Cyclic trinuclear Rh2M complexes (M = Rh, Pt, Pd, Ni) supported by meso-1,3-bis[(diphenylphosphinomethyl)phenylphosphino]propane

Article abstract of DOI:10.1021/om300278k

Reaction of [MCl₂(cod)] (M = Pd, Pt) with a tetraphosphine, meso-1,3-bis[(diphenylphosphinomethyl)phenylphosphino]propane (dpmppp), afforded the mononuclear complexes [MCl₂(dpmppp)] (M = Pd (3a), Pt (3b)), in which the dpmppp ligand coordinated to the M ion by two inner phosphorus atoms to form a six-membered chelate ring with two outer phosphines uncoordinated. The pendant outer phosphines readily reacted with [RhCl(CO)₂] ₂ to give the cationic heterotrinuclear complexes [MRh ₂(μ-Cl)₃(μ-dpmppp)(CO)₂]X (X = [RhCl ₂(CO)₂], M = Pd (4a), Pt (4b); X = PF₆, M = Pd (5a), Pt (5b)). The nickel analogue [NiRh₂(μ-Cl) ₃(μ-dpmppp)(CO)₂]PF₆ (5c) was also prepared. A neutral homotrinuclear Rh₃ complex, [Rh₃(μ-Cl) ₃(μ-dpmppp)(CO)₂] (6), was synthesized by the reaction of [RhCl(CO)₂]₂ with dpmppp and was further reacted with HgX₂ (X = Cl, Br, I) to afford the Rh₃Hg tetranuclear complexes [Rh₃(HgX)(μ-Cl)₂(μ-X)(μ-dpmppp)(CO) ₂]PF₆ (X = Cl (7a), Br (7b), I (7c)), where the Rh ₃(μ-Cl)₂(μ-X) cores act as tridentate ligands to form three donor-acceptor Rh→Hg interactions. The two CO ligands of 7a-c were replaced by XylNC to yield [Rh₃(HgX)(μ-Cl) ₂(μ-X)(μ-dpmppp)(XylNC)₂]PF₆ (X = Cl (8a), Br (8b), I (8c)). The isocyanides had an appreciable influence on the three Rh→Hg interactions, which was monitored by the ²J _HgP values observed in the ³¹P{¹H} NMR spectra and discussed on the basis of DFT calculations. Complex 6 also reacted with CuCl and HBF₄ to give [Rh₃(CuCl)(μ-Cl)₃(μ- dpmppp)(CO)₂] (9) and [Rh₃(μ₃-H)(μ-Cl) ₃(μ-dpmppp)(CO)₂]BF₄ (10), respectively. These results suggested that the new tetraphosphine dpmppm proved quite useful in constructing fine-tunable heterometallic frameworks.

Full text of DOI:10.1021/om300278k

Article
pubs.acs.org/Organometallics
Cyclic Trinuclear Rh2M Complexes (M = Rh, Pt, Pd, Ni) Supported by
meso-1,3-Bis[(diphenylphosphinomethyl)phenylphosphino]propane
Takayuki Nakajima,* Sachi Kurai, Sayo Noda, Maki Zouda, Bunsho Kure, and Tomoaki Tanase*
Department of Chemistry, Faculty of Science, Nara Women’s University, Kitauoya-nishi-machi, Nara 630-8506, Japan
S
* Supporting Information
ABSTRACT: Reaction of [MCl2(cod)] (M = Pd, Pt) with a tetraphosphine,
meso-1,3-bis[(diphenylphosphinomethyl)phenylphosphino]propane (dpmppp),
afforded the mononuclear complexes [MCl2(dpmppp)] (M = Pd (3a), Pt
(3b)), in which the dpmppp ligand coordinated to the M ion by two inner
phosphorus atoms to form a six-membered chelate ring with two outer
phosphines uncoordinated. The pendant outer phosphines readily reacted with
[RhCl(CO)2]2 to give the cationic heterotrinuclear complexes [MRh2(μ-Cl)3(μ-
dpmppp)(CO)2]X (X = [RhCl2(CO)2], M = Pd (4a), Pt (4b); X = PF6, M =
Pd (5a), Pt (5b)). The nickel analogue [NiRh2(μ-Cl)3(μ-dpmppp)(CO)2]PF6
(5c) was also prepared. A neutral homotrinuclear Rh3 complex, [Rh3(μ-Cl)3(μ-
dpmppp)(CO)2] (6), was synthesized by the reaction of [RhCl(CO)2]2 with
dpmppp and was further reacted with HgX2 (X = Cl, Br, I) to afford the Rh3Hg tetranuclear complexes [Rh3(HgX)(μ-Cl)2(μ-
X)(μ-dpmppp)(CO)2]PF6 (X = Cl (7a), Br (7b), I (7c)), where the Rh3(μ-Cl)2(μ-X) cores act as tridentate ligands to form
three donor−acceptor Rh→Hg interactions. The two CO ligands of 7a−c were replaced by XylNC to yield [Rh3(HgX)(μ-
Cl)2(μ-X)(μ-dpmppp)(XylNC)2]PF6 (X = Cl (8a), Br (8b), I (8c)). The isocyanides had an appreciable influence on the three
Rh→Hg interactions, which was monitored by the 2JHgP values observed in the 31P{1H} NMR spectra and discussed on the basis
of DFT calculations. Complex 6 also reacted with CuCl and HBF4 to give [Rh3(CuCl)(μ-Cl)3(μ-dpmppp)(CO)2] (9) and
[Rh3(μ3-H)(μ-Cl)3(μ-dpmppp)(CO)2]BF4 (10), respectively. These results suggested that the new tetraphosphine dpmppm
proved quite useful in constructing fine-tunable heterometallic frameworks.
[(diphenylphosphinomethyl)phenylphosphino]methane
(dpmppm, tetraphos-1,1,1), which has proven very effective in
assembling linearly ordered tetrametallic chains of group 11
metal ions. Two dpmppm ligands support a flexible tetragold(I)
chain with a bent {Au4(μ-dpmppm)2}4+ motif which captured a
counteranion (X = PF6, Cl) having intriguing switching
luminous properties.5a Ag(I) and Cu(I) ions have also been
assembled by two dpmppm ligands to form the bent and linear
chains {Ag4(μ-dpmppm)2}4+ and {Cu4(μ-X)3(μ-dpmppm)2}+
with a variety of ancillary ligands,5b,c and the latter CuI4 chains
could further be transformed to the ladder-type CuI8 complexes
[Cu8(μ-X)2(μ3-X)6(μ-dpmppm)2] (X = Cl, Br, I). The
heterometallic octanuclear rings {[Au2MCuCl2(μ-
dpmppm)2]2}4+ (M = Au, Ag, Cu) were also synthesized and
elucidated to incorporate a BF4− anion into the ring in the solid
and solution states.5d The flexible coordination behavior of
dpmppm further organized the stepwise assembly of the
heterotrinuclear metal ions [PdCl2(Cp*M′Cl2)(Cp*MCl2)(μ-
dpmppm-κ2,κ1,κ1)] and [PdCl(μ-Cl)(Cp*M′Cl)(Cp*MCl2)(μ-
dpmppm-κ2,κ1,κ1)]+ (M, M′ = Rh, Ir, Cp* = pentamethylcy-
clopentadienyl).5e These studies demonstrated the potential
versatility of multimetallic structures constructed by utilizing
methylene-bridged tetraphosphine ligands.
INTRODUCTION
■
Transition-metal clusters are of potential interest due to their
diverse properties as molecular-based functional materials such
as catalysts and electronic and magnetic devices induced by
synergistic effects between adjacent metal centers.1 Designing
metal supporting ligands is crucial to tuning metal−metal
interactions in various structures of multinuclear complexes.
Among a number of polydentate ligands stabilizing multi-
metallic systems, polyphosphine ligands such as bis-
(diphenylphosphino)methane (dppm) and bis-
(diphenylphosphinomethyl)phenylphosphine (dpmp) have
been widely used to create metal−metal-bonded homo- and
heteromultinuclear structures.2 However, tetraphosphine li-
gands, in contrast to di- and triphosphines, have still been
limited due to their synthetic difficulty and complicated
stereoisomerism. The linearly ordered tetraphosphines bis-
[((2-diphenylphosphino)ethyl)phenylphosphino]methane (tet-
raphos-2,1,2), 1,2-bis[((2-diphenylphosphino)ethyl)-
phenylphosphino]ethane (tetraphos-2,2,2), and 1,3-bis[((2-
diphenylphosphino)ethyl)phenylphosphino]propane (tetra-
phos-2,3,2) and their derivatives have been known to form
mono- and dinuclear systems;3 however, multinuclear struc-
tures containing more than three metal ions supported by these
linear tetraphosphines are limited to a few examples with Au4,
Re4, Pt2Pd, and PdRu2 centers.4 Recently, we have synthesized
a methylene-bridged linear tetraphosphine ligand, meso-bis-
Received: April 6, 2012
Published: May 22, 2012
© 2012 American Chemical Society
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Organometallics
Article
(KBr): ν 1433 (s), 735 (s), 691 (s) cm−1. UV−vis (CH2Cl2): λmax (log
ε) 331 nm (4.95). ESI-MS (CH2Cl2): m/z 796.860 (z1, [PdCl-
(dpmppp)]+ (797.082)).
[PtCl2(dpmppp)]·0.5CH2Cl2 (3b·0.5CH2Cl2). By a procedure
similar to that for 3a, treating 2 (37 mg, 0.056 mmol) with
[PtCl2(cod)] (21 mg, 0.056 mmol), colorless crystals of 3b·0.5CH2Cl2
were isolated in 42% yield (22 mg). Anal. Calcd for C41.5H41Cl3P4Pt:
C, 51.65; H, 4.28. Found: C, 51.72; H, 4.02. IR (KBr): ν 1434 (s), 736
(s), 691 (s) 490 (m) cm−1. ESI-MS (CH2Cl2): m/z 886.945 (z1,
[PtCl(dpmppp)]+ (887.142)).
