Intramolecular metal-fluorocarbon coordination, C-F bond activation and lanthanoid-fluoride clusters with tethered polyfluorophenylamide ligands

Article abstract of DOI:10.1002/chem.200802294

Metalation of either N,N-diethyl- or N,N-dimethyl-N′-2,3,5,6-tetra- fluorophenylethane-1,2-diamines (HL 1a, 1b respectively) with [M{N(SiMe ₃)₂}] (M = Na, K) or [Yb{N(SiMe₃) ₂}₂(thf)₂] yiel

Full text of DOI:10.1002/chem.200802294

DOI: 10.1002/chem.200802294
ꢀ
Intramolecular Metal–Fluorocarbon Coordination, C F Bond Activation and
Lanthanoid–Fluoride Clusters with Tethered Polyfluorophenylamide Ligands
Glen B. Deacon,* Craig M. Forsyth, Peter C. Junk,* and Jun Wang[a]
3082
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3082 – 3092

FULL PAPER
Abstract: Metalation of either N,N-di-
ethyl- or N,N-dimethyl-N’-2,3,5,6-tetra-
fluorophenylethane-1,2-diamines (HL
1a, 1b respectively) with [M{N-
[K2(L)
G
connectivity of [Yb4(L)6F6], as shown
by the X-ray structures, comprised a
crystalline compounds, whilst crystalli-
sation of 4a from DME gave [Yb(L)2-
AHCTUNGTRENN(GUN dme)] (7a). Their structures have che-
lating metal–amide and NR2 donors
and additional intramolecular M-F-C
connectivity with relatively short bond
lengths (Na F 2.65–3.00 ꢁ; K F 2.70–
3.00 ꢁ; Yb F 2.56 ꢁ). The Yb com-
circular Yb
opposing Yb centres having either one
L ligand and a Yb2A(m-F)2 bridge or two
4ACHTNUGTREN(UNGN m-F)4 periphery with two
A
CHTUNGTRENNUNG
A
U
L ligands. Each polyfluorophenylamide
exhibits additional intramolecular Yb-
F-C coordination from one of the
ortho-F atoms resulting in seven or
eight coordinate Yb centres. An at-
tempt to synthesise 4a by redox trans-
metalation/ligand exchange using Hg-
ꢁ
R
Yb complexes were also synthesised by
redox transmetalation/ligand exchange
plexes undergo C F activation in solu-
tion forming [Yb4(L)6F6] (8a, 8b). The
from Yb, Hg
N
4a from a reaction of 3a with YbI2 in
THF. In the presence of N,N,N’,N’-
tetramethyl-1,2-ethanediamine
AHCTUNGERTG(NNUN C CPh)2 as the mercury reagent gave
Keywords: alkali metals · C F acti-
vation
N ligands · ytterbium
ꢁ
[Yb4(O)2(L)4ACTHUNTRGENN(UG C CPh)4ACHTUNGTNER(NUGN thf)2]·THF
(TMEDA) the complexes 2a and 3a
(9a·THF), most likely as a result of ox-
yielded [Na(L)2Na
N
idation of the initially formed product.
ꢀ
Introduction
many cases, lanthanoid-induced C F activation leads to the
formation of heteroleptic fluorides,[4,19,21–25,27] [Ln(L)2F],
[Ln(L)F2], or more complex species including cages and
rings.[19,22,23,27a,c] Other examples of these compounds have
been made by selective deprotonation of tris(cyclopenta-
An exciting recent development in rare-earth-metal–organic
chemistry is the observation of bonds between fluorine
atoms of polyfluoroaryl groups and metal atoms (C(Ar)-F-
Ln).[1–16] These range from agostic interactions (ca. 3.0 ꢁ) to
quite strong bonds (ca. 2.5 ꢁ). In most cases the polyfluor-
oaryl group is coordinated both through fluorine and anoth-
er donor atom, for example, 1) carbon (C,F bridging[1] and
[29]
[30]
AHCTUNGTRENNUNG
dienyl)lanthanoids[28] and by Sn F and Pb F activation,
ꢀ
ꢀ
but rare earth heteroleptic fluorides remain a limited class.
Their existence is of considerable interest given the poten-
tial for rearrangement into the corresponding highly stable
and insoluble LnF3 compounds. In this paper, we report a
series of ytterbium(II) polyfluoroorganoamides with strong
C,F chelating[2–5]
) in polyfluorophenyl–rare-earth com-
pounds, 2) nitrogen in polyfluorophenylamides,[6–8] 3) oxygen
in polyfluorophenolates[9] and 4) sulfur in polyfluorothio-
C(Ar)-F-Yb coordination and that undergo C F activation
ꢀ
ꢀ
lates.[10–12] In addition, B
N
to
give
the
fluoro(organoamido)lanthanoid
cages
as C(Ar)-F-Ln donors, often chelating through two fluorine
atoms.[13–15] Even discrete fluorine-bonded complexes be-
[Yb4F6(L)6] (L=p-HC6F4N
(CH2)2NR2; R=Et or Me). In
each of the ytterbium complexes, as well as in the alkali
metal derivatives prepared as metathesis reagents, the N,N-
dialkyl-N’-2,3,5,6-tetrafluorophenyl-ethane-1,2-diamin-
tween [ScACHTUNGTRENNUNG
(C5Me5)2]+ and fluorobenzene or 1,2-difluoroben-
zene have been characterised as BPh4ꢀ salts,[14] whilst the en-
capsulation of La3+ in a cage with polyfluoroarene, N-
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG(amine) and OACHTUNGTRENNUNG(ether) donor atoms has closer interactions
with F than O or N.[16] (There is also related structural
chemistry involving fluoroalkyl groups.[17,18]) Such complexes
ꢀ
ꢀ
are poised for C F activation, since the very strong C F
Results and Discussion
bonds[19,20] are weakened by coordination.[16] Indeed it has
been shown that S,F-chelated [Sm
G
N,N-Dialkyl-N’-2,3,5,6-tetrafluorophenylethane-1,2-di-
heating[11] and C,F-chelated [Ce(C5H2-tBu3-1,2,4)2C6F5] de-
aminate(1ꢀ) ligands were first reported in the platinum(II)
composes into the corresponding fluoride and tetrafluoro-
complexes [Pt(L)X(py)] (X=Cl, Br, I) in which the ligands
were assembled in situ by a combination of decarboxylation
and nucleophilic substitution processes.[31a,b] The ligand HL
(1a, 1b) can be more conveniently prepared from the ap-
propriate N,N-dialkylethane-1,2-diamine and C6F5H heated
to reflux in EtOH (Scheme 1).[31c] Subsequent metalation re-
benzyne.[4,5] Other cases of lanthanoid induced C F activa-
tion[21] involve actual[22] or postulated[23–25] polyfluorophenyl–
or polyfluorobenzoato–lanthanoid complexes[26] that plausi-
bly form C(Ar)-F-Ln interactions as a step in activation. In
actions with [M{N
(SiMe3)2}2A(thf)2] in THF or PhMe/THF mixtures readily
yielded the corresponding metal complexes [M(L)] (R=Et;
M=Na 2a, K 3a) or [Yb(L)2A(thf)2] (R=Et 4a, R=Me 4b)
in good yields (Scheme 1). The Yb complexes were also syn-
thesised by redox transmetalation/ligand exchange reactions
ACHTUGNRTEN(NUGN SiMe3)2}] (M=Na, K) or [Yb{N-
[a] Prof. Dr. G. B. Deacon, Dr. C. M. Forsyth, Prof. Dr. P. C. Junk,
Dr. J. Wang
G
CHTUNGTRENNUNG
School Of Chemistry, Monash University
Clayton VIC 3800 (Australia)
Fax : (+61)399054597
CTHUNGTRENNUNG
E-mail: glen.deacon@sci.monash.edu.au
Chem. Eur. J. 2009, 15, 3082 – 3092
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3083

G. B. Deacon, P. C. Junk et al.
in 171Yb NMR shifts with increasing coordination number
has been observed previously for series of complexes in
which the anionic ligand is the same or closely related.[32b,c]
The similarity of the chemical shift of 4a at low temperature
and in the presence of THF with that of the DME complex
7a suggests that the coordinated THF is dissociatively labile
(Scheme 2), consistent with the analytical data. Eight coor-
Scheme 2.
dinate ytterbium is indicative of tridentate (N,N’,F) binding
of the polyfluorophenylamide ligands as observed in the
solid-state (below).
