{Rh(PiBu3)2}+ fragments ligated to arenes: From benzene to polyaromatic hydrocarbons, part I - An experimental approach

Article abstract of DOI:10.1002/ejic.201001263

We report the synthesis, structural characterisation andsolution-phase dynamics of a series of polyaromatic hydrocarbon complexes of the 12-electron {Rh(PiBu₃)₂}⁺ fragment. Crystal structures of this fragment with benzene, naphthalene, anthracene, pyrene, triphenylene and coronene are described, alongside their solution NMR spectroscopic data. The ligands map out a systematic increase in size of the aromatic subunit, and represent an approach to the limiting case of coordination to a graphene surface. The solid-state and solution structures of a {Rh(COD)}⁺ fragment coordinated to a hexa-peri-hexabenzocoronene are also reported. A range of polyaromatic hydrocarbons of increasing size (naphthalene through coronene) have been prepared and their solid-state and solution structures investigated. Copyright

Full text of DOI:10.1002/ejic.201001263

FULL PAPER
DOI: 10.1002/ejic.201001263
{Rh(PiBu3)2}+ Fragments Ligated to Arenes: From Benzene to Polyaromatic
Hydrocarbons, Part I[‡] – An Experimental Approach
Anthony Woolf,[a] Adrian B. Chaplin,[a] John E. McGrady,[a] Muhsen A. M. Alibadi,[a]
Nicholas Rees,[a] Sylvia Draper,[b] Frances Murphy,[b] and Andrew S. Weller*[a]
Keywords: Rhodium / Arenes / Arene ligands / Pi interactions / Hydrocarbons / Polyaromatic hydrocarbons
We report the synthesis, structural characterisation and
The ligands map out a systematic increase in size of the aro-
solution-phase dynamics of a series of polyaromatic hydro- matic subunit, and represent an approach to the limiting case
carbon complexes of the 12-electron {Rh(PiBu3)2}+ fragment.
Crystal structures of this fragment with benzene, naphth-
alene, anthracene, pyrene, triphenylene and coronene are
described, alongside their solution NMR spectroscopic data.
of coordination to a graphene surface. The solid-state and
solution structures of a {Rh(COD)}+ fragment coordinated to
a hexa-peri-hexabenzocoronene are also reported.
plex of coronene (L7) has been reported.[16] Coordination
to even larger PAH molecules including corannulene
(C20H10), the curved carbon fragment of buckminsterfuller-
ene,[17–19] and the C42 PAH hexa-peri-hexabenzocoronene
(HBC, L8[20]) is also known.[21,22] Related functionalized
HBC analogues in which a metal coordinates to a periph-
eral Lewis base incorporated into the PAH have been re-
ported.[23] PAHs and their metal complexes (e.g. of iron)
have been proposed as the source of the aromatic infrared
bands observed in many astronomical objects and could be
important intermediates in the formation of small mole-
cules in interstellar space. This observation has motivated a
Introduction
The π coordination chemistry of transition-metal fragments
with simple arenes is now a well developed area,[1–3] dating
back to the first rational synthesis of Cr(η6-C6H6)2 in
1955.[4] Coordination complexes of simple fused aromatics,
also called polycyclic aromatic hydrocarbons (PAH), such
as naphthalene (L3, Scheme 1) and anthracene (L4) are
also common.[2,5,6–10] Examples with larger PAH systems,
for example triphenylene (L5),[10,11,12–14] and pyrene
(L6),[10,12,13,15] are less well represented in the literature.
Only one crystallographically characterized d-block com-
Scheme 1.
number of gas-phase studies on metal ion ligation to ex-
tended π-systems.[24] The incorporation of transition metal
centers onto the surface of PAH systems can moderate their
reactivity,[25] as well as the photophysical[26] and elec-
tronic[19] properties of the hydrocarbon moiety. Transition
metal functionalized PAHs also represent important mod-
els[27] for the coordination of metals to graphene and other
extended carbon surfaces.[28]
[‡] Part II: A. Woolf, M. A. M. Alibadi, A. B. Chaplin, J. E.
McGrady, A. S. Weller, Eur. J. Inorg. Chem. 2011, 1626–1634
(following paper).
[a] Department of Chemistry, Inorganic Chemistry Laboratories,
Oxford, OX1 3QR, UK
[b] School of Chemistry, University of Dublin, Trinity College,
Dublin, D2, Ireland
E-mail: andrew.weller@chem.ox.ac.uk
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201001263.
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From Benzene to Polyaromatic Hydrocarbons, Part I
Transition metals coordinated to arenes can adopt a
range of hapticities from η6 through to η1 depending on
the electronic requirements of both the metal and ligand.[2]
Thus the adoption of stable 18- and 16-electron configura-
tions on one hand and the retention of maximal aromatic
stabilization in the ligand on the other provide important,
and potentially conflicting, driving forces for the adoption
of a particular structure. In polycyclic aromatic systems
haptotropic rearrangements where the metal moves from
one aromatic ring to another[8,18,29] can also occur. The mi-
gration pathways in these reactions presumably reflect the
best compromise where disruptions to the electronic envi-
ronments of metal and ligand are minimized.
Results and Discussion
Synthesis and Solid-State and Solution Structures
The majority of the new complexes reported here have
been synthesized by the same procedure: combination of 1
with the appropriate arene (L1 to L7, 5 equiv.) in CH2Cl2
solution. Recrystallisation from CH2Cl2/pentane afforded
crystalline material that was initially characterised by NMR
spectroscopy. Ligand L8 required a different metal frag-
ment, {Rh(COD)}+. Apart from one case (anthracene, vide
infra), solution NMR spectroscopic data for the complexes
prepared in situ were the same as for the isolated crystalline
material. For larger PAH systems (L6 and L7) decomposi-
tion in solution occurred on removal of excess arene and so
NMR spectroscopic data for these species were recorded
from rapidly prepared crystalline samples at sub-ambient
temperatures. Analysis by ESI-MS did not give the parent
ion or indeed any useful information. However, analytical
data on crystalline material demonstrates purity. In the fol-
lowing sections we discuss how the structural features of
the complexes evolve as the PAH framework is extended.
We have recently reported the synthesis of a formally 12-
electron rhodium(I) complex [Rh(PiBu3)2][BArF4] [ArF
=
C6H3(CF3)2] that reacts with arenes, even weakly binding
fluorinated ones such as C6H5F[30] and 1,2-C6H4F2,[31] to
give the associated π-coordination complexes, e.g.
[Rh(C6H5F)(PiBu3)2][BArF4] (1) (Scheme 2). With chloro-
and bromo-substituted arenes C–X activation occurs via an
η-bound intermediate.[30,32] No C–H activation of the arene
has been observed, in contrast to the chemistry of the re-
lated {Rh(η5-C5Me5)(PMe3)} systems.[10] Given that 1 is a
readily available synthon and reacts cleanly with simple ar-
enes by the straightforward substitution of a weakly bound
fluorobenzene ligand we reasoned that this would be an
Benzene and tert-Butylbenzene
The new compounds [Rh(PiBu3)2(benzene)][BArF4] (2)
ideal precursor for the formation of rhodium complexes of and [Rh(PiBu3)2(tBu-benzene)][BArF4] (3) were isolated in
a range of aromatic ligands of increasing size.
good yield as red-brown crystalline materials. The solid-
state structures of both have been determined. Complex 2
is disordered in both the arene and PiBu3 ligands but the
disorder could be modeled satisfactorily, albeit it with the
caveat that the benzene ligand was constrained to be planar
in the refinement. We discuss one of these components, as
the structural metrics for all are similar. The Rh–P dis-
tances in 2 are rather similar [2.2753(11) and 2.2695(12) Å],
as are the Rh–C distances which range from 2.255(9)–
2.430(9) Å, and are similar to those reported for [Rh(PPh3)2-
(benzene)][BArF4], 2.283(4)–2.366(4) Å.[33] The Rh–C dis-
tances in
2
fall into three, closely separated,
ranges: C2/C3, 2.272(1)/2.255(9); C1/C4, 2.360(10)/2.328(8);
and C5/C6, 2.414(9)/2.430(9) Å. A precise definition of the
hapticity of 2 is therefore not straightforward as the distinc-
tion between bonded and non-bonded distances is not
large, suggesting an η6 (18-electron) formulation, but the
pattern of Rh–C bond lengths suggests a distinct slip
Scheme 2. General synthetic scheme (# dimeric species, * with the
{Rh(COD)}+ fragment).
