Contrasting binding modes in lanthanoid pyrazolate and pseudo-pyrazolates prepared by oxidation of lanthanoid(II) complexes and lanthanoid metals with thallium(I) reagents

Article abstract of DOI:10.1021/om990932f

Oxidation of Yb(C₅Me₅)₂ with [Tl(Ph₂pz)] and [Tl(azin)] (Ph₂pz = 3,5-diphenylpyrazolate, azin = 7-azaindolate) yields [Yb(C₅Me₅)₂(Ph₂pz)] (1) and [Yb(C₅Me₅)₂(azin)] (2). X-ray crystal structures of 1 and 2 reveal monomeric eight-coordinate complexes with η²-Ph₂pz or azin ligands. Treatment of neodymium metal with [Tl(Ph₂pz)] yields [Nd(Ph₂pz)₃(dme)₂] (3), which is a nine-coordinate monomer with three η²-pyrazolate ligands and a chelating and a unidentate dme ligand. Oxidation of Sm(C₅Me₅)₂ with [TI(1,4,2-P₂SbC₂Bu^t₂)]/[TI(1,2,4-P₃C₂ Bu^t₂)] (approximately 4:1) gave a mixture of [Sm(C₅Me₅)₂(1,2,4-P₃C₂Bu^t₂)] (4) and [Sm(C₅Me₅)₂(1,4,2-P₂SbC₂Bu^t₂)]. The former was shown to be a nine-coordinate monomer with novel pseudo-pyrazolate η²-(P₂)-[1,2,4-P₃C₂Bu^t₂] coordination of the triphosphacyclopentadienide ligand. After metathesis routes to Ln(1,4,2-P₂SbC₂Bu^t₂)_n complexes failed, redox transmetalation between ytterbium metal and [Tl(1,4,2-P₂EC₂Bu^t₂)] (E = Sb, P) containing a substantial impurity of [Li(tmeda)₂][1,4,2-P₂EC₂Bu^t₂] yielded the first lanthanoid diphosphastibacyclopentadienide complex in a mixture with [1,2,4-P₃C₂Bu^t₂] species. An X-ray investigation of single crystals containing an isomerically diverse mixture enabled the structure of [Li(thf)₄]-[Yb(1,4,2-P₂SbC₂Bu^t₂)₃] (5) to be determined, and it was shown to contain a π-η² and two η⁵-[1,4,2-P₂SbC₂Bu^t₂] ligands. In the series 1, 4, and 5, the η²-ring varies from edge-on to side-on, reflecting a progression from σ to π coordination. [Li(tmeda)₂][1,4,2-P₂SbC₂Bu^t₂] (6) has been successfully crystallized from a [Li(tmeda)₂][P₂EC₂Bu^t₂] mixture and structurally characterized.

Full text of DOI:10.1021/om990932f

Organometallics 2000, 19, 1713-1721
1713
Con tr a stin g Bin d in g Mod es in La n th a n oid P yr a zola te
a n d P seu d o-p yr a zola tes P r ep a r ed by Oxid a tion of
La n th a n oid (II) Com p lexes a n d La n th a n oid Meta ls w ith
Th a lliu m (I) Rea gen ts
Glen B. Deacon, Ewan E. Delbridge, and Gary D. Fallon
Department of Chemistry, Monash University, Clayton, Victoria, 3168, Australia
Cameron J ones, David E. Hibbs, and Michael B. Hursthouse
Department of Chemistry, University of Wales, Cardiff, Park Place, Cardiff, CF10 3TB, U.K.
Brian W. Skelton and Allan H. White
Department of Chemistry, The University of Western Australia, Nedlands, 6907, Australia
Received November 26, 1999
Oxidation of Yb(C5Me5)2 with [Tl(Ph2pz)] and [Tl(azin)] (Ph2pz ) 3,5-diphenylpyrazolate,
azin ) 7-azaindolate) yields [Yb(C5Me5)2(Ph2pz)] (1) and [Yb(C5Me5)2(azin)] (2). X-ray crystal
structures of 1 and 2 reveal monomeric eight-coordinate complexes with η2-Ph2pz or azin
ligands. Treatment of neodymium metal with [Tl(Ph2pz)] yields [Nd(Ph2pz)3(dme)2] (3), which
is a nine-coordinate monomer with three η2-pyrazolate ligands and a chelating and a
unidentate dme ligand. Oxidation of Sm(C5Me5)2 with [Tl(1,4,2-P2SbC2But )]/[Tl(1,2,4-P3C2-
2
But )] (approximately 4:1) gave a mixture of [Sm(C5Me5)2(1,2,4-P3C2But )] (4) and [Sm(C5-
2
2
Me5)2(1,4,2-P2SbC2But )]. The former was shown to be a nine-coordinate monomer with novel
2
pseudo-pyrazolate η2-(P2)-[1,2,4-P3C2But ] coordination of the triphosphacyclopentadienide
2
ligand. After metathesis routes to Ln(1,4,2-P2SbC2But ) complexes failed, redox transmeta-
2 n
lation between ytterbium metal and [Tl(1,4,2-P2EC2But )] (E ) Sb, P) containing a substantial
2
impurity of [Li(tmeda)2][1,4,2-P2EC2But ] yielded the first lanthanoid diphosphastibacyclo-
2
pentadienide complex in a mixture with [1,2,4-P3C2But ] species. An X-ray investigation of
2
single crystals containing an isomerically diverse mixture enabled the structure of [Li(thf)4]-
[Yb(1,4,2-P2SbC2But )3] (5) to be determined, and it was shown to contain a π-η2 and two
2
η5-[1,4,2-P2SbC2But ] ligands. In the series 1, 4, and 5, the η2-ring varies from edge-on to
2
side-on, reflecting a progression from σ to π coordination. [Li(tmeda)2][1,4,2-P2SbC2But ] (6)
2
has been successfully crystallized from a [Li(tmeda)2][P2EC2But ] mixture and structurally
2
characterized.
Sch em e 1. Som e Coor d in a tion Mod es of
P yr a zola te a n d P seu d o-p yr a zola te Liga n d s
In tr od u ction
Since 1996, pyrazolate coordination has been trans-
formed by the discovery of new binding modes.1 In
lanthanoid complexes, the σ-η2 binding mode, with the
ring edge-on to the metal and coplanar with it (I), is
dominant1a-c,2 (Scheme 1). However, µ-η1:η1 bonding is
also known,2 while the µ-η2:η2 mode has recently been
discovered.1a,b
(1) (a) Deacon, G. B.; Delbridge, E. E.; Skelton, B. W.; White, A. H.
Angew. Chem., Int. Ed. 1998, 37, 2251. (b) Deacon, G. B.; Gitlits, A.;
Skelton, B. W.; White, A. H. Chem. Commun. 1999, 1213. (c) Deacon,
G. B.; Delbridge, E. E.; Forsyth, C. M. Angew. Chem., Int. Ed. 1999,
38, 1766. (d) Falvello, L. R.; Fornie´s, J .; Martin, A.; Navarro, R.; Sicilia,
V.; Villarroya, P. Chem. Commun. 1998, 2429. (e) Perera, J . R.; Heeg,
M. J .; Schlegel H. B.; Winter, C. H. J . Am. Chem. Soc. 1999, 121, 4536.
(f) Ye´lamos, C.; Heeg, M. J .; Winter, C. H. Inorg. Chem. 1998, 37, 3892.
