Syntheses and spectroscopic characteristics of dialkylpalladium(II) complexes; PdR2(cod) as precursors for derivatives with N- or P-donor ligands

Article abstract of DOI:10.1016/S0022-328X(98)01071-7

Cycloocta-1,5-diene dialkylpalladium(II) derivatives, PdR₂(cod), (R=CH₂SiMe₃, CH₂SiMe₂Ph) have been isolated and used conveniently as precursors in the preparation of dialkylpalladium complexes, PdR

Full text of DOI:10.1016/S0022-328X(98)01071-7

Journal of Organometallic Chemistry 577 (1999) 257–264
Syntheses and spectroscopic characteristics of dialkylpalladium(II)
complexes; PdR2(cod) as precursors for derivatives with N- or P-donor
ligands
Yi Pan, G. Brent Young *
Inorganic Chemistry Laboratories, Department of Chemistry, Imperial College, London SW7 2AY, UK
Received 14 September 1998
Abstract
Cycloocta-1,5-diene dialkylpalladium(II) derivatives, PdR2(cod), (R=CH2SiMe3, CH2SiMe2Ph) have been isolated and used
conveniently as precursors in the preparation of dialkylpalladium complexes, PdR2L2, with N- or P-donor ancillary ligands
(R=CH2SiMe3; L2=bipy, phen, dppp, dpkt or tmen; L=PMe3; R=CH2SiMe2Ph; L2=bipy; dpkt). The complexes
Pd(CH2CMe2Ph)2(dppe) and PdMe2(bipy) were also prepared from their cyclooctadiene analogues. All have been characterized by
1H-, 13C- and 31P-NMR and IR spectroscopy. © 1999 Published by Elsevier Science S.A. All rights reserved.
Keywords: Palladium; Alkylpalladium; Organometallic; Ligand-exchange
1. Introduction
reviews [7]. The main synthetic methods feature direct
transalkylations on appropriate carboxylato- or halo-
palladium(II) species, with the target ancillary ligands
already in place or available in situ [7,8]. Platinum
complexes of the type, PtR2(cod), (cod=cycloocta-1,5-
diene) are often readily accessible. These have been
used frequently as precursors to further organoplatinu-
m(II) derivatives, via displacement of the labile diene
[9]. The same has not been true for their palladium
analogues (although substitution of certain labile N-
donor ligands has been developed recently as a syn-
thetic counterpart [10,11]). Thus, PdMe2(cod), which
was among the earliest organopalladium(II) complexes
to be reported [12], remains the only characterized
dialkylpalladium compound of its class [13] and only a
few examples of the related monohalopalladium(II)
type—for instance, Pd(Me)Cl(cod) [13], Pd[CH(SiMe3)-
PMe2Ph]Cl(cod) [14] and Pd(C6F5)Cl(cod) [15]—pre-
cede the present work. The lability of these complexes
might stem in part from the high (Pd–alkene bond-
weakening) trans-influence of the s-hydrocarbyl ligands
[16].
Recently, we have sought to explore the unusual
reactivity of heteromethyl platinum(II) complexes, cis-
Pt(CH2YRR% ) L2 and cis-Pt(CH2YRR% )(R¦)L2 [R, R%,
n 2
n
R¦=(variously) alkyl, alkenyl, alkynyl or aryl; Y=Si,
Ge, Sn, n=2; Y=S, n=0; L=phosphine] [1–4].
Among these rearrangements, the most singular, per-
haps, are the b-carbon migrations exhibited by sila-
alkyl [1] and germa-alkyl [2] derivatives of platinum.
We were interested in evaluating the incidence of this
mode of thermolytic reactivity for corresponding com-
plexes of other metals including, quite naturally, nickel
[5] and palladium. This has led us to explore new
synthetic approaches to such dialkylpalladium(II) spe-
cies, on which we report here.
Because of the catalytic importance of the metal and
its derivatives, alkylpalladium chemistry has prolifer-
ated greatly, as reflected in texts [6] and compendious
* Corresponding author. Fax: +44-171-594-5804.
