Synthesis and reactivity of [Au(2-CH2-6-RC5H3N)(PPh3)] (R = H, Me). X-ray structure of [Ag{Au(2-CH2-6-MeC5H3N)(PPh3)} 2][ClO4]

Article abstract of DOI:10.1039/a903703i

The reaction of Li(2-CH₂-6-RC₅H₃N) with [AuCl(PPh₃)] leads to the mononuclear complexes [Au(2-CH₂-6-RC₅H₃N)(PPh₃)] (R = H, Me). These react further with other copper, silver or gold compounds to give heteronuclear derivatives, [M{Au(2-CH₂-6-RC₅H₃N)(PPh₃)} ₂][X] (M = Cu, X = PF₆ or M = Ag, X = ClO₄), or the dinuclear complex [Au(2-CH₂-6-MeC₅H₃N)]₂. The crystal structure of [Ag{Au(2-CH₂-6-MeC₅H₃N)(PPh₃)} ₂][ClO₄] has been determined by X-ray diffraction studies and shows short interactions between the gold and silver centres.

Full text of DOI:10.1039/a903703i

View Article Online / Journal Homepage / Table of Contents for this issue
Synthesis and reactivity of [Au(2-CH2-6-RC5H3N)(PPh3)]
(R ؍ H, Me). X-Ray structure of [Ag{Au(2-CH2-6-
MeC5H3N)(PPh3)}2][ClO4]
J. Enrique Casas,a M. Concepción Gimeno,a Peter G. Jones,b Antonio Laguna*a and
Mariano Lagunaa
a Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón,
Universidad de Zaragoza-CSIC, E-50009 Zaragoza, Spain
b Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig,
Postfach 3329, D-38023 Braunschweig, Germany
Received 10th May 1999, Accepted 30th June 1999
The reaction of Li(2-CH2-6-RC5H3N) with [AuCl(PPh3)] leads to the mononuclear complexes [Au(2-CH2-6-
RC5H3N)(PPh3)] (R = H, Me). These react further with other copper, silver or gold compounds to give heteronuclear
derivatives, [M{Au(2-CH2-6-RC5H3N)(PPh3)}2][X] (M = Cu, X = PF6 or M = Ag, X = ClO4), or the dinuclear
complex [Au(2-CH2-6-MeC5H3N)]2. The crystal structure of [Ag{Au(2-CH2-6-MeC5H3N)(PPh3)}2][ClO4] has been
determined by X-ray diffraction studies and shows short interactions between the gold and silver centres.
One of the more interesting developments in gold chemistry1
over the last few years has been in the area of di- and poly-
nuclear systems. Potentially bidentate ligands, with the correct
geometry to hold two metal centres close to each other, have
been widely investigated. However, anionic ligands obtained
from 2-methylpyridine or 2,6-dimethylpyridine (2-CH2-6-
RC5H3N, R = H, Me) have been studied far less, and no gold
derivative has been described. The only related derivative is the
dinuclear [Au{2-C(SiMe3)2C5H4N}]2.2
This paper reports the preparation of [Au(2-CH2-6-RC5H3-
N)(PPh3)] (R = H, Me) and the homo- and hetero-nuclear
derivatives obtained from the reactions with other copper,
silver or gold compounds. The molecular structure of [Ag-
{Au(2-CH2-6-RC5H3N)(PPh3)}2][ClO4] has been established by
single-crystal X-ray studies, showing short interactions between
the gold and silver centres.
probably attributable to similar J(HH) constants. The methyl-
enic protons of 3 are not equivalent and appear as singlets at
δ 2.39, 2.44, and 2.59.
As suggested by the formation of [M ϩ AuPPh3]ϩ species in
the mass spectra, complexes 1–3 can serve as building blocks
for preparing heteronuclear complexes. We have studied their
reactions with several silver or copper derivatives. Thus the
treatment of complexes 1, 2 or 3 with AgClO4 in molar ratio
2:1 gives the trinuclear derivatives [Ag{Au(2-CH2-6-RC5-
H3N)(PPh3)}2][ClO4] (R = H 4, Me 5) or [Ag{Au(2-CH2-3,5,6-
Me3C4N2)(PPh3)}2][ClO4] 6. A similar reaction of complexes 1
or 2 with [Cu(NCMe)4][PF6] leads to the complexes [Cu{Au(2-
CH2-6-RC5H3N)(PPh3)}2][PF6] (R = H 7, Me 8) (Scheme 1).
