Oxidation of Complexes by (O2CPh)2 and (ER)2 (E = S, Se), Including Structures of Pd(CH2 CH2CH2CH2)(SePh)2(bpy) (bpy = 2,2′-Bipyridine) and MMe2(SePh)2 (L2) (M = Pd, Pt; L2 = bpy, 1,10-Phenanthroline) and C?O and C?E Bond Formation at Palladium(IV)

Article abstract of DOI:10.1021/ic9715005

Oxidation of PdMe₂(L₂) [L₂ = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen)] by diphenyl diselenide provides the first examples of stable dimethylpalladium(IV) complexes PdMe₂(SePh)₂(L₂), and pallada(IV)cyclic Pd(CH₂- CH₂CH₂CH₂)(SePh)₂(bpy) may be similarly isolated. X-ray structural studies of the octahedral dimethylpalladium-(IV) complexes and their isomorphous platinum(IV) analogues have been completed [L₂ = bpy, orthorhombic Pnma; L₂ = phen, triclinic P1?; an additional phase for PtMe₂(SePh)₂(phen), tetragonal, I4₁/a]. The complexes PdMe₂(SePh)₂(L₂) decompose at moderate temperatures in CDCl₃ following first-order behavior [L₂ = bpy, E_a ? 46 kJ mol^-1, ΔS?(20°C) ～ -170 J K^-1 mol^-1; L₂ = phen, E_a ～36 kJ mol^-1, ΔS?(20°C) ～ -204 J K^-1 mol^-1] to give ethane and Se(Ph)Me, together with small quantities of SePh₂. Similar C?C, C?O, C?S, and C?Se bond formation processes occur on decomposition of palladium(IV) species that are too unstable to be isolated on the oxidation of PdMe₂(bpy) or Pd(CH₂CH₂CH₂CH₂)(bpy) by (O₂CPh)₂ or (SPh)₂.

Full text of DOI:10.1021/ic9715005

Inorg. Chem. 1998, 37, 3975-3981
3975
Oxidation of Complexes by (O2CPh)2 and (ER)2 (E ) S, Se), Including Structures of
Pd(CH2CH2CH2CH2)(SePh)2(bpy) (bpy ) 2,2′-Bipyridine) and MMe2(SePh)2(L2) (M ) Pd,
Pt; L2 ) bpy, 1,10-Phenanthroline) and C‚‚‚O and C‚‚‚E Bond Formation at Palladium(IV)
Allan J. Canty,*,† Hong Jin,† Brian W. Skelton,‡ and Allan H. White‡
Departments of Chemistry, University of Tasmania, Hobart, Tasmania, Australia 7001, and
University of Western Australia, Nedlands, Western Australia, Australia 6907
ReceiVed NoVember 26, 1997
Oxidation of PdMe2(L2) [L2 ) 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen)] by diphenyl diselenide provides
the first examples of stable dimethylpalladium(IV) complexes PdMe2(SePh)2(L2), and pallada(IV)cyclic Pd(CH2-
CH2CH2CH2)(SePh)2(bpy) may be similarly isolated. X-ray structural studies of the octahedral dimethylpalladium-
(IV) complexes and their isomorphous platinum(IV) analogues have been completed [L2 ) bpy, orthorhombic
Pnma; L2 ) phen, triclinic P1h; an additional phase for PtMe2(SePh)2(phen), tetragonal, I41/a]. The complexes
PdMe2(SePh)2(L2) decompose at moderate temperatures in CDCl3 following first-order behavior [L2 ) bpy, Ea ∼
46 kJ mol-1, ∆Sq(20 °C) ∼ -170 J K-1 mol-1; L2 ) phen, Ea ∼36 kJ mol-1, ∆Sq(20 °C) ∼ -204 J K-1 mol-1
]
to give ethane and Se(Ph)Me, together with small quantities of SePh2. Similar C‚‚‚C, C‚‚‚O, C‚‚‚S, and C‚‚‚Se
bond formation processes occur on decomposition of palladium(IV) species that are too unstable to be isolated
on the oxidation of PdMe2(bpy) or Pd(CH2CH2CH2CH2)(bpy) by (O2CPh)2 or (SPh)2.
Introduction
at ambient temperature in solution allowing detailed mechanistic
studies of reductive elimination at a d6 metal center.7,8
Since the report of [PtIMe3]4 in 19071 organoplatinum(IV)
chemistry has become one of the most important systems for
investigations of structure and reactivity at d6 metal centers,2,3
and the more recent development of organopalladium(IV)
chemistry has provided new perspectives in d6 chemistry.4,5 For
example, structural studies of isomorphous [MMe3{(pz)3CH}]I
[M ) Pd, Pt; (pz)3CH ) tris(pyrazol-1-yl)methane] show that
Pd-N > Pt-N for nitrogen donors trans to alkyl groups,6 and
although PtIMe3(bpy) (bpy ) 2,2′-bipyridine) is an exceptionally
stable complex,7 PdIMe3(bpy) undergoes facile decomposition
It has recently been shown that platinum(IV) forms stable
thiolate and selenolate complexes PtMe2(EPh)2(phen) (E ) S,
Se; phen ) 1,10-phenanthroline),9 but there are no reports of
thiolate or selenolate complexes in organopalladium(IV) chem-
istry. We have explored the formation of such complexes via
oxidation of palladium(II) reagents by (ER)2 in the expectation
that less stable palladium(IV) complexes may be accessible and
allow the study of decomposition processes at palladium(IV)
in the presence of group 16 donor atoms. In addition to (EPh)2
(E ) S, Se) we have included (O2CPh)2 as a related group 16
oxidant.
† University of Tasmania.
‡ University of Western Australia.
