Ortho-Metallated triphenylphosphine chalcogenide complexes of platinum and palladium: Synthesis and catalytic activity

Article abstract of DOI:10.1039/c4dt01236d

Treatment of [PtI₂(COD)] (COD = 1,5-cyclooctadiene) with 2-LiC₆H₄P(S)Ph₂ gives the complex cis-[Pt{κ²-2-C₆H₄P(S)Ph₂} ₂] (1) containing a pair of ortho-metallated triphenylphosphine sulfide rings. The selenium counterpart, [Pt{κ²-2-C ₆H₄P(Se)Ph₂}₂] (2), which exists as cis- and trans-isomers in solution, and the palladium analogues, cis-[Pd{κ²-2-C₆H₄P(X)Ph₂} ₂] [X = S (3), Se (4)], are obtained by transmetallation of [MCl ₂(COD)] with the organotin reagent 2-Me₃SnC ₆H₄P(X)Ph₂ in a 1:2 mol ratio. The reaction of [PdCl₂(COD)] with 2-Me₃SnC₆H ₄P(X)Ph₂ in a 1:1 mol ratio, and the reaction of 3 with palladium(ii) acetate, give dinuclear, anion-bridged complexes [Pd ₂(μ-Cl)₂{κ²-2-C₆H ₄P(X)Ph₂}₂] [X = S (5), Se (6)] and [Pd ₂(μ-OAc)₂{κ²-2-C₆H ₄P(S)Ph₂}₂] (8), respectively. Complexes 5 and 8 could not be made directly from triphenylphosphine sulfide by standard ortho-palladation procedures. The bridging framework in complexes 5 and 6 is cleaved by tertiary phosphines to give mononuclear derivatives [PdCl{κ²-2-C₆H₄P(X)Ph₂} (PR₃)] [X = S, R = Ph (11); X = Se, R = Ph (13); X = Se, R = 4-tolyl (15)]. The selenium-containing compounds 13 and 15 decompose slowly in solution giving dinuclear complexes [PdCl(μ₂-Se-κ²-P,Se-2- SeC₆H₄PPh₂)PdCl(μ-2-C₆H ₄PPh₂)(PR₃)] [R = Ph (14), 4-tolyl (16)]. The structure of complex 16 establishes that the bridging 2-C₆H ₄PPh₂ group is generated by reduction of the phosphine selenide unit, not by ortho-metallation of the coordinated triphenylphosphine. The chloro-bridges of 5 and 6 are also cleaved by acetylacetonate (acac) and deprotonated Schiff bases forming mononuclear species [Pd{κ²-2- C₆H₄P(X)Ph₂}L₂] [L₂ = acac, X = S (9), Se (10); L₂ = 2-OC₆H₄CHNC ₆H₄-4-R, X = S, R = OMe (17), NO₂ (18); X = Se, R = OMe (19), NO₂ (20)]. The ability of complexes 5, 6 and the Schiff base-derivatives 17-20 to catalyse Heck-Mizoroki and Suzuki-Miyaura C-C bond-forming reactions has also been investigated. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4dt01236d

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ortho-Metallated triphenylphosphine
chalcogenide complexes of platinum and
palladium: synthesis and catalytic activity†
Cite this: Dalton Trans., 2014, 43,
12000
Steven H. Privér,a Martin A. Bennett,b Anthony C. Willis,b Srinivas Pottabathula,a,c
M. Lakshmi Kantamc and Suresh K. Bhargava*a
Treatment of [PtI2(COD)] (COD = 1,5-cyclooctadiene) with 2-LiC6H4P(S)Ph2 gives the complex cis-[Pt{κ2-
2-C6H4P(S)Ph2}2] (1) containing a pair of ortho-metallated triphenylphosphine sulfide rings. The selenium
counterpart, [Pt{κ2-2-C6H4P(Se)Ph2}2] (2), which exists as cis- and trans-isomers in solution, and the pal-
ladium analogues, cis-[Pd{κ2-2-C6H4P(X)Ph2}2] [X = S (3), Se (4)], are obtained by transmetallation of
[MCl2(COD)] with the organotin reagent 2-Me3SnC6H4P(X)Ph2 in a 1 : 2 mol ratio. The reaction of
[PdCl2(COD)] with 2-Me3SnC6H4P(X)Ph2 in a 1 : 1 mol ratio, and the reaction of 3 with palladium(II)
acetate, give dinuclear, anion-bridged complexes [Pd2(μ-Cl)2{κ2-2-C6H4P(X)Ph2}2] [X = S (5), Se (6)] and
[Pd2(μ-OAc)2{κ2-2-C6H4P(S)Ph2}2] (8), respectively. Complexes 5 and 8 could not be made directly from
triphenylphosphine sulfide by standard ortho-palladation procedures. The bridging framework in com-
plexes 5 and 6 is cleaved by tertiary phosphines to give mononuclear derivatives [PdCl{κ2-2-C6H4P(X)Ph2}-
(PR3)] [X = S, R = Ph (11); X = Se, R = Ph (13); X = Se, R = 4-tolyl (15)]. The selenium-containing com-
pounds 13 and 15 decompose slowly in solution giving dinuclear complexes [PdCl(μ2-Se-κ2-P,Se-
2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2)(PR3)] [R = Ph (14), 4-tolyl (16)]. The structure of complex 16 estab-
lishes that the bridging 2-C6H4PPh2 group is generated by reduction of the phosphine selenide unit, not
by ortho-metallation of the coordinated triphenylphosphine. The chloro-bridges of 5 and 6 are also
cleaved by acetylacetonate (acac) and deprotonated Schiff bases forming mononuclear species [Pd{κ2-
2-C6H4P(X)Ph2}L2] [L2 = acac, X = S (9), Se (10); L2 = 2-OC6H4CHvNC6H4-4-R, X = S, R = OMe (17), NO2
(18); X = Se, R = OMe (19), NO2 (20)]. The ability of complexes 5, 6 and the Schiff base-derivatives 17–20
to catalyse Heck–Mizoroki and Suzuki–Miyaura C–C bond-forming reactions has also been investigated.
Received 28th April 2014,
Accepted 19th June 2014
DOI: 10.1039/c4dt01236d
www.rsc.org/dalton
Alper,1 Pfeffer et al.2,3 showed that thioethers, such as benzyl
methyl sulfide, could be metallated in moderate to good yields
Introduction
There are still relatively few examples of ortho-metallated by palladium(II) acetate in acetic acid (Scheme 1). Previous
S-donor complexes, especially of Pd(II), compared with the attempts based on [PdCl4]2− had been unsuccessful, although
plethora of ortho-metallated complexes derived from N-donors. this reagent, in the presence of sodium acetate, is able to ortho-
Following the first synthesis of ortho-palladated and ortho- metallate the doubly activated compound 1,3-bis(t-butylthio-
platinated compounds derived from thiobenzophenone by methyl)benzene, 1,3-C6H4(CH2StBu)2, to form
a
pincer
complex (Scheme 2);4 the bis(methylthiomethyl) analogue can
aSchool of Applied Sciences (Applied Chemistry), RMIT University, GPO Box 2476,
Melbourne, Victoria 3001, Australia. E-mail: suresh.bhargava@rmit.edu.au
bResearch School of Chemistry, Australian National University, Canberra, ACT 0200,
Australia
cInorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical
Technology, Hyderabad, 500 607, India
†Electronic supplementary information (ESI) available: Crystal data and details
of data collection (Table S1) and X-ray crystallographic data in CIF format for
complexes 1, 2, 4, 8, 9, 11–14, 16, 17 and 20. CCDC 999160–999172. For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4dt01236d
Scheme 1
12000 | Dalton Trans., 2014, 43, 12000–12012
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showed at least four 31P NMR resonances in the region of
δ 43–45. The chemical shifts did not correspond with those
of the chloro- or acetato-bridged ortho-palladated complexes of
Ph3PvS obtained by transmetallation (see below) and the
species present were not investigated further. The failure to
achieve direct ortho-palladation of Ph3PvS is surprising
because similar procedures have been used successfully in the
case of triphenylphosphine imine derivatives.16–18
Scheme 2
Bis(chelate) complexes
only be obtained by an exchange reaction between 1,3-
C6H4(CH2SMe)2 and [Pd2(μ-Cl)2(κ2-2-C6H4CH2NMe2)2].2,3 Sel-
enium analogues of the singly- and doubly-cyclopalladated
sulfur compounds have been synthesized and shown to be
more powerful catalysts for the Heck–Mizoroki reaction than
their sulfur analogues.5 The ortho-palladated compounds
formed from [Pd(OAc)2]3 and benzylic tert-butyl thioethers are
excellent catalysts for Heck–Mizoroki and Suzuki–Miyaura C–C
bond forming reactions.6,7
Cyclopalladated or cycloplatinated thiophosphoryl pincer
complexes can be derived by direct metallation of 1,3-disubsti-
tuted aromatic compounds containing, for example, two P(S)-
Ph2 groups, one P(S)Ph2 group and one thioamido group, or
one P(S)Ph2 and one P(S)R1R2 group (R1 = R2 = NMe2, NEt2,
Ph; R1 = Me, R2 = OBu).8–10 However, there appear to be no
reported examples of ortho-palladation or ortho-platination of
triphenylphosphine sulfide or its selenium analogue, Ph3PvX
(X = S, Se), even though these compounds are readily ortho-
metallated on heating with [PhCH2Mn(CO)5].11 The products
are [(OC)4Mn{κ2-2-C6H4P(X)Ph2}] which, in the case of X = S,
undergo insertion reactions of the alkynes C2(CO2Me)2 and
HCO2Me into the Mn–C σ-bond to form seven-membered
manganacycles.12
In a reaction similar to that used for the preparation of cis-[Pt-
(κ2-2-C6H4PPh2)2],19,20 treatment of the organolithium reagent
2-LiC6H4P(S)Ph2 with [PtI2(COD)] (COD = 1,5-cyclooctadiene)
gave the cyclometallated bis(chelate) complex cis-[Pt{κ2-2-
C6H4P(S)Ph2}2] (1) as a pale yellow solid in good yields
1
(Scheme 3). The H NMR spectrum showed the expected aro-
matic multiplets and the 31P NMR spectrum showed a single
resonance at δ 51.6, flanked by 195Pt satellites (2JPtP 79.0 Hz).
