Homoleptic lanthanide(ii)-bis(guanidinate) complexes, [Ln(Giso) 2] (Giso = [(ArN)2CN(C6H11) 2]-, Ar = C6H3Pri 2-2,6): Planar 4-coordinate (Ln = Sm or Eu) vs distorted tetrahedral (Ln = Yb) geometries

Article abstract of DOI:10.1039/b614028a

The first homoleptic lanthanide(II)-guanidinate complexes have been prepared and shown to have differing coordination geometries that depends on the size of the lanthanide metal. Synthetic route to very bulky guanidinate ligands was developed and utilized in the stabilization of novel low oxidation state main group complexes. The bulky ligands could also stabilize low coordinate lanthanide(II) complexes. The stabilizing properties of Giso^- appears to be similar to the bulky β-diketiminates that is utilized in the formation of tetrahedral Yb(II) complexes. A property of the yellow 4 was observed to reduce pressure at 25 °C in the solid state for several minutes. Recrystallization of the solid from toluene afforded red crystals. NMR spectra of the related complexes are symmetrical and unchanging at temperature down to -90°C. The molecular structure of heteroleptic 4 reveals it to form dimeric units through effectively symmetrically bridging iodide ligands.

Full text of DOI:10.1039/b614028a

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Homoleptic lanthanide(II)–bis(guanidinate) complexes, [Ln(Giso)2] (Giso =
[(ArN)2CN(C6H11)2]−, Ar = C6H3Pri2-2,6): planar 4-coordinate (Ln = Sm
or Eu) vs distorted tetrahedral (Ln = Yb) geometries†
Dennis Heitmann,a Cameron Jones,*a Peter C. Junk,b Kai-Alexander Lipperta and Andreas Stascha,b
Received 26th September 2006, Accepted 6th November 2006
First published as an Advance Article on the web 20th November 2006
DOI: 10.1039/b614028a
The first homoleptic lanthanide(II)–guanidinate complexes
have been prepared and shown to have differing coordination
geometries (including unprecedented examples of planar 4-
coordination) that depend on the size of the lanthanide metal.
The chemistry of amidinato- and guanidinato-lanthanide(III)
complexes has been extensively developed and such compounds
have found a number of applications, mainly as polymerisation
catalysts.1 Considering the significant potential that related lan-
thanide(II) complexes have as soluble one-electron reductants in
3
organic and organometallic synthesis (e.g. SmI22 and SmCp*2 ), it
Scheme 1 Reagents and conditions: i, 2 K[Giso], THF, −KI; ii, Ln = Yb,
is surprising that to date only two bis(amidinato)lanthanide(II)
K[Giso], THF, −KI; iii, −YbI2(THF)n; iv, THF.
complexes have been structurally characterised, viz. trans-
octahedral [Sm{(ArN)2CH}2(THF)2] (Ar = C6H3Pri2-2,6)4 and
[Yb{(Me3SiN)2CPh}2(THF)2].5 If homoleptic examples could be
YbI2(THF)n. It seems likely that the Sm and Eu analogues of 4 are
prepared, the accessibility of their metal centres to substrates,
and thus their usefulness as reductants, may be significantly
enhanced. We have recently developed synthetic routes to very
bulky guanidinate ligands, e.g. [(ArN)2CN(C6H11)2]− (Giso−), and
have utilised these in the stabilisation of novel low oxidation state
main group complexes, e.g. [{M(Giso)}n] (n = 1, M = Ga, In or
Tl;6 n = 2, M = Ge7). It seemed reasonable that bulky ligands
of this type could also stabilise low coordinate lanthanide(II)
complexes. In this respect, it is noteworthy that the stabilising
properties of Giso− appear to be similar to those of bulky, N,Nꢀ-
chelating b-diketiminates [{(R1)NC(R2)}2CR3]− (nacnac−), which
have recently been utilised in the formation of tetrahedral Yb(II)
complexes, [Yb(nacnac)2].8 Here, we report the first examples of
structurally characterised homoleptic Ln(II)–guanidinates, two of
which contain the first examples of planar 4-coordinate lanthanide
centres.
