Syntheses of mono- and dinuclear diiodoboryl complexes of platinum

Article abstract of DOI:10.1021/ic7011028

Treatment of [Pt(PCy₃)₂] (Cy = cyclohexyl) with BI₃ afforded trans-[(Cy₃P)₂Pt(I)(BI ₂)] by the oxidative addition of a B-I bond. The title compound represents the first diiodoboryl complex and was fully characterized by NMR spectroscopy and X-ray diffraction analysis. The latter revealed a very short Pt-B distance, thus indicating a pronounced π contribution to this bond. By the addition of another 1 equiv of BI₃ to trans-[(Cy ₃P)₂Pt(I)(BI₂)], a new Pt species [(Cy ₃P)(I₂B)Pt(μ-I)]₂ was formed with concomitant buildup of the phosphine borane adduct [Cy₃P-BI ₃]. The former is obviously obtained by abstraction of PCy ₃ from trans-[(Cy₃P)₂Pt(I)(BI₂)] and the subsequent dimerization of two remaining fragments. Interestingly, the dimerization is reversible, and the dinuclear compound can be converted to trans-[(Cy₃P)₂Pt(I)(BI₂)] upon the addition of PCy₃.

Full text of DOI:10.1021/ic7011028

Inorg. Chem. 2007, 46, 8796−8800
Syntheses of Mono- and Dinuclear Diiodoboryl Complexes of Platinum
Holger Braunschweig,* Krzysztof Radacki, and Katharina Uttinger
Julius-Maximilians UniVersita¨t Wu¨rzburg, Am Hubland, 97074 Wu¨rzburg, Germany
Received June 5, 2007
Treatment of [Pt(PCy3)2] (Cy
I bond. The title compound represents the first diiodoboryl complex and was fully characterized by NMR
spectroscopy and X-ray diffraction analysis. The latter revealed a very short Pt B distance, thus indicating a
pronounced contribution to this bond. By the addition of another 1 equiv of BI3 to trans-[(Cy3P)2Pt(I)(BI2)], a new
Pt species [(Cy3P)(I2B)Pt( -I)]2 was formed with concomitant buildup of the phosphine borane adduct [Cy3P BI3].
) cyclohexyl) with BI3 afforded trans-[(Cy3P)2Pt(I)(BI2)] by the oxidative addition of a
B
−
−
π
µ
−
The former is obviously obtained by abstraction of PCy3 from trans-[(Cy3P)2Pt(I)(BI2)] and the subsequent dimerization
of two remaining fragments. Interestingly, the dimerization is reversible, and the dinuclear compound can be converted
to trans-[(Cy3P)2Pt(I)(BI2)] upon the addition of PCy3.
Introduction
sors for a variety of substitution and addition reactions at
the metal-coordinated Hal2B group (Hal ) halogen), thus
leading to highly unusual coordination modes of boron-
centered ligands. For example, the addition of 8-amino-
quinoline to the dichloroboryl complex [(Ph3P)2(OC)Os-
(BCl2)Cl] afforded a base-stabilized borylene complex, which
was reported by Roper et al. Further substitution chemistry
resulted in a range of tethered boryl- and base-stabilized
borylene compounds.4 Recently, a series of dichloroboryl
complexes trans-[(R3P)2Pt(Cl)(BCl2)] (R3 ) Ph3, Ph2Me,
PhMe2, Me3) were obtained by reacting the corresponding
Pt(0) species with BCl3. The latter shows reactivity toward
Lewis bases, forming trans-[(Me3P)2Pt(Cl){BCl2(L)}] (L )
NEt3, NC5H5), and the substitution of one or two boron-
bound chlorides by HNEt2, piperidine, or catechol is also
possible.5
Among the wide variety of boryl complexes, correspond-
ing dihaloboryl species [LnM-BX2] represent synthetically
rather challenging targets, most of which were only recently
achieved.1 Spectroscopically fully characterized difluoroboryl
complexes such as [(η5-C5Me5)IrH(BF2)(PMe3)] were first
reported by Bergman et al.,2 while Norman and co-workers
recently described cis-[(Ph3P)2Pt(BF2)2] and fac-[(Ph3P)2-
(OC)Ir(BF2)3], which were prepared by the oxidative addition
of B2F4 to Pt(0) or Ir(I) precursors.3 In the case of these
difluoro derivatives, no further functionalization is reported
so far, presumably due to the high thermodynamic stability
of the B-F bond and the decreased Lewis acidity of the
boron center.
