calcd for C88H92N2O8P6Cl2Pd2:
C, 59.5; N, 1.6; H, 5.2%. Found: C, 59.0; N, 1.5; H, 5.3%. ; νmax
/
cm-1 (CdN) 1621 m. δH 5.65 [d, 2H, J(PH) ) 6.4 Hz, H2,5]. δp 80.9
[t, 1P, J(PP) ) 26.3 Hz], 41.9 [d, 2P]. Specific molar conductivity,
Λm 310 ohm-1 cm2 mol-1 (in dry acetonitrile).
Complexes 6, 7, and 8 were synthesized similarly.
[Pd{C6H4NdNC6H5}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4] 6: (Yield:
0.07 g, 82%.) Anal. Calcd for C46H42N2O4P3ClPd: C, 59.9; N, 3.0; H,
4.6%. Found: C, 59.7; N; 3.1; H 4.5%. δH 8.04 [dd, 1H, J(HH) ) 7.6
and 2.6 Hz, H2], 6.47 [t, 1H, J(HH) ) 7.3 Hz, H4], 5.85 [t, 1H, J(PH)
) 7.3 Hz, J(HH) ) 7.3 Hz, H5]. δp 84.2 [t, 1P, J(PP) ) 25.0 Hz], 42.7
[d, 2P]. Specific molar conductivity, Λm 104 ohm-1 cm2 mol-1 (in dry
acetonitrile).
[Pd{4-(CHO)C6H3C(H)dNCy}{(Ph2PCH2CH2)2PPh-P,P,P}]-
[ClO4] 7: (Yield: 0.05 g, 80%.) Anal. Calcd for C48H49NO5P3ClPd:
C, 60.4; N, 1.5; H, 5.2%. Found: C, 60.0; N; 1.7; H 4.9%. νmax/cm-1
(CdN) 1609 m, (CdO) 1690 s. δH 8.89 [s, 1H, HCdO], 8.22 [s, 1H,
HCdN], 6.02 [d, 1H, J(HP) 7.8 ) Hz, H5]. δp 83.5 [t, 2P, J(PP))
25.4 Hz], 42.6 [d, 2P]. Specific molar conductivity, Λm 170 ohm-1
cm2 mol-1 (in dry acetonitrile).
[Pd{3-(CHO)C6H3C(H)dNCy}{(Ph2PCH2CH2)2PPh-P,P,P}]-
[ClO4] 8: (Yield: 0.05 g, 80%.) Anal. Calcd for C48H49NO5P3ClPd:
C, 60.4; N, 1.5; H, 5.2%. Found: C, 60.1; N; 1.5; H 4.9%. νmax/cm-1
(CdN) 1615 m, (CdO) 1690 s. δH 9.78 [s, 1H, HCdO], 8.19 [s, 1H,
HCdN], 6.84 [d, 1H, J(HH) ) 7.8 Hz, H4], 6.07 [t, 1H, J(PH) ) 7.8
Hz, H5]. δp 84.2 [t, 2P, J(PP) ) 25.4 Hz], 42.4 [d, 1P]. Specific molar
conductivity, Λm 165 ohm-1 cm2 mol-1 (in dry acetonitrile).
Crystal Structure Determination. For complexes 5, 6, and 7, three-
dimensional, room-temperature X-ray data were collected (on a Siemens
Smart CCD diffractometer for 5 and a Siemens P4 diffractometer for
6 and 7) by the omega scan method. All the reflections measured were
corrected for Lorentz and polarization effects. A semi-empirical
absorption correction based on symmetry-equivalent and repeated
reflections was performed for complex 5 only. The structures were
solved by direct methods and refined by full matrix least squares on
F2 with allowance for thermal anisotropy of all non-hydrogen atoms.
