Carbon-fluorine bond activation in the reactions between 1,2-bis[bis-(2,6-difluorophenyl)phosphino]ethane and [{MCl(μ-Cl)(η5-C5Me5)}2] (M = Rh or Ir)

Article abstract of DOI:10.1039/a800515j

The new fluorine-containing diphosphine (C₆H₃F₂-2,6)₂PCH₂CH ₂P(C₆H₃F₂-2,6)₂ I has been prepared and structurally characterized by single-crystal X-ray diffraction. The reaction between [{RhCl(μ-Cl)(η⁵-C₅Me₅)}₂] and I in refluxing benzene yielded the cationic species [RhCl{η⁵-C₅Me₃[(2-CH₂C ₆H₃F-6)P(C₆H³F ₂-2,6)CH₂]₂-1,3}]⁺, which was characterized as the BF₄^- salt 1. The reaction involved the regiospecific activation of two C-F bonds and two C-H bonds and the formation of two C-C bonds. In contrast, the reaction between [{IrCl(μ-Cl)-(η⁵-C₅Me₅)}₂] and I did not involve C-F bond activation, but resulted in the formation of the dinuclear complex [{IrCl₂(η⁵-C₅Me⁵)[P(C ₆H₃F₂-2,6)₂CH₂]} ₂] 2, the characterization of which was confirmed by the synthesis of the (C₆F₅)₂PCH₂CH₂P(C ₆F₅)₂ analogue [{IrCl₂(η⁵-C₅Me₅)[P(C ₆F₅)₂CH²]}₂] 3. The complexes [MCl{(C₆H₃F₂-2,6)₂PCH ₂CH²P(C₆H₃F₂-2,6) ₂}(η⁵-C₅Me₅)]₊BF ₄^- (M = Rh 4 or Ir 5), unlike their (C₆F₅)₂PCH₂CH₂P(C ₆F₅)₂ analogues, did not undergo C-F and C-H bond activation and C-C bond formation on thermolysis. The structures of complexes 2-4 have been determined by single-crystal X-ray diffraction.

Full text of DOI:10.1039/a800515j

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Carbon–fluorine bond activation in the reactions between 1,2-bis[bis-
(2,6-difluorophenyl)phosphino]ethane and [{MCl(ì-Cl)(ç5-C5Me5)}2]
(M ؍ Rh or Ir)
John Fawcett,a Steffi Friedrichs,a John H. Holloway,a Eric G. Hope,a Vickie McKee,b
Mark Nieuwenhuyzen,b David R. Russella and Graham C. Saunders*,†,a,b
a Department of Chemistry, University of Leicester, Leicester, UK LE1 7RH
b School of Chemistry, The Queen’s University of Belfast, David Keir Building, Belfast,
UK BT9 5AG
The new fluorine-containing diphosphine (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 I has been prepared and
structurally characterized by single-crystal X-ray diffraction. The reaction between [{RhCl(µ-Cl)(η5-C5Me5)}2]
and I in refluxing benzene yielded the cationic species [RhCl{η5-C5Me3[(2-CH2C6H3F-6)P(C6H3F2-2,6)CH2]2-
1,3}]ϩ, which was characterized as the BF4Ϫ salt 1. The reaction involved the regiospecific activation of two C᎐F
bonds and two C᎐H bonds and the formation of two C᎐C bonds. In contrast, the reaction between [{IrCl(µ-Cl)-
(η5-C5Me5)}2] and I did not involve C᎐F bond activation, but resulted in the formation of the dinuclear complex
[{IrCl2(η5-C5Me5)[P(C6H3F2-2,6)2CH2]}2] 2, the characterization of which was confirmed by the synthesis of
the (C6F5)2PCH2CH2P(C6F5)2 analogue [{IrCl2(η5-C5Me5)[P(C6F5)2CH2]}2] 3. The complexes [MCl{(C6H3F2-
2,6)2PCH2CH2P(C6H3F2-2,6)2}(η5-C5Me5)]ϩBF4Ϫ (M = Rh 4 or Ir 5), unlike their (C6F5)2PCH2CH2P(C6F5)2
analogues, did not undergo C᎐F and C᎐H bond activation and C᎐C bond formation on thermolysis. The
structures of complexes 2–4 have been determined by single-crystal X-ray diffraction.
We have recently demonstrated that two ortho bonds of the
diphosphine (C6F5)2PCH2CH2P(C6F5)2 (dfppe) can be activated
under mild conditions by the transition-metal complexes
[{MCl(µ-Cl)(η5-C5Me5)}2] (M = Rh or Ir) to form the cations
[MCl{η5-C5Me3[2-CH2C6F4P(C6F5)CH2]2-1,3}]ϩ in quantit-
ative yield.1,2 We are currently carrying out extensive investig-
ations into these remarkable reactions to determine the
mechanism. In particular, we anticipate that variation of
the reagents will aid in our understanding of the reactions.
One possible mechanism for the activation of C᎐F bonds
involves single-electron transfer from an electron-rich source to
the electron-accepting fluoroaromatic.3 This type of mechanism
is supported by ESR evidence from the reaction between trans-
[PtH2{P(cyclo-C6H11)3}2] and C6F5CN.4 The degree of fluorin-
ation of an aromatic ring strongly affects its electron-accepting
ability, i.e. hexafluorobenzene is more electron-accepting than
fluorobenzene.5 Richmond and co-workers6 have reported that
the activation of one ortho C᎐F bond of the Schiff base Me2-
Fig. 1 Experimental (a) and simulated (b) 19F-{1H} NMR spectra of
(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 I
NCH CH N᎐CHC F H by a tungsten(0) complex occurs
᎐
2
2
6
x
5Ϫx
whatever the degree of fluorination (x = 1–5), provided there
is at least one ortho C᎐F bond. In contrast, Crespo and co-
workers7 found that one C᎐F bond of the Schiff base Ph-
CH N᎐CHC F H5Ϫx is activated by a platinum() complex only
᎐
2
6
x
when x > 2 and both ortho positions are fluorinated. Here, we
report the reactions between [{MCl(µ-Cl)(η5-C5Me5)}2] (M =
Rh or Ir) and the new diphosphine (C6H3F2-2,6)2PCH2CH2-
P(C6H3F2-2,6)2, which is fluorinated only in the ortho positions,
to establish whether the degree of fluorination of the diphos-
phine is significant in our system.
