Oxidative addition of some mono, di or tetra haloalkanes to organoplatinum(II) complexes

Article abstract of DOI:10.1016/j.jorganchem.2011.11.018

Dimethylplatinum(II) complexes [PtMe₂(NN)] {NN = bpy (2,2′-bipyridine), phen (1,10-phenanthroline) or bu₂bpy (4,4′-di-tert-butyl-2,2′-bipyridine)} were reacted with alkyl halides (RX = EtI or EtBr, NN = bu₂bpy; RX = ⁿ

Full text of DOI:10.1016/j.jorganchem.2011.11.018

Journal of Organometallic Chemistry 700 (2012) 83e92
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Journal of Organometallic Chemistry
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Oxidative addition of some mono, di or tetra haloalkanes to organoplatinum(II)
complexes
,
b
a
c
d
Badri Z. Momeni a , Mehdi Rashidi , Mohammad M. Jafari , Brian O. Patrick , Alaa S. Abd-El-Aziz
*
a Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran 15418, Iran
b Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
c Department of Chemistry, Faculty of Science, The University of British Columbia, Vancouver, BC, Canada V6T 1Z1
d Department of Chemistry, University of Prince Edward Island, Charlottetown, PEI, Canada C1A 4P3
a r t i c l e i n f o
a b s t r a c t
Dimethylplatinum(II) complexes [PtMe2(NN)] {NN ¼ bpy (2,20-bipyridine), phen (1,10-phenanthroline) or
bu2bpy (4,40-di-tert-butyl-2,20-bipyridine)} were reacted with alkyl halides (RX ¼ EtI or EtBr, NN ¼ bu2bpy;
RX ¼ nBuBr, NN ¼ bpy; RX ¼ CHPh2Br, NN ¼ bpy, phen, or bu2bpy) to yield the Pt(IV) complexes
[PtMe2RX(NN)]. On the basis of NMR data, the Pt(IV) product of each reaction contains almost exclusively
the kinetic trans isomer, and only in a few cases, very small traces of the thermodynamic cis isomers are
Article history:
Received 12 October 2011
Received in revised form
5 November 2011
Accepted 15 November 2011
observed. The binuclear complexes [Pt2Me4Br2{
m
-(CH2)2}(NN)2] (NN ¼ bpy, phen) were obtained from
Keywords:
Platinum
Kinetic
Oxidative addition
Spectroscopy
Crystal structure
reaction of [PtMe2(NN)] with 1,2-dibromoethane. Notably, the mononuclear complex fac-[PtMe3Br(bpy)],
obtained as a byproduct during the reaction of [PtMe2(bpy)] with 1,2-dibromoethane, was characterized
by X-ray crystallography from the reaction of [PtMe2(bpy)] with 1,2-dibromoethane. On the other hand,
the reaction of [PtMe2(bu2bpy)] with 1,2-dibromoethane resulted in formation of the mononuclear
complex trans-[PtMe2Br{(CH2)2Br}(bu2bpy)]. The reaction of [PtMe2(NN)] with 1,2-bis(dibromomethyl)
xylene in a 1:1 or 2:1 mol ratio afforded the mononuclear complexes [PtMe2(CHBr-o-C6H4CHBr2)Br(NN)]
(NN ¼ bpy, phen, or bu2bpy) or binuclear complexes [Pt2Me4Br2{ -o-(CHBr)2C6H4}(NN)2] (NN ¼ bpy, or
m
phen), respectively. Finally, 1,3-dibromobutane was oxidatively added to the organoplatinum(II)
complexes [PtR2(NN)] (R2 ¼ (CH2)4, NN ¼ bpy, or phen; R ¼ Me; NN ¼ bpy) via an SN2 mechanism from the
less sterically hindered CeBr side to yield the complexes trans-[PtR2Br{(CH2)2CHBrCH3}(NN)]. The prod-
ucts were fully characterized by 1H and 13C NMR spectroscopy and elemental analysis. The platinacycle
complex [Pt(CH2)4(bpy)] was shown to react faster, as compared to the dimethyl analogue complex
[PtMe2(bpy)], by a factor of 3.8e4.2. The reactions of [Pt(CH2)4(bpy)] or [Pt(CH2)4(phen)] with 1,3-
dibromobutane were faster as compared to those with 1,4-dibromobutane, due to the activation effect
of the platinum.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
dimethylplatinum(II) or platinacyclopentane complexes including
diimine ligands have been investigated [8e11]. The kinetic studies
Oxidative addition reactions are recognized as a fundamental
step in many catalytic processes [1]. The synthetic chemistry of
alkylplatinum(IV) compounds containing nitrogen ligands have
been thoroughly studied [2e7]. In these reactions, the electron rich
platinum center attacks alkyl halides usually by an SN2 mechanism,
however, there are a few reactions which proceed by a radical
mechanism or concerted three-center addition [1,2]. Bimolecular
have shown that the metal has an activating effect on the carbon-
halide bond [12e14]. The oxidative addition methodology has
been useful in synthesizing the first alkyl transition metal oligo-
mers and polymers [15]. Halogenoalkyl complexes of transition
metals are classified as the functionalized alkyl complexes of
transition metals [16]. These complexes can be precursors for the
preparation of homo and heteronuclear complexes [17e19]. A
common synthetic route to halogenoalkyl complexes involves the
oxidative addition of polyhalogenoalkanes to a lower valence of
transition metal complex; however these types of oxidative addi-
tion reactions have not been studied as thoroughly as those
involving monohaloalkanes [16,20]. There are some reported
binuclear platinum complexes each containing a bridging (CH2)n
oxidative addition reactions of SN2 type involving addition of a,u-
dibromoalkanes and a variety of alkyl bromides and iodides to
* Corresponding author. Tel.: þ98 21 22850266; fax: þ98 21 22853650.
E-mail address: momeni@kntu.ac.ir (B.Z. Momeni).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.11.018

84
B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
group [10,17,18]. For example, reaction of the platinum(II)
complexes [PtMe2(phen)] or platinacycles [Pt(CH2)4(NN)]
(NN ¼ bpy, or phen) with 1,2-diiodoethane or 1,2-dibromoethane
has been shown to give binuclear complexes of platinum(IV) con-
2.3. Synthesis of [PtMe2EtBr(bu2bpy)], 5
Following the same procedure as the synthesis of 4, this was
prepared using [PtMe2(bu2bpy)] (80 mg, 0.16 mmol) and an excess
of ethyl bromide (1 mL). Yield: 80%; m.p. 158e160 ꢀC (dec.). Anal.
Calc. for C22H35BrN2Pt: C, 43.86; H, 5.86; N, 4.65. Found: C, 43.06; H,
taining m-(CH2)2 group [10,17]. Oxidative addition methodology has
also been used to synthesize the binuclear platinum(IV) complexes
containing bridging substituted xylendiyl or bipyridyl groups. In
these reactions, the bromoalkyl groups incorporate as a substituent
to the xylene or bipyridine ligand [18,19,21e23]. These compounds
have higher thermal stability relative to the binuclear complexes
5.74; N, 4.54%. NMR data in CDCl3: d
(1H) (trans isomer) 1.44 (s, 18H,
tBu), 1.34 [s, 6H, 2J(PtH)
¼
70.4 Hz, Pt-Me], 0.15 [t, 3H,
3J(PtH) ¼ 67.3 Hz, 3J(HH) ¼ 7.5 Hz, CH3 group of Et], 1.41 [m, 2H,
3J(HH)
¼
7.4 Hz, Pt-CH2]; bu2bpy protons: 7.60 (dd, 2H,
containing
m-(CH2)n groups [22]. The electron rich platinum(II)
3J(HH) ¼ 5.6 Hz, 4J(HH) ¼ 1.5 Hz, H5), 8.12 (d, 2H, 4J(HH) ¼ 1.6 Hz,
H3), 8.81 (d, 2H, 3J(HH) ¼ 6.0 Hz, H6); Resolved 1H NMR data for cis
isomer: 0.49 [s, 3H, 2J(PtH) ¼ 75.1 Hz, Pt-Me], 0.55 [s, 3H,
complexes of formula [PtMe2(NN)], where NN is a diimine ligand
such as 2,20-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,40-
bis-tert-butyl-2,20-bipyridine (bu2bpy), are particularly suitable for
investigation of the oxidative addition reactions because they have
high reactivities and are deeply colored that are changed to color-
less during oxidation of Pt(II) to Pt(IV) [9,24]. This paper describes
the chemistry of some new iodo-alkyl and bromo-alkyl complexes
of organoplatinum(IV). The kinetics of reactions of plati-
nacyclopentane(II) complexes with 1,3-dibromobutane were also
studied in order to investigate the electronic and steric effects on
the formation of organoplatinum(IV) complexes; the results are
compared with that involving the corresponding dimethylplati-
num(II) complex.
2J(PtH) ¼ 75.6 Hz, Pt-Me];
d(
13C) (trans isomer) 30.4 (s, terminal C of
tBu), 35.5 (s, central C of tBu), ꢁ4.0 [s, 1J(PtC) ¼ 714 Hz, Pt-Me], 13.1
[s, 1J(PtC) ¼ 689 Hz, Pt-CH2], 15.3 [s, 2J(PtC) ¼ 40 Hz, CH3 group of
Et]; bu2bpy carbons: 163.1 (C2), 119.7 (C3), 154.9 (C4), 124.0 (C5),
146.6 (C6); Resolved 13C NMR data for cis isomer: ꢁ5.4 [s,
1J(PtC) ¼ 683 Hz, Pt-CH3], 6.9 [s, 1J(PtC) ¼ 677 Hz, Pt-Me].
