Organometallics
Addition/Correction
distilled from CaH2. [Pt(dba)2]4 and 2-(diphenylphosphino)-1-
methylimidazole5 were prepared by literature methods. All other
reagents were purchased form Sigma-Aldrich. NMR data were
recorded on a Varian MRF 400 or a Varian VNMRS 400 spectrometer
at room temperature unless stated otherwise. Chemical shifts are
reported relative to the residual solvent signals (1H, 13C), external
H3PO4 85% in water (31P), or external SnMe4 (1 M, 119Sn) in
benzene.
butene). The replacement of the triphenylphosphine ligands by
2-pyridyldiphenylphosphine effectively prevents the reversibility
of the Sn−Cl oxidative addition step by stabilizing the Sn−Cl
oxidative products such as [11]Cl.
When the observed Pd chemistry is compared to the Pt
chemistry reported by Eaborn and Pidcock (references
provided in the original article), it can be conluded that the
Pd(0) and Pt(0) precursors in a qualitative sense display similar
chemistry with respect to monoorganotin trichlorides (Scheme
3 (revised)). Concerning the insertion of SnCl2 in trans-
Synthesis of trans-[PdCl(SnCl2(Ph)(2-PyPPh2)2)] (12). A
Schlenk flask was charged with [Pd(dba)2] (230 mg, 0.4 mmol) and
2-PyPPh2 (0.22 g, 0.4 mmol). A 10 mL portion of dry, degassed
toluene was then added, and the resulting orange-brown solution was
stirred for 1 h at room temperature. The reaction mixture was filtered
by cannula, resulting in a clear, bright orange solution to which was
added PhSnCl3 (116 mg, 0.063 mL, 0.4 mmol). After 1 h, the resulting
suspension was concentrated in vacuo, followed by washing with
diethyl ether (3 × 20 mL). The resulting solid was then dissolved in 20
mL of dichloromethane and filtered over a plug of Celite. The product
was obtained as an analytically pure off-white solid after concentration
of the resulting solution and drying in vacuo. Yield: 0.33 g (325 mg,
0.35 mmol, 91%). Crystals suitable for single-crystal X-ray analysis
were obtained from layering a dichloromethane solution with toluene.
1H NMR (400 MHz, CD2Cl2): δ 8.70 (d, 3JHH = 6.8 Hz, 2H, 6-Py-H),
Scheme 3 (revised). Comparison of the Reactivity of RSnCl3
on Pt(0) and Pd(0) Precursors
3
3
7.88 (m, JHH = 8.4 Hz, 2H, 4-Py-H), 7.77 (d, JHH = 6.4 Hz, 8H, o-
3
PPh-H), 7.62 (dd, JHH = 8.4 Hz, 6.8 Hz, 2 H, 5-Py-H), 7.60 (m, 2H,
SnPh-H), 7.50 (t, 3JHH = 7.2 Hz, 4H, p-PPh-H), 7.45−7.40 (m, 11 H,
m-PPh-H, SnPh-H), 7.36 (m, 2H, 3-Py-H). 13C{1H} NMR (100.54
MHz, CD2Cl2): δ 150.3 (t, JPC = 30.0 Hz, 2-Py-CH), 148.8 (s, i-SnPh-
C), 147.8 (t, JPC = 8.4 Hz, 6-Py-CH), 139.7 (s, 4-Py-CH), 136.3 (s, o-
SnPh-CH), 134.3 (t, JPC = 6.9 Hz, o-PPh-CH), 131.5 (t, JPC = 8.3 Hz,
3-Py-CH), 131.1 (s, p-PPh-CH), 129.9 (t, JPC = 24.4 Hz, i-PPh-C),
129.7 (s, p-SnPh-CH), 128.8 (s, m-SnPh-CH), 128.5 (t, JPC = 8.3 Hz,
m-PPh-CH), 126.8 (s, 5-Py-CH). 31P{1H} NMR (161.85 MHz,
CD2Cl2): δ 62.4 (JSnP = 443 Hz). 119Sn{1H} NMR (149.07 MHz,
CD2Cl2): δ −274.1 (broad, lwhh = 2990 Hz). HRMS (ESI): exact
mass (monoisotopic) calcd for PdSnCl2P2N2C40H33 m/z 898.9580,
found 898.9531 [M − Cl]+.
[MCl(R)L2] (L = phosphine ligand; M = Pd, Pt; R = Ph, Me,
nBu) there is a striking difference. Whereas for Pt the reaction
results in the well-known trichlorostannyl derivatives cis- and
trans-[MR(SnCl3)L2], for Pd the reaction products observed
are the organostannyl derivatives cis- and trans-[MCl(SnCl2R)-
L2], which can be trapped in their ionic form if 2-
pyridyldiphenylphosphine is used as the ligand rather than
triphenylphosphine.