Fig. 2 Experimental (a) and simulated (b) 31P-{1H} NMR spectra of
(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 I
column chromatography in 40% yield. Compound 1 was
obtained pure after recrystallization from diethyl ether and
characterized by elemental analysis, high-resolution mass spec-
trometry and multinuclear NMR spectroscopies (Table 1). The
19F-{1H} and 31P-{1H} NMR spectra, recorded in CDCl3
(Figs. 1 and 2), represent the A and X parts respectively of an
AAЈX4XЈ4 spin system. These have been successfully simulated
using the values 3J(PPЈ) = 47.2, 3J(PF) = 30.1, 6J(PFЈ) = 1.2 and
Results and Discussion
Addition of Cl2PCH2CH2PCl2 to Liϩ[C6H3F2-2,6]Ϫ, formed by
addition of LiBun to C6H3BrF2-2,6 in diethyl ether at Ϫ78 ЊC
afforded a dark red slurry, from which the new diphos-
phine (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 I was isolated by
† E-Mail: g.saunders@qub.ac.uk
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484
1477

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Table 1 Analytical, mass spectral and NMR data for compounds I and 1–5
Compound Analysis (%)a and m/z NMRb
I
C, 58.0 (57.6); H, 2.8 (3.0)
1H: 7.26 (4 H, m, Hp), 6.80 [8 H, ddd, 3J(HmF) ≈ 3J(HmHp) 8.2, 4J(HmP) 1.3, Hm], 2.53
[4 H, vt, ¹| 2J(PH) ϩ 3J(PH)| 6.0, CH2]
542 (Mϩ), 429 ([M Ϫ C6H3F2]ϩ), 285 ([M Ϫ
2C6H3F2]ϩ) [Found: 542.059 96. C26H16F8P2
(Mϩ) requires 542.059 95]c
¯
²
19F-{1H}: Ϫ101.39 (X part of an AAЈX4XЈ4 spectrum)
31P-{1H}: Ϫ46.8 (A part of an AAЈX4XЈ4 spectrum)
1
C, 44.1 (44.8); H, 3.55 (3.2)d
1H: 7.44 (4 H, m), 6.87 (8 H, m), 4.40 [2 H, dm, 2J(HH) 17.6, C6H3FCH2], 4.01 [2 H,
775 ([M Ϫ BF4]ϩ), 739
d, J(HH) 17.6, C6H3FCH2], 3.75 (2 H, m, CH2), 3.42 (2 H, m, CH2), 2.01 [6 H, d,
2
([M Ϫ BF4 Ϫ Cl Ϫ H]ϩ), 627
([M Ϫ BF4 Ϫ Cl Ϫ C6H3F2]ϩ)e
4J(PH) 7.2, 4- and 5-CH3], 1.27 (3 H, s, 2-CH3)
19F-{1H}: Ϫ93.96 (2 F, s, CH2C6H3F), Ϫ101.22 (4 F, br s, C6H3F2), Ϫ152.50 (4 F, br s,
Ϫ
BF4
)
31P-{1H}: 60.0 [d, 1J(RhP) 139]
2 f
3
C, 41.6 (41.3); H, 3.6 (3.4)
C, 35.4 (35.5); H, 2.2 (2.2)
1384 ([M Ϫ Cl Ϫ C5Me5]ϩ), 1349 ([M Ϫ
2Cl Ϫ C5Me5]ϩ)e
1H: 3.05 (4 H, s, CH2), 1.39 (30 H, s, CH3)
19F: Ϫ125.90 [8 F, d, 3J(FoFm) 20.4, Fo], Ϫ146.96 [4 F, t, 3J(FmFp) 21.0, Fp], Ϫ159.23 (8
F, dd, Fm)
31P-{1H}: Ϫ23.3 (s)
4g
C, 48.7 (48.8); H, 3.8 (3.9); Cl, 3.4 (3.7)
1H: 7.76 (2 H, m, Hp), 7.40 (2 H, m, Hp), 6.96 [4 H, dd, 3J(HmF) ≈ 3J(HmHp) 8.5, Hm],
6.85 [4 H, dd, 3J(HmF) ≈ 3J(HmHp) 9.0, Hm], 3.15 (2 H, m, CH2), 2.91 (2 H, m, CH2),
1.66 [15 H, t, 4J(PH) 4.4, CH3]
815 ([M Ϫ BF4]ϩ), 780 ([M Ϫ BF4 Ϫ Cl]ϩ)e
19F-{1H}: Ϫ96.02 (4 F, s), Ϫ97.65 (4 F, s), Ϫ154.66 and Ϫ154.71 (4 F, 2s, ca. 1:4,
Ϫ
)
BF4
19F-{1H} [170 K, (CD3)2CO]: Ϫ93.50 (2 F, s, C6H3F2), Ϫ96.99 (2 F, s, C6H3FЈ2),
Ϫ97.62 (2 F, s, C6H3FЈ2), Ϫ98.11 (2 F, s, C6H3F2)
31P-{1H}: 28.3 [d, 1J(RhP) 147]
4
5
C, 43.2 (43.6); H, 2.8 (3.2)
1H: 7.47 (2 H, m, Hp), 7.37 [2 H, tt, J(HpF) ≈ 3J(HmHp) 7.2, Hp], 6.93 [4 H, dd,
905 ([M Ϫ BF4]ϩ), 870 ([M Ϫ BF4 Ϫ Cl]ϩ)e
3J(HmF) ≈ 3J(HmHp) 8.0, Hm], 6.78 [4 H, dd, 3J(HmF) ≈ 3J(HmHp) 9.3, Hm], 2.93 (4 H,
m, CH2), 1.37 [15 H, t, 4J(PH) 4.4, CH3]
19F-{1H}: Ϫ96.44 (4 F, s), Ϫ97.47 (4 F, s), Ϫ154.66 and Ϫ154.72 (4 F, 2s, ca. 1:4,
Ϫ
)
BF4
19F-{1H} [210 K, (CD3)2CO]: Ϫ96.35 (2 F, s, C6H3F2), Ϫ97.66 (2 F, s, C6H3FЈ2),
Ϫ98.57 (2 F, s, C6H3FЈ2), Ϫ99.22 (2 F, s, C6H3F2)
31P-{1H}: 1.0 (s)
a Required values are given in parentheses. b Unless stated otherwise, recorded in CDCl3 at 298 K. Data given as chemical shift (δ) [relative intensity,
multiplicity, J/Hz, assignment], s = singlet, d = doublet, t = triplet, vt = virtual triplet, m = multiplet. c EI. d Satisfactory analysis could not be
obtained due to contamination by other salts, such as 4, from which 1 could not be separated. e Positive-ion fast-atom bombardment with m-
nitrobenzyl alcohol as matrix. f Insufficiently soluble for NMR. g Crystallized with 1 Me2CO.