2.4. Synthesis of [PtMen2BuBr(bpy)], 6
Once again following the same procedure as the preparation of
4, the reaction of [PtMe2(bpy)] (80 mg, 0.21 mmol) and n-butyl
bromide (0.5 mL) in acetone (40 mL) gave a pale yellow solid using
CH2Cl2/hexane. Yield: 80%; m.p. 160 ꢀC (dec.). Anal. Calc. for
C16H23BrN2Pt: C, 37.07; H, 4.47; N, 5.40. Found: C, 36.70; H, 4.41; N,
2. Experimental
2.1. General remarks
5.50%. NMR data in CDCl3: d
(1H) (trans isomer) 1.37 [s, 6H,
2J(PtH) ¼ 70.2 Hz, Pt-Me], 1.33 [m, 2H, Pt-CH2], 0.97 [m, 2H,
PtCH2CH2], 0.48 [m, 2H, CH2CH3], 0.53 [t, 3H, 3J(HH) ¼ 7.3 Hz, CH3];
bpy protons: 7.59 (m, 2H, 3J(HH) ¼ 6.0 Hz, H5), 7.97 (t, 2H,
3J(HH) ¼ 7.9 Hz, 4J(HH) ¼ 1.1 Hz, H4), 8.22 (d, 2H, 3J(HH) ¼ 8.1 Hz,
All procedures were performed under an atmosphere of argon.
Diethyl ether was distilled over sodium/benzophenone ketyl and
dichloromethane was distilled over P2O5. All other reagents were
used without further purification. Elemental analyses were per-
formed by Heraous CHNeO or PerkineElmer 2400 II elemental
analyzers. NMR data were recorded using a Bruker Avance DPX 250
or a DRX 500 spectrometer. All the chemical shifts and coupling
H3), 8.89 (m, 2H, H6);
d
(
13C) ꢁ3.3 [s, 1J(PtC) ¼ 688 Hz, Pt-Me], 20.1
[s, 1J(PtC) ¼ 686 Hz, Pt-C1], 23.8 [s, 2J(PtC) ¼ 89 Hz, Pt-C2], 32.8 [s,
3J(PtC) ¼ 31 Hz, Pt-C3], 13.7 [s, Pt-C4]; bpy carbons: 154.9 (C2), 123.6
(C3), 138.8 (C4), 126.7 (C5), 147.0 (C6).
constants are reported in ppm and Hz, respectively. The 1H and 13
C
NMR spectra are reported relative to TMS as an external reference.
The kinetic studies were carried out using a Philips PU 8675 Vis
spectrometer, with the temperature controlled by an external
circulator. The complexes [PtMe2(NN)] (NN ¼ bpy, phen, or bu2bpy)
and [Pt(CH2)4(NN)] (NN ¼ bpy, or phen) were prepared according
to the literature [8,10,25,26].
2.5. Synthesis of [PtMe2(CHPh2)Br(bpy)], 7
To a solution of [PtMe2(bpy)] (60 mg, 0.16 mmol) in acetone
(20 mL) was added bromodiphenylmethane (400 mg, 1.62 mmol).
The reaction mixture was stirred for 4 h after which a pale yellow
solution had developed. The solvent was removed at reduced
pressure and the residue was solidified using CH2Cl2/n-hexane to
give a pale yellow solid. Yield: 65%; m.p. 165e167 ꢀC (dec.). Anal.
Calc. for C25H25BrN2Pt. CH2Cl2: C, 43.77; H, 3.81; N, 3.93. Found: C,
2.2. Synthesis of [PtMe2EtI(bu2bpy)], 4
To a solution of [PtMe2(bu2bpy)] (80 mg, 0.16 mmol) in acetone
(30 mL) was added a large excess of ethyl iodide (1 mL). The reaction
mixture was stirred for 2 h after which a pale yellow solution had
developed. The solvent was removed at reduced pressure, leaving
a pale yellow solid. This was solidified using CH2Cl2/n-hexane
solution. Yield: 85%; m.p. 157e159 ꢀC (dec.). Anal. Calc. for
C22H35IN2Pt: C, 40.68; H, 5.43; N, 4.31. Found: C, 39.85; H, 5.14; N,
44.03; H, 3.63; N, 4.51%. NMR data in acetone.d6: d
(1H) (trans
isomer) 1.71 [s, 6H, 2J(PtH) ¼ 71.7 Hz, Pt-Me], 4.99 [s, 1H, 2J(PtH) not
resolved, Pt-CHPh2]; 6.79 and 7.06 [m, Ph groups]; bpy protons 7.81
(t, 2H, 3J(HH) ¼ 6.4 Hz, 4J(HH) ¼ 1.1 Hz, H5), 8.16 (t, 2H,
3J(HH) ¼ 7.8 Hz, 4J(HH) ¼ 1.6 Hz, H4), 8.44 (d, 2H, J(HH) ¼ 8.4 Hz,
3
H3), 9.06 (d, 2H, 3J(HH) ¼ 5.3 Hz, H6); Resolved 1H NMR data for cis
isomer: 0.48 [s, 3H, 2J(PtH) ¼ 73.8 Hz, Pt-Me], 1.35 [s, 3H,
2J(PtH) ¼ 70.3 Hz, Pt-Me], 5.60 [s, 1H, 2J(PtH) not resolved, Pt-
4.27%. NMR data in CDCl3: d
(1H) (trans isomer) 1.45 (s,18H, tBu),1.52
[s, 6H, 2J(PtH) ¼ 72.3 Hz, Pt-Me], 0.04 [t, 3H, 3J(PtH) ¼ 68.8 Hz,
3J(HH) ¼ 7.1 Hz, CH3 group of Et], 1.42 [m, 2H, 3J(HH) ¼ 7.5 Hz, Pt-
CH2]; bu2bpy protons: 7.59 (dd, 2H, 3J(HH) ¼ 5.2 Hz, 4J(HH) ¼ 1.0 Hz,
H5), 8.12 (d, 2H, 4J(HH) ¼ 1.8 Hz, H3), 8.84 (d, 2H, 3J(HH) ¼ 6.0 Hz,
H6); Resolved 1H NMR data for cis isomer: 0.62 [s, 3H,
CHPh2];
d
(
13C) in CDCl3 (trans isomer) ꢁ5.2 [s, 1J(PtC) ¼ 677 Hz, Pt-
Me], 87.3 [s, Pt-CHPh2]; 122.8e154.8 [m, Ph groups]; Resolved 13C
NMR data for cis isomer: ꢁ5.9 [s, 1J(PtC) ¼ 521 Hz, Pt-Me], ꢁ1.9 [s,
1J(PtC) not resolved, Pt-Me].
2J(PtH) ¼ 74.1 Hz, Pt-Me], 0.59 [s, 3H, 2J(PtH) ¼ 74.1 Hz, Pt-Me];
2.6. Synthesis of [PtMe2(CHPh2)Br(phen)], 8
t
d(
13C) (trans isomer) 30.0 (s, terminal C of Bu), 35.0 (s, central C
of tBu), ꢁ4.3 [s, 1J(PtC) ¼ 555 Hz, Pt-Me],19.6 [s, 1J(PtC) ¼ 676 Hz, Pt-
Following the same procedure as for the preparation of 7, this
was prepared from complex [PtMe2(phen)] (60 mg, 0.15 mmol) and
bromodiphenylmethane (360 mg, 1.46 mmol). Yield: 50%; m.p.
174e176 ꢀC (dec.). Anal. Calc. for C27H25BrN2Pt. 0.5 CH2Cl2: C, 47.53;
CH2], 14.4 [s, 2J(PtC) ¼ 198 Hz, CH3 group of Et]; bu2bpy carbons:
162.7 (C2), 119.4 (C3), 154.4 (C4), 123.6 (C5), 146.5 (C6); Resolved 13
C
NMR data for cis isomer: ꢁ5.4 [s, 1J(PtC) ¼ 526 Hz, Pt-Me].

B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
85
H, 3.77; N, 4.03. Found: C, 46.76; H, 3.66; N, 4.58%. NMR data in
C22H34Br2N2Pt: C, 38.78; H, 5.03; N, 4.11. Found: C, 37.97; H, 4.79; N,
t
CDCl3:
d
(1H) (trans isomer) 2.01 [s, 6H, 2J(PtH) ¼ 71.0 Hz, Pt-Me],
3.99%. NMR data in CD2Cl2: d
(1H) (trans isomer) 1.43 (s, 18H, Bu),
4.89 [s, 1H, 2J(PtH) not resolved, Pt-CHPh2], 6.49 [d, 4H,
3J(HH) ¼ 7.2 Hz, ortho hydrogens of Ph groups], 6.92 [t, 4H,
3J(HH) ¼ 7.7 Hz, meta hydrogens of Ph groups], 7.00 [t, 2H,
3J(HH) ¼ 7.3 Hz, Para hydrogens of Ph groups]; phen protons: 7.82
0.73 [s, 6H, 2J(PtH) ¼ 70.8 Hz, Pt-Me], 1.41 [s, 2H, 2J(PtH) ¼ not
resolved, PtCH2], 3.69 [br s, 2H, CH2Br]; bu2bpy protons: 7.60 (d, 2H,
3J(HH) ¼ 5.2 Hz, H5), 8.18 (s, 2H, H3), 8.54 (d, 2H, 3J(HH) ¼ 5.8 Hz,
H6);
d(
13C) 30.1 (s, terminal C of tBu), 35.4 (s, central C of
(m, 2H, 3J(HH)
¼
6.4, H3), 7.85 (s, 2H, H5), 8.33 (dd, 2H,
tBu), ꢁ5.0 [s, 1J(PtC) ¼ 710 Hz, Pt-Me], 24.3 [t, 1J(PtC) ¼ 617 Hz,
Pt-CH2]; bu2bpy carbons: 163.4 (C2), 120.0 (C3), 154.9 (C4), 123.9
(C5), 146.3 (C6).