The room-temperature 19F NMR spectra of complexes 2a,
3a, 4a, 4b, 5a, and 6a showed only two resonances for the
ortho (ca. d=ꢀ169(ꢂ4) ppm) and meta (ca. d=
ꢀ148(ꢂ3) ppm) fluorine nuclei. These values show a distinct
high-field shift (ca. 17 ppm) for the ortho-fluorine resonance
when compared with those for the platinum(II) complex
trans-[Pt(N(R)CH2CH2NMe2))Cl(py)] (R=C6F4-p-H; d=
ꢀ144.4 and ꢀ152.1 ppm).[31a] In contrast, the ytterbium com-
plex 7a showed four separate resonances (in an approxi-
mately 1:1:1:1 ratio) at ꢀ142.9 ꢀ148.8, ꢀ162.2 and
ꢀ166.6 ppm which coalesced to two broad signals at ꢀ145.8
and ꢀ164.3 ppm on heating above 508C. Similarly, cooling
samples of 3a and 4a enabled resolution into four separate
resonances at ꢀ708C. These data are consistent with a flux-
ional system in which restricted rotation of the N-C6F4H
ring leads to a lower symmetry environment. The small
chemical-shift separation of the two ortho- and meta-F reso-
Scheme 1. Synthesis of ligands (HL) and metal complexes i) [Na{N-
(SiMe3)2}], THF; ii) [K{N(SiMe3)2}], THF; iii) [Yb{N(SiMe3)2}2A(thf)2],
THF; iv) TMEDA, PhMe; v) DME.
G
E
E
CHTUNGTRENNUNG
of HL (1a or 1b) with Yb metal and HgACHTNURGTNEUNG(C6F5)2 in THF and
4a by metathesis from 3a and YbI2 (Scheme 1). The Na and
K derivatives were obtained as powders insoluble in PhMe
and without coordination by additional donors (e.g., THF).
However, addition of N,N,N’,N’-tetramethyl-1,2-ethanedi-
ACHTUNGTRENNUNG
A
CHTUNGTRENNUNG
CHTUNGTRENNUNG
The metal complexes were characterised spectroscopically
and single-crystal X-ray structures were determined for 5a,
6a and 7a. IR spectra showed absorptions attributable to
ꢀ
ꢀ
the ligands and the n
N
nances (ca. 4 ppm) may be attributed to M···F C interac-
with deprotonation and coordination to the metal. For the
Na and K complexes 2a and 3a, there were no spectroscopic
features attributable to the presence of residual solvent
(THF) and the compositions were confirmed by elemental
analyses. The presence of TMEDA in 5a and 6a was con-
tions that are observed in the crystal structures (see below)
ꢀ
and would lead to inequivalent fluorine atoms. No Yb F
coupling[33] was observed in 171Yb NMR spectra, although at
ꢀ808C the resonance for 4a was very broad (ca. 300 Hz)
and showed evidence of a shoulder.
1
firmed by the H NMR spectra, but the elemental analyses
The single-crystal X-ray structures of one example each
of the Na, K, and Yb complexes were determined to clarify
the bonding of these amide ligands to the metals. The Na
complex 5a (Figure 1) is composed of a dinuclear arrange-
ment with the two Na centres bridged by the amido N
atoms with the pendant CH2CH2NEt2 arms both chelating
to Na(1). The tmeda ligand binds to Na(2). The correspond-
ing complex with the larger K cation (Figure 2) shows a
symmetrical dinuclear structure also with bridging amido N
atoms, but with one of the chelating CH2CH2NEt2 arms and
one bidentate tmeda coordinating to each K centre. These
structural motifs have previously been observed in com-
plexes with an alkoxysilylamido ligand, for example, [Na{N-
were consistently low in the percentage of C present, attrib-
utable to partial loss of TMEDA on standing. The analyses
corresponded to the compositions [Na4(L)
[K4(L)4A(tmeda)3]. Similarly, the composition of the
ytterbium(II) complexes 4a and 4b was established by their
4ACHTUNGTRENUN(NG tmeda)] and
CHTUNGTRENNUNG
ACHTUNGTRENNUNG
1H NMR spectra, but the elemental analyses indicated loss
of one THF molecule. In contrast, 7a gave satisfactory ele-
mental analyses. The room-temperature 171Yb NMR data for
4a (d=490 ppm in C7D8) and 7a (d=389 ppm in C6D6) are
in the region observed for the eight coordinate complex
[Yb
G
G
(Ph2pz=3,5-diphenylpyrazola-
te)(d=480 ppm).[32a] However, the resonances of 4a were
markedly solvent- and temperature-dependent. Either cool-
ing or addition of THF caused an upfield shift (d=405 ppm
at ꢀ808C, d=398 ppm in 1:1 C6D6/THF) indicative of an in-
crease in the coordination number. A progressive decrease
A
ACHTUNGTREN(UNGN bpy)] (Type A) and [K2{N-
A
CHTUNGTRENNUNG
ꢀ
AHCTUNGTERG(NNUN amido) distances (Table 1) are
3084
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ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3082 – 3092

Metal–Fluorocarbon Coordination
FULL PAPER
Table 1. Selected bond lengths [ꢁ] in [Na(L)2Na
ACHTUNGTRENNUNG
A
U
5a
6a
7a
ꢀ
ꢀ
ꢀ
Na(1) N(1) 2.410(2) K(1) N(1)
2.782(2) Yb(1) N(1) 2.428(3)
[a]
ꢀ
ꢀ
ꢀ
Na(2) N(1) 2.429(2) K(1) N(1)*
2.792(2) Yb(1) N(3) 2.436(3)
ꢀ
ꢀ
ꢀ
Na(1) N(2) 2.558(2) K(1) N(2)
2.996(2) Yb(1) N(2) 2.729(3)
ꢀ
ꢀ
ꢀ
Na(2) N(3) 2.518(2) K(1) N(3)
2.973(2) Yb(1) N(4) 2.728(3)
ꢀ
ꢀ
K(1) N(4)
2.885(2) Yb(1) O(1) 2.560(3)
ꢀ
Yb(1) O(2) 2.588(3)
ꢀ
ꢀ
ꢀ
Na(1) F(1) 3.000(2) K(1) F(1)
2.867(1) Yb(1) F(1) 2.558(2)
ꢀ
ꢀ
ꢀ
Na(2) F(1) 2.653(1) K(1) F(1)
3.009(1) Yb(1) F(5) 2.560(2)
[a] Symmetry operator *: ꢀx+1, ꢀy+2, ꢀz+1.
ꢀ
the M-(m-N)2-M plane. For the Na derivative 5a, one Na F
ꢀ
distance to Na(2) is only 0.15 ꢁ longer than the Na N-
ꢀ
A
range 2.298–2.995 ꢁ,[35a] with the closest analogue (in terms
of chelate ring size) being [{Na
AHCTUNGTRENNUNG
ACHTUNTGRENNGU{(C6H4-o-F)NCNACHTUNGTERN(NUNG C6H4-o-F)}-
(OEt2)}2], 2.345(2) ꢁ.[35b] With the Na F contacts included,
ꢀ
Figure 1. Molecular diagram of [NaCATHNUGTNER(NNUG p-HC6F4NACHUTNTRGEG(NNNU CH2)2NEt2)2NaACHTNUGERTN(NUGN tmeda)]
(5a) as shown with 50% thermal ellipsoids and hydrogen atoms omitted
for clarity (* denotes symmetry generated atom). Inset: schematic repre-
sentation of general structural motif L=bidentate ligand.
the two sodium environments are six coordinate and form
distorted trigonal prisms, sharing a rectangular face. In 6a
ꢀ
the K2 mF interactions are more symmetrically disposed
with distances within the range reported for previous exam-
ples of this type of interaction (e.g., [KACHTNUGTRENN{UGN (C6H4-o-F)NCN-
AHCTUNGTRENNUNG
dination number is seven, consistent with the larger ionic
radius than Na,[36] with the donor atoms having an irregular
geometry.
Figure 3. Molecular diagram of [YbCATHNUGTNER(NNUG p-HC6F4NACHUTNTRGEG(NNNU CH2)2NEt2)2ACHTNUGTRNEN(UGN dme)] (7a)
shown with 50% thermal ellipsoids and hydrogen atoms omitted for
clarity. The Yb-o-F contacts are indicated by dashed bonds.
Figure 2. Molecular diagram of [KCATHNUGTNER(NNUG p-HC6F4NACHUTNTRGEG(NNNU CH2)2NEt2)ACHTNUGTERNUN(GN tmeda)]2 (6a)
as shown with 50% thermal ellipsoids and hydrogen atoms omitted for
clarity (* denotes symmetry generated atom). Inset: schematic represen-
tation of general structural motif, L=bidentate ligand.
