Unsymmetrical organodiplatinum(II) and organodiplatinum(IV) complexes containing bis(diphenylphosphino)methane as bridging ligand: General approaches for synthesis and characterization by multinuclear NMR studies

Article abstract of DOI:10.1016/S0022-328X(01)01057-9

Reaction of cis-[PtR₂(SMe₂)₂] (R=Ph or p-MeC₆H₄) with [PtMe₂(dppm)] or [Pt{(CH₂)₄}(dppm)] (dppm=Ph₂PCH₂PPh₂) gave the unsymmetrical cis,cis-diaryl-dialkyl diplatinum(II) complexes cis,cis-[R₂Pt(μ-SMe₂)(μ-dppm)PtMe₂], 1a and 2a, or cis,cis-[R₂Pt(μ-SMe₂)(μ-dppm)Pt{(CH ₂)₄}], 1b and 2b, respectively. Complexes 1a and 2a were also prepared by reaction of [Pt₂Me₄(μ-SMe₂)₂] with [PtR₂(dppm)]. The unsymmetrical complex cis,cis-[Me₂Pt(μ-SMe₂)(μ-dppm)Pt{(CH ₂)}₄] (3b) was prepared by the same method using [Pt{(CH₂)₄}(dppm)] and [Pt₂Me₄(μ-SMe₂)₂]. The symmetrical complex cis,cis-[Me₂Pt(μ-SMe₂)(μ-dppm)PtMe₂] (3a) was prepared by reaction of [Pt₂Me₄(μ-SMe₂)₂] with either one equivalent of dppm or [PtMe₂(dppm)]. The complexes 2 and 3 reacted with MeI to give the unsymmetrical diplatinum(IV) complexes fac,fac-[R₂MePt(μ-I)₂(μ-dppm)PtMeR′ ₂] (4a, R=R′=Me; 4b, R=Me, R′₂=(CH₂)₄; 5a, R=p-MeC₆H_4, R′=Me; 5b, R=p-MeC₆H_4, R′₂=(CH₂)₄). The reactions probably occurred by a S_N2-type mechanism and the entering Me groups stereoselectively remained in the equatorial positions (Pt-P taken as axial direction), unless for fac-PtMe₃ moiety that Me scrambling was taken place. Reaction of cis,cis-dialkyl-dialkyl diplatinum(II) complexes 3 with one equivalent of dppm gave bis(dppm-bridged) complexes cis,cis-[R₂Pt(μ-dppm)₂PtR′₂] (6a, R=R′=Me; 6b, R=Me, R′₂=(CH₂)₄). The complexes were fully characterized using multinuclear (¹H-, ¹³C{¹H}-, ³¹P{¹H}-, ¹⁹⁵Pt{¹H}-) NMR spectroscopy.

Full text of DOI:10.1016/S0022-328X(01)01057-9

Journal of Organometallic Chemistry 633 (2001) 105–113
www.elsevier.com/locate/jorganchem
Unsymmetrical organodiplatinum(II) and organodiplatinum(IV)
complexes containing bis(diphenylphosphino)methane as bridging
ligand: general approaches for synthesis and characterization by
multinuclear NMR studies
Mehdi Rashidi *, Sirous Jamali, Majid Hashemi
Department of Chemistry, College of Sciences, Shiraz Uni6ersity, Shiraz 71454, Iran
Received 17 April 2001; accepted 30 May 2001
Abstract
Reaction of cis-[PtR2(SMe2)2] (R=Ph or p-MeC6H4) with [PtMe2(dppm)] or [Pt{(CH2)4}(dppm)] (dppm=Ph2PCH2PPh2) gave
the unsymmetrical cis,cis-diaryl-dialkyl diplatinum(II) complexes cis,cis-[R2Pt(m-SMe2)(m-dppm)PtMe2], 1a and 2a, or cis,cis-
[R2Pt(m-SMe2)(m-dppm)Pt{(CH2)4}], 1b and 2b, respectively. Complexes 1a and 2a were also prepared by reaction of [Pt2Me4(m-
SMe2)2] with [PtR2(dppm)]. The unsymmetrical complex cis,cis-[Me2Pt(m-SMe2)(m-dppm)Pt{(CH2)}4] (3b) was prepared by the
same method using [Pt{(CH2)4}(dppm)] and [Pt2Me4(m-SMe2)2]. The symmetrical complex cis,cis-[Me2Pt(m-SMe2)(m-dppm)PtMe2]
(3a) was prepared by reaction of [Pt2Me4(m-SMe2)2] with either one equivalent of dppm or [PtMe2(dppm)]. The complexes 2 and
3 reacted with MeI to give the unsymmetrical diplatinum(IV) complexes fac,fac-[R2MePt(m-I)2(m-dppm)PtMeR%2] (4a, R=R%=
Me; 4b, R=Me, R%2=(CH2)4; 5a, R=p-MeC6H4, R%=Me; 5b, R=p-MeC6H4, R2% =(CH2)4). The reactions probably occurred
by a SN2-type mechanism and the entering Me groups stereoselectively remained in the equatorial positions (PtꢀP taken as axial
direction), unless for fac-PtMe3 moiety that Me scrambling was taken place. Reaction of cis,cis-dialkyl-dialkyl diplatinum(II)
complexes 3 with one equivalent of dppm gave bis(dppm-bridged) complexes cis,cis-[R2Pt(m-dppm)2PtR2%] (6a, R=R%=Me; 6b,
R=Me, R%2=(CH2)4). The complexes were fully characterized using multinuclear (1H-, 13C{1H}-, 31P{1H}-, 195Pt{1H}-) NMR
spectroscopy. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Platinum; Organodiplatinum(II); Organodiplatinum(IV)
1. Introduction
cases metal–metal bonds are present as well [3,4]. Un-
common anionic dinuclear platinum(II) complexes with
general formula [NBu4][(C6F5)2Pt(m-X)(m-dppm)Pt-
(C6F5)2] and a corresponding neutral complex [(C6F5)2-
Pt(m-SC4H8)(m-dppm)Pt(C6F5)2] have recently been
synthesized and structurally characterized [5,6]. Also a
simple route has been developed recently to synthesize a
series of diplatinum(II) complexes of general formula
It is well known that two metals kept in close prox-
imity could react cooperatively with substrate molecules
