Reversible oxidative addition of a diaryl diselenide to a diorganopalladium(II) complex, carbon-selenium bond formation at palladium(IV), and structural studies of palladium(II) and platinum(IV) selenolates

Article abstract of DOI:10.1016/j.jorganchem.2003.12.010

Methyl(4-methoxyphenyl)(2,2^′-bipyridine)palladium(II) (1) reacts with bis(4-chlorophenyl) diselenide in dichloromethane to form an equilibrium with the Pd(IV) complex Pd(SeC₆ H₄Cl)₂Me(C₆H₄O

Full text of DOI:10.1016/j.jorganchem.2003.12.010

Journal of Organometallic Chemistry 689 (2004) 672–677
www.elsevier.com/locate/jorganchem
Reversible oxidative addition of a diaryl diselenide to a
diorganopalladium(II) complex, carbon–selenium bond formation
at palladium(IV), and structural studies of palladium(II)
and platinum(IV) selenolates
a,
a
a
a
Allan J. Canty *, Melanie C. Denney , Jim Patel , Huailin Sun ,
b
Brian W. Skelton , Allan H. White
b
a
School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, Tasmania, Australia
b
School of Biomedical and Chemical Sciences, University of Western Australia, Crawley 6009, Western Australia, Australia
Received 23 October 2003; accepted 4 December 2003
Abstract
Methyl(4-methoxyphenyl)(2,20-bipyridine)palladium(II) (1) reacts with bis(4-chlorophenyl) diselenide in dichloromethane to
form an equilibrium with the Pd(IV) complex Pd(SeC6H4Cl)2Me(C6H4OMe)(bpy) (2) for which the forward reaction exhibits
DH ¼ ꢀ130 ꢁ 12 kJ molꢀ1 and DS ¼ ꢀ472 ꢁ 49 J Kꢀ1 molꢀ1, and with K ¼ 754 ꢁ 145 at )25 °C. The Pd(IV) complex is isolable at
)40 °C, and when the equilibrium mixture is kept at )25 °C, a temperature at which the Pd(II) complex is stable, selective reductive
elimination of Me–SeC6H4Cl occurs very slowly from the Pd(IV) complex to form Pd(SeC6H4Cl)(C6H4OMe)(bpy) (3). In contrast,
(ClC6H4Se)2 reacts with PdMe2(dmpe) (4) [dmpe ¼ 1,2-bis(dimethylphosphino)ethane] to form Pd(SeC6H4Cl)Me(dmpe) (5) and
Me–SeC6H4Cl. A second equivalent of (ClC6H4Se)2 reacts with 5 to cleave the second Pd–Me bond to give Pd(SeC6H4Cl)2(dmpe)
(6) and Me–SeC6H4Cl. Similarly, PdMeTol(dmpe) (7) (Tol ¼ 4-tolyl) forms predominantly Pd(SeC6H4Cl)Tol(dmpe) (8) together
with some Pd(SeC6H4Cl)Me(dmpe) (5), and 8 reacts with (ClC6H4Se)2 to form Pd(SeC6H4Cl)2(dmpe) (6) and Tol-SeC6H4Cl. Bis(4-
chlorophenyl) diselenide reacts with PtTol2(bpy) (9) (Tol ¼ 4-tolyl) to form Pt(SeC6H4Cl)2Tol2(bpy) (10) which, together with 2, has
a trans-configuration for the selenolate ligands. X-ray structural studies of octahedral 10 as the solvate 10 ꢂ 3CHCl3 and square
planar 5 are reported.
Ó 2003 Elsevier B.V. All rights reserved.
1. Introduction
here studies of a Pd(IV) complex containing both alkyl
and aryl groups, Pd(SeC6H4Cl)2Me(C6H4OMe)(bpy) (2)
(SeC6H4Cl ¼ 4-chloroselenophenolate, C6H4OMe ¼ 4-
methoxyphenyl), to probe selectivity in C(sp2)–Se
and C(sp3)–Se bond formation. This approach has
led to detection of a reversible oxidative addition of
(ClC6H4Se)2 to PdMe(C6H4OMe)(bpy) (1), related to a
similar equilibrium reported for Pt(II) exemplified in Eq.