We report here the synthesis and structural chemistry of
isomorphous metal(IV) complexes MMe2(SePh)2(L2) (M ) Pd,
(1) Pope, W. J.; Peachey, S. J. Proc. Chem. Soc. 1907, 23, 86.
(2) Anderson, G. K. In ComprehensiVe Organometallic Chemistry, 2nd
ed.; Puddephatt, R. J., Ed.; Pergamon: Oxford, U.K., 1995; Vol. 9,
Chapter 9, p 431.
(3) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University
Science Books: Mill Valley, CA, 1987.
(4) (a) Byers, P. K.; Canty, A. J.; Skelton, B. W.; White, A. H. J. Chem.
Soc., Chem. Commun. 1986, 1722. (b) Canty, A. J. Acc. Chem. Res.
1992, 25, 83. (c) Canty, A. J. In ComprehensiVe Organometallic
Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.
(Puddephatt, R. J., Vol. 9 Ed.); Pergamon: Oxford, U.K., 1995; Vol.
9, Chapter 5, p 225.
(5) Recent reports and references therein: (a) Kruis, D.; Markies, B. A.;
Canty, A. J.; Boersma, J.; van Koten, G. J. Organomet. Chem. 1997,
532, 2354. (b) Catellani, M.; Chiusoli, G. P. Gazz. Chim. Ital. 1993,
123, 1. (c) Kla¨ui, W.; Glaum, M.; Wagner, T.; Bennett, M. A. J.
Organomet. Chem. 1994, 472, 355. (d) van Asselt, R.; Rijnberg, E.;
Elsevier, C. J. Organometallics 1994, 13, 706. (e) van Belzen, R.;
Hoffmann, H.; Elsevier: C. J. Angew. Chem., Int. Ed. Engl. 1997,
36, 1743.
Pt; L2 ) bpy, phen), the structure of Pd(CH2CH2CH2CH2)-
(SePh)2(bpy), and studies of the formation and decomposition
of a range of palladium(IV) complexes involving C‚‚‚C, C‚‚‚
O, C‚‚‚S, and C‚‚‚Se bond formation processes.
Experimental Section
The reagents [PtMe2(SEt2)]2,10 PdMe2(tmeda) (tmeda ) N,N,N′,N′-
tetramethylethylenediamine),11,12 PdMe2(L2) (bpy,12,13 phen13), PtMe2-
(8) Du¨cker-Benfer, C.; van Eldik, R.; Canty, A. J. Organometallics, 1994,
13, 2412.
(9) Aye, K.-T.; Vittal, J. J.; Puddephatt, R. J. J. Chem. Soc., Dalton Trans.
1993, 1835.
(10) Kuyper, J.; van der Laan, R.; Jeanneaus, F.; Vrieze, K. Transition
Met. Chem. 1976, 1, 199.
(6) Byers, P. K.; Canty, A. J.; Skelton, B. W.; White, A. H. Organome-
tallics 1990, 9, 826.
(7) Byers, P. K.; Canty, A. J.; Crespo, M.; Puddephatt, R. J.; Scott, J. D.
Organometallics 1988, 7, 136.
(11) de Graaf, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten,
G. Organometallics 1989, 8, 2907.
(12) Byers, P. K.; Canty, A. J.; Jin, H.; Kruis, D.; Markies, B. A.; Boersma,
J.; van Koten, G. Inorg. Synth., in press.
S0020-1669(97)01500-0 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/24/1998

3976 Inorganic Chemistry, Vol. 37, No. 16, 1998
Canty et al.
(L2) (L2 ) bpy,10 phen14), and Pd(CH2CH2CH2CH2)(bpy)15 were
prepared as described; other reagents were used as received. Solvents
were dried and distilled, and all procedures were carried out under
nitrogen. Microanalyses were by the Central Science Laboratory,
University of Tasmania, and NMR spectra were recorded with a Bruker
AM 300 spectrometer with chemical shifts given in ppm relative to
SiMe4.
Analysis of Decomposition Products. The decomposition products
of palladium(IV) complexes in acetone-d6 or CDCl3 were detected by
1H NMR spectroscopy and by sampling the gas/liquid phases using a
microsyringe and a HP 5890 gas chromatograph connected to a HP
5970B mass selective detector (70 eV ET with He carrier gas). 1H
NMR spectra allowed determination of the yield of liquid-phase
products containing a methyl group, e.g. E(Ph)Me (E ) S, Se), and
the presence of this product in GC-MS data allowed yield determination
for other products. Ethane was detected by 1H NMR and GC-MS, but
its yield was not determined. Methane was not detected as a product
in any decompositions.
decomposes in solution above -20 °C to give butenes, cyclobutane,
Se(Ph)C4H9 and Se(Ph)C4H7 (NMR, GC-MS identification), and a red-
brown solid. 1H NMR (CDCl3 at -20 °C): δ 8.50 (d, 3J ) 5.2 Hz, 2,
H6), 7.63 (t, 3J ) 6.3 Hz, 2, H4 or 5), 7.29 (m, 4, H3 and 4 or 5), 6.77
(t) and 6.61 (d) and 6.42 (t) (10, Ph), 4.07 (b, 2, PdCH2), 1.87 (b, 2,
CH2). 13C{1H} NMR (CDCl3 at -20 °C): δ 149.5 (bpy), 137.5, 137.4,
127.6, 125.7, 125.2, 122.0, 111.4 (Ph), 48.2 (PdCH2), 35.5 (CH2). Anal.
Calcd for C26H26N2PdSe2: C, 49.50; H, 4.15; N, 4.44. Found: C, 49.30;
H, 4.30; N, 4.95.