In this contribution we report the synthesis of complexes towards η4 (16-electron). The Rh–C distances are compar-
of the {Rh(PiBu3)2}+ fragment with various arenes ranging able to those in other η4-arene complexes of RhI. For exam-
from benzene to coronene (L1–L7, Scheme 2). These are ple, [Rh{η4-(C6H5)NHCH2Ph}(PPh3)2][PF6][34] has Rh–C
characterized in the solid state and using solution-phase bonding distances spanning the range 2.288(3)–2.310(4) Å,
NMR spectroscopy. This synthetic methodology is similar while those assigned as non-bonding are at 2.442(3)–
to that recently reported for metal complexes of corannu- 2.524(3) Å. The complex [(μ2,η1:η4:η1-{1,4-bis[2-(diphenyl-
[35]
lene (C20H10), e.g. [Rh(COE)2(corannulene)][PF6].[18] In ad- phosphanyl)ethoxy]naphthalene})2Rh2][BF4]2
has
a
dition, a solid-state structure for a {Rh(COD)}+ (COD = naphthalene ligand that is slipped to η4, with bonding and
1,5-cyclooctadiene) fragment bound to HBC (L8) is re- non-bonding distances in the range 2.211(6)–2.419(6) and
ported. In Part II (following paper) we describe a computa- 2.507(6)–2.569(9) Å, respectively. [(η4-C6H8)Rh(PPh3)2]-
tional investigation of these species that provides a detailed [closo-CB11H6Br6] also shows similar bonded Rh–C dis-
insight into the binding and motion of {Rh(PR3)2}+ frag- tances [2.157(3)–2.291(3) Å].[36] As shown in Scheme 3, the
ments across increasingly extended carbon surfaces.
plane defined by the {RhP2} fragment lies at an angle of
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A. S. Weller et al.
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20.2° relative to the C1–C4–Rh1 plane. The presence of a cale. A single environment is also observed for the iBu
tBu-group in 3 prevents the disorder of the arene ligand methyl groups. The 1H NMR spectrum also indicates equiv-
(although the phosphane alkyl groups are still disordered) alent iBu groups, with a single environment for CHMe2 ob-
and no constraints on the arene ring were necessary in the served as a doublet, and the CH2CHMe2 environment as
structural refinement. The solid-state structure of 3 shows an integral 12 H doublet of doublets [J(P,H) = 2, J(H,H) =
a coordination mode similar to that of 2 although the dis- 8 Hz]. These data are broadly similar to those reported for
[33]
tinction between bonded and non-bonded Rh–C distances [Rh(PPh3)2(benzene)][BArF
]
and [Rh(C6H5F)(PiBu3)2]-
4
is again not large [range 2.274(3)–2.441(3) Å]. The {RhP2} [BArF4].[30] The NMR spectroscopic data for 3 are similar
fragment is rotated away from the bulky tBu group (twist to 2 and show equivalent iBu groups. This is noteworthy as
angle 71.4°). No close π-π stacking between arenes was evi- the introduction of the tBu group on the arene reduces the
dent from the extended crystal structures of 2 or 3 (Fig- highest possible symmetry to Cs, in which case the dia-
ure 1).
stereotopic methyl groups on the iBu ligands should be in-
equivalent in a static structure. A simple libration of the
{Rh(PiBu3)2}+ fragment would not make the methyl groups
equivalent. We thus suggest that the metal fragment is rotat-
ing about the pseudo-C6 axis of the arene ring. In support
of this assignment we have recently reported examples of
complexes that also show equivalent phosphorus environ-
ments in the 31P{1H} NMR spectrum, have Cs symmetry
but do not undergo exchange. These show two sets of
clearly-resolved iBu resonances, in contrast to 3.[32]
Naphthalene
The solid-state structure of [Rh(PiBu3)2(naphthalene)]-
[BArF4] (4) is shown in Figure 2. The arene ligand is disor-
dered over two closely related conformations differentiated
by a slight twist of the ligand with regard to the RhP2 plane.
Only parameters for the major component (69% occu-
pancy) are discussed. The Rh–C distances span two distinct
ranges: 2.263(10)–2.405(7) (C1–C4) and 2.553(11),
2.603(8) Å (C5, C6) and the bonding is thus defined as be-
ing η4 and the metal centre is 16-electron. The naphthalene
ligand in 4 is hinged about C1–C4 [8.5(5)°] with a relatively
small distortion from planarity compared to that in 18-elec-
tron Rh(η5-C5Me5)(η4-naphthalene) ca. 35°,[9] and Ru(P-
Et3)(η4-COD)(η4-naphthalene) ca. 41.5°.[6] The {RhP2}
plane in 4 is also twisted away from the C1–C4–Rh1 plane
by 29.4° (Scheme 3).
Scheme 3. Orientation of the RhP2 fragments relative to the arene
rings in the solid-state structures.
Figure 1. Solid-state structures of the cationic portion of complex
2 and 3. Anion and hydrogen atoms on the phosphane group are
not shown, nor is the minor disordered component of the alkyl
phosphane groups or the benzene ligand in 2. Thermal ellipsoids
are shown at the 30% probability level. For 2: Selected distances
[Å]: Rh1–C1 2.360(10), Rh1–C2 2.272(10), Rh1–C3 2.255(9), Rh1–
C4 2.328(8), Rh1–C5 2.414(9), Rh1–C6 2.430(9), Rh1–P1
2.2753(11), Rh1–P2 2.2695(12). Selected angle: P1–Rh1–P2:
95.59(4)°. For 3: selected distances [Å]: Rh1–C1 2.441(3), Rh1–
C2 2.333(3), Rh1–C3 2.274(3), Rh1–C4 2.350(4) Rh1–C5 2.441(3),
Rh1–C6 2.330(4), Rh1–P1 2.274(3) Rh1–P2 2.2294(15). Selected
angle: P1–Rh1–P2 97.56(6)°.
In solution at room temperature complex 2 shows a
single, upfield-shifted singlet resonance in the 1H NMR
spectrum for the bound arene at δ = 6.48 (cf. free C6H6, δ
= 7.35 ppm), consistent with coordination to a metal frag-
ment.[1] The 31P{1H} NMR spectrum shows a single sharp
doublet at δ = 25.6 [J(RhP) = 199 Hz]. In the 13C{1H}
NMR spectrum the arene ligand is observed as a single en-
vironment showing coupling to 103Rh, δ = 101.3 [d, J(RhC)
Figure 2. Solid-state structure of the cationic portion of complex
4. See Figure 1 legend for details. Selected distances [Å]: Rh1–C1
2.405(7), Rh1–C2 2.328(7), Rh1–C3 2.243(9), Rh1–C4 2.263(10),
Rh1–C5 2.553(11), Rh1–C6 2.603(8), Rh1–P1 2.3173(7), Rh1–P2
2.2485(7). Selected angles: P1–Rh1–P2 98.34(2)°.
