Organometallics
Article
were calculated for the B- or In-based FLPs. In order to
increase the acceptor strength of boron-based FLPs, they
usually contain electron-withdrawing substituents such as
pentafluorophenyl groups attached to boron. In accordance
with these results adducts of Al FLPs with various substrates
1602 m, 1585 w, 1554 w, 1535 s phenyl, ν(CC), ν(CO); 1490 m,
1
465 vs, 1446 vs, 1403 m, 1382 m, 1353 m, 1342 m, 1290 m, 1241 s
δ(CH ); 1189 m, 1155 w, 1116 vs, 1070 m, 1027 m, 1012 w, 985 vw,
3
9
23 m, 883 w, 848 m, 809 m, 786 s, 769 m, 746 vs, 703 s ν(CC); 692
m, 665 m, 645 s phenyl; 587 s, 572 w, 557 m, 535 m, 495 m, 460 m,
47 s ν(PC), ν(GaC), δ(CC). MS (EI, 20 EV, 373 K): m/z (%) 554
4
such as CO and amidoboranes are comparably inert and do
+
2
(3) [3 ]. Anal. Calcd for C H GaPO (660.3): C, 74.4; H, 7.9.
41 52
not show secondary reactions in many cases. They may be
considered as thermodynamic sinks. In contrast, adducts of the
Found: C, 74.2; H, 8.0.
Reaction of 3 with CS : Synthesis of 6. A solution of 3 (0.21 g,
2
Ga FLP 3 are less stable. The CO complex was detectable by
0.38 mmol) in 5 mL of n-hexane was treated with CS (23 μL, 29 mg,
2
2
NMR spectroscopy only at low temperature, and benzaldehyde
coordinated to 3 only via a Ga−O bond. The polarizing
capability of gallium atoms is obviously not strong enough to
activate the CO bonds, to increase the positive charge at the
carbonyl carbon atoms, and to facilitate P−C interactions. For
the same reason, the H B−NH adduct of 3 shows a unique
0.38 mmol). The brown mixture was stirred at room temperature. Red
single crystals were obtained from the solution at room temperature
(
91 mg, 38%). Compound 6 decomposed slowly in the solid state and
in solution. Therefore, we did not observe satisfactory analytical data,
and the 13C NMR spectra showed impurities of unknown substances.
1
Mp (argon, sealed capillary): 105 °C dec. H NMR (C D , 300 K): δ
1
6
6
2
2
t
.10 (s, 18H, Ga Bu ), 1.95 (s, 6H, p-CH ), 2.30 (s, 12H, o-CH ), 6.00
2 3 3
reactivity. In contrast to the comparable adduct of 1 it
4
3
[
d, J = 3.7 Hz, 4H, m-H(Mes)], 7.05 [t, J = 7.5 Hz, 1H, p-
PH HH
dissociates in solution, and the secondary products react further
3
3
H(Ph)], 7.14 [pseudo-t, J = 7.5 Hz, 2H, m-H(Ph)], 7.33 [d, J
=
C
HH
HH
13
3
by H elimination. Small quantities of 3 are sufficient to catalyze
7.5 Hz, 2H, o-H(Ph)], 7.62 (d, J = 33.4 Hz, 1H, PCCH).
2
PH
3
hydrogen transfer reactions or dehydrocoupling with formation
of oligomeric or polymeric B−N compounds. These results will
stimulate systematic investigations into the generation of FLPs
with finely adjusted properties, which by systematic exchange of
the Lewis acidic B, Al, Ga, or In atoms may help in finding
optimized systems for a specific application in various
transformations.
NMR (C D , 300 K): δ 20.8 (s, p-CH ), 24.9 (d, J = 3.7 Hz, o-
6
6
3
PC
3
CH
), 25.7 (d, JPC = 4.1 Hz, Ga(CMe
)
), 32.5 (s, Ga(CMe
) ), 121.3
3 2
3
3
2
1
[
d, J = 72.3 Hz, ipso-C(Mes)], 128.1 [s, o-C(Ph)], 129.4 [s, m-
PC
3
C(Ph)], 129.7 [s, p-C(Ph)], 132.6 [d, J = 11.0 Hz, m-C(Mes)],
1
C(Ph)], 142.9 [d, J = 2.9 Hz, p-C(Mes)], 145.0 [d, J = 8.5 Hz, o-
PC
1
3
39.5 (d, J = 8.0 Hz, PCCH), 140.8 [d, J = 29.2 Hz, ipso-
PC
PC
4
2
PC PC
2
1
C(Mes)], 156.4 (d, J = 2.2 Hz, PCCH), 238.4 (d, J = 49.4 Hz,
PC
PC
31
1
SCS). P{ H} NMR (C D , 300 K): δ 33.6. MS (EI, 20 EV, 353 K):
6
6
+
m/z (%) 554 (3) [3 ].