and thus there has been a great interest in developing
ligand systems able to lock two metals in such a
position [1,2]. In this regard there has been a great
interest in bis(diphenylphosphino)methane (dppm=
Ph2PCH2PPh2) as a versatile ligand which usually
bridges two metal centers forming homo or hetero-
binuclear complexes, although there are cases in which
it acts as a chelate or a monodentate ligand [3,4]. Most
platinum complexes that contain dppm acting as bridg-
ing ligand contain M2(m-dppm)2 units, and in many
cis,cis-[Ar2Pt(m-SMe2)(m-dppm)PtAr%], in which Ar and
2
Ar% are identical or different aryl ligands Ph, p-
MeC6H4, m-MeC6H4 or p-MeOC6H4 [7]. These uncom-
mon complexes each contain two neutral bridging
ligands, a dppm and a dimethylsulfide. It has been
shown in the present study that the route could be
extended to synthesize corresponding unsymmetrical
cis,cis-diaryl-dialkyl or cis,cis-dialkyl-dialkyl diplatinu-
m(II) complexes with general formula cis,cis-[R2Pt(m-
* Corresponding author. Fax: +98-71-20027.
E-mail address: rashidi@chem.susc.ac.ir (M. Rashidi).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01057-9

106
M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
SMe2)(m-dppm)PtR%] (1–3). These are expected to be
tions trans to I and Me group on the same platinum
center occupies the position trans to phosphorus, is
possible, only the indicated isomer 4b was formed. The
known complex 4a has been prepared by the reaction of
[Pt2Me4(m-SMe2)2] with MeI followed by the addition
of dppm [8]. The diaryl-dialkyl complexes 2a or 2b
reacted with neat MeI at 0 °C and gave organodiplat-
inum(IV) complexes 5a or 5b, respectively, only with
the isomeric forms shown, although other isomeric
forms are possible.
2
interesting in the sense that while a bridging dppm
group holds the dinuclear integrity, the other labile
bridging group, SMe2, could create an interesting chem-
istry. Thus in this article, oxidative addition of MeI to
the diplatinum(II) complexes, which is accompanied by
displacement of SMe2, has been shown to be a suitable
general route to organodiplatinum(IV) complexes of
general
formula
fac,fac-[MeR2Pt(m-I)2(m-dppm)-
PtMeR%] (4 and 5). Also, where R and R% are alkyl
2
groups, the organodiplatinum(II) complexes undergo
reaction with dppm to displace SMe2 and present a new
route to bis(dppm-bridged)diplatinum(II) complexes,
[R2Pt(m-dppm)2PtR%].
2
2. Results and discussion
2.1. Synthesis of organodiplatinum(II) complexes
containing dppm and SMe2 as bridging ligands
The reaction of dialkyl complexes [PtMe2(dppm)] or
[Pt{(CH2)4}(dppm)] with diaryl complexes cis-[PtR2-
(SMe2)2], R=Ph or p-MeC6H4, gave unsymmetrical
cis,cis-diaryl-dialkyl diplatinum(II) complexes 1a and
2a or 1b and 2b, respectively. The dimethyl complexes
1a and 2a were also prepared by reaction of [Pt2Me4(m-
SMe2)2] with two equivalents of the corresponding di-
aryl complexes [PtR2(dppm)].
When reactions were carried out at higher tempera-
tures, e.g. room temperature, considerable decomposi-
tion took place. For the reactions of complexes 2 one
clear decomposition product in both cases was [Pt(p-
MeC6H4)2MeI(dppm)] as confirmed by the 31P{1H}-
NMR data [9]. Also, complex 5b when dissolved in
CDCl3 was, to some extent, converted to some uniden-
tified compounds. Deuterium labeling studies using
1
CD3I (see H-NMR data in Section 2.3) suggest that in
these reactions, CD3I reacts in a SN2-type manner,
whereby the metal centers in complexes 2 and 3 (shown
by the general formula cis,cis-[R2Pt(m-SMe2)(m-
dppm)PtR%]) attack the carbon atom of CD3I to afford
2
the transient cationic dinuclear intermediate of the type
[CD3R2Pt(m-SMe2)(m-dppm)PtR%CD3]2+. The anions
2
I− then enter the coordination spheres from the trans
positions of attacking CD3 followed by the displace-
ment of SMe2 to form the platinum(IV) complexes 4
and 5. When R or R% are Me groups, the scrambling of
CD3 and Me groups takes place in the fac-
trimethylplatinum moiety, whereas when R is p-
The cis,cis-dimethyl-dimethyl complex 3a was pre-
pared by the reaction of [Pt2Me4(m-SMe2)2] with either
two equivalents of [PtMe2(dppm)] or one equivalent of
dppm. The dimethylplatinum-platinacycle complex 3b
was prepared by reaction of [Pt2Me4(m-SMe2)2] with
two equivalents of [Pt{(CH2)4}(dppm)]. The above re-
actions were carried out at room temperature in
CH2Cl2 or C6H6 for several hours.