In this study, we have extended our study with dpmppm to
that with
a new tetraphosphine, meso-1,3-bis-
[(diphenylphosphinomethyl)phenylphosphino]propane
(dpmppp, tetraphos-1,3,1), aiming to construct various homo-
and heteromultinuclear structures by tuning the length of the
central methylene chain to a 1,3-propylene unit. The dpmppp
ligand has been shown to stabilize cyclic trinuclear Rh2M
complexes, [Rh3(μ-Cl)3(μ-dpmppp)(CO)2] and [MRh2(μ-
Cl)3(μ-dpmppp)(CO)2]+ (M = Pt, Pd, Ni). In addition, the
homotrinuclear Rh3 complex was revealed to further react with
HgII and CuI salts to form tetranuclear Rh3Hg complexes,
[Rh3(HgX)(μ-Cl)2(μ-X)(μ-dpmppp)(CO)2]+ (X = Cl, Br, I),
and [Rh3(CuCl)(μ-Cl)3(μ-dpmppp)(CO)2]. We wish to report
herein the synthesis, characterization, and electronic structures
of the tri- and tetranuclear complexes assembled by the new
tetraphosphine ligand dpmppp.
[PdRh2(μ-Cl)3(μ-dpmppp)(CO)2][RhCl2(CO)2] (4a). A dichloro-
methane solution (10 mL) of 3a (18 mg, 0.020 mmol) and
[RhCl(CO)2]2 (8.5 mg, 0.020 mmol) was stirred at room temperature
for 1 h. The solvent was concentrated to ca. 3 mL. After addition of
diethyl ether, the solution was allowed to stand in the refrigerator to
afford orange crystals of 4a. Yield: 12 mg, 44%. Anal. Calcd for
C45H40Cl5O4P4PdRh3: C, 39.71; H, 2.96. Found: C, 39.36; H, 3.00. IR
(KBr): ν 2067 (s), 2008 (s), 1996 (s), 1984 (s), 1434 (m) cm−1. UV−
vis (CH2Cl2): λmax (log ε) 332 nm (3.94). 1H NMR (CD2Cl2): δ 0.88
(br, 2H, CH2), 1.36 (br, 2H, CH2), 2.41 (br, 2H, CH2), 3.08 (br, 2H,
CH2), 3.99 (br, 2H, CH2), 7.3−8.3 (m, 30H, Ph). 31P{1H} NMR
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were carried out under a
nitrogen atmosphere using standard Schlenk techniques. 1,3-Bis-
(phenylphosphino)propane was prepared by the reported procedure.6
Reagent grade solvents were dried by standard procedures and were
freshly distilled prior to use. IR spectra were recorded on a Jasco FT/
IR-410 spectrophotometer. 1H and 31P{1H} NMR spectra were
recorded on a Bruker AV-300N spectrometer at 300 and 121 MHz,
(CD2Cl2): δ 13.0 (d, JPP = 20 Hz, Pin), 38.2 (dd, JPRh = 167 Hz, JPP
=
20 Hz, 2P, Pout).
[PtRh2(μ-Cl)3(μ-dpmppp)(CO)2][RhCl2(CO)2]·0.5CH2Cl2
(4b·0.5CH2Cl2). By a method similar to that for 4a, using 3b (19 mg,
0.020 mmol) and [RhCl(CO)2]2 (8.2 mg, 0.021 mmol), orange
crystals of 4b·0.5CH2Cl2 were isolated. Yield: 12 mg, 40%. Anal. Calcd
for C45.5H41Cl6O4P4PdRh3: C, 36.72; H, 2.77. Found: C, 36.79; H,
2.55. IR (KBr): ν 2067 (s), 2009 (s), 1996 (s), 1985 (s), 1434 (m),
1
respectively. H NMR spectra were referenced to TMS as an external
standard, and 31P{1H} NMR spectra were referenced to 85% H3PO4 as
an external standard. ESI-TOF MS spectra were recorded on a JEOL
JMS-T100LC high-resolution mass spectrometer with positive
ionization mode.
1
1098(m) cm−1. UV−vis: λmax (log ε) 358 (4.02), 430 nm (3.99). H
NMR (CD2Cl2): δ 1.15 (br, 3H, CH2), 2.15 (br, 1H, CH2), 2.55 (br,
2H, CH2), 3.03 (br, 2H, CH2), 3.84 (br, 2H, CH2), 7.2−8.2 (m, 30H,
Ph). 31P{1H} NMR (CD2Cl2): δ −8.1 (dd, JPP = 10, 5 Hz, JPPt = 3479
Hz, 2P, Pin), 38.4 (ddd, JPRh = 166 Hz, JPP = 10, 5 Hz, 2P, Pout).
[PdRh2(μ-Cl)3(μ-dpmppp)(CO)2](PF6) (5a). To a solution of 3a
(20.5 mg, 0.025 mmol) and [RhCl(CO)2]2 (9.7 mg, 0.025 mmol) in
dichloromethane (5 mL) were added NH4PF6 (21 mg, 0.13 mmol)
and methanol (5 mL), and the reaction mixture was refluxed for 1 h.
Concentration of the solvent gave orange crystals of 5a. Yield: 16 mg,
46%. Anal. Calcd for C43H40Cl3F6O2P5PdRh2: C, 40.47; H, 3.16.
Found: C, 40.36; H, 3.41. IR (KBr): ν 2010 (s), 1435 (m), 836 (s)
cm−1. UV−vis (CH2Cl2): λmax (log ε) 348 nm (3.22). ESI-MS
(CH2Cl2): m/z 1130.552 (z1, [PdRh2Cl3(dpmppp)(CO)2]+
meso-/rac-Bis[(trimethylsilylmethyl)phenylphosphino]-
propane (1; tmsppp). To a solution of 1,3-bis(phenylphosphino)-
propane (4.98 g, 17.8 mmol) in THF (140 mL) was added dropwise
n-BuLi (25 mL, 39.3 mmol, 1.57 M in hexane) at −78 °C. At the same
temperature, N,N,N′,N′-tetramethyl-1,2-diaminoethane (TMEDA; 0.55
mL, 3.67 mmol) was added. Then, the cooling bath was removed and
the mixture was stirred at room temperature for 1.5 h. To the mixture
was added (chloromethyl)trimethylsilane (10 mL, 71.6 mmol) at −78
°C. The resultant solution was stirred overnight at room temperature
before degassed H2O (140 mL) was added. The organic phase was
separated, and the aqueous phase was extracted with Et2O (20 mL ×
3). The combined organic extract was dried over Na2SO4, filtered, and
concentrated under reduced pressure to give 1 (7.2 g, 93%). 1H NMR
(CDCl3): δ −0.10 (s, 18H, CH3), −0.09 (s, 18H, CH3), 0.88 (m, 8H,
CH2), 1.25 (m, 4H, CH2), 1.66 (m, 8H, CH2), 7.3−7.5 (m, 20H, Ph).
31P{1H} NMR (CDCl3): δ −31.1 (s, 2P), −31.0 (s, 2P).
1
(1130.818)). H NMR (CD2Cl2): δ 0.88 (br, 2H, CH2), 1.26 (br,
2H, CH2), 2.18 (br, 2H, CH2), 2.87 (br, 2H, CH2), 4.05 (br, 2H,
CH2), 7.3−8.4 (m, 30H, Ph). 31P{1H} NMR (CD2Cl2): δ 12.2 (d, JPP
= 20 Hz, Pin), 38.2 (dd, JPRh = 167 Hz, JPP = 20 Hz, 2P, Pout), −144.5
(sep, JPF = 712 Hz, 1P).
[PtRh2(μ-Cl)3(μ-dpmppp)(CO)2](PF6)·CH2Cl2 (5b·CH2Cl2). By a
procedure similar to that for 5a, using 3b (20 mg, 0.021 mmol),
[RhCl(CO)2]2 (8.5 mg, 0.022 mmol), and NH4PF6 (18 mg, 0.11
mmol), orange crystals of 5b·CH2Cl2 were isolated. Yield: 16 mg, 55%.
Anal. Calcd for C44H42Cl5F6O2P5PdRh2: C, 36.45; H, 2.92. Found: C,
36.22; H, 2.89. IR (KBr): ν 2010 (s), 1436 (m), 1098 (m), 840 (s)
cm−1. UV−vis (CH2Cl2): λmax (log ε) 364 nm (4.02), 432 (3.99). ESI-
MS (CH2Cl21): m/z 1218.974 (z1, [PtRh2Cl3(dpmppp)(CO)2]+
(1218.879)). H NMR (CD2Cl2): δ 1.15 (br, 3H, CH2), 2.08 (br,
1H, CH2), 2.26 (br, 2H, CH2), 2.76 (br, 2H, CH2), 3.87 (br, 2H,
CH2), 7.2−8.2 (m, 30H, Ph). 31P{1H} NMR (CD2Cl2): −8.8 (dd, JPP
= 10, 5 Hz, JPPt = 3478 Hz, 2P, Pin), 38.5 (ddd, JPRh = 165 Hz, JPP = 10,
5 Hz, 2P, Pout), −144.6 (sep, JPF = 711 Hz, 1P).
[NiRh2(μ-Cl)3(μ-dpmppp)(CO)2](PF6) (5c). To a solution of
dpmppp (52 mg, 0.078 mmol) in dichloromethane (10 mL) and
methanol (7.5 mL) was added NiCl2·6H2O (18 mg, 0.077 mmol), and
the reaction mixture was stirred at room temperature for 1 h. The
solvent was removed under reduced pressure to dryness, and the
residue was washed with Et2O (5 mL × 3) and extracted with 10 mL
of dichloromethane. To the extract were added [RhCl(CO)2]2 (30 mg,
0.076 mmol) and NH4PF6 (66 mg, 0.40 mmol), and the reaction
mixture was stirred at room temperature for 12 h. The mixture was
m e s o - 1 , 3 - B i s [ ( d i p h e n y l p h o s p h i n o m e t h y l ) -
phenylphosphino]propane (2; dpmppp). To 7.20 g (16.6 mmol)
of 1 was added PPh2Cl (7.35 g, 33.3 mmol) at room temperature, and
the mixture was refluxed at 120 °C for 1 h. By addition of dry EtOH
(140 mL) white precipitates were formed, which were filtered off,
washed with Et2O (20 mL × 3), and dried under vacuum to give
dpmppp as a mixture of meso and rac isomers (2; meso:rac = 3:1; 2.13
g, 20%). 1H NMR (CDCl3): δ 1.39 (m, 2H, CH2), 1.78 (m, 4H, CH2),
2.37 (m, 4H, CH2), 7.3−7.4 (m, 30H, Ph). 31P{1H} NMR (CDCl3): δ
−30.8 (d, JPP = 116 Hz, rac), −30.6 (d, JPP = 115 Hz, meso), −22.7 (d,
JPP = 115 Hz, meso), −22.6 (d, JPP = 116 Hz, rac).
