Selective formation of cis-diacyl, cis-PPh2R rhodium(III) complexes by the reaction of rhodium(III) cis-diacyl, trans-PPh2R complexes with aliphatic diamines

Article abstract of DOI:10.1039/b913244a

The cis-diacyl, trans-PPh₂R complex [RhCl(PPh ₂(o-C₆H₄CO))₂(pyridine)] (1) reacts with substituted aliphatic diamines to afford selectively cationic cis-diacyl, cis-PPh₂R, diamine derivativ

Full text of DOI:10.1039/b913244a

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Selective formation of cis-diacyl, cis-PPh2R rhodium(III) complexes
by the reaction of rhodium(III) cis-diacyl, trans-PPh2R complexes
with aliphatic diamines†
Mar´ıa A. Garralda,*a Ricardo Herna´ndez,a Elena Pinilla,b M. Rosario Torresb and Malkoa Zarandonaa
Received 3rd July 2009, Accepted 10th September 2009
First published as an Advance Article on the web 30th September 2009
DOI: 10.1039/b913244a
The cis-diacyl, trans-PPh2R complex [RhCl(PPh2(o-C6H4CO))2(pyridine)] (1) reacts with substituted
aliphatic diamines to afford selectively cationic cis-diacyl, cis-PPh2R, diamine derivatives
[Rh(PPh2(o-C6H4CO))2(NN¢)]+ (NN¢ = 1,2-diphenylethylenediamine, 2; 1,2-propanediamine, 3;
N-methylethylenediamine, 4; N,N-dimethylethylenediamine, 5; N,N¢-dimethylethylenediamine, 6;
N,N,N¢-trimethylethylenediamine, 7) with high stereoselectivity depending on the N-donor ligand
employed. Complexes 2 and 3 contain a single isomer, while 4 is a mixture of two isomers, 4a and 4b.
Formation of 4a occurs first and is followed by isomerisation to 4b until the equilibrium 4a:4b = 1:4
ratio is attained. In contrast, 5 and 6 contain a single isomer. More basic amino groups prefer positions
trans to an acyl group while less basic amino groups are trans to a phosphine group. The preferred
intramolecular N—H ◊ ◊ ◊ O hydrogen bond formation between an amino and an acyl coordinated
ligands, trans to the phosphorus atoms, appears to be relevant to the selectivity observed. 7 is a mixture
of two isomers 7a and 7b in a 7a:7b = 5.7:1 ratio. N,N,N¢,N¢-tetramethylethylenediamine or
N,N¢-diphenylethylenediamine led to the elimination of the N-donor ligands and the formation of a
mixture of isomers of [Rh2(m-Cl)(m-PPh2(o-C6H4CO))2(PPh2(o-C6H4CO))2]+ (8), where the Rh atoms
are triply bridged by two acyl groups in a head-to-tail arrangement and by a chloride. The reaction of
[Rh(PPh2(o-C6H4CO))2(ndmeen)]ClO4 (5) with acids led to the displacement of the diamine and the
formation of a [8a]+:[8b]+:[8c]+ = 1:1:3 mixture. 8c, containing the weakest s-donor oxygen atoms trans
to the strongest s-donor acyl groups, represents the most electronically favourable geometry for 8. All
the complexes were fully characterized spectroscopically. Single crystal X-ray diffraction analysis was
performed on 5, 6, 8a and 8b.
=
=
C O and C N double bonds have been of paramount importance
in research involving diamines as ligands. High efficiency, chemos-
electivity, and, in the case of prochiral ketones, enantioselectivity
were attained.6 Ruthenium dihydrides [RuH2(diamine)(PR3)2],
which can potentially exist as several geometric isomers, have been
proposed to be among the active catalysts for these reactions.7
Taking into account electronic considerations, the most stable
isomer would be the cis-dihydride, trans-PR3 isomer, with the
hydrides trans to the amino groups, since the hydride, having
the largest trans influence and being the best s-donor, would
prefer to be trans to the amino group with the lowest trans
influence, being the weakest s-donor.8,9 Though less favourable
from this point of view, some octahedral complexes of the platinum
metals containing trans-hydride ligands have also been reported.10
Studies on the formation of [RuH2(diamine)(PR3)2] have shown
a succession of isomerisation reactions so that the least stable
trans-dihydride, cis-PR3 isomer is formed first and isomerises
to the most stable cis-dihydride, trans-PR3 isomer, via the cis-
dihydride, cis-PR3 intermediate, to reach equilibrium mixtures
of the two latter isomers containing a higher proportion of
the most stable isomer.7c Cationic [MH2(amine)2(PR3)2]+ (M =
Rh, Ir) have been reported to be of the cis-dihydride, trans-
PR3 type.11 Calculations on [IrHCl(PMe3)4]+ complexes have
shown that the trans- and cis-H, Cl structures are nearly iso-
energetic.9
Introduction
Organometallic rhodium complexes containing phosphorus lig-
ands play an important role in the transformation of many
organic compounds.1,2 More recently, nitrogen ligands are be-
ing more widely used in the design of regio- and/or enan-
tioselective catalytic systems.3 Rhodium(I) complexes such as
[Rh(CO)2(diamine)][Rh(CO)2Cl2], in the absence of a phosphorus
ligand, are able to catalyze the hydroformylation of olefins
under mild conditions and afford also a novel route to 1,2,3,4-
tetrahydroquinolines in a highly chemo- and regioselective manner
and in good isolated yields.4 Other rhodium systems with chiral
amino-containing bidentate ligands allow the reduction of a-
acylaminocinnamate derivatives or of prochiral carbonyl com-
pounds with excellent enantioselectivities.5
Noyori’s pioneering reports on ruthenium complexes
[RuCl2(diamine)(phosphine)2], containing both diamine and
phosphine or diphosphine ligands, as catalysts in the reduction of
aFacultad de Qu´ımica de San Sebastia´n, Universidad del Pa´ıs Vasco, Apdo.
1072, 20080, San Sebastia´n, Spain. E-mail: mariaangeles.garralda@ehu.es
bDepartamento de Qu´ımica Inorga´nica, Laboratorio de Difraccio´n de
Rayos X, Facultad de Ciencias Qu´ımicas, Universidad Complutense, 28040,
Madrid, Spain.
† CCDC reference numbers 738631–738634. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b913244a
9860 | Dalton Trans., 2009, 9860–9869
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Recently we have reported on the formation of rhodium(III)
bis(acylphosphine) complexes containing acyl groups, whose trans
effect is almost as high as that of hydride.12 [RhCl(PPh2(o-
C6H4CO))2(pyridine)] (1) is the expected cis-diacyl, trans-PPh2R
complex, while [RhCl(PPh2(o-C6H4CO))2(2-aminopyridine)] (1¢)
contains a mixture of cis-diacyl, trans-PPh2R and trans-diacyl,
cis-PPh2R isomers (Scheme 1), the most and least electronically
favoured respectively. Also, the reaction of 1¢ with bidentate
N-donors was extraordinarily selective to afford [Rh(PPh2(o-
C6H4CO))2(NN¢)]+ complexes that were only cis-diacyl, trans-
PPh2R isomers when NN¢ = diimines. When NN¢ contained
amino groups, isomerisation reactions were observed, assisted
by ion pairing formation via hydrogen bonding, to afford cis-
diacyl, cis-PPh2R derivatives.13 We report now on the reactions of
1, a cis-diacyl, trans-PPh2R complex, with differently substituted
chelating diamines to give different isomer ratios of cis-diacyl, cis-
PPh2R, complexes, depending on the diamine. Crystallographic
studies on the obtained complexes are also reported.