E-mail address: gby@ic.ac.uk (G.B. Young)
0022-328X/99/$ - see front matter © 1999 Published by Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01071-7

258
Y. Pan, G.B. Young / Journal of Organometallic Chemistry 577 (1999) 257–264
Scheme 1.
In the course of our own studies, we have recently
analysis of the rearrangement of cis-Pd(CH2SiMe3)2-
(PMe)2 will appear in due course [19].
accumulated ample evidence that the heteromethyl
groups, which interest us, exert substantially smaller
trans-influences than those of their b-carbon analogues,
CH2CRR% [1–4,17]. Employing two such ligands, we
2. Results and discussion
2
now report on the isolation and characterization of two
new dialkylpalladium(II) species, Pd(CH2SiMe3)2(cod)
and Pd(CH2SiMe2Ph)2(cod), both of which are suffi-
ciently robust to allow their convenient use as precur-
sors to families of dialkylpalladium(II) complexes with
P- and N-donor ligands, PdR2L2 (Scheme 1) [R=
CH2SiMe3, L2=2,2%-bipyridyl (bipy), 1,10-phenanthro-
line (phen), 1,3-bis(diphenylphosphino)propane (dppp),
di(2-pyridyl)ketone (dpkt), (Me2NCH2)2 (tmen), L=
PMe3; R=CH2SiMe2Ph, L2=bipy, dpkt]. As a confir-
mation of the generality of this approach, two other
palladium complexes—the known PdMe2(bipy) [12,13]
and a new derivative, Pd(CH2CMe2Ph)2(dppe) [dppe=
1,2-bis(diphenylphosphino)ethane] —were also pre-
pared from corresponding PdR2(cod), prepared in situ
(Scheme 1). All the new compounds have been fully
2.1. Synthesis
Alkylations of PdCl2(cod) using Mg(CH2SiMe3)Cl or
Mg(CH2SiMe2Ph)Cl were performed in diethylether at
low temperature and proceeded very smoothly, to af-
ford clear colorless solutions. Although it is essential to
carry out the alkylation under an atmosphere of inert
gas and to maintain the temperature below −10°C
throughout alkylation, Pd(CH2SiMe3)2(cod) and
Pd(CH2SiMe2Ph)2(cod) were isolated as relatively ther-
molytically and oxidatively inert crystals in high yields.
As dry solids, these compounds survive for several
hours at ambient temperature in air, without evidence
of decomposition. At −20°C under argon, they may be
stored indefinitely.
Ligand exchange between Pd(CH2SiMe3)2(cod) or
Pd(CH2SiMe2Ph)2(cod) and N- or P- donor ligands has
proved to be an extremely facile, effectively instanta-
neous process—much more rapid than for their plat-
inum analogues [3a–c]. Yields are, generally, almost
quantitative. An exception is the reaction between
Pd(CH2SiMe3)2(cod) and tetramethylethylenediamine,
for which prolonged reaction time and, in consequence,
very low temperatures were necessary. Synthesis of
1
characterized by H-, 13C- and 31P-NMR spectroscopy,
IR spectroscopy and by satisfactory elemental analyses.
As has emerged from our investigations, the major
thermolytic preference for cis-Pd(CH2SiMe3)2(PMe)2 is
reductive C–C elimination, generating Me3SiCH2CH2-
SiMe3. This is in contrast to the unusual reactivity of its
platinum analogue [1] but is in broad accord with
established patterns of behaviour for many cis-dialkyl-
palladium(II) complexes [7b,18]. A detailed mechanistic

Y. Pan, G.B. Young / Journal of Organometallic Chemistry 577 (1999) 257–264
259
Pd(CH2SiMe3)2(PMe3)2 by this route afforded the cis-
isomer as the sole product. This contrasts with the
direct alkylation of palladium acetate in the presence of
PMe3, which resulted in only the trans-isomer [8]. In a
similar fashion, however, cis-PdMe2(PMePh2)2 is the
only product of amine displacement from PdMe2(tmen)
by the requisite phosphine [10]. Dipyridylketone was
also found to readily replace the diene and
Pd(CH2SiMe3)2(dpkt) and Pd[CH2SiMe2Ph]2(dpkt)
were isolated in almost quantitative yields. The suscep-
tibility of the carbonyl group towards nucleophilic ad-
dition would preclude syntheses of these derivatives by
transalkylations of PdCl2(dpkt).
