The substitution chemistry of the tris(3,5-dimethylpyrazolyl)-methanerhodium complex [Rh(CO)2{HC(pz′)3}]+

Article abstract of DOI:10.1039/b302440g

The complex [Rh(CO)₂{HC(pz′)₃}][PF₆], 1 ⁺[PF₆]^- {HC(pz′)₃ = tris(3,5-dimethylpyrazolyl)methane}, prepared by reacting [{Rh(CO)₂(μ-Cl)}₂] with HC(pz′)₃ in the presence of Tl[PF₆], has a distorted square pyramidal structure with a κ³-HC(pz′)₃ ligand. Carbonyl substitution with Lewis bases gives [Rh(CO)L{HC(pz′)₃}] [PF₆] {L = PPh₃, 2⁺[PF₆]^-; L = AsPh₃, 3⁺[PF₆]^-; L = P(o-tolyl)₃, 4⁺[PF₆]^-}, which have square planar κ² structures, confirmed by X-ray crystallography for 2⁺[PF₆]^-. The cations 2⁺ and 3⁺ have the third pyrazolyl ring orientated pseudo-parallel to the square planar metal whereas 4⁺ more likely has the third ring orientated exo to that plane. One-electron oxidation of 2⁺ and 3⁺ gives the Rh(II) dications [Rh(CO)(PPh₃){HC(pz′)₃}]²⁺, 2²⁺, and [Rh(CO)(AsPh₃){HC(pz′)₃}]²⁺, 3²⁺, characterised by ESR spectroscopy. Complex 1⁺[PF₆]^- reacts with PhC≡CPh to give [Rh(CO)(η²-PhC≡CPh)-{HC(pz′)₃}] [PF₆], 5⁺[PF₆]^-, in which the two-electron donor alkyne occupies an equatorial position in a trigonal bipyramidal κ³ structure. With MeC≡CR (R = Me or Et), 1⁺[PF₆]^- gives the κ² square planar complexes [Rh{η⁴-C₄Me₂R₂C(O)}{HC(pz′ )₃}][PF₆] (R = Me, 6⁺[PF₆]^-; R = Et, 7⁺[PF₆]^-) in which the cyclopentadienone ligands are coordinated via two Rh-monoalkene bonds; the structurally characterised form of 7⁺ has the two alkyne units linked head-to-head with the CEt termini bound to the ketonic CO group. With HC≡CPh or HC≡CH, 1⁺ gives the octahedral, κ³ rhodium(III) metallacyclopentadienes [Rh(CO)(η¹:η^1′-CHCRCHCR) {HC(pz′)₃}][PF₆] (R = Ph, 8⁺[PF₆]^-; R = H, 9⁺[PF₆]^-) with the two alkynes linked head-to-tail in 8⁺. The reaction of 1⁺ with HC≡CH also gives the cycloheptatrienone (tropone) derivative [Rh{η⁴-C₆H₆C(O)}{HC(pz′)₃} ][PF₆], 10⁺[PF₆]^-, with a κ³ ligand and the cycloheptatrienone ligand bound to the metal via two Rh-C σ-bonds and one Rh-monoalkene interaction.

Full text of DOI:10.1039/b302440g

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The substitution chemistry of the tris(3,5-dimethylpyrazolyl)-
methanerhodium complex [Rh(CO)2{HC(pzЈ)3}]؉
Christopher J. Adams,a Neil G. Connelly,*a David J. H. Emslie,a Owen D. Hayward,a
Tania Manson,a A. Guy Orpena and Philip H. Riegerb
a School of Chemistry, University of Bristol, Bristol, UK BS8 1TS
b Department of Chemistry, Brown University, Rhode Island, RI 02912, USA
Received 3rd March 2003, Accepted 23rd May 2003
First published as an Advance Article on the web 20th June 2003
The complex [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ {HC(pzЈ)3 = tris(3,5-dimethylpyrazolyl)methane}, prepared by
reacting [{Rh(CO)2(µ-Cl)}2] with HC(pzЈ)3 in the presence of Tl[PF6], has a distorted square pyramidal structure
with a κ3-HC(pzЈ)3 ligand. Carbonyl substitution with Lewis bases gives [Rh(CO)L{HC(pzЈ)3}][PF6] {L = PPh3,
2ϩ[PF6]Ϫ; L = AsPh3, 3ϩ[PF6]Ϫ; L = P(o-tolyl)3, 4ϩ[PF6]Ϫ}, which have square planar κ2 structures, confirmed by X-ray
crystallography for 2ϩ[PF6]Ϫ. The cations 2ϩ and 3ϩ have the third pyrazolyl ring orientated pseudo-parallel to the
square planar metal whereas 4ϩ more likely has the third ring orientated exo to that plane. One-electron oxidation
of 2ϩ and 3ϩ gives the Rh() dications [Rh(CO)(PPh3){HC(pzЈ)3}]2ϩ, 22ϩ, and [Rh(CO)(AsPh3){HC(pzЈ)3}]2ϩ, 32ϩ
,
ϩ
Ϫ
2
᎐
᎐
characterised by ESR spectroscopy. Complex 1 [PF ] reacts with PhC᎐CPh to give [Rh(CO)(η -PhC᎐CPh)-
᎐
᎐
6
{HC(pzЈ)3}][PF6], 5ϩ[PF6]Ϫ, in which the two-electron donor alkyne occupies an equatorial position in a trigonal
3
ϩ
Ϫ
2
᎐
bipyramidal κ structure. With MeC᎐CR (R = Me or Et), 1 [PF ] gives the κ square planar complexes
᎐
6
[Rh{η4-C4Me2R2C(O)}{HC(pzЈ)3}][PF6] (R = Me, 6ϩ[PF6]Ϫ; R = Et, 7ϩ[PF6]Ϫ) in which the cyclopentadienone
ligands are coordinated via two Rh–monoalkene bonds; the structurally characterised form of 7ϩ has the two alkyne
ϩ
᎐
᎐
units linked head-to-head with the CEt termini bound to the ketonic CO group. With HC᎐CPh or HC᎐CH, 1 gives
᎐
᎐
the octahedral, κ3 rhodium() metallacyclopentadienes [Rh(CO)(η1:η1Ј-CHCRCHCR){HC(pzЈ)3}][PF6] (R = Ph,
ϩ
Ϫ
ϩ
Ϫ
ϩ
ϩ
᎐
8 [PF ] ; R = H, 9 [PF ] ) with the two alkynes linked head-to-tail in 8 . The reaction of 1 with HC᎐CH also
᎐
6
6
gives the cycloheptatrienone (tropone) derivative [Rh{η4-C6H6C(O)}{HC(pzЈ)3}][PF6], 10ϩ[PF6]Ϫ, with a κ3 ligand
and the cycloheptatrienone ligand bound to the metal via two Rh–C σ-bonds and one Rh–monoalkene interaction.
elemental analysis, IR (Table 1) and NMR spectroscopy (Table
2) and X-ray crystallography.
Introduction
Tris(3,5-dimethylpyrazolyl)methane, HC(pzЈ)3, is a neutral
analogue of the hydrotris(3,5-dimethylpyrazolyl)borate anion,
[HB(pzЈ)3]Ϫ (TpЈϪ), and may also be considered related to
arenes, C6R6, in that both are neutral six-electron donors
(cf. the formal relationship between TpЈϪ and the cyclopenta-
dienide anions C5R5Ϫ). Rhodium complexes of hydrotris-
(pyrazolyl)borate anions are well studied,1–8 particularly
dicarbonyls such as [Rh(CO)2TpЈ] which act as photocatalysts
for the activation of hydrocarbons.9 By contrast, there are
relatively few rhodium complexes of tris(pyrazolyl)methane
ligands, e.g. [RhL2{HC(pz)3}][RhCl2L2] {pz = pyrazolyl, L2 =
cycloocta-1,5-diene (cod), norbornadiene (nbd), tetrafluoro-
benzobarrelene (tfb) or (CO)2}, [Rh(cod){HC(pz)3}][ClO4] and
[Rh(nbd){HC(pz)3}][PF6].10,11
The IR spectrum of 1ϩ[PF6]Ϫ in CH2Cl2 shows four carbonyl
bands, at 2099w, 2079s, 2039w and 2011s cmϪ1. For analogous
rhodium dicarbonyl hydrotris(pyrazolyl)borate complexes
three isomers have been identified (Fig. 1); ν(CO) is higher
in energy for the κ2 forms (A and B) than the κ3 form (C).4–7
Which of the three isomers is observed depends on the
pyrazolyl ring substituents (and, when CO substitution occurs,
on the ligand, L, of [Rh(CO)LTpЈ] 12). Thus, the IR spectrum
of 1ϩ suggests two isomers in solution, in an approximate 1 : 10
ratio, i.e. with κ2 (2099 and 2039 cmϪ1) and κ3 structures
(2079 and 2011 cmϪ1) respectively. By contrast, the Nujol
IR spectrum (Table 1) suggests 1ϩ[PF6]Ϫ exists only as the
κ3 isomer in the solid state, confirmed by X-ray crystal-
lography (see below), and as suggested for the hydrotris(3,5-
dimethylpyrazolyl)borate complex [Rh(CO)2TpЈ].4 (The
Our discovery12 that one-electron oxidation of [Rh(CO)LTpЈ]
{L = PPh3, P(NMe2)3, etc.} gave stable Rh() cations [Rh(CO)-
LTpЈ]ϩ led us to investigate the possibility of similar behaviour
for tris(3,5-dimethylpyrazolyl)methane analogues. We now
describe the synthesis of [Rh(CO)2{HC(pzЈ)3}][PF6] 1ϩ[PF6]Ϫ,
its reactions with Lewis bases, L, to give redox-active
[Rh(CO)L{HC(pzЈ)3}][PF6], and the isolation of a variety of
organometallic products with alkynes which differ from
those formed with the cyclopentadienyl analogues [Rh(CO)2-
(η-C5R5)] (R = H, Me, etc.).13–18
analogue [Rh(CO)2L] {L
= hydrotris(3-trifluoromethyl-5-
methylpyrazolyl)borate} does adopt7 the κ3 form in the solid
state, though the sterically crowded compound [Rh(CO)2L]
{L = hydrotris(3-phenyl-5-methylpyrazolyl)borate} has a κ2
structure.8)
The X-ray structure of 1ϩ[PF6]Ϫ (Fig. 2; selected bond lengths
and angles in Table 3) confirms the HC(pzЈ)3 ligand to be κ3
Results and discussion
Synthesis and characterisation of [Rh(CO)2{HC(pzЈ)3}][PF6],
1؉[PF6]؊
The reaction of [{Rh(CO)2(µ-Cl)}2] with two equivalents of
HC(pzЈ)3 in CH2Cl2 gave
a solution of [Rh(CO)2{HC-
(pzЈ)3}][Rh(CO)2Cl2]11 {and unreacted HC(pzЈ)3} to which two
equivalents of Tl[PF6] were added to give yellow crystals
of [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ, characterised by
Fig. 1 The isomers of [Rh(CO)2Tp].
