Preparation, crystal structures and spectroscopic properties of novel [MIIICl3 - N(P)3 + n]n+ (M = Co, Rh; N = 0, 1, 2 or 3) series of complexes containing tripodal tridentate phosphine, 1,1,1-tris(dimethylphosphinomethyl)ethane

Article abstract of DOI:10.1016/j.ica.2005.02.008

Cobalt(III) and rhodium(III) complexes of the series of [M ^IIICl_{3 - n}(P)_{3 + n}]ⁿ⁺ (M = Co or Rh; n = 0, 1, 2 or 3) have been prepared with the use of 1,1,1- tris(dimethylphosphinomethyl)ethane (tdmme) and mono- or didentate phosphines. The single-crystal X-ray analyses of both series of complexes revealed that the M-P and M-Cl bond lengths were dependent primarily on the strong trans influence of the phosphines, and secondarily on the steric congestion around the metal center resulting from the coordination of several phosphine groups. In fact, the M-P(tdmme) bonds became longer in the order of [MCl₃(tdmme)] < [MCl₂(tdmme)(PMe₃)]⁺ < [MCl(tdmme)(dmpe)] ²⁺ (dmpe = 1,2-bis(dimethylphosphino)ethane) < [M(tdmme) ₂]³⁺ for both Co^III and Rh^III series of complexes, while the M-Cl bond lengths were shortened in this order (except for [M(tdmme)₂]³⁺). Such a steric congestion around the metal center can also account for the structural and spectroscopic characteristics of the series of complexes, [MCl(tdmme)(dmpm, dmpe or dmpp)]²⁺ (dmpm = bis(dimethylphosphino)methane, dmpp = 1,3-bis(dimethylphosphino)propane). The X-ray analysis for [CoCl(tdmme)(dmpm or dmpe)](BF₄)₂ showed that all Co-P bonds in the dmpm complex were shorter by 0.03-0.04 ? than those in the dmpe complex. Furthermore, the first d-d transition energy of the Co^III complexes and the ¹J_Rh-P(tdmme) coupling constants observed for the Rh^III complexes indicated an unusual order in the coordination bond strengths of the didentate diphosphines, i.e., dmpm > dmpe > dmpp.

Full text of DOI:10.1016/j.ica.2005.02.008

Inorganica Chimica Acta 358 (2005) 2501–2512
www.elsevier.com/locate/ica
Preparation, crystal structures and spectroscopic properties of
novel [MIIICl3 ꢀ n(P)3 + n]n+ (M = Co, Rh; n = 0, 1, 2 or 3) series
of complexes containing tripodal tridentate phosphine,
1,1,1-tris(dimethylphosphinomethyl)ethane
a,
a
a
a
Takayoshi Suzuki *, Toshiaki Tsukuda , Masakazu Kiki , Sumio Kaizaki ,
b
Kiyoshi Isobe , Hideo D. Takagi , Kazuo Kashiwabara
c
c
a
Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
Department of Chemistry, Graduate School of Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
b
c
Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
Received 8 January 2005; accepted 6 February 2005
Available online 14 March 2005
Abstract
Cobalt(III) and rhodium(III) complexes of the series of [MIIICl3 ꢀ n(P)3 + n
]
n+ (M = Co or Rh; n = 0, 1, 2 or 3) have been prepared
with the use of 1,1,1-tris(dimethylphosphinomethyl)ethane (tdmme) and mono- or didentate phosphines. The single-crystal X-ray
analyses of both series of complexes revealed that the M–P and M–Cl bond lengths were dependent primarily on the strong trans
influence of the phosphines, and secondarily on the steric congestion around the metal center resulting from the coordination of
several phosphine groups. In fact, the M–P(tdmme) bonds became longer in the order of [MCl3(tdmme)] < [MCl2(tdmme)-
(PMe3)]+ < [MCl(tdmme)(dmpe)]2+ (dmpe = 1,2-bis(dimethylphosphino)ethane) < [M(tdmme)2]3+ for both CoIII and RhIII series
of complexes, while the M–Cl bond lengths were shortened in this order (except for [M(tdmme)2]3+). Such a steric congestion around
the metal center can also account for the structural and spectroscopic characteristics of the series of complexes,
[MCl(tdmme)(dmpm, dmpe or dmpp)]2+ (dmpm = bis(dimethylphosphino)methane, dmpp = 1,3-bis(dimethylphosphino)propane).
The X-ray analysis for [CoCl(tdmme)(dmpm or dmpe)](BF4)2 showed that all Co–P bonds in the dmpm complex were shorter
III
˚
by 0.03–0.04 A than those in the dmpe complex. Furthermore, the first d–d transition energy of the Co complexes and the
1JRh–P(tdmme) coupling constants observed for the RhIII complexes indicated an unusual order in the coordination bond strengths
of the didentate diphosphines, i.e., dmpm > dmpe > dmpp.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Tripodal tridentate phosphine; Cobalt(III) and rhodium(III) complexes; Crystal structures; Trans influence; Steric congestion
1. Introduction
but also the octahedral 18-electron rhodium(III)-phos-
phine complexes have been investigated extensively [1].
However, there have been surprisingly few studies on
the rhodium(III) complexes containing more than four
phosphino donor groups. For instance, tris(didentate
diphosphine)rhodium(III) complexes, [Rh(dmpm or
dmpe)3]3+ (dmpm = Me2PCH2PMe2; dmpe = Me2PCH2-
CH2PMe2), have recently been reported for the first
time as [RhIII(P)6]3+-type complexes [2], although their
In relation to the efficient catalytic abilities of rho-
dium-phosphine complexes for, e.g., (asymmetric)
hydrogenation or hydroformylation of alkenes, not only
the coordinatively unsaturated rhodium(I) complexes
*
Corresponding author. Tel.: +81 6 6850 5410; fax: +81 6 6850 5408.
E-mail address: suzuki@chem.sci.osaka-u.ac.jp (T. Suzuki).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.02.008

