Synthesis and reactivity of [Pd2L2R2(μ-OH)2]-type complexes (L = PEt3 or PPh3; R = Me, PhCH2 or Ph). Crystal structure of [Pd2(PPh3)2Ph 2(μ-OH)(μ-NHC6H4OMe-p)]

Article abstract of DOI:10.1039/a704203e

The metathesis of Cl^- by OH^- in [Pd₂(PEt₃)₂R₂(μ-Cl)₂] gave the binuclear hydroxo complexes [Pd₂(PEt₃)₂R₂(μ-OH)₂] (R = Me or PhCH₂) which in CDCl₃ solution exist as 1:1 mixtures of syn and anti isomers. They reacted with 3,5-dimethylpyrazole (Hdmpz) in 1:2 molar ratio to yield the corresponding azolate complexes anti-[Pd₂(PEt₃)₂R₂(μ-dmpz) ₂] and with oxalic acid (H₂ox), in 1:1 molar ratio, to afford the corresponding oxalate complexes anti-[Pd₂(PEt₃)₂R₂(μ-ox)]. The cleavage of the OH bridges of the di-μ-hydroxo complexes yields the mononuclear [Pd(PEt₃)₂R(OH)] which in solution are present as 1:1 mixtures of cis and trans isomers. Binuclear μ-hydroxo-μ-amido palladium complexes [Pd₂L₂R₂(μ-OH)(ν-NHR″)₂] (R = Me, L = PEt₃; R = Ph, L = PPh₃; R″ = Ph, C₆H₄Me-p, C₆H₄OMe-p, C₆H₄Cl-p or C₆H₄NO₂-p) have been prepared by reaction of [Pd₂L₂R₂(μ-OH)₂] with the corresponding aromatic amine R″NH₂. The NMR data indicate that the isolated complexes are the anti isomers. The crystal structure of complex [Pd₂(PPh₃)₂Ph ₂(μ-OH)(μ-NHC₆H₄OMe-p)] has been established; the Pd₂ON ring is severely bent.

Full text of DOI:10.1039/a704203e

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Synthesis and reactivity of [Pd2L2R2(ì-OH)2]-type complexes
(L = PEt3 or PPh3; R = Me, PhCH2 or Ph). Crystal structure of
[Pd2(PPh3)2Ph2(ì-OH)(ì-NHC6H4OMe-p)]
José Ruiz,a Venancio Rodríguez,a Gregorio López,*,a Penny A. Chalonerb and P. B. Hitchcockb
a Departamento de Química Inorgánica, Universidad de Murcia, 30071-Murcia, Spain
b School of Chemistry, Physics and Environmental Science, University of Sussex, Brighton,
UK BN1 9QJ
The metathesis of ClϪ by OHϪ in [Pd2(PEt3)2R2(µ-Cl)2] gave the binuclear hydroxo complexes [Pd2(PEt3)2R2-
(µ-OH)2] (R = Me or PhCH2) which in CDCl3 solution exist as 1:1 mixtures of syn and anti isomers. They
reacted with 3,5-dimethylpyrazole (Hdmpz) in 1:2 molar ratio to yield the corresponding azolate complexes
anti-[Pd2(PEt3)2R2(µ-dmpz)2] and with oxalic acid (H2ox), in 1:1 molar ratio, to afford the corresponding
oxalate complexes anti-[Pd2(PEt3)2R2(µ-ox)]. The cleavage of the OH bridges of the di-µ-hydroxo complexes
yields the mononuclear [Pd(PEt3)2R(OH)] which in solution are present as 1:1 mixtures of cis and trans isomers.
Binuclear µ-hydroxo-µ-amido palladium complexes [Pd2L2R2(µ-OH)(µ-NHRЉ)2] (R = Me, L = PEt3; R = Ph,
L = PPh3; RЉ = Ph, C6H4Me-p, C6H4OMe-p, C6H4Cl-p or C6H4NO2-p) have been prepared by reaction of
[Pd2L2R2(µ-OH)2] with the corresponding aromatic amine RЉNH2. The NMR data indicate that the isolated
complexes are the anti isomers. The crystal structure of complex [Pd2(PPh3)2Ph2(µ-OH)(µ-NHC6H4OMe-p)] has
been established; the Pd2ON ring is severely bent.
