Synthesis and characterisation of 1-alkyl-2-imidazoline complexes of noble metals; crystal structure of trans-[PtCl2{N=C(H)N(Et)CH2CH2}(PEt 3)]

Article abstract of DOI:10.1039/a608360i

Treatment of a 1-alkyl-2-imidazoline N(R)(CH₂)₂N=CH with a μ-dichloro-dirhodium(I) or -diplatinum(II) complex [{Rh(μ-Cl)(cod)}₂] or [{Pt(μ-Cl)Cl(PEt₃)}₂] gave the mononuclear 1-alkyl-2-imidazoline complex [RhCl{N=C(H)N(R)CH₂CH2)(cod)] (R = Et 1a or CH₂Ph 1b) or trans[PtCl₂{N=C(H)N(R)CH₂CH₂}(PEt₃)] (R = Et 2a or CH₂Ph 2b) (cod = cycloocta-1,5-diene). A single-crystal X-ray diffraction study of 2a revealed it to have a square-planar geometry about platinum, the imidazoline ring being coplanar with this plane, and a Pt-N distance of 2.088(11) A; the Pt-P bond length of 2.231(4) A indicates that the imidazoline ligand has a marginally stronger trans influence than analogues of its isomer such as CN(R)(CH₂)₂NR. The rhodium complexes 1a and 1b have been shown to catalyse cyclopropanation of styrene and ethyl diazoacetate in high yields.

Full text of DOI:10.1039/a608360i

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Synthesis and characterisation of 1-alkyl-2-imidazoline complexes
of noble metals; crystal structure of trans-
[PtCl {N᎐C(H)N(Et)CH CH }(PEt )]*
᎐
2
2
2
3
Bekir Çetinkaya,a Engin Çetinkaya,a Peter B. Hitchcock,b Michael F. Lappert b and
Ismail Özdemir a
a
Department of Chemistry, Inönü University, 44280-Malaya, Türkiye
b The Chemistry Laboratory, University of Sussex, Brighton BN1 9QJ, UK
Treatment of a 1-alkyl-2-imidazoline N(R)(CH ) N᎐CH with a µ-dichloro-dirhodium() or -diplatinum() complex
᎐
2
2
[{Rh(µ-Cl)(cod)}2] or [{Pt(µ-Cl)Cl(PEt3)}2] gave the mononuclear 1-alkyl-2-imidazoline complex
[RhCl{N᎐C(H)N(R)CH CH }(cod)] (R = Et 1a or CH Ph 1b) or trans-[PtCl {N᎐C(H)N(R)CH CH }(PEt )]
᎐
᎐
2
2
2
2
2
2
3
(R = Et 2a or CH2Ph 2b) (cod = cycloocta-1,5-diene). A single-crystal X-ray diffraction study of 2a revealed it to
have a square-planar geometry about platinum, the imidazoline ring being coplanar with this plane, and a Pt᎐N
distance of 2.088(11) Å; the Pt᎐P bond length of 2.231(4) Å indicates that the imidazoline ligand has a marginally
stronger trans influence than analogues of its isomer such as CN(R)(CH2)2NR. The rhodium complexes 1a and 1b
have been shown to catalyse cyclopropanation of styrene and ethyl diazoacetate in high yields.
The co-ordination chemistry of imidazole and related com-
pounds, including benzimidazoles, benzoxazoles and benzthia-
zoles, has been extensively studied in part because of their role
in aspects of catalysis and biomimetics.1,2 Since some of these
heterocycles are corrosion inhibitors, their metal complexes
may also have some relevance to anticorrosion mechanisms.3 In
addition, some have a variety of pharmacological effects, such
as antitumour activity; for instance bis(acetato)bis(imidazole)-
copper()4,5 and imidazolium tetrachlorobis(imidazole)ruthen-
ate()6 were reported to be highly active antagonists toward
tumour models. The presence of planar nitrogen-centred lig-
ands L in trans-[PtCl2L2] often appeared to enhance their cyto-
toxity relative to the corresponding cis isomer or to cis-[PtCl2-
(NH3)2].7
H
N
(OC)5Mo
(OC)5Mo
N
N
R
N
R
I
II
bacterial activity15 and were effective catalysts for cyclisation of
(Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran.16
In this paper we describe the synthesis, isolation and spectro-
scopic characterisation of four new 1-alkyl-2-imidazoline com-
plexes of rhodium() (1a and 1b) and platinum() (2a and 2b)
derived from the imidazoline N(R)(CH ) N᎐CH (R = Et or
᎐
2
2
Imidazole and its derivatives are bound through N3 of the
imidazole ring.8,9 However, conversion of an imidazolemetal
complex into the isomeric (imidazolium ylide)metal complex,
having a C2᎐M bond, has been described.10 In contrast, results
on the related chemistry of 1-alkyl-4,5-dihydroimidazoles, the
N-(or 1-)alkyl-2-imidazolines, are as yet much more sparse.