Table 2 Bond lengths (Å) and angles (Њ) with estimated standard
deviations (e.s.d.s) in parentheses for (C6H3F2-2,6)2PCH2CH2P(C6H3F2-
2,6) I
P᎐C(1)
P᎐C(11)
1.839(3)
1.829(3)
1.375(5)
1.354(5)
1.369(6)
1.366(11)
1.331(12)
1.376(8)
1.356(6)
1.391(5)
C(1)᎐C(1Ј)
P᎐C(21)
1.533(5)
1.837(3)
1.376(4)
1.357(3)
1.371(4)
1.375(5)
1.363(5)
1.373(4)
1.353(4)
1.385(4)
C(11)᎐C(12)
C(12)᎐F(12)
C(12)᎐C(13)
C(13)᎐C(14)
C(14)᎐C(15)
C(15)᎐C(16)
C(16)᎐F(16)
C(16)᎐C(11)
C(21)᎐C(22)
C(22)᎐F(22)
C(22)᎐C(23)
C(23)᎐C(24)
C(24)᎐C(25)
C(25)᎐C(26)
C(26)᎐F(26)
C(26)᎐C(21)
P᎐C(1)᎐C(1Ј)
C(1)᎐P᎐C(21)
P᎐C(11)᎐C(12)
P᎐C(11)᎐C(16)
C(12)᎐C(11)᎐C(16) 115.2(4)
C(11)᎐C(12)᎐F(12) 117.6(3)
C(11)᎐C(12)᎐C(13) 123.6(5)
C(13)᎐C(12)᎐F(12) 118.8(5)
C(12)᎐C(13)᎐C(14) 118.3(7)
C(13)᎐C(14)᎐C(15) 120.8(7)
C(14)᎐C(15)᎐C(16) 120.6(7)
C(15)᎐C(16)᎐F(16) 121.2(5)
C(15)᎐C(16)᎐C(11) 121.5(6)
C(11)᎐C(16)᎐F(16) 117.3(4)
108.3(3)
106.07(13)
125.9(2)
118.9(3)
C(1)᎐P᎐C(11)
C(11)᎐P᎐C(21)
P᎐C(21)᎐C(22)
P᎐C(21)᎐C(26)
C(22)᎐C(21)᎐C(26) 113.0(2)
C(21)᎐C(22)᎐F(22) 116.9(2)
C(21)᎐C(22)᎐C(23) 125.5(3)
C(23)᎐C(22)᎐F(22) 117.6(3)
C(22)᎐C(23)᎐C(24) 117.9(3)
C(23)᎐C(24)᎐C(25) 120.2(3)
C(24)᎐C(25)᎐C(26) 118.9(3)
C(25)᎐C(26)᎐F(26) 116.6(3)
C(25)᎐C(26)᎐C(21) 124.5(3)
C(21)᎐C(26)᎐F(26) 118.9(2)
99.09(13)
100.53(12)
118.0(2)
Fig. 3 Molecular structure of (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2
I. Displacement ellipsoids are shown at the 30% probability level
128.7(2)
9J(FFЈ) = Ϫ0.4 Hz (the signs are relative). The value of δP is
similar to that of Ϫ44.4 for dfppe8 recorded in CDCl3, and the
value of δF is similar to that of Ϫ101.47 for P(C6H3F2-2,6)3.9
3
The absolute value of J(PF) is similar to that of PPh(C6F5)2,9
but is considerably lower than those of ca. 40 Hz observed
in the 2,6-difluorophenylphosphines PPh3Ϫx(C6H3F2-2,6)x (x =
1–3).9
Diphosphine I was further characterized by single-crystal
X-ray diffraction. The structure (Fig. 3) is very similar to those
of dppe10 and dfppe,11 with the centre of the C(1)᎐C(1Ј) bond
on a crystallographic centre of symmetry. Bond lengths and
angles are listed in Table 2. The bond lengths and the P᎐C᎐C,
C᎐P᎐C and C᎐C(P)᎐C angles are identical within experimental
error of those of dfppe.11 The most significant difference in the
geometry about the phosphorus atoms between the two struc-
tures is the C(P)᎐C᎐F angles. For dfppe these angles lie in the
range 118.8(3) to 121.4(4)Њ with an average of 120.2Њ, whereas
the C(P)᎐C᎐F angles of I are more acute, lying in the range
116.9(2) to 118.9(2)Њ with an average of 117.7Њ.
Treatment of [{RhCl(µ-Cl)(η5-C5Me5)}2] with I in refluxing
benzene for 16 h afforded in high yield [RhCl{η5-C5Me3-
1478
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484

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+
Cl
(i), (ii)
Cl
Cl
–
BF4
M
Cl
M
Rh
P
P
Cl
F
F
C6H3F2
C6H3F2
1
(iii), (iv)
(v)
+
–
BF4
C6H3F2
P
M
Ir
C6H3F2
(vi)
Cl
R
Cl
F2H3C6
P
P
Cl
R
C6H3F2
R
Cl
Cl
P
Ir
R
4 M = Rh
5 M = Ir
2 R = C6H3F2-2,6
3 R = C6F5
Scheme 1 (i) M = Rh, I, C6H6, heat; (ii) NH4BF4, Me2CO; (iii) NH4BF4, MeOH; (iv) I, CH2Cl2; (v) M = Ir, I or dfppe, C6H6, heat; (vi) R = C6H3F2-
2,6, NH4BF4, Me2CO
1
[(2-CH2C6H3F-6)P(C6H3F2-2,6)CH2]2-1,3}]ϩClϪ as an orange
precipitate via C᎐F and C᎐H bond activation and concomitant
C᎐C bond formation (Scheme 1). This product was character-
ized by mass spectrometry, which showed peaks at m/z 774 and
738 assigned to [M Ϫ Cl Ϫ H]ϩ and [M Ϫ 2Cl Ϫ 2H]ϩ respect-
ively, but was found to be insoluble in all common organic
solvents, precluding an NMR study. However, the tetrafluoro-
borate salt, 1, formed by anion metathesis, is readily soluble in
polar organic solvents. Salt 1 was characterized by elemental
analysis, mass spectrometry and multinuclear NMR spectro-
scopies (Table 1). The NMR spectroscopic data indicate that
1 was contaminated by small amounts of similar complexes
(such as 4) from which it could not be separated, and this was
confirmed by the analytical data which are not as required. The
31P-{1H} NMR spectrum, recorded in CDCl3, exhibits a doub-
let of multiplets at δ 60.0 with an absolute value of 1J(RhP) of
139 Hz. These values can be compared to those of δ 71.3 and
144 Hz for [RhCl{η5-C5Me3[2-CH2C6F4P(C6F5)CH2]2-1,3}]ϩ-
ClϪ in the same solvent.1 The 1H NMR spectrum includes two
multiplets at δ 7.44 and 6.87, with relative intensities 1:2, which
are assigned to the twelve hydrogen atoms of the phenyl groups.
