Synthesis of a bimetallic platinum-tungsten complex with a bridging μ-diboranyl-oxycarbyne moiety

Article abstract of DOI:10.1039/b714763e

The novel bimetallic μ-diboranyl-oxycarbyne bridged platinum-tungsten complex [W{η¹,μ-CO-B(NMe₂)-B(NMe ₂)-(η⁵-C₅H₄)}(CO) ₂{Pt(PPh₃)₂}] (W-Pt) (3) has been synthesised by a two-step reaction, starting from the dilithiated half-sandwich compound Li[W(η⁵-C₅H₄Li)(CO)₃] (1) via the ansa-diboranyl-oxycarbyne tungsten complex [W{η¹-CO- B(NMe₂)B(NMe₂)(η⁵-C₅H ₄)}(OC)₂] (2) by use of stoichiometric amounts of B ₂(NMe₂)₂Br₂ and [Pt(η ²-C₂H₄)(PPh₃)₂], respectively. The Royal Society of Chemistry.

Full text of DOI:10.1039/b714763e

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www.rsc.org/dalton | Dalton Transactions
Synthesis of a bimetallic platinum–tungsten complex with a bridging
l-diboranyl–oxycarbyne moiety†‡
Holger Bera, Holger Braunschweig,* Rainer Do¨rfler and Krzysztof Radacki
Received 25th September 2007, Accepted 1st November 2007
First published as an Advance Article on the web 9th November 2007
DOI: 10.1039/b714763e
5
The novel bimetallic l-diboranyl–oxycarbyne bridged
B(NMe2)B(NMe2)-{M(CO)3(g -C5H5)] (M = Mo, W), character-
ized by one metal–boron linkage (Fig. 1).2
1
platinum–tungsten complex [W{g ,l-CO-B(NMe2)-B(NMe2)-
5
Over the course of our studies on diborane(4)yl complexes of
tungsten, we now have succeeded in combining these two topics,
thus revealing a new reactivity pattern of the boryl–oxycarbyne
triple bond.
In this communication we report the synthesis of the first half-
sandwich ansa-complex bearing a diboranyl–oxycarbyne bridge
between the cyclopentadienyl ligand and the tungsten centre (2)
and its stabilisation by complexation to a Pt0 centre to yield the
bimetallic ansa-platinum–tungsten complex 3.§ Furthermore, a
single-crystal X-ray diffraction study was carried out to establish
unequivocally the structure of 3 in the solid state.¶
(g -C5H4)}(CO)2{Pt(PPh3)2}] (W–Pt) (3) has been synthesised
by
a
two-step reaction, starting from the dilithiated
5
half-sandwich compound Li[W(g -C5H4Li)(CO)3] (1) via the
1
ansa-diboranyl–oxycarbyne tungsten complex [W{g -CO-
5
B(NMe2)B(NMe2)(g -C5H4)}(OC)2] (2) by use of stoichio-
2
metric amounts of B2(NMe2)2Br2 and [Pt(g -C2H4)(PPh3)2],
respectively.
Since 1980, Stone and co-workers proved that metal–carbon
triple bonds can be complexed by zero-valent platinum, thus
synthesising e.g. the bimetallic platinum–tungsten species [W(l-
Reaction of the lithiated tungsten complex Li[W(C5H4Li)(CO)3]
(1) with one equivalent of B2(NMe2)2Br2 in benzene at room
temperature leads to the generation of 2 by alkali salt elimination,
according to Scheme 1. However, the poor thermal stability of this
strained ansa-compound prevents its work-up and isolation as well
as obtaining satisfactory 13C NMR data. A crucial characteristic
feature in the 1H NMR spectrum of 2 is the splitting of the
cyclopentadienyl resonances into four sets of multiplets (d = 5.91,
5.63, 5.47 and 5.40 ppm), indicating C1 symmetry in solution.
Such geometry would appear to arise from the existence of a
B2(NMe2)2 ansa-bridge and torsion of the N(Me2)2 fragments, thus
imposing slow equilibration with respect to the NMR time scale. A
corresponding spectroscopic phenomenon was already observed
in our group in context with boron-bridged constrained geometry
5
C-C6H4Me-p)-(g -C5H5)(CO)2{Pt(PR3)2}] (W–Pt) (R3 = Me2Ph,
Me3) with a l-bridging carbyne ligand (Fig. 1).1
1
5
complexes of titanium, namely for [Ti{g -NPh-(BNSiMe3)(g -
C5H4)Cl2].3 Owing to chemical inequivalence and hindered
Fig. 1 Complexes specifically mentioned in the introductory paragraph.