(2) [6].
Formation of carbon(sp2)-heteroatom bonds by re-
ductive elimination from Pd(IV) centres has been pro-
posed in catalytic processes for C–O bond formation
[1–3]. Model reactions relevant to this catalysis have been
reported, but coupling from a Pd(IV) intermediate con-
taining both Pd–C and Pd–O bonds has not been de-
tected [4]. However, related carbon–selenium bond
formation from Pd(IV) species such as Pd(SePh)2Me2
(L2) [L2 ¼ 2,20-bipyridine] (Eq. (1)) has been documented,
with coupling involving a C(sp3) group [5]. We report
PdMe2ðbpyÞ ðP!hSeÞ2 PdðSePhÞ Me2ðbpyÞ
! Me–Me þ 2Me–SePh
ð1Þ
PtMefCHðCO2MeÞ gð4; 40-Bu2t bpyÞ þ ðPhSeÞ
* Corresponding author. Tel.: +61362262162; fax: 61362262858.
E-mail address: Allan.Canty@utas.edu.au (A.J. Canty).
2
¼ PtðSePhÞ Mef2CHðCO2MeÞ gð4; 40-But2-bpyÞ ð2Þ
2
2
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.12.010

A.J. Canty et al. / Journal of Organometallic Chemistry 689 (2004) 672–677
673
Thermodynamic parameters for the Pd(II)/Pd(IV)
equilibrium have been determined and the Pd(IV) spe-
cies shown to decompose by C(sp3)–Se bond formation.
Carbon(sp3)–selenium coupling is also observed on the
reaction of (ClC6H4Se)2 with PdMe2(dmpe) (4) and
Pd(SeC6H4Cl)Me(dmpe) (5) [dmpe ¼ 1,2-bis(dimethyl-
phosphino)ethane], both C(sp3)–Se and C(sp2)–Se cou-
pling for PdMeTol(dmpe) (7) (Tol ¼ 4-tolyl), and
C(sp2)–Se coupling for Pd(SeC6H4Cl)Tol(dmpe) (8).
The stable Pt(IV) complex Pt(SeC6H4Cl)2Tol2(bpy) (10)
has been prepared as a model for unstable Pd
(SeC6H4Cl)2Me(C6H4OMe)(bpy) (2).
environments, one selenolate and 4-methoxyphenyl en-
vironment) and Me–SeC6H4Cl by NMR and GC–MS.
PdðSeC6H4ClÞ MeðC6H4OMeÞðbpyÞ ð2Þ
2
! PdðSeC6H4ClÞðC6H4OMeÞðbpyÞ ð3Þ
þ Me–SeC6H4Cl
ð3Þ
An extension of this approach to include a complex
containing a bidentate phosphine, PdMe2(dmpe) (4) led
to the formation of Me–SeC6H4Cl at )15 °C and the
isolation of Pd(SeC6H4Cl)Me(dmpe) (5) without detec-
tion of a potential Pd(IV) intermediate (Eq. (4)). Complex
1
5 was identified by H and 31P{1H}NMR spectroscopy
and a crystal structure analysis (see below) and, on ad-
dition of a second equivalent of (ClC6H4Se)2, it forms
Pd(SeC6H4Cl)2(dmpe) (6) and Me–SeC6H4Cl (Eq. (5)).
In similar reactions, PdMeTol(dmpe) (7) forms predom-
inantly Pd(SeC6H4Cl)Tol(dmpe) (8) and Me–SeC6H4Cl
(Eq. (6)); addition of a second equivalent of (ClC6H4Se)2
results in cleavage of Pd–Me and Pd–Tol bonds of 5
and 8 according to Eqs. (5) and (7), respectively.
2. Results and discussion
2.1. Studies of reactivity
Preliminary NMR studies at low temperature indi-
cated the presence of the equilibrium shown in Scheme 1
with the Pd(IV) complex (2) dominant at low tempera-
tures. The Pd(IV) complex (2) was isolated from reac-
tions at )40 °C using an excess of diselenide, allowing
confirmation of assignment of NMR spectra for the
equilibrium, and allowing a study of the equilibrium over
a temperature range using a pure sample of the complex.
