Evidence for a strong trans influence of the diboran(4)yl ligand

Article abstract of DOI:10.1002/chem.201203220

Diboran(4)yl Pt^II complexes: Selective oxidative addition of one B-I bond in B₂(NMe₂)₂I₂ to [Pt(PiPr₃)₂] affords a trans-diboran(4)yl platinum(II) complex (see scheme; Ar^F=3,5-(CF₃)₂C ₆H₃). Comparison of its Pt-I bond lengths and the Pt-Br bond lengths of its bromine analogue with related species served to evaluate the trans influence of the ligand. The trans influence enabled facile halide abstraction to generate T-shaped 14-electron diboran(4)yl platinum(II) complexes.

Full text of DOI:10.1002/chem.201203220

COMMUNICATION
DOI: 10.1002/chem.201203220
Evidence for a Strong trans Influence of the Diboran(4)yl Ligand
Holger Braunschweig,* Alexander Damme, and Thomas Kupfer[a]
Recent years have seen increasing interest in transition-
metal boryl complexes[1] because of their high significance in
catalysis. Thus, catalytic processes such as the hydrobora-
tion[2] and diboration[3] of unsaturated organic substrates
For a more accurate description of the trans influence of
the diboran(4)yl group, we set out to prepare the corre-
sponding iodine derivative trans-[(iPr3P)2Pt(I){B
B(NMe2)(I)}] (6) by oxidative addition of B2A(NMe2)2I2 to
low-valent platinum compound [Pt(PiPr3)2]. We will also
ACHTUNGTRENNUNG(NMe2)-
G
CHTUNGTRENNUNG
À
and the selective C H bond functionalization of alkanes
ACHTUNGTRENNUNG
and arenes[4] strongly depend on the presence of such boryl
species as important intermediates. Being comparatively
well-established, platinum boryl complexes of the type, cis-
show that the diboran(4)yl ligands in 5 and 6 feature strong
trans-labilizing abilities enabling selective halide abstraction
reactions to afford T-shaped diboran(4)yl species trans-
[(R3P)2Pt
N
[(iPr3P)2Pt{B
ACHTUGNTNERN(NUG NMe2)BACHTUNGRETG(NNUN NMe2)2(X)}]ACHTGUNTERNNUG I
[BArF ] (X=Br (7),
4
garding the trans influence of the boryl substituent.[5] Sever-
al experimental studies implied a strong trans influence and
trans-labilizing ability of the boryl group.[1,6] Theoretical
works by Marder and Lin subsequently revealed the strong
s-donor character of the boryl ligand as the predominant
cause of this behavior; the s-donor strength was also found
highly dependent on the substitution pattern at boron.[7] De-
tailed studies in our research group completely verified the
theoretical results. Thus, we were able to specify the trans
influence of different bromoboryl ligands by evaluation of
(8); ArF =3,5-(CF3)2C6H3).
À
Selective oxidative addition of one B I bond of
B2(NMe2)2I2 occurred spontaneously at room temperature
[13]
upon mixing the diborane(4) with [Pt
After work-up, the 16-electron PtII complex, trans-
[(iPr3P)2Pt(I){B(NMe2)B(NMe2)(I)}] (6) was isolated as col-
orless crystals (72%, Scheme 1). The yields of isolated com-
(PiPr3)2][14] in benzene.
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
À
the Pt Br bonds in the molecular structures of several 16-
electron platinum(II) complexes of the type, trans-
[(Cy3P)2Pt(Br)ACHTUNGTRENNUNG
(BXX’)] (Figure 2; 1–3).[5,7] As a consequence
Scheme 1. Oxidative addition of B2ACHTUNGTRENUNG(NMe2)2I2 to afford 6.
