Synthesis and characterization of 11-vertex platinaborane compounds having nido-PtB10H12 and nido-Pt2B9H 10 skeletons

Article abstract of DOI:10.1016/j.poly.2011.10.019

The reaction of closo-[B₁₀H₁₀]^2- with [PtCl₂(PPh₃)₂] in MeOH at reflux affords the B-methoxy substituted 11-vertex nido-platinaborane compound [(PPh ₃)₂PtB₁₀H₁₀-8-H _0.5(OCH₃)_0.5-10-(OCH₃)] (1) and the known species [(PPh₃)₂PtB₁₀H ₁₁-8-(OCH₃)] (2) and 1,6-(PPh₃) ₂B₁₀H₈ (3). The same reaction under solvothermal condition gives the partially degraded diplatinaborane [(PPh ₃)₂(μ-PPh₂)Pt₂B₉H ₇-3,9,11-(OMe)₃] (4) with a novel nido-Pt ₂B₉H₁₀ skeleton. The new metallaborane compounds have been characterized by spectroscopic methods and single-crystal X-ray analyses. In particular, computational/theoretical chemistry supports the ultimate structural confirmation of 4. The structures of these metallaboranes exhibit interesting intra- and/or intermolecular C-H...O hydrogen bonding interactions.

Full text of DOI:10.1016/j.poly.2011.10.019

Polyhedron 31 (2012) 607–613
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Polyhedron
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Synthesis and characterization of 11-vertex platinaborane compounds having
nido-PtB10H12 and nido-Pt2B9H10 skeletons
a
b
a
c
c
Yong Nie a, , Jin-Ling Miao , Chun-Hua Hu , Hai-Yan Chen , Man Sing Cheung , Zhen-Yang Lin ,
⇑
Markus Enders d, Walter Siebert d
a School of Chemistry and Chemical Engineering, Shandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials, University of Jinan, 106 Jiwei Road, 250022
Jinan, PR China
b Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA
c Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China
d Anorganisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
a r t i c l e i n f o
a b s t r a c t
The reaction of closo-[B10H10]
2À with [PtCl2(PPh3)2] in MeOH at reflux affords the B-methoxy substituted
11-vertex nido-platinaborane compound [(PPh3)2PtB10H10-8-H0.5(OCH3)0.5-10-(OCH3)] (1) and the known
species [(PPh3)2PtB10H11-8-(OCH3)] (2) and 1,6-(PPh3)2B10H8 (3). The same reaction under solvothermal
Article history:
Received 20 July 2011
Accepted 12 October 2011
Available online 19 October 2011
condition gives the partially degraded diplatinaborane [(PPh3)2(l-PPh2)Pt2B9H7-3,9,11-(OMe)3] (4) with
a novel nido-Pt2B9H10 skeleton. The new metallaborane compounds have been characterized by spectro-
scopic methods and single-crystal X-ray analyses. In particular, computational/theoretical chemistry sup-
ports the ultimate structural confirmation of 4. The structures of these metallaboranes exhibit interesting
intra- and/or intermolecular C–HÁ Á ÁO hydrogen bonding interactions.
Keywords:
Borane
Metallaborane
Platinaborane
Synthesis
Ó 2011 Elsevier Ltd. All rights reserved.
Crystal structure
1. Introduction
is often obtained, the resulting metallaborane compounds have
been found to be mainly in two categories, i.e. closo/isocloso 11-ver-
Metallaborane cluster chemistry has been expanded rapidly
since the seminal work of the first preparation of metallacarbor-
anes by Hawthorne et al. [1] and metallaboranes by Greenwood
and McGinnety [2]. Hundreds of metallaborane compounds have
been reported, including their synthesis, characterization, reactiv-
ity studies and electronic structures [3]. Despite the vast informa-
tion accumulated, it is still not straightforward to obtain certain
metallaboranes by design or directed synthesis. There are still
opportunities to obtain new structures by simply tuning the reac-
tion conditions.
tex MB10 species with the iron triad and nido-MB10 compounds
(Chart 1) with the nickel triad.