MeC6H4 or R% is (CH2)4, the scrambling of CD3 group
2
is ceased by steric effects or ring constraints, respec-
tively, and the entering CD3 groups remain in the
equatorial positions (PtꢀP taken as axial direction). The
studies are consistent with the stereoselective formation
of complexes 4b and 5a exclusively with the indicated
less symmetrical isomers. Also on this basis, it is not
surprising to observe that the Me groups remain in the
equatorial positions in complex 5b to exclusively form
the indicated isomer.
2.2. Reactions of the organodiplatinum(II) complexes
The reactions of the dialkyl-dialkyl diplatinum(II)
complexes 3a or 3b with MeI in CH2Cl2 and at 0 °C
gave organodiplatinum(IV) complexes 4a or 4b, respec-
tively. Although for 4b a more symmetrical isomer, in
which two ring a-carbon atoms coordinate the posi-

M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
107
When dialkyl–dialkyl complexes 3 reacted with one
2.3. Characterization of complexes
equivalent of dppm, bis(dppm-bridged) complexes 6
were formed by displacement of SMe2. The symmetrical
diplatinum(II) complexes 6a or [{Pt{(CH2)4}(m-
dppm)}2] have been prepared [10,11] by reaction of
[Pt2Me4(m-SMe2)2] or [{Pt{(CH2)4}(m-SEt2)}2] with two
equivalents of dppm. We believe that in these reactions,
3a or [{Pt{(CH2)4}}2(m-SEt2)(m-dppm)], respectively,
should have been formed as intermediates.
The complexes were fully characterized using multin-
uclear (1H-, 13C{1H}-, 31P{1H}-, 195Pt{1H}-) NMR
spectroscopy (Tables 1–4) and microanalysis (Table 5).
2.3.1. Organodiplatinum(II) complexes 1–3
In the 31P{1H}-NMR spectra of each of the unsym-
metrical complexes 1 and 2 (Fig. 1a), the two phospho-
rus atoms are inequivalent, appeared as two doublet
signals, and showed short-range as well as long-range
coupling platinum satellites. The first signal has
1
parameters (l around 13–15; JPPt$1800 Hz and
Table 1
1H-NMR data for diplatinum(II) complexes 1–3, diplatinum(IV) complexes 4, 5 and bis(dppm-bridged)diplatinum(II) complex 6b in CDCl3
a
Complex
SMe2
dppm
PtꢀCH3 (trans to
P)
PtꢀCH3 (trans to
SMe2)
CH2 protons of platinacycle
ring
X b
l(CH3) (3JPtH
)
l(CH2) (2JPH
,
l(CH3) (3JPtH
2JPH
,
l(CH3) (2JPtH
3JPH
,
l(CH2)
l(CH3)
3JPtH
)
)
)
c
1a
1b
2a
2b
3a
3b
1.65 (19.0)
1.97 (17.8)
1.84 (19.2)
1.91 (18.1)
2.38 (19.3)
2.38 (18.3)
3.2 (7.5,
)
0.01 (66.2, 7.2)
–
0.19 (66.5, 7.2)
–
0.15 (66.0, 7.5)
0.35 (66.2, 10.2)
0.28 (86.4, 9.1)
–
0.45 (87.3, 9.1)
–
0.19 (85.5, 9.1)
0.4 (86.9, 7.0)
–
–
–
c
3.49 (7.3,
3.38 (7.5,
3.43 (7.3,
3.17 (8.7, 17.9)
3.15 (8.4, 17.5)
)
)
)
1.04–1.75
–
0.96–1.67
–
1.1–1.8
c
c
2.00, 2.06
2.02, 2.10
–
–
PtꢀCH3 (trans to I) PtꢀCH3 (trans to P)
l(CH3) (2JPtH l(CH3) (2JPtH
3JPH 3JPH
2.1 (6H) (61.5, 8.5)
,
,
)
)
4a
4b
–
–
5.0 (2H) (c)
0.92 (12H) (74.5,
7.0)
–
–
–
4.0 (1H), 4.7 (1H) 0.8 (3H) (74.5, 7.4) 2.0 (3H) (60.2, 7.3) 3.8 (1a-H) (2J(PtH)=97)
(c)
1.1 (6H) d (77.9,
Other protons 1–2.6 m
7.3)
5a
5b
–
–
4.6 (1H), 5.0 (1H) 0.4 (3H) (73.2, 7.6) 1.9 (3H) (59.4, 7.6)
1.9
2.1
(c)
1.1 (3H) (75.1, 7.5)
1.3 (3H) d (72.4,
7.4)
4.9 (1H), 5.4 (1H) 1.6 (3H) (77.2, 7.6)
–
–
4.4 (1a-H) (2J(PtH)=92)
Other protons 1–3 m
2.4
2.5
(c)
1.77 (3H) (73.8,
6.6)
PtꢀCH3 (trans to
PtꢀCH3 (trans to
PA)
PC)
l(CH3) (2JPtH
,
l(CH3) (2JPtH
,
3JPH
2.7 (2H), 4.2 (2H) −0.28 (3H) (70.2,
(c)
8.9)
)
3JPH
0.67 (3H) (68.7, 8.1) 0.5–2 (separated signals)
)
6b e
–
–
a Appeared as a quintet with a relative intensity 1:8:18:8:1.