of the trans-labilizing effect of the boryl group, halide ab-
straction at the platinum center is a facile process and pro-
ceeds with high selectivity to afford 14-electron cationic T-
shaped platinum(II) boryl species.[8] By contrast, the trans
influence of diboran(4)yl ligands in transition-metal com-
plexes has not been elucidated so far, a fact that is related
to the lack of experimental data. The few examples that
have appeared in the literature are as follows:
plex significantly improved by using low-valent [Pt
ACHTUNGTRENNUNG(PiPr3)2]
instead of its precursor [Pt(PiPr3)3], which generates one
AHCTUNGTRENNUNG
equivalent of PiPr3 during the reaction, thus resulting in the
formation of unwanted side products. No further oxidative
À
addition of the remaining B I bond was observed even
when excess [Pt
A
(i) species obtained by a salt-elimination reaction of
posed no difficulties and data obtained from NMR spectro-
scopy (1H, 11B, 13C, 31P), elemental analysis, and X-ray dif-
fraction clearly substantiate a selective oxidative-addition
event. Thus, the presence of an unsymmetrical diboran(4)yl
group is evident in all solution-state NMR spectra of 6 in
C6D6. Whereas four signals are found for the NMe2 substitu-
B2(NMe2)2X2 (X=Cl,[9] Br,[10] I[11]) with anionic half-
sandwich carbonyl complexes M’ACTHNUTRGNEG[NU CpM(CO)n] (M=Mo,
W, Fe, Ru)
(ii) trans-[(Et3P)2Pt(Br){BACHTUNTGRENNUG(Mes)BACHTUNGTERN(NUNG Mes)(Br)}] (4) with a
dative bonding interaction between the platinum
center and the empty p orbital of the remote boron
1
ents in the H NMR (d=2.57, 2.91, 2.94, 3.10 ppm; each: s,
atom [Pt···{B
G
3H) and 13C NMR spectra (d=50.53, 48.62, 46,94,
45.24 ppm), the 11B NMR spectrum of 6 displays two reso-
nances, at d=51.8 and 38.4 ppm, representing the boron
nuclei at platinum and iodine, respectively. As expected, the
coordination of one boron atom to platinum leads to a
11B NMR signal that is significantly shifted to higher field
G
(NMe2)(Br)}] (5)[12]
[a] Prof. Dr. H. Braunschweig, Dipl.-Chem. A. Damme, Dr. T. Kupfer
Institut fꢀr Anorganische Chemie
Julius-Maximilians-Universitꢁt Wꢀrzburg
Am Hubland, 97074 Wꢀrzburg (Germany)
Fax : (+49)931-31-84623
with respect to that of B2ACHTUNGRTNEUNG(NMe2)2I2 (d=35.6 ppm; Dd=
16 ppm) and the signal of the intact -BACTHNURTGNENUG(NMe2)I fragment
E-mail: h.braunschweig@uni-wuerzburg.de
(d=38.4 ppm; Dd=3 ppm).
Chem. Eur. J. 2012, 18, 15927 – 15931
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
15927

As expected, the 31P NMR spectrum of 6 shows a single
than in other trans-P2PtI species with boryl (9),[15] gallyl
(10)[16] or carbon-based ligands (11–14; Table 1).[17–20] By
contrast, the size of P1-Pt-P2 angle in these systems is not
31P NMR resonance with a chemical shift (d=30.5 ppm) and
1
a J
N
for a trans-bisphosphine–PtII species (compare with 5: d=
34.1 ppm; 1J(P,Pt)=3118 Hz).[12] Accordingly, the 31P NMR
signal is shifted to higher field by 43 ppm with respect to
that of [Pt
(PiPr3)3] (d=73.3 ppm; 1J(P,Pt)=4101 Hz)[14a]
À
Table 1. Pt I bond lengths [ꢃ] and P-Pt-P bond angles [8] in different
trans-P2PtI complexes.