Hydrogen atoms were included in calculated positions and refined in
riding mode. For complex 5, the perchlorate anion was found to be
disordered, with the pairs Cl1/Cl1′ and O3/O3′ having 64/35%
occupancies. The structure solution and refinement were carried out
using the program package SHELX-97.12
Results and Discussion
Reaction of the cyclometalated complexes 1, 2, 3, and 4 with
triphos followed by treatment with sodium perchlorate in a
water/acetone mixture yielded the dinuclear and mononuclear
cyclometalated complexes [{(Ph2PCH2CH2)2PPh-P,P,P}Pd-
{N(Cy)d(H)-C}C6H2{C(H)dN(Cy)}Pd{(Ph2PCH2CH2)2PPh-P,P,P}]-
[ClO4]2(5),[Pd{C6H4NdNC6H5}{(Ph2P-CH2CH2)2PPh-P,P,P}]-
[ClO4] (6), [Pd{4-(CHO)C6H3C(H)dNCy}{(Ph2PCH2CH2)2-
PPh-P,P,P}][ClO4] (7), and [Pd{3-(CHO)C6H3C(H)dNCy}{(Ph2-
PCH2CH2)2PPh-P,P,P}][ClO4] (8), respectively, as pure and air-
stable solids (see Scheme 1) which were fully characterized (see
Experimental section).
The phosphorus resonances in the 31P-{1H} NMR spectra
of the complexes were downfield shifted from their values in
the free phosphine, suggesting coordination of all the phosphorus
atoms to the metal center. A triplet resonance at ca. δ 82 was
assigned to the central 31P nucleus, which was trans to the phenyl
carbon atom, and a doublet signal at ca. δ 42 was assigned to
the two equivalent, mutually trans phosphorus nuclei. The latter
signal appeared at lower frequency in accordance with the high
trans influence of the phosphine ligand.13 The resonance of the
protons in the ortho position to the metalated carbon appeared
as a doublet (for complexes 5 and 7) or a triplet (for complexes
6 and 8), showing coupling to the central 31P atom [J(PH) )
6.4, 7.3, 7.8, and 7.8 Hz for 5, 6, 7, and 8, respectively]; no
coupling was observed to the terminal phosphorus nuclei. These
data are in accordance with a disposition in which the metalated
ring is nearly perpendicular to the plane defined by the three
phosphorus atoms; these observations were confirmed by
selective decoupling experiments. The absence of the ν(Pd-
(7) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann: Woburn, MA, 1996.
(8) Vila, J. M.; Gayoso, M.; Pereira, M. T.; Lo´pez-Torres, M.; Ferna´ndez,
J. J.; Ferna´ndez, A.; Ortigueira, J. M. Z. Anorg. Allg. Chem. 1997,
623, 844.
(9) Cope, A. C.; Siekman, R. W. J. Am. Chem. Soc. 1965, 87, 3272.
(10) Vila, J. M.; Gayoso, M.; Pereira, M. T.; Lo´pez, M.; Alonso, G.;
Ferna´ndez, J. J. J. Organomet. Chem. 1993, 445, 287.
(11) Vila, J. M.; Gayoso, M.; Pereira, M. T.; Lo´pez-Torres, M.; Ferna´ndez,
J. J.; Ferna´ndez, A.; Ortigueira, J. M. J. Organomet. Chem. 1996,
506, 165.
(12) Sheldrick, G. M. SHELX-97, An integrated system for solVing and
refining crystal structures from diffraction data; University of Got-
tingen: Germany, 1997.
(13) Pregosin, P. S.; Kuntz, R. W. 31P and 13C NMR of Transition Metal
Phosphine Complexes; Diehl, P., Fluck, E., Kosfeld, R., Eds.;
Springer: Berlin, 1979; p 52.

Cyclometalated Palladium(II) Compounds
Inorganic Chemistry, Vol. 40, No. 18, 2001 4585
Figure 3. Perspective view (ORTEP) of the cation of complex 7.
perchlorate anions. The structure of 6 comprises two discrete
[Pd{C6H4NdNC6H5}{(Ph2PCH2CH2)2PPh-P,P,P}]+ cations
(which are slightly different and will be labeled as 6a and 6b),
two perchlorate anions, and a chloroform and a methanol solvent
molecule per asymmetric unit. The asymmetric unit of 7 contains
a [Pd{4-(CHO)C6H3C(H)dNCy}{(Ph2PCH2CH2)2PPh-P,P,P}]+
cation and a perchlorate counterion.
Figure 1. Perspective view (ORTEP) of the cation of complex 5.
In each structure, the palladium atom is bonded to the adjacent
ortho carbon of the phenyl ring, to one nitrogen atom, and to
the three phosphorus atoms of the tridentate phosphine ligand.
