Syntheses and structural characterization of heterometallic bis(pyrazolyl)methane complexes of rhenium and platinum

Article abstract of DOI:10.1016/j.jorganchem.2007.08.029

The new heterometallic complex {μ-1,3,5-[CH(pz)₂]₃C₆H₃}[Re(CO)₃Br][Pt(p-tolyl)₂]₂ has been prepared by reaction of 1 equiv. of the dimer [Pt(p-tolyl)₂(μ-SEt₂

Full text of DOI:10.1016/j.jorganchem.2007.08.029

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5414–5420
www.elsevier.com/locate/jorganchem
Syntheses and structural characterization of heterometallic
bis(pyrazolyl)methane complexes of rhenium and platinum
*
Daniel L. Reger , Russell P. Watson, Mark D. Smith
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
Received 2 August 2007; received in revised form 23 August 2007; accepted 23 August 2007
Available online 29 August 2007
Abstract
The new heterometallic complex {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br][Pt(p-tolyl)2]2 has been prepared by reaction of 1 equiv. of the
dimer [Pt(p-tolyl)2(l-SEt2)]2 with the monometallic rhenium precursor {1,3,5-[CH(pz)2]3C6H3}Re(CO)3Br, where 1,3,5-[CH(pz)2]3C6H3
is the tritopic, arene-linked bis(pyrazolyl)methane ligand 1,3,5-tris[bis(1-pyrazolyl)methyl]benzene. Similarly, the heterometallic complex
{l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2[Pt(p-tolyl)2] has been made by the reaction of the dirhenium compound {l-1,3,5-[CH(pz)2]3-
C6H3}[Re(CO)3Br]2 and one-half of an equivalent of [Pt(p-tolyl)2(l-SEt2)]2. X-ray crystallographic studies of the new compounds reveal
significant noncovalent interactions in their molecular and supramolecular structures.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Bis(pyrazolyl)methane; Tricarbonylrhenium(I); Ditolylplatinum(II); Supramolecular
1. Introduction
reactivity and catalytic applications compared to their
homometallic analogues [4], prompted us to investigate a
series of multimetallic complexes that could potentially
be made using a symmetric, tritopic ligand linked by an
aromatic group. The related tritopic compound
1,3,5-(CH3)3C6[CH2OCH2C(pz)3]3, containing tridentate
tris(pyrazolyl)methyl groups bound through aliphatic ether
groups to a mesitylene ring, had already been prepared [5],
and this ligand was termed ‘‘semi-rigid’’ considering the
flexibility of the ether linkages and the rigidity of the arene
ring. We wished to prepare heterometallic complexes with
more fixed ligands so as to gain more control over the ori-
entation of the metal centers. Based on our experience,
however, with the low solubility of a more rigid (‘‘fixed’’)
ligand in which tridentate heteroscorpionate groups were
substituted directly onto the arene ring [6], we reasoned
that the fixed, bidentate bis(pyrazolyl)methane compound
would be more useful.
We previously reported the direct synthesis of the hete-
robimetallic complex {l-m-[CH(pz)2]2C6H4}[Re(CO)3Br]-
[Pt(p-tolyl)2] by the addition of a tricarbonylrhenium(I)
fragment to the bitopic, bis(pyrazolyl)methane ligand, m-
[CH(pz)2]2C6H4, to give the monometallic intermediate
{m-[CH(pz)2]2C6H4}Re(CO)3Br, followed by the addition
of the ditolylplatinum center [1]. This heterometallic
complex is the first to have been isolated with this class
of symmetrical third-generation bis(pyrazolyl)methane
compounds, where two or more bis(pyrazolyl)methyl
groups are linked through organic spacers of varying flex-
ibilities to produce polytopic ligands capable of forming
multimetallic complexes [2]. Thus, we achieved the fre-
quently unfeasible, selective formation [3] of a monometal-
lic intermediate containing a ligating site available for
subsequent coordination to a second metal fragment type.