À
Compound
[(iPr3P)2Pt(I){B
[(Cy3P)2Pt(I)(BI2)]
[(Cy3P)2Pt(I)(GaI2)]
[(Et3P)2(I)Pt(m-C6H4)Pt(I)
[(Et3P)2(I)Pt(m-C12H8)Pt(I)
[(Ph3P)2Pt(I){C(O)CHCMe2}]
[(Me3P)2(I)Pt(m-C2)Pt(I)(PMe3)2]
Pt I
P-Pt-P
upon changing the oxidation state of Pt and the JACTHNUTRGENUG(N P,Pt) cou-
6
9
G
E
E
2.8226(3)
2.7813(7)
2.6900(5)
2.7136(6)
2.697(1)
172.21(3)
165.31(6)
167.86(4)
168.71(4)
179.1(4)
pling constant decreases at the same time.
R
ACHTUNGTRENNUNG
The X-ray structure of 6 confirmed a selective oxidative-
addition event and reveals an ideal square-planar platinum
complex (SPt =360.78) with iodine and diboran(4)yl substitu-
ents in trans positions (Figure 1). Because both boron atoms
10
11
12
13
14
E
ACHTUNGTRENNUNG
E
U
G
E
N
2.7236(8)
2.646(4)
171.24(9)
170.1(4)
A
N
indicative of the strength of the trans influence, but is rather
dependent on the nature and size of the phosphine. In addi-
tion, the exceptional trans influence also becomes evident in
À
the analysis of the Pt Br bond lengths of 5 and related plati-
À
num species (Figure 2). Accordingly, the Pt Br bond lenght
in 5 (2.6470(5) ꢃ) is even longer than in platinum–boryl
complexes of the type trans-[(Cy3P)2Pt(Br)ACTHNURTGNEU(GN BXX’)] (2.56–
2.64 ꢃ), which already feature ligands with a strong trans-in-
fluence.[5] Hence, the diboran(4)yl ligand rank among the
most potent trans-influence ligands known so far, if not the
strongest, which is evidently due to the presence of an elec-
tropositive boron substituent at the platinumn-bound boryl
group.
Figure 1. Molecular structure of 6 in the solid state. Thermal ellipsoids
are displayed at the 50% probability level. For clarity, hydrogen atoms
and thermal ellipsoids of the carbon atoms have been omitted. Selected
À
À
bond lengths [ꢃ] and bond angles [8]: Pt1 I1 2.8226(3), Pt1 P1
À
À
À
À
2.3565(10), Pt1 P2 2.3241(10), Pt1 B1 2.087(4), B1 B2 1.738(6), B1 N1
À
À
1.399(5), B2 N2 1.388(5), B2 I2 2.234(4), P1-Pt1-P2 172.21(3), I1-Pt1-B1
173.23(12), Pt1-B1-B2 120.6(3), Pt1-B1-N1 120.4(3), N1-B1-B2 119.0(3),
B1-B2-I2 116.6(3), B1-B2-N2 128.5(3), I2-B2-N2 114.7(3), N2-B2-B1-N1
56.1(6).
À
Figure 2. Pt Br bond lengths (in ꢃ) and trans influence of the di-
A
are electronically saturated by p donation of the NMe2 sub-
stituents, no evidence for any dative bonding interactions
between Pt1 and B2 similar to that found for 4[12] is present
for 6. The molecular structure of 6 rather resembles that of
boran(4)yl ligand in 5 and related boryl species.[5]
The trans influence and the trans-labilizing ability of the
À
the bromine analogue 5, and the B1 B2 (6: 1.738(6) ꢃ; 5:
diboran(4)yl ligand was also assessed experimentally by the
facile removal of the platinum-bound iodine atom through
salt-elimination reactions. Thus, halide abstraction with
À
À
1.742(8) ꢃ), Pt1 B1 (6: 2.087(4) ꢃ; 5: 2.073(5) ꢃ), Pt1 B2
À
(6: 3.227 ꢃ; 5: 3.298 ꢃ) and Pt P bond lengths (6:
2.3565(10) ꢃ, 2.3241(10) ꢃ; 5: 2.3452(11) ꢃ, 2.3146(11) ꢃ)
are of similar magnitude.[12] However, the coordination of
one boron center to platinum results in an elongation of the
Na[BArF ] in fluorobenzene is fast for both 5 and 6, and
4
proceeds quantitatively at room temperature within minutes
to afford cationic T-shaped complexes 7 and 8, which were
isolated in moderate yields (7: 79%; 8: 57%). The reactions
were highly selective and only the halogen atom at platinum
is removed under these reaction conditions (Scheme 2).