The chemical shift is consistent with a tertiary phosphine
2
sulfide coordinated to Pt(II) and the magnitude of JPtP is con-
sistent with the location of the phosphine sulfide group trans
to a ligand of high trans influence. For comparison, we cite cis-
[Pt(SvPPh3)(κ2-C6H3-5-Me-2-PPh2)(PPh2-4-tolyl)] (68.7 Hz)21
and [Pt(dppmS2)(dppe)](ClO4)2 (81.9 Hz)22 in which the phos-
phine sulfide group is trans to σ-aryl and tertiary phosphine,
respectively. In contrast, in cis-[PtCl2(SvPPh3)(DMSO)], where
the phosphine sulfide group is trans to chloride, a ligand of
relatively low trans-influence, JPtP is 116 Hz.23 The spectro-
2
scopic data suggest that the phosphine sulfide groups in
complex 1 are mutually cis, and this was confirmed by single
crystal X-ray diffraction (this and the other structurally charac-
terised complexes will be discussed later).
The selenium analogue of 1, [Pt{κ2-2-C6H4P(Se)Ph2}2] (2)
could not be prepared by an analogous method; under the
reaction conditions, attempted lithiation of 2-BrC6H4P(Se)Ph2
resulted in reduction of the PvSe group. However, 2 could be
prepared in good yields by transmetallation of the organotin
reagent 2-Me3SnC6H4P(Se)Ph2 with [PtCl2(COD)] in refluxing
dichloromethane (Scheme 4). The 31P NMR spectrum of the
isolated solid showed two singlet resonances at δ 37.2 and
36.5, suggesting the presence of two species; the ratio of
the two peaks varied between preparations but was ca. 3 : 1.
The downfield resonance is flanked by broad 195Pt satellites
A possible entry into complexes containing ortho-metallated
triphenylphenylphosphine sulfide and triphenylphosphine
selenide is transmetallation, as demonstrated, for example, by
the preparation of the cycloaurated complexes [AuCl2{κ2-2-
C6H4P(X)Ph2}] (X = S, Se).13 Transmetallation may provide a
general method for the preparation of a new family of com-
plexes containing ortho-metallated triphenylphosphine chalco-
genide ligands, thus opening up the burgeoning field of
catalysis based on them to further study. In light of this, we
report here on transmetallation routes to cycloplatinated
and cyclopalladated complexes of triphenylphosphine sul-
fide and triphenylphosphine selenide, and on the catalytic
ability of selected palladium complexes in C–C bond-forming
reactions.
Results and discussion
Attempted ortho-palladation of triphenylphosphine sulfide
Under standard conditions,3,14,15 e.g., Li2[PdCl4] (in the pres-
ence or absence of NaOAc), [Pd(OAc)2]3, or [Pd2(μ-Cl)2(κ2-2-
C6H4CH2NMe2)2] (in the presence or absence of CF3COOH)
reacted with Ph3PvS to give poorly soluble brown solids that
Scheme 3
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complexes similar to 5 and 6, while treatment of the organo-
lithium reagent 2-LiC6H4P(vNPh)Ph2 with [PdCl2(COD)] gives
a mixture of the chloro-bridged species [Pd2(μ-Cl)2{2-C6H4P-
(vNPh)Ph2}2] and the bis(chelate) complex cis-[Pd{κ2-C,N-
2-C6H4P(vNPh)Ph2}2].18 Attempts to prepare the chloro-
bridged platinum complexes [Pt2(μ-Cl)2{κ2-2-C6H4P(X)Ph2}2]
(X = S, Se) analogous to 5 and 6 using the appropriate organo-
tin reagent and [PtCl2(COD)] were unsuccessful and only
unreacted starting materials were recovered.
The mixed-ligand bis(chelate) complex [Pd{κ2-2-C6H4P(S)-
Ph2}{κ2-2-C6H4P(Se)Ph2}] (7) could be prepared in an impure
state by treating a dichloromethane suspension of 5 or 6 with
two equivalents of 2-Me3SnC6H4P(X)Ph2 (X = Se, S, respecti-
vely); also formed are the bis(phosphine sulfide) and bis-
(phosphine selenide) complexes 3 and 4. The ratio of 3 : 4 : 7
was 1 : 1 : 2 and attempts to separate the three species by
chromatography were unsuccessful. Complex 7 shows a pair of
resonances in the 31P NMR spectrum at δ 31.1 and 48.1 assign-
able to the phosphine selenide and phosphine sulfide,
respectively, split into doublets of 1.0 Hz due to coupling of
the inequivalent phosphorus nuclei. The two resonances also
show 77Se satellites of 555 and 27.4 Hz, respectively, consistent
with one- and three-bond coupling (cf. 557 and 29.8 Hz in 4).
Attempts to make 7 by refluxing equimolar amounts of 3 and 4
in toluene for 24 h were unsuccessful and only unreacted
started materials were detected by 31P NMR spectroscopy.
The acetato-bridged dimer [Pd2(μ-OAc)2{κ2-2-C6H4P(S)Ph2}2]
(8) was prepared in good yields from the reaction of 3 with [Pd-
(OAc)2]3. The 1H NMR spectrum showed the expected aromatic
multiplets together with a methyl singlet at δ 2.09 due to the
acetate group and the 31P NMR spectrum showed a singlet res-
onance at δ 47.0, comparable to that observed for 3 (δ 46.9).
The IR spectrum of 8 (nujol mull) showed bands at 1588, 1578
and 1415 cm−1, corresponding to the CvO and C–O stretching
vibrations, respectively; the separation of ca. 170 cm−1 is con-
sistent with the presence of bridging acetate groups24 which
was confirmed by X-ray diffraction.
Scheme 4
(2JPtP 70.6 Hz) and two sets of 77Se satellites (1JSeP 534 Hz,
3JSeP 26.9 Hz). The 77Se satellites are further split into doublets
of 2.2 Hz due to four-bond P–P coupling, arising from inequi-
valence of the phosphorus atoms in the isotopomer containing
only one 77Se nucleus. The upfield resonance at δ 36.5 shows
broad 195Pt satellites of 73.0 Hz and one set of 77Se satellites
(1JSeP 506 Hz) which are further split into doublets of
ca. 0.7 Hz due to P–P coupling. By comparison to the spectro-
scopic data for its palladium analogue (see later), the upfield
resonance is tentatively assigned to cis-[Pt{κ2-2-C6H4P(Se)-
Ph2}2], and the less shielded resonance at δ 37.2 to the trans
isomer. The Se–P couplings are also reproduced in the 77Se
NMR spectrum, which shows a pair of resonances at δ −130.2
and +42.5. The former resonance is flanked by 195Pt satellites
of 230 Hz; due to the low intensity of the downfield peak,
coupling to platinum was not observed. The structure of cis-
[Pt{κ2-2-C6H4P(Se)Ph2}2] was confirmed by X-ray diffraction.
Complexes 1 and 2 could also be prepared in lower yields by
heating toluene solutions of [Pt(κ2-2-C6H4PPh2)2] with elemen-
tal sulfur or selenium, respectively.
The palladium analogues of complexes 1 and 2 were pre-
pared by transmetallation of 2-Me3SnC6H4P(X)Ph2 with
[PdCl2(COD)] to give cis-[Pd{κ2-2-C6H4P(X)Ph2}2] [X = S (3),
Se (4)] as pale yellow solids in high yields (Scheme 4). The
31P NMR spectrum of 3 showed a singlet resonance at δ 46.9,
comparable to that of complex 1. In contrast to its platinum
analogue 2, the 31P NMR spectrum of 4 showed only a singlet
resonance at δ 32.6 with 77Se satellites of 29.8 and 557 Hz
which were further split by 4.0 Hz due to 4JPP coupling and the
77Se NMR spectrum showed the expected doublet of doublets
centred at δ −119.5. The structures of 2 and 4 have been con-
firmed by X-ray crystallography.
Reaction of [Pd2(μ-Cl)2{κ2-2-C6H4P(X)Ph2}2] [X = S (5), Se (6)]
with Na(acac) gave the mononuclear complexes [Pd(κ2-O,O′-
acac){κ2-2-C6H4P(X)Ph2}] [X = S (9), Se (10)]. The 1H NMR
spectra for 9 and 10 each showed three singlet resonances at
ca. δ 1.9, 2.0 and 5.3 due to the acac ligand, assignable to the
two inequivalent methyl and methine groups, respectively,
together with aromatic multiplets. The 31P NMR spectra each
showed a single resonance, the chemical shifts of which are
comparable to those of the appropriate bis(chelate) complexes
(3 or 4) and chloro-bridged dimers (5 or 6).
Anion-bridged dipalladium complexes and their derivatives
When stirred in dichloromethane at room temperature, equi-
The chloro-bridges in 5 are also cleaved by PPh3, giving the
molar amounts of 2-Me3SnC6H4P(X)Ph2 (X = S, Se) and mononuclear complex [PdCl{κ2-2-C6H4P(S)Ph2}(PPh3)] (11) as a
[PdCl2(COD)] gave the poorly soluble chloro-bridged dimers mixture of cis and trans isomers (Scheme 5), these terms refer-
[Pd2(μ-Cl)2{κ2-2-C6H4P(X)Ph2}2] [X = S (5), Se (6)]. Both com- ring to PPh3 cis and trans, respectively, to the sulfur atom of
plexes showed a pair of singlet resonances in their 31P NMR PvS. The 31P NMR spectrum of 11 showed a pair of singlet res-
spectra (δ 46.7 and 47.8 for 5; δ 25.8 and 26.8 for 6), consistent onances at δ 34.4 and 43.8 assignable to the cis isomer and a
with the presence of syn- and anti-isomers. The direct ortho- pair of doublets at δ 17.5 and 50.2 due to the trans isomer, split
palladation of triphenylphosphine imines by Li2[PdCl4]16 or by ca. 60 Hz due to P–P coupling. In both cases, the high field
17
[Pd(OAc)2]3 has also been reported to give chloro- or acetato- resonance was due to the phosphorus atom of the coordinated
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Scheme 5
PPh3 ligand and the low field resonance to the phosphorus in the prisms were those of a rearranged product, [PdCl(μ2-Se-κ2-
the phosphine sulfide chelate group. The first attempt to obtain P,Se-2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2)(PPh3)] (14). Dinuclear
X-ray quality crystals of 11 unexpectedly gave the trinuclear complex 14 is structurally different from the trinuclear
complex [Pd3Cl3(μ2-S-κ2-P,S-2-SC6H4PPh2)3] (12), which is for- complex 12 (Scheme 5); it is formally obtained by loss of a
mally derived by loss of PPh3, reduction of the phosphine PPh3 ligand and selenium atom (possibly as Ph3PvSe), and
sulfide group and insertion of the sulfur atom into the palla- reduction of the phosphine selenide group and insertion of
dium–carbon bond (Scheme 5); a second attempt gave crystals the selenium atom into a Pd–C bond.
of the expected structure. It is not clear how 12 was formed
In contrast to the stability of 11, when a 3 : 1 CD2Cl2–MeOH
from a spectroscopically pure sample of 11 and it could not be solution of 13 was left to stand at ambient temperature, three
detected by 31P NMR spectroscopy when a sample of 11 in 3 : 1 new resonances began to appear in the 31P NMR spectrum
CD2Cl2–MeOH was set aside; even after four weeks, only 11 was after 24 h. These resonances, a doublet of doublets at δ 20.9
present. A low-yielding synthesis of 12 has been reported25 and (JPP 6.1, 478 Hz) and doublets at δ 27.6 (JPP 6.1 Hz) and 49.0
other complexes containing a six-membered Pd3S3 ring are (JPP 478 Hz), are consistent with the formation of 14 and are
known.26,27
assigned to the phosphorus atoms in the six-membered ring,
The selenium analogue of 11, [PdCl{κ2-2-C6H4P(Se)Ph2}- PPh3 ligand and five-membered chelate ring, respectively.