There are four resonances between δ 3.0 and 4.5 of equal
integral which are assigned to pairs of PCH2 and C6H3FCH2
methylene hydrogen atoms. Resonances assigned to PCH2
occur as two multiplets with coupling to phosphorus. The
hydrogen atoms of each PCH2 moiety are endo and exo with
respect to the cyclopentadienyl ring and, hence, are non-
equivalent. Presumably, the equivalence of the two PCH2
moieties arises due to the flexibility of the chelate ring. The
resonances assigned to the C6H3FCH2 methylene hydrogen
atoms occur as a multiplet with coupling to phosphorus, as
indicated by the H-{31P} NMR spectrum, and a doublet with
a coupling to hydrogen, 2J(HH), of 17.6 Hz. The 4- and
5-methyl hydrogen resonance is a doublet at δ 2.01 with a coup-
ling to one phosphorus atom, 4J(PH), of 7.2 Hz. The 2-methyl
1
hydrogen resonance is a broad singlet at δ 1.27. The H NMR
spectrum is consistent with those of [RhCl{η5-C5Me3-
[2-CH2C6F4P(C6F5)CH2]2-1,3}]ϩXϪ (XϪ = ClϪ or BF4 ).1,2 The
Ϫ
19F-{1H} NMR spectrum exhibits a singlet at δ Ϫ93.96, which
is assigned to the fluorine atoms of the two CH2C6H3F moi-
eties, and a broad singlet at δ Ϫ101.22, which is assigned to the
four fluorine atoms of the C6H3F2 groups. This resonance is
broadened due to hindered rotation about the P᎐C bond, as is
found for [RhCl{η5-C5Me3[2-CH2C6F4P(C6F5)CH2]2-1,3}]ϩXϪ
(XϪ = ClϪ or BF4 ).1,2 Unfortunately, it was not possible to
Ϫ
grow crystals of 1 suitable for X-ray diffraction.
In contrast to the reaction between [{RhCl(µ-Cl)(η5-C5-
Me5)}2] and I, treatment of [{IrCl(µ-Cl)(η5-C5Me5)}2] with 2
equivalents of I in refluxing benzene for 8 h did not cause acti-
vation of C᎐F bonds. Instead, the neutral dinuclear complex
[{IrCl2(η5-C5Me5)[P(C6H3F2-2,6)2CH2]}2] 2 was formed. No
other phosphine-containing iridium species were detected in the
reaction mixture. Complex 2 was characterized by elemental
analysis (Table 1), but is not sufficiently soluble to permit an
NMR study and the mass spectrum did not show the parent
ion. The characterization of 3 was corroborated by the syn-
thesis of the dfppe analogue [{IrCl2(η5-C5Me5)[P(C6F5)2CH2]}2]
3, which was formed in quantitative yield on treatment of dfppe
with 1.4 equivalents of [{IrCl(µ-Cl)(η5-C5Me5)}2] in refluxing
benzene. Complex 3, which is soluble in polar organic solvents,
was characterized by elemental analysis and multinuclear NMR
spectroscopies (Table 1), but, as for 2, the mass spectrum did
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484
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Table 3 Selected bond distances (Å) and angles (Њ) with e.s.d.s in parentheses for [{IrCl2(η5-C5Me5)[P(C6H3F2-2,6)2CH2]}2]ؒ2Me2CO 2ؒ2Me2CO and
of [{IrCl2(η5-C5Me5)[P(C6F5)2CH2]}2]ؒ2Me2CO 3ؒ2Me2COa
3ؒ2Me2CO
2ؒ2Me2CO
Molecule 1
Molecule 2b
Cp*᎐Ir
Ir᎐P
Ir᎐Cl
P᎐CH2
CH2᎐CHЈ2
P᎐C (aryl)
1.828(7)
2.334(3)
2.423(3), 2.397(3)
1.817(11)
1.54(2)
1.825(7)
2.304(2)
2.407(2), 2.388(2)
1.837(7)
1.524(14)
1.816(9)
2.306(3)
2.412(2), 2.404(2)
1.896(14), 1.862(14)
1.52(3), 1.50(3)
1.90(2), 1.87(2)
1.865(10), 1.865(10)
1.40(2), 1.37(2)
1.43(3), 1.34(3)
1.32(2), 1.26(2)
1.55(2), 1.52(3)
1.36(2), 1.32(2)
1.35(2), 1.33(2)
1.38(2), 1.37(2)
1.33(2), 1.28(3)
1.831(12), 1.828(12)
1.855(7), 1.846(7)
C(P)᎐C
1.40(2), 1.39(2)
1.39(2), 1.41(2)
1.396(10), 1.377(10)
1.390(10), 1.386(10)
C᎐F (ortho)
1.356(14), 1.366(14)
1.366(14), 1.340(13)
1.353(9), 1.331(9)
1.343(8), 1.339(9)
Cp*᎐Ir᎐P
Cp*᎐Ir᎐Cl
P᎐Ir᎐Cl
136.4(3)
136.5(3)
137.0(3)
124.5(3), 120.7(3)
90.75(11), 81.73(10)
88.66(3)
123.5(3), 121.4(3)
90.63(7), 82.77(7)
87.45(8)
124.1(3), 121.2(3)
89.73(10), 81.65(9)
88.49(9)
Cl᎐Ir᎐Cl
Ir᎐P᎐CH2
P᎐CH2᎐CHЈ2
Ir᎐P᎐C (aryl)
112.2(4)
116.3(10)
121.0(4), 110.9(3)
117.3(2)
112.3(6)
120.5(2), 110.0(2)
124.9(5), 104.1(5)
109.3(13), 106.8(13)
130.3(5), 114.6(6)
110.1(3), 110.1(3)
120.1(6), 96.5(6)
95.6(6), 92.4(6)
111.0(7), 93.7(6)
134.7(14), 109.8(13)
125.4(14), 117(2)
111.6(13), 110.8(11)
136.6(10), 124.9(12)
122(2), 119.7(14)
122(2), 121(2)
C (aryl)᎐P᎐CH2
107.2(5), 99.5(5)
103.3(3), 99.9(3)
C (aryl)᎐P᎐C (aryl)
P᎐C᎐C(F)
104.7(5)
126.1(9), 121.0(9)
125.4(9), 121.0(8)
103.8(3)
123.8(5), 120.3(6)
126.2(6), 118.5(5)
C(P)᎐C᎐F
117.9(10), 118.2(10)
119.9(10), 116.8(10)
122.2(7), 119.8(7)
121.0(7), 120.3(6)
133(2), 130(2)
112(2), 111(2)
115(2), 117(2)
C(F)᎐C(P)᎐C(F)
112.2(11), 113.3(10)
115.7(7), 115.1(7)
137(2), 98.4(14)
a Cp* denotes the cyclopentadienyl centroid. b Some of the bond lengths and angles for this molecule are given as pairs due to disorder of the C6F5
rings and the CH2 atoms. The relevant atoms were modelled for two sites with 50% occupancy and refined as isotropic.
Fig.
4
Molecular structure of [{IrCl2(η5-C5Me5)[P(C6H3F2-2,6)2-
CH2]}2] 2. Displacement ellipsoids are shown at the 30% probability
level. The hydrogen atoms are omitted for clarity
Fig. 5 Molecular structure of one of the independent molecules of
[{IrCl2(η5-C5Me5)[P(C6F5)2CH2]}2] 3. Details as in Fig. 4
not show the parent ion. Complexes 2 and 3 were structurally
characterized by single-crystal X-ray diffraction. Attempts
to prepare [{RhCl2(η5-C5Me5)[P(C6F5)2CH2]}2] by similar
methods have been unsuccessful, leading only to the formation
of [RhCl{η5-C5Me3[2-CH2C6F4P(C6F5)CH2]2-1,3}]ϩXϪ, even
when a large excess of [{RhCl(µ-Cl)(η5-C5Me5)}2] was used.