Solution-phase NMR spectroscopy on complexes 7 and 8
was fully consistent with these complexes having a T-shaped
structure. Whereas the 11B NMR (7: d=36.4 ppm (br); 8:
d=39.5, 32.8 ppm) and 31P NMR chemical shifts (7: d=
À
B1 B2 bond by approximately 5 pm with respect to the di-
borane(4) precursor B
(NMe2)2I2 (1.684(6) ꢃ). A similar be-
havior is observed for the torsion angle N1-B1-B2-N2 of the
diboran(4)yl ligand, the value for 6 (À56.1(6)8) and 5
(À54.3(6)8)[12] being comparable but significantly smaller
than that of B2ACHTUNGTRENNUNG(NMe2)2I2 (N1-B1-N1’-B1’: 77.0(6)8). This
effect is most likely related to the steric requirements of the
bulky platinum bisphosphine moiety.
1
57.7 ppm; 8: d=57.1 ppm) indicate a cationic species, the J-
À
Evaluation of the Pt I bond length in 6 clearly highlights
the strong trans influence of the diboran(4)yl moiety. Thus,
ACHTUNGTREN(NUGN P,Pt) coupling constants (7: 3118 Hz; 8: 3112 Hz) clearly
imply that the trans arrangement of the phosphine ligands is
À
the Pt1 I1 bond in 6 (2.8226(3) ꢃ) is considerably longer
retained in both cases upon halide abstraction. Similar
15928
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ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 15927 – 15931

trans Influence of the Diboran(4)yl Ligand
COMMUNICATION
trans influence was also evident in the strong trans-labilizing
ability of the diboran(4)yl ligand; this trans influence was
exemplified by facile halide abstraction involving the plati-
num-bound halogen atoms in 5 and 6 to afford cationic T-
shaped complexes 7 and 8 containing a diboran(4)yl unit.
Scheme 2. Halide abstraction reactions of 4 and 6 to afford T-shaped
complexes 7 and 8.
Experimental Section
NMR characteristics, that is, highfield-shifted 11B NMR and
lowfield-shifted 31P NMR resonances, have already been re-
ported for the related platinum boryl complexes, trans-
General procedure: All manipulations were conducted either under an
atmosphere of dry argon or in vacuo using either standard Schlenk line
or glovebox techniques. Solvents were purified by distillation from CaH2
under dry argon and stored over molecular sieves. C6D6 and CD2Cl2 were
degassed by three freeze-pump-thaw cycles and stored over molecular
[(Cy3P)2Pt(Br)
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG(BXX’)] and cationic trans-[(Cy3P)2Pt-
(BXX’)]+.[8] Notably, only one broad 11B NMR signal could
sieves.
[Pt
(NMe2)2I2,[13] and Na[BArF
ACHTUNGTERNNUNG ]
4
(PiPr3)3],[14]
trans-[(iPr3P)2Pt(Br){B
N
ACHTUNGTRNEN(UNG NMe2)2(Br)}]
be observed for the two boron nuclei in 7.
[21]
(5),[12]
B
N
X-ray diffraction studies served to verify the cationic and
T-shaped nature of the diboran(4)yl complexes 7 and 8 in
the solid state (Figure 3). As expected, abstraction of the
lished procedures. NMR spectra were acquired either on
a
Avance 500 (1H: 500.1 MHz, 11B: 160.4 MHz, 13C: 125.7 MHz, 31P:
202.4 MHz) or on a Bruker Avance 400 (1H: 400.1 MHz, 11B: 128.3 MHz,
13C: 100.6 MHz, 31P: 161.9 MHz) FT-NMR spectrometer. 1H, 13C, and
13C{1H} NMR spectra were referenced to external TMS using either the
residual protons of the solvent (1H) or the deuterated solvent itself (13C).