The 2 : 1 reactions of K[Giso] with LnI2 (Ln = Sm, Eu or Yb) in
THF afforded the deeply coloured homoleptic complexes, 1–3, in
moderate yields (Scheme 1). When the reactions were carried out in
1 : 1 stoichiometries 1–3 were also the major products. This is not
surprising given the known propensity of (amido)lanthanide(II)
halides to undergo redistribution reactions.9 However, from the
1 : 1 or 2 : 1 reactions that gave deep green 3, was also isolated
a small amount (6%) of yellow 4. When this was re-dissolved in
THF it redistributed over several hours at 25 ◦C to give 3 and
too short-lived to be isolated as their respective redistributions to
1 and 2 are more facile due to the larger ionic radii of the metals
2+
involved (values for 7-coordinate Ln: Sm2+ 1.22 A, Eu 1.20 A
˚
˚
10
and Yb2+ 1.08 A).
˚
An interesting property of yellow 4 was observed when it was
subject to reduced pressure (ca. 10−2 mmHg) at 25 ◦C in the
solid state for several minutes, whereupon it took on a deep red
coloration. Recrystallisation of this solid from toluene afforded red
crystals of 5 (Scheme 1). Therefore, it appears that, not only are
the coordinating THF molecules of 4 readily removed in vacuo,
but that this process also involves a change in the coordination
1
6
mode of the Giso− ligand from j2-N,Nꢀ-chelating in 4 to g -N,g -
arene-chelating in 5. This rearrangement is quantitatively reversed
by dissolving 5 in THF.11
Due to the paramagnetic nature of 1 and 2, no useful informa-
tion could be obtained from their NMR spectra. Those for 3 and 4‡
are consistent with their proposed structures, whereas the solution
state NMR spectra of 5 are more symmetrical than its solid state
structure would suggest. This observation is compatible with a
fluxional process occurring in solution, though an examination
of this by variable temperature NMR studies was thwarted by
the low solubility of 5 in D8-toluene below ambient temperature.
It is noteworthy, however, that the NMR spectra of the related
1
3
complex, [Tl(g -N,g -Ar-Giso)],6 are similarly symmetrical and
unchanging at temperatures down to −90 ◦C. In that case, this was
said to be indicative of a low energy fluxional process. No signals
aSchool of Chemistry, Main Building, Cardiff University, Cardiff, UK CF10
3AT. E-mail: jonesca6@cardiff.ac.uk
1
were observed in the 171Yb{ H} NMR spectrum of a strong sample
of 3 at 25 ◦C, despite closely related [Yb(nacnac)2] complexes
displaying signals at d 2650 200 ppm in their spectra.8b However,
in those cases, the signals are usually very broad and sometimes
not observable.