b CH3 substitution on aryl ligands.
c Not resolved.
d Intensity (3H) was lost when the diplatinum(IV) complex was prepared from CD3I. The relative intensities of Me groups on fac-PtMe2(CD3)
moiety of course remained 1:1:1 due to scrambling of different methyl groups.
e At −60 °C, using a Bruker Avance DRX 500 MHz NMR spectrometer. The data at room temperature: l=3.96 and 2.69 (CH2 of dppm);
l=0.1 (very broad, methyl groups); l=0.5–2 (very broad, platinacycle ring protons).

Table 2
13C{1H}-NMR data for diplatinum(II) complexes 1–3, diplatinum(IV) complex 4b and bis(dppm-bridged)diplatinum(II) complex 6b in CDCl3
Complex
SMe2
dppm
PtCHa2orPtCH3
PtCHa2orPtCH3
PtCH2b (trans to PtCHb2 (trans to C1ofAr a (trans C1ofAr a (trans to X b
(trans to P)
(trans to SMe2)
P)
SMe2)
to P)
SMe2)
l(CH2) l(CH2), (1JPC
)
l(CH2) or
l(CH2) or l(CH3),
l(CH2), (2JPtC
,
l(CH2), (2JPtC
,
l(C1), (1JPtC
,
l(C1), (1JPtC
,
l(CH3)
l(CH3), (1JPtC
,
(1JPtC
,
2JPC
)
3JPC
)
3JPC
)
2JPC
)
2JPC
)
2JPC
)
1a
1b
2a
2b
3a
3b
24.3
25.0
24.3
25.0
25.3
25.1
22.8 (15)
22.8 (17)
22.8 (15)
22.8 (15)
21.7 (14)
21.0 (14)
7.0 (661, 106)
36.9 (701, 94)
7.0 (661, 106)
36.8 (701, 94)
7.2 (634, 106)
−4.5 (748, 4)
28.6 (777, 3)
−4.5 (747, 4)
–
–
163.9 (896, 116) 145.1 (1044, 8)
163.8 (920, 116) 154.6 (1116, 8)
159.7 (908, 117) 140.5 (1060, 8)
159.5 (917, 117) 141.0 (1041, 8)
–
–
/
38.6 (31, 14)
–
38.8 (31, 14)
–
37.7 (32, 13)
34.7 (55, 5)
–
34.6 (56, 5)
–
33.5 (54, 5)
21.4, 21.6
21.0, 21.3
–
–
28.5 (784, 3)
c
−5.1 (737,
)
–
–
–
–
6.3 d (660, 106)
36 e (700, 94)
−5.9 d (740, 4)
27.4 e (780, 3)
a-CH2 (trans to
a-CH2 (trans to I)
b-CH2 (trans to b-CH2 (trans to PtꢀCH3 (trans to I)
PtꢀCH3 (trans to
P)
P)
I)
P)
l(CH2), (1JPtC
,
l(CH2), (1JPtC
)
l(CH2), (1JPtC
,
l(CH2), (2JPtC
,
l(CH3), (1JPtC
)
l(CH3), (1JPtC
,
f
f
2JPC
)
3JPC
)
3JPC
)
2JPC
10.6 (520, 123)
)
4b
–
35.9 (11)
28.5
39.9 (533, 108)
44.6 (663)
36.5 (19, 12)
35.5 (30, 6)
13.4 (654)
10.1 (657)
8.7 (721)
a-CH2
b-CH2
PtꢀCH3
l(CH3)
l(CH2) (1JPtC
,
l(CH2)
633
2JPC
40.5 (658, 90)
)
)
6b g
37
10.4
105
a C1 is aryl carbon directly attached to Pt.
b X is CH3 substitution on aryl ligands.
c Not resolved.
1
d PtꢀCH3 group.
e PtꢀaCH2 group.
f 2
J
not resolved.
PC
g The data at −60 °C (using a Bruker Avance DRX 500 MHz NMR spectrometer) are: the two Me carbons were appeared at l(CH3)=8.5 (2JPC=100 Hz) and l=11.8 (2JPC=100 Hz);
other signals were not resolved due to low intensity.