11B{1H} NMR spectra were referenced to external BF3·OEt2 and 31P{1H}
NMR spectra to 85% H3PO4. Microanalyses (C, H, N) were performed
on a Leco Instruments elemental analyzer, type CHNS 932.
trans-[(iPr3P)2Pt(I){B
0.07 mmol) was placed in a J.Young NMR tube and heated at 558C over
a period of 1 h under high vacuum to afford [Pt(PiPr3)2]. B2A(NMe2)2I2
ACHTNUGTRNEU(NNG NMe2)BACHUTNRTGEN(GNNU NMe2)(I)}] (6): [PtCAHTNUGTREN(NUGN PiPr3)3] (50.0 mg,
A
CHTUNGTRENNUNG
(26.9 mg, 0.07 mmol) was added, and the solid mixture was dissolved in
C6D6 (0.6 mL). The reaction occurred spontaneously and was quantitative
within seconds. The solvent was allowed to evaporate slowly at room
temperature in a glovebox. The colorless crystals formed were washed
with pentane (0.5 mL) and dried under reduced pressure to yield analyti-
cally pure 2 (46.5 mg, 0.05 mmol, 72%). 1H NMR (500.1 MHz, C6D6,
293 K, TMS): d=3.10 (s, 3H; NMe2), 3.07 (m br, 6H; PCH), 2.94 (s, 3H;
NMe2), 2.91 (s, 3H; NMe2), 2.57 (s, 3H; NMe2), 1.36 ppm (m, 3J
ACHTUNGTRENNUNG(H,P)=
Figure 3. Molecular structure of 7 (left) and 8 (right) in the solid state.
44.0 Hz, 36H; PCCH3); 11B{1H} NMR (160.4 MHz, C6D6, 293 K,
BF3·OEt2): d=51.8 (br; BPt), 38.4 ppm (br; BBr); 13C{1H} NMR
(125.7 MHz, C6D6, 293 K, TMS): d=50.53 (s; NMe2), 48.62 (s; NMe2),
Thermal ellipsoids are displayed at the 50% probability level. For clarity,
À
hydrogen atoms, the [BArF
]
counterions, and thermal ellipsoids of the
4
carbon atoms have been omitted.
46.94 (s; NMe2), 45.24 (s; NMe2), 28.15 (d, 1J
ACTHNUTRGNE(UNG C,P)=27.6 Hz; CH), 21.36
(s; CHCH3), 20.81 ppm (s; CHCH3); 31P{1H} NMR (202.4 MHz, C6D6,
1
293 K, 85% H3PO4): d=30.5 ppm (s, J
N
ysis calcd (%) for C22H54B2I2N2P2Pt (879.134): C 29.99, H 6.41, N 3.18;
found: C 30.17, H 6.20, N 3.23.
halide ligand at the Pt center and the generation of a posi-
À
tive charge in 7 and 8 results in Pt1 B1 [7: 2.026(3) ꢃ; 8:
Preparation of cationic diboran(4)yl complexes 7 and 8: To a solid mix-
À
À
2.030(4) ꢃ], B1 B2 [7: 1.708(4) ꢃ; 8: 1.708(5) ꢃ], and Pt P
bonds [7: 2.3159(6), 2.3350(6) ꢃ; 8: 2.3062(9), 2.3269(8) ꢃ]
that are shorter than those of the neutral square-planar pre-
cursors 5[11] and 6. Moreover, P1-Pt1-P2 angles of 168.15(2)8
in 7 and 163.88(3)8 in 8 clearly ascertain the T-shaped struc-
ture and the trans position of the phosphines, even though
distortion from an ideal arrangement is more pronounced
than for the precursor molecules 5 (171.75(4)8)[11] and 6
(172.21(3)8). By contrast, the torsion angle N1-B1-B2-N2 re-
mains essentially identical (7: À53.1(4)8; 8: 57.5(5)8).