This successful synthesis using a bitopic ligand and the
propensity for heterometallic complexes to show unique
Accordingly, we prepared the tritopic bis(pyrazol-
yl)methane ligand 1,3,5-[CH(pz)2]3C6H3 and demon-
strated that it was possible to selectively add one, two,
or three [Re(CO)3Br] units to yield the mono-, bi-, and
trimetallic complexes {1,3,5-[CH(pz)2]3C6H3}Re(CO)3Br,
*
Corresponding author. Fax: +1 803 777 9521.
E-mail address: reger@mail.chem.sc.edu (D.L. Reger).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.029

D.L. Reger et al. / Journal of Organometallic Chemistry 692 (2007) 5414–5420
5415
{l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2, and {l-1,3,5-[CH-
(pz)2]3C6H3}[Re(CO)3Br]3 [7]. Herein, we report the use of
the mono- and dirhenium complexes to prepare the
heterometallic compounds {l-1,3,5-[CH(pz)2]3C6H3}[Re-
(CO)3Br][Pt(p-tolyl)2]2 (1) and {l-1,3,5-[CH(pz)2]3C6H3}-
[Re(CO)3Br]2[Pt(p-tolyl)2] (2). The solid state molecular
and supramolecular structures of these heterometallic
complexes are also presented.
HRMS: ESI(+) (m/z) Calc. for C58H52BrN12NaO3Pt2Re,
[M + Na]+, 1644.2209; found 1644.2207.
2.2.2. {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2-
[Pt(p-tolyl)2] (2)
A suspension of {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2
(0.10 g, 0.082 mmol) and [Pt(p-tolyl)2(l-SEt2)]2 (0.040 g,
0.043 mmol) in 20 mL of CH2Cl2 was stirred at room tem-
perature for 2 d. The white product was isolated by gravity
filtration, washed with 5 mL of CH2Cl2 and dried in vacuo.
Yield = 0.064 g (49%). M.p.: >300 ꢁC. IR, mCO (KBr,
cmÀ1): 2026, 1924, 1892. 1H NMR (400 MHz, acetone-
d6): d 8.60 (s, 2H, CH(pz)2[Re]), 8.33, 7.39 (br s, br s;
2H, 2H, 3,5-H pz[Pt]), 8.26 (s, 1H, CH(pz)2[Pt]), 8.09,
8.06 (d, J = 2.0 Hz, br s; 4H, 4H, 3,5-H pz[Re]), 6.96 (d,
J = 7.6 Hz, JPtH = 72 Hz, 4H, 2,6-C6H4CH3), 6.67 (d,
J = 7.6 Hz, 4 H, 3,5-C6H4CH3), 6.56 (t, J = 2.6 Hz, 4H,
4-H pz[Re]), 6.49 (t, J = 2.6 Hz, 2H, 4-H pz[Pt]), 5.96 (br
s, 2H, C6H3), 5.91 (br s, 1H, C6H3), 2.08 (s, 6H,
C6H4CH3). MS: ESI(+) m/z (Rel. Int.%) [assgn]: 1612
(80) [M + NH4]+, 1595 (50) [M + H]+, 1503 (100)
[M À C6H4CH3]+, 1487 (60) [M À Br À CO]+. Crystals
for X-ray studies were grown by the vapor diffusion of
diethyl ether in acetonitrile solutions of the solid and were
taken directly from the mother liquor.
2. Experimental
2.1. General considerations
Air-sensitive materials were handled under a nitrogen
atmosphere using standard Schlenk techniques. All sol-
vents were dried and distilled by conventional methods
prior to use. The compounds {1,3,5-[CH(pz)2]3C6H3}Re-
(CO)3Br [7], {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2 [7],
and [Pt(p-tolyl)2(l-SEt2)]2 [8] were prepared as previously
described. All other chemicals were purchased from
Aldrich or Fisher Scientific and used as received. Reported
melting points are uncorrected. IR spectra were obtained
1
on a Nicolet 5DXBO FTIR spectrometer. H NMR spec-
tra were recorded on a Mercury/VX 300 or Mercury/VX
400 spectrometer. All chemical shifts are in ppm and are
secondary-referenced using the signals from residual
undeuterated solvents. Mass spectrometric measurements
were obtained on a MicroMass QTOF spectrometer. Ele-
mental analyses were performed on vacuum-dried samples
by Robertson Microlit Laboratories (Madison, NJ).