Coordination around the palladium atom may be view as a
distorted trigonal bipyramid, with the palladium, nitrogen, and
terminal phosphorus atoms in the equatorial plane (rms for the
mean planes; 0.0282, 0.0189, 0.0169, and 0.0138 Å for 5, 6a,
6b, and 7, respectively); the maximum deviation of palladium
from this plane is -0.056, 5, 0.0339, 6a, 0.0378, 6b, and
-0.0276 Å, 7. The metalated carbon atom and the central
phosphorus atom are at the apical positions.
Pd(II) five-coordinate complexes, with trimethyl-, triethyl-,
and triphenylphosphine, as well as with bis(diphenylphosphino)-
methane (dppm), have been reported showing Pd‚‚‚N weak
interactions in the range 2.576(4)-2.805(5).16 D. Weaver was
the first to report the crystal structure of a palladated azobenzene
compound with two triethylphosphine ligands where the closest
Pd-N distance was 3.12 Å, therefore, the nitrogen atoms were
not bonded to the palladium atom.17 More recently, in a related
structure by J. Dehand, the Pd-N distance was reported to be
greater, 4 Å.18 The present results show that the triphosphine
ligand used here has an altogether different effect on the
coordination of the metal atom in all cases, regardless of the
metalated organic moiety. We have recently reported an even
shorter distance of 2.359(4) Å.4 However, in the case of complex
Figure 2. Perspective view (ORTEP) of the cation of complex 6.
Cl) band in the IR spectrum confirms Pd-Cl bond cleavage
upon coordination of the palladium atom to the three phosphorus
atoms. For complexes 5, 7, and 8, the shift of the ν(CdN)
stretching vibration to lower wavenumbers14 and the upfield shift
of the HCdN proton resonance in the 1H NMR spectra15 indicate
the existence of a palladium-nitrogen interaction in solution.
Conductivity measurements show the expected values for 1:2
(5) and 1:1 electrolytes (6-8).
Crystal Structures of Complexes 5, 6, and 7. Complexes
5, 6, and 7 have been characterized crystallographically. A view
of the molecular structures is shown in Figures 1 , 2, and 3.
Crystal data are given in the Table 1 , and selected bond
distances and angles with estimated standard deviations are
shown in Tables 2 , 3, and 4. Selected geometric parameters
are summarized in Table 5.
(16) (a) Granell, J.; Sainz, D.; Sales, J.; Solans, X.; Font-Altaba, M. J.
Chem. Soc, Dalton Trans. 1986, 1785. (b) Granell, J.; Sales, J.;
Vilarrasa, J.; Declercq, J. P.; Germain, G.; Miravilles, C.; Solans, X.
J. Chem. Soc, Dalton Trans. 1983, 2441. (c) Taira, Z.; Yamazaki, S.
Bull. Chem. Soc. Jpn. 1986, 59, 649. (d) Vicente, J.; Arcas, A.;
Bautista, D.; Jones, P. G. Organometallics 1997, 16, 2127. (e)
Villanueva, L. A.; Abboud, K.; Boncella, J. M. Organometallics 1991,
10, 2969. (f) Onggo, D.; Craig, D. C.; Rae, A. D.; Goodwin, H. A.
Aust. J. Chem. 1991, 44, 219. (g) Schlager, O.; Wieghardt, K.; Nuber,
B. Inorg. Chem. 1995, 34, 6449. (h) Albert, J.; Go´mez, M.; Granell,
J.; Sales, J. Organometallics 1990, 9, 1405.
The molecular structure of 5 contains a discrete centosym-
metric dinuclear cation of [{(Ph2PCH2CH2)2PPh-P,P,P}Pd-
{N(Cy)d(H)C}C6H2{C(H)dN(Cy)}Pd{(Ph2PCH2CH2)2PPh-
P,P,P}]2+ (half of the cation per asymmetric unit) and two
(14) Onoue, M.; Moritani, I. J. Organomet. Chem. 1972, 43, 431.
(15) Ustynyuk, Y.; Chertov, V. A.; Barinov, J. V. J. Organomet. Chem.
1971, 29, C53.
(17) Weaver, D. Inorg. Chem. 1970, 10, 2250.
(18) Dehand, J.; Fischer, J.; Pfeffer, M.; Mitschler, A.; Zinzius, M. Inorg.
Chem. 1975, 15, 2675.

4586 Inorganic Chemistry, Vol. 40, No. 18, 2001
Lo´pez-Torres et al.