The reactions between [B10H10]
2À and [PtX2(PR3)2] (X = Cl, Br, I;
R = alkyl or aryl) in alcohols have been previously studied
[3a,6b,c,7]. It was found that the reactions might go via a PtB10H10
intermediate which, on attack by alcohols and the metal complexes,
gave the 11-vertex {PtB10} 7-platinaundecaboranes (Chart 1) with
metal insertion. While the spectroscopic results [6b] showed that
the possible alkoxy substitution could occur at 2-, 3-, 5-, 6-, 8-, 9-,
10-, 11-positions in the resulting {PtB10} cluster, experimental stud-
ies in different alcohols (MeOH, EtOH and iPrOH) revealed that the
alkoxy substituents can occupy various boron atoms as (for mono-
alkoxy substitution) 8-, 9-, 10-, 11-, or (for dialkoxy substitution)
8,10-positions. Recently Dou et al. [7a,b,8] introduced the solvother-
mal method to this reaction system (in EtOH and iPrOH, respec-
tively) and isolated several partial degradation compounds with a
novel {Pt2B9H9} cluster core.
There is considerable current interest in the construction of the
non-classical C–HÁ Á ÁX (X = C, N, O, S) [9] hydrogen bonding and X–
HÁ Á ÁH–Y (X = C, N, O, S; Y = M, B, Si, etc. where M represents metal
atoms) dihydrogen bonding systems [10]. In particular, such weak
inter- or intramolecular interactions have been described in borane
adducts [11], polyhedral boranes and carboranes [12] and metalla-
carboranes [13]. We have recently reported a B-acetoxy 11-vertex
As
[B10H10
a
]
useful metallaborane synthon, the closo-decaborate
2À (Chart 1) has been extensively investigated due to its high
thermal and chemical stability, three-dimensional aromaticity and
easy availability [4]. It can undergo various types of transformations,
including cluster hydride substitution, oxidative coupling and cage
opening-metal insertion to form metallaborane compounds, mainly
with late transition metal complexes [4,5]. In some special cases,
degradation leads to interestingly different structural types,
depending on the transition metal complex and the reaction condi-
tions utilized [3a,5]. Although the cage-opening mechanism [6] of
closo-[B10H10]
2À is rather complex and thus a mixture of compounds
⇑
Corresponding author. Tel.: +86 531 82767367; fax: +86 531 82767367.
E-mail address: chm_niey@ujn.edu.cn (Y. Nie).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.10.019

608
Y. Nie et al. / Polyhedron 31 (2012) 607–613
Ph3P
Ph3P
1
H
Pt
B
OMe
B
B
H
H
M
2-
5
MeOH
B
B
11
B
PtCl2(PPh3)2
B10H10
+
MeO/H
2
6
4
8
H
10
3
9
8
2
B
9
6
B
B
B
1
3
7
5
4
PPh3
B
10
1
Ph3P
Ph3P
2À
Chart 1. Schematic representation and numbering of the closo-B10H10 and nido-
7-MB10 skeletons (each vertex with a number represents a BH).
H
Pt
B
B
B
H
B
B
B
B
B
B
B
B
MeO
+
+
platinaundecaborane [7,7-(PPh3)2-7-PtB10H11-11-(OCOMe)] in
which intra- and intermolecular C–HÁ Á ÁO hydrogen bonding and
C–HÁ Á ÁH–B dihydrogen bonding interactions lead to a 1-D supra-
molecular structure [14]. In this paper we show examples of B-alk-
oxy platinaborane compounds in which the intra- and/or
intermolecular hydrogen bonds can result in 1-D or 2-D supramo-
lecular structures.
B
B
B
B
B
B
PPh3
B
B
2
3
2À
Scheme 1. Reaction of B10H10 with PtCl2(PPh3)2 in refluxing MeOH.
On the other hand, computational/theoretical chemistry has
been developed rapidly in recent years and has mutually benefited
from the involvement in nearly all aspects of experimental chemis-
try. In particular, it has found various applications in elucidating
unusual chemical bonding, assisting structure determinations,
establishing important chemical concepts and impacting experi-
mental studies [15]. In order to get more information on the me-
opening/metal insertion, but also transition metal mediated/cata-
lyzed B–H bond activation, although to a lesser extent.
