Organometallics
Communication
1
4
derived from palladium, rhodium, iridium, etc. For example,
manganese-catalyzed silylation and hydroarylation of alkenes
Table 1. Screening of Metal Carbonyls
15
were achieved recently. Furthermore, bimetallic catalysis
represents a frontier area for C−C and C−X coupling
1
6
processes. Ritter and co-workers hypothesized that the
bimetallic pathway has a lower activation barrier in Pd-
17
catalyzed carbon−heteroatom bond-forming reactions. Here-
in we report an unprecedented Mn (CO) -catalyzed intra-
yield (%)
2
10
molecular dimerization of 1,1-diphosphiranylmethane deriva-
tives (Scheme 1d).
time
a
entry
1
[M]
solvent
THF
(h)
1a:2a:3a
2a
3a
A series of unexpected biphosphirane complexes 1a−d were
W(CO) ·THF
1 equiv)
2
10:4:1
5
(
synthesized following the established phosphiranide complex
1
8
2
Mo(CO) ·THF
THF
2
10:1:1
protocol. With careful control of the reaction conditions,
a−d were prepared in 48−77% yield (Scheme 2). By contrast,
5
(
1 equiv)
1
3
4
5
6
7
Co (CO) (1 equiv)
THF
THF
2
2
1
3
5:0:1
0:7:1
0:1:0
0:0:1
0:1:0
2
8
Fe (CO) (1 equiv)
2
8
Scheme 2. Preparation of Phosphirane Complexes 1a−d and
Single-Crystal Structure of 1b
Mn (CO) (1 equiv) THF
80
2
10
Mn (CO) (1 equiv) toluene
51
2
10
Mn (CO) (50
THF
THF
THF
THF
THF
1.5
78
78
74
60
0
2
10
mol %)
8
9
Mn (CO) (10
3
7
0:1:0
0:1:0
0:20:3
0
2
10
mol %)
Mn (CO) (5
2
10
mol %)
1
1
0
1
Mn (CO) (2.5
24
7
2
10
mol %)
BrMn(CO) (5
0
5
mol %)
reaction of the phosphiranide complex with methyl chlor-
oformate produced the ester-substituted phosphirane com-
aThe 1a:2a:3a ratio was determined by 31P NMR spectroscopy.
1
8
plex. The structure of 1b was unambiguously established by
X-ray crystallographic analysis (Scheme 2). The small bonding
angle (C11−P1−C12 = 48.2°) and the short P1−C12 bond
length (1.82 Å) indicate the strain of the phosphirane ring.
Encouraged by our recent success in developing a Mo-
Scheme 3. Mn (CO) -Catalyzed Intramolecular
Dimerization of 1a−d and Single-Crystal Structure of 2c
2
10
(
CO) -promoted carbonylative ring expansion of a 1-
6
13
iminylphosphirane complex, we examined the reaction of
a with a series of metal carbonyls (Table 1). The results
1
showed that a slow reaction occurred at room temperature
with 1 equiv of M(CO) ·THF (M = W, Mo) (entries 1 and 2).
5
To enhance the reaction rate, several binuclear metal carbonyls
were then evaluated at room temperature in THF (entries 3−
13.2 ppm in the 31P NMR spectrum. The sums of angles
5
). With the addition of 1 equiv of Mn (CO) , the reaction
around phosphorus are 288.7° for P1 and 288.9° for P2, which
2
10
19
was complete in 1 h and afforded 1,4-diphosphanorbornane
complex 2a selectively in good yield (80%; entry 5).
Interestingly, when toluene was used as the solvent instead
of THF, the reaction provided 3a selectively (51% yield; entry
are smaller than that of Duphos Pt complexes (ca. 305°).
The small cone angles of P1 and P2 are probably due to the
strain of the bicyclic rings. The strain also promotes the σ-
donating ability of phosphorus, as indicated by the short P1−
X-ray crystal analysis (see Figure S3). 3a has the same 1,4-
diphosphanorbornane skeleton as 2c. It is worth noting that
the high rigidity of these bicyclic species prevents the inversion
of the pyramidal phosphorus center during catalytic processes.
For example, 1-phosphanorbornadiene derivatives have been
applied as P-stereogenic ligands in a copper(I)-catalyzed
6
). Moreover, the reaction also took place with a catalytic
amount of Mn (CO) (Table 1, entries 7−10). Notably, the
reaction did not proceed with mononuclear BrMn(CO)
2
10
5
(
entry 11). This result highlights the crucial role of zero-
valent metal carbonyls during the activation of the phosphirane
ring in 1a and excludes the possibility of the Mn(I) → Mn(III)
catalytic process. The optimized conditions for further research
were Mn (CO) (5 mol %), THF, and room temperature. As
20
enantioselective 1,3-dipolar cycloaddition. However, the 1-
phosphanorbornane backbone has never been reported in the
literature since it cannot be synthesized by cycloaddition of
2
10
shown in Scheme 3, 2a and 2b were obtained selectively in
good yields (73−80%). All of the new compounds were
characterized by NMR spectroscopy and X-ray crystallography.
It is noteworthy that the splitting or expansion reactions of 1-
functionalized phosphiranes normally occurred at high temper-
ature because of the high energy barrier of the transition
21
2H-phosphole with unsaturated bonds.
Many decarboxylative transformations using metal or
2
2
photocatalysis have been reported in the past decade.
Therefore, we further explored the transformation of 3a to
2a with Mn (CO) . As expected, 3a was converted into 2a
9
,10
state.
2
10
Single crystals of 2c (Scheme 3) suitable for an X-ray
diffraction study were obtained from a mixture of n-hexane and
dichloromethane. The structure of 2c has two symmetric
bridgehead phosphorus atoms that give rise to a single peak at
with 5 mol % Mn (CO) in THF along with p-cresol, which
2 10
23
indicated the elimination of CS2. This result suggests that 3a
is an intermediate product of the reaction from 1a to 2a
(Scheme 4a). Besides, 1,2-diphosphiranylethane−W(CO)5
3
07
Organometallics 2021, 40, 306−309
Wang, Min