1H NMR Studies of the Reactions of Palladium(II) Complexes
with Oxidizing Agents. PdMe2(bpy)/(O2CPh)2. Dibenzoyl peroxide
(0.0074 g, 0.031 mmol) in acetone-d6 (0.3 mL) was cooled to -70 °C
and added to a precooled solution of PdMe2(bpy) (0.009 g, 0.031 mmol)
in acetone-d6 (0.3 mL) in an NMR tube. The complex PdMe2{OC-
(O)Ph}2(bpy) was detected at -50 °C [δ 9.02 (d, 2, H6), 8.57 (d, 2
H3), 8.19 (t, 2, H4), 8.10 (d) and 7.78 (t) and 7.68 (t) (Ph), 7.16 (t, 2,
H5), 1.72 (s, 6, PdMe)] but at higher temperatures decomposed to give
ethane, PhCO2Me (∼35%), PhCO2H (∼15%), and a yellow solid
[∼61% assuming Pd(O2CPh)2(bpy)]. The yellow solid has properties
expected for Pd(O2CPh)2(bpy): 1H NMR (acetic acid-d4): δ 8.45 (d,
3J ) 8.0 Hz, 2, H6), 8.29 (t, 3J ) 8.0 Hz, 2, H4 or 5), 7.63 (m, 2, H3),
7.50 (m, 2, H4 or 5). 13C{1H} NMR (acetic acid-d4): δ 192.0 (O2C),
157.8, 152.1, 135.8, 129.3, 125.7, 143.6, 132.1, 131.5, 130.6. IR (KBr
Synthesis of Metal(IV) Complexes MMe2(ER)2(L2) (L2 ) bpy,
phen). PtMe2(SePh)2(bpy) (1). Diphenyl diselenide (0.081 g, 0.260
mmol) was added to a solution of PtMe2(bpy) (0.075 g, 0.260 mmol)
in acetone (6 mL) and the solution stirred for 1 h to give a yellow
solution. The solvent was evaporated in a vacuum and the residue
washed with diethyl ether and dried in a vacuum to give a yellow solid
(93%). Crystals may be obtained from dichloromethane/diethyl ether.
disk): 1640 vs, 1600 vs, 1560 s, 1340 vs cm-1
. Anal. Calcd for
C24H18N2O4Pd: C, 57.10; H, 3.59; N, 5.55. Found: C, 56.91; H, 3.68;
N, 5.59.
3
3
1H NMR (CDCl3): δ 8.67 (d, J ) 4.0 Hz, JPtH ) 7.0 Hz, 2, H6),
7.72 (t, 3J ) 8.0 Hz, 2, H4 or 5), 7.48 (d, 3J ) 8.0 Hz, 2, H3), 7.38 (t,
3J ) 8.0 Hz, 2, H4 or 5), [6.78 (m) and 6.61 (d) and 6.46 (m), 10, Ph],
PdMe2(bpy)/(SPh)2. Following a similar procedure, reaction com-
menced on warming to 20 °C with decomposition of an intermediate
[resonance at 1.98 ppm assigned to the PdIVMe group of unstable
PdMe2(SPh)2(bpy)] occurring at the same temperature to form ethane,
S(Ph)Me (∼17%), SPh2 (∼49%), and an orange solid. The orange
solid was very insoluble and difficult to characterize.
2
3
1.62 (s, JPtH ) 70.6 Hz, JSeH ) 7.2 Hz, 6, PtMe). 13C{1H} NMR
(CDCl3): δ 154.0, 147.4, 137.5, 127.7, 122.8 (bpy); δ 137.9, 127.8,
126.4, 125.6 (Ph); δ -6.1 (1JPtC ) 590 Hz, PtMe). Anal. Calcd for
C24H24N2PtSe2: C, 41.57; H, 3.49; N, 4.04. Found: C, 41.25; H, 3.49;
N, 4.09.
PtMe2(SePh)2(phen) (2). The complex was prepared as reported9
and crystallized from chloroform/diethyl ether for X-ray diffraction
studies.
Pd(CH2CH2CH2CH2)(bpy)/(O2CPh)2. Following a similar proce-
dure, reaction commenced on warming to 20 °C to form cyclobutane,
butenes, C4H7O2CPh, C4H9O2CPh, PhCO2H and an orange solid.
PdMe2(SePh)2(bpy) (3). Diphenyl diselenide (0.033 g, 0.100 mmol)
in acetone (1 mL) at -70 °C was added to a solution of PdMe2(bpy)
(0.030 g, 0.100 mmol) in acetone (1.5 mL) at -70 °C. The solution
was allowed to slowly warm to -30 °C with stirring (93%). The pale
yellow solution became red-orange as a dark red solid precipitated.
The solid was isolated below -25 °C and dried in a vacuum at -20
°C to give a dark red crystalline solid (0.044 g, 73%). Solutions of
the complex decompose quickly above -10 °C, but the solid sample
can be kept for at least 1 week at -20 °C without detectable
decomposition. Crystals may be obtained from chloroform/diethyl
Pd(CH2CH2CH2CH2)(bpy)/(SPh)2. Following a similar procedure,
reaction commenced on warming to 20 °C to form cyclobutane, butenes,
S(Ph)C4H7, S(Ph)C4H9, SPh2, and a red solid.