Recently, we obtained a series of novel oxycarbyne com-
5
plexes, namely [{(g -C5H5)(OC)2M≡CO}2-B2(NMe2)2] (M =
Cr, Mo, W), from reaction of the diborane(4) B2(NMe2)2I2
with Group 6 metal carbonylates. The Mo and W com-
plexes underwent a quantitative rearrangement to give the ther-
5
modynamically favoured complexes [{(g -C5H5)(OC)2M≡CO}-
Institut fu¨r Anorganische Chemie, Universita¨t Wu¨rzburg, Am Hubland,
D-97074, Wu¨rzburg, Germany. E-mail: h.braunschweig@mail.uni-
wuerzburg.de; Fax: +49-931/888-4623; Tel: +49-931/888-5260
† This paper is dedicated to Prof. Dr. Ken Wade FRS on the occasion of
his 75th birthday.
‡ CCDC reference number 661353. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b714763e
Scheme 1 Synthesis of the l-diboranyl–oxycarbyne bridged platinum—
tungsten complex 3, via the strained ansa-diboranyl–oxycarbyne tungsten
complex 2.
440 | Dalton Trans., 2008, 440–443
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rotation, four resonances are detected for the aminomethyl groups
atmosphere at +5 ◦C for several months without decomposition.
The NMR spectroscopic data are in full agreement with the
formation of a C1-symmetric compound. As already observed
1
in the H NMR spectrum (d = 3.07, 3.00, 2.80 and 2.73 ppm).
Spectroscopic proof for the formation of the highly unusual
C–O–B–B ansa-bridge with nucleophilic attack of the carbonyl
oxygen atom at boron2 is provided by the 11B NMR resonances
at 44.3 and 35.7 ppm. The former resonance is indicative of
metallocenophanes with bis(dimethylamino)diborane bridges (e.g.
1
for 2, the H NMR spectrum of 3 shows four multiplets (d =
5.41, 5.37, 5.11 and 4.89 ppm). Consequently, four singlets were
detected for the aminomethyl groups (d = 2.75, 2.62, 2.34 and
1.74 ppm). The complexation of the platinum fragment to the
W≡C triple bond does not lead to any significant shift of the
11B NMR resonances which are found at d = 43.41 (BC) and
34.77 (BO) ppm. The 31P NMR spectrum exhibits two singlets
at d = 41.51 and 31.61 ppm which are flanked by characteristic
5
[Fe{(g -C5H4)2(BNMe2)2}], d = 44.4 ppm),4 while the latter falls
5
in the typical range of boryloxycarbyne complexes (e.g. [{(g -
C5H5)(OC)2W≡CO}2-B2(NMe2)2], d = 30.8 ppm),2 thus indicating
the presence of a B–O bond.
1
The formation of a metal–boron bond, which is usually
observed for the reaction of anionic half-sandwich complexes with
B2(NMe2)2Hal2 (Hal = Cl, Br), would result in a characteristically
deshielded signal at dB > 60.2,5 The preference of B–O over W–
B bond formation observed here, may be ascribed either to an
enhanced nucleophilicity of the anionic (OC)3W fragment as a
result of the attachment of the diborane moiety to the Cp ligand
or is just the result of a better accessibility of the linear W–CO
unit. In any case, attempts to convert 2 into a possibly thermody-
namically favoured compound bearing a W–B bond failed and led
to decomposition.
31P–195Pt satellites with coupling constants of JPt–P = 4293 and
1JPt–P = 2825 Hz, respectively. The two PPh3 ligands in 3 are
1
thus non-equivalent, and the small value of JPt–P (2825 Hz) is
characteristic for a cis-Pt(PPh3)2 arrangement and the larger 195Pt–
31P coupling associated with the resonance at 41.51 ppm can be
assigned to the phosphine ligand trans to the Pt–W bond.1,6
3
displays carbonyl stretching bands in the IR spectrum at 1939
and 1920 cm−1 which are blue-shifted when compared with [W(l-
5
C-C6H4Me-p)-(g -C5H5)(CO)2{Pt(PMe2Ph)2}] (W–Pt) (1898 and
1818 cm−1).
