Syntheses and structures of mono- and dinuclear cationic base-stabilized platinum borylene complexes

Article abstract of DOI:10.1021/om800689h

A series of fully characterized cationic, base-stabilized borylene complexes of the type trans[(Cy₃P)₂Pt(Br) (B(NC ₅H₄-4-R)X J][BAr₄^f] (R = Me, X = NMe₂, Pip, Br; R = tBu, X = Pip) were synthesized by addition of Na[BAr₄^f] and a pyridine Lewis base to boryl complexes rrans-[(Cy₃P)₂-Pt(Br){B(Br)X}], inducing a formal 1,2-bromide shift from the boron atom to the platinum center. Furthermore, the reactions of [Pt(PCy₃)₂] with 1,4-(Br₂B) ₂-C₆H₄ allowed for the isolation of the dinuclear boryl complex 1,4-trans-[{(Cy₃P)₂(Br)Pt(BBr)} ₂-C₆H₄] and irans-[(Cy₃P) ₂Pt(Br)-1-{B(Br)-C₆H₄-4-(BBr ₂(PCy₃)}}]. The former was treated with K[B(C ₆F₅)₄], which afforded the abstraction of both platinum-bound bromides and formation of the dicationic boryl complex 1,4-trans-[{(Cy₃P)₂Pt(BBr)}₂-C ₆H₄][B(C₆F₅)₄] ₂. This compound was converted into the base-stabilized borylene species 1,4-trans-[{(Cy₃P)₂(Br)Pt(B(NC₅H ₄-4-Me)}}₂-C₆H₄][B(C ₆F₅)₄]₂ by reaction with 4-methylpyridine.

Full text of DOI:10.1021/om800689h

Organometallics 2008, 27, 6005–6012
6005
Syntheses and Structures of Mono- and Dinuclear Cationic
Base-Stabilized Platinum Borylene Complexes
Holger Braunschweig,* Krzysztof Radacki, and Katharina Uttinger
Institut fu¨r Anorganische Chemie, Julius-Maximilians-UniVersita¨t Wu¨rzburg,
Am Hubland, 97074 Wu¨rzburg, Germany
ReceiVed July 21, 2008
A series of fully characterized cationic, base-stabilized borylene complexes of the type trans-
[(Cy3P)2Pt(Br){B(NC5H4-4-R)X}][BArf4] (R ) Me, X ) NMe2, Pip, Br; R ) tBu, X ) Pip) were
synthesized by addition of Na[BArf4] and a pyridine Lewis base to boryl complexes trans-[(Cy3P)2-
Pt(Br){B(Br)X}], inducing a formal 1,2-bromide shift from the boron atom to the platinum center.
Furthermore, the reactions of [Pt(PCy3)2] with 1,4-(Br2B)2-C6H4 allowed for the isolation of the dinuclear
boryl complex 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] and trans-[(Cy3P)2Pt(Br)-1-{B(Br)-C6H4-4-
{BBr2(PCy3)}}]. The former was treated with K[B(C6F5)4], which afforded the abstraction of both platinum-
bound bromides and formation of the dicationic boryl complex 1,4-trans-[{(Cy3P)2Pt(BBr)}2-
C6H4][B(C6F5)4]2. This compound was converted into the base-stabilized borylene species 1,4-trans-
[{(Cy3P)2(Br)Pt{B(NC5H4-4-Me)}}2-C6H4][B(C6F5)4]2 by reaction with 4-methylpyridine.
the past decade. These include heterodinuclear bridged,7
semibridged,8 metallo group,9 and main group as well as metal
base stabilized borylene species.10
Introduction
Transition metal boryl and borylene complexes have attracted
considerable interest,1 especially due to the fact that the former
are important key intermediates for transition metal-catalyzed
hydro-2 and diboration,3 as well as for the C-H functionaliza-
tion4 of organic substrates. In addition to the first bridged5 and
terminal6 borylene complexes a wide variety of different
coordination modes have been realized for B-R ligands over
Most commonly, salt elimination, halide abstraction, and
thermally or photochemically induced borylene transfer reactions
are employed for the synthesis of borylene complexes. The first
method provided, for example, group 6 borylene complexes
[(OC)5MdBN(SiMe3)2] (M ) Cr, Mo, W),6,11 the bridged
compounds [{(η5-C5R5)(OC)M}2{µ-B(NSiMe3)2}(µ-CO)] (M )
Fe, R ) H, Me; M ) Ru, R ) H),12 or the metalloborylene
complexes [(η5-C5H5)(OC)2FedBdM(CO)n] (M ) Fe, n ) 4;
M ) Cr, n ) 5).9 Aldridge and co-workers employed halide
abstraction for the preparation of the cationic species [(η5-
C5Me5)(OC)2FedBR]+ (R ) 2,4,6-Me3-C6H2, NCy2, NiPr2)
from corresponding haloboryl complexes [(η5-C5Me5)(OC)2Fe-
* Correspondingauthor.E-mail:h.braunschweig@mail.uni-wuerzburg.de.
Fax: (+49)931-888-4623. Tel: (+49)931-888-5260.
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10.1021/om800689h CCC: $40.75
2008 American Chemical Society
Publication on Web 10/24/2008

6006 Organometallics, Vol. 27, No. 22, 2008
Braunschweig et al.
Chart 1. Different Base-Stabilized Borylene Complexes
Results and Discussion
Preparation of Mononuclear Base-Stabilized Borylene
Complexes. To determine whether the aforementioned behavior
of platinum complex 4, which was prepared from trans-
[(Cy3P)2Pt(Br){B(Br)Fc}] (8) and Na[BArf4], toward Lewis
bases is exceptional or can be exploited as a general access to
platinum borylene species, different complexes of the type trans-
[(Cy3P)2Pt(Br){B(Br)X}] (X ) NMe2, Pip, Br) (9-11) (Pip )
piperidyl)19a were reacted with Na[BArf4], yielding the corre-
sponding cationic T-shaped boryl species, namely, trans-
[(Cy3P)2Pt{B(Br)X}[BArf4], as determined by multinuclear
NMR spectroscopy.19b Subsequent addition of 4-methylpyridine
induced a formal 1,2-bromide shift from the boron atom to the
platinum center. 31P{1H} NMR data indicate the clean conver-
sion of the starting materials into trans-[(Cy3P)2Pt(Br){B(NC5H4-
4-Me)X}][BArf4] (X ) NMe2, Pip, Br) (12-14) by means of a
resonance at around 26 ppm and a coupling constant of
approximately 2500 Hz, which is significantly decreased by
about 300 Hz in comparison to the neutral species 8-11 (Table
1). Likewise, a corresponding reaction of 10 with Na[BArf4]
and 4-tert-butylpyridine allowed for the isolation of trans-
[(Cy3P)2Pt(Br){B(NC5H4-4-tBu)Pip}][BArf4] (15) (Scheme 1).
All compounds were isolated as analytically pure, colorless, air-
and moisture-sensitive solids in yields up to 84%.