Since the OHϪ ligand is an σ,π-electron donor there has been
[R(PEt3)Pd(µ-Cl)2Pd(PEt3)R]
the deceptive perception that late transition-metal hydroxides
are unstable because π donation to electron-rich metal centres
(i )
should be unfavorable. Until recently the only reported organo-
(iv )
palladium hydroxo complexes were of the type [Pd(PPh3)2-
R(OH)], prepared by Yoshida et al.1 Recent work, however,
suggests that late metal–hydroxide bonds are not particularly
weak relative to M᎐H or M᎐C bonds, but the presence of lone
electron pairs gives these compounds modes of reactivity not
normally available to metal alkyls and hydrides.2 In fact, their
reactivity and catalytic properties have stimulated the recent
surge of interest in the chemistry of late-metal hydroxides.2,3
Binuclear organopalladium hydroxo complexes [Pd2R4-
(µ-OH)2]2Ϫ (R = C6F5,4 C6Cl5,5 or C6F3H2-2,4,66), [Pd2L2R2-
[Pd(PEt3)2R(OH)]
[R(PEt3)Pd(µ-OH)2Pd(PEt3)R]
R = Me 1, PhCH2 2
R = Me 7, PhCH2 8
(iii )
(ii )
PEt3
R
O
O
O
R
C
C
Pd
Pd
Et3P
O
Me
Me
Pd
Me
R = Me 5, PhCH2
6
PEt3
R
N
N
N
N
R
Pd
9
(µ-OH)2] (L = PPh3; R = Me,7 Ph,8 C6F5 or C6Cl5 ) and
Et3P
[Pd2(L᎐LϪ)2(µ-X)(µ-OH)]
[L᎐LϪ = 8-quinolylmethyl,
X =
carboxylate;10 L᎐LϪ = 2-(dimethylaminomethyl)phenyl, X =
Br11] are known. The reaction of a labile precursor such as cis-
[MR2(NCPh)2] with [NBu4]OH or the metathesis of XϪ by OHϪ
in a binuclear M(µ-X)2M complex are the methods used for the
preparation of hydroxo complexes.12 The equilibrium between
[Pd(PR3)2RЈ(OH)] and [Pd2(PR3)2RЈ2(µ-OH)2] has been investi-
gated very recently.13
Me
R = Me 3, PhCH2
4
Scheme 1 (i) OHϪ; (ii) Hdmpz (3,5-dimethylpyrazole); (iii) H2ox
(oxalic acid); (iv) PEt3
H
O
H
O
R
L
R
L
L
R
L
The basic character of these hydroxo complexes allows the
preparation of a variety of mono- and bi-nuclear complexes
by reaction with a protic electrophile (M᎐OH ϩ HX →
M᎐X ϩ H2O). For example, aryloxo14 and amido15,16 com-
plexes of palladium have been prepared by reaction of a
hydroxopalladium complex with phenols and amines, respect-
ively. The binuclear complex [Pd2(C6F5)4(µ-OH)2]2Ϫ is an effi-
cient basic catalyst for the cyclotrimerization of malononitrile
to 4,6-diamino-2-cyanomethylpyridine-3,5-dicarbonitrile.17
In this paper we report the preparation of hydroxopalladium
complexes of the type [Pd2(PEt3)2R2(µ-OH)2] and their reac-
tions with 3,5-dimethylpyrazole, oxalic acid, triethylphosphine
and a number of arylamines.
M
M
M
M
R
O
H
O
H
syn
anti
R2(µ-Cl)2] with [NBu4]OH(aq) leads to the formation of the
bis(µ-hydroxo) complexes 1 and 2 shown in Scheme 1. The
metathesis of ClϪ by OHϪ occurs smoothly at room temper-
ature and the hydroxo complexes are isolated in ca. 90% yields.
The presence of the hydroxo ligand is manifested by the obser-
vation of characteristic IR absorptions in the vicinity of 3500
cmϪ1 and of high-field proton resonances at δ Ϫ1.4 (1) and
Ϫ3.3 (2). The NMR data (Table 1) reveal that complexes 1 and
2 exist in CDCl3 solution as 1:1 mixtures of syn and anti iso-
mers: two 31P resonances are found for the phosphines and two
1H and 13C resonances are also observed for the CH3Pd and
CH2P groups. For the methyl nickel analogue [Ni2(PMe3)2-
Results and Discussion