3J(HH) ¼ 8.1 Hz, 4J(HH) ¼ 1.3 Hz, H4), 9.31 (dd, 2H, 3J(HH) ¼ 4.9 Hz,
4J(HH) ¼ 1.2 Hz, H2); Resolved 1H NMR data for cis isomer: 0.58 [s,
3H, 2J(PtH) ¼ 74.8 Hz, Pt-Me], 1.59 [s, 3H, 2J(PtH) ¼ 70.3 Hz, Pt-Me],
5.85 [s, Pt-CHPh2];
d
(
13C) (trans isomer) ꢁ2.5 [s, 1J(PtC) ¼ 622 Hz,
2.11. Synthesis of [PtMe2(CHBr-o-C6H4CHBr2)Br(bpy)], 14
Pt-Me], 87.1 [s, PtCHPh2]; 124.9e146.8 [m, Ph and phen carbons];
Resolved 13C NMR data for cis isomer: ꢁ5.8 and ꢁ6.9 [s, 1J(PtC) not
resolved, Pt-Me].
To a solution of [PtMe2(bpy)] (55 mg, 0.14 mmol) in acetone
(10 mL) was added 1,2-bis(dibromomethyl)benzene (59 mg,
0.14 mmol). The solution color changed from orange to yellow and
the reaction mixture was stirred for 24 h. The solvent was removed
at reduced pressure, leaving a yellow residue which was crystal-
lized from CH2Cl2/diethyl ether to give a pale yellow solid. Yield:
85%, m.p. 145e147 ꢀC. Anal. Calc. for C20H20Br4N2Pt: C, 29.91; H,
2.7. Synthesis of [PtMe2(CHPh2)Br(bu2bpy)], 9
To a solution of [PtMe2(bu2bpy)] (51 mg, 0.10 mmol) in acetone
(5 mL) was added bromodiphenylmethane (247 mg, 1.00 mmol).
The solution color changed from orange to yellow and the reaction
mixture was stirred for 3 h. The solvent was then removed under
reduced pressure and the resulting residue was layered with
diethyl ether and stored in the refrigerator overnight. The product,
a light brown solid, was filtered off and washed with n-pentane.
Yield: 80%; m.p. 112e114 ꢀC. Anal. Calc. for C33H41BrN2Pt: C, 53.51;
H, 5.58; N, 3.78. Found: C, 52.41; H, 5.34; N, 3.72%. NMR data in
2.51; N, 3.49. Found: C, 30.61; H, 2.63; N, 4.09%. NMR data: d
(1H) in
CDCl3 (trans isomer) 1.43 [s, 6H, 2J(PtH) ¼ 69.7 Hz, Pt-Me], 1.82 [s,
1H, 2J(PtH) ¼ 68.5 Hz, PtCHBr], 5.60 [s, 1H, 5J(PtH) ¼ 48.0 Hz,
CHBr2]; (the other conformation of trans isomer as a minor
product) 0.55 [s, 3H, 2J(PtH) ¼ 74.9 Hz, Pt-Me], 2.17 [s, 3H,
2J(PtH) ¼ 77.4 Hz, Pt-Me], 1.98 [s, 1H, 2J(PtH) ¼ 66.7 Hz, PtCHBr],
6.30e7.21 [m, Ph protons], 7.55e9.11 [m, bpy protons]; Resolved 1H
NMR signals for the both conformations of the cis isomers as
a minor product: 0.48 [s, 3H, 2J(PtH) not resolved, Pt-Me], 1.35 [s,
3H, 2J(PtH) ¼ 72.8 Hz, Pt-Me], 1.56 [s, 2J(PtH) ¼ 68.4 Hz, Pt-Me], 1.60
[s, 2J(PtH) ¼ 68.6 Hz, Pt-Me], 2.43 [s, 1H, 2J(PtH) not observed,
CDCl3:
d
(1H) (trans isomer) 1.40 (s, 18H, tBu), 1.83 [s, 6H,
2J(PtH) ¼ 70.0 Hz, Pt-Me], 4.93 [s, 1H, 2J(PtH) not resolved, Pt-
CHPh2], 6.77 [d, 4H, 3J(HH) ¼ 7.4 Hz, ortho hydrogens of Ph groups],
7.07 [m, other hydrogens of Ph groups]; bu2bpy protons: 7.57 (d, 2H,
3J(HH) ¼ 5.4 Hz, H5), 7.88 (s, 2H, H3), 8.92 (d, 2H, 3J(HH) ¼ 5.6 Hz,
PtCHBr],
d(
13C) in DMSO.d6: (both conformations of the trans
H6);
d(
13C) (trans isomer) 30.4 (s, terminal C of tBu), 35.4 (s, central C
isomer) ꢁ3.2 [s, 1J(PtC) ¼ 579 Hz, Pt-Me], 0.8 [s, 1J(PtC) ¼ 646 Hz, Pt-
Me], 3.9 [s, 1J(PtC) ¼ 534 Hz, Pt-Me], 32.1 [s, 1J(PtC) ¼ 887 Hz,
PtCHBr], 30.8 [s, 1J(PtC) not resolved, PtCHBr], 37.8 [s, CHBr2], 41.1
[s, CHBr2], 123.9e154.7 [m, bpy and Ph groups].
of tBu), ꢁ2.2 [s, 1J(PtC) ¼ 626 Hz, PtMe], 86.9 [s, Pt-CHPh2];
119.5e146.7 [m, Ph and bu2bpy carbons].
2.8. Synthesis of [Pt2Me4Br2{m-(CH2)2}(bpy)2], 10
2.12. Synthesis of [PtMe2(CHBr-o-C6H4CHBr2)Br(phen)], 15
To a solution of [PtMe2(bpy)] (55 mg, 0.14 mmol) in acetone
(10 mL) was added a large excess of 1,2-dibromoethane (0.3 mL).
The solution color changed from orange to yellow. The reaction
mixture was then stirred for 24 h. The product, a white solid, was
filtered off and washed with diethyl ether. Yield: 70%, m.p.
225e227 ꢀC (dec.). Anal. Calc. for C26H32Br2N4Pt2: C, 32.85; H, 3.39;
N, 5.89. Found: C, 32.97; H, 3.26; N, 5.75%. The remaining yellow
solution was reduced in volume to 0.5 mL and then solidified with
diethyl ether. The solution was filtered off and the resulting solu-
Following the same procedure as for the preparation of complex
14, this was prepared using [PtMe2(phen)] (100 mg, 0.25 mmol)
and 1,2-bis(dibromomethyl)benzene (104 mg, 0.25 mmol). Yield:
85%, m.p. 148e150 ꢀC. Anal. Calc. for C22H20Br4N2Pt: C, 31.95; H,
2.44; N, 3.39. Found: C, 32.94; H, 2.62; N, 3.95%. NMR data in CDCl3:
d
(1H) (trans isomer) 1.72 [s, 3H, 2J(PtH) ¼ 68.8 Hz, Pt-Me], 1.97 [s,
3H, 2J(PtH) ¼ 70.0 Hz, Pt-Me], 2.31 [s, 1H, 2J(PtH) ¼ 71.3 Hz, Pt-
CHBr], 5.68 [s, 1H, 5J(PtH) ¼ 47.5 Hz, CHBr2], 5.78e7.66 [m, Ph
protons], 7.81e9.41 [m, phen protons]; Resolved 1H NMR for the
other conformation of trans isomer as a minor product: 1.58 [s, 3H,
2J(PtH) ¼ 70.2 Hz, Pt-Me], 1.74 [s, 3H, 2J(PtH) ¼ 68.7 Hz, Pt-Me], 2.52
[s, 1H, 2J(PtH) overlapped, PtCHBr]; Resolved 1H NMR for both
conformations of the cis isomer as a very minor product: 0.28 [s, 3H,
2J(PtH) ¼ 70.4 Hz, Pt-Me], 0.58 [s, 3H, 2J(PtH) ¼ 74.5 Hz, Pt-Me], 1.21
[s, 3H, 2J(PtH) ¼ 69.5 Hz, Pt-Me], 1.36 [s, 3H, 2J(PtH) ¼ 74.3 Hz, Pt-
tion was kept for
1 week to grow single crystals of fac-
[PtMe3Br(bpy)], 12, suitable for X-ray crystallographic study.
2.9. Synthesis of [Pt2Me4Br2{m-(CH2)2}(phen)2], 11
Following the same procedure as for the preparation of complex
10, this was prepared using [PtMe2(phen)] (80 mg, 0.20 mmol) and
1,2-dibromoethane (0.3 mL). Yield: 75%, m.p. 220e222 ꢀC (dec.).
Anal. Calc. for C30H32Br2N4Pt2: C, 36.08; H, 3.23; N, 5.61. Found: C,
36.59; H, 3.11; N, 5.58%.
Me];
d(
13C) (trans isomer) ꢁ2.8 [s, 1J(PtC) ¼ 652 Hz, Pt-Me], 2.6 [s,
1J(PtC) ¼ 644 Hz, Pt-Me], 31.3 [s, 1J(PtC) ¼ 880 Hz, Pt-CHBr], 38.7 [s,
CHBr2], 123.1e150.3 [m, Ph and phen carbons].
2.10. Synthesis of [PtMe2{(CH2)2Br}Br(bu2bpy)], 13
2.13. Synthesis of [PtMe2(CHBr-o-C6H4CHBr2)Br(bu2bpy)], 16
To a solution of [PtMe2(bu2bpy)] (100 mg, 0.20 mmol) in acetone
(20 mL) was added a large excess of 1,2-dibromoethane (0.6 mL).