In contrast to 5a and 6a, the Yb complex 7a is mononu-
clear (Figure 3), with a distorted trigonal prismatic geometry
(N(1), N(2), O(2) and N(3), N(4), O(1) comprising the
alkoxysilylamido complexes (Na 2.450(6), 2.451(7);
K
2.853(4), 2.892(3) ꢁ),[33] whereas the M N
N
trigonal faces). The Yb N
T
ACHTUNGTREN(NUNG amine) moiet-
ꢀ
ꢀ
ꢀ
ꢀ
lengths are typical for M–tmeda complexes, for example, Na
2.511(2), 2.510(6) ꢁ and K 2.824(2), 2.906(3) ꢁ in six coor-
ies show the expected shorter Yb N bonds for the negative-
ly charged amido nitrogen atoms (Table 1). This contrasts
binding of delocalised NCN ligands, such as amidinates,
(tmeda)2].[34b]
dinate [M2ACHTUNGTRENNUNG(m-NMePy)2AHCTUNGTRNENGUN
ꢀ
In both the Na and K structures, each metal centre also
interacts with one ortho-fluorine atom of the polyfluoro-
which show symmetrical, but marginally longer, Yb N dis-
tances (e.g., in six-coordinate [Yb(L)
2A
ꢀ
phenylamide ligands. The M F contacts form a bridge be-
(NSiMe3)2 2.468(2), 2.478(2) ꢁ).[37] A significant feature of
7a is the observation of ytterbium–fluorine contacts to one
tween the two metal atoms, approximately perpendicular to
Chem. Eur. J. 2009, 15, 3082 – 3092
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3085

G. B. Deacon, P. C. Junk et al.
of the ortho-F atoms on the C6F4-p-H substituent of each
lanthanoid fluorides are rare, but [La(L)2F
ACHTUNGTRENNUNG
ligand. These contacts cap two of the rectangular faces of
+150.2 ppm) and [Sm(L)2F
ACHTUNGTRENNUNG
ꢀ
the Yb trigonal prism and the Yb F distances are compara-
(C6H3-2,6-iPr2)NC(H)N(C6H3-2,6-iPr2)] have been report-
ed,[24] and are in the region of the current data. Unfortunate-
ly, once crystallised, both 8a and 8b were insoluble in THF
and no satisfactory NMR spectra could be obtained for the
isolated materials and it is possible that the above data are
for an intermediate species.
Crystal structures were obtained for both complexes, as
varying different solvates for example, 8a (without lattice
solvent), 8a·C6D6, 8b·2thf, 8b·4PhMe, but the dried bulk
compounds gave satisfactory microanalyses for the solvent
free compositions 8a or 8b. The structures are all closely
similar (Table 2), each comprising a centrosymmetric mole-
ꢀ
ble to the Yb O bond lengths of the O
N
ꢀ
shorter than the Yb N
(amine) distances. Corroborating the
description of these Yb F interactions as genuine metal co-
ordination bonds, the Yb N and Yb O bond lengths in 7a
are generally longer than for an analogous six-coordinate
complex with bidentate (N,O) amido ligands (e.g., [Yb{N-
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ACHTUNGTRENNUNG(SiMe3)(C6H4-o-OMe)}2ACHTUNTGREN(NUNG dme)] Yb N 2.353(4), Yb O
2.40(1)–2.55(1) ꢁ),[38] consistent with an approximate 0.10 ꢁ
increase in ionic radii for eight coordinate Yb.[36] The most
closely analogous lanthanoid organoamide complex with
ꢀ
Ln F interactions is [Sm{NACHTUNTRGENNUG(SiMe3)ACHTUNTGRENN(GUN C6F5)}3] in which each
ligand has one close SmIII F contact in the range 2.561–
ꢀ
2.587 ꢁ.[6] Related EuII complexes with XC6F5 (X=O, S) li-
Table 2. Selected bond lengths [ꢁ] in [Yb4(L)6F6] complexes (L=p-
(CH2)2NMe2 8b).[a]
HC6F4NACHTNUTRGENNUG(CH2)2NEt2 8a, L=p-HC6F4NACHTUTGNRENNUGN
gands have significantly longer bonds (e.g., [Eu
(dme)4], 2.928(2), 3.013(2) ꢁ and [Eu(SC6F5)
3.006(6) ꢁ).[9,11]
The ytterbium(II) complexes 4a and 4b are thermally un-
stable. This was initially observed when the crude materials
from evaporation of filtered solutions from redox transmeta-
lation/ligand exchange syntheses of 4a or 4b (see Scheme 1)
were dissolved in PhMe and allowed to stand at room tem-
perature for several weeks. After this time, pale yellow crys-
(OC6F5)6-
A
R
CHTUNGTRENNUNG
8a
8a·C6D6
8b·2THF
8b·4PhMe
ꢀ
Yb(1) N(1)
2.301(4)
2.285(4)
2.279(4)
2.642(4)
2.601(4)
2.511(4)
2.489(3)
2.504(3)
2.555(3)
2.162(2)
2.190(2)
2.158(2)
2.173(2)
2.169(2)
2.150(2)
2.297(10)
2.292(9)
2.269(9)
2.629(9)
2.652(9)
2.525(10)
2.486(7)
2.490(7)
2.511(7)
2.183(5)
2.165(5)
2.165(5)
2.175(6)
2.169(6)
2.164(5)
2.309(5)
2.294(4)
2.311(5)
2.549(5)
2.559(5)
2.450(4)
2.511(3)
2.491(3)
2.519(3)
2.201(3)
2.176(3)
2.162(3)
2.170(3)
2.177(3)
2.142(3)
2.284(5)
2.307(5)
2.303(5)
2.549(5)
2.568(5)
2.456(5)
2.503(3)
2.490(3)
2.468(3)
2.191(3)
2.187(3)
2.148(3)
2.169(3)
2.167(3)
2.151(3)
ꢀ
Yb(1) N(3)
ꢀ
Yb(2) N(5)
ꢀ
Yb(1) N(2)
ꢀ
Yb(1) N(4)
ꢀ
Yb(2) N(6)
ꢀ
Yb(1) F(1)
ꢀ
Yb(1) F(5)
tals had deposited that were shown to be the ytterbium
fluoride cluster compounds [Yb4F6(L)6] 8a and 8b·4PhMe
(Scheme 3). Crystals of 8b·2THF were also obtained direct-
A
ꢀ
Yb(2) F(9)
ꢀ
Yb(1) F(13)
[a]
[a]
ꢀ
Yb(1) F(15)*
ꢀ
Yb(2) F(13)
ꢀ
Yb(2) F(14)
ꢀ
Yb(2) F(14)*
ꢀ
Yb(2) F(15)
[a] Atom labelling corresponding to that in Figure 5 is the same for all
complexes. Symmetry operators *: 8a: ꢀx+1, ꢀy+1, ꢀz+1; 8a·C6D6:
ꢀx+3/2, ꢀy+1/2, ꢀz+1; 8b·2THF: ꢀx+1, ꢀy+1, ꢀz+1; 8b·4PhMe
ꢀx, ꢀy, ꢀz.
Scheme 3. Synthesis of the fluoride cluster complex [Yb4(L)6F6] 8a/8b
from the YbII precursors 4a/4b.
ly from the reaction solution. NMR scale studies of the de-
composition of freshly isolated and pure 4a (in C6D6) or 4b
(in PhMe/C7D8), showed complete disappearance of the
19F NMR signals for these compounds over time. In the case
of 4b, growth of four new resonances at d=+103.1, ꢀ30.6,
ꢀ130.5, and ꢀ182.3 ppm in an approximate ratio of 1:2:6:6
were observed. Accompanying these changes, crystals of
8a·C6D6 or 8b·4PhMe formed in the NMR tube and these
were characterised by X-ray crystallography (see below).