Chart 2. Diverse Platinum Boryl and Borylene Complexes
B(Hal)R] (Hal ) Cl, Br),10a,13 whereas the complexes [(η5-
C5H5)(OC)3VdB(NSiMe3)2],14 [L(OC)3M{µ-BN(SiMe3)2}(µ-
CO)M′(PCy3)] (Cy ) cyclohexyl) (L ) CO, PCy3; M ) Cr,
Mo, W; M′ ) Pd, Pt),8 [{(η5-C5H5)(OC)Co}{µ-BN(Si-
Me3)2}{W(CO)5}],15 or [(OC)2Rh(µ-Cl)2Rh{µ-BN(SiMe3)2}2(µ-
The 13C{1H} NMR spectra exhibit the expected signals for
the coordinated base [average values δ ) 165 (s, Cpara), 145
(s, Cortho), 127 (s, Cmeta), 22 (s, Me)/30 (s, Me, tBu) ppm], and
the 1H NMR spectra two multiplets at around δ ) 8.9 and 7.7
ppm for the aromatic protons. However, the bromoborylene
complex 14 shows a different 1H NMR spectrum with four broad
resonances at δ ) 10.66, 9.57, 7.95, and 7.83 ppm. The former
signal is significantly deshielded, which most likely can be
attributed to an interaction of this proton with the boron-bound
bromide (Figure 1), thus accounting for the decreased symmetry
observed for this species in solution.20
Suitable crystals for X-ray analyses were obtained for trans-
[(Cy3P)2Pt(Br){B(NC5H4-4-Me)X}][BArf4] (X ) NMe2, Pip)
(12, 13) and trans-[(Cy3P)2Pt(Br){B(NC5H4-4-tBu)Pip}][BArf4]
(15) by layering dichloromethane solutions with hexane and
slow evaporation of the solvent (Figure 2).
The molecular structures of 12, 13, and 15 show B-N2
(Lewis base) separations [12, 1.585(4) Å; 13, 1.565(5) Å; 15,
1.581(6) Å] similar to that in trans-[(Cy3P)2Pt(Br){B(NC5H4-
4-Me)Fc}][BArf4] (5) [B-N 1.582(6) Å].10f The B-N1 dis-
tances [12, 1.406(4) Å; 13, 1.388(5) Å; 15, 1.402(7) Å] are
indicative of BdN double bonds and, thus, effective B-N
π-donation; despite this, the boron center is still Lewis acidic
and available for base coordination. The Pt-Br bond lengths
[12, 2.5909(3) Å; 13, 2.5986(4) Å; 15, 2.5857(5) Å; 5, 2.6057(5)
Å] are comparable to those in neutral boryl complexes trans-
[(Cy3P)2Pt(Br){B(Br)X}] [X ) NMe2 (9), 2.6087(3) Å; X )
Pip (10), 2.6313(5) Å; X ) Fc (8), 2.6183(8) Å]19a,21 and
demonstrate that boryl and base-stabilized borylene moieties
impose a similar trans-influence. The pronounced steric demand
of the borylene ligand dB(L)R imposes a twist of the plane
containing the borylene fragment dB(L)R toward the PtP2 plane
[12, 79.45°; 13, 75.56°; 15, 73.7(4)°]; commonly an angle of
approximately 90° is preferred [9, 88.93°; 10, 83.83°].19a
16
CO)]2 were prepared via partial or total borylene transfer.
However, none of these former methods are suitable for the
synthesis of base-stabilized borylene complexes, which were
obtained by (i) addition of a Lewis base to a borylene complex,
furnishing, for example, [(η5-C5Me5)(OC)2FedB(L)NCy2]+ (L
) THF, NC5H4-4-Me) (1),10a (ii) reaction of [B2H4(PMe3)2] with
[Co2(CO)8] to give [{(OC)3Co}2(µ-CO)(µ-BHPMe3)] (2),10b or
(iii) addition of a Lewis base to a haloboryl complex and
concomitant 1,2-halide shift, yielding osmium borylene com-
plexes such as 310c-e (Chart 1).
Recently, we communicated preliminary results on the
reactivity of the T-shaped cationic boryl complex trans-
[(Cy3P)2Pt{B(Br)Fc}][BArf4] (4; Fc ) ferrocenyl) toward
4-methylpyridine.10f This strong Lewis base surprisingly did not
coordinate to the vacant site at the platinum center in trans-
position to the boryl ligand, but to the boron atom with formation
of the cationic complex trans-[(Cy3P)2Pt(Br){B(NC5H4-4-
Me)Fc}][BArf4] (5) and formal 1,2-shift of bromide from boron
to platinum.10f In addition to this base-stabilized borylene
complex, further platinum borylene species trans-[(Cy3P)2Pt-
(Br){B(2,4,6-Me3-C6H2)}][B(C6F5)4] (6)17 and trans-[(Cy3P)2-
Pt(Br){BN(AlCl3)SiMe3}] (7)18 have been reported (Chart 2),
which, however, display two-coordinate boron centers and, thus,
are characterized by a more pronounced Pt-B multiple bond
character.
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Platinum Borylene Complexes
Organometallics, Vol. 27, No. 22, 2008 6007
Table 1. Selected Data of the Base-Stabilized Borylene Complexes trans-[(Cy3P)2Pt(Br){B(L)X}]+ (5, 12-15) Compared to the Starting
Materials trans-[(Cy3P)2Pt(Br){B(Br)X}] (8-11)19a (δ in ppm, J in Hz)
-B(L)X
compound
δ (31P) (1JP-Pt
)
starting material δ (31P) (1JP-Pt
)
yield
X ) Fc, L ) NC5H4-4-Me10f
X ) NMe2, L ) NC5H4-4-Me
X ) Pip, L ) NC5H4-4-Me
X ) Br, L ) NC5H4-4-Me
X ) Pip, L ) NC5H4-4-tBu
5
12
13
14
15
25.0 (2554)
26.2 (2532)
27.0 (2548)
23.9 (2373)
27.2 (2557)
8
9
10
11
10
21.5 (2892)
24.0 (2815)
24.6 (2867)
19.4 (2683)
24.6 (2867)
75%
84%
65%
35%
69%
Scheme 1. Synthesis of Different Cationic, Base-Stabilized
Borylene Complexes of Platinum
at δ ) -7.9 ppm. From concentrated reaction mixtures, the
air- and moisture-sensitive product precipitated and was isolated
in analytically pure form. Recrystallization yielded colorless
single crystals, which were analyzed by X-ray diffraction,
showing that the constitution of the product was not that of the
species 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] (17), but trans-
[(Cy3P)2Pt(Br)-1-{B(Br)-C6H4-4-{BBr2(PCy3)}}] (18) (Fig-
ure 3).
Obviously, only one B-Br bond was oxidatively added to
platinum and a PCy3 molecule coordinated to the second boron
center. The abstraction of PCy3 from platinum with Lewis acidic
boranes with formation of corresponding phosphine boranes was
reported before25 and accounts for the formation of 18. The
gradual darkening of the reaction mixture observed here is
attributed to the deposition of Pt(0). The 11B{1H} NMR
spectrum of 18 features two broad signals for both distinct boron
centers [δ ) 73 (Pt-B), -5 ppm (P-B)]. The former one shows
a value typical for arylboryl complexes,19a and the high-field
shifted signal is characteristic for a four-coordinated boron atom.