The solution color changed from orange to yellow and the reaction
mixture was stirred for 2 h. The solvent was removed at reduced
pressure, leaving a yellow solid. This was solidified using CH2Cl2/
diethyl ether. Yield: 75%, m.p. 224e226 ꢀC (dec.). Anal. Calc. for
This was prepared using [PtMe2(bu2bpy)] (80 mg, 0.16 mmol)
and 1,2-bis(dibromomethyl)benzene (68 mg, 0.16 mmol). The
solution was stirred for 4 h. The solvent was removed at reduced
pressure, leaving a yellow residue. This was recrystallized from
dichloromethane/diethyl ether. Yield: 87%, m.p. 143e145 ꢀC. Anal.
Calc. for C28H36Br4N2Pt: C, 36.74; H, 3.96; N, 3.06. Found: C, 35.77;

86
B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
H, 4.49; N, 3.90%. NMR data in CDCl3:
d
(1H) (trans isomer) 1.39 (s,
Found: C, 36.09; H, 3.50; N, 4.31%. NMR data in CDCl3: d
(1H) (trans
9H, Bu), 1.50 (s, 9H, Bu); 1.46 [s, 3H, 2J(PtH) overlapped, Pt-Me],
isomer) 2.21 [m, 2H, 2J(PtH) ¼ 54.5 Hz, Pt-CHa2], 3.28 [m, 2H,
2J(PtH) ¼ 112.5 Hz, Pt-CH2a], 1.42 [m, 2H, Pt-CH2b], 1.56 [m, 2H, Pt-
CHb2], 1.61 [m, 2H, PtCH2], 0.95 [m, 2H, PtCH2CH2], 3.69 [m, 1H,
CHBr], 1.33 [d, 3H, 3J(HH) ¼ 6.6 Hz, CH3]; phen protons: 7.88 (m, 2H,
3J(HH) ¼ 8.3, H3), 7.98 (m, 2H, H5), 8.49 (d, 2H, H4), 9.12 (m, 2H, H2);
t
t
1.48 [s, 3H, 2J(PtH)
¼
60.8 Hz, Pt-Me], 1.79 [s, 1H,
2J(PtH) ¼ 67.4 Hz, PtCHBr], 5.60 [s, 1H, 5J(PtH) ¼ 48.8 Hz, CHBr2],
6.81e9.00 [m, bu2bpy and Ph protons];
30.1e36.0 [m, central and terminal
d
(
13C) (trans isomer)
of tBu], ꢁ2.5 [s,
C
1J(PtC) ¼ 646 Hz, Pt-Me], 2.4 [s, 1J(PtC) ¼ 570 Hz, Pt-Me], 38.9 [s,
CHBr2], 119.4e164.0 (m, bu2bpy and Ph carbons).
d
(
13C) (trans isomer) 26.5 [s, 1J(PtCa) ¼ 704 Hz, 2 Ca atoms of plat-
inacycle], 33.4 [s, 2J(PtCb) ¼ 17 Hz, 2 Cb atoms of platinacycle], 14.7
[s, 1J(PtC) ¼ 772 Hz, Pt-C1], 52.2 [s, 2J(PtC) ¼ 118 Hz, Pt-C2], 41.5 [s,
3J(PtC) ¼ 31 Hz, Pt-C3], 26.7 [s, Pt-C4]; phen carbons: 147.6 (C2),
125.6 (C3), 137.8 (C4), 128.0 (C5), 146.1 (C11), 131.0 (C12).
2.14. Synthesis of [Pt2Me4Br2{m-o-(CHBr)2C6H4}(bpy)2], 17
This was prepared using [PtMe2(bpy)] (100 mg, 0.26 mmol) and
1,2-bis(dibromomethyl)benzene (55 mg, 0.13 mmol). The solution
was stirred for 4 h. The solvent was removed at reduced pressure,
leaving a yellow residue. This was recrystallized from CHCl3/
hexane. Yield: 80%, m.p. 155e157 ꢀC. Anal. Calc. for C32H34Br4N4Pt2:
C, 32.45; H, 2.89; N, 4.73. Found: C, 31.84; H, 3.00; N, 5.26%. NMR
2.18. Synthesis of [PtMe2Br{(CH2)2CHBrCH3}(bpy)], 23
To a solution of [PtMe2(bpy)] (70 mg, 0.18 mmol) in acetone
(60 mL) was added an excess of 1,3-dibromobutane (1 mL). The
reaction mixture was stirred for 10 h during which time a pale
yellow solution developed. The solvent was removed and the pale
yellow residue was recrystallized from CH2Cl2/n-hexane. Yield:
70%; m.p. 95 ꢀC (dec.). Anal. Calc. for C16H22Br2N2Pt: C, 32.18; H,
3.71; N, 4.69. Found: C, 32.90; H, 3.61; N, 4.79%. NMR data in CDCl3:
data in CDCl3:
d
(1H) (trans, trans isomer) 1.59 [s, 6H,
2J(PtH) ¼ 68.2 Hz, Pt-Me], 2.16 [s, 6H, 2J(PtH) ¼ 70.0 Hz, Pt-Me], 1.65
[s, 2H, 2J(PtH) ¼ 67.0 Hz, PtCHBr], 7.63e8.96 [m, phen and Ph
protons]; Resolved 1H NMR data for trans, cis isomer as a minor
product: 0.54 [s, 3H, 2J(PtH) ¼ 70.2 Hz, Pt-Me], 0.65 [s, 3H,
2J(PtH) ¼ 71.2 Hz, Pt-Me].
d
(1H) (trans isomer) 1.38 [s, 6H, 2J(PtH) ¼ 69.8 Hz, Pt-Me], 1.81 [m,
2H, Pt-CH2], 1.03 [m, 2H, PtCH2CH2], 3.74 [m, 1H, CHBr], 1.38 [d, 3H,
CH3]; bpy protons: 7.64 (t, 2H, 3J(HH) ¼ 6.3 Hz, H5), 8.02 (t, 2H,
3J(HH) ¼ 7.5 Hz, H4), 8.23 (m, 2H, 3J(HH) ¼ 8.0 Hz, H3), 8.89 (d, 2H,
H6); Resolved 1H NMR data for cis isomer: 0.53 [s, 6H,
2J(PtH) ¼ 74.6 Hz, Pt-Me], 0.51 [s, 6H, 2J(PtH) ¼ 74.5 Hz, Pt-Me];
2.15. Synthesis of [Pt2Me4Br2{m-o-(CHBr)2C6H4}(phen)2], 18
This was prepared using [PtMe2(phen)] (100 mg, 0.25 mmol)
and 1,2-bis(dibromomethyl)benzene (52 mg, 0.12 mmol). Yield:
80%, m.p. 140e142 ꢀC. Anal. Calc. for C36H26Br4N4Pt2: C, 35.31; H,
2.14; N, 4.58. Found: C, 35.14; H, 2.64; N, 4.41%. NMR data in CDCl3:
d
(
13C) trans isomer ꢁ3.3 [s, 1J(PtC) ¼ 681 Hz, Pt-Me], 15.6 [s,
1J(PtC) ¼ 707 Hz, Pt-C1], 52.2 [s, 2J(PtC) ¼ 111 Hz, Pt-C2], 42.0 [s,
3J(PtC) ¼ 27 Hz, Pt-C3], 26.0 [s, Pt-C4]; bpy carbons: 155.2 (C2), 124.0
(C3), 139.4 (C4), 127.2 (C5), 147.3 (C6).
d
(1H) (trans, cis isomer) 1.58 [s, 6H, 2J(PtH) ¼ 70.3 Hz, Pt-Me], 0.57
2
[s, 3H, J(PtH) ¼ 74.9 Hz, Pt-Me], 2.31 [s, 3H, 2J(PtH) ¼ 71.6 Hz, Pt-
Me], 1.50 [s, 1H, 2J(PtH)
¼
68.7 Hz, PtCHBr], 1.74 [s, 1H,
2.19. Kinetic studies of the reactions of [Pt(CH2)4(NN)] (NN ¼ bpy,
2J(PtH) ¼ 70.0 Hz, PtCHBr], 7.64e9.27 [m, phen and Ph protons];
Resolved 1H NMR data for cis, cis isomer as a minor product: 0.51 [s,
3H, 2J(PtH) ¼ 75.5 Hz, Pt-Me], 1.36 [s, 3H, 2J(PtH) not resolved, Pt-
Me], 2.51 [s, 3H, 2J(PtH) not resolved, Pt-Me], 2.30 [s, 1H, 2J(PtH)
obscured, PtCHBr].
phen) with 1,3-dibromobutane
A solution of [Pt(CH2)4(bpy)] in acetone (3 mL, 4.88 ꢂ 10ꢁ4 M) in
a cuvette was thermostatted at 10 ꢀC and a known excess of 1,3-
dibromobutane was added using a syringe. After rapid stirring,
the absorbance at
l
¼ 480 nm was collected with time. The
2.16. Synthesis of [Pt(CH2)4Br{(CH2)2CHBrCH3}(bpy)], 21
absorbance-time curves were analyzed by pseudo-first order
methods. The final absorbance values (AN) were evaluated by
KezdyeSwinbourne equation (Eq. (1)), considering the first-order
To a solution of [Pt(CH2)4(bpy)] (200 mg, 0.49 mmol) in benzene
(50 mL) was added a large excess of 1,3-dibromobutane (2 mL). The
reaction mixture was stirred for 8 h. After filtration, the solvent was
removed and the orange residue recrystallized from CH2Cl2/diethyl
ether. Yield: 92%; m.p.167 ꢀC (dec.). Anal. Calc. for C18H24Br2N2Pt: C,
34.69; H, 3.88; N, 4.49. Found: C, 34.00; H, 3.71; N, 4.69%. NMR data
kinetic data at time t and a time
s
later [27].