Scheme 2
The 31P{ H} NMR spectrum contains two doublets of doublets
consistent with an AMX pattern due to two mutually cis phos-
phorus atoms (J(P,P) of 15 Hz). The resonance at lower field
(PA, 57.8 ppm) agrees with a phosphorus atom being trans to
nitrogen (J(Rh,P) = 156 Hz),8 while the resonance at higher field
(PM, 15.9 ppm) is consistent with a phosphorus atom trans to
1
Scheme 1
Results and discussion
1
The reaction of 1 with different aliphatic chelating diamines
proceeds with displacement of the pyridinic ligand and
also of chloride to afford selectively cationic cis-diacyl, cis-
PPh2R, diamine complexes [Rh(PPh2(o-C6H4CO))2(NN¢)]+
(NN¢ = 1,2-diphenylethylenediamine (stien), 2; 1,2-propane-
diamine (pn), 3; N-methylethylenediamine (meen), 4; N,N-
dimethylethylenediamine (ndmeen), 5; N,N¢-dimethylethyl-
enediamine (dmeen), 6; N,N,N¢-trimethylethylenediamine
(trimeen), 7) (Scheme 2), which were isolated as the corresponding
perchlorate salts by addition of sodium perchlorate (see
Experimental section). The obtained complexes show the
expected features in their IR spectra, their FAB spectra contain
the parent peaks and they behave as 1:1 electrolytes in acetone
solution.14
an acyl group (J(Rh,P) = 74 Hz).15 Accordingly, the 13C{ H}
NMR spectrum shows two doublets of doublets at low field.
The resonance at lower field (CA, 237.7 ppm) is due to the acyl
group trans to phosphorus (J(P,C) = 105 Hz), while the reso-
nance at higher field (CM, 231.4 ppm) corresponds to the
1
acyl group trans to nitrogen. The H NMR spectrum contains
four resonances due to the amino groups in a broad range, 5.38–
1.48 ppm. The corresponding chemical shift values could well
result as a combination of a downfield shift due to coordination to
the metal that can be enhanced by some extent of hydrogen bond
formation,13b,16 and an upfield shift due to the ring current effects
originated by the aromatic rings of the phosphine.17 The non-
symmetric 1,2-diaminopropane gives selectively a single complex,
3, although two isomers are possible. The relative stereochemistry
of the amino groups remains uncertain and the structure shown
in Scheme 2ii is tentative. The 31P chemical resonances of the acyl-
phosphine fragments in 3 (PA, 63.5 ppm; PM, 26.9 ppm) appear at
1,2-Diphenylethylenediamine, containing two primary amino
groups, leads to complex [Rh(PPh2(o-C6H4CO))2(stien)]ClO4 (2)
(Scheme 2i) that was fully characterized by spectroscopic means.
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˚
lower field than in 2, and the resonances due to the amino groups
appear in the 3.80–1.23 ppm range.
Table 1 Selected bond lengths (A) and angles (deg) for 5 and 6 including
the hydrogen bonds
The reaction of 1 with N-methyl-substituted-ethylenediamines
may afford different isomers and the selectivity of the re-
action depends markedly on the diamine employed. N-
Methylethylenediamine led to the formation of compound
[Rh(PPh2(o-C6H4CO))2(meen)]ClO4 (4). By following the course
of this reaction by NMR we observed the initial formation of
isomer 4a, shown in Scheme 2iii, formulated as containing the
primary amino group trans to an acyl group. 4a then undergoes
an isomerisation reaction to afford 4b, until a mixture of both
complexes in a ca. 4a:4b = 1:4 ratio is attained. We find most likely
that 4b contains the more basic of the amino groups trans to an
acyl group as observed in complex 5 (vide infra). The isomerisation
reaction is rather slow at room temperature (3 days) and can be
made faster by heating in CHCl3 (3 h). By addition of NaClO4,
[4b]ClO4 can be obtained pure, probably due to a lower solubility.
Upon dissolution, the isomerisation of [4b]ClO4 into [4a]ClO4
occurs until the 4a:4b = 1:4 ratio equilibrium mixture is reached.
The spectroscopic features of compound 4 are similar to those of
3. The resonances due to the amino groups for 4b appear in the
5.09–0.95 ppm range.
5
6
Rh–P1
Rh–P2
Rh–C20
Rh–Cl
Rh–N2
Rh–N1
C20–O2
C1–O1
N2–H21
N2–H22
O2 ◊ ◊ ◊ H21
O2A ◊ ◊ ◊ H22
N2 ◊ ◊ ◊ O2
N2 ◊ ◊ ◊ O2A
2.460(1)
2.304(1)
2.068(5)
2.009(5)
2.155(4)
2.374(4)
1.222(6)
1.213(6)
0.91
0.95
2.08
2.37
2.793(6)
3.022(6)
Rh–P1
Rh–P2
2.465(1)
2.293(1)
2.061(3)
2.003(3)
2.174(2)
2.282(2)
1.221(3)
1.220(3)
1.07
1.10
1.83
2.11
2.766(3)
3.074(4)
Rh–C20
Rh–C1
Rh–N2
Rh–N1
C20–O2
C1–O1
N1–H1
N2–H2
O2 ◊ ◊ ◊ H2
O6 ◊ ◊ ◊ H1
N2 ◊ ◊ ◊ O2
N1 ◊ ◊ ◊ O6
P1–Rh–P2
98.39(5)
168.5(2)
92.7(1)
84.1(2)
100.6(1)
82.6(2)
167.8(1)
88.9(2)
104.3(1)
85.6(2)
84.4(2)
90.2(2)
87.1(2)
78.6(2)
165.0(2)
133.4
P1–Rh–P2
97.70(3)
171.8(1)
94.7(1)
83.8(1)
99.4(1)
82.1(1)
166.8(1)
88.4(1)
102.9(1)
85.0(1)
88.0(1)
88.6(1)
88.3(1)
79.6(1)
167.7(1)
140.1
P1–Rh–C20
P1–Rh–N2
P1–Rh–C1
P1–Rh–N1
P2–Rh–C20
P2–Rh–N2
P2–Rh–C1
P2–Rh–N1
C20–Rh–N2
C20–Rh–C1
C20–Rh–N1
C1–Rh–N2
N1–Rh–N2
C1–Rh-N1
N2-H21 ◊ ◊ ◊ O2
N2-H22 ◊ ◊ ◊ O2A
P1–Rh–C20
P1–Rh–N2
P1–Rh–C1
P1–Rh–N1
P2–Rh–C20
P2–Rh–N2
P2–Rh–C1
P2–Rh–N1
C20–Rh–N2
C20–Rh–C1
C20–Rh–N1
N2–Rh–C1
N2–Rh–N1
C1–Rh–N1
N2-H2 ◊ ◊ ◊ O2
N1-H1 ◊ ◊ ◊ O6
In contrast to this behaviour, the reaction of
1 with
N,N-dimethylethylenediamine is totally selective to the
formation of only one isomer, compound [Rh(PPh2(o-
C6H4CO))2(ndmeen)]ClO4 (5) shown in Scheme 2iv, containing
the more basic of the amino groups trans to an acyl group.