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T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
(P)]+, [MIIICl(tdmme)(P–P)]2+, and [MIII(tdmme)2]3+
,
because the dimethyl-substituted tripodal tridentate
phosphine, tdmme, is sterically as compact as to incor-
porate some other phosphine donors in the metal coor-
dination sphere. In this article, we deal with the
preparation, crystal structures, and spectroscopic prop-
erties of the above mentioned series of RhIII and CoIII
complexes (Scheme 1), through the reactions of
[MCl3(tdmme)] and either a monodentate P-ligand
{PMenPh3 ꢀ n or P(OMe)nPh3 ꢀ n}, a didentate diphos-
phine {dmpm, dmpe or dmpp (=Me2PCH2CH2CH2-
PMe2)}, or a tripodal triphosphine (tdmme).
2. Experimental
2.1. Materials and spectroscopic measurements
The phosphines, tdmme [10] and dmpp [11], were pre-
pared according to the literature methods, and the other
P-ligands were purchased from Aldrich or Strem Chem-
icals, Inc. The complexes, [CoCl3(tdmme)] (1) [5] and
[RhX3(tdmme)] {X = Cl (2), Br (20) or I (200)} [9], were
prepared by the methods described previously. All reac-
tions involving free P-ligands were handled under a dini-
trogen atmosphere using Schlenk techniques. All of the
solvents used for the preparation of phosphines and
their complexes were deaerated with dinitrogen for
20 min immediately before use. The 1H, 13C{1H},
31P{1H} and 59Co{1H} NMR spectra were recorded at
30 ꢁC on a JEOL GSX-400, EX270, or Lambda 500
spectrometer using tetramethylsilane as an internal ref-
Scheme 1.
crystal structures have not yet been determined.
For the analogous [CoIII(P)6]3+-type complexes,
[Co(dmpe or o-Me2PC6H4PMe2)3]3+ and [Co(tdmme)2]3+
{tdmme = MeC(CH2PMe2)3} have been prepared [3–5],
and the crystal structure of [Co(tdmme)2][Co(CN)6] Æ
nH2O has been analyzed by X-ray [5].1 The cyclotriphos-
phate ðP33ꢀÞ or cyclothiadiphosphate (P2S2ꢀ) complexes
1
erence for H and 13C and 85% H3PO4 as an external
reference for 31P NMR spectra. The 59Co NMR chemi-
cal shifts were reported in reference to the signal of
K3[Co(CN)6] in D2O. The UV–vis absorption spectra
were recorded on a Perkin-Elmer Lambda 19 spectro-
photometer at ambient temperature.
of [MIII(tdpme)(g3-P3 or g3-P2S)](0 or +) {M = Co,
Rh; tdpme = MeC(CH2PPh2)3} [6] and a few other
[MIII(P)6]n+-type complexes prepared by oxidative
addition of white phosphorus (P4) [7] have also been de-
scribed, but there have been no studies concerning the
[MIIICl(P)5]2+-type complexes to our best knowledge.
Since most of the phosphines used in the prepara-
tion of their metal complexes have bulky substituents
on P atom(s), the steric congestion arising from their
substituents might become severe to prevent aggrega-
tion of more than four phosphino donor groups on a
metal center. However, we expected from our previous
studies [5,8,9] that ‘‘MIII(tdmme)’’ fragment should be
a good candidate for preparation of the series of
complexes, such as [MIIICl3(tdmme)], [MIIICl2(tdmme)-
2.2. Preparation of complexes
2.2.1. [MCl2(tdmme)(P)]BF4 (M = Co or Rh)
To a suspension of [CoCl3(tdmme)] (1; 462 mg, 1.16
mmol) in methanol (5 cm3) was added a toluene solution
of PMe3 (1.0 M, 1.0 cm3) dropwise with stirring. The
mixture was stirred at ambient temperature for 30 min
and filtered to remove unreacted CoIII complex. To
the red orange filtrate was added a methanol solution
(2 cm3) of LiBF4 (284 mg, 3.03 mmol); an orange precip-
itate formed was collected by filtration. The crude prod-
uct was recrystallized from hot methanol to deposit red
plate crystals of [CoCl2(tdmme)(PMe3)]BF4 (3). Yield:
446 mg (70% based on Co). Anal. Calc.
for C14H36BCl2CoF4P4: C, 30.86; H, 6.66. Found: C,
30.79; H, 6.57%. The following CoIII and RhIII
1
The revision of the X-ray analysis for this compound has
previously been reported briefly in [21]; CCDC deposition No. 176058.

T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
2503
complexes were prepared by a similar method, using (a
methanol solution of) the respective P-ligand instead
of a toluene solution of PMe3 and/or [RhCl3(tdmme)]
(2) instead of 1. [CoCl2(tdmme){P(OMe)3}]BF4 (4):
red microcrystalline solid. Yield: 50%. Anal. Calc. for
C14H36BCl2CoF4O3P4: C, 28.36; H, 6.12. Found: C,
28.37; H, 6.05%. [CoCl2(tdmme)(PMe2Ph)]BF4 (5):
red-purple prismatic crystals. Yield: 77%. Anal. Calc.
for C19H38BCl2CoF4P4: C, 37.59; H, 6.31. Found: C,
37.46; H, 6.29%. [RhCl2(tdmme)(PMe3)]BF4 (6): color-
less prismatic crystals. Yield: 71%. Anal. Calc. for
C14H36BCl2F4P4Rh: C, 28.55; H, 6.16. Found: C,
28.56; H, 6.09%. [RhCl2(tdmme){P(OMe)3}]BF4 (7):
colorless microcrystalline solid. Yield: 55%. Anal. Calc.
for C14H36BCl2F4O3P4Rh: C, 26.40; H, 5.70. Found:
C, 26.58; H, 5.59%. [RhCl2(tdmme)(PMe2Ph)]BF4 (8):
colorless prismatic crystals. Yield: 62%. Anal. Calc. for
C19H38BCl2F4P4Rh: C, 34.57; H, 5.96. Found: C,
34.58; H, 6.00%. [RhCl2(tdmme){P(OMe)2Ph}]BF4 (9):
colorless microcrystalline solid. Yield: 71%. Anal. Calc.
for C19H38BCl2F4O2P4Rh: C, 33.41; H, 5.61. Found:
C, 33.22; H, 5.58%.
evaporated to dryness under reduced pressure. The res-
idue was vigorously washed with diethyl ether (50 cm3)
and extracted with a minimum amount of methanol. A
methanol solution of LiBF4 (750 mg, 8.00 mmol) was
added with stirring to the extract to give a white precip-
itate. The crude product was recrystallized by diffusion
of dichloromethane vapor into an acetonitrile solution,
depositing colorless microcrystalline solids of
[RhCl(tdmme)(dmpm)](BF4)2 (13). Yield: 80%. Anal.
Calc. for C16H41B2ClF8P5Rh: C, 27.44; H, 5.90. Found:
C, 27.44; H, 5.87%.
2.2.4. [Rh(Cl or Br)(tdmme)(dmpe or dmpp)](BF4)2
These complexes were prepared by a similar method
to that for complex 13 using dmpe or dmpp
and/or [RhBr3(tdmme)] (20). [RhCl(tdmme)(dmpe)]-
(BF4)2 Æ CH3CN (14 Æ AN): colorless prismatic crystals.
Yield: 82%. Anal. Calc. for C19H46B2ClF8NP5Rh: C,
30.21; H, 6.14, N, 1.85. Found: C, 29.91; H, 6.04; N,
1.84%. [RhCl(tdmme)(dmpp)](BF4)2 Æ CH3CN (15 Æ AN):
colorless needle crystals. Yield: 74%. Anal. Calc. for
C20H48B2ClCoF8NP5Rh: C, 31.10; H, 6.26; N, 1.81.
Found: C, 30.97; H, 6.29; N, 1.74%. [RhBr(tdmme)(dm-
pe)](BF4)2 (140): colorless crystals. Yield: 79%. Anal.
Calc. for C17H43B2BrF8P5Rh: C, 26.16; H, 5.71. Found
(after drying completely in vacuo): C, 26.16; H, 5.61%.
[RhBr(tdmme)(dmpp)](BF4)2 (150): colorless microcrys-
talline solids. Yield: 51%. Anal. Calc. for C18H45B2-
BrF8P5Rh: C, 27.98; H, 5.88. Found (after drying
completely in vacuo): C, 27.98; H, 5.88%.
2.2.2. [CoCl(tdmme)(P–P)](BF4)2
To a red suspension of 1 (614 mg, 1.47 mmol) in
methanol (10 cm3) was added dmpm (200 mg, 1.47
mmol) dropwise with stirring. The mixture turned
immediately to a clear red orange solution. After stirring
at room temperature for 4 h, the solution was evapo-
rated to dryness under reduced pressure. The residue
was vigorously washed with diethyl ether (50 cm3) and
dissolved in a minimum amount of methanol. To the fil-
tered solution was added a methanol solution of LiBF4
(750 mg, 8.00 mmol) with stirring. The resulting orange
yellow precipitate was collected by filtration. The crude
product was recrystallized by diffusion of dichlorometh-
ane vapor into an acetonitrile solution, affording orange
prismatic crystals of [CoCl(tdmme)(dmpm)](BF4)2 Æ
H2O (10 Æ H2O). Yield: 849 mg (88%). Anal. Calc. for
C16H43B2ClCoF8OP5: C, 28.50; H, 6.43. Found: C,
28.54; H, 6.36%. The corresponding dmpe and dmpp
complexes were prepared by an analogous method de-
scribed above. [CoCl(tdmme)(dmpe)](BF4)2 Æ CH3CN
(11 Æ AN): orange prismatic crystals. Yield: 70%. Anal.
Calc. for C19H46B2ClCoF8NP5: C, 32.08; H, 6.52; N,
1.97. Found: C, 31.56; H, 6.49; N, 1.44%. [CoCl(tdm-
me)(dmpp)](BF4)2 Æ CH3CN (12 Æ AN): orange needle
crystals. Yield: 57%. Anal. Calc. for C20H48B2-
ClCoF8NP5: C, 33.11; H, 6.67; N, 1.93. Found: C,
32.84; H, 6.62; N, 2.20%.
2.2.5. [RhI(tdmme)(dmpe or dmpp)]I2 Æ H2O
To a methanol suspension (5 cm3) of [RhI3(tdmme)]
(258 mg, 0.351 mmol) was added a methanol (0.6 cm3)
solution of dmpe (60 mg, 0.40 mmol) dropwise with stir-
ring. The mixture was refluxed under a nitrogen atmos-
phere for 20 h and cooled to room temperature. The
resulting yellow precipitate was collected by filtration.
The crude product was recrystallized from hot methanol,
affording yellow plate crystals of [RhI(tdmme)(dmpe)]-
I2 Æ H2O (1400 Æ H2O): Yield: 51%. Anal. Calc. for
C17H45I3OP5Rh: C, 22.59; H, 5.02. Found: C, 22.58;
H, 4.91%. [RhI(tdmme)(dmpp)]I2 Æ H2O (1500 Æ H2O): yel-
low crystals. Yield: 61%. Anal. Calc. for C18H47I3OP5Rh:
C, 23.55; H, 5.16. Found: C, 23.47; H, 5.04%.
2.2.6. [Rh(tdmme)2](BF4)3 Æ NaBF4 (170)
To an aqueous solution (10 cm3) of [Rh(tdmme)2-
(l-OH)3](BF4)3 [9] (542 mg, 0.496 mmol) were added
tetrafluoroboric acid (42%, 311 mg, 1.487 mmol) and
tdmme (250 mg, 0.991 mmol), and the mixture was re-
fluxed for 20 h. After cooling the reaction mixture to
ambient temperature, excess NaBF4 (solid) was added
with vigorous stirring, affording a white precipitate.
The crude product was filtered off and recrystallized
from acetonitrile/dichloromethane/diethyl ether to give
2.2.3. [RhCl(tdmme)(dmpm)](BF4)2
A mixture of complex 2 (678 mg, 1.45 mmol) and
dmpm (200 mg, 1.47 mmol) in methanol (10 cm3) was
refluxed for 20 h, affording a clear pale yellow solution.
After cooling to room temperature, the solution was