Subsequently, larger scale (1 mmol) conversions of 4b!8b
were performed in PhMe or PhMe/perfluorohexane and
gave 8b·4PhMe in good yield (Scheme 3). The 19F NMR res-
onances observed during the decomposition of 4b (see
above) were broad and the wide chemical shift range is con-
cule with four ytterbium centres, two with one L ligand co-
ordinated and two with two N,N-dialkyl-N’-2,3,5,6-tetra-
fluorophenylethane-1,2-diaminate(1ꢀ) ligands (see for ex-
ample 8b·4PhMe in Figure 4). At the core of the molecule,
a double fluoride bridged dinuclear {(L)Yb
ACHTUNGRTENUN(NG m-F)2Yb(L)}
unit is capped, above and below, by a {(L)2Yb(m-F)2} moiety
AHCTUNGTRENNUNG
through fluoride bridging (Figure 4, inset). Although not ob-
served previously for lanthanoids, this type of fluoride-bridg-
ed metal array is present in tetranuclear [{TiCpF3}4],[39] as
well as in heterobimetallic fluorides [{MCp*(Me)}2-
AHCTUNGTREN(GNUN AlMe2)2F6]·PhMe (M=Ti, Zr, Hf, the Group 4 metals occu-
pying the two central metal sites).[40] As with the Na, K and
YbII complexes above, the N,N-dialkyl-N’-2,3,5,6-tetrafluoro-
phenylethane-1,2-diaminate(1ꢀ) ligands are each bound to
Yb in a distinctly tridentate fashion through the two N and
one of the o-F atoms (Figure 4 inset).
sistent with the presence of a paramagnetic ytterbiumACHTUNTRGNEUNG(III)
centre. The two more intense resonances, d=ꢀ130.5 and
ꢀ182.3 ppm, are reasonably assigned to the ortho- and meta-
fluorine atoms of the ligands by comparison with data for
ꢀ
[Ln
G
N
With the Yb F
G
ꢀ96.3 to ꢀ132.5 and ꢀ148.4 to ꢀ179.9 ppm for Ln=Ce, Ho,
coordinate with a bi-capped trigonal prismatic coordination
geometry, N(1), N(2), F(13) and N(3), N(4), F(15) forming
the triangular faces with F(1) and F(5) as the capping atoms.
Er, Sm, Yb).[10] The remaining two peaks may therefore rep-
resent ytterbium
ACHTUNGTRENNUNG
3086
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ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3082 – 3092

Metal–Fluorocarbon Coordination
FULL PAPER
Figure 5. Molecular
structure
of
[Yb4(O)2(L)4ACTHNGUTREN(NUG CCPh)4ACHTUNGTNER(NUNG thf)2]·THF
(9a·THF), as shown with 50% thermal ellipsoids along with a schematic
representation. Hydrogen atoms and the lattice THF molecule have been
omitted for clarity.
Figure 4. Molecular diagram (and schematic representation—inset) of
[Yb4(L)6F6] (L=p-HC6F4NACTHNUTRGEN(UGN CH2)2NMe2; 8b·4PhMe) shown with 50%
thermal ellipsoids and hydrogen atoms and lattice PhMe omitted for
clarity. The Yb-o-F contacts are indicated by dashed bonds. (* denotes
symmetry generated atom)
been observed in both lanthanoid(II) and lanthanoidACHTUNGTRENNUNG(III)
systems (see above), it has been proposed for low-valent
lanthanoids that such reactions proceed by single-electron
transfer (SET) generating LnIII F and an organic radical
ꢀ
On the other hand, Yb(2) is seven coordinate and has a
ACHTUNGTRENNUNG
(Scheme 4), which can abstract a H atom from THF.[25,26]
GC/MS analyses of hydrolysed reaction mixtures after con-
version of 4a or 4b in C6D6 to 8a or 8b showed evidence of
defluorination of the ligand. The data for 4a!8a were com-
plex with more than ten components observed in the GC
trace, the majority of which appeared to be lower molecular
weight compounds, presumably degradation products of LH.
ACHTUNGTRENNUNG
F(15) apical (trans angle 8a 162.2(1), 8b·4PhMe 162.7(1)8).
Analysis of the bond lengths (Table 2) shows shorter (ca.
ꢀ
ꢀ
0.15 ꢁ) Yb N and Yb F(Ar) bonds by comparison with the
ytterbium(II) complex 7a, as expected on the basis of the
respective ionic radii.[36] The Yb F
from 2.148(3) to 2.191(3) ꢁ,and the average distance to
Yb(2) is marginally shorter than to Yb(1) consistent with
G
ꢀ
ꢀ
the higher coordination number of the latter. The Yb F dis-
tances in 8a and 8b are comparable to those of known
ytterbium
ple, in eight coordinate [Yb
[Yb3(Cp)6A
(m-F)3] (av 2.156 ꢁ).[41]
The reaction pathway leading from the ytterbium(II)
compounds [Yb(L)2A(solv)n], to the fluoride-bridged clusters
ACHTUNGTRENNUNG
C
CHTUNGTRENNUNG
CHTUNGTRENNUNG
CHTUNGTRENNUNG
ꢀ
8a and 8b evidently involves C F activation and fluorine
atom abstraction from the N,N-dialkyl-N’-2,3,5,6-tetrafluoro-
phenylethane-1,2-diaminate ligands (rather than from Hg-
II
ACHTUNGTRENNUNG
ꢀ
Scheme 4. Possible C F activation pathways involving SET from Yb
(upper) or Fꢀ transfer and benzyne formation at YbIII (lower).
Chem. Eur. J. 2009, 15, 3082 – 3092
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3087

G. B. Deacon, P. C. Junk et al.
At longer retention times, three major fractions were ob-
served, containing LH (1a m/z 264), L*H (1aꢀF
C6F3H2N(H)CH2CH2Et2, m/z 246) and L**H (1aꢀ2F
C6F2H3N(H)CH2CH2Et2, m/z 228). The trace for 4b!8b
was much simpler and showed only two major fractions (in
approximately 20:1 ratio) comprising LH (1b, m/z 236) and
L*H (1bꢀF C6F3H2N(H)CH2CH2Me2, m/z 218) respectively.
The origin of L*H is presumably from the radical reaction
intermediate (Scheme 4, upper). However, the observation
of the doubly defluorinated ligand L**H clearly shows that
more than one fluorine can be extracted. Furthermore,
some of the shorter retention time components of the GC
trace resulting from 4a!8a can be assigned to species with
an even lower F content, for example, m/z 207 C12H16N2F+
(LHꢀ3F]+), plausibly derived from isomers of a mono-
fluorinated ligand. Given the presence of L*H (and L**H)
in the reaction solution after hydrolysis, it is notable that no
L* was detected in any of the products. Hydrolysis of a bulk
sample of 8a showed LH as the sole significant product.
Doubly and triply defluorinated ligands may no longer have
o-F atoms to enable tridentate coordination to ytterbium
trum and 19F NMR resonances were observed at d=ꢀ134.3
and ꢀ153.1 ppm, which are near the range observed for par-
amagnetic [LnACHTNUTRGENN(UG SC6F6)3ACHTUTGNREN(NUNG solv)x] complexes, although different
from those of observed during the decomposition of 4a or
4b (see above). Elemental analyses for the dried bulk mate-
rial were consistent with the structural formula, assuming
loss of the lattice THF molecule. The structure of the prod-
uct (Figure 5) displays a four-rung ladder with the outer
ꢁ
rings linked by two m-C CPh and an O bridge, whilst the
central rings have Yb
2A
plexes described above, the amido ligands are bound to yt-
ꢀ
ꢀ
terbium in a tridentate (N,N’,F) mode with Yb N and Yb F
distances (Table 3) comparable with those of 8a and 8b.
Table 3. Selected bond lengths [ꢁ] in [Yb4(O)2(L)4ACHTNUTRGENNUG(CCPh)4CAHTUNGTRENN(UGN thf)2]·THF
(9a·THF; L=p-HC6F4NACHTNUGTRNEUG(N CH2)2NEt2).
ꢀ
ꢀ
Yb(1) N(1)
2.315(6)
2.558(7)
2.526(5)
2.469(8)
2.469(10)
2.067(5)
2.337(5)
Yb(2) N(3)
2.335(6)
2.583(7)
2.527(5)
2.603(7)
2.451(9)
2.253(5)
2.101(5)
ꢀ
ꢀ
Yb(1) N(2)
Yb(2) N(4)
ꢀ
ꢀ
Yb(1) F(1)
Yb(2) F(5)
ꢀ
ꢀ
Yb(1) C(25)
Yb(2) C(25)
ꢀ
ꢀ
Yb(1) C(33)
Yb(2) C(33)
ꢀ
ꢀ
Yb(1) O(2)
Yb(2) O(2)
ꢀ
and even in the case of L*, putative Yb o-F binding may be
[a]
ꢀ
ꢀ
Yb(1) O(1)
Yb(2) O(2)*
weakened, since it has been shown that for [Ce(C5H2-tBu3-
[a] Symmetry operator *: ꢀx, ꢀy+1, ꢀz.