The structures of complexes 2 and 3 are shown in Figs. 4 and
5 respectively and selected bond lengths and angles are given in
Table 3. The structure of 3 comprises two crystallographically
1480
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484

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Table 4 Selected bond distances (Å) and angles (Њ) with e.s.d.s in
parentheses for [RhCl{(C6H3F2-2.6)2PCH2CH2P(C6H3F2-2.6)2}(η5-C5-
Ϫ
Me5)]ϩBF4 ؒMe2CO 4ؒMe2CO
Cp*᎐Rh
Rh᎐P(1)
P(1)᎐C(1)
P(2)᎐C(2)
1.868(4)
2.329(1)
1.913(11)
1.782(8)
1.529(13)
1.843(4)
1.833(6)
1.397(7)
1.387(7)
1.355(7)
1.362(6)
1.384(9)
1.404(7)
1.344(6)
1.351(9)
Rh᎐Cl
Rh᎐P(2)
2.385(1)
2.349(1)
1.784(11)
1.961(8)
1.530(11)
1.826(5)
1.833(4)
1.396(7)
1.385(8)
1.347(8)
1.354(6)
1.387(7)
1.376(6)
1.343(7)
1.363(5)
P(1)᎐C(1Ј)
P(2)᎐C(2Ј)
C(1b)᎐C(2Ј)
P(1)᎐C(21)
P(2)᎐C(41)
C(21)᎐C(22)
C(21)᎐C(26)
C(22)᎐F(22)
C(26)᎐F(26)
C(41)᎐C(42)
C(41)᎐C(46)
C(42)᎐F(42)
C(46)᎐F(46)
C(1)᎐C(2)
P(1)᎐C(11)
P(2)᎐C(31)
C(11)᎐C(12)
C(11)᎐C(16)
C(12)᎐F(12)
C(16)᎐F(16)
C(31)᎐C(32)
C(31)᎐C(36)
C(32)᎐F(32)
C(36)᎐F(36)
Cp*᎐Rh᎐Cl
Cp*᎐Rh᎐P(2)
Cl᎐Rh᎐P(2)
Rh᎐P(1)᎐C(11)
Rh᎐P(1)᎐C(1)
Rh᎐P(2)᎐C(31)
Rh᎐P(2)᎐C(2)
C(11)᎐P(1)᎐C(1)
C(21)᎐P(1)᎐C(1)
C(11)᎐P(1)᎐C(21)
C(31)᎐P(2)᎐C(2Ј)
C(41)᎐P(2)᎐C(2Ј)
P(1)᎐C(11)᎐C(12)
P(1)᎐C(11)᎐C(16)
C(12)᎐C(11)᎐C(16)
C(21)᎐C(22)᎐F(22)
C(21)᎐C(26)᎐F(26)
P(2)᎐C(31)᎐C(32)
P(2)᎐C(31)᎐C(36)
C(32)᎐C(31)᎐C(36)
C(41)᎐C(42)᎐F(42)
C(41)᎐C(46)᎐F(46)
120.1(14)
135.5(13)
87.10(4)
123.9(2)
107.2(3)
122.0(2)
108.0(3)
91.1(4)
115.5(4)
102.8(2)
110.9(4)
98.7(3)
122.1(4)
123.3(4)
114.0(4)
119.2(6)
118.0(4)
126.0(4)
120.4(5)
113.5(5)
118.8(5)
116.8(4)
Cp*᎐Rh᎐P(1)
Cl᎐Rh᎐P(1)
P(1)᎐Rh᎐P(2)
Rh᎐P(1)᎐C(21)
Rh᎐P(1)᎐C(1Ј)
Rh᎐P(2)᎐C(41)
Rh᎐P(2)᎐C(2Ј)
C(11)᎐P(1)᎐C(1Ј)
C(21)᎐P(1)᎐C(1Ј)
C(31)᎐P(2)᎐C(2)
C(41)᎐P(2)᎐C(2)
C(31)᎐P(2)᎐C(41)
C(11)᎐C(12)᎐F(12)
C(11)᎐C(16)᎐F(16)
P(1)᎐C(21)᎐C(22)
P(1)᎐C(21)᎐C(26)
C(22)᎐C(21)᎐C(26)
C(31)᎐C(32)᎐F(32)
C(31)᎐C(36)᎐F(36)
P(2)᎐C(41)᎐C(42)
P(2)᎐C(41)᎐C(46)
C(42)᎐C(41)᎐C(46)
131.6(13)
82.20(4)
83.00(5)
114.7(2)
105.7(3)
118.70(14)
104.7(3)
106.2(4)
101.1(4)
88.7(4)
Fig. 6 Molecular structure of [RhCl{(C6H3F2-2,6)2PCH2CH2P(C6-
H3F2-2,6)2}(η5-C5Me5)]ϩBF4Ϫ 4. Details as in Fig. 4
PPh(C6F5)2 and PPh2(C6F5) respectively,9 suggesting that it is
the steric effect which dominates. It is also noted that the mean
Ir᎐Cl distances in 2 (2.41 Å) and 3 (2.40 Å) are slightly larger
than the values of 2.37 and 2.38 Å for [IrCl2(PMe3)(η5-
C5Me5)]12 and [IrCl2{P(OC6H3F2-2,6)3}(η5-C5Me5)]13 respect-
ively. The bond lengths and angles of the diphosphine ligand
in 2 are the same as for I, except for the C (aryl)᎐P᎐C (aryl)
and P᎐CH2᎐CHЈ2 angles which are larger for 2 by ca. 4 and 7Њ
respectively and the C(P)᎐C᎐F angles which have a slightly
larger mean value of 118.2Њ. The bond lengths and angles
for the dfppe ligand in the non-disordered molecule of 3 are
similar to those of dfppe,11 except for the C (aryl)᎐P᎐C (aryl)
and P᎐CH2᎐CHЈ2 angles which are larger for 3 by ca. 4 and 3Њ
respectively.
116.6(3)
99.5(2)
118.5(4)
118.5(4)
126.3(5)
120.2(4)
113.5(5)
119.3(5)
117.8(6)
128.5(4)
118.7(3)
113.2(4)
independent molecules in the unit cell, one of which shows dis-
ordered C6F5 rings and disordered methylene carbon atoms.