[PdCl2(dpmppp)]·0.75CH2Cl2 (3a·0.75CH2Cl2). To a solution of
2 (46 mg, 0.071 mmol) in dichloromethane (10 mL) was added
[PdCl2(cod)] (20 mg, 0.071 mmol), and the reaction mixture was
stirred at room temperature for 1 h. The solvent was removed under
reduced pressure to dryness, and the residue was washed with Et2O (5
mL × 3) and extracted with 5 mL of dichloromethane. The extract was
concentrated to ca. 3 mL. After addition of diethyl ether, the solution
was allowed to stand in the refrigerator to afford pale yellow crystals of
3a, which were collected by filtration, washed with Et2O, and dried
under reduced pressure. Yield: 44 mg, 75%. Anal. Calcd for
C41.75H40.5Cl3.5P4Pd: C, 55.86; H, 4.66. Found: C, 55.92; H, 4.55. IR
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Organometallics
Article
Table 1. Crystallographic Data of Complexes 3a, 3b·H2O, and 4a,b
3a
3b·H2O
4a
4b
formula
formula wt
cryst syst
space group
a, Å
C41H40Cl2P4Pd
833.97
C41H42Cl2OP4Pt
940.67
C45H40Cl5O4P4PdRh3
1361.09
C45H40Cl5O4P4PtRh3
1449.78
triclinic
triclinic
monoclinic
P21/n
monoclinic
P21/n
P1
̅
P1
̅
12.9431(6)
12.9473(1)
14.0177(4)
79.240(15)
70.22(1)
60.12(1)
1916.2(1)
2
12.9466(2)
12.9941(2)
14.0856(1)
81.45(2)
70.32(2)
60.17(2)
1935.0(4)
2
14.751(1)
22.467(1)
15.888(1)
14.806(5)
22.404(7)
15.943(5)
b, Å
c, Å
α, deg
β, deg
γ, deg
113.480(3)
113.955(4)
V, Å3
4829.4(6)
4
4833(3)
4
Z
temp, °C
D
μ(Mo Kα), mm−1
−120
1.445
−120
1.614
−120
1.872
1.822
6−55
0.070
43 730
10 774
7065
−120
1.992
4.329
6−55
0.048
44 130
10 879
8726
561
calcd, g cm−3
0.820
3.947
2θ range, deg
6−55
0.015
6−55
0.033
Rint
no. of rflns collected
no. of unique rflns
no. of obsd rflns (I > 2σ(I))
no. of variables
17 246
8281
17 661
8441
7613
7838
435
443
565
a
R1
0.028
0.038
0.038
0.077
0.033
0.075
0.935
b
wR2
0.073
0.100
GOF
0.948
1.023
0.880
a
b
2
2
R1 = ∑||Fo| − |Fc||/∑|Fo| (for observed reflections with I > 2σ(I)). wR2 = [∑w(Fo − Fc2)2/∑w(Fo )2]1/2 (for all reflections).
passed through a filter and concentrated to ca. 3 mL. After addition of
diethyl ether, the solution was allowed to stand in the refrigerator to
afford dark brown crystals of 5c. Yield: 39 mg, 40%. Anal. Calcd for
C43H40Cl3F6O2P5NiRh2: C, 42.04; H, 3.28. Found: C, 41.84; H, 3.68.
IR (KBr): ν 2009 (s), 1436, 1098 (s), 837 (m). ESI-MS (CH2Cl2): m/
NMR (CD3CN): δ 2.11 (m, 1H, CH2), 2.50 (m, 2H, CH2), 2.81
(m, 1H, CH2), 2.98 (m, 2H, CH2), 3.24 (m, 2H, CH2), 3.47 (m, 2H,
CH2), 7.17−7.91 (br, 30H, Ph). 31P{1H} NMR (CD3CN): δ 30.7 (dt,
1JRhP = 131 Hz, JPP = 6 Hz, 2JHgP = 335 Hz), 39.5 (dt, 1JRhP = 151, Hz
2
JPP = 7 Hz, JHgP = 66 Hz), −144.2 (sep, JPF = 706 Hz, 1P).
1
z 1082.900 (z1, [NiRh2Cl3(dpmppp)(CO)2]+ (1082.848)). H NMR
[Rh3(HgBr)(μ-Cl)2(μ-Br)(μ-dpmppp)(CO)2]PF6·0.5CH2Cl2
(7b·0.5CH2Cl2). By a procedure similar to that for 7a, 6 (24.6 mg,
0.021 mmol) was reacted with HgBr2 (8.1 mg, 0.023 mmol) and
NH4PF6 (27.3 mg, 0.17 mmol) to afford purple crystals of
7 b · 0 . 5 C H 2 C l2 ( 1 3 . 6 m g , 3 9 % ) . A n a l . C a l c d f o r
C43.5H41Br2Cl3F6HgO2P5Rh3: C, 31.86; H, 2.52. Found: C, 31.63; H,
2.56. IR (KBr): ν 2042 (s), 2019 (s) 1435 (m), 1097 (m), 836 (s)
cm−1. UV−vis (CH2Cl2): λmax (log ε) 546 nm (4.36). ESI-MS
(CH2Cl2): m/z 1451.766 (z1, [Rh3(HgBr)Cl2Br(dpmppp)(CO)2]+
(1451.648)). 1H NMR (CD3CN): δ 2.04 (m, 1H, CH2), 2.50 (m, 2H,
CH2), 2.82 (m, 1H, CH2), 3.00 (m, 2H, CH2), 3.25 (m, 2H, CH2),
3.48 (m, 2H, CH2), 7.18−7.86 (br, 30H, Ph). 31P{1H} NMR
(CD2Cl2): δ 0.93 (br, 2H, CH2), 1.19 (br, 1H, CH2), 1.78 (br, 2H,
CH2), 2.00 (br, 1H, CH2), 2.50 (br, 2H, CH2), 3.71 (br, 2H, CH2),
7.3−8.3 (m, 30H, Ph). 31P{1H} NMR (CD2Cl2): δ 3.3 (t, JPP = 11 Hz,
2P, Pin), 38.3 (dt, JPRh = 164 Hz, JPP = 11 Hz, 2P, Pout), −144.6 (sep,
JPF = 711 Hz, 1P).
[Rh3(μ-Cl)3(μ-dpmppp)(CO)2]·0.25CH2Cl2 (6·0.25CH2Cl2). To a
solution of 2 (28 mg, 0.042 mmol) in dichloromethane (10 mL) was
added [RhCl(CO)2]2 (25 mg, 0.063 mmol), and the reaction mixture
was stirred at room temperature for 1 h. The solvent was removed
under reduced pressure to dryness, and the residue was washed with
Et2O (5 mL × 3) and extracted with 5 mL of dichloromethane. The
extract was concentrated to ca. 3 mL, and diethyl ether was carefully
added; this mixture was allowed to stand in the refrigerator to afford
red crystals of 6·0.25CH2Cl2. Yield: 17 mg, 37%. Anal. Calcd for
C43.25H40.5Cl3.5O2P4Rh3: C, 45.21; H, 3.55. Found: C, 45.19; H, 3.86.
IR (KBr): ν 1980 (s), 1433 (m), 735 (s), 691 (s) cm−1. UV−vis
(CH2Cl2): λmax (log ε) 300 nm (3.52), 434 (3.53). 1H NMR
(CD2Cl2): δ 0.96 (br, 3H, CH2), 1.24 (br, 1H, CH2), 1.75 (br, 2H,
CH2), 2.48 (br, 2H, CH2), 3.80 (br, 2H, CH2), 7.2−8.3 (m, 30H, Ph).
31P{1H} NMR (CD2Cl2): δ 22.5 (ddd, JPRh = 175 Hz, JPP = 20, 12 Hz,
2P, Pin), 38.7 (ddd, JPRh = 173 Hz, JPP = 20, 20 Hz, 2P, Pout).