Boron–boron bonds are prone to undergo facile oxida-
tive addition towards a variety of low-valent transition metal
complexes7 with concomitant formation of bis(boryl)–metal com-
plexes [LxM(BR2)2],8 thus effectively enabling the transition-
metal-catalysed diboration of alkenes, alkynes and 1,3-dienes.7
Interestingly, the reaction of complex 2 which is characterised by
2
When treated consecutively with B2(NMe2)2Br2 and [Pt(g -
C2H4)(PPh3)2] in benzene at room temperature, respectively, 1
converts to the novel bimetallic l-diboranyl–oxycarbyne bridged
1
5
platinum–tungsten complex [W{g ,l-CO-B(NMe2)-B(NMe2)-(g -
C5H4)}(CO)2{Pt(PPh3)2}] (W–Pt) (3) (Fig. 2). After work-up, 3
was obtained as a yellow powder in 35% yield. The complexation
of the Pt(PPh3)2 moiety leads to a release of the molecular strain
due to change of the hybridisation of the carbyne C atom from
sp to sp2, and hence, an increased thermal stability compared
to its precursor 2 may be assumed for the ansa-complex 3, thus
allowing its facile isolation. Moreover, 3 can be stored under Ar
2
two reactive centres (B–B and W≡C) with [Pt(g -C2H4)(PPh3)2]
leads to complexation of the Pt0 centre to the W≡C triple bond
rather than oxidative addition of the B–B bond. This result
may be ascribed to the decreased steric demand of the environ-
ment at the carbyne unit in comparison to the boron–boron
bond.
The constitution of 3 was confirmed by single crystal X-ray
diffraction. Suitable crystals were grown from slow evaporation of
a saturated solution of 3 ind6-benzene at ambient temperature. The
result of this analysis is depicted in Fig. 2. The complex crystallises
in the monoclinic space group P21/n. The entire C–O–B–B ansa-
bridge is disordered and its metric parameters have to be regarded
carefully (see CIF for further details).
An important structural element of 3 is the C–O–B–B ansa-
bridge, which imposes moderate molecular ring strain, which
is best reflected by the C–B–B [C11–B2–B1 115.3(8)◦] and the
B–B–O [O1–B1–B2 117.2(8)◦] angles that are slightly smaller
than expected for an ideally sp2-hybridised boron atom. The
˚
boron–boron bond itself [B1–B2 1.702(17) A] is neither affected
by ring formation nor by Pt0 complexation and is almost identical
5
to that found in [(g -C5H5)(OC)3W-{B(NMe2)-B(NMe2)Cl}]
5a
5
˚
[1.690(1) A] or [{(g -C5H5)(OC)2Mo≡CO}-B(NMe2)B(NMe2)-
5
2b
˚
{Mo(CO)3(g -C5H5)] [1.704(6) A].
Another characteristic
structural feature is the three-membered ring consisting of
tungsten, carbon and platinum, showing parameters [W1–Pt1
1
Fig. 2 View of the molecular structure of [W{g ,l-CO-B(NMe2)-
˚
2.7748(4), W1–C1 1.98(1) or Pt1–C1 1.99(1) A] very similar to
5
B(NMe2)-(g -C5H4)}(CO)2{Pt(PPh3)2}] (W–Pt) (3) with the atom labelling
5
those of [W(l-C-C6H4Me-p)-(g -C5H5)(CO)2{Pt(PMe2Ph)2}] (W–
scheme. Ellipsoids are drawn at the 50% probability level, and t◦he
1
˚
Pt). The W–C1 distance is significantly longer (est. 0.16 A) than
˚
hydrogen atoms have been omitted. Selected bond lengths [A], angles [ ]:
5
the M–C(carbyne) separations in [W(≡CC6H4Me-p)(CO)2(g -
W1–Pt1 2.7718(9), W1–C1 1.98(1), Pt1–C1 1.99(1), Pt1–P1 2.2540(18),
Pt1–P2 2.3361(18), C1–O1 1.337(10), O1–B1, 1.432(12), B1–B2 1.702(17);
C11–B2–B1 115.3(8), O1–B1–B2 117.2(8), W1–Pt1–C1 45.4(4) and
P1–Pt1–P2 103.22(6).