At room temperature in solution complex 4 shows sig-
1
= 2 Hz]. The observation of 103Rh-13C coupling suggests nals in the H and 13C{1H} NMR spectra that are fully
that arene dissociation is not occurring on the NMR times- consistent with the arene coordination mode revealed by
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From Benzene to Polyaromatic Hydrocarbons, Part I
Scheme 4. Rotation of {RhP2}+ fragment and interchange of MeA and MeB. Rotation around the Rh–P bond is assumed.
the crystal structure. The symmetry of the arene is reduced 6.04, 2H each). The 31P{1H} NMR spectrum shows a sharp
to Cs and two upfield shifted aromatic resonances are ob- doublet at δ = 13.6 [J(RhP) = 191 Hz]. These data are con-
1
served in the H NMR spectra at δ = 6.74 (2 H) and 6.03 sistent with time-averaged Cs symmetry, and a structure in
(2 H) (for H1/4 and H2/3, respectively). Two further signals solution similar to 4. After 5 min, however, complex 6, a
are essentially unshifted (δ = 7.54–7.46 m, 4 H) from free 2:1 adduct [Rh(PiBu3)2(anthracene)2][BArF4]2, starts to pre-
naphthalene (δ = 7.86 and 7.49 ppm). A single resonance cipitate as dark blue crystals in high yield (based on Rh).
(doublet) is observed in the 31P{1H} NMR spectrum at δ = Addition of a larger excess of anthracene failed to prevent
16.7 [J(RhP) = 196 Hz]. The 13C{1H} NMR spectrum also the formation of 6. Of all the complexes reported here, 6 is
shows two upfield shifted resonances with clear coupling to the only bis adduct observed. The data summarized above
103Rh, viz. δ = 96.0 [C1/4, d, J(RhC) = 3 Hz], δ = 89.5 [C2/ suggest a process as outlined in Scheme 5. We suggest the
3, d, J(RhC) = 3 Hz] and three sets of resonances in the preferential formation of 6 over 5 is determined by the rela-
region of free naphthalene showing no coupling to 103Rh tive solubilities of monocationic 5 vs. dicationic 6, which
(δ = 130.3, 127.5, 125.3). These assignments, confirmed by drives this equlibrium in favour of 6 under the reaction con-
HSQC and 1H-1H COSY experiments, show that decoordi- ditions.
nation of the naphthalene ring is not occurring on the
Complex 6 crystallizes with crystallographically imposed
NMR timescale. Crabtree has noted similar chemical shifts centrosymmetry, with the metal fragments arranged anti to
in [Ir(PPh3)2(2-ethylnaphthalene)][SbF6].[37] Just as for 3, one another (Figure 3). Each {Rh(PiBu3)2}+ fragment has
only a single set of iBu resonances is observed at room tem- four short Rh–C distances [2.203(4)–2.310(3) Å, Rh–C2
perature, suggesting that a process that results in rotation and Rh–C3 being the shortest] and the anthracene ligand
of the {Rh(PiBu3)2}+ fragment on the arene is relatively is hinged around C1/C4 by 12.6(1)°, a somewhat larger an-
low energy. In principle, this could be achieved by a simple gle than in 4, leading to non-bonded distances to C5 and
rotation about the butadiene fragment C1–C4 (Scheme 4), C6 of 2.704(4) and 2.708(4) Å [compared to 2.553(11),
possibly involving an η3-allyl-like transition state similar 2.603(8) Å in 4]. We characterize the coordination mode
to that reported for
a
ring walking process in here as being η4-, similar to 4 and Mo(PMe3)3(anthr-
[Ni(R2PCH2CH2PR2)(η2-arene)] systems.[38] It is interesting acene).[7] As expected for a structure with metals coordinated
to note that Ru(PMe2Ph)3(η4-naphthalene),[39] which has to both faces of the PAH, there is no π-π stacking in the
an 18-electron configuration at the metal centre, has a solid state. The Rh–P distances are the same within error,
strongly hinged structure and is static on the NMR times- 2.3096(9) and 2.3069(9) Å. There are only a few other crys-
cale.
tallographically characterized examples where two metals
coordinate to anthracene.[13,40,41] A closely related example
where two metal fragments coordinate to phenazine also
adopts an anti arrangement.[41]
Anthracene
Mixing 1 with 5 equiv. of anthracene in CH2Cl2 solution
1H and 31P{1H} NMR spectra of 6 in dilute CD2Cl2 (ob-
immediately gave a blood-red solution assigned to a 1:1 tained by dissolving isolated crystals in excess solvent, a
complex [Rh(PiBu3)2(anthracene)][BArF4], 5. NMR spectra procedure that was necessary as 6 is sparingly soluble),
measured immediately after mixing show a characteristic show the presence of both 5 and 6. The spectrum of 6 shows
2:2:2:2:2 pattern of resonances between δ = 7.89 and 6.04 only three resonances in the aromatic region, consistent
in the aromatic region, with two higher-field resonances as- with the higher symmetry of the bis adduct (C2v). These are
signed to the coordinated portion of the arene (δ = 6.52, in the ratio 2:4:4, with the most downfield signal (H7) a
Scheme 5.
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A. S. Weller et al.
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tion modes. NMR data (vide infra) indicate Cs symmetry
for this coordination motif, suggesting either that a truly
symmetric η3 geometry is the equilibrium structure in solu-
tion or that interconversion of two equivalent η2 structures
occurs on the NMR timescale. A closely-related complex
[Ir(η5-C5Me5)(pyrene)][BF4]2 has been assigned a η6-struc-
ture and therefore an 18-electron count, with Ir–C distances
in the range 2.229(4)–2.314(5).[12]
Figure 3. Solid-state structure of the dicationic portion of complex
6. See Figure 1 legend for details. Selected distances [Å]: Rh1–C1
2.310(3), Rh1–C2 2.204(3), Rh1–C3 2.203(4), Rh1–C4 2.303(3),
Rh1–C5 2.704(3), Rh1–C6 2.708(4), Rh1–P1 2.3096(9), Rh1–P2
2.3069(9). Selected angle: P1–Rh1–P2 96.57(3)°.
singlet (δ = 7.34 ppm) and the two integral 4 H signals
shifted upfield (δ = 6.65, H2/3; δ = 5.76, H1/4), typical for
metal coordination. After 1 h at room temperature complex
5 was the dominant species in solution (ca. 95%). The liber-
ated [Rh(PiBu3)2]+ is not observed and we presume it de-
composes under the reaction conditions. This mixture is not
stable and after 24 h partial decomposition of the organo-
metallic compounds to give free anthracene is observed.
Figure 4. Solid-state structure of the cationic portion of one of the
independent cations in the unit cell of complex 7. See Figure 1 leg-
end for details. Selected distances [Å]: Rh1–C1 2.285(3), Rh1–C2
2.255(3), Rh1–C3 2.404(3), Rh1–C4 2.586(3), Rh1–C5 2.643(3),
Rh1–C6 2.532(3), Rh1–P1 2.2148(7), Rh1–P2 2.2888(6). Selected
angle: P1–Rh1–P2 96.40(2)°.