Both molecules of 3 possess similar bond angles and distances
about the iridium atom. For complex 2 and both molecules of 3
the centre of each H2C᎐CH2 bond lies on a crystallographic
centre of symmetry and, thus, there is a trans arrangement
about the C᎐C bond. The geometry about the iridium atoms is
that of a three-legged piano stool with the P᎐Ir᎐Cl and Cl᎐
Ir᎐Cl angles lying in the range 81.65(9) to 90.75(11)Њ. The
Cp*centroid᎐Ir᎐Cl angles lie in the range 120.7(3) to 124.5(3)Њ,
and the Cp*centroid᎐Ir᎐P angles are ca. 136.5Њ, consistent with
the structures of other [IrCl2(PR3)(η5-C5Me5)] complexes.12,13
The Cp*centroid᎐Ir distances of 2 and 3 are the same within
experimental error and the Ir᎐Cl distances are similar. The Ir᎐P
distance of 2 is ca. 0.03 Å longer than those of 3, which are
significantly longer than the values of 2.281(7) and 2.211(2) Å
for [IrCl2(PMe3)(η5-C5Me5)]12 and [IrCl2{P(OC6H3F2-2,6)3}(η5-
C5Me5)]13 respectively. The Ir᎐P bond lengths in [IrCl2(PX3)(η5-
C5Me5)] complexes would be expected to decrease with increas-
ing π-acceptor strength of the phosphorus ligands, which fol-
lows the order of substituents, X, Ph < Me < OR < C6F5.14 For
electronic reasons alone, it is anticipated that the Ir᎐P bond
length of 3 should be shorter than that of [IrCl2{P(OC6H3F2-
2,6)3}(η5-C5Me5)]. The length of the Ir᎐P bond of 3 is, there-
fore, evidently a consequence of the bulk of the ligand. The
longer Ir᎐P bond of 2 may be a consequence of both the lower
π-acceptor strength and the greater steric pressure, induced by
the more acute C(P)᎐C᎐F angles, of I compared to dfppe. It has
been shown that the σ-donor and π-acceptor properties of the
2,6-difluorophenylphosphines P(C6H3F2-2,6)3, PPh(C6H3F2-
2,6)2 and PPh2(C6H3F2-2,6) closely resemble those of P(C6F5)3,
The cations [MX{(C6F5)2PCH2CH2P(C6F5)2}(η5-C5Me5)]ϩ
have been shown to be intermediates in the reactions between
[{MX(µ-X)(η5-C5Me5)}2] and dfppe in both ethanol (M = Rh,
X = Cl or Br; M = Ir, X = Cl)2,15 and benzene (M = Rh, X =
Br),15 and it would be reasonable to assume that an analogous
cation is an intermediate in the reaction between [{RhCl(µ-Cl)-
(η5-C5Me5)}2] and I. The tetrafluoroborate salts [MCl{(C6H3F2-
2,6)2PCH2CH2P(C6H3F2-2,6)2}(η5-C5Me5)]ϩBF4Ϫ (M = Rh 4 or
Ir 5) were synthesized by addition of I to solutions of [{MCl-
(µ-Cl)(η5-C5Me5)}2] and NH4BF4 in methanol. The iridium
salt 5 was also formed on addition of NH4BF4 to complex 2
(Scheme 1). Salts 4 and 5 were characterized by elemental
analysis, mass spectrometry and multinuclear NMR spectro-
scopies (Table 1). The 31P-{1H} NMR spectrum of 4 exhibits a
doublet at δ 28.3 with a rhodium–phosphorus coupling 1J(RhP)
of 147 Hz, consistent with the values of δ 35.1 and 150.5 Hz
for [RhCl{(C6F5)2PCH2CH2P(C6F5)2}(η5-C5Me5)]ϩBF4Ϫ 6.2 The
31P-{1H} NMR spectrum of 5 exhibits a singlet resonance
at δ 1.0 consistent with that of [IrCl{(C6F5)2PCH2CH2P-
Ϫ
(C6F5)2}(η5-C5Me5)]ϩBF4 at
δ
9.8.2 Variable-temperature
19F-{1H} NMR spectroscopic studies of 4 and 5 in (CD3)2CO
indicate that for each complex cation the C6H3F2 groups of
each P(C6H3F2-2,6)2 moiety are non-equivalent and there is
hindered rotation about both pairs of P᎐C6H3F2 bonds. The
activation energies for rotation, ∆G‡, are calculated to be
33 2 and 43 2 kJ molϪ1 for 4 and 42 2 and 46.5 3 kJ
molϪ1 for 5. These are the same within experimental error as
the respective values for [MCl{(C6F5)2PCH2CH2P(C6F5)2}-
(η5-C5Me5)]ϩBF4Ϫ (M = Rh or Ir).2 In addition, the structure of
salt 4 (Fig. 6) was determined by single-crystal X-ray diffrac-
tion. Selected bond distances and angles for 4 are presented in
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484
1481

View Article Online
Table 4. The structure of the cation of 4 is of the three-legged
piano-stool type similar to that of the cation of 6.2 The Rh᎐Cl
the C᎐F bond activation process in these intriguing reactions in
order to elucidate the mechanisms.
and Cp*centroid᎐Rh distances and the respective Cp*centroid
-
᎐Rh᎐X angles of 4 and 6 are identical within experimental
error. However, there are some significant differences in the
bond lengths and angles about the rhodium atom. In particular,
the Rh᎐P distances of 4 are ca. 0.02 Å shorter than those of 6
[2.362(2) and 2.342(2) Å] and, consequently, the P᎐Rh᎐P angle
is ca. 1Њ more acute in 4. Comparison of the Rh᎐P distances
and variable-temperature NMR data of 4 with those of 6 sug-
gest that the ligand I is sterically less demanding than dfppe in
these complexes, allowing a closer approach of the phosphorus
atoms to the rhodium without leading to more restricted
rotation about the P᎐C bonds. It is unclear as to how this arises
since the P᎐C (aryl), PC᎐C and C᎐F bond lengths and P᎐C᎐C
and PC᎐C᎐F bond angles of 4 are the same within experi-
mental error as the analogous bond lengths and angles of
6, which might be expected to lead to the ligands displaying
similar steric properties. It is also noted that the order of the
Rh᎐P distances of 4 and 6 is opposite to that for the Ir᎐P
distances of 2 and 3.
Experimental
Physical measurements
The 1H, 19F and 31P NMR spectra were recorded using Bruker
ARX250, DPX300 or DRX400 spectrometers; 1H (250.13,
300.01 or 400.13 MHz) were referenced internally using the
residual protio solvent resonance relative to SiMe4 (δ 0), 19F
(235.36, 282.26 or 376.50 MHz) externally to CFCl3 (δ 0) and
31P (101.26, 121.45, 161.98 MHz) externally to 85% H3PO4
(δ 0). All chemical shifts are quoted in δ (ppm), using the high
frequency positive convention, and coupling constants in Hz.
The NMR simulations were performed using the gNMR simu-
lation package.16 Position-ion FAB mass spectra were recorded
on a Kratos Concept 1H mass spectrometer. Elemental anal-
yses were carried out by Butterworths Ltd. or by A.S.E.P., The
School of Chemistry, The Queen’s University of Belfast.