5
C5H5)] and [{(g -C5H5)(OC)2Mo≡CO}-B(NMe2)B(NMe2)-
5
9
˚
{Mo(CO)3(g -C5H5)] [1.82(2) and 1.825(4) A], respectively, and
=
hence, can be classified as a W C double bond interaction,
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©

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although delocalisation within the W–C–Pt three-membered ring
is probable, too.1 Notable pertinent metric parameters around
the platinum centre, which displays a distorted square-planar
calculations. C48H46B2N2O3P2PtW, Mr = 1161.37, orange block, 0.18 ×
˚
0.10 × 0.09 mm, monoclinic, space group P21/n,◦a = 10.4940(2) A, b =
3
˚
˚
˚
24.5737(6) A, c = 17.0162(4) A, b = 93.4940(10) , V = 4379.92(17) A ,
Z = 4, qcalcd = 1.761 g cm−3, l = 5.932 mm−1, F(000) = 2256, T = 100(2)
K, R1 = 0.0523, wR2 = 0.1114, Rint = 0.058, 8742 independent reflections
[2h ≤ 52.46] and 586 parameters.
˚
environment, include the Pt–W [Pt1–W1 2.7718(9) A], the Pt–C
˚
[Pt1–C1 1.99(1) A] bond lengths, the Pt–P distances [Pt1–P1
◦
˚
2.2540(18), Pt1–P2 2.3361(18) A], the W–Pt–C angle [45.4(4) ],
and the P–Pt–P bond angle [103.22(6)◦] all of which lie within
previously reported ranges.1,10 The carbon–oxygen and oxygen–
1 T. V. Ashworth, J. A. K. Howard and F. G. A. Stone, J. Chem. Soc.,
Dalton Trans., 1980, 9, 1609.
2 (a) H. Braunschweig, M. Koster and K. W. Klinkhammer, Angew.
Chem., 1999, 111, 2368, (Angew. Chem., Int. Ed. Engl., 1999, 38, 2229);
(b) H. Braunschweig, M. Koster, K. W. Klinkhammer and K. Radacki,
Chem.–Eur. J., 2003, 9, 1303; (c) H. Braunschweig, C. Kollann, M.
Koster, U. Englert and M. Mu¨ller, Eur. J. Inorg. Chem., 1999, 2277.
3 (a) H. Braunschweig, C. von Koblinski and U. Englert, Chem.
Commun., 2000, 1049; (b) H. Braunschweig, F. M. Breitling, C. v.
Koblinski, A. J. P. White and D. J. Williams, Dalton Trans., 2004,
938.
˚
boron distances of 1.337(10) and 1.432(12) A resemble those
5
5
in [{(g -C5H5)(OC)2Mo≡CO}–B(NMe2)-B(NMe2){Mo(CO)3(g -
C5H5)] and suggest that the bonding situation should be described
in terms of a carbonyl–oxygen double and a oxygen–boron single
bond.
4 M. Herberhold, U. Do¨rfler and B. Wrackmeyer, J. Organomet. Chem.,
1997, 530, 117.
Notes and references
§ All manipulations were conducted either under an atmosphere of dry
argon or in vacuo using standard Schlenk line or glove box techniques.
Solvents (benzene and pentane) were purified by distillation from ap-
propriate drying agents (sodium and sodium wire) under dry argon,
immediately prior to use. C6D6 was degassed by three freeze–pump–
thaw cycles and stored over molecular sieves. IR spectra were recorded as
solutions between KBr plates on a Bruker Vector 22 FT-IR-spectrometer.
NMR spectra were recorded on either a Bruker 200 Avance spectrometer
at 200.1 (1H, internal standard TMS) and 64.2 MHz (11B, BF3·OEt2
in C6D6 as external standard), a Bruker 400 Avance spectrometer at
5 (a) H. Braunschweig, B. Ganter, M. Koster and T. Wagner, Chem.
Ber., 1996, 129, 1099; (b) H. Braunschweig, M. Koster and R. Wang,
Inorg. Chem., 1999, 38, 415; (c) H. Braunschweig and M. Koster,
J. Organomet. Chem., 1999, 588, 231; (d) H. Braunschweig and
M. Koster, Z. Naturforsch., B: Chem. Sci., 2002, 57, 483; (e) H.
Braunschweig, H. Bera, D. Go¨tz and K. Radacki, Z. Naturforsch.,
B: Chem. Sci., 2006, 61, 29; (f) for reviews covering aspects of
diborane(4)yl complexes see: H. Braunschweig, Angew. Chem., 1998,
110, 1882, (Angew. Chem., Int. Ed, 1998, 37, 1786); (g) H. Braunschweig
and M. Colling, J. Organomet. Chem., 2000, 614–615, 18; (h) H.
Braunschweig and M. Colling, Coord. Chem. Rev., 2001, 619, 305;
(i) for reviews covering borylmetallocenes see: H. Braunschweig, F. M.
Breitling, E. Gullo and M. Kraft, J. Organomet. Chem., 2003, 680, 31;
(j) S. Aldridge and C. Bresner, Coord. Chem. Rev., 2003, 244, 71; (k) P. J.