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T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
colorless microcrystals. Yield: 50%. Anal. Calc. for C22-
H54B4F16NaP6Rh: C, 27.03; H, 5.57. Found: C, 27.33;
H, 5.61%.
17 Æ 4H2O; the number of water molecules of hydration
was revised to be 4, which was consistent with the ana-
lytical data [5].
2.2.7. [Rh(tdmme)2][Co(CN)6] Æ 4H2O (17 Æ 4H2O)
Compound 170 was dissolved in water and the solu-
tion was layered on an aqueous solution of
K3[Co(CN)6]. The mixture was allowed to stand at
ambient temperature for several days, depositing color-
less prismatic crystals in a nearly quantitative yield.
Anal. Calc. for C28H54CoN6P6Rh: C, 40.89; H, 6.62;
N, 10.22. Found (after drying completely in vacuo): C,
40.08; H, 6.30; N, 10.21%.
2.3.2. The others
The X-ray diffraction data of 3 and 10 Æ 2H2O were
measured at 23(2) ꢁC on a Rigaku R-axis rapid imaging
plate detector equipped with a graphite-monochromated
˚
Mo Ka radiation (k = 0.71073 A). Each crystal of 3 (red
plate) or 10 Æ 2H2O (yellow plate) was glued on the top
of a glass fiber and used for the diffraction study. A total
of 44 images with the oscillation angle of x = 5ꢁ were
collected with two different goniometer settings
(8 6 2h 6 55ꢁ). Data were processed by the Process-
Auto program [15] and the lattice parameters were
determined by the least-squares treatment using the set-
ting angles of all observed reflections. Empirical absorp-
tion corrections were applied by the multi-scan method
[12b].
2.3. Crystallography
2.3.1. 17 Æ 4H2O and re-analysis of 16 Æ 4H2O
(see footnote 1)
A colorless prismatic crystal of 17 Æ 4H2O was sealed
in a glass capillary tube. The X-ray diffraction data were
measured at 23(2) ꢁC with a graphite-monochromated
For the crystals of 6 Æ 2MeOH, 8 Æ H2O, 11 Æ AN,
14 Æ AN, and 140 Æ AN, the X-ray diffraction experiments
were performed on a Rigaku AFC-5R diffractometer (k
˚
Mo Ka radiation (k = 0.71073 A) on a Rigaku AFC-
˚
5R diffractometer. Final lattice constants were deter-
mined by the least-squares treatment using the setting
angles of 25 reflections in the range of 22 6 2h 6 30ꢁ.
Three standard reflections were monitored every 150,
showing no serious decomposition. The intensities in a
(+h,+k,+l) octant up to 2h 6 60ꢁ were collected and
absorption corrections were made by the numerical inte-
gration method [12a]. The observed independent reflec-
tions with Fo P 3r(Fo) were used for the structural
calculation. Systematic absences indicated the space
group Pmab or P21ab and the structure was successfully
solved based on the former space group by the direct
method using SHELXS-86 program [13a]. In an asymmet-
ric unit there were two halves of Rh(tdmme)2 and two
halves of Co(CN)6 moieties, as well as three and two
halves of O atoms for water molecules. The Rh(A),
Rh(B), Co(C), and Co(D) atoms were located at the site
(Mo Ka) = 0.71073 A) at 23(2) ꢁC. Each crystal suitable
for the X-ray study was sealed in a glass capillary tube
and used for the collection of the diffraction data
(2h 6 60ꢁ). Final lattice constants were determined by
the least-squares treatment using the setting angles of
25 reflections in the range of 22 6 2h 6 30ꢁ. Three stan-
dard reflections were monitored every 150 and no seri-
ous decomposition was observed except for 11 Æ AN,
for which (|Fo|final/|Fo|initial = 0.899) a linear decay cor-
rection was made. Absorption corrections were made
Table 1
Crystal data for [Rh(tdmme)2][Co(CN)6] Æ 4H2O (17 Æ 4H2O)
Formula
Formula weight
T (K)
C28H62CoN6O4P6Rh
894.52
296(2)
ꢀ
Crystal color, shape
Crystal size (mm)
Crystal system
Space group
Z
colorless, plate
0.40 · 0.20 · 0.10
orthorhombic
Pmab
symmetries of 2, m.., 1, and m.., respectively. The func-
tion,
P
wiFo| ꢀ |Fci2 with wꢀ1 = r2(|Fo|) + (0.015|Fo|)2,
was minimized on F using anisotropic thermal parame-
ters for all non-hydrogen atoms. Hydrogen atoms were
not included in the calculations. All calculations were
carried out on a Fujitsu IX-4 workstation using the
Xtal-3.2 software package [14a].
8
˚
a (A)
23.713(2)
31.756(4)
10.571(2)
7960(3)
1.49
˚
b (A)
˚
c (A)
3
˚
V (A )
This result for 17 Æ 4H2O prompted us to re-analyze
the crystal structure of the analogous CoIII complex,
16 Æ nH2O, because these complexes were most likely
isomorphic to each other, but the CoIII complex was
previously analyzed based on the corresponding non-
centrosymmetric space group, Pca21. The diffraction
data that were corrected for absorption effects were pro-
vided by Prof. S. Ohba (Keio University). We have
re-analyzed the crystal structure, based on the space
group of Pcam, by a similar method to that for
Dcalc (Mg mꢀ3
F(000)
)
3727
1.11
l (Mo Ka) (mmꢀ1
Tmin, Tmax
)
0.809, 0.906
11885/3808
480
Number of measured/observeda reflections
Number of parameters
Rb
Rw
0.081
0.075
c
a
Fo > 3r(Fo).
P
P
b
c
R = iFo| ꢀ |Fci/ |Fo|.
P
P
Rw = ( wiFo| ꢀ |Fci2/ w|Fo|2)1/2; (wꢀ1 = r2(|Fo|) + (0.015|Fo|)2).