Complex 2 exhibits two pyridyl group environments and
one selenolate environment, consistent with a trans
orientation for the selenolate ligands as observed in
crystal structure analyses of Pd(SePh)2Me2 (L2) (L2 ¼
bpy, 1,10-phenanthroline) and the Pt(IV) complex
Pt(SeC6H4Cl)2Tol2(bpy) (10) (see below). Equilibrium
constants for the forward reaction of Scheme 1 were
estimated from 1H NMR integrations, and a plot of ln K
versus Tꢀ1, leading to estimation of DH ¼ ꢀ130 ꢁ 12
kJ molꢀ1 and DS ¼ ꢀ472 ꢁ 49 J Kꢀ1 molꢀ1. At higher
temperatures ()25 to )20 °C) very small amounts of
reductive elimination products were apparent and, al-
though the decomposition may have minimal impact on
the determination of equilibrium constants, the values
determined are not considered sufficiently reliable to al-
low detailed comparison with related data for platinum
chemistry referred to above [6].
PdMe2ðdmpeÞ ð4Þ þ ðClC6H4SeÞ
2
! PdðSeC6H4ClÞMeðdmpeÞ ð5Þ þ Me–SeC6H4Cl
ð4Þ
PdðSeC6H4ClÞMeðdmpeÞ ð5Þ þ ðClC6H4SeÞ
2
! PdðSeC6H4ClÞ ðdmpeÞ ð6Þ þ Me–SeC6H4Cl
ð5Þ
2
PdMeTolðdmpeÞ ð7Þ þ ðClC6H4SeÞ
2
! ꢃ 0:8½PdðSeC6H4ClÞTolðdmpeÞ ð8Þ þ Me–SeC6H4Clꢄ
þ ꢃ 0:2½PdðSeC6H4ClÞMeðdmpeÞ ð5Þ
þ Tol-SeC6H4Clꢄ
ð6Þ
PdðSeC6H4ClÞTolðdmpeÞ ð8Þ þ ðClC6H4SeÞ
2
! PdðSeC6H4ClÞ ðdmpeÞ ð6Þ þ Tol-SeC6H4Cl
ð7Þ
2
The reaction of Eq. (2) indicates that C(sp3)–Se ra-
ther than C(sp2)–Se coupling occurs from Pd(IV) centres
containing nitrogen donor ligands. Palladium(IV) in-
termediates may occur in the reactions of Eqs. (4)–(7),
and if so, the reaction of Eq. (6) is consistent with the
preference for C(sp3)–Se coupling. In related studies,
Steinborn and coworkers [11] found that PdMe2(dppe)
[dppe ¼ 1,2-bis(diphenylphosphino)ethane] reacts with
(PhSe)2 to form Pd(SePh)Me(dppe) (91%) and Pd(SePh)
2(dppe) (9%). Although the palladium(IV) complex 2
The palladium(II) reagent is stable at )25 °C, al-
lowing determination of the decomposition behaviour of
2 to be as shown in Eq. (3), together with a small
quantity (<5%) of Me–C6H4OMe. Complex 3 was
1
identified by H NMR spectroscopy (two pyridyl ring
SeC6H4Cl
N
N
MeOC6H4
MeOC6H4
+
(ClC6H4Se)2
Pd
Pd
N
N
Me
Me
SeC6H4Cl
1
2
Scheme 1.

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A.J. Canty et al. / Journal of Organometallic Chemistry 689 (2004) 672–677
proved to be too unstable to allow successful attempts to
obtain crystals suitable for X-ray diffraction, a related
arylplatinum(IV) complex Pt(SeC6H4Cl)2Tol2(bpy) (10)
was readily obtained on reaction of PtTol2(bpy) (9) with
(ClC6H4Se)2 in acetone and crystals obtained from
CH2Cl2/diethyl ether.
2.2. Structural studies of 5 and 10
The results of the single crystal X-ray structure de-
terminations are consistent with the above stoichiome-
tries and connectivities, despite, in the case of 10,
difficulties associated with the material and solvent dis-
order which somewhat adversely affected the precision
of the study (Fig. 1(a), Tables 1 and 2). Also, for this
complex, one-half of the formula unit comprises the
asymmetric unit, the substrate molecule and one of the
solvent molecules being disposed about crystallographic
2-axes, which, in the case of the substrate, pass through
the metal atom and the mid-point of the bpy ligand.