bSchool of Chemistry, Monash University, Melbourne, PO Box 23, Victoria,
2800, Australia
† Electronic supplementary information (ESI) available: Full synthetic de-
tails for 1–5 and ORTEP diagrams for 2 and 3. See DOI: 10.1039/b614028a
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Dalton Trans., 2007, 187–189 | 187
©

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The X-ray crystal structures§ of homoleptic 1 (Fig. 1, relevant
geometrical parameters for 2 and 3 included in caption) and 2
are isomorphous and both possess planar 4-coordinate metal
centres, as evidenced by the small twist angles◦between their
CN2LnC(adjacent backbone) least squares planes (1: 1.4 , 2: 1.7◦)†. In
contrast, the coordination geometry of 3 can be considered a◦s
distorted tetrahedral (cf. [Yb(nacnac)2]8), as the same angle is 57.9
for that compound. There is no crystallographic or spectroscopic
evidence to suggest the presence of hydride ligands in either 1
or 2. The guanidinate ligands in all three complexes appear to
be largely delocalised and their Ln–N distances are in the normal
ranges12 and decreasing from Ln = Sm > Eu > Yb. The differences
in the coordination geometry of 3 presumably arise from the
considerably smaller Ln2+ ionic radius of Yb relative to the other
two metals. To the best of our knowledge, there are no previously
reported examples of complexes containing planar 4-coordinate
Ln2+ centres, and it seems that in 1 and 2 this geometry is not
enforced by the steric bulk of the ligands when the tendency
towards tetrahedral coordination of the smaller metal in 3 is
considered.13 If the Giso− ligands of 1–3 are regarded as single
point donors, then they are notionally related to the formally 2-
coordinate Ln(II)–bis(alkyls), [Ln{C(SiMe3)3}2] (Ln = Sm, Eu or
Yb).14 However, the latter complexes are bent (C–Ln–C angle: Sm
143.4◦, Eu 136.0◦, Yb 137.0◦) whereas the C(1)–Ln–C(38) angles
in 1 (171.4◦) and 2 (170.1◦) are close to linear. It might be expected
that in these planar complexes, Ln · · · Me agostic interactions
might occupy sites on either side of the coordination plane.
Although such interactions are well known for Ln3+ complexes,
they have been rarely reported for Ln2+ species.15 However, in both
˚
complexes there is only one Ln · · · C interaction less than 3.7 A
˚
˚
(1: 3.64 A, 2: 3.61 A), which can, at best, be considered as at the
upper end of the Sm2+ · · · Me or Eu2+ · · · Me agostic interaction
ranges.12,15 Indeed, these interactions are considerably longer than
˚
in other Ln(II)–amides, e.g. closest Ln · · · C interaction: 3.32 A in
[Sm{N(SiMe3)2}2(THF)2]16 and 2.971 A in Na[Eu{N(SiMe3)2}3].
17
˚
It is an appealing possibility that the planar geometries of 1 and
2 could lend them to use as soluble 1-electron reductants of small
organic substrates that may be able to access their metal centres
in solution, despite the unsolvated nature of these centres in the
solid state.
The molecular structure of heteroleptic 4 (Fig. 2) reveals it to
form dimeric units through effectively symmetrically bridging io-
dide ligands. Each metal centre is chelated by a largely delocalised
Giso− ligand and additionally coordinated by a THF molecule
to give them heavily distorted trigonal bipyramidal geometries. In
line with this proposal are the longer Yb–N bonds from the apical
nitrogens, N(1), than those from the equatorial N-centres, N(2).
Considering the lability of the coordinated THF molecules, it is
surprising that the Yb–O distances lie close to the mean for those
in all previously reported Yb–THF interactions (3.88 A).12 It is of
˚
note that the structure of a related monomeric Yb–nacnac com-
6
plex has been reported, viz. [YbCl{j2N,Nꢀ-(ArNCMe)2CH}(g -
C7H8)],18 and this has been used as an effective pre-catalyst for the
polymerisation of methyl methacrylate.
Fig. 1 Molecular structure of 1 (hydrogen atoms omitted). Selected
bond lengths (A) and angles ( ): Sm(1)–N(1) 2.529(2), Sm(1)–N(4)
Fig. 2 Molecular structure of 4 (hydrogen atoms omitted). Selected
bond lengths (A) and angles ( ): Yb(1)–N(2) 2.373(3), Yb(1)–N(1)
◦
◦
˚
˚
2.426(3), Yb(1)–O(1) 2.441(3), Yb(1)–I(1)ꢀ 3.1129(8), Yb(1)–I(1)
3.1424(9), N(1)–C(1) 1.343(5), C(1)–N(2) 1.351(5), C(1)–N(3) 1.405(5);
N(2)–Yb(1)–N(1) 55.55(11), Yb(1)ꢀ–I(1)–Yb(1) 86.58(3), N(1)–C(1)–N(2)
112.3(3). Symmetry operation ꢀ: −x + 1, −y + 1, −z + 1.