2.3. X-ray crystallographic analyses
Details of the data collections for 1 and 2 Æ CH3CN are
given in Table 1. X-ray diffraction intensity data for
2 Æ CH3CN were measured at 150(1) K on a Bruker
SMART APEX diffractometer (Mo Ka radiation,
2.2. Syntheses
˚
k = 0.71073 A) [9]. Crystals of 1 suffered rapid (within a
2.2.1. {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]-
[Pt(p-tolyl)2]2 (1)
few seconds) clouding and loss of crystallinity when
removed from the mother liquor, even under paratone-N
oil. Despite repeated efforts a successful transfer of an
intact crystal of 1 to the cold stream for a low-temperature
data collection could not be achieved before decomposi-
tion. The crystals are stable indefinitely in the acetone/ether
growth solvent mixture, and therefore the data collection
was carried out using a crystal mounted in the mother
liquor inside a thin-walled capillary tube sealed on both
ends with putty and epoxy. The X-ray intensity data for
1 were measured at 294(1) K on the same Bruker diffrac-
tometer as above. Raw area detector data frame integra-
tion was performed with SAINT+ [9]. Both data sets were
corrected for absorption effects with SADABS [9]. Direct or
Patterson methods structure solution, difference Fourier
calculations, and full-matrix least-squares refinement
against F2 were performed with SHELXTL [10]. Important
notes regarding the solution and refinement for both struc-
tures follow.
{1,3,5-[CH(pz)2]3 C6H3} Re(CO)3Br (0.10 g, 0.12 mmol)
and [Pt(p-tolyl)2(l-SEt2)]2 (0.12 g, 0.13 mmol) were dis-
solved in 15 mL of CH2Cl2 and stirred at room tempera-
ture for 24 h. The solvent was removed by rotary
evaporation and the resulting solid recrystallized by the
vapor diffusion of diethyl ether into acetone solutions of
the product. Crystals for X-ray studies were taken directly
from the mother liquor. Crystals for all other characteriza-
tion were removed, rinsed with diethyl ether, and dried in
vacuo, resulting in loss of the solvent of crystallization.
M.p.: 184 ꢁC dec. Anal. Calc. for C58H52BrN12O3Pt2Re:
C, 42.97; H, 3.23; N, 10.37. Found: C, 43.14; H, 2.92; N,
10.19%. IR, mCO (KBr, cmÀ1): 2025, 1925, 1882. 1H
NMR (300 MHz, acetone-d6): d 8.83 (s, 1H, CH(pz)2[Re]),
8.38 (s, 2H, CH(pz)2[Pt]), 8.22, 7.31 (br s, d, J = 1.8 Hz; 4
H, 4H, 3,5-H pz[Pt]), 8.11, 7.89 (d, J = 1.8 Hz, br s; 2H, 2
H, 3,5-H pz[Re]), 6.94 (d, J = 8.1 Hz, JPtH = 54 Hz, 8H,
2,6-C6H4CH3), 6.65 (d, J = 7.2 Hz, 8H, 3,5-C6H4CH3),
6.37 (t, J = 2.6 Hz, 4H, 4-H pz[Pt]), 6.32 (t, J = 2.6 Hz,
2H, 4-H pz[Re]), 5.52 (br s, 2H, C6H3), 5.01 (br s, 1H,
C6H3), 2.12 (s, 12H, C6H4CH3). MS: ESI(+) m/z (Rel.
Int.%) [assgn]: 1660 (70) [M + K]+, 1622 (15) [M + H]+.
Complex 1 refined normally with the exception of one of
the two –C6H4CH3 substituents bound to Pt(2). This group
(C(111)–C(117)/C(211)–C(217)) is disordered equally over
two orientations. The Pt(2)-bound carbon (C(111)/
C(211)) was kept common to both disorder components,

5416
D.L. Reger et al. / Journal of Organometallic Chemistry 692 (2007) 5414–5420
Table 1
tion correction methods. There is no evidence of twinning
or degradation of the data crystal, and currently there is
no explanation for this peak.