[Rh3(HgCl)(μ-Cl)3(μ-dpmppp)(CO)2]PF6 (7a). To a solution of 6
(50 mg, 0.044 mmol) in dichloromethane (13 mL) were added HgCl2
(12 mg, 0.045 mmol) and NH4PF6 (52 mg, 0.32 mmol), and the
reaction mixture was stirred at room temperature overnight. The
solvent was concentrated to ca. 3 mL. After addition of diethyl ether,
the solution was allowed to stand in the refrigerator to afford dark
purple crystals of 7a. Yield: 47 mg, 71%. Anal. Calcd for
C43H40Cl4F6HgO2P5Rh3: C, 34.23; H, 2.67. Found: C, 34.47; H,
2.77. IR (KBr): ν 2043 (s), 1436 (m), 1097 (m), 839 (s) cm−1. UV−
vis (CH2Cl2): λmax (log ε) 544 nm (4.35). ESI-MS (CH2Cl2): m/z
1362.837 (z1, [Rh3(HgCl)Cl3(dpmppp)(CO)2]+ (1362.758)). 1H
1
2
(CD3CN): δ 29.3 (dt, JRhP = 135 Hz, JPP = 6 Hz, JHgP = 302 Hz),
38.7 (dt, 1JRhP = 150 Hz, JPP = 7 Hz, 2JHgP = 69 Hz), −144.3 (sep, JPF
=
706 Hz, 1P).
[Rh3 (HgI)(μ-Cl)2 (μ-I)(μ-dpmppp)(CO)2 ]PF6 ·3CH2 Cl2
(7c·3CH2Cl2). By a procedure similar to that for 7a, using 6 (52 mg,
0.045 mmol), HgI2 (21 mg, 0.047 mmol), and NH4PF6 (54 mg, 0.33
mmol), complex 7c·3CH2Cl2 was isolated as dark purple crystals (52
mg, 59%). Anal. Calcd for C46H46Cl8F6Hg I2O2P5Rh3: C, 28.29; H,
2.38. Found: C, 28.26; H, 2.48. IR (KBr): ν 2036 (s), 2013 (s) 1436
(m), 1098 (m), 836 (s) cm−1. UV−vis (CH2Cl2): λmax (log ε) 382
(4.36), 548 nm (4.18). ESI-MS (CH3CN): m/z 1545.711 (z1,
1
[Rh3(HgI)Cl2I(dpmppp)(CO)2]+ (1546.631)). H NMR (CD3CN):
δ 1.60 (m, 1H, CH2), 2.35 (m, 2H, CH2), 2.62 (m, 1H, CH2), 2.84
(m, 2H, CH2), 3.19 (m, 2H, CH2), 3.38 (m, 2H, CH2), 7.17−7.91 (m,
1
30H, Ph). 31P{1H} NMR (CD3CN): δ 26.4 (br d, JRhP = 139 Hz,
1
2JHgP = 253 Hz), 35.1 (br d, JRhP = 148 Hz), −144.2 (sep, JPF = 706
Hz, 1P).
[Rh3(HgCl)(μ-Cl)3(μ-dpmppp)(XylNC)2]PF6 (8a). To a solution
of 7a (13 mg, 8.3 μmol) in acetonitrile (10 mL) was added 2,6-xylyl
isocyanide (XylNC) (2.5 mg, 0.019 mmol), and the reaction mixture
was stirred at room temperature overnight. The solvent was
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Table 2. Crystallographic Data of Complexes 5a·1.5CH2Cl2, 5b·2CH2Cl2, 5c·2CH2Cl2, 6, and 7a·2CH2Cl2
5a·1.5CH2Cl2
5b·2CH2Cl2
5c·2CH2Cl2
6
7a·2CH2Cl2
formula
formula wt
cryst syst
space group
a, Å
C44.5H43Cl6F6O2P5PdRh
1403.62
monoclinic
P21/c
C45H44Cl7F6O2P5RhPd
1534.77
monoclinic
P21/c
C45H44Cl7F6NiO2P5Rh2
1398.38
monoclinic
P21/c
C43H40Cl3O2P4Rh3
1127.76
C45H44Cl8F6HgO2P5Rh3
1678.63
monoclinic
P21/n
trigonal
P3
̅
28.966(6)
9.3394(3)
17.9855(6)
32.255(1)
90.333(2)
5417.9(3)
4
9.3739(8)
18.0130(2)
32.212(3)
90.7900(9)
5438.5(8)
4
9.4603(9)
18.403(1)
31.204(2)
98.529(4)
5372.6(7)
4
12.881(6)
19.929(8)
21.468(9)
100.104(5)
5425(4)
4
b, Å
c, Å
9.561(2)
β, deg
V, Å3
6948(3)
6
Z
temp, °C
D
μ(Mo Kα), mm−1
2θ range, deg
Rint
−120
1.721
−120
1.874
−120
1.729
−120
1.617
1.399
6−55
0.081
64 804
10 634
7539
498
−120
2.055
calcd, g cm−3
1.429
3.702
1.507
4.323
6−55
0.033
6−55
0.034
6−55
0.055
6−55
0.032
no. of rflns collected
no. of unique rflns
50 574
44 089
48 286
50 583
12 321
12 180
12 156
12 307
no. of obsd rflns (I > 2σ(I)) 10 851
10 726
9466
10 851
no. of variables
608
623
613
621
a
R1
0.057
0.162
1.086
0.047
0.066
0.068
0.208
0.037
b
wR2
0.126
0.194
0.100
GOF
1.083
1.099
0.987
1.092
a
b
2
2
R1 = ∑||Fo| − |Fc||/∑|Fo| (for observed reflections with I > 2σ(I)). wR2 = [∑w(Fo − Fc2)2/∑w(Fo )2]1/2 (for all reflections).
Table 3. Crystallographic Data of Complexes 7b·2CH2Cl2, 7c·2CH2Cl2, 8a·4CH2Cl2, 8b·3.5CH2Cl2, and 8c·3.5CH2Cl2
7b·2CH2Cl2
7c·2CH2Cl2
8a·4CH2Cl2
8b·3.5CH2Cl2
8c·3.5CH2Cl2
formula
C45H44Br2Cl6F6HgO2P5Rh3 C45H44Cl6
C63H66Cl10F6HgN2P5Rh3
C62.5H65Br2Cl9F6HgN2P5Rh3
C62.5H65Cl9F6HgI2N2P5Rh3
F6HgI2O2P5Rh3
1861.53
formula wt
cryst syst
space group
a, Å
1767.53
monoclinic
P21/n
2019.38
monoclinic
P21/c
2101.27
monoclinic
P21/c
2195.27
monoclinic
P21/c
monoclinic
P21/c
12.894(10)
20.027(14)
21.505(16)
99.159(12)
5482(7)
4
12.896(4)
20.279(6)
21.529(7)
99.757(4)
5549(3)
4
10.069(5)
40.21(2)
17.987(8)
90.570(4)
7282(6)
4
10.164(7)
40.57(3)
18.108(13)
90.263(7)
7466(9)
4
10.095(7)
40.30(3)
18.002(12)
90.680(12)
323(9)
4
b, Å
c, Å
β, deg
V, Å3
Z
temp, °C
D
−120
2.141
−120
2.228
−120
1.842
−120
1.864
−120
1.991
calcd, g cm−3
μ(Mo Kα), mm−1
2θ range, deg
Rint
5.643
5.244
3.343
4.262
4.095
6−55
0.059
6−55
0.039
6−55
0.066
6−55
0.054
6−55
0.064
no. of rflns
collected
65 420
51 907
52 478
54 178
41 958
no. of unique rflns 12 519
12 625
10 713
15 947
11 900
15 196
11 408
14 925
10 520
no. of obsd rflns (I 11 033
> 2σ(I))
no. of variables
631
659
824
824
814
a
R1
0.041
0.119
1.117
0.042
0.106
1.104
0.068
0.190
1.063
0.063
0.192
0.065
0.188
1.011
b
wR2
GOF
1.088
a
b
2
2
R1 = ∑||Fo| − |Fc||/∑|Fo| (for observed reflections with I > 2σ(I)). wR2 = [∑w(Fo − Fc2)2/∑w(Fo )2]1/2 (for all reflections).
concentrated to ca. 3 mL. After addition of diethyl ether, the solution
was allowed to stand in the refrigerator to afford dark purple crystals of
8a. Yield: 8.0 mg, 61%. Anal. Calcd for C59H58N2Cl4F6P5HgRh3: C,
41.32; H, 3.41; N, 1.63. Found: C, 41.58; H, 3.31; N, 1.63. IR (KBr): ν
2130 (s), 1435 (m), 1097 (m), 840 (s) cm−1. UV−vis (CH3CN): λmax
(log ε) 570 nm (3.97). ESI-MS (CH2Cl2): m/z 1568.969 (z1,
[Rh3(HgCl)Cl3(dpmppp)(XylNC)2]+ (1568.916)). 1H NMR
(CD3CN): δ 1.19 (m, 2H, CH2), 1.71 (s, 12H, o-CH3), 2.58 (m,
2H, CH2), 2.73 (m, 2H, CH2), 3.36 (m, 2H, CH2), 6.54 (d, 4H, Xyl),
6.74 (t, 2H, Xyl), 7.2−7.8 (m, 30H, Ph). 31P{1H} NMR (CD3CN): δ
29.1 (ddd, JPRh = 150 Hz, JPP = 13, 8 Hz, JPHg = 189 Hz, 2P, Pin), 40.0
(ddd, JPRh = 150 Hz, JPP = 13, 7 Hz, JPHg = 111 Hz, 2P, Pout) −144.5
(sep, JPF = 707 Hz, 1P).
[Rh3(HgBr)(μ-Cl)2(μ-Br)(μ-dpmppp)(XylNC)2]PF6·Et2O
(8b·Et2O). By a procedure similar to that for 8a, using 7b (8.9 mg, 5.4
μmol) and XylNC (1.5 mg, 11.4 μmol), dark purple crystals of
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8b·Et2O were isolated. Yield: 5.2 mg, 53%. Anal. Calcd for
C63H68N2OCl2Br2F6P5HgRh3: C, 40.29; H, 3.65; N, 1.49. Found: C,
39.97; H, 3.54; N, 1.47. IR (KBr): ν 2128 (s), 1435 (m), 1096 (m),
840 (s) cm−1. ESI-MS (CH3CN): m/z 1614.920 (z1, [Rh3HgCl3Br-
(dpmppp)(XylNC)2]+ (1614.865)), 1658.902 (z1, [Rh3(HgBr)Cl2Br-
of 1,3-bis(phenylphosphino)propane with n-BuLi and subse-
quent addition of Me3SiCH2Cl in the presence of TMEDA
afforded 1 (tmsmppp) in 93% yield. Addition of Ph2PCl to 1,
followed by precipitation from EtOH and washing with Et2O,
afforded dpmppp (2) in 20% yield as a mixture of meso and rac
isomers, the ratio of which was determined as ca. 3:1 by NMR
spectroscopic methods (Scheme 1). The meso isomer rich
mixture of dpmppp was used in the preparation of the following
metal complexes.