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2835

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Fig. 2 The molecular structure of the cation of [Rh(CO)2{HC(pzЈ)3}-
][PF6], 1ϩ[PF6]Ϫ. Hydrogen atoms have been omitted for clarity.
co-ordinated with the rhodium atom in a distorted square
pyramid. The axial Rh(1)–N(2) bond (average value of 2.44 Å
for the two independent molecules in the unit cell) is longer
than the Rh(1)–N(4) and Rh(1)–N(6) bonds in the square plane
(average value 2.13 Å). The angles N(6)–Rh(1)–C(2) and N(4)–
Rh(1)–C(1) across this plane are less than 180Њ (average values
163.4 and 173.7Њ, respectively), and thus the molecule has
adopted an elevated square pyramidal geometry, raising the
rhodium atom above the square plane towards the apical
nitrogen atom. It therefore lies on the reaction coordinate for
the formation of trigonal bipyramidal complexes from square
pyramidal intermediates.19 This may be compared with the
flattened square pyramidal geometry adopted by [Rh(CO)-
{P(OPh)3}TpЈ], with a longer apical rhodium–nitrogen distance
of 2.764(2) Å, and angles across the basal plane of 176.0(1) and
178.0(1)Њ.12
Reactions of [Rh(CO)2{HC(pzЈ)3}][PF6], 1؉[PF6]؊
Cationic [Rh(CO)2{HC(pzЈ)3}]ϩ, 1ϩ, appears to be more
reactive towards Lewis bases than is the neutral analogue
[Rh(CO)2TpЈ].12 For example, the reaction of the latter with
PPh3 in n-hexane under reflux was complete only after 24
hours, whereas that between 1ϩ and PPh3 in CH2Cl2, to give
[Rh(CO)(PPh3){HC(pzЈ)3}][PF6], 2ϩ[PF6]Ϫ, was complete in five
minutes. In addition, [Rh(CO)2TpЈ] did not react with AsPh3
or P(o-tolyl)3 whereas 1ϩ and AsPh3 in CH2Cl2 gave a yellow
solution of [Rh(CO)(AsPh3){HC(pzЈ)3}][PF6], 3ϩ[PF6]Ϫ, after
four days, and heating a thf solution of 1ϩ[PF6]Ϫ with P(o-
tolyl)3 under reflux for two days gave [Rh(CO){P(o-tolyl)3}-
{HC(pzЈ)3}][PF6], 4ϩ[PF6]Ϫ. The reaction of 1ϩ with P(OPh)3
in CH2Cl2 for four hours gave a yellow solution showing ν(CO)
at 2030 cmϪ1, consistent with the formation of [Rh(CO)-
{P(OPh)3){HC(pzЈ)3}]ϩ, but the product could not be isolated.
With halides, HC(pzЈ)3 displacement occurs from 1ϩ, giving
the anions [RhX2(CO)2]Ϫ(X = Cl, Br, I).20 The reactions with
Lewis bases show, therefore, that although the additional
positive charge of 1ϩ (cf. neutral [Rh(CO)2TpЈ]) weakens the
Rh–CO bonds, leading to carbonyl substitution products
more readily, HC(pzЈ)3 is also more easily displaced, cf. the
hydrotris(3,5-dimethylpyrazolyl)borate anion.
Characterisation of [Rh(CO)L{HC(pzЈ)3}][PF6], 2؉[PF6]؊–
4؉[PF6]؊
Complexes 2ϩ[PF6]Ϫ–4ϩ[PF6]Ϫ were characterised by elemental
analysis and IR (Table 1) and 1H, 13C–{1H} and 31P NMR
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2836

Table 2 Proton, 13C–{1H} and 31P NMR spectroscopic data for rhodium tris(3,5-dimethylpyrazolyl)methane complexesa
Complex
1H
13C–{1H}
31P
[Rh(CO)2{HC(pzЈ)3}]
[PF6], 1ϩ[PF6]Ϫ
7.84 {s, 1H, HC(pzЈ)3}, 6.17 (s, 3H, pzЈ CH), 2.54 (d, 9H, J 1, pzЈ
CH3), 2.46 (s, 9H, pzЈ CH3)
185.83 (d, JC,Rh 71, CO), 154.48 (d, J 1, pzЈ CCH3), 142.93 (s, pzЈ
CCH3), 109.07 (s, pzЈ CH), 69.71 {s, HC(pzЈ)3}, 15.42 (s, pzЈ CH3),
11.29 (s, pzЈ CH3)
—
[Rh(CO)(PPh3){HC(pzЈ)3}]
[PF6], 2ϩ[PF6]Ϫ
7.68 {s, 1H, HC(pzЈ)3}, 7.50–7.35 (m, 15H, PPh3), 5.99 (s, 3H, pzЈ
CH), 2.26 (s, 9H, pzЈ CH3), 1.84 (s, 9H, pzЈ CH3)
188.13 (dd, JC,Rh 73, JC,P 24, CO), 154.27 (s, pzЈCCH3), 144.04 (s,
pzЈCCH3), 135–129 {m, P(C6H5)3}, 110.06 (s, pzЈCH), 75.04 {s,
HC(pzЈ)3}, 14.81 (s, pzЈCH3), 11.52 (s, pzЈCH3)
42.10 (d, JP,Rh 162, PPh3},
Ϫ144.45 {sept, JP, F 710, PF6)
[Rh(CO)(AsPh3){HC(pzЈ)3}]
[PF6], 3ϩ[PF6]Ϫ
7.76 {s, 1H, HC(pzЈ)3}, 7.50–7.35 (m, 15H, AsPh3), 5.99 (s, 3H,
pzЈ CH), 2.27 (s, 9H, pzЈ CH3), 1.86 (s, 9H, pzЈ CH3)
187.34 (d, JC,Rh 70, CO), 154.19 (s, pzЈ CCH3), 144.04 (s, pzЈ
CCH3), 133.6–129.5 {m, As(C6H5)3}, 109.89 (s, pzЈ CH), 75.00 {s,
HC(pzЈ)3}, 14.96 (s, pzЈ CH3), 11.50 (s, pzЈ CH3)
—
[Rh(CO){P(o-tolyl)3}{HC(pzЈ)3}]
[PF6], 4ϩ[PF6]Ϫ
8.00–6.85 {m, 12H, P(C6H4CH3)3}, 7.57 {s, 1H, HC(pzЈ)3}, 6.36 (s,
1H, pzЈ CH), 6.28 (s, 1H, pzЈ CH ), 5.89 (s, 1H, pzЈ CH), 3.64 {s,
3H, pzЈ CH3 or P(C6H4CH3)3}, 2.46 {s, 6H, pzЈ CH3 or
P(C6H4CH3)3}, 2.43, 1.85, 1.80, 1.49, 1.38, 1.21 {s, 3H, pzЈ CH3 or
P(C6H4CH3)3}.b
155.76 (s, pzЈ CCH3), 154.65 (s, pzЈ CCH3), 151.78 (s, pzЈ CCH3),
145.8–140.6 {m, 3 pzЈ CCH3 and P(C6H4CH3)3}, 133.0–126.1 {m,
P(C6H4CH3)3}, 111.74 (pzЈ CH), 109.54 (pzЈ CH), 108.63 (pzЈ
CH), 74.93 {HC(pzЈ)3}, 25.96 {P(C6H4CH3)3}, 23.27
{P(C6H4CH3)3}, 21.83 {P(C6H4CH3)3}, 16.1 (pzЈ CH3), 13.8 (pzЈ
CH3), 13.4 (pzЈ CH3), 12.1 (pzЈ CH3), 11.0 (pzЈ CH3)
184.53 (d, JC,Rh 68, CO), 156.90 (s, pzЈ CCH3), 154.59 (s, pzЈ
CCH3), 142.09 (s, pzЈ CCH3), 141.96 (s, pzЈ CCH3), 131.00,
129.70, 129.12, 128.70 (s, C6H5), 110.55 (s, pzЈ CH), 108.82 (s, pzЈ
CH), 82.50 (d, JC,Rh 16, CPh), 68.45 {s, HC(pzЈ)3}, 15.29 (s, pzЈ
CH3), 13.58 (s, pzЈ CH3), 11.50 (s, pzЈ CH3), 11.08 (s, pzЈ CH3)