The isolation of the platinaboranes 1 and 2 proves the similar
type of metal insertion/cage opening pattern as in the aforemen-
tioned metallaborane reactions. In the present case, the smallest
methoxy substituents occupy the 8,10- (in 1) and 8-positions (in
2) in the resulting metallaborane clusters. It should be noted that
tal-mediated cage-opening process of [B10H10
]
2À, we have studied
2À
the reactions of [B10H10
]
with [PtCl2(PPh3)2] in MeOH at reflux
the formation of 2 was previously achieved by the reaction [7c] of
2À
and under solvothermal conditions, respectively, and obtained
mono-nuclear and dinuclear platinaundecaboranes. In the case of
the diplatinaborane compound, we have carried out theoretical
and experimental studies for the ultimate structural confirmation
of its novel nido-Pt2B9H10 skeleton. Herein we report on the details
of thesynthesis and structural characterizationof these platinabora-
ne compounds.
[B10H10
]
with a mixture of [PtCl2(PPh3)2] and [RuCl2(PPh3)3] in
refluxing methanol where a preferred reaction with the platinum
complex was observed.
As the structure of 2 has already been communicated, we only
discuss here the spectroscopic data and some previously unre-
ported structural characteristic especially the intramolecular
hydrogen bond. In the 11B NMR spectrum of 2, a typical pattern
of the monosubstituted nido-PtB10 cluster was observed with eight
partially overlapped resonance peaks similar to those reported for
the B-ethoxy substituted analogs [6b]. The 1H NMR spectrum
exhibits a singlet for the B-bound OMe group at d = 3.41 and a
broad peak for the bridging cluster hydrogen at À2.79 ppm. Be-
cause of the monosubstitution on the cluster vicinal to the Pt
atom, the 31P{1H} NMR spectrum gives two signals.
The molecular structure of 2 contains an 11-vertex nido-PtB10
skeleton in which the Pt atom lies in the open PtB4 face. In addi-
tion, there exists intramolecular hydrogen bonding interaction
between the C–H moiety of one of the PPh3 ligands and the meth-
oxy substituent, with the C66Á Á ÁO1 distance being 3.064(9) Å.
The structure of 1 was determined by single-crystal X-ray studies
at room temperature and low temperature as well, giving essentially
the same results, therefore only the data from the low temperature
determination are provided and discussed here. According to the
X-ray crystallographic study, compound 1 is actually a solid solution
which contains two components: [(PPh3)2PtB10H11-10-(OCH3)] (1a)
and [(PPh3)2PtB10H10-8,10-(OCH3)2] (1b) in a ratio of 1:1. Accord-
ingly, the 1H NMR spectrum shows three singlets for the B-bound
methoxy groups at d = 2.91, 3.03 and 3.49 ppm, respectively, with
the integral ratio being ca. 2:1:2. In addition, three broad signals
associated with the cluster bridging hydrogen atoms are found at
À0.51, À0.69 and À0.98 ppm, respectively. In the 11B NMR spectrum
of 1, in total ca. 15 partially overlapped resonance peaks are ob-
served. Moreover, the HR-MS spectra with the two peaks at m/
z = 871.3441 and 901.3594, corresponding to the molecular ions
[1a+] and [1b+], respectively, prove the coexistence of the two
2. Results and discussion
2.1. Platinaboranes 1 and 2 having nido-PtB10H12 skeleton
The reaction of [B10H10]
2À with [PtCl2(PPh3)2] was carried out in
refluxing methanol (Scheme 1), which resulted in a deep-red
solution and a yellow precipitate. With the aid of TLC separation,
two yellow solid compounds were isolated from the precipitate
and characterized to be the 11-vertex nido-platinaundecaboranes
2 [7c] and 1 with B-methoxy substituent(s), respectively, whose
solid state structures were established by single-crystal X-ray anal-
yses (see below). A small amount of crystals were obtained from
the red filtrate and identified by X-ray crystallography to be the
known species 1,6-(PPh3)2B10H8 (3) [16].