In acetone or acetone–methanol the reaction of [Pd2(PEt3)2-
J. Chem. Soc., Dalton Trans., 1997, Pages 4271–4276
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Table 1 The NMR data (J in Hz) for the palladium complexes 1–8 (in CDCl3)
Complex
1H δ(SiMe4)
13C δ(SiMe4)
31P δ(H3PO4)
1
1.6 (m, 24 H, CH2P)
1.3 (m, 36 H, CH3CH2P)
0.46 (s, 6 H, CH3Pd)
0.39 (s, 6 H, CH3Pd)
Ϫ1.4 (br, OH)
16.1 (d, CH2P, JCP 27.7)
15.5 (d, CH2P, JCP 29.4)
8.1 (s, CH3CH2P)
Ϫ0.2 (br, CH3Pd)
Ϫ3.1 (br, CH3Pd)
28.71 (s)
28.60 (s)
2
3
4
7.0 (m, 20 H, C6H5)
128.4 (br s, CH of PhCH2)
128.1 (br s, CH of PhCH2)
123.6 (br s, CH of PhCH2)
23.5 (br, CH2Pd)
20.6 (br, CH2Pd)
16.0 (br, CH2P)
28.49 (s)
28.18 (s)
2.52 (d, 4 H, CH2Pd, JPH 3.8)
2.47 (d, 4 H, CH2Pd, JPH 4.0)
1.6 (m, 24 H, CH2P)
1.0 (m, 36 H, CH3CH2P)
Ϫ2.3 (br, OH)
Ϫ2.4 (br, OH)
Ϫ3.3 (br, OH)
5.46 (s, 2 H, 4-H of dmpz)
2.17 (s, 6 H, Me of dmpz)
2.08 (s, 6 H, Me of dmpz)
1.56 (m, 12 H, CH2P)
1.07 (m, 18 H, CH3CH2P)
0.15 (d, 6 H, CH3Pd, JPH 4.1)
15.4 (br, CH2P)
8.1 (s, CH3CH2P)
145.4 (s, 3-C of dmpz)
144.7 (s, 5-C of dmpz)
101.4 (s, 4-C of dmpz)
15.8 (d, CH2P, JCP 27.7)
14.2 (s, Me of dmpz)
13.7 (s, Me of dmpz)
8.2 (s, CH3CH2P)
25.07 (s)
22.43 (s)
Ϫ8.8 (br, CH3Pd)
7.0 (m, 10 H, C6H5)
171.7 (s, CCH2 of PhCH2)
145.6 (s, 3- and 5-C of dmpz)
128.7 (s, CH of PhCH2)
127.6 (s, CH of PhCH2)
122.3 (s, CH of PhCH2)
101.8 (d, 4-C of dmpz, JCP 3.2)
17.0 (d, CH2Pd, JCP 6.1)
15.5 (d, CH2P, JCP 27.3)
14.5 (s, Me of dmpz)
13.4 (s, Me of dmpz)
8.7 (s, CH3CH2P)
5.33 (s, 2 H, 4-H of dmpz)
3.00 (d, 2 H, CHAPd, JHH 8.9)
2.44 (dd, 2 H, CHBPd, JHH = JPH 8.9)
2.19 (s, 6 H, Me of dmpz)
1.75 (s, 6 H, Me of dmpz)
1.57 (m, 12 H, CH2P)
1.09 (m, 18 H, CH3CH2P)
5
1.65 (m, 12 H, CH2P)
1.11 (m, 18 H, CH3CH2P)
0.48 (s, 6 H, CH3Pd)
7.6 (m, 4 H, C6H5)
15.7 (d, CH2P, JCP 30.7)
8.1 (s, CH3CH2P)
Ϫ6.3 (br, CH3Pd)
129.0 (s, CH of PhCH2)
128.2 (s, CH of PhCH2)
124.2 (s, CH of PhCH2)
19.5 (d, CH2Pd, JCP 3.8)
14.7 (d, CH2P, JCP 29.4)
7.6 (s, CH3CH2P)
37.22 (s)
32.59 (s)
6*
7.0 (m, 6 H, C6H5)
3.06 (br s, 4 H, CH2Pd)
1.18 (m, 12 H, CH2P)
0.68 (m, 18 H, CH3CH2P)
7
8
1.75 (m, 24 H, CH2P)
14.6 (t, CH2P, JCP 12.7)
14.0 (t, CH2P, JCP 12.5)
8.3 (s, CH3CH2P)
15.95 (s)
14.87 (s)
1.05 (m, 36 H, CH3CH2P)
0.22 (t, 3 H, CH3Pd, JPH 5.8)
0.11 (t, 3 H, CH3Pd, JPH 6.0)
8.2 (s, CH3CH2P)
Ϫ6.6 (t, CH3Pd, JCP 4.0)
Ϫ9.2 (t, CH3Pd, JCP 4.7)
17.9 (s, CH2Pd)
7.3 (m, 4 H, C6H5)
7.0 (m, 6 H, C6H5)
13.61 (s)
12.35 (s)
15.6 (s, CH2Pd)
2.69 (t, 2 H, CH2Pd, JPH 7.1)
2.59 (t, 2 H, CH2Pd, JPH 7.1)
1.71 (m, 12 H, CH2P)
1.00 (m, 18 H, CH3CH2P)
14.6 (t, CH2P, JCP 12.6)
13.9 (t, CH2P, JCP 12.4)
8.3 (s, CH3CH2P)
8.2 (s, CH3CH2P)
* In C6D6.
Me2(µ-OH)2] a mixture of syn and anti isomers was also found
in a ratio depending on the polarity of the solvent,18 whereas
the benzylnickel complex [Ni2(PMe3)2(CH2Ph)2(µ-OH)2]19 and
the perhalogenophenyl complexes [Pd2(PPh3)2R2(µ-OH)2] (R =
C6F5 or C6Cl5)9 were exclusively anti isomers. The recently
reported complex [Pd2(PPh3)2Ph2(µ-OH)2] exists in solution as a
4:1 mixture of anti and syn isomers, although the anti geometry
for this complex was found in the crystalline state.8
they yielded the corresponding azolate-bridged complexes
[Pd2(PEt3)2R2(µ-dmpz)2] (R = Me 3 or PhCH2 4).