191.28 (s, CO), 166.36 (d, JC,Rh 22), 157.16 (d, JC,Rh 3), 155.12 (d,
JC,Rh 6), 154.93 (s, pzЈ CCH3), 154.03 (s, pzЈ CCH3), 144.70 (s, pzЈ
CCH3), 143.39 (s, pzЈ CCH3), 142.74 (s, pzЈ CCH3), 142.08 (s, pzЈ
CCH3), 131.43 (s), 129.41, 129.21, 128.76, 128.71, 128.17, 127.37,
126.65, 126.38 (s, C6H5), 110.44 (s, pzЈ CH), 108.61 (s, pzЈ CH),
108.44 (s, pzЈ CH), 68.93 (s, CPh), 54.81 {s, HC(pzЈ)3}, 15.43 (s,
pzЈ CH3), 13.29 (s, pzЈ CH3), 11.79 (s, pzЈ CH3), 11.69 (s, pzЈ CH3),
10.82 (s, pzЈ CH3), 10.66 (s, pzЈ CH3)
161.73 {s, C4Me4C(O)}, 155.35 (s, pzЈ CCH3), 143.84 (s, pzЈ
CCH3), 111.44 (s, pzЈ CH), 95.89 (d, JC,Rh 12, C4Me4CO), 73.90 {s,
HC(pzЈ)3}, 72.31 (d, JC,Rh 9, C4Me4CO), 15.28 (s, pzЈ CH3), 13.01
(s, C4Me4CO), 11.46 (s, pzЈ CH3), 8.64 (s, C4Me4CO)
184.26 (d, JC,Rh 71, CO), 159.56 (d, J 2), 159.04 (s), 155.94 (d, J 4),
155.57 (s), 155.13 (s), 145.97 (s)d, 143.96 (d, JC,Rh 2, C3), 142.97 (s),
142.44 (d, J 6)d, 139.78 (d, JC,Rh 26, C1), 138.18 (d, J 2)d, 128.99,
128.74, 127.52, 127.30, 126.84, 125.40 (s, C6H5), 110.70 (s, pzЈ
CH), 109.38 (s, pzЈ CH), 109.23 (s, pzЈ CH), 68.78 {s, HC(pzЈ)3},
14.54 (s, pzЈ CH3), 12.99 (s, pzЈ CH3) 12.68 (s, pzЈ CH3), 11.63 (s,
pzЈ CH3), 11.26 (s, pzЈ CH3), 11.15 (s, pzЈ CH3)
30.44 {d, JP,Rh 159, P(o-tolyl)3},
Ϫ144.48 (sept, JP, F 711, PF6)
2
᎐
[Rh(CO)(η -PhC᎐CPh){HC(pzЈ)3}]
7.89 {s, 1H, HC(pzЈ)3}, 7.89–7.82 (m, 4H, C6H5), 7.47–7.38 (m,
6H, C6H5), 6.28 (s, 2H, pzЈ CH), 5.79 (s, 1H, pzЈ CH), 2.64 (s, 6H,
pzЈ CH3), 2.55 (s, 3H, pzЈ CH3), 2.51 (s, 6H, pzЈ CH3), 1.73 (s, 3H,
pzЈ CH3)
—
—
᎐
[PF6], 5ϩ[PF6]Ϫ
2
᎐
[Rh(CO)(η -PhC᎐CPh){HC(pzЈ)3}]
7.81 {s, 1H, HC(pzЈ)3}, 7.45–7.15 (m, 10H, C6H5), 6.18 (s, 1H, pzЈ
CH), 6.11 (s, 1H, pzЈ CH), 6.02 (s, 1H, pzЈ CH), 2.60 (s, 3H, pzЈ
CH3), 2.58 (s, 3H, pzЈ CH3), 2.54 (s, 3H, pzЈ CH3), 2.52 (s, 3H, pzЈ
CH3), 2.24 (s, 3H, pzЈ CH3), 1.49 (s, 3H, pzЈ CH3)
᎐
[PF6], 5ϩ[PF6]Ϫ c
[Rh{η4-C4Me4C(O)}{HC(pzЈ)3}]
[PF6], 6ϩ[PF6]Ϫ
7.37 {s, 1H, HC(pzЈ)3}, 6.23 (s, 3H, pzЈ CH), 2.41 (s, 9H, pzЈ CH3),
2.17 (s, 9H, pzЈ CH3), 1.92 (s, 6H, CCH3), 1.06 (s, 6H, CCH3)
—
—
[Rh(CO)(η1:η1Ј-CHCPhCHCPh)
{HC(pzЈ)3}][PF6], 8ϩ[PF6]Ϫ
7.96 {s, 1H, HC(pzЈ)3}, 7.85 (dd, 1H, J 3, 1, H1), 7.58–6.55 (m, 2H,
Ph), 7.40–7.10 (m, 6H, Ph), 6.91–6.87 (m, 3H, H3 and Ph), 6.23 (s,
1H, pzЈ CH), 6.12 (s, 1H, pzЈ CH), 5.97 (s, 1H, pzЈ CH), 2.70 (s,
3H, pzЈ CH3), 2.63 (s, 6H, pzЈ CH3), 2.53 (s, 3H, pzЈ CH3), 2.40 (s,
3H, pzЈ CH3), 1.38 (s, 3H, pzЈ CH3)c
.
[Rh(CO)(η1:η1Ј-C4H4) {HC(pzЈ)3}]
[PF6], 9ϩ[PF6]Ϫ
7.85 {s, 1H, HC(pzЈ)3}, 7.52 (ddd, 2H J 5, 4, 1, H1,4), 6.51 (ddd,
2H, J 5, 4, 2, H2,3), 6.20 (s, 2H, pzЈ CH), 6.00 (s, 1H, pzЈ CH), 2.61
(s, 6H, pzЈ CH3), 2.56 (s, 3H, pzЈ CH3), 2.45 (s, 9H, pzЈ CH3)c
184.46 (d, JC,Rh 71, CO), 159.02 (s, pzЈ CCH3), 155.18 (s, pzЈ
CCH3), 147.65 (d, JC,Rh 2, C2,3), 145.47 (d, JC,Rh 26, C1,4), 142.39 (s,
pzЈ CCH3), 142.28 (s, pzЈ CCH3), 110.32 (d, J 1, pzЈ CH), 109.20
(s, pzЈ CH), 68.67 {s, HC(pzЈ)3}, 14.35 (s, pzЈ CH3), 12.49 (s, pzЈ
CH3) 11.40 (s, pzЈ CH3), 11.11 (s, pzЈ CH3)
—
—
[Rh{η4-C6H6C(O)}{HC(pzЈ)3}]
[PF6], 10ϩ[PF6]Ϫ
7.72 {s, 1H, HC(pzЈ)3}, 6.74 (dddd, 1H, J 7.5, 5, 0.5, 0.5, H5), 6.57
(dddd, 1H, J 7, 5, 0.5, 0.5, H6), 6.51 (dd, J 11, 7, H3), 6.12 (s, pzЈ
CH), 6.03 (broad s, pzЈ CH), 5.60 (ddd, J 11, 2, 1, H2), 3.93 (ddd, J
7, 1, 1, H7), 3.69 (dd, J 7.5, 7, H4), 2.53 (broad s, pzЈ CH3), 2.36
(broad s, pzЈ CH3)
201.67 (s, C1O), 157.70 (s, pzЈ CCH3), 151.04 (s, pzЈ CCH3), 141.82
(s, C3), 127.86 (s, C2), 110.28 (s, pzЈ CH), 89.58 (d, JC,Rh 6, C5),
85.08 (d, JC,Rh 6, C6), 68.00 {s, HC(pzЈ)3}, 44.18 (d, JC,Rh 17, C4 or
C7), 34.02 (d, JC,Rh 17, C4 or C7), 14.99 (s, pzЈ CH3), 11.31 (s, pzЈ
CH3), 11.23 (s, pzЈ CH3)
a Chemical shift (δ) in ppm, J values in Hz, spectra in CD2Cl2 at 20 ЊC unless stated otherwise, atom numbering in Scheme 1. b At Ϫ40 ЊC. c In CD3CN. d pzЈ CH3, Ph or CPh carbons.

View Article Online
Table 3 Selected bond lengths (Å) and angles (Њ) for [Rh(CO)2{HC-
(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ, and [Rh(CO)(PPh3){HC(pzЈ)3}][PF6]ؒ2CH2Cl2,
2ϩ[PF6]Ϫؒ2CH2Cl2
1aϩ a
1bϩ a
2aϩ b
2bϩ b
Rh(1)–N(6)
Rh(1)–N(4)
Rh(1)–N(2)
Rh(1)–C(1)
Rh(1)–C(2)
Rh(1)–P(1)
N(4)–Rh(1)–N(6)
N(6)–Rh(1)–C(1)
C(1)–Rh(1)–C(2)
C(1)–Rh(1)–P(1)
P(1)–Rh(1)–N(4)
C(2)–Rh(1)–N(4)
N(2)–Rh(1)–N(4)
N(2)–Rh(1)–N(6)
N(2)–Rh(1)–C(1)
N(2)–Rh(1)–C(2)
N(4)–Rh(1)–C(1)
N(6)–Rh(1)–C(2)
N(6)–Rh(1)–P(1)
2.159(2)
2.103(2)
2.431(2)
1.839(3)
1.847(3)
—
82.1(1)
95.6(1)
85.9(1)
—
2.149(2)
2.119(2)
2.440(2)
1.835(3)
1.848(3)
—
84.0(1)
94.1(1)
84.5(1)
—
2.106(5)
2.125(6)
3.597(5)
1.821(8)
—
2.266(2)
81.3(2)
172.0(3)
—
86.5(2)
171.9(2)
—
—
—
2.104(5)
2.121(5)
3.614(6)
1.818(7)
—
2.264(2)
82.3(2)
170.9(3)
—
86.1(2)
171.8(2)
—
—
—
—
—
94.3(1)
85.5(1)
77.1(1)
100.6(1)
120.8(1)
172.9(1)
161.6(1)
—
95.9(1)
79.8(1)
80.6(1)
105.1(1)
114.2(1)
174.4(1)
165.1(1)
—
Fig. 3 The molecular structure of the cation of [Rh(CO)(PPh3)-
{HC(pzЈ)3}][PF6]ؒ2CH2Cl2, 2ϩ[PF6]Ϫؒ2CH2Cl2. Hydrogen atoms have
been omitted for clarity.