Crystal data and refinement details for {l-1,3,5-[CH(pz)2]3C6H3}[Re-
(CO)3Br][Pt(p-tolyl)2]2 (1) and {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2-
[Pt(p-tolyl)2] Æ CH3CN (2 Æ CH3CN)
1
2 Æ CH3CN
3. Results and discussion
Empirical formula
Formula weight
Temperature (K)
Crystal system
C
58H52BrN12O3Pt2Re C49H41Br2N13O6PtRe2
1621.41
294(1)
Triclinic
1635.26
150(1)
Monoclinic
P21/c
3.1. Syntheses
ꢀ
The monometallic rhenium complex 1,3,5-[CH(pz)2]3-
C6H3}Re(CO)3Br reacted with 1 equiv. of dimeric [Pt(p-
tolyl)2(l-SEt2)]2 in dichloromethane at room temperature
to afford the heterometallic complex {l-1,3,5-[CH(pz)2]3-
C6H3}[Re(CO)3Br][Pt(p-tolyl)2]2 (1) in which two plati-
num(II) centers were incorporated into the uncoordinated
ligating sites of the monorhenium precursor (Scheme 1).
Similarly, one-half of an equivalent of [Pt(p-tolyl)2(l-
SEt2)]2 reacted with the dirhenium complex {l-1,3,5-
[CH(pz)2]3C6H3}[Re(CO)3Br]2 to yield the compound
Space group
P1
Unit cell dimensions
˚
a (A)
11.9947(17)
16.725(2)
21.646(3)
106.909(3)
94.465(3)
95.647(3)
4108.6(10)
2
12.1586(5)
25.7553(10)
17.0329(7)
90
102.5290(10)
90
5206.8(4)
4
2.086
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg mÀ3
)
1.311
5.390
Absorption coefficient
(mmÀ1
8.914
{l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2[Pt(p-tolyl)2]
(2;
)
Absorption correction
F(000)
Semi-empirical from equivalents
Scheme 1), which contains one platinum(II) center.
1
1548
3088
The H NMR spectra of 1 and 2 can be assigned based
on the spectra of the mono- and dirhenium starting mate-
rials [7] and the relative integrations of the observed sig-
nals. That is, in 1 the ratio of signal integrations of the
bis(pyrazolyl)methyl groups coordinated to the platinum
centers to those pyrazolyl groups coordinated to the rhe-
nium center is 2:1, and the same ratio in 2 is 1:2. For exam-
ple, in 1 the methine proton associated with the rhenium
center resonates at 8.83 ppm, whereas the methine protons
associated with the platinum centers resonate at 8.38 ppm
with double the integration of the former. Similarly, the
3/5-pyrazolyl protons on rings bound to rhenium are
detected at 8.11 and 7.89 ppm, while signals from the anal-
ogous protons associated with platinum appear at 8.22 and
7.31 ppm and again integrate at twice the value as the rhe-
nium-bound rings. The central aromatic ring in 1 contains
two protons ortho to both rhenium- and platinum-bound
bis(pyrazolyl)methyl substituents. These protons resonate
at 5.52 ppm with twice the integration of the remaining res-
onance, which is between two platinum-associated bis(pyr-
azolyl)methyl groups and is detected upfield at 5.01 ppm.
The tolyl groups bound to platinum are identified by reso-
nances at 6.94, 6.65, and 2.12 ppm, with the expected 195Pt-
induced satellites around the signal at 6.94 ppm giving JPtH
Crystal size (mm3)
0.46 · 0.24 · 0.18
0.30 · 0.12 · 0.06
1.46–26.39
h Range for data collection 1.72–24.16
(ꢁ)
Index ranges
À13 6 h 6 13,
À15 6 h 6 15,
À32 6 k 6 32,
À21 6 l 6 21
À19 6 k 6 19,
À24 6 l 6 24
Mo Ka, 0.71073
38677
˚
Radiation, k (A)
Reflections collected
Independent reflections
Completeness to hmax (%) 99.9
Final R indices [I > 2r(I)] R1 = 0.0338;
wR2 = 0.0841
Goodness-of-fit on F2
58330
13138
10657
99.9
R1 = 0.0429;
wR2 = 0.1067
1.091
0.954
and the geometry of both was restrained to be similar to
that of a normal tolyl group (C(81)–C(87)). Six indepen-
dent solvent regions were located. The electron density fea-
tures in three of these regions resembled acetone molecules;
the remaining regions were featureless. All potential ace-
tone molecules were apparently fractionally occupied over
multiple orientations and were unstable toward refinement
despite numerous modeling attempts. For this reason all
disordered solvent was treated with the SQUEEZE option
in PLATON [11]. The program calculated a solvent-accessible
3
˚
volume of 1561.2 A (37.3% of the total unit cell volume),
1
corresponding to 155 electrons per cell. The contribution of
these electrons was then removed from subsequent struc-
ture factor calculations. The reported FW, density, and
F(000) reflect known unit cell contents only. The high sol-
vent content and loosely bound (disordered) nature of
these molecules explains the rapid decomposition (desolva-
tion) of the crystals when removed from the mother liquor.