These ligand-substitution reactions may also be car-
ried out without isolation of the diene complexes. This
may be convenient in cases where PdR2(cod) is more
thermolytically labile than is the case for the sila-alkyl-
palladium precursors. By way of illustration, both
PdMe2(bipy) and Pd(CH2CMe2Ph)2(dppe) were ob-
tained in high yields using PdCl2(cod) as precursor. In
these instances, quenching of excess Grignard reagent
was achieved conveniently by addition of acetone to the
reaction mixture prior to introduction of the new
ligand.
IR data for each complex are listed in the experimen-
tal section. For silicon-containing compounds, w(Si–C)
vibrations are apparent at ca. 830 cm−1. Characteristic
w(Pd–C) modes were observed at ca. 530 cm−1 in most
cases.
3. Experimental
3.1. General procedure
All manipulations were performed under purified
dinitrogen. Solvents were heated under reflux with
sodium-benzophenone and distilled under dinitrogen
prior to use. NMR spectra were recorded on Bruker
AM500 (1H, 500.15 MHz), Bruker WM250 (1H, 250.13
MHz; 13C, 62.9 MHz), and JEOL FX90Q (1H, 89.55
MHz; 31P, 36.21 MHz) instruments. IR spectra were
collected on a Perkin-Elmer 683 spectrophotometer as
Nujol mulls on KBr plates. Elemental analyses were by
Imperial College Microanalysis Laboratory.
Cycloocta-1,5-diene, 2,2%-bipyridyl, 1,10-phenathro-
line, di(2-pyridyl)ketone, 1,2-bis(diphenylphosphino)-
ethane and 1,3-bis(diphenylphosphino)propane were all
obtained from Aldrich Chemical Co. and were used as
supplied. Trimethylphosphine was supplied by Strem
Chemicals and was stored under dinitrogen. The com-
pounds chloromethyltrimethylsilane, chloromethyldi-
methyl-phenylsilane and 1-chloro-2-methyl-2-phenyl-
propane (neophyl chloride) were obtained from Aldrich
Chemical Co. and were distilled prior to use. The
compound MgMeCl was supplied as a 1.0 M solution
in THF by Aldrich Chemical Co. and was used as
supplied.
2.2. Spectroscopic characteristics
1
2.2.1. H-NMR spectroscopy
1H-NMR data are presented in Table 1. For the
phenyldimethylsilylmethyl (sila-neophyl) ligand, a sin-
gle prime denotes numbering associated with the Si-
bonded phenyl group.
The methylene hydrogens of both silylmethyl ligands
resonate characteristically to high field, in the range of
0.9 to −0.2 ppm, dependent on the nature of the
ancillary ligands. Despite their remoteness, the chemical
shifts attributable to the silicon-bound methyl hydro-
gens are also sensitive to the auxiliary ligands. Relative
to the trimethylsilylmethyl ligand, the sila-neophyl
group induces a noticeable upfield shift in signals asso-
ciated with the ancillary ligand. This net shielding
might be a result of the anisotropic magnetic influence
of the aromatic ring (although a corresponding effect is
not immediately evident in 13C-NMR spectra; see below
and Table 2).
Diethyl ether solutions of Mg(CH2SiMe3)Cl [3a]
Mg(SiCH2Me2Ph)Cl [3b] and Mg(CH2CMe2Ph)Cl [20]
were prepared with flame-activated magnesium by pre-
viously published methods. The compound PdCl2(cod)
was also synthesized according to a published proce-
dure [21].