However, dichloro- and dibromoboryl complexes provide
an interesting chemistry and were already utilized as precur-
Our group succeeded in preparing iron and manganese
complexes via the salt elimination of corresponding carbo-
nylates and BX3 (X ) Br, Cl) or BF3‚OEt2, resulting in the
formation of [(η5-C5R5)(OC)2Fe(BX2)] (R ) H, Me; X ) F,
Cl, Br) and [(OC)5Mn(BX2)] (X ) Cl, Br).6 Of these, [(η5-
C5H5)(OC)2Fe(BCl2)] was the first dichloroboryl complex
* To whom correspondence should be addressed. E-mail:
h.braunschweig@mail.uni-wuerzburg.de. Tel: +49 931 888 5260. Fax: +49
931 888 4623.
(1) (a) Irvine, G. I.; Lesley, M. J. G.; Marder, T. B.; Norman, N. C.;
Rice, C. R.; Robins, E. G.; Roper, W. R.; Whittell, G. R.; Wright, L.
J. Chem. ReV. 1998, 98, 2685-2722. (b) Braunschweig, H.; Colling,
M. Coord. Chem. ReV. 2001, 223, 1-51. (c) Braunschweig, H. Angew.
Chem. 1998, 110, 1882-1898. Braunschweig, H. Angew. Chem., Int.
Ed. 1998, 37, 1786-1801. (d) Aldridge, S.; Coombs, D. L. Coord.
Chem. ReV. 2004, 248, 535-559. (e) Braunschweig, H.; Kollann, C.;
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8796 Inorganic Chemistry, Vol. 46, No. 21, 2007
10.1021/ic7011028 CCC: $37.00
© 2007 American Chemical Society
Published on Web 09/14/2007

Diiodoboryl Complexes of Platinum
to be structurally characterized by X-ray diffraction,7 while
spectroscopic evidence was initially reported by Aldridge
et al.8 Despite its coordination to the potentially π-donating
metal fragment, Lewis bases can be added to the boron atom,
and compounds such as [(η5-C5Me5)(OC)2Fe{BX2(NC5H4-
4-Me)}] (X ) Cl, Br) were isolated.6,7 In addition, dichloro-
and dibromoboryl complexes served as precursors for met-
alloborylenes [(η5-C5Me5)(OC)2Fe(µ2-B)M(CO)n] (M ) Cr,
n ) 5; M ) Fe, n ) 4)9 and metal-base-stabilized
metalloborylenes [(η5-C5Me5)(OC)Fe(µ-CO)M(PCy3)(µ-Br)-
Pt(PCy3)Br(µ3-B)] (M ) Pd, Pt; Cy ) cyclohexyl),10 where
the boron atom is exclusively coordinated to two or three
transition metals. Aside from those, bridging boryl [(η5-C5-
Me5)Fe(µ-CO)2(µ-BCl2)Pd(PCy3)]11 and heterodinuclear bo-
rylene complexes [(η5-C5Me5)Fe(CO)(µ-CO)(µ-BBr)PdBr-
(PCy3)]12 were obtained.
Despite recent advances in the preparation of dihaloboryl
complexes, fully characterized transition-metal compounds
displaying B-I bonds are still absent. Herein, we report on
the synthesis and full characterization of two diiodoboryl
complexes, obtained by the oxidative addition of BI3 to [Pt-
(PCy3)2].
Figure 1. Molecular structure of 2. Thermal ellipsoids at 50% probability
level. The unit cell contains two independent molecules and one molecule
of C6H6. Only one molecule is represented, and hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (deg): Pt1-B1 1.947(8),
Pt1-P1 2.3524(15), Pt1-P2 2.3579(15), Pt1-I1 2.7813(7), B1-I2 2.189-
(7), B1-I3 2.185(8), B1-Pt1-P1 90.3(2), P1-Pt1-I1 91.63(4), P1-Pt1-
P2 165.31(6), B1-Pt1-I1 168.2(2), I3-B1-I2 110.4(3), Pt1-B1-I2
129.1(4), Pt1-B1-I3 120.5(4), P1-Pt1-B1-I2 97.8(3); Pt1′-B1′ 1.952-
(7), Pt1′-P1′ 2.3561(17), Pt1′-P2′ 2.3627(17), Pt1′-I1′ 2.7495(6), B1′-
I2′ 2.196(7), B1′-I3′ 2.183(7), B1′-Pt1′-P1′ 90.7(2), P1′-Pt1′-I1′
90.23(4), P1′-Pt1′-P2′ 167.22(6), B1′-Pt1′-I1′ 169.6(2), I3′-B1′-I2′
110.1(3), Pt1′-B1′-I2′ 129.5(4), Pt1′-B1′-I3′ 120.4(4), P1′-Pt1′-B1′-
I2′ 97.5(4).