As expected, N,N¢-dimethylethylenediamine affords only one
compound [Rh(PPh2(o-C6H4CO))2(dmeen)]ClO4 (6) shown in
Scheme 2v. Complexes 5 and 6 show similar spectroscopic
features to those of 4. The 31P chemical shifts of the acyl-
phosphine fragments in 5 or 6 (PA, 60.8 or 62.8 ppm; PM, 20.2 or
20.9 ppm) appear at higher field than in 3, and the resonances
due to the amino groups appear at 4.04 and 3.10 ppm for 5 or at
5.09 and 4.35 ppm for 6.
125.4
148.7
(A) -x + 1, -y + 2, -z + 1.
Complexes 5 and 6 could also be characterised by single crystal
X-ray diffraction. 5 crystallizes in the P21/c monoclinic group
and 6 crystallizes in the Pbca orthorhombic group. Fig. 1 and
Fig. 2 show ORTEP views of complexes 5 and 6 respectively
with the labelling schemes of the asymmetric unit. Selected bond
distances and angles are listed in Table 1. In both complexes
the formula unit consists of one complex cation [Rh(PPh2(o-
C6H4CO))2(ndmeen)] for 5 or [Rh(PPh2(o-C6H4CO))2(dmeen)] for
6 and a perchlorate anion. The coordinative environment of the
rhodium atom is distorted octahedral with four positions occupied
by the two bidentate acyl-phosphine ligands and the other two
positions occupied by the also bidentate diamino ligand. The
P1–Rh–P2 angles (98.39 (5) and 97.70(3)◦) confirm that in both
5 and 6 the phosphorus atoms are mutually cis, and trans to
an acyl or to an amino group. In complex 5, the P2–Rh–N2
angle (167.8(1)◦) indicates that a phosphorus atom is trans to
the primary amino group and consequently the more basic
dimethylamino group is trans to acyl (C1–Rh–N1 = (165.0(2)◦).
Inspection of the bond lengths in these complexes shows that the
Rh–N, Rh–P and Rh–C distances are in the expected ranges,13,17b
and that the corresponding values for each type of bond differ
significantly and agree with the trans influence order of the
ligands: acyl ꢀ phosphine > amine.12,18 The difference between
Fig. 1 ORTEP view of the cation in compound 5 showing the atomic
numbering (20% probability ellipsoids) and the intramolecular hydrogen
bond. The labelling of some carbon atoms and the hydrogen atoms except
two have been omitted for clarity.
containing secondary amino groups, follows this order. The rather
large difference between the Rh–N1 and Rh–N2 bond lengths of
˚
the Rh–N1 and Rh–N2 bond lengths of 0.108(2) A in complex 6,
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Fig. 2 ORTEP view of 6 showing the atomic numbering (40% probability ellipsoids) and the intramolecular and intermolecular hydrogen bonds. The
labelling of some carbon atoms and the hydrogen atoms except two have been omitted for clarity.
˚
According to the previous results, the reaction of 1 with N,N,N¢-
trimethylethylenediamine, containing a secondary and a tertiary
amino group, affords a mixture of two isomers 7a:7b = 5.7:1,
shown in Scheme 2vi. Complex 7 was characterized spectroscop-
ically. Its spectral features are similar to those of complexes 2–6
and the resonance due to the amino group appears at 5.10 ppm.
Following our previous results we propose that the most abundant
isomer 7a contains the more basic amino group trans to an acyl
group.
0.219(4) A in complex 5 can also be related to a higher difference
of steric crowding between the dimethylamino group (N1) and the
primary amino group (N2).
In both complexes 5 and 6, the N2 atom of the amino group
trans to phosphorus forms a strong intramolecular hydrogen bond
with the oxygen atom of the acyl group trans to the other phos-
˚
phorus atom N2–H21 ◊ ◊ ◊ O2 for 5 (N2 ◊ ◊ ◊ O2 = 2.793(6) A) and
˚
N2–H2 ◊ ◊ ◊ O2 for complex 6 (N2 ◊ ◊ ◊ O2 = 2.766(3) A). Hydrogen
bonding plays a key role in chemical and catalytic processes among
others and metals can play a considerable and varied role in
hydrogen bonding.19 We observe that the intramolecular hydrogen
bond formation in 5 and 6 occurs between the amino group with
the shortest Rh–N distance (trans to PA) and the acyl group with
the longest Rh–C distance (trans to PM) suggesting that the relative
situation of both groups appears most suitable for the formation
of this strong hydrogen bond. We believe that the formation of
these hydrogen bonds is relevant to the preference observed in
5 to locate the more basic amino group trans to the acyl group
thus making the primary amino group trans to phosphorus and
available for the observed intramolecular hydrogen bond forma-
tion. In related cis-diacyl, cis-PPh2R [Rh(PPh2(o-C6H4CO))2(2-
(aminomethyl)pyridine)]ClO4, containing a primary amino group
trans to acyl, no intramolecular hydrogen bond formation has
been observed.13b Steric effects in these crowded molecules may
also play a role in the observed selectivity.
Attempts to isolate diacyl complexes similar to 2–7 using
more sterically demanding aliphatic diamines such as N,N,N¢,N¢-
tetramethylethylenediamine or N,N¢-diphenylethylenediamine
proved unsuccessful. Instead, the formation of a mixture of
isomers 8a and 8b (Scheme 3) of the dimer cationic species [Rh2(m-
Cl)(m-PPh2(o-C6H4CO))2(PPh2(o-C6H4CO))2]+ (8) occurred. Most
likely these ligands also promote the displacement of pyridine and
chloride from 1, but their higher steric hindrance leads to the
elimination of these N-donor ligands and to the formation of 8.
The protonation of 1 also affords the formation of 8 along with
pyridinium salts, therefore the reaction of 1 with aqueous HClO4
or with HBF4·OEt2 allowed the isolation of a [8a]A:[8b]A = 1:1.5
mixture (A = ClO4 or BF4).
Compound [8]ClO4 behaves as 1:1 electrolyte in acetone so-
lution and the FAB spectrum shows the [M]+ peak at 1397 as
expected for such a dinuclear species. It shows an IR stretch
at 1653 cm-1 due to the terminal acyl groups and a strong
stretch at 1548 cm-1 that can be assigned to bridging acyl groups.