Pyrene
The solid-state structure of [Rh(PiBu3)2(pyrene)][BArF
]
4
7 is shown in Figure 4. The pyrene ring in 7 is planar, with
a r.m.s. deviation of 0.02 Å2. The extended structure (Fig-
ure 5) shows close π-π stacking with a distance between ar-
enes of 3.40(4) Å, similar to the interlayer distance of
3.35 Å in graphite. There are two independent molecules in
the unit cell that differ only in the degree of twist of the
{Rh(PR3)2}+ fragment. In other respects the bond lengths
and angles in the two units are very similar, and only one
set is discussed. The Rh–C(arene) distances fall into three
distinct ranges, Rh–C1 and Rh–C2 being the shortest
[2.255(3), 2.285(3) Å], Rh–C3 intermediate [2.404(3) Å] and
Rh–C4–Rh–C6 spanning the range 2.532(3) Å (C6)–
2.643(3) Å (C5). The metal fragment is orientated such that
one phosphane sits over the PAH ring and the other off the
side, twisted by 26.6° relative to the C2–C5–Rh1 plane. The
two short Rh–C distances suggest an η2-coordination
Figure 5. Packing diagram of 7 showing the interplanar separation
of 3.40(4) Å.
Unlike the adducts of benzene, naphthalene, anthracene
mode,[10] giving a formal 14-electron count to the metal cen- and triphenylene (vide infra) the room temperature 1H
tre. However, if the relatively short Rh–C3 distance is also NMR spectrum of 7 shows very broad signals in the arene
viewed as bonding then the ligand adopts an η3-allyl-like region that contrast with the very sharp signals due to
structure, giving a 16-electron count at the metal centre and [BArF4]– anion. The 31P{1H} NMR spectrum shows three
some degree of charge separation in the aromatic ligand. very broad peaks in an approximate 1:4:1 ratio centred at
Both η2- and η3-coordination modes have precedent in RhI ca. δ = 44, 22 and 13, respectively. On progressive cooling
complexes. For example (C5Me5)Rh(PMe3)(phenanthrene) (Figure 6) to 190 K all these signals resolve into a set of
is η2,[10] while {LMeRh}2(mesitylene) is η3 (L = 2,6- sharp resonances at δ = 46.8, 21.8 and 13.5, in a similar
C6H3Me2)NC(Me)CHC(Me)N(2,6-C6H3Me2).[42] Interest- ratio to that at room temperature. These data indicate that
ingly, this latter complex has been proposed as a model for slowly interconverting isomeric species, 7A and 7B, are
the transition state in the fluxional pathway for movement present (Scheme 6) over the entire temperature range. An
of the metal from chemically equivalent η4 to η4 coordina- approximate 1:0.35 ratio at 190 K equates to an energy dif-
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From Benzene to Polyaromatic Hydrocarbons, Part I
ference of only 0.5 kcal mol–1 between the two isomers. The
central peak in the 31P{1H} NMR spectrum is assigned to
7A while the outer two resonances, which also show mutual
31P coupling [J(P,P) = 37 Hz], are assigned to 7B. All three
resonances show coupling to 103Rh, although the magni-
tude of this varies: J(Rh–P) = 209 Hz 7A (similar to the
other compounds reported here) but 243 and 181 Hz for
the peaks at δ = 46.8 and 13.5 respectively assigned to 7B.
In the 1H NMR spectrum, two upfield shifted environments
are observed at δ = 7.41 (t, 1 H) and δ = 6.69 (d, 2 H) for
the coordinated arene in 7A. For 7B an upfield shifted sing-
let resonance (2 H) is observed for the coordinated arene at
δ = 6.41. Aromatic signals between δ = 8.17 and δ = 7.62
are also observed and assigned to uncoordinated arene pro-
tons by 1H-1H COSY, HMQC and NOESY experiments. A
13C{1H} NMR experiment was not successful due to slow
decomposition of 7 in solution.
Scheme 6. Isomers 7A and 7B.
would result in an effective Cs-symmetric η3-coordinated in-
termediate with equivalent phosphorus envrionments. 7B
also has Cs symmetry, but the observation of inequivalent
phosphane environments and a single upfield-shifted singlet
in the aromatic region suggest that the metal fragment is
η2-bound to C7/C8 and not undergoing rotation at this
temperature. The very different J(RhP) coupling constants
and chemical shifts observed for this isomer are consistent
with a T-shaped coordination environment at rhodium that
places one phosphane trans to a vacant site, very similar to
the geometry observed in the solid-state structure of the
coronene complex 9 (vide infra).
Upon warming the separate signals assigned to 7A and
7B in the 1H NMR spectrum broaden and coalesce at
250 K. Simulation of this process afforded rate constants
for exchange, for which an Eyring analysis (supporting ma-
terials) over the temperature range 220–250 K gave the acti-
vation parameters: ΔH‡ = (11.1Ϯ0.8) kcal/mol and ΔS‡ =
(–1.3Ϯ1) kcal/mol/K; corresponding to an activation free
energy of ΔG(298)‡ = (11.5Ϯ1) kcal/mol. Sharp peaks due
to trace free pyrene are observed up to 230 K showing that
rapid intermolecular exchange is not occurring at this tem-
perature. At room temperature these peaks have broadened
significantly. This available experimental data suggests that
the two possible mechanisms for the isomerisation are oc-
curring: an intramolecular haptotropic shift at lower tem-
peratures and an additional intermolecular process where
the bound-ligand exchanges with free pyrene at higher tem-
peratures. The computed barrier for the intramolecular pro-
cess (see Part II, following paper in this issue) is 11.7 kcal/
mol, and the close to zero activation entropy, offers strong
support that the first of the two possibilities is operating
at low temperature. That intermolecular exchange is also
possible at room temperature, is show by addition of d10-
pyrene (1 equiv.) to a CD2Cl2 solution of 7 that results in
the formation of free protio-pyrene while the {Rh-
(PiBu3)2}+ remains coordinated to the arene (by 31P{1H}
NMR). The suggested equilibrium (at 298 K) between 5
and 6 (vide supra) also suggests an intermolecular process
can operate at room temperature.
Figure 6. Variable temperature (270–190 K) 1H and 31P{1H} NMR
spectra for 7; * indicates free pyrene.
The presence of a single 31P resonance (and hence at least
time-averaged Cs point symmetry) in the dominant isomer,
7A, appears inconsistent with the solid-state structure of 7.
Triphenylene
The structure of [Rh(PiBu3)2(triphenylene)][BArF4] 8 is
However, as noted above, only a relatively minor translation shown in Figure 7. The bond lengths clearly indicate an η4-
of the {Rh(PiBu3)2}+ fragment along the C1/C2/C3 unit binding mode, with four relatively close contacts, 2.252(3)–
Eur. J. Inorg. Chem. 2011, 1614–1625
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1619

A. S. Weller et al.
FULL PAPER
2.346(3) Å, and two significantly longer (C1/C6 2.540(4)
and 2.535(4) Å, respectively). This gives the metal centre a
16-electron count. There is a slight hinging about the C2–
C5 axis (7.3°). The geometry of the {Rh(PiBu3)2}+ frag-
ment is similar to that observed for anthracene and naphth-
alene, with the RhP2 plane rotated away from C2–C5–
Rh1 plane by 24.8°. We note that [M(triphenylene)-
(Cp*)][BF4] (M = Rh, Ir)[12] and Cr(CO)3(η6-triphenyl-
ene)[14] have been assigned as η6-structures, although the
M–C bond lengths show very similar trends to those of 8
(viz. four short and two marginally longer). The extended
structure shows close π-π stacking with an average distance
between arenes of 3.3(1) Å.
Figure 8. (a) Side and (b) space-fill (van der Waals radii) of 9. Hy-
drogen atoms on the phosphane and the [BArF4]– anion are omit-
ted. Thermal ellipsoids are shown that the 30% probability level.