(PPh3)] (13) was prepared similarly from [Pd2(μ-Cl)2{κ2-2- Additionally, a small singlet resonance at δ 35.2 was observed,
C6H4P(Se)Ph2}2] (6) and PPh3 (Scheme 6). Like its sulfur ana- which is tentatively assigned to Ph3PvSe (δP 35.8 in CDCl3).28
logue, the 31P NMR spectrum of 13 showed a pair of singlet The remaining selenium atom has evidently migrated into the
resonances at δ 27.3 and 32.6 with additional couplings to 77Se Pd–C σ-bond and the transformation can be described by the
of 529 and 96.2 Hz, respectively, and a second pair of reso- equation:
nances at δ 16.4 and 31.1, split into doublets of ca. 60 Hz. In
this case, no 77Se satellites were observed owing to the low
abundance of this isomer. The former pair of resonances are
assigned to the cis isomer and the latter to the trans (cis : trans
ratio ca. 10 : 1). Slow crystallization of a solution of 13 from
2 ½PdClf2-C6H4PðSeÞPh2gðPPh3Þꢀ
! ½Pd2Cl2ð2-SeC6H4PPh2Þð2-C6H4PPh2ÞðPPh3Þꢀ
þ Ph3PvSe
CH2Cl2–MeOH gave crystals with two different morphologies,
yellow blocks and yellow prisms. The blocks proved to be the
After five weeks, the new resonances comprised ca. 25% of
expected complex [PdCl{κ2-2-C6H4P(Se)Ph2}(PPh3)] (13) while the reaction mixture, as estimated by integration of the 31P
Scheme 6
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Scheme 7
NMR spectrum. Longer reaction times led to further decompo- structure of 1 is shown in Fig. 1 and selected bond lengths and
sition and unidentified products.
angles for complexes 1, 2 and 4 are listed in Table 1.
To determine if the bridging 2-C6H4PPh2 group in 14 was
Crystals of the bis(chelate) complexes 2 and 4 obtained
derived by deselenisation of a phosphine selenide group or by from 1,2-dichloroethane were isomorphous (monoclinic C2/c)
ortho-metallation of the coordinated PPh3 ligand, [PdCl{κ2-2- and contained one disordered solvent molecule per asym-
C6H4P(Se)Ph2}{P(4–tolyl)3}] (15) was prepared analogously to metric unit, whereas crystals of complex 1 (monoclinic P21/c)
13 using P(4-tolyl)3. The spectroscopic parameters for 15 are were solvent-free. In all three complexes, the metal atom is
generally comparable to those of 13. Yellow crystals deposited bound by two mutually cis metallated aryl groups and two
from a 3 : 1 CH2Cl2–MeOH solution of 15 over a period of phosphine chalcogenides, the geometry being approximately
several weeks. One of them proved to be [PdCl(μ2-Se-κ2-P,Se-2- square planar. The Pt–C bond lengths in 1 [2.003(4), 2.014(4) Å]
SeC6H4PPh2)PdCl(μ-2-C6H4PPh2){P(4–tolyl)3}] (16), the 4-tolyl
analogue of 14, thus confirming that the bridging 2-C6H4PPh2
unit is derived by reduction of coordinated 2-C6H4P(Se)Ph2,
not by metallation of coordinated PPh3 in the parent complex.
Cleavage of PvSe bonds has been observed in the reactions of
tertiary phosphine selenides with metal carbonyl clusters.29
Schiff base derivatives
The chloro-bridges in [Pd2(μ-Cl)2{κ2-2-C6H4P(X)Ph2}2] [X =
S (5), Se (6)] are also cleaved by bidentate anionic ligands.
Thus, reaction of
5
and
6
with the Schiff bases
2-HOC6H4CHvNC6H4-4-R (R = OMe, NO2) in the presence of a
base gave mononuclear species of the type [Pd{κ2-2-C6H4P(X)-
Ph2}(κ2-2-OC6H4CHvNC6H4-4-R)] {X = S, R = OMe (17), NO2
(18); X = Se, R = OMe (19), NO2 (20)} (Scheme 7) as yellow (R =
OMe) or orange-red (R = NO2) solids in high yields.
Fig. 1 Molecular structure of cis-[Pt{κ2-2-C6H4P(S)Ph2}2] (1). Ellipsoids
show 30% probability levels and hydrogen atoms have been omitted for
clarity.
The 31P NMR spectra of complexes 17 and 18 each showed
a singlet resonance at ca. δ 45, and complexes 19 and 20 a
singlet at ca. δ 26, the chemical shifts of which are comparable
to those of other complexes containing the 2-C6H4P(X)Ph2
chelate group. As expected, the resonances for complexes 19
and 20 show additional coupling to 77Se of about 500 Hz; this
coupling is also reproduced in the 77Se NMR spectra. The
structures of 16 and two different modifications of 19 have
been confirmed by X-ray diffraction.
Table 1 Selected bond lengths (Å) and angles (deg) in cis-[Pt{κ2-2-
C6H4P(S)Ph2}2] (1), cis-[Pt{κ2-2-C6H4P(Se)Ph2}2]·2(C2H4Cl2) (2) and cis-
[Pd{κ2-2-C6H4P(Se)Ph2}2]·2(C2H4Cl2) (4)
Complex 1a
Complex 2b
2.028(7)
Complex 4c
2.030(2)
M(1)–C(2)
M(1)–C(32)
2.003(4)
2.014(4)
M(1)–X(1)
M(1)–X(2)
2.4107(10)
2.4014(10)
176.46(11)
175.94(12)
87.22(11)
88.79(12)
94.22(16)
87.84(4)
2.5045(8)
172.57(19)
90.1(2)
2.5158(3)
172.37(6)
90.75(6)
C(2)–M(1)–X(2)
C(32)–M(1)–X(1)
C(2)–M(1)–X(1)
C(32)–M(1)–X(2)
C(2)–M(1)–C(32)
X(1)–M(1)–X(2)
X-ray crystallography
The structures of cis-[Pt{κ2-2-C6H4P(S)Ph2}2] (1), cis-[Pt{κ2-2-
92.6(4)
88.01(4)
91.725(13)
87.716(13)
C6H4P(Se)Ph2}2] (2) and cis-[Pd{κ2-2-C6H4P(Se)Ph2}2] (4) were
confirmed by single crystal X-ray diffraction. The molecular a M = Pt, X = S. b M = Pt, X = Se. c M = Pd, X = Se.
12004 | Dalton Trans., 2014, 43, 12000–12012
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are similar to those observed in the phosphine sulfide pincer to S are about 0.06 Å shorter than those trans to C, as expected
complex [PtCl(4-CH3C6H2-2,6-{P(S)Ph2}2)] [2.02(2) Å].11 In con- on the basis of relative trans-influences.
trast, the Pt–S bond lengths are significantly longer in 1 than
Although the complexes are isostructural, crystals of trans-
in the pincer complex [2.4107(10), 2.4014(10) Å vs. 2.307(5) Å], [PdCl{κ2-2-C6H4P(X)Ph2}(PPh3)] [X = S (11), Se (13)] (Fig. 4),
owing to the greater trans-influence of the σ-C groups relative grown from CH2Cl2–methanol, were not isomorphous (11: tri-
ˉ
to that of the phosphine sulfide moiety. The Pt–C bond clinic P1, 13: monoclinic P21/n). As expected, the geometry
lengths in 2 and 4 [2.028(7), 2.030(2) Å, respectively] are com- about the metal centres is approximately square planar and
parable to those in 1, while the M–Se bond lengths [2.5045(8), the Pd–X bond length is ca. 0.1 Å longer for X = Se compared
2.5158(3), respectively] are ca. 0.1 Å greater than the Pt–S bond to X = S (Table 2), similar to that observed in the bis(chelate)
lengths in 1; a similar trend was observed for the cyclometal- complexes 1, 2 and 4.
lated manganese carbonyl complexes [(OC)4Mn{κ2-2-C6H4P(X)
The metrical parameters in the trinuclear complex
Ph2}] [X = S, 2.410(1) Å; Se, 2.514(1) Å].8
[Pd3Cl3(μ2-S-κ2-P,S-2-SC6H4PPh2)3] (12), obtained as a methanol
In the structure of [Pd2(μ-OAc)2{κ2-2-C6H4P(S)Ph2}2] (8), solvate, are comparable to those of the reported dichloro-
shown in Fig. 2 (together with selected bond lengths and methane solvate.25
angles), each palladium atom is bound by a chelating C6H4P(S)-
Ph2 group and two bridging acetate ligands. The two C6H4P(S)-
Ph2 groups adopt a face-to-face orientation that brings the
metal atoms into close contact, the Pd⋯Pd separation
[2.92983(19) Å] being similar to those observed in the struc-
turally similar complexes [Pd2(μ-OAc)2(κ2-2-C6H4CH2SMe2)2]30
[2.9483(3) Å] and [Pd2(μ-OAc)2(κ2-2-C6H4CHMeStBu2)2]31 [2.9565(4)
Å] containing cyclopalladated thioether ligands. In general,
the bond lengths and angles about the Pd atoms in 8 are also
similar to those in the thioether complexes, although the Pd–S
bond lengths are significantly longer [ca. 2.29 Å vs. 2.25 Å],
consistent with the poorer donor strength of the sulfur atom
in the phosphine sulfide group. The bond lengths and angles
about the metal atom in [Pd(κ2-O,O′-acac){κ2-2-C6H4P(S)Ph2}2]
(9) (Fig. 3) are generally similar to those observed in the
acetato complex 8, although the Pd–O bond lengths are
ca. 0.05 Å shorter. In both cases, the Pd–O bond lengths trans
Fig. 3 Molecular structure of [Pd(κ2-O,O’-acac){κ2-2-C6H4P(S)Ph2}]
(9). Ellipsoids show 30% probability levels and hydrogen atoms have
been omitted for clarity. Only one molecule in the asymmetric unit is
shown. Selected bond lengths (Å) and angles (deg): Pd(1)–C(2) 1.994(4),
Pd(1)–S(1) 2.3075(11), Pd(1)–O(11) 2.023(3), Pd(1)–O(12) 2.084(3), C(2)–
Pd(1)–O(12) 178.28(14), S(1)–Pd(1)–O(11) 178.56(9), C(2)–Pd(1)–S(1)
90.08(12), C(2)–Pd(1)–O(11) 89.18(14), S(1)–Pd(1)–O(12) 89.31(8), O(11)–
Pd(1)–O(12) 91.47(11).