X-ray Structure Determinations. Room-temperature four-circle
diffractometer data sets were as specified in Table 1 (2θ/θ scan mode;
monochromatic Mo KR radiation), yielding N independent reflections,
No of which, with I > 3σ(I), were considered “observed” and used in
the full matrix least-squares refinements after analytical absorption
correction. Anisotropic thermal parameter forms were refined for the
3
ether. 1H NMR (CDCl3 at -20 °C): δ 8.60 (d, J ) 4.0 Hz, 2, H6),
non-hydrogen atoms, (x, y, z, Uiso
) being constrained at estimated
H
3
3
3
values, those for the methyl groups being inferred from difference map
residues as these permitted. Conventional residuals R and Rw on |F|
are quoted, statistical weights derivative of σ2(I) ) σ2(Idiff) + 0.0004σ4-
(Idiff) being employed. Neutral atom complex scattering factors were
employed,16 computation using the XTAL 3.4 program system.17
7.71 (t, J ) 8.0 Hz, 2, H4), 7.50 (d, J ) 8.0 Hz, 2, H3), 7.35 (t, J
) 5.3 Hz, 2, H5), [6.82 (m) and 6.701 (d) and 6.51 (m), 10, Ph], 2.07
(s, JSeH ) 7.1 Hz, 6, PdMe). 13C{1H} NMR (CDCl3, -20 °C): δ
3
152.5, 147.8, 137.4, 127.9, 122.3 (bpy); δ 138.0, 123.2, 126.0, 125.7
(Ph); δ 15.7 (PdMe). Anal. Calcd for C24H24N2PdSe2: C, 47.66; H,
4.00; N, 4.63. Found: C, 47.50; H, 3.95; N, 4.65.
Specific difficulties encountered in individual structure determina-
tions are documented in the footnotes to Table 1. The principal
difficulties encountered more generally were high absorption (analytical
corrections were applied as the crystals were well formed and fiber-
mounted), dominant heavy atoms located in some cases on or near
crystallographic symmetry elements (where possible data were measured
extensively and redundantly to assist in considerations of assignment
of crystal symmetry/space group and in enhancement of precision of
the determination after merging where it was considered valid to do
so), and extensive decomposition of the palladium complexes on the
time scale of the order of 1 day (compensated for by appropriate
scaling).
PdMe2(SePh)2(phen) (4). This complex was isolated as a dark red
solid by a similar procedure to that for the bpy analogue (85%), and
crystals were similarly obtained. 1H NMR (CDCl3 at -20 °C): δ [8.91
3
3
(d, J ) 5.0 Hz, 2), 8.16 (d, J ) 8.0 Hz, 2), 7.67 (m, 2), 7.63 (s, 2)
(phen)], [6.51 (t), 6.38 (d), 6.151 (t), 10, Ph], 2.20 (s, 3JSeH ) 11.0 Hz,
6, PdMe). 13C{1H} NMR (CDCl3 at -20 °C): δ 147.7, 136.7, 126.9,
124.7 (bpy); δ 136.8, 127.3, 125.4 (Ph); δ 15.1 (PdMe). Anal. Calcd
for C26H24N2PdSe2: C, 49.66; H, 3.85; N, 4.45. Found: C, 49.65; H,
3.82; N, 4.54.
Pd(CH2CH2CH2CH2)(SePh)2(bpy) (5). This complex was isolated
by a similar procedure to that for the dimethylpalladium(IV) analogue
(8) (69%), and crystals were similarly obtained. The isolated complex
Crystal data and selected geometries of the complexes are given in
Tables 1 and 2, and views of the complexes are shown in Figures 1-5.
(13) Byers, P. K.; Canty, A. J. Organometallics 1990, 9, 210.
(14) Monaghan, P. K.; Puddephatt, R. J. Organometallics 1984, 3, 210.
(15) (a) Diversi, P.; Ingrosso, G.; Lucherini, A.; Murtas, S. J. Chem. Soc.,
Dalton Trans. 1980, 1633. (b) Diversi, P.; Ingrosso, G.; Lucherini,
A. Inorg. Synth. 1993, 22, 167.
(16) International Tables for X-ray Crystallography; Ibers, J. A., Hamilton,
W. C., Eds.; Kynoch Press: Birmingham, England, 1974; Vol. 4.
(17) Hall, S. R.; King, G. S. D.; Stewart, J. M. The XTAL User’s Manual,
version 3.4; University of Western Australia: Lamb, Perth, 1995.

Oxidation of Complexes by (O2CPh)2 and (ER)2
Inorganic Chemistry, Vol. 37, No. 16, 1998 3977
Table 1. Specific Crystallographic Details for MMe2(SePh)2(L2) (L2 ) bpy, phen) and Pd(CH2CH2CH2CH2)(SePh)2(bpy)a
complex
PdMe2(SePh)2-
PtMe2(SePh)2-
PdMe2(SePh)2-
PtMe2(SePh)2-
(phen) (2a)
PtMe2(SePh)2-
Pd(CH2CH2CH2CH2)-
(bpy) (3)b
(bpy) (1)c
(phen) (4)d
(phen) (2b)e
(SePh)2(bpy) (5)f
formula
cryst system
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V, Å3
C24H24N2PdSe2
orthorhombic
Pnma (No. 62)
13.906(5)
12.578(4)
13.072(3)
C24H24N2PtSe2
orthorhombic
Pnma (No. 62)
13.920(5)
12.575(4)
13.038(6)
C26H24N2PdSe2
triclinic
P1h (No. 2)
11.689(8)
11.108(5)
10.009(6)
66.48(4)
85.99(4)
81.64(4)
1179
C26H24N2PtSe2
triclinic
P1h (No. 2)
11.759(6)
11.094(6)
9.976(6)
66.13(4)
86.01(4)
81.46(4)
1177
C26H24N2PtSe2
tetragonal
I41/a (No. 88)
13.874(3)
C26H26N2PdSe2
orthorhombic
Pna21 (No. 33)
14.271(6)
13.832(8)
12.065(9)
25.14(3)
2286
4
2282
4
4839
8
2381
4
Z
2
2
Mr
604.8
1.757
40
693.5
2.018
94
628.8
1.771
39
46
3274
2085
0.059
0.070
717.5
2.024
91
60
6833
5291
0.039
0.049
717.5
1.970
88
630.9
1.759
39
Dc/g cm-3
µ
Mo/cm-1
2θmax/deg
50
65
60
50
N
2109
1320
0.045
0.055
4282
2361
0.042
0.052
3531
2098
0.036
0.043
2202
1867
0.034
0.040
No
R
Rw
2
a R ) ∑∆/∑|Fo|; Rw ) (∑w∆2/∑wFo )1/2; w ) 1/σ2(Fo); T ∼ 295 K; λ ) 0.71073 Å. b The molecule lies astride a crystallographic mirror plane,
one of the phenyl rings being modeled as “disordered” and the other exhibiting high “thermal” motion, no disorder being resolvable. Of a number
of rapidly measured data sets, that cited was the most satisfactory, Rint 0.07 for a hemisphere of data, scaled after 58% decomposition. c Isomorphous
d
with 3, Rint (orthorhombic) ) 0.065 for a hemisphere of data; cf. 0.058-0.061 for the various monoclinic possibilities. Rint ) 0.077 for a full
sphere of data (75% decomposition); no disorder in triclinic or tetragonal forms. e The subject of a previous less precise study,9 at unspecified
temperature, with a different cell volume. f A hemisphere of data was measured, spanning 53% decomposition. In the final model adopted, in the
noncentrosymmetric Pna21 array, derivative of the centrosymmetric Pnma form of the dimethylmetal(IV) complexes, disorder was found in the
tetramethylene array but not in the phenyl groups. Merging of data related by the 2-axis gave Rint 0.048, absolute structure being indeterminate; the
structure was then refined on a fully merged hemisphere (Rint ) 0.067).