See Figure 1 legend for details. Selected distances [Å]: Rh1–C2
2.247(4), Rh1–C3 2.247(4), Rh1–C1 2.535(4), Rh1–C4 2.523(4),
Rh1–C19 2.688(4), Rh1–C20 2.682(3), Rh1–P1 2.249(3), Rh1–P2
2.296(5). Selected angles: P1–Rh1–P2 99.5(2)°.
Complex 9 crystallises with a slightly disordered RhP2
fragment, with the phosphanes occupying two closely re-
lated sites. The Rh-arene interactions, in contrast, are not
disordered. Only one set of metrics is discussed here. Rather
like complex 7 the metal fragment appears to adopt an η2-
coordination mode (14-electron at metal) in the solid-state,
but in this case the bonding is more clear-cut with two dis-
tances, 2.247(4)/2.247(4) Å (to C2/C3), considerably shorter
that the rest [2.535(4)/2.523(4) Å for Rh–C1 and Rh–C4
and 2.688(4)/2.682(4) Å, for Rh–C19 and Rh–C20, respec-
tively]. The Rh centre adopts a pseudo T-shaped geometry,
coordinated to two phosphanes and an alkene (C2/C3).
This orientation of the metal fragment places one phos-
phane over the arene ring-system (P2) and one off the side
(P1), giving the molecule approximate Cs symmetry. A very
slight hinging about the C1–C4 axis (2.3°) displaces C2 and
C3 above the plane of the rest of the ligand, which is essen-
tially planar (sum of least-squares: 0.04 Å2). The cations
pack graphitically (Bernal stacking) in the extended lattice,
Figure 9, with an average interlayer separation of 3.39(4) Å.
As far as we are aware complex 9 is the first transition metal
complex of coronene that has been crystallographically
characterized, although AgI [16] and CuI [43] complexes have
been reported, both of which show η2-metal–ligand interac-
tions in the solid-state.
Figure 7. Solid-state structure of the cationic portion of complex
8. See Figure 1 legend for details. Selected distances [Å]: Rh1–C1
2.540(4), Rh1–C2 2.346(3), Rh1–C3 2.312(3), Rh1–C4 2.252(3),
Rh1–C5 2.286(3), Rh1–C6 2.535(3), Rh1–P1 2.2927(9), Rh1–P2
2.2603(9). Selected angle: P1–Rh1–P2 95.13(3)°.
The solution NMR spectroscopic data for complex 8
show that the metal fragment remains coordinated to one
of the triphenylene rings in solution. Thus two, upfield-
shifted, multiplets (2H) are observed at δ = 7.16 and 6.86
and are assigned to the aromatic ring coordinated to the
{Rh(PiBu3)2}+ fragment. The remaining signals observed
between δ = 8.73 and 7.77, in the ratio 2:2:2:2, are essen-
tially unshifted from free triphenylene (δ = 8.64 and 7.64 in
CDCl3). In the crystal structure the arene in 8 is not rigor-
ously planar, with the two rings furthest away from the
metal puckered slightly such that they become inequivalent.
The fact that these rings also become equivalent on the
NMR timescale suggests that this distortion is not energeti-
cally significant. The 31P{1H} NMR spectrum displays a
single environment at δ = 18.7 [J(RhP) = 200 Hz]. In the
13C{1H} NMR spectrum 103Rh coupling is observed for
only two 13C environments, δ = 99.1 [d, J(RhC) = 3 Hz]
and δ = 86.4 [d, J(RhC) = 3 Hz]. A single environment ob-
served for the iBu methyl groups in both the room tempera-
ture 1H and 13C{1H} NMR spectra, consistent with a rapid
rotation of the metal fragment on the coordinated arene, as
noted for 3 and 4.
Attempts to measure NMR spectra for complex 9 at
room temperature were frustrated by decomposition in the
absence of excess arene ligand. To attenuate this problem a
sample in CD2Cl2 was frozen (liquid N2) and placed in a
pre-cooled spectrometer at 190 K. On warming to 210 K
decomposition starts to occur rapidly and free coronene (δ
= 8.8 ppm) appears in the spectrum. At 190 K five distinct
resonances are observed for the arene in the 1H NMR spec-
trum, in the ratio 4:2:2:2:2. The highest-field resonance
(2H) is shifted considerably from the others (δ = 6.4 vs.
8.50–7.81 ppm) indicating that the η2-coordination ob-
served in the solid-state persists in solution. The 31P{1H}
NMR spectrum at 190 K shows two sets of resonances
(doublets of doublets) in a 1:1 ratio, very similar to those
assigned to the pyrene complex 7B at 190 K: δ = 45.2
Coronene
The structure of [Rh(PiBu3)2(coronene)][BArF4] 9 is [J(RhP) 237, J(P,P) = 36 Hz], δ = 13.0 [J(RhP) = 191, J(P,P)
shown in Figure 8. = 36 Hz]. These data suggest that the metal fragment lies
1620
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Eur. J. Inorg. Chem. 2011, 1614–1625

From Benzene to Polyaromatic Hydrocarbons, Part I
tions sandwiched between two HBC rings. These outward
facing arene rings show relatively close π-π stacking with a
distance between arenes of 3.6(1) Å. As far as we are aware
there is only one other crystallographically characterized
example of a metal fragment coordinated to HBC, the
{Cr(CO)3} complex reported by Mullen and co-workers.[22]
In this example the {Cr(CO)3} fragment is also coordinated
to one of the outer arene rings, and there is a similar in-
terplanar spacing of 3.59 Å.
Figure 9. Packing diagram of 9 showing the interplanar separation
of 3.39(4) Å.
on a reflection plane with the phosphanes asymmetrically
disposed, as observed in the solid-state structure. Further
support for this solution structure comes from inspection
1
of the iBu region of the low-temperature H NMR spec-
trum, which shows two sets of distinct environments. A
broad set of multiple resonances between δ = 2.1–0.3 that
integrates to 48 H is partnered with a broad signal centered
at δ = –0.55 ppm that integrates to 6 H. We assign this
upfield shifted peak to a set of methyl groups from one iBu
ligand sitting directly over the surface of the arene ring and
experiencing ring-current effects.[44] Due to decomposition
at temperatures much above 200 K, we were unable to es-
tablish whether fluxional processes analogous to those oc-
curring in the pyrene complex are accessible close to room
temperature.
Figure 10. Solid-state structure of complex 10. Only one of the dis-
ordered {Rh(COD)} components is shown. Hydrogen atoms and
–
the [BArF
]
4
anion are omitted. Thermal ellipsoids are shown at
the 30% probability level. See Figure 1 legend for details.
HBC
Addition of 1 to HBC in CH2Cl2 solution did not result
in a reaction, with separate metal and ligand (HBC) frag-
ments observed in solution. Reasoning that the bulky HBC
ligand might bind very weakly, and therefore be unable to
displace the fluorobenzene ligand in 1, we also tried the
arene-free synthon [Rh(PiBu3)2][BArF4],[30] but without suc-
cess. However, the less sterically demanding {Rh(COD)}+
fragment does bind to HBC: addition of 0.5 equiv. of
Figure 11. Packing diagram of 10 showing the interplanar separa-
tion of 3.6(1) Å.
