Crystal structure of di[(μ-benzoato-O,O′)bis(η 5-methylcylopentadienyl)-ytterbium(III)]

Article abstract of DOI:10.1002/1521-3749(200107)627:7<1431::AID-ZAAC1431>3.0.CO;2-T

Transparent orange-red crystals of [Yb(MeCp)₂-(O₂CPh)]₂ obtained by oxidation of Yb(MeCp)₂ with TI(O₂CPh) in tetrahydrofuran have a dimeric structure with bridging bidentate (O,O′)-benzoate groups and eight-coordinate ytterbium. WILEY-VCH Verlag GmbH, 2001.

Full text of DOI:10.1002/1521-3749(200107)627:7<1431::AID-ZAAC1431>3.0.CO;2-T

Crystal Structure of Di[ꢀl-benzoato-O,O')bisꢀg5-methylcylopentadienyl)-
ytterbiumꢀIII)]
Glen B. Deacon a, Catharina C. Quitmann a,b, Klaus MuÈller-Buschbaum a,b, and Gerd Meyer b,
*
a Clayton/Australia, Department of Chemistry, Monash University
b KoÈln, Institut fuÈr Anorganische Chemie, UniversitaÈt zu KoÈln
ReceivedMarch 29th, 2001.
Dedicated to Professor Hanskarl MuÈller-Buschbaum on the occasion of his 70th birthday
Abstract. Transparent orange-redcrystals of [Yb*MeCp)
-
Keywords: Lanthanides; Benzoate; Crystal structure; Ytter-
2
*O2CPh)]2 obtainedby oxaidtion of Yb*MeCp)
with
bium; Methylcylopentadienyl
2
Tl*O2CPh) in tetrahydrofuran have a dimeric structure with
bridging bidentate *O,O')-benzoate groups andeight-coordi-
nate ytterbium.
Considerable variety in carboxylate coordination has been
observedin crystallographically characterizedcarboxylato-
bis*cyclopentadienyl)lanthanide*III) complexes, viz. O,O'-
2054.90*4) pm, b = 119.43*3)°, l = 57.28 cm±1, MoKa,
5.08 £ 2 h £ 56.85°, ±27 £ h £ 27, ±12 £ k £ 10, ±27 £ l £ 27,
F*000) = 1768, R1 = 0.443 for 5222 reflections [I > 2r*I)],
R1 = 0.0922 andwR 2 = 0.0966 for 8041 unique reflections,
GOOF on F2 = 1.033. Structure solution: SHELXS-86 [10],
structure refinement: SHELXL-97 [11].
IR *Nujol): 3070 w *m*CH) MeCp), 1606 s and1567 s
*mas*CO2)), 1418 vs *ms*CO2)), 1306 m *m*CC)), 1027 m
*b*CH) MeCp), 776 s *c*CH) MeCp), 717 s *ring def.) cm±1.
UV/VIS/near IR *thf/dme): kmax *E) 420*261), 876*4),
949*12), 966*27), 987 sh*19), 995*33) nm.
chelation *g2) in monomeric [Lu*g5-C5Me4 Bu)2*O2CMe)]
t
[1], [Y*g5-Cp)2[g2-O2C*CH2)3NMe2] [2], [Sc*g5-Cp)2*O2C)-
C6H4CH3] [3], bridging bidentate *l-g'*O),g'*O')) in [Yb*g5-
Cp)2*O2CC6F5)]2 [4], [Y*g5-C5HMe4)2*O2CMe)]2 [5], [Sc*g5-
Cp)2*O2CSi*SiMe3)3)]2 [6] and bridging tridentate *l3-g2-
*O,O), g'*O')) in [Yb*g5-C5H4X)2Yb*O2CMe)]2 *X = H or
PPh2) [7] and[Ln* g5-C5HMe4)2*O2CMe)]2 *Ln = La, Sm)
[5]. In view of these possibilities, the coordination behaviour
of the unsubstitutedbenzoate ion is of interest. Mass spec-
trometry suggests Yb*Cp)2*O2CPh) to be dimeric, but single