ꢀ
1,2,4)2R], Ce-o F bonding is weakened in the series R=
C6F5 >m-HC6F4 >o-HC6F4.[5]
The data described above clearly establishes that 8a or 8b
are derived from 4a or 4b and that the fluoride source is
Each ytterbium atom is seven coordinate, bound to an
amido ligand, two bridging phenylacetylides, a m3-oxide and
ꢀ
the
N,N-dialkyl-N’-2,3,5,6-tetrafluorophenylethane-1,2-di-
a THF ligand (Yb(1)) or two m3-oxides (Yb(2)). The Yb C
G
distances of the bridging phenylacetylide fragments, apart
from one outlier (Table 3), are generally consistent with an
redox transmetalation/ligand exchange method raises the
ꢀ
possibility of a contribution from a second C F activation
process. These reactions are also known to give fluoride-
containing products through decomposition of intermediate
ytterbium
ACHTUNGTREN(NUNG III) oxidation state, being about 0.12 ꢁ shorter
than for the seven coordinate ytterbium(II) complex [{YbI-
A
(dme)2}2] (av Yb C 2.593 ꢁ)[42a]—see also mixed
ACHTUNGTRENNUNG
ꢁ
ꢀ
valent [YbIII IIA III(Cp*)2]
ACHTUGNRTNEUN(G Cp*)2ACHTUGTNERNNUG(m-C CPh)2Yb CHTGNUERTN(NNUG m-C CPh)2Yb ACHTUNGTRENNUNG
ꢁ
ꢁ
lanthanoid
NAr; Scheme 4, lower).[23–24] Whilst initial formation of 4a
or 4b from Yb/Hg(C6F5)2/LH reactions has been shown (see
(III) [Ln(L)2C6F5] species (L=OAr or ArNC-
(av 2.528 ꢁ to YbII and 2.401 ꢁ to YbIII[42b]). The presence
ꢁ
N
of residual C CPh moieties in the “oxidised” product
showed that the ligand exchange reaction of the intermedi-
above), involvement of such a reaction path is still plausible.
In an attempt to reduce the possible sources of fluoride, we
performed the redox transmetalation/ligand exchange reac-
ꢁ
ꢁ
ate {Yb
N
contrasts the high yield of 4a when Hg
the mercurial (see above).
N
tion of Yb, Hg
(C CPh)2 and 1a in THF. This reaction ini-
tially gave a dark-brown-yellow solution, but we were
unable to isolate a crystalline product. However, after sever-
al weeks, pale yellow crystals formed that were shown to be
ꢁ
Conclusion
an oxidation product, namely, [Yb4(L)4ACHTNUTRGENNUG(m-C CPh)4ACHUTGNTREN(NUNG m3-O)2-
(thf)2]·THF (9a·THF) by X-ray crystallography. This com-
This study has shown that divalent ytterbium(II) complexes
with tridentate (N,N’,F) N,N-dialkyl-N’-2,3,5,6-tetrafluoro-
phenylethane-1,2-diaminate(1ꢀ) ligands (L) thermally de-
plex has presumably resulted from accidental exposure to
air and we were only able to prepare a bulk sample in mod-
erate yield by deliberate addition of dry air to the reaction
solution (Scheme 5).
compose to heteroleptic ytterbium
ACHTUNGTRENNUNG
ytterbium(II) species [Yb(L)2ACHTUNGTRENNUNG
ꢁ
The presence of the C CPh moiety was confirmed by ob-
be readily synthesised by ligand exchange, metathesis or
redox transmetalation/ligand exchange reactions, but are
isolated only at low temperature. The subsequent formation
of the fluoride cluster [Yb4(L)6F6] is believed to result from
fluorine atom abstraction from the polyfluorophenylamido
ligands. In this context, the binding of the N,N-dialkyl-N’-
2,3,5,6-tetrafluorophenylethane-1,2-diaminate(1ꢀ) ligands to
ytterbium (in either the II or III oxidation state), is exclu-
ꢀ1
ꢁ
servation of a n
A
Scheme 5. Synthesis of 9a resulting from an attempted redox transmeta-
lation/ligand exchange reaction.
3088
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ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3082 – 3092

Metal–Fluorocarbon Coordination
FULL PAPER
(w), 788 (m), 710 (m), 662 (w), 565 (w), 526 (w), 464 cmꢀ1 (w); 1H NMR
sively tridentate through the amido and amine nitrogen
(CDCl3, 298 K): d=2.26 (brs, 6H; CH3), 2.51 (t, 3J
ACTHNUTRGNE(NUG H,H)=5.78 Hz, 2H;
ꢀ
atoms as well as one of the ortho fluorine atoms. The Yb F
3
CH2NMe2), 3.41 (m, 2H; CH2NAr), 4.64 (brs, 1H; NH), 6.35 ppm (tt, J-
interaction is strong, as indicated by the shorter metal–
donor bond length than to the more classical dialkyl amine
donor group. Furthermore, the sodium and potassium com-
A
ACHTUNGTRENNUNG
282.4 MHz): d=ꢀ142.3 (m, 2F; F3,5), ꢀ161.0 ppm (m, 2F; F2,6); ele-
mental analysis calcd (%) for C10H12F4N2 (236.21): C 50.85, H 5.12, F
32.17, N 11.86; found: C 51.0, H 5.1, F 32.0, N 12.0.
plexes [Na(L)2NaACHTUNGTRENNUNG(tmeda)] and [K2(L)2ACHTUNGTERN(NUGN tmeda)2], prepared
[Na(p-HC6F4NC2H4NEt2)] (2a): A solution of NaNACHTNUTRGNE(NUG SiMe3)2 in THF (1m,
ꢀ
by ligand exchange, also show o-F M coordination, suggest-
ing that tridentate N,N’,F coordination may be the dominant
6.0 mL, 6.0 mmol) was added with stirring to a solution of 1a (1.59 g,
6.0 mmol) in THF (20 mL). The mixture was stirred for 0.5h and the sol-
vent was then removed under vacuum. The residue was washed with tolu-
ene (10 mLꢂ2) and dried under vacuum for 1h to leave 2a as an off-
white powder (1.58 g, 92%). M.p. 158–1628C. IR: n˜ =1641 (s), 1557 (s),
1452 (s), 1385 (m), 1344 (s), 1291 (s), 1256 (w), 1236 (m), 1188 (w), 1175
(w), 1145 (m), 1066 (m), 1050 (w), 1002 (m), 924 (s), 855 (m), 799 (w),
748 (w), 733 (m), 716 (w), 688 cmꢀ1 (w); 1H NMR (C4D8O, 303 K): d=
mode for these ligands with electropositive elements. In the
II
ꢀ
case of low-valent Yb , C F bond activation through Yb-o-
F-C(Ar) coordination is
ACHTUNGTRENNUNGformation.
a precursor to metal–fluoride
3
0.78 (t, J=7.17 Hz, 6H; CH3), 2.35 (brs, 4H; CH2, NEt2), 2.51 (brs, 2H;
CH2NEt2), 4.02 (brs, 2H; CH2NAr), 5.61 ppm (brs, 1H; HC6F4);
19F NMR (C4D8O, 303 K): d=ꢀ147.8 (brs, 2F; F3,5), ꢀ173.1 ppm (brs,
2F; F2,6); elemental analysis calcd (%) for C12H15F4N2Na (286.24): C
50.35, H 5.28, N 9.79; found: C 50.41, H 5.35, N 9.10.