Fig. 2 Molecular structure of [Pd2(μ-OAc)2{κ2-2-C6H4P(S)Ph2}2] (8).
Ellipsoids show 30% probability levels and hydrogen atoms have been
omitted for clarity. One phenyl group is disordered by rotation about the
P–C bond and only one orientation is shown. Selected bond lengths (Å)
and angles (deg): Pd(1)–Pd(2) 2.92983(19), Pd(1)–C(2) 1.9801(18), Pd(1)–
S(1) 2.2977(6), Pd(1)–O(11) 2.0745(15), Pd(1)–O(21) 2.1456(15), Pd(2)–
C(32) 1.9827(17), Pd(2)–S(2) 2.2936(5), Pd(2)–O(12) 2.1372(13), Pd(2)–
O(22) 2.0661(15), C(2)–Pd(1)–O(21) 177.22(7), S(1)–Pd(1)–O(11) 166.87(5),
C(2)–Pd(1)–S(1) 92.08(5), C(2)–Pd(1)–O(11) 90.79(7), S(1)–Pd(1)–O(21)
87.58(5), O(11)–Pd(1)–O(21) 90.16(7), C(32)–Pd(2)–O(12) 175.42(7), S(2)–
Pd(2)–O(22) 176.83(5), C(32)–Pd(2)–S(2) 90.63(6), C(32)–Pd(2)–O(22)
90.52(7), S(2)–Pd(2)–O(12) 88.13(5), O(12)–Pd(2)–O(22) 90.50(6).
Fig. 4 Molecular structure of trans-[PdCl{κ2-2-C6H4P(S)Ph2}(PPh3)]
(11). Ellipsoids show 30% probability levels and hydrogen atoms have
been omitted for clarity.
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Table 2 Selected bond lengths (Å) and angles (deg) in trans-[PdCl{κ2-
Table 3 Selected bond lengths (Å) and angles (deg) in [PdCl(μ2-Se-κ2-
P,Se-2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2)(PPh3)]·0.376(CH3OH) (14) and
[PdCl(μ2-Se-κ2-P,Se-2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2){P(4–tolyl)3}]·CH2Cl2·
CH3OH (16)
2-C6H4P(S)Ph2}(PPh3)] (11), and trans-[PdCl{κ2-2-C6H4P(Se)Ph2}(PPh3)]
(13)
Complex 11a
Complex 13b
Complex 14
Complex 16
Pd(1)–C(2)
Pd(1)–X(1)
Pd(1)–Cl(1)
Pd(1)–P(2)
C(2)–Pd(1)–Cl(1)
X(1)–Pd(1)–P(2)
C(2)–Pd(1)–X(1)
C(2)–Pd(1)–P(2)
X(1)–Pd(1)–Cl(1)
Cl(1)–Pd(1)–P(2)
2.0391(18)
2.3894(4)
2.3703(5)
2.2842(4)
171.13(5)
169.659(16)
89.74(5)
93.06(5)
84.596(16)
93.713(16)
2.013(3)
2.4906(3)
2.3947(7)
2.2947(7)
170.53(7)
163.93(2)
88.24(2)
93.02(7)
88.24(2)
92.34(3)
Pd(1)–Se(1)
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–Cl(1)
Pd(2)–Se(1)
Pd(2)–P(3)
Pd(2)–C(32)
Pd(2)–Cl(2)
2.3872(2)
2.2949(5)
2.3296(5)
2.3350(5)
2.4869(2)
2.2905(5)
2.0137(17)
2.3933(5)
3.2760(2)
175.863(16)
175.731(18)
87.241(14)
90.214(13)
91.617(19)
90.682(18)
172.845(14)
172.24(5)
81.50(5)
2.4023(4)
2.2823(9)
2.3420(8)
2.3390(9)
2.4744(4)
2.2760(8)
2.007(3)
2.4037(9)
3.1872(3)
175.82(3)
172.08(3)
86.27(2)
90.92(2)
89.90(3)
92.66(3)
170.99(2)
173.34(9)
82.41(8)
96.35(2)
91.63(8)
90.33(3)
Pd(1)⋯Pd(2)
Se(1)–Pd(1)–Cl(1)
P(1)–Pd(1)–P(2)
Se(1)–Pd(1)–P(1)
Se(1)–Pd(1)–P(2)
P(1)–Pd(1)–Cl(1)
P(2)–Pd(1)–Cl(1)
Se(1)–Pd(2)–P(3)
C(32)–Pd(2)–Cl(2)
Se(1)–Pd(2)–C(32)
Se(1)–Pd(2)–Cl(2)
C(32)–Pd(2)–P(3)
P(3)–Pd(2)–Cl(2)
a X = S. b X = Se.
In the molecular structure of 14, shown in Fig. 5, the sel-
enium atom asymmetrically bridges two palladium atoms
[Pd(1)–Se(1) 2.3872(2), Pd(2)–Se(1) 2.4869(2)], in an arrange-
ment similar to that observed for the sulfur atoms in complex
12,25 and the Pd⋯Pd separation [3.2760(2) Å] suggests little or
no metal–metal interaction. The metrical parameters in the
P(4-tolyl)3 analogue 16 are generally similar to those observed
in 14 (Table 3), although the Pd⋯Pd separation [3.1872(3) Å] is
significantly smaller, presumably due to the greater donor
strength of P(4-tolyl)3 compared to PPh3.
95.726(14)
92.10(5)
91.029(18)
The structures of the Schiff base complexes [Pd{κ2-2-C6H4P-
(S)Ph2}(κ2-2-OC6H4CHvNC6H4-4-OMe)] (17) and [Pd{κ2-2-
C6H4P(Se)Ph2}(κ2-2-OC6H4CHvNC6H4-4-NO2)] (20) were con-
firmed by X-ray diffraction, and in the case of 20, two crystal
modifications were obtained. The structures of 20a (shown in
Fig. 6) and 20b differ by rotation of the nitrophenyl group
along the N–Caryl bond by approximately 30°. In all cases, the
metrical parameters of 17, 20a and 20b are unremarkable
(Table 4).
Fig. 6 Molecular
structure
of
[Pd{κ2-2-C6H4P(Se)Ph2}(κ2-2-
OC6H4CHvNC6H4-4-NO2)] (20a). Ellipsoids show 30% probability levels
and hydrogen atoms have been omitted for clarity.
Table 4 Selected bond lengths (Å) and angles (deg) in [Pd{κ2-2-C6H4P-
(S)Ph2}(κ2-2-OC6H4CHvNC6H4-4-OMe)] (17) and [Pd{κ2-2-C6H4P(Se)-
Ph2}(κ2-2-OC6H4CHvNC6H4-4-NO2)] (20a)
Complex 17a
Complex 20ab
Pd(1)–X(1)
Pd(1)–C(2)
Pd(1)–N(1)
Pd(1)–O(1)
X(1)–Pd(1)–O(1)
C(2)–Pd(1)–N(1)
X(1)–Pd(1)–C(2)
X(1)–Pd(1)–N(1)
N(1)–Pd(1)–O(1)
C(2)–Pd(1)–O(1)
2.3138(5)
2.017(2)
2.1057(17)
2.0325(15)
176.65(5)
175.22(7)
89.17(6)
93.18(5)
90.04(6)
87.68(7)
2.4195(3)
2.015(3)
2.115(2)
2.0283(18)
175.62(6)
174.14(9)
90.11(7)
93.87(6)
88.40(8)
87.92(9)
Fig. 5 Molecular structure of [PdCl(μ2-Se-κ2-P,Se-2-SeC6H4PPh2)PdCl-
(μ-2-C6H4PPh2)(PPh3)]·0.376(CH3OH) (14). Ellipsoids show 30% prob-
ability levels. Hydrogen atoms and methanol of crystallisation have been
omitted for clarity.
a X = S. b X = Se.
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Catalysis
entry 1). Only low yields of coupled product were obtained
when the Schiff base-containing complexes 17 and 18 were
used as catalysts (Table 6, entries 4 and 6) owing to the for-
mation of palladium black; the yields of coupled products
were improved significantly when LiOH as base and DMA as
solvent were used, and no formation of palladium black was
observed (Table 6, entries 5 and 7). High yields of coupled
product could also be obtained from bromobenzene and 4-bro-
motoluene (Table 6, entries 10 and 11) using LiOH–DMA.
Under the reaction conditions, all complexes containing the
phosphine-selenide group were catalytically inactive (Table 6,
entries 3, 8 and 9) due to thermal decomposition.
The Suzuki–Miyaura coupling reaction (Scheme 9) of 4-bromo-
anisole and phenylboronic acid was also investigated. Using
complex 5 as a test catalyst, the optimal reaction conditions
were determined similarly to that of the Heck–Mizoroki reac-
tion above, and, as shown in Table 7, excellent conversions
were obtained using K2CO3 or LiOH·H2O in MeOH (Table 7,
entries 1 and 3, respectively).
The catalytic activities of selected palladacycles were investi-
gated in the Heck–Mizoroki coupling reaction (Scheme 8). To
determine optimal reaction conditions, the coupling of 4-bromo-
anisole (1 mmol) and styrene (2 mmol) was carried out in the
presence of the chloro-bridged complex 5 as catalyst (0.5 mol
%) using a variety of solvents (3 mL) and bases (2 mmol)
at 140 °C. As shown in Table 5, a 75% conversion (66% iso-
lated yield) of the coupled product 4-methoxy-trans-stilbene
was obtained after 10 h using DMF as solvent and K2CO3 as
base; good yields were also obtained using DMA as solvent.
Using these reaction conditions, selected palladacycles (5, 6,
17–20) were further investigated (Table 6) and it was shown
that a good isolated yield of coupled product was obtained for
the chloro-bridged phosphine sulfide complex 5 (Table 6,
Using LiOH as base and methanol as solvent, compounds
5, 6 and 17–20 were tested for their activity to catalyse the
coupling of aryl bromides and phenylboronic acid (Table 8).