The formation of compound 3 apparently has something to do
with the platinum complex(es) present in the reaction mixture,
2À
as 3 was also produced in the reaction of [B10H10
]
with
[PdCl2(PPh3)2] in refluxing ethanol [16]. In this connection, it was
reported that the reaction [17a] of [PdCl2(PMe2Ph)2] with
[B10H10]
2À, as well as the [PdCl2(PPh3)2]/CuI catalyzed reaction
[17b] of [B10H9N2]1À with Ph2PH gave phosphine-bound decabora-
ne compounds similar to 3. An additional example is that
[NHMe3][7-Me-
[PdCl2(PPh3)2] in refluxing ethanol solution to afford PPh3 addition
compounds such as [5-PPh3-7-Me- -(9,10-HMeC)-nido-7-CB10H9]
l-(9,10-HMeC)-nido-7-CB10H10
]
reacts
with
l
[18]. These results suggest that the reaction shown in Scheme 1
involves not only the metal complex/alcohol mediated cage-

Y. Nie et al. / Polyhedron 31 (2012) 607–613
609
components in compound 1. Recently we have reported a similar
platinaborane compound [(PPh3)2PtB10H10-9,10-(H0.7Cl0.3)2] which
was isolated from the same reaction in refluxing tBuOH [19].
The molecular structure and selected bond parameters of 1 are
presented in Fig. 1. While 1 has the same type of nido-PtB10 cluster
as in 2, its methoxy group substitution occurs at the B8 and B10
atom(s). On the B8 atom, the methoxy substituent and the hydrogen
atom each has an occupancy of 0.5 as optimized by X-ray analyses.
The Pt center further coordinates to two exo-polyhedral PPh3 li-
gands. The Pt7–B8 and Pt7–B11 bond lengths in 1 of 2.322(4),
2.320(4) Å, respectively, are slightly longer than those of 2.235(4)
and 2.247(4) Å for Pt7–B2 and Pt7–B3, suggesting that the Pt–B
bonds involved in the open PtB4 face are slightly weaker than the
other two Pt–B bonds [3a]. The present Pt–B distances are found to
be similar to those reported for analogous clusters, e.g. 2.214
reaction at reflux for 65 h, this reaction afforded, after TLC separa-
tion, a small amount of the partially degraded diplatinaundecabo-
rane cluster [(PPh3)2(l-PPh2)Pt2B9H7-3,9,11-(OMe)3] (4) as a red
solid, along with a number of unidentified metallaborane species
(all in small amount, some of which were preliminarily character-
ized by IR spectroscopy). It was difficult to measure the solution
NMR (11B, 13C and 31P) of 4 due to the low yield (<5 mg), however,
the 1H NMR spectrum (after expansion) does exhibit two singlets
for the B-OMe groups at d = 3.33 and 3.78 ppm, in an integral ratio
of ca. 1:2, in accord with the X-ray crystallographic results (see be-
low). Surprisingly, the attempts by both EI and FAB mass spectro-
metric methods failed to give definite molecular information.
In 2007 Kennedy and co-workers [20] reported a closely related
dipalladaundecaborane of the formula [(PPh3)2(l-PPh2)Pd2B9H8-
9,11-(OEt)2] which satisfies the Wade–Mingos rules [21] and has
an endo cluster hydrogen atom. In this case, all the cluster hydro-
gen atoms could be located crystallographically which poses a
question of whether the platinum analogs [7a,b,8] should have a
nido-Pt2B9H10 rather than nido-Pt2B9H9 cluster skeleton. In order
to confirm the molecular formula of compound 4, we used a com-
bination of experimental and computational methods.