The N2 atom of the primary amino group in complex 5 also
forms a weaker intermolecular hydrogen bond, N2–H22 ◊ ◊ ◊ O2A,
with the O2 atom of a centrosymmetric cation (N2 ◊ ◊ ◊ O2A =
1
Consequently the 13C{ H} NMR spectrum contains multiplets at
˚
ca. 220 ppm due to terminal acyl groups and also resonances at
ca. 260 ppm, with high J(P,C) coupling constants of ca. 100 Hz,
that we assign to bridging acyl groups with carbon atoms trans
to phosphorus atoms. Bridging acyls can be described by acyl ↔
3.022(6) A). This intermolecular interaction leads to the formation
of dimers. In complex 6 the N1 atom of the amino group
not involved in the intramolecular hydrogen bond, forms a
weaker intermolecular hydrogen bond, N1–H1 ◊ ◊ ◊ O6, with the
=
˚
oxycarbene resonance structures and the energy of the v(C O)
oxygen atom of the perchlorate anion (N1 ◊ ◊ ◊ O6 = 3.074 (4) A)
band and the shift of the carbon atom in the 13C NMR spectrum
(see Fig. 2).
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1,1-bis(diphenylphosphino)methane rhodium(I) complexes such
-1
13
=
=
as [Rh2(m-CH3CO)(CO)2(m-dppm)2] (v(C O), 1485 cm ; d C O,
322.0 ppm),21 or [RhM(CF3SO3)(CO)2(m-CO)(m-CH3CO)(m-
13
=
dppm)2]CF3SO3 (d C O, 304.8 (M = Ru) or 313.3 (M =
Os) ppm),22 while for [RhRu(CO)2(m-(CH3)2C CCH2CH2CO)(m-
=
13
=
dppm)2]CF3SO3 (d C O, 250.7 ppm) a lower carbene-character
has been suggested.23 Comparison of these data with those of 8
suggests a low oxycarbene character for the acyl bridges in 8.
The 31P{ H} NMR spectrum of the mixture of 8a and 8b consists
1
of two sets of resonances. Two doublets of doublets consistent
with an AMX pattern form one set due to 8a containing two
equivalent rhodium fragments. The other set is formed by four
doublets of doublets due to the presence of four non-equivalent
acylphosphine fragments, two per rhodium atom of 8b. The J(P,P)
coupling constants agree with both phosphorus atoms bonded
to the same rhodium atom being mutually cis and the J(Rh,P)
coupling constants agree with phosphorus atoms being trans to
oxygen or to acyl in 8a or to oxygen, chlorine or acyl in 8b.
We succeeded in isolating compounds [8a]BF4 and [8b]ClO4
as single crystals suitable for X-ray diffraction by fractional
crystallization. These compounds crystallize in the C2c and
P2(1)/n monoclinic groups respectively. For 8a the Cl atom and
the B atom lie on a twofold axis, therefore the asymmetric unit
-
consists of a half dimeric cation and a half BF4 anion. For 8b
-
the asymmetric unit consists of a dinuclear cation and a ClO4
anion. Figs. 3 and 4 show ORTEP views of the cations with the
labelling scheme of the asymmetric unit. Selected bond distances
and angles are listed in Table 2. In both isomers two acyl groups
in a head-to-tail arrangement and a chloride bridge the Rh atoms.
In 8a the geometry around each Rh atom is pseudo-octahedral
with the chloro ligand trans to the carbon atoms of terminal acyl
Scheme 3
toward lower field have been reported to be strongly dependent on
the amount of oxycarbene character present in the bridging acyl
ligands.20 Carbene-like character has been proposed for several
˚
groups. The bridging Rh–Cl distance (2.510(3) A) is similar to
˚
Table 2 Selected bond lengths (A) and angles (deg) for 8a and 8b
8a
8b
Rh1–P1
Rh1–P2
2.372(3)
2.249(3)
2.01(1)
1.96(1)
2.510(3)
2.18(1)
1.22(1)
1.26(3)
3.522(2)
Rh1–P1
Rh1–P2
Rh1–C20
Rh1–C1
Rh1–CL1
Rh1–O4
C20–O2
C1–O1
2.387(2)
2.266(2)
2.030(6)
1.992(6)
2.454(2)
2.292(4)
1.246(6)
1.220(7)
3.582(1)
Rh2–P3
Rh2–P4
Rh2–C58
Rh2–C39
Rh2–CL1
Rh2–O2
C39–O3
C58–O4
2.388(2)
2.254(2)
2.040(6)
2.011(6)
2.514(2)
2.144(4)
1.201(7)
1.240(7)
Rh1–C20
Rh1–C1
Rh1—CL
Rh1–O2
C20–O2A
C1–O1
Rh1-Rh1A
Rh1-Rh2
P1–Rh1–P2
P1–Rh1–C20
P1–Rh1–O2
P1–Rh1–C1
P1–Rh1—CL
P2–Rh1–C20
P2–Rh1–O2
P2–Rh1–C1
P2–Rh1–CL
C20–Rh1–O2
C20–Rh1–C1
C20–Rh1–CL
O2–Rh1–C1
O2–Rh1–CL
CL–Rh1-C1
101.8(1)
175.2(3)
85.7(2)
83.5(3)
96.5(1)
81.9(3)
167.6(2)
87.8(4)
102.9(1)
90.1(3)
93.7(4)
85.5(3)
83.3(4)
85.8(2)
169.1(4)
P1–Rh1–P2
99.8(1)
177.6(2)
88.7(1)
84.3(2)
95.6(1)
81.4(2)
168.1(1)
84.8(2)
104.4(1)
89.9(2)
93.8(3)
86.1(2)
87.7(2)
170.6(2)
82.9(1)
P3–Rh2–P4
P3–Rh2–C58
P3–Rh2–O2
101.5(1)
175.7(2)
86.4(1)
98.7(1)
84.2(2)
80.2(2)
168.8(1)
101.9(1)
89.0(2)
90.8(2)
84.3(2)
92.3(3)
84.5(1)
83.9(2)
167.9(2)
P1–Rh1–C20
P1–Rh1–CL1
P1–Rh1–C1
P1–Rh1–O4
P2–Rh1–C20
P2–Rh1–CL1
P2–Rh1–C1
P2–Rh1–O4
C20–Rh1–CL1
C20–Rh1–C1
C20–Rh1–O4
C1–Rh1–CL1
C1–Rh1–O4
CL1–Rh1–O4
P3–Rh2–CL1
P3–Rh2–C39
P4–Rh2–C58
P4–Rh2–O2
P4–Rh2–CL1
P4–Rh2–C39
C58–Rh2–O2
C58–Rh2–CL1
C58–Rh2–C39
O2–Rh2–CL1
O2–Rh2–C39
CL1–Rh2–C39
(A) -x, y, -z + 3/2.