3.2. Preparation of bis(trimethylsilylmethyl)-
(cycloocta-1,5-diene)palladium(II) (1)
A solution of Mg(CH2Si Me3)Cl in diethyl ether (7
ml, 0.45 M, 3.2 mmol) was added to a stirred suspen-
sion of PdCl2(cod) (0.29 g, 1 mmol) in the same solvent
(30 ml) at −78°C. The mixture was allowed to warm
to about −10°C and stirred at that temperature for 30
min, after which all volatiles were removed in vacuo. At
no time thereafter were temperatures of dissolved prod-
ucts allowed to exceed −10°C. The residue was ex-
tracted with chilled, degassed n-hexane (2×30 ml) and
the combined hexane filtrates were again evaporated to
dryness in vacuo. Chilled, degassed acetone (ca. 30 ml)
was added to the residue. After filtration, the solution
2.2.2. 13C-, 31P-NMR and IR spectroscopy
{1H}13C- and {1H}31P-NMR data appear in Table 2.
For silylmethyl ligands, palladium-bound carbon res-
onates upfield from 12 ppm. The most notable upfield
shifts for these carbons are associated with heteroaro-
matic N-donor ancillary ligands. For P-donor ancillary
ligands, these carbons generate doubled doublet pat-
terns, as a result of the coupling to both 31P nuclei.
31P-NMR spectra of these phosphorus-containing com-
pounds were also recorded; all generate singlets.

Table 1
a
1H-NMR characteristics of PdR2L2
Compounds
CH2Pd
SiCH3
Other 1H: l /ppm(assignment)
1. Pd(CH2SiMe3)2(cod)b
2. Pd(CH2SiMe2Ph)2(cod)
3. Pd(CH2SiMe3)2(bipy)
0.67(s)
0.88(s)
0.08(s)
0.28(s)
0.55(s)
−0.03(s)
5.09 (s, br, 4H, ꢀCH), 1.90 (s, br, 8H, CH2)
7.69–7.72 (m, 4H, H2%), 6.99–7.26 (m, 6H, H3%, 4%), 4.81 (s, br, 4H, ꢀCH), 1.65 (s, br, 8H, CCH2)
8.82 (dd, JH6–H5 5.27, JH6–H4 1.0, 2H, H6), 8.46 (dd, JH3–H4 7.92, JH3–H5 0.99, 2H, H3), 8.17 (ddd, JH4–H5 7.58, 2H, H4), 7.71
(ddd, 2H, H5)
/
4. Pd(CH2SiMe3)2(phen)
5. Pd(CH2SiMe3)2(dpkt)
0.24(s)
−0.13(s)
−0.02(s)
−0.13(s)
9.16 (dd, JH2–H3 4.95, JH2–H4 1.32, 2H, H2), 8.77 (dd, JH4–H3 8.25, JH4–H2 1.65, 2H, H4), 8.17 (s, 2H, H5), 8.06 (dd, 2H, H3)
8.81 (ddd, JH6–H5 5.28, JH6–H4 1.65, JH6–H3 0.66, 2H, H6), 8.46 (ddd, JH3–H4 7.59, JH3–H5 1.65, 2H, H3), 8.19 (ddd, JH4–H5 7.76,
2H, H4), 7.80 (ddd, 2H, H5)
6. Pd(CH2SiMe3)2(dppp)
0.24(d, br, −0.22(s)
JP–H 5.0)
7.56–7.63 (m, 8H, H2, 6), 7.37–7.41 (m, 12H, H3, 4, 5), 2.50–2.57 (m, 4H, CH2P), 1.72–1.98 (m, 2H, CH2CP)
7. cis-Pd(CH2SiMe3)2(Pme3)2 0.49(dd,
0.32(s)
0.88 (d, JP–H 6.56, CH3P)
Jcis5.5,
Jtrans10.7)
8. Pd(CH2SiMe3)2(tmen)
9. Pd(CH2SiMe2Ph)2(bipy)
−0.11(s)