Our initial X-ray crystal structure determination (at 298 K) of 4
showed that the diplatinaundecaborane cluster has a molecular for-
mulaof [(PPh3)2(l-PPh2)Pt2B9H6-3,9,11-(OMe)3]. Withthisformula,
the cluster should [20] have an odd number of electrons and one
would expect that the cluster is paramagnetic. However, in our
NMR tests the locking and shimming had no apparent problem
and the proton signals were found in the normal region, suggesting
that the sample is diamagnetic. In addition, on the basis of the
Wade–Mingos electron counting rules and the 16-electron rule
commonly used for Pt and Pd complexes, we believe that one hydro-
gen atom has not been located in the cluster. In other words, the
(7)–2.303(7) Å for 2, 2.178(16)–2.326(16) Å for [(PPh3)2PtB10H11
-
8-(OiPr)] [7c], 2.205(6)–2.327(6) Å for [(PPh3)2PtB10H11-9-(OiPr)]
[7c], 2.223(6)–2.330(6) Å for [(PPh3)2PtB10H10-8,10-(OEt)2], 2.215
(10)–2.340(11) Å for [(PPh3)2PtB10H10-8,10-(OiPr)2] [7d] and 2.23
4(8)–2.311(7) Å for [(PPh3)2PtB10H10-9,10-(H0.7Cl0.3)2] [19]. The B–
B distances (1.745(6)–1.994(6) Å) in 1 are also found to be similar
to those in the above-mentioned structures. The similar bond
lengths found in these structures indicate that, despite the substitu-
tion with different alkoxy groups at different position(s), the PtB10
cluster core is essentially not influenced.
Interestingly, there are multiple weak hydrogen bonding inter-
actions in the structure of 1. As shown in Fig. 2, intramolecular C–
HÁ Á ÁO hydrogen bonding interaction (C42Á Á ÁO1 3.197(6) Å) is
found. In addition, the intermolecular C–HÁ Á ÁO hydrogen bonds
(C55Á Á ÁO2 3.166(4) Å) link the platinaborane molecules into a 1-
D zigzag chain. Finally, the molecules are assembled into a 2-D
supramolecular structure by another set of intermolecular C–
HÁ Á ÁO hydrogen bonds (C23Á Á ÁO2 3.303(4) Å), as demonstrated in
Fig. 2. It should be noted that some analogous B-methoxy substi-
tuted platinaboranes with other phosphine ligands such as PMe2Ph
have been reported but not structurally characterized [3a].
cluster should have a formula of [(PPh3)2(l-PPh2)Pt2B9H7-3,9,11-
(OMe)3].
In order to locate the extra hydrogen atom missed from the ini-
tial X-ray crystal structure determination, we carried out geometry
optimization calculations using density functional theory. A num-
ber of initial structures were prepared for doing the geometry opti-
mization calculations by adding a hydrogen atom to different sites
of the single crystal X-ray-determined structure, having the added
hydrogen atom at the center of the boron cage or of the Pt2B3 open
pentagonal face, as an atom bridging each of the five bonds in the
Pt2B3 open pentagonal ring, or as a terminal atom bonded to a bor-
on in the open face. Remarkably, all of the geometry optimization
calculations led to a common final structure, no matter which ini-
tial structure was used. The common final structure, shown in
Fig. S1, has the added hydrogen terminally bonded to the non-me-
tal-bonded boron in the Pt2B3 open pentagonal face, a manner very
similar to the X-ray crystal structure of the dipalladaundecaborane
cluster reported [20].
2.2. Diplatinaborane 4 having nido-Pt2B9H10 skeleton
2À
The reaction of [B10H10
]
with [PtCl2(PPh3)2] in methanol was
further studied under a solvothermal condition under autogenous
pressure (Scheme 2). Much different from the above-mentioned
In Fig. S1 the selected calculated bond distances are compared
against their initially X-ray-determined parameters. A good agree-
ment between theory and experiment can be found. With these re-
sults in hand, we went on for a re-refinement of the same data
used for the initial structural solution. It turned out that the extra
hydrogen atom can indeed be located in the difference Fourier
map. Thus the location of the terminal endo-hydrogen atom on
the specific boron atom is finally confirmed.
The molecular structure of 4 from the re-refinement is shown in
Fig. 3. As can be seen, the compound has an 11-vertex nido-Pt2B9
skeleton, with the two Pt atoms occupying the adjacent positions.
Fig. 1. The molecular structure of
1
in 1Á2CH2Cl2, with atom labels and 25%
probability displacement ellipsoids. The hydrogen atoms except those on the
cluster were omitted for clarity. For the same reason only the ipso-carbon atoms of
the PPh3 groups are shown. Selected bond lengths (Å) and angles (°): Pt7–P1,
2.3674(8), Pt7–P2 2.3297(8), Pt7–B8 2.322(4), Pt7–B11 2.320(4), Pt7–B2 2.235(4),
Pt7–B3 2.247(4), B8–B9 1.851(6), B9–B10 1.994(6), B10–B11 1.857(5), B5–B9
1.756(6), B5–B10 1.745(6), B8–O1 1.335(6), B10–O2 1.387(4); P1–Pt7–P2 95.43(3).