Discussion
In an extension of our recent work on boryl complexes
being obtained by the oxidative addition of B-Br bonds to
late transition metals,12,13 [Pt(PCy3)2] was reacted with
equimolar amounts of BI3, and multinuclear NMR spectros-
copy of the benzene reaction mixture revealed the complete
consumption of the starting materials and the predominant
formation of one new species. The 31P{1H} NMR spectrum
showed a singlet at 10.3 ppm flanked by Pt satellites (J )
2737 Hz), with the coupling constant possessing a typical
magnitude for boryl complexes with phosphine ligands in
mutual trans disposition.5,13,14 In addition, a broad resonance
Scheme 1. Formation of 2 and 3.
(7) Braunschweig, H.; Radacki, K.; Seeler, F.; Whittell, G. R. Organo-
metallics 2004, 23, 4178-4180.
(8) (a) Aldridge, S.; Calder, R. J.; Baghurst, R. E.; Light, M. E.;
Hursthouse, M. B. J. Organomet. Chem. 2002, 649, 9-14. (b)
Aldridge, S.; Calder, R. J.; Coles, S. J.; Hursthouse, M. B. J. Chem.
Crystallogr. 2003, 33, 805-810.
(9) (a) Braunschweig, H.; Radacki, K.; Scheschkewitz, D.; Whittell, G.
R. Angew. Chem. 2005, 117, 1685-1688. Angew. Chem., Int. Ed.
2005, 44, 1658-1660. (b) Braunschweig, H.; Whittell, G. R. Chem.s
Eur. J. 2005, 11, 6128-6133.
at -26.6 ppm could be observed, indicating the presence of
the phosphine borane adduct [Cy3P-BI3] (1) (vide infra).
After 15 min, some fine white powder precipitated from the
red-brown solution, which was separated and washed with
hexane and turned out to be the desired product trans-
[(Cy3P)2Pt(I)(BI2)] (2) (41% yield) (Scheme 1). The 11B-
{1H} NMR spectrum of the isolated material featured a broad
(10) Braunschweig, H.; Radacki, K.; Rais, D.; Seeler, F. Angew. Chem.
2006, 118, 1087-1090. Braunschweig, H.; Radacki, K.; Rais, D.;
Seeler, F. Angew. Chem., Int. Ed. 2006, 45, 1066-1069.
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2005, 117, 1217-1219. Braunschweig, H.; Radacki, K.; Rais, D.;
Whittell, G. R. Angew. Chem., Int. Ed. 2005, 44, 1192-1194.
(12) Braunschweig, H.; Radacki, K.; Rais, D.; Seeler, F.; Uttinger, K. J.
Am. Chem. Soc. 2005, 127, 1386-1387.
1
signal at 31.0 ppm, and the 13C{1H} and H NMR data
(13) (a) Braunschweig, H.; Radacki, K.; Rais, D.; Seeler, F., Organome-
tallics 2004, 23, 5545-5549. (b) Braunschweig, H.; Radacki, K.; Rais,
D.; Uttinger, K. Angew. Chem. 2006, 118, 169-172. Braunschweig,
H.; Radacki, K.; Rais, D.; Uttinger, K. Angew. Chem., Int. Ed. 2006,
45, 162-165. (c) Braunschweig, H.; Radacki, K.; Uttinger, K. Angew.
Chem. 2007, 119, 4054-4057. Braunschweig, H.; Radacki, K.;
Uttinger, K. Angew. Chem., Int. Ed. 2007, 46, 3979-3982. (d)
Braunschweig, H.; Radacki, K.; Rais, D.; Scheschkewitz, D. Angew.
Chem. 2005, 117, 5796-5799. Braunschweig, H.; Radacki, K.; Rais,
D.; Scheschkewitz, D. Angew. Chem., Int. Ed. 2005, 44, 5651-5654.