ꢀ
ꢁ
s
s
Abst ¼ AbsN 1 ꢁ ek þ Abstþsek
(1)
Thus, the pseudo-first order rate constants (Kobs) were deter-
mined. A plot of Kobs versus [Br(CH2)2CHBrCH3] was liner (Fig.1) and
the slope gave the second-order rate constant. The same method
was used at other temperatures (20 ꢀC, 30 ꢀC, 40 ꢀC) and activation
parameters were obtained from Arrhenius and Eyring equations
(Eqs. (2)e(3) and Fig. 2) [28].
in CDCl3:
d
(1H) (trans isomer) 2.05 [m, 2H, 2J(PtH) ¼ 50.3 Hz, Pt-
CHa2], 3.11 [m, 2H, 2J(PtH) ¼ 107.3 Hz, Pt-CH2a], 1.35 [m, 2H, Pt-CHb2],
1.54 [m, 2H, Pt-CHb2], 1.60 [m, 2H, PtCH2], 1.04 [m, 2H, PtCH2CH2],
3.78 [m, 1H, CHBr], 1.42 [d, 3H, 2J(HH) ¼ 6.6 Hz, CH3]; bpy protons:
7.58 (t, 2H, 3J(HH) ¼ 6.4, H5), 8.02 (t, 2H, 3J(HH) ¼ 7.6, 4J(HH) ¼ 1.4,
H4), 8.22 (d, 2H, 3J(HH) ¼ 7.9, H3), 8.80 (d, 2H, H6);
d(
13C) (trans
isomer) 26.5 [s, 1J(PtCa) ¼ 704 Hz, 2 Ca atoms of platinacycle], 33.7
Ea
RT
[s, 2J(PtCb)
¼
16 Hz, 2
Cb atoms of platinacycle], 15.4 [s,
lnk2 ¼ lnA ꢁ
(2)
(3)
1J(PtC) ¼ 772 Hz, Pt-C1], 52.6 [s, 2J(PtC) ¼ 122 Hz, Pt-C2], 42.1 [s,
3J(PtC) ¼ 31 Hz, Pt-C3], 26.4 [s, Pt-C4]; bpy carbons: 154.8 (C2), 123.9
(C3), 138.7 (C4), 127.4 (C5), 149.2 (C6).
ꢂ
ꢃ
ꢂ
ꢃ
k2
T
kB
h
D
S#
D
H#
ln
¼ ln
þ
ꢁ
R RT
2.17. Synthesis of [Pt(CH2)4Br{(CH2)2CHBrCH3}(phen)], 22
In a similar way, the rate constants and activation parameters
were determined for the reaction of [Pt(CH2)4(phen)] (at
Following the same procedure as the preparation of 21, this was
prepared using [Pt(CH2)4(phen)] (180 mg, 0.42 mmol) and 1,3-
dibromobutane (1.1 mL) to give a yellow solid. Yield: 80%; m.p.
98e100 ꢀC. Anal. Calc. for C20H24Br2N2Pt: C, 37.11; H, 3.74; N, 4.33.
l
¼ 475 nm, 3 mL, 3.56 ꢂ 10ꢁ4 M) or [PtMe2(bpy)] (at
l
¼ 473 nm,
3 mL, 3.15 ꢂ 10ꢁ4 M) and the results are shown in Table 1. Similar
methods were used to study the reaction of [PtMe2(bpy)] with 1,4-
dibromobutane and the data are shown in Table 1.

B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
87
collected at a temperature of ꢁ183.0 ꢃ 0.1 ꢀC to a maximum 2
q
value of 55.9ꢀ. Data were collected in a series of
f
and
u
scans in
0.5ꢀ oscillations using 5.0 s exposures. The crystal-to-detector
distance was 40.00 mm. Of the 26 687 reflections that were
collected, 3335 were unique (Rint ¼ 0.059); equivalent reflections
were merged. Data were collected and integrated using the Bruker
SAINT [29] software package. The linear absorption coefficient,
m,
for Mo-K
a
radiation was 129.17 cmꢁ1. Data were corrected for
absorption effects using the multi-scan technique (SADABS) [30],
with minimum and maximum transmission coefficients of 0.515
and 0.679, respectively. The data were corrected for Lorentz and
polarization effects. The structure was solved by direct methods
[31]. All non-hydrogen atoms were refined anisotropically. All
hydrogen atoms were placed in calculated positions. The final cycle
of full-matrix least-squares refinement [32] on F2 was based on
3335 reflections and 157 variable parameters and converged
(largest parameter shift was 0.00 times its esd) with unweighted
and weighted agreement factors of (Eqs. (4)e(5):
.
X
h
X
R1
¼
jjFoj ꢁ jFcjj
jFoj ¼ 0:046
(4)
Fig. 1. Plots of first-order rate constants (103 kobs/sꢁ1) versus concentration of
a,u-
dibromoalkanes for the reaction of (a) [Pt(CH2)4(bpy] with 1,3-dibromobutane in
ꢀ
X
ꢀ
ꢁ ꢁ.
ꢀ
X
ꢀ
ꢁ ꢁi
2
2
1=2
acetone at T ¼ 40 ꢀC (b) [Pt(CH2)4(bpy] with 1,3-dibromobutane in acetone at T ¼ 30 ꢀ
C
wR2
¼
w Fo2 ꢁ Fc2
w Fo2
¼ 0:050
(5)
(c) Pt(CH2)4(phen] with 1,3-dibromobutane in acetone at T ¼ 10 ꢀC (d) [PtMe2(bpy]
with 1,4-dibromobutane in acetone at
T
¼
40 ꢀC (e) PtMe2(bpy] with 1,3-
dibromobutane in acetone at T ¼ 10 ꢀC.
The standard deviation of an observation of unit weight [33] was
1.00. The weighting scheme was based on counting statistics. The
maximum and minimum peaks on the final difference Fourier map
corresponded to 0.92 and ꢁ0.68 e Åꢁ3, respectively. Neutral atom
scattering factors were taken from Cromer and Waber [34].
Anomalous dispersion effects were included in Fcalc [35]; the
-8
-9
values for Df’ and Df" were those of Creagh and McAuley [36]. The
(a)
(b)
values for the mass attenuation coefficients were those of Creagh
and Hubbell [37]. All refinements were performed using the
SHELXL-97 [38] via the WinGX [39] interface. A summary of the
crystal data, experimental details and refinement parameters is
given in Table 2.
-10
-11
-12
-13
(c)
(d)
3. Results and discussion
3.1. Synthesis and characterization of the new organoplatinum(IV)
complexes
3.1
3.2
3.3
3.4
3.5
3.6
1000 / T (K-1)
Reactions of the complexes [PtMe2(NN)] {NN ¼ bu2bpy (1), bpy
(2), or phen (3)} with alkyl halides, RX, resulted in formation of the
yellow platinum(IV) complexes [PtMe2RX(NN)] {R ¼ Et, X ¼ I (4),
X ¼ Br (5); R ¼ nBu, X ¼ Br (6)}in good to high yields according to
Scheme 1. The new complexes were characterized unambiguously
by 1H and 13C NMR spectroscopy and elemental analysis. The
reactions proceeded almost exclusively with a trans addition of
alkyl halide, although on the basis of the NMR spectra, traces of the
cis isomers were also observed in the case of EtI or EtBr.
Fig. 2. Eyring plots for the reaction of (a) [Pt(CH2)4(phen)] with 1,3-dibromobutane (b)
[Pt(CH2)4(bpy)] with 1,3-dibromobutane (c) [PtMe2(bpy)] with 1,3-dibromobutane (d)
[PtMe2(bpy)] with 1,4-dibromobutane.
2.20. X-ray structure determination
A colourless prism crystal of C13H17N2PtBr, having approximate
dimensions of 0.03 ꢂ 0.10 ꢂ 0.10 mm, was mounted on a glass fiber.
All measurements were made on a Bruker APEX DUO diffractom-
The 1H NMR spectrum of complex [PtMe2EtI(bu2bpy)] (4) in
CDCl3 contains a singlet at
d
¼ 1.52 ppm that is flanked by plat-
inum satellites with 2J(PtH) ¼ 72.3 Hz. This singlet is assigned to
eter with graphite monochromated Mo-Ka radiation. The data were
Table 1
Second-order rate constants and activation parameters for the reaction of [Pt(CH2)4(NN)] (NN ¼ bpy, phen) or [PtMe2(bpy)] with 1,3-dibromobutane or 1,4-dibromobutane in
acetone.
Complex
a,
u-dibromoalkane
103 k2(10 ꢀC)
(L molꢁ1 sꢁ1
103 k2(20 ꢀC)
(L molꢁ1 sꢁ1
103 k2(30 ꢀC)
(L molꢁ1 sꢁ1
103k2(40 ꢀC)
Ea
D
Ss
(J molꢁ1 Kꢁ1
)
)
)
)
(L molꢁ1 sꢁ1
)
(kJ molꢁ1
)
[Pt(CH2)4(bpy)]
[Pt(CH2)4(phen)]
[PtMe2(bpy)]
[Br(CH2)2(CHBr)CH3]
[Br(CH2)2(CHBr)CH3]
[Br(CH2)2(CHBr)CH3]
[Br(CH2)4Br]
25.49 ꢃ 1.37
37.54 ꢃ 3.00
6.27 ꢃ 0.03
1.72 ꢃ 0.11
38.72 ꢃ 1.15
50.89 ꢃ 4.64
9.20 ꢃ 0.11
3.58 ꢃ 0.16
55.48 ꢃ 3.48
65.97 ꢃ 8.60
14.34 ꢃ 0.16
6.47 ꢃ 0.59
75.79 ꢃ 4.12
98.10 ꢃ 1.76
20.15 ꢃ 0.40
10.05 ꢃ 0.54
26.76 ꢃ 0.67
23.14 ꢃ 1.86
29.04 ꢃ 0.88
43.43 ꢃ 2.48
ꢁ188.97 ꢃ 2.00
ꢁ198.85 ꢃ 6.00
ꢁ192.76 ꢃ 3.00
ꢁ152.24 ꢃ 8.00
[PtMe2(bpy)]

88
B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
established by 1H and 13C NMR spectroscopy. NMR data show that
the complexes [PtMe2(CHPh2)Br(bpy)] (7) and [PtMe2(CHPh2)
Br(phen)] (8) are existed as a mixture of two isomers, the major
corresponding to that of trans oxidative addition. Thus, the trans:cis
isomer ratios are estimated as 4:1 and 5:1 for 7 and 8, respectively.