Table 2
Crystal data for complexes
Complex
3
6 Æ 2MeOH
8 Æ H2O
10 Æ 2H2O
11 Æ AN
14 Æ AN
140 Æ AN
Formula
Formula weight
T (K)
C14H36BCl2CoF4P4 C16H44BCl2F4O2P4Rh C19H40BCl2F4OP4Rh C16H45B2ClCoF8O2P5 C19H46B2ClCoF8NP5 C19H46B2ClF8NP5Rh C19H46B2BrF8NP5Rh
544.95
296(2)
653.01
296(2)
669.01
296(2)
692.37
296(2)
711.42
296(2)
755.40
296(2)
799.86
296(2)
Crystal color, shape
Crystal size (mm)
Crystal system
Space group
Z
red, plate
0.40 · 0.40 · 0.10
orthorhombic
Pna21
colorless, plate
0.50 · 0.30 · 0.20
monoclinic
P21/c
colorless, column
0.46 · 0.26 · 0.26
monoclinic
P21/n
yellow, plate
0.10 · 0.10 · 0.05
monoclinic
P21/n
orange, block
0.40 · 0.35 · 0.35
monoclinic
P21/c
colorless, prism
0.40 · 0.30 · 0.30
monoclinic
P21/c
colorless, prism
0.50 · 0.40 · 0.25
monoclinic
P21/c
4
4
4
4
4
4
4
˚
a (A)
18.582(7)
11.314(5)
11.563(4)
90
12.824(2)
13.158(2)
17.402(2)
96.75(1)
2916.0(7)
1.487
9.255(2)
21.597(3)
14.408(2)
95.38(1)
2867.1(7)
1.550
10.234(6)
21.318(10)
13.914(6)
99.11(4)
2977(2)
1.534
11.017(2)
17.564(2)
17.356(2)
108.03(1)
3193.4(7)
1.480
11.022(3)
17.681(5)
17.449(3)
107.83(1)
3237(1)
11.028(2)
17.532(2)
17.605(2)
107.190(8)
3251.7(7)
1.634
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
2431(2)
1.489
1128
Dcalc (Mg mꢀ3
F(000)
)
1.550
1544
1344
1.024
1368
1.043
1432
0.993
1472
0.931
1616
2.058
l (Mo Ka) (mmꢀ1
Rint
)
1.218
0.043
0.642, 0.888
0.916
0.013
0.009
0.628, 0.921
8502/274
0.030
0.646, 0.773
8343/290
0.064
0.907, 0.952
6848/317
0.012
0.707, 0.737
9314/336
0.016
0.426, 0.627
9483/335
Tmin, Tmax
0.711, 0.771
9442/336
Reflection/parameter 5560/236
ratio
R1 ½F 2o > 2rðF 2oÞꢁ
wR2 (all reflections)
Goodness-of-fit
0.033
0.077
0.961
0.041
0.123
1.017
0.044
0.191
1.066
0.063
0.196
1.003
0.047
0.131
1.019
0.041
0.112
1.028
0.041
0.116
1.002

2506
T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
either by the numerical integration method [12c] or by
_
or 2 reacted to produce a clear (pale) yellow solution.
However, it was not possible to isolate the desired com-
plex, [MCl2(tdmme){PMePh2 or P(OMe)Ph2}]+, due
probably to the dissociation equilibrium of the P-ligand
in solution. In fact, the 31P NMR spectra (in CD3CN) of
the reaction product showed resonances corresponding
to the [MCl2(tdmme){PMePh2 or P(OMe)Ph2}]+ and
[MCl2(tdmme)(CD3CN)]+ complexes. It should be
noted that the difficulty of isolation and the probable
thermal instability of the PPh3, PMePh2 and P(OMe)Ph2
complexes seem to originate from the steric bulkiness of
the P-ligands, being irrelevant to the electronic proper-
ties such as r-donor/p-acceptor abilities of the P-
ligands.
an empirical method based on three sets of W-scan data
[12d].
The data reduction and the following structural cal-
culation were performed using the CrystalStructure soft-
ware package [14b]. The structures were solved by the
direct method with the SIR-92 program [13b] and refined
on F2 with all independent reflections using the SHELXL-
97 program [13c]. All non-hydrogen atoms were refined
anisotropically, and H atoms (except for the water mol-
ecules of 10 Æ 2H2O) were introduced at the theoretically
calculated positions and treated with riding models.
Crystal data of 17 Æ 4H2O and the others are collected
in Tables 1 and 2.
The reactions of complex 1 with didentate dimethyl-
substituted phosphines (dmpm, dmpe or dmpp) at
ambient temperature gave novel [CoCl(P)5]2+-type com-
plexes, which were isolated in high yields as yellow crys-
tals of [CoCl(tdmme)(dmpm, dmpe or dmpp)](BF4)2
(10, 11 or 12). The crystal structures of 10 Æ H2O and
11 Æ AN were determined by the X-ray analyses, and
the molecular structures of the cationic complexes,
[CoCl(tdmme)(dmpm or dmpe)]2+, are illustrated in
Fig. 2. It was shown that dmpm and dmpe ligands
formed a four- and a five-membered chelated ring,
respectively, in the complexes. For preparation of the
analogous RhIII complexes, an elevated reaction temper-
ature was required to complete the reaction. In fact,
although a mixture of complex 2 and an equimolar
amount of dmpm at room temperature afforded a clear
pale yellow solution, it contained several different spe-
cies as confirmed by 31P NMR spectroscopy. However,
refluxing the reaction mixture for 20 h, followed by
addition of LiBF4, afforded the colorless crystals of
[RhCl(tdmme)(dmpm)](BF4)2 (13) in a nearly quantita-
tive yield. Analogous [RhCl(tdmme)(dmpe or dmpp)]-
(BF4)2 Æ CH3CN (14 Æ AN or 15 Æ AN) complexes were
prepared in the same manner with the respective diden-
tate diphosphines. In addition, the corresponding bro-
mo (140 or 150) and iodo (1400 Æ H2O or 1500 Æ H2O)
complexes were synthesized from [RhBr3(tdmme)] (20)
and [RhI3(tdmme)] (200), respectively, in high yields.
The crystal structures of the dmpe complexes, 14 Æ AN
and 140 Æ AN, were also determined.
3. Results and discussion
3.1. Preparation of complexes
The [CoCl3(tdmme)] (1) complex was obtained by a
stoichiometric reaction of trans-[CoCl2(py)4]Cl and
tdmme in dry pyridine at room temperature [5]. When
the reaction mixture was refluxed for a while, red com-
plex 1 disproportionated to yield yellow [Co(tdmme)2]3+
and the original green trans-[CoCl2(py)4]+ complexes,
which were successfully separated by the cation-
exchange chromatography. The bis(tdmme) complex,
[Co(tdmme)2]3+, was also prepared quantitatively by a
reaction of 1 with anꢀequimolar tdmme in methanol,
and isolated as the BF4 ð160Þ or [CoIII(CN)6]3ꢀ (16) salt
[5]. In contrast, the corresponding RhIII complex,
[RhCl3(tdmme)] (2), was thermally stable and no dispro-
portionation reaction was observed [9].
When (a toluene solution of) PMe3 was added to a
red suspension of complex 1 in methanol, the reaction
mixture gave immediately a clear red orange solution,
from which red crystals of [CoCl2(tdmme)(PMe3)]BF4
(3) were isolated by addition of LiBF4. The analogous
P(OMe)3 and PMe2Ph complexes, [CoCl2(tdmme)-
{P(OMe)3 or PMe2Ph}]BF4 (4 or 5), were prepared in
the same manner and isolated as red crystals. The corre-
sponding RhIII complexes, [RhCl2(tdmme){PMe3,
P(OMe)3, PMe2Ph or P(OMe)2Ph}]BF4 (6–9), were ob-
tained also from the mixture of complex 2 and the
respective P-ligand. The crystal structures of 3,
6 Æ 2MeOH and 8 Æ H2O were determined by the X-ray
analyses, which revealed the structures of the mono-
meric [MIIICl2(tdmme)(P)]+-type complex cations. The
structures of the cationic part of RhIII complexes in
6 Æ 2MeOH and 8 Æ H2O are shown in Fig. 1. On the
other hand, a similar reaction of complex 1 or 2 with
PPh3 in methanol did not take place; the dissolution
of trichloro complex was not observed upon addition
of PPh3 (for complex 2, even when the mixture was re-
fluxed). With PMePh2 or P(OMe)Ph2, the complex 1
Although the formation of [Co(tdmme)2]3+ was ther-
modynamically favorable as described above, the analo-
gous RhIII complex, [Rh(tdmme)2]3+, was found to be
less easy to synthesize because of the kinetic robustness
of the Rh–Cl bond. Reaction of complex 2 with an equi-
molar tdmme in methanol at room temperature immedi-
ately gave a clear pale yellow solution, from which
colorless needle crystals were obtained by addition of
LiBF4, followed by recrystallization from acetonitrile/
methanol. The elemental analysis of this product indi-
cated the composition of Rh(tdmme)2HCl(BF4)3(H2O)2
(Found: C, 27.89; H, 6.36%. C22H59B3ClF12O2P6Rh