(14) Clegg, W.; Lawlor, F. J.; Lesley, G.; Marder, T. B.; Norman, N. C.;
Orpen, A. G.; Quayle, M. J.; Rice, C. R.; Scott, A. J.; Souza, F. E. S.
J. Organomet. Chem. 1998, 550, 183-192.
showed appropriate resonances for the cyclohexyl groups.
Single crystals suitable for X-ray diffraction analysis were
obtained from a benzene solution by slow evaporation, and
the molecular structure is shown in Figure 1. The molecule
crystallizes in the space group C2/c and adopts a slightly
distorted square-planar geometry around platinum and a
mutual trans arrangement of the phosphine ligands. (The
parameters of only one of two independent molecules found
in the unit cell will be considered in this discussion, whereas
Inorganic Chemistry, Vol. 46, No. 21, 2007 8797

Braunschweig et al.
the important data from the second molecule can be found
in the figure caption.)
The diiodoboryl group is oriented almost perpendicular
to the PtP2I fragment, as indicated by the torsion angle P1-
Pt1-B1-I2 of 97.8(3)°. The most noticeable structural
feature is the Pt1-B1 distance of 1.947(8) Å, which is very
small compared with that of the other complexes of trans-
[(Cy3P)2Pt(Br){B(Br)R}] (R ) Fc ) ferrocenyl, distance )
1.9963(34) Å;13a R ) Mes ) mesityl, distance ) 2.009(4)
Å),13c trans-[(Cy3P)2Pt{B(Br)Fc}][BArf4] (Arf ) 3,5-C6H3-
(CF3)2; distance ) 1.966(4) Å),13d or trans-[(Ph3P)2Pt(Cl)-
(BCat)] (Cat ) catecholato; distance ) 2.008(8) Å).14
Likewise, even dichloroboryl complexes of the type trans-
[(R3P)2Pt(Cl)(BCl2)] display a longer Pt-B bond (1.963(6)-
1.988(3) Å).5 The significantly reduced Pt-B separation
observed here reflects the less-effective B-Hal π overlapping
in the case of iodine in comparison with the smaller halogens
and oxygen, thus imposing an increased Pt-B π back-
donation. The B-I bonds (B1-I2 ) 2.189(7) Å, B1-I3 )
2.185(8) Å) are slightly elongated with comparison to those
in the only structurally characterized compound possessing
a BI2 moiety, i.e., [(I2B)(Me)(H)C)]2BI (BI2, B3-I2 ) 2.13-
(1) Å, B3-I3 ) 2.12(1) Å; BI, B1-I1 ) 2.15(1) Å).15 The
Pt-I bond length of 2.7813(7) Å is remarkably longer (>7
pm) than that in trans-[(Cy3P)2PtI2]16 or trans-[(Ph3P)2Pt-
{CHdC(CH3)2}I]17 with Pt-I separations of 2.612(1) and
2.709(4) Å, respectively, which is in line with the strong
trans influence of the boryl group,18 whereas the Pt-P
distances for trans-[(Cy3P)2PtI2]16 and 2 are similar (2.371-
(2) Å versus 2.3524(15)/2.3579(15) Å).
Figure 2. Molecular structure of 3. Thermal ellipsoids at 50% probability
level. Hydrogen atoms and one molecule of C6H6 are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Pt1-B1 2.002(11), Pt1-P1
2.267(2), Pt1-I1 2.8024(7), Pt1-I2 2.6689(7), B1-I3 2.108(12), B1-I4
2.167(11), Pt2-B2 1.971(12), Pt2-P2 2.268(2), Pt2-I1 2.6646(7), Pt2-
I2 2.7962(7), B2-I5 2.182(19), B2-I6 2.151(11), Pt1-I1-Pt2 81.81(2),
I1-Pt1-I2 83.74(2), B1-Pt1-I1 168.1(3), P1-Pt1-I2 172.90(6), B1-
Pt1-P1 95.2(3), I3-B1-I4 115.3(5), P1-Pt1-B1-I4 92.7(5).
repeated rinsing with benzene and was isolated in 43% yield
as an analytically pure beige solid. The new dinuclear species
3 proved to be extremely sensitive toward air and moisture
and to slowly decompose in solution with formation of red
[Pt2(µ-I)2I2(PCy3)2],19 as indicated by 31P{1H} NMR data.