ture of either the neutral diboran(4)yl complex 1 or 2 and NaACTHNUTRGNEUNG
[BArF4] was
added fluorobenzene (0.6 mL). The reaction mixtures immediately
turned yellow and a fine white solid (NaBr/NaI) precipitated. After 1 h,
the suspensions were filtered and the filtrate layered with pentane
(0.6 mL). After 12 h at À258C, yellow crystals of the cationic diboran(4)-
yl complexes 7 and 8 formed, which were washed with pentane and dried
in vacuo. Crystals suitable for X-ray diffraction analysis were grown from
a solution in dichloromethane at À258C.
trans-[(iPr3P)2Pt{B
{B(NMe2)B(NMe2)2(Br)}]
one day from the reaction of Na
[(iPr3P)2Pt(Br){B(NMe2)BACHTNUTRGNEU(GN NMe2)2(Br)}] (4) (20.0 mg, 0.025 mmol).
A
ACHTNUGTNERN(UNG NMe2)2(Br)}]ACHNUTTGRNENUG ] (7): trans-[(iPr3P)2ACHTUNGTRENNUNGPt-
[BArF
4
A
E
N
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
T
In this communication, we showed the diboran(4)yl ligand
in PtII complexes have a strong trans influence. Thus, the
1H NMR (400.1 MHz, CD2Cl2, 300 K, TMS): d=7.70–7.74 (m, 8H; o-CH,
BArF4), 7.56 (br s, 4H; p-CH, BArF4), 3.24 (s, 3H; NCH3), 3.02 (s, 3H;
À
Pt I bond in 6, which was obtained by oxidative addition of
NCH3), 2.84 (s, 3H; NCH3), 2.79 (s, 3H; NCH3), 2.35–2.54 (br m, 6H;
3
À
PCH), 1.35 ppm (m, J
(H,P)=40.6 Hz, 36H; P{H
N
B
C
G
(128.3 MHz, CD2Cl2, 300 K, BF3·OEt2): d=36.4 (br s; BBr, BPt),
cently reported bromine analogue, 5, are significantly longer
than those in other related trans-P2PtI species. This feature
is most likely related to the presence of an electron-with-
drawing boron substituent at the boryl group. The strong
À6.70 ppm (s; BArF4); 13C{1H} NMR (100.6 MHz, CD2Cl2, 300 K, TMS):
ACTHNUTRGNEUNG
d=162.1 (q, 1J(C,B)=49.7 Hz; i-C, BArF4), 135.2 (m; o-CH, BArF4),
128.7–129.8 (m; m-CH, BArF4), 125.0 (d, 1J
(C,F)=272 Hz; CF3, BArF4),
ACHTUNGTRENNUNG
117.8 (m; p-CH, BArF4), 48.4 (s; NCH3), 43.8 (s; NCH3), 42.3 (s; NCH3),
Chem. Eur. J. 2012, 18, 15927 – 15931
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
15929

H. Braunschweig et al.
41.7 (s; NCH3), 25.1 (t, 1J
19.6 ppm (s; PCHCH3); 31P{1H} NMR (161.9 MHz, CD2Cl2, 300 K, 85%
H3PO4): d=57.7 ppm (s; 1J
(P,Pt)=3118 Hz); elemental analysis calcd
G
for this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
(%) for C54H66B3BrF24N2P2Pt (1568.439): C 41.35, H 4.24, N 1.79; found:
C 41.92, H 4.33, N 1.92.
trans-[(iPr3P)2Pt{B
(NMe2)B(NMe2)2(I)}]
day from the reaction of Na
[(iPr3P)2PtI{B (NMe2)2(I)}] (6) (20.0 mg, 0.022 mmol). 1H NMR
(NMe2)BACHTUNGTRENNUNG
N
[BArF4] (8): trans-[(iPr3P)2Pt{B-
ACHUTGTNERN(NUG NMe2)2(I)}]AHCUTNGTRNENGUN
E
E
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
G
Acknowledgements
This work was supported by the Deutsche Forschungsgemeinschaft
(DFG).