Reaction of Dimethylamine−Borane with FLP 3: NMR
Experiment. H B←NHMe (2 mg, 0.04 mmol) and 3 (20 mg,
0.04 mmol) were dissolved in 0.6 mL of C in a Young NMR tube.
Full conversion to the dimeric amidoborane (H was
observed after 22 h at room temperature. The NMR spectra showed
the resonances of unchanged FLP 3 and the amidoborane. H NMR
(C
(s, 6H, NMe
113.3 Hz, 2H, BH
3), 6.81 (pseudo-d, J = 7.5 Hz, 1H, p-H , 3), 6.92 (pseudo-t, J
7.5 Hz, 2H, o-H , 3), 7.03 (pseudo-t, J = 7.5 Hz, 2H, m-H , 3),
EXPERIMENTAL SECTION
General Considerations. All procedures were carried out under
an atmosphere of purified argon in dried solvents (n-hexane and
■
3
2
D
6
6
cyclopentane with LiAlH ; toluene with Na/benzophenone). NMR
2
B−NMe )
2 2
4
spectra were recorded in C D at ambient probe temperature using the
6
6
1
13
31
1
Bruker instruments Avance I ( H, 400.13 MHz; C, 100.62 MHz; P,
11
1
13
t
1
1
61.98 MHz; B, 128 MHz) and Avance III ( H, 400.03 MHz; C,
6
D
6
, 300 K): δ 1.05 (s, 18H, Ga Bu
2
, 3), 2.09 (s, 6H, p-CH
, 3), 3.02 (q, JBH
, amidoborane), 6.77 (d, JPH = 2.8 Hz, 4H, m-HMes
3
, 3), 2.22
00.59 MHz; 31P, 161.92 MHz) and referenced internally to residual
1
, amidoborane), 2.51 (s, 12H, o-CH
=
2
3
1
3
4
solvent resonances (chemical shift data in δ). C NMR spectra were
all proton decoupled. IR spectra were recorded as paraffin mulls
between CsBr plates or as KBr pellets on a Shimadzu Prestige 21
2
,
3
3
=
HH
Ph
HH
3
Ph
HH
Ph
3
31
1
spectrometer. The Al/P-based FLP Mes P−C(CH−Ph)−Al-
7.40 (d, J = 16.8 Hz, 1H, PCCH, 3). P{ H} NMR (C D , 300
2
PH
6
6
11
1
(
CMe ) (1) and the Ga/P-based FLP Mes P−C(CH−Ph)−
K): δ −14.2 (3). B{ H} NMR (C D , 300 K): δ 5.45 (s, BH ,
3
2
2
6
6
2
5
a,13
Ga(CMe ) (3) were obtained according to literature procedures.
amidoborane).
3
2
The assignment of NMR spectra is based on HMBC, H,H-ROESY,
HSQC, and DEPT135 data.
Reaction of 3 with the Ammonia−Borane Adduct: Synthesis
of 7. A solution of 3 (0.20 g, 0.36 mmol) in 5 mL of toluene was
treated with the ammonia−borane adduct (13 mg, 0.42 mmol) at
room temperature. The mixture was stirred overnight at room
temperature. The solvent was removed in vacuo, and the residue was
recrystallized from n-pentane at 2 °C (90 mg, 43%). Small quantities
of uncoordinated FLP 3 were observed in the NMR spectra and may
indicate the beginning of secondary reactions. Mp (argon, sealed
Reaction of 3 with Benzaldehyde: Synthesis of 5. A solution
of 3 (0.13 g, 0.23 mmol) in 2 mL of cyclopentane was treated with
benzaldehyde (20 μL, 24 mg, 0.23 mmol). The mixture was stirred
overnight to afford a red solution. Cooling of the solution to −40 °C
yielded the pure compound 5 as a yellow solid (45 mg, 30%).
Attempts at recrystallization from several polar or nonpolar solvents
1
1
t
failed. Mp (argon, sealed capillary): 97 °C dec. H NMR (C D , 300
capillary): 141 °C. H NMR (C
6
D
6
, 300 K): δ 1.16 (s, 18H, Ga Bu
2
),
6
6
t
3
K): δ 1.15 (s, 18H, Ga Bu ), 2.05 (s, 6H, p-CH ), 2.42 (s, 12H, o-
CH ), 6.71 [d, J = 2.7 Hz, 4H, m-H(Mes)], 6.96 [t, J = 7.4 Hz,
1.23 (d, JPH = 15.0 Hz, 2H, NH
), 1.99 (s, 6H, p-CH ), 2.33 (s, 12H,
2
3
2
3
4
3
4
o-CH ), 3.19 (s br, 2H, BH ), 6.64 [d, J = 2.8 Hz, 4H, m-H(Mes)],
3
PH
HH
3 2 PH
3
3
1
H, p-H(Ph)], 6.98 [pseudo-t overlap, J = 7.1 Hz, 2H, m-H(O
7.03 [d, J = 7.6 Hz, 1H, o-H(Ph)], 7.12 [pseudo-t overlap, 2H, m-
HH
HH
3
3
3
CPh)], 7.01 [d overlap, J = 7.4 Hz, 2H, o-H(Ph)], 7.05 [m overlap,
H(Ph)], 7.41 [d, J = 7.9 Hz, 2H, o-H(Ph)], 7.97 (d, J = 35.7 Hz,
HH
HH PH
3
13
5
1
7
1
2
3
1
H, p-H(OCPh)], 7.07 [pseudo-t, J = 7.4 Hz, 2H, m-H(Ph)],
1H, PCCH). C NMR (C D , 300 K): δ 20.8 (d, J = 1.1 Hz, p-
HH
6
6
PC
3
3
3
3
.48 [d, J = 7.1 Hz, 2H, o-H(OCPh)], 7.55 (d, J = 21.0 Hz,
CH ), 22.5 [d, J = 5.2 Hz, Ga(CMe ) ], 25.3 (d, J = 4.2 Hz, o-
HH
PH
3 PC 3 2 PC
1
3
4
H, PCCH), 8.96 (s, 1H, OCH). C NMR (C D , 300 K): δ
CH ), 32.7 [s, Ga(CMe ) ], 128.5 [d, J = 1.5 Hz, o-C(Ph)], 128.8
6
6
3 3 2 CP
3
1
0.9 (s, p-CH ), 24.4 (s, o-CH ), 28.1 (d, J = 1.8 Hz, Ga(CMe ) ),
[d, J = 46.6 Hz, ipso-C(Mes)], 128.95 [s, m-C(Ph)], 129.01 [s, p-
PC
3
3
PC
3
2
4
4
3
4
1.0 (d, J = 1.4 Hz, Ga(CMe ) ), 125.1 [d, J = 1.3 Hz, o-C(Ph)],
C(Ph)], 131.4 [d, J = 8.7 Hz, m-C(Mes)], 140.1 [d, J = 2.5 Hz,
PC
3
2
PC
PC PC
3
2
28.0 [s, p-C(Ph)], 128.6 [s, m-C(OCPh)], 129.3 [s, o-C(O
p-C(Mes)], 142.3 [d, J = 24.3 Hz, ipso-C(Ph)], 142.5 [d, J = 8.4
PC PC
1
1
2
CPh)], 130.1 [s, m-C(Ph)], 130.2 [d, J = 7.1 Hz, ipso-C(Mes)],
Hz, o-C(Mes)], 145.4 (d, J = 21.7 Hz, PCCH), 157.4 (d, J
=
PC
PC
PC
3
31
1
11
1
1
30.5 [d, J = 4.8 Hz, m-C(Mes)], 132.5 [s, p-C(OCPh)], 138.1
7.9 Hz, PCCH). P{ H} NMR (C D , 300 K): δ 19.6. B{ H}
PC
6
6
4
−1
[
s, ipso-C(OCPh)], 139.1 [d, J = 0.8 Hz, p-C(Mes)], 143.3 [d,
NMR (C D , 300 K): δ −12.0. IR (KBr pellets, cm ): 3356 m, 3306
PC
6 6
2
3
J
= 12.9 Hz, o-C(Mes)], 145.0 [d, J = 16.6 Hz, ipso-C(Ph)],
m ν(NH ); 3080 vw, 3059 vw, 3022 m, 2957 s, 2928 s, 2911 s, 2864 s,
PC
PC
2
1
1
45.4 (s, PCCH), 155.6 (d, J = 46.7 Hz, PCCH), 168.9 (s,
2826 vs, 2760 w, 2731 vw, 2698 w ν(C−H); 2426 s, 2351 m ν(BH );
PC
2
31
1
−1
CO). P{ H} NMR (C D , 300 K): δ −4.3. IR (KBr pellets, cm ):
2170 vw, 1969 vw, 1948 vw, 1803 vw, 1738 w, 1722 w, 1653 w, 1603 s,
6
6
3
052 m, 3025 m, 2952 s, 2929 s, 2916 s, 2865 s, 2813 vs, 2752 m, 2692
1547 s phenyl, ν(CC, δ(NH ); 1487 m, 1464 s, 1447 s, 1400 m,
2
m ν(C−H); 1945 w, 1893 vw, 1743 vw, 1720 vw, 1702 w, 1654 vw,
1379 m, 1356 m, 1333 vw, 1286 w, 1246 w δ(CH ), ν(BN); 1190 m
3
G
Organometallics XXXX, XXX, XXX−XXX