(2) (a) Cosgriff, J . E.; Deacon, G. B. Angew. Chem., Int. Ed. 1998,
37, 287. (b) Trofimenko, S. Chem. Rev. 1972, 72, 497. (b) Trofimenko,
S. Prog. Inorg. Chem. 1986, 34, 115. (c) Sadimenko A. P.; Basson, S.
S. Coord. Chem. Rev. 1996, 147, 247. (d) LaMonica G.; Ardizzoia, G.
A. Prog. Inorg. Chem. 1997, 46, 151.
It is of interest to compare coordination of lanthanoids
by pyrazolates (≡1,2-diazacyclopentadienides) with co-
ordination by heavier group 15-substituted cyclopenta-
10.1021/om990932f CCC: $19.00 © 2000 American Chemical Society
Publication on Web 03/30/2000

1714 Organometallics, Vol. 19, No. 9, 2000
Deacon et al.
dienides [1,4,2-P2EC2But ] (E ) P3-5 or Sb5), which can
than observed for [Ln(C5H4Me)3].7 Compounds 1 and 2
have similar electronic spectra. A broad intense peak
near 510 nm has intensity similar to a corresponding
band of [YbCp3]8 or [Yb(C5Me5)2Cl]9 attributable to
ligand f metal charge transfer. Absorption bands at
930-980 nm are attributable to 4f f 4f transitions,8
and the molar absorption coefficients are similar to
those observed for YbCp3 and [Yb(C5Me5)2Cl] in this
region.8,9 However the molar absorption coefficients (ca.
200) for the bands near 1000 nm are more intense than
those observed for [YbCp3]8 or [Yb(C5Me5)2Cl]9 com-
plexes (ca. 30 and 80, respectively) and perhaps have
some contribution from charge transfer in addition to
4f f 4f transitions.
Redox transmetalation between lanthanoid metals
and thallium(I) 3,5-diphenylpyrazolate [Tl(Ph2pz)] has
now been shown to be a route to trivalent lanthanoid
pyrazolate complexes since treatment of neodymium
metal with [Tl(Ph2pz)] in thf and recrystallization from
dme afforded [Nd(Ph2pz)3(dme)2] (3) in good yield (eq
3). Thallium 3,5-diphenylpyrazolate has previously been
used only to give divalent lanthanoids by redox trans-
metalation (eq 1), apart from isolation of impure [Sm-
(Ph2pz)3(dme)2] from an attempt to prepare the Sm(II)
derivative by eq 1 (Ln ) Sm).6
2
be viewed as pseudo-pyrazolates. The latter are π-bond-
ed to other metals, with η5 (II), µ-η5:η5, µ-η5:η1, and η1
ligation observed,3-5 but σ-η2 (analogous to I) and π-η2
(III) can be envisaged if the pyrazolate analogy is valid.
Although lanthanoid complexes of P- and As-substituted
cyclopentadienyl ligands are known,3 only one lantha-
noid complex of [1,4,2-P2EC2But ] ligands is known, viz.,
2
an η5-bonded [1,2,4-P3C2But ] derivative of the unex-
2
pected Sc(I) oxidation state.4 Accordingly, we now report
the synthesis and structures of some lanthanoid com-
plexes with the 3,5-diphenylpyrazolate (Ph2pz), the
7-azaindolate (azin), and [1,4,2-P2EC2But ] ligands and
2
a comparison of their binding modes. We also report the
structure of the of the commonly used5 reagent [Li-
(tmeda)2][1,4,2-P2SbC2But ], crystals having been ob-
2
tained from a mixture with [Li(tmeda)2][1,2,4-P3C2But ]
2
by fractional crystallization. The syntheses feature
oxidation of Ln(II) complexes and lanthanoid metals by
the recently prepared [Tl(Ph2pz)],6 [Tl(azin)],6 and [Tl-
(1,4,2-P2EC2But )].5d The first two complexes have re-
2
cently been introduced as redox transmetalation re-
agents for the synthesis of lanthanoid(II) pyrazolate and
azaindolate complexes (eq 1),6 while [Tl(1,4,2-P2SbC2-
But )] and [Tl(1,2,4-P3C2But )] are obtained as an in-
2
2
separable mixture on a preparative scale by the orga-
nolithium route.5d
Nd + 3Tl(Ph2pz) f Nd(Ph2pz)3 + 3TlV
(3)
Unequivocal characterization of 3 was provided by an
X-ray crystallography study (below). Compound 3 has
been prepared previously10 by redox transmetalation/
ligand exchange in dme (eq 4).
2Tl(R2pz or azin) + Ln f Ln(R2pz or azin)2 + 2Tl
(1)
Ln ) Eu or Yb
2Nd + 3Hg(C6F5)2 + 6Ph2pzH f
2Nd(Ph2pz)3 + 6C6F5H+ 3HgV (4)
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion . [Yb(C5Me5)2(thf)]
has been oxidized by either [Tl(Ph2pz)] or [Tl(azin)] in
dme or thf to yield the heteroleptic complexes [Yb(C5-
Me5)2(Ph2pz)] (1) or [Yb(C5Me5)2(azin)] (2), respectively,
and thallium metal (eq 2).
The chemistry of the 1,4,2-diphosphastibacyclopen-
tadienide ligand is bedevilled by its synthesis as an
(normally) inseparable mixture with the 1,2,4-triphos-
phacyclopentadienide species.5,11 Accordingly, a [Tl(P2-
EC2But )] (E ) Sb, P) mixture was used in syntheses.
2
Yb(C5Me5)2 + TlL 9
S8 [Yb(C5Me5)2(L)] + TlV (2)
The structure of the former has been determined on a
serendipitously isolated single crystal, but separation
was impossible on a preparative scale.5d Oxidation of
L ) Ph2pz, S ) dme; L ) azin, S ) thf
[Sm(C5Me5)2(thf)2] by [Tl(P2EC2But )] in thf afforded
2
In both cases the redox reaction was nearly instanta-
neous, as evidenced by the precipitation of thallium
metal and the change in the solution color from orange
to deep purple. Both 1 and 2 were obtained in good yield
with satisfactory analyses for unsolvated compositions
[Yb(C5Me5)2L] (L ) Ph2pz or azin), which were con-
firmed by X-ray crystallography (below). Their mass
spectra showed progressive loss of C5Me5 groups fol-
lowed by Ph2pz or azin ligands and were less complex
thallium metal and a mixture of samarium(III) com-
plexes, [Sm(C5Me5)2(P2EC2But )(thf)] (eq 5), which were
2
obtained in low yield on crystallization from light
petroleum.
[Sm(C5Me5)2(thf)2] + [Tl(P2EC2But )] f
2
[Sm(C5Me5)2(P2EC2But )(thf)] + thf + Tl (5)
2
E ) P, Sb
(3) (a) Nief, F. Coord. Chem. Rev. 1998, 178-180, 13. (b) Ashe, A.
J ., III; Al-Ahmed, S. Adv. Organomet. Chem. 1996, 39, 325. (c) Dillon,
K. B.; Mathey, F.; Nixon, J . F. Phosphorus: The Carbon Copy; Wiley:
Chichester, 1998.
(4) Arnold, P. L.; Cloke, F. G. N.; Hitchcock, P. B.; Nixon, J . F. J .
Am. Chem. Soc. 1996, 118, 7630.
(5) (a) Black, S. J .; Francis, M. D.; J ones, C. J . Chem. Soc., Dalton
Trans. 1997, 2183. (b) Black, S. J .; J ones, C. J . Organomet. Chem. 1997,
534, 89. (c) Black, S. J .; Hibbs, D. E.; Hursthouse, M. B.; J ones, C.;
Malik, K. M. A.; Thomas, R. C. J . Chem. Soc., Dalton Trans. 1997,
4321. (d) Francis, M. D.; J ones, C.; Deacon, G. B.; Delbridge, E. E.;
J unk, P. C. Organometallics 1998, 17, 3826.
The products are a new class of heteroleptic tris-
(7) Paolucci, G.; Fisher, R. D.; Breitbach, H.; Pelli, B.; Traldi, P.
Organometallics, 1988, 7, 1918.
(8) (a) Pappalardo, R.; J ørgensen, C. K. J . Chem. Phys. 1967, 46,
632. (b) Calderazzo, F.; Pappalardo, R.; Losi, S. J . Inorg. Nucl. Chem.
1966, 28, 987.