At the outset of this work the only previous studies had been
concerned with the bidentate imidazoline complexes of some
late first-row transition metals.11,12 Recently, the reaction of 2-
phenylimidazoline with some palladium() complexes yielding
cyclometallated products was described.13
CH2Ph) and
the molecular
structure of
trans-
[PtCl {N᎐C(H)N(Et)CH CH }(PEt )] 2a, which we believe pro-
᎐
2
2
2
3
vides the first such data on a 1-alkyl-2-imidazolineplatinum()
complex. The complexes 1a and 1b were shown to be effective
catalysts for a cyclopropanation reaction.
Results and Discussion
An enetetramine [᎐CN(R)(CH ) NR] (abbreviated as LR 2) has
᎐
2
2
2
been shown to behave as a C-centred nucleophile in readily
cleaving a di-µ-dichloro-dimetal complex such as [{Rh(µ-
Cl)(cod)}2] A or [{Pt(µ-Cl)Cl(PEt3)}2] B to give the imidazolidin-
2-ylidene(or carbene)metal complex [RhCl(cod)(LR )] or [PtCl2-
(LR )(PEt3)].17 A similar approach was used in the present study.
In 1977 we reported that an attempt at an in situ synthesis of
an NH-substituted imidazolidin-2-ylidene(or carbene)molyb-
denum(0) complex I, containing an Mo{CN(R)(CH2)2NH}
moiety, from [Mo(CO)6], CH(OMe)2NMe2 and H2N(CH2)2-
NHR led instead to the isomeric N-bonded 2-imidazoline-
molybdenum(0) complexes II;14 the latter were also accessible
Thus, 2 equivalents of the imidazoline N(R)(CH ) N᎐CH
᎐
2
2
(R = Et or CH2Ph) were heated with A or B affording the
appropriate mononuclear 1-alkyl-2-imidazoline-rhodium() 1
or -platinum() 2 complex in good yield (Table 1), Scheme 1 [(i)
or (ii)].
from [Mo(CO) ] and N(R)(CH ) N᎐CH (R = H or Et) as was
᎐
6
2 2
[RhCl{N᎐C(H)N(R)CH CH }(cod)] from [{Rh(µ-Cl)(cod)} ]
᎐
2
2
2
and N(R)(CH ) N᎐CH (cod = cycloocta-1,5-diene). The present
Each of the complexes 1a, 1b, 2a and 2b was obtained in
moderate to high yield as air-stable crystals, which were charac-
terised by elemental analysis and IR (Table 1), 1H NMR (Table
2) and 13C-{1H} NMR (Table 3) spectra; the tables also include
᎐
2
2
paper reports an extension of these experiments.
A further reason for our pursuing the present study is that the
imidazoline complexes [RhCl{N᎐C(H)N(R)CH CH }(cod)]
᎐
2
2
(R = Et 1a or CH2Ph 1b) showed significant selective anti-
corresponding data on the imidazolines N(R)(CH ) N᎐CH
᎐
2 2
[R = Et (an oil at ambient temperature) or CH2Ph] which were
reported briefly.18
* Non-SI unit employed: mmHg ≈ 133 Pa.