Displacement parameter amplitudes are rather high,
particularly at the molecular peripheries, possibly indi-
cating minor unresolved disorder, and thus geometries
should be treated with caution. Disorder is also resolv-
able in one of the bridging methylene groups of the
dmpe ligand of 5, apparently impacting on the dis-
placement parameters of the nearby methyl groups of
the ligand, disorder not being resolvable in the latter.
With these reservations, the Pt–Se bond distance
Fig. 1. Projections of molecules of (a) Pd(SeC6H4Cl)Me(dmpe) (5) and
(b) Pt(SeC6H4Cl)2Tol2(bpy) (10) in its chloroform solvate 10 ꢂ 3CHCl3.
ꢀ
[2.519(1) A] in 10 is similar to those reported for
ꢀ
ꢀ
throline (2.491(1), 2.486(1) A], the Pt–N distance
ꢀ
[2.02(1) A] is also similar [2.055(8); 2.058 (9), 2.049(8)
ꢀ ꢀ
A]. The Pd–Se distance in 5 [2.4483(8) A] compares well
Pt(SePh)2Me2(L2) [L2 ¼ bpy (2.498(1) A), 1,10-phenan-
ꢀ
[2.140(9) A] is similar to that in the latter complexes
ꢀ
[2.162(5); 2.150(5), 2.168(6) A], and the Pt–C distance
ꢀ
with Pd(SePh)2(dppe) [2.444(1), 2.480(1) A] which also
has the selenolate group trans to a phosphine donor [12].
Table 1
Selected geometries for Pd(SeC6H4Cl)Me(dmpe) (5)
Atoms
Parameter
Atoms
Parameter
ꢀ
Distances (A)
Pd–P(1)
Pd–P(2)
2.230(1)
2.305(2)
1.746(6)
Pd–C(0)
Pd–Se
Se–C(1)
2.116(6)
2.4483(8)
1.916(6)
C(4)–Cl(4)
Angles (°)
P(1)–Pd–P(2)
P(1)–Pd–C(0)
P(1)–Pd–Se
85.79(8)
89.4(2)
P(2)–Pd–C(0)
P(2)–Pd–Se
C(0)–Pd–Se
175.2(2)
88.20(4)
96.6(2)
173.78(6)
118.5(2)
117.1(4)
107.1(5)
105.9(5)
Pd–P(1)–C(11)
Pd–P(1)–C(12)
Pd–P(1)–C(01)
Pd–P(1)–C(010)
Pd–P(2)–C(21)
Pd–P(2)–C(22)
Pd–P(2)–C(02)
Pd–Se–C(1)
117.9(3)
117.5(2)
107.5(2)
110.7(2)
Torsion angles (carbon atoms denoted by number only)
P(2)–Pd–P(1)–C(01)
P(2)–Pd–P(1)–C(010)
Pd–P(1)–C(01)–C(02)
Pd–P(1)–C(010)–C(02)
Pd–Se–C(1)–C(2)
20.8(5)
)17.5(5)
)43.5(9)
39.7(11)
97.2(5)
P(1)–Pd–P(2)–C(02)
Pd–P(2)–C(02)–C(01)
Pd–P(2)–C(02)–C(010)
P(2)–C(02)–C(01)–P(1)
P(2)–C(02)–C(010)–P(1)
0.2(3)
)26.6(8)
28.3(10)
45.0(10)
)43.1(11)
Pd lies 0.031(2) out of the P2SeC donor plane (v2 ¼ 36); the P2SeC/phenyl C6 interplanar dihedral angle is 88.3(2).