Interestingly, the formation of 3 is reversible: the addition
of PCy3 to a solution of 3 in benzene instantaneously afforded
the mononuclear complex 2, which in return could be
converted to the dimer 3 and the adduct 1 by the addition of
BI3 to a benzene solution of 2 and the subsequent heating
of the resulting mixture (Scheme 1).
Interestingly, the formation of the mononuclear complex
2 strongly depends on the stoichiometry of the reaction, as
an excess of BI3 leads to a different product. Initially, after
mixing [Pt(PCy3)2] and BI3 in a 1:2 ratio, multinuclear NMR
spectroscopy revealed, in addition to the presence of 2 and
some unreacted BI3, the formation of the phosphine borane
adduct 1 as indicated by a broad quartet at -26.6 ppm (J )
117 Hz) in the 31P{1H} NMR spectrum and a significantly
shielded doublet at -74.1 ppm (J ) 117 Hz) in the 11B{1H}
NMR spectrum, as well as a new compound with a 31P{1H}
NMR resonance at 15.8 ppm indicative of a Pt-bound
phosphine (J ) 4460 Hz). Heating for 2-3 h at 55 °C led
to completion of the reaction as indicated by the gradual
decrease of the signal associated with 2 and the concomitant
increase of the other two resonances. The spectroscopic data
of the new compound are in agreement with its formulation
as a dinuclear complex [(Cy3P)(I2B)Pt(µ-I)]2 (3), which was
apparently formed upon the abstraction of PCy3 from 2 by
the Lewis-acidic BI3 with the subsequent dimerization of two
[(Cy3P)(I2B)Pt(I)] fragments. Compound 3 was separated
from the accompanying adduct 1 by crystallization and
Single crystals of 3 suitable for X-ray diffraction were
obtained from a concentrated benzene solution (Figure 2).
In the solid state, both Pt atoms display a slightly distorted
square-planar arrangement and the boryl groups are oriented
almost orthogonally toward the corresponding PtPI fragment
as indicated by the torsion angle from P1-Pt1-B1-I4 of
92.7(5)°. The Pt2I2 fragment adopts the geometry of a folded
rhombus (123.3° between the two planes of I1-Pt1-I2 and
I1-Pt2-I2), a geometry which was observed earlier for [Rh2-
Cl2(CO)4] or [{(F5C6)(Ph3P)Pt(µ-PPh2)(µ-I)}2Pt].20 The large
Pt1-Pt2 distance of 3.582 Å appears to exclude the
possibility of any metal-metal interaction.20b The Pt-I
separations in trans position to the boryl moieties are longer
(Pt1-I1 ) 2.8024(7) Å, Pt2-I2 ) 2.7962(7) Å) than those
in trans position to the phosphine ligands (Pt1-I2 ) 2.6689-
(7) Å, Pt2-I1 ) 2.6646(7) Å), corroborating the high trans
influence of a boryl residue.18 The longer Pt-I distances are
comparable to those in 2, and the smaller ones are compa-
rable to those in other complexes bearing iodine in trans
position to a phosphine group, e.g., [Pt2(µ-I)2dppm][BF4]2
with 2.669(1) and 2.662(1) Å21 or [Pt2(µ-I)2I2(PCy3)2] with
(15) Derforth, T.; Kaschke, M.; Stock, H.; Pritzkow, H.; Siebert, W. Z.
Naturforsch., B: Chem. Sci. 1997, 52b, 823-830.
(19) Al-Najjar, I. M. Inorg. Chim. Acta 1987, 128, 93-104.
(20) (a) Dahl, L. F.; Martell, C.; Wampler, D. L. J. Am. Chem. Soc. 1961,
83, 1761-1762. (b) Ara, I. Chaouche, N.; Fornie´s, J.; Consuelo
Fortun˜o, C.; Kribii, A.; Tsipis, A. C.; Tsipis, C. A. Inorg. Chim. Acta
2005, 358, 1377-1385.
(21) Neve, F.; Crispini, A.; Ghedini, M.; De Munno, G. Inorg. Chim. Acta
1990, 176, 23-25.
(16) (a) Alcock, N. W.; Levingston, P. G. J. Chem. Soc., Dalton Trans.
1974, 1834-1836. (b) Hitchcock, P. B.; Jacobson, B.; Pidcock, A. J.
Chem. Soc., Dalton Trans. 1977, 2038-2042.
(17) Stang, P. J.; Zhong, Z.; Kowalski, M. H. Organometallics 1990, 9,
833-838.