(9) Watson, P. L.; Whiteney, J . F.; Harlow, R. L. Inorg. Chem. 1981,
20, 3271.
(10) Cosgriff, J . E.; Deacon, G. B.; Fallon, G. D.; Gatehouse, B. M.;
Schumann, H.; Weimann, R. Chem. Ber. 1996, 129, 953.
(11) Francis, M. D.; Hibbs, D. E.; Hursthouse, M. B.; J ones, C.; Abdul
Malik, K. M. J . Organomet. Chem. 1997, 527, 291.
(6) Deacon, G. B.; Delbridge, E. E.; Skelton, B. W.; White, A. H. Eur.
J . Inorg. Chem. 1998, 543; 1999, 751.

Oxidation of Lanthanoid(II) Complexes
Organometallics, Vol. 19, No. 9, 2000 1715
(cyclopentadienyl)lanthanoid complex. The 1H NMR
spectrum of the mixture revealed paramagnetically
broadened overlapping signals precluding satisfactory
integration and assignment of some peaks. However, a
resonance at 0.35 ppm was assigned to the C5Me5
protons, while singlets at 0.85, 1.15, and 1.25 ppm were
indicative of three different types of But group arising
from the presence of both [P2SbC2But ] and [P3C2But ]
resonances of single crystals of [Tl(P2SbC2But )] cor-
2
responded to those of the major component of the bulk
material.) Previously, an analogous thallate complex,
[Li(pmdeta)][TlCp2] (pmdeta ) (Me2NCH2CH2)2NMe),
was isolated.12 1H and 31P resonances of the single
crystals were in the normal range and thus were
consistent with the diamagnetic YbII oxidation state.
Four peaks were observed in the latter spectrum, with
the two highest frequency peaks corresponding to the
2
2
ligands. Only a single thf resonance could be located.
The 31P NMR spectrum had four resonances, as ex-
pected for a mixture of [P2SbC2But ] and [P3C2But ]
phosphorus atoms of the [P2SbC2But ] ligand (1:1 ratio).
2
The signal at highest δ value (315 ppm) is attributed
to the phosphorus adjacent to the relatively electrophilic
and quadrupolar antimony center, and the other signal
(283 ppm) corresponds to P4. The other two signals in
the 31P NMR spectrum arise from the phosphorus atoms
2
2
ligands. While the signals were not greatly shifted from
those of the diamagnetic [Li(tmeda)2][P2EC2But ] (E )
2
Sb, P) compounds,11 the signals were considerably
broadened by Sm(III) paramagnetism such that cou-
pling constants could not be determined and integra-
tions provided only a qualitative guide. Approximately
equal intensity resonances at 279 and 281 ppm were
in the [P3C2But ] ring system, where the lowest fre-
2
quency signal (246 ppm) is assigned to P1 and P2, being
twice the intensity of the peak at 263 ppm (P4). The
overall 2:1 ratio of the [P2SbC2But ]/[P3C2But ] ligands
assigned to P4 and P1, respectively, of the [P2SbC2But ]
2
2
2
found in this spectrum corresponds to the ratio estab-
lished in the structure refinement for this complex (see
below). It was impossible to confirm the relative amounts
ligand, while unequal resonances at 287 and 308 ppm
were assigned to P1,2 and P4, respectively, of the [P3C2-
But ] ligand. Estimation of the relative amounts of the
2
1
of the [P2SbC2But ] and [P3C2But ] ligands from the H
2
2
two ligands was problematical due to the exceptional
broadness of the signal at 308 ppm. However, there
appeared to be more [P3C2But ] than [P2SbC2But ]
NMR spectrum owing to broadening of the resonances.
The spectrum did however display three different But
resonances, consistent with the presence of the two
ligands as well as peaks attributable to the R and â thf
protons. Peaks at 1045 and 889 cm-1 in the infrared
spectrum of the complex are assigned to ν(C-O-C) of
coordinated thf and are lowered from free ligand values
2
2
ligands present in the sample, by contrast with the
composition of the thallium(I) reactant mixture but
consistent with the low yield of the product. Slow
fractional crystallization of the [Sm(C5Me5)2(P2EC2But )-
2
(thf)] mixture from light petroleum gave single crystals
909 and 1070 cm-1 13
The EI mass spectrum of the
.
of pure [Sm(C5Me5)2(P3C2But )(thf)], consistent with a
2
complex (scan range 0-1000 amu) revealed a number
of ytterbium-containing fragments, but no lithium spe-
cies were observed. Fragmentation patterns were con-
sistent with the predicted formulation since the highest
larger proportion of [P3C2But ] than [P2SbC2But ] in the
2
2
bulk reaction product. Possibly the minor component
[Tl(P3C2But )] is a better oxidant than [Tl(P2SbC2But )]
2
2
for Sm(C5Me5)2 leading to [Sm(C5Me5)2(P3C2But )(thf)]
2
m/z value of 818 corresponded to [Yb(P2SbC2But ) ]+ and
2 2
as the main product but in low yield.
clusters at m/z 726 and 636 corresponded to the mixed
The failure to isolate an X-ray characterizable com-
species [{Yb(P2SbC2But )(P3C2But )}-H]+ and the tri-
2
2
plex containing the [1,4,2-P2SbC2But ] ligand or the
2
phospholyl species [Yb(P3C2But ) ]+, respectively.
2 2
[1,4,2-P2EC2But ] mixture from eq 5 led to alternative
2
[Li(tmeda)2][P2EC2But ] alone does not react with
2
approaches to this objective. Metathesis reactions be-
ytterbium metal, but crystallization from the ensuing
tween NdCl3 or [YbI2(thf)2] and [Li(tmeda)2][P2EC2But ]
2
mixture realized pure [Li(tmeda)2][P2SbC2But ] (6) free
2
were attempted, but surprisingly no reaction was ob-
served. Redox transmetalation between ytterbium metal
from any triphosphacyclopentadienyl ligands.
X-r a y Discu ssion . Str u ctu r e Deter m in a tion of 1
and 2. The X-ray crystal structures of 1 and 2 have
shown both to be eight-coordinate monomers with the
C5Me5 ligands η5 bound to the ytterbium atom and the
diaza ligand chelating edge-on through the nitrogen
atoms (Figure 1). Dinuclear structures with bridging (µ-
η1:η1) pyrazolates have been proposed for the related
[Y(C5Me5)2(RR′pz)] (R ) R′ ) H, Me; R ) H, R′ ) Me)
since [{Ln(O(CH2CH2C5H4)2)}2(µ-Me2pz)(µ-OH)]14 and
[Nd(η2-Me2pz)2(µ-Me2pz)(µ-thf)]215 are dimeric with µ-η1:
η1 pyrazolate ligands. It is possible that the increased
steric bulk of the Ph2pz and azin ligands over Me2pz
and pz makes adoption of a bridging arrangement less
favorable. The steric coordination number is smaller for
and [Tl(P2EC2But )] afforded thallium metal and an
2
ytterbium(II) complex identified by X-ray crystallogra-
phy as [Li(thf)4][Yb(1,4,2-P2EC2But ) ] (E ) Sb:P ) 2:1).
2 3
Clearly a very significant amount of [Li(tmeda)2][P2EC2-
But ], the reactant in the preparation of [Tl(P2EC2But )],
2
2
was present in the thallium reagent and was a major
factor in obtaining a crystallizable product. Subsequent
examination of a sample of [Tl(P2EC2But )] from another
2
preparation showed the presence of lithium by 7Li NMR
spectroscopy, but no 31P resonances independent of
those of [Tl(P2EC2But )] and certainly none correspond-
2
ing to [Li(tmeda)2][P2EC2But ] were observed. Given
2
that the sample used in the redox transmetalation
reaction showed only 31P resonances attributable to [Tl-
(P2SbC2But )] and [Tl(P3C2But )], it appears that lithium
2
2
(12) Armstrong, D. R.; Herbst-Irmer, R.; Kulm, A.; Moncreiff, D.;
Paver, M. A.; Russell, C. A.; Stakle, D.; Steiner, A.; Wright, D. S.