The two Pt atoms are bridged by a
l-PPh2 group, while each Pt
atom further coordinates to a PPh3 ligand. Different from those
in 1 and 2, in compound 4 three OMe substituents are found at
the platinum-bound B1, B3 and B5 atoms, with the B1 and B3
atoms in the upper belt and the B5 atom at the lower belt.

610
Y. Nie et al. / Polyhedron 31 (2012) 607–613
Fig. 2. (top) The 1-D zigzag chain by intermolecular C–HÁ Á ÁO hydrogen bonds in 1; (bottom) the 2-D assembly by intermolecular C–HÁ Á ÁO hydrogen bonds in 1 viewed along
the a axis.
Ph2
P
PPh3
Ph3P
Pt
PtCl2(PPh3)2
+
Pt
OMe
B
B
H
MeOH
B
B
B
B
MeO
solvothermal
2-
B10H10
B
B
MeO
B
4
2À
Scheme 2. Solvothermal reaction of B10H10 with PtCl2(PPh3)2 in MeOH.
The Pt–Pt distance of 2.6488(5) Å in 4 is similar to those reported in
analogous structures reported (2.6357(8)–2.6672(11) Å) by Dou et al.
[7a,b,8], but shorter than that in the closo-diplatinaborane [(PMe
2Ph)3ClPt2B10H9(PMe2Ph)] (2.863 Å) [22], [(PMe2Ph)4Pt2B10H10] (2.96
Fig. 3. The molecular structure of 4 after a re-refinement, with atom labels and 25%
probability displacement ellipsoids for non-H atoms. The hydrogen atoms except
those on the cluster were omitted for clarity. For the same reason only the ipso-
5(1) Å) [23], and the
l-PPh2-containing cluster [Pt3(l-PPh2)
carbon atoms of the PPh3 and l-PPh2 groups are shown. Selected bond lengths (Å)
3Ph(PPh3)2] (2.758(3)–3.074(4) Å) [24]. The Pt–B bond lengths
(2.215(11)–2.305(12) Å) and Pt–P bond lengths (2.294(2)–2.324
(2) Å) in 4 are similar to the values reported for the related compounds.
The Pt(1)–P(1)–Pt(2) bond angle of 70.20(6)° is somewhat smaller that
and angles (°): Pt1–Pt2 2.6488(5), Pt1–P1 2.294(2), Pt1–P2 2.304(2), Pt2–P1
2.312(2), Pt2–P3 2.324(2), Pt1–B3 2.215(11), Pt1–B4 2.278(11), Pt1–B5 2.252(11),
Pt2–B1 2.305(12), Pt2–B5 2.295(11), Pt2–B6 2.260(10), B1–B2 1.863(16), B2–B3
1.965(15), B2–B7 1.733(15), B2–B8 1.758(14), B1–O1 1.393(12), B3–O2 1.370(12),
B5–O3 1.395(12); Pt1–P1–Pt2 70.20(6).
the mean Pt–P–Pt angle (88.2°) in [Pt3(l-PPh2)3Ph(PPh3)2] [24]. The
mean B–O bond length (1.390 Å) in 4 is similar to those found in 1
and 2.
3.318(14) Å) link the diplatinaborane molecules into a 1-D zigzag
chain. Similar C–HÁ Á ÁO hydrogen bonds could be observed (not
mentioned in the original papers) in the related alkoxy-substituted
platinaborane compounds [7a,b,8] that have CÁ Á ÁO distances rang-
ing from 3.153(18) to 3.224(13) Å.