In the 1H NMR spectrum of [PtMe2(CHPh2)Br(bu2bpy)] (9), no
resonances attributable to the product of cis oxidative addition are
observed. The presence of the CHPh2 ligand in 7e9 is confirmed by
Table 2
Experimental details, crystal data and refinement parameters for complex fac-
[PtMe3Br(bpy)].
Empirical formula
Formula weight (g/mol)
Temperature (K)
Wavelength (Å)
Crystal size (mm)
Crystal system
Lattice type
a (Å)
C13H17BrN2Pt
476.29
90 (0.1)
0.71073
0.03 ꢂ 0.10 ꢂ 0.10
Orthorhombic
the observation of a singlet at
d d
w4.9 (1H) and w 87 (13C) ppm,
Primitive
12.8532(3)
11.8395(4)
18.3143(6)
2787.0(2)
Pbca
8
2.270
1776.00
55.9
Total: 26 687
although the expected platinum satellites are not resolved.
The oxidative addition of [PtMe2(NN)] (NN ¼ bpy, or phen) with
difunctional reagent 1,2-dibromoethane occurred rapidly at room
temperature to give the binuclear platinum(IV) complexes
b (Å)
c (Å)
Volume (Å3)
Space group
Z
[Pt2Me4Br2{
m
-(CH2)2}(NN)2] (NN ¼ bpy (10), or phen (11) (Eq. (6)).
Dcalc (g/cm3)
F(000)
The complexes 10e11 were almost insoluble in common organic
solvents; their 1H NMR spectra could not be obtained and therefore
were characterized only by elemental analysis. Similarly, reaction of
the platina(II)cyclopentane complexes with 1,2-dibromoethane
resulted in the formation of insoluble products, which were char-
acterized as binuclear platinum(IV) complexes with each contain-
2
qmax(ꢀ)
No. of reflections measured
Unique: 3335 (Rint ¼ 0.059)
Absorption (Tmin ¼ 0.515, Tmax ¼ 0.679)
Lorentz-polarization
Full-matrix least-squares on F2
Sw (F2o ꢁ F2c)2
Corrections
Refinement
Function minimized
Least squares weights
No. observations (I > 0.00s(I))
No. variables
ing a m-(CH2)2 group on the basis of elemental analysis [10]. Single
w ¼ 1/(
3335
157
s
2 (F2o) þ (0.0194P)2 þ 1.1971P)
crystals of the known complex fac-[PtMe3Br(bpy)] (12) [5], which is
soluble and is formed as byproduct (see Eq. (6)), were obtained and
the solid structure of (12) was determined for the first time by X-ray
crystallography. We suggest that the unexpected product 12
probably formed through decomposition of the intermediate
monomeric form of complex 10, i.e. [PtMe2Br{(CH2CH2Br)(bpy)].
Reflection/parameter ratio
21.24
0.046; 0.050
Residuals (refined on F2, all data):
R1; wR2
Goodness-of-fit (GOF)
1.00
2454
0.024, 0.044
No. observations (I > 2
s(I))
Residuals (refined on F2, I > 2
R1, wR2
s(I):
NN = bpy
[Pt2Me4Br2{µ-(CH2)2}(bpy)2] + fac-[PtMe3Br(bpy)]
10
12
Max./min. peak in final
0.92/ꢁ0.68
Diff. map, (e Åꢁ3
)
e
1,2-(CH2Br)2
NN = phen
[PtMe2(NN)]
[Pt2Me4Br2{µ-(CH2)2}(phen)2]
11
the protons of the methyl ligands of the trans isomer of complex 4.
In addition, the two resonances due to different methyl ligands of
the minor less symmetrical complex (cis isomer) are observed at
NN = bu2bpy
trans-[PtMe2Br(CH2CH2Br)(bu2bpy)]
13
(6)
d
¼ 0.59 (2J(PtH) ¼ 74.1 Hz) and 0.62 (2J(PtH) ¼ 74.1 Hz). A triplet
¼ 0.04 with 2J(PtH) ¼ 68.8 Hz and 3J(HH) ¼ 7.1 Hz is assigned
In contrast, by using the bu2bpy derivative of [PtMe2(NN)], the
related monomeric Pt(IV) complex trans-[PtMe2Br
at
d
to the CH3 group of the Et ligand while the CH2 group of Et ligand
is appeared as a multiplet at
¼ 1.42 ppm with 3J(HH) ¼ 7.5 Hz.
{(CH2)2Br}(bu2bpy)] (13) was prepared, but it was not possible to
d
synthesize the corresponding binuclear Pt(IV) derivative. The 1H
The other dimethylplatinum(IV) complexes are characterized
similarly (see the Experimental Section). Note that in 13C NMR
spectrum of the complex [PtMen2BuBr(bu2bpy)] (6), carbons of the
nBu ligand are assigned by using the magnitude of 195Pt-C
coupling constants, assuming that the coupling decreased the
further the carbon is from the platinum. Details of the 13C NMR
data for the complexes are given in the Experimental Section. The
resonances due to the diimine ligands are assigned according to
the literature [6,10].
NMR spectrum of 13 in CD2Cl2 displays a singlet at
d
¼ 0.73 pp with
2J(PtH) ¼ 70.8 Hz due to the methyl ligands trans to bu2bpy. The Pt-
CH2 resonance appears at
appear as a broad signal at
d
¼ 1.41 while the protons of CH2Br ligand
d
¼ 3.69 ppm. Observation of the latter
signal shows that the product is the mononuclear complex 13.
Besides, the 13C NMR spectrum of 13 in CD2Cl2 contains a singlet at
d
¼ ꢁ5.0 ppm with 1J(PtC) ¼ 710 Hz which is assigned to the Pt-CH3
ligands. The signal due to the Pt-CH2 appears at
d
¼ 24.3 which is
accompanied by platinum satellites with 1J(PtC) ¼ 617 Hz. The
resonance due to the CH2Br group is obscured by the more intense
signal of the tBu group. It may be possible that excessive steric bulk
of bu2bpy groups inhibits the formation of the binuclear analogous
The oxidative addition reactions of bromodiphenylmethane are
also shown in Scheme 1. The structures of the complexes are
Me
R
[Pt2Me4Br2{m-(CH2)2}(bu2bpy)2].
N
N
R
We have recently studied the oxidative addition of a polyhalo-
ethane, i.e. 1,2-dibromotetrachloroethane to dimethylplatinum(II)
complex [PtMe2(bu2bpy)] which resulted in the simultaneous
formation of Pt(II) and Pt(IV) complexes of [PtBr2(bu2bpy)] and
trans-[PtMe2BrCl(bu2bpy)], rather than the formation of a binuclear
Me
Me
N
N
Me
Me
N
N
+
Pt
X
Pt
X
Pt
+ RX
Me
NN
R
Et
X
I
Br
Br
complex containing Pt2-m-(CCl2)2 group [40].
4
5
6
7
8
9
bu2bpy
bu2bpy
bpy
Et
The dimethylplatinum(II) complexes 1e3 reacted with 1 equiv.
of tetrafunctional reagent 1,2-bis(dibromomethyl)benzene, to give
the mononuclear complexes [PtMe2(CHBr-o-C6H4CHBr2)Br(NN)]
{bpy (14), phen (15), or bu2bpy (16)} as shown in Scheme 2. The
resulting products were characterized by 1H, 13C NMR spectroscopy
nBu
bpy
CHPh2 Br
CHPh2 Br
CHPh2 Br
phen
bu2bpy
Scheme 1. Oxidative addition of organoplatinum(II) complexes with alkyl halides.

B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
89
Pt:Reagent / 1:1
Br
Br
C
CHBr2
H
CHBr2
C
Pt
N
H
Me
Me
Me
Br
N
Pt
+
N
Me
N
Br
[PtMe2(NN)]
NN =bpy (14), phen (15), bu2bpy (16)
+ 1,2-(CHBr2)C6H4
H
Pt:Reagent / 2:1
Br
C
C
Br
N
H
N
+
Me
Me
Me
Me
Pt
Pt
N
N
Br
Br
NN = bpy (17)
H
Br
C
Pt
N
C
H
Br
N
Me Me
Me
Pt
Br
N
N
Br
Me
NN = phen (18)
Scheme 2. Synthesis of mono and binuclear organoplatinum(IV) complexes 14e18.
and elemental analysis. The most convincing 1H NMR evidence for
formation of the monomers comes from the observation of an
containing the BrPtCHBr axis due to the presence of chiral carbon
of PtCHBrAr group. Therefore, for such an unsymmetrical isomer,
two Pt-Me and one PtCHBr resonances are expected in a 3:3:1
ratio. In addition, the 1H NMR spectra of the complexes 14e16 are
rather complicated due to the magnitudes of the coupling
constants 2J(PtH) for Pt-Me and Pt-CHBr being almost the same
(see the Experimental Section).
unusual singlet at
long range coupling of CHBr2 group with platinum. Consistently in
the 13C NMR spectra of these monomers, a singlet at
w 38 is
d
w5.8 with 5J(PtH) w 48 Hz, probably due to the
d
observed which is assigned to the CHBr2 group. In addition, the
PtCHBr resonance appears at
d
d
¼ 32.1 (1J(PtC) ¼ 887 Hz) for 14 and
¼ 31.3 (1J(PtC) ¼ 880 Hz) for 15, however, this characteristic signal
for 16 is obscured by the much more intense resonances due to
terminal carbons of bu2bpy.