—
—
95.0(3)
—
98.2(2)
—
—
95.2(3)
—
97.7(2)
The one-electron oxidation of 1؉–4؉
The cyclic voltammogram (CV) of 1ϩ[PF6]Ϫ in CH2Cl2 at
a glassy carbon electrode in CH2Cl2 shows a one-electron
oxidation wave [(Ep)ox = 1.17 V] which is only partially revers-
ible at scan rates between 100 mV sϪ1 and 2 V sϪ1. Complex
1ϩ[PF6]Ϫ is also irreversibly reduced at (Ep)red = Ϫ1.55 V with a
product wave at (Ep)ox = 0.87 V. The oxidation of [Rh(CO)2TpЈ]
is better defined, showing a reversible wave at a considerably
less positive potential (0.52 V), commensurate with the lower
overall charge of the neutral complex.12
a 1aϩ and 1bϩ are the two independent molecules of 1ϩ in the unit
cell. b 2aϩ and 2bϩ are the two independent molecules of 2ϩ in the
unit cell.
spectroscopy (Table 2). In addition, the redox chemistry
of these complexes was investigated by cyclic voltammetry,
and the structure of [Rh(CO)(PPh3){HC(pzЈ)3}][PF6]ؒ
2CH2Cl2, 2ϩ[PF6]Ϫؒ2CH2Cl2, was determined by X-ray crystal-
lography.
The CVs of complexes 2ϩ[PF6]Ϫ and 3ϩ[PF6]Ϫ are also better
defined than that of 1ϩ[PF6]Ϫ, showing reversible one-electron
oxidations (EЊЈ = 0.81 and 0.80 V, respectively). Complex
In CH2Cl2 each of 2ϩ–4ϩ shows only one carbonyl band in
the IR spectrum; the carbonyl stretching frequencies of the
PPh3 {and the supposed P(OPh)3} complexes are 20–25 cmϪ1
higher in energy than those of the TpЈ analogues (1978 and
2007 cmϪ1), reflecting a decrease in electron density at the metal
in the cations. As noted above, the dicarbonyl cation 1ϩ exists as
a mixture of the κ2 and κ3 isomers in solution. Replacement of
a carbonyl ligand by a more bulky, and more electron-donating,
ligand would be expected to shift the equilibrium in the direc-
tion of κ2 co-ordination, as found in the TpЈ analogues,12 so
that 2ϩ–4ϩ are likely to be κ2 co-ordinated in solution (as is the
case for 2ϩ in the solid state, see below).
3ϩ[PF6]Ϫ also shows an irreversible second oxidation at (Ep)ox
=
1.62 V and an irreversible reduction at (Ep)red = Ϫ1.91 V. As
with the TpЈ complexes, the peak-to-peak separation for the
one-electron oxidation process increases dramatically, and the
oxidation peak becomes severely broadened, at a platinum
electrode.12
The CV of 4ϩ[PF6]Ϫ is very different from those of 2ϩ[PF6]Ϫ
and 3ϩ[PF6]Ϫ in showing a poorly defined, irreversible oxidation
at (Ep)ox ca. 1.30 V with a small product peak at (Ep)red ca.
0.65 V. The irreversibility and high positive potential of the
oxidation probably arises because the formation of a five-
co-ordinate Rh() complex (as observed in the formation of the
κ3 cations [Rh(CO)LTpЈ]ϩ 12) is not possible, either because
isomerisation on oxidation of 4ϩ to 42ϩ is prevented by the
steric bulk of the phosphine (if the B-isomer) or because of the
exo-arrangement of the third pyrazolyl group (if the A-isomer).
The complex [Rh(CO)(PCy3)TpPh] {TpPh = hydrotris(1-phenyl-
pyrazolyl)borate} is κ2 co-ordinated as the A-isomer in solu-
tion, and the cyclic voltammogram shows a similar irreversible
oxidation wave at high potential.23
On the NMR spectroscopic timescale all three pyrazolyl
rings in cations 2ϩ and 3ϩ are equivalent due to fast exchange
of the co-ordinated and unco-ordinated rings. In contrast,
all three pyrazolyl rings of 4ϩ are inequivalent, in the room
temperature 1H NMR spectrum and in the 13C NMR spectrum
at Ϫ40 ЊC. There is only one major isomer present, but whether
this has the A- or B-form (Fig. 1) is unknown. In an A-isomer,
all three pyrazolyl rings are likely to remain inequivalent; in a
B-isomer, the co-ordinated and unco-ordinated pyrazolyl rings
are likely to exchange only slowly due to the steric bulk of the
P(o-tolyl)3 ligand.
Although attempts to isolate salts of [Rh(CO)L{HC(pzЈ)3}]2ϩ
failed [cf. the stability of solid [Rh(CO)LTpЈ][PF6] {L = PPh3
and P(NMe2)3}12], the Rh() dications [Rh(CO)L{HC(pzЈ)3}]2ϩ
(L = PPh3, 22ϩ and AsPh3, 32ϩ) were generated in the cavity of
an ESR spectrometer by oxidising 2ϩ[PF6]Ϫ or 3ϩ[PF6]Ϫ with
An X-ray structural study showed that, in the solid state
at least, 2ϩ (for which there are two independent molecules in
the unit cell) exists in the B-form with the HC(pzЈ)3 ligand
κ2 co-ordinated to square planar rhodium (Fig. 3). As with κ2
co-ordinated hydrotris(pyrazolyl)borate complexes such as
[Fe(η-C5H5)(η-C5H4COMe)][PF6] at 220
K in dichloro-
12
[Rh(CO)LTpЈ] {L = PPh3, PCy3, P(NMe2)3, P(m-tolyl)3 and
methane–1,2-dichloroethane (1 : 1). The resulting solutions
were cooled to 100 or 120 K to obtain the anisotropic ESR
spectra, and the temperature was then raised to 290 K for the
isotropic spectra. The anisotropic spectrum of 22ϩ is shown in
Fig. 4 and the spectroscopic data for both Rh() complexes are
given in Table 4.
PMe3 21} and [Rh(CO)(PMePh2)LЈ] {LЈ = hydrotris(3,5-
dimethyl-4-chloropyrazolyl)borate}22
the
uncoordinated
pyrazolyl ring is orientated pseudo-parallel to the rhodium
coordination plane. The angle between the rhodium square
plane and the plane of the unbound pyrazolyl ring (38.0 and
52.4Њ for the two independent molecules of 2ϩ) reflects this
orientation which results in an average Rh–Napical separation
of 3.61 Å. Overall, the bond lengths and angles of 2ϩ (Table 3)
are remarkably similar to those of [Rh(CO)(PPh3)TpЈ].12
The anisotropic spectrum of 22ϩ is similar to that of
12
[Rh(CO)2TpЈ]ϩ in showing coupling to 103Rh and the apical
14N atom in all three g components as well as 31P coupling in the
high field feature. As with the RhIITpЈ complexes, the isotropic
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2838

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ϩ
a
Table 4 ESR spectroscopic data for [Rh(CO)L{HC(pzЈ)3}]2 (L = PPh3, 22ϩ; AsPh3, 32ϩ
)
Complex
g1
g2
g3
gave
giso
A1(103Rh)
A2(103Rh)
A3(103Rh)
A1(14N)
A2(14N)
A3(14N)
A3(31P)
22ϩ
32ϩ
2.272
2.287
2.180
2.170
1.993
1.995
2.148
2.151
2.163
2.171
22
—
14
—
27.3(2)
21.6(4)
22
—
24
—
28.0(1)
30.9(3)
6.4
—
a Anisotropic spectra were computer-simulated; A-values for less well-resolved features were analysed by least-squares fits of portions of the spectra
to sets of Gaussian absorption lines. Hyperfine couplings in 10Ϫ4 cmϪ1
.
᎐
᎐
᎐
Scheme 1 (i) PhC᎐CPh; (ii) MeC᎐CR (R = Me or Et); (iii) RC᎐CH,
᎐
᎐
᎐
Fig.
4
(a) The anisotropic ESR spectrum of [Rh(CO)(PPh3)-
᎐
R = Ph or H; (iv) HC᎐CH. N–N represents the third pyrazolyl ring.
᎐
{HC(pzЈ)3}][PF6]2, 22ϩ{[PF6]Ϫ}2, in 1 : 1 CH2Cl2–1,2-dichloroethane at
120 K. The high field component is expanded in (b).
the dinuclear metallacyclopentadiene [Rh2(µ-C4Ph4)(η-C5H5)2],
and trinuclear [Rh3(µ3-CO)(µ3-PhC2Ph)(η-C5H5)3].18
Complex 5ϩ[PF6]Ϫ was characterised by elemental analysis,
by IR spectroscopy (Table 1), showing one terminal carbonyl
absorption at 2043 cmϪ1, and by 1H and 13C NMR spectroscopy
(Table 2) which shows a 2 : 1 ratio for the three pyrazolyl rings.
g-value, giso, is more positive than gave, perhaps indicating a
significant change in the electronic structure with temperature,
and possibly due to some departure from square pyramidal
geometry leading to admixture of other metal d-orbital char-
acter to the SOMO. Further detailed studies of the variable
temperature spectra are in progress.