T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
2507
Fig. 2. ORTEPs (30% probability level, hydrogen atoms omitted) of
the cationic parts in (a) 10 Æ H2O and (b) 11 Æ AN. Selected bond
˚
lengths (A) and angles (ꢁ) are: (a) Co–P1 2.242(2), Co–P2 2.251(2), Co–
P3 2.219(2), Co–P4 2.287(2), Co–P5 2.295(2), Co–Cl1 2.282(2), P1–
Co–P2 89.09(5), P1–Co–P3 88.62(5), P2–Co–P3 87.23(6), P4–Co–P5
72.38(5), P1–Co–P4 167.63(5), P2–Co–P4 100.97(5), P3–Co–P4
98.96(5), P1–Co–P5 96.47(6), P2–Co–P5 168.43(5), P3–Co–P5
102.99(6), P3–Co–Cl1 174.98(5), P4–Co–Cl1 81.98(5), P5–Co–Cl1
82.01(6); (b) Co–P1 2.2797(9), Co–P2 2.2754(9), Co–P3 2.2520(8),
Co–P4 2.3233(9), Co–P5 2.3345(8), Co–Cl1 2.2852(8), P1–Co–P2
87.86(3), P1–Co–P3 86.90(3), P2–Co–P3 86.75(3), P4–Co–P5 83.62(3),
P1–Co–P4 169.74(3), P2–Co–P4 92.32(3), P3–Co–P4 103.36(3), P1–
Co–P5 95.44(3), P2–Co–P5 174.37(3), P3–Co–P5 97.96(3), P3–Co–Cl1
174.39(3), P4–Co–Cl1 81.44(3), P5–Co–Cl1 85.38(3).
Fig. 1. ORTEPs (30% probability level) of the cationic parts in (a)
6 Æ 2MeOH and (b) 8 Æ H2O (hydrogen atoms are omitted for clarity).
Selected bond lengths (A) and angles (ꢁ) are: (a) Rh–P1 2.3454(9), Rh–
˚
P2 2.2865(9), Rh–P3 2.2721(8), Rh–P4 2.4221(10), Rh–Cl1 2.4213(9),
Rh–Cl2 2.4214(9), P1–Rh–P2 87.56(3), P1–Rh–P3 88.02(3), P2–Rh–P3
87.82(3), P1–Rh–P4 169.77(3), P2–Rh–P4 102.02(3), P3–Rh–P4
95.84(3), Cl1–Rh–Cl2 87.50(4), P2–Rh–Cl1 174.61(4), P3–Rh–Cl2
176.91(3), P4–Rh–Cl1 82.51(4), P4–Rh–Cl2 86.62(3); (b) Rh–P1
2.344(1), Rh–P2 2.271(1), Rh–P3 2.282(1), Rh–P4 2.423(1), Rh–Cl1
2.417(1), Rh–Cl2 2.441(1), P1–Rh–P2 87.89(5), P1–Rh–P3 88.20(4),
P2–Rh–P3 86.66(4), P1–Rh–P4 167.70(4), P2–Rh–P4 97.67(4), P3–Rh–
P4 97.67(4), Cl1–Rh–Cl2 89.94(5), P2–Rh–Cl1 176.56(4), P3–Rh–Cl2
176.22(4), P4–Rh–Cl1 84.26(4), P4–Rh–Cl2 80.75(4).
part of [RhIII(tdmme-j3P,P0,P00)2]3+ (Fig. 3) was ob-
tained by X-ray analysis of the [Co(CN)6]3ꢀ salt,
[Rh(tdmme)2][Co(CN)6] Æ 4H2O (17 Æ 4H2O).
requires C, 28.09; H, 6.32%.), and the 31P NMR
spectrum (in CD3CN) suggested the existence of
3.2. Crystal structures
[RhCl(tdmme-j3P,P0,P00)(tdmme-j2P,P0)]2+
complex
cation. These facts imply that the last Cl ligand does
not tend to dissociate from the RhIII center, even when
the reaction mixture was refluxed for several hours.
The desired [Rh(tdmme)2]3+ complex was, therefore,
prepared from the Cl-free starting material,
[Rh(tdmme)2(l-OH)3](BF4)3. The tris(aqua) complex of
[Rh(tdmme)-(H2O)3]3+ was prepared in situ by a reaction
of [{Rh(tdmme)}2- (l-OH)3](BF4)3 and HBF4 in water
[9], and the reaction with an equimolar amount of tdmme
In this study, the crystal structures of CoIII–PMe3
complex (3), RhIII–PMe3 and PMe2Ph complexes (6
and 8), CoIII-dmpm and dmpe complexes (10 and 11),
RhIII-dmpe complexes (14 and 140), and RhIII–(tdmme)2
complex (17) were determined. All of these analyses re-
vealed the mononuclear structures of [MIIICl2(P)4]+,
[MIIICl(P)5]2+ or [MIII(P)6]3+-type complex cations
(Figs. 1–3). The bite angles of tdmme ligands were var-
ied in the typical range for the tripodal phosphines: 83–
89ꢁ (Table 3). Three arms (C2–Cn+2–Pn–M; n = 1, 2 or
3) of the tripod were screwed in the same direction, as
afforded
colorless
microcrystalline
solid
of
[Rh(tdmme)2](BF4)3 (170). The structure of the cationic

