Bis[(μ-iodo)iodo-η-cyclopentadienylruthenium(III)], 'CpRuI 2' = [CpRuI2]2: A further example of a [CpXM(μ-X)2MXCp] parent with cis arrangement

Article abstract of DOI:10.1002/zaac.200800019

The very limited array of (structurally described) adducts of the form [CpMX₂]₂ ≡ [CpMX(μ-X)₂MXCp] with the unsubstituted/parent Cp (≡ C₅H₅, cyclopentadienyl) ligand is augmented by a study of [CpIRu(μ-I)₂RuICp], found to be isotypic with the recently described chloride and, with it, providing the only examples of such dimers in their 'cis' form, i.e., the terminal-X and Cp pairs to the same side of the Ru₂(μ-X)₂ arrays, which are appreciably folded at the X...X lines, with the short Ru...Ru distances (2.7748(6) (X = Cl), 2.9034(8) A (X = I)), consistent with the presence of appreciable metal-metal bonding (cf. the M = Cr, X = Cl counterpart which is trans, Cr...Cr 3.3447(8) A).

Full text of DOI:10.1002/zaac.200800019

DOI: 10.1002/zaac.200800019
Bis[(μ-iodo)iodo-η-cyclopentadienylruthenium(III)], ‘CpRuI2’ ؍ [CpRuI2]2:
a Further Example of a [CpXM(μ-X)2MXCp] Parent with cis Arrangement
Michael I. Brucea,*, Martyn Jevrica, Brian W. Skeltonb, and Allan H. Whiteb
a Adelaide 5005/South Australia, University of Adelaide, School of Chemistry and Physics
b Crawley 6009/Western Australia, School of Biomedical, Biomolecular and Chemical Sciences, Chemistry M313, The University of
Western Australia
Received January 19th, 2008.
Abstract. The very limited array of (structurally described) adducts
of the form [CpMX2]2 ϵ [CpMX(μ-X)2MXCp] with the unsubsti-
tuted/parent Cp (ϵ C5H5, cyclopentadienyl) ligand is augmented
by a study of [CpIRu(μ-I)2RuICp], found to be isotypic with the
recently described chloride and, with it, providing the only ex-
amples of such dimers in their ‘cis’ form, i.e., the terminal-X and
Cp pairs to the same side of the Ru2(μ-X)2 arrays, which are appre-
ciably folded at the X···X lines, with the short Ru···Ru distances
(2.7748(6) (X ϭ Cl), 2.9034(8) A (X ϭ I)), consistent with the pres-
˚
ence of appreciable metal-metal bonding (cf. the M ϭ Cr, X ϭ Cl
˚
counterpart which is trans, Cr···Cr 3.3447(8) A).
Keywords: Ruthenium; Halides; Iodine; Binuclear complexes;
Metal-metal bond; Crystal structure
Introduction
obtained only in small quantity, with its authentication and
characterization being dependent on the X-ray work.
Reactions between pentamethylcyclopentadiene (HC5Me5
In the course of
a study of the reactions of
ϵ
HCp*) and ruthenium(III) chloride yield either
[Ru(CϵCC6F5)(PPh3)2Cp], we sought to make the related
iodovinylidene complex, [Ru{ϭCϭCI(C6F5)}(PPh3)2Cp]ϩ,
by treatment of the alkynyl complex with [I(py)2](BF4).
While initial formation of a deep green compound sug-
gested that the sought-for vinylidene had been formed, at-
tempted purification resulted in a colour change to deep
red. Crystallization (hexane-chloroform) afforded crystals
which were shown to consist of the title complex. Forma-
tion of this compound may have occurred because of the
presence of the strongly electron-withdrawing C2C6F5 li-
gand (oxidation potential of the starting complex is
ϩ0.56 V) and the use of [I(py)2]ϩ, a strong oxidizing agent.
[RuCl2Cp*]2 [1, 2] or [Ru(μ3-Cl)Cp*]4 [3], according to con-
ditions, both compounds being useful precursors for RuCp*
chemistry; more recently, analogous osmium complexes
have been obtained from H2OsBr6 and HC5Me5 [4]. XRD
structures of ruthenium(III) and osmium(III) complexes
[CpЈXM(μ-X)2MXCpЈ] (M ϭ Ru, X ϭ Cl, Br, CpЈ substitu-
ents(s) R ϭ diverse [5Ϫ8]; M ϭ Os, X ϭ Br, CpЈ ϭ Cp*
[4]) have been reported. In contrast, reactions between
RuCl3 and cyclopentadiene afford either ruthenocene,
[RuCp2] [9], or, if carried out in the presence of other li-
gands, L, the ruthenium(II) complexes [RuCl(L)2Cp] [10].