0.31(s)
0.47(s)
0.24(s)
1.92 (s, 12H, NCH3), 1.52 (s, 4H, NCH2)
8.62 (dd, JH6–H5 5.28, JH6–H4 1.59, 2H, H6), 8.25 (d, JH3–H4 7.92, 2H, H3), 8.11 (ddd, JH4–H5 7.59, 2H, H4), 7.54 (ddd, 2H, H5),
7.63 (m, 4H, H2%), 7.15 (m, 6H, H3%4%
8.57 (ddd, JH6–H5 5.28, JH6–H4 1.65, JH6–H3 0.66, 2H, H6), 8.06 (ddd, JH4–H3 7.59, JH4-H5 7.91, 2H, H4), 7.90–7.94 (m, 2H, H3),
7.56 (ddd, JH5–H3 1.32, 2H, H5), 7.61–7.65 (m, 4H, H2%), 7.18–7.24 (m, 6H, H3%4%
8.70 (m, JH6–H5 5.27, 2H, H6), 6.87 (m, 2H, H3), 6.82 (m, 2H, H4), 6.43 (ddd, JH5–H4 6.93, JH5–H3 1.64, 2H, H5)
7.46 (m, 4H, H2%), 7.02–7.06 (m, 6H, H3%, 4%), 7.58–7.65 (m, 8H, H2, 6), 7.36–7.42 (m, 12H, H3, 5), 1.80–1.86 (m, 4H, CH2P)
)
10. Pd(CH2SiMe2Ph)2(dpkt)
0.16(s)
0.13(s)
1.23(s)
57777
)
11. PdMe2(bipy)
12. Pd(CH2CMe2Ph)2(dppe)
1.11(s)
(1999)1999)
2.48 (dd,
,
4
Jcis6.6,
Jtrans11.9
25757
26464
a In acetone-d6, unless otherwise specified; l/ppm relative to external TMS; J/Hz.
b In benzene-d6.

Table 2
a
13C- and 31P-NMR characteristics of PdR2L2
Compounds
CH2Pd
SiCH3
13Cb other: l/ppm (assignment)
31Pc l/ppm
1. Pd(CH2SiMe3)2(cod)d
2. Pd[CH2SiMe2Ph)2(cod)
3. Pd(CH2SiMe3)2(bipy)
4. Pd(CH2SiMe3)2(phen)
5. Pd(CH2SiMe3)2(dpkt)
6. Pd(CH2SiMe3)2(dppp)
11.5
8.4
3.4
3.8
1.0
0.8
3.4
3.7
4.6
111.8 (CH), 29.0 (CH2)
143.6 (C1%), 133.0 (C2%), 127.4 (C4%), 126 (C3%), 112.1 (CH), 28.2 (CH2)
155.4 (C2), 148.6 (C6), 138.6 (C3), 126.5 (C4), 122.8 (C5)
156.8 (C2), 148.6 (C6), 143.3 (C3), 137.7 (C5), 127.4 (C4), 125.5 (C7)
188.9 (CꢀO), 154.7 (C2), 151.2 (C6), 139.5 (C3), 128.7 (C4), 125.8 (C5)
135.7 (t, JP–C 16.5, C1%), 134.4 (t, JP–C 5.5, C2%6%),130.4 (s, C4%), 128.8 (t, JP–C 4.2, C3%,5%), 28.4 (t, JP–C 11.6,
CH2P), 20.2 (t, JP–C 4.2, CH2)
/
0.2
0.1
8.2e
6.4
7. cis-Pd(CH2SiMe3)2(PMe3)2
9.8f
−6.7
−0.4
−1.1
5.54
4.8
2.1
2.6
17.6 (t, JP–C 24.75, PC)
58.8 (CH2N), 47.8 (NCH3)
−25.4
d
8. Pd(CH2SiMe3)2(tmen)
9. Pd(CH2SiMe2Ph)2(bipy)
10. Pd(CH2SiMe2Ph)2(dpkt)
155.3 (C2), 148.6 (C6), 138.5 (C3), 126.4 (C4), 122.6 (C5), 145.8 (C1%), 134.1 (C2%), 127.8 (C4%), 127.4 (C3%)
189.0 (CꢀO), 154.7 (C2), 151.6 (C6), 139.8 (C3), 128.8 (C4), 126.1 (C5), 146.2 (C1%), 134.7 (C2%), 128.2 (C3%), 128.5
(C4%)
155.6 (C2), 148.2 (C6), 138.6 (C3), 126.8 (C4), 122.9 (C5)
136.3 (d, JP–C 24.4, C1%), 134.4 (d, JP–C 12.2, C2%), 129.2 (d, JP–C 9.6, C3%), 130.5 (C4%), 25.0 (t, JP–C 18.0)
11. PdMe2(bipy)d
−6.6
12. Pd(CH2CMe2Ph)2(dppe)d
34.6g
37.9
29.4
57777
a In acetone-d6, unless otherwise specified; J/Hz.