J. Chem. Soc., Dalton Trans., 1997, Pages 1359–1362
1359

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1
The IR spectra of each of the four complexes showed an
The H NMR spectral chemical shifts of the metal-bound
imidazolines in complexes 1b and 2b were found at higher fre-
quency than in the free imidazoline, but the effect was least
obvious for the CH2 protons and was not as marked as in the
related imidazole complexes,19 perhaps due to the aromaticity
of the imidazole ligands. The variations in the 13C NMR chem-
ical shifts as between 1b and 2b on the one hand, and the free
imidazoline on the other, were less pronounced.
intense absorption band at 1605 ± 12 cmϪ1 assigned to ν(C᎐N)
᎐
which decreased in frequency relative to the free imidazolines in
the case of 1a and 1b, while for 2a and 3b the opposite was the
case, which may be because the ligand in the last two complexes is
trans to a tertiary phosphine rather than an alkene, as in 1a or 1b.
The 13C-{1H} NMR spectra were particularly diagnostic
as to the nature of the bonding in these new complexes, estab-
lishing them to be N3-bound 2-imidazolines rather than C2-
(i)
[RhCl{N C(H)N(R)CH2CH2}cod]
R
N
1
bound imidazolidin-2-ylidenes. Thus, the imino N᎐CH signal
᎐
was observed as
a
singlet at
δ
161.3 for [RhCl-
N
{N᎐C(H)N(CH Ph)CH CH }(cod)] 1b, but a doublet centred at
᎐
2
2
2
(ii)
δ 158.4 for trans-[PtCl {N᎐C(H)N(CH Ph)CH CH }(PEt )] 2b,
᎐
2
2
2
2
3
trans-{PtCl2{N C(H)N(R)CH2CH2}(PEt3)]
4J(13C᎐31P) = 2 Hz. By contrast, in RhI᎐LR or PtII᎐LR complexes,
the carbene carbon atom showed a large 13C᎐103Rh or 13C᎐195Pt
coupling constant, e.g. 1J(13C᎐103Rh) in the range 38–65 Hz.20
The 31P-{1H} NMR spectra of complexes 2a and 2b showed
2
a R = Et
b R = CH2Ph
Scheme 1 Routes to 1-alkyl-2-imidazoline complexes 1 and 2: (i)
[{Rh(µ-Cl)(cod)}2] (0.5 equivalent), toluene, 110 ЊC, 2 h; (ii) [{Pt(µ-
Cl)Cl(PEt3)}2] (0.5 equivalent), toluene, 110 ЊC, 2 h
singlets at
δ
1.12 and 0.71 with 195Pt satellites,
1J((31P᎐195Pt) = 3345 and 3314.1 Hz, respectively.
Table 1 Yields, melting points, IR a and analytical data for the new compounds
Analysis (%)b
M.p. ( ЊC)
ν(C᎐N)a/
᎐
Compound
N(Et)(CH2)2N᎐CH
Yield (%)
[b.p. (ЊC, mmHg)]
cmϪ1
C
H
N
90
84
[44–46, 0.5]
1605
1605
᎐
75.5
7.15
17.7
N(CH2Ph)(CH2)2N᎐CH
39–40
᎐
(75.0)
55.7
(54.4)
45.4
(45.3)
27.4
(26.9)
35.3
(7.5)
6.5
(6.0)
5.95
(6.4)
5.2
(5.25)
4.95
(4.8)
(17.5)
6.0
(6.7)
8.95
(8.15)
5.8
(6.15)
5.15
(5.7)
1a
1b
2a
2b
95
72
62
88
112–113
120–121
92–93
1595
1593
1610
1616
103–104
(34.9)
a As KBr discs. b Calculated values in parentheses.