They are white or pale brown air- and moisture-stable solids.
Complexes 4, 7 and 8 behave as 1:1 electrolytes in acetone
solution; however the silver complexes 5 and 6 show conduc-
tivities (188 and 228 ΩϪ1 cm2 molϪ1, respectively) higher than
that of 1:1 electrolytes, probably because of interactions with
the solvent forming new ions, such as [Ag(OCMe2)4]ϩ. Their IR
spectra show, apart from the bands arising from the heterocycle
or the phosphine, those of the perchlorate at 1100vs (br) and
625m cmϪ1 or hexafluorophosphate at 850s (br) and 558s cmϪ1.
The positive-ion LSIMS exhibit peaks corresponding to the
cations [AuPPh3]ϩ (m/z = 459), [Au(PPh3)2]ϩ (m/z = 721), [(2-
CH2-6-RC5H3N)(AuPPh3)]ϩ [m/z = 552 (4 or 7) or 566 (5 or 8)],
[(2-CH2-3,5,6-Me3C4N2)(AuPPh3)]ϩ (m/z = 595, 6), [(2-CH2-6-
RC5H3N)(AuPPh3)2]ϩ [m/z = 1010 (4 or 7) or 1024 (5 or 8)],
or [(2-CH2-3,5,6-Me3C4N2)(AuPPh3)2]ϩ (m/z = 1053, 6). The
cation molecular peaks, [Ag{Au(2-CH2C5H4N)(PPh3)}2]ϩ
(m/z = 1211, 30%) or [Ag{Au(2-CH2-3,5,6-Me3C4N2)(PPh3)}2]ϩ
(m/z = 1297, 30%) are only observed for complexes 4 and 6.
Results and discussion
The reaction of 2-CH3-6-RC5H3N (R = H, Me) in diethyl ether
with LiBun leads to the lithium derivatives Li(2-CH2-6-
RC5H3N),3–9 which react further with [AuCl(PPh3)] to give the
mononuclear complexes [Au(2-CH2-6-RC5H3N)(PPh3)] [R =
H (1), Me (2)]. A similar reaction starting from tetramethyl-
pyrazine (2,3,5,6-Me4C4N2) gives the derivative [Au(2-CH2-
3,5,6-Me3C4N2)(PPh3)] 3. Complexes 1–3 are white air- and
moisture-stable solids and are non-conducting in acetone
solutions. Their IR spectra show the ν(C᎐N) and ν(C᎐C) vibra-
᎐
᎐
tions of the heterocycle at 1587s and 1568s 1, 1589s and 1557s
2, and 1535s cmϪ1 3. The positive liquid secondary ion mass
spectra (LSIMS) show the cation molecular peaks at m/z (%):
551 (26) 1, 565 (22) 2, or 594 (22) 3. Other peaks appear at m/z
459 ([AuPPh3]ϩ, 95 1, 70 2, or 100% 3) and 721 ([Au(PPh3)2]ϩ,
98 1, 70 2, or 90% 3). The most intense peaks correspond to the
cation [M ϩ AuPPh3]ϩ (m/z 1010 1, 1024 2, or 1053 3).
1
The H NMR spectra show a doublet for the methylene
protons, because of coupling with the phosphorus of the
phosphine. Other resonances are collected in Table 1. Complex
6 presents a singlet for each of the three different methyl groups.
The 31P-{1H} NMR spectra present only one singlet for the two
equivalent phosphorus atoms.