One 13C signal for the alkyne carbon atoms, at 82.5 ppm (JC,Rh
=
16 Hz) characteristic of a two-electron alkyne,25 suggests the
᎐
alkyne to be disposed such that the C᎐C bond is orthogonal to
᎐
the Rh–C–O linkage (Scheme 1), a suggestion confirmed by an
Reactions of [Rh(CO) {HC(pzЈ) }][PF6], 1؉[PF6]؊, with alkynes
2
3
2
᎐
X-ray diffraction study on the solvate [Rh(CO)(η -PhC᎐CPh)-
᎐
In contrast to the cyclopentadienyl complexes [Rh(CO)2-
(η-C5R5)], which react with alkynes to give a variety of
products many of which are multinuclear,13–18 and [Rh(CO)2-
TpЈ], which is unreactive, [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ,
{HC(pzЈ)3}][PF6]ؒ1.5thf.
The cation 5ϩ is shown in Fig. 5 and bond lengths and angles
are given in Table 5; general features of the molecular structure
2
᎐
are similar to those of [Rh{η -(MeCO )C᎐C(CO Me)}-
᎐
2
2
᎐
(PPh3)Tp] {Tp = hydrotris(pyrazolyl)borate}.3 The HC(pzЈ)3
ligand is κ3 coordinated and the C2Ph2 ligand is η2-bonded with
the alkyne substituents bent back from the metal by approx-
imately 31Њ. The geometry at rhodium may be described as
trigonal bipyramidal, with the carbonyl axial and the alkyne
equatorial, [C(1)–Rh–N(3) = 178.9(3), N(1)–Rh–N(5) = 81.9(2),
N(1)–Rh–X(1) = 140.2(3), N(5)–Rh–X(1) = 137.4(3)Њ, X(1) =
midpoint of C(3)–C(4)]. The two equatorial Rh–N bonds
pseudo-trans to the alkyne [Rh–N(1), 2.200(6); Rh–N(5),
2.185(6)] are somewhat longer than the axial bond pseudo-trans
to the CO ligand [Rh–N(3), 2.167(7)].
᎐
and RC᎐CRЈ give mononuclear products the identities of
which depend on R and RЈ (Scheme 1).
2
᎐
Synthesis and characterisation of [Rh(CO)(ꢀ -PhC᎐CPh)-
᎐
{HC(pzЈ)3}][PF6], 5؉[PF6]؊
Heating a thf solution of 1ϩ[PF6]Ϫ and PhC᎐CPh under reflux
᎐
᎐
2
᎐
for five days gave [Rh(CO)(η -PhC᎐CPh){HC(pzЈ) }][PF ],
᎐
3
6
5ϩ[PF6]Ϫ, a rare example of an isolable mononuclear rhodium
complex containing both a carbonyl ligand and an η2-bonded
2
᎐
alkyne. (The analogue [Co(CO)(η -PhC᎐CPh)(η-C H )] was
᎐
5
5
2
᎐
detected at Ϫ78 ЊC on UV irradiation of a mixture of
Dissolution of [Rh(CO)(η -PhC᎐CPh){HC(pzЈ) }][PF ],
᎐
3
6
[Co(CO) (η-C H )] and PhC᎐CPh 24.) By contrast, [Rh(CO)2-
5ϩ[PF6]Ϫ, in either MeCN or ButCN at room temperature gave
yellow solutions the IR spectra of which show the terminal
metal–carbonyl band at 2043 cmϪ1 replaced by a ketonic
᎐
᎐
2
5
5
᎐
(η-C H )] reacted with PhC᎐CPh to give a mixture of C Ph ,
᎐
5
5
6
6
the cyclopentadienone complex [Rh{η4-C4Ph4C(O)}(η-C5H5)],
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2839

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spectrum of the product, in CD2Cl2, indicated a mixture of
species.
Synthesis and characterisation of [Rh{ꢀ4-C4Me2R2C(O)}-
{HC(pzЈ)3}][PF6] (R ؍ Me, 6؉[PF6]؊ or Et, 7؉[PF6]؊)
ϩ
᎐
The reaction of 1 with MeC᎐CMe in CH Cl at room temper-
᎐
2
2
ature gave the red–pink cyclopentadienone complex [Rh{η4-
C4Me4C(O)}{HC(pzЈ)3}][PF6], 6ϩ[PF6]Ϫ, [ν(CO) = 1667 cmϪ1] in
which two alkynes and a carbonyl ligand are linked. Small
quantities of a second, yellow product, with ν(CO) = 2046 cmϪ1
,
remained in solution after precipitation of 6ϩ[PF6]Ϫ from
CH2Cl2 with n-hexane. Though not further characterised, this
complex is most likely the η2-alkyne complex [Rh(CO)-
2
᎐
(η -MeC᎐CMe){HC(pzЈ) }][PF ] on the basis of the close
᎐
3
6
similarity between its carbonyl stretching frequency and that of
5ϩ[PF6]Ϫ [ν(CO) = 2043 cmϪ1]. (By comparison, the reaction
Fig.
5
The molecular structure of the cation of [Rh(CO)(η2-
ϩ Ϫ
᎐
᎐
between [Rh(CO) (η-C H )] and MeC᎐CMe gave a mixture of
PhC᎐CPh){HC(pzЈ)3}][PF6]ؒ1.5thf, 5 [PF6] ؒ1.5thf. Hydrogen atoms
᎐
᎐
2
5
5
the cyclopentadienone complex [Rh{η4-C4Me4C(O)}(η-C5H5)]
and the duroquinone complex [Rh(η4-C6Me4O2-p)(η-C5H5)],14
but with [Rh(CO)2(η-C5Me5)] the major product was [Rh-
{η4-C4Me4C(O)}(η-C5Me5)].15)
have been omitted for clarity.
carbonyl band, at 1692 and 1700 cmϪ1 respectively. In contrast
to the 1H and 13C NMR spectra of 5ϩ[PF6]Ϫ in CD2Cl2, those in
MeCN show three inequivalent pyrazolyl rings. In addition, the
13C spectrum in CD3CN shows a ketonic carbonyl group, at
191.28 ppm, and a CPh carbon resonance at 54.81 ppm.
The 1H NMR spectrum of 6ϩ[PF6]Ϫ shows two singlet reson-
ances for the two inequivalent pairs of methyl groups on the
cyclopentadienone ring. Only one resonance is observed for the
pyrazolyl ring protons and only two singlets for the methyl
groups in the 3- and 5-positions of the rings. Similarly, the 13C
NMR spectrum shows only one signal for each of the two
different pyrazolyl ring methyls and one for the ring protons;
the diene carbons show couplings of 9 and 12 Hz to the
rhodium atom. Although the NMR spectra imply that the three
pyrazolyl rings are equivalent, an X-ray structural study
revealed that this equivalence is most likely due to a fluxional
process in which two bound and one unbound pyrazolyl groups
of a κ2 ligand interconvert.
Further characterisation of this species proved impossible
although evaporating the MeCN or ButCN solutions to dryness
and dissolving the residues in CH2Cl2 resulted in the reappear-
ance of the IR band at 2043 cmϪ1, i.e. in the reformation of 5ϩ.
By contrast, when 5ϩ[PF6]Ϫ was heated under reflux in MeCN, a
yellow solution {with ν(CO) at 1713 cmϪ1} was formed from
which 5ϩ[PF6]Ϫ could not be recovered; the complex H NMR
1
Table 5 Selected bond lengths (Å) and angles (Њ) for [Rh(CO)-
(η2-C2Ph2){HC(pzЈ)3}][PF6]ؒ1.5thf, 5ϩ[PF6]Ϫؒ1.5thf
The molecular structure of 6ϩ is shown in Fig. 6 with import-
ant bond lengths and angles given in Table 6. If the rhodium–
alkene bonds are defined as those from rhodium to the centres
Rh(1)–N(1)
Rh(1)–N(3)
Rh(1)–N(5)
Rh(1)–C(1)
2.185(6)
2.167(7)
2.200(6)
1.796(9)
Rh(1)–C(3)
Rh(1)–C(4)
C(3)–C(4)
2.068(8)
2.061(9)
1.251(11)
1.967
of the C᎐C bonds [i.e. X(1) = midpoint of C(18)–C(19), X(2) =
Rh(1)–X(1)
᎐
midpoint of C(20)–C(21)], then the geometry about rhodium
is approximately square planar. The HC(pzЈ)3 ligand is κ2
co-ordinated with the uncoordinated pyrazolyl ring orientated
pseudo-parallel to the rhodium coordination plane; the angle
between the rhodium square plane and that of the unbound
pyrazolyl ring is 60.9Њ. The dienone ring is orientated such that
the oxygen atom of the ketone group is located at only 3.37 Å
from the centre of the unbound pyrazolyl ring.
C(1)–Rh(1)–C(4)
C(1)–Rh(1)–C(3)
C(1)–Rh(1)–N(3)
C(3)–Rh(1)–N(3)
C(4)–Rh(1)–N(3)
C(1)–Rh(1)–N(1)
C(1)–Rh(1)–N(5)
N(5)–Rh(1)–C(4)
87.1(4)
86.6(3)
178.9(3)
94.5(3)
93.7(3)
96.9(3)
94.6(3)
119.8(3)
C(3)–Rh(1)–N(5)
N(3)–Rh(1)–N(5)
N(1)–Rh(1)–N(5)
C(3)–C(4)–C(31)
C(4)–C(3)–C(21)
N(1)–Rh(1)–X(1)a
N(5)–Rh(1)–X(1)a
155.0(3)
84.4(3)
81.9(2)
150.3(10)
147.8(9)
140.2
137.4
a X(1) = midpoint of C(3)–C(4).