2.530(2), Sm(1)–N(2) 2.554(2), Sm(1)–N(5) 2.570(2), N(1)–C(1)
1.355(3), N(2)–C(1) 1.344(3), N(3)–C(1) 1.399(3), N(4)–C(38) 1.348(3),
N(5)–C(38) 1.342(3), N(6)–C(38) 1.401(3), N(1)–Sm(1)–N(2) 52.55(7),
N(4)–Sm(1)–N(5) 52.18(7); N(2)–C(1)–N(1) 113.0(2), N(5)–C(38)–N(4)
◦
˚
113.0(2). Selected bond lengths (A) and angles ( ) for 2: Eu(1)–N(4)
2.525(2), Eu(1)–N(1) 2.527(2), Eu(1)–N(2) 2.544(2), Eu(1)–N(5)
2.563(2), N(1)–C(1) 1.351(3), N(2)–C(1) 1.349(3), N(3)–C(1) 1.400(3),
N(4)–C(38) 1.345(3), N(5)–C(38) 1.345(3), N(6)–C(38) 1.403(3);
N(1)–Eu(1)–N(2) 52.81(6), N(4)–Eu(1)–N(5) 52.41(6), N(2)–C(1)–N(1)
Complex 5 is also an iodide bridged dimer (Fig. 3), though its
Giso− ligands have rearranged upon THF desolvation to “chelate”
1
6
its ytterbium centres via g -amide and g -arene interactions.19 The
former is shorter than the Yb–N interactions of 3 and 4, and
the N3C fragment of the ligand appears to be significantly more
localised than in those complexes. There is a close relationship
˚
113.2(2), N(5)–C(38)–N(4) 113.2(2). Selected bond lengths (A)
and angles (◦) for 3: Yb(1)–N(2) 2.378(2), Yb(1)–N(5) 2.385(2),
Yb(1)–N(4) 2.397(2), Yb(1)–N(1) 2.430(2), N(1)–C(1) 1.345(4), N(2)–C(1)
1.356(3), N(3)–C(1) 1.400(3), N(4)–C(38) 1.366(4), N(5)–C(38) 1.345(3),
N(6)–C(38) 1.391(3); N(2)–Yb(1)–N(1) 55.79(8), N(5)–Yb(1)–N(4)
56.48(8), N(5)–Yb(1)–N(1) 132.92(8), N(2)–Yb(1)–N(4) 127.82(8),
N(1)–C(1)–N(2) 112.8(2), N(5)–C(38)–N(4) 113.1(2).
1
between the Giso–M interaction in 5 and that in monomeric [Tl(g -
3
N,g -Ar-Giso)].6
In conclusion, the first examples of homoleptic
bis(guanidinato)lanthanide(II) complexes have been reported,
188 | Dalton Trans., 2007, 187–189
This journal is
The Royal Society of Chemistry 2007
©

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R (on F) 0.0392, wR (on F2) 0.0810 (I > 2rI). 2·(C6H6): C80H118N6Eu,
˚
M = 1315.76, monoclinic, space group P2◦1/n, a = 12.631(3) A, b =
3
˚
˚
˚
30.988(6) A, c = 18.627(4) A, b = 99.16(3) , V = 7198(2) A , Z = 4,
Dc = 1.214 g cm−3, F(000) = 2812, l(Mo-Ka) = 0.918 mm−1, 150(2)
K, 13989 unique reflections [R(int) 0.0232], R (on F) 0.0387, wR (on
F2) 0.0843 (I > 2rI). 3·(C7H8)2: C88H128N6Yb, M = 3904.7(14), triclinic,
¯
˚
˚
˚
space gr◦oup P1, a = 13.822(3) A, b =◦16.195(3) A, c = 17.916(4) A, a =
◦
3
˚
89.75(3) , b = 78.04(3) , c = 84.48(3) , V = 3904.7(14) A , Z = 2, Dc =
1.227 g cm−3, F(000) = 1536, l(Mo-Ka) = 1.245 mm−1, 150(2) K, 15245