Table 2 Proton NMR chemical shifts (δ) and coupling constants (J/Hz)
Ring
Compound
N(Et)(CH2)2N᎐CH
C2H
4,5-CH2
Others
6.76 (s)
2.85 (m), 3.66 (m)
0.96 (t, J = 7.0, CH2CH3), 2.85 (q, J = 6.0, CH2CH3)
3.67 (s, CH2C6H5), 7.1 (m, CH2C6H5)
᎐
N(CH2Ph)(CH2)2N᎐CH
6.70 (s)
7.61 (s)
2.70 (m), 3.70 (m)
3.30 (t, J = 11.4), 3.47
(t, J = 11.4)
3.20 (t, J = 10.7), 3.51
(t, J = 10.7)
3.3 (t, J = 10.0), 4.0
(t, J = 10.0)
3.3 (t, J = 10.4), 4.07
(t, J = 10.4)
᎐
1a
1b
2a
2b
1.1 (t, J = 7.25, CH2CH3), 1.69 (d, J = 4.9), 2.23 (d, J = 7.4, cod CH2),
3.14 (q, J = 7.25, CH2CH3), 3.79 (s) and 4.37 (s) (cod C᎐H)
᎐
7.83 (s)
7.56 (s)
7.78 (s)
1.73 (d, J = 8.6), 2.39 (d, J = 4.9, cod CH2), 3.82 (s) and 4.44 (s) (cod
C᎐H), 4.29 (s, CH2C6H5), 7.30 (m, CH2C6H5)
᎐
1.0 (t, J = 7.0, CH2CH3, 1.19 (t, J = 7.6, PCH2CH3), 1.80 (q, J = 7.6,
PCH2CH3), 3.2 (q, J = 7.0, CH2CH3)
1.20 (t, J = 7.6, PCH2CH3), 1.80 (q, J = 7.6, PCH2CH3), 4.33 (s,
CH2C6H5), 7.32 (m, CH2C6H5)
Table 3 13C-{1H} NMR chemical shifts (δ) and coupling constants (J/Hz)
Ring
Compound
N(Et)(CH2)2N᎐CH
C2H
4,5-CH2
Others
157.2
42.3, 48.6
14.1 (CH2CH3), 55.8 (CH2CH3)
᎐
N(CH2Ph)(CH2)2N᎐CH
157.2
161.1
48.6, 52.0
30.2, 31.6
56.1 (CH2C6H5), 127.6, 128.2, 128.9 (CH2C6H5)
13.6 (CH2CH3), 41.8, 47.4 (cod CH2), 50.7 (CH2CH3), 75.0 (d, J = 14.4) and 81.8
(d, J = 11.7) (cod CH)
30.1, 31.4 (cod CH2), 51.3 (CH2C6H5), 75.1 (d, J = 13.0) and 81.9 (d, J = 11.0) (cod
CH), 127.7, 128.1, 128.8, 134.8 (CH2C6H5)
7.4 (d, J = 3.1, PCH2CH3), 12.1 (CH2CH3), 13.8 (d, J = 39.4, PCH2CH3), 41.7
(CH2CH3)
᎐
1a
1b
2a
2b
161.3
157.7
158.4
47.2, 50.9
47.1, 50.7
47.4, 51.2
7.6 (d, J = 3.0, PCH2CH3), 13.9 (d, J = 39.0, PCH2CH3), 51.6 (CH2C6H5), 127.8,
128.1, 128.8, 134.8 (CH2C6H5)
1360
J. Chem. Soc., Dalton Trans., 1997, Pages 1359–1362

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Ph
(i)
Ph
+
+
N2CHCO2R
R = Et
–N2
CO2R
Ph
CO2R
trans
cis
Scheme 2 (i) Rhodium() complex 1a or 1b
prepared by published methods. The 1-alkyl-2-imidazolines
N(R)(CH ) N᎐CH (R = Et or CH Ph) were readily prepared
᎐
2
2
2
from CH(OMe)2NMe2 and the appropriate diamine H2N-
(CH2)2NHR.18
Fig. 1 Structure of trans-[PtCl2{N᎐C(H)N(Et)CH2CH2}(PEt3)] 2a
᎐
The IR spectra were recorded as samples in KBr discs or as
Nujol mulls on a Unicam 2100 grating spectrophotometer,
NMR spectra, for samples in CDCl3 solution, on a Bruker WM
360 or AC-250SY instrument. Elemental analyses were
obtained in the Middle East Technical University, Ankara.