The single resonance observed in the 31P NMR spectra of
complexes 3 and 4 indicates that these are found exclusively as a
single isomer in CDCl3 solution. If the syn symmetry is
assigned to 3 and 4 the CH group of the dmpz ring should give
1
two H and two 13C resonances in the respective spectra. The
experimental NMR data (Table 1) indicate that in CDCl3 solu-
tion only the anti isomers are present because a single signal is
observed for the CH group. Note that the two resonances
The reaction of the bis(hydroxo) complexes [M2R4(µ-OH)2]2Ϫ
(M = Ni, Pd or Pt) with protic electrophiles (HL) has previ-
ously been used for the synthesis of complexes of the types
[M2R4(µ-L)2]2Ϫ.4,17,20,21 Of these protic electrophiles, azoles
have been most used because by deprotonation they produce
the very versatile azolate anions which usually act as exobiden-
tate ligands.22 When complexes 1 and 2 were treated with 3,5-
dimethylpyrazole (Hdmpz) in methanol, in a 1:2 molar ratio,
1
observed in both the H and the 13C NMR spectra for the Me
substituents of the dmpz ligand as well as the two different 13
C
signals for C3 and C4 of the dmpz ring cannot be used to differ-
1
entiate the anti and syn isomers. The H NMR spectrum of
compound 4 also shows that the CH2 protons of the benzyl
ligand are diastereotopic, a doublet and a doublet of doublets
4272
J. Chem. Soc., Dalton Trans., 1997, Pages 4271–4276

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[R(R′3P)Pd(µ-OH)2Pd(PR′3)R]
(i )
H
O
R
L
L
Pd
Pd
N
R
H
R′′
9 R = Me, L = PEt3, R′′ = C6H5
10
11
12
13
14
15
16
17
18
p-MeC6H4
p-MeOC6H4
p-ClC6H4
p-O2NC6H4
C6H5
Fig. 1 An ORTEP34 drawing of complex 16 showing the non-H atoms
as 20% thermal vibration ellipsoids. The phenyl groups are numbered
sequentially around the rings and only the first two atoms of each ring
are labelled
R = Ph, L = PPh3, R′′ =
p-MeC6H4
p-MeOC6H4
p-ClC6H4
p-O2NC6H4
palladium complexes [Pd2(PPh3)2(C6F5)2(µ-OH)(µ-NHRЉ)]15
are characterized by an anti structure, whereas the mixed
acetate–amide cyclopalladated complexes [{Pd2(L᎐L)2(µ-O2-
CMe)(µ-NHRЉ)] (L᎐L = 8-quinolylmethyl)10 are characterized
by a syn structure for the C,N chelate. The two resonances
observed in the 31P NMR spectra of the new palladium com-
plexes 10–18 (Table 2), together with the observation of only
Scheme 2 (i) NH2RЉ
being observed; the last signal is seen as a pseudo-triplet due to
the accidental coincidence of the coupling constants involved
(JHH = JPH = 8.9 Hz). On irradiation of the doublet at δ 3.00 the
original pseudo-triplet was transformed into
a doublet
1
(JPH = 8.9 Hz) and on irradiation of the pseudo-triplet at δ 2.44
the original doublet was seen as a singlet. The absence of a
symmetry plane in complex 4 may be a consequence of the
folded basket structure which is characteristic of this type of
complex.23
The reactions of the di-µ-hydroxo complexes 1 and 2 with
oxalic acid (H2ox) in 1:1 molar ratio lead to the formation of
the corresponding oxalate complexes [Pd2(PEt3)2R2(µ-ox)]
(R = Me 5 or PhCH2 6). Their IR spectra exhibit a strong
absorption at 1600 cmϪ1 arising from the asymmetric OCO
stretching mode of doubly bridging tetradentate oxalate.24 The
NMR data show the presence of only one isomer. Accordingly,
we suggest for them the structure shown in Scheme 1, which is
similar to that found in [Ni2(PPh3)2Me2(µ-ox)] or [Pd2(SBu2)2-
Ph2(µ-ox)].25,26
Complexes 1 and 2 readily undergo bridge-cleavage reactions
with PEt3 to give the mononuclear hydroxo complexes
[Pd(PEt3)2R(OH)] (R = Me 7 or PhCH2 8) shown in Scheme 1.
Their NMR spectra (Table 1) indicate that both compounds
exist in solution as 1:1 mixtures of cis and trans isomers. The
virtual coupling gives rise to a triplet for the phosphine methyl-
ene group in the 13C NMR spectrum of the trans isomers.
Methyl(aryloxo)palladium complexes of the type [Pd(PEt3)2-
R(ORЉ)] have been shown by 1H NMR spectroscopy to exist in
solution in the trans configuration with M᎐Me signals (δ 0.19)
as triplets due to coupling with two magnetically equivalent
phosphorus nuclei.27
The reactions of [Pd2L2R2(µ-OH)2] with aniline and some p-
substituted anilines (p-XC6H4NH2; X = H, Me, MeO, Cl or
NO2) have also been studied. The reactions take place in di-
chloromethane, in 1:1 molar ratio, and the corresponding
binuclear µ-hydroxo–µ-amido palladium complexes 10–18
(Scheme 2) are obtained in 67–80% yields. The analytical data
for these air-stable compounds are consistent with the proposed
formulae. Late transition-metal amides are still relatively
uncommon28–30 and the recent interest in their chemistry stems
from their potential use to facilitate the formation of carbon–
nitrogen bonds through the insertion of unsaturated organic
molecules into the metal–nitrogen bond.† Monomeric aryl-
amido and dimeric alkylamido complexes of palladium that
produce arylamines through carbon–nitrogen bond-forming
reductive elimination have been isolated.32,33
one set of H resonances for the arylamide ligand, are consist-
ent with the anti structure proposed for them in Scheme 2. Two
IR bands at 3610–3600 and 3320–3300 cmϪ1 are assigned to the
OH and NH stretching vibrations, respectively. The presence of
the hydroxo ligand is also established by the observation of a
high-field proton resonance at δ ca. Ϫ2.1 in the spectra of com-
plexes 15–18, which appears as a doublet due to coupling to the
31P nucleus trans to it; this OH resonance could not be detected
for 10–14. Similarly, a broad 1H resonance was observed for the
amide NH group only in the spectra of 15–18. On addition of
deuteriated water to a solution of complex 18 in CDCl3 the NH
and OH resonances disappeared. Two 1:1 doublets for the
methyl protons of 10–14 provide further evidence of their anti
structures.