The solution NMR for 10 are consistent with the solid-
[Rh(COD)Cl]2/Na[BArF4] to HBC in CH2Cl2 solution re- state data, both indicating a Cs-symmetric structure. The 1H
sulted in the formation of
a
new complex NMR spectrum shows four tBu environments in the ratio
[Rh(COD)(HBC)][BArF
]
(10), dark-brown crystals of 9:9:18:18 H. Six distinct aromatic environments between δ
4
which could be isolated in 83% yield. The solid-state struc- = 9.59 and 8.06 are observed in the ratio 2:2:2:2:2:2 H. We
ture of 10 is shown in Figure 10. Complex 10 crystallises suggest the highest field resonance is that associated with
with the {Rh(COD)}+ fragment disordered equally over the bound metal fragment (H10/H38). Resonances due to
two chemically equivalent sites on the outermost, tBu-sub- the COD ligand are also observed. The 13C{1H} gives com-
stituted, arene rings, that are related by a reflection across plementary information, with four iBu environments and a
the centre of the ligand. The metal fragment is bound η6, total of 24 aromatic environments observed, four of which
with Rh–C distances spanning a narrow range 2.342(4)– show coupling to 103Rh. These data show that the metal is
2.382(4) Å. In the extended lattice (Figure 11) the not mobile over the surface of the PAH ring on the NMR
{Rh(COD)}+ fragments occupy mutually adjacent posi- timescale.
Eur. J. Inorg. Chem. 2011, 1614–1625
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1621

A. S. Weller et al.
FULL PAPER
(0.030 g, 0.021 mmol, 2.2 equiv.) and 6-tBu-HBC (0.010 g,
0.012 mmol, 2 equiv.) CH2Cl2 (3 cm3) was added and stirred for
5 min. The solution was layered with pentane at room temperature;
Conclusions
This paper has set out a detailed experimental investiga-
tion of the {Rh(PiBu3)2}+ fragment bound to progressively slow diffusion of the pentane led to isolated product crystal forma-
tion over 48 h. Crystals obtained were washed with pentane
larger PAH ligands. With naphthalene, anthracene and tri-
phenylene the metal fragment adopts an η4-coordination
mode (16-electron at metal) and is not fluxional over the
surface of the ligand. For pyrene and coronene the observed
hapticities are lower, η3 and η2, and the metal fragment is
fluxional over the surface of the ligand at low temperatures,
or at the very least much more weakly bound. In the follow-
ing paper a computational analysis leads to a detailed pic-
tured of the underlying factors that drive both the equilib-
rium structures and dynamic processes (for pyrene and co-
ronene) occurring in these systems.
(3ϫ10 cm3).
[Rh(benzene)(PiBu3)2][BArF4] (2): 1H NMR (CD2Cl2, 500 MHz,
290 K): δ = 7.72 (br., 8 H, BArF4), 7.56 (s, 4 H, BArF4), 6.48 (s, 6
H, HAr), 2.00–1.89 (m, 6 H, PCH2CH), 1.56 (dd, JHH = 8, JHP
=
2 Hz, 12 H, CH2), 1.08 (d, JHH = 7 Hz, 36 H, Me) ppm. 31P{1H}
1
NMR (CD2Cl2, 121 MHz, 290 K): δ = 25.6 (d, JRhP = 198 Hz)
ppm. 13C{1H} NMR (CD2Cl2, 126 MHz, 290 K): δ = 162.31 (q,
2
1JBC = 50 Hz, BArF4), 135.36 (s, BArF4), 129.43 (qq, JFC = 32,
1
4JBC = 3 Hz, BArF4), 125.16 (q, JFC = 272 Hz, BArF4), 118.14–
1
117.93 (m, BArF4), 101.31 (d, JRhC = 2 Hz, CAr), 39.96–39.81 (m,
CH2), 26.89 (s, Me), 25.64–25.58 (m, PCH2CH) ppm.
[Rh(tert-butylbenzene)(PiBu3)2][BArF
]
(3): 1H NMR (CD2Cl2,
4
500 MHz, 290 K): δ = 7.72 (br., 8 H, BArF4), 7.56 (s, 4 H, BArF4),
Experimental Section
7.23 (t, JHH = 6 Hz, 1 H, H4), 6.18 (d, JHH = 6 Hz, 2 H, H2), 5.92
(t, JHH = 6 Hz, 2 H, H3), 1.98 (m, 6 H, PCH2CH), 1.58 (dd, JHH
General: All manipulations, unless otherwise stated, were per-
formed under an atmosphere of argon, using standard Schlenk and
glove-box techniques. Glassware was oven dried at 130 °C over-
night and flamed under vacuum prior to use. CH2Cl2, and pentane
were dried using a Grubbs type solvent purification system (M.
Braun SPS-800) and degassed by successive freeze-pump-thaw cy-
1
= 6, JHP = 2 Hz, 12 H, CH2), 1.38 (s, 9 H, tBu), 1.07 (d, JHH
=
7 Hz, 36 H, Me2) ppm. 31P{1H} NMR (CD2Cl2, 121 MHz, 290 K):
δ = 26.1 (d, JRhP = 203 Hz) ppm. 13C{1H} NMR (CD2Cl2,
126 MHz, 290 K): δ = 162.32 (q, JBC = 50 Hz, BArF4), 142.08 (s,
C1), 135.36 (s, BArF4), 129.42 (qq, JFC = 32, JBC = 3 Hz, BArF4),
125.17 (q, JFC = 272 Hz, BArF4), 118.23–117.92 (m, BArF4), 105.71
cles.[45] [RhCl(COD)]2, [Rh(PiBu3)2][BArF4],[30] [Rh(C6H5F)-
1
(s, C4), 97.58 (s, JRhC = 2 Hz, C2), 95.28 (s, JRhC = 2 Hz, C3),
[46]
(PiBu3)2][BArF4] (1),[30] and Na[BArF
]
were prepared by litera-
4
40.22–39.91 (m, CH2), 34.70 (s, CtBu), 31.38 (s, tBu), 26.85–26.44
(m, Me), 25.69 (s, PCH2CH) ppm.
ture methods. All other liquid substrates were degassed by freeze-
pump-thaw cycles and stored under argon over 3 Å molecular si-
eves; solid substrates were used as received from supplier. CD2Cl2
was distilled under vacuum from CaH2 and stored over 3 Å molec-
ular sieves. HBC was prepared by the published procedure.[22] All
other materials were purchased from commercial sources. All the
new complexes discussed have been characterized in solution by
NMR spectroscopy. Unless stated NMR spectra were recorded in
CD2Cl2 solutions. Assignments were aided by 1H-1H COSY and
HSQC experiments. NMR spectra were recorded on a Bruker AVC
500 MHz or a Varian Unity Plus 500 MHz spectrometer at 298 K
unless otherwise stated. All samples, deuterated and non-deuter-
ated, were locked and referenced to CD2Cl2 (1 H δ = 5.32 ppm).
[Rh(naphthalene)(PiBu3)2][BArF
]
(4): 1H NMR (CD2Cl2,
4
500 MHz, 290 K): δ = 7.72 (br., 8 H, BArF4), 7.56 (s, 4 H, BArF4),
7.54–7.46 (m, 4 H, H7 and H8), 6.76–6.72 (m, 2 H, H1), 6.06–6.01
(m, 2 H, H2), 1.85–1.73 (m, 6 H, PCH2CH), 1.59 (dd, JHH = 8,
JHP = 2 Hz, 12 H, CH2), 1.00 (d, JHH = 7 Hz, 36 H, Me) ppm.
