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M. Hashemi, M. Rashidi / Journal of Organometallic Chemistry 690 (2005) 982–989
phosphoros atoms. A signal at d = 22.6 (1J(PC) = 16
Hz) was assigned to the CH2 carbon of dppm. Two sig-
nals were clearly assigned to the two different carbons of
Me ligands. The first signal due to Me group trans to
phosphoros atom was appeared at d = 6.9 with
the CH2 protons of the platinacycle moiety appeared
around d = 0.90–2.4.
The H NMR spectra of the fluxional analogs 3g–3j
1
(Table 5) were more clear-cut. A signal around d 1.8
was assigned to the Me groups of SMe2 ligands. For
the dimethyl analogs 3g and 3i, in each case, a signal
2
1J(PtC) = 661 Hz and J(PC) = 106 Hz. The second sig-
2
3
nal appeared at d = ꢁ4.5 and was assigned to Me group
close to d 0.1 with J(PtH) = 66.4 Hz and J(PH) = 7.4
Hz was assigned to the Me ligand trans to phosphoros
and the signal for Me ligand trans to SMe2 was appeared
1
trans to SMe2, which has a higher J(PtC) value of 748
Hz due to the higher trans influence of phosphoros li-
gand compared to SMe2 ligand. As expected, this signal
2
has a cis coupling to phosphoros with a J(PC) value of
only 4 Hz.
2
at d = 0.38 (for 3g) or 0.27 (for 3i) with a J(PtH) value
of 86.5 Hz (for 3g) or 84.9 Hz (for 3i) and J(PH) = 9.1
3
Hz. As expected on the basis of the higher trans influ-
ence of phosphine compared to SMe2, the 2J(PtH) value
for the Me ligand trans to SMe2 is some 30% higher
The metallacycle analog cis,cis-[(m-MeC6H4)2Pt(l-
SMe2)(l-dppm)Pt{(CH2)4}], 3h, was similarly assigned,
except that the two different CHa2 carbon atoms of plati-
nacycle moiety were appeared at d = 36.8 (trans to phos-
phoros, with 1J(PtC) = 700 Hz and 2J(PC) = 93 Hz) and
2
than the J(PtH) value for Me ligand trans to the phos-
phoros atom. The CH2 protons of the platinacycle
moiety appeared as overlapping of multiplets around
d = 0.90–1.69.
1
at d = 28.6 (trans to SMe2, with J(PtC) = 768 Hz and
no observable coupling to the cis phosphoros). The
1J(PtC) value for CHa2 carbon atoms of platinacycle in
1
3h is 20–39 Hz larger than the J(PtC) values for Me
3. Experimental
groups in3g and this reflects the higher donor ability
of CH2 groups of the metallacycle compared to Me
groups[6,8]. The signals for the different CHb2 carbons
of the platinacycle were appeared at d = 38.5
(2J(PtC) = 32 Hz and 3J(PC) = 14 Hz, for CHb2 trans
to phosphoros) and at d = 34.7 (2J(PtC) = 56 Hz and
3J(PC) = 5 Hz, for CH2b trans to SMe2). The other flux-
ional molecules 3i and 3j were similarly assigned.
1
The H and 13C NMR spectra were recorded on a
Bruker Avance DPX 250 MHz spectrometer. 31P and
195Pt spectra were recorded on a Bruker Avance DRX
500 MHz. References were TMS (1H and 13C), H3
PO4 (31P), and aqueous K2PtCl4 (195Pt), and CDCl3
was used as solvent in all cases. All the chemical shifts
and coupling constants are in ppm and Hz, respectively.
The monomeric precursors cis-[PtR2 (SMe2)2],
R = Ph,p-MeC6H4, m-MeC6H4 and p-MeOC6H4 were
made by the known methods [5,10,11]. The complex
cis-[Pt(o-MeC6H4)2 (SMe2)2] was prepared as follows:
In a typical experiment, a freshly prepared solution of
o-MeC6H4 Li (10 mL of 1 M solution in diethylether)
(prepared from o-MeC6H4 Br and Li metal) was added
slowly to a stirred, ice-cold solution of [PtCl2 (SMe2)2]
(500 mg; 1.25 mmol) in dry ether (20 mL) under Ar
atmosphere. The reaction mixture was stirred for 2 h
at 0 °C and subsequently hydrolyzed with a few mL
saturated solution of NH4Cl in water. Separation of or-
ganic layer, extraction with ether, and evaporation of
solvent gave a mixture of cis-[Pt(o-MeC6H4)2 (SMe2)2]
and [Pt2(o-MeC6H4)4(l-SMe2)2]. The white residue was
treated with SMe2 (1 mL) in CH2Cl2 (20 mL) in order
to convert the coexisted dimeric species into the mono-
mer. The solvent was evaporated and the residue was
washed with a few mL of dry ether. Yield 58%;
1
In the H NMR spectrum of cis,cis-[Ph2Pt(l-SMe2)-
(l-dppm)Pt(o-MeC6H4)2], 3a, Table 4, four signals each
having the appearance of a quintet with relative inten-
3
sity 1:8:18:8:1 with a J(PtH) value close to 19 Hz were
observed. Although some of the peaks were overlapped,
these quintets are characteristic of SMe2 acting as bridg-
ing ligand between platinum centers, but with unusual
chemical shift d = 1.52–1.76 [5,10]. Thus, each of the iso-
mers X or Y gives two signals for Mea and Meb protons
of SMe2 ligand. The CH2 protons of dppm ligand in
both isomers were overlapped and appeared at d = 3.3.
As expected, two signals at d = 1.98 and 2.12 for isomer
X and two signals at d = 2.29 and 2.39 for isomer Y were
assigned to the different ortho-methyl substituents on
o-MeC6 H4 ligands. Other similar non-fluxional com-
plexes 3b–3d were assigned similarly.
For the non-fluxional di-o-MeC6H4, dimethyl–diplat-
inum analog 3e (Table 5), the signals for Me groups of
SMe2 ligands were mostly overlapped. For the Me li-
gand trans to phosphoros in isomer X, a signal at
1
m.p. = 160 °C (d); H NMR (CDCl3): d = 2.27 (broad,
12 H, SMe2), 2.8 (s, 12 H, ArCH3), 7.5 (s, JPtH = 70.4
Hz, ortho H of Ar), 6.8 (m, the other H of Ar); 13C
NMR (CDCl3): d = 21 (SMe2), 27.6 (ArCH3), 145.8
(1JPtC = 1116, C1 of Ar), 141.3, 135.5, 128.6, 124.7,
123.2 (the other C of Ar groups).
2
3
3
d = ꢁ0.01 with J(PtH) = 66.7 Hz and J(PH) = 6.7 Hz
was observed. For isomer Y, this signal appeared at
3
d = 0.10 with J(PH) = 6.8 Hz and no resolvable plati-
num satellites. The Me ligand trans to SMe2 for both
isomers was overlapped and appeared at d = 0.21 with
3
2J(PtH) = 86.8 Hz and J(PH) = 8.8 Hz. In the metalla-
cycle analog 3f, the overlapping was more extensive and
The dppm containing monomers [PtPh2(dppm)],
[Pt(p-MeC6H4)2(dppm)], [Pt(m-MeC6H4)2 (dppm)],
Hashemi, Majid