Angew. Chem., Int. Ed. Engl. 1993, 32, 1774.
(13) Clark, R. J . H.; Lewis, J .; Machin, D. J .; Nyholm, R. S. J . Chem.
Soc. 1963, 379.
(14) Schumann, H.; Loebel, J .; Pickardt, J .; Qian, C.; Xie, Z.
Organometallics 1991, 10, 215.
(15) Deacon, G. B.; Gatehouse, B. M.; Nickel, S.; Platts, S. N. Aust.
J . Chem. 1991, 44, 613.
may be present as a thallate complex, e.g., [Li(tmeda)2]-
[Tl(P2EC2But ) ], which has 31P resonances indistin-
2 2
guishable from those of [Tl(P2EC2But )]. (The possibility
2
that the bulk [Tl(P2EC2But )] originally obtained, and
2
for which 31P NMR data were reported, was in fact a
thallate complex seems unlikely, as the 13P NMR

1716 Organometallics, Vol. 19, No. 9, 2000
Deacon et al.
disorder arising from the two different possible orienta-
tions of the low-symmetry azin ligand (refined in a 1:1
occupancy) (molecule 2) and the other having no iso-
meric diversity (molecule 1). Only the data from mol-
ecule 1 are discussed here. Analysis of the Yb-C bond
lengths of 1 and 2 indicates symmetrical binding of the
C5Me5 ligands to ytterbium, with average Yb-C bond
lengths of 2.59 and 2.60 Å, respectively (Table 2). These
bond lengths are typical of eight-coordinate [Yb(C5Me5)2-
XY] complexes.16 Subtraction of the ionic radius17 for
eight-coordinate ytterbium from Yb-C gives a typical18
1.61 Å. The Yb-cen distances (cen ) centroid of the C5-
Me5 ligand) are 2.30 Å for 1 and 2.31 and 2.30 Å for 2.
In 2, the Yb-N bond lengths (Table 2) of 1 and 2 are
2.25(2) and 2.279(8) Å (for the amide nitrogen of the
azin ligand), respectively. The Yb(1)-N(17) bond dis-
tance of 2.362(8) Å is significantly longer, which is
expected since N(17) is a pyridine-type nitrogen. The
(C5Me5)cen-Yb-cen(C5Me5) angles of 1 and 2 are 142°
and 141°, respectively, which are at the extreme end of
those for other eight-coordinate bis(cyclopentadienyl)-
ytterbium(III) complexes19 and approach the large value
(143°) in seven-coordinate [Sc(C5Me5)2]2C2.20 Because of
the planar nature of the Ph2pz (dihedral angle of the
phenyl substituents to the C3N2 (pz) ring, 17°) and azin
ligands and their small bite angles (34.5(6)° (1) and 60.0-
(3)° (2)), there is abundant space for wide separation of
the C5Me5 rings. The Yb-N bond lengths for 1 and the
Yb-N(amide) length for 2 (Table 2) approach closely
values for [Er(But pz)3(thf)2]21 and [Nd(But pz)3(µ-
2
2
dme)]n10, where differences in ionic radii are considered.
Ytterbium is approximately coplanar with the C5Me5
ring centroids and the center of the N-N bond (or
vector) of 1 or 2.
It is apparent from these two crystal structures that
the diaza ligands bind in an edge-on fashion (η2-σ, I,
Scheme 1) and not side-on or face-on (π) to the ytterbium
center. This is exemplified by the angle (180°) between
Yb-cen(N-N) (the center of the N-N bond of Ph2pz)
and the pyrazolate ring plane for 1, and the angle of
(175.8°) for 2. For exact end-on binding, the angle should
be 180°. This type of bonding contrasts that found in
phosphorus- and antimony-substituted cyclopentadienyl
ligands (see below).
Str u ctu r e Deter m in a tion of 3. Single crystals of 3
as a C6D6 solvate were shown to contain a nine-
coordinate neodymium atom with three chelating pyra-
zolate ligands and a chelating and a unidentate dme.
Since the complex has the same molecular structure as
[Er(Ph2pz)3(dme)2]10 (Table 1), no diagram is displayed.
Bond distances and angles (provided in Supporting
Information) are comparable with those reported10 for
the erbium complex when differences in ionic radii17 are
F igu r e 1. Projections of the ytterbium(III)/diazaligand
complexes, 1 and 2, showing 20% thermal ellipsoids for the
non-hydrogen atoms, hydrogen atoms having arbitrary
radii of 0.1 Å. Carbon atoms are designated by numbers
without letters. A zero precedes the number for C5Me5
carbons in (a). (a) 1 projected normal to the molecular
(crystallographic) 2-axis. (b) 2 (molecule 1 (the nondisor-
dered molecule)), projected normal to its approximate
2-axis.
(16) (a) Schumann, H.; Meese-Marktscheffel, J . A.; Esser, L. Chem.
Rev. 1995, 95, 865, and references therein. (b) Watson, P. L.; Tulip, T.
H.; Williams, I. Organometallics 1990, 9, 1999. (c) Zalkin, A.; Berg, D.
J . Acta Crystallogr. 1988, C44, 1488. (d) Tilley, T. D.; Andersen, R. A.;
Zalkin, A.; Templeton, D. H. Inorg. Chem. 1982, 21, 2644.
(17) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(18) Raymond, K. N.; Eigenbrot, C. W., J r. Acc. Chem. Res. 1980,
13, 276.
(19) Deacon, G. B.; Fallon, G. D.; Gatehouse, B. M.; Rabinovich, A.;
Skelton, B. W.; White, A. H. J . Organomet. Chem. 1995, 501, 23, and
references therein.
(20) St. Clair, M.; Schaefer, W. P.; Bercaw, J . E. Organometallics
1991, 10, 525.
a chelating Me2pz than two bridging Me2pz ligands at
a metal center.15 These compounds are the first struc-
turally characterized bis(cyclopentadienyl)pyrazolato- or
azaindolatolanthanoid complexes. There is a high degree
of crystallographic symmetry in 1 (Table 1), with only
one C5Me5 ligand and half the Ph2pz ligand comprising
the asymmetric unit, with the rest of the molecule being
generated by the appropriate symmetry operation. In
2 two molecules are in the asymmetric unit, one having
(21) Cosgriff, J . E.; Deacon, G. B.; Gatehouse, B. M.; Hemling, H.;
Schumann, H. Aust. J . Chem. 1994, 47, 1223

Oxidation of Lanthanoid(II) Complexes
Organometallics, Vol. 19, No. 9, 2000 1717
Ta ble 1. Cr ysta llogr a p h ic Da ta (1-6)
1b
2c
3d
4e
5f
6g
formula
Mr
cryst syst
space group (no.) P41212 (#92)
a (Å)
C35H41N2Yb
662.8
tetragonal
C27H35N2Yb
560.6
monoclinic
P21/c (#14)
15.448(1)
8.504(3)
C65H53D12N6NdO4 C34H56OP3Sm
C46H86LiO4P7.07Sb1.93Yb C22H50LiN4P2Sb
1150.6
triclinic
P1h (#2)
8.917(6)
13.625(8)
23.599(19)
83.28(6)
89.20(6)
83.97(5)
2831
724.1
1337.5
561.3
monoclinic
P21/c (#14)
15.574(4)
13.083(1)
17.4910(6)
monoclinic
P21/c (#14)
12.184(1)
24.220(3)
20.650(2)
monoclinic
P21/ n (# 14)
13.955(2)
14.118(2)
16.583(2)
10.137(4)
b (Å)
c (Å)
29.95(1)
38.524(5)
R (deg)
â (deg)
γ (deg)
V (Å3)
Dc (g cm-3
Z (f.u.)