(18) Zhu, J.; Lin, Z.; Marder, T. B. Inorg. Chem. 2005, 44, 9384-9390.
8798 Inorganic Chemistry, Vol. 46, No. 21, 2007

Diiodoboryl Complexes of Platinum
Experimental Section
General Considerations. All manipulations were conducted
under an atmosphere of dry argon or in vacuo using standard
Schlenk-line or glovebox techniques. Benzene, toluene, and hexane
were purified by distillation from Na/K alloy under dry argon and
stored over molecular sieves in the glovebox. C6D6 and C7D8 were
degassed by three freeze-pump-thaw cycles and stored over
molecular sieves in the glovebox. NMR spectra were recorded on
1
a Bruker Avance 500 NMR spectrometer. H and 13C{1H} NMR
spectra were referenced to external TMS via the residual protio
solvent (1H) or the solvent itself (13C). 11B{1H} and 31P{1H} NMR
spectra were referenced to external BF3‚OEt2 and 85% H3PO4,
respectively. Microanalyses for C and H were performed on a
Elementar Vario MICRO cube instrument. [Pt(PCy3)2] and BI3 were
synthesized according to previously published procedures.
Figure 3. Molecular structure of 1. Thermal ellipsoids at 50% probability
level. Hydrogen atoms and half a molecule of C6H6 are omitted for clarity.
Selected bond lengths (Å): P1-B1 1.972(3), B1-I1 2.249(3), B1-I2 2.236-
(3), B1-I3 2.237(3).
[Cy3P-BI3] (1): [Pt(PCy3)2] (200 mg, 0.265 mmol) and BI3 (260
mg, 0.794 mmol) were dissolved in toluene (4.0 mL). The mixture
immediately turned brown. After 3 h at 55 °C, yellow crystalline
material had been formed, which was separated from the brown
solution via cannula and dried in vacuo, yielding 70 mg (39%) of
pure colorless [Cy3P-BI3]. Alternatively, equimolar amounts of
PCy3 and BI3 were dissolved in C6H6, yielding 1. Single crystals
were obtained by the slow evaporation of the solvent.
2.6707(17) Å (trans to PCy3) and 2.597(2) Å (trans to I).22
The Pt-P bond lengths in 3 (Pt1-P1 ) 2.267(2) Å, Pt2-
P2 ) 2.268(2) Å) are 9 pm shorter than those in the
monomeric complex 2 (Pt1-P1 ) 2.3524(15) Å, Pt1-P2
) 2.3579(15) Å) but comparable to other I-bridged com-
plexes, for example, [Pt2(µ-I)2dppm][BF4]2 (2.243(2) and
2.240(2) Å)21 or [Pt2(µ-I)2I2(PCy3)2] (2.327(5) Å).22 The
Pt-B bonds with separations of 2.002(11) and 1.971(12) Å
are longer than those in 2 but still in the range of the Pt-
boryl distances.
1H NMR (500.1 MHz, C6D6, 23 °C): δ 2.89 (m, 3H, Cy), 2.27
(m, 6H, Cy), 1.57 (m, 12H, Cy), 1.46 (m, 3H, Cy), 1.11 (m, 6H,
Cy), 0.94 (m, 3H, Cy). 13C{1H} NMR (125.8 MHz, C6D6, 23 °C):
1
3
δ 35.5 (d, JC-P ) 31 Hz, C1, Cy), 28.5 (d, JC-P ) 4 Hz, C3,5
,
Cy), 27.2 (d, 2JC-P ) 10 Hz, C2,6, Cy), 25.8 (d, 4JC-P ) 1 Hz, C4,
Cy). 11B{1H} NMR (160.5 MHz, C6D6, 23 °C): δ -74.1 (d, 1JB-P
) 117 Hz). 31P{1H} NMR (202.4 MHz, C6D6, 22 °C): δ -26.6
In addition, the phosphine borane adduct 1, which in
contrast to to the aforementioned procedure can be directly
obtained from the reaction of Cy3P and BI3, was subjected
to a single-crystal X-ray analysis (Figure 3).
1
(q, JP-B ) 117 Hz). Elemental Anal. Calcd for C18H36BI3P: C
32.17, H 4.95. Found: C 32.85, H 5.13.
trans-[(Cy3P)2Pt(I)(BI2)] (2): A pale yellow solution of [Pt-
(PCy3)2] (100 mg, 0.132 mmol) in C6H6 (0.6 mL) was added to a
colorless solution of BI3 (52 mg, 0.132 mmol) in C6H6 (0.4 mL).