Attempts to prepare bis(µ-amido) complexes by treating the
[Pd2L2R2(µ-OH)2] complexes (R = Me, L = PEt3; R = Ph, L =
PPh3) with 2 molar equivalents of the corresponding aromatic
amine were unsuccessful, possibly due to kinetic factors.
The structure of complex 16 was determined by X-ray dif-
fraction (Table 3, Fig. 1). The anti structure is further con-
firmed. Co-ordination at each of the palladium centres is
approximately square planar, with predictable narrowing of the
N᎐Pd᎐O angles (80.5, 80.9Њ) to accommodate the bridged
structure. The angle between the co-ordination planes is 52.5Њ,
indicating a substantially bent structure. Predictably the Pd᎐N
distance when the N is trans to the aryl ligand is longer (2.147
Å) than when it is trans to phosphorus (2.099 Å). Similar differ-
ences in the Pd᎐O distances are also noted.
A number of complexes of the type [Pd2L4(µ-X)(µ-Y)]
and platinum analogues have been structurally characterized,
and complexes with either a planar or a puckered M2XY ring
are known. Thus [Pd2(N3)6]2Ϫ,35 [Pt2(NH3)4(µ-OH)2]CO3ؒ
2H2O,36 [Pt2(dmso)4(µ-OH)2][ClO4]2 (dmso = dimethyl sulfox-
ide),37 [Pt2(C4H8SO)(µ-OH)2][NO3]2,38 [NBu4]2[Pd2(C6F5)4-
(µ-OH)2]4 and [NBu4]2[Pt2(dppf)(µ-OH)2][BF4]2 [dppf = 1,1Ј-
bis(diphenylphosphino)ferrocene]39 all have planar M2X2 cores.
However, [NBu4]2[Pd2(dppe)(µ-OH)2]X2 (dppe = Ph2PCH2-
† For example, the reported reaction of amines with hydroxo-bridged
palladium() and platinum() complexes in the presence of CS2 to give
dialkyldithiocarbamate complexes, >M(µ-OH)2M< ϩ 2 RNH2 ϩ 2
CS2 → 2>MS2CNHR2 ϩ 2 H2O, might be the insertion of CS2 into
the M᎐N bond of an intermediate amido complex.31
The previously reported mixed amide–pentafluorophenyl
J. Chem. Soc., Dalton Trans., 1997, Pages 4271–4276
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Table 2 The NMR data (J in Hz) for the amide complexes (in CDCl3)
Table 3 Selected bond lengths (Å) and angles (Њ) for complex 16
Complex 1H δ(SiMe4)
31P δ(H3PO4)
Pd(1)᎐O(1)
Pd(1)᎐C(8)
Pd(2)᎐O(1)
Pd(2)᎐C(32)
2.093(4)
1.994(7)
2.159(5)
1.979(8)
Pd(1)᎐P(1)
Pd(1)᎐N
Pd(2)᎐P(2)
Pd(2)᎐N
2.213(2)
2.147(6)
2.242(2)
2.099(5)
9
7.21 [d, 1 H, Ho, J(HoHm) 8.1]
7.17 [d, 1 H, Ho, J(HoHm) 8.1]
7.00 (m, 2 H, Hm)
25.3 (s)
24.5 (s)
6.63 (dd, 2 H, Hp, J 7.7)
1.54 (m, 12 H, CH2P)
O(1)᎐Pd(1)᎐N 80.9(2)
O(1)᎐Pd(2)᎐N 80.5(2)
Pd(1)᎐O(1)᎐Pd(2) 87.9(2)
Pd(1)᎐N᎐Pd(2) 87.9(2)
1.06 (m, 18 H, CH3CH2P)
0.18 (d, 3 H, CH3Pd, JPH 3.4)
0.11 (d, 3 H, CH3Pd, JPH 3.4)
7.13 [d, 1 H, Ho, J(HoHm) 8.0]
7.09 [d, 1 H, Ho, J(HoHm) 8.0]
6.81 [d, 2 H, Hm, J(HoHm) 8.0]
2.15 (s, 3 H, CH3 of p-MeC6H4)
1.55 (m, 12 H, CH2P)
structure shows one of the most puckered rings observed to
date; looking at the data available for comparison it is tempting
to attribute this to steric interference between the bulky phos-
phine and the bridging group, but this cannot be conclusive.