A.J. Canty et al. / Journal of Organometallic Chemistry 689 (2004) 672–677
675
Table 2
Selected geometries for Pt(SeC6H4Cl)2Tol2(bpy) (10) in (10 ꢂ 3CHCl3)
3.2. Synthesis of Pd(SeC6H4Cl)Me(dmpe) (5)
primed atoms are related by the intramolecular 2-axis
A solution of (ClC6H4Se)2 (0.014 g, 0.038 mmol) in
CH2Cl2 (2 ml) was added to a stirred solution of
PdMe2(dmpe) (0.011 g, 0.037 mmol) in CH2Cl2 (2 ml)
at )50 °C. The solution was allowed to warm slowly
to ambient temperature with stirring. The volume was
reduced to near dryness under a vacuum, and pentane
added to precipitate the product as an orange solid
which was collected by filtration, rinsed with pentane
(3 ꢅ 5 ml) and dried under a vacuum. Yield: 0.016 g
Atoms
Parameter
Atoms
Parameter
ꢀ
Distances (A)
Pt–C(01)
Pt–N(1)
2.02(1)
2.140(9)
2.519(1)
Se–C
C(4)–Cl(4)
1.93(1)
1.77(2)
Pt–Se
Angles (°)
Se–Pt–N(1)
Se–Pt–N(10)
Se–Pt–C(01)
Se–Pt–C(010)
Se–Pt–Se0
95.2(2)
85.0(2)
92.0(3)
87.8(3)
179.7(2)
N(1)–Pt–N(10)
N(1)–Pt–C(01)
N(1)–Pt–C(010)
C(01)–Pt–C(010)
Pt–Se–C(11)
76.4(4)
97.8(5)
173.2(4)
88.1(6)
102.0(3)
1
3
(95%). H NMR (CDCl3): d 7.60 (d, 2H, J ¼ 8:4 Hz,
3
C6H4), 7.01 (d, 2H, J ¼ 8:4 Hz, C6H4), 1.88–1.58 (m,
2
Interplanar dihedral angles: N(1, 10) C(01, 010)/C(1–6), C(01–06)
14.0(4), 53.1(5); C(1–6)/C(01–06) is 44.0(5).
4H, PCH2), 1.48 (s, 6H, JPH ¼ 10:0 Hz, PMe2), 1.13
2
3
(s, 6H, JPH ¼ 8:4 Hz, PMe2), 0.15 (t, 3H, JPH ¼ 6:8
Hz and 6.0 Hz, PdMe). 31P{1H}(CDCl3): d 21.4.
Anal. Calcd.: C, 33.79; H, 5.02. Found: C, 33.78; H,
5.08%.
3. Experimental
3.3. Synthesis of Pd(SeC6H4Cl)2(dmpe) (6)
The reagents PdMe(C6H4OMe)(bpy) [7], PdMe2
(dmpe) [8] PdMeTol(bpy) [7] and PtTol2(bpy) [9] were
prepared as described. Solvents were dried and distilled,
stored under nitrogen, and all procedures were carried
out under nitrogen. NMR spectra were recorded on a
Varian Unity Inova 400 MHz wide bore instrument, at
399.7 MHz for 1H and 161.8 MHz for 31P, at room
temperature unless indicated otherwise. Chemical shifts
are given in ppm relative to SiMe4 and external H3PO4.
Microanalyses were performed by the Central Science
Laboratory, University of Tasmania. GC–MS analyses
were performed using an HP5890 gas chromatograph
equipped with an HP5790 MSD and a 25 m ꢅ 0.32 mm
HP1 column (0.52 m film thickness, He at 10 psi).
A solution of PdMe2(dmpe) (0.010 g, 0.036 mmol)
and (ClC6H4Se)2 (0.035 g, 0.091 mmol) in CH2Cl2
(0.8 ml) was allowed to react at ambient temperature
for 2 h to give an orange solution. Pentane was added
to precipitate the product, the suspension was centri-
fuged and the yellow supernatant removed. The or-
ange product was rinsed with pentane (2 ꢅ 1 ml) and
diethyl ether (2 ml), and dried under a vacuum. Yield:
0.010 g (44%). 1H NMR (CD2Cl2): d 7.51 (d, 4H,
3J ¼ 8:0 Hz, C6H4), 6.97(d, 4H, 3J ¼ 8:0 Hz, C6H4),
2
1.80 (d(br), 4H, JPH ¼ 20:0 Hz, PCH2), 1.42 (d, 12H,
2JPH ¼ 10:8 Hz, PMe2). 31P{1H}(CD2Cl2): d 37.6.