Some related osmium chemistry has also been reported [4b].
To our knowledge, the only structurally authenticated ex-
ample of a parent Cp-ruthenium(III) or osmium(III) halide
is the recent report of ‘CpRuCl2’ [11], which prompts us to
record our parallel study of the iodide counterpart.
Structure determination
A full sphere of CCD area-detector diffractometer data was meas-
ured (Bruker AXS instrument, monochromatic Mo Kα radiation,
˚
λ ϭ 0.71073 A; ω-scans, 2θmax ϭ 70°; T ca. 150 K), yielding 13763
reflections, these merging to 3508 unique (Rint ϭ 0.045) after ‘em-
pirical’/multiscan absorption correction (proprietary software),
2761 with F > 4σ(F) being considered ‘observed’ and used in the
full matrix least squares refinements on F2, refining anisotropic dis-
placement parameter forms for the non-hydrogen atoms, hydrogen
atoms being included following a riding model. At convergence, R,
Rw were 0.055, 0.096 (reflection weights: (σ2(F2) ϩ 7.8F2)Ϫ1); neu-
tral atom complex scattering factors were employed within the
XTAL 3.7 program system [12]. Pertinent results are given below
and in Table 1 and the Figure (the latter showing 50 % displace-
ment probability amplitudes for the non-hydrogen atoms, hydrogen
Experimental Section
Synthesis
As was also the case with the chloride counterpart [11], the
synthesis of ‘CpRuI2’ was adventitious, the product being
* Prof. Dr. M.I. Bruce
School of Chemistry and Physics
University of Adelaide
Adelaide, 5005 South Australia
Tel.: (618) 8303 5939; Fax ϩ (618) 8303 4358
E-mail: michael.bruce@adelaide.edu.au
˚
atoms having arbitrary radii of 0.1 A). Full crystallographic data
for the structure have been deposited with the Cambridge Crystal-
lographic Data Centre, CCDC 664969. Copies of the data can be
obtained free of charge on application to The Director CCDC, 12
Z. Anorg. Allg. Chem. 2008, 634, 1093Ϫ1096
© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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M. I. Bruce, M. Jevric, B. W. Skelton, A. H. White
3
˚
˚
c ϭ 15.884(2) A, β ϭ 102.433(3)°, V ϭ 1596 A . Dc (Z ϭ 4) ϭ
3.497 g cmϪ3. μMo ϭ 9.6 mmϪ1; specimen: 0.12 x 0.10 x 0.03 mm;
‘T’min/max ϭ 0.50.
Table 1 Selected (non-hydrogen) descriptors, ’CpRuX2’, X ϭ Cl, I
Primed atoms are related by the intradimer ([CpXRu(μ-X)2RuXCp]
two-fold crystallographic axis. Counterpart values for the isotypic
chloride are given in italics.
Atoms
Parameter
Atoms
Parameter
Results and Discussion
˚
Distances/A
A plethora of arrays of the form “CpЈMX2” (X ϭ halide)
has been synthesized and structurally characterized, for de-
rivatives of substituted cyclopentadienes, particularly so for
complexes of the pentamethylcyclopentadienyl ligand, Cp*,
and for X ϭ Cl, these taking the binuclear form [CpЈXM(μ-
X)2MXCpЈ]. Such arrays are often crystallographically cen-
trosymmetric, consistent with a seemingly universal tend-
ency to adopt the ‘trans’ isomeric form, with the pair of
terminal X atoms disposed to either side of the (obligate)
planar MX2M array, also true of the CpЈ substituents. Re-
markably, with ruthenium in particular in the present con-
text, forms crystallizing with more than one molecular com-
ponent in the asymmetric unit have been identified [5, 6],
with, in one of these cases Ϫ that of [Cp*RuCl2]2 [5] Ϫ the
two components being so different in Ru···Ru separations
Ru-X(1)
Ru-X(1Ј)
Ru-X(2)
Ru···RuЈ
X···XЈ
2.3591(8), 2.6285(9) Ru-C(1)
2.3788(8), 2.6584(8) Ru-C(2)
2.195(3), 2.205(11)
2.229(3), 2.22(2)
2.207(3), 2.222(10)
2.167(3), 2.189(9)
2.156(3), 2,203(11)
2.19, 2.207
2.3851(8), 2.735(1)
Ru-C(3)
2.7748(6), 2.9034(8) Ru-C(4)
3.430(1), 4.1304(9) Ru-C(5)
<Ru-C>
Ru-C(0)
1.828, 1.848
Angles/°
X(1)-Ru-X(1Ј) 92.76(2), 102.75(3)
Ru-X(1)-RuЈ 71.70(2), 66.62(2)
X(2)-Ru-X(1) 87.87(3), 88.54(3)
X(2)-Ru-X(1Ј) 86.61(3), 87.28(3)
C(0)-Ru-X(2) 116.1, 119.1
C(0)-Ru-X(1) 129.4, 123.7
C(0)-Ru-X(1Ј) 130.1, 124.8
Interplanar dihedral angles/°
Cp/CpЈ
71.1(1), 71.9(5)
63.81(6), 56.78(6)
Cp/I2Ru
Cp/I2RuЈ
67.4(1), 64.3(4)
4.5(1), 7.7(4)
RuI2/I2RuЈ
Union Road, Cambridge CB2 1EX, UK (Fax: int. code ϩ (1223)
336-033; email for inquiry:fileserv@ccdc.cam.ac.uk; email for
deposition: deposit@ccdc.cam.ac.uk).