Experimental Section
General: The compounds described herein were prepared and handled
by using conventional air-sensitive techniques. IR spectra for 1a/1b were
recorded as Nujol and HCB mulls on KBr plates with a Perkin Elmer
180 spectrophotometer, whilst spectra for metal complexes were recorded
as Nujol mulls on NaCl plates with a Perkin Elmer 1600 FTIR spectro-
photometer. Multinuclear NMR spectra were recorded by using a Bruker
DPX 300 spectrometer. Chemical shifts were referenced to the residual
1H resonances of the deuterated solvents (1H) or external CCl3F (19F) or
[K(p-HC6F4NC2H4NEt2)] (3a): By using a similar procedure, a solution
of KNACTHNURTGNE(NUG SiMe3)2 in PhMe (0.5m, 12 mL, 6.0 mmol) and 1a (1.59 g,
6.0 mmol) in THF (20 mL) gave 3a as an off-white powder (1.72 g,
95%). M.p. 192–1968C; IR: n˜ =1644 (m), 1550 (m), 1504 (w), 1353 (w),
1284 (w), 1268 (w), 1229 (w), 1192 (w), 1169 (w), 1138 (m), 1086 (w),
1058 (w), 1024 (m), 924 (m), 890 (w), 863 (w), 706 (w), 688 (w), 668 cmꢀ1
(w); 1H NMR (C4D8O, 303 K): d=0.86 (t, 3J=7.18 Hz, 6H; CH3), 2.45
(q, 3J=7.14 Hz, 4H; CH2, NEt2), 2.51 (t, 3J=5.86 Hz, 2H; CH2NEt2),
3.75 (m, 2H; CH2NAr), 5.30 ppm (m, 1H; HC6F4); 19F NMR (C4D8O,
303 K): d=ꢀ148.2 (brs, 2F; F3,5), ꢀ170.0 ppm (brs, 2F; F2,6); 19F NMR
(C4D8O, 203 K): d=ꢀ147.7 (s, 1F, F3 or F5), ꢀ151.4 (s, 1F, F3 or F5),
ꢀ168.7 (s, 1F, F2 or F6), ꢀ173.3 ppm (s, 1F, F2 or F6); elemental analysis
calcd (%) for C12H15F4N2K (302.35): C 47.67, H 5.00, N 9.27; found: C
47.11, H 5.35, N 9.10.
[Yb
mined in sealed glass capillaries under nitrogen and are uncalibrated.
ACHTUNGTRENNUNGMicroanalyses were determined by the Australian Microanalytical Serv-
ACHTUNGTRENNUNG(C5Me5)2] (0.15m) in THF/C6D6 (
171Yb). Melting points were deter-
ice (1a/1b) or the Campbell Microanalytical Service, University of Otago
(New Zealand). GC/MS data were obtained with a Agilent 6890 series
GC fitted with a 5% phenylmethylsiloxane capillary column (Agilent
19091S-433HP-5mS) and interfaced to a Agilent 5987 network mass se-
lective detector. N,N-Diethylethane-1,2-diamine, N,N-dimethylethane-
[Yb(p-HC6F4NC2H4NEt2)
2ACHTUNGTRENNUNG
1,2-diamine, NaNACHTUNGTRENNUNG(SiMe3)2 (1m solution in THF) and KNACHTUNGTERN(NUNG SiMe3)2 (0.5m
Method A: A solution of [Yb{N
G
solution in toluene) were from Aldrich. Pentafluorobenzene from Bristol
[43b]
Organics was dried over sieves (4 ꢁ). Hg
(C6F5)2,[43a] Hg
E
ꢁ
hexane (20 mL) was added to a solution of 1a (1.06 g, 4.0 mmol) in THF
(3.0 mL). The mixture was stored at ꢀ308C overnight during which time
deep orange crystals of 4a deposited, which were collected by decanta-
tion and dried under vacuum (1.20 g, 71%). M.p. 98–1028C; IR: n˜ =1640
(s), 1558 (w), 1353 (m), 1301 (m), 1245 (w), 1147 (s), 1056 (m), 943 (s),
YbI2 (0.02m solution in THF)[43c] and [Yb{N
(SiMe3)2}
N
prepared by literature methods.
Synthesis of p-HC6F4NHC2H4NEt2 ACTHNUTRGENUGN(1a): Pentafluorobenzene (13.3 g,
79 mmol) and N,N-diethylethane-1,2-diamine (18.2 g, 157 mmol) in dry
ethanol (15 mL) were heated to reflux under nitrogen for 12 h. Evaporat-
ing the solution under vacuum, gave an orange gel The gel was treated
with diethyl ether/water and was extracted four times with ether. The
combined organic extracts were dried over MgSO4 and then evaporated
under vacuum leaving a high boiling point liquid. Two distillations under
vacuum, gave pure 1a (8.4 g, 40%). B.p. 54–568C (5ꢂ10ꢀ3 mmHg); IR:
n˜ =3335 (m, br), 3097 (w), 2970 (s), 2938 (m), 2896 (m), 2876 (m), 2818
(m), 1648 (vs), 1605 (m), 1521 (vs), 1507 (sh), 1482 (s), 1471 (s), 1455 (s),
1401 (w), 1382 (m), 1371 (m), 1346 (m), 1297 (m), 1272 (w), 1257 (m),
1240 (m), 1201 (m), 1159 (s), 1143 (s), 1126 (m), 1065 (s), 1019 (w), 948
(m), 922 (w), 908 (m), 817 (w), 791 (m), 740 (w), 709 (m), 663 (w), 566
(w), 466 (w), 432 cmꢀ1 (w); 1H NMR (CDCl3, 298 K): d=1.02 (t, 3J-
900 (w), 877 (w), 738 (w), 726 cmꢀ1 (w); H NMR (C6D6, 303 K): d=0.68
1
(brt, 12H; CH3), 1.30 (brs, 8H; OC4H8), 2.39–2.44 (brm, 12H; CH2,
NEt2 +CH2NEt2), 3.47 (brs, 8H; OC4H8), 3.81 (brs, 4H; CH2NAr),
5.72 ppm (brm, 2H; HC6F4); 19F NMR (C6D6, 303 K): d=ꢀ145.3 (brs,
4F; F3,5), ꢀ164.8 ppm (brs, 4F; F2,6); 19F NMR (C7H8, 203 K): d=
ꢀ141.6 (s, 2F; F3 or F5), ꢀ148.2 (s, 2F; F3 or F5), ꢀ159.8 (brs, 2F; F2 or
F6), ꢀ167.1 ppm (s, 2F; F2 or F6); 171Yb NMR (C7D8, 303 K): d=490
(brs); (203 K), 405 ppm (brs); 171Yb NMR (C6D6/THF, v/v, 2:1, 303 K):
d=398 ppm; elemental analysis calcd (%) for C28H38F8N4OYb (loss of
one THF, 771.65): C 43.58, H 4.96, N 7.26; found: C 42.77, H 5.09, N
7.30.
Method B: Yb metal powder (0.69 g, 4.0 mmol), HgACHTUNRGTNEUNG(C6F5)2 (1.07 g,
(H,H)=7.12 Hz, 6H; CH3), 2.52 (q, 3J
2.65 (t, 3J
(H,H)=5.68 Hz, 2H; CH2, CH2NEt2), 3.40 (m, 2H; CH2NAr),
4.83 (brs, 1H; NH), 6.34 ppm (tt, 3J(H,F)=10.10 Hz, 4J
ACTHNUGTRNENUNG ACTHUNGTRENNU(G H,F)=7.06 Hz,
ACHTUGNTRENUN(NG H,H)=7.12 Hz, 4H; CH2, NEt2),
2.0 mmol), and 1a (1.06 g, 4.0 mmol) in THF (30 mL) were stirred at
room temperature for 48 h. The reaction mixture was filtered, followed
by evaporation of THF under vacuum to 3 mL. Hexane (20 mL) was
added and the mixture was stored at ꢀ308C overnight depositing deep
orange crystals of 4a (yield: 0.71 g, 46%). The 1H NMR and 19F NMR
spectra were identical with those given above.
ACHTUNGTRENNUNG
Method C: A solution of 3a (0.60 g, 2.0 mmol) in THF (20 mL) was
added to a solution of YbI2 in THF (0.02m, 50 mL, 1.0 mmol). The mix-
ture was stirred for 2 h, followed by evaporation of THF under vacuum
and addition of toluene (30 mL). The resulting precipitate was filtered
off and the volume of the filtrate was reduced to 4 mL under vacuum.
Hexane (20 mL) was added and the mixture was stored at ꢀ308C over-
night depositing deep orange crystalline 4a (1.00 g, 64%). The 1H NMR
and 19F NMR spectra were identical with those given above.
Synthesis of p-HC6F4NHC2H4NMe2 ACTHNUTRGENUGN(1b): By using a similar procedure,
1b (12.6 g, 41%) was obtained from pentafluorobenzene (21.8 g,
130 mmol) and N,N-dimethylethane-1,2-diamine (22.0 g, 250 mmol) in
dry ethanol (20 mL). B.p. 538C (5ꢂ10ꢀ2 mmHg); IR: n˜ =3357 (m, br),
3094 (w), 2977 (m), 2927 (s), 2889 (m), 2861 (m), 2813 (s), 2774 (s), 1649
(vs), 1608 (m), 1523 (vs), 1511 (sh), 1481 (s), 1459 (vs), 1401 (m), 1376
(w), 1347 (m), 1328 (w), 1282 (m), 1261 (m), 1243 (s), 1182 (m), 1160
(vs), 1140 (vs), 1098 (m), 1073 (s), 1056 (s), 1040 (s), 968 (s), 925 (vs), 873
Chem. Eur. J. 2009, 15, 3082 – 3092
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3089

G. B. Deacon, P. C. Junk et al.
[Yb(p-HC6F4NC2H4NMe2)
Method A: The preparation was effected as in method A for 4a from
[Yb{N(SiMe3)2}2A(thf)2] (1.28 g, 2.0 mmol) and 1b (0.94 g, 4.0 mmol) and
G
ꢀ169.6 ppm (brs, 4F; F2,6); elemental analysis calcd (%) for
C33H54F8K2N7 (loss of 0.5 tmeda, 779.01): C 50.88, H 6.99, N 12.59; found:
C 50.42, H 6.52, N 12.83.