10
24.9 (s)
24.1 (s)
1.08 (m, 18 H, CH3CH2P)
0.18 (d, 3 H, CH3Pd, JPH 3.3)
0.11 (d, 3 H, CH3Pd, JPH 3.3)
7.20 [d, 2 H, Ho, J(HoHm) 8.3]
6.63 [d, 2 H, Hm, J(HoHm) 8.3]
3.67 (s, 3 H, CH3 of p-MeOC6H4)
1.55 (m, 12 H, CH2P)
1.05 (m, 18 H, CH3CH2P)
0.18 (d, 3 H, CH3Pd, JPH 3.0)
0.11 (d, 3 H, CH3Pd, JPH 3.0)
7.12 [d, 1 H, Ho, J(HoHm) 7.9]
7.10 [d, 1 H, Ho, J(HoHm) 7.9]
6.92 [d, 2 H, Hm, J(HoHm) 7.9]
1.52 (m, 12 H, CH2P)
1.07 (m, 18 H, CH3CH2P)
0.15 (d, 3 H, CH3Pd, JPH 3.0)
0.08 (d, 3 H, CH3Pd, JPH 3.0)
7.94 [d, 2 H, Ho, J(HoHm) 9.0]
7.17 [d, 2 H, Hm, J(HoHm) 9.0]
1.60 (m, 12 H, CH2P)
1.11 (m, 18 H, CH3CH2P)
0.39 (d, 3 H, CH3Pd, JPH 3.0)
7.4–6.4 (aromatics)
Experimental
The analyses (C, H, N) were performed with a Carlo Erba
model EA 1108 microanalyzer. Decomposition temperatures
were determined with a Mettler TG-50 thermobalance at a
heating rate of 5 ЊC minϪ1 and the solid samples under a nitro-
gen flow (100 cm3 minϪ1). The NMR spectra were recorded on a
Bruker AC 200E or a Varian Unity 300 spectrometer, infrared
spectra on a Perkin-Elmer 1430 spectrophotometer using Nujol
mulls between polyethylene sheets. Solvents were dried by the
usual methods. The precursor [Pd2(PEt3)2Me2(µ-Cl)2] was pre-
pared by the procedure described elsewhere19 and [Pd2(PEt3)2-
(CH2Ph)2(µ-Cl)2] by the following method. A commercially
available diethyl ether solution (1 ) of Mg(CH2Ph)Cl (1 cm3, 1
mmol) was added to an orange suspension of [Pd2(PEt3)2Cl2-
(µ-Cl)2] (0.2 g, 0.338 mmol) in diethyl ether–tetrahydrofuran
(1:1 v/v, 14 cm3). The mixture was stirred for 1.5 h to give
a yellow solution. Methanol was then added to solvolyse
the magnesium by-product and the solvent was completely
evaporated. The residue was extracted with diethyl ether–
dichloromethane (1:1 v/v, 14 cm3), and then the extract was
concentrated to dryness. Addition of hexane followed by vigor-
ous stirring rendered a yellow suspension, from which a yellow
solid was filtered off and air-dried. Yield 0.146 g, 62%.
11
12
13
24.7 (s)
23.9 (s)
25.8 (s)
25.0 (s)
26.0 (s)
25.4 (s)
14
15
33.2 (s)
30.2 (s)
1.61 (br, NH)
Ϫ2.10 (d, 1 H, OH)
7.4–7.1 (m, 30 H, C6H5Pd)
6.96 (m, 4 H, Ho of C6H5Pd)
6.81 (d, 2 H, Ho of p-MeC6H4N, J 7.5)
6.7–6.5 (m, 8 H, Hm ϩ Hp of C6H5Pd and
Hm of p-MeC6H4N)
33.1 (s)
30.0 (s)
Preparations
2.19 (s, 3 H, CH3)
1.60 (br, NH)
Complex 1. To a solution of [{Pd(PEt3)Me(µ-Cl)}2] (0.2 g,
0.364 mmol) in acetone (10 cm3) was added 20% [NBu4]OH
(aq) (0.95 cm3, 0.728 mmol), with constant stirring for 15 min.
After partial evaporation of the solvent under reduced pressure,
addition of water followed by vigorous stirring and filtration
afforded a white solid which was air-dried. Yield 90% (Found:
C, 32.2; H, 7.2. Calc. for C14H38O2P2Pd2: C, 32.8; H, 7.5%).
M.p. 112 ЊC (decomp.). IR (Nujol, cmϪ1): 3520 (OH str) and
525 (PdC str).
Ϫ2.12 (d, 1 H, OH, JPH 3.3)
7.5–7.1 (m, 30 H, C6H5P)
7.02 (m, 4 H, Ho of C6H5Pd)
6.86 (d, 2 H, Ho of p-MeOC6H4N, J 7.8)
6.7–6.5 (m, 8 H, Hm ϩ Hp of C6H5Pd and
Hm of p-MeOC6H4N)
3.78 (s, 3 H, MeO)
1.62 (br, NH)
Ϫ2.09 (d, 1 H, OH, JPH 3.6)
7.4–7.1 (m, 30 H, C6H5P)
6.94 (m, 4 Ho, C6H5Pd)
16
34.1 (s)
30.7 (s)
17
18
33.2 (s)
30.4 (s)
6.8–6.5 (m, 8 H, Hm ϩ Hp of C6H5Pd and
Hm of p-ClC6H4N)
1.55 (br, NH)
Ϫ2.11 (d, 1 H, OH, JPH 3.3)
7.75 (d, 2 H, J 9.3)
7.4–7.0 (m, 34 H, C6H5P ϩ Ho of C6H5Pd)
6.8–6.4 (m, 8 H, Hm ϩ Hp of C6H5Pd and
Hm of p-O2NC6H4N)
Complex 2. To a solution of [{Pd(PEt3)(PhCH2)(µ-Cl)}2] (0.2
g, 0.285 mmol) in acetone–methanol (1:1, 10 cm3) was added
20% [NBu4]OH (aq) (0.74 cm3, 0.57 mmol). After 5 min of
stirring solvent was partially evaporated under reduced pres-
sure. Addition of water gave a yellow precipitate which was
filtered off and air-dried. Yield 89% (Found: C, 46.6; H, 6.8.