Similar to those in 1, there are also multiple hydrogen bonding
interactions in the structure of 4. As shown in Fig. 4, the intramo-
lecular C–HÁ Á ÁO hydrogen bonds (C14Á Á ÁO2 3.002(9), C26Á Á ÁO3
3.235(14) and C38Á Á ÁO1 3.148(14) Å, respectively) are found. Addi-
tionally, the intermolecular C–HÁ Á ÁO hydrogen bonds (C47Á Á ÁO3

Y. Nie et al. / Polyhedron 31 (2012) 607–613
611
Fig. 4. The 1-D zigzag chain by intermolecular C–HÁ Á ÁO hydrogen bonds in 4.
tion of the diplatinaborane 4 are definitely associated with the
Table 1
alcohol/transition metal mediated cage opening mechanism of
Details of the crystal parameters, data collection and refinement for 1 and 4.
[B10H10]
2À in these reactions, for which more experimental studies
Compound
1Á2CH2Cl2
4
are needed and probably theoretical chemistry could be involved.
The intra- and/or intermolecular C–HÁ Á ÁO hydrogen bonding inter-
actions found in these structures further prove the potential of
metallaborane compounds for the construction of supramolecular
assemblies. Taking the diplatinaundecaborane 4 as example, we
have shown that theoretical/computational chemistry plays an
important role in the structural determination of novel metallabo-
rane compounds.
Chemical formula
T (K)
Formula mass
Crystal system
Space group
a (Å)
C
39.50H49B10Cl4O1.50P2Pt C51H56B9O3P3Pt2
100(2)
298(2)
1054.72
monoclinic
P21/c
11.7273(4)
16.2486(6)
23.8116(9)
90.00
96.0760(10)
90.00
4511.9(3)
4
1297.34
orthorhombic
P212121
13.4455(16)
14.0029(17)
26.792(2)
90.00
90.00
90.00
5044.4(10)
4
1.708
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
4. Experimental
Unit cell volume (Å3)
Z
Dcalc (Mg mÀ3
)
1.553
3.451
4.1. General
l
(mmÀ1
)
5.678
F(000)
2096
2528
All reactions were carried out under a dry nitrogen atmosphere,
and the subsequent workup were all performed in air. Solvents
used for reactions were dried, distilled, and saturated with nitro-
gen. NMR spectra were recorded on a Bruker Avance II 400 spec-
trometer (1H: 399.89 MHz, 11B: 128.30 MHz, 13C: 100.55 MHz,
31P: 161.88 MHz) in CDCl3 as solvent. Et2OÁBF3 was used as exter-
nal standard for 11B NMR. As internal references for 1H and 13C
NMR, the signals of the deuterated solvents were used, the shifts
were calculated relative to TMS and given in ppm. MS: ZAB-2F
VH Micromass CTD and JEOL MS Station JMS 700 spectrometers.
The starting materials [NEt4]2B10H10 [25] and [PtCl2(PPh3)2] [26]
were prepared according to the literature.
Crystal size (mm3)
h (°)
0.21 Â 0.14 Â 0.13
1.52–27.00
À14 6 h 6 14
À20 6 k 6 20
À30 6 l 6 30
59296
0.33 Â 0.28 Â 0.24
1.52–26.00
À16 6 h 6 16
À17 6 k 6 11
À22 6 l 6 33
22678
Limiting indices
No. of reflections measured
No. of independent
reflections
9853
9874
Rint
0.0451
0.6625, 0.5310
0.0636
0.3427, 0.2559
Maximum and minimum
transmission
Goodness-of-fit (GOF) on F2
1.044
0.0265
0.0614
0.0344
0.0634
0.765, À1.075
1.017
0.0409
0.0818
0.0583
R1 (I > 2
r(I))
wR(F2) (I > 2
R1 (all data)
r(I))
wR(F2) (all data)
0.0886
4.2. Synthetic procedures
D
qmax,
(e ÅÀ3
)
1.368, À0.755
min
Flack parameter
À0.031(9)
4.2.1. Synthesis of platinaboranes 1 and 2
A mixture of [PtCl2(PPh3)2] (316 mg, 0.4 mmol), (Et4N)2B10H10
(150 mg, 0.4 mmol) and methanol (30 ml) were put into a 50-ml
Schlenk flask and refluxed for 65 h. The resulting mixture was fil-
tered to give a yellow residue and an red filtrate. The residue
was dissolved with CH2Cl2, which was chromatographed by pre-
parative TLC using dichloromethane/petroleum ether (4:1, V/V)
as the eluting medium. Two yellow bands at Rf = 0.83 and
3. Conclusions
We have synthesized new B-OMe substituted 11-vertex nido-
platinaborane cluster compounds by the reaction of [B10H10
2À
]
with [PtCl2(PPh3)2] in MeOH at reflux and under solvothermal con-
ditions, respectively. The platinaborane compounds have been
structurally characterized by spectroscopic methods and X-ray
studies, which show different skeletons (nido-PtB10H12 from a re-
flux reaction and nido-Pt2B9H10 from a solvothermal reaction), fur-
ther proving that a fine tuning of the reaction conditions could
result in new structures. For these alkoxy substituted platinabor-
anes, the OR group(s) are found to be located at various positions.