crystals have been elusive [8], andan incomplete, low resolu-
tion structure determination of Yb*MeCp)2*O2CPh) sug-
gested a dimer but no details could be provided [9]. We have
now been able to successfully determine the structure, which
reveals disorder problems that may have been the origin of
the failure of an earlier study [9].
Discussion
[Yb*MeCp)2*O2CC6H5)]2 crystallizes with the mono-
clinic crystal system in space group P 21/n with two
crystallographically independent Yb positions. The
structure consists of dimeric molecules, whose halves
are relatedby symmetry centres. The cooridnation
spheres of both ytterbium atoms are made up of two
*g5-MeCp) andtwo * l-O2CPh) ligands to yield a coor-
dination number of eight *Fig. 1). This is similar to the
structure of [YbCp2*O2CC6F5)]2 [4] containing a fully
substituted bridging bidentate benzoate ligand *cf.
bridging tridentate leading to ninefold coordination
for the less bulky acetate [7]). In [Yb*MeCp)2-
*O2CPh)]2 the Yb±C distances average to 260 pm.
Subtraction of the ionic radius of eight-coordinate
Yb*III) [12] results in a radius of the Cp anion of
162 pm corresponding to the value derived from
[YbCp2*O2CC6F5)]2 [4] andbeing in the usual range
[13]. With bridging bidentate coordination, the
Yb1±Yb2 distances *484 and 509 pm) are much longer
than in the bridging tridentate [Yb*g5-C5H4X)2-
*O2CMe)]2 *390 pm) [7]. The separations of the carb-
oxylate oxygen atoms from the non-bonded Yb atoms
are 372±409 pm, much longer than the 240 pm for the
longest Yb±O bond in bridging tridentate coordina-
tion [7]. Despite the similarity of the Yb±O bond
lengths in the present compound, the Yb±O±C angles
Experimental
Under an atmosphere of purified nitrogen Yb*MeCp)2 and
Tl*O2CPh) *each 0.89 mmol) were reactedin tetrahydrofuran
*15 ml) to give an orange-redsolution anda precipitate of thal-
lium, which was removedby filtration. Large air-sensitive orange-
red needles of the title product *yield 70%) were obtained from
a mixture of dme/thf *3 : 1) by cooling over several days.
thf
Yb*MeCp)2 + Tl*O2CPh) ! Yb*MeCp)2*O2CPh) + Tl
Data collection for single crystal X-ray determination was
carriedout on a j-CCD diffractometer *Enraf-Nonius).
Crystallographic data for C38H42O4Yb2: monoclinic, P21/n,
Z = 4, T = 123*2) K, a = 2027.03*3), b = 900.76*2), c =
* Prof. Dr. GerdMeyer ,
Institut fuÈr Anorganische Chemie,
UniversitaÈt zu KoÈln,
Greinstraûe 6,
D-50939 KoÈln,
Fax: 02 21 4 70 50 83
E-mail: gerd.meyer@uni-koeln.de
Z. Anorg. Allg. Chem. 2001, 627, 1431±1432 Ó WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001 0044±2313/01/6271431±1432 $ 17.50+.50/0 1431