Anal. Calcd.: C, 33.91; H, 3.79. Found: C, 33.77; H,
3.98%.
3.1. Synthesis of Pd(SeC6H4Cl)2Me(C6H4OMe)(bpy)
(2)
3.4. Synthesis of PdMeTol(dmpe) (7)
A solution of (ClC6H4Se)2 (0.060 g, 0.157 mmol) in
CH2Cl2 (2 ml) was added to solid PdMe(C6H4OMe)
(bpy) (0.038 g, 0.098 mmol) precooled to )40 °C. The
solution quickly became dark red and stirring was
continued for 2 h at )40 °C. The volume was reduced to
near dryness, and pentane added to precipitate a red
solid which was collected by filtration, rinsed with
pentane (2 ꢅ 3 ml) and diethyl ether (2 ml) and dried
under a vacuum. The product was stored at )20 °C.
Yield: 0.070 g (93%). 1H NMR (CDCl3, )50 °C): d 8.97
(d, 1H, 3J ¼ 5:2 Hz, H6), 8.25 (d, 1H, 3J ¼ 5:2 Hz, H60),
7.93(t, 3J ¼ 7:6 Hz, H4), 7.79 (t, 3J ¼ 7:6 Hz, H40), 7.69
(d, 1H, 3J ¼ 8:0 Hz, H3), 7.53 (m, 4H, H30, H5 and
ortho-C6H4), 7.25 m, H50), 6.90 (d, 2H, 3J ¼ 8:4 Hz,
1,2-Bis(dimethylphosphino)ethane (52 ll, 0.31 mmol)
was added to a solution of PdMeTol(tmeda) (0.100 g,
0.300 mmol) in benzene (1 ml). After several minutes of
stirring a white precipitate formed. Pentane (2 ml) was
added and the solution decanted. The white solid was
rinsed with pentane (2 ꢅ 5 ml) and diethyl ether (2 ꢅ 2
ml) and dried under a vacuum. Yield: 0.110 g (100%).
1H NMR (acetone-d6): d 7.21 (t, 2H, J ¼ 7:0 Hz, ortho-
3
Tol), 6.73 (d, 2H, J ¼ 6:0 Hz, meta-Tol), 2.14 (s, 3H,
2
Me), 1.38 (d, 6H, JPH ¼ 8:0 Hz, PMe2), 1.17 (d, 6H,
2JPH ¼ 8:0 Hz, PMe2), 0.01 (dd, 3H, JPH ¼ 7:2 Hz,
JPH ¼ 8:8 Hz, PdMe). 31P{1H} (acetone-d6): d 25.5 (d,
JPP ¼ 24:0 Hz), 22.3 (d, JPP ¼ 24:4 Hz).
3
meta-C6H4), 6.48 (d, 4H, J ¼ 8:0 Hz, SeC6H4Cl), 6.42
3.5. Synthesis of Pt(SeC6H4Cl)2(Tol)2(bpy) (10)
(d, 4H, 3J ¼ 8:0 Hz, SeC6H4Cl), 3.84 (s, 3H, OMe), 2.58
(s, 3H, PdMe). Anal. Calcd.: C, 47.05; H, 3.42; N, 3.66.
Found: C, 46.98; H, 3.36; N, 3.58%.
A solution of (ClC6H4Se)2 (0.030 g, 0.080 mmol) in
acetone (1 ml) was added to a stirred solution of

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A.J. Canty et al. / Journal of Organometallic Chemistry 689 (2004) 672–677
Pt(Tol)2(bpy) (0.0398 g, 0.080 mmol) in acetone (5 ml).