However, treatment of 1,4-(Br2B)2-C6H4 (16) with a larger
excess of [Pt(PCy3)2] led to the buildup of another resonance
in the 31P{1H} NMR spectrum at δ ) 23.5 ppm (1JP-Pt ) 2845
Hz), which indicated the formation of the target product 1,4-
trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] (17). Precipitated material
(predominantly 18) was removed from the mixture, and the
remaining solvent was allowed to evaporate slowly in order to
isolate pure, air- and moisture-sensitive 17, which resembles a
rare example of a dinuclear, boryl-bridged complex (Scheme
2). The only other fully characterized examples are [(η5-
C5R5)(OC)2FeB-spacer-BFe(CO)2(η5-C5R5)] (R5 ) H5, H4Me,
Me5, B-spacer-B ) BO2C6H2O2B; R5 ) H5, B-spacer-B )
spiro-B(OCH2)2C(CH2O)2B), which were reported by Aldridge26
and 1,4-trans-[{(Cy3P)2(Br)Pt(B{NHiBu}NH)}2-C6H4], which
was synthesized by a 1,2 dipolar addition of 1,4-(H2N)2-C6H4
to the Bt N triple bond of 2 equiv of the iminoboryl complex
trans-[(Cy3P)2Pt(Br)(BNiBu)] (Chart 3).27
The Pt-B bond distances [12, 2.018(4) Å; 13, 2.046(4) Å;
15, 2.023(5) Å] resemble those of the corresponding neutral
boryl complexes trans-[(Cy3P)2Pt(Br){B(Br)X}] [9, 2.009(3) Å;
10, 2.021(5) Å].19a This phenomenon was already observed for
trans-[(Cy3P)2Pt(Br){B(NC5H4-4-Me)Fc}][BArf4] (5) [2.014(5)
Å]10f and its precursor 8 [1.9963(34) Å]21 and is in line with
the coordination number of three and the steric demands of the
substituents on boron. In contrast, platinum complexes with two
coordinate borylene centers, trans-[(Cy3P)2Pt(Br){B(2,4,6-Me3-
C6H2)}][B(C6F5)4] (6)17 and trans-[(Cy3P)2Pt(Br){BN(AlCl3)-
SiMe3}] (7),18 are characterized by significantly decreased Pt-B
separations of 1.859(3) and 1.904(3) Å, respectively. These
findings emphasize the “boryl” character of the metal bound
-B(L)R ligand and its decreased M-B multiple bond character.
Similar observations were made for the aforementioned osmium
complexes with base-stabilized borylene ligands such as 3 and
for base-stabilized silylene complexes.22
Compounds 12-15 were formed by addition of pyridine bases
to the boron centers with concomitant 1,2-bromide shift to the
central metal, thus increasing the coordination number at
platinum. Corresponding intramolecular shifts, especially of
R-hydrogen atoms, were found to be kinetically favored, in case
of coordinatively unsaturated metal centers.23 This route already
allowed for the first synthesis of platinum silylene complexes24
and seems to have a similar potential for the preparation of
borylene species from haloboryl complexes.
Preparation of a Dinuclear Bisboryl Complex. In order to
synthesize a base-stabilized diborylene species of the type
[(Cy3P)2Pt(Br){B(L)spacerB(L)}Pt(Br)(PCy3)2] in an analogous
way, [Pt(PCy3)2] was first reacted with the bisborylated benzene
derivative 1,4-(Br2B)2-C6H4 (16) in benzene in order to prepare
the corresponding bisboryl complex. Monitoring the reaction
by multinuclear NMR spectroscopy revealed the formation of
different products depending on the boron-platinum ratio. In
a typical experiment, 0.044 mmol of 16 was reacted with a 1.5-
fold excess of [Pt(PCy3)2] and the 31P{1H} NMR spectrum
revealed one dominating sharp signal at δ ) 21.4 ppm flanked
by platinum satellites (1JP-Pt ) 2829 Hz) and a broad resonance
The 11B{1H} NMR spectrum of 17 shows one broad
resonance at δ ) 75 ppm for both boron centers, and thus a
similar chemical shift to the platinum-bound boron in 18.
Likewise, in the 1H NMR spectrum only one signal [δ ) 8.46
ppm] was detected for the aromatic protons, indicating an
increased symmetry in comparison to 18. Pale yellow, single
(22) Grumbine, S. K.; Straus, D.; Tilley, T. D. Polyhedron 1995, 14,
127–148.
(23) (a) Goddard, R. J.; Hoffmann, R.; Jemmis, E. D. J. Am. Chem.
Soc. 1980, 102, 7667–7676. (b) Ziegler, T.; Versluis, L.; Tschinke, V. J. Am.
Chem. Soc. 1986, 108, 612–617.
(24) (a) Mitchell, G. P.; Tilley, T. D. Angew. Chem., Int. Ed. 1998, 37,
2524–2526. (b) Mitchell, G. P.; Tilley, T. D. J. Am. Chem. Soc. 1998, 120,
7635–7636.
(25) Braunschweig, H.; Radacki, K.; Uttinger, K. Inorg. Chem. 2007,
46, 8796–8800.
(26) (a) Aldridge, S.; Calder, R. J.; Dickinson, A. A.; Willock, D. J.;
Steed, J. W. Chem. Commun. 2000, 1377–1378. (b) Aldridge, S.; Calder,
R. J.; Rossin, A.; Dickinson, A. A.; Willock, D. J.; Jones, C.; Evans, D. J.;
Steed, J. W.; Light, M. E.; Coles, S. J.; Hursthouse, M. B. J. Chem. Soc.,
Dalton Trans. 2002, 2020–2026.
(27) Braunschweig, H.; Kupfer, T.; Radacki, K.; Schneider, A.; Seeler,
F.; Uttinger, K.; Wu, H. J. Am. Chem. Soc. 2008, 130, 7974–7983.
Figure 1. Schematic picture of a possible bromine hydrogen
interaction in 14.

6008 Organometallics, Vol. 27, No. 22, 2008
Braunschweig et al.
Figure 2. Molecular structures of the cationic, base-stabilized borylene complexes 12, 13, and 15. Counterions, hydrogen atoms, and
cocrystallized solvent molecules (12, 2 CH2Cl2; 13, 2 C6H14) are omitted for clarity. In 15 two cyclohexyl groups bound to P2 are disordered.
Thermal ellipsoids represent 50% probability. Selected bond lengths [Å] and angles [deg]: 12, Pt-B 2.018(4), Pt-Br 2.5909(3), B-N1
1.406(4), B-N2 1.585(4), P1-Pt-P2 173.30(3), B-Pt-Br 179.29(11), P2-Pt-B-N1 79.3(3); 13, Pt-Br 2.5986(4), Pt-B 2.046(4),
B-N1 1.388(5), B-N2 1.565(5), P1-Pt-P2 170.13(3), B-Pt-Br 178.17(11), P1-Pt-B-N1 76.6(4); 15, Pt-Br 2.5857(5), Pt-B 2.023(5),
B-N1 1.402(7), B-N2 1.581(6), P1-Pt-P2 165.63(4), B-Pt-Br 164.92(16), P1-Pt-B-N1 106.3(4).
Scheme 2. Synthesis of the Boryl Complexes 17 and 18
Figure 3. Molecular structure of trans-[(Cy3P)2Pt(Br)-1-{B(Br)-
C6H4-4-{BBr2(PCy3)}}] (18). Solvent molecules (2.5 C6H6 and 0.5
C6H14) and hydrogen atoms are omitted for clarity. Thermal
ellipsoids represent 50% probability. Selected bond lengths [Å] and
angles [deg]: B1-P1 2.036(5), B1-Br1 2.047(5), B1-Br2 2.055(6),
B1-C1 1.608(7), B2-Br3 1.994(5), B2-C4 1.567(7), Pt-B2
1.986(5), Pt-Br4 2.6287(5), C1-B1-P1 112.3(3), C1-B1-Br1
111.1(3), C1-B1-Br2 111.2(3), P3-Pt-P2 165.82(4), Br4-Pt-B2
167.55(15), P2-Pt-B2-C4 96.5(4), Pt-B2-C4-C5 176.6(3).
are comparable to the ones in trans-[(Cy3P)2Pt(Br)(BBr2)] [1.963(6)
Å]19a or trans-[(Cy3P)2Pt(Br){B(Br)tBu}] [1.983(5) Å]19a and
provide evidence for an effective Pt-B π-back-donation due to
less effective π-stablization of the boron by its substituents. The
B-Br and B-C bond lengths [17, 1.994(5) and 1.567(7) Å; 18,
B2-Br3 2.006(3) and B2-C4 1.567(7) Å] are comparable to those
in related boryl complexes.19a
crystals of 17 were obtained by recrystallization and analyzed
by X-ray diffraction, identifying the expected product (Fig-
ure 4).