1
(dpmppp)(XylNC)2]+ (1658.814)). H NMR (CD3CN): δ 1.19 (m,
CH2), 1.82 (s, o-CH3), 1.25 (m, CH2), 2.44 (m, CH2), 2.59 (m, CH2),
2.79 (m, CH2), 3.29 (m, CH2), 3.55 (m, CH2), 6.62−6.90 (m, Xyl),
7.2−7.9 (m, Ph). 31P{1H} NMR (CD3CN): δ 29.9 (d, JPRh = 150 Hz),
38.2 (d, JPRh = 150 Hz, main), 38.9 (d, JPRh = 149 Hz, minor), −144.5
(sep, JPF = 707 Hz).
[Rh3(HgI)(μ-Cl)2(μ-I)(μ-dpmppp)(XylNC)2]PF6·(CH3)2CO
(8c·(CH3)2CO). By a procedure similar to that for 8a, using 7c (13.8
mg, 7.1 μmol) and XylNC (2.1 mg, 16 μmol), from acetone/diethyl
ether solution, dark purple crystals of 8c·(CH3)2CO were isolated.
Yield: 8.7 mg, 65%. Anal. Calcd for C62H64N2OCl2I2F6P5HgRh3: C,
38.07; H, 3.30; N, 1.43. Found: C, 38.46; H, 3.07; N, 1.45. IR (KBr): ν
2125 (s), 1436 (m), 1096 (m), 842 (s) cm−1. ESI-MS (CD3CN): m/z
1660.963 (z1, [Rh3HgCl3I(dpmppp)(XylNC)2]+ (1660.852)),
Scheme 1
1
1752.923 (z1, [Rh3(HgI)Cl2I(dpmppp)(XylNC)2]+ (1752.788)). H
NMR (CD3CN): δ 1.20 (m, CH2), 1.82 (s, o-CH3), 1.88 (s, o-CH3),
1.25 (m, CH2), 2.46 (m, CH2), 2.61 (m, CH2), 2.72 (m, CH2), 3.26
(m, CH2), 3.65 (m, CH2), 6.62−7.00 (m, Xyl), 7.2−8.0 (m, Ph).
31P{1H} NMR (CD3CN): δ 27.4 (JPRh = 153 Hz, main), 27.9 (ddd,
JPRh = 152 Hz, minor), 35.7 (d, JPRh = 160 Hz), −144.5 (sep, JPF = 707
When [MCl2(cod)] (M = Pd, Pt) was treated with 1 equiv of
dpmppp in dichloromethane, the mononuclear complexes
[MCl2(dpmppp-κ2)] (M = Pd (3a), Pt (3b)) were obtained
in 75 and 42% yields, respectively. Complexes 3a,b were
characterized by elemental analysis, ESI-MS spectra, and X-ray
crystallography (Figure 1 and Figure S5 (see the Supporting
Hz).
[Rh3(CuCl)(μ-Cl)3(μ-dpmppp)(CO)2]·Et2O·0.5CH2Cl2
(9·Et2O·0.5CH2Cl2). To a solution of 6 (16 mg, 0.014 mmol) in
dichloromethane (10 mL) was added CuCl (1.4 mg, 0.014 mmol), and
the reaction mixture was stirred at room temperature overnight. From
a dichloromethane/diethyl ether solution at 2 °C, dark violet
microcrystals of 9·Et2O·0.5CH2Cl2 were obtained in 68% yield (12
mg). Anal. Calcd for C47.5H51Cl5Cu3P4Rh3: C, 42.47; H, 3.83. Found:
C, 42.35; H, 4.01. IR (KBr): ν 2024 (s), 1434 (m), 1095 (m), 840 (s),
705 (s) cm−1. 1H NMR (CD2Cl2): δ 1.23 (m, 2H, CH2), 2.38 (m, 2H,
CH2), 3.00 (m, 2H, CH2), 3.44 (m, 2H, CH2), 3.62 (m, 2H, CH2),
7.21−8.01 (br, 30H, Ph). 31P{1H} NMR (CD2Cl2): δ 26.4 (ddd, 1JRhP
= 164 Hz, JPP′ = 14, 8 Hz), 37.6 (ddd, 1JRhP = 158 Hz, JPP′ = 14, 8 Hz).
X-ray Crystallography. Crystals of 3a, 3b·H2O, 4a,b,
5a·1.5CH2Cl2, 5b·2CH2Cl2, 5c·2CH2Cl2, 6, 7a·2CH2Cl2,
7b·2CH2Cl2, 7c·2CH2Cl2, 8a·4CH2Cl2, 8b·3.5CH2Cl2, and
8c·3.5CH2Cl2 suitable for X-ray analyses were obtained by
recrystallization from dichloromethane/diethyl ether solutions and
were quickly coated with Paratone N oil and mounted on top of a loop
fiber at room temperature. Crystal and experimental data are
summarized in Tables 1−3. All data were collected at −120 °C on a
Rigaku AFC8R/Mercury CCD diffractometer equipped with graphite-
monochromated Mo Kα radiation using a rotating-anode X-ray
generator (50 kV, 180 mA) and a Rigaku VariMax Mo/Saturn CCD
diffractometer equipped with graphite-monochromated Mo Kα
radiation using an RA-Micro7 rotating-anode X-ray generator (50
kV, 24 mA). A total of 1440−2160 oscillation images, covering a whole
sphere of 6° < 2θ < 55°, were corrected by the ω-scan method. The
crystal-to-detector (70 × 70 mm) distance was set at 45 or 60 mm.
The data were processed using the Crystal Clear 1.3.5 program
(Rigaku/MSC)7 and corrected for Lorentz−polarization and absorp-
tion effects.8 The structures of complexes were solved by direct
methods with SHELX-979 (4a,b, 6, 7b,c, 8c), SIR-9210a (5c, 7a, 8a,b),
and SIR-9710b (3a, 3b, 5a, 5b), and were refined on F2 with full-matrix
least-squares techniques with SHELXL-979 using the CrystaStructure
4.0 package.11 All non-hydrogen atoms were refined with anisotropic
thermal parameters, and the C−H hydrogen atoms were calculated at
ideal positions and refined with riding models. All calculations were
carried out on a Windows PC with the Crystal Structure 4.0 package.11
Figure 1. ORTEP diagram for the complex [PdCl2(dpmppp)] (3a).
Thermal ellipsoids are drawn at the 40% probability level, and the
hydrogen atoms are omitted for clarity.
Information)). The solid-state structures of 3a,b are iso-
morphous with each other, having a square-planar MII center
coordinated by a dpmppp ligand and two chloride anions. The
dpmppp ligand attaches to the M ion by two inner phosphorus
atoms (P2−Pd−P3 = 88.67(2)° (3a), P2−Pt−P3 = 91.18(3)°
(3b)) to form a six-membered chelate ring with the two outer P
atoms being uncoordinated. The square-planar structures
around MII centers for 3a,b are similar to those found in
[MCl2(dppp)].12 The structures of 3a,b are entirely different
from the case for 1,2-bis[((2-diphenylphosphino)ethyl)-
phenylphosphino]ethane (tetraphos-2,2,2), where the mono-
nuclear complexes [M(tetraphos-2,2,2)]2+ (M = Ni, Pd, Pt)3a−e
were formed with four coordinating phosphorus atoms. The
difference could be attributed to methylene-bridged diphos-
phine units in dpmppp, since the four-membered chelate ring is
known to be less stable than five- and six-membered rings. Due
to the presence of uncoordinated outer phosphines, complexes
3a,b could be good precursors to assemble other metal ions.
The ESI-MS spectra of 3a,b in CH2Cl2 exhibited the parent
peaks for [PdCl(dpmppp)]+ (m/z 796.860) and [PtCl-
RESULTS AND DISCUSSION
■
Mononuclear PdII and PtII Complexes with dpmppp.
The dpmppp ligand was synthesized by a modification of the
procedure used for the synthesis of dpmppm.5a Deprotonation
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(dpmppp)]+ (m/z 886.945), showing the presence of
mononuclear species in the solution state. However, the
31P{1H} NMR spectra of 3a,b in CD2Cl2 showed only broad or
complicated signals in the range of −10 to −50 ppm, which
indicated fluxional behavior of th dpmppp ligand and/or the
presence of asymmetric structures generated by the coordina-
tion of outer phosphorus atoms to the metal center and
simultaneous dissociation of chloride anions from the metal
and vice versa.
Cyclic Heterotrinuclear Complexes of [MRh2(μ-Cl)3(μ-
dpmppp)(CO)2]X (X = [RhCl2(CO)2], M = Pd (4a), Pt (4b);
X = PF6, M = Pd (5a), Pt (5b), Ni (5c)). Treatment of 3a and
3b with 1 equiv of [RhCl(CO)2]2 in dichloromethane yielded
cyclic Rh2M heterotrinuclear complexes formulated as
[MRh2(μ-Cl)3(μ-dpmppp)(CO)2][RhCl2(CO)2] (M = Pd
(4a), Pt (4b)) in 44 and 40% yields, respectively (Scheme
2). The 31P{1H} NMR spectrum of 4a showed two sets of
Scheme 2
Figure 2. ORTEP diagrams for the complex cations of (a)
[PdRh2Cl3(dpmppp)(CO)2][RhCl2(CO)2] (4a) and (b)
[PdRh2Cl3(dpmppp)(CO)2]PF6 (5a). The thermal ellipsoids are
drawn at the 40% probability level, and the hydrogen atoms are
omitted for clarity.
resonances at δ 13.0 (d, JPP = 20 Hz) and 38.2 ppm (dd, 1JPRh
=
2
167, JPP = 20 Hz), which are assigned to two inner P atoms
bound to Pd atom and two outer P atoms bound to Rh atoms,
in light of the characteristically large P−Rh coupling constant.
In the spectrum of 4b, the signal for the inner P atoms
significantly shifted to lower frequency in comparison to that of
4a and was observed at δ −8.1 ppm as a doublet of doublets
(JPP = 10, 5 Hz) accompanied by one-bond 195Pt satellite peaks
(1JPPt = 3479 Hz), and the signal for the outer atoms appeared
at δ 38.4 ppm as a doublet of doublets (JPP = 10, 5 Hz) with
31P−103Rh coupling (1JPRh = 166 Hz).