N
CHTUNGTRENNUNG
[Yb(p-HC6F4NC2H4NEt2)2ACTHUNRGTNE(NUG dme)] (7a): DME (15 mL) was added to 4a
afforded deep orange crystalline 4b (yield: 1.00 g, 73%). M.p. 1268C
(decomp); IR: n˜ =1645 (m), 1558 (w), 1456 (m), 1298 (w), 1142 (m), 1060
(w), 958 (w), 926 (m), 789 cmꢀ1 (w). 1H NMR (C6D6, 300.132 MHz): d=
1.23 (brs, 8H; OC4H8), 1.85 (s, 12H; NCH3), 2.13 (brs, 4H; CH2NR2),
3.43 (brs, 8H; OC4H8), 3.78 (brs, 4H; CH2NAr), 5.73 ppm (brs, 2H;
HC6F4); 19F NMR (C6D6, 303 K): d=ꢀ145.1 (brs, 4F; F3,5), ꢀ165.0 ppm
(brs, 4F; F2,6); elemental analysis calcd (%) for C24H30F8N4OYb (loss of
one THF, 715.55): C 40.28, H 4.23, N 7.83; found: C 40.58, H 4.71, N
7.55.
(0.84 g, 1.0 mmol), and the mixture was warmed up gently and kept at
408C till all solid was dissolved. The solution was stored at ꢀ308C for
three days, during which time, deep orange prisms of 7a were deposited
and collected by filtration (yield: 0.64 g, 81%). M.p. 1528C (decomp);
IR: n˜ =1645 (s), 1558 (m), 1500 (m), 1456 (s), 1351 (m), 1298 (m), 1269
(w), 1244 (w), 1208 (w), 1148 (s), 1061 (s), 1036 (w), 945 (s), 904 (w), 862
(m), 788 (w), 728 (m), 692 cmꢀ1 (w); 1H NMR (C6D6, 303 K): d=0.78
(brs, 12H; NCH3), 2.50 (brs, 12H; NEt2 +CH2NEt2), 2.86 (brs, 6H;
OCH3), 2.96 (brs, 4H; OCH2), 3.80 (brs, 4H; CH2NAr), 5.68 ppm (brs,
2H; HC6F4); 19F NMR (C6D6, 303 K): d=ꢀ142.9 (brs, 2F; F3 or F5),
ꢀ148.8 (brs, 2F; F3 or F5), ꢀ162.2 (brs, 2F; F2 or F6), ꢀ166.6 ppm (brs,
2F; F2 or F6); 19F NMR (C6D6, 333 K): d=ꢀ145.8 (brs, 4F; F3,5),
ꢀ164.3 ppm (brs, 4F; F-2,6); 171Yb NMR (C6D6, 303 K): d=389 ppm
(brs); elemental analysis calcd (%) for C28H40F8N4O2Yb (789.67): C
42.59, H 5.11, N 7.09; found: C 42.30, H 5.28, N 7.16
Method B: The reaction was effected as in method B for 4a using Yb
metal powder (0.69 g, 4.0 mmol), HgACTHNUTRGNE(UNG C6F5)2 (1.07 g, 2.0 mmol), and 1b
(0.94 g, 4.0 mmol) and afforded deep orange crystalline 4b (yield: 0.73 g,
61%). The 1H NMR and 19F NMR spectra were identical with those
given above.
ACHTUNGTRENNUNG[Na2(p-HC6F4NC2H4NEt2)2ACHUTGNTREN(NUGN tmeda)] (5a): TMEDA (2.09 g, 18 mmol) and
PhMe (5 mL) were added to 2a (0.86 g, 3.0 mmol) and the resulting
slurry was warmed to leave a clear faintly purple solution. After storing
at ꢀ308C for one week, colourless crystals of 5a were collected by filtra-
tion and dried under vacuum (0.66 g, 70%). M.p. 152–1568C; IR: n˜ =
1637 (m), 1556 (w), 1342 (m), 1299 (m), 1264 (w), 1239 (w), 1186 (w),
1141 (m), 1122 (w), 1064 (m), 1006 (w), 932 (s), 855 (w), 788 (w), 733
(m), 690 cmꢀ1 (w); 1H NMR (C4D8O, 303 K): d=0.66 (brs, 12H; CH3),
1.65 (s, 4H; NCH2, tmeda), 1.82 (s, 12H; NCH3, tmeda), 2.19 (brs, 8H;
CH2, NEt2), 2.58 (brs, 4H; CH2NEt2), 3.84 (brs, 4H; CH2NAr), 5.70 ppm
(brs, 2H; HC6F4); 19F NMR (C4D8O, 303 K): d=ꢀ145.7 (brs, 4F; F3,5),
ꢀ171.0 ppm (brs, 4F; F2,6); elemental analysis calcd (%) for
C27H38F8N5Na2 (loss of 0.5 tmeda, 630.59): C 51.43, H 6.07, N 11.11;
found: C 50.51, H 6.37, N 11.42.
AHCTUNGTRENNUNG
AHCTNUGERTG(NNUN C6F5)2 (1.60 g,
3.0 mmol), and 1a (1.59 g, 6.0 mmol) in THF (40 mL) were stirred at
room temperature for 48 h. The reaction mixture was filtered and the sol-
vent was removed under vacuum giving a light orange solid. The material
was dissolved in toluene (15 mL), stored at ambient temperature for four
weeks and yielded crystalline, light yellow 8a (1.01 g, 56%). M.p. 236–
2408C; IR: n˜ =1640 (s), 1559 (m), 1353 (m), 1301 (m), 1148 (s), 1056 (m),
943 (m), 905 (w), 878 cmꢀ1 (w); elemental analysis calcd (%) for
C72H90F30N12Yb4 (2385.68): C 36.25, H 3.80, N 7.05; found: C 37.26, H
4.17, N 6.90.
Method B: An NMR tube was charged with 4a (42 mg, 0.050 mmol) and
toluene (0.7 mL). The mixture was shaken until the solid dissolved. The
solution was then stored at ambient temperature for two weeks, during
which time, light yellow crystals of 8a precipitated and were collected by
decanting the solution (22 mg, 75%). The identity of 8a was confirmed
by crystallography (unit cell data, a=12.846, b=13.740, c=14.176 ꢁ, a=
110.503, b=91.705, g=116.4468, V=2045.7 ꢁ3).