b l/ppm relative to external TMS.
c l/ppm relative to external H3PO4.
d In benzene-d6.
(1999)1999)
25757
trans
P–C
cis
e dd, J
f dd, J
g dd, J
104.3, J
101.7, J
102.5, J
20.1.
15.1.
9.7.
P–C
cis
P–C
cis
P–C
trans
P–C
trans
P–C
26464

262
Y. Pan, G.B. Young / Journal of Organometallic Chemistry 577 (1999) 257–264
was concentrated to ca. 5 ml and stored at ca. −30°C.
The pure product was recovered by filtration as
white crystals and was dried in vacuo. (Yield: 0.35 g,
80%). Analyses: found (calc.): %C, 49.1 (49.4); %H, 8.8
(8.8).
3.6. Preparation of bis(trimethylsilylmethyl)-
[di(2-pyridyl)ketone]palladium(II) (5)
This derivative was synthesized by a procedure ex-
actly analogous to that of 3 (above), from an equimolar
conjunction of di(2-pyridyl)ketone and Pd(CH2SiMe3)2-
(cod) in diethyl ether. Pure orange crystalline 5 was
recovered after recrystallization from hexane (yield:
95%). Analyses; found (calc.): C, 49.2 (49.1); H, 6.6
(6.5); N, 6.0 (6.0); IR (cm−1): 2957vs, 2909s, 2844s,
1690m, 1589w 1466m, 1238m, 846m, 817m, 754m,
527w.
IR (cm−1): 2958s, 2964vs, 2907vs, 2885sh, 1466m,
1451m, 1429s, 1251s, 1239vs, 843vs, 824vs, 675s,
512w.
3.3. Preparation of bis(dimethylphenylsilylmethyl)-
(cycloocta-1,5-diene)palladium(II) (2)
This compound was prepared by a procedure ex-
actly analogous to that of 1 (above), from PdCl2(cod)
(0.29 g, 1 mmol) in diethyl ether (30 ml) and
3.7. Preparation of bis(trimethylsilylmethyl)-
[bis-1,3-(diphenylphosphino)propane]palladium(II) (6)
Mg(SiCH2Me2Ph)Cl (6 ml, 0.40
M solution, 2.4
mmol). After the reaction, a degassed solution of ace-
tone (ca. 1 ml) and hexane (ca. 20 ml) was added to
the reaction mixture at −78°C and the mixture was
allowed to warm to about −10°C. The volatiles were
removed in vacuo. The residue was treated with hex-
ane, the resulting solution was cold filtered and di-
ethyl ether added to induce crystallisation. The pure
product was obtained as pale needles. (Yield: 0.46 g,
90%). Analyses: found (calc.): %C, 60.8 (60.9); %H,
7.5 (7.5). IR (cm−1): 3063m, 2974vs, 2882vs, 1588vw,
1565w, 1482m, 1462s, 1240vs, 1109vs, 823vs, 736vs,
518m.