M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
109
Table 3
31P{1H}-NMR data for diplatinum(II) complexes 1–3, diplatinum(IV) complexes 4, 5 and bis(dppm-brigded)diplatinum(II) complex 6b in CDCl3
Complex
P (phosphorus trans to aryl)
P (Phosphorus trans to alkyl)
2JPP
l(P), (1JPtP,3JPtP
)
l(P), (1JPtP,3JPtP
)
1a
2a
3a
1b
2b
3b
13.3 (1801, 23)
13.0 (1798, 24)
22.3 a (1879, 38)
22.0 a (1879, 38)
17.5 a (1896, 29)
21.3 b (1807, 29)
21.1 b (1805, 37)
18.2 a (1887, 31)
17.4 b (1819, 31)
47
47
50
51
51
53
–
c
14.6 (1800,
)
14.4 (1798, 26)
–
4a d
4b
–
–
−21.9 a (1056, –)
−19.3 a (1069, –)
−19.1 b (1006, –)
−20.6 a (1104, –)
−21.6 b (1037, –)
–
15
5a
5b
−19.8 (996, –)
−19.6 (991, –)
6
9
Phosphorus trans to methyl
l(PA)
Phosphorus trans to CH2 of metallacycle
l(PC)
l(PB)
l(PD)
(1JPtP
(2JPDPC
(2JPDPB
6.1
(1810)
(1JPtP
(2JPAPB
(2JPAPC
5.8
(1864)
)
(1JPtP
)
(1JPtP
)
)
)
)
(2JPCPD
)
)
(2JPBPA
)
)
)
)
(2JPCPA
(2JPBPD
6b e
11.5
(1815)
12.5
(1807)
(43)
(10)
(44)
(11)
(43)
(11)
(45)
(10)
a Trans to CH3 group.
b Trans to CH2 group of platinacycle ring.
c Not resolved.
d Taken from Ref. [8].
e At −60 °C.
3JPPt$25 Hz) close to those found in aryldiplatinu-
due to coupling with the adjacent inequivalent platinum
atom through the bridging SMe2 ligand.
m(II) complexes cis,cis-[Ar2Pt(m-SMe2)(m-dppm)PtAr%]
2
In the 13C{1H}-NMR spectra of dimethyl complexes
1a and 2a, in each case, the two methyl groups which
are attached to the same platinum center are inequiva-
and therefore was assigned to the phosphorus atom of
dppm which is connected to the R2Pt (R=aryl) moiety
[7]. The second signal (around l=21–22) was assigned
1
to the dialkyl Pt moiety. This has a JPtP value of 1879
Hz for complexes 1a and 2a (where alkyl is Me) which
is higher than the JPtP value of 1806 Hz for complexes
Table 4
195Pt{1H}-NMR data for diplatinum(II) complexes 2 and 3, diplatini-
um(IV) complexes 4b, 5, and bis(dppm-bridged)diplatinum(II) com-
plex 6b in CDCl3
1
1b and 2b (where dialkyl is (CH2)4). This difference,
although modest, could be due to chelating (CH2)4
ligand in the latter that exerts a significantly higher
trans influence than the methyl group [12,13].
Complex
Pt (attached to aryls) Pt (attached to alkyls) JPtPt
l(Pt),(1JPtP 3JPtP l(Pt), (1JPtP 3JPtP
In the 31P{1H}-NMR spectrum of 3b, the two in-
equivalent phosphorus atoms appeared as an AB pat-
,
)
,
)
2a
2b
3a
3b
−4535 (1788, 43)
−4529 (1788, 43)
−4612 a (1863, 32)
−4705 b (1798, 32)
−4642 (1885, –)
143
150
–
1
tern, and as expected the JPtP for the phosphorus trans
1
to methyl group is higher than the JPtP for the phos-
–
–
−4636 a (1894, 32)
−4734 b (1820, 32)
−3935 a (1060, –)
−4015 b (996, –)
−3975 a (1104, –)
−4050 b (1038, –)
−49 143 a (1831, –)
−4964 b (1820, –)
150
phorus trans to CH2 group of platinacycle. The two
equivalent phosphorus atoms in the symmetrical com-
plex 3a resonated as a singlet and showed short-range
as well as long-range coupling platinum satellites.
The 195Pt{1H}-NMR spectra of the typical complexes
2 and 3b each contains two doublet of doublets signals
4b
–
5a
−3371 (996, –)
−3360 (996, –)
–
–
–
–
5b
6b c
1
due to the two inequivalent platinum atoms with JPtP
values close to the values obtained from the 31P{1H}-
NMR data described above. Also, each signal is accom-
a Attached to Me group.
b Attached to CH2 group of platinacycle.
2
panied by platinum satellites with JPtPt around 150 Hz
c At −60 °C.

110
M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
Table 5
SMe2 signal appeared at the usual chemical shift of
l=2.38. In the spectra of dimethyl complexes 1a–3a
and 3b, two signals in the region l=0–0.4 were as-
Characterization data for diplatinum complexes 1–6
Complex
Yield (%)
Melting
Elemental analysis b (%)
signed to Me group trans to phosphorus atom (2JPtH
=
point a(°C)
3
ca. 66 Hz, JPH=ca. 7.4 Hz) and Me group trans to
C
H
3
SMe2 (2JPtH=ca. 86 Hz, JPH=9.1Hz). For metallacy-
1a
1b
2a
2b
3a
3b
4b
5a
5b
6b
90
88
92
89
82
74
80
75
70
85
145
160
142
162
170
135
215
155
165
205
47.7 (48.2)
48.7 (49.3)
48.6 (49.2)
49.5 (50.2)
41.7 (41.5)
42.7 (42.9)
34.3 (34.4)
40.6 (40.6)
41.8 (41.6)
53.8 (54.0)
4.3 (4.3)
4.4 (4.4)
4.6 (4.5)
4.6 (4.6)
4.4 (4.4)
4.4 (4.5)
3.6 (3.6)
4.0 (3.8)
3.8 (4.0)
4.7 (4.6)
a Decomposed.