Boron atom B1 in 18 is tetrahedrally coordinated [C1-B1-P1
112.3(3)°, C1-B1-Br1 111.1(3)°, C1-B1-Br2 111.2(3)°] and
displays B-P [2.036(5) Å] and B-Br distances [B1-Br1
2.047(5), B1-Br2 2.055(6) Å] that are slightly longer than in
known phosphine borane adducts [Me3P-BBr3: B-P 1.924(12)
Å, B-Br 2.021(10) Å;28 Pr3P-BBr3: B-P 1.95(1) Å, B-Br
2.009(3) Å]29 most likely due to the increased steric demands
of the phosphine and the aryl substituent. The B-C distance
[B1-C1 1.608(7) Å] is in line with a typical carbon-boron
single bond.30
In the solid state the platinum centers of 17 and 18 exhibit
slightly distorted square-planar geometries [17, P1-Pt-P2
165.61(3)°, B-Pt-Br2 162.51(9)°; 18, P3-Pt-P2 165.82(4)°,
Br4-Pt-B2 167.55(15)°] and are bound to three-coordinate boron
atoms. The boryl ligands are oriented almost perpendicular to the
PtP2 plane [17, P1-Pt-B-C1 98.8(2)°; 18, P2-Pt-B2-C4
96.5(4)°]. Relatively long Pt-Br bonds indicate [17, 2.6153(3) Å;
18, 2.6287(5) Å] the expected degree of trans-influence for boryl
groups with this particular substitution pattern.19a The significantly
decreased Pt-B distances in 17 [1.965(3) Å] and 18 [1.986(5) Å]
Stepwise Preparation of a Bridged Base-Stabilized Dibo-
rylene Complex. Reaction of the dinuclear complex 17 with 2
equiv of K[B(C6F5)4] yielded 1,4-trans-[{(Cy3P)2Pt(BBr)}2-

Platinum Borylene Complexes
Organometallics, Vol. 27, No. 22, 2008 6009
Chart 3. Bridged Iron (top) and Platinum (bottom) Diboryl
Complexes
the boryl ligand is twisted by 108° toward the PtP2 plane
[P2-Pt-B1-C1 107.87(16)°]. Compared to the starting mate-
rial 17 the Pt-B bond length is slightly shorter [19, 1.938(2)
Å; 17, 1.965(3) Å], which is in line with observations made
for other cationic boryl complexes.10f,31 The B-Br and B-C1
bonds [1.939(2) and 1.563(3) Å] lie in the range of similar boryl
complexes.19a The shortest Pt · · · H(C) and Pt · · · C distances
amount to Pt · · · H(C9) 2.572 Å and Pt · · · C9 3.232 Å and, thus,
prove the absence of notable agostic interactions.10f,33
Treatment of 19 with 2 equiv of 4-methylpyridine afforded
the expected 1,4-trans-[{(Cy3P)2(Br)Pt{B(NC5H4-4-Me)}}2-
C6H4][B(C6F5)4]2 (20) (Scheme 4), which was identified by
NMR spectroscopy and elemental analysis.
The 1H NMR spectrum exhibits three signals in the aromatic
region [δ ) 9.4 (4H, 2 NC5H4-4-Me), 8.08 (4H, C6H4), 7.91
(4H, 2 NC5H4-4-Me)]. The corresponding resonances for the
pyridine ligand in the 13C{1H} NMR spectrum were detected
at δ ) 165.5 (s, Cpara), 144.1 (s, Cortho), 128.2 (s, Cmeta), and
23.1 (s, Me) ppm and lie in the range of the signals observed
for 5 and 12-14, verifying the coordination of the base at the
boron center.
Conclusions
C6H4][B(C6F5)4]2 (19) (Scheme 3) with abstraction of both
platinum-bound bromide ligands, as indicated by a typical
downfield shift of about 20 ppm10f,31 in the 31P{1H} NMR
spectrum [δ ) 43.0 ppm (1JP-Pt ) 2776 Hz)] compared to the
starting material.
In conclusion we have described a series of fully characterized
cationic, base-stabilized borylene complexes of the type trans-
[(Cy3P)2Pt(Br){B(NC5H4-4-R)X}][BArf4] (R ) Me, X ) NMe2,
Pip, Br; R ) tBu, X ) Pip). These compounds were obtained
from bromo boryl comlexes of the general formula trans-
[(Cy3P)2Pt(Br){B(Br)X}] upon removal of the bromide with
Na[BArf4] and coordination of the Lewis base to the boron
center, thus indicating a general applicability of this method.
Furthermore, the dinuclear boryl complexes 1,4-trans-[{(Cy3P)2-
(Br)Pt(BBr)}2-C6H4] and trans-[(Cy3P)2Pt(Br)-1-{B(Br)-C6H4-
4-{BBr2(PCy3)}}] were isolated. The former was reacted with
K[B(C6F5)4] with formation of the dicationic boryl complex 1,4-
trans-[{(Cy3P)2Pt(BBr)}2-C6H4][B(C6F5)4]2, which was con-
verted into the diborylene base-stabilized species 1,4-trans-
[{(Cy3P)2(Br)Pt{B(NC5H4-4-Me)}}2-C6H4][B(C6F5)4]2 by addition
of 4-methylpyridine. In agreement with previous results, the
structural data of the cationic species 12, 13, and 15 indicate
that ligands of the type dB(R)L, while formally representing
base-stabilized borylenes, are characterized by a metal-boron
linkage of little multiple bond character and, thus, resemble boryl
ligands -BR2.
1
The H NMR spectrum shows only one resonance for the
aromatic protons at δ ) 8.29 ppm, and the 11B{1H} NMR
spectrum exhibits a sharp signal for the anion at δ ) -17.6
ppm. A signal for the platinum-bound boron atoms was not
detected, most likely due to high dilution and unresolved
coupling to platinum and posphorus nuclei, as observed before
in many cases.10f,32 Suitable crystals for X-ray analysis were
obtained by layering hexane on concentrated reaction mixtures
and storage at -35 °C (Figure 5).
In 19 both platinum fragments adopt a slightly distorted
T-shaped geometry [P1-Pt-P2 166.717(17)°], and the plati-
num(II) atoms are only three-coordinate. The plane containing
Experimental Section
Synthesis of trans-[(Cy3P)2Pt(Br){B(NC5H4-4-Me)NMe2}][BArf4]
(12). trans-[(Cy3P)2Pt(Br){B(Br)NMe2}] (9) (0.020 g, 0.021 mmol)
and [NaBArf4] (0.018 g, 0.021 mmol) were loaded in a J. Young
NMR tube and dissolved in CD2Cl2 (0.6 mL). The reaction mixture
immediately turned yellow, and some fine powder (NaBr) precipi-
(28) Black, D. L.; Taylor, R. C. Acta Crystallogr., Sect. B 1975, B31,
1116–1120.