9864 | Dalton Trans., 2009, 9860–9869
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Fig. 3 ORTEP view of the cation in compound [8a]BF4 showing the atomic numbering (20% probability ellipsoids). The hydrogen atoms and the labels
of some carbon atoms have been omitted for clarity (symmetry operation -x, y, -z + 3/2).
Fig. 4 ORTEP view of the cation in compound [8b]ClO4 showing the atomic numbering (20% probability ellipsoids). The hydrogen atoms and the labels
of some carbon atoms have been omitted for clarity.
carbene-like character,21–23 the Rh–C distances (2.01(1) A) are in
the Rh–Cl distances reported for complexes containing a terminal
˚
˚
or a bridging chlorine ligand trans to acyl (2.521(1) A) or benzyl
˚
the upper end of the range reported (1.907(7)–2.05(2) A) and
the (C–O) distances (1.22(1) A) are somewhat shorter than the
13a,24
˚
(2.507(2) and 2.522(2) A) groups respectively.
Carbene-like
˚
character in bridging acyls is reflected by shorter M–C and longer
C–O bond distances than in terminal acyl ligands. The Rh–C
and the C–O distances of the bridging and terminal acyl groups
in 8a are equal. Compared to other rhodium complexes with
˚
range observed (1.24–1.29 A). These observations confirm the low
carbenoid character of the bridging acyl groups in 8, suggested
by the spectroscopic data. In 8b the rhodium atoms Rh1 and
Rh2 show a different disposition of the ligands. Consequently the
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chlorine ligand is trans through Rh2 to the carbon atom of a
terminal acyl group, as in 8a, and to a phosphorus atom through
the Rh1 atom. In accordance with the different trans influence, the
with a Nicolet FTIR 510 spectrophotometer in the range 4000–
400 cm-1 using KBr pellets. NMR spectra were recorded with
Bruker Avance DPX 300 or Bruker Avance 500 spectrometers, 1H
and 13C{ H} (TMS internal standard), 31P{ H} (H3PO4 external
standard) and 2D spectra were measured from CDCl3 solutions.
Mass spectra were recorded on a VG Autospec, by liquid
secondary ion (LSI) MS using nitrobenzyl alcohol as matrix and
a caesium gun (Universidad de Zaragoza).
1
1
˚
Rh2–Cl distance (2.514(2) A) is longer than the Rh1–Cl distance
˚
2.454(2) A. Other structural features are similar to those in 8a.
The Rh–P distances reflect the decreasing trans influence in the
˚
series: acyl (Rh1–P1 = Rh2–P3 = 2.387(2) A) ꢀ chlorine
˚
˚
(Rh1–P2 = 2.266(2) A) > oxygen (Rh2–P4 = 2.254(2) A).
The dihedral angles between the best least-square planes of the
metallocycle and the condensed ring depend on the chelating
or bridging-chelating nature of the ligand and also on the
coordinative environment of the rhodium atom.25 In all cases
the highest deviation from planarity corresponds to the bridging-
chelating ligands. Surroundings such as those in 8a also lead to a
larger deviation from planarity.
[Rh(PPh2(o-C6H4CO))2(stien)]ClO4 (2). To
a
dichloro-
methane suspension of [RhCl(PPh2(o-C6H4CO))2(py)] (60 mg,
0.075 mmol) was added stilbenodiamine (16.0 mg, 0.074 mmol)
whereupon a yellow solution was formed. After stirring for 1 h,
a methanol solution of NaClO4·H2O (10.5 mg, 0.075 mmol)
was added. Evaporation to dryness and dissolution of the solid
residue in dichloromethane was followed by filtration through
A third isomer, 8c shown in Scheme 3, is also possible. In the re-
action of 1 with acids the starting material contains mutually trans
phosphorus atoms and the formation of 8 requires a displacement
reaction and also an isomerisation reaction. We reasoned that
by using a starting material containing cis phosphorus atoms,
complex 8c could be more easily obtained. 8c, containing the
weakest s-donor oxygen atoms trans to the strongest s-donor acyl
groups, represents the most electronically favourable geometry for
8. Indeed, the reaction of [Rh(PPh2(o-C6H4CO))2(ndmeen)]ClO4
(5) with HCl led to the displacement of the diamine and the
formation of a [8a]A:[8b]A:[8c]A = 1:1:3 mixture (A = ClO4)
where the most abundant isomer is 8c. In 8c a cisoid disposition of
the phosphine groups of the bridging-chelating ligands binding to
the same face of the complex, and also a cisoid disposition of the
acyl-phosphine terminal groups is observed. Repeated attempts to
obtain single crystals of 8c to perform an X-ray diffraction study
proved unsuccessful.
R
Celiteꢀ. Addition of diethyl ether gave a yellow solid that was
filtered off, washed with diethyl ether and vacuum dried. Yield:
-1
=
75%. IR (KBr, cm ): 3344(s), 3293(s), n(NH); 1648(s), n(C O).
KM (X-1 cm2 mol-1): 152 (acetone). H NMR (CDCl3): d 5.38
1
(m, 1H, NH); 4.80 (m, 1H, CH); 4.31 (m, 1H, NH); 3.60 (m,
1
1H, CH); 3.33 (m, 1H, NH), 1.48 (m, 1H, NH). 31P{ H} NMR
(CDCl3): d 57.8 (dd, J(Rh,P) = 156 Hz, J(P,P) = 15 Hz, PA);
1
15.9 (dd, J(Rh,P) = 74 Hz, PM ). 13C{ H} NMR (CDCl3): d 237.3
(dd, J(P,C) = 105 Hz, J(Rh,C) = 30 Hz, RhCAO); 231.4 (dd,
J(P,C) = 10, J(Rh,C) = 29 Hz, RhCM O); 64.7 (s, CH); 57.2 (s,
CH). FAB-MS: calcd for C52H44N2O2P2Rh, 893; obsd, 893 [M+].
Anal. calc. for C52H44ClN2O6P2Rh: C, 62.88; H, 4.47; N, 2.82;
found: C, 62.56; H, 4.74; N, 2.88%.
[Rh(PPh2(o-C6H4CO))2(pn)]ClO4 (3). To a chloroform sus-
pension of [RhCl(PPh2(o-C6H4CO))2(py)] (50 mg, 0.063 mmol)
was added 1,2-propanediamine (4.7 mg, 0.063 mmol) whereupon
a yellow solution was formed. After refluxing over 4 h, a
methanol solution of NaClO4·H2O (8.9 mg, 0.063 mmol) was
added. Evaporation to dryness and dissolution of the solid residue
Conclusions
R
in dichloromethane was followed by filtration through Celiteꢀ.
Cationic diacyl, bis(phosphine), aliphatic diamine rhodium(III)
complexes adopt selectively the cis-diacyl, cis-PPh2R geometry. In
complexes containing N-methyl substituted diamines, more basic
amino groups prefer positions trans to an acyl group while less
basic amino groups are trans to a phosphine group. The preferred
intramolecular N—H ◊ ◊ ◊ O hydrogen bond formation between an
amino and an acyl coordinated ligand, trans to phosphorus atoms,
appears to be relevant to the selectivity observed. Elimination of
the N-donor ligands allow the preparation of dimer complexes
containing two acyl groups in a head-to-tail arrangement and
a chloride bridging the Rh atoms. A mixture of three possible
isomers can be obtained with a higher amount of the isomer
showing the most electronically favourable geometry.