1H NMR Study of the Decomposition of Palladium(IV) Com-
plexes PdMe2(SePh)2(L2) (L2 ) bpy, phen). PdMe2(SePh)2(bpy) (3).
A solution of PdMe2(SePh)2(bpy) (0.007 g, 0.012 mmol) in CDCl3 (0.6
mL) was prepared at -70 °C in a 5 mm NMR tube, and a trace of
1,4-dioxane was added as an internal integration standard. The tube
was immediately inserted into an NMR probe precooled to the
temperature required for kinetic studies. Kinetic data were obtained
from the PdIVMe resonance with time intervals of 4-10 min depending
on the temperature. First-order rate constants of 3.3 × 10-5 (-4 °C),
5.0 × 10-5 (4 °C), 1.17 × 10-4 (11 °C), 1.3 × 10-4 (19 °C), and 2.5
× 10-4 s-1 (25 °C) were obtained. A plot of ln k against 1/T results
in estimates of Ea ∼ 46 kJ mol-1 and ∆Sq (20 °C) ∼ -170 J K-1
(ER ) O2CPh, SPh),9 but their reactions with palladium(II)
1
complexes were characterized by H NMR spectroscopy in
acetone-d6 as shown in eqs 1-4.
PdMe2(bpy) + (O2CPh)2 -50 °C8
PdMe2(O2CPh)2(bpy) -50 °C8
MeMe + MeO2CPh + PhCO2H + Pd(O2CPh)2(bpy) (1)
∼35%
∼15%
∼61%
PdMe2(bpy) + (SPh)2 20 °C8
mol-1
. NMR spectra show the formation of ethane and Se(Ph)Me
PdMe2(SPh)2(bpy) 20 °C8 MeMe + MeSPh + SPh2 (2)
(∼50%) during the reaction, and these products together with SePh2
(∼1%) were also characterized by GC-MS. A red solid of very low
solubility was obtained.
∼17%
∼49%
PdMe2(SePh)2(phen) (4). A study similar to that above gave first-
order rate constants of 3.33 × 10-5 (0 °C), 6.67 × 10-5 (14 °C), 1.17
× 10-4 (25 °C), and 1.83 × 10-4 s-1 (31 °C), leading to estimates of
Ea ∼ 36 kJ mol-1 and ∆Sq (20 °C) ∼ -204 J K-1 mol-1. NMR and
GC-MS studies indicate that ethane, Se(Ph)Me (∼27%), and SePh2 (8%)
are formed. A red solid of very low solubility was obtained.
Pd(CH2CH2CH2CH2)(bpy) + (SPh)2 20 °C8
Pd(CH2CH2CH2CH2)(SPh)2(bpy) f
undetected
(CH2)4 + butenes + C4H7SPh + C4H9SPh + SPh2 (3)
Results and Discussion
Pd(CH2CH2CH2CH2)(bpy) + (O2CPh)2 20 °C8
Studies were initially confined to MMe2(bpy) (M ) Pd, Pt),
leading to the isolation of the selenolate complexes MMe2-
(SePh)2(bpy), and were expanded to include MMe2(phen) and
Pd(CH2CH2CH2CH2)(O2CPh)2(bpy) 20 °C8
undetected
(CH2)4 + butenes + C4H7O2CPh + C4H9O2CPh +
Pd(CH2CH2CH2CH2)(bpy) as reagents primarily for crystal-
lographic studies (Scheme 1). The dimethylmetal(IV) com-
1
plexes exhibit simple H NMR spectra, in particular showing
PhCO2H
(4)
one methyl environment for 1-4, consistent with the configura-
tions established for these complexes by X-ray crystallography
(see below).
Dibenzoyl peroxide and (SPh)2 were not explored as oxidants
for PtMe2(bpy) in view of the earlier report of PtMe2(ER)2(phen)
Thus, the complexes PdMe2(O2CPh)2(bpy) (eq 1) and PdMe2-
(SPh)2(bpy) (eq 2) decompose soon after they are formed and
exhibit H NMR resonances similar to those of the platinum-
1
(IV) analogues and PdMe2(SePh)2(bpy), in particular showing

3978 Inorganic Chemistry, Vol. 37, No. 16, 1998
Canty et al.