(29) Aubauer, C.; Davidge, K.; Klapotke, T. M.; Mayer, P.; Piotrowski,
H.; Schulz, A. Z. Anorg. Allg. Chem. 2000, 626, 2373–2378.
(30) Wilkinson, G.; Stone, F. G. A.; Abel, E. W. ComprehensiVe
Organometallic Chemistry; Pergamon Press Ltd.: Oxford, U.K., 1982; Vol.
1, p 10.
(31) Braunschweig, H.; Green, H.; Radacki, K.; Uttinger, K. Dalton
Trans. 2008, 3531–3534.
(32) Iverson, C. N.; Smith, M. R., III. J. Am. Chem. Soc. 1995, 117,
4403–4404.
(33) (a) Baratta, W.; Stoccoro, S.; Doppiu, A.; Herdtweck, E.; Zucca,
A.; Rigo, P. Angew. Chem., Int. Ed. 2003, 42, 105–109. (b) Ingleson, M. J.;
Mahon, M. F.; Weller, A. S. Chem. Commun. 2004, 2398–2399.
Figure 4. Molecular structure of 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-
C6H4] (17). Solvent molecules (3 CH2Cl2) and hydrogen atoms are
omitted for clarity. Thermal ellipsoids represent 50% probability.
Selected bond lengths [Å] and angles [deg]: Pt-Br2 2.6153(3),
Pt-B 1.965(3), B-Br1 2.006(3), B-C1 1.570(4), P1-Pt-P2
165.61(3), B-Pt-Br2 162.51(9), C1-B-Br1 114.9(2), C1-B-Pt
121.5(2),Pt-B-Br1123.6(2),P1-Pt-B-C198.8(2),Pt-B-C1-C3
177.6(2).

6010 Organometallics, Vol. 27, No. 22, 2008
Scheme 3. Synthesis of the Spacer-Bridged Dicationic Diboryl Complex 19
Braunschweig et al.
Scheme 4. Synthesis of the Spacer-Bridged Dicationic Base-Stabilized Diborylene Complex 20
tated. After filtering over glass fiber filter paper 4-methylpyridine
Synthesis of trans-[(Cy3P)2Pt(Br){B(NC5H4-4-Me)Pip}][BArf4] (13).
trans-[(Cy3P)2Pt(Br){B(Br)Pip}] (10) (0.025 g, 0.025 mmol) and
[NaBArf4] (0.022 g, 0.025 mmol) were put in a vial in the glovebox
and dissolved in CD2Cl2 (0.6 mL). The reaction mixture im-
mediately turned yellow, and some fine powder (NaBr) precipitated.
After 2 h the suspension was filtered over glass fiber filter paper,
and 4-methylpyridine (0.002 g, 0.025 mmol) was added to the
solution. Over 1-2 h the mixture turned colorless. Crystals of trans-
[(Cy3P)2Pt(Br){B(NC5H4-4-Me)Pip}][BArf4] (13) were obtained by
layering the solution with hexane (2 mL) and slow evaporation of
the solvent, yielding 0.026 g (65%).
(0.002 g, 0.021 mmol) was added. After 8 h the solution was layered
with hexane (2 mL) and allowed to evaporate slowly. After 3 weeks
and several recrystallization cycles pure trans-[(Cy3P)2Pt(Br){B-
(NC5H4-4-Me)NMe2}][BArf4] (12) precipitated (0.031 g, 84%).
1H NMR (500 MHz, CD2Cl2, 24 °C): δ 8.83 (d, 3JH-H ) 7 Hz,
3
2H, NC5H4-4-Me), 7.64 (m, 8H, BArf4), 7.62 (d, JH-H ) 7 Hz,
2H, NC5H4-4-Me), 7.48 (br s, 4H, BArf4), 3.16 (s, 3H, NMe2), 2.68
(s, 3H, NMe2), 2.51 (s, 3H, Me, NC5H4-4-Me), 2.05-1.05 (m, 66H,
Cy). 13C{1H} NMR (126 MHz, CD2Cl2, 24 °C): δ 162.0 (q, 1JC-B
) 50 Hz, Cipso, BArf4), 161.0 (s, Cpara, NC5H4-4-Me), 146.6 (s,
Cortho, NC5H4-4-Me), 135.1 (br s, Cortho, BArf4), 129.1 (qq, 2JC-F
3
1H NMR (500 MHz, CD2Cl2, 23 °C): δ 8.99 (br d, JH-H ) 6
3
3
) 32 Hz, JC-B ) 3 Hz, Cmeta, BArf4), 127.1 (s, Cmeta, NC5H4-4-
Hz, 2H, NC5H4-4-Me), 7.72 (m, 8H, BArf4), 7.69 (d, JH-H ) 6
1
3
Me), 124.9 (q, JC-F ) 272 Hz, CF3, BArf4), 117.7 (sep, JC-F
)
Hz, 2H, NC5H4-4-Me), 7.56 (br s, 4H, BArf4), 3.71 (m, 2H, NCH2,
Pip), 3.02 (m, 2H, NCH2, Pip), 2.61 (s, 3H, Me, NC5H4-4-Me),
2.05 (m, 6H, Cy), 1.85-1.16 (m, 60H+6H, Cy and Pip). 13C{1H}
4 Hz, Cpara, BArf4), 47.0 (s, NMe2), 40.6 (s, NMe2), 37.0 (vt, N )
|1JC-P + 3JC-P| ) 28 Hz, C1, Cy), 31.1 (br s, C3,5, Cy), 30.4 (br s,
C3,5, Cy), 28.0 (vt, N ) |2JC-P + JC-P| ) 11 Hz, C2,6, Cy), 27.7
NMR (126 MHz, CD2Cl2, 23 °C): δ 162.1 (q, 1JC-B ) 50 Hz, Cipso
,
4
(vt, N ) |2JC-P + 4JC-P| ) 10 Hz, C2,6, Cy), 26.5 (s, C4, Cy), 22.3
(s, Me, NC5H4-4-Me). 11B{1H} NMR (160 MHz, CD2Cl2, 24 °C):
δ -7.6 (s, BArf4). 31P{1H} NMR (202 MHz, CD2Cl2, 24 °C): δ
26.2 (s, 1JP-Pt ) 2532 Hz). Anal. Calcd for C76H91N2B2BrF24P2Pt:
C, 49.42; H, 4.97; N, 1.52. Found: C, 49.09; H, 5.08; N, 1.48.
BArf4), 161.3 (s, Cpara, NC5H4-4-Me), 146.7 (br s, Cortho, NC5H4-
2 3
4-Me), 135.2 (s, Cortho, BArf4), 129.2 (qq, JC-F ) 31 Hz, JC-B
) 3 Hz, Cmeta, BArf4), 127.1 (s, Cmeta, NC5H4-4-Me), 125.0 (q,
3
1JC-F ) 272 Hz, CF3, BArf4), 117.8 (sep, JC-F ) 4 Hz, Cpara
,
BArf4), 55.0 (s, NCH2, Pip), 50.7 (s, NCH2, Pip), 36.9 (N ) |1JC-P
+ JC-P| ) 26 Hz, C1, Cy), 31.1 (br s, C3,5, Cy), 30.6 (br s, C3,5
,
3
Cy), 28.1 (vt, N ) |2JC-P + 4JC-P| ) 11 Hz, C2,6, Cy), 27.9 (vt, N
) |2JC-P + JC-P| )10 Hz, C2,6, Cy), 27.7 (s, Pip), 26.6 (s, C4,
4
Cy), 26.1 (s, Pip), 24.9 (s, Pip), 22.6 (s, Me, NC5H4-4-Me). 11B{1H}
NMR (160 MHz, CD2Cl2, 23 °C): δ -7.6 (s, BArf4). 31P{1H} NMR
1
(202 MHz, CD2Cl2, 23 °C): δ 27.0 (s, JP-Pt ) 2548 Hz). Anal.