˚
(2.930(1), cf. 3.752(1) A) as to provoke the descriptor ‘de-
formational isomers’, with differing electronic properties
consistent with the presence or absence of Ru···Ru bonding
(Table 2).
By contrast, only two such arrays have been defined for
the parent Cp ligand. The chromium(III)/chloride complex,
[CpCrCl2]2, has long been known and structurally defined
Crystal Data
[CpIRu(μ-I)2RuICp] ϭ C10H10I4Ru2, M ϭ 839.4. Monoclinic,
space group C2/c (C62h, No. 15), a ϭ 7.608(1), b ϭ 13.520(2),
Table 2 Comparative descriptors, [Cp(*)XM(μ-X)2MXCp(*)] (Cp(*) ϭ Cp, Cp*; X ϭ Cl, Br, I; M diverse
(a) [Cp(*)XM(μ-X)2MXCp(*)], (M ϭ Rh, Ir see part (b) below)
Cp(y)
M/X
Cp(cis)
Cp(trans) Cp*(trans)
Cr/Clc) Cr/Cl(1;2)d)
Ru/Cla) Ru/Ib)
Cr/Ie)
Ru/Cl(a,b)f)
Ru/Br (2 mols.)f)
Os/Brg) Al/Clh) Al/Bri) Ti/Clj)
Co/Brk)
˚
Distances/A
M···M
X···X
M-X(B)
M-X(B)
M-X(T)
2.7748(6) 2.9034(8) 3.3447(8) 3.450(1); 3.439(1) 3.771(3) 2.930(1); 3.752(1) 3.098(2); 2.989(2) 2.970(1) 3.459(2) 3.691(2) 3.3344(8) 3.616(2)
3.430(1) 4.1304(10) 3.3680(9) 3.327(1); 3.292(2) 3.914(1) 3.717(2); 3.135(2) 3.878(4); 3.944(4) 3.977(2) 3.163(2) 3.416(1) 3.449(1) 3.321(1)
2.3591(8) 2.6285(9) 2.3713(8) 2.394(1); 2.372(1) 2.712(2) 2.366(1); 2.445(1) 2.473(3)Ϫ2.495(4) 2.482(2) 2.340(1) 2.516(2) 2.4010(9) 2.458(2)
2.3788(8) 2.9034(8) 2.3754(8) 2.398(1); 2.388(1) 2.723(2) 2.366(2); 2.458(2) 2.482(2) 2.346(2) 2.513(2) 2.3962(10) 2.451(1)
2.2780(7) 2.287(1); 2.294(2) 2.672(2) 2.418(2); 2.365(2) 2.541(3)Ϫ2.550(3) 2.559(1) 2.149(1) 2.311(2) 2.2655(6) 2.398(2)
2.3851(8) 2.735(1)
Angles/°
M-X-M
71.70(2) 66.62(2)
89.60(3) 92.1(1), 92.5(1)
87.86(6) 76.50(4); 100.24(5) 74.32(9)Ϫ77.31(10) 73.51(4) 95.12(6) 94.4(1) 88.07(3)
92.14(6) 103.50(4); 79.76(5) 102.3(1)Ϫ105.7(1) 106.94(4) 84.88(5) 85.6(1) 91.93(3)
94.87(5)
85.13(5)
X(B)-M-X(B) 92.76(2) 102.75(3) 90.40(3) 87.9(1), 87.5(1)
X(B)-M-X(T) 87.87(8) 88.54(3)
86.61(3) 87.28(3)
96.00(3) 97.1(1), 96.8(1)
97.18(3) 95.8(1), 97.2(1)
95.35(6) 89.99(6); 91.50(6) 88.65(9)Ϫ90.38(10) 89.74(4) 97.1(1) 97.4(1) 101.09(4) 92.58(5)
93.52(6) 89.63(7); 97.39(6)
88.99(5) 97.7(1) 96.9(1) 102.89(3) 93.94(5)
(b) Trans-[Cp*XM(μ-X)2MXCp*], M ϭ Rh/Irl)
M/X
Rh/Cl
Rh/Br
Rh/I
Ir/Cl
Ir/Br
Ir/I
˚
Distances/A
M···M
X···X
M-X(B)
M-X(T)
3.719(1)
3.217(2)
2.459(9)
2.397(1)
3.848(9)
3.427(2)
2.576(9)
2.528(6)
4.132(1)
3.604(1)
2.741(1)
2.706(1)
3.769(1)
3.141(6)
2.453(5)
2.387(4)
3.902(13)
3.348(6)
2.570(6)
2.519(5)
4.072(1)
3.576(1)
2.710(4)
2.694(1)
Angles/°
M-X-M
98.29(3)
81.71(3)
91.5(11)
96.62(11)
83.38(3)
91.2(9)
97.80(1)
82.20(1)
93.29(1)
100.45(12)
79.55(12)
89.1(8)
98.74(8)
81.26(8)
89.4(6)
97.42(2)
82.58(2)
90.8(10)
X(B)-M-X(B)
X(B)-M-X(T)
a) Ref. [11]; b) This work; c) Ref. [13b]; d) Ref. [14] (two molecules); e) Ref. [15] (cocrystallized with [Cp*I3Cr(μ-I)]2, which interacts distantly with the terminal iodine (I···I
3.542(1) A); f) Ref. [5]; see also [16]; although the determination does not feature in the paper, there is an associated CCDC deposition (JIVHUR01) (molecule 1 is