The different substitution mode of the OR groups and the forma-
Rf = 0.47 were separated from which yellow solid 2 [7c] (53 mg,
2À
15.2%, based on
B
10H10
)
and
1
(204 mg, 57.2%, based on
B10H102À), respectively, were obtained. From the red filtrate a small
amount of brownish crystals were obtained which was identified
by X-ray analysis to be 1,6-(PPh3)2B10H8 (3).
2: IR (KBr)
mmax = 3436 (m), 2931 (w), 2528 (s), 1630 (w), 1436
(s), 1093 (s), 693 (s) cmÀ1
.
1H NMR (298 K): dH = 7.28–7.36 (m,
30H, PhH), 3.41 (s, 3H, OMe), À2.79 (s, br. 2H, BHB) ppm. 11B{1H}
NMR (298 K): dB = 30.9, 24.2, 9.2, 1.0, À4.5, À18.8, À21.4,

612
Y. Nie et al. / Polyhedron 31 (2012) 607–613
À31.6 ppm. 13C NMR (298 K): dC = 57.7 (OMe), 128.1, 130.6, 134.7
Acknowledgements
(Ph) ppm. 31P NMR (298 K): dP = 31.45 (s, 1 195Pt–31P = 2636.7 Hz),
J
29.71 (s,
J
1 195Pt–31P = 2566.9 Hz) ppm.
max = 3436 (m), 2930 (w), 2531 (s), 1632 (w), 1436
The authors thank the University of Jinan (No. B0605) and the
NSFC (20702020) and SRF for ROCS, SEM (SQT0804) for financial
support of this work. We thank Prof. Hubert Wadepohl for his ef-
forts on the structural determination of 4.
1: IR (KBr):
m
(s), 1229 (s), 695 (s). 1H NMR (298 K): dH = 7.14–7.42 (m, 30H,
PhH), 3.49 (s, 3H, OMe), 3.03 (s, 3H, OMe), 2.91 (s, 3H, OMe), À0.51
(s, br. 1H, BHB), À0.69 (s, br. 2H, BHB), À0.98 (s, br. 1H, BHB).
11B{1H} NMR (298 K): dB = 33.8, 22.3, 19.7, 14.2, 10.2, 5.9, 0.95,
À3.2, À5.9, À8.5, À19.2, À24.8, À27.4, À30.0, À34.4 ppm. 13C NMR
(298 K): dC = 135.2, 135.1, 134.6, 134.5, 134.2, 134.1, 127.8, 127.7,
128.2, 128.1 (Ph), 58.0 (OMe), 56.9 (OMe), 56.5 (OMe) ppm. EI-MS:
Appendix A. Supplementary data
CCDC 720908 and 686236 contain the supplementary crystallo-
graphic data for 1 and 4. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: de-
posit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2011.10.019.
failed to give definite results. HR-FAB-MS: m/z = 871.3441 [1a+],
11
Calcd. for
C
37H46OP2
B
10
195Pt 871.3445
(D
m = À0.5 mmu);
901.3594 [1b+], Calcd. for C38H46O2P210B11B9196Pt 901.3552
(D
m = 4.2 mmu).
Single crystals of 1 suitable for X-ray study were grown by dif-
fusion method [dichloromethane/n-hexane (1:4, V/V)] after 24 h at
room temperature.
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