Calcd for C79H95N2B2BrF24P2Pt: C, 50.28; H, 5.07; N, 1.48. Found:
C, 50.18; H, 4.76; N, 1.44.
Synthesis of trans-[(Cy3P)2Pt(Br){B(NC5H4-4-Me)Br}][BArf4] (14).
trans-[(Cy3P)2Pt(Br)(BBr2)] (11) (0.015 g, 0.015 mmol) and Na-
[BArf4] (0.013 g, 0.015 mmol) were loaded in a J. Young NMR
tube and dissolved in CD2Cl2 (0.6 mL). The reaction mixture
immediately turned orange, and some fine powder (NaBr) precipi-
tated. After filtering over glass fiber filter paper 4-methylpyridine
(0.001 g, 0.015 mmol) was added. After 3 h the yellow solution
was layered with hexane (1 mL) and stored at -35 °C, and after 2
weeks yellow crystals of trans-[(Cy3P)2Pt(Br){B(NC5H4-4-Me)Br}]-
[BArf4] (14) were isolated (0.010 g, 35%).
Figure 5. Molecular structure of 1,4-trans-[{(Cy3P)2Pt(BBr)}2-
C6H4][B(C6F5)4]2 (19). Couterions, solvent molecules (2 CH2Cl2),
and hydrogen atoms are omitted for clarity. Thermal ellipsoids
represent 50% probability. Selected bond lengths [Å] and angles
[deg]: Pt-B 1.938(2), B-C1 1.563(3), B-Br 1.939(2), P1-
Pt-P2 166.717(17), P2-Pt-B-C1 107.87(16), Pt-B-C1-C2
158.18(15).
1H NMR (500 MHz, CD2Cl2, 23 °C): δ 10.66 (br s, 1H, NC5H4-
4-Me, H · · · Br), 9.57 (br s, 1H, NC5H4-4-Me), 7.95 (br s, 1H,
NC5H4-4-Me), 7.83 (br s, 1H, NC5H4-4-Me), 7.71 (m, 8H, BArf4),
7.55 (br s, 4H, BArf4), 2.70 (s, 3H, Me, NC5H4-4-Me), 2.61 (br s,
6H, Cy), 2.13-2.02 (m, 6H, Cy), 1.85-1.78 (m, 6H, Cy),

Platinum Borylene Complexes
Organometallics, Vol. 27, No. 22, 2008 6011
1.70-1.48 (m, 30H, Cy), 1.30-1.15 (m, 12H, Cy), 1.00-0.90 (br
s, 6H, Cy). 13C{1H} NMR (126 MHz, CD2Cl2, 25 °C): δ 166.7 (s,
Cpara, NC5H4-4-Me), 162.0 (q, 1JC-B ) 49 Hz, Cipso, BArf4), 144.2
(br s, Cortho, NC5H4-4-Me, HMQC), 135.1 (s, Cortho, BArf4), 129.1
solid was washed with hexane (2 × 0.5 mL) and dried (19 mg,
30%). Single crystals of 18 suitable for X-ray analysis were obtained
by recrystallization from a C6H6/hexane mixture and slow evaporation.
1H NMR (500 MHz, CD2Cl2, 25 °C): δ 8.88 (br s, 1H, CH,
C6H4), 8.13 (br s, 1H, CH, C6H4), 7.84 (2 overlapping s, 2H, CH,
C6H4), 2.60 (m, 6H, Cy), 2.37 (m, 3H, Cy), 2.24-2.11 (m, 12H,
Cy), 1.87-1.50 (m, 51H, Cy), 1.30-0.94 (m, 27H, Cy). 13C{1H}
2
3
(qq, JC-F ) 32 Hz, JC-B ) 3 Hz, Cmeta, BArf4,), 128.4 (br s,
Cmeta, NC5H4-4-Me), 124.9 (q, 1JC-F ) 272 Hz, CF3, BArf4), 117.7
3
(sep, JC-F ) 4 Hz, Cpara, BArf4), 36.3 (br s, C1, Cy), 30.9 (s,
4
C3,5, Cy), 30.8 (s, C3,5, Cy), 27.8 (vt, N ) |2JC-P + JC-P| ) 11
NMR (126 MHz, CD2Cl2, 25 °C): δ 134.8 (br s, CH, C6H4), 35.6
4
Hz, C2,6, Cy), 27.7 (vt, N ) |2JC-P + JC-P| ) 11 Hz, C2,6, Cy),
1
(br s, C1, CyPt), 32.8 (d, JC-P ) 29 Hz, C1, CyB), 30.9 (s, C3,5
,
26.5 (s, C4, Cy), 23.3 (s, Me, NC5H4-4-Me). 11B{1H} NMR (160
CyPt), 30.1 (s, C3,5, CyPt), 28.7 (d, 3JC-P ) 4 Hz, C3,5, CyB), 28.0
(vt, N ) |2JC-P + 4JC-P| ) 11 Hz, C2,6, CyPt), 27.8 (vt, N ) |2JC-P
+ 4JC-P| ) 10 Hz, C2,6, CyPt), 27.6 (d, 2JC-P ) 10 Hz, C2,6, CyB),
26.9 (s, C4, CyPt), 26.3 (s, C4, CyB) (due to the poor solubility, the
dilution of the sample, and unresolved coupling to boron atoms,
not all signals of the C6H4 group were detected). 11B{1H} NMR
(160 MHz, CD2Cl2, 25 °C): δ 73 (br s, B-Pt), -5 (br s, B-P).
31P{1H} NMR (202 MHz, CD2Cl2, 25 °C): δ 21.4 (s, 1JP-Pt ) 2829
Hz), -7.9 (br s, P-B). Anal. Calcd for C60H103B2Br4P3Pt: C, 49.57;
H, 7.14. Found: C, 50.05; H, 6.94.
MHz, CD2Cl2, 24 °C): δ -7.6 (s, BArf4). 31P{1H} NMR (202 MHz,
1
CD2Cl2, 24 °C): δ 23.9 (s, JP-Pt ) 2373 Hz). Anal. Calcd for
C74H85B2Br2F24NP2Pt: C, 47.20; H, 4.55; N, 0.74. Found: C, 47.09;
H, 4.56; N, 0.67.
Synthesis of trans-[(Cy3P)2Pt(Br){B(NC5H4-4-tBu)Pip}][BArf4] (15).
Similarly to the synthesis of trans-[(Cy3P)2Pt(Br){B(NC5H4-4-
Me)Pip}][BArf4] (12) trans-[(Cy3P)2Pt(Br){B(NC5H4-4-tBu)Pip}]-
[BArf4] (15) (0.033 g, 69%) was isolated starting from trans-
[(Cy3P)2Pt(Br){B(Br)(Pip)}] (10) (0.025 g, 0.025 mmol), Na[BArf4]
(0.022 g, 0.025 mmol), and NC5H4-4-tBu (0.003 g, 0.025 mmol).