b Found (calculated).
lent. Thus, the carbon atoms trans or cis to phosphorus
appeared at l=7 (2JPC(trans)=106 Hz) and l= −4.5
(2JPC(cis)=4 Hz), respectively. Also, 1JPtC for the carbon
atom trans to phosphorus atom is about 87 Hz lower
than 1JPtC for the carbon atom trans to SMe2 due to the
higher trans influence of phosphorus over sulfur. In the
13C{1H} spectra of the metallacycle complexes 1b and
2b again two signals with similar coupling patterns were
observed for the two inequivalent a-CH2Pt groups of
the platinacycle ring. Also, in these complexes two
signals at l 38.6 and l 34.7 were assigned to the two
inequivalent b-CH2 groups of ring trans to phosphorus
3
(2JPtC=31 Hz and JPC=14 Hz) and cis to phosphorus
3
(2JPtC=55 Hz and JPC=5 Hz), respectively. The aryl
carbon atoms attached directly to the platinum center
in R2Pt moiety of complexes 1 and 2, appeared further
downfield from the other aromatic carbons and showed
that the two aryl groups are inequivalent. Thus, the
carbon atoms trans or cis to phosphorus atom gave
2
2JPC(trans)=116 Hz and JPC(cis)=8 Hz, respectively. As
1
expected, the JPtC for the carbon atom trans to the
1
phosphorus atom is some 150 Hz lower than the JPtC
for the carbon atom trans to SMe2.
The unsymmetrical complex 3b contains both PtMe2
and Pt{(CH2)4} moieties and therefore its 13C{1H}-
NMR spectrum contained signals expected for these
moieties with similar coupling patterns as discussed
above for complexes 1 and 2. Similarly the 13C{1H}-
NMR spectrum of the symmetrical complex 3a confi-
rmed that the two Me groups attached to the same
platinum atom are inequivalent.
1
In the H-NMR spectra of each of the diaryl–dialkyl
complexes 1 and 2, a quintet with relative intensity
1:8:18:8:1 was observed, which is characteristic of SMe2
acting as bridging ligand between platinum centers, but
with the unusual chemical shift l=1.65–1.94 [7,8].
However, for dialkyl–dialkyl complexes 3, the bridging
Fig. 1. 31P{1H}-NMR spectra (202.5 MHz) of: (a) cis,cis-[(p-
MeC6H4)2Pt(m-SMe2)(m-dppm)Pt{(CH2)4}] (2b); (b) [Me3Pt(m-I)2(m-
dppm)Pt{(CH2)4}Me] (3b); and (c) [Me2Pt(m-dppm)2Pt{(CH2)4}] (6b)
at −60 °C.

M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
111
1
cle complexes 1b–3b, the ring protons appeared as
broad multiplets around l=1–1.8. For complexes 2,
the Me substituted aryl ligands attached to the same
platinum center, gave two Me resonances which further
confirmed the inequivalency of the aryl ligands.
The H-NMR spectra of the unsymmetrical diplatin-
um(IV) complexes 4b and 5 each gave two broad
multiplets around l=5 for the two nonequivalent CH2
groups of bridging dppm. For 4b, the three Me groups
2
trans to I were appeared around l=1 with JPtH ca. 75
Based on the above results, as originally described
Hz, while the Me group trans to the phosphorus atom
appeared around l=2 with a lower JPtH value of 60.1
2
for
diaryl–diaryl
complexes
[Ar2Pt(m-SMe2)(m-
dppm)PtAr%] [7], structure and fluxionality mechanism
Hz. One characteristic broad signal at high chemical
2
2
given in Eq. (1) is suggested for complexes 1–3. This
leads to equivalence of the two Me groups on sulfur
atom and also the two CH2 protons of dppm, while the
two organic ligands attached to the same platinum
center remain inequivalent.
shift of l=3.83 with JPtH=97 Hz was observed for
one proton of one of the a-CH2 groups of metallacycle
ring, and the other ring protons appeared as broad
peaks around l=1–2.6. The data for complex 5a
indicated three resonances for Me groups trans to I and
one resonance for the Me group trans to phosphorus
atom, and the inequivalency of the aryl ligands was
confirmed by the observation of two singlets for the
(1)
1
methyl substituents. Similarly, the H-NMR data for
complex 5b confirmed the isomeric form shown as the
sole product. The 2/1 ratio of (Me trans to I)/(Me trans
1
to P) in the H-NMR spectrum of 4a was also observed
1
in the H-NMR spectrum of the corresponding com-
2.3.2. Organodiplatinum(IV) complexes 4b and 5
plex formed from CD3I and this confirms that the
methyl groups on the fac-Me3Pt unit scramble. The
changes observed for complexes 4b and 5a upon using
CD3I are indicated in the footnote of Table 1.