There are two extremes for the bonding of a metal to a
1,3-diene unit, as shown in Fig. 7. In Fig. 7(a) the metal is
Table 6 Selected bond lengths (Å) and angles (Њ) for [Rh{η4-C4Me4C(O)}{HC(pzЈ)3}][PF6], 6ϩ[PF6]Ϫ, and [Rh{η4-C4Me2Et2C(O)}{HC-
(pzЈ)3}][PF6]ؒH2O, 7ϩ[PF6]ϪؒH2O
6
7
6
7
Rh(1)–N(4)
Rh(1)–N(6)
2.143(4)
2.155(4)
3.484(4)
2.173(5)
2.147(5)
2.133(5)
2.145(5)
2.416(5)
2.135(5)
2.118(7)
3.570(6)
2.142(6)
2.151(7)
2.141(6)
2.156(8)
2.348(6)
Rh(1)–X(1)
Rh(1)–X(2)
C(18)–C(19)
C(19)–C(20)
C(20)–C(21)
C(21)–C(17)
C(18)–C(17)
C(17)–O(1)
2.040
2.018
2.029
2.030
Rh(1) ؒ ؒ ؒ N(2)
Rh(1)–C(18)
Rh(1)–C(19)
Rh(1)–C(20)
Rh(1)–C(21)
Rh(1) ؒ ؒ ؒ C(17)
1.416(7)
1.453(7)
1.420(7)
1.465(7)
1.490(7)
1.230(6)
1.403(9)
1.448(9)
1.407(10)
1.468(9)
1.486(8)
1.237(7)
N(4)–Rh(1)–N(6)
N(4)–Rh(1)–X(1)a
N(4)–Rh(1)–X(2)a
N(6)–Rh(1)–X(1)a
N(6)–Rh(1)–X(2)a
C(18)–C(19)–C(20)
82.3(2)
163.0
108.6
111.9
163.3
83.7(2)
165.3
110.9
109.5
164.5
C(19)–C(20)–C(21)
C(20)–C(21)–C(17)
C(21)–C(17)–C(18)
C(17)–C(18)–C(19)
C(21)–C(17)–O(1)
C(18)–C(17)–O(1)
108.2(4)
108.6(4)
103.7(4)
108.4(4)
127.9(5)
128.2(5)
107.8(6)
109.3(6)
103.9(5)
108.3(5)
128.4(6)
127.4(6)
107.7(4)
108.6(5)
a X(1) = midpoint of C(18)–C(19), X(2) = midpoint of C(20)–C(21).
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2840

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Fig. 9 The molecular structure of the cation of [Rh{η4-C4Me2-
Et2C(O)}{HC(pzЈ)3}][PF6]ؒH2O, 7ϩ[PF6]ϪؒH2O. Hydrogen atoms have
been omitted for clarity.
Fig. 6 The molecular structure of the cation of [Rh{η4-C4Me4-
C(O)}{HC(pzЈ)3}][PF6], 6ϩ[PF6]Ϫ. Hydrogen atoms have been omitted
for clarity.
Reactions with terminal alkynes: synthesis and characterisation
of [Rh(CO)(ꢀ1:ꢀ1Ј-C4R2RЈ2){HC(pzЈ)3}][PF6] (R ؍ H, RЈ ؍ Ph,
8؉[PF6]؊; R ؍ RЈ ؍ H, 9؉[PF6]؊) and [Rh{ꢀ4-C6H6C(O)}-
{HC(pzЈ)3}][PF6], 10؉[PF6]؊
᎐
᎐
᎐
The terminal alkynes HC᎐CPh and HC᎐CH react very differ-
᎐
ently with 1ϩ than do internal alkynes. Thus, HC᎐CPh and
᎐
᎐
1ϩ[PF6]Ϫ in CH2Cl2 gave the cream metallacyclopentadiene
Fig. 7 The two extremes of bonding of a butadiene fragment to a
metal, (a) as an η4-diene, and (b) as a metallacyclopentene.
complex
[Rh(CO)(η1:η1Ј-CHCPhCHCPh){HC(pzЈ)3}][PF6],
ϩ
Ϫ
᎐
8 [PF ] , whereas HC᎐CH gave a mixture of the yellow
᎐
6
analogue [Rh(CO)(η1:η1Ј-C4H4){HC(pzЈ)3}][PF6], 9ϩ[PF6]Ϫ,
plus small amounts of the orange cycloheptatrienone (tropone)
complex [Rh{η4-C6H6C(O)}{HC(pzЈ)3}][PF6], 10ϩ[PF6]Ϫ, an
coordinated to two independent alkene units, C(1)–C(2) and
C(3)–C(4), and in Fig. 7(b) to an alkene, C(2)–C(3), and the two
terminal carbon atoms, C(1) and C(4). The carbon–carbon
bond lengths in the C4Me4C(O) ring of 6ϩ [C(18)–C(19),
1.416(7); C(19)–C(20), 1.453(7); C(20)–C(21), 1.420(7) Å]
suggest that the bonding is closer to that shown in Fig. 7(a).
The planarity of the dienone ring (fold angle at C(18) ؒ ؒ ؒ C(21)
3.9Њ) is also consistent with this bonding mode, i.e. with sp2
hybridisation at carbons C(19) and C(21).
analogue of which was isolated from the reaction between
16
᎐
᎐
[Rh(CO) Cp] and the diyne MeC᎐CC᎐CMe.
᎐
᎐
2
The IR spectra of complexes 8ϩ[PF6]Ϫ and 9ϩ[PF6]Ϫ (Table 1)
each show a peak for the terminal carbonyl ligand (2083 and
2080 cmϪ1, respectively), but at higher wavenumber than the
Rh(I) complex, 5ϩ[PF6]Ϫ, (2043 cmϪ1), consistent with the
presence of the higher oxidation state Rh().
The reaction of 1ϩ with MeC᎐CEt in CH Cl at room tem-
᎐
᎐
2
2
The structure of cation 9ϩ (Fig. 10, Table 7) is similar to that
of [Ir(η-C2H4)(η1:η1Ј-CRCRCRCR)Tp] (R = CO2Me),26 with
an octahedral metal centre κ3-bound to the tris(3,5-dimethyl-
pyrazolyl)methane ligand. The Rh–Npyrazolyl bond trans to the
carbonyl ligand [Rh–N(2) = 2.110(3)] is shorter than those trans
to the carbon atoms of the metallacyclopentadiene ring [Rh–
N(6) = 2.185(4), Rh–N(4) = 2.194(4) Å]. The two phenyl rings
are positioned asymmetrically on the five-membered metal-
lacycle such that the two alkynes are linked head-to-tail (cf.
head-to-head linkage in the cyclopentadienone complex 7ϩ).
In agreement with the structural study, all three pyrazolyl
rings in 8ϩ are inequivalent in the 1H and 13C–{1H} NMR spec-
tra (Table 2). In the 1H NMR spectrum the phenyl proton
signals partly obscure those for H1 and H3 (see Scheme 1 for
numbering), and C1 and C3 are amongst the twelve 13C NMR
signals between 160 and 138 ppm. However, DEPT NMR
spectroscopy allowed the C1 and C3 signals to be assigned, at
139.78 and 143.96 ppm (with coupling to rhodium of 26 and
perature also gave a red solid the elemental analysis and IR
spectrum [ν(CO) = 1661 cmϪ1] of which were consistent with the
formation of an analogue of 6ϩ, namely [Rh{η4-C4Me2-
1
Et2C(O)}{HC(pzЈ)3}][PF6], 7ϩ[PF6]Ϫ. However, the H and 13C
NMR spectra were complex, suggesting only that a mixture of
all three possible cyclopentadienone isomers was formed, i.e.
the symmetric head-to-head isomers (a) and (b) and the
asymmetric head-to-tail isomer (c) shown in Fig. 8. Slow
diffusion of a concentrated CH2Cl2 solution of the red solid
into n-hexane at Ϫ10Њ gave red crystals of 7ϩ[PF6]Ϫ, an X-ray
study on which (Fig. 9, Table 6) showed a very similar structure
to that of 6ϩ[PF6]Ϫ. In the case of 7ϩ[PF6]Ϫ, however, the two
asymmetric alkyne units are linked head-to-head and the two
CEt termini are bound to the ketonic CO group, i.e. as in
Fig. 8(a) (R1 = Et, R2 = Me). Again, the dienone ring is
orientated such that the oxygen atom of the ketone group is
close to the centre of the unbound pyrazolyl ring (at ca. 3.26 Å).
1
2 Hz, respectively), and H/13C correlated NMR spectroscopy
then enabled the peaks due to H1 and H3 to be located, one at
7.85 ppm and the other within a 3H multiplet between 6.91 and
6.87 ppm.
In cation 9ϩ, which contains a symmetrical metallacyclo-
pentadiene ring, the pyrazolyl groups are observed in a 2 : 1
ratio. In addition, the 1H signals for the protons of the C4H4Rh
ring were more easily identified (at 7.52 and 6.51 ppm for H1/H4
Fig. 8 Head-to-head [(a) and (b)] and head-to-tail (c) isomers of a
cyclopentadienone.
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2841

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Fig. 10 The molecular structure of the cation of [Rh(CO)(η1:η1Ј-
CHCPhCHCPh){HC(pzЈ)3}][PF6]ؒ2CH2Cl2, 8ϩ[PF6]Ϫؒ2CH2Cl2. Most
hydrogen atoms have been omitted for clarity.
Fig. 11 The molecular structure of the cation of [Rh{η4-C6H6C(O)-
}{HC(pzЈ)3}][PF6], 10ϩ[PF6]Ϫ. Hydrogen atoms have been omitted for
clarity.