Synthesis of 1,4-trans-[{(Cy3P)2Pt(BBr)}2-C6H4][B(C6F5)4]2
(19). 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] (17) (0.015 g, 0.008
mmol) and K[B(C6F5)4] (0.012 g, 0.016 mmol) in CD2Cl2 (0.6 mL)
were reacted in a J. Young NMR tube and dissolved in CD2Cl2
(0.6 mL). The reaction mixture immediately turned yellow, and
some fine solid (KBr) precipitated. After filtering over glass fiber
filter paper the yellow solution was layered with hexane (1 mL)
and stored at -35 °C. After 1 week crystals of 1,4-trans-
[{(Cy3P)2Pt(BBr)}2-C6H4][B(C6F5)4]2 (19) (0.016 g, 62%) were
isolated.
1H NMR (500 MHz, CD2Cl2, 23 °C): δ 8.99 (m, 2H, NC5H4-
4-tBu), 7.86 (m, 2H, NC5H4-4-tBu), 7.72 (m, 8H, BArf4), 7.56 (br
s, 4H, BArf4), 3.71 (br s, 2H, NCH2, Pip), 3.04 (br s, 2H, NCH2,
Pip), 2.05 (m, 6H, Cy), 1.85-1.16 (m, 60H+6H, Cy and Pip) 1.41
(s, 9H, tBu, NC5H4-4-tBu). 13C{1H} NMR (126 MHz, CD2Cl2, 23
1
°C): δ 173.45 (s, Cpara, NC5H4-4-tBu), 162.1 (q, JC-B ) 50 Hz,
Cipso, BArf4,), 147.0 (br s, Cortho, NC5H4-4-tBu), 135.2 (s, Cortho
,
2
3
BArf4), 129.2 (qq, JC-F ) 31 Hz, JC-B ) 3 Hz, Cmeta, BArf4),
1
125.0 (q, JC-F ) 273 Hz, CF3, BArf4), 123.7 (s, Cmeta, NC5H4-
3
4-tBu), 117.8 (sep, JC-F ) 4 Hz, Cpara, BArf4), 54.9 (s, NCH2,
1H NMR (500 MHz, CD2Cl2, 25 °C): δ 8.29 (s, 4H, CH, C6H4),
2.25 (m, 12H, Cy), 2.00-1.70 (m, 60H, Cy), 1.60-1.48 (m, 24H,
Cy), 1.27-1.16 (m, 36H, Cy). 13C{1H} NMR (126 MHz, CD2Cl2,
25 °C): δ 148.5 (br d, 1JC-F ) 244 Hz, Cpara, B(C6F5)4), 143.2 (s,
Pip), 50.5 (s, NCH2, Pip), 37.2 (s, C, tBu), 36.9 (vt, N ) |1JC-P
+
,
3JC-P| ) 27 Hz, C1, Cy), 31.1 (br s, C3,5, Cy), 30.6 (br s, C3,5
4
Cy), 30.0 (s, Me, tBu), 28.1 (vt, N ) |2JC-P + JC-P| ) 11 Hz,
4
C2,6, Cy), 27.8 (vt, N ) |2JC-P + JC-P| ) 11 Hz, C2,6, Cy), 27.6
1
Cipso, C6H4, HMBC), 138.6 and 136.7 (2 overlapping br d, JC-F
(s, Pip), 26.6 (s, C4, Cy), 26.0 (s, Pip), 24.9 (s, Pip). 11B{1H} NMR
) 243 Hz, Cortho,meta, B(C6F5)4), 138.1 (s, CH, C6H4, HMQC),
(160 MHz, CD2Cl2, 23 °C): δ -7.6 (s, BArf4). 31P{1H} NMR (202
3
124.2 (br s, Cipso, B(C6F5)4), 34.9 (vt, N ) |1JC-P + JC-P| ) 27
1
Hz, C1, Cy), 30.6 (s, C3,5, Cy), 30.4 (s, C3,5, Cy), 27.4 (2
MHz, CD2Cl2, 23 °C): δ 27.2 (s, JP-Pt ) 2557 Hz). Anal. Calcd
4
overlapping vt, N ) |2JC-P + JC-P| ) 11 Hz, C2,6, Cy), 26.0 (s,
for C82H101N2B2BrF24P2Pt: C, 51.05; H, 5.28; N, 1.45. Found: C,
51.38; H, 5.73; N, 1.42.
C4, Cy). 11B{1H} NMR (160 MHz, CD2Cl2, 25 °C): δ -17.6 (s,
B(C6F5)4). 31P{1H} NMR (202 MHz, CD2Cl2, 25 °C): δ 43.0 (s,
1JP-Pt ) 2776 Hz). Anal. Calcd for C126H136B4Br2F40P4Pt2 ·
2(CH2Cl2): C, 46.62; H, 4.28. Found: C, 45.91; H, 3.66.
Synthesis of 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] (17). 1,4-
(BBr2)2-C6H4 (16) (0.014 g, 0.033 mmol) and [Pt(PCy3)2] (0.050
g, 0.066 mmol) were added to a J. Young NMR tube and dissolved
in C6D6 (0.6 mL). A white solid of trans-[(Cy3P)2Pt(Br)-1-{B(Br)-
C6H4-4-{BBr2(PCy3)}}] (18) precipitated, and the solution turned
brown-yellow. After 2 days the solid was separated (0.014 g) and
discarded. The remaining solution was allowed to evaporate slowly
in the glovebox. The first crystallized fraction (0.007 g) still
contained side products and was therefore discarded, whereas the
second fraction was pure 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4]
(17) (0.015 g, 24%).
Synthesis of 1,4-trans-[{(Cy3P)2Pt(B(NC5H4-4-Me)Br)}2-C6H4]-
[B(C6F5)4]2 (20). Similarly to the above-described procedures the
reaction of 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] (17) (0.015 g,
0.008 mmol) and K[B(C6F5)4] (0.012 g, 0.016 mmol) afforded 1,4-
trans-[{(Cy3P)2Pt(BBr)}2-C6H4][B(C6F5)4]2 (19), which was treated
with NC5H4-4-CH3 (0.002 g, 0.016 mmol). The mixture was layered
with hexane (1 mL) and stored at -35 °C, yielding yellow crystals
of 1,4-trans-[{(Cy3P)2Pt(B(NC5H4-4-Me)Br)}2-C6H4][B(C6F5)4]2
(20) (0.010 g, 39%).