F(000)
95.311(9)
101.05(1)
104.28(1)
111.484(2)
3078
1.430
4
1340
30.6
5039
1.458
8
2248
37.3
3498
1.375
4
5905
1.488
4
3040
1.229
4
)
1.35
2
1178
9.7
1500
18.4
2686
26.3
1176
10.3
µ
Mo (cm-1
)
specimen (mm)
Tmin,max
Ntotal
0.18 × 0.30 × 0.28 0.18 × 0.50 × 0.40
0.15 × 0.25 × 0.15 0.15 × 0.20 × 0.18 0.25 × 0.30 × 0.20
0.40 × 0.30 × 0.20
0.71, 0.84
34 742 (sphere)
7611 (0.023)
5766
0.51, 0.64
6049 (quadrant)
2686(0.071)
1555 (n ) 3)
0.052
0.35. 0.60
0.81, 1.0
18 894 (hemisphere) 10 428
13 126
22 983
N (Rint)
8829 (0.037)
6348 (n ) 3)
0.044
9070 (0.045)
6020 (n ) 3)
0.045
5033 (0.079)
3480 (n ) 2)
0.037
8823 (0.11)
2919 (n ) 2)
0.036
N
R
o (I > nσ(I))
0.038
0.048
a
Rw/wR2
0.052
0.051
0.032
0.040
0.032
a
2
2
b
R ) ∑∆|F|/∑|Fo|, Rw ) (∑w∆|F| /∑w|Fo| )1/2 for 1-3; for 4, 5, wR2 ) {∑w(∆F2)/∑w(∆(F2))2}1/2
.
The absolute structure parameter (xabs)
refined to -0.05(6). c The azaindole chelate of molecule 2 was disordered over the two possible orientations, modeled in the refinement
as superimposed rigid bodies (site occupancies set as 0.5 after trial refinement) with isotropic thermal parameter forms. Unresolved
concomitant disorder is also suggested in the thermal envelopes of the peripheral C5Me5 substituents. The asymmetric unit contains
d
two molecules of C6D6. The complex has the same molecular structure as [Er(Ph2pz)3(dme)2].10 e The coordinated thf exhibited high
“thermal motion”, suggestive of unresolved disorder for the peripheral carbon atoms; similarly, anomalously high “thermal motion” was
observed in the peripheral methyl substituent atoms of the other moieties, particularly Cp (1), in a manner suggestive of rotation about
the Sm-centroid “bond”. f While atom E at position 4 of all three ligands was modeled agreeably in terms of total E ) P occupancy (and
set as such), sites 1,2 for all ligands appeared to be composites of P and Sb components. With the constraint of occupancy of unity for the
sum of the fragments, P ()x), Sb ()1-x) occupancies were refined for each of the six sites across the three ligands, yielding, for sites 11,
12, 21, 22, 31, 32, x ) 0.488(5), 0.714(5); 0.501(5), 0.908(4); 0.679(4), 0.776(4) with P‚‚‚Sb separations correspondingly of 0.42(4), 0.49(4);
0.33(6), 0.32(6); 0.15(3), 0.38(2) Å, a total P occupancy of 4.07, cf. Sb 1.93, total 6, tempting the inferences that sites 11,21 are equally
occupied and that overall the P:Sb ratio is essentially 2:1. Despite measurement of data at 150 K, apparent “thermal motion” throughout
g
the structure is high, presumably as a consequence of pervasive unresolved disorder among the non-E components of the structure. P,
Sb components of sites 1,2 were refined initially without constraint, total occupancies not being significantly different from occupancy of
unity for each type; refinement was continued with stoichiometric constraint of P1Sb1, x(P(1)), refining to 0.856(1) with other occupancies
ensuing. P(1)‚‚‚Sb(1), as modeled, refines to 0.108(6), with P(2)‚‚‚Sb(2) 0.46(2) Å.
considered. In addition the Nd-N and Nd-O distances
are in good agreement with those of nine-coordinate
[Nd(Ph2pz)3(thf)3].22 Unidentate dme bonding is rela-
tively unusual,10,23,24 but is known for lanthanoids10,24
and indicates that the lanthanoid(III) center is unable
to accommodate two chelating dme ligands.
This average is well within the range found for the
numerous crystallographically characterized nine-coor-
dinate [Sm(C5Me5)2XYZ] complexes.25 Subtraction of the
ionic radius for nine-coordinate Sm3+ gives a typical
value18 of 1.59 Å.
The Sm-P bond lengths are rather long at 3.135(2)
and 3.164(2) Å and, after subtraction of the ionic radius
of nine-coordinate Sm3+ (1.132 Å), give values of 2.002
and 2.033 Å, respectively. A corresponding subtraction
from either a related eight-coordinate samarium(II)
π-benzophospholyl complex or a nine-coordinate σ-bond-
ed tris(bis(diphenylphosphino)methanido)samarium(III)
gives a value of 1.81 or 1.72 Å, respectively. Presumably
Str u ctu r e Deter m in a tion of 4. The X-ray crystal
structure 4 revealed a samarium(III) compound that
was free from antimony (Figure 2a). This compound is
the first lanthanoid complex in a normal oxidation state
containing the [P3C2But ] ion. A novel scandium(I)
2
complex that contains two [P3C2But ] ligands in a triple-
2
decker sandwich complex has been reported.4 In this
monomeric complex, samarium is formally nine-coordi-
the large steric bulk of the [P3C2But ] ligand (the related
2
nate, with the [P3C2But ]- ion ligated through adjacent
1,3-(Me3Si)2C5H3 ligand has a large steric coordination
2
number of 2.6026) accounts for the relatively long Sm-P
phosphorus atoms (P(1) and P(2)), two η5-C5Me5 groups,
and a thf oxygen. The C5Me5 ligands are bound sym-
metrically to samarium, as indicated by the Sm-C bond
lengths, which range closely between 2.702(8) and
2.742(8) Å, with an average value of 2.72 Å (Table 2).
bond lengths for η2-bonding of the [P3C2But ] ligand to
2
samarium.
Remarkably, the η2-[P3C2But ] ligand binds to sa-
2
marium midway (IV, Scheme 1) between edge-on (I) and
side-on (III) (Figure 2a) and contrasting with the edge-
on binding of the diaza ligands in 1 and 2. This is
exemplified by the angle between Sm(1)-cen(PP) (cen-
(22) Cosgriff, J . E.; Deacon, G. B.; Gatehouse, B. M. Aust. J . Chem.
1993, 46, 1881.
(23) (a) McGeary, M. J .; Coan, P. S.; Folting, K.; Streib W. E.;
Caulton, K. G. Inorg. Chem. 1991, 30, 1723. (b) McGeary, M. J .; Cayton,
R. H.; Folting, K.; Huffmann J . C.; Caulton, K. G. Polyhedron 1992,
11, 1369. (c) Coan, P. S.; Streib W. E.; Caulton, K. G. Inorg. Chem.
1991, 30, 5019. (d) Hahn, F. E.; Keck, M.; Raymond, K. N. Inorg. Chem.
1995, 34, 1402.
ter of the P-P bond) and the [P3C2But ] ring planes,
2
viz., 143.8°, which differs from the corresponding angles
(ca. 180°) of 1 and 2, but is much larger than 90° for
(24) Bochkarev, M. N.; Fedushkin, I. L.; Fagin, A. A.; Petrovskaya,
T. V.; Ziller, J . W.; Broomhall-Dillard R. N. R.; Evans, W. J . Angew.
Chem., Int. Ed. Engl. 1997, 36, 133.
(25) Evans, W. J .; Drummond, D. K. Organometallics 1988, 7, 797,
and references therein.
(26) Marc¸alo, J .; De Matos, A. P. Polyhedron 1989, 8, 2431.