Isolated yields of greater than 85% of the coupled products
were obtained using the phosphine sulfide-containing com-
plexes (Table 8, entries 1, 3, 4, 7 and 8). In contrast, yields of
50% or less were obtained when the phosphine selenide com-
plexes were used (Table 8, entries 2, 5 and 6), owing to their
poor thermal stability.
Scheme 8
Table 5 Heck–Mizoroki coupling of 4-bromoanisole and styrene cata-
lysed by complex 5a
Entry
Solvent
Base
Conversionb (%)
1
2
3
4
5
6
7
8
9
DMF
DMF
DMF
DMF
K2CO3
75
0
29
0
12
58
30
63
18
NaHCO3
LiOH·H2O
K3PO4
Cs2CO3
K2CO3
K2CO3
K2CO3
DMF
DMSO
1,4-Dioxane
DMA
DMA
LiOH·H2O
Scheme 9
a Reaction conditions: 4-bromoanisole (1 mmol), styrene (2 mmol),
complex 5 (0.5 mmol%), base (2 mmol), solvent (3 mL), 140 °C, 10 h.
b GC-conversion with respect to 4-bromoanisole; average of two runs.
Table 7 Suzuki–Miyaura coupling of 4-bromoanisole and phenylboro-
nic acid catalysed by complex 5a
Table 6 Heck–Mizoroki coupling of an aryl bromide and styrenea
Entry
Solvent
Base
Conversionb (%)
Entry
Aryl bromide
Catalyst
Isolated yieldb (%)
1
2
3
4
5
6
7
8
MeOH
MeOH
MeOH
MeOH
MeOH
DMF
2-Propanol
t-Butanol
DMSO
Toluene
THF
K2CO3
KF
LiOH·H2O
K3PO4
Cs2CO3
LiOH·H2O
LiOH·H2O
LiOH·H2O
LiOH·H2O
LiOH·H2O
LiOH·H2O
97
75
99
72
72
20
85
0
1
2
3
4
5
6
7
8
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
Bromobenzene
4-Bromotoluene
5
5
6
66
12c
0
17
17
18
18
19
20
18
18
11
69c
6
72c
0
9
10
11
3
16
24
9
10
11
0
84c
78c
a Reaction conditions: 4-bromoanisole (1 mmol), phenylboronic acid
a Reaction conditions: aryl bromide (1 mmol), styrene (2 mmol), (1.5 mmol), complex 5 (0.5 mol%), base (2 mmol), solvent (3 mL),
catalyst (0.5 mol%), K2CO3 (2 mmol), DMF (3 mL), 140 °C, 10 h. 80 °C, 10 h. b GC-conversion with respect to 4-bromoanisole; average of
b Average of two runs. c Using LiOH·H2O (2 mmol) and DMA (3 mL).
two runs.
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Perkin Elmer Station 400F Raman spectrometer and MALDI
mass spectra on a Bruker Biflex II spectrometer. Electrospray
(ESI) mass spectra were measured on HP 5970 MSD and
Waters spectrometers in the Mass Spectrometry Unit of the
Research School of Chemistry, ANU. Elemental analyses were
carried out by the Microanalytical Unit at the same School.
Table 8 Suzuki–Miyaura coupling of an aryl bromide and phenylboro-
nic acida
Entry
Aryl bromide
Catalyst
Isolated yieldb (%)
1
2
3
4
5
6
7
8
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
4-Bromoanisole
Bromobenzene
4-Bromotoluene
5
6
17
18
19
20
5
92
50
85
84
20
16
94
91
X-ray crystallography
Crystals suitable for X-ray crystallography were grown by slow
evaporation of 1,2-dichloroethane (1, 2, 4), dichloromethane
layered with methanol (8, 9, 11–14, 16) or dichloromethane
layered with hexane (17, 20). Data were collected at 200 K on a
Nonius-Kappa CCD diffractometer using graphite-monochro-
mated Mo Kα radiation (λ = 0.71073 Å). Crystal data and
details of data collection are given in Table S1.† Data were
measured by use of COLLECT.36 The intensities of reflections
were extracted and the data were reduced by use of the compu-
ter programs Denzo and Scalepack.37 The crystal structures
were solved by direct methods38 and refined by use of the
program CRYSTALS.39 Neutral atom scattering factors,40 the
values of Δf‘ and Δf″, and mass attenuation coefficients41 were
taken from standard compilations.
5
a Reaction conditions: aryl bromide (1 mmol), phenylboronic acid
(1.5 mmol), catalyst (0.5 mol%), LiOH·H2O (2 mmol), methanol
(3 mL), 80 °C, 10 h. b Average of two runs.
Conclusions
ortho-Metallated platinum and palladium complexes of tri-
phenylphosphine sulfide and selenide were prepared by trans-
metallation procedures, either from the appropriate
organolithium or organotin reagent. Unaccountably, the
methods that have been applied successfully to the direct
ortho-palladation of thioethers and triphenylphosphine imines
failed for triphenylphosphine sulfide. Over a period of weeks
at room temperature, the complex trans-[PdCl{κ2-2-C6H4P(Se)-
Ph2}(PPh3)] (13) in solution undergoes reduction of its co-
ordinated triphenylphosphine selenide, accompanied by
migration of selenium into a Pd–C σ-bond, to give [PdCl(μ2-Se-
κ2-P,Se-2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2)(PPh3)] (14). Selected
palladacycles were also shown to catalyse Heck–Mizoroki and
Suzuki–Miyaura coupling reactions, the triphenylphosphine
selenide-based complexes being generally less efficacious
owing to their poorer thermal stability.
Catalysis
General procedure for the Heck–Mizoroki reaction. A
mixture of aryl bromide (1 mmol), styrene (2 mmol), catalyst
(0.005 mmol), base (2 mmol) and solvent (3 mL) was heated to
140 °C for 10 h and the progress of the reaction was monitored
by GC. After the mixture had been cooled to room tempera-
ture, ethyl acetate (30 mL) was added and the mixture was
washed successively with 1 M HCl and water. The organic
phase was separated, dried (Na2SO4) and the solvents evapor-
ated. The residue was passed down a silica gel column, eluting
with ethyl acetate, to afford the coupled product in high
purity.
General procedure for the Suzuki–Miyaura reaction. A
mixture of aryl bromide (1 mmol), phenylboronic acid
(1.5 mmol), catalyst (0.005 mmol), base (2 mmol) and solvent
(3 mL) was heated to 80 °C for 10 h, monitoring the progress
of the reaction by GC. After the mixture had been cooled to
room temperature, ethyl acetate (30 mL) was added and the
mixture was washed successively with 1 M HCl and water. The
organic phase was separated, dried (Na2SO4) and the solvents
evaporated. Purification by column chromatography (silica gel,
ethyl acetate) gave the coupled product in high purity.
Experimental section
General comments
All experiments involving organolithium and organotin
reagents were performed under an atmosphere of dry argon
with use of standard Schlenk techniques. Diethyl ether,
dichloromethane, toluene and hexane were dried by passage
through solvent drying columns. The compounds
2-BrC6H4PPh2,32 [PtI2(COD)]33 and [PdCl2(COD)]34 were pre-
pared by literature methods and the methoxy- and nitro-substi-
tuted Schiff bases by the usual condensation reaction between
salicylaldehyde and the appropriate amine;35 all other reagents
were commercially available and used as received.
1H (300 MHz), 13C (75 MHz), 31P (121 MHz) and 77Se (57 MHz)
Attempted direct cyclopalladation of triphenylphosphine
sulfide
NMR spectra were measured on a Bruker Avance 300 spectro- (a) A mixture of PdCl2 (0.1 g, 0.56 mmol) and LiCl (0.05 g,
meter at room temperature in CDCl3. Coupling constants are 1.12 mmol) in MeOH (5 mL) was stirred with gentle warming
given in Hertz (Hz) and chemical shifts (δ) in ppm, internally for 30 min. The red-brown solution was filtered through Celite
referenced to residual solvent signals (1H and 13C), external into a solution of Ph3PvS (0.16 g, 0.56 mmol) in THF (7 mL).
85% H3PO4 (31P) or external Ph3PvSe (77Se, δ −262). Infrared Almost immediately the mixture became turbid and a yellow
spectra were obtained on a Perkin Elmer Spectrum 100 FT-IR orange precipitate slowly formed. After stirring the mixture at
spectrometer as KBr discs or nujol mulls, Raman spectra on a room temperature for 24 h, the solid was isolated by filtration,
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washed with MeOH and dried (225 mg). 31P NMR: δ 45.1, 44.9, (d, JPC 9.9 Hz, JSnC 339, 355 Hz), 128.3 (d, JPC 6.3 Hz), 128.4 (s,
44.3, 43.3. JSnC 43.9 Hz), 128.8 (s, JSnC 9.7 Hz), 133.3 (d, JPC 18.5 Hz), 134.2
(b) In a similar reaction to (a) above, a solution of NaOAc (s, JSnC 39.9 Hz), 136.0 (d, JPC 20.2 Hz, JSnC 39.2 Hz), 137.9 (d,
(0.093 g, 1.13 mmol) in MeOH (3 mL) was added to the THF JPC 10.8 Hz), 144.8 (d, JPC 1.8 Hz, JSnC 39.0, 41.6 Hz), 152.8 (d,
solution of Ph3PvS prior to the addition of the palladium JPC 66.0 Hz, JSnC 449, 470 Hz). 31P NMR: δ −3.5 (s, JSnP 40.9,
solution. After stirring at room temperature for 24 h, a dark 43.1 Hz). ESI-MS (m/z): 427 [M + H]+. Anal. Calcd for
brown/black mixture was obtained. Filtration of this suspen- C21H23PSn: C 59.34, H 5.45 P 7.29. Found: C 59.68, H 5.08
sion gave a dark brown solid which was washed with MeOH P 7.00.
and dried (236 mg). 31P NMR: δ 45.1, 44.9, 44.3, 43.3.
This compound, m.p. 58–59 °C, was first prepared by
Weichmann and Schmoll,42 who treated 1,2-dichlorobenzene
successively with LiSnMe3 and LiPPh2. Our 1H and 31P NMR
Syntheses
2-BrC6H4P(S)Ph2. To a solution of 2-BrC6H4PPh2 (4.0 g, spectroscopic data agree reasonably well with those reported.