The structures of 4a,b were determined by X-ray
crystallography to be isomorphous with each other; ORTEP
views for the complex cations of 4a,b are given in Figure 2a and
Figure S6 (Supporting Information), respectively, and the
structural parameters are given in Table S1 (Supporting
Information). The complex cation of 4 involves a cyclic six-
membered {MRh2(μ-Cl)3} core, in which the MII ion is
chelated by the inner phosphine units of dpmppp and the two
Rh(I) metals are coordinated by the outer P atoms. The
interatomic distances between three metal ions (2.9917(3)−
3.3748(4) Å (4a) and 3.0163(3)−3.3883(4) Å (4b)) indicate
the absence of metal−metal bonding interactions. The square-
planar structure around the M atom is retained as found in 3,
and each RhI metal adopts a square-planar geometry with a
terminal CO ligand and the outer P and two μ-Cl atoms. An
agnostic or weak interaction between Rh2 and the o-H atom
(H1) of the phenyl ring bound to the P4 atom is observed
(Rh2−H1 = 2.85 (4a), 2.90 Å (4b)), which brings about a
slight distortion of the square-planar geometry around the Rh2
center with the CO ligand tilted away from the square plane
(Cl2−Rh2−C2 = 166.9(1) (4a), 166.7(1)° (4b)). Such an
interaction and distortion was not observed around the Rh1
atom (Cl1−Rh1−C1 = 174.1(1) (4a), 173.8(1)° (4b)), leading
to asymmetrical structures in the solid state, which should be
contrasted with the symmetrical features in the solution state.
−
Analogous complexes with a PF6 counteranion, [MRh2(μ-
Cl)3(μ-dpmppp)(CO)2]PF6 (M = Pd (5a), Pt (5b)), were
synthesized by reacting 3a,b with 1 equiv of [RhCl(CO)2]2 in
the presence of an excess amount of NH4PF6 in 46 and 55%
yields, respectively (Scheme 2). The Rh2Ni analogue [NiRh2(μ-
Cl)3(μ-dpmppp)(CO)2]PF6 (5c) was prepared in 40% yield by
successive reactions of NiCl2·6H2O, first treated with 1 equiv of
dpmppp in methanol and followed by 1 equiv of [RhCl(CO)2]2
in the presence of NH4PF6. The crystal structures of 5a−c are
isomorphous and essentially identical. A perspective plot for the
complex cation of 5a is illustrated in Figure 2b (those of 5b,c
are shown in Figures S7 and S8, Supporting Information), and
the representative structural parameters are given in Table 4.
The complex cations of 5a−c possess pseudo-Cs symmetry and
are similar to those of 4a,b except for the absence of the weak
Rh−H interaction. For the six-membered {MRh2(μ-Cl)3} cores
in 5a−c, the metal−metal distances in 5c (3.0558(7)−
3.1961(6) Å) are shorter by ca. 0.1−0.2 Å than the
corresponding distances in 5a,b (3.1884(4)−3.2975(4) (5a),
3.2565(4)−3.3112(5) Å (5b)), which is ascribed mainly to the
Ni−Cl bond lengths being shorter than those for Pd and Pt
ions. The ν(CO) frequency of 5a−c appeared around 2010
cm−1, consistent with the presence of terminal CO. In the
31P{1H} NMR spectrum of 5a−c, two sets of resonances were
observed (Figure S13, Supporting Information); the peaks for
the outer P atoms appeared at δ 38.2 (5a), 38.5 (5b), and 38.3
1
ppm (5c) with characteristic Rh−P couplings of JRhP = 167
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Table 4. Structural Parameters of 5a−c
Scheme 3
5a
5b
5c
M
Pd
Pt
Ni
M···Rh1, Å
M···Rh2, Å
Rh1···Rh2, Å
M−P2, Å
M−P3, Å
Rh1−P1, Å
Rh2−P4, Å
M−Cl1, Å
M−Cl2, Å
Rh1−Cl1, Å
Rh1−Cl3, Å
Rh2−Cl2, Å
Rh2−Cl3, Å
Rh1−C1, Å
3.2584(4)
3.1884(4)
3.2975(4)
2.2467(9)
2.2570(9)
2.225(1)
2.230(1)
2.3952(9)
2.3920(9)
2.396(1)
2.4170(9)
2.398(1)
2.4349(9)
1.811(5)
1.811(5)
88.91(3)
88.79(3)
88.90(3)
85.69(3)
83.46(3)
85.63(3)
175.0(2)
175.5(2)
3.2702(4)
3.2565(4)
3.3112(5)
2.236(1)
2.246(1)
2.231(1)
2.229(1)
2.402(1)
2.390(1)
2.413(1)
2.424(1)
2.411(1)
2.449(1)
1.811(7)
1.811(6)
87.06(4)
88.54(4)
89.23(4)
85.57(3)
85.43(4)
85.60(3)
176.6(2)
173.0(2)
3.1026(8)
3.0558(7)
3.1961(6)
2.169(2)
2.179(2)
2.228(1)
2.248(2)
2.247(2)
2.206(3)
2.391(2)
2.434(2)
2.353(3)
2.452(1)
1.803(7)
1.812(8)
89.03(8)
87.75(6)
87.35(7)
83.91(7)
84.10(8)
81.70(5)
175.3(3)
175.9(3)
31P{1H} NMR spectrum of 6 showed two sets of resonances at
δ 22.5 (JPRh = 175 Hz) and 38.7 ppm (JPRh = 173 Hz) (Figure
S14a, Supporting Information), which are assignable to two
1
inner and two outer P atoms, respectively, by 2D H−31P
Rh2−C2, Å
HMBC NMR techniques (Figure S15, Supporting Informa-
tion).
Cl1−M−Cl2, deg
Cl1−Rh1−Cl3, deg
Cl2−Rh2−Cl3, deg
M−Cl1−Rh1, deg
M−Cl2−Rh2, deg
Rh1−Cl3−Rh2, deg
Cl1−Rh1−C1, deg
Cl2−Rh2−C2, deg
(5a), 165 (5b), and 164 Hz (5c), while the peaks for the inner
P atoms significantly shifted depending on the M ion at δ 12.2
(5a), −8.8 (5b), and 3.3 ppm (5c). The ESI−MS spectra in
dichloromethane showed monovalent parent peaks at m/z
1130.552 (5a), 1218.974 (5b), and 1082.900 (5c) correspond-
ing to {MRh2Cl3(dpmppp)(CO)2}+ with m/z 1130.818 (M =
Pd), 1218.879 (M = Pt), and 1082.848 (M = Ni), indicating
that the solid-state structures were retained in solution.
A few related complexes with cyclic M3(μ-Cl)3 (M = Rh, Pd,
Pt) structures have been reported so far; however, all of these
were homotrimetallic compounds.13 The complexes 4a,b and
5a−c are the first examples of such heteronuclear complexes,
demonstrating that the dpmppm ligand is effective in
assembling heterometal ions into the cyclic MRh2(μ-Cl)3
motif in two steps. In the first step, the inner phosphines
bind to MII ions to form a stable six-membered chelate ring,
and in the second step, the uncoordinated outer phosphines
trap the Rh2 fragment to complete the unusual cyclic {MRh2(μ-
Cl)3} core in good yields.
Homotrinuclear Complex [Rh3(μ-Cl)3(μ-dpmppp)-
(CO)2] (6). Reaction of dpmppp with 1.5 equiv of [RhCl-
(CO)2]2 in dichloromethane afforded a neutral Rh3 homo-
trinuclear complex, [Rh3(μ-Cl)3(μ-dpmppp)(CO)2] (6), in
37% yield (Scheme 3). Unlike the stepwise formation of the
Rh2M complexes (M = Pd, Pt, Ni), any mononuclear complex
formulated as {RhCl(CO)(dpmppm)} were not obtained even
when 2 was treated with 0.5 equiv of [RhCl(CO)2]2. The
Figure 3. ORTEP diagram of [Rh3Cl3(dpmppp)(CO)2] (6). The
thermal ellipsoids are drawn at the 40% probability level, and the
hydrogen atoms are omitted for clarity.
The solid-state structure of 6 (Figure 3, Table 5) is closely
similar to those of 4 and 5, in which the divalent MII ion (M =
Pd, Pt, Ni) is replaced by a monovalent RhI ion, resulting in a
neutral complex with a Rh3(μ-Cl)3 cyclic structure. Three RhI
ions form an equilateral triangle without any bonding
interaction between them (Rh−Rh = 3.1461(7)−3.2293(7)
Å), the values of which are comparable to those found in the
related trinuclear rhodium complexes [Rh3(μ-Cl)3(MeN-
(PF2)2)3] (Rh−Rh = 3.0964(1) Å (average))13a and [Rh3(μ-
Cl)3(CH2(P(OPh)2)2)3] (Rh−Rh = 3.2023(3)−3.4627(4)
Å).13b Whereas the Rh−CO distances (average 1.809 Å) are
not appreciably reduced from those of complexes 5a−c, the
ν(CO) frequency of 6 (1980 cm−1) shifted remarkably to lower
energy from the corresponding values of complexes 5a−c
(2009−2010 cm−1), suggesting stronger π back-donation from
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Table 5. Structural Parameters of 6, 7a, and 8a
6
7a
8a
Rh1−Hg, Å
Rh2−Hg, Å
Rh3−Hg, Å
Rh1···Rh2, Å
Rh1···Rh3, Å
Rh2···Rh3, Å
Rh1−P1, Å
Rh2−P2, Å
Rh2−P3, Å
Rh3−P4, Å
Rh1−Cl1, Å
Rh1−Cl3, Å
Rh2−Cl1, Å
Rh2−Cl2, Å
Rh3−Cl2, Å
Rh3−Cl3, Å
2.7414(9)
2.6408(8)
2.7295(9)
3.194(1)
3.617(1)
3.265(1)
2.254(1)
2.228(1)
2.222(1)
2.280(1)
2.383(1)
2.447(1)
2.432(1)
2.426(1)
2.374(1)
2.436(1)
1.830(4)
1.825(4)
72.76(3)
82.77(2)
74.88(2)
91.46(4)
87.20(4)
87.67(5)
83.08(4)
85.73(4)
95.59(5)
2.733(1)
2.685(1)
2.707(1)
3.282(2)
3.533(2)
3.271(2)
2.235(3)
2.226(3)
2.226(3)
2.237(3)
2.378(3)
2.419(3)
2.408(3)
2.412(3)
2.384(3)
2.426(3)
1.880(9)
1.876(9)
74.56(3)
81.01(3)
74.71(3)
89.80(8)
87.44(7)
92.10(8)
86.56(8)
86.00(7)
93.65(8)
3.1813(9)
3.2293(7)
3.1461(7)
2.225(2)
2.180(2)
2.191(2)
2.216(2)
2.393(2)
2.416(2)
2.441(2)
2.416(2)
2.402(2)
2.429(2)
1.80(1)
Rh1−C1, Å
Rh3−C2, Å
1.817(8)
Rh1−Hg−Rh2, deg
Rh1−Hg−Rh3, deg
Rh2−Hg−Rh3, deg
Cl1−Rh1−Cl3, deg
Cl1−Rh2−Cl2, deg
Cl2−Rh3−Cl3, deg
Rh1−Cl1−Rh2, deg
Rh2−Cl2−Rh3, deg
Rh1−Cl3−Rh2, deg
87.98(6)
89.46(5)
87.86(6)
82.33(4)
81.53(5)
83.61(4)
the Rh1 and Rh3 atoms occurring due to the presence of the
Rh2 atom.