PCH), 1.26–1.47 ppm (m, 3J (CH3)2}3); 11B{1H}
ACTHUNRTGENN(GU H,P)=44.8 Hz, 36H; P{HAHCTUNGTRENNGUN
NMR (128.3 MHz, CD2Cl2, 300 K, BF3·OEt2): d=39.5 (br s; BPt), 32.8
(br s; BBr), À6.70 ppm (s; BArF4); 13C{1H} NMR (100.6 MHz, CD2Cl2,
Keywords: boron · diboran(4)yl · ligand effects · platinum ·
T-shaped geometry
ACTHNUTRGNEUNG
300 K, TMS): d=162.1 (q, 1J(C,B)=49.6 Hz; i-C, BArF4), 135.2 (m; o-
CH, BArF4), 129.0–129.7 (m; m-CH, BArF4), 124.9 (d, 1J
ACTHNUGRTENUNG(C,F)=272 Hz;
CF3, BArF4), 117.8 (m; p-CH, BArF4), 47.8 (s; NCH3), 47.6 (s; NCH3),
44.6 (s; NCH3), 41.6 (s; NCH3), 25.1–25.4 (m; PCH2), 20.9 (s; PCHCH3),
19.6 ppm (s; PCHCH3); 31P{1H} NMR (161.9 MHz, CD2Cl2, 300 K, 85%
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98, 2685–2722.
H3PO4): d=57.1 ppm (s, 1J
ACTHNUGRTENUNG(P,Pt)=3112 Hz); elemental analysis calcd
(%) for C54H66B3F24IN2P2Pt (1615.439): C 40.15, H 4.12, N 1.73; found: C
41.02, H 4.33, N 1.89.
B2ACHTUNGTRENNUNG(NMe2)2I2: B2ACHTUNGTRENNUNG(NMe2)2I2 was synthesized according to the literature.
Suitable crystals for X-ray diffraction were obtained from a pentane solu-
tion at À258C. 1H NMR (400.1 MHz, C6D6, 300 K, TMS): d=2.67 (s, 1J-
ACHTUNGTRENNUNG ACHTUNGTERN(NUGN H,C)=136.8 Hz, 6H;
(H,C)=136.9 Hz, 6H; NCH3), 2.46 ppm (s, 1J
NCH3); 11B{1H} NMR (128.3 MHz, C6D6, 300 K, BF3·OEt2): d=36.3 (s,
BB) ppm; 13C NMR (100.6 MHz, C6D6, 300 K, TMS): d=44.8 (m, 1J-
ACHTUNGTRENNUNG ACHTUNGTERN(NUGN C,H)=136.8 Hz, 2C;
(C,H)=136.9 Hz, 2C; NCH3); 42.9 ppm (m, 1J
[2] a) I. Beletskaya, A. Pelter, Tetrahedron 1997, 53, 4957–5026; b) K.
Burgess, M. J. Ohlmeyer, Chem. Rev. 1991, 91, 1179–1191; c) C. M.
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402; b) T. B. Marder, N. C. Norman, Top. Catal. 1998, 5, 63–73; c) I.
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ma, N. Miyaura, Chem. Rec. 2004, 3, 271–280.
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f) I. A. I. Mkhalid, D. N. Conventry, D. Albesa-Jove, A. S. Batsanov,
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tinger, Chem. Eur. J. 2007, 13, 7171–7176.
NCH3).
Crystal structure determination: The crystal data of 6–8 were collected
on a Bruker x8apex diffractometer with a CCD area detector and multi-
layer mirror monochromated MoKa radiation. The crystal data of B2-
ACHTUNGTRENNUNG(NMe2)2I2 were collected on a Bruker apex diffractometer with a CCD
area detector and graphite monochromated MoKa radiation. The struc-
tures were solved using direct methods, refined with the ShelX software
package (G. Sheldrick, Acta Cryst. 2008, A64, 112–122) 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 factors calculations.