Table 1. Crystallographic Data for Complexes 5, 6, and 7
5
6
7
chemical formula
fw
C88H92N2Cl2O8P6Pd2
1775.16
C47H44.5N2O4.5Cl2.5P3Pd
997.28
C49H50NO5Cl4P3Pd
1074.01
T
λ
293(2) °C
293(2) °C
0.71073 Å
triclinic
293(2) °C
0.71073 Å
monoclinic
P21/c
0.71073 Å
monoclinic
P21/n
cryst syst
space group
P1-bar
a
b
c
11.529(1) Å
22.359(1) Å
16.071(1) Å
13.527(6) Å
17.542(5) Å
20.100(6) Å
98.71(1)°
97.73(3)°
100.22(2)°
4575(3) Å3
4
18.058(6) Å
12.896(6) Å
21.464(5) Å
R
â
97.996(1)°
98.47(2)°
γ
V
Z
4102.5(1) Å3
2
4944(3) Å3
4
µ
6.78 cm-1
1.473 g cm-3
0.0473
7.03 cm-1
1.448 g cm-3
0.0677
7.35 cm-1
1.443 g cm-3
0.0576
Fcalc.
a
R1
b
wR2
0.1173
0.1987
0.1443
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, [F > 4σ(F)]. b wR2 ) [∑[w(Fo - Fc2)2/∑w(Fo )2]1/2, all data.
2
2
Table 2. Selected Bond Distances (Å) and Angles (Deg) for
Complex 5
Table 4. Selected Bond Distances (Å) and Angles (Deg) for
Complex 7
Pd(1)-C(1)
2.049(3) N(1)-C(4)
2.338(3) N(1)-C(5)
2.318(1) C(1)-C(3)
2.312(1) C(3)-C(4)
2.338(3)
1.281(4)
1.480(4)
1.411(4)
1.447(4)
Pd(1)-C(5)
2.075(6) N(1)-C(11)
2.437(5) N(1)-C(12)
2.304(1) C(5)-C(10)
2.331(1) C(3)-C(4)
2.348(1)
1.263(7)
1.479(7)
1.410(8)
1.483(8)
Pd(1)-N(1)
Pd(1)-N(1)
Pd(1)-P(1)
Pd(1)-P(1)
Pd(1)-P(2)
Pd(1)-P(2)
Pd(1)-P(3)
Pd(1)-P(3)
P(2)-Pd(1)-P(1)
C(1)-Pd(1)-N(1)
128.35(3)
78.3(1)
P(2)-Pd(1)-P(3)
84.75(3)
84.63(3)
P(2)-Pd(1)-P(1)
C(5)-Pd(1)-N(1)
P(2)-Pd(1)-N(1)
149.51(6)
76.9(2)
99.2(1)
P(2)-Pd(1)-P(3)
85.49(6)
85.64(6)
P(1)-Pd(1)-P(3)
P(1)-Pd(1)-P(3)
P(2)-Pd(1)-N(1) 115.12(7)
N(1)-Pd(1)-P(3) 108.40(7)
P(1)-Pd(1)-N(1) 116.21(7)
N(1)-Pd(1)-P(3) 111.4(1)
P(1)-Pd(1)-N(1) 111.2(1)
C(1)-Pd(1)-P(3) 173.26(9)
C(5)-Pd(1)-P(3) 171.7(1)
C(5)-Pd(1)-P(2) 93.0(1)
C(1)-Pd(1)-P(2)
93.20(9)
C(1)-Pd(1)-P(1)
91.66(9)
C(5)-Pd(1)-P(1)
91.7(1)
Table 3. Selected Bond Distances (Å) and Angles (Deg) for
Complex 6
Table 5. Selected Geometric Parameters for Complexes 5, 6, and 7
5
6a
6b
7
6a
6b
Pd-N
2.338(3)
2.049(3)
116.21(7)
115.12(7)
2.366(5)
2.052(6)
117.3(2)
103.6(2)
139.02(7)
176.1(2)
2.560(6)
2.062(7)
113.2(1)
95.5(1)
151.06(7)
171.3(2)
2.437(5)
2.075(6)
111.2(1)
99.2(1)
149.51(6)
171.7(1)
Pd-C
Pd(1a)-C(5a)
Pd(1a)-P(2a)
Pd(1a)-P(3a)
Pd(1a)-P(1a)
Pd(1a)-N(1a)
N(1a)-C(11a)
N(1a)-N(2a)
C(5a)-C(10a)
C(10a)-N(2a)
2.052(6) Pd(1b)-C(5b)
2.341(2) Pd(1b)-P(2b)
2.312(2) Pd(1b)-P(1b)
2.303(2) Pd(1b)-P(3b)
2.366(5) Pd(1b)-N(1b)
1.437(8) N(1b)-C(11b)
1.261(7) N(1b)-N(2b)
2.062(7)
2.324(2)
2.305(2)
2.285(6)
2.560(6)
1.433(9)
1.251(8)
1.40(1)
N-Pd-Pterm.