The 31P-{1H} NMR spectra at room temperature show a
1
singlet at ca. δ 42.9. The H NMR spectra of complexes 1
and 2 are as expected and are summarised in Table 1. The
methylene protons appear as doublets because of coupling with
the phosphorus atom, confirming the coordination of the gold
centre to the CH2 group. Some resonances (H4 in 2, or H5 in 1)
are apparent triplets, rather than doublets of doublets, which is
The crystal structure of complex 5 has been confirmed by an
X-ray diffraction study; its cation is shown in Fig. 1, with a
selection of bond lengths and angles in Table 2. The silver
centre lies on a two-fold axis and thus only half of the molecule
corresponds to the asymmetric unit. The gold atoms have a
J. Chem. Soc., Dalton Trans., 1999, 2819–2822
2819

View Article Online
Table 1 1H NMR data for complexes.a Coupling constants in parentheses
Complex
CH3
CH2
H5
H3
H4
H6
2-MeC5H4N
2,6-Me2C5H3N
1
2.50 (s)
2.42 (s)
7.01 (t)
6.83 (d)
6.67 (t)
(3.1)
6.58 (d)
(7.3)
7.07 (d)
6.83 (d)
7.02 (d)
(7.8)
6.85 (d)
(7.8)
7.33 (dt)
8.42 (d)
8.28 (d)
7.33 (t)
b
2.88 (d)
(10.8)
2.79 (d)
(11.0)
2.68 (d)
(11.2)
2
3
2.44 (s)
7.25 (t)
2.39 (s)
2.44 (s)
2.59 (s)
b
b
4
5
6
3.13 (d)
(10.5)
3.24 (d)
(10.5)
2.88 (d)
6.54 (m)
7.02 (m)
8.05 (m)
2.20 (s)
6.72 (d)
(7.3)
6.98 (d)
(7.8)
2.41 (s)
2.56 (s)
2.59 (s)
(9.5)
b
b
b
b
7
8
3.10 (d)
(9.5)
3.28 (d)
(10.2)
3.22 (d)
(10.7)
3.28 (d)
(10.6)
6.54 (m)
6.60 (d)
7.02 (m)
6.98 (d)
8.05 (m)
8.34 (m)
2.06 (s)
(7.3)
(7.3)
b
b
9
10
11a
11b
2.80 (s)
3.318 (s)
2.67 (s)
6.74 (d)
(6.0)
6.48 (d)
(7.4)
6.70 (d)
(7.4)
6.99 (d)
(8.1)
7.0 (d)
(7.4)
7.03 (d)
(7.4)
3.44 (s)
7.27 (t)
7.32 (t)
3.17 (s)
a In CDCl3 solutions at Ϫ60 ЊC, δ from external SiMe4; s = singlet, d = doublet, t = triplet, dt = doublet of triplets, m = multiplet. b Overlapped with
the resonances of the phenyl groups.
Table 2 Selected bond lengths (Å) and angles (Њ) for complex 5
Au–C(1)
Au–P
Ag–N
P–C(21)
P–C(41)
2.084(6)
2.2813(16)
2.162(5)
1.815(6)
1.818(6)
P–C(31)
1.819(6)
1.452(9)
1.347(7)
1.346(8)
C(1)–C(11)
C(11)–N
C(15)–N
C(1)–Au–P
N#1–Ag–N
C(21)–P–C(41)
C(21)–P–C(31)
C(41)–P–C(31)
C(21)–P–Au
175.32(17)
159.6(2)
105.7(2)
104.5(2)
104.6(2)
111.43(18)
C(41)–P–Au
C(31)–P–Au
C(11)–C(1)–Au
C(15)–N–Ag
C(11)–N–Ag
116.26(18)
113.39(18)
112.3(4)
121.0(4)
116.2(4)
a Symmetry transformations used to generate equivalent atoms: #1
Ϫx ϩ 1, y, Ϫz ϩ 1/2.
Scheme 1 (i) [AuCl(PPh3)]; (ii) 1/2 AgClO4 or 1/2 [Cu(NCMe)4][PF6];
(iii) HBF4; (iv) [AuCl(AsPh3)].
Fig. 1 Molecular structure of the cation of complex 5 showing the
atom numbering scheme. Hydrogen atoms are omitted for clarity.
slightly distorted linear geometry with a P–Au–C(1) angle of
175.3(2)Њ, possibly associated with a weak interaction with
the silver centre, Au ؒ ؒ ؒ Ag 3.428(1) Å; in contrast, the gold
atoms are located far from each other, Au ؒ ؒ ؒ Au# 5.115(2) Å
(#: 1 Ϫ x, y, 0.5 Ϫ z). The silver centre has a very distorted
linear geometry, N–Ag–N# 159.6(2)Њ, probably attributable to
weak contacts to oxygen atoms of the (disordered) perchlorate
2820
J. Chem. Soc., Dalton Trans., 1999, 2819–2822

View Article Online
Syntheses
[Au(2-CH2-6-RC5H3N)(PPh3)] (R ؍ H, 1; Me, 2) and [Au(2-
CH2-3,5,6-Me3C4N2)(PPh3)] 3. To a solution of 2-CH3-6-
CH2
Au
Me
N
Me
Me
N
CH2
Au
Au
CH2
RC5
H N (R = H, 60 µl, 0.5 mmol; Me, 50 µl, 0.5 mmol) or
Au
3
2,3,5,6-Me4C4N2 (0.068 g, 0.5 mmol) in diethyl ether (40 cm3)
was added a n-hexane solution of LiBun (0.31 ml, 1.6 M,
0.5 mmol) and the mixture was stirred for 10 min. An orange,
Li(2-CH2-6-RC5H3N), or red Li(2-CH2-3,5,6-Me3C4N2), preci-
pitate was formed. To this suspension was added [AuCl(PPh3)]
(0.247 g, 0.5 mmol). After stirring for 1 h the mixture was
filtered through a layer of celite and the solvent was evaporated
to ca. 5 cm3. Addition of hexane (10 cm3) gave complexes 1–3
N
Me
N
CH2
Fig. 2 The two isomers of complex 11.