Reactions of 6 Leading to Tetranuclear Rh3Hg and
Rh3Cu Complexes. The cluster cores of the Rh2M and Rh3
complexes can be recognized as two-apex-truncated cubanes
(Chart 1), possessing two vacant sites surrounded by three
with 1 equiv of HgX2 (X = Cl, Br, I) in the presence of an
excess amount of NH4PF6 to afford Rh3Hg tetranuclear
complexes formulated as [Rh3(HgX)(μ-Cl)2(μ-X)(μ-dpmppp)-
(CO)2]PF6 (X = Cl (7a), Br (7b), I (7c)) in 71, 39, and 59%
yields, respectively (Scheme 3). An ORTEP diagram for the
complex cation of 7a is given in Figure 4a (those of 7b,c are
shown in Figures S9 and S10 in the Supporting Information),
and the structural parameters are summarized in Table 5 and
Table S2 (Supporting Information). The complex cations of
7a−c have an incomplete cubane framework comprised of a
{Rh3(HgX)(μ-Cl)2(μ-X)} core, where the d10 HgIIX fragment
occupies three apical positions of the square-pyramidal
coordination geometry of each rhodium ion in a Rh3(μ3-
HgX) fashion. The chloride ion bridging Rh1 and Rh3 in 6 is
selectively replaced by an X− ion (X = Br, I) in 7b,c; the other
bridging chloride ions were not replaced by X− even on
treatment with an excess amount of HgX2, monitored by
31P{1H} NMR spectra. Although there have been many
examples of M3(μ3-Hg) clusters reported so far,14 the
Rh3Hg(μ-Cl)2(μ-X) cores found in 7 are the first example of
complexes containing three Rh→Hg dative bonds with a
Rh3(μ3-HgX) mode and are similar to those found in the
complexes (NBu4 )[Pt3 PbCl3 (C6 F5 )6 ],15 (NBu4 )-
[Pt3 SnCl3 (C6 F5 )6 ],1 6 and (NBu4 )2 [Pt3 (HgCl)-
Chart 1
metal ions (site A) and by three chloride anions (site B); hence,
we have tried to examine their reactions with d10 HgII and CuI
salts to build up the cubane framework. At first, the
heterotrinuclear Rh2M complexes 5a−c were examined and
no longer reacted with HgCl2 as well as with CuCl and HBF4.
In contrast, the Rh3 homotrinuclear complex 6 readily reacted
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and Hg[RhCl2(PPh3)2]2 (2.5494(8) Å).24 The three Rh−Rh
distances (3.194(1)−3.265(1) (7a), 3.210(2)−3.660(2) (7b),
and 3.2335(5)−3.7560(5) Å (7c)) are elongated systematically
from those of 6 (3.1461(7)−3.2293(7) Å) by introduction of
μ3-HgX and μ-X bridging units. In particular, the halide anions
(X = Cl, Br, I) bridging the Rh1 and Rh3 atoms bring about
structural changes in the Rh3(μ-Cl)2(μ-X) cores depending on
their ionic radii, where the Rh1−Rh3 distances become longer
and the Rh1−X−Rh3 angles smaller in the order I− > Br− >
Cl−. The Rh1−Hg−Rh3 angles (82.77(2) (7a), 83.99(4) (7b),
86.47(1)° (7c)) are slightly larger than the other Rh1−Hg−
Rh2 and Rh2−Hg−Rh3 angles (average 73.82 (7a), 73.97
(7b), 74.71° (7c)) and become larger in the order I− > Br− >
Cl−. These values are comparable to those found in
(NBu4)2[Pt3(HgCl)(OH)3(C6F5)6] but larger than those
found in well-known face-capped M3(μ3-Hg) clusters.14a,b
The ν(CO) vibrational bands in 7a−c appeared at 2043
(7a), 2042 (7b), and 2036 cm−1 (7c), respectively, which were
considerably shifted to higher energy as compared with that of
the parent complex 6 (1980 cm−1), suggesting that the electron
density of Rh1 and Rh3 was reduced by the Rh→Hg donor−
acceptor interactions. The 31P{1H} NMR spectra of 7a,b
exhibited two sets of resonances (39.5, 30.7 (7a); 38.7, 29.3
ppm (7b)) (Figures S14b and S16a, Supporting Information),
which are assigned to two inner and outer P atoms,
respectively, by 1H−31P HMBC NMR techniques and are
accompanied by one-bond 103Rh−31P coupling and two-bond
199Hg−31P satellites. In the case of 7c (Figure S16b, Supporting
Information), two sets of resonances at δ 35.1 and 26.4 ppm are
broad and the two-bond 199Hg−31Pout satellite peaks are not
2
well resolved. The JHgP values of 334 (7a) and 302 Hz (7b)
in
2
are fairly larger than the JHgP values (66 (7a) and 69 Hz
out
(7b)), clearly demonstrating that the Rh2−Hg interaction is
stronger than the other two Rh1/Rh3−Hg interactions in the
solution state. These results are in agreement with the
differences of Rh−Hg distances observed in the crystal
structures. The ESI-MS spectra of 7a−c in acetonitrile showed
parent peaks corresponding to [Rh3(HgX)Cl2X(dpmppp)-
(CO)2]+, consistent with the X-ray and NMR results.
Figure 4. ORTEP diagrams for the complex cations of (a)
[Rh3(HgCl)Cl3(dpmppp)(CO)2]PF6 (7a) and (b) [Rh3(HgCl)-
Cl3(dpmppp)(XylNC)2]PF6 (8a). The thermal ellipsoids are drawn
at the 40% probability level, and the hydrogen atoms are omitted for
clarity.
With an aim of tuning the electronic properties of the Rh3Hg
tetranuclear complexes, an attempt was made to introduce
terminal isocyanide ligands which have stronger σ-donating and
weaker π-accepting abilities in comparison to those of CO
ligands. Complexes 7a−c were treated with 2 equiv of 2,6-xylyl
isocyanide (XylNC) to afford [Rh3(HgX)(μ-Cl)2(μ-X)(μ-
dpmppp)(XylNC)2]PF6 (X = Cl (8a), Br (8b), I (8c)) in 61,
53, and 65% yields, respectively (Scheme 3). The structures of
8a−c were determined by X-ray crystallographic analyses; an
ORTEP diagram for the complex cation of 8a is shown in
Figure 4b (those for 8b,c are shown in Figures S11 and S12 in
the Supporting Information), and the structural parameters are
given in Table 5 and Table S2 (Supporting Information). The
structures of 8a−c are isomorphous and similar to those of 7a−
c, where two CO ligands are replaced by two XylNC ligands.
Importantly, these replacements lead to a remarkable change in
the three Rh−Hg interactions as follows. The Rh2−Hg
distances (2.685(1) (8a), 2.709(2) (8b), 2.679(2) Å (8c)) in
8a−c are still the shortest among the three Rh−Hg interactions
and, however, are appreciably longer than those of the
corresponding bonds in 7a−c (2.6408(8) (7a), 2.666(2)
(7b), 2.6483(3) Å (7c)). On the other hand, the Rh1−Hg
and Rh3−Hg bond distances (average 2.7199 (8a), 2.7310
(OH)3(C6F5)6],17 which involve three Pt→M dative inter-
actions with Pt3(μ3-M) structures. In other words, the cyclic
Rh3(μ-Cl)2(μ-X) core act as a tridentate ligand with three Rh
centers serving as donors to the Lewis acidic HgII ion. Among
the three Rh−Hg interactions, Rh2−Hg distances (2.6408(8)
(7a), 2.6660(15) (7b), 2.6483(3) Å (7c)) are significantly
shorter than the other two distances (Rh1−Hg and Rh3−Hg;
average 2.7355 (7a), 2.7350 (7b), and 2.7414 Å (7c)),
indicating that Rh2→Hg dative interactions are stronger than
the other two Rh1→Hg and Rh3→Hg interactions because the
Rh2 ion attached by the two inner P atoms is more electron-
rich than the Rh1 and Rh3 ions, which are each coordinated by
one outer phosphine and an electron-withdrawing CO ligand.