The solution was stirred at ambient temperature for
12 h, the solvent removed in a vacuum, and the solid
washed with diethyl ether (3 ꢅ 1 ml). The solid was
recrystallised from CH2Cl2/diethyl ether to give orange
3.7. X-ray data collection and structure determination,
and refinement for complexes 5 and 10
Crystals of 5 and 10 ꢂ CHCl3 were obtained by
recrystallisation from CHCl3/diethyl ether and CH2Cl2/
diethyl ether, respectively, and full spheres of CCD area-
detector diffractometer data were measured (Bruker
AXS instrument, 2hmax ¼ 58°, x-scans, monochromatic
1
–red crystals of the product. Yield: 0.030 g (41%). H
3
NMR (CDCl3): d 8.95 (d, 2H, J ¼ 5:5 Hz, JPtH ꢃ 18
3
4
Hz, H6), 7.77 (td, J ¼ 8:0 Hz, J ¼ 1:2 Hz, H4), 7.47
3
ꢀ
(m, 6H, H3 and ortho-Tol), 7.36 (t, J ¼ 6:2 Hz, H5),
Mo Ka radiation, k ¼ 0:71073 A; T ca. 153 K) yielding
6.92 (d, 4H, 3J ¼ 8:4 Hz, meta-Tol), 6.63 (d, 4H,
3J ¼ 8:0 Hz, SeC6H4Cl), 6.36 (d, 4H, 3J ¼ 8:4 Hz,
SeC6H4Cl), 2.35 (s, 6H, Me). Anal. Calcd.: C, 47.28;
H, 3.31. Found: C, 47.26; H, 3.38%.
N
reflections, merging to N unique (Rint cited) after
ðtotalÞ
ÔempiricalÕ/multiscan absorption correction (proprietary
software), No with F > 4rðF Þ considered ÔobservedÕ and
used in the full-matrix least squares refinements, refining
anisotropic displacement parameter forms for the non-
hydrogen atoms, (x; y; zUiso H being included and con-
)
3.6. NMR studies
strained at estimated values. Conventional residuals R,
Rw (weights: ðr2ðF Þ þ 0:0004F 2Þꢀ1) on jF j are cited at
convergence. Neutral atom complex scattering factors
were employed within the Xtal 3.7 program system [10].
Pertinent results are given in Tables 1 and 2 and
Fig. 1(b), the latter showing 50% probability displace-
ment amplitudes for the non-hydrogen atoms, hydrogen
In a typical experiment for the determination of
equilibrium constants for the reaction of Scheme 1, a
sample of Pd(SeC6H4Cl)2Me(C6H4OMe)(bpy) (2)
(0.0040 g, 0.0052 mmol) was cooled to the required
temperature then dissolved in CD2Cl2 (600 ll). The
sample was kept at the required temperature for several
hours until equilibrium was reached. The concentration
of each compound was determined by integration, and
5% tolerance in integration was assumed (K ¼ 35408 ꢁ
7750 at )40 °C, 4628 ꢁ 950 at )35 °C, 2010 ꢁ 400 at )30
°C, 754 ꢁ 145 at )25 °C, 116 ꢁ 20 at )20 °C). In a typ-
ical experiment relating to the reactions of Eqs. (4)–(7),
a solution of (ClC6H4Se)2 (0.0040 g, 0.0105 mmol) in
CD2Cl2 (0.4 ml) was added to a solution of PdMeR
(dmpe) (R ¼ Me, Tol) (0.0105 mmol) in CD2Cl2 (0.2
ml). The sample was monitored by 1H and/or 31P NMR
spectroscopy to the completion of the reaction. To this
was added a second equivalent of (ClC6H4Se)2 (0.0040
g, 0.0105 mmol) and the reaction monitored to its
completion. NMR spectra (in CD2Cl2) of products are
listed above for complexes 5 and 6; Me–SeC6H4Cl: d
ꢀ
atoms having arbitrary radii of 0.1 A. Individual vari-
ations in procedure and difficulties are cited as ÔvariataÕ.
4. Crystal/refinement data
4.1. Pd(SeC6H4Cl)Me(dmpe) (5)
C13H23ClP2PdSe, M ¼ 462:1. Orthorhombic, space
group Pna21 ðC29v, No. 33), a ¼ 16:919ð3Þ, b ¼ 6:1734
3
ꢀ
ꢀ
ð9Þ, c ¼ 16:906ð3Þ A, V ¼ 1766 A . Dc ðZ ¼ 4Þ ¼ 1:738
g cmꢀ3. lMo ¼ 34 cmꢀ1; specimen: 0.20 ꢅ 0.17 ꢅ 0.14
mm; Tmin=max ¼ 0.88. 2hmax ¼ 75°; Nt ¼ 36023, N ¼ 4731
(Rint ¼ 0:051), No 2953; R ¼ 0:034, Rw ¼ 0:037.