11 mmol) in CH2Cl2 (30 mL) was added elemental sulfur 2-Me3SnC6H4P(S)Ph2. To a solution of 2-Me3SnC6H4PPh2
(0.4 g, 12 mmol) and the mixture was stirred at room tempera- (1.8 g, 4.2 mmol) in CH2Cl2 (20 mL) was added elemental
ture for 2 h. The slightly turbid solution was filtered and the sulfur (0.15 g, 4.6 mmol) and the mixture was stirred at room
solvent was removed in vacuo. The yellow gummy solid was temperature for 24 h. After filtration, the solvent was removed
recrystallised from hot EtOH to give the product as colourless in vacuo and the gummy solid was recrystallised from hot
1
crystals (4.15 g, 95%). M.p.: 124–126 °C. H NMR: δ 7.12–7.24 EtOH (hot filtration) to give the product as colourless crystals
1
(m, 1H, aromatic), 7.24–7.38 (m, 2H, aromatic), 7.42–7.60 (m, (1.65 g, 85%). M.p.: 98–100 °C. H NMR: δ 0.14 (s, JSnH 53.1,
6H, aromatic), 7.64–7.72 (m, 1H, aromatic), 7.78–7.92 (m, 4H, 55.6 Hz, 9H, Me), 6.96–7.03 (m, 1H, aromatic), 7.18–7.24 (m,
aromatic). 13C NMR: δ 126.7 (d, 6.2 Hz), 126.9 (d, 11.1 Hz), 1H, aromatic), 7.40–7.54 (m, 7H, aromatic), 7.58–7.65 (m, 4H,
128.4 (d, 11.9 Hz), 131.3 (d, 87.2 Hz), 131.5 (d, 2.0 Hz), 132.0 aromatic), 7.83–7.85 (m, 1H, aromatic). 13C NMR: δ −3.95 (s,
(d, 11.1 Hz), 132.7 (d, 3.1 Hz), 132.8 (d, 88.0 Hz), 134.8 (d, 11.3 JSnC 353.8, 371.0 Hz), 127.1 (d, 12.7 Hz), 128.4 (d, 11.4 Hz),
Hz), 135.4 (d, 7.0 Hz). 31P NMR: δ 46.4 (s). IR (KBr, cm−1): 636 130.1 (d, 3.5 Hz), 131.4 (d, 2.4 Hz), 132.4 (d, 10.3 Hz), 132.7 (d,
(PvS str). ESI-MS (m/z): 375 [M + H]+. Anal. Calcd for 15.1 Hz), 133.3 (d, 84.0 Hz), 138.6 (d, 18.4 Hz), 139.5 (s), 149.6
C18H14BrPS: C 57.92, H 3.78, Br 21.41, P 8.30, S 8.59. Found: (d, 24.3 Hz). 31P NMR: δ 48.3 (s, JSnP 46.6, 48.7 Hz). IR (KBr,
C 57.96, H 3.94, Br 21.19, P 8.42, S 8.87.
cm−1): 636 (PvS str). ESI-MS (m/z): 459 [M + H]+. Anal. Calcd
2-BrC6H4P(Se)Ph2. This was prepared similarly to the corres- for C21H23PSSn: C 55.18, H 5.07, P 6.78, S 7.01. Found: C
ponding sulfide, with use of selenium powder (1.2 g, 54.97, H 5.13, P 6.53, S 7.18.
15 mmol) in place of sulfur and the mixture was stirred at
2-Me3SnC6H4P(Se)Ph2. This was prepared similarly to the
room temperature for 24 h. Recrystallisation from hot EtOH corresponding sulfide, with use of selenium powder (0.35 g,
gave the product as colourless crystals (5.1 g, 92%). M.p.: 4.4 mmol) in place of sulfur. After 24 h, the dark suspension
1
134–135 °C. H NMR: δ 7.12–7.22 (m, 1H, aromatic), 7.24–7.38 was filtered through Celite and the filtrate was evaporated to
(m, 2H, aromatic), 7.42–7.58 (m, 6H, aromatic), 7.64–7.72 (m, dryness. Recrystallisation from hot EtOH gave the product as
1H, aromatic), 7.82–7.96 (m, 4H, aromatic). 13C NMR: δ 127.0 colourless crystals (2.0 g, 94%). M.p.: 138–140 °C. 1H NMR:
(d, 7.0 Hz), 127.1 (d, 11.1 Hz), 128.5 (d, 12.6 Hz), 130.1 (d, 78.4 δ 0.13 (s, JSnH 54.4, 55.2 Hz, 9H, Me), 6.88–6.95 (m, 1H, aro-
Hz), 131.6 (d, 3.0 Hz), 131.6 (d, 79.8 Hz), 132.7 (d, 10.8 Hz), matic), 7.15–7.21 (m, 1H, aromatic), 7.37–7.53 (m, 7H, aro-
132.8 (d, 1.5 Hz), 135.0 (d, 11.2 Hz), 135.6 (d, 7.0 Hz). matic), 7.61–7.68 (m, 4H, aromatic), 7.82–7.84 (m, 1H,
31P NMR: δ 37.7 (s, JSeP 744 Hz). 77Se NMR: δ −263.2 (d, aromatic). 13C NMR: δ −3.64 (s, JSnC 354.0, 370.1 Hz), 127.2 (d,
JSeP 745 Hz). IR (KBr, cm−1): 567 (PvSe str). ESI-MS (m/z): 421 11.4 Hz), 128.5 (d, 11.0 Hz), 130.0 (d, 3.5 Hz), 131.5 (d, 2.4 Hz),
[M + H]+. Anal. Calcd for C18H14BrPSe: C 51.46, H 3.36, Br 132.4 (d, 17.1 Hz), 132.6 (d, 11.7 Hz), 132.9 (d, 10.6 Hz), 137.8
19.02, P 7.37. Found: C 51.62, H 3.43, Br 19.12, P 7.24.
(s), 138.7 (d, 20.3 Hz), 150.6 (d, 24.7 Hz). 31P NMR: δ 40.83 (s,
2-Me3SnC6H4PPh2. To a solution of 2-BrC6H4PPh2 (6.8 g, JSeP 712 Hz, JSnP 50.0, 52.0 Hz). 77Se NMR: δ 71.8 (d, JSeP 712
20 mmol) in Et2O (100 mL), cooled to 0 °C, was added BuLi Hz, unresolved JSeSn 10.1 Hz). IR (KBr, cm−1): 565 (PvSe str).
n
(1.6 M in hexanes, 12.5 mL, 20 mmol) dropwise. After stirring ESI-MS (m/z): 505 [M + H]+. Anal. Calcd for C21H23PSeSn:
for 30 min, Me3SnCl (1.0 M in hexanes, 20 mL, 20 mmol) was C 50.04, H 4.60, P 6.15. Found: C 50.40, H 4.69, P 6.07.
added slowly and the mixture was allowed to come to room
cis-[Pt{κ2-2-C6H4P(S)Ph2}2] (1). (a) To
a
solution of
temperature with stirring. The suspension was hydrolysed and 2-BrC6H4P(S)Ph2 (0.6 g, 1.6 mmol) in Et2O (100 mL) cooled to
the Et2O layer separated. The aqueous phase was extracted −78 °C was added nBuLi (1.6 M in hexanes, 1.0 mL, 1.6 mmol)
with Et2O (3 × 20 mL) and the combined organic phases were and the mixture was stirred for 30 min. To the clear yellow
dried (MgSO4). After filtration, the solvent was removed solution was added solid [PtI2(COD)] (0.4 g, 0.7 mmol) and
in vacuo and the gummy solid, after recrystallisation from hot stirring was continued at −78 °C for 4 h, then at room temp-
MeOH, gave the title compound as colourless crystals (6.7 g, erature overnight. The very pale yellow solid was filtered off,
80%). M.p.: 55–56 °C. 1H NMR: δ 0.29 (d, JPH 1.1 Hz, JSnH 52.9, extracted with CH2Cl2, and the solution was filtered. Methanol
55.1 Hz, 9H, Me), 7.10–7.20 (m, 1H, aromatic), 7.20–7.39 (m, was added to the filtrate and the volume was reduced in vacuo.
12H, aromatic), 7.49–7.70 (m, 1H, aromatic). 13C NMR: δ −6.8 The pale yellow solid that precipitated was isolated by fil-
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Dalton Transactions
tration, washed with MeOH, and dried (0.45 g, 80%). 1H NMR: cipitation of a pale orange solid, which was isolated by fil-
δ 6.79–6.86 (m, 1H, aromatic), 6.89–6.95 (m, 1H, aromatic), tration, washed with MeOH and dried in vacuo (23 mg, 38%).
1
3
7.05–7.10 (m, 1H, aromatic), 7.37–7.41 (m, 1H, aromatic), 31P NMR: δ 37.2 (s, JPtP 68.2 Hz, JSeP 532 Hz, JSeP 26.6 Hz,
7.43–7.57 (m, 6H, aromatic), 7.73–7.80 (m, 4H, aromatic). 4JPP 3.0 Hz) (cis isomer).
1
31P NMR: δ 51.6 (s, JPtP 79.0 Hz). IR (KBr, cm−1): 623 (PvS str).
Complex 4: (0.33 g, 92%). H NMR: δ 6.45–6.71 (m, 1H, aro-
ESI-MS (m/z): 782 [M + H]+. Anal. Calcd for C36H28P2PtS2: matic), 6.80–6.86 (m, 1H, aromatic), 6.99–7.04 (m 1H, aro-
C 55.31, H 3.61, P 7.92, S 8.20. Found: C 55.13, H 3.71, P 8.14, matic), 7.17–7.19 (m, 1H, aromatic), 7.43–7.55 (m, 6H,
S 8.11. (b) To a solution of [Pt(κ2-2-C6H4PPh2)2] (45 mg, aromatic), 7.72–7.79 (m, 4H, aromatic). 31P NMR: δ 32.6 (s,
0.06 mmol) in toluene (10 mL) was added sulfur (4 mg, 1JSeP 557 Hz, JSeP 29.8, JPP 1.9 Hz). 77Se NMR: δ −119.5 (dd,
3
4
0.12 mmol) and the mixture refluxed for 24 h. The pale yellow 1JSeP 557 Hz, JSeP 29.7 Hz). IR (KBr, cm−1): 552 (PvSe str).
3
solution was evaporated to dryness and the residue was recrys- ESI-MS (m/z): 787 [M]+. Anal. Calcd for C36H28P2PdSe2:
tallised from CH2Cl2–MeOH to give 1 as a pale yellow solid C 54.95, H 3.59. Found: C 54.72, H 3.62.