G. B. Deacon, C. C. Quitmann, K. MuÈller-Buschbaum, G. Meyer
show that the bonding of the benzoate ligands to the
metal centres is unsymmetrical *for distances and
angles between atoms, see legendto Figs. 1 and2).
The differences between corresponding angles, e. g.
C1±O1±Yb1 andC1±O2±Yb1 *10±12 °) are substantial
but less than those *14±34°) of the marginally more
crowded pentafluorobenzoate [4]. Further, this asym-
metry in coordination foreshadows the intrinsic asym-
metry of bridging tridentate coordination where the
differences between corresponding pairs of Yb±O±C
angles lie in the range of 50±70°. On both dimeric mo-
lecules, the MeCp ligands allow two equally probable
positions for the methyl groups. Not relatedto this is
a disorder of the Yb2 atoms which subsequently re-
sults in a disorder of one of the coordinated MeCp li-
gands in a ratio of one third to two thirds and an
asymmetric coordination of the non-disordered MeCp
ring to the weaker representedYb2 positions *Fig. 2).
All atoms, including the disordered ones, were refined
anisotropically [14] giving a more reasonable result of
the refinement than averagedatomic positions.
The disorder might be explained by a block structure
but not by intergrown individuals. Furthermore, no
evidence of a suitable twinning law was found nor a
possible lower symmetry. The close relation of the
Fig. 1 Dimeric molecule 1 in the structure of [Yb*MeCp)2-
*O2CC6H5)]2. The thermal ellipsoids are scaled to a proba-
bilty density of 50%. The methyl groups C8 and C14 are dis-
ordered in a 1 : 1 ratio. Selected distances/pm and angles/°:
present compoundto YbCp *O2CC6H5) [8] suggests a
2
similar dimeric structure for the latter.
Yb1±O1 218.5*4), Yb1±O2 215.6*4), Yb1±C9 262.3*6), Yb1±C10 259.2*6),
Yb1±C11 255.1*7), Yb1±C15 259.6*7), Yb1±C16 255.8*7), Yb1±C19
262.1*6), C1±O1 125.6*6), C1±O2 121.7*6); Yb1±O1±C1 151.6*4),
Yb1±O2±C1 162.2*4), O1±Yb1±*centroidC9±C13) 105.3*6), O2±Yb1±
*C9±C13) 107.7*6), *C9±C13)±Yb1±*centroidC15±C19) 130.4*6),
O1±Yb1±*C15±C19) 107.1*6), O2±Yb1±*C15±C19) 105.3*6).
This work was supportedby the Australian Research Coun-
cil, the Deutsche Forschungsgemeinschaft, andthe Studien-
stiftung des Deutschen Volkes.
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[14] Further information about the crystal structure deter-
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can be requestedby giving the author names andthe
deposition number CCDC-160132.
Fig. 2 Dimeric molecule 2 in the structure of [Yb*MeCp)2-
*O2CC6H5)]2. The Yb2 atoms as well as one of the Cp rings
are disordered in a 2 : 1 ratio. The individual with the higher
occupation is shown by darker bonds and atoms. Methyl
group C27 is disordered in a 1 : 1 ratio. Selected distances/
pm andangles/ °:
Yb2±O3 225.4*6), Yb2±O4 205.8*6), Yb2'±O3 199*1), Yb2'±O4 235*1),
Yb2±C31 260.4*7), Yb2±C32 266.7*7), Yb2±C35 255.7*7), Yb2±C37
264*2), Yb2'±C29 233*2), Yb2'±C31 259.1*8), Yb2'±C36' 255*2), Yb2'±C34'
269*2), C20±O3 127.1*7), C20±O4 125.6*7); Yb2±O3±C20 139.2*5),
Yb2±O4±C20 152.3*5), Yb2'±O3±C20 148.7*6), Yb2'±O4±C20 156.4*5),
O3±Yb2±*centroidC28±C32) 100.0*7), O4±Yb2±*C28±C32) 105.2*7),
*C28±C32)±Yb2±*centroidC34±C38) 134.7*9), O3±Yb2±*C34±C38)
108.4*8), O4±Yb2±*C34±C38) 104.7*8), O3±Yb2'±*centroidC28±C32)
117*1), O4±Yb2'±*C28±C32) 103*1), *C28±C32)±Yb2'±*centroidC34 '±C38')
129*2), O3±Yb2'±*C34'±C38') 98*2), O4±Yb2'±*C34'±C38') 107*2).
1432
Z. Anorg. Allg. Chem. 2001, 627, 1431±1432