Variata: Within the present space group, one of the
bidentate methylene groups is modelled as disordered
over a pair of sites, occupancies set at 0.5 after trial
refinement. ÔFriedelÕ data were preserved distinct, xabs
refining to 0.02(1).
3
3
7.35 (d, 2H, J ¼ 8:4 Hz), 7.23 (d, 2H, J ¼ 8:8 Hz),
2.34 (s, 3H, Me); Tol-SeC6H4Cl: d 7.40 (d, 2H, 3J ¼ 8:0
Hz), 7.31 (m) and 7.21 (m) overlapping, 7.13 (d, 2H,
3J ¼ 7:8 Hz), 2.33 (s, 3H, Me); Pd(SeC6H4Cl)
3
(C6H4OMe)(bpy) (3): d 9.06 (d, 1H, J ¼ 4:0 Hz, bpy),
8.10 (m, 2H, bpy), 8.00 (m, 2H, bpy), 7.92 (d, 1H,
3
3J ¼ 5:2 Hz, bpy), 7.69 (d, 2H, J ¼ 8:4 Hz, SeC6H4Cl
4.2. Pt(SeC6H4Cl)2(Tol)2(bpy) ꢂ 3CHCl3
or C6H4OMe), 7.45 (m, 1H, bpy), 7.35 (m, 1H, bpy
3
overlapping with other resonances), 7.21 (d, 2H, J ¼
(10 ꢂ 3CHCl3) ꢆ C39H33Cl11N2PtSe2, M ¼ 1272:7. Mo-
noclinic, space group C=c (C26h, No.15), a ¼ 24:345 ð3Þ,
3
8:4 Hz, SeC6H4Cl or C6H4OMe), 6.86 (d, 2H, J ¼ 8:4
3
ꢀ
Hz, SeC6H4Cl or C6H4OMe), 6.67 (d, 2H, J ¼ 8:0 Hz,
b ¼ 14:405ð2Þ, c ¼ 15:848ð2Þ A, b ¼ 127:032ð2Þ°,
3
ꢀ
SeC6H4Cl or C6H4OMe), 3.74 (s, 3H, OMe);
Pd(SeC6H4Cl)Tol(dmpe) (8): d 7.13 (m, 2H, Tol
or SeC6H4Cl), 6.89 (d(b), 2H, 3J ¼ 7:8 Hz, Tol or
SeC6H4Cl), 6.82 (d(b), 2H, 3J ¼ 6:8 Hz, Tol or
SeC6H4Cl), 2.20 (s, 3H, PdTol), 1.70 (m, 4H, CH2), 1.22
(d, 6H, JPH ¼ 10:4 Hz, PMe2), 1.05 (d, 6H, JPH ¼ 8:8
Hz, PMe2), 31P{1H} d 28.2 (d, JPP ¼ 20:9 Hz), 22.5 (d,
JPP ¼ 20:6 Hz).
V ¼ 4437 A . Dc (Z ¼ 4 f.u.) ¼ 1:905 g cmꢀ3. lMo ¼ 55
cmꢀ1; specimen: 0.35 ꢅ 0.12 ꢅ 0.12 mm; Tmin=max ¼ 0.57.
2hmax ¼ 50°; Nt ¼ 51575, N ¼ 3905 (Rint ¼ 0:11), No ¼
3260; R ¼ 0:059, Rw ¼ 0:072.
Variata: One of the solvent molecules was modelled
as disordered about a crystallographic 2-axis in the
present space group. The material presented as sub-
stantial, readily desolvating specimens, from which a

A.J. Canty et al. / Journal of Organometallic Chemistry 689 (2004) 672–677
677
transparent fragment was excised and transferred to the
diffractometer low temperature system.
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Cambridge Crystallographic Data Cente (Deposition
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mation can be obtained free of charge from The Di-
rector, CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK (fax: +44-1223-336-033; email: deposit@ccdc.cam.
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Acknowledgements
We thank the Australian Research Council for fi-
nancial support and Dr. Evan Peacock of the Central
Science Laboratory for technical support with NMR
spectroscopy.
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