Calc. for C26H46O2P2Pd2: C, 46.9; H, 7.0%). M.p. 112 ЊC
(decomp.). IR (Nujol, cmϪ1): 3500 (OH str) and 525 (PdC str).
32.8 (s)
31.3 (s)
1.70 (br, 1 H, NH)
Ϫ1.90 (d, 1 H, OH, JPH 3.4)
Complexes 3–6. To a solution of the corresponding hydroxo
complex (1 or 2) (0.156 mmol) in methanol was added 3,5-
dimethylpyrazole (0.312 mmol) or oxalic acid (0.156 mmol)
with constant stirring for 1 h to afford a suspension from which
solvent was partially evaporated under reduced pressure. The
precipitate was filtered off and air-dried. Complex 3: yield 69%
(Found: C, 42.8; H, 7.5; N, 8.1. Calc. for C24H50N4P2Pd2: C,
43.1; H, 7.5; N, 8.4%); m.p. 266 ЊC (decomp.); IR (Nujol, cmϪ1)
525 (PdC str). Complex 4: yield 68% (Found: C, 52.2; H, 6.8; N,
CH2PPh2) has an angle between the PdO2 planes of 33.8(8)Њ40
and the angle between the PtN2 planes in [Pt2(PMe2Ph)4(µ-
NH2)2][BF4]2 is 32Њ.41 With few exceptions, phosphine ligands
seem to predispose complexes to adopt a puckered form.
Examples include [Pt2(PEt3)4(µ-OH)2][BF4]2 (36.4Њ),42 [Pt2-
(PPh3)2Cl2(µ-NH2)2] (45Њ),43 [Pt2(PPh3)2Me2(µ-NH2)2] (45Њ)30
and anti-[{Pd(ButNC)(C6F5)(µ-NHPh)}2] (32.7Њ).15 The present
4274
J. Chem. Soc., Dalton Trans., 1997, Pages 4271–4276

View Article Online
7.0. Calc. for C36H58N4P2Pd2: C, 52.6; H, 7.1; N, 6.8%); m.p.
210 ЊC (decomp.). Complex 5: yield 65% (Found: C, 33.6; H,
6.2. Calc. for C16H36NO4P2Pd2: C, 33.9; H, 6.4%); m.p.: 186 ЊC
(decomp.); IR (Nujol, cmϪ1) 1600 (CO2 asym str) and 545 (PdC
str). Complex 6: yield 70% (Found: C, 46.6; H, 5.2. Calc. for
C28H44O4P2Pd2: C, 46.8; H, 6.2%); m.p. 206 ЊC (decomp.); IR
(Nujol, cmϪ1) 1600 (CO2 asym str).
Crystal data. C56H51Cl2NO2P2Pd2, M = 1115.7, crystal size
0.2 × 0.2 × 0.1 mm, triclinic, space group P1 (no. 2), a =
9.834(4), b = 12.388(3), c = 21.345(10) Å, α = 94.18(3), β =
93.40(4), γ = 94.04(3)Њ, U = 2581.5(2) Å3 (by least-squares
refinement on 25 reflections 7 < θ < 9Њ, λ = 0.710 73 Å), Z = 2,
Dc = 1.44 g cmϪ3, µ(Mo-Kα) = 8.9 cmϪ1, F(000) = 1132.
¯
Data collection and processing. Enraf-Nonius CAD 4 dif-
fractometer, θ–2θ mode, graphite-monochromated Mo-Kα
radiation, h 0–11, k Ϫ14 to 14, l Ϫ25 to 25, 2 < θ < 25Њ. 9075
Total unique reflections measured, 6519 significant reflections
[|F2| > 2σ(F2)]. Maximum change in standard reflections
Ϫ0.4%, no decay correction. Empirical absorption, Tmax = 1.00,
Tmin = 0.80 from ψ scans, T = 293 K.
Complexes 7 and 8. Triethylphosphine (0.312 mmol) was
added to a solution of complex 1 or 2 (0.156 mmol) in acetone
(6 cm3). The solution was stirred for 15 min and concentrated
under reduced pressure. On addition of water 7 or 8 precip-
itated as a solid which was filtered off and air-dried. Complex
7: yield 63% (Found: C, 41.0; H, 8.8. Calc. for C13H34OP2Pd:
C, 41.7; H, 9.1%); m.p. 216 ЊC (decomp.); IR (Nujol, cmϪ1) 515
(PdC str). Complex 8: yield 65% (Found: C, 49.9; H, 8.1. Calc.
for C19H38OP2Pd: C, 50.6; H, 8.5%); m.p. 191 ЊC (decomp.).