Synthesis of trans-[PdCl(SnCl(nBu)(2-ImPPh2)2)][nBuSnCl4]
([13][nBuSnCl4]). In a Schlenk flask containing neat [Pd(dba)2]
(102 mg, 0.18 mmol) was placed 2-(diphenylphosphino)-1-methyl-
imidazole (115 mg, 0.43 mmol, 2.5 equiv) in toluene (5 mL). The
mixture was stirred at room temperature for 1 h, and a small amount of
palladium black was removed by cannula filtration. Monobutyltin
trichloride (101 mg, 0.36 mmol, 2 equiv) was added slowly to the
orange-brown solution. After 1 h the solvent was removed under
vacuum and the residue was washed with ether (3 × 10 mL) to give
[13][nBuSnCl4] (182 mg, 0.15 mmol, 84% yield) as a yellow powder.
Crystals suitable for single-crystal X-ray analysis were obtained by
CONCLUSIONS
■
The above studies show that the reaction of monoorganotin
trichlorides with Pd(0)−phosphine complexes proceeds
predominantly through an oxidative addition of the Sn−Cl
bond, which is qualitatively similar to observations for related
Pt(0) precursors, although the stability of the resulting
complexes appears to be lower for Pd. By using [Pd(2-
PyPPh2)3] as a precursor instead of [Pd(PPh3)4], it became
possible to efficiently block degradation of the initially formed
palladium−organostannyl products and to synthesize in a single
step cationic alkylstannylenepalladium complexes that are
stabilized by intramolecular coordination of the pyridyl groups
of two 2-pyridyldiphenylphosphine ligands to the stannylene
moiety. The latter is in strong contrast to organostannyl
derivatives obtained from [Pd(PPh3)4] that undergo facile cis−
trans isomerization, elimination of SnCl2, and/or degradation
through β-H elimination. The unique P−SnII−P terdentate
ligand, through its stannylene donor function, can be expected
to induce new interesting properties to derived metal
complexes, the synthesis and reactivity of which are currently
under investigation.
1
recrystallization from diethyl ether. H NMR (399.80 MHz, CD2Cl2):
δ 7.66−7.61 (m, 12H, H2, H6, H8, H9), 7.54−7.53 (m, 12H, H3, H4,
H5), 3.24 (s, 6H, N−CH3), 2.18 (t, JHH = 7.4 Hz, 2H,
Cl4SnCH2CH2CH2CH3), 1.96 (t, JHH
= 7.7 Hz, 2H,
ClSnCH2CH2CH2CH3), 1.92−1.84 (m, 2H, Cl4SnCH2CH2CH2CH3),
1.51−1.38 (m, 4H, ClSnCH2CH2CH2CH3, Cl4SnCH2CH2CH2CH3),
1.18−1.09 (m, 2H, ClSnCH2CH2CH2CH3), 0.94 (t, JHH = 7.3 Hz, 3H,
Cl4SnCH2CH2CH2CH3), 0.65 (t, JHH
= 7.2 Hz, 3H,
ClSnCH2CH2CH2CH3). 13C{1H} NMR (100.54 MHz, CD2Cl2): δ
1
2
139.5 (t, JCP = 34 Hz, C7), 133.7 (t, JCP = 7 Hz, C2,3 C6), 133.3
3
(broad, C4, C9), 130.5 (t, JCP = 6 Hz, C3, C5), 128.5 (t, JCP = 8 Hz,
1
C8), 125.9 (t, JCP = 26 Hz, C1), 45.4 (s, Cl4SnCH2CH2CH2CH3),
37.1 (s, N-CH3), 32.7 (s, ClSnCH2CH2CH2CH3), 29.1 (s,
ClSnCH2CH2CH2CH3), 28.4 (s, Cl4SnCH2CH2CH2CH3), 27.4 (s,
ClSnCH2CH2CH2CH3), 26.3 (s, Cl4SnCH2CH2CH2CH3), 14.3 (s,
Cl4SnCH2CH2CH2CH3), 14.1 (s, ClSnCH2CH2CH2CH3). 31P{1H}
NMR (161.85 MHz, CD2Cl2): δ 30.6 (s, JPSn = 87 Hz). 119Sn{1H}
NMR (149.07 MHz, CD2Cl2): δ −121.1 (broad, ω1/2 = 173 Hz,
EXPERIMENTAL SECTION
■
All reactions and manipulations were performed under a nitrogen
atmosphere in a glovebox or using conventional Schlenk techniques.
All nondeuterated solvents were dried using an MBraun SPS-800
solvent purification system and degassed prior to use, except for
dichloromethane-d2 and chloroform-d, which were dried over and
n
SnClnBu), −248.1 (broad, ω1/2 = 745 Hz, SnCl4 Bu). HRMS (ESI):
exact mass (monoisotopic) calcd for C36H39Cl2N4P2PdSn 885.0085,
found 885.0146 [M − BuSnCl]+.
2917
dx.doi.org/10.1021/om500005y | Organometallics 2014, 33, 2914−2918