In the 31P{1H}-NMR spectra of the unsymmetrical
complexes 4b and 5 (Fig. 1b) in each case, the two
phosphorus atoms are inequivalent, appeared as an AB
pattern around l ca. −20, and showed short-range
coupling platinum satellites (1JPtP) while the long-range
2.3.3. Bis(dppm-bridged)diplatinum(II) complex 6b
Based on the multinuclear NMR data (see below), as
originally described for complex 6a [10] and then for
[{Pt{(CH2)4}(m-dppm)}2] [11], the structure and fluxion-
ality shown in Eq. (2) (Newman projection down PtPt
axis, a and a% represent non-equivalent Me groups while
b and b% indicate non-equivalent CH2 groups of platina-
cycle) was suggested for the unsymmetrical dimer 6b.
Thus, the eight-membered Pt2P4C2 dimetallacycle in the
static solution structure (at low temperatures) has the
twist–boat conformation which in contrast to the sym-
metrical dimers, e.g. 6a [10], does not possess the C2
symmetry. Therefore, in the low temperature 31P{1H}-
NMR spectrum (Fig. 1c), the four phosphorus atoms
are different and in fact four signals with the corre-
sponding platinum satellites were observed with the
expected [10,11] parameters. The fine structure of each
signal was lost at room temperature, however, due to
the fluxionality of the Pt2P4C2 skeleton which occurs
via a simple twisting motion going through a boat–
boat (saddle) intermediate [10].
coupling satellites (3JPtP) were not resolved. The JPtP
1
values are in the expected range of 990–1100 Hz and
are in agreement with the trans influence series p-
MeC6H4\CH2 of metallacycle ring\Me.
The 195Pt{1H}-NMR spectra of complexes 4b and 5
1
each contained two doublet signals with JPtP values
exactly as could be predicted from the 31P{1H}-NMR
data described above. However, in contrast to the
corresponding diplatinum(II) precursors 2 and 3b, no
platinum–platinum coupling was observed.
The 13C{1H}-NMR spectrum of 4b was more useful
for structure determination. The methyl group trans to
phosphorus atom occurred as a doublet at l=10.6
2
1
with trans coupling JPC=123 Hz and with JPtC=519
Hz. The other methyl resonances trans to I (having a
lower trans influence than phosphorus) occurred
1
around the same region as singlets with JPtC values
1
about 140 Hz more than the JPtC value for the Me
group trans to phosphorus atom and with no resolvable
cis coupling to phosphorus atom. The resonances for
a-CH2 and b-CH2 groups of the metallacycle ring were
appeared in the expected region of l=35–45 [12,13].
The a-CH2 group trans to phosphorus atom appeared
2
1
as a doublet with JPC=108 Hz and JPtC=533 Hz,
while the a-CH2 group trans to I had no observable cis
(2)
1
coupling to phosphorus atom and a higher JPtC value
of 662 Hz. Also, the data for the b-CH2 resonances
similarly confirmed the stereochemistry of the metalla-
cycle ring.

112
M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
[Pt{(CH2)4}(dppm)]; 3a, using [Pt2Me4(m-SMe2)2] with
The data has a good connectivity with the data
obtained from the 195Pt{1H}-NMR spectrum in which
two apparent triplet signals were observed for the two
inequivalent Pt atoms.
either dppm (one equivalent) or [PtMe2(dppm)] (two
equivalents) and stirring for 3 h; 3b, using [Pt2Me4(m-
SMe2)2] with [Pt{(CH2)4}(dppm)] (two equivalents) and
stirring for 3 h.
In the 1H-NMR spectrum at −60 °C, the two
nonequivalent Me groups were appeared at l= −0.28
(2JPtH=70.2 Hz and 3JPH=8.9 Hz) and l=0.67
(3JPtH=68.7 Hz and 3JPH=8.1 Hz) (these were col-
lapsed to a broad hump at l=0.14 at room tempera-
ture). Also, the ring protons appeared as separated
signals around l=0.5–2 and two broad multiplets
were observed for the CH2P2 protons.
3.2. [Me3Pt(v-I)2(v-dppm)Pt{(CH2)4}Me] (4b)
To a solution of 3b (100 mg, 0.11 mmol), in CH2Cl2
(20 ml) at 0 °C, was added excess MeI (2 ml) and the
reaction mixture was stirred for 3 h. The solvent and
excess of MeI was removed and residue was washed
twice with MeOH (2 ml).The white solid was dried in
vacuo.
In the 13C{1H}-NMR spectrum at room temperature,
the PtꢀaCH2 groups of the ring appeared as a doublet
1
at l=28.5 (2J(PC(trans)=89 Hz, J(PtC)=657 Hz). Also,
The compound 4a was prepared similarly using 3a.
a broad signal at l=10.4 was assigned to the Me
groups (which was split into two doublets at l=8.5
3.3. [Me3Pt(v-I)2(v-dppm)PtMe(p-MeC6H4)2] (5a)
(2JP C=100 Hz), and l=11.8 (2JP C=100 Hz) at
−60 °C, although the platinum satellites were not
resolved).
A
A
Compound 2a (200 mg) was dissolved in neat MeI (5
ml) at 0 °C and was stirred at this condition for 1.5 h.