The complexes 14e16 are shown by NMR to exist as a mixture
of two isomers, the major product corresponding to that of trans
oxidative addition. Syn and anti isomers were also observed
in the reaction of bis(2-pyridyl)ethylenediimineplatinum(II)
complex with 1,2-dibromomethylxylene, depending on the rela-
tive orientation of dimethylplatinum unit [41]. Therefore, on the
basis of 1H and 13C NMR spectra, there are two conformations for
each of the isomers due to the different orientation of the xylyl
group relative to the diimine ligand, as shown in Scheme 3. On
the other hand, nonequivalence of the Me2Pt protons is expected
in an unsymmetrical trans isomer having no plane of symmetry
CHBr2
BrHC
Pt
BrHC
Pt
CHBr2
N
N
Me
Me
Me
Me
N
N
Br
Br
Scheme 3. Possible conformational isomers for 14, 15 and 16.

90
B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
In the 1H NMR spectrum of the major isomer of complex
[PtMe2(CHBr-o-C6H4CHBr2)Br(phen)] (15) in CDCl3, two Pt-Me
is not stable, probably due to the steric hindrance between bu2bpy
groups on the platinum atoms.
In order to investigate the steric effects of a,u-dibromoalkanes
resonances at
d
¼ 1.72 and 1.97 with 2J(PtH) ¼ 68.8 and 70.0 Hz,
respectively, and one PtCHBr resonance at
d
¼
2.31 with
on the oxidative addition of organoplatinum(II) complexes, we
performed the reactions of platina(II)cyclpentane complexes
[Pt(CH2)4(NN)] {NN ¼ bpy (19), orphen (20)}ordimethylplatinum(II)
complex [PtMe2(bpy)] (2) with 1,3-dibromobutane having two C-Br
bonds for oxidative addition with one of the C-Br bonds sterically
morecrowded than the other bond. The reaction ofcomplexes 19e20
with 1,3-dibromobutane in benzene gave the platina(IV)cyclo-
pentane complexes [Pt(CH2)4Br{(CH2)2CHBrCH3}(NN)] {NN ¼ bpy
(21), or phen (22)} (Eq. (7) and Table 3). The products of each reaction
are shown to be predominantly that for trans addition of 1,3-
dibromobutane but traces of the cis isomer are also obtained.
2J(PtH) ¼ 71.3 Hz in a 3:3:1 ratio are observed which are assigned to
the trans isomer of 15.
A
resonance at
d
¼
5.68 with
5J(PtH) ¼ 47.5 Hz is assigned to the CHBr2 group. The 13C NMR
spectrum of 15 shows two signals at
d
¼ ꢁ2.8 and 2.6 ppm with
1J(PtC) ¼ 652 and 644 Hz, respectively, due to the inequivalent Pt-
CH3 groups of the trans isomer. The resonance for PtCHBr appears at
d
¼ 31.3 with 1J(PtC) ¼ 880 Hz while CHBr2 group appears as
a singlet at
d
¼ 38.7 ppm. On the other hand, several other Pt-Me
resonances at 0.28 (2J(PtH) ¼ 70.4 Hz), 0.58 (2J(PtH) ¼ 74.5 Hz),
1.21 (2J(PtH) ¼ 69.5 Hz) and 1.36 (2J(PtH) ¼ 74.3 Hz) are observed
which are tentatively assigned to both conformations of the cis
isomer as the minor product. For the major product of 14, i.e. trans-
[PtMe2(CHBr-o-C6H4CHBr2)Br(bpy)], only one signal for the two Pt-
CH2CH2CHBrCH3
N
N
N
N
¼ 1.43 with 2J(PtH) ¼ 69.7 Hz, that is
+
1CH2Br2CH23CHBr4CH3
(7)
Me moieties is observed at
d
Pt
Pt
suggested to be due to free rotation of the organic ligand -CHBr-o-
C6H4CHBr2 around the related Pt-C bond making the two Me
ligands equivalent in the NMR time scale.
Br
NN = bpy (21), phen (22)
NN = bpy (19), phen (20)
The binuclear products [Pt2Me4Br2{m-o-(CHBr)2C6H4}(NN)2]
{NN ¼ bpy (17), or phen(18)} were also isolated as air-stable, pale
yellow solids from the reactions of complexes 1e2 with 1,2-
C6H4(CHBr2)2 in a 2:1 mol ratio that gave satisfactory analytical
data.1H NMR data for the complex 17 displays twoPt-Me resonances
and one Pt-CHBr resonance in a 6:6:2 ratio, respectively, complying
with the binuclear trans oxidative addition of 1,2-C6H4(CHBr2)2
The 1H NMR spectrum of complex [Pt(CH2)4Br{(CH2)2CHBrCH3}
(bpy)] (21) in CDCl3 displays the characteristic signals of aCH2
protons as two multiplets at
d
¼ 2.05 and 3.11 ppm with
2J(PtH) ¼ 50.3 and 107.3, respectively. The bCH2 protons of the
platina(IV)cyclopentane ring appears as overlapping multiplets at
giving trans, trans-[Pt2Me4Br2{m-o-(CHBr)2C6H4}(bpy)2] (17). Thus,
d
¼ 1.35 and 1.54 ppm. A characteristic multiplet appearing at
the complex 17 is expected to have two different kinds of Pt-Me
ligands due to the relative orientations of Pt-Me bonds to
hydrogen and bromine atoms of PtCHBrAr groups, as shown in
Scheme 2. On the other hand, the 1H NMR data for complexes 18
reflects three Pt-Me resonances in a 6:3:3 ratio and two Pt-CHBr
d
¼ 3.78 ppm is assigned to the CHBr proton which resonates at
the highest chemical shift in the aliphatic region relative to the
signals for other protons. Another characteristic doublet observed
at
d
¼ 1.42 ppm with 3J(HH) ¼ 6.6 Hz, is assigned to the protons of
the CH3 group. The observation of the multiplet for CHBr group
and the doublet for CH3 group clearly indicates that the C1-Br
bond rather than C3-Br bond oxidative addition has taken place,
since the C3 atom is experiencing more crowding due to the CH3
resonances which are assigned to trans, cis-[Pt2Me4Br2{m-o-
(CHBr)2C6H4}(bpy)2]. Thus, one of the platinum atoms of 18 has two
equivalent Me ligands (at
is different from the other platinum atom with two inequivalent Me
d
¼ 1.58 ppm with 2J(PtH) ¼ 70.3 Hz), that
group. In the 13C NMR spectrum of complex 21, a peak at
d
¼ 26.5
¼ 0.57 and 2.31 ppm with 2J(PtH) ¼ 74.9 and 71.6 Hz,
flanked by platinum satellites with 1J(PtC) ¼ 704 Hz is assigned to
the carbons of the two aCH2 groups of the platina(IV)cyclopentane
ring. The observation of only one signal confirms the symmetrical
stereochemistry of complex 21. The carbons of bCH2 groups
ligands (at
d
respectively). Two resonances for the two different PtCHBr moieties
are appeared at
d
¼ 1.74 ppm, with 2J(PtH) ¼ 70.0 Hz, and at
d
¼ 1.50,
with 2J(PtH) ¼ 68.7H. Moreover, the cis, cis products [Pt2Me4Br2{
m-o-
(CHBr)2C6H4}(NN)2] are also characterized in the 1H NMR spectrum
(see the Experimental Section).
appeared at
d
¼ 33.7 with 2J(PtC) ¼ 16 Hz. For the carbon atoms of
the halognoalkyl chain, the assignments are made on the basis of
the magnitude of 195Pt-C coupling constants. The peak at
d
¼ 52.6
An attempt to form the related binuclear analogous complex
[Pt2Me4Br2{m-o-(CHBr)2C6H4}(bu2bpy)2], by the reaction of
[PtMe2(bu2bpy)] with 1,2-C6H4(CHBr2)2 in a mole ratio of 2:1, was
unsuccessful and instead gave the mononuclear complex 16 as
confirmed by 1H NMR spectroscopy in CDCl3. It therefore seems
with 2J(PtC) ¼ 122 Hz is assigned to the PtCH2CH2 group while the
CHBr group appears at
d
¼ 42.1 ppm with 3J(PtC) ¼ 31 Hz. The CH3
group resonates further upfield at
groups of complexes 21e22 appear at marginally higher chemical
d
¼ 26.4. The Cb of PtCH2CH2
that the binuclear complex [Pt2Me4Br2{m-o-(CHBr)2C6H4}(bu2bpy)2
shifts relative to those of analogous 1,3-dibromopropane or
Table 3
Selected 1H (13C) chemical shift data for [PtR2Br{(CH2)nBr}(NN)] (n ¼ 3, 4) and [PtR2Br{(CH2)2CHBr}(NN)] in CDCl3.
Complex
PtCH2
PtCH2CH2
CH2CH2Br
CHBr
CH2Br
CH3
[PtBr{(CH)2}4{(CH2)3Br}(bpy)]a
[PtBr{(CH)2}4{(CH2)3Br}(phen)]a
[PtBr{(CH)2}4{(CH2)4Br}(bpy)]a
[PtBr{(CH)2}4{(CH2)4Br}(phen)]a
[PtBr{(CH)2}4{(CH2)2CHBr}(bpy)]b
[PtBr{(CH)2}4{(CH2)2CHBr}(phen)]b
[PtBrMe2{(CH2)2CHBrCH3}(bpy)]b
[PtBrMe2{(CH2)4Br}(bpy)]c
1.54 (15.7)
1.41 (15.5)
1.58 (18.1)
1.50 (17.5)
1.60 (15.4)
1.61 (14.7)
1.81 (15.6)
1.50 (17.9)
1.26 (33.6)
1.05 (33.6)
0.65 (29.2)
0.50 (28.7)
1.04 (52.6)
0.95 (52.2)
1.03 (52.2)
0.63 (33.4)
e
e
3.09 (33.9)
2.77 (34.0)
3.14 (34.4)
3.01 (34.0)
e
e
e
e
e
1.28 (34.2)
1.27 (34.0)
e
e
e
e
e
3.78 (42.1)
3.69 (41.5)
3.74 (42.0)
e
1.42 (26.4)
1.33 (26.7)
1.38 (26.0)
e
e
e
e
e
1.27 (28.7)
3.08 (33.8)
a
Ref. [10].