(38 mg, 78%). 31P NMR: δ 51.6 (s, JPtP 78.9 Hz).
cis-[Pd{κ2-2-C6H4P(S)Ph2}2]
(3). To
[Pd2(μ-Cl)2{κ2-2-C6H4P(S)Ph2}2] (5). To
of 2-Me3SnC6H4P(S)Ph2 (0.16 g, 0.35 mmol) in CH2Cl2 (10 mL)
a
solution of
a
solution
2-Me3SnC6H4P(S)Ph2 (0.46 g, 1.0 mmol) in CH2Cl2 (10 mL) was was added [PdCl2(COD)] (0.10 g, 0.35 mmol) and the mixture
added [PdCl2(COD)] (0.14 g, 0.5 mmol) and the yellow solution was stirred for 24 h. The yellow precipitate of 5 was filtered off,
1
was refluxed for 24 h. Hexane was added to the cooled suspen- washed with MeOH and dried in vacuo (0.13 g, 82%). H NMR:
sion and the sandy-coloured solid was filtered off, washed with δ 6.6–6.8 (m, 2H, aromatic), 6.9–7.1 (m, 2H, aromatic), 7.4–7.9
hexane and extracted with CH2Cl2. Methanol was added to the (m, 10H, aromatic). 31P NMR: δ 46.7 (s), 47.8 (s). Raman
filtered extract and the volume was reduced in vacuo to precipi- (cm−1): 306, 282 (Pd–Cl str). MALDI-MS (m/z): 835 [M − Cl]+.
tate complex 3 as a pale yellow solid, which was filtered off, Anal. Calcd for C36H28Cl2P2Pd2S2: C 49.68, H 3.24, Cl 8.15,
washed with MeOH and dried (0.32 g, 94%). 1H NMR: S 7.37. Found: C 49.56, H 3.25, Cl 8.37, S 7.14.
δ 6.72–6.79 (m, 1H, aromatic), 6.84–6.91 (m, 1H, aromatic),
[Pd2(μ-Cl)2{κ2-2-C6H4P(Se)Ph2}2] (6). This was prepared ana-
7.05–7.11 (m, 1H, aromatic), 7.32–7.35 (m, 1H, aromatic), logously to 5 from 2-Me3SnC6H4P(Se)Ph2 (0.20 g, 0.4 mmol)
7.43–7.57 (m, 6H, aromatic), 7.73–7.81 (m, 4H, aromatic). and [PdCl2(COD)] (0.11 g, 0.4 mmol) to give an orange precipi-
31P NMR: δ 46.9 (s). IR (KBr, cm−1): 625 (PvS str). ESI-MS tate which was filtered off, washed with MeOH and dried
(m/z): 693 [M + H]+. Anal. Calcd for C36H28P2PdS2: C 62.39, (0.12 g, 87%). 1H NMR: δ 6.5–7.2 (m, 6H, aromatic), 7.4–7.8
H 4.07, S 9.25. Found: C 62.30, H 4.13, S 9.09.
(m, 8H, aromatic). 31P NMR: δ 25.8 (s, 77Se satellites not
cis-[M{κ2-2-C6H4P(Se)Ph2}2] [M = Pt (2), Pd (4)]. To a solu- observed), 26.8 (s, 77Se satellites not observed). Raman (cm−1):
tion of 2-Me3SnC6H4P(Se)Ph2 (0.48 g, 0.95 mmol) in CH2Cl2 301, 269 (Pd–Cl str). MALDI-MS (m/z): 929 [M − Cl]+. Anal.
(10 mL) was added [MCl2(COD)] (M = Pt, 0.17 g, 0.45 mmol; Calcd for C36H28Cl2P2Pd2Se2: C 44.85, H 2.93, Cl 7.35. Found:
Pd, 0.13 g, 0.46 mmol) and the mixture was refluxed for 24 h. C 44.80, H 2.96, Cl 7.72.
Hexane was added to the suspension and the yellow solid
[Pd{κ2-2-C6H4P(S)Ph2}{κ2-2-C6H4P(Se)Ph2}] (7). (a) A suspen-
was filtered off, washed with hexane and dissolved in sion of 3 (45 mg, 0.06 mmol) and 4 (51 mg, 0.06 mmol) in
CH2Cl2. Addition of methanol and evaporation of the solution CH2Cl2 (40 mL) was refluxed for 24 h, during which time the
in vacuo caused the product (2 or 4) to precipitate as a solid dissolved. Methanol was added and the solution was
pale yellow solid, which was filtered off, washed with MeOH evaporated in vacuo, causing a pale yellow solid to precipitate.
and dried.
This was isolated by filtration, washed with MeOH and dried
Complex 2: (0.27 g, 68%). 1H NMR: δ 6.72–6.24 (m, 14H, in vacuo (89 mg). 31P NMR spectroscopy showed this to be a
aromatic), 7.34–7.78 (m, 34H, aromatic), 8.22–8.34 (m with 1 : 1 : 2 mixture of 3 : 4 : 7. Attempts to separate this mixture by
broad Pt satellites, JPtH ca. 31 Hz, 1H, aromatic). 31P NMR: chromatography were unsuccessful. 1H NMR: δ 6.6–7.9 (m,
δ 36.5 (s, JPtP 73.0 Hz, JSeP 506 Hz, JSeP not observed, JPP 0.7 28H, aromatic). 31P NMR: δ 31.3 (d, JPP 1.0 Hz, JSeP 555 Hz),
1
3
4
4
1
3
4
1
Hz) (trans isomer), 37.2 (s, JPtP 70.6 Hz, JSeP 534 Hz, JSeP 26.9 48.1 (d, JPP 1.0 Hz, JSeP 27.4 Hz) (complex 7), 32.6 (s, JSeP
4
3
4
Hz, JPP 2.2 Hz) (cis isomer). cis/trans ratio ca. 3 : 1. 77Se NMR: 557 Hz, JSeP 29.8, JPP 1.9 Hz) (complex 4), 46.9 (s) (complex
δ −130.2 (dd, JSeP 532 Hz, JSeP 26.7 Hz, JSePt 230 Hz) (cis 3). 77Se NMR: δ −114.2 (dd, JSeP 555 Hz, JSeP 26.4 Hz)
1
3
1
3
1
3
1
3
isomer), 42.5 (d, JSeP 505 Hz, JSeP and JSePt not observed) (complex 7), −119.6 (dd, JSeP 556 Hz, JSeP 29.8 Hz) (complex
(trans isomer). IR (KBr, cm−1): 551 (PvSe str). ESI-MS (m/z): 4). ESI-MS (m/z): 693 [M + H]+ (complex 3), 741.0 [M + H]+
876 [M]+. Anal. Calcd for C36H28P2PtSe2: C 49.38, H 3.22, (complex 7), 786.9 [M + H]+ (complex 4).
P 7.08. Found: C 49.01, H 3.23, P 7.02. Complex 2 could also
(b) To a suspension of 5 (50 mg, 0.05 mmol) in CH2Cl2
be prepared as follows. To a solution of [Pt(κ2-2-C6H4PPh2)2] (40 mL) was added 2-Me3SnC6H4P(Se)Ph2 (60 mg, 0.1 mmol)
(50 mg, 0.07 mmol) in toluene (10 mL) was added selenium and the mixture was refluxed for 24 h. The solution was evap-
powder (11 mg, 0.14 mmol) and the mixture was refluxed for orated to dryness and the residue was dissolved in CH2Cl2.
24 h. The solvent was removed in vacuo and the residue was Addition of MeOH and partial evaporation caused a pale
extracted with CH2Cl2. The suspension was filtered through yellow solid to precipitate, which was isolated, washed with
Celite to remove some insoluble black material, and MeOH MeOH and dried in vacuo (80 mg). The 31P NMR spectrum was
added to the filtrate. Partial evaporation resulted in the pre- identical to that in (a).
12010 | Dalton Trans., 2014, 43, 12000–12012
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(c) To a suspension of 6 (50 mg, 0.05 mmol) in CH2Cl2 aromatic), 6.6–6.8 (m, 3H, aromatic), 7.2–7.7 (m, 21H, aro-
(40 mL) was added 2-Me3SnC6H4P(S)Ph2 (50 mg, 0.1 mmol) matic), 7.8–8.0 (m, 4H, aromatic). 31P NMR: δ 34.4 (s), 43.8 (s)
and the mixture was refluxed for 24 h. The orange solution (cis isomer), 17.5 (d, JPP 58.2 Hz), 50.2 (d, JPP 58.5 Hz) (trans
was evaporated to dryness and the residue was taken up in isomer). cis/trans ratio: 12 : 1. MALDI-MS (m/z): 661 [M − Cl]+.
CH2Cl2. Methanol was added to the solution and the volume Anal. Calcd for C36H29ClP2PdS: C 61.99, H 4.19, Cl 5.08, S 4.60.
was reduced in vacuo, causing an orange solid to precipitate. Found: C 61.90, H 4.27, Cl 4.64, S 4.35.
This was filtered off, washed with MeOH and dried in vacuo
[PdCl{κ2-2-C6H4P(Se)Ph2}(PR3)] {R = Ph (13), 4-tolyl (15)}. In
a similar reaction to that of complex 11 described above,
(51 mg). The 31P NMR spectrum was identical with that in (a).
[Pd2(μ-OAc)2{κ2-2-C6H4P(S)Ph2}2] (8). A solution containing complex 6 (100 mg, 0.10 mmol) in CH2Cl2 (20 mL) was treated
a mixture of 3 (105 mg, 0.15 mmol) and [Pd(OAc)2]3 (34 mg, with solid PR3 (PPh3, 55 mg; P(tolyl)3, 65 mg; 0.22 mmol) to
0.05 mmol) in CH2Cl2 (60 mL) was stirred at room temperature give the title products as yellow solids.
1
for 48 h. Hexane was then added and the volume was reduced
R = Ph (13): 151 mg, 98%. H NMR: δ 6.3–6.8 (m, 4H, aro-
in vacuo. The precipitated yellow solid was filtered off, washed matic), 7.1–7.7 (m, 21H, aromatic), 7.7–7.9 (m, 4H, aromatic).
1
with hexane and dried (120 mg, 86%). H NMR: δ 2.09 (s, 6H, 31P NMR: δ 27.3 (s, JSeP 529 Hz), 32.6 (s, JSeP 96.2 Hz) (cis
Me), 6.6–8.1 (m, 28H, aromatic). 31P NMR: δ 47.0 (s). IR (nujol, isomer), 16.4 (d, JPP 61.9 Hz), 31.1 (d, JPP 61.6 Hz) (trans
cm−1): 1588, 1578 (COO), 1415 (C–O), 622 (PvS str). ESI-MS isomer). cis/trans ratio: 10 : 1. 77Se NMR: δ 65.4 (dd, JSeP 96.4,
(m/z): 941 [M + Na]+. Anal. Calcd for C40H34O4P2Pd2S2: C 52.36, 529 Hz) (cis isomer); trans isomer not observed. MALDI-MS
H 3.73, S 6.99. Found: C 52.10, H 3.75, S 6.79.