1H NMR (500 MHz, CD2Cl2, 24 °C): δ 8.46 (br s, 4H, CH,
C6H4), 2.65 (br s, 12H, Cy), 2.16 (br s, 12H, Cy), 1.90-1.50 (m,
72H, Cy), 1.40-1.00 (m, 36H, Cy). 13C{1H} NMR (126 MHz,
CD2Cl2, 24 °C): δ 35.9 (br s, C1, Cy), 30.8 (s, C3,5, Cy), 30.2 (s,
1H NMR (500 MHz, CD2Cl2, 23 °C): δ 9.45 (br s, 4H, 2 NC5H4-
4-Me), 8.08 (s, 4H, CH, C6H4), 7.91 (br s, 4H, 2 NC5H4-4-Me),
2.71 (s, 6H, 2 NC5H4-4-Me), 2.10-1.10 (m, 132H, Cy). 13C{1H}
NMR (126 MHz, CD2Cl2, 23 °C): δ 165.5 (s, Cpara, NC5H4-4-
4
C3,5, Cy), 28.0 (vt, N ) |2JC-P + JC-P| ) 11 Hz, C2,6, Cy), 27.8
(vt, N ) |2JC-P + 4JC-P| ) 11 Hz, C2,6, Cy), 26.8 (s, C4, Cy) (due
to high dilution and unresolved coupling to the boron atoms, no
signals were deteted for the C6H4 group). 11B{1H} NMR (160 MHz,
CD2Cl2, 24 °C): δ 75 (br s). 31P{1H} NMR (202 MHz, CD2Cl2,
Me), 148.5 (br d, 1JC-F ) 244 Hz, Cpara, B(C6F5)4), 144.1 (s, Cortho
,
1
NC5H4-4-Me), 138.6 and 136.6 (2 overlapping br d, JC-F ) 243
Hz, Cortho,meta, B(C6F5)4), 137.0 (s, CH, C6H4, HMQC), 128.2 (br
s, Cmeta, NC5H4-4-Me), 37.4 (br s, C1, Cy), 30.8 (br s, C3,5, Cy),
27.7 (br s, C2,6, Cy), 26.2 (br s, C4, Cy), 23.1 (s, Me, NC5H4-4-
Me). 11B{1H} NMR (160 MHz, CD2Cl2, 23 °C): δ -17.6 (s,
B(C6F5)4). 31P{1H} NMR (202 MHz, CD2Cl2, 23 °C): δ 43.0 (s,
1JP-Pt ) 2776 Hz); due to the high dilution of the sample and
unresolved couplings, not all signals were detected in the 13C{1H}
and 11B{1H} NMR spectra. Anal. Calcd for C138H150B4Br2F40-
N2P4Pt2: C, 50.02; H, 4.56; N, 0.85. Found: C, 49.42; H, 4.52; N,
1.06.
1
24 °C): δ 23.2 (s, JP-Pt ) 2833 Hz). Anal. Calcd for
C78H136B2Br4P4Pt2: C, 48.56; H, 7.11. Found: C, 49.10; H, 7.24.
Synthesis of trans-[(Cy3P)2Pt(Br)-1-{B(Br)-C6H4-4-{BBr2(PCy3)}}]
(18). 1,4-(BBr2)2-C6H4 (16) (0.018 g, 0.044 mmol) was added to a
solution of [Pt(PCy3)2] (0.050 g, 0.066 mmol) in C6D6 (0.6 mL).
The resulting precipitate was separated from the yellow solution
and extracted twice with toluene (2 × 0.5 mL). The solvent was
allowed to evaporate slowly in the glovebox, and the precipitated

6012 Organometallics, Vol. 27, No. 22, 2008
Braunschweig et al.
Crystal Structure Determination. The crystal data of 12, 13,
15, and 17-19 were collected on a Bruker X8APEX diffractometer
with CCD area detector and multilayer mirror monochromated Mo
KR radiation. The structures were solved using direct methods,
refined with the Shelx software package,34 and expanded using
Fourier techniques. All non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms were assigned to idealized positions
and were included in structure factor calculations.
) 12.7827(4) Å, b ) 24.4857(7) Å, c ) 16.2173(5) Å, ꢀ )
90.412(2)°, V ) 5075.8(3)Å3, Z ) 4, Fcalcd ) 1.596 g · cm-3, µ )
4.746 mm-1, F(000) ) 2444, T ) 100(2) K, R1 ) 0.0493, wR2 )
0.0711, 16 084 independent reflections [2θ e 64.18°] and 509
parameters.
Crystal data for 18: C78H125B2Br4P3Pt, Mr ) 1692.04, yellow
plate, 0.190 × 0.120 × 0.04 mm3, monoclinic space group P21/n,
a ) 14.9389(5) Å, b ) 24.4311(9) Å, c ) 21.7945(6) Å, ꢀ )
90.9880(10)°, V ) 7953.2(5) Å3, Z ) 4, Fcalcd ) 1.413 g · cm-3, µ
) 3.874 mm-1, F(000) ) 3464, T ) 100(2) K, R1 ) 0.0814, wR2
) 0.1168, 22 237 independent reflections [2θ e 59.62°] and 766
parameters.
Crystal data for 12: C78H95B2BrCl4F24N2P2Pt, Mr ) 2016.92,
3
j
colorless bar, 0.19 × 0.18 × 0.09 mm , triclinic space group P1,
a ) 13.0986(7) Å, b ) 17.2349(7) Å, c ) 20.2400(10) Å, R )
101.036(2)°, ꢀ ) 102.763(2)°, γ ) 94.732(2)°, V ) 4336.6(4) Å3,
Z ) 2, Fcalcd ) 1.545 g · cm-3, µ ) 2.333 mm-1, F(000) ) 2028,
T ) 100(2) K, R1 ) 0.0444, wR2 ) 0.1079, 24 755 independent
reflections [2θ e 61.12°] and 1085 parameters.
Crystal data for 19: C64H70B2BrCl2F20P2Pt, Mr ) 1648.66, yellow
3
j
block, 0.235 × 0.135 × 0.120 mm , triclinic space group P1, a )
14.1057(3) Å, b ) 14.7139(3) Å, c ) 18.4361(5) Å, R )
66.9520(10)°, ꢀ ) 68.6530(10)°, γ ) 78.7260(10)°, V ) 3273.14(13)
Å3, Z ) 2, Fcalcd ) 1.673 g · cm-3, µ ) 2.982 mm-1, F(000) )
1642, T ) 293(2) K, R1 ) 0.0242, wR2 ) 0.0547, 16 124
independent reflections [2θ e 56.62°] and 829 parameters.
Crystal data for 13: C91H123B2BrF24N2P2Pt, Mr ) 2059.47,
3
j
colorless plate, 0.20 × 0.11 × 0.03 mm , triclinic space group P1,
a ) 13.4787(10) Å, b ) 19.3931(14) Å, c ) 19.6039(14) Å, R )
102.695(4)°, ꢀ ) 104.641(4)°, γ ) 97.209(4)°, V ) 4746.9(6) Å3,
Z ) 2, Fcalcd ) 1.441 g · cm-3, µ ) 2.024 mm-1, F(000) ) 2104,
T ) 100(2) K, R1 ) 0.0744, wR2 ) 0.1187, 27 746 independent
reflections [2θ e 65.68°] and 1201 parameters.
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Center as supplementary publication nos.
CCDC 695416-695421. These data can be obtained free of charge
from the Cambridge Crystallographic Data Centre via www.ccd-
c.cam.ac.uk/data_request/cif.
Crystal data for 15: C82H101B2BrF24N2P2Pt, Mr ) 1929.21,
colorless plate, 0.18 × 0.16 × 0.095 mm3, monoclinic space group
P21/n, a ) 15.5886(4) Å, b ) 14.4814(3) Å, c ) 38.1580(10) Å,
ꢀ ) 92.9160(10)°, V ) 8602.8(4) Å3, Z ) 4, Fcalcd ) 1.490 g · cm-3
,
Acknowledgment. The authors thank the DFG and FCI
for financial support.
µ ) 2.228 mm-1, F(000) ) 3904, T ) 100(2) K, R1 ) 0.0511,
wR2 ) 0.1197, 17 000 independent reflections [2θ e 52.18°] and
1228 parameters.
Supporting Information Available: Crystallographic data of
compounds 7, 11 and 14-16 (cif). This material is available free
of charge Via the Internet at http://pubs.acs.org.
Crystal data for 17: C42H74BBr2Cl6P2Pt, Mr ) 1219.37, yellow
block, 0.32 × 0.21 × 0.19 mm3, monoclinic space group P21/c, a
(34) Sheldrick, G. Acta Crystallogr. A 2008, 64, 112–122.
OM800689H