This work.
Ref. [7].
b
c

B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
91
1,4-dibromobutane complexes [Pt(CH2)4Br{(CH2)nBr}(NN)] (n ¼ 3,
4; NN ¼ bpy, or phen) (see Table 3) [7,10]. It therefore seems that
replacement of the hydrogen by CH3 group has a considerable
deshielding effect on the chemical shift of the PtCH2CH2 group.
The synthesis of complex [PtMe2Br{(CH2)2CHBrCH3}(bpy)] (23)
was carried out by a similar method to that described for 21e22, by
the reaction of [PtMe2(bpy)] (2) with 1,3-dibromobutane in acetone
(Eq. (8)).
demand of 1,3-dibromobutane. It seems that the steric effects play
an important role in the transition state, affecting the reactivity.
Furthermore, the 1J(PtC1) value of the alkyl chain for complex 21
(772 Hz) is considerably larger than that of 23 (707 Hz) which may
be related to the kinetics of the reaction of [Pt(CH2)4(bpy)] as
compared to that of [PtMe2(bpy)]. The considerable increase in the
second-order rate constants for the reaction of [Pt(CH2)4(bpy)]
with 1,3-dibromobutane as compared to that with 1,3-
dibromopropane (3.1e6.8) [10] may be due to the geometrical
effect of CH3 group in the former resulting in the better interaction
of the far Br atom with platinum. The rate acceleration in the
reactions of [Pt(CH2)4(bpy)] and [Pt(CH2)4(phen)] with 1,3-
dibromobutane as compared with 1,4-dibromobutane (4.5e12.6
for bpy and 3.2e7.3 for phen analogue) [10] or the reaction of
[PtMe2(bpy)] with 1,3-dibromobutane as compared with 1,4-
dibromobutane (2.0e3.6) is suggested to be due to the activation
effect of the platinum which falls off as the alkyl chain length
increases [13,14].
CH2CH2CHBrCH3
Me
Me
N
N
Me
Me
N
N
+ CH3CHBrCH2CH2Br
Pt
Pt
(8)
Br
23
NN = bpy (2)
The 1H or 13C NMR spectrum of 23 each contains one methyl-
platinum resonance at
d
(1H) 1.38 ppm (2J(PtH) ¼ 69.8 Hz) or
d(
13C) ꢁ3.3 ppm (1J(PtC) ¼ 681 Hz), respectively, typical of the
dimethylplatinum(IV) complexes resulting from the trans oxidative
3.3. Description and discussion of the crystal structure of fac-
[PtMe3Br(bpy)] (12)
addition of dihaloalkane. In a similar way, the presence of a charac-
teristic multiplet at
d
¼ 3.74 ppm and a doublet at ¼ 1.38 ppm in the
d
1H NMR spectrum confirms that C1-Br bond oxidative addition has
taken place. A similar deshielding effect for PtCH2CH2 group is
The structure of complex fac-[PtMe3Br(bpy)] was determined by
X-ray crystallography and is shown in Fig. 3. The selected bond
lengths and bond angles are also included in Table 4. The crystal
structure of fac-[PtMe3Br(bpy)] reveals an octahedral geometry for
platinum with a fac-[PtMe3] group, as found in the other related
triorganoplatinum(IV) complexes [14,42]. The molecule fac-
[PtMe3Br(bpy)] is located on a crystallographic mirror plane. The
Pt-N bond distances are not equal (2.159(4) and 2.148(4) Å). Simi-
larly, the Pt-C bond distances for equatorial [PtMe2(bpy)] are not
equal (2.044(4) and 2.042(4) Å) and are different from that of fac-
[PtMe3I(bpy)] (2.054(7) Å) [43]. The axial Pt-C bond distance
(2.059(4) Å) is longer than that of fac-[PtMe3I(bpy)] (2.024(10) Å)
[43]. Moreover, the PteC bond length trans to bromide (2.059(4) Å)
is longer than those trans to the N ligating atoms of bpy (2.044(4)
and 2.042(4) Å), reflecting the higher trans influence of bromide
relative to bpy.
observed in the
analogues 1,4-dibromobutane complex [PtBrMe2{(CH2)nBr}(bpy)]
¼ 33.4) (Table 3) [7].
d(
13C) of complex 23 (
d
¼ 52.2) as compared to that of
(d
3.2. The kinetic study
The organoplatinum(II) complexes containing diimine ligand
are all intensely colored. The colors are useful in monitoring
oxidative addition reactions. The colors are assigned to 5d
(Pt) / p* (diimine) metal to ligand charge transfer bands (MLCT).
There have been very few mechanistic studies of the oxidative
addition reactions involving platina(II)cyclopentane complexes.
The kinetics of oxidative addition of 1,3-dibromobutane to orga-
noplatinum(II) complexes of [Pt(CH2)4(NN)] (NN ¼ bpy, or phen)
and [PtMe2(bpy)] in acetone were studied by UVevis spectros-
copy. In each case, an excess of
the disappearance of MLCT band at
(20) or
a
,
u
-dibromoalkane was used and
¼ 480 nm (19), ¼ 475 nm
¼ 473 nm (2) was used to monitor the reactions. The
l
l
l
complex [PtMe2Br{(CH2)4Br}(bpy)] has already been prepared by
the reaction of [PtMe2(bpy)] with 1,4-dibromobutane [7]. For
comparison, the oxidative addition reaction of 1,4-dibromobutane
to [PtMe2(bpy)] was also studied and the activation parameters
were determined in each case (Table 1). The reactions followed
good second-order kinetics with remarkable reproducibility. The
large negative
DS
# values strongly supported the SN2 mechanism
of oxidative addition for all cases [1,2]. Moreover, the rates were
not retarded by radical scavengers such as galvinoxyl and there
was no induction period, so any free radical chain mechanism was
ruled out.
The increase in the rate constants for the reactions of
[Pt(CH2)4(NN)] with 1,3-dibromobutane, by going from bpy
analogue 19 to phen one 20, is about 1.2e1.7, in accordance with
the more nucleophilic character of the phen complex. Thus, the
rate of nucleophilic attack is faster for phen analogue than bpy
analogue. The increase in the rate of metallacycle complex 19, as
compared to that of dimethyl analogue 2, suggests that the plat-
inum center in the former complex is richer in electrons than in
the latter one, consistent with the higher trans influence of
methylene group of metallacycle than the methyl group of
dimethyl complex. This increase (3.8e4.2) is considerably more
than the reported values [10], which may be related to the steric
Fig. 3. The molecular structure of complex fac-[PtMe3Br(bpy)], showing 50% proba-
bility displacement ellipsoids and the atomic numbering.

92
B.Z. Momeni et al. / Journal of Organometallic Chemistry 700 (2012) 83e92
Table 4
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[PtMe3Br(bpy)].
C(1)ePt(1)
C(2)ePt(1)
C(4)eN(1)
C(8)eN(1)
C(9)eN(2)
C(13)eN(2)
C(3)ePt(1)
N(1)ePt(1)
2.044(4)
2.042(4)
1.340(6)
1.349(5)
1.346(5)
1.337(6)
2.059(4)
2.159(4)
2.148(4)
2.6061(4)
109.5
N(2)ePt(1)
Br(1)ePt(1)
Pt(1)eC(1)eH(1A)
Pt(1)eC(2)eH(2A)
N(1)eC(4)eC(5)
Pt(1)eC(3)eH(3A)
C(4)eN(1)ePt(1)
C(8)eN(1)ePt(1)
C(13)eN(2)ePt(1)
C(9)eN(2)ePt(1)
C(2)ePt(1)eC(1)
C(2)ePt(1)eC(3)
C(1)ePt(1)eC(3)
C(2)ePt(1)eN(2)
C(1)ePt(1)eN(2)
C(3)ePt(1)eN(2)
C(2)ePt(1)eN(1)
C(1)ePt(1)eN(1)
C(3)ePt(1)eN(1)
N(2)ePt(1)eN(1)
C(2)ePt(1)eBr(1)
C(1)ePt(1)eBr(1)
C(3)ePt(1)eBr(1)
N(2)ePt(1)eBr(1)
N(1)ePt(1)eBr(1)
109.5
123.1(4)
109.5
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115.0(3)
124.9(3)
115.6(3)
86.40(18)
86.05(19)
87.85(18)
97.66(17)
175.87(17)
91.63(16)
172.95(16)
99.25(16)
89.92(16)
76.65(14)
92.35(13)
91.62(13)
178.35(13)
89.01(9)
91.71(9)
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Acknowledgements
We would like to thank the Science Research Council of K.N.
Toosi University of Technology for financial support. The generous
loan of platinum metal salt by Johnson Matthey is gratefully
appreciated.
[32] Least squares function minimized: Sw(F2oꢁFc2)2.
[33] Standard deviation of an observation of unit weight: [Sw(F2oꢁFc2)2/(NoꢁNv)]1/2
where: No ¼ number of observations, Nv ¼number of variables.
,
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Appendix A. Supplementary material
CCDC 845622; contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif.
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