unique reflections [R(int) 0.0387], R (on F) 0.0426, wR (on F2) 0.0930 (I >
¯
2rI). 4·(C6H6)0.5: C44H67IN3OYb, M = 953.95, triclinic, space group P1,
◦
˚
˚
˚
a = 11.277(2) A, b = 1◦1.998(2) A, c = 17.583(4) A, a = 76.56(3) , b =
◦
3
−3
˚
88.31(3) , c = 71.46(3) , V = 2191.2(8) A , Z = 2, Dc = 1.446 g cm
,
F(000) = 966, l(Mo-Ka) = 2.872 mm−1, 150(2) K, 9509 unique reflections
Fig. 3 Molecular structure of 5 (hydrogen atoms omitted). Selected
[R(int) 0.0327], R (on F) 0.0367, wR (on F2) 0.0792 (I > 2rI). 5·(C7H8):
◦
ꢀ
˚
bond lengths (A) and angles ( ): Yb(1)–N(1) 2.360(3), Yb(1)–I(1)
¯
˚
C44H64IN3Yb, M = 934.92, triclinic, space◦group P1, a = ◦10.530(2) A, b =
◦
3.0478(7), Yb(1)–I(1) 3.0992(10), Yb(1)–Ar centroid 2.424(4), N(1)–C(1)
1.361(4), C(1)–N(2) 1.325(4), C(1)–N(3) 1.405(4); N(1)–Yb(1)–I(1)ꢀ
119.56(7), N(1)–Yb(1)–I(1) 130.93(7), N(1)–Yb(1)–Ar centroid 93.49(2),
I(1)ꢀ–Yb(1)–I(1) 90.69(3), Yb(1)ꢀ–I(1)–Yb(1) 89.31(3), N(2)–C(1)–N(1)
120.6(3). Symmetry operation ꢀ: −x + 1, −y, −z.
˚
˚
13.562(3) A, c = 15.958(3) A, a = 80.99(3) , b = 71.19(3) , c = 80.40(3) ,
V = 2114.2(7) A , Z = 2, Dc = 1.469 g cm−3, F(000) = 944, l(Mo-Ka) =
3
˚
2.974 mm−1, 150(2) K, 9217 unique reflections [R(int) 0.0263], R (on F)
0.0320, wR (on F2) 0.0713 (I > 2rI). CCDC reference numbers 619010–
619014. For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b614028a
1 See, for example: (a) F. T. Edelmann, D. M. M. Freckmann and
H. Schumann, Chem. Rev., 2002, 102, 1851; (b) F. T. Edelmann,
Coord. Chem. Rev., 1994, 137, 403; (c) C. Villiers, P. Thuery and M.
Ephritikhine, Eur. J. Inorg. Chem., 2004, 4624; (d) A. A. Trifonov, G. G.
Skvortsov, D. M. Lyubov, N. A. Skorodumova, G. K. Fukin, E. V.
Baranov and V. N. Glushakova, Chem.–Eur. J., 2006, 12, 5320 and
references therein.
two of which contain the first structurally characterised planar
4-coordinate lanthanide centres. The use of these as 1-electron
reductants in organic and organometallic synthesis is currently
being examined.
We gratefully acknowledge financial support from the Lever-
hume Trust (postdoctoral fellowship for AS), and the ERASMUS
scheme of the European Union (travel grants for D.H. and
K.-A.L.). Thanks also go to the EPSRC Mass Spectrometry
Service.
2 G. A. Molander and C. R. Harris, Chem. Rev., 1996, 96, 307 and
references therein.
3 See, for exapmle: W. J. Evans, R. A. Keyer and J. W. Ziller, J. Organomet.
Chem., 1990, 394, 87.