The mixture immediately turned red-brown, and after 15 min, a
white, fine solid precipitated. The next day hexane (1 mL) was
added to increase the amount of the precipitate. The solid was
separated and washed with hexane (2 × 0.5 mL), yielding 62 mg
(41%) of pure trans-[(Cy3P)2Pt(I)(BI2)]. Single crystals were
obtained by slow evaporation of the solvent from a benzene
solution. Alternatively, a stoichiometric amount of PCy3 (4 mg,
0.014 mmol) was added to a solution of [(Cy3P)(I2B)Pt(µ-I)]2 (11
mg, 0.007 mmol) in benzene. Multinuclear NMR data immediately
showed complete conversion of the starting materials to trans-
[(Cy3P)2Pt(I)(BI2)].
The arrangement around the boron is tetrahedral, and the
phosphine adopts a staggered conformation with respect to
the iodine atoms. The P-B distance of 1.972(3) Å is slightly
elongated in comparison to the one found in [(H2CdCH)3Ps
BI3] (1.944(4) Å)23 or [Me3P-BI3] (1.918(15) Å),24 which
is probably induced by the greater sterical demands of the
cyclohexyl groups. The other structural parameters of 1 are
similar to those of the other BI3 phosphine adducts.23,24 The
average B-I bond lengths for the adducts are 2.249(12) Å
for [Me3P-BI3], 2.229(4) Å for [(H2CdCH)3PsBI3], and
2.241(3) Å for 1.
Conclusion
1H NMR (500.1 MHz, C6D6, 24 °C): δ 2.86 (m, 6H, Cy), 2.15
(m, 12H, Cy), 1.82-1.70 (m, 30H, Cy), 1.30 (m, 18H, Cy). 13C-
In conclusion, we prepared and fully characterized the first
diiodoboryl complex trans-[(Cy3P)2Pt(I)(BI2)], which is
characterized by a very short Pt-B distance and the strong
trans influence of the boryl group. Furthermore, trans-
[(Cy3P)2Pt(I)(BI2)] was converted into the iodine-bridged
diiodoboryl complex trans-[(Cy3P)(I2B)Pt(µ-I)]2 by the ad-
dition of BI3. This dimerization is reversible, and the reaction
with PCy3 affords trans-[(Cy3P)2Pt(I)(BI2)].
1
{1H} NMR (125.8 MHz, C6D6, 24 °C): δ 36.7 (vt, N ) | JC-P
+
+
2
3JC-P| ) 28 Hz, C1, Cy), 31.0 (s, C3,5, Cy), 27.6 (vt, N ) | JC-P
4JC-P| ) 12 Hz, C2,6, Cy), 26.6 (s, C4, Cy). 11B{1H} NMR (160.5
MHz, C6D6, 24 °C): δ 31.0 (br s). 31P{1H} NMR (202.4 MHz,
C6D6, 24 °C): δ 10.3 ppm (s, 1JP-Pt ) 2737 Hz). Elemental Anal.
Calcd for C36H66B2I6P2Pt‚0.5(C6H6): C 39.48, H 5.86. Found: C
38.94, H 5.69.
[(Cy3P)(I2B)Pt(µ-I)]2 (3): [Pt(PCy3)2] (205 mg, 0.271 mmol) and
BI3 (228 mg, 0.582 mmol) were placed in a Schlenk tube and
dissolved in C6H6 (2.0 mL). The mixture immediately turned red-
brown and a fine white solid precipitated. After 3 h at 55 °C, yellow
crystalline material had been formed, which was separated from
the brown solution via a cannula and dried in vacuo. The solid
was washed 17 times with benzene (0.3 mL), yielding 102 mg
(22) Be´ni, Z.; Ros, R.; Tassan, A.; Scopelliti, R.; Roulet, R. Dalton Trans.
2005, 315-325.
(23) Monkowius, U.; Nogai, S.; Schmidbaur, H. Dalton Trans. 2003, 987-
991.
(24) (a) Denniston, M. L.; Martin, D. R. J. Inorg. Nucl. Chem. 1974, 36,
1461-1464. (b) Black, D. L.; Taylor, R. C. Acta Crystallogr., Sect.
B 1975, B31 (4), 1116-1120.
Inorganic Chemistry, Vol. 46, No. 21, 2007 8799

Braunschweig et al.