1718 Organometallics, Vol. 19, No. 9, 2000
Ta ble 2. Selected Geom etr ies (1, 2, 4, a n d 5)a
1: Primed Atoms Are Related by the Intramolecular Crystallographic 2-Axisb
Deacon et al.
atom
r
C(0)
N(1′)
C(0′)
N(1)
C(0)
2.25(2)
2.30
109.4
34.5(6)
107.1
141.8
2: Values for (the Two Disordered Components of) Molecule 2 Lie below Those for Molecule 1c
N(7) C(10)
60.0(3) 105.6
atom
N(1)
r
C(20)
2.362(8)
107.9
(2.325(8)/2.298(10))
2.279(8)
(62.7(3)/65.4(3))
106.9/107.1
106.8
108.2/106.8
106.5
N(7)
(2.569(10)/2.425(11))
(105.5/104.4))
(104.9/106.4)
141.3
141.3
C(10)
C(20)
2.322
2.307
2.303
2.296
4d
atom
r
P(2)
38.71(5)
C(10)
C(20)
O(101)
P(1)
P(2)
C(10)
C(20)
O(101)
3.135(2)
3.164(2)
2.465
2.448
2.496(4)
112.8
95.7
108.4
104.8
134.4
82.9(1)
120.8(1)
101.1
102.4
5: For Ligand 3; the Major Components of E(31,32) Are Given
atom
r
P(32)
C(01)
C(02)
Sb(31)
P(32)
C(10)
C(20)
3.24(3)
3.09(2)
2.61
41.8(4)
115.4
111.9
104.0
108.4
137.3
2.65
a
Metal atom environments are presented in matrix form, r (Å) being the metal-ligand distance, the other entries being the angles
b
(deg) subtended at the metal by the relevant atoms at the head of the row and column. C(n0) is the ring center of ligand n. Yb-C(01-
05) range between 2.57(2) and 2.62(2) Å. Yb is obligate coplanar with the C3N2 (pz) ring; the dihedral angle of the latter to the associated
C6 phenyl plane is 17(1)°. c Yb(n)-C(nm1-5) range between 2.551(9) and 2.616(8) Å. Yb lies 0.15(1); 0.03(1)/0.01(1) Å out of the associated
azaindolate skeletal planes. In C5Me5(n), Sm-C(nm) (m ) 1-5) are (n ) 1) 2.742(8), 2.724(9), 2.72(1), 2.736(8), 2.740(8); (n ) 2), 2.709(7),
2.734(7), 2.735(7), 2.734(8), 2.702(8) Å. P(1)-P(2) is 2.088(3) Å.
d
face-on coordination. Thus the bonding can be viewed
as midway between σ (nine-coordinate) and π (eight-
coordinate).
But ] ligand to bind η3, η4, or η5 to the ytterbium center
or to accommodate a donor solvent molecule as in 4.
2
There is disorder in this complex due, first, to the
isomeric diversity arising from the two different ar-
rangements, which each of the low-symmetry [P2SbC2-
Str u ctu r e Deter m in a tion of 5. The X-ray structure
of 5 revealed a charge-separated complex with a [Li-
(thf)4]+ cation (frequently a counterion in lanthanoid
But ] ligands can adopt, and also due to cocrystallization
2
“ate” complexes27) and a [Yb(1,4,2-P2SbC2But ) ]- anion,
of species with the related triphosphacyclopentadienyl
ligand. It was found from the refinement that sites Sb-
(1), Sb(2), and Sb(3) (Figure 2b) have partial phosphorus
occupancies of 50, 50, and 70%, respectively, while P(1),
P(3), and P(5) have partial antimony occupancies of 25,
10, and 20%, respectively. The optimum refinement
corresponded to an approximately 2:1 ratio of [P2SbC2-
But ] to [P3C2But ], in agreement with the ratio from
2 3
in which the ytterbium center is surrounded by one side-
on η2-[P2SbC2But ] (III) and two η5-[P2SbC2But ] (II)
2
2
ligands (Figure 2b). The one other example of an X-ray-
characterized complex containing a Ln-Sb bond has the
Zintl ion Sb3- coordinated to three samarium centers,
viz., [{Sm(C5Me5)2}3(µ-η2:η2:η1-Sb3)(thf)].28 The bonding
arrangement of the η2-[P2SbC2But ] ligand has not
2
2
2
previously been observed and is different from the η2-
31P NMR spectroscopy (see above). Because of the
disorder, no detailed discussion of bond distances and
angles is warranted. However, Yb(II)-C bond lengths
(2.97(1)-3.07(1) Å) of the η5-bonded ligands do appear
significantly lengthened from those of seven-coordinate
[Yb(C5Me5)2(thf)]29 (average 2.66 Å) owing to the com-
bined effects of the large P/Sb substituents and the
bulky But groups.
pyrazolate (I), η2-azindolate (I), or η2-[P3C2But ] (IV)
2
coordination described above for 1, 2, or 4. In [Yb(P2SbC2-
But ) ]-, the η2-[P2SbC2But ] ligand appears to be π-bound
2 3
2
to the ytterbium(II) center since Yb(1)-cen(SbP) (cen-
(SbP) ) center of the P(5)-Sb(3) bond) makes an angle
of 112.8° to the plane of the η2-bonded ring. Thus
ytterbium is formally seven-coordinate. Presumably the
coordination sphere around ytterbium(II) is sterically
saturated and thus unable to allow the third [P2SbC2-
Str u ctu r e Deter m in a tion of 6. Slow crystallization
of [Li(tmeda)2][P2EC2But ] (E ) P, Sb) from petroleum
2
spirit afforded large yellow single crystals, which X-ray
crystallography established as the charge-separated [Li-
(27) Bochkarev, M. N.; Zakharov, L. N.; Kalinina, G. S. Organo-
derivatives of Rare Earth Elements; Kluwer Academic Press: Dor-
drecht, 1995.
(28) Evans, W. J .; Gonzales, S. L.; Ziller, J . W. J . Chem. Soc., Chem.
Commun. 1992, 1138.
(29) Tilley, T. D.; Andersen, R. A.; Spencer, B.; Ruben, H.; Zalkin,
A.; Templeton, D. H. Inorg. Chem. 1980, 19, 2999.

Oxidation of Lanthanoid(II) Complexes
Organometallics, Vol. 19, No. 9, 2000 1719
having partial antimony occupancy (denoted Sb(2)) (site
occupancies of Sb(1) and P(1) refined to 85:13 and Sb-
(2) and P(2) refined to 12:84) (Figure 3). Consequently,
it would be unwise to comment in detail on the bond
lengths and angles in [P2SbC2But ]-. Although [Li(12-
2
crown-4)2][P2EC2But ] (E ) Sb, P) has previously been
2
structurally characterized, it contained both [P2SbC2-
But ] and [P3C2But ] ligands. As a result, that structure
2
2
solution had complications additional to those arising
from disorder in the P1 and Sb2 ring positions.
Con clu sion s. The present reactions demonstrate the
versatility of [Tl(Ph2pz)] and [Tl(azin)] as oxidants in
the synthesis of lanthanoid(III) Ph2pz and azin com-
plexes and have provided the first X-ray-characterized
lanthanoid(II or III) complexes of the novel [P3C2But ]-
2
and [P2SbC2But ]- ligands. There is an intriguing varia-
2
tion in the η2-bonding of the Ph2pz-, [P3C2But ]-, and
2
[P2SbC2But ]- ligands from σ, through σ/π, to π, respec-
2
tively. The increasingly diffuse nature of the lone pairs
on the heteroatoms in the sequence N, P, Sb makes
them increasingly less suitable for electrostatic interac-
tion with the hard Ln3+ ions. Thus there is a switch to
π-bonding with Sb incorporation, consistent with the
quasi-cyclopentadienyl nature of [P2SbC2But ]-.