2508
T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
or 0.05 A (for RhIII). Hence, it can be stated that the
˚
n+
] -
M–P(tdmme) bond lengths in the [MIIICl3 ꢀ n(P)3 + n
series of complexes were governed primarily by the trans
influence of the trans-positioned ligand.
For the RhIII–PMe3 and PMe2Ph complexes (6 and 8),
the P1–Rh–P4(PMe3 or PMe2Ph) bond angles were
169.77(3)ꢁ for 6 and 167.70(4)ꢁ for 8, while the P2–Rh–
P4 and P3–Rh–P4 angles were relatively larger than the
right angle (95.8–103.1ꢁ). These deviations from the regu-
lar octahedron were attributable to the steric interaction
between tdmme and PMe3/PMe2Ph. Although sterically
more bulky PMe2Ph was expected to induce larger distor-
tion of the coordination geometry from the regular octa-
hedron, the structural parameters around the RhIII
center, including the Rh–P4 bond length, were similar
to each other for both PMe2Ph and PMe3 complexes.
For instance, although the phenyl group of the PMe2Ph
complex (8) was located close to P3 atom of tdmme, the
P3–Rh–P4 angle (103.01(4)ꢁ) was similar to the corre-
sponding angle of the PMe3 complex (6, P2–Rh–P4:
102.02(3)ꢁ); it seems that similarity of these structures
originates from the conformation for the phenyl ring that
is located to minimize the steric interaction with tdmme
(Fig. 1(b)). However, the analogous PMePh2, P(OMe)Ph2
and PPh3 complexes seem to be thermodynamically
unstable, since (at least two) phenyl substituents on the
P-ligands cannot avoid the steric hindrance of the tdmme
moiety in these complexes.
Fig. 3. ORTEP (50% probability level) of one of the crystallograph-
ically independent cationic complexes in 17 Æ 4H2O.
observed for the trichloro complexes 1 and 2 [8,9].
Hence, each complex cation was inherently chiral,
although all complexes formed as racemic crystals.
The coordination bond lengths in [MIIICl2(tdmme)-
(P)]+ and [MIIICl(tdmme)(P–P)]2+-type complexes clearly
indicated the elongation of the M–P(tdmme) bonds due to
the strong trans influence of the phosphines (P or P–P li-
gands). As listed in Table 3, the M–P bond trans to
˚
PMe3 was longer than that trans to Cl by 0.04 A in the
III
CoIII complex (3) or by 0.065 A in the Rh complex
˚
(8). In the dmpe complexes (11 and 14), such an elonga-
III
tion of the M–P bond was as much as 0.03 A (for Co )
˚
Table 3
˚
Comparison of (averaged) bond lengths (A) and angles (ꢁ) of the complexes
Complex
Number of Cl ligands
P-ligand
1
Cl3
3
Cl2
10
Cl
11
Cl
16
(PMe3)
(dmpm)
(dmpe)
(tdmme)
Co–Cl
(trans P)
Co–P(tdmme)
2.323(3)
2.203(2)
2.287(1)
2.282(2)
2.2852(8)
(trans Cl)
(trans P)
2.216(1)
2.256(1)
2.219(2)
2.247(2)
2.252(1)
2.278(1)
2.331(4)
84.8(1)
Co–P(P-ligand)
(trans tdmme)
P–Co–P(tdmme)
(bite angle of tdmme)
P–Co–P(dmpm or dmpe)
(bite angle of dmpm or dmpe)
2.329(1)
88.22(4)
2.289(2)
88.31(5)
2.329(1)
87.17(3)
89.57(4)
72.38(5)
83.62(3)
Complex
Number of Cl ligands
P-ligand
2
Cl3
6
Cl2
8
Cl2
14
Cl
17
(PMe3)
(PMe2Ph)
(dmpe)
(tdmme)
Rh–Cl
(trans P)
2.444(3)
2.253(2)
2.421(1)
2.429(1)
2.410(1)
Rh–P(tdmme)
(trans Cl)
(trans P)
2.279(1)
2.345(1)
2.277(1)
2.342(1)
2.303(1)
2.352(1)
2.402(6)
84.2(2)
Rh–P(P-ligand)
(trans tdmme)
P–Co–P(tdmme)
(bite angle of tdmme)
P–Rh–P(dmpe)
(bite angle of dmpe)
2.422(1)
87.80(3)
2.423(1)
87.58(4)
2.404(1)
86.66(4)
89.1(1)
82.35(3)