Table 7 Selected bond lengths (Å) and angles (Њ) for [Rh(CO)(η1:η1Ј-
CHCPhCHCPh){HC(pzЈ)3}][PF6]ؒ2CH2Cl2, 8ϩ[PF6]Ϫؒ2CH2Cl2
Table 8 Selected bond lengths (Å) and angles (Њ) for [Rh{η4–
C6H6C(O)}{HC(pzЈ)3}][PF6], 10ϩ[PF6]Ϫ
Rh(1)–N(4)
Rh(1)–N(6)
Rh(1)–N(2)
Rh(1)–C(1)
Rh(1)–C(18)
2.194(4)
2.185(4)
2.110(3)
1.861(5)
2.061(4)
Rh(1)–C(33)
C(18)–C(25)
C(25)–C(26)
C(26)–C(33)
2.033(4)
1.347(6)
1.458(6)
1.346(6)
Rh(1)–N(1)
Rh(1)–N(3)
Rh(1)–N(5)
Rh(1)–C(4)
Rh(1)–C(5)
Rh(1)–C(6)
Rh(1)–C(7)
C(1)–O(1)
2.175(8)
2.159(8)
2.200(9)
2.116(11)
2.105(11)
2.087(10)
2.118(10)
1.225(13)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(1)
1.439(16)
1.352(17)
1.465(16)
1.433(16)
1.391(16)
1.423(15)
1.475(15)
C(1)–Rh(1)–N(2)
C(1)–Rh(1)–N(6)
C(1)–Rh(1)–N(4)
C(1)–Rh(1)–C(18)
C(1)–Rh(1)–C(33)
C(18)–Rh(1)–C(33)
C(18)–Rh(1)–N(2)
176.7(2)
98.3(2)
97.4(2)
83.4(2)
81.1(2)
79.6(2)
93.9(2)
C(18)–Rh(1)–N(6)
C(33)–Rh(1)–N(2)
C(33)–Rh(1)–N(6)
N(2)–Rh(1)–N(6)
N(2)–Rh(1)–N(4)
N(4)–Rh(1)–N(6)
174.0(2)
96.7(2)
95.0(2)
84.3(1)
84.9(1)
84.2(1)
N(3)–Rh(1)–N(5)
N(3)–Rh(1)–C(4)
C(4)–Rh(1)–C(7)
C(7)–Rh(1)–N(5)
N(1)–Rh(1)–N(3)
81.4(3)
95.7(4)
81.8(4)
98.4(4)
84.2(3)
N(1)–Rh(1)–N(5)
N(1)–Rh(1)–C(4)
N(1)–Rh(1)–C(7)
N(5)–Rh(1)–C(4)
N(3)–Rh(1)–C(7)
84.2(3)
108.3(4)
107.5(3)
166.9(4)
168.2(4)
and H2/H3, respectively), 1H/13C correlated NMR spectroscopy
then showing that C1/C4 and C2/C3 occur at 145.47 and 147.65
ppm, respectively in the 13C NMR spectrum.
chemical shifts with those of the α,β-unsaturated ketone
The IR spectrum of the η4-cycloheptatrienone (tropone)
2,3-cyclohexenone (C2, 130 ppm; C3, 151).29 The C5 and C6
complex 10ϩ[PF6]Ϫ shows not only a ketonic peak [ν(CO)
1
signals were assigned by H/13C correlated NMR spectroscopy
(CH2Cl2, 1640 cmϪ1; Nujol, 1635 cmϪ1)], but also a ν(C᎐C)
which shows coupling of protons H5 and H6 to signals at 89.58
(C5) and 85.08 (C6) ppm, respectively. The rhodium couplings
are larger for the σ-bound carbon atoms C4 and C7 (17 Hz) than
for C5 and C6 (6 Hz).
᎐
absorption (CH2Cl2, 1616 cmϪ1; Nujol, 1609 cmϪ1), similar to
those of [Fe(CO)3{η4-C6H6C(O)}] (1637 and 1613 cmϪ1
,
respectively)27 and the molecular structure of cation 10ϩ
(Fig. 11, Table 8) is also similar to that of the iron compound.28
Unlike the cyclopentadienone complexes 6ϩ[PF6]Ϫ and
7ϩ[PF6]Ϫ, the cycloheptatrienone derivative 10ϩ[PF6]Ϫhas a κ3
co-ordinated HC(pzЈ)3 ligand, and a very different bonding
mode for the diene unit. Thus, in cation 10ϩ the C–C bond
distances [C(4)–C(5), 1.433(16); C(5)–C(6), 1.391(16); C(6)–
C(7), 1.423(15) Å] suggest dominance of the bonding mode
shown in Fig. 7(b), i.e. with two Rh–C σ-bonds and one
Rh–alkene interaction; the fold angle at C(4) ؒ ؒ ؒ C(7) (49.8Њ) is
also consistent with σ-bonds between sp3-hybridised carbon
atoms C4 and C7 and the metal. The bonding between the
metal and cyclopentadienone shows, therefore, that the κ3
coordinated HC(pzЈ)3 ligand acts as a better net donor than the
κ2 form in 6ϩ and 7ϩ, with consequently enhanced donation
from metal to diene.
Conclusion
The dicarbonyl [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ, easily
prepared in high yield, provides an excellent route into rhodium
tris(3,5-dimethylpyrazolyl)methane chemistry. The cation
reacts more readily than the TpЈ analogue [Rh(CO)2TpЈ],
undergoing carbonyl substitution to give [Rh(CO)L{HC-
(pzЈ)3}][PF6] with Lewis bases and giving a range of products
with alkynes, including mononuclear cyclopentadienone, metal-
lacyclopentadiene and cycloheptatrienone complexes.
Experimental
Finally, the unbound part of the cycloheptatrienone ring,
C(1)–C(3), is orientated away from the third (bound) pyrazolyl
ring in 10ϩ, cf. the orientation of the ketonic carbonyl group of
the cyclopentadienone ring of 6ϩ (towards the third, unbound,
pyrazolyl ring), presumably for steric reasons.
The preparation, purification and reactions of the complexes
described were carried out under an atmosphere of dry nitrogen
using dried, distilled and deoxygenated solvents; reactions were
monitored by IR spectroscopy where necessary. Percentage
yields are based upon the rhodium-containing starting
materials. Unless stated otherwise, complexes (i) were purified
by dissolution in CH2Cl2, filtration of the solution through
Celite, addition of n-hexane to the filtrate and reduction of the
volume of the mixture in vacuo to induce precipitation, and (ii)
are stable under nitrogen and dissolve in polar solvents such as
CH2Cl2 and thf.
The 1H NMR spectrum of 10ϩ[PF6]Ϫ shows six signals for the
1
protons of the η4-C6H6O ring, assigned by H/1H correlated
spectroscopy. The 13C–{1H} NMR spectrum shows seven peaks
for C1–C7. The peak above 200 ppm is characteristic of a
ketonic carbon atom (C1) and the peaks at 127.86 and 141.82
ppm have been assigned as C2 and C3 by comparison of the
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2842

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The compounds [{Rh(CO)2(µ-Cl)}2],30 and [Fe(η-C5H5)-
(η-C5H4COMe)][PF6]31 were prepared by published methods.
The ligand HC(pzЈ)3 was synthesised by a combination of two
literature preparations.32,33
IR spectra were recorded on a Nicolet 5ZDX FT spectro-
meter. NMR spectra were recorded on a JEOL λ300 spectro-
meter with SiMe4 as an internal standard for 1H and 13C
spectra, and external H3PO4 as a 31P standard. X-band ESR
spectra were recorded on a Bruker ESP300 spectrometer
equipped with a Bruker variable temperature accessory and
a Hewlett-Packard 5350B microwave frequency counter. The
field calibration was checked by measuring the resonance of
the dpph radical before each series of spectra.
ing yellow solution was evaporated to smaller volume in vacuo,
and then toluene was added to precipitate a bright yellow solid
which was dried in vacuo for 24 h. The product was dissolved
in CH2Cl2, layered with n-hexane, and then slowly stirred to
give a yellow crystalline solid, yield 230 mg (72%).
[Rh(CO){P(o-tolyl)3}{HC(pzЈ)3}][PF6]ؒ0.5CH2Cl2,
4؉[PF6]؊ؒ0.5CH2Cl2. A solution of [Rh(CO)2{HC(pzЈ)3}][PF6],
1ϩ[PF6]Ϫ (200 mg, 0.33 mmol), and P(o-tolyl)3 (202 mg, 0.66
mmol) in thf (40 cm3) was heated under reflux for 2 d and then
evaporated to dryness in vacuo. The residue was dissolved in
CH2Cl2 (20 cm3) and then n-hexane (ca. 30 cm3) was added to
give a grey precipitate which was removed by filtration and
discarded. The volume of the filtrate was reduced in vacuo until
a yellow precipitate started to form which was again removed
by filtration and discarded. Addition of n-hexane to the filtrate
then gave the product as a bright yellow solid, yield 90 mg
(29%).
Electrochemical studies were carried out in CH2Cl2 using an
EG&G model 273A potentiostat in conjunction with a three-
electrode cell. The auxiliary electrode was a platinum wire and
the working electrode a glassy-carbon disc (3.0 mm diameter).
The reference was an aqueous saturated calomel electrode
separated from the test solution by a fine porosity frit and an
agar bridge saturated with KCl. Solutions were 1.0 × 10Ϫ3 mol
2
᎐
[Rh(CO)(ꢀ -PhC᎐CPh){HC(pzЈ) }][PF ]ؒCH Cl ,
᎐
3
6
2
2
dmϪ3 in the test compound and 0.1 mol dmϪ3 in [NBun ][PF6]
5؉[PF6]؊ؒCH2Cl2. A solution of [Rh(CO)2{HC(pzЈ)3}][PF6],
4
1ϩ[PF6]Ϫ (400 mg, 0.66 mmol), and PhC᎐CPh (124 mg, 0.70
᎐
as the supporting electrolyte. Under the conditions used, EЊЈ
for the one-electron oxidation of [Fe(η-C5H5)2] or [Fe(η-C5H4-
COMe)2], added to the test solutions as internal calibrants,
is 0.47 and 0.97 V, respectively. Microanalyses were carried out
by the staff of the Microanalysis Service of the School of
Chemistry, University of Bristol.