31P{1H} NMR (CD2Cl2, 121 MHz, 290 K): δ = 16.7 (d, JRhP
=
196 Hz) ppm. 13C{1H} NMR (CD2Cl2, 126 MHz, 290 K): δ =
162.31 (q, JBC = 50 Hz, BArF4), 135.36 (s, BArF4), 130.31 (s, C7 or
C8), 129.42 (qq, JFC = 31, JBC = 3 Hz, BArF4), 127.49 (s, C5),
125.27 (s, C7 or C8), 125.16 (q, JFC = 272 Hz, BArF4), 118.16–
117.94 (m, BArF4), 96.01 (d, JRhC = 3 Hz, C1), 89.51 (d, JRhC
=
3 Hz, C2), 39.06–38.80 (m, CH2), 26.63 (s, Me), 25.54–25.26 (m,
General Synthetic Methodology for Compounds 2 to 9: To a Young
crystallisation tube containing 1 (0.030 g, 0.021 mmol), the relevant
arene ligand (0.102 mmol, 5 equiv.) and CH2Cl2 (3 cm3) were added
and stirred for 5 min. The solution was layered with pentane at
room temperature; slow diffusion of the pentane led to crystallisa-
tion isolated product formation over 1–4 d. Crystals obtained were
washed with pentane (3ϫ10 cm3). Yields and microanalytical data
are presented in Table 1.
PCH2CH) ppm.
1
[Rh(anthracene)(PiBu3)2][BArF4] (5): H NMR (CD2Cl2, 500 MHz,
290 K): δ = 7.94 (s, 2 H, H3), 7.89–7.84 (m, H4 or H5), 7.72 (br., 8
H, BArF4), 7.61–7.58 (m, H4 or H5), 7.56 (s, 4 H, BArF4), 6.55–
6.49 (m, 4 H, H2), 6.09–6.04 (m, 4 H, H1), 1.81–0.85 (m, iBu) ppm.
1
31P{1H} NMR (CD2Cl2, 121 MHz, 290 K): δ = 13.6 (d, JRhP
=
191 Hz) ppm.
[Rh(COD)(6-tBu-HBC)][BArF4] (10): To a Young crystallisation
[{Rh(PiBu3)2}2(anthracene)][BArF
]
(6): 1H NMR (CD2Cl2,
4 2
tube containing [RhCl(COD)]2 (0.003 g, 0.006 mmol), Na[BArF
]
4
500 MHz, 290 K): δ = 7.72 (br., 8 H, BArF4), 7.56 (s, 4 H, BArF4),
Table 1. Isolated yields and analytical data for the new complexes.
Complex
Mass [mg]
Yield [%]
Crystal colour
Calcd. C, H (%)
Found C, H (%)
2
26.8
23.1
25.8
49.7
26.1
26.9
18.6
33.7
88
73
82
81
79
80
53
83
red-brown
red-brown
brown
dark-blue
yellow-brown
brown
52.47, 5.08
53.67, 5.36
52.89, 4.98
54.28, 4.95
54.98, 4.87
55.58, 4.92
57.50, 4.70
65.84, 4.69
52.32, 4.84
53.15, 5.46
52.32, 4.84
53.80, 5.30
54.13, 4.70
55.42, 4.64
56.60, 5.41
65.76, 4.72
3
4
6
7
8
9
dark-brown
dark-brown
10
1622
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 1614–1625

From Benzene to Polyaromatic Hydrocarbons, Part I
7.34 (s, 2 H, H7), 6.68–6.63 (m, 4 H, H1), 5.79–5.74 (m, 4 H, H2), 190 K): δ = 46.8 [dd, JRhP = 243, JPP = 37 Hz, P1], 21.8 [d, JRhP
=
1.81–0.85 (m, iBu) ppm. 31P{1H} NMR (CD2Cl2, 121 MHz,
209 Hz, outer-RhP2], 13.5 (dd, JRhP = 181, JPP = 37 Hz, P2) ppm.
1
290 K): δ = 14.4 (d, JRhP = 190 Hz) ppm.
13C{1H} NMR (CD2Cl2, 500 MHz, 190 K): δ = 132.3 (CD), 129.8
(CH), 128.3 (CE), 124.0 (CC), 122.6 (CF), 120.7 (CJ), 114.9 (Ci),
112.1 (CG), 98.9 (CA), 91.0 (CB), 130.7 (CVII), 127.9 (CII & CV),
127.3 (CIV), 124.9 (CI), 120.5 (CVI), 117.2 (CVIII), 84.4 (CIII). See
Scheme 6 for labelling scheme.
[Rh(pyrene)(PiBu3)2][BArF4] (7): 1H NMR (CD2Cl2, 500 MHz,
290 K): δ = 7.9 (br., 10 H, HAr), 7.72 (br., 8 H, BArF4), 7.56 (s, 4
H, BArF4), 1.76 (br., 6 H, PCH2CH), 1.36 (br., 12 H, CH2), 0.94
(d, JHH = 6 Hz, 36 H, Me) ppm. 31P{1H} NMR (CD2Cl2,
1
121 MHz, 290 K): δ = 44.2 (vbr.), 22.1 (vbr.), 13.7 (vbr.) ppm. H
[Rh(triphenylene)(PiBu3)2][BArF
]
4
(8): 1H NMR (CD2Cl2,
NMR (CD2Cl2, 500 MHz, 190 K): δ = 8.21 (d, JHH = 6.24 Hz, He),
8.20 (d, JHH = 6.24 Hz, Hd), 8.02 (f, JHH = 6.24 Hz, Hf), 7.65 (d,
500 MHz, 290 K): δ = 8.73 (d, JHH = 8 Hz, 2 H, H16), 8.39 (d, JHH
= 8 Hz, 2 H, H17), 7.87 (t, JHH = 7 Hz, 2 H, H16 or H15), 7.77 (t,
JHH = 7 Hz, 2 H, H16 or H15), 7.72 (br., 8 H, BArF4), 7.56 (s, 4 H,
BArF4), 7.19–7.14 (m, 2 H, H2), 6.89–6.82 (m, 2 H, H1),1.72–1.60
1JHH = 9.03 Hz, Hc), 7.45 (t, JHH = 6.24 Hz, Ha), 6.70 (d, JHH
=
6.24 Hz, Hb), 8.14 (d, JHH = 7.55 Hz, HIV), 8.05 (d, JHH = 7.90 Hz,
HII), 7.95 (vt, JHH = 7.9 Hz, HI), 6.44 (s, HIII), 1.50 (s, 6 H, (m, 6 H, PCH2CH), 1.48 (dd, JHH = 7, JHP = 2 Hz, 12 H, CH2),
PCH2CH), 1.20 (s, 6 H, PCH2), 0.74 (d, JHH = 7 Hz, 36 H, Me), 0.86 (d, JHH = 7 Hz, 36 H, Me) ppm. 31P{1H} NMR (CD2Cl2,
1
0.41 (s br, 6 H, PCH2) ppm. 31P{1H} NMR (CD2Cl2, 121 MHz, 121 MHz, 290 K): δ = 18.7 (d, JRhP = 200 Hz) ppm. 13C{1H}
Table 2. Crystallographic data.