Crystal data for 6: C22H54B2I2N2P2Pt, Mr =879.12, colorless plate, 0.50ꢄ
0.40ꢄ0.13 mm3, Monoclinic space group P21/c, a=14.4276(4) ꢃ, b=
11.6289(3) ꢃ, c=19.1831(5) ꢃ, b=99.7000(10)8, V=3172.47(15) ꢃ3, Z=
4, 1calcd =1.841 gcmÀ3, m=6.483 mmÀ1, F
ACTHNUTRGEN(UNG 000)=1696, T=100(2) K, R1 =
0.0306, wR2 =0.0689, 6456 independent reflections [2qꢀ52.768] and 296
parameters.
Crystal data for 7: C54H66B3BrF24N2P2Pt, Mr =1568.46, yellow plate, 0.28ꢄ
0.16ꢄ0.12 mm3, Triclinic space group P-1, a=18.1416(11) ꢃ, b=
19.2790(12) ꢃ, c=19.8802(12) ꢃ, a=72.785(3)8, b=79.380(3)8, g=
72.109(3)8, V=6287.0(7) ꢃ3, Z=4, 1calcd =1.657 gcmÀ3, m=3.027 mmÀ1, F-
ACHTUNGTRENNUNG
(000)=3112, T=100(2) K, R1 =0.0267, wR2 =0.0568, 25793 independent
[6] a) G. Sivignon, P. Fleurat-Lessard, J.-M. Onno, F. Volatron, Inorg.
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Marder, N. C. Norman, Inorg. Chem. 2004, 43, 2541–2547.
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416.
reflections [2qꢀ52.888] and 1622 parameters.
Crystal data for 8: C54H66B3F24IN2P2Pt, Mr =1615.45, yellow block, 0.39ꢄ
0.32ꢄ0.21 mm3, Triclinic space group P-1, a=14.0526(9) ꢃ, b=
14.9736(11) ꢃ, c=17.8992(13) ꢃ, a=75.523(3)8, b=74.672(3)8, g=
84.855(3)8, V=3515.9(4) ꢃ3, Z=2, 1calcd =1.526 gcmÀ3, m=2.577 mmÀ1, F-
ACHTUNGTRENNUNG
(000)=1592, T=100(2) K, R1 =0.0306, wR2 =0.0747, 13823 independent
reflections [2qꢀ52.268] and 830 parameters.
Crystal data for B2ACHTUNGTRENNUNG(NMe2)2I2: C4H12B2I2N2, Mr =363.58, colorless block,
0.11ꢄ0.06ꢄ0.05 mm3, Monoclinic space group C2/c, a=13.013(3) ꢃ, b=
6.6569(14) ꢃ, c=13.000(3) ꢃ, a=90.008, b=92.286(3)8, g=90.008, V=
[11] a) H. Braunschweig, M. Koster, K. W. Klinkhammer, Angew. Chem.
1999, 111, 2368–2370; Angew. Chem. Int. Ed. 1999, 38, 2229–2231;
b) H. Braunschweig, K. W. Klinkhammer, M. Koster, K. Radacki,
Chem. Eur. J. 2003, 9, 1303–1309.
1125.2(4) ꢃ3, Z=4, 1calcd =2.146 gcmÀ3, m=5.534 mmÀ1, F
ACTHNUGRTENUNG(000)=664, T=
174(2) K, R1 =0.0252, wR2 =0.0558, 1408 independent reflections [2qꢀ
56688] and 48 parameters.
CCDC-898496 (6), CCDC-898497 (7), CCDC-898498 (8), and CCDC-
898499 (B2ACHTUNGTRENNUNG(NMe2)2I2) contain the supplementary crystallographic data
[12] H. Braunschweig, A. Damme, T. Kupfer, Angew. Chem. 2011, 123,
7317–7320; Angew. Chem. Int. Ed. 2011, 50, 7179–7182.
15930
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ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 15927 – 15931

trans Influence of the Diboran(4)yl Ligand
COMMUNICATION
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Received: September 10, 2012
Published online: November 8, 2012
Chem. Eur. J. 2012, 18, 15927 – 15931
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
15931