Pterm-Pd-Pterm. 128.35(3)
C-Pd-Pcentr. 173.26(9)
disposition of the phenyl rings attached to the central phospho-
rus, P(3), and to the N(1) atom could explain the different bond
lengths (Figure 4 shows the different coordination geometry of
6a and 6b). While in 6b these are almost parallel, the crystal
structure of 6a shows the P(3) phenyl ring to be twisted toward
the N(1) phenyl ring. As a consequence of this, the minimum
distance between phenyl carbon atoms is 3.5 Å for 6b and 3.3
Å for 6a. Therefore, the steric repulsion “pushes” the N(1a)
ring, and thus the N(1a) nitrogen atom, enlarging the Pd-N
bond distance. The Pd(1)-N(1) bond distance of 2.437(5) Å
for 7 is intermediate between those for 5 and 6.
1.39(1)
C(5a)-C(10a)
1.412(9) C(10a)-N(2a)
1.410(9)
P(2a)-Pd(1a)-P(1a) 139.02(7)
C(5a)-Pd(1a)-N(1a) 74.4(2)
P(2b)-Pd(1b)-P(1b) 151.06(7)
C(5b)-Pd(1b)-N(1b)
P(2b)-Pd(1b)-N(1b)
71.7(2)
95.5(1)
P(2a)-Pd(1a)-N(1a) 103.6(2)
P(1a)-Pd(1a)-N(1a) 117.3(2)
C(5a)-Pd(1a)-P(3a) 176.1(2)
P(1b)-Pd(1b)-N(1b) 113.2(1)
C(5b)-Pd(1b)-P(3b) 171.3(2)
P(2a)-Pd(1a)-P(3a)
P(1a)-Pd(1a)-P(3a)
85.70(7)
84.10(7)
P(2b)-Pd(1b)-P(3b)
P(1b)-Pd(1b)-P(3b)
85.30(7)
84.43(8)
N(1a)-Pd(1a)-P(3a) 109.5(1)
N(1b)-Pd(1b)-P(3b) 116.4(2)
C(5a)-Pd(1a)-P(2a)
C(5a)-Pd(1a)-P(1)
93.4(2)
94.2(2)
C(5b)-Pd(1b)-P(2b)
C(5b)-Pd(1b)-P(1b)
91.0(2)
95.2(2)
The differing Pd-N bond lengths may move coordination at
palladium from trigonal bypiramidal to distorted square-base
pyramidal. This is evident from the variation of the bond angles
at the metal center on going from 5 to 6a, 7 and 6b. In 5, the
P(1)-Pd(1)-N(1), P(2)-Pd(1)-N(1), and P(1)-Pd(1)-P(2)
bond angles are in the proximity of the ideal value of
120° expected for planar trigonal geometry, with values of
116.21(7), 115.12(7), and 128.35(3)°, respectively. However,
in 6b, opening of the P(1)-Pd(1)-P(2) bond angle brings the
bond angles at palladium to P(1b)-Pd(1b)-N(1b) 113.2(1),
P(2b)-Pd(1b)-N(1b) 95.5(1), and P(1b)-Pd(1b)-P(2b)
151.06(7)°, the latter is more in accordance with a distorted
square pyramidal geometry. This puts the nitrogen atom at the
apical position with subsequent lengthening of the Pd-N
5, the Pd-N bond length, 2.338(3) Å, is yet, to the best of our
knowledge, the shortest distance known for these type of
compounds, and it is very close to the Pd-N bond length of
2.23(2) Å found in an authentic pentacoordinated palladium-
(II) complex,19 making compound 5 first doubly cyclometalated
palladium(II) compound with two pentacoordinated metal
centers. The Pd-N bond length, 2.366(5) Å, in complex 6b is
close to the value reported by us, whereas in complex 6a a rather
longer Pd-N distance of 2.560(5) Å was observed. The differing
Pd-N bond lengths in 6a and 6b may be rationalized in terms
of packing forces within the crystal lattice. The relative
(19) Cecconi, F.; Ghilardi, C. A.; Midollini, S.; Moneti, S.; Orlandini, A.;
Scapacci, G. J. Chem. Soc., Dalton Trans. 1989, 211.