[K2(p-HC6F4NC2H4NEt2)2CAHTUNGTREN(GUN tmeda)2] (6a): Using a similar procedure,
TMEDA (2.09 g, 18 mmol) and 3a (0.91 g, 3.0 mmol) in THF (5.0 mL)
gave colourless crystals of 6a (0.77 g, 61%). M.p. 177–1818C; IR: n˜ =
1648 (m), 1550 (w), 1524 (w), 1294 (w), 1143 (m), 1034 (w), 925 (w), 782
(w), 688 cmꢀ1 (w); 1H NMR (C4D8O, 303 K): 1.03 (t, 3J=7.50 Hz, 12H;
CH3), 2.18 (s, 24H; NCH3, tmeda), 2.33 (s, 8H; NCH2, tmeda), 2.58–2.63
(m, 12H; CH2, NEt2 +CH2NEt2), 3.70 (m, 4H; CH2NAr), 5.22 ppm (brs,
2H; HC6F4); 19F NMR (C4D8O, 282.4 MHz): d=ꢀ148.7 (brs, 4F; F3,5),
Method C: In
a similar procedure as to method B 4a (42 mg,
0.050 mmol) dissolved in C6D6 (0.7 mL) gave light yellow crystals of
Table 4. Crystal and refinement data
5a
6a
7a
8a
8a·C6D6
8b·4PhMe
8b·2THF
9a·THF
formula
C30H46F8N6Na2 C36H62F8K2N8 C28H40F8O2Yb C72H90F30N12Yb4 C78H90D6F30N12Yb4 C88H98F30N12Yb4 C68H82F30N12O2Yb4 C92H104F16N8O5Yb4
Mr
688.71
837.14
789.68
monoclinic
P21/n
12.3616(2)
17.8526(3)
13.9943(2)
90
90.223(1)
90
3088.33(8)
4
2385.72
triclinic
P1
2469.86
monoclinic
C2/c
25.4776(7)
12.9552(4)
28.7497(8)
90
114.199(2)
90
8655.5(5)
4
1.895
4.397
50.0
20425
7515 (0.082)
4470
0.059/0.130
0.118/0.156
0.996
2585.94
triclinic
P1
2361.62
triclinic
P1
2397.99
monoclinic
P21/n
15.6045(4)
15.3027(4)
18.7041(5)
90
94.635(1)
90
4451.8(2)
2
1.789
4.253
55.0
143633
10288 (0.048)
8671
crystal system monoclinic
space group
a [ꢁ]
b [ꢁ]
c [ꢁ]
triclinic
¯
¯
¯
¯
C2/c
P1
16.6428(3)
14.1155(4)
16.2581(4)
90
115.75(2)
90
3439.67(14)
4
1.330
0.132
55.0
13362
3919 (0.065)
2956
10.3338(4)
10.9026(4)
11.5087(5)
85.214(2)
65.010(2)
70.277(2)
1103.64(8)
1
1.260
0.283
55.0
19591
4926 (0.034) 5419 (0.029)
4576
0.049/0.125
0.053/0.128
1.103
1.045/ꢀ0.424 2.35/ꢀ0.77
12.8010(3)
13.6775(3)
14.1239(5)
110.462(1)
91.795(1)
116.416(1)
2022.85(10)
1
1.958
4.700
55.0
26436
9245 (0.045)
7440
0.034/0.063
0.049/0.067
1.062
12.4627(3)
13.2767(3)
16.1705(4)
87.763(1)
67.482(1)
72.820(1)
2353.02(10)
1
1.825
4.048
55.0
22742
10527 (0.059)
7896
0.047/0.108
0.070/0.119
1.007
11.7179(3)
13.7708(4)
14.3926(4)
113.182(2)
95.523(1)
109.630(1)
1939.58(10)
1
2.022
4.902
55.0
23029
8849 (0.055)
6296
0.040/0.066
0.076/0.075
1.015
a [8]
b [8]
g [8]
V [ꢁ3]
Z
1calcd [gcmꢀ3
]
1.698
3.109
50.0
55357
m [mmꢀ1
2Vmax
Nt
]
N (Rint
)
N [I>2s(I)]
R1/wR2[a]
R1/wR2[b]
GOF
4567
0.056/0.157
0.080/0.173
1.037
0.571/ꢀ0.497
0.024/0.059
0.031/0.065
1.062
0.049/0.103
0.065/0.116
1.189
max/min De
1.190/ꢀ1.894
2.457/ꢀ2.227
2.504/ꢀ2.489
1.216/ꢀ1.332
3.963/ꢀ3.145[c]
[eꢁꢀ3
]
[a] [I>2s(I)]. [b] All data. [c] Highest residual peak 3.963 eꢁꢀ3 is located 0.793 ꢁ from Yb(1).
3090
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3082 – 3092

Metal–Fluorocarbon Coordination
FULL PAPER
8a·C6D6 (22 mg, 70%). The compound was identified by X-ray crystal-
lography (see Table 4).
These data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Acknowledgement
6.0 mmol) to afford light yellow crystals of 8b·4PhMe (1.16 g, 67%).
M.p. 2108C (decomp); IR: n˜ =1650 (m), 1578 (m), 1353 (m), 1300 (w),
1281 (w), 1141 (s), 1058 (m), 958 (m), 929 (m), 758 (w), 728 (m),
694 cmꢀ1 (w). elemental analysis calcd (%) for C60H66F30N12Yb4 (loss of
toluene of solvation, 2217.36): C 32.50, H 3.00, N 7.58; found: C 31.92, H
3.16, N 7.27. Crystals of 8b·2THF were obtained by crystallisation from
initial filtered THF solution.
Dr D. P. Buxton is gratefully acknowledged for the initial synthesis of the
ligands 1a and 1b. This work was financially supported by grants from
the Australian Research Council.
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Method B: A flask was charged with 4b (0.79 g, 1.0 mmol) and toluene
(5 mL). The solution was kept at 508C for 2 h and then stored at ambient
temperature for three weeks, during which time, light yellow crystals of
8b·4PhMe deposited (0.47 g, 82%). The identity of 8b·4PhMe was con-
firmed by IR and crystallography (unit cell data, a=12.443(4), b=
13.267(4), c=16.144(5) ꢁ, a=87.74(3), b=67.54(3), g=72.79(3), V=
2344.3(12) ꢁ3). In a parallel experiment performed in an NMR tube, 4b
(39 mg, 0.050 mmol) in toluene/C7D8 (1:1, 0.7 mL) was kept at ambient
temperature for two weeks. 19F NMR (303 K): d=103.1 (brs, 2F), ꢀ30.6
(s, 4F), ꢀ130.5 (s, 12F; F3,5), ꢀ182.3 ppm (s, 12F; F2,6).
Method C: A flask containing 4b (0.79 g, 1.0 mmol) and perfluorohexane
(5 drops) in toluene (5 mL) was kept at 508C for 2 h and then stored at
ambient temperature for three weeks, during which time, light yellow
crystalline 8b·4PhMe deposited (0.31 g, 54%). The identity of 8b·4PhMe
was confirmed by IR and crystallography.
GC/MS analyses of reaction mixtures: Following the procedures above,
4a or 4b (ca. 50 mg) was loaded into a NMR tube and dissolved in C6D6.
These solutions were kept at ambient temperature for two weeks and
were monitored by 19F NMR spectroscopy. During this time, yellow crys-
tals of 8a or 8b formed. The reactions were quenched by addition of
EtOH or MeOH, and the filtered organic fractions analysed by GC/MS.
4a!8a (major fractions only): Rt: 4.65 (m/z 104), 5.33 (m/z 129), 9.00
(m/z 207), 9.24 (m/z 207), 9.97 (m/z 158), 10.29 (m/z 207), 10.62 (m/z
207), 14.43 (m/z 264, [LH]+), 15.21 (m/z 246 [LH2ꢀF]+), 15.63 min (m/z
228, [LH3ꢀ2F+]). 4b!8b (major fractions only): Rt: 10.04 (m/z 236,
[LH]+), 10.68 min (m/z 218, [LH2ꢀF]+). An isolated sample of 8a (ca
40 mg) was hydrolysed in PhMe/EtOH and the filtered organic fraction
was analysed by GC/MS: Rt: 10.90 min (m/z 264 [LH]+).
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(m), 1573 (w), 1504 (m), 1353 (w), 1303 (w), 1148 (m), 1062 (m), 948 (m),
758 (m), 694 cmꢀ1 (w); 19F NMR (C6D6, 303 K): d=ꢀ134.3 (brs, 8F,
F3,5), ꢀ153.1 ppm (brs, 8F, F2,6); elemental analysis calcd (%) for
C88H96F16N8O4Yb4 (loss of THF of solvation, 2325.89): C 45.44, H 4.16, N
4.82; found: C 45.23, H 4.49, N 4.52. A significant yield of 9a could not
be obtained without the admission of dry air.
X-ray crystallography: Crystalline samples of compounds were mounted
in a thin-walled glass capillary (6a) or on glass fibres in highly viscous
perfluoropoly ether oil (5a) or paraffin oil (7a, 8a, 8a·C6D6, 8b·2THF,
8b·4PhMe and 9a·THF). Diffraction data were obtained at ꢀ1508C
(123 K) by using an Enraf–Nonius Kappa CCD or Bruker X8 APEX II
CCD diffractometer (MoKa radiation, l=0.71073 ꢁ). Each data set was
empirically corrected for absorption (SORTAV;[44a] SADABS[44b]) then
merged (Rint as quoted) to N unique reflections. The structures were
solved by conventional methods and refined by full-matrix least-squares
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cal user interface.[44d] Crystal data and refinement details are given in
Table 4. CCDC-707324 (5a), 707325 (6a), 707326 (7a), 707327 (8a),
707328 (8a·C6D6), 707329 (8b·2THF) 707330 (8b·4PhMe) and 707331
(9a·THF) contain the supplementary crystallographic data for this paper.
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Received: November 5, 2008
Published online: February 16, 2009
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