4 M. L. Cole and P. C. Junk, Chem. Commun., 2005, 2695.
5 M. Wedler, M. Noltemeyer, U. Pieper, H.-G. Schmidt, D. Stalke and
F. T. Edelmann, Angew. Chem., Int. Ed. Engl., 1990, 29, 894. NB: A
solvent free Yb(II)–bis(amidinate) complex was also reported, though
not structurally characterised.
6 C. Jones, P. C. Junk, J. A. Platts and A. Stasch, J. Am. Chem. Soc., 2006,
128, 2206.
7 S. P. Green, C. Jones, P. C. Junk, K.-A. Lippert and A. Stasch, Chem.
Commun., 2006, 3978.
Notes and references
‡ Selected data for 1: Yield: 64% (deep violet crystals); mp 205–206 ◦C. IR
m/cm−1 (Nujol): 1612(m), 1583(m), 1387(m), 1319(m), 1022(m), 931(m);
MS (EI 70 eV), m/z (%): 544 [GisoH+, 32], 501 [GisoH+ − Pri, 68]. 2:
◦
Yield: 48% (red-orange crystals); mp 205–207 C. IR m/cm−1 (Nujol):
8 (a) S. Harder, Angew. Chem., Int. Ed., 2004, 43, 2714; (b) A. G. Avent,
P. B. Hitchcock, A. V. Khostov, M. F. Lappert and A. V. Protchenko,
Dalton Trans., 2003, 1070.
1612(m), 1583(m), 1377(m), 1318(m), 1023(m), 931(m); MS (EI 70 eV),
m/z (%): 544 [GisoH+, 36], 501 [GisoH+ − Pri, 82]. 3: Yield: 50% (deep
green crystals); mp 222–224 ◦C. 1H NMR (400 MHz, C6D6, 298 K): d
0.82–1.40 (m, 40 H, CH2), 1.32 (br. overlapping m, 48 H, CH(CH3)2),
3.35 (br. m, 8 H, CH(CH3)2), 3.59 (br. m, 4 H, NCH), 6.85–7.16 (m,
9 N. M. Scott and R. Kempe, Eur. J. Inorg. Chem., 2005, 1319 and
references therein.
1
12 H, ArH); 13C{ H} NMR (100.6 MHz, C6D6, 298 K): d 20.8 (CH2),
10 R. D. Shannon, Acta Crystallogr., Sect. A, 1976, 32, 751.
11 The reversible removal of THF from Ln(II) centres has been previously
observed. See, for example: J. Wang, R. I. J. Amos, A. S. P. Frey, M. G.
Gardiner, P. C. Junk and M. L. Cole, Organometallics, 2005, 24, 2259.
12 As determined from a survey of the Cambridge Crystallographic
Database, August, 2006.
13 In contrast, homoleptic, Ar-substituted bis(amidinato)–first row tran-
sition metal complexes appear to have a steric preference for planar
4-coordinate over tetrahedral geometries: C. A. Nijhuis, E. Jellema,
T. J. J. Sciarone, A. Meetsma, P. H. M. Budzelaar and B. Hessen,
Chem.–Eur. J., 2005, 2089.
14 (a) G. Qi, Y. Nitto, A. Saiki, T. Tomohiro, Y. Nakayama and H. Yasuda,
Tetrahedron, 2003, 59, 10409; (b) C. Eaborn, P. B. Hitchcock, K. Izod,
Z.-R. Lu and J. D. Smith, Organometallics, 1996, 15, 4783; (c) C.
Eaborn, P. B. Hitchcock, K. Izod and J. D. Smith, J. Am. Chem. Soc.,
1994, 116, 12071.
15 X. Chen, S. Lim, C. E. Plecnik, S. Liu, B. Du, E. A. Meyers and S. G.
Shore, Inorg. Chem., 2005, 44, 6052 and references therein.