anion, Ag ؒ ؒ ؒ O 3.10, 3.16 Å. The silver–nitrogen bond length
of 2.162(5) Å is similar to values reported for two-coordinate
and pseudo two-coordinate complexes of silver() with σ-
bonding ligands such as [Ag(2,6-Me2py)2][ClO4] (2.166(4) Å),10
although shorter than in the complex [(Ph3P)(O3ClO)AgN-
(Ph2PAuPPh2)2NAg(OClO3)(PPh3)] (2.239(4) Å),11 perhaps as
a consequence of the trans influence of the phosphine ligand.
The reaction of complexes 1 or 2 with HBF4 in a 2:1 molar
ratio leads to protonation of half of the heterocyclic ligand
and to the formation of the dinuclear complexes [(2-CH2-6-
RC5H3N)(AuPPh3)2][BF4] (R = H 9, Me 10). They are white
air- and moisture-stable solids and behave as 1:1 electrolytes
in acetone solution. In the IR spectra the vibrations from the
anion appear at 1100s and 1053s (br) cmϪ1. The 31P-{1H} NMR
spectra present two singlets at δ 42.7 and 30.3 9 and δ 41.8
and 29.4 10 from the two different phosphines and confirm the
coordination of the second gold centre to the nitrogen atom.
as white solids. Complex 1: yield 59%. ΛM 1 ΩϪ1 cm2 molϪ1
.
Elemental analysis (%), Found: C, 51.85; H, 3.8; N, 2.3. Calc.
for C24H21AuNP: C, 52.27; H, 3.8; N, 2.5. 31P-{1H} NMR,
δ: 42.9 (s). Complex 2: yield 67%. ΛM 1 ΩϪ1 cm2 molϪ1. Elemental
analysis (%), Found: C, 53.0; H, 4.15; N, 2.4. Calc. for
C25H23AuNP:C,53.1;H,4.15;N,2.45.31P-{1H}NMR,δ:43.0(s).
Complex 3: yield 77%. ΛM 8 ΩϪ1 cm2 molϪ1. Elemental analysis
(%), Found: C, 52.15; H, 4.7; N, 4.25. Calc. for C26H26AuN2P:
C, 52.55; H, 4.4; N, 4.7. 31P-{1H} NMR, δ: 42.8 (s).
[M{Au(2-CH2-6-RC5H3N)(PPh3)}2][X] (M ؍ Ag, X ؍ ClO4,
R ؍ H, 4; Me, 5; M ؍ Cu, X ؍ PF6, R ؍ H, 7; Me, 8) or
[Ag{Au(2-CH2-3,5,6-Me3C4N2)(PPh3)}2][ClO4] 6. To a solution
of AgClO4 (0.031 g, 0.15 mmol) or [Cu(NCMe)4][PF6] (0.028 g,
0.15 mmol) in diethyl ether (4, 5) or dichloromethane (6–8)
(30 cm3) was added complex 1 (0.165 g, 0.3 mmol), 2 (0.169 g,
0.3 mmol) or 3 (0.178 g, 0.3 mmol). The reaction mixture
was stirred in the dark for 30 min. Evaporation of the diethyl
ether to ca. 5 cm3 or concentration of the solution (dichloro-
methane) to ca. 5 cm3 and addition of diethyl ether (10 cm3)
gave complexes 4–8 as white (4–6) or pale brown (7, 8) solids.