Structure analysis and refinement. Non-H atoms located by
heavy-atom methods (SHELXS 86).44 Full-matrix least squares
refinement with non-H atoms anisotropic (MOLEN).45 Hydro-
gen atoms on O(1) and C(7) were omitted; the rest were calcu-
lated positions, Uiso = 1.3 Ueq for parent atom. R = 0.058,
RЈ = 0.065, S = 1.7. Number of variables 586, number of
observed reflections 6519. (∆/σ)max = 0.5, (∆/ρ)max,min ϩ 1.37,
Complexes 9–13. The appropriate amine RЉNH2 (0.1169
mmol) was added to a solution of [Pd2(PEt3)2Me2(µ-OH)2] (60
mg, 0.1169 mmol) in dichloromethane (4 cm3) and the solution
stirred at room temperature for 30 min and concentrated to
dryness under vacuum. The residue was treated with PriOH and
the pale yellow (orange for 5) solid was filtered off and air-
dried. Complexes 9–13 were recrystallized from dichloro-
methane–hexane. Complex 9: yield 76% (Found: C, 40.5; H,
7.2; Calc. for C20H34NOP2Pd2: C, 40.8; H, 7.4; N, 2.4%); m.p.
167 ЊC (decomp.); IR (Nujol, cmϪ1) 3605 (OH str) and 3305
(NH str). Complex 10: yield 71% (Found: C, 41.5; H, 7.3; N,
2.1. Calc. for C21H45NOP2Pd2: C, 41.9; H, 7.5; N, 2.3%); m.p.
169 ЊC (decomp.); IR (Nujol, cmϪ1) 3600 (OH str) and 3300
(NH str). Complex 11: yield 75% (Found: C, 40.4; H, 7.1; N,
2.4. Calc. for C21H45NO2P2Pd2: C, 40.8; H, 7.3; N, 2.3%); m.p.
169 ЊC (decomp.); IR (Nujol, cmϪ1) 3600 (OH str) and 3300
(NH str). Complex 12: yield 67% (Found: C, 38.2; H, 6.5; N, 2.2.
Calc. for C20H42ClNOP2Pd2: C, 38.6; H, 6.8; N, 2.3%); m.p.
165 ЊC (decomp.); IR (Nujol, cmϪ1) 3605 (OH str) and 3305
(NH str). Complex 13: yield 71% (Found: C, 37.6; H, 6.5; N,
4.5. Calc. for C20H42N2O3P2Pd2: C, 37.9; H, 6.7; N, 4.4%); m.p.
187 ЊC (decomp.); IR (Nujol, cmϪ1) 3600 (OH str) and 3300
(NH str).
¹
Ϫ3
2
2
2
Ϫ2
²
Ϫ0.15 e Å . σ(F ) = [σ (I) ϩ (0.04I) ] Lρ, w = σ (F), Σw(|Fo| Ϫ
|Fc|)2 minimised.
CCDC reference number 186/685.
Acknowledgements
Financial support from the Dirección General de Investigación
Científica y Técnica (project PB94-1157), Spain is gratefully
acknowledged. V. R. thanks the Dirección General Universidad
de la Comunidad Autónoma de Murcia, Spain, for a research
grant.
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mmol) was added to a solution of [Pd2(PPh3)2(µ-OH)2] (80 mg,
0.0866 mmol) in dichloromethane (6 cm3) and the solution was
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air-dried. Complexes 14–18 were recrystallized from dichloro-
methane–hexane. Complex 14: yield 79% (Found: C, 64.5; H,
4.6; N, 1.5. Calc. for C54H47NOP2Pd2: C, 64.8; H, 4.7; N,
1.4%); m.p. 178 ЊC (decomp.); IR (Nujol, cmϪ1) 3600 (OH str)
and 3320 (NH str). Complex 15: yield 78% (Found: C, 65.1; H,
4.9; N, 1.5. Calc. for C55H49NOP2Pd2: C, 65.1; H, 4.9; N, 1.4%);
m.p. 176 ЊC (decomp.); IR (Nujol, cmϪ1) 3610 (OH str) and 3320
(NH str). Complex 16: yield 77% (Found: C, 63.9; H, 4.9; N,
1.4. Calc. for C55H49NO2P2Pd2: C, 64.1; H, 4.8; N, 1.4%); m.p.
178 ЊC (decomp.); IR (Nujol, cmϪ1) 3605 (OH str) and 3305
(NH str). Complex 17: yield 76% (Found: C, 62.6; H, 4.5; N,
1.4. Calc. for C54H46ClNOP2Pd2: C, 62.7; H, 4.5; N, 1.4%); m.p.
184 ЊC (decomp.); IR (Nujol, cmϪ1) 3605 (OH str) and 3315
(NH str). Complex 18: yield 80% (Found: C, 62.2; H, 4.6; N,
2.6. Calc. for C54H46N2O3P2Pd2: C, 62.0; H, 4.4; N, 2.7%); m.p.
182 ЊC (decomp.); IR (Nujol, cmϪ1) 3605 (OH str) and 3315
(NH str).
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Suitable crystals (dichloromethane solvated) of complex 16
were obtained from dichloromethane–hexane.
J. Chem. Soc., Dalton Trans., 1997, Pages 4271–4276
4275

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Received 16th June 1997; Paper 7/04203E
4276
J. Chem. Soc., Dalton Trans., 1997, Pages 4271–4276