ForÀ compound 2 Æ CH3CN there is a single large
of 54 Hz. The H NMR spectrum of 2 is completely anal-
ogous but with the already mentioned difference that the
protons associated with rhenium coordination account
for twice the signal integration of those protons on plati-
num-bound bis(pyrazolyl)methyl groups.
The positive ion electrospray mass spectrum of 1 shows
peaks corresponding to the molecule associated with potas-
sium cation and a proton at m/z of 1660 and 1622, respec-
tively. The spectrum of 2 shows ammonium ion association
(1612) and protonation (1595) as well as the fragments at
1503, the base peak corresponding to loss of a tolyl group,
and at 1487, corresponding to loss of a bromide and a car-
bonyl group. Infrared spectra of 1 and 2 indicate facial
3
˚
(4.90 e /A ) residual electron density peak in the final dif-
ference map, located in a chemically impossible position
˚
˚
(1.28 A from H(1) and 1.49 A from H(21)). The next larg-
À
3
˚
˚
est peak is 2.96 e /A , located <1 A from Pt(1). The large
peak persists despite trial application of different absorp-

D.L. Reger et al. / Journal of Organometallic Chemistry 692 (2007) 5414–5420
5417
Scheme 1. Preparation of {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br][Pt(p-tolyl)2]2 (1) and {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2[Pt(p-tolyl)2] (2).
coordination of the carbonyl groups coordinated to the
rhenium atoms.
3.2. Solid state structures
An ORTEP representation of the heterometallic com-
plex {l-1,3,5-[CH(pz)2]3C6H3} [Re(CO)3Br][Pt(p-tolyl)2]2
(1) is shown in Fig. 1, and selected bond distances and
angles are given in Table 2. One of the tolyl groups
attached to a platinum center is disordered over two orien-
tations in the crystal, but only one orientation is shown in
the figure. The complex molecule adopts a conformation in
which the two Pt(p-tolyl)2 groups are oriented on opposite
sides of the arene rings with the rhenium group oriented on
roughly the same side of the arene linker as one of the plat-
inum groups. As observed in similar rhenium carbonyl
complexes [1,7], a carbonyl ligand (C(73)–O(73)) in 1 is ori-
ented above the arene-linker indicating intramolecular
pCO–pAr interactions. The shortest (perpendicular) distance
between the CO bond centroid and the arene ring plane is
˚
2.897(7) A while the distance between the CO bond cen-
˚
troid and the arene ring centroid is 3.639(7) A. These dis-
Fig. 1. ORTEP representation of {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]-
[Pt(p-tolyl)2]2 (1). Displacement ellipsoids are drawn at the 20% proba-
bility level. Only one component of the C(111)–C(117)/C(211)–C(217)
disordered group is shown. Hydrogen atoms are omitted for clarity.
tances reflect relatively strong pCO–pAr interactions [12].
Analysis of the extended structure of 1 is hindered by
disorder, but two important features can be identified.