This complex was synthesized by a procedure exactly
analogous to that of 3 (above), from dppp and
(cod)Pd(CH2SiMe3)2. The product was obtained as
colourless needles after recrystallization from an
ether–hexane mixture (Yield: 88%). Analyses; found
(calc.): %C, 60.7 (61.0); %H, 7.0 (6.4). IR (cm−1):
3073w, 2962vs, 2901vs, 2892s, 1587vw, 1482m, 1467m,
1437m, 1263m, 1098m, 845m, 818m, 742m, 695s, 509s,
483m.
3.8. Preparation of cis-bis(trimethylsilylmethyl)bis-
(trimethylphosphine)palladium(II) (7)
3.4. Preparation of bis(trimethylsilylmethyl)-
(2,2%-bipyridyl)palladium(II) (3)
Excess PMe3 (ca. 3-fold) was added via syringe to a
stirred solution of Pd(CH2SiMe3)2(cod) (0.25 g, 0.64
mmol) in diethyl ether (5 ml) at −10°C. The mixture
was allowed to warm to ambient temperature and the
volatiles were removed in vacuo. Compound 7 was
obtained as a white gummy solid (yield: 100%). Analy-
ses; found (calc.): %C, 38.9 (38.8); %H, 9.3 (9.3). IR
(cm−1): 2950vs, 2878vs, 1462vs, 1270s, 1237vs, 823s,
674s, 520w.
A solution of 2,2%-bipyridyl (0.076 g, 0.5 mmol) in
diethyl ether (10 ml) was added slowly to a stirred
solution of Pd(CH2SiMe3)2(cod) (0.195 g, 0.5 mmol)
in the same solvent (10 ml) at −5°C. The mixture
was stirred at ambient temperature for 5 min. The
volatiles were removed in vacuo. Pure yellow crys-
talline product was obtained by recrystallization from
an acetone–hexane mixture (yield: 0.20 g, 92%).
Analyses; found (calc.): %C, 49.3 (49.5); %H, 6.9 (6.9);
%N, 6.4(6.4). IR (cm−1): 2963vs, 2959sh, 2861s,
1595w, 1564vw, 1468m, 1234m, 834m, 831m, 818m,
757m, 531w.
3.9. Preparation of bis(trimethylsilylmethyl)(tetra-
methylethylenediamine)palladium(II) (8)
Excess N,N,N%,N%-tetramethylethylenediamine (ca. 2-
3.5. Preparation of bis(trimethylsilylmethyl)-
(1,10-phenanthroline)palladium(II) (4)
fold) was added via syringe to a solution of
Pd(CH2SiMe3)2(cod) (0.20 g, 0.51 mmol) in diethyl
ether (8 ml) under argon at −78°C. The mixture was
stored at ca. −30°C overnight, volatiles were removed
in vacuo, below −5°C. The pure compound was ob-
tained as white needles, after recrystallization of the
residue from n-hexane (yield: 0.12 g, 60%). Analyses;
found (calc.): %C, 42.3 (42.4); %H, 9.9 (9.7); %N,
7.0 (7.1). IR (cm−1): 2945vs, 2868vs, 2833s, 2788m,
1616w, 1460vs, 1274sh, 1236vs, 845vs, 823vs, 795s,
673s, 523w.
This complex was prepared by a procedure exactly
analogous to that of 3 (above), from a 1:1 admixture of
1,10-phenanthroline and Pd(CH2SiMe3)2(cod) in diethyl
ether. A yellow crystalline product was obtained from
acetone hexane in quantitative yield. Analyses; found
(calc.): %C, 52.3 (52.1); %H, 6.6 (6.6); %N, 5.8 (6.1). IR
(cm−1): 2938vs, 2898s, 2859m, 1625w, 1511m, 1467m,
1435s, 1250sh, 1235s, 840vs, 724s, 530w.