T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
2509
In the dmpm complex (10), the four-membered che-
late ring formed by dmpm is not planar; the P4–C14–
P5 plane was bent from the P4–Co–P5 plane by
17.0(2)ꢁ to avoid the steric repulsion between the methyl
substituents of dmpm and tdmme (Fig. 2(a)). For the
CoIII-dmpe complex (11), the five-membered ring
formed by the chelation of dmpe had a typical skew con-
formation; the five-membered chelate ring was in the d-
configuration for the complex having a k-screwed
tdmme. The molecular modeling study indicates that
this configurational set for the combination of tdmme/
dmpe ligands is the most favorable to avoid the steric
interaction between the methyl substituents. We have
also analyzed the two RhIII-dmpe complexes (14 Æ AN
and 140 Æ AN), which were isomorphous to 11 Æ AN,
and found the same configurational set, d(dmpe)-
k(tdmme)/k(dmpe)d(tdmme), for the complex cations.
For both complexes of 10 and 11, the Co–P1 and Co–
˚
P2 bonds were longer by ca. 0.025 A than the Co–P3
bond due to the trans influence of the P–P (dmpm or
dmpe) ligand. It should also be noted that both types
of Co–P(tdmme) bonds in the dmpe complex (11) were
˚
longer by ca. 0.03 A than those in the dmpm complex
(10) (Table 3). Furthermore, the Co–P(dmpe: i.e., P4
˚
or P5) bonds in 11 (2.3233(9) and 2.3345(8) A) were
remarkably longer than the Co–P(dmpm: P4 or P5)
˚
bonds in 10 (2.287(2) and 2.295(2) A). Since the bite an-
gle (P4–Co–P5) of dmpm is considerably small
(72.38(5)ꢁ in 10) as compared to that of dmpe
(83.62(3)ꢁ in 11), it is expected that a larger steric inter-
action between dmpe and tdmme induces the longer Co–
P(tdmme or dmpe) bonds in 11. By the same reason, the
Co–P(dmpe) bonds in 11 were much longer than the
Co–P bond lengths in trans-[CoCl2(dmpe)2]ClO4 (av.
Fig. 4. UV–vis absorption spectra of (a) [CoCl3(tdmme)] (– Æ – Æ –)
in dichloromethane, [CoCl2(tdmme)(PMe2Ph)]+ (——), [CoCl-
(tdmme)(dmpe)]2+ (- - - - -), and [Co(tdmme)2]3+ (– – – –); (b)
[CoCl(tdmme)(dmpm)]2+ (——), [CoCl(tdmme)(dmpe)]2+ (- - - - -),
and [CoCl(tdmme)(dmpp)]2+ (– Æ – Æ –) in acetonitrile at ambient
temperature.
˚
2.260(1) A) [16]. Moreover, the Co–P(dmpm) bonds in
10 were longer than the mutually trans Co–P bonds
in [Co(Me2dtc)(dmpm)2](BF4)2 (Me2dtc = N,N-dimethyl-
for RhIII. This order is consistent with the inertness of
the RhIII–Cl bonds in the series of complexes.
˚
dithiocarbamate; 2.222(5)–2.264(5) A) [17], indicating
that steric congestion around CoIII center affected the
elongation of the Co–P coordination bonds.
3.3. Absorption spectra
The complex cation of [RhIII(tdmme)2]3+ in 17 exhib-
˚
ited much longer Rh–P(tdmme) bonds (av. 2.402(6) A)
The trichloro complex [CoCl3(tdmme)] (1) showed
the first d–d transition band at 20120 cmꢀ1 (e = 1350
molꢀ1 dm3 cmꢀ1). With this value and the correspond-
ing first d–d transition energies for [Co-
(NH3)3(tdmme)]3+ and [Co(CN)3(tdmme)], the complex
of [Co(tdmme)2]3+ was expected to exhibit the first d–d
band at ca. 27000–30000 cmꢀ10. However, the first d–d
transition band of complex 16 was observed at 23920
cmꢀ1 (e = 891 molꢀ1 dm3 cmꢀ1). It seems that this
remarkable weakening of the ligand-field strength of
tdmme was caused by the strong mutual trans influence
of tdmme [5] and the severe steric congestion around the
CoIII center. In this study, we have prepared the
compared with complexes 2, 8, and 14. It seems that the
steric congestion, which depends on the number of coor-
dinated phosphine groups, is important to account for
the Rh–P bond lengths, although the elongation of
Rh–P bonds is primarily governed by the strong
trans influence of phosphines. The order of the MIII–
P(tdmme) bond lengths, [MIIICl3(P)3] < [MIIICl2(P)4]+
< [MIIICl(P)5]2+ < [MIII(P)6]3+ in both CoIII and RhIII
complexes (Table 3), can be explained on this basis. On
the other hand, the MIII–Cl bonds in the series of com-
plexes were gradually shortened as the number of the
phosphine donor groups increased: 1 (av. 2.323(3)
III
A) > 3 (av. 2.287(1) A) > 11 (2.2852(8) A) for Co and
[CoIIICl2(tdmme)(P)]+ and [CoIIICl(tdmme)(P–P)]2+
type complexes, and compared the absorption spectra,
-
˚
˚
˚
˚
2 (av. 2.444(3) A) > 6 (av. 2.421(1) A) > 14 (2.410(1) A)
˚
˚

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T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
especially the first d–d transition energy, of the
n+
d–d transition energies of the RhIII complexes were
shifted to higher energy region, resulting in obscuration
by overlapping the intense charge-transfer bands.
[CoIIICl3 ꢀ n(P)3 + n
]
series of complexes (Fig. 4(a)).
The simplest estimation, on the basis of Yamatera
rule [18] with the assumption of equal ligand-field
strengths for PMe3/PMe2Ph, dmpm/dmpe/dmpp and
tdmme, would predict that the first d–d transition band
was split into two components at 20100 and 22000 cmꢀ1
for [CoIIICl2(tdmme)(P)]+, and at 22000 and 23900
cmꢀ1 for [CoIIICl(tdmme)(P–P)]2+. In fact, the complex
of cis-[CoIIICl2(dmpe)2]+, which has the same cis-
[CoIIICl2(P)4]+ chromophere as [CoIIICl2(tdmme)(P)]+,
exhibited two absorption bands at 19500 (e = 250) and
22470 cmꢀ1 (e = 417 molꢀ1 dm3 cmꢀ1) corresponding
to the predicted splitting components of the first d–d
band [19]. However, the [CoIIICl2(tdmme)(P)]+-type
complexes examined in this study did not show an expli-
cit splitting of the first d–d band; the PMe3 complex (3)
gave a broad absorption band centered at 21350 cmꢀ1
(e = 1000 molꢀ1 dm3 cmꢀ1) accompanied by a shoulder
around 20000 cmꢀ1. The P(OMe)3 and PMe2Ph com-
plexes (4 and 5) exhibited a similar broad d–d transition
band centered at 21880 (e = 795) and 21560 cmꢀ1
(e = 1050 molꢀ1 dm3 cmꢀ1), respectively.
The complex, [CoCl(tdmme)(dmpe)](BF4)2 (11),
showed an absorption band at 21690 cmꢀ1 (e = 437
molꢀ1 dm3 cmꢀ1), which may correspond to the one
(a1Eg 1A1g) of the splitting components of the first
d–d transition bands. Although the other component
(1A2g 1A1g) was expected to be located at 23900
cmꢀ1 or at positions higher in energy, any explicit
absorption band corresponding to this component was
not observed in this region. Interestingly, while the dmpp
complex (12) exhibited the corresponding d–d transition
band at 21320 cmꢀ1 (e = 562 molꢀ1 dm3 cmꢀ1), analo-
gous dmpm complex (10) exhibited such a band at a
higher energy region, 22880 cmꢀ1 (e = 575 molꢀ1
dm3 cmꢀ1) (Fig. 4(b)). This order of d–d transition
energy, dmpp < dmpe < dmpm, is unusual, since dmpm
ligand that forms a four-membered chelate ring is
expected to have a weaker interaction with the central
metal ion. In fact, the d–d transition energy was shifted
in the order of dmpp < dmpe > dmpm for the series of
[CoIII(Me2dtc)2(P–P)]+ and [CoIII(Me2dtc)(P–P)2]2+
complexes; this order was also confirmed by the AOM
analysis [17]. As seen in the crystal structures, the bite an-
gles of dmpm and dmpe ligands were within the ordinary
range for the CoIII complexes [17], while the Co–P bond
3.4. 59Co NMR spectra
It has been well established that the 59Co NMR chem-
ical shift, d(59Co), correlates well to the reciprocal
1T1g 1A1g (the first d–d) transition energy of the com-
plex [20]. The [Co(dmpe)3](BF4)3 complex was reported
to exhibit the 59Co NMR resonance at the very high-field
region (d(59Co) = ꢀ2530) [3], while the 59Co NMR spec-
trum of the analogous [Co(P)6]3+-type complex of [Co-
(tdmme)2](BF4)3 (160) showed its resonance at d(59Co) =
+ 180. The first d–d transition band of complex 160 was
observed at markedly lower energy region (23920 cmꢀ1
)
than that of [Co(dmpe)3](BF4)3 (26300 cmꢀ1), which cor-
relates well with the d(59Co) values for these complexes.
Furthermore, the [Co(P)3(S)3]3+-type complex, [Co-
(tdmme)(ttcn)](BF4)3 (ttcn = 1,4,7-trithiacyclononane),
showed the first d–d transition band at 24600 cmꢀ1 [21];
the 59Co NMR signal observed at d(59Co) = ꢀ200 is well
accommodated with this simple relation.
The 59Co NMR signals for the [CoCl(tdmme)(P–
P)]2+-type complexes (10–12) were observed at
d(59Co) = +710, +770, and +1330 for P–P = dmpm
(10), dmpe (11), and dmpp (12), respectively. Although
the absorption band appeared in the visible region orig-
inates from the splitting (a1Eg 1A1g) component of
the first d–d transition band, the order of the observed
transition energy was consistent with that of the
d(59Co) values; the ligand-field strength of dmpe in com-
plex 11 was weaker than that of dmpm in 10 due to the
steric congestion around the CoIII center.
The 59Co NMR resonances of the [CoCl2-
(tdmme)(P)]2+-type complexes were observed at much
lower-field region; d(59Co) = +2040 for the PMe3 com-
plex (3), +1710 for the P(OMe)3 complex (4), and
+2220 for the PMe2Ph complex (5), although the corre-
sponding absorption band maxima were observed in a
similar energy region to those of [CoCl(tdmme)-
(P–P)]2+-type complexes. The d(59Co) values of these
complexes indicated that the ligand-field strength of
P(OMe)3 on CoIII ion was larger than that of
PMe3 [22], while it was obscured in their absorption
spectra.
3.5. 31P NMR spectra
˚
lengths of dmpm complex 10 were shorter by 0.03–0.04 A
than those of dmpe complex 11. This is due to the steric
congestion around the CoIII center. This seems to be the
reason why the unusual order of the d–d transition
energy was observed for the series of complexes with
didentate P–P ligands.
For the RhIII series of complexes, the same tendency
of their d–d transition bands was observed, although the
The 31P NMR spectral data for the RhIII complexes are
listed in Table 4. In this series of complexes, clear tenden-
cies in the chemical shifts, d(31P), and/or the coupling con-
1
2
stants, JRh–P or JP–P, were observed. The trichloro
complex of [RhCl3(tdmme)] (2) showed a doublet
1
resonance at d 18.6 with JRh–P = 100.8 Hz. For the