Table 4 Selected bond lengths (Å) and angles (Њ) with estimated
standard
deviations
in
parentheses
for
trans-[PtCl2-
{N᎐C(H)N(Et)CH2CH2}(PEt3)] 2a
᎐
Pt᎐Cl(1)
Pt᎐P
P᎐C(6)
2.283(4)
2.231(4)
1.82(2)
1.83(2)
1.57(2)
1.48(2)
1.51(3)
1.53(3)
1.52(3)
Pt᎐Cl(2)
Pt᎐N(1)
P᎐C(8)
N(1)᎐C(1)
N(2)᎐C(1)
N(2)᎐C(4)
C(4)᎐C(5)
C(8)᎐C(9)
2.291(5)
2.088(11)
1.85(2)
1.29(2)
1.33(2)
1.41(2)
1.52(2)
1.56(2)
Preparations
1-Ethyl-2-imidazoline.
A solution of N-ethylethane-1,2-
P᎐C(10)
diamine (12.55 g, 124 mmol) and CH(OMe)2NMe2 (19.06 g,
160 mmol) was slowly heated. When the oil-bath temperature
reached 75–80 ЊC, NMe2H and MeOH began to distil off. The
brown residue was distilled at 34–36 ЊC (0.4 mmHg) to obtain a
colourless liquid.
N(1)᎐C(3)
N(2)᎐C(2)
C(2)᎐N(3)
C(6)᎐C(7)
C(10)᎐C(11)
Cl(1)᎐Pt᎐Cl(2)
Cl(1)᎐Pt᎐N(1)
Cl(2)᎐Pt᎐N(1)
Pt᎐P᎐C(6)
178.6(2)
88.6(3)
90.2(3)
116.1(5)
110.7(5)
106.6(8)
128.1(9)
107(1)
125(1)
116(1)
103(1)
116(1)
Cl(1)᎐Pt᎐P
Cl(2)᎐Pt᎐P
P᎐Pt᎐N(1)
Pt᎐P᎐C(8)
C(6)᎐P᎐C(8)
C(8)᎐P᎐C(10)
Pt᎐N(1)᎐C(3)
C(1)᎐N(2)᎐C(2)
C(2)᎐N(2)᎐C(4)
N(2)᎐C(2)᎐C(3)
N(2)᎐C(4)᎐C(5)
P᎐C(8)᎐C(9)
88.7(2)
92.5(2)
177.0(3)
114.1(5)
105.3(7)
102.9(7)
124.8(9)
109(1)
124(1)
104(1)
116(1)
111(1)
1-Benzyl-2-imidazoline. A solution of N-benzylethane-1,2-
diamine (2.0 g, 13.3 mmol) in cyclohexane (4 cm3) was added to
CH(OMe)2NMe2 (1.29 g, 15 mmol) and the mixture was heated
under distillation conditions, allowing the produced NMe2H
and MeOH to distil off. Then volatiles were removed under
vacuum. The residue (1.79 g) was crystallised from toluene (1.5
cm3)–hexane (6 cm3).
Pt᎐P᎐C(10)
C(6)᎐P᎐C(10)
Pt᎐N(1)᎐C(1)
C(1)᎐N(1)᎐C(3)
C(1)᎐N(2)᎐C(4)
N(1)᎐C(1)᎐N(2)
N(1)᎐C(3)᎐C(2)
P᎐C(6)᎐C(7)
(1-Alkyl-2-imidazoline)chloro(cycloocta-1,5-diene)rhodium(I)
1a and 1b. A solution of 1-ethyl-2-imidazoline (0.16 g, 1.6
mmol) in toluene (15 cm3) and [{Rh(µ-Cl)(cod)}2] (0.40 g, 0.80
mmol) was heated for 2 h under reflux. Hexane (5 cm3) was
added to the warm solution. Upon cooling to room temper-
ature yellow-orange crystals of complex 1a (0.47 g) were filtered
off, washed with cold hexane (2 × 5 cm3) and dried in a vacuum.
Similarly, from the same rhodium() starting material (0.60 g,
1.21 mmol) and 1-benzyl-2-imidazoline (0.38 g, 2.43 mmol),
orange crystals of complex 1b (0.89 g) were obtained.