Complex 4: yield 82%. ΛM 152 ΩϪ1 cm2 molϪ1. Elemental
analysis (%), Found: C, 45.15; H, 3.15; N, 2.0. Calc. for
C48H42AgAu2ClN2O4P2: C, 44.9; H, 3.05; N, 2.15. 31P-{1H}
1
The H NMR data are collected in Table 1. The mass spectra
are similar to those of complexes 1 and 2 and the cations
[M Ϫ BF4]ϩ appear at m/z (%) 1010 (55) 9 or 1024 (30) 10.
The reaction of the lithium derivative Li(2-CH3-6-
MeC5H3N) with [AuCl(AsPh3)], with the weakly coordinating
ligand AsPh3, leads to the dinuclear complex [Au(2-CH2-6-
MeC5H3N)]2 11. It is a white air- and moisture-stable solid and
a non-conductor in acetone solution. The ν(Au–Cl) vibrations
and those of the arsine are not present in its IR spectrum and
only those of the 2-CH2-6-MeC5H3N ligand are observed. The
1H NMR spectrum (Table 1) is in agreement with the presence
of two isomers (Fig. 2), in a molar ratio 11a:11b = 4:1.
The same complex is obtained from the reaction of complex
2 with [AuCl(tht)] (tht = tetrahydrothiophene) (eqn. (1)), but
now with a different molar ratio for the two isomers
(11a:11b = 1:4), as observed from the 1H NMR spectrum.
Complex 11 reacts with PPh3 to give the mononuclear deriv-
ative 2 (84% yield).
NMR, δ: 42.9 (s). Complex 5: yield 86%. ΛM 188 ΩϪ1 cm2 molϪ1
.
Elemental analysis (%), Found: C, 45.2; H, 3.4; N, 1.95. Calc.
for C50H46AgAu2ClN2O4P2: C, 44.75; H, 3.5; N, 2.1. 31P-{1H}
NMR, δ: 43.8 (s). Complex 6: yield 63%. ΛM 227 ΩϪ1 cm2 molϪ1
.
Elemental analysis (%), Found: C, 52.15; H, 4.7; N, 4.25. Calc.
for C46H40AgAu2ClN4O4P2: C, 52.55; H, 4.4; N, 4.7. 31P-{1H}
NMR, δ: 43.5 (s). Complex 7: yield 61%. ΛM 147 ΩϪ1 cm2 molϪ1
.
Elemental analysis (%), Found: C, 43.55; H, 2.85; N, 1.85. Calc.
for C48H42Au2CuF6N2P3: C, 43.95; H, 3.05; N, 2.15. 31P-{1H}
NMR, δ: 42.7 (s). Complex 8: yield 72%. ΛM 164 ΩϪ1 cm2 molϪ1
.
[Au(2-CH2-6-RC5H3N)(PPh3)] ϩ [AuCl(tht)] →
[Au(2-CH2-6-MeC5H3N)]2 ϩ [AuCl(PPh3)] ϩ tht (1)
Elemental analysis (%), Found: C, 44.3; H, 3.3; N, 3.25. Calc.
for C50H46Au2CuF6N2P3: C, 44.8; H, 3.4; N, 2.1. 31P-{1H}
NMR, δ: 42.4 (s).
Experimental
[(2-CH2-6-RC5H3N)(AuPPh3)2][BF4] (R ؍ H, 9; Me, 10).
To a solution of complex 1 (0.110 g, 0.2 mmol) or 2 (0.112 g,
0.2 mmol) in 40 cm3 of diethyl ether was added HBF4 (54%
diethyl ether solution, 13.6 µl, 0.1 mmol) and the mixture
stirred for 15 min. A white precipitate of 9 or 10 was obtained.
Complex 9: yield 73%. ΛM 103 ΩϪ1 cm2 molϪ1. Elemental
analysis (%), Found: C, 45.6; H, 2.95; N, 1.35. Calc. for
C42H36Au2BF4NP2: C, 45.95; H, 3.3; N, 1.25. 31P-{1H} NMR,
δ: 42.7 (s, C-Au-PPh3), 30.3 (s, N-Au-PPh3). Complex 10: yield
78%. ΛM 120 ΩϪ1 cm2 molϪ1. Elemental analysis (%), Found:
C, 46.0; H, 3.3; N, 1.6. Calc. for C43H38Au2BF4NP2: C, 46.45;
H, 3.45; N, 1.25. 31P-{1H} NMR, δ: 41.8 (s, C-Au-PPh3), 29.4
(s, N-Au-PPh3).