Addition of diethyl ether gave a yellow solid that was filtered
off, washed with diethyl ether and vacuum dried. Yield: 59%. IR
-1
=
(KBr, cm ): 3323(m), 3283 (m), n(NH); 1637(s), n(C O). KM
(X-1 cm2 mol-1): 121 (acetone). 1H NMR (CDCl3): d 3.80 (s, 2H,
NH); 2.93 (m, 1H, CH2); 2.66 (s, 1H, NH); 2.34 (m, 1H, CH2), 1.92
1
(s, 1H, CH); 1.23 (s, 1H, NH); 0.95 (m, 3H, CH3). 31P{ H} NMR
(CDCl3): d 63.5 (dd, J(Rh,P) = 151 Hz, J(P,P) = 18 Hz, PA); 26.9
1
(dd, J(Rh,P) = 79 Hz, PM ). 13C{ H} NMR (CDCl3): d 239.6 (dd,
J(P,C) = 109 Hz, J(Rh,C) = 30 Hz, RhCAO); 234.2 (dd, J(P,C) =
9 Hz, J(Rh,C) = 29 Hz, RhCM O); 53.2 (s, CH); 46.8 (s, CH2); 20.0
(s, CH3). Anal. calc. for C41H38ClN2O6P2Rh·0.5CH2Cl2: C, 55.54;
H, 4.38; N, 3.12; found: C, 55.68; H, 4.96; N, 3.43%.
[Rh(PPh2(o-C6H4CO))2(meen)]ClO4 (4). To
a
dichloro-
Experimental
methane suspension of [RhCl(PPh2(o-C6H4CO))2(py)] (40 mg,
0.05 mmol) was added N-methylethylenediamine (3.7 mg,
0.05 mmol) whereupon a yellow solution was formed. After
stirring for 3 days, a methanol solution of NaClO4·H2O (7.0 mg,
0.05 mmol) was added. Evaporation of dichloromethane gave
a yellow solid that was filtered off, washed with methanol and
vacuum dried. Yield: 42%. IR (KBr, cm-1): 3327(m), 3287(m),
General procedures
The preparation of the metal complexes was carried out at
room temperature under nitrogen by standard Schlenk techniques.
[RhCl(PPh2(o-C6H4CO))2(py)] (1)13a was prepared as previously
reported. Microanalyses were carried out with a Leco CHNS–932
microanalyser. Conductivities were measured in acetone solution
with a Metrohm 712 conductimeter. IR spectra were recorded
n(NH); 1631(s), n(C O). KM (X-1 cm2 mol-1): 127 (acetone). Data
=
1
for 4a. 31P{ H} NMR (CDCl3): d 64.5 (dd, J(Rh,P) = 157 Hz,
9866 | Dalton Trans., 2009, 9860–9869
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R
by filtration through Celiteꢀ. Addition of diethyl ether gave a
yellow solid that was filtered off, washed with diethyl ether and
vacuum dried. Yield: 48%. IR (KBr, cm-1): 3263(m), n(NH);
1
J(P,P) = 18 Hz, PA); 23.2 (dd, J(Rh,P) = 74 Hz, PM ). 13C{ H}
NMR (CDCl3): d 52.5 (s, CH2); 43.3 (s, CH2); 40.8 (s, CH3). Data
for 4b. 1H NMR (CDCl3): d 5.09 (s, 1H, NH); 3.98 (s, 1H, NH);
3.18 (m, 1H, CH2); 2.60 (m, 2H, CH2); 2.31 (m, 1H, CH2); 1.82
1636(s), n(C O). KM (X-1 cm2 mol-1): 107 (acetone). FAB-MS:
=
calcd for C43H42N2O2P2Rh, 783; obsd, 783 [M+]. Anal. calc. for
(m, 3H, CH3); 0.95 (m, 1H, NH). 31P{ H} NMR (CDCl3): d 62.3
1
C43H42ClN2O6P2Rh·0.5CH2Cl2: C, 56.45; H, 4.68; N, 3.03; found:
(dd, J(Rh,P) = 150 Hz, J(P,P) = 18 Hz, PA); 23.8 (dd, J(Rh,P) =
1
80 Hz, PM ). 13C{ H} NMR (CDCl3): d 240.1 (dd, J(Rh,C) =
1
C, 56.06; H, 4.24; N, 3.23%. Data for 7a. H NMR (CDCl3):
d 5.10 (s, 1H, NH); 2.90 (m, 1H, CH2); 2.85 (m, 3H, CH3);
30 Hz, J(P,CO) = 108 Hz, RhCAO); 237.4 (dd, J(Rh,C) = 29 Hz,
J(P,CO) = 8 Hz, RhCM O); 56.5 (s, CH2); 40.8 (s, CH2); 38.9 (s,
CH3). FAB-MS: calcd for C41H38N2O2P2Rh, 755; obsd, 755 [M+].
Anal. calc. for C41H38ClN2O6P2Rh: C, 57.59; H, 4.48; N, 3.28;
found: C, 57.08; H, 4.07; N, 3.60%.
2.74 (m, 2H, CH2); 2.35 (m, 1H, CH2); 1.85 (m, 3H, CH3); 1.12
(m, 3H, CH3). 31P{ H} NMR (CDCl3): d 57.8 (dd, J(Rh,P) =
1
156 Hz, J(P,P) = 15 Hz, PA); 15.9 (dd, J(Rh,P) = 76 Hz, PM ).
13C{ H} NMR (CDCl3): d 235.9 (dd, J(Rh,C) = 32 Hz, J(P,CO) =
1
104 Hz, RhCAO); 231.6 (m, br, RhCM O); 61.2 (s, CH2); 54.5 (s,
CH3); 53.5 (s, CH2); 51.5 (s, CH3); 39.2 (s, CH3). Data for 7b. 1H
NMR (CDCl3): d 2.85 (m, 1H, CH2); 2.40 (m, 3H, CH3); 2.29
(m, 3H, CH3); 2.20 (m, 1H, CH2); 2.04 (m, 1H, CH2); 1.73 (m,
[Rh(PPh2(o-C6H4CO))2(ndmeen)]ClO4 (5). To
a dichloro-
methane suspension of [RhCl(PPh2(o-C6H4CO))2(py)] (50 mg,
0.063 mmol) was added N,N-dimethylethylenediamine, (5.6 mg,
0.063 mmol) whereupon a yellow solution was formed. After
stirring for 1 h, a methanol solution of NaClO4·H2O (8.9 mg,
0.063 mmol) was added. Evaporation of dichloromethane gave
a yellow solid that was filtered off, washed with methanol and
vacuum dried. Yield: 69%. IR (KBr, cm-1): 3330(m), 3237(w),
n(NH); 1634(s), n(C O). KM (X-1 cm2 mol-1): 140 (acetone). H
NMR (CDCl3): d 4.04 (s, 1H, NH); 3.10 (s, 1H, NH); 2.85 (m,
3H, CH3). 31P{ H} NMR (CDCl3): d 61.4 (dd, J(Rh,P) = 162 Hz,
1
J(P,P) = 18 Hz, PA); 21.2 (dd, J(Rh,P) = 70 Hz, PM). 13C{ H}
1
NMR (CDCl3): d 235.7 (dd, J(Rh,C) = 32 Hz, J(P,CO) = 104 Hz,
RhCAO); 231.6 (m, br, RhCM O); 63.4 (s, CH2); 55.7 (s, CH2); 50.1
(s, CH3); 45.0 (s, CH3); 37.7 (s, CH3).