The solvent was removed and the residue was washed
twice with MeOH (2 ml) and Et2O (2 ml). The white
solid was dried in vacuo.
3. Experimental
A similar procedure was followed to prepare com-
pound 5b from 2b.
The 31P{1H}- and 195Pt{1H}-NMR spectra were
recorded on a Bruker Avance DRX 500 MHz spec-
trometer. Unless otherwise stated, the 1H- and 13C{1H}-
NMR spectra were recorded on a Bruker Avance DPX
250 MHz spectrometer. References were TMS (1H- and
13C{1H}-NMR), 85% H3PO4 (31P{1H}-NMR), and
aqueous K2[PtCl4] (195Pt{1H}-NMR), and CDCl3 was
used as solvent in all cases. All the chemical shifts and
coupling constants are in ppm and Hz, respectively.
The complexes [PtR2(dppm)] and cis-[PtR2(SMe2)2] in
which R=Ph or p-MeC6H4, are prepared as previously
described [7]. The complexes [Pt{(CH2)4}(dppm)] [14],
[PtMe2(dppm)] [15] and [Pt2Me4(m-SMe2)2] [16], were
prepared by literature methods.
The
deuterated
complexes
[Me2CD3Pt(m-I)2-
(m-dppm)PtMe2CD3],
[Me2CD3Pt(m-I)2(m-dppm)Pt-
{(CH2)4}CD3] and [Me2CD3Pt(m-I)2(m-dppm)PtCD3(p-
MeC6H4)2] were made similarly in about 10 mg scale
using CD3I.
3.4. [Me2Pt(v-dppm)2Pt{(CH2)4}] (6b)
Compound 3b (200 mg, 0.22 mmol) and dppm (84.5
mg, 0.22 mmol) were dissolved in C6H6 (15 ml). After 2
h at r.t., the volume of the solution was reduced and
pentane was added to precipitate the product as a white
solid, which was recrystallized from CH2Cl2–pentane.
The compound 6a was made similarly using an
equimolar mixture of [Me2Pt(m-SMe2)(m-dppm)PtMe2]
(3a) and dppm.
3.1. cis,cis-[Ph2Pt(v-SMe2)(v-dppm)PtMe2] (1a)
A mixture of cis-[PtPh2(SMe2)2] (78 mg, 0.16 mmol)
and [PtMe2(dppm)] (100 mg, 0.16 mmol) in CH2Cl2 (20
ml) was stirred at room temperature (r.t.) for 8 h. The
solvent was removed, and the white residue was washed
twice with MeOH (2 ml) and dried in vacuo.
4. Conclusions
Diplatinum(II) complexes cis,cis-[R2Pt(m-SMe2)(m-
A similar procedure using [Pt2Me4(m-SMe2)2] (150
mg, 0.26 mmol) and [PtPh2(dppm)] (317 mg, 0.52
mmol) in C6H6 (15 ml) gave the same product.
dppm)PtR%] are prepared generally by the reaction of
2
diorgano monomer cis-[PtR2(SMe2)2] with diorgano
monomer [PtR%(dppm)]. The reaction of the diplatinu-
The following compounds were made similarly using
the appropriate precursors: 2a, using either an equimo-
lar mixture of cis-[Pt(p-MeC6H4)2(SMe2)2] and
[PtMe2(dppm)] or [Pt2Me4(m-SMe2)2] and [Pt (p-
MeC6H4)2(dppm)] (two equivalents); 1b and 2b, using
an equimolar mixture of cis-[PtR2(SMe2)2] and
2
m(II) complexes with MeI or dppm is accompanied by
the displacement of the labile ligand SMe2 and forma-
tion of diplatinum(IV) complexes fac, fac-[MeR2Pt(m-
I)2(m-dppm)PtMeR%] or diplatinum(II) complexes
2
cis,cis-[R2Pt(m-dppm)2PtR%], respectively.
2

M. Rashidi et al. / Journal of Organometallic Chemistry 633 (2001) 105–113
113
[7] M. Rashidi, M. Hashemi, M. Khorasani-Motlagh, R.J. Pud-
dephatt, Organometallics 19 (2000) 2751.
Acknowledgements
[8] M. Rashidi, Z. Fakhroeian, R.J. Puddephatt, J. Organomet.
Chem. 406 (1991) 261.
[9] F.S.M. Hassan, D.M. McEwan, P.G. Pringle, B.L. Shaw, J.
Chem. Soc. Dalton Trans. (1985) 1501.
We thank the Shiraz University Research Council,
Iran (Grant. No. 78-SC-1277-670) for financial support
and Professor Firouzabadi for his help in equiping
parts of our computer facility.
[10] L.M. Muir, K.W. Muir, A.A. Frew, S.S.M. Ling, M.A. Thom-
son, R.J. Puddephatt, Organometallics 3 (1984) 1637.
[11] M. Rashidi, A.R. Esmaeilbeig, N. Shahabadi, S. Tangestanine-
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[12] S. Tangestaninejad, M. Rashidi, R.J. Puddephatt, J. Organomet.
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[13] M. Rashidi, N. Shahabadi, A.R. Esmaeilbeig, M. Joshaghani,
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[14] P.G. Pringle, B.J. Shaw, J. Chem. Soc. Dalton Trans. (1984)
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