˚
devoid of symmetry, molecule 2 is centrosymmetric); g) Ref [4a]; h) Ref. [17]; i) Ref. [18]; j) Ref. [19]; k) Ref. [20] (molecule 1; molecule 2 is disordered); l) As summarized
in Refs. [21, 22].
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Z. Anorg. Allg. Chem. 2008, 1093Ϫ1096

Bis[(μ-iodo)iodo-η-cyclopentadienylruthenium(III)]
as the above binuclear form in its trans-configuration [13],
˚
Cr···Cr distances of 3.362(1) (295 K), 3.3447(8) A (203 K)
consistent with the presence of only limited metal···metal
bonding (cf. the aluminium and titanium analogues, Table
2). In the other example, the recently reported ru-
thenium(III)/chloride complex, the pairs of chloride and Cp
ligands lie cis with respect to the RuCl2Ru core which, here,
is disposed about a crystallographic 2-axis, rather than an
˚
inversion centre. Ru···Ru (2.7748(6) A) is much shorter than
Cr···Cr, despite M-Cl (bridging, x 2) which are very similar
˚
(2.3713(8), 2.3754(8) (M ϭ Cr); 2.3591(8), 2.3788(8) A
(M ϭ Ru). The M-Cl (terminal) distances differ appreci-
˚
ably: 2.2780(7), 2.3851(8) A, suggestive of much stronger
metal-metal bonding within the ruthenium complex, poss-
ibly the origin of and/or facilitated by the considerable
‘folding’ feature of the RuCl2Ru array across the Cl···Cl
line, a feature not possible if the dimer is truly centrosym-
metric as in many of the trans complexes and where the
formation of the cis form may be hindered by the Cp sub-
stituents.
The results of the present single crystal X-ray study are
fully consistent with the description of the present complex
as [CpIRu(μ-I)2RuICp], (Fig. 1), the structure being iso-
typic with the recently described chloride counterpart with
which its dimensions are compared in Table 1. The Ru···Ru
bond is somewhat longer in the iodide complex, consistent
with the presence of the much larger halogen atoms. The
latter perhaps dictate the decrease in ‘fold’ angle across the
the X···X line, concomitant with a distortion comprising a
twist about the intramolecular 2-axis and encompassing the
development of a differential between the Ru-I distances,
the bridging ones becoming shorter and one longer (mean
˚
˚
2.77 A), cf. the Ru-I (terminal) distance of 2.735(1) A (per-
haps a useful datum, since all three Ru-Cl distances in the
˚
chloride counterpart lie within a range of 0.026 A), with the
further constraint that the inner hydrogen atoms of the pair
˚
of Cp ligands contact (est. 2.3 A) within their van der Waals
sum. The molecules pack in sheets about z ϭ 0.25, 0.75 of
opposed polarity, as shown in Fig. 1(b).
Acknowledgement. We thank the ARC for support of this work and
Johnson Matthey plc, Reading, UK, for a generous loan of
RuCl3 ·nH2O.
Fig. 1 (a) Molecular projection of [CpIRu(μ-I)2RuICp]; the
crystallographic 2-axis lies quasi-vertical in the page. (b) Unit cell
contents projected down a.
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