16 W. J. Evans, D. K. Drummond, H. Zhang and J. L. Atwood, Inorg.
Chem., 1988, 27, 575.
24.7 (CH2), 26.4 (CH(CH3)3), 25.9 (CH(CH3)3), 27.2 (CH(CH3)3), 34.9
(CH2), 57.7 (NCH), 120.6, 122.0, 139.4, 145.2 (ArC), 164.7 (N3C); IR
m/cm−1 (Nujol): 1612(m), 1583(m), 1109(m), 1023(m), 931(m); MS (EI
70 eV), m/z (%): 1259 [MH+, 3%], 544 [GisoH+, 15], 501 [GisoH+
−
Pri, 26]. 4: Yield: 6%; mp 158–160 ◦C (decomp.). 1H NMR (400 MHz,
C6D6, 298 K): d 0.88–1.86 (m, 40 H, CH2), 1.44 (br. overlapping m, 48 H,
CH(CH3)2), 1.58 (br., 8 H, THF), 3.31 (br., 8 H, OCH2), 3.42 (br. m, 4 H,
1
NCH), 3.79 (br. m, 8 H, CH(CH3)2), 7.03–7.38 (m, 12 H, ArH); 13C{ H}
NMR (100.6 MHz, C6D6, 298 K): d 22.0 (CH2), 22.8 (CH2), 24.9 (THF),
26.0 (CH(CH3)3), 27.1 (CH(CH3)3), 28.4 (CH(CH3)3), 35.2 (CH2), 58.4
(CHN), 69.4 (THF), 121.3, 123.1, 141.2, 145.2 (ArC), CN3 not observed.;
IR m/cm−1 (Nujol): 1611(m), 1583(m), 1108(m), 1020(m), 933(m); MS (EI
70 eV), m/z ◦(%): 544 [GisoH+, 21], 501 [GisoH+ − Pri, 52]. 5: Yield: 5%;
mp 218–220 C (decomp.). 1H NMR (400 MHz, C6D6, 298 K): d 1.11–1.75
(m, 40 H, CH2), 1.22 (br. overlapping m, 48 H, CH(CH3)2), 2.94 (br. m,
4 H, NCH), 3.26 (br. m, 8 H, CH(CH3)2), 6.73–7.18 (m, 12 H, ArH);
1
13C{ H} NMR (100.6 MHz, C6D6, 298 K): d 21.5 (CH2), 22.0 (CH2), 25.9
(CH(CH3)3), 27.0 (CH(CH3)3), 28.9 (CH(CH3)3), 32.6 (CH2), 58.0 (CHN),
123.1, 125.5, 137.6, 145.2 (ArC), CN3 not observed.; IR m/cm−1 (Nujol):
1611(m), 1583(m), 1108(m), 1023(m), 893(m); MS (EI 70 eV), m/z (%):
844 [(Giso)YbI, 1], 544 [GisoH+, 36], 501 [GisoH+− Pri, 56].
17 T. D. Tilley, R. A. Andersen and A. Zalkin, Inorg. Chem., 1984, 23,
2271.
18 Y. Yao, Y. Zhang, Z. Zhang, Q. Shen and K. Yu, Organometallics, 2003,
§ Crystal data for 1·(C6H6): C80H118N6Sm, M = 1314.15, monoclinic, space
˚
˚
˚
22, 2876.
group P◦21/n, a = 12.620(3) A, b = 31.033(6) A, c = 18.640(4) A, b =
6
3
99.11(3) , V = 7208(2) A , Z = 4, Dc = 1.211 g cm−3, F(000) = 2808, l(Mo-
˚
19 Ln(II)–g -arene interactions are well known. See, for example: G. B.
Ka) = 0.861 mm−1, 150(2) K, 13347 unique reflections [R(int) 0.0330],
Deacon and Q. Shen, J. Organomet. Chem., 1996, 511, 1.
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 187–189 | 189
©