Table 2. Selected Bond Distances (Å), Angles (deg), and Other Structural Data for MMe2(SePh)2(bpy), MMe2(SePh)2(phen), and
Pd(CH2CH2CH2CH2)(SePh)2(bpy)a
bpy (orthorhombic)
M ) Pd (3) M ) Pt (1)
phen (triclinic)
phen (tetragonal)
M ) Pt (2b)
M ) Pd (4)
M ) Pt (2a)
Pd(CH2CH2CH2CH2)(SePh)2(bpy) (5)
Bond Distances
2.058(9)
2.049(8)
2.150(5)
2.168(6)
2.491(1)
2.486(1)
1.911(6)
1.912(7)
M-C(1)
2.036(8)
2.179(5)
2.055(8)
2.162(5)
2.02(1)
2.03(1)
2.160(9)
2.20(1)
2.494(1)
2.487(1)
1.92(1)
1.91(1)
2.056(8)
2.143(6)
2.4896(9)
1.917(8)
2.08(1)
2.05(1)
M-C(1′)
M-N(1)
2.185(8)
2.181(8)
2.503(1)
2.506(1)
1.923(8)
1.935(9)
M-N(1′)
M-Se(1)
M-Se(1′)
Se(1)-C(11)
Se(1′)-C(11′)
2.479(1)
2.501(2)
1.90(2)
1.87(1)
2.478(1)
2.498(1)
1.92(2)
1.93(1)
Bond Angles
85.7(3)
98.0(3)
175.2(3)
176.2(3)
99.0(3)
89.1(2)
88.7(2)
85.8(2)
88.3(2)
77.2(2)
93.6(1)
92.4(1)
90.1(1)
C(1)-M-C(1′)
C(1)-M-N(1)
C(1)-M-N(1′)
C(1′)-M-N(1)
C(1′)-M-N(1′)
C(1)-M-Se(1)
C(1)-M-Se(1′)
C(1′)-M-Se(1)
C(1′)-M-Se(1′)
N(1)-M-N(1′)
N(1)-M-Se(1)
N(1)-M-Se(1′)
N(1′)-M-Se(1)
N(1′)-M-Se(1′)
Se(1)-M-Se(1′)
M-N(1)-C(2)
M-N(1′)-C(2′)
M-N(1)-C(6)
M-N(1′)-C(6′)
M-Se(1)-C(11)
M-Se(1′)-C(11′)
83.9(3)
100.2(3)
175.8(3)
86.6(3)
98.5(3)
174.9(3)
83.8(5)
98.2(4)
174.9(4)
177.6(4)
101.1(5)
88.7(3)
88.7(3)
85.2(3)
88.4(3)
76.8(3)
93.6(2)
92.9(2)
90.2(2)
92.8(2)
173.27(6)
129.3(9)
128.3(8)
114.5(6)
112.8(7)
105.2(3)
104.0(3)
85.6(3)
98.6(3)
175.8(3)
83.0(5)
99.6(4)
175.3(4)
177.4(4)
101.6(4)
90.6(3)
87.7(3)
84.9(4)
88.2(4)
75.8(3)
94.7(2)
92.2(2)
90.7(2)
91.6(2)
173.07(5)
125.7(7)
125.1(8)
113.9(6)
115.8(7)
102.4(2)
102.7(3)
87.2(2)
87.4(2)
87.6(2)
87.5(2)
87.2(2)
88.9(2)
75.6(2)
92.8(1)
93.0(1)
76.4(2)
92.8(1)
92.5(1)
77.2(2)
90.9(1)
93.2(1)
92.6(1)
172.69(5)
126.0(4)
173.24(4)
125.3(4)
173.82(3)
128.1(5)
128.0(5)
114.0(4)
112.8(4)
105.1(1)
104.2(2)
174.70(3)
128.6(5)
115.5(4)
114.6(4)
114.3(4)
103.7(2)
103.2(5)
102.9(3)
103.4(4)
103.1(3)
a Italicized entries involve atoms adjoining regions of the structure modeled as disordered and as such inherently involving values of rather less
reliability than the bulk of the structure.
Scheme 1. Synthesis of Diorganometal(IV) Complexes
Despite the difficulties encountered in characterization of
inorganic products, the results obtained for the reaction of eq 1
are consistent with decomposition according to eq 5, involving
PdMe2(O2CPh)2(bpy) f
∼0.6[MeMe + Pd(O2CPh)2(bpy)] + ∼0.4[MeO2CPh +
“PdMe(O2CPh)(bpy)”] (5)
C‚‚‚C and C‚‚‚O bond formation pathways and the presence of
moisture during workup giving benzoic acid from partial
decomposition of (presumably) “PdMe(O2CPh)(bpy)”. For the
reaction of eq 2, similar processes of C‚‚‚C and C‚‚‚S coupling
occur; the formation of diphenyl disulfide is discussed below.
For the palladacyclopentane complexes (eqs 3 and 4) yields
of products were not determined from NMR spectra because
of the low solubility of the reagent and the absence of well-
separated resonances for products. The intermediate palladium-
(IV) species could not be detected, apparently also owing to
the low solubility of the Pd(CH2CH2CH2CH2)(bpy) reagent
resulting in the presence of a low concentration of the unstable
palladium(IV) intermediate. The decomposition products are
consistent with occurrence of several independent processes:
fragmentation of the pallada(IV)cyclopentane ring via both C‚
‚‚C coupling and elimination of butenes and C‚‚‚E coupling
between the thiolate or carboxylate ligands and the pallada-
(IV)cyclopentane ring to form palladium(II) species PdIICH2-
CH2CH2CH2EPh which decompose to form alkene (C4H7EPh)
and alkane (C4H9EPh) products (E ) O2C, S).