P᎐C(10)᎐C(11)
112(1)
Single crystals of complex 2a were grown from CH2Cl2᎐Et2O
at ambient temperature. The molecular structure is shown in
Fig. 1 and selected bond lengths and angles are given in Table 4.
The platinum is in a square-planar environment, with the chlor-
ides trans to one another. The Pt᎐Cl [average 2.287(4) Å] and
Pt᎐P [2.231(4) Å] bond lengths may be compared with those in
trans-[PtCl2(LPh)(PEt3)] III [LPh = CN(Ph)(CH2)2NPh]; Pt᎐Cl
2.301(6) (average) and Pt᎐P 2.291(4) Å].21 Hence it appears that
the trans influence of the 1-ethyl-2-imidazoline ligand in 2a is
slightly greater than that of the carbene (or imidazolidin-2-
ylidene) ligand LPh in III.
For the cyclopropanation of alkanes with diazo compounds
various efficient transition-metal catalysts have been reported.
Although those available have proved useful in many instances,
the search for alternatives goes on. Recently, bis(2-oxazolin-2-
yl)(pyridine)ruthenium() complexes have been introduced as
efficient cyclopropanation catalysts, which give good trans–cis
selectivities.22 Hence, we have checked the new rhodium() com-
pounds 1a and 1b in the same context (Scheme 2).With 0.9 mol
% catalyst at 80 ЊC styrene gave an excellent yield (91–95%) of
the cyclopropanation product with ethyl diazoacetate. The
mechanistic details of this catalytic reaction are currently under
investigation.
trans-(1-Alkyl-2-imidazoline)dichloro(triethylphosphine)plat-
inum(II) 2a and 2b. A solution of 1-ethyl-2-imidazoline (0.14 g,
1.43 mmol) in toluene (10 cm3) was added to [{Pt(µ-Cl)-
Cl(PEt3)}2] (0.56 g, 0.73 mmol) and the mixture was heated for
2 h under reflux. Upon addition of hexane (6 cm3) to the result-
ing yellow solution and cooling to room temperature, yellow
crystals of complex 2a (0.48 g) were filtered off, washed with
hexane (2 × 10 cm3) and dried under vacuum.
Yellow microcrystals of compound 2b (0.56 g) were obtained
similarly from 1-benzyl-2-imidazoline (0.20 g, 1.25 mmol) and
the same platinum() starting material (0.50 g, 0.65 mmol).
Cyclopropanation reactions
In a typical experiment, the catalyst 1 (0.009 mmol) and styrene
(20 mmol, 2.3 cm3) were introduced into a Schlenk tube and
then ethyl diazoacetate (1 mmol) in styrene (1 cm3) was added.
The mixture was stirred in an oil-bath at 80 ЊC for 4 h. The
yields and the ratio of isomers were determined by GC.
Experimental
Crystallography
Unless otherwise stated, manipulations were carried out
under argon using a high-vacuum manifold and conventional
Schlenk techniques. Solvents were distilled over appropriate
drying agents and thoroughly degassed prior to use. The com-
plexes [{Rh(µ-Cl)(cod)}2]23 and [{Pt(µ-Cl)Cl(PEt3)}2]24 were
Crystal data. C11H25Cl2N2PPt, M = 482.3, tetragonal, space
group I4 (no. 82), a = b = 20.997(2), c = 7.549(1) Å, U = 3327.9
Å3, Z = 8, Dc = 1.93 g cmϪ3, F(000) = 1856, µ(Mo-Kα) = 89.2
cmϪ1, 293 K.
J. Chem. Soc., Dalton Trans., 1997, Pages 1359–1362
1361

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Data collection, structure solution and refinement. X-Ray
diffraction data were collected on a crystal of dimensions
0.3 × 0.2 × 0.2 mm, in a Lindemann capillary sealed under
argon, on an Enraf-Nonius CAD4 diffractometer in the θ–2θ
mode with a scan width of ∆θ = (0.8 ϩ 0.35 tan θ)Њ, maximum
scan time of 1 min and Mo-Kα radiation (λ = 0.71069 Å). A
total of 1112 unique reflections was measured for 2 < θ < 22Њ
and ϩh ϩk ϩl; 1010 reflections with |F2| > 3σ(F2), where
σ(F2) = [σ2(I ) ϩ (0.04I )2]/Lp, were used in the refinement. There
was no crystal decay during the data collection. A correction
(maximum 1.22, minimum 0.85) for absorption was applied
using DIFABS25 after isotropic refinement.