2
Exp er im en ta l Section
Gen er a l P r oced u r es. The compounds described here are
extremely air- and moisture-sensitive, and consequently all
operations were carried out in an inert atmosphere (purified
argon or nitrogen). Unless indicated otherwise, handling
methods and solvent purification were as described previ-
ously.6 Melting points are uncorrected, with air-sensitive
samples being sealed in capillaries under argon. IR data
(4000-650 cm-1) were obtained for Nujol mulls sandwiched
between NaCl plates with a Perkin-Elmer 1600 FTIR spec-
trometer. Mass spectra were obtained with a VG Trio-1 GC
mass spectrometer. Each listed m/z value for metal-containing
ions (where the metal has more than one isotope) is the most
intense peak of a cluster with an isotope pattern in good
agreement with the calculated pattern. Room-temperature (20
°C) NMR spectra were recorded on a Bruker AC 200, AM 300,
WM 250, or AC 400 spectrometer. The chemical shift refer-
ences were the residual solvent signals ([D6] benzene δH 7.15,
δC 128.0; [D8] THF δH 1.73, 3.58, δC 25.3, 67.4; [D8] toluene δH
2.09) or external 85% H3PO4 (31P δ ) 0.0). Degrees of
substitution for 13C nuclei were determined using 1H/13C
J -modulation pulse sequences. Deuterated solvents (Cam-
bridge Isotopes) were dried over either sodium/potassium alloy
or CaH2 and were then vacuum transferred to greaseless
Schlenk tubes and stored under purified argon. Visible/near-
infrared spectra (350-1400 nm) were obtained using either a
Cary 17 or a Cary 5G spectrophotometer with solutions sealed
in a 1 mm silica glass cell fitted with a Rotaflo tap. Lanthanoid
analyses were by EDTA titration30 with Xylenol orange indica-
tor of solutions prepared by digestion of accurately weighed
samples in concentrated HNO3/2% concentrated H2SO4 fol-
lowed by dilution with water and buffering with hexamine.
Microanalysis samples were sealed in glass ampules under
purified argon and were determined by the Campbell Mi-
croanalytical Service, University of Otago, New Zealand.
Lanthanoid elements as either powders or distilled metal
ingots were obtained from Rhoˆne-Poulenc. Unless stated
otherwise, all commercially available reagents were used
without any further purification. Thallium(I) chloride was
purchased from Avocado Chemicals. Bis(pentamethylcyclo-
F igu r e 2. Projections of the [P2EC2But ] (E ) P, Sb)
2
complex 4 and anion of 5 similarly but showing 50%
thermal ellipsoids for the non-hydrogen atoms. (a) 4
approximately through the P(1)-P(2) line, i.e., the thf/Sm/
P2-ring “plane”, (b) anion of 5 similarly.
F igu r e 3. Projection of the anion of 6 normal to the ring
plane.
(tmeda)2][P2SbC2But ] 6 (Figure 3). The structure solu-
2
tion established that only the [P2SbC2But ]- anion was
2
present and that it is essentially planar. There is
positional disorder arising from the two possible ar-
rangements adopted by the [P2SbC2But ] ligand in the
2
structure. This results in the Sb(1) site having partial
phosphorus occupancy (denoted P(1)) and the P(2) site
(30) Atwood, J . L.; Hunter, W. E.; Wayda, A. L.; Evans, W. J . Inorg.
Chem. 1981, 20, 4115.

1720 Organometallics, Vol. 19, No. 9, 2000
Deacon et al.
pentadienyl)bis(tetrahydrofuran)samarium(II),31 bis(penta-
methylcyclopentadienyl)(tetrahydrofuran)ytterbium(II)‚0.5-
(toluene),29 3,5-diphenylpyrazolatothallium(I),6 7-azaindolato-
thallium(I),6 and the inseparable mixtures of [Li(tmeda)2][P2-
EC2But ]11 and [Tl(P2EC2But )]5d (E ) P and Sb) were synthe-
sized by the indicated methods. The inseparable mixtures were
identified by 31P NMR spectroscopy and used without any
further purification.
(s, (P2SbC2But )), 281 (s, (P2SbC2But )), 287 (br s, (P3C2But )),
2
2
2
308 (vbr s, (P3C2But )). Very broad signals precluded satisfac-
2
tory integration, but it was evident that the [P3C2But ] species
2
was in excess over the [P2SbC2But ]. A small number of single
2
crystals suitable for X-ray analysis were grown at -30 °C from
2
2
a saturated solution in light petroleum and were found to be
solely the [Sm(C5Me5)2(P3C2But )(thf)] complex 4.
2
Syn th esis of [Li(th f)4][Yb(P 2EC2Bu t2)3] (E ) P , Sb), 5.
[Tl(P2EC2But )] (1.05 g, 2.0 mmol) (which presumably also
2
Syn th esis of [Yb(C5Me5)2(P h 2p z)], 1. Tl(Ph2pz) (0.38 g,
0.89 mmol) was added to a dme solution (30 mL) of [Yb(C5-
Me5)2(thf)]‚0.5(C7H8) (0.50 g, 0.89 mmol), causing an immediate
color change from orange to deep purple in addition to
formation of a gray suspended solid, which was filtered from
the solution. The dme was removed under vacuum to give a
pink solid, which was then recrystallized from light petroleum
to give large purple crystals of [Yb(Ph2pz)(C5Me5)2] (0.50 g,
85%). IR: ν ) 1605 cm-1 m, 1179 w, 1070 w, 1037 m, 1025 m,
968 s, 904 w, 830 w, 802 w, 752 vs, 722 w, 702 m, 692 m, 680
vs, 665 w. Visible/near-IR (thf) λmax (ꢀ): 513 br (236), 933 (34),
975 (3), 1004 (205) nm. MS (70 eV, EI) m/z (%): 663 (15) [M+],
528 (35) [Yb(C5Me5)(Ph2pz)+], 393 (35) [Yb(Ph2pz)+], 174 (35)
[Yb+], 135 (55) [C5Me5+], 119 (100) [C9H11+], 105 (70) [C8H9+],
91 (45) [C7H7+], 77 (15) [C6H5+]. Anal. Calcd for C35H41N2Yb
(662.7): C 63.43, H 6.24, N 4.23, Yb 26.11. Found: C 62.93, H
5.37, N 4.38, Yb 25.72. Single crystals suitable for X-ray
analysis were grown at -20 °C from a saturated solution in
light petroleum.
contained a substantial amount of a lithium-containing spe-
cies) and ytterbium metal (1.73 g, 10.0 mmol) in thf (30 mL)
were stirred at room temperature under argon for 2 h followed
by ultrasonication for 48 h to give a green/yellow solution. The
precipitated thallium and excess ytterbium were filtered off
and thf was removed to give a sticky black residue, which was
extracted with light petroleum (bp 60-80 °C). Slow cooling of
the solution afforded black crystals, suitable for X-ray analysis,
of [Li(thf)4][Yb(P2EC2But )3], which also contained species with
2
(P3C2But ) rings (0.48 g, 35%), mp 116 °C dec. IR: ν ) 1358
2
cm-1 s, 1293 w, 1261 w, 1218 m, 1045 vs, 916 w, 889 m, 800
w, 722 w. 1H NMR (250 MHz; C7D8): δ 1.00 (vbr s, â-thf) 1.25
(br s, But), 1.52 (br s, But), 2.03 (br s, But), 3.51 (vbr s, R-thf).
Very broad, overlapping signals precluded satisfactory integra-
tion and assignment of the But resonances. 31P NMR (101
MHz; C7D8): δ 246 (br s, 2P, P1 and P2 (P3C2But )), 263 (br s,
2
1P, P4 (P3C2But )), 283 (br s, 1P, P4 (P2SbC2But )), 315 (br s,
2
2
1P, P1 (P2SbC2But )). Ratio [P2SbC2But ] rings to [P3C2But ]
2
2
2
rings ) ∼2:1. MS (70 eV, EI): m/z (%): 818 (20) [Yb(P2SbC2-
Syn th esis of [Yb(C5Me5)2(a zin )], 2. Similar treatment of
[Yb(C5Me5)2(thf)]‚(C7H8)0.5 (0.84 g, 1.49 mmol) in thf (30 mL)
with Tl(azin) (0.48 g, 1.49 mmol) and a similar purification
gave large purple crystals of [Yb(azin)(C5Me5)2] (0.62 g, 74%).