PdMe resonances downfield from that of the PdMe2(bpy)
reagent. The relative quantities of gas phase (ethane) and liquid-
phase organic products have not been determined, but the yields
of liquid-phase products were determined by a combination of
NMR and GC-MS methods for the reactions of eqs 1 and 2.
Benzoic acid (eq 1) is assumed to be formed by decomposition/
hydrolysis of (benzoato)palladium(II) product(s) during workup.
The inorganic product Pd(O2CPh)2(bpy) (eq 1) was identified,
but the very insoluble orange solids from the reactions of eqs
2-4 were not characterized. Detailed mass balances were not
attempted for the reactions of eqs 1-4 since finely divided
palladium metal as a product cannot be discounted, and some
inorganic products may remain undetected in solution.

Oxidation of Complexes by (O2CPh)2 and (ER)2
Inorganic Chemistry, Vol. 37, No. 16, 1998 3979
Figure 1. Unit cell contents of PtMe2(SePh)2(bpy) (1) projected down
b. The crystallographic mirror plane of space group Pnma lies normal
to that axis.
X-ray Structural Studies of Selenophenolate Complexes
MMe2(SePh)2(L2) (M ) Pd, Pt; L2 ) bpy, phen). The 2,2′-
bipyridine complexes formed isomorphous crystals in space
group Pnma, while PdMe2(SePh)2(phen) crystallized from
chloroform/diethyl ether in the triclinic space group P1h. In view
of an earlier structural analysis of PtMe2(SePh)2(phen), which
crystallized from acetone in the tetragonal space group I41/a,9
this complex was also crystallized from chloroform/diethyl ether
and found to form two phases, one of which is isomorphous
with triclinic PdMe2(SePh)2(phen) and the other tetragonal but
with cell dimensions rather different from those reported earlier.
Thus, the structural studies for isomorphous pairs of complexes
MMe2(SePh)2(bpy) (orthorhombic), MMe2(SePh)2(phen) (tri-
clinic), and a tetragonal phase of PtMe2(SePh)2(phen) provide
some opportunity for comparisons of coordination geometry in
organopalladium(IV) and platinum(IV) chemistry where crystal
packing effects, even if significant as the cell projections suggest,
are constant within isomorphous pairs.
The complexes have distorted octahedral geometry containing
a square-planar “MMe2(L2)” moiety and trans-selenophenolate
groups (Figures 1-5 and Table 2). One of the selenophenolate
groups in MMe2(SePh)2(bpy) is disordered about the crystal-
lographic mirror plane (Figure 1), and the molecules in the
various structures exhibit different levels of crystallographic
symmetry: MMe2(SePh)2(bpy) (mirror plane through “MSe2”),
triclinic MMe2(SePh)2(phen) (no crystallographic symmetry),
and tetragonal PtMe2(SePh)2(phen) (2-fold axis). In all of the
complexes the phenyl groups lie above and below the bpy or
phen groups.
Figure 2. A single molecule of PtMe2(SePh)2(bpy) (1) projected (a)
approximately through the plane and (b) approximately down the Se-
Pt-Se “axis”, showing the disorder of the phenyl group of one of the
ligands about the mirror plane in that model. Thermal ellipsoids (20%)
are shown for the non-hydrogen atoms, and hydrogen atoms have been
given an arbitrary radius of 0.1 Å in this and other figures.
Decomposition Reactions of Palladium(IV) Complexes.
There are several reports of the decomposition of isolated
triorganopalladium(IV) complexes,4,5a,b,d,6-8 but studies of di-
organopalladium(IV) complexes are restricted to unstable PdI2-
Me2(N2) [N2 ) bis(p-tolylimino)acenaphthene, bis(phenylimino)-
camphane] which give a mixture of ethane and iodomethane.5d
Complexes 3 and 4 represent the first isolable “simple”
dialkylpalladium(IV) complexes, and thus they provide the first
opportunity to compare decomposition of trialkyl- and dialkyl-
palladium(IV) complexes.
Trialkylpalladium(IV) complexes decompose almost exclu-
sively by C‚‚‚C bond formation, with C‚‚‚X (X ) halide)
detected in mixtures of products of decomposition of a few
complexes5d,20 and as the major product on decomposition of
an unstable dibromopallada(IV)cyclopentadiene complex.5e In
contrast, PdMe2(SePh)2(L2) (3, 4) decompose via both C‚‚‚C
and C‚‚‚Se bond formation to give ethane and Se(Ph)Me,
respectively, together with a small quantity of SePh2 for L2 )
Detailed comparisons of bond lengths for palladium and
platinum complexes are rendered difficult by the disorder and
other factors encountered during structure determinations (Table
1), although for the isomorphous pairs of complexes (1 and 3,
2a and 4) Pd-C < Pt-C and Pd-N > Pt-N. Similar trends,
Pd-C < Pt-C and Pd-L > Pt-L, have been noted for
isomorphous complexes [fac-MMe3{(pz)3CH-N,N′,N′′}]I (M )
Pd, Pt)6 and fac-[MMe3{Co(Cp)(PR2O)3-O,O′,O′′}] (M ) Pd,
R ) Me;5c M ) Pt, R ) Et18), and also for the nonisomorphous
pair fac-[MMe3{(ind)3BH}] (M ) Pd, Pt; [(ind)3BH]- ) tris-
(indazol-1-yl)borate).19
(18) Marsh, R. E.; Schaefer, W. P.; Lyon, D. K.; Labinger, J. A.; Bercaw,
J. E. Acta Crystallogr. 1992, C48, 1603.
(19) Canty, A. J.; Dedieu, A.; Jin, H.; Milet, A.; Skelton, B. W.;
Trofimenko, S.; White, A. H. Submitted for publication.