(43%) of pure beige [(Cy3P)(I2B)Pt(µ-I)]2. Single crystals were
obtained by the slow evaporation of the solvent from a benzene
solution. Alternatively, the reaction of equimolar amounts of BI3
(5 mg, 0.013 mmol) and trans-[(Cy3P)2Pt(I)(BI2)] (15 mg, 0.013
mmol) in benzene led to [(Cy3P)(I2B)Pt(µ-I)]2. After 1 h at 60 °C,
NMR spectra showed the complete conversion of the starting
materials and the formation of the products [(Cy3P)(I2B)Pt(µ-I)]2
and [Cy3P-BI3].
8.2530(2) Å, b ) 11.9107(3) Å, c ) 13.6448(3) Å, R ) 108.6880-
(10)°, â ) 95.8110(10)°, γ ) 90.8790(10)°, V ) 1262.40(5) Å3, Z
) 2, Fcalcd ) 1.870 g‚cm-3, µ ) 3.782 mm-1, F(000) ) 682, T )
100(2) K, R1 ) 0.0207, R2 ) 0.0548, 5032 independent reflections
[2θ e 52.54°], and 232 parameters.
Crystal data for 2: C36H66BI3P2Pt‚1/2(C6H6), Mr ) 1186.48,
yellow plate, 0.08 × 0.21 × 0.38 mm3, monoclinic space group
C2/c, a ) 53.108(6) Å, b ) 10.3619(13) Å, c ) 38.802(5) Å, â )
126.230(4)°, V ) 17224(4) Å3, Z ) 16, Fcalcd ) 1.830 g‚cm-3, µ
) 5.509 mm-1, F(000) ) 9200, T ) 100(2) K, R1 ) 0.0792, R2 )
0.1296, 25577 independent reflections [2θ e 62.06°], and 829
parameters.
1H NMR (500.1 MHz, C7D8, 22 °C): δ 2.25-2.10 (m, 18H,
Cy), 1.78-1.58 (m, 30H, Cy), 1.28-1.11 (m, 18H, Cy). 13C{1H}
1
NMR (125.8 MHz, C7D8, 23 °C): δ 37.4 (d, JC-P ) 30 Hz, C1,
2
Cy), 30.7 (s, C3,5, Cy), 27.6 (d, JC-P ) 12 Hz, C2,6, Cy), 26.5 (s,
C4, Cy). 11B{1H} NMR (160.5 MHz, C7D8, 22 °C): no signal could
be detected, due to the poor solubility of the compound. 31P{1H}
Crystal data for 3: C36H66B2I6P2Pt2‚(C6H6), Mr ) 1812.14,
colorless needle, 0.25 × 0.04 × 0.03 mm3, monoclinic space group
P21/c, a ) 17.6997(14) Å, b ) 19.2051(15) Å, c ) 16.9665(13)
Å, â ) 114.661(2)°, V ) 5241.3(7) Å3, Z ) 4, Fcalcd ) 2.296
g‚cm-3, µ ) 8.955 mm-1, F(000) ) 3352, T ) 173(2) K, R1 )
0.0551, R2 ) 0.0974, 10387 independent reflections [2θ e 52.24°],
and 487 parameters.
1
NMR (202.4 MHz, C7D8, 22 °C): δ 15.8 (s, JP-Pt ) 4460 Hz).
Elemental Anal. Calcd for C36H66B2I6P2Pt‚C6H6: C 27.84, H 4.00.
Found: C 28.03, H 4.03.
Crystal-Structure Determination. The crystal data of 1-3 were
collected at a Bruker X8 APEX diffractometer with a CCD area
detector and multilayer mirror-monochromated Mo KR radiation.
The structures were solved using direct methods, refined with the
SHELX software package (G. Sheldrick, University of Go¨ttingen,
1997), and expanded using Fourier techniques. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were assigned
idealized positions, and they were included in structure-factor
calculations.
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Center as supplementary publication nos.
CCDC 649528-649530. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccd-
c.cam.ac.uk/data_request/cif.
Acknowledgment. This work was supported by the DFG.
Crystal data for 1: C18H33BI3P‚1/2(C6H6), Mr ) 710.98, colorless
block, 0.18 × 0.12 × 0.09 mm3, triclinic space group P1h, a )
IC7011028
8800 Inorganic Chemistry, Vol. 46, No. 21, 2007