Materials
The cation of complex 4, similar to that of 6, possesses some
short F ؒ ؒ ؒ CH3 distances. In particular, F(26) ؒ ؒ ؒ C(3a),
F(32) ؒ ؒ ؒC(5a) and F(46) ؒ ؒ ؒ C(5a) are 3.102, 3.032 and 3.061 Å
respectively. There are a number of short F ؒ ؒ ؒ CH3 and
F ؒ ؒ ؒ C(CH3) distances between fluorine atoms of the tetra-
fluoroborate anion and carbon atoms of the pentamethyl-
cyclopentadienyl ring. In particular, F(1) ؒ ؒ ؒ C(1), F(1a) ؒ ؒ ؒ
C(6), F(2) ؒ ؒ ؒ C(7), F(3a) ؒ ؒ ؒ C(4) and F(3a) ؒ ؒ ؒ C(4a) are
3.109, 3.014, 3.013, 2.971 and 3.043 Å respectively. Further-
more, there are four short distances between the anion and aryl
carbon atoms of other cations: F(1a) ؒ ؒ ؒ C(15), F(2a) ؒ ؒ ؒ C(45),
F(3) ؒ ؒ ؒ C(33) and F(3) ؒ ؒ ؒ C(34) are 3.056, 2.898, 2.988 and
2.965 Å respectively. However, in contrast to the established
reactivity of [MCl{(C6F5)2PCH2CH2P(C6F5)2}(η5-C5Me5)]ϩ-
BF4Ϫ (M = Rh or Ir),2 neither 4 nor 5 underwent C᎐F and C᎐H
bond activation and C᎐C bond formation on thermolysis in
ethanol.
The compounds Cl2PCH2CH2PCl2, [{MCl(µ-Cl)(η5-C5Me5)}2]
(M = Rh or Ir) (Aldrich), NH4BF4 (BDH), C6H3BrF2-2,6
and (C6F5)2PCH2CH2P(C6F5)2 (Fluorochem) were used as
supplied. Diethyl ether was dried by distillation under nitrogen
from over sodium. Light petroleum (b.p. 40–60 ЊC) was used
throughout.
Preparations
(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 I. A 1.6  solution of
LiBun in hexane (48.8 cm3, 0.078 mol) was diluted with diethyl
ether (25 cm3) and added during 2 h to C6H3BrF2-2,6 (20.48 g,
0.104 mol) in diethyl ether at Ϫ78 ЊC. The mixture was stirred at
Ϫ78 ЊC for 3 h. A solution of Cl2PCH2CH2PCl2 (1.95 cm3, 0.013
mol) in diethyl ether (50 cm3) was added during 1 h, during
which time the mixture darkened. The mixture was allowed to
warm to room temperature over 12 h. The resulting dark
red slurry was washed with 20% NH4Cl(aq) (200 cm3), 10%
NH4Cl(aq) (200 cm3) and water (2 × 200 cm3). The organic
layer was separated, dried over anhydrous MgSO4 and filtered.
The solvent was removed by rotary evaporation and the prod-
uct purified by column chromatography and recrystallization
from diethyl ether to afford colourless crystals of I. Yield 2.77 g
(40%).
Conclusion
We have demonstrated that the reaction between the diphos-
phine (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 and [{MCl(µ-Cl)-
(η5-C5Me5)}2] in benzene proceeds differently for M = Rh and
M = Ir. In the former case activation of two ortho C᎐F bonds
occurs to yield the cation [RhCl{η5-C5Me3[(2-CH2C6H3F-6)-
P(C6H3F2-2,6)CH2]2-1,3}]ϩ. In the latter case no C᎐F bond
activation is observed and the product is a dinuclear complex
comprising a bridging disphosphine, [{IrCl2(η5-C5Me5)[P-
(C6H3F2-2,6)2CH2]}2]. It is not clear as to why these reactions
should give very different products, but it is noted that the
reactions between (C6F5)2PCH2CH2P(C6F5)2 and an excess of
[{MCl(µ-Cl)(η5-C5Me5)}2] (M = Rh or Ir) give the activated
[RhCl{η5-C5Me3[CH2C6F4P(C6F5)CH2]2-1,3}]ϩ and the bridged
[{IrCl2(η5-C5Me5)[P(C6F5)2CH2]}2] respectively as the only
products. It is also noted that the M᎐P distances of [RhCl-
[RhCl{ç5-C5Me3[(2-CH2C6H3F-6)P(C6H3F2-2,6)CH2]2-
؊
1,3}]؉BF4 1. A slurry of [{RhCl(µ-Cl)(η5-C5Me5)}2] (0.10 g,
0.16 mmol) and compound I (0.18 g, 0.32 mmol) in benzene (50
cm3) was refluxed under nitrogen for 16 h, during which time an
orange precipitate of the chloride salt of 1 was formed. The
solid was filtered off and washed with light petroleum. Yield
0.21 g (81%). The salt was slurried in acetone (30 cm3) and
NH4BF4 (1.0 g, 9.5 mmol) added. After 16 h the solvent was
removed by rotary evaporation and the solid extracted into
dichloromethane. The extract was filtered and the solvent
removed by rotary evaporation to afford 1 as a yellow solid,
which was dried in vacuo.
Ϫ
{(C6F5)2PCH2CH2P(C6F5)2}(η5-C5Me5)]ϩBF4 are longer than
those of [RhCl{(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2}(η5-C5-
Ϫ
Me5)]ϩBF4 , whereas the M᎐P distance of [{IrCl2(η5-C5Me5)-
[P(C6F5)2CH2]}2] is shorter than that of [{IrCl2(η5-C5Me5)-
[P(C6H3F2-2,6)2CH2]}2]. These differences may be a conse-
quence of the steric differences between (C6H3F2-2,6)2PCH2-
CH2P(C6H3F2-2,6)2 and (C6F5)2PCH2CH2P(C6F5)2, caused by
the more acute C(P)᎐C᎐F angles of the former.
[{IrCl2(ç5-C5Me5)[P(C6H3F2-2,6)2CH2]}2] 2.
A slurry of
[{IrCl(µ-Cl)(η5-C5Me5)}2] (0.10 g, 0.13 mmol) and compound
I (0.18 g, 0.32 mmol) in benzene (50 cm3) was refluxed under
nitrogen for 8 h. After cooling, the resultant yellow precipitate
was filtered off and recrystallized from acetone–light petroleum
to afford yellow crystals of 2. Yield 0.10 g (57%).