˚
First, a 2.39 A CH–Br interaction [13] joins adjacent com-
plex molecules into dimeric units throughout the crystal-
line structure as shown in Fig. 2; and second, these
dimeric units form layers of complex molecules that stack
along the b-axis with layers of the extensively disordered
solvent region in an alternating fashion comparable to
the stacking found in the previously reported homometal-
lic rhenium complexes of this ligand [7]. Additional intra-
layer noncovalent interactions among the dimeric units are
not observed so it is likely that solvent molecules assist in

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D.L. Reger et al. / Journal of Organometallic Chemistry 692 (2007) 5414–5420
Table 2
˚
Selected bond distances (A) and angles (ꢁ) for {l-1,3,5-[CH(pz)2]3C6H3}-
[Re(CO)3Br][Pt(p-tolyl)2]2 (1)
Re(1)–C(71)
Re(1)–C(72)
Re(1)–C(73)
Re(1)–N(11)
Re(1)–N(21)
Re(1)–Br(1)
Pt(1)–C(81)
Pt(1)–C(91)
Pt(1)–N(31)
Pt(1)–N(41)
Pt(2)–C(101)
Pt(2)–C(111)
Pt(2)–N(51)
Pt(2)–N(61)
1.904(9)
1.877(9)
1.890(7)
2.155(5)
2.180(5)
2.6168(8)
2.004(5)
1.997(6)
2.099(4)
2.114(4)
2.011(5)
1.967(6)
2.113(4)
2.088(5)
C(71)–Re(1)–N(11)
C(72)–Re(1)–N(11)
C(72)–Re(1)–C(71)
C(71)–Re(1)–Br(1)
N(11)–Re(1)–Br(1)
C(91)–Pt(1)–C(81)
C(91)–Pt(1)–N(31)
C(81)–Pt(1)–N(31)
C(91)–Pt(1)–N(41)
C(111)–Pt(2)–C(101)
C(111)–Pt(2)–N(61)
C(101)–Pt(2)–N(61)
C(111)–Pt(2)–N(51)
174.7(3)
93.3(3)
88.9(3)
90.8(3)
84.42(13)
88.6(2)
91.4(2)
175.25(18)
177.5(2)
90.8(3)
176.2(2)
91.1(2)
Fig. 3. ORTEP representation of the complex molecule in {l-1,3,5-
[CH(pz)2]3C6H3}[Re(CO)3Br]2[Pt(p-tolyl)2] Æ CH3CN (2 Æ CH3CN). Dis-
placement ellipsoids are drawn at the 40% probability level. Hydrogen
atoms are omitted for clarity.
90.2(2)
listed in Table 3. The complex molecule adopts a confor-
mation similar to 1 in which the two rhenium groups are
oriented on opposite sides of the arene rings, with the plat-
inum group oriented on roughly the same side of the arene
linker as one of the rhenium groups. As for compound 1,
compound 2 Æ CH3CN exhibits strong pCO–pAr interactions
on both sides of the arene ring (C(73)–O(73), C(83)–O(83))
with both rhenium groups (shortest distances: 3.028(7) and
˚
˚
3.135(8) A; centroid–centroid distances: 3.413(7) and
3.599(8) A). Noncovalent interactions create a three-
dimensional extended structure for 2 Æ CH3CN. Most dom-
inant are CH–p, CH–Br, and CH–O interactions involving
methine and pyrazolyl groups as hydrogen atom donors.
Pyrazolyl groups, along with the bromine and carbonyl
oxygen atoms, also serve as hydrogen atom acceptors.
It is interesting that in both complexes the ‘‘homobime-
tallic’’ groups are oriented on opposite sides of the linking
arene ring. If these orientations are driven by simple steric
factors, the opposite result might have been expected. That
is, if one metal center is clearly larger that the other, the
complex with two of the larger metal units would be oppo-
site while the one with the two smaller metals centers would
have these smaller metal centers on the same side of the
ring. In the case of 2, the factor driving the [Re(CO)3Br]
fragments to reside on opposite sides of the central arene
ring is that this orientation allows two strong pCO–pAr
interactions. The fact that the two [Pt(p-tolyl)] groups in
1 are on opposite sides possibly implies they are the larger
group, but the difference is likely small.
Fig. 2. Illustration of dimeric association of complex molecules in 1
created by weak, CH–Br hydrogen bonds (dashed lines). Only one
component of the tolyl group disorder is shown.
organizing these layers. The disorder in the solvent region,
however, prevents the identification of these interactions.