Shapiro, Eur. J. Inorg. Chem., 2001, 321.
1
400.13 (1H, internal standard TMS) and 100.61 MHz (13C{ H}, APT,
internal standard TMS) or a Bruker Avance 500 at 500.13 MHz (1H,
1
internal standard TMS), 125.77 MHz (13C{ H}, APT, internal standard
TMS) and 160.46 MHz (11B, BF3·OEt2 as external standard). Elemental
analyses (C, H, N) were obtained from a Vario Micro (Elementar
Analysensysteme). Starting materials were prepared according to literature
6 N. Carr, D. F. Mullica, E. L. Sappenfield, F. G. A. Stone and M. J.
Went, Organometallics, 1993, 12, 4350.
5
11
12
2
procedures: Li[W(g -C5H4Li)(CO)3] (1),
B2(NMe2)2Br2 and [Pt(g -
5
C2H4)(PPh3)2].13 [W{g -CO-B(NMe2)-B(NMe2)-(g -C5H4)}(CO)2] (2): A
7 (a) T. Ishiyama and N. Miyaura, J. Organomet. Chem., 2000, 611, 392;
(b) H. Braunschweig, T. Kupfer, M. Lutz, K. Radacki, F. Seeler and R.
Sigritz, Angew. Chem., 2006, 118, 8217, (Angew. Chem., Int. Ed., 2006,
45, 8048); (c) H. Braunschweig, M. Lutz, K. Radacki, A. Schaumlo¨ffel,
F. Seeler and C. Unkelbach, Organometallics, 2006, 25, 4433; (d) H.
Braunschweig, M. Lutz and K. Radacki, Angew. Chem., 2005, 117,
3829, (Angew. Chem., Int. Ed., 2005, 44, 3763); (e) for a review on
transition metal catalysed diboration: T. B. Marder and N. C. Norman,
Top. Catal., 1998, 5, 63.
1
5
suspension of 0.52 g (0.82 mmol) of Li[W(g -LiC5H4)(CO)3] (1) in 5 mL
benzene was treated with 0.84 mL (0.22 g, 0.82 mmol, 0.97 M solution
in toluene) of B2(NMe2)2Br2 at ambient temperature. The solvent was
removed in vacuo and the residue was extracted with C6D6 for NMR
spectroscopy. Further isolation was not possible due to poor stability of
the product. 1H NMR (200.0 MHz, C6D6): d = 5.91 (m, 1 H, C5H4),
5.63 (m, 1 H, C5H4), 5.47 (m, 1 H, C5H4), 5.40 (m, 1 H, C5H4), 3.07 (s,
3 H, Me), 3.00 (s, 3 H, Me), 2.80 (s, 3 H, Me), 2.73 (s, 3 H, Me) ppm.
1
11B{ H} NMR (160.5 MHz, C6D6): d = 44.32 (br, B–C), 35.7 (br, B–O)
8 (Pt): (a) N. Lu, N. C. Norman, A. G. Orpen, M. J. Quayle, P. L. Timms
and G. R. Whittell, J. Chem. Soc., Dalton Trans., 2000, 4032; (b) D.
Curtis, M. J. G. Lesley, N. C. Norman, A. G. Orpen and J. Starbuck,
J. Chem. Soc., Dalton Trans., 1999, 1687; (c) W. Clegg, F. J. Lawlor,
T. B. Marder, P. Nguyen, N. C. Norman, A. G. Orpen, M. J. Quayle,
C. R. Rice, E. G. Robins, A. J. Scott, F. E. S. Souza, G. Stringer and
G. R. Whittell, J. Chem. Soc., Dalton Trans., 1998, 301; (d) T. Ishiyama,
N. Matsuda, N. Miyaura and A. Suzuki, J. Am. Chem. Soc., 1993, 115,
11018; (e) T. Ishiyama, N. Matsuda, M. Murata, F. Ozawa, A. Suzuki
and N. Miyaura, Organometallics, 1996, 15, 713; (f) C. N. Iverson and
M. R. Smith, III., J. Am. Chem. Soc., 1995, 117, 4403; (g) G. Lesley,
P. Nguyen, N. J. Taylor, T. B. Marder, A. J. Scott, W. Clegg and N. C.
Norman, Organometallics, 1996, 15, 5155; (h) A. Kerr, T. B. Marder,
N. C. Norman, A. G. Orpen, M. J. Quayle, C. R. Rice, P. L. Timms
and G. R. Whittell, Chem. Commun., 1998, 319; (i) W. Clegg, F. J.