(m/z): 709 [M − Cl]+. Anal. Calcd for C36H29ClP2PdSe: C 58.09,
[Pd(κ2-O,O′-acac){κ2-2-C6H4P(S)Ph2}] (9). To a suspension of H 3.93, Cl 4.76. Found: C 58.36, H 4.18, Cl 4.42.
5 (100 mg, 0.1 mmol) in CH2Cl2 (20 mL) was added Na(acac)
R = tolyl (15): 145 mg, 87%. 1H NMR: δ 2.28 (s, 9H, Me),
(50 mg, 0.4 mmol) in MeOH (20 mL). Almost immediately the 6.3–6.5 (m, 1H, aromatic), 6.5–6.6 (m, 2H aromatic), 6.7–6.8
solid dissolved and after being stirred for 10 min, the solution (m, 1H, aromatic), 6.9–7.0 (m, 6H, aromatic), 7.2–7.4 (m, 6H,
was evaporated to dryness. The yellow solid was dissolved in aromatic), 7.4–7.6 (m, 6H, aromatic), 7.8–7.9 (m, 4H, aro-
CH2Cl2, the solution was filtered through Celite, and MeOH matic). 31P NMR: δ 26.6 (d, JPP 5.6 Hz, JSeP 532 Hz), 30.5 (d,
added to the filtrate. The yellow solid that precipitated when JPP 5.6 Hz, JSeP 98.4 Hz) (cis isomer). 77Se NMR: δ 52.3 (dd, JSeP
the solution was evaporated in vacuo was isolated, washed with 98.7, 532 Hz) (cis isomer); trans isomer not observed. ESI-MS
1
MeOH and dried (106 mg, 93%). H NMR: δ 1.95 (s, 3H, Me), (m/z): 751 [M − Cl]+. Anal. Calcd for C39H35ClP2PdSe: C 59.56,
2.07 (s, 3H, Me), 5.33 (s, 1H, CH), 6.7–6.8 (m, 1H, aromatic), H 4.49, Cl 4.51. Found: C 59.25, H 4.41, Cl 4.32.
6.95–7.05 (m, 1H, aromatic), 7.2–7.3 (m, 1H, aromatic), 7.45–7.65
[Pd{κ2-2-C6H4P(X)Ph2}(κ2-OC6H4CHvNC6H4-4-R)] {X
= S,
(m, 6H, aromatic), 7.7–7.9 (m, 5H, aromatic). 31P NMR: δ 48.5 (s). R = OMe (17), NO2 (18); X = Se, R = OMe (19), NO2
ESI-MS (m/z): 399 [M − acac]+. Anal. Calcd for C23H21O2PPdS: (20)}. Typical procedure for complexes containing Schiff base
C 55.38, H 4.24, S 6.43. Found: C 55.40, H 4.40, S 6.43.
ligands: to a solution of Schiff base (0.2 mmol) in a
[Pd(κ2-O,O′-acac){κ2-2-C6H4P(Se)Ph2}] (10). To a suspension 4 : 1 mixture of CH2Cl2–MeOH (10 mL) was added LiOH
of 6 (100 mg, 0.1 mmol) in CH2Cl2 (20 mL) was added (0.25 mmol) followed by the chloro-bridged palladium
Na(acac) (50 mg, 0.4 mmol) in MeOH (20 mL). Almost immedi- complex (0.1 mmol). After stirring at room temperature for
ately the solid dissolved and after the mixture had been stirred 24 h the solvent was removed in vacuo and the residue was
for 10 min, the solvent was removed in vacuo. The residue was taken up in CH2Cl2. The suspension was filtered through
dissolved in CH2Cl2 and the solution, after filtration through Celite, hexane was added to the filtrate and the volume was
Celite, was treated with MeOH. The volume of the solution was reduced. The precipitated solid was isolated by filtration,
reduced in vacuo, and the solution became turbid. After 24 h washed with hexane and dried in vacuo.
at −18 °C, 10 had formed as a golden-yellow solid, which was
Complex 17: yellow solid, 94% yield. 1H NMR: δ 3.83 (s, 3H,
isolated, washed with MeOH and dried (93 mg, 82%). OMe), 6.52–6.57 (m, 1H, aromatic), 6.76–6.82 (m, 1H aromatic),
1H NMR: δ 1.92 (s, 3H, Me), 2.06 (s, 3H, Me), 5.32 (s, 1H, CH), 6.89 (d, J 8.7 Hz, 2H, aromatic), 6.99–7.00 (m, 5H, aromatic),
6.6–6.7 (m, 1H, aromatic), 6.95–7.05 (m, 1H, aromatic), 7.2–7.3 7.26–7.34 (m, 2H, aromatic), 7.44–7.70 (m, 10H, aromatic), 7.93
(m, 1H, aromatic), 7.45–7.7 (m, 6H, aromatic), 7.7–7.8 (m, 4H, (s, 1H, CHvN), 8.19–8.22 (m, 1H, aromatic). 31P NMR: δ 45.5
aromatic), 7.8–7.9 (m, 1H, aromatic). 31P NMR: δ 27.0 (s, JSeP (s). ESI-MS (m/z): 626 [M + H]+. Anal. Calcd for C32H26NO2PPdS:
501 Hz). 77Se NMR: δ −61.7 (d, JSeP 501 Hz). ESI-MS (m/z): 447 C 61.40, H 4.19, N 2.24. Found: C 61.63, H 4.35, N 2.11.
[M − acac]+. Anal. Calcd for C23H21O2PPdSe: C 50.62, H 3.88.
Found: C 50.36, H 4.05.
Complex 18: orange-red solid, 92% yield. 1H NMR:
δ 6.54–6.59 (m, 1H, aromatic), 6.76–6.82 (m, 1H, aromatic),
[PdCl{κ2-2-C6H4P(S)Ph2}(PPh3)] (11). To a suspension of 5 7.01–7.11 (m, 2H, aromatic), 7.17 (dd, J 1.8, 8.1 Hz, 1H, aro-
(100 mg, 0.1 mmol) in CH2Cl2 (20 mL) was added solid PPh3 matic), 7.25–7.29 (m, 2H, aromatic), 7.31–7.38 (m, 2H, aro-
(61 mg, 0.23 mmol). Almost immediately, a clear yellow solu- matic), 7.46–7.52 (m, 4H, aromatic), 7.58–7.67 (m, 6H,
tion was obtained, which was stirred for 10 min. Hexane was aromatic), 7.92 (s, 1H, CHvN), 8.15–8.19 (m, 1H, aromatic),
added and the solution was evaporated in vacuo. The precipi- 8.23–8.28 (m, 2H, aromatic). 31P NMR: δ 45.9 (s). ESI-MS (m/z):
tated pale yellow solid was isolated by filtration, washed with 641 [M + H]+. Anal. Calcd for C31H23N2O3PPdS: C 58.07,
1
hexane and dried (150 mg, 94%). H NMR: δ 6.4–6.5 (m, 1H, H 3.62, N 4.37, S 5.00. Found: C 57.92, H 3.62, N 4.13, S 4.87.
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Complex 19: yellow solid, 86% yield. 1H NMR: δ 3.82 (s, 3H, 18 P. Wei, K. T. K. Chan and D. W. Stephan, Dalton Trans.,
OMe), 6.53 (dd, J 7.2, 7.5 Hz, 1H, aromatic), 6.70 (dd, J 8.1, 2003, 3804.
10.2 Hz, 1H, aromatic), 6.88 (d, J 8.6 Hz, 2H, aromatic), 19 M. A. Bennett, D. E. Berry, S. K. Bhargava, E. J. Ditzel,
6.98–7.16 (m, 5H, aromatic), 7.27–7.35 (m, 2H, aromatic),
7.42–7.70 (m, 10H, aromatic), 7.88 (s, 1H, CHvN), 8.24 (dd,
G. B. Robertson and A. C. Willis, J. Chem. Soc., Chem.
Commun., 1987, 1613.
J 2.7, 7.8 Hz, 1H, aromatic). 31P NMR: δ 25.8 (s, JSeP 501 Hz). 20 M. A. Bennett, S. K. Bhargava, M. Ke and A. C. Willis,
77Se NMR: δ −45.7 (d, JSeP 501 Hz). ESI-MS (m/z): 674 [M + H]+.
Anal. Calcd for C32H26NO2PPdSe: C 57.12, H 3.89, N 2.08. 21 M. A. Bennett, S. K. Bhargava, S. H. Privér and A. C. Willis,
Found: C 56.98, H 4.07, N 1.87. Eur. J. Inorg. Chem., 2008, 3467.
Complex 20: orange-red solid, 86% yield. 1H NMR: 22 S. Isişli and L. Alkan, Synth. React. Inorg. Met.-Org. Chem.,
δ 6.52–6.58 (m, 1H, aromatic), 6.67–6.73 (m, 1H, aromatic), 2004, 34, 1817.
7.00–7.08 (m, 2H, aromatic), 7.16 (dd, J 1.8, 8.1 Hz, 1H, aro- 23 A. N. Skvortsov, A. N. Reznikov, D. A. de Vekki, A. I. Stash,
J. Chem. Soc., Dalton Trans., 2000, 3537.
matic), 7.25–7.36 (m, 4H, aromatic), 7.45–7.51 (m, 4H, aro-
matic), 7.56–7.68 (m, 6H, aromatic), 7.87 (s, 1H, CHvN), 8.19
V. K. Belsky, V. N. Spevak and N. K. Skvortsov, Inorg. Chim.
Acta, 2006, 359, 1031.
(dd, J 0.9, 3.3 Hz, 1H, aromatic), 8.21–8.26 (m, 2H, aromatic). 24 K. Nakamoto, Infrared and Raman Spectra of Inorganic and
31P NMR: δ 25.9 (s, JSeP 497 Hz). 77Se NMR: δ −41.6 (d, JSeP 497
Coordination Compounds, Part B, John Wiley & Sons,
New York, 5th edn, 1997.
Hz). ESI-MS (m/z): 689 [M
+
H]+. Anal. Calcd for
C31H23N2O3PPdSe: C 54.13, H 3.37, N 4.07. Found: C 54.09, 25 I. Sárosi, A. Hildebrand, P. Lönnecke, L. Silaghi-Dumitrescu
H 3.45, N 3.45.
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12012 | Dalton Trans., 2014, 43, 12000–12012
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