The Rh−Hg bond lengths are comparable to those found for
donor−acceptor bonds in [Rh2(HgCl)(PPh3)2(CO)2Cl2(pz)2]
(pz = pyrazole; 2.804(3) Å),18 [Rh2(HgCl)(H)(CO)2(EtN(P-
(OPh)2)2)] (2.711(1), 2.778(1) Å),19 [Cp2Rh2(HgCl2)(CO)-
(dppm)] (2.692(1), 2.774(2) Å),20 and Hg[CpFe2Rh(COMe)-
(CO)7]2 (2.737(2) Å)21 but slightly longer than the covalent
bonds in [Rh(HgCl)(CO)Cl2(PPh2Py)2] (2.572(1) Å),22
[Rh(HgPh)Cl(CCCH2OMe)(PiPr3)2] (2.5008(4) Å),23
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(8b), 2.7158 Å (8c)) are shorter than those in 7a−c (average
2.7355 (7a), 2.7350 (7b), 2.7417 Å (7c)). These results
indicate that the Rh2−Hg interaction becomes weaker and the
Rh1/Rh3−Hg interactions become stronger upon replacement
of CO ligands by XylNC. The 31P{1H} NMR spectrum of 8a
(Figure S14c, Supporting Information) is consistent with these
2
structural changes, showing that the JHgP value for the inner P
atoms (189 Hz) is smaller and that for the outer P atoms (111
Hz) is larger than the respective corresponding values in 7a
2
(2JHgP = 334 Hz, JHgP = 66 Hz). The interesting structural
in
out
switch could be recognized as the introduction of the σ-
donating isocyanides increasing the electron density on the Rh1
and Rh3 centers and, consequently, increasing the strength of
the Rh1/Rh3→Hg donor−acceptor interactions.25
Figure 5. (a) 1H{31P} NMR and (b) 1H NMR spectra for the hydride
peak of 10 in CD2Cl2 at room temperature.
When complex 6 was treated with 1 equiv of CuCl, dark
violet microcrystals of [Rh3(CuCl)(μ-Cl)3(μ-dpmppp)(CO)2]
(9) were obtained in good yield. The IR spectrum showed the
presence of terminal CO ligands at 2023 cm−1, and the 31P{1H}
NMR spectrum (Figure S14d, Supporting Information)
exhibited two sets of resonances (doublet of doublets) at δ
with their crystal structures, apart from a systematic elongation
of distances between heavy atoms usually observed in DFT
methods. For 6, higher-lying MOs (HOMO, HOMO-1,
HOMO-4, and HOMO-5) are depicted in Figure S18
(Supporting Information) and are mainly derived from
combinations of dσ orbitals of Rh atoms with respect to the
square coordination planes. The energy level of the most
symmetrical MO (HOMO-4), composed of an in-phase
interaction between the three dσ orbitals, is −5.664 eV, which
is remarkably higher in comparison with the corresponding
MO of 5a (HOMO-21 −10.202 eV) due to the lower energy of
Pd d orbitals (Figure S19, Supporting Information). An energy
mismatch between the occupied Pd d orbitals and empty Hg
sp-hybridized orbital might be responsible for the robust nature
of 5a against the d10 HgIX unit.
37.6 (1JRhP = 158 Hz, JPP′ = 14, 8 Hz) and 26.8 ppm (1JRhP
=
164 Hz, JPP′ = 14, 8 Hz). By analogy to the spectral data of 7a
and 8a, complex 9 is assumed to have a Rh3Cu tetranuclear
structure as depicted in Chart 2, where the d10 CuCl unit caps
Chart 2
For 7a, the symmetrical MO (HOMO-4) of 6 interacts well
with an empty sp-hybridized orbital of the HgX fragment to
generate the LUMO with an antibonding interaction at −5.674
eV and HOMO-25 with a bonding interaction at −10.224 eV
(Figure 6). The latter MO is quite stabilized and is thus
responsible for the Rh3(μ-Hg) bonding interaction in an Rh→
Hg dative fashion. The natural charge population (Rh1, −0.54;
Rh2, −0.61; Rh, −0.51; Hg, +0.88) and Wiberg bond indices
(Hg−Rh1, 0.234; Hg−Rh2, 0.303; Hg−Rh3, 0.233)25 suggest a
stronger dative interaction for Hg−Rh2 than for Hg−Rh1 and
Hg−Rh3 (Figure S20, Supporting Information). In the case of
8a with terminal XylNC ligands instead of COs, the
symmetrical MO (HOMO-4) of 6 interacts more intensely
with the empty sp-hybridized orbital of HgX fragment to
generate an antibonding MO as the LUMO at −4.944 eV and a
bonding MO of HOMO-38 at −10.935 eV (Figure 6), and as a
result, the bonding MO is more stabilized by 0.711 eV on
replacing CO with XylNC. The natural charge population
(Rh1, −0.46; Rh2, −0.61; Rh, −0.45; Hg, +0.86) and Wiberg
bond indices (Hg−Rh1, 0.267; Hg−Rh2, 0.278; Hg−Rh3,
0.266)26 definitively demonstrate that degree of the Hg−Rh2
dative interaction decreases and, instead, those of Hg−Rh1 and
Hg−Rh3 increase (Figure S20, Supporting Information), which
is in good agreement with the results of X-ray crystallographic
and 31P NMR spectroscopic analyses of 7a and 8a as described
above.
the apex surrounded by the three RhI ions with Rh→Cu dative
interactions. Complex 6 readily reacted with 1 equiv of HBF4 to
give the adduct [Rh3(μ-H)(μ-Cl)3(μ-dpmppp)(CO)2]BF4 (10)
in solution quantitatively, which was analyzed by 1H and
31P{1H} NMR spectroscopy. The 31P{1H} NMR spectrum
(Figure S14e, Supporting Information) showed two resonances
at δ 42.7 (1JRhP = 156 Hz, JPP′ = 17, 9 Hz) and 27.9 ppm (1JRhP
= 143 Hz, JPP′ = 17, 9 Hz), the spectral patterns of which were
close to those of 9 except for a further downfield shift of the
1
Pout signals. In the H{31P} NMR spectrum (Figure 5), a
hydride peak was clearly observed at δ −12.32 as a doublet of
1
triplets with JRhH = 29 and 12 Hz. These spectral features are
in good agreement with a hydride-bridged Rh3 structure as
shown in Chart 2, in which the hydride is assumed to interact
more strongly with Rh2 and more weakly with Rh1 and Rh3
centers.
DFT Calculations on 5a, 6, 7a, and 8a. In order to
understand the electronic structures of the Rh3Hg complexes,
especially the Rh→Hg dative interactions, DFT calculations
were performed on complexes 5a, 6, 7a, and 8a with the
Gaussian 03 software package. The initial structures from the
X-ray data were optimized with B3LYP methods using the
lanl2dz basis set; the Los Alamos ECP plus DZ basis set was
used for heavy atoms. The fully optimized structures (Figure
S17a−d, Supporting Information) are essentially consistent
CONCLUSION
■
In the present study, the tetraphosphine dpmppp (meso-1,3-
bis[(diphenylphosphinomethyl)phenylphosphino]propane)
was prepared and proved to be effective in assembling unusual
cyclic MRh2(μ-Cl)3 complexes, [MRh2(μ-Cl)3(μ-dpmppp)-
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Figure 6. Representative MO diagrams for the optimized structures of 7a (left) and 8a (right) by DFT calculations with B3LYP methods.
(CO)2]+ (4, 5: M = Ni, Pd, Pt), in a stepwise fashion through
the mononuclear intermediate complexes [MCl2(dpmppp)]
ASSOCIATED CONTENT
* Supporting Information
■
S
(3), in which the outer phosphine units of dpmppp are
uncoordinated. The cyclic homotrinuclear complex [Rh3(μ-
Cl)3(μ-dpmppp)(CO)2] (6) was also stabilized by dpmppp
and showed interesting reactivity toward Lewis acidic d10 HgIIX
and CuICl units as well as HBF4, yielding the donor−acceptor
adducts [Rh3(HgX)(μ-Cl)2(μ-X)(μ-dpmppp)(CO)2]PF6 (7),
[Rh3(CuCl)(μ-Cl)3(μ-dpmppp)(CO)2] (9), and [Rh3(μ-H)(μ-
Cl)3(μ-dpmppp)(CO)2]BF4 (10), whereas the analogous
Rh2M complexes would not react with such species. Further,
the π-acidic carbonyl ligands of 7 were readily replaced by σ-
donating XylNC ligands to afford [Rh3(HgX)(μ-Cl)2(μ-X)(μ-
dpmppp)(XylNC)2]PF6 (8). In light of the X-ray crystal
Tables, figures, and CIF files giving the structural parameters of
4a,b, 7b,c, and 8b,c, ESI-MS of 3a,b, 5a−c, 7a−c, and 8a−c,
crystal structures of 3b, 4b, 5b,c, 7b,c, and 8b,c, 31P−1H
HMBC spectrum of 6, 31P{1H} NMR spectra of 5a−c, 6, 7a−c,
8a, 9, and 10, results of DFT calculations on 5a, 6, 7a, and 8a,
and crystallographic data for 3a,b, 4a,b, 5a−c, 6, 7a−c, and 8a−
c. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: tanase@cc.nara-wu.ac.jp (T.T.); t.nakajima@cc.nara-
wu.ac.jp (T.N.). Fax: +81 742-20-3847. Tel: +81 742-20-3399.
■
2
structures, 31P{1H} NMR spectral data with JHgP values, and
Notes
The authors declare no competing financial interest.
DFT calculations for 7 and 8, replacement of the auxiliary
terminal ligands (L) from CO to XylNC brought about an
interesting structural change with respect to the Rh→Hg dative
interactions in the Rh3(μ3-Hg) bonding system. These results
suggested that heterometallic multinuclear complexes were
effectively built up by utilizing dpmppm and their electronic
properties could be tuned by varying the auxiliary ligands.
ACKNOWLEDGMENTS
■
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Area 2107 (No. 22108521) from the
Ministry of Education, Culture, Sports, Science and Technol-
ogy of Japan. T.T. is grateful to Nara Women’s University for a
research project grant. T.N. is grateful to Tokuyama Science
4293
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