IR: ν ) 1588 cm-1 m, 1415 m, 1328 m, 1286 s, 1260 m, 1201
w, 1170 vs, 1115 w, 1064 w, 1023 m, 916 s, 900 w, 793 s, 769
vs, 743 m, 726 vs, 625 m. Visible/near-IR (thf) λmax (ꢀ): 510 br
(296), 953 (64), 980 (60), 1000 (219) nm. MS (70 eV, EI) m/z
(%): 561 (25) [M+], 426 (70) [Yb(C5Me5)(azin)+], 291 (100) [Yb-
(azin)+], 174 (20) [Yb+], 135 (18) [C5Me5+], 119 (35) [C9H11+],
105 (33) [C8H9+], 91 (38) [C7H7+], 77 (25) [C6H5+]. Anal. Calcd
for C27H35N2Yb (560.6): C 57.85, H 6.29, N 5.00, Yb 30.87.
Found: C 56.58, H 6.39, N 5.24, Yb 30.79. Single crystals of
2, suitable for X-ray analysis, were grown at -20 °C from a
saturated solution in light petroleum.
But )2+], 726 (30) [(Yb(P2SbC2But )(P3C2But ))-H)+], 636 (20)
2
2
2
[Yb(P3C2But )2+], 405 (20) [Yb(P3C2But )+], 321 (40) [P2SbC2-
2
2
But +], 231 (35) [P3C2But +], 169 (85) [PC2But +], 69 (100)
2
2
2
[ButC+].
Attem p ted Rea ction betw een [Li(tm ed a )2][P 2EC2Bu t
]
2
2
(E ) P , Sb) a n d Ytter biu m Meta l. [Li(tmeda)2][P2EC2But ]
(1.08 g, 2.0 mmol), ytterbium metal (1.73 g, 10.0 mmol), and
mercury metal (ca. 0.2 mL) in thf (30 mL) were subjected to
ultrasonication for 2 days, after which time the yellow solution
remained unchanged. Filtration of the unreacted ytterbium
metal and concentration of the thf solution yielded a yellow
solid, which was extracted with light petroleum. Concentration
of the light petroleum solution afforded yellow crystals, suit-
able for X-ray analysis, of [Li(tmeda)2][P2SbC2But ], 6.
2
Rea ction betw een [Li(tm ed a )2][P 2EC2Bu t2] a n d Nd Cl3.
Syn th esis of [Nd (P h 2p z)3(d m e)2], 3. Tl(Ph2pz) (0.42 g, 1.0
mmol) and neodymium metal (0.30 g, 2.1 mmol) in thf (30 mL)
were subjected to ultrasonication for 3 days, after which time
gray solids had deposited from a blue solution. Filtration of
the precipitate followed by removal of the thf and recrystal-
lization of the residue from dme afforded the blue crystalline
[Nd(Ph2pz)3(dme)2] (0.23 g, 71%). Spectroscopic data were
identical with those reported.10 Single crystals of 3‚(C6D6)
suitable for X-ray analysis were grown at room temperature
from a C6D6 solution of the product.
[Li(tmeda)2][P2EC2But ] (1.08 g, 2.0 mmol) and NdCl3 (0.25 g,
2
1.0 mmol) in thf (30 mL) were stirred for 12 h at room
temperature, after which time unreacted NdCl3 remained. A
31P NMR spectrum of the reaction mixture revealed unreacted
[Li(tmeda)2][P2EC2But ].
2
Rea ction betw een [Li(tm ed a )2][P 2EC2Bu t2] a n d [YbI2-
(th f)2]. [Li(tmeda)2][P2EC2But ] (1.08 g, 2.0 mmol) and [YbI2-
2
(thf)2] (0.57 g, 1.0 mmol) in dme (30 mL) were stirred at room
temperature for 12 h. A 31P NMR spectrum of the brown
reaction mixture revealed unreacted [Li(tmeda)2][P2EC2But ].
2
Syn th esis of [Sm (C5Me5)2(P 2EC2Bu t2)(th f)] (E ) P , Sb).
Str u ctu r e Deter m in a tion s. These were executed at three
venues with the following local conditions: 1-2, University
of Western Australia, single counter/sequential instrument,
T ca. 295 K, capillary mounted specimens, Gaussian absorp-
tion correction, Xtal 3.2 program package;32 3, Monash Uni-
versity, Nicolet (Siemens) R3m/V four-circle diffractometer T
ca. 173 K; teXsan crystallographic software package;33 4, 5,
University of Cardiff, FAST area-detector instrument, T ca.
150 K, SHELX program system34 (final cycles Xtal), no
absorption correction; 6, UWA, Bruker AXS CCD area-detector
instrument, T ca. 153 K, “empirical” absorption correction, Xtal
[Tl(P2EC2But )] (0.67 g, 1.27 mmol) and [Sm(C5Me5)2(thf)2]
2
(0.71 g, 1.27 mmol) in thf (30 mL) were stirred at room
temperature for 2 h, giving a red-orange solution and a gray
precipitate of thallium, which was filtered off. Removal of thf
under vacuum gave a sticky red residue, which was extracted
with light petroleum. Slow cooling of the solution afforded a
red crystalline material containing both [Sm(C5Me5)2(P2SbC2-
But )(thf)] and [Sm(C5Me5)2(P3C2But )(thf)] (0.09 g, 10%), mp
2
2
215 °C. IR: ν ) 1652 cm-1 s, 1641 s, 1355 vs, 1224 m, 1010 m,
858 m, 722 w. 1H NMR (250 MHz; C6D6): δ 0.35 (br s, C5Me5),
0.85 (br m, But), 1.15 (br m, But), 1.25 (br s, But), 2.25 (br m,
thf). Very broad, overlapping signals precluded satisfactory
integration and assignment of the But resonances, and the
broadness of the signals prevented resolution of two thf
(32) Hall, S. R., Flack, H. D., Stewart, J . M., Eds. The Xtal 3.2
Reference Manual; Universities of Western, Geneva and Maryland,
1992.
(33) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corporation, 1985 and 1992.
resonances. 31P NMR (101 MHz; C6D6):
δ
279
(34) Sheldrick, G. M. SHELX 93, Program for Crystal Structure
Determination; Universita¨t Go¨ttingen, 1993.
(31) Evans, W. J .; Ulibarri, T. A. Inorg. Synth. 1990, 27, 155.

Oxidation of Lanthanoid(II) Complexes
Organometallics, Vol. 19, No. 9, 2000 1721
3.2 program package. In all venues, Mo KR radiation was
employed (λ ) 0.71073 (1, 2, 6), 0.71069 Å (3-5), 2θmax being
50° for all determinations (6 excepted: 58°). For 3, a unique
data set was measured; for the others redundant equivalents
(Nt(otal) reflections) merging, after absorption correction, to N
unique (Rint quoted), No of these with I > nσ(I) being considered
“observed” and used in the full-matrix least-squares refine-
ments. Anisotropic thermal parameters were refined for the
given in the figures and tables, individual variations in
procedure being noted in the footnote to Table 1.
Ack n ow led gm en t. The ARC, EPSRC, and DIST are
acknowledged for financial support as well as a Monash
Postgraduate Publications award and an Australian
Postgraduate Award to E.E.D.
non-hydrogen atoms, (x, y, z, Uiso
)
being constrained at
H
Su p p or tin g In for m a tion Ava ila ble: This material is
available free of charge via the Internet at http://pubs.acs.org.
estimated values. Residuals as in Table 1 are quoted at
convergence, statistical weights being employed. Neutral atom
complex scattering factors were used. Pertinent results are
OM990932F