Organometallics
ARTICLE
with a fine white precipitate. No attempts were made to isolate this
complex. 1H NMR (500 MHz, CD2Cl2, 25 °C): δ 7.54 (app t, 1H, H6),
7.47 (br tt, 1H, H4), 7.41 (m, 1H, H5), 7.38 (t, 3JHꢀH = 5.0 Hz, 1H, H1),
(d, J = 5.1 Hz, Cy CH2), 29.1 (s, Cy CH2), 28.7 (d, JPꢀC = 13 Hz, Cy
CH2), 28.4 (d, JPꢀC = 7.7 Hz, Cy CH2), 26.9 (s, Cy CH2). 31P{1H}
NMR (202 MHz, CD2Cl2, 25 °C): δ 27.5 (d, 1JRhꢀP = 148 Hz). Anal.
Calcd for C32H43ClPRh: C, 64.38; H, 7.26. Found: C, 63.38; H, 7.12.
[(COD)Rh(PCy2biPh)][B(ArF)4] (7). To an oven-dried round-
bottom flask was added complex 6 (0.005 g, 0.09 mmol) in air.
NaB(ArF)4 (0.008 g, 0.009 mmol) was added in the drybox, dry CH2Cl2
was added to dissolve the solids, and the mixture was stirred for 2 h at
room temperature. A yellow-orange solution was obtained with a white
precipitate. The sample was filtered in air through a PTFE syringe filter
to remove the NaCl. The solvent was removed by vacuum to yield an
3
6.75 (br d, 1H, H3), 6.57 (d, JHꢀH = 5.0 Hz, 2H, H2), 4.52 (heptet,
3JHꢀH = 6.0 Hz, 2H, iPr methine), 4.29 (s, 2H, NBD olefin), 3.69 (s, 2H,
NBD CH), 3.61 (s, 2H, NBD olefin), 2.15 (br q, 4H, Cy), 1.83 (m, 4H,
Cy), 1.74 (br s, 5H, 1H NBD bridgehead located by HMQC and 4H
Cy), 1.42 (m, 3H, 2H Cy, 1H NBD bridgehead located by HMQC), 1.37
3
i
(d, JHꢀH = 6.0 Hz, 6H, Pr CH3), 1.34ꢀ1.05 (m, 8H, Cy), 0.98 (d,
3JHꢀH = 6.5 Hz, 6H, Pr CH3). 13C{1H} NMR (125 MHz, CD2Cl2,
i
25 °C): δ 157.7 (s, C4), 146.0 (d, 2JPꢀC = 23 Hz, C2), 135.9 (d, 1JPꢀC
=
1
40 Hz, C1), 134.2 (s), 132.8 (d, JPꢀC = 2.5 Hz), 131.8 (s), 131.7 (s),
128.1 (d, J = 5.0 Hz), 107.2 (s, C5), 106.2 (app t,22 JRhꢀC ≈ JPꢀC = 3.8
Hz, C3), 91.4 (s, NBC Cd), 72.5 (s, iPr CH), 68.0 (d, JRhꢀC = 5.0 Hz,
NBD bridgehead), 53.2 (d, JRhꢀC = 11 Hz, NBD olefin), 50.5 (s, NBD
CH), 35.6 (d, 1JPꢀC = 24 Hz, Cy CH), 29.8 (d, J = 2.5 Hz, Cy CH2), 27.6
(d, JPꢀC = 13 Hz, Cy CH2), 27.1 (d, JPꢀC = 10 Hz, Cy CH2), 27.1 (s, Cy
CH2), 22.2 (s, iPr CH3), 21.9 (s, iPr CH3). 31P{1H} NMR (202 MHz,
CD2Cl2, 25 °C): δ 45.0 (d, 1JRhꢀP = 157 Hz).
orange powder (0.120 g, 0.084 mmol, 100%). H NMR (500 MHz,
CD2Cl2, ꢀ70 °C): diagnostic signals for 7-η6 δ 7.45 (aromatic), 6.89 (d,
3JHꢀH = 5.0 Hz, 2H), 6.78 (d, 3JHꢀH = 5.0 Hz, 2H), 5.90 (t, 3JHꢀH = 5.0
Hz, 1H), 5.52 (s, unbound COD olefin), 3.75 (br s, 2H, COD bound
olefin), 2.35ꢀ1.05 (m, Cy signals). 13C from HMQC (referenced to ArF
Co/Ho): δ 130.3 (unbound COD Cd) 111.2 (η6-arene), 103.7 (η6-
arene), 98.7 (η6-arene), 71.6 (bound COD Cd). 31P{1H} NMR (202
MHz, CD2Cl2, ꢀ70 °C): δ 75.4 (d, 1JRhꢀP = 185 Hz). 1H NMR (500
MHz, CD2Cl2, ꢀ70 °C): diagnostic signals for 7-η2 δ 7.42ꢀ7.53
Addition of H2 to 4 to Generate a Dihydride Complex. An
NMR tube fitted with a resealable Teflon valve (J. Young type)
containing a degassed solution of 4 in CD2Cl2 was pressurized to 90
psi of H2. The reaction was complete after 7 days at room temperature,
and the solution turned from yellow to colorless. 1H NMR (300 MHz,
CD2Cl2, 25 °C): δ 6.59 (d, 3JHꢀH = 9.0 Hz, 2H, pendent ring Hm) 6.36
3
(aromatic), 7.01 (d, JHꢀH = 5.0 Hz, 2H), 6.92 (m, 1H), 4.02 (br s,
2H, COD olefin), 3.53 (br s, 2H, COD bound olefin), 2.15ꢀ0.80 (m, Cy
signals). 13C from HMQC (referenced to ArF Co/Ho): δ 121.7 (η2-
arene), 113.1 (bound COD Cd), 76.6 (bound COD Cd). 31P{1H}
NMR (202 MHz, CD2Cl2, ꢀ70 °C): δ 41.6 (d, 1JRhꢀP = 135 Hz). Anal.