The lack of C᎐F bond activation on thermolysis of [MCl-
Ϫ
{(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2}(η5-C5Me5)]ϩBF4 (M
= Rh or Ir) in ethanol may be ascribed to electronic differences
between (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 and (C6F5)2P-
CH2CH2P(C6F5)2 and is not inconsistent with an electron-
transfer mechanism. We are carrying out further studies into
[{IrCl2(ç5-C5Me5)[P(C6F5)2CH2]}2] 3. A slurry of [{IrCl-
(µ-Cl)(η5-C5Me5)}2] (0.14 g, 0.18 mmol) and dfppe (0.10 g, 0.13
mmol) in benzene (50 cm3) was refluxed under nitrogen for 8 h
to yield a orange solution. The solvent was removed by rotary
1482
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484

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Table 5 X-Ray crystallographic data collection, solution and refinement detailsa for (C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2 I, [{IrCl2-
(η5-C5Me5)[P(C6H3F2-2,6)2CH2]}2]ؒ2Me2CO 2ؒ2Me2CO, [{IrCl2(η5-C5Me5)[P(C6F5)2CH2]}2]ؒ2Me2CO 3ؒ2Me2CO and [RhCl{(C6H3F2-2,6)2PCH2-
Ϫ
CH2P(C6H3F2-2,6)2}(η5-C5Me5)]ϩBF4 ؒMe2CO 4ؒMe2CO
I
2
3
4
Formula
M
C26H16F8P2
542.33
C26H29Cl2F4IrOP
727.56
C52H46Cl4F20Ir2O2P2
1671.03
C39H37BClF12OP2Rh
960.80
Crystal system
Space group
Triclinic
P1
Monoclinic
P21/n
Triclinic
P1
Monoclinic
P21/n
¯
¯
a/Å
b/Å
c/Å
α/Њ
7.372(1)
9.458(1)
9.846(1)
117.15(1)
93.32(1)
98.07(1)
598.99(12)
1
9.983(2)
16.220(5)
16.605(3)
—
99.95(3)
—
12.149(2)
12.650(3)
19.663(4)
86.30(2)
79.36(2)
78.87(2)
2913.0(11)
2
10.938(1)
20.915(1)
17.352(1)
—
101.681(6)
—
β/Њ
γ/Њ
U/Å3
2648.5(11)
4
3887.5(4)
4
Z
T/K
293
0.257
186
5.350
153
4.906
153
0.68
µ/mmϪ1
Total data
Unique data, Rint
R1, wR2 [I > 2σ(I)]b
(all data)
2254
6920
10 772
7641
1780, 0.073
0.0474, 0.1209
0.0543, 0.1261
5485, 0.0428
0.0617, 0.1450
0.0880, 0.1902
10 249, 0.0240
0.0429, 0.0827
0.0640, 0.0916
6831, 0.0370
0.0422, 0.0931
0.0535, 0.1040
a Details in common: Siemens P4 diffractometer, λ(Mo-Kα) = 0.710 73 Å, graphite monochromator, scan type ω. b R1 = Σ||Fo| Ϫ |Fc||/Σ|Fo|;
¹
2
wR2 = [Σw(Fo2 Ϫ Fc2)2/Σw(Fo )2]².
evaporation and the solid recrystallized from acetone–light
petroleum. Yield ca. 0.2 g (ca. 100%).
non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms were included in calcu-
lated positions (C᎐H 0.96 Å) with a fixed isotropic displace-
ment parameter 1.5Ueq(C) for the methyl groups and 1.2Ueq(C)
for the remainder. All crystals examined exhibited split diffrac-
tion peaks and the data resulting from the best crystal were
scanned and 46 suspect reflections rejected. Analytical and
empirical absorption corrections did not improve the R factors
or residual electron-density peaks from refinement with uncor-
rected data, and a correction based on the method of Blessing18
was applied to the data.
The structure of complex 3 was solved by direct methods and
refined on F2 using SHELXL 93.19 The pentafluorophenyl rings
and the methylene carbon atoms of one of the independent
molecules in the asymmetric unit showed disorder. All were
modelled for two sites with 50% occupancy. All non-hydrogen
atoms except the fluorine and carbon atoms of the disordered
phenyl rings were refined anisotropically. All hydrogen atoms
were included in calculated positions (C᎐H 0.96 Å) with a fixed
isotropic displacement parameter 1.5Ueq(C) for the methyl
groups and 1.2Ueq(C) for the methylene groups.
[RhCl{(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2}(ç5-C5Me5)]؉-
؊
BF4 4. The salt NH4BF4 (1.0 g, 9.5 mmol) was added to
[{RhCl(µ-Cl)(η5-C5Me5)}2] (0.10 g, 0.16 mmol) in methanol
(40 cm3). After 20 min compound I (0.18 g, 0.32 mmol) in
dichloromethane (20 cm3) was added and the mixture stirred for
2 h. The solvent was removed by rotary evaporation and the
orange solid extracted into dichloromethane and filtered
through Celite. The solvent was removed by rotary evaporation
and the solid recrystallized from acetone–light petroleum to
afford orange crystals of 4ؒMe2CO. Yield 0.13 g (42%).
[IrCl{(C6H3F2-2,6)2PCH2CH2P(C6H3F2-2,6)2}(ç5-C5Me5)]؉-
BF4؊ 5. The compounds [{IrCl(µ-Cl)(η5-C5Me5)}2] (0.10 g, 0.13
mmol), NH4BF4 (1.0 g, 9.5 mmol) and I (0.18 g, 0.32 mmol)
were treated as for 4. The product was obtained as a lemon-
yellow crystalline solid. Yield 0.19 g (76%).
Crystallography
The structure of complex 4 was solved by direct methods and
refined on F2 using SHELXL 93.19 All non-hydrogen atoms
were refined with anisotropic parameters. Three fluorine atoms
of BF4Ϫ and the methylene carbon atoms showed disorder. All
were modelled for two sites with 50% occupancy. All hydrogen
atoms were included in calculated positions (C᎐H 0.96 Å) with
a fixed isotropic displacement parameter 1.5Ueq(C) for the
methyl groups and 1.2Ueq(C) for the remainder.
Crystals of compounds I and 2, suitable for diffraction, were
grown from CDCl3–light petroleum and acetone–light petrol-
eum respectively, those of 3 and 4 from acetone. The crystal
data and experimental parameters for the compounds are given
in Table 5. Unit-cell parameters for I were determined from the
optimized setting angles of 38 reflections in the range 5.1 < θ <
12.5Њ, for 2 from 23 reflections in the range 5.1 < θ < 12.6Њ, for 3
from 35 reflections in the range 5.0 < θ < 12.5Њ and for 4 from
36 reflections in the range 5.3 < θ < 12.6Њ. A semiempirical
absorption correction was applied to the data for 3 and 4 (based
on ψ scans), and the data were corrected for Lorentz-polariz-
ation effects. Crystal stability was monitored by the observation
of the intensities of three standard check reflections; for no
structure was there any loss of intensity.
The structure of compound I was solved by direct methods
and refined on F2 using SHELXL 96.17 Only one molecule is
found in the unit cell, with the centre of the C᎐C bond linking
the two phosphorus atoms on a centre of symmetry. All non-
hydrogen atoms were refