S
1
Terminal Mo Carbide
and Carbyne
Reactivity: H
2
Cleavage, B
–
C
Bond Activation, and C
–
C Coupling
Gwendolyn A. Bailey
and
Theodor Agapie
*
Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E.
California Blvd.
MC 127
-
72, Pasadena, CA, USA
Supporting Information
Contents
I.
Experimental Details
S
2
General Considerations
S
2
H
2
splitting with carbide
1
S
2
Figure S1
—
3
1
P{
1
H}
NMR spectra (202 MHz, THF, 23 °C) showing
(a) clean carbide
1
, prior to addition of H
2
;
(b)
carbide
1
in the absence of H
2
(t = 18 h); (c) the reaction of carbide
1
+ H
2
(t = 18 h).
S
3
Figure S
2
—
3
1
P{
1
H}
NMR spectr
um
(202 MHz, THF, 23 °C) showing
reaction of carbide
1
with D
2
.
S
4
Figure S
3
—
2
H NMR spectrum
(61 MHz, THF, 23 °C) showing appearance of key methylene
-
d
2
signals
(
d
1.07, 0.66) for
4
on treatment of carbide
1
with D
2
.
S
4
Borylcarbene
6
and intermediate borane adduct
5
S
4
In situ observation of intermediate borane adduct
S
4
Figure S
4
—
3
1
P
{
1
H} NMR spectrum (
202
MHz,
THF
,
–
20
°C) of
5
.
S
5
Figure S
5
—
13
C{
1
H} NMR spectrum (126 MHz, C
6
D
6
, 23 °C) of
5
.
S
5
Conversion to
6
S
6
Figure S6
—
31
P
{
1
H} (202 MHz, THF, 23 °C) NMR spectra
showing
the conversion of carbide
1
to
borylcarbene
6
via intermediate
adduct
5
.
S
6
Preparation of
6
S
6
Figure S
7
—
1
H NMR spectrum (400 MHz, C
6
D
6
, 23 °C) of
6
(*
denotes residual THF).
S7
Figure S
8
—
31
P{
1
H} NMR spectrum (202 MHz, C
6
D
6
, 23 °C) of
6
.
S7
Figure S
9
—
13
C{
1
H} NMR spectrum (126 MHz, C
6
D
6
, 23 °C) of
6
.
S8
C
–
C coupling of methylidyne
2’
S
8
Synthesis of ketenyl complex
7
S
8
Figure S
10
—
3
1
P{
1
H}
NMR spectra (202 MHz, THF, 23 °C)
showing attempted syntheses of ketenyl
complex
5
on a reasonable time scale.
S
9
Table S1
—
Com
parison of key bond lengths (Å) and angles (°) for
h
2
-
C,C
-
ketenyl complex
7
,
h
1
-
ketenyl
complex
8
, free ketene
, and previously reported
h
2
-
C,C
-
ketenyl complexes
.
S
10
Chart S1
—
Proposed resonance forms for ketenyl complex
7
, and the structure of previously reported
h
1
-
ketenyl complex
8
for comparison in Table S1
.
S
10
Calculation of
hydricity requirement for
H
2
cleavage by
1
+ borane FLP
S
1
0
Figure S
1
1
—
Thermodynamic scheme
for thermoneutral H
2
cleavage by carbide
1
and borane.
S
1
1
II.
Computational Details
S
1
2
General Considerations
S
12
Borylcarbene
6
S
1
2
Table S
2
—
Comparison of experimental and calculated bond lengths (Å) and angles (°) for
6
.
S
1
2
Figure S
1
2
—
(a) DFT
-
optimized structure of borylcarbene
6
with radii scaled by 50%. (b) Calculated
HOMO of borylcarbene
6
(isocontours 0.05).
S
1
2
Figure S1
3
—
Stereographic pair for 3D viewing of HOMO of borylcarbene
6
(0.05 e/Å
3
isocontours).
S
1
3
Ketenyl complex
5
S
1
3
Table S
3
—
Comparison of experimental and calculated bond lengths (Å) and angles (°) for
7.
S
1
3
S
2
Figure S
1
4
—
(a) DFT
-
optimized structure of
ketenyl complex
7
with radii scaled by 50%. (b) Calculated
HOMO
-
2
of
ketenyl complex
7
showing key Mo
-
ketenyl
p
bonding orbital
(isocontours 0.0
5
).
S
1
3
III.
Crystallographic Information
S
1
4
Data Collection and
Refinement Details
S
1
4
Table S
4
—
Crystal and Refinement Data for Complexes
6
and
7
.
S
1
4
Figure S
1
5
—
Structural Drawing of
6
S
1
5
Figure S
1
6
—
Structural Drawing of
7
S
1
5
References
S
1
6
I.
EXPERIMENTAL DETAILS
General Considerations
A
ll operations were carried out
under a nitrogen atmosphere
in an MBraun drybox or using
standard Schlenk
techniques. Solvents were dried over sodium benzophenone ketyl, or by the method of Grubbs.
1
Solvents,
once dried and degassed, were stored under inert atmosphere over 4 Å molecular sieves.
Methylidyne
2
and
carbide
1
were prepared according to literature procedures
.
2
CO (gas, ≥99%; Sigma
-
Aldrich)
,
BPh
3
(Sigma
Aldrich)
, and
BMes
3
(Sigma Aldrich)
were used as received
.
NaBPh
4
(Oakwood Chemicals) was dried at 60
°C in vacuo for 16 h.
NMR spectra were recorded on
a
Bruker
400 MHz spectrometer (Prodigy broadband
cryoprobe or broadband iProbe)
or Varian 400 MHz spectrometer
(broadband auto
-
tune OneProbe)
. C
hemical
shifts
are
repor
ted in parts per million (ppm)
.
1
H and
13
C{
1
H}
chemical shifts
are referenced to residual sol-
vent peaks
,
3
31
P{
1
H} chemical shifts are referenced to an external
sample of
85% H
3
PO
4
(0 ppm)
, and
2
H
chemical shifts are referenced
internally
to C
6
D
6
(spiked into the reaction mixture
;
7.16 ppm).
Multiplicities
are abbreviated as follows: s = singlet, d = doublet, t = triplet, dd = doublet of doublets, dt = doublet of
triplets, td = triplet of doublets, m = multiplet, br = broad.
Infrared
(IR)
spectra
were collected
on a
Thermo
Fischer Nicolet 6700 FTIR spectrometer
.
Elemental analysis was performed using a
PerkinElmer 2400 Series
II CHN Elemental Analyzer.
H
2
gas (Airgas; 99.9%) and D
2
gas (Cambridge Isotopes; 99.8%) were rigorously dried by i
mmersion
(3/4
height)
of a sealed
1
L round bottom flask at 1 atm in liquid N
2
for 3 min
. The gas was then transferred to the
reaction flask via an oven
-
dried transfer bridge.
>
Safety hazard
:
C
ondensation of water in a sealed flask at
cryogenic
temperatures poses a significant safety hazard in case there is a leak in the setup, since O
2
from the
atmosphere may condense in the trap and subsequently explode.
To minimize
the explosion hazard, the trap
setup should be rigorously leak
-
checked and the
drying time should be minimized (3
-
5 min is sufficient to
ensure drying, while minimizing potential O
2
condensation hazard).
Additionally, the setup should be con-
tained behind a blast shield at all times.
H
2
splitting with carbide 1
After degassing via three consecutive freeze/pump/thaw cycles, a cold in situ
-
generated solution of
1
(0.047 mmol
in 1.5 mL THF) in a 10 mL reaction vessel was subjected to pre
-
dried H
2
(1 atm
) and then warmed to RT.
After
temperature equilibration, t
he ve
ssel was sealed shut using a
Kontes
valve and the solution was stirred at RT for
2
0
h.
31
P{
1
H} NMR (202 MHz, THF, 23 °C; Figure S
1
):
89.0 (br s
;
ca. 1
0
%
), 88.1 (s
; minor
)
85.3 (d,
4
J
PP
= 17.4 Hz,
P
P
i
Pr
i
Pr
i
Pr
i
Pr
C
C
O
Mo
1
P
P
i
Pr
i
Pr
i
Pr
i
Pr
Mo
C
H
H
C
O
4
H
2
THF, RT
S
3
Mo
–
P
of
4
;
9
%
),
82.
4
(s
; 1
0
%
), 77.
4
(d
,
J
= 21.8 MHz
;
4
%
), 77.
1
(d,
J
= 21. 8 MHz
;
4
%
), 48.
9
(d,
4
J
PP
= 17.5 Hz,
Mo
–
CH
2
P
of
4
; 1
1
%
),
-
3.5 (free P2
; 3
4
%
)
,
-
4.3 (s
;
19
%
)
.
31
P{
1
H} NMR chemical shifts and
J
-
couplings for
4
matched those of an independently prepared sample in THF
(Figure S1d)
.
2
Figure S
1
—
3
1
P{
1
H}
NMR spectra (202 MHz, THF, 23 °C) showing
(a) clean carbide
1
, prior to addition of H
2
;
(b)
carbide
1
in the absence of H
2
(t = 18 h); (c)
the reaction of
carbide
1
+ H
2
(t = 18 h)
; (d)
clean
4
(independently prepared
2
).
Similar results
were obtained on reaction of
1
with D
2
under identical conditions, only the proportion of the impurity
signal at
d
P
82.38 was increased (Figure S2).
2
H NMR
(61 MHz, THF, 23 °C; Figure S3): 3.44 (s, THF), 1.59 (s,
THF + unidentified), 1.07 (s, P
–
C
D
2
of
4
), 0.55 (s, P
–
C
D
2
of
4
). The solvent peak
s (THF
-
H
8
) complicate analysis
of the
1
H NMR spectrum, so that absence of the P
–
C
H
2
peaks could not be discerned.
Repeating the same reaction
in the absence of H
2
/D
2
,
4
was not observed, though several of the products formed were the same. Consistent with
previous results,
2
the primary species identified was carbide
1'
, PMo(C:)(CO)P, an isomer of
1
in wh
ich one phos-
phine arm has become unbound and the central arene moiety is bound in an
h
6
fashion.
31
P{
1
H} NMR (202 MHz,
THF, 23 °C; Figure S1
c
):
90.8 (br s, Mo
–
P of
1'
), 82.4 (s), 77.4 (d,
J
= 21.8 MHz), 77.1 (d,
J
= 21. 8 MHz), 48.9
(d,
4
J
PP
= 17.5 Hz, Mo
–
CH
2
P
of
4
),
-
3.5 (free P2),
-
4.2 (br s, free phosphine arm of
1'
).
Figure S
2
—
3
1
P{
1
H}
NMR spectr
um
(202 MHz, THF, 23 °C) showing
products formed on reaction of carbide
1
with D
2
.
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
f
1
(
p
p
m
)
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
f
1
(
p
p
m
)
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
f
1
(
p
p
m
)
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
f
1
(
p
p
m
)
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
1
0
0
f
1
(
p
p
m
)
1’
1’
free P2
1
1
(a)
(b)
(c)
4
4
free P2
(d)
P
i
Pr
i
Pr
Mo
P
i
Pr
i
Pr
C
O
C
1’
:
P
P
i
Pr
i
Pr
i
Pr
i
Pr
Mo
C
H
H
C
O
4
8
5
.
0
8
5
.
2
8
5
.
4
8
5
.
6
f
1
(
p
p
m
)
8
5
.
2
9
8
5
.
4
0
4
8
.
6
4
8
.
8
4
9
.
0
4
9
.
2
f
1
(
p
p
m
)
4
8
.
8
2
4
8
.
9
2
-
1
5
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
f
1
(
p
p
m
)
-
1
5
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
f
1
(
p
p
m
)
4
4
free P2
S
4
Figure S
3
—
2
H NMR spectrum
(
61
MHz, THF, 23 °C) showing
appearance of key methylene
-
d
2
signals (
d
1.07, 0.66)
for
4
on treatment of carbide
1
with D
2
.
Asterisks
(*) indicate the THF solvent (natural abundance
2
H); the signal at 1.59 is
likely
overlapping with an unidentified impurity.
KCl
-
free c
ontrol experiment
s
. KCl
-
free carbide
1
was generated by pumping down cold solutions of
1
(kept <0 °C
in a liquid N
2
-
chilled cold well), extracting into thawing C
6
H
6
, and lyophilizing. Subjecting
to 1 atm H
2
as above
yielded clear orange solutions and
an insoluble
pink precipitate.
31
P{
1
H} NMR (orange solution, 202 MHz, THF,
23 °C): silent
.
Boryl
carbene
6
and intermediate borane adduct 5
In situ observation of
intermediate
5
:
To a
freshly
prepared thawing solution of carbide
1
(0.062 mmol) in THF
(1.5 mL) was added BPh
3
(15.3 mg, 0.062 mmol, 1 equiv) in THF
(0.5 mL)
.
A slight lightening of the
deep
red
color was
observed
during the addition
.
An aliquot
was taken for NMR analysis and warmed to
-
20 °C inside the
probe.
31
P{
1
H} NMR (202 MHz
,
THF,
–
20 °C
; Figure S4
):
43.
2 (s),
-
6.29 (s
; minor impurity
)
.
11
B NMR (C
6
D
6
, 128
MHz, 23 °C): no signals.
13
C{
1
H} NMR (C
6
D
6
, 101 MHz, 23 °C; Figure S
5
): 157.21 (br
s, Mo
–
C
O
), 147.85 (t
,
J
PC
= 6.2 Hz
, aryl
-
C
), 138.01 (t
,
J
PC
= 3.2 Hz
, aryl
-
C
), 137.39 (s
, aryl
-
C
), 135.14 (s
, aryl
-
C
), 132.20 (s
, aryl
-
C
), 130.37
(s
, aryl
-
C
),
128.70 (s, aryl
--
C
),
128.67 (s
, aryl
-
C
), 128.28 (s
, aryl
-
C
), 128.05 (s
, aryl
-
C
), 127.92 (s
,
aryl
-
C
). 125.48
(s
, aryl
-
C
), 125.05 (s
, aryl
-
C
), 122.57 (s
, aryl
-
C
)
, 29.63 (s
,
–
C
H(CH
3
)
2
), 27.73 (d
,
J
PC
=
7.4
Hz,
–
C
H(CH
3
)
2
), 27.64
(d
,
J
PC
=
8.6
Hz,
–
C
H(CH
3
)
2
), 20.51 (d
,
J
PC
=
8.7
Hz,
–
C
H(CH
3
)
2
), 19.29 (s
,
–
CH(
C
H
3
)
2
), 18.67 (s
,
–
CH(
C
H
3
)
2
),
18.24 (s
,
–
CH(
C
H
3
)
2
), 17.54 (s
,
–
CH(
C
H
3
)
2
)
, 13.59 (s,
–
CH(
C
H
3
)
2
)
.
No
signals
were detected in the
13
C{
1
H} NMR
spectrum
in the region from
592
-
162
ppm, nor in the
11
B NMR
spectrum
from 100 ≥
d
≥
-
100 ppm
. Likewise, in a
1
H
–
13
C HMQC experiment
, the carbide
13
C signal was not detected
in the region from 570
-
162 ppm
. The carbide
13
C signals and the
11
B
Ph
3
signals may be masked at this temperature due to broadness
.
-
0
.
5
0
.
0
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
f
1
(
p
p
m
)
0
.
6
6
1
.
0
7
1
.
5
9
3
.
4
4
*
*
P
P
i
Pr
i
Pr
i
Pr
i
Pr
C
C
O
Mo
1
BPh
3
, THF
-40 °C to RT
P
i
Pr
i
Pr
Mo
P
i
Pr
i
Pr
C
O
C
Ph
B
Ph
Ph
6
P
P
i
Pr
i
Pr
i
Pr
i
Pr
C
C
O
Mo
proposed structure
Ph
3
B
5
S
5
Figure S
4
—
3
1
P
{
1
H} NMR spectrum (
202
MHz,
THF
,
–
20
°C) of
intermediate
5
.
Figure S
5
—
13
C{
1
H} NMR spectrum (126 MHz, C
6
D
6
, 23 °C) of
intermediate
5
.
(*) indicates solvent peaks
(THF)
.
C
onversion to borylcarbene
6
.
The solution
from above
was allowed to warm to RT, over which time a color change
from deep red to brown occurred.
31
P{
1
H} NMR
spectra taken at RT
over
4
h
revealed consumption of this inter-
mediate species, and
gradual
conversion to
6
.
31
P{
1
H}
NMR (THF, 202 MHz, 23 °C,
t = 2 h
; F
igure S
6
): 7
6
.
2
(s
,
Mo
–
P
of
6
, major
),
4
3
.2
(s,
5
, minor),
-
5.0
(s
, free
P
i
Pr
2
of
6
, major
)
,
-
5
.4
(s, free P2
, minor
)
.
-
1
0
0
-
9
0
-
8
0
-
7
0
-
6
0
-
5
0
-
4
0
-
3
0
-
2
0
-
1
0
0
1
0
2
0
3
0
4
0
5
0
6
0
7
0
8
0
9
0
1
0
0
1
1
0
1
2
0
1
3
0
1
4
0
f
1
(
p
p
m
)
-
6
.
2
9
4
3
.
2
0
-40 °C to RT
P
P
i
Pr
i
Pr
i
Pr
i
Pr
C
C
O
Mo
proposed structure
Ph
3
B
5
1
0
2
0
3
0
4
0
5
0
6
0
7
0
8
0
9
0
1
0
0
1
1
0
1
2
0
1
3
0
1
4
0
1
5
0
1
6
0
f
1
(
p
p
m
)
1
5
7
.
2
1
1
7
1
8
1
9
2
0
2
1
2
2
2
3
2
4
2
5
2
6
2
7
2
8
2
9
3
0
f
1
(
p
p
m
)
1
7
.
5
4
1
8
.
2
4
1
8
.
8
7
1
9
.
2
9
2
0
.
4
6
2
0
.
5
5
2
7
.
6
1
2
7
.
7
0
2
7
.
7
8
2
9
.
6
3
-40 °C to RT
P
P
i
Pr
i
Pr
i
Pr
i
Pr
C
C
O
Mo
proposed structure
Ph
3
B
5
*
*
*
*
*
1
2
0
1
2
2
1
2
4
1
2
6
1
2
8
1
3
0
1
3
2
1
3
4
1
3
6
1
3
8
1
4
0
1
4
2
1
4
4
1
4
6
1
4
8
1
5
0
f
1
(
p
p
m
)
1
2
2
.
5
7
1
2
5
.
0
5
1
2
5
.
4
8
1
2
7
.
9
2
1
2
8
.
0
5
1
2
8
.
2
8
1
2
8
.
6
7
1
2
8
.
7
0
1
3
0
.
3
7
1
3
2
.
2
0
1
3
5
.
1
4
1
3
7
.
3
9
1
3
8
.
0
1
1
4
7
.
8
5
*
S
6
Figure S
6
—
31
P
{
1
H} (202 MHz, THF, 23 °C) NMR spectra
showing
the conversion of carbide
1
to borylcarbene
6
via inter-
mediate
5
.
Preparation
of
borylcarbene
6
.
This
reaction was
conducted
as above,
but
with 0.125 mmol carbide
1
, BPh
3
(30.5
mg, 0.125 mol), and THF (4 mL).
After addition of the BPh
3
, t
he solution was allowed to warm to RT,
prompting
a color change from deep red to brown.
After 4 h, the
reaction was concentrated in vacuo and the resulting oily solid
was suspended
three times
with
vigorous
stirring in hexanes (2 mL), concentrating each ti
me to remove residual
THF.
After extracting into benzene (6 mL) and lyophilizing, the product was crystallized by vapor diffusion of
pentane into THF
solutions
. Filtration and drying in vacuo afforded 6 as a dark brown crystalline solid
(
61
mg,
5
8
%).
1
H
NMR (C
6
D
6
, 400 MHz, 23 °C; Figure S
7
): 8.04 (dd,
J
= 23.6 Hz,
J
= 7.6 Hz, 4H, BPh
2
o
-
C
H
), 7.59
–
7.
09
(overlapping m, 8H, aryl
H
), 7.00
–
6.69 (overlapping m, 9H, aryl
H
), 5.66 (d,
J
= 5.6 Hz, 1H, central arene
–
H
), 5.24
(d,
J
= 6.0 Hz, 1H, central arene
–
H
), 2.
00
–
1.83 (m, 1H, C
H
(CH
3
)
2
) 1.79
–
1.61 (m,
3
H, C
H
(CH
3
)
2
). 1.
32
–
1.1
7
(m,
1H, C
H
(CH
3
)
2
), 1.17
–
1.06 (m, 3H, CH(C
H
3
)
2
), 1.04
–
0.82 (m, 9H, CH(
C
H
3
)
2
), 0.81
–
0.52 (m, 12H, CH(C
H
3
)
2
).
31
P{
1
H} NMR (
C
6
D
6
, 202 MHz, 23 °C
; Figure S8
): 77.
4
(s),
-
4.2
(s).
11
B NMR (C
6
D
6
,
128 MHz, 23 °C): no signals.
13
C{
1
H} NMR (C
6
D
6
, 1
01
MHz, 23 °C; Figure S
9
): 242.1
3
(s, Mo
–
C
O), 151.0
8
(s,
aryl
-
C
), 144.
60
(d,
J
= 19.9 Hz,
aryl
-
C
), 143.8
7
(d,
J
=
10.6
Hz, aryl
-
C
), 143.
61
(
d
,
J
= 5.6 Hz,
aryl
-
C
), 136.2
4
(d,
J
= 33.1 Hz, aryl
-
C
), 134.
35
(d,
J
= 23.4 Hz, aryl
-
C
), 133.0
9
(d,
J
= 4.8 Hz, aryl
-
C
), 131.87 (d,
J
= 2.7 Hz, aryl
-
C
), 129.8
4
(s, aryl
-
C
), 129.
37
(d,
J
= 1.3 Hz, aryl
-
C
) 128.
92
(s, aryl
-
C
). 128.78 (d,
J
= 37.6 Hz, aryl
-
C
), 127.0
7
(s, aryl
-
C
), 126.7
5
(d,
J
=
9.4 Hz, aryl
-
C
), 126.52 (s, aryl
-
C
), 126.09 (s, aryl
-
C
), 125.79 (s, aryl
-
C
), 124.0
5
(s, aryl
-
C
), 123.
37
(d,
J
= 4.3 Hz, aryl
-
C
),
110.
32
(
2
d,
J
= 4.5 Hz, central arene
-
C
), 106.6
0
(d,
J
= 6.8 Hz, central arene
-
C
), 100.9
6
(d,
J
= 14.9 Hz, central
arene
-
C
), 94.
20
(d,
J
= 38.0 Hz, central arene
-
C
), 29.2
2
(d,
J
= 18.5 Hz,
–
C
H(CH
3
)
2
), 27.54 (d,
J
= 22.1 Hz,
–
C
H(CH
3
)
2
), 26.3
4
(d,
J
= 15.6 Hz,
–
C
H(CH
3
)
2
), 2
5.00
(d,
J
= 13.5 Hz,
–
C
H(CH
3
)
2
), 20.
45
(d,
J
=
29.9
Hz,
–
CH(
C
H
3
)
2
),
20.28
(d,
J
=
22.4
Hz,
–
CH(
C
H
3
)
2
), 19.61 (d,
J
= 4.4 Hz,
–
CH(
C
H
3
)
2
), 18.
92
(d,
J
= 7.7 Hz,
–
CH(
C
H
3
)
2
),
18.5
3
(d,
J
= 3.0 Hz,
–
CH(
C
H
3
)
2
),
18.15 (s,
–
CH(
C
H
3
)
2
),
16.
89
(d,
J
= 3.5 Hz,
–
CH(
C
H
3
)
2
), 13.9
2
(
s
,
–
CH(
C
H
3
)
2
).
The carbene
13
C resonance was detected via
1
H
–
13
C HMQC (C
6
D
6
, 23 °C):
346.15 (s, Mo=
C
)
.
IR (solution in THF,
cm
-
1
):
1802
.
Anal. calcd (%) for
C
50
H
55
BMoOP
2
(M
w
=
840
.70
): C,
71.43
; H,
6.59
. Fo
und: C,
71.73
; H,
6.47.
Crystals for single crystal X
-
ray diffraction studies were grown by vapor diffusion of pentane into THF solutions.
-
2
0
-
1
5
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
f
1
(
p
p
m
)
Carbide
1
, prior to BPh
3
addition
t
= 0, RT
t
= 10 min, RT
t
= 25 min, RT
t
= 2 h, RT
1
5
6
6
-
2
0
-
1
5
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
9
0
9
5
f
1
(
p
p
m
)