1
=
[Rh2(l-Cl)(l-PPh2(o-C6H4CO))2(PPh2(o-C6H4CO))2]BF4 [8]BF4.
To a dichloromethane solution of [RhCl(PPh2(o-C6H4CO))2(py)]
(50 mg, 0.063 mmol) was added HBF4·OEt2 (20.4 mg,
0.126 mmol). Stirring for 30 min gave a suspension. Filtration
2H, CH2); 2.60 (m, 3H, CH3); 1.95 (m, 2H, CH2); 1.20 (m, 3H,
CH3). 31P{ H} NMR (CDCl3): d 60.8 (dd, J(Rh,P) = 158 Hz,
1
1
J(P,P) = 18 Hz, PA); 20.2 (dd, J(Rh,P) = 76 Hz, PM ). 13C{ H}
R
of the white [pyH]BF4 through Celiteꢀ, followed by addition of
NMR (CDCl3): d 236.0 (dd, J(Rh,C) = 31 Hz, J(P,CO) = 106 Hz,
RhCAO); 228.8 (dd, J(Rh,C) = 29 Hz, J(P,CO) = 7 Hz, RhCM O);
61.4 (s, CH2); 53.9 (s, CH3); 51.3 (s, CH3); 41.6 (s, CH2). FAB-
MS: calcd for C42H40N2O2P2Rh, 769; obsd, 769 [M+]. Anal. calc.
for C42H40ClN2O6P2Rh·0.25CH2Cl2: C, 57.00; H, 4.58; N, 3.15;
found: C, 56.94; H, 3.98; N, 3.22%.
diethyl ether to the solution gave a yellow solid containing a
mixture of 8a and 8b (8a:8b = 1:1.5) that was filtered off, washed
with diethyl ether and vacuum dried. Yield: 35%. Anal. calc.
for C76H56BF4ClO4P4Rh2·0.5CH2Cl2: C, 60.14; H, 3.76; found: C,
60.12; H, 3.99%.
[Rh2(l-Cl)(l-PPh2(o-C6H4CO))2(PPh2(o-C6H4CO))2]ClO4
[8]ClO4.
[Rh(PPh2(o-C6H4CO))2(dmeen)]ClO4 (6). To
a dichloro-
methane suspension of [RhCl(PPh2(o-C6H4CO))2(py)] (60 mg,
0.075 mmol) was added N,N¢-dimethylethylenediamine, (6.6 mg,
0.075 mmol) whereupon a yellow solution was formed. After
stirring for 1 h, a methanol solution of NaClO4·H2O (10.5 mg,
0.075 mmol) was added. Evaporation of dichloromethane gave
a yellow solid that was filtered off, washed with methanol and
vacuum dried. Yield: 50%. IR (KBr, cm-1): 3270(m), 3160(m),
Method a. To a methanol suspension of [RhCl(PPh2(o-
C6H4CO))2(py)] (65 mg, 0.082 mmol) was added aqueous 11.7 M
HClO4 (24.7 mg, 0.246 mmol). Stirring for 3 h gave a yellow solid
containing a mixture of 8a and 8b (8a:8b = 1:1.5) that was filtered
off, washed with methanol and vacuum dried. Yield: 70%.
Method b. HCl gas was bubbled at room temperature through
a methanol suspension of [Rh(PPh2(o-C6H4CO))2(ndmeen)]ClO4
(5) (30 mg, 0.035 mmol) for 45 min whereupon dissolution of
the solid occurred. Evaporation to dryness and dissolution of
the solid residue in dichloromethane was followed by filtration
n(NH); 1629(s), n(C O). KM (X-1 cm2 mol-1): 130 (acetone). Data
=
for 5a. 1H NMR (CDCl3): d 5.09 (s, 1H, NH); 4.35 (s, 1H, NH);
3.19 (m, 1H, CH2); 2.42 (m, 3H, CH2); 1.83 (m, 3H, CH3); 1.29 (m,
1
3H, CH3). 31P{ H} NMR (CDCl3): d 62.8 (dd, J(Rh,P) = 156 Hz,
R
through Celiteꢀ. Addition of diethyl ether gave a yellow solid
J(P,P) = 18 Hz, PA); 20.9 (dd, J(Rh,P) = 77 Hz, PM ). 13C{ H}
1
containing a mixture of 8a, 8b and 8c (8a:8b:8c = 1:1:3)
NMR (CDCl3): d 238.7 (dd, J(Rh,C) = 31 Hz, J(P,CO) = 106 Hz,
RhCAO); 235.2 (dd, J(Rh,C) = 29 Hz, J(P,CO) = 10 Hz, RhCM O);
54.3 (s, CH2); 52.1 (s, CH2); 41.3 (s, CH3); 39.1 (s, CH3). FAB-MS:
calcd for C42H40N2O2P2Rh, 769; obsd, 769 [M+]. Anal. calc. for
C42H40ClN2O6P2Rh: C, 58.04; H, 4.64; N, 3.22; found: C, 58.42;
H, 5.02; N, 3.36%.
that was filtered off, washed with diethyl ether and vacuum
-1
=
dried. Yield: 49%. IR (KBr, cm ): 1653(s), n(C O)t; 1548(s),
n(C O)b. KM (X-1 cm2 mol-1): 92 (acetone). FAB-MS: calcd
=
for C76H56ClO4P4Rh2, 1397; obsd, 1397 [M+]. Anal. calc. for
C76H56Cl2O8P4Rh2: C, 60.94; H, 3.77; found: C, 61.21; H, 4.08%.