᎐
mmol) in thf (40 cm3) was heated under reflux for 5 d and then
filtered through Celite and evaporated to dryness in vacuo. The
product was washed with diethyl ether and then purified to give
a fawn precipitate which was collected, washed with diethyl
ether and dried in vacuo, yield 300 mg (54%).
[Rh{ꢀ4-C4Me4C(O)}{HC(pzЈ)3}][PF6], 6؉[PF6]؊. A solution
of [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ (100 mg, 0.17 mmol),
Syntheses
Tris(3,5-dimethylpyrazolyl)methane, HC(pzЈ)3. Solid K2CO3
(49.8 g, 360 mmol) was dried by heating in vacuo. After cooling
the sample to room temperature, 3,5-dimethylpyrazole (6.92 g,
3
᎐
and MeC᎐CMe (150 µl, 1.92 mmol) in CH Cl (20 cm ) was
᎐
2
2
stirred for 2 d and then allowed to diffuse slowly into n-hexane
at Ϫ10 ЊC to give a salmon-pink solid. A concentrated CH2Cl2
solution of the solid was allowed to diffuse slowly into diethyl
ether at room temperature to give dark red crystals which were
72 mmol), [NBun ][HSO4] (1.22 g, 3.6 mmol) and CHCl3
4
(75 cm3) were added, and the mixture was heated under reflux
for 24 h. The brown mixture was filtered and the solid washed
with boiling CHCl3 (3 × 50 cm3). The filtrate and washings were
evaporated to dryness in vacuo to leave a brown oil which was
dissolved in CH2Cl2 (25 cm3), adsorbed onto silica and applied
(in air) to a water-cooled silica–n-hexane chromatography
column (30–40 cm long). The colourless product was eluted, as
the second eluate, by using a diethyl ether–n-hexane mixture
and slowly changing the ratio of the two solvents from 1 : 4 to
1 : 1. The fractions containing only the desired product were
evaporated to low volume in vacuo and n-hexane was added to
give a white solid and bright yellow mother liquors. The solid
was collected, washed with n-hexane (4 × 20 cm3) and dried
in vacuo for 24 h, yield 2.9 g (41%).
dried in vacuo, yield 67 mg (59%).
᎐
A similar reaction with MeC᎐CEt gave a mixture of isomers
᎐
of [Rh{η4-C4Me2Et2C(O)}{HC(pzЈ)3}][PF6], 7ϩ[PF6]Ϫ.
[Rh(ꢀ1:ꢀ1Ј-CHCPhCHCPh)(CO){HC(pzЈ)3}][PF6], 8؉[PF6]؊.
A solution of [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ (100 mg,
᎐
0.17 mmol), and HC᎐CPh (200 µl, 1.82 mmol) in CH Cl
᎐
2
2
(10 cm3) was stirred for 3 h and then n-hexane was added to
precipitate a pale yellow solid. Purification gave a cream solid
which was dried in vacuo, yield 112 mg (90%).
[Rh(CO)(ꢀ1:ꢀ1Ј-C4H4){HC(pzЈ)3}][PF6], 9؉[PF6]؊, and [Rh-
{ꢀ4-C6H6C(O)}{HC(pzЈ)3}][PF6], 10؉[PF6]؊. Gaseous ethyne
was slowly bubbled through a solution of [Rh(CO)2{HC-
(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ (150 mg, 0.25 mmol), in CH2Cl2 (75 cm3)
for 8 h to give a bright yellow solution which was evaporated to
dryness in vacuo. The oily orange residue was dissolved in
CH2Cl2 before diethyl ether was added to give small amounts of
an orange precipitate of [Rh{η4-C6H6C(O)}{HC(pzЈ)3}][PF6],
10ϩ[PF6]Ϫ. The mother liquors were then concentrated in vacuo,
and diethyl ether was added to precipitate pale yellow
[Rh(CO)(η1:η1Ј-C4H4){HC(pzЈ)3}][PF6], 9ϩ[PF6]Ϫ, which was
dried in vacuo, yield 65 mg (42%).
[Rh(CO)2{HC(pzЈ)3}][PF6], 1؉[PF6]؊. A solution of [{Rh-
(CO)2(µ-Cl)}2] (0.70 g, 1.80 mmol) and HC(pzЈ)3 (1.06 g,
3.60 mmol) in CH2Cl2 (100 cm3) was stirred for 30 min before
Tl[PF6] (1.47 g, 3.78 mmol) was added. After 5 h the solution
was filtered through Celite, concentrated in vacuo and layered
with n-hexane. Slowly stirring the layered mixture then gave
a yellow, crystalline precipitate which was dried in vacuo for
24 h, yield 2.04 g (94%).
[Rh(CO)(PPh3){HC(pzЈ)3}][PF6]ؒCH2Cl2, 2؉[PF6]؊ؒCH2Cl2.
A solution of [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ, (100 mg,
0.17 mmol) and PPh3 (44 mg, 0.17 mmol) in CH2Cl2 (10 cm3)
was stirred for 5 min before n-hexane was added to precipitate a
yellow microcrystalline solid. A concentrated CH2Cl2 solution
of the solid was allowed to diffuse slowly into n-hexane at
Ϫ10 ЊC to give yellow crystals, yield 90 mg (64%).
Crystal structure determinations of [Rh(CO)2{HC(pzЈ)3}]-
[PF6], 1؉[PF6]؊, [Rh(CO)(PPh3){HC(pzЈ)3}][PF6]ؒ2CH2Cl2,
2
2؉[PF6]؊ؒ2CH2Cl2, [Rh(CO)(ꢀ -PhC᎐CPh){HC(pzЈ) }][PF ]ؒ
᎐
᎐
3
6
1.5thf, 5؉[PF6]؊ؒ1.5thf, [Rh{ꢀ4-C4Me4C(O)}{HC(pzЈ)3}][PF6],
6؉[PF6]؊, [Rh{ꢀ4-C4Me2Et2C(O)}{HC(pzЈ)3}][PF6], 7؉[PF6]؊ؒ
H2O,
[Rh(CO)(ꢀ1:ꢀ1Ј-CHCPhCHCPh){HC(pzЈ)3}][PF6]ؒ
2CH2Cl2, 8؉[PF6]؊ؒ2CH2Cl2, and [Rh{ꢀ4-C6H6C(O)}{HC-
(pzЈ)3}][PF6], 10؉[PF6]؊. Crystals suitable for X-ray diffraction
study were grown as follows: 1ϩ[PF6]Ϫ, slow diffusion of a
concentrated CH2Cl2 solution of the complex into n-hexane at
room temperature; 2ϩ[PF6]Ϫؒ2CH2Cl2, 7ϩ[PF6]ϪؒH2O and
[Rh(CO)(AsPh3){HC(pzЈ)3}][PF6]ؒCH2Cl2, 3؉[PF6]؊ؒCH2Cl2.
A solution of [Rh(CO)2{HC(pzЈ)3}][PF6], 1ϩ[PF6]Ϫ (200 mg,
0.33 mmol), and AsPh3 (407 mg, 1.33 mmol) in CH2Cl2 (10 cm3)
was stirred for 4 d and then filtered through Celite. The result-
D a l t o n T r a n s . , 2 0 0 3 , 2 8 3 5 – 2 8 4 5
2843

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8ϩ[PF6]Ϫؒ2CH2Cl2, slow diffusion of a concentrated CH2Cl2
solution of the complex into n-hexane at Ϫ10 ЊC; 5ϩ[PF6]Ϫؒ
1.5thf, slow diffusion of a thf solution of the complex into n-
hexane at room temperature; 6ϩ[PF6]Ϫ, slow diffusion of a
CH2Cl2 solution of the complex into diethyl ether at Ϫ10 ЊC;
10ϩ[PF6]Ϫ, slow diffusion of a concentrated thf solution of
complex 9ϩ[PF6]Ϫ into n-hexane at Ϫ10 ЊC. X-Ray diffraction
measurements were made at 173 K (for 1ϩ[PF6]Ϫ and 5ϩ[PF6]Ϫ–
8ϩ[PF6]Ϫ) or 293 K (for 2ϩ[PF6]Ϫ and 10ϩ[PF6]Ϫ). Many of the
other details of the structure analyses are presented in Table 9.
The unit cells of 1ϩ[PF6]Ϫ and 5ϩ[PF6]Ϫؒ1.5thf each contain
one disordered [PF6]Ϫ anion, which has been modelled in each
case with a central phosphorus atom with 100% occupancy. The
major component of the disordered structure is modelled as an
octahedral array of fluorine atoms about this phosphorus
atom, with any remaining electron density peaks assigned as
fluorine atoms in the minor orientation of the anion. The
combined occupancy of the two parts was constrained to 100%.
The structure of 2ϩ[PF6]Ϫؒ2CH2Cl2 contains two CH2Cl2
solvent molecules, one of which is disordered over two sites
in an approximate 4 : 1 ratio; again the total occupancy is
constrained to 100%. The solution for 5ϩ[PF6]Ϫؒ1.5thf contains
one thf molecule, and a second that is badly disordered over
a special position. The latter has been modelled with 50%
occupancy with no hydrogen atoms. Hydrogen atoms were not
assigned to the water molecule in 7ϩ[PF6]ϪؒH2O.
CCDC reference numbers 205489–205495.
See http://www.rsc.org/suppdata/dt/b3/b302440g/ for crystal-
lographic files in CIF format.
Acknowledgements
We thank the EPSRC for Research Studentships (to D.J.H.E
and O.D.H.).
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