T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
2511
Table 4
31P NMR data for the RhIII complexes (chemical shift from 85% H3PO4 in d-scale; J in Hz)
#
P-ligand
d(P) [JRh–P]
P
2
18.6 [100.8]
P
P
Cl
Cl
Rh
Cl
#
P-ligand
d(PA) [JRh–PA
]
d(PB) [JRh–PB
]
d(PC) [JRh–PC
]
(JPA-PB
)
(JPA-PC
)
(JPB-PC)
+
2+
3+
PB
6
7
8
9
–
PMe3
0.43 [76.3]
ꢀ1.19 [74.7]
2.19 [77.2]
1.30 [74.2]
6.16 [79.8]
13.56 [101.1]
15.74 [99.1]
12.04 [103.0]
14.95 [100.3]
9.75 [101.8]
ꢀ10.94 [83.7]
97.36 [143.4]
ꢀ6.97 [80.9]
(34.9)
(35.1)
(36.8)
(35.7)
(35.7)
(429.3)
(665.3)
(430.2)
(584.2)
(431.7)
(18.4)
(22.9)
(14.7)
(16.5)
(16.5)
PB
PA
PC
Cl
P(OMe)3
PMe2Ph
P(OMe)2Ph
PMePh2
Rh
Cl
131.81 [122.4]
ꢀ0.97 [82.5]
#
P—P
d(PA) [JRh–PA
]
d(PB) [JRh–PB
]
d(PC) [JRh–PC
]
(JPA-PB
)
(JPA-PC
)
(JPB-PC)
PB
Rh
Cl
13
14
15
dmpm
dmpe
dmpp
ꢀ0.23 [77.2]
ꢀ7.34 [75.3]
ꢀ6.37 [74.1]
11.08 [102.0]
6.51 [100.2]
4.74 [98.9]
ꢀ34.66 [69.9]
33.27 [80.2]
(42.3)
(36.4)
(36.6)
(342.9)
(312.2)
(315.6)
(19.3)
(17.7)
(17.9)
PA
PA
PC
PC
ꢀ16.61 [78.5]
#
d(P) [JRh–P
]
P
17
ꢀ14.02 [73.2]
P
P
P
Rh
P
P
[RhCl2- (tdmme)(P)]+- and [RhCl(tdmme)(P–P)]2+-type
complexes, there are two kinds of chemically non-equiva-
lent P atoms of tdmme; one (PA) is trans to P (of the phos-
phines) and the other (PB) is trans to Cl. The resonance
P–P ligands. Both d(31PA) and d(31PB) values exhibited
higher-field shifts in the order of dmpm < dmpe < dmpp.
1
1
Moreover, both JRh–PA and JRh–PB constants became
smaller in this order (Table 4). These observations are
consistent with the order of the Rh–P bond strengths;
dmpm > dmpe > dmpp, that is governed by the steric
congestion around the metal center (vide infra). On the
contrary, both the chemical shift, d(31PC), and the
1JRh–PC coupling constant of the P–P ligand decreased
in the order of dmpe (d 33.3, J = 80.2 Hz) > dmpp (d
ꢀ16.6, J = 78.5 Hz) ꢂ dmpm (d ꢀ34.7, J = 69.9 Hz),
which is consistent with the chelate ring size effect [23] ob-
served for the other series of complexes with P–P ligands.
1
due to the PB atom provides the JRh–PB values nearly
equal to 100Hz for all complexes, while the 1JRh–PA values
were remarkably smaller (73–80 Hz), which seems to orig-
inate from the mutual trans influence as observed in cis-
[RhCl2(dmpe or dmpp)2]+ [11]. Since the Rh–P bond
lengths became longer in the order [RhCl3(tdmme)] <
[RhCl2(tdmme)(P)]+ < [RhCl(tdmme)(P–P)]2+ < [Rh(td-
1
mme)2]3+, the JRh–P coupling constant is expected to
1
decrease in this order, although the difference in JRh–P
values for this series of complexes was too small to be dis-
cussed. On the other hand, the chemical shifts of the P
atoms on tdmme, d(31PA) and d(31PB), exhibited gradual
shifts toward the higher-field region in the above order;
i.e., d(31PB):[RhCl3(tdmme)](18.6) > [RhCl2(tdmme)(P)]+
(from 9–16) > [RhCl(tdmme)(P–P)]2+ (from 4.5–11);
d(31PA): [RhCl2(tdmme)(P)]+ (from ꢀ1.2 to 6) > [RhCl-
(tdmme)(P–P)]2+ (from ꢀ7.5 to 0) > [Rh(tdmme)2]3+
(ꢀ14.0).
4. Conclusion
In this study, the cobalt(III) and rhodium(III) com-
plexes of the series of [MIIICl3(P)3], [MIIICl2(P)4]+,
[MIIICl(P)5]2+, and [MIII(P)6]3+ have been completed with
the use of tripodal tridentate phosphine, 1,1,1-tris(dim-
ethylphoshinomethyl)ethane (tdmme), as a common
ligand. The single-crystal X-ray analyses of both series
of complexes revealed that the M–P and M–Cl bond
lengths were dependent primarily on the strong (mutual)
For the [RhCl(tdmme)(P–P)]2+-series complexes, the
chemical shifts and the coupling constants were found
to be dependent on the chelate ring size formed by the

2512
T. Suzuki et al. / Inorganica Chimica Acta 358 (2005) 2501–2512
trans influence of the phosphines; the steric congestion
around the metal center as a function of the number of
the coordinated phosphine donor groups is the secondary
important factor. The M–P(tdmme) bonds were found to
become longer in the order of [MCl3(tdmme)] < [MCl2-
(tdmme)(PMe3)]+ < [MCl(tdmme)(dmpe)]2+ < [M(tdm-
me)2]3+ for both CoIII and RhIII series of complexes, while
the M–Cl bonds were compressed in this order. This sec-
ondary steric effect, congestion around the metal center, is
also related to the structural and spectroscopic properties
of the series of [MCl(tdmme)(dmpm, dmpe or dmpp)]2+
complexes. The X-ray analysis for [CoCl(tdmme)(dmpm
or dmpe)](BF4)2 showed that all Co–P bonds in the dmpm
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