2
3
4
6
Formula
M
C62H72BF24P2Rh
1448.86
C66H80BF24P2Rh
1504.96
C66H74BF24P2Rh
1498.91
C126H142B2F48P4Rh2
2919.72
T [K]
Crystal System
Space group
210(2)
monoclinic
P21/n
150(2)
monoclinic
P21/c
150(2)
monoclinic
P21/c
150(2)
triclinic
¯
P1
a [Å]
b [Å]
c [Å]
α [°]
22.00140(10)
13.16180(10)
25.5819(2)
90
113.9717(3)
90
6768.99(8)
4
1.422
13.31840(10)
13.50660(10)
39.2845(2)
90
98.5126(3)
90
6988.89(8)
4
1.430
19.7734(2)
13.57780(10)
25.6956(2)
90
97.5578(4)
90
6838.80(10)
4
1.456
12.74970(10)
16.0482(2)
17.8161(2)
75.1320(6)
89.9429(5)
81.2896(5)
3479.93(6)
1
β [°]
γ [°]
V [Å3]
Z
Density [gcm–3]
1.393
0.392
μ [mm–1]
0.402
0.393
0.401
θ range [°]
Reflections collected
Rint
5.10Յ θ Յ25.03
23091
0.0185
5.12Յ θ Յ26.37
27115
0.0293
5.10Յ θ Յ26.37
24998
0.0193
5.09Յ θ Յ26.37
24985
0.0269
Data/restraints/parameters
R1 [IϾ2σ(I)]
11839/2326/1282
0.0587
0.1685
1.018
0.729, –0.813
14114/1798/1235
0.0489
0.1319
1.039
1.163, –1.514
13815/1154/1112
0.0411
0.1055
1.023
0.808, –0.488
14093/1716/1154
0.0464
0.1339
1.079
0.682, –0.574
wR2 [all data]
GoF
Largest diff. pk and hole [eÅ–3]
7
8
9
10
Formula
M
C73H78BCl2F24P2Rh
1657.91
C74H78BF24P2Rh
1599.02
C80H78BF24P2Rh
1671.08
C106H90BF24Rh
1933.50
T [K]
Crystal System
Space group
150(2)
150(2)
orthorhombic
Pbca
150(2)
150(2)
triclinic
triclinic
triclinic
¯
¯
¯
P1
P1
P1
a [Å]
b [Å]
c [Å]
α [°]
20.0331(2)
20.1330(2)
21.1109(2)
110.3310(5)
105.1706(5)
100.2469(4)
7358.12(12)
4
18.43130(10)
24.51990(10)
32.3168(2)
90
90
90
14605.05(13)
8
1.454
14.8314(2)
17.7262(2)
18.1889(3)
113.5908(6)
106.7840(7)
97.4030(7)
4029.53(10)
2
13.66330(10)
19.4347(2)
21.1239(3)
107.3148(5)
94.1354(5)
97.9542(6)
5265.36(10)
2
β [°]
γ [°]
V [Å3]
Z
Density [gcm–3]
1.497
0.451
1.377
0.348
1.220
0.247
μ [mm–1]
0.381
θ range [°]
Reflections collected
Rint
5.13Յ θ Յ26.37
50990
0.0222
5.10Յ θ Յ26.37
97799
0.0675
5.12Յ θ Յ25.03
29289
0.0220
5.13Յ θ Յ26.37
37185
0.0279
Data/restraints/parameters
R1 [IϾ2σ(I)]
29393/1313/2180
0.0416
0.1136
1.034
0.640, –0.603
14812/1134/1170
0.0462
0.1259
1.033
0.797, –0.556
16326/2202/1414
0.0627
0.1924
1.065
0.939, –0.680
21347/1795/1622
0.0901
0.2535
1.057
1.695, –0.610
wR2 [all data]
GoF
Largest diff. pk and hole [eÅ–3]
Eur. J. Inorg. Chem. 2011, 1614–1625
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1623

A. S. Weller et al.
FULL PAPER
NMR (CD2Cl2, 126 MHz, 290 K): δ = 162.31 (q, JBC = 50 Hz,
data for the exchange process in 7; Figure S2, Eyring plot and
BArF4), 135.37 (s, BArF4), 131.22 (s, C8), 130.19 (s, C15), 129.42 activation parameters for the exchange process in 7.
(qq, JFC = 31, JBC = 3 Hz, BArF4), 129.02 (s, 2 H, C16), 126.00 (s,
2 H, C13), 125.16 (q, JFC = 272 Hz, BArF4), 124.73 (s, 2 H, C14),
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Germany, 2006.
BArF4), 99.07 (d, JRhC = 3 Hz, 2 H, C2), 86.37 (d, JRhC = 3 Hz, 2
[2] S. M. Hubig, S. V. Lindeman, J. K. Kochi, Coord. Chem. Rev.
H, C3), 39.03–38.64 (m, CH2), 26.46 (s, Me), 25.50–25.11 (m,
2000, 200, 831–873.
PCH2CH) ppm.
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290 K): δ = 8.52 (vbr, 12 H, HAr), 7.72 (br., 8 H, BArF4), 7.56 (s,
4 H, BArF4), 2.02 (br., 6 H, PCH2CH), 1.55 (br., 12 H, CH2), 0.58
(br., 36 H, Me) ppm. 31P{1H} NMR (CD2Cl2, 121 MHz, 290 K):
δ = 48.4 (br.), 26.4 (br.) ppm. 1H NMR (CD2Cl2, 500 MHz, 200 K):
δ = 8.72 (obscured, HAr), 8.35 (s, 2 H, H), 8.32 (d, JHH = 7 Hz, 2
H, H), 8.18–8.11 (m, 4 H, H), 7.90 (d, JHH = 7 Hz, 2 H, 2 H), 7.72
(br., 8 H, BArF4), 7.56 (s, 4 H, BArF4), 1.86 (br.), 1.45 (br.), 0.81
(t, 6 H), –0.45 (br., 6 H, Me on P2) ppm. 31P{1H} NMR (CD2Cl2,
121 MHz, 190 K): δ = 45.2 (dd, JRhP = 237, JPP = 36 Hz, P1), 13.0
(dd, JRhP = 191, JPP = 36 Hz, P2) ppm.
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[Rh(6-tBu-HBC)(COD)][BArF4] (10): 1H NMR (CD2Cl2, 500 MHz,
290 K): δ = 9.59 (s, 2 H, HAr), 9.48 (s, 2 H, HAr), 9.45 (s, 2 H,
HAr), 9.42 (s, 2 H, HAr), 8.82 (s, 2 H, HAr), 8.06 (s, 2 H, H1), 7.72
(br., 8 H, BArF4), 7.56 (s, 4 H, BArF4), 3.73 (s, 4 H, C4H8C4H4),
1.96 (s, 9 H, tBu), 1.86 (s, 9 H, tBu), 1.85 (s, 18 H, tBu), 1.81 (s,
18 H, tBu), 1.60 (s, 8 H, C4H8C4H4) ppm. 13C{1H} NMR (CD2Cl2,
126 MHz, 290 K): δ = 151.82 (d, JRhC = 3 Hz, CAr), 151.60 (s, CAr),
135.35 (s, BArF4), 132.38 (s, CAr), 131.35 (d, JRhC = 4 Hz, CAr),
130.30 (s, CAr), 129.44 (qq, JFC = 32, JBC = 3 Hz, BArF4), 125.14
(q, JFC = 272 Hz, BArF4), 125.02 (s, CAr), 124.82 (s, CAr), 124.23
(s, CAr coupled to HAr), 123.72 (s, CAr), 123.62 (s, CAr), 122.47 (s,
CAr), 121.09 (s, CAr coupled to HAr), 120.92 (s, CAr coupled to
HAr), 120.87 (s, CAr), 120.54 (s, CAr coupled to HAr), 120.38 (s, CAr
coupled to HAr), 120.06 (s CAr), 118.22–117.93 (m, BArF4), 115.13
(s CAr), 109.13 (s CAr), 108.87 (d, JRhC = 2 Hz, CAr), 102.78 (s
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CAr), 91.48 (d, JRhC = 2 Hz, C1), 83.45 (d, JRhC = 13 Hz, C2),
36.44 (t, CtBu coupled to HtBu), 32.19 (s, tBu), 32.05 (s, tBu), 31.25
(s, tBu), 31.17 (s, tBu) ppm.
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Crystallography: Relevant details about the structure refinements
are given in Table 2. Data were carried on an Enraf Nonius Kappa
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www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 1614–1625

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Received: December 2, 2010
Published Online: February 21, 2011
Eur. J. Inorg. Chem. 2011, 1614–1625
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1625