The structure of {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2-
[Pt(p-tolyl)2] Æ CH3CN (2 Æ CH3CN) is shown by the
ORTEP drawing in Fig. 3. The asymmetric unit of the crys-
tal contains a disordered molecule of acetonitrile. The
metal complex in 2 Æ CH3CN, however, is fully ordered.
Selected bond angles and distances for 2 Æ CH3CN are

D.L. Reger et al. / Journal of Organometallic Chemistry 692 (2007) 5414–5420
5419
Table 3
ccdc.cam. ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem. 2007.08.029.
˚
Selected bond distances (A) and angles (ꢁ) for {l-1,3,5-[CH(pz)2]3C6H3}-
[Re(CO)3Br]2[Pt(p-tolyl)2] Æ CH3CN (2 Æ CH3CN)
Re(1)–C(71)
Re(1)–C(72)
Re(1)–C(73)
Re(1)–N(11)
Re(1)–N(21)
Re(1)–Br(1)
Re(2)–C(81)
Re(2)–C(82)
Re(2)–C(83)
Re(2)–N(31)
Re(2)–N(41)
Re(2)–Br(2)
Pt(1)–C(91)
Pt(1)–C(101)
Pt(1)–N(51)
Pt(1)–N(61)
1.921(9)
1.900(9)
1.914(9)
2.175(7)
2.180(7)
2.6189(9)
1.907(9)
1.939(9)
1.904(8)
2.182(7)
2.182(7)
2.6398(8)
1.989(7)
1.991(8)
2.105(6)
2.105(6)
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C(71)–Re(1)–N(11)
C(72)–Re(1)–N(11)
N(11)–Re(1)–N(21)
C(71)–Re(1)–Br(1)
C(81)–Re(2)–N(31)
C(82)–Re(2)–N(31)
N(31)–Re(2)–N(41)
N(31)–Re(2)–Br(2)
C(91)–Pt(1)–C(101)
C(91)–Pt(1)–N(61)
N(51)–Pt(1)–N(61)
C(91)–Pt(1)–N(51)
174.2(3)
90.7(3)
84.1(2)
89.2(3)
174.4(3)
90.6(3)
86.0(2)
82.18(15)
91.5(3)
89.3(3)
89.3(2)
178.5(3)
3.3. Summary
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[Pt(p-tolyl)2(l-SEt2)]2 with the homometallic rhenium
carbonyl complexes {l-1,3,5-[CH(pz)2]3C6H3}Re(CO)3Br
and {l-1,3,5-[CH(pz)2]3C6H3}[Re(CO)3Br]2, respectively.
These compounds demonstrate that heterometallic species
may be prepared by sequential incorporation of different
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Intramolecular pCO–pAr stacking appears to be an impor-
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Acknowledgements
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We thank the National Science Foundation (CHE-
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P. Sloan Foundation for support of R.P.W.
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Appendix A. Supplementary material
CCDC 654353 and 654354 contain the supplementary
crystallographic data for 1 and 2 Æ CH3CN. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
(m) N. Guo, L. Li, T.J. Marks, J. Am. Chem. Soc. 126 (2004) 6542;

5420
D.L. Reger et al. / Journal of Organometallic Chemistry 692 (2007) 5414–5420
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Am. Chem. Soc. 125 (2003) 10788;
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Sun, G. van Koten, Inorg. Chim. Acta 327 (2002) 15.
[9] SMART Version 5.630, SAINT+ Version 6.45 and SADABS Version 2.10.
Bruker Analytical X-ray Systems Inc., Madison, Wisconsin, USA,
2003.
[10] G.M. Sheldrick, SHELXTL Version 6.1; Bruker Analytical X-ray
Systems Inc., Madison, Wisconsin, USA, 2000.
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Utrecht, The Netherlands, Spek, A.L., 1998.
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noncovalent interactions, see D.L. Reger, R.F. Semeniuc, V. Rasso-
lov, M.D. Smith, Inorg. Chem. 43 (2004) 537.
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(p) J. Wang, H. Li, N. Guo, L. Li, C.L. Stern, T.J. Marks,
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(q) G.P. Abramo, L. Li, T.J. Marks, J. Am. Chem. Soc. 124 (2002)
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