Data for 8a. 31P{ H} NMR (CDCl3): d 61.9 (dd, J(Rh,P) =
1
[Rh(PPh2(o-C6H4CO))2(trimeen)]ClO4 (7). To
a
dichloro-
181 Hz, J(P,P) = 15 Hz, Pb); 32.6 (dd, J(Rh,P) = 92 Hz, Pa). Data
1
methane suspension of [RhCl(PPh2(o-C6H4CO))2(py)] (50 mg,
0.063 mmol) was added N,N,N¢-trimethylethylenediamine
(6.5 mg, 0.062 mmol). After stirring for 1 h, a methanol solution
of NaClO4·H2O (8.9 mg, 0.062 mmol) was added, whereupon
a yellow solution was formed. Evaporation to dryness and
dissolution of the solid residue in dichloromethane was followed
for 8b. 31P{ H} NMR (CDCl3): d 65.5 (dd, J(Rh,P) = 178 Hz,
J(P,P) = 18 Hz, Pb); 64.3 (dd, J(Rh,P) = 172 Hz, J(P,P) = 18 Hz,
Pd ); 28.6 (dd, J(Rh,P) = 89 Hz, J(P,P) = 18 Hz) and 28.2 (dd,
J(Rh,P) = 89 Hz, J(P,P) = 18 Hz) for Pa and Pc. 13C{ H} NMR
1
(CDCl3): d 269.1 (dd, J(Rh,C) = 31 Hz, J(P,C) = 114 Hz) and
264.6 (dd, J(Rh,C) = 31 Hz, J(P,C) = 113 Hz) for RhCbO and
This journal is
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©

View Article Online
Table 3 Crystal data and structure refinement for compounds 5, 6, 8a and 8b
Crystal data
5
6
8a
8b
Empirical formula
[C42H40N2O2P2Rh]
ClO4
[C42H40N2O2P2Rh]
ClO4
[C76H56Cl1O4P4Rh2]BF4
C4H10O
[C76H56Cl1O4P4Rh2]ClO4
Formula weight
Crystal system
Space group
869.06
Monoclinic
P21/c
12.099(1)
15.619(1)
20.840(1)
99.823(1)
3880.3(4)
4
1.488
0.642
w and j
1784
869.06
Orthorhombic
Pbca
15.477(1)
18.986(1)
26.371(1)
—
7748.8(7)
8
1.490
0.643
w and j
3568
1630.19
Monoclinic
C2/c
17.918(2)
18.406(2)
20.657(3)
92.365(3)
6807(1)
1497.81
Monoclinic
P21/n
20.297(1)
11.823(1)
28.380(2)
98.824(1)
6729.6(7)
4
1.478
0.722
w and j
3040
˚
a/A
˚
b/A
˚
c/A
b/◦
Volume (A )
3
˚
Z
4
D(calcd), g cm-3
Absorption coefficient (mm-1)
scan technique
F(000)
1.591
0.763
w and j
3312
1.59 to 25.00
-21, -21, -24 to 21,
21, 22
range ( for data collection (◦)
Index ranges
1.64 to 29.00
-16, -21, -28 to 16,
20, 28
1.54 to 29.09
-20, -25, -31 to 21,
25, 34
1.15 to 25.00
-24, -13, -33 to 24,
14, 33
Reflections collected
36545
71166
25936
50730
Independent reflections
Completeness to theta
Data/restraints/parameters
Ra( refl. obser.) [I>2s(I)]
9649 [R(int) = 0.0790]
9838 [R(int) = 0.0726]
6001 [R(int) = 0.1735]
11825 [R(int) = 0.0864]
93.5%
94.7%
100%
100%
9649/0/469
0.0556(4706)
0.1717
9838/0/489
0.0361 (5640)
0.0918
6001/0/393
0.0845 (2267)
0.2442
11825/6/799
0.0497 (6562)
0.1514
b
RwF (all data)
-3
˚
Largest diff. peak and hole (e A )
1.237 and -1.014
0.629 and -0.385
1.864 and -1.276
1.426 and -0.953
2
1/2
a RꢁFo| - |Fcꢁ/R|Fo| b {R[w(Fo - Fc2)2]/R[w(Fo2)2]}
.
-
RhCd O; 222.2 (dd, J(Rh,C) = 30 Hz, J(P,C) = 8 Hz) and 218.0 (dd,
J(Rh,C) = 29 Hz, J(P,C) = 7 Hz) for RhCaO and RhCcO. Data
atoms in this phenyl ring and the oxygen atoms of the ClO4
group were refined isotropically. In compound [8a]BF4, the BF4
-
1
for 8c. 31P{ H} NMR (CDCl3): d 68.2 (dd, J(Rh,P) = 178 Hz,
anion was included with fixed isotropic contributions. In the last
cycles of refinement some diffuse electronic residual density could
not be properly modelled. Therefore, the SQUEEZE program,
a part of the PLATON package of crystallographic software,26
was used to calculate the solvent disorder area and remove its
contribution to the overall intensity data. An improvement was
observed in all refinement parameters and residuals when this
procedure is applied. The number of electrons in the solvent region
corresponds to one diethyl ether molecule per dimer molecule in
the crystal. In all cases the hydrogen atoms were included with fixed
isotropic contributions at their calculated positions determined
by molecular geometry and refined riding on the corresponding
bonded atom, except for the H1 and H2 bonded to N1 and N2
for 6 and 5, which were located from the Fourier map included
and were not refined. All the calculations were carried out with
SHELX-97.27
1
J(P,P) = 24 Hz, Pd ); 26.4 (dd, J(Rh,P) = 89 Hz, Pc). 13C{ H}
NMR (CDCl3): d 265.8 (dd, J(Rh,C) = 33 Hz, J(P,C) = 117 Hz,
RhCd O); 219.0 (dd, J(Rh,C) = 29 Hz, J(P,C) = 7 Hz, RhCcO).
X-ray structure determination of 5, 6, [8a]BF4 and [8b]ClO4
Good quality crystals of 5 and 6 suitable for X-ray experi-
ments were obtained by slow diffusion of diethyl ether into
dichloromethane solutions. Crystals of [8a]BF4 and [8b]ClO4 were
obtained by fractional crystallisation. In both cases slow diffusion
of diethyl ether into dichloromethane solutions afforded solids
that were filtered. Yellow crystals of [8a]BF4 were obtained by
dissolution of the corresponding solid in chloroform and slow
diffusion of diethyl ether into this solution. Yellow crystals of
[8b]ClO4 were obtained by slow diffusion of diethyl ether into the
remaining original dichloromethane solution. A summary of the
fundamental crystal and refinement data are given in Table 3.
In all the cases a yellow crystal was resin epoxy coated and
mounted on a Bruker Smart CCD diffractometer, with graphite-
monochromated Mo-Ka (l = 0.71073) radiation, operating at 50
kV and 20 mA. Data were collected over a hemisphere of the
reciprocal space by combination of three exposure sets. All the
structures were solved by direct methods and conventional Fourier
techniques and refined by applying full-matrix least-squares on
F2 with anisotropic thermal parameters for the non-hydrogen
atoms, with some exceptions. For 5, the oxygen atoms of the
ClO4- group were refined isotropically. For [8b]ClO4, due to a non-
resolvable positional disorder, the carbon atoms of one phenyl
ring were refined with restrained C–C distances. Two carbon
Acknowledgements
Financial support by MICINN (CTQ2008-2967/BQU), UPV and
Diputacio´n Foral de Guipuzcoa are gratefully acknowledged.
CCDC reference numbers: 738631 (5), 738632 (6), 738633 (8a),
738634 (8b).
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Dalton Trans., 2009, 9860–9869 | 9869
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