12 J. Bremer, S. Uhlenbrock, A. A. Pinkerton and B. Krebs, Z. Anorg.
Allg. Chem., 1993, 619, 1183.
13 C. Navarro-Ranninger, F. Zamora, I. López-Solera, A. Monge and
J. R. Masaguer, J. Organomet. Chem., 1996, 506, 149.
14 P. B. Hitchcock, M. F. Lappert and P. L. Pye, J. Chem. Soc., Dalton
Trans., 1977, 2160.
15 B. Çetinkaya, E. Çetinkaya, H. Küçükbay and R. Durmaz,
Arzneim.-Forsch., Drug Res., 1996, 46, 821.
16 B. Çetinkaya, I. Özdemir, C. Bruneau and P. H. Dixneuf,
unpublished work.
17 M. F. Lappert, J. Organomet. Chem., 1988, 358, 185.
18 E. Çetinkaya and M. F. Lappert, Chemistry and Chemical Engineer-
ing Symposium, Abstracts, Kusadasý, 1989, p. 140.
19 F. Bonati, L. A. Oro, M. T. Pinillos, C. Tejel, M. C. Apreda,
C. Foces-Foces and F. H. Cano, J. Organomet. Chem., 1989, 369,
253.
20 B. Çetinkaya, P. B. Hitchcock, M. F. Lappert, D. B. Shaw,
K. Spyropoulos and N. J. W. Warhurst, J. Organomet. Chem., 1993,
459, 311.
The structure was solved using the heavy-atom routines of
SHELX 8626 and non-hydrogen atoms were refined on F with
anisotropic thermal parameters by full-matrix least squares.
Hydrogen atoms were held at calculated positions with
Uiso = 1.3Ueq for the parent atom. Final parameters were
R = 0.026, RЈ = 0.033, S = 1.26, 154 variables, w = 1/σ2(F ),
(∆/σ)max = 0.01 and (∆ρ)max,min ϩ0.57, Ϫ0.65 e ÅϪ3 on a final
difference map. Programs from the SDP-PLUS package27
were run on a Micro Vax II computer.
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 186/428.
21 L. Manojlovic´-Muir and K. W. Muir, J. Chem. Soc., Dalton Trans.,
1974, 2427.
Acknowledgements
22 S.-B. Park, N. Sakata and H. Nishiyama, Chem. Eur. J., 1996, 3, 303;
H. Nishiyama, Y. Itoh, Y. Sugawara, H. Matsumoto, K. Aoki and
K. Itoh, Bull. Chem. Soc. Jpn., 1995, 68, 1247.
23 J. Chatt and L. M. Venanzi, J. Chem. Soc., 1957, 4735.
24 J. Chatt and L. M. Venanzi, J. Chem. Soc., 1957, 2351.
25 N. Walker and D. Stuart, Acta Crystallogr., Sect. A., 1983, 39, 158.
26 G. M. Sheldrick, SHELXS 86, Program for the Solution of Crystal
Structure Refinement, University of Göttingen, 1986.
27 SDP-PLUS, Enraf-Nonius, Delft, 1978.
We thank Professor P. H. Dixneuf for helpful discussions, the
Leverhulme Trustees for an Emeritus Fellowship (for M. F. L.)
and the EPSRC for support.
References
1 A. L. Abuhijleh, Polyhedron, 1996, 15, 285.
2 K. Nonoyama, W. Mori and M. Nonoyama, Polyhedron, 1994, 13,
891; S. Bennett, S. M. Brown, G. Conole, M. Kessler, S. Rowling,
E. Sinn and S. Woodward, J. Chem. Soc., Dalton Trans., 1995, 367.
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Received 12th December 1996; Paper 6/08360I
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J. Chem. Soc., Dalton Trans., 1997, Pages 1359–1362