Infrared spectra were recorded on a Perkin-Elmer 883 spectro-
photometer, over the range 4000–200 cmϪ1, using Nujol mulls
between polyethylene sheets. Conductivities were measured in
ca. 5 × 10Ϫ4 mol dmϪ3 solutions with a Philips 9509 conducti-
meter. C, H, and N analyses were carried out with a Perkin-
Elmer 2400 microanalyser. Mass spectra were recorded on a VG
Autospec, with the liquid secondary-ion mass spectra (LSIMS)
technique, using 3-nitrobenzyl alcohol as matrix. 1H and
31P-{1H} NMR spectra were recorded on a Varian UNITY 300
or Bruker ARX 300 apparatus in CDCl3 solutions (stored over
Na2CO3); chemical shifts are quoted relative to SiMe4 (external,
1H) and 85% H3PO4 (external, 31P).
The starting materials [AuCl(tht)],12 [AuCl(PPh3)],12
[AuCl(AsPh3)],13 [Au(C6F5)(tht)],12 and [Cu(NCMe)4][PF6]14
were prepared by published procedures. All other chemicals
used were commercially available and used without further
purification. CAUTION: perchlorate salts with organic cations
may be explosive.
[Au(2-CH2-6-MeC5H3N)]2 11. To a suspension of Li(2-CH2-
6-MeC5H3N) (0.5 mmol), prepared as above (complex 2), in
40 cm3 of diethyl ether was added [AuCl(AsPh3)] (0.269 g,
0.5 mmol). After stirring for 1 h the mixture was filtered
through a layer of Celite and the solvent was evaporated to ca. 5
J. Chem. Soc., Dalton Trans., 1999, 2819–2822
2821

View Article Online
Table 3 Details of data collection and structure refinement for com-
plex 5
ment factor components and to local ring symmetry was used.
Further details are given in Table 3.
CCDC reference number 186/1548.
See http://www.rsc.org/suppdata/dt/1999/2819/ for crystallo-
graphic files in .cif format.
Formula
M
Crystal system
Space group
C50H46AgAu2ClN2O4P2
1388.08
Monoclinic
C2/c
a/Å
b/Å
c/Å
14.593(5)
17.237(6)
19.330(7)
108.11(3)
4621(3)
4
Acknowledgements
We thank the Dirección General de Enseñanza Superior (No.
PB97-1010-C02-01) and the Fonds der Chemischen Industrie
for financial support.
β/Њ
U/Å3
Z
T/ЊC
Ϫ95
6.927
4382
4052
0.018
0.031
0.081
µ(Mo-Kα)/mmϪ1
No. of reflections measured
No. of unique reflections
Rint
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11 R. Usón, A. Laguna, M. Laguna, M. C. Gimeno, P. G. Jones,
C. Fittschen and G. M. Sheldrick, J. Chem. Soc., Chem. Commun.,
1986, 509.
12 R. Usón and A. Laguna, Organomet. Synth., 1986, 3, 322.
13 A. D. Westland, Can. J. Chem., 1969, 47, 4135.
14 G. J. Kubas, Inorg. Synth., 1979, 19, 90.
cm3. Addition of hexane (10 cm3) gave complex 11 as a white
solid. Yield 42%. ΛM 12 ΩϪ1 cm2 molϪ1. Elemental analysis (%),
Found: C, 28.0; H, 2.85; N, 4.2. Calc. for C14H16Au2N2: C,
27.75; H, 2.65; N, 4.6.
Crystallography
The crystal was mounted in inert oil on a glass fibre and trans-
ferred to the cold gas stream of a Siemens R3 diffractometer
equipped with an LT-2 low temperature attachment. Data were
collected using monochromated Mo-Kα radiation (λ = 0.71073
Å). Scan type ω. Cell constants were refined from setting angles
of 50 reflections in the range 2θ 20–22Њ. An absorption correc-
tion was applied on the basis of ψ-scans. The structure was
solved by the heavy-atom method and refined on F2 using the
program SHELXL-97.15 The perchlorate anion was refined
with a two-fold disorder model. All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included using
a riding model. A system of restraints to light-atom displace-
15 G. M. Sheldrick, SHELXL-97, A program for crystal structure
refinement, University of Göttingen, Germany, 1993.
Paper 9/03703I
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J. Chem. Soc., Dalton Trans., 1999, 2819–2822