Lawlor, G. Lesley, T. B. Marder, N. C. Norman, A. G. Orpen, M. J.
Quayle, C. R. Rice, A. J. Scott and F. E. S. Souza, J. Organomet.
Chem., 1998, 550, 183; (j) (Co): C. Dai, G. Stringer, J. F. Corrigan, N. J.
Taylor, T. B. Marder and N. C. Norman, J. Organomet. Chem., 1996,
513, 273; (k) C. J. Adams, R. A. Baber, A. S. Batsanov, G. Brabham,
J. H. P. Charmant, M. F. Haddow, J. A. K. Howard, W. H. Lam, Z.
Lin, T. B. Marder, N. C. Norman and A. G. Orpen, Dalton Trans.,
2006, 1370; (l) (Rh): P. Nguyen, G. Lesley, N. J. Taylor, T. B. Marder,
N. L. Pickett, W. Clegg, M. R. J. Elsegood and N. C. Norman, Inorg.
Chem., 1994, 33, 4623; (m) C. Dai, G. Stringer, T. B. Marder, A. J.
Scott, W. Clegg and N. C. Norman, Inorg. Chem., 1997, 36, 272; (n) M.
Campian, J. L. Harris, N. Jasmi, R. N. Perutz, T. B. Marder and A. C.
Whitwood, Organometallics, 2006, 25, 5093; (o) (Ir):C. Dai, G. Stringer,
T. B. Marder, R. T. Baker, A. J. Scott, W. Clegg and N. C. Norman,
1
5
ppm. [W{g ,l-CO-B(NMe2)-B(NMe2)-(g -C5H4)}(CO)2{Pt(PPh3)2}] (W–
5
Pt) (3): Similar to above, 350 mg (0.55 mmol) of Li[W(g -LiC5H4)(CO)3]
(1) in 10 mL benzene and 570 lL (148 mg, 0.55 mmol, 0.97 M solution
in toluene) of B2(NMe2)2Br2 were added at ambient temperature. After
2
5 min of stirring 412 mg (0.55 mmol) [Pt(g -C2H4)(PPh3)2] were added and
the mixture was stirred for another 2 h. The benzene was removed under
reduced pressure and the brown residue was dried in vacuo thoroughly.
After extraction with cyclohexane (6 × 15 mL) the combined extracts
were filtered through Celite and the solvent was removed under reduced
pressure. The residue was washed with cyclohexane (1 × 3 mL), pentane
(3 × 5 mL) and finally dried in vacuo. Yield 224 mg (0.19 mol, 35%).
1
Yellow powder. H NMR (500.0 MHz, C6D6): d = 7.90–6.80 (m, 30 H,
Ph), 5.41 (m, 1 H, C5H4), 5.37 (m, 1 H, C5H4), 5.11 (m, 1 H, C5H4), 4.89
(m, 1 H, C5H4), 2.75 (s, 3 H, Me), 2.62 (s, 3 H, Me), 2.34 (s, 3 H, Me),
1
1.74 (s, 3 H, Me) ppm. 11B{ H} NMR (160.5 MHz, C6D6): d = 43.41
1
(br, BC), 34.77 (br, BO) ppm. 13C{ H} NMR (125.8 MHz, CDCl3): d =
216.40 (s, CO), 216.30 (s, CO), 134.42–127.53 (m, Ph), 101.76 (s, C5H4),
100.72 (s, C5H4), 96.28 (s, C5H4), 94.77 (s, C5H4), 45.01 (s, Me), 42.19 (s,
1
Me), 40.45 (s, Me), 37.49 (s, Me) ppm. 31P{ H} NMR (202.5 MHz, C6D6):
2
1
2
d = 41.51 [d, JP–P = 33.2 Hz, JPt–P = 4293 Hz, PPh3], 31.61 [d, JP–P
=
33.2 Hz, 1JPt–P = 2825 Hz, PPh3] ppm. IR (hexane) m(C O) = 1939 (vs),
=
1920 (vs) cm−1
.
¶ The crystal data of 3 were collected on a Bruker X8APEX diffractometer
with CCD area detector and multi-layer mirror monochromated MoKa
radiation. The structure was solved using direct methods, refined with
SHELX software package14 and expanded using Fourier techniques.
All non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were assigned idealised positions and were included in structure factors
442 | Dalton Trans., 2008, 440–443
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The Royal Society of Chemistry 2008
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