Cyclometalated Palladium(II) Compounds
Inorganic Chemistry, Vol. 40, No. 18, 2001 4587
The mean deviation from the CPdP3 least squares plane
(which could be regarded as the basal plane for a square
pyramid) shows the magnitude of the distortion toward square-
base pyramidal geometry. The mean deviation is larger in the
complexes with the shortest Pd-N bond length (mean deviation
0.4368, 0.3564, 0.2341, and 0.2139 for complexes 5, 6a, 7, and
6b, respectively).
The Pd-C bond lengths of 2.049(3), 2.052(6), 2.062(7), and
2.075(6) Å for 5, 6a, 6b, and 7 are similar to those found in
related cyclometalated complexes20,4 with C trans to phosphorus
but longer than Pd-C distances found in cyclometalated
complexes with carbon trans to nitrogen or chlorine, supporting
a phosphine ligand in the trans position. The Pd-P bond lengths
are similar to those found in related Pd(II) complexes4,20,21and
suggest that slightly partial double bond between the palladium
and phosphorus atoms may exist.22
In summary, the reaction of cyclometalated complexes with
the triphosphine ligand, triphos, constitutes a systematic route
for promoting pentacoordination in palladium(II) complexes in
the solid state regardless of the nature of the ligand and of the
specific properties of the starting complex. This is shown by
the X-ray crystal structures, one of which constitutes the first
example of a doubly five-coordinate cyclometalated pallad-
ium(II) complex with trigonal bipyramidal geometry at each
metal center.
Figure 4. Comparative view of the cations of 6a and 6b. Phosphine
phenyl rings have been omitted for clarity.
Acknowledgment. We thank the DGESIC (Proyecto PB98-
0638-C02-01/02) and the University of La Corun˜a for financial
support.
distance to 2.560(6) Å, a value still below those reported of
2.576-2.805 Å. The distortion is not so noticeable in 6a, with
bond angles of P(1a)-Pd(1a)-N(1a) 117.3(2), P(2a)-Pd(1a)-
N(1a) 103.6(2), and P(1a)-Pd(1a)-P(2a) 139.02(7)°, thus
bringing the Pd-N bond length to 2.366 Å. Bond angle values
for 7 are intermediate between those for 6b and 6a (P(1)-
Pd(1)-N(1) 111.2(1), P(2)-Pd(1)-N(1) 99.2(1), and P(1)-
Pd(1)-P(2) 149.51(6)°) in agreement with the Pd(1)-N(1) bond
length of 2.437(5)°. The C-Pd-P(3) bond angle is in all cases
close to the value of 180°, as would be expected for the
metalated carbon and P(3) atoms in the axial positions of a
trigonal bymiramid or situated at opposite positions of the base
in the square pyramid.
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determinations of 5, 6, and 7. This
material is available free of charge via the Internet at http://pubs.acs.org.
IC001094G
(20) Ferna´ndez, A.; Lo´pez-Torres, M.; Sua´rez, A.; Ortigueira, J. M.; Pereira,
T.; Ferna´ndez, J. J.; Vila, J. M.; Adams, H. J. Organomet. Chem.
2000, 598, 1.
(21) (a) Housecroft, C. E.; Shaykh, B. A. M.; Rheingold, A. L.; Haggerty,
B. S. Acta Crystallogr. Sect. C: 1990, 46, 1549. (b) DuBois, B. L.;
Miedaner, A.; Haltiwanger, R. C. J. Am. Chem. Soc. 2000, 119, 8753.
(22) Vila, J. M.; Gayoso, M.; Lo´pez-Torres, M.; Ferna´ndez, J. J.; Ferna´ndez,
A.; Ortigueira, J. M.; Bailey, N. A.; Adams, H. J. Organomet. Chem.
1996, 511, 129.