(20) Canty, A. J.; Watson, A. A.; Skelton, B. W.; White, A. H. J.
Organomet. Chem. 1989, 367, C25.

3980 Inorganic Chemistry, Vol. 37, No. 16, 1998
Canty et al.
Figure 4. (a) Unit cell contents of PtMe2(SePh)2(phen) (tetragonal
form) (2b) projected down c. (b) A single molecule of PtMe2(SePh)2-
(phen) (2b).
Figure 3. (a) Unit cell contents of PtMe2(SePh)2(phen) (triclinic form)
(2a) projected down c. (b) A single molecule of PtMe2(SePh)2(phen)
(2a).
phen (eq 6). Yields of Se(Ph)Me and SePh2 were determined
PdMe2(SePh)2(L2) f MeMe + a MeSePh + b SePh2 (6)
L2 ) bpy (3), a ∼ 50%, b ∼1%
L2 ) phen (4), a ∼ 27%, b ∼ 8%
by a combination of NMR and GC-MS methods. Thus, the
decomposition processes for 3 and 4 appear to be closely related
to those for the unstable complexes PdMe2(O2CPh)2(bpy) and
PdMe2(SPh)2(bpy) which also exhibit carbon‚‚‚carbon and
carbon‚‚‚chalcogen coupling (eqs 1 and 2).
The formation of SPh2 in the reaction of PdMe2(bpy) with
(SPh)2, via unstable PdMe2(SPh)2(bpy) (eq 2), and the formation
of minor quantities of SePh2 on the decomposition of PdMe2-
(SePh)2(L2) (L2 ) bpy, phen) are assumed to result from a
similar process. It appears unlikely that EPh2 could form
directly from PdMe2(EPh)2(L2), and a more likely route may
involve reaction of the E(Ph)Me product with a palladium(II)
decomposition product, “PdII(EPh)”, to give “PdIV(Ph)(EMe)-
(EPh)” followed by reductive elimination of EPh2.
Figure 5. A single molecule of Pd(CH2CH2CH2CH2)(SePh)2(bpy) (5).
bpy) and ∼9.71 × 10-5 s-1 (L2 ) phen) at 20 °C, and yield
activation parameters Ea ∼46 kJ mol-1, ∆Sq (20 °C) ∼ -170
J K-1 mol-1 (L2 ) bpy) and Ea ∼36 kJ mol-1, ∆Sq (20 °C) ∼
-204 J K-1 mol-1 (L2 ) phen). Other solvents were found to
be unsuitable for NMR studies; e.g. the complexes are insoluble
in acetone, acetonitrile, and toluene.
1H NMR studies of the decompositions of 3 and 4 in CDCl3
indicate first-order behavior where the bpy complex decomposes
faster than the phen complex, e.g. k ∼ 1.69 × 10-4 s-1 (L2 )

Oxidation of Complexes by (O2CPh)2 and (ER)2
Inorganic Chemistry, Vol. 37, No. 16, 1998 3981
The complex PdIMe3(bpy) decomposes by first-order kinetics
to give ethane and PdIMe(bpy),7,8 and the negative ∆Sq for this
reaction in acetone at 20 °C (-66 ( 34 kJ mol-1), together
with retardation by added iodide, was taken to indicate dis-
sociation of I- for the dominant pathway and formation of a
(presumably) solvated intermediate [PdMe3(bpy)(acetone)]+
followed by reductive elimination. For PdMe2(SePh)2(L2), the
highly negative values found for ∆Sq, together with Ea values
considerably lower than estimates of the Pd-Me bond energy
(∼130 kJ mol-1),7 are consistent with a process similar to that
for PdIMe3(bpy). Thus, a polar transition state is implicated
with either partial or complete ionization to form [PdMe2-
(SePh)(bpy)]+[SePh]-, where the palladium center may well
be solvated, followed by C‚‚‚C or C‚‚‚Se bond formation.
Pd-C < Pt-C and Pd-N > Pt-N. The low stability of
organopalladium(IV) complexes renders them ideal candidates
for studies of decomposition at d6 metal centers, and the
dominance of C‚‚‚C bond formation from triorganopalladium-
(IV) complexes is not reflected in diorganopalladium(IV)
complexes in the presence of group 16 donor atoms (E) where
C‚‚‚E coupling becomes an important feature. The observation
of C‚‚‚O coupling at palladium(IV) is relevant to the proposed
catalytic role of palladium(IV) in the acetoxylation of arenes.21
Acknowledgment. We thank the Australian Research Coun-
cil for financial support and Johnson Matthey Ltd. for generous
loans of palladium and platinum salts.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for the structure determinations of complexes MMe2-
(SePh)2(bpy) [M ) Pt (1), Pd (3)], MMe2(SePh)2(phen) [M ) Pt (2a,b),
Concluding Remarks
The results reported here illustrate several new phenomena
in organopalladium(IV) chemistry: isolation of stable dimeth-
ylpalladium(IV) complexes and selenolate complexes and
detection of unstable thiolate complexes; formation of C‚‚‚O,
C‚‚‚S, and C‚‚‚Se bonds on decomposition; structural studies
allowing detailed comparisons between palladium(IV) and
platinum(IV) showing that Pd-Se ) Pt-Se for the “trans-
M(SePh)2” moiety in MMe2(SePh)2(L2) (L2 ) bpy, phen) but
Pd (4)], and Pd(CH2CH2CH2CH2)(SePh)2(bpy) (5) are available on the
Internet only. Access information is given on any current masthead
page.
IC9715005
(21) (a) Stock, L. M.; Tse, K.-t.; Vorvick, L. J.; Walstrum, S. A. J. Org.
Chem. 1981, 46, 1759. (b) Yoneyama, T.; Crabtree, R. H. J. Mol.
Catal A 1996, 108, 35.