Calcd for C64H55BF24PRh: C, 53.90; H, 3.89. Found: C, 54.36; H, 3.78.
Addition of H2 to in Situ Generated 7. An NMR tube fitted
with a resealable J. Young-type valve was charged with complex 6 (0.011
g, 0.019 mmol) and NaB(ArF)4 (0.016 g, 0.018 mmol). CD2Cl2 was
vacuum transferred to the tube, yielding an orange solution with a fine
white precipitate. The sample was degassed three times by free-
zeꢀpumpꢀthaw cycles and then pressurized with 90 psi of H2. The
3
(t, JHꢀH = 9.0 Hz, 1H, pendent ring Hp), remainder of the aromatic
resonances under the ꢀB(ArF)4 counteranion resonances, 4.48 (heptet,
3JHꢀH = 6.0 Hz, 2H, iPr methine), 2.07ꢀ0.97 (multiplets, Cy), 1.27 (d,
3JHꢀH = 6.0 Hz, 6H, iPr CH31), 1.11 (d, 3JHꢀH = 6.0 Hz, 6H, iPr CH3)
1
ꢀ12.1 (dd, JPꢀH = 21 Hz, JRhꢀH = 27 Hz, 2H, hydride). 31P{1H}
NMR (122 MHz, CD2Cl2, 25 °C): δ 95.2 (d, 1JRhꢀP = 163 Hz). When
the reaction was heated to 60 °C, decomposition was observed.
1
reaction was monitored by H and 31P NMR spectroscopy. A new
species without a hydride resonance was observed after 1 h at room
1
temperature in the H NMR spectrum. A new phosphorus doublet
resonance was also observed. No further reaction with hydrogen was
observed at room temperature (see below for characterization). Pro-
longed heating at 60 °C yielded small quantities of dihydride complex 5
and lead to decomposition (see below).
(COD)Rh(PCy2biPh)Cl (6). [(COD)RhCl]2 (0.102 g, 0.206
mmol) and PCy2biPh (0.171 g, 0. 489 mmol) were added to an oven-
dried round-bottom flask. Dry CH2Cl2 (10.0 mL) was added to the flask,
yielding a yellow-orange solution, which was stirred for 1.5 h. The
solvent was removed in vacuo to yield a yellow powder. The solid was
then washed with 15.0 mL of pentane and filtered through a frit in air,
yielding a yellow powder (0.204 g, 0.342 mmol, 83%). 1H NMR (500
MHz, CD2Cl2, 25 °C): δ 8.17 (br s, 2H, H1), 7.49 (t, 2H, 3JHꢀH = 5.0
Hz, H2), 7.44 (app d, 1H, 3JHꢀH = 5.0 Hz, H3), 7.36 (m, 3H, H4,5,6), 7.22
(br s, 1H, H7), 5.19 (br s, 2H, COD olefin), 3.27 (br s, 2H, COD olefin),
2.59 (br s, 2H) 2.33 (br m, 4H), 1.88 (m, 6H), 1.77 (m, 2H), 1.57 (m,
9H), 1.31 (br q, 2H), 1.13 (br q, 4H), 1.03 (br t, 2H). 13C{1H} NMR
(125 MHz, CD2Cl2, 25 °C): δ 146.1 (d, JPꢀC = 7.4 Hz, C2), 142.8 (s,
C3), 133.0 (d, J = 6.4 Hz), 132.4 (s), 130.5 (s), 129.3 (d, 1JPꢀC = 27 Hz,
C1), 129.3 (s), 128.6 (s), 128.2 (s), 126.7 (d, J = 6.3 Hz), 100.0 (dd, J =
8.0 Hz, J = 11 Hz, COD C=), 70.8 (d, J = 14 Hz, COD C=), 36.8 (d,
1JPꢀC = 16 Hz, Cy CH), 33.5 (s, COD CH2), 32.2 (s, COD CH2), 31.0
[(COE)Rh(PCy2biPh)][B(ArF)]4 (8). To a dry side-arm flask with a
Teflon sealable top were added [(COE)2RhCl]2 (0.107 g, 0.143 mmol),
PCy2biPh (0.100 g, 0.285 mmol), and NaB(ArF)4 (0.290 g, 0.327
mmol). CH2Cl2 (10 mL) was added, and the reaction was stirred at
room temperature overnight. The solvent was removed in vacuo to yield
a dark brown foam, which turned to an oil. The oil was dissolved in
CH2Cl2 and filtered through a syringe filter in the drybox, yielding an
orange-brown solution. The solvent was removed under vacuum, and
the product was washed with pentane (10.0 mL). The sample was then
filtered and collected as a yellow-brown powder (0.235 g, 0.163 mmol,
58%). 1H NMR (500 MHz, CD2Cl2, 25 °C): δ three aromatic
ꢀ
resonances under B(ArF)4 signal at 7.59, 7.48 (t, J = 5.9 Hz, 1H),
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dx.doi.org/10.1021/om1009473 |Organometallics 2011, 30, 2105–2116