Y. Pan, G.B. Young / Journal of Organometallic Chemistry 577 (1999) 257–264
263
3.10. Preparation of bis(dimethylphenylsilylmethyl)-
(2,2%-bipyridyl)palladium(II) (9)
(cm−1): 3071w, 2956sh, 2944vs, 2851s, 1586w, 1482m,
1468m, 1434s, 1228m, 1093m, 740s, 692vs, 529s.
This complex was synthesized by a procedure exactly
analogous to that of 3 (above), from equimolar admix-
ture of 2,2%-bipyridyl and Pd(CH2SiMe2Ph)2(cod) in
diethyl ether. The product was obtained as yellow
crystals (yield: 95%). Analases; found (calc.): %C, 60.0
(59.9); %H, 6.1 (6.1); %N, 5.0 (5.0). IR (cm−1): 3078m,
2949vs, 2853vs, 1597m, 1584w, 1468s, 1441s, 1236s,
1106s, 835s, 804s, 756vs, 552w, 540.
4. Conclusions
With careful manipulation, bis(silylmethyl)palla-
dium(II) complexes with h-diene ligands—Pd(CH2-
SiMe3)2(cod) and Pd(CH2SiMe2Ph)2(cod)—may be iso-
lated in good yields. Via diene-displacement, these are
convenient precursors to a related series of dialkylpalla-
dium derivatives with N- and P-donor ancillary ligands.
Isolation of the h-diene–metal intermediate is not al-
ways necessary for success, however, and PdMe2(bipy)
and Pd(CH2CMe2Ph)2(dppe) have been prepared in
excellent yields (\80%) in this way (Scheme 1).
3.11. Preparation of
bis(dimethylphenylsilylmethyl)[di(2-pyridyl)ketone]-
palladium(II) (10)
This derivative was synthesized by a procedure ex-
actly analogous to that of 3 (above), from addition of
di(2-pyridyl)ketone to equimolar Pd(CH2SiMe2Ph)2-
(cod) in diethyl ether. The product was obtained as a
gummy orange semi-solid in essentially quantitative
yield. Analyses; found (calc.): %C, 59.2 (59.1); %H, 5.8
(5.8); %N, 4.8 (4.7). IR (cm−1): 3064s, 2947vs, 2892s,
2854s, 1683vs, 1590s, 1425s, 1307s, 1238s, 1105s, 804vs,
537w.
Acknowledgements
We are most grateful to the British Council and to
the EPSRC for successive awards of Postdoctoral Fel-
lowships (to P. Yi) and to the Nuffield Foundation for
the award of a Research Fellowship (to G.B. Young) in
the course of this work. We additionally thank Johnson-
Matthey for their continued support by way of gener-
ous loans of palladium precursors. Thanks are also due
to Dick Sheppard and Paul Hammerton for invaluable
assistance with high-field NMR measurements.
3.12. Preparation of dimethyl(2,2%-bipyridyl)-
palladium(II) (11)
The compound MgMeCl in THF (2.5 ml, 1.0 M, 2.5
mmol) was added to a suspension of PdCl2(cod) (0.29
g, 1 mmol) diethyl ether (30 ml) at −78°C. The
mixture was allowed to warm to about −10°C, and
stirred at this temperature for 30 min. After cooling the
mixture to −78°C, a prepared mixture of acetone (1
ml) and hexane (10 ml) was added slowly, followed by
a solution of 2,2%-bipyridyl (0.16 g, 1 mmol) in diethyl
ether (10 ml). The mixture was allowed to warm to
ambient temperature. After stirring for 20 min, the
solution was filtered. The filtrate was evaporated to
dryness in vacuo. Pure product was obtained as yellow
crystals after recrystallization of the residue from an
acetone–hexane mixture (yield: 0.25 g, 86%). Analyses;
found (calc.): %C, 49.0 (49.2); %H, 4.6 (4.8); %N, 9.5
(9.6). IR (cm−1): 3073vw, 2922vs, 2850s, 1599s, 1467s,
1442vs, 1311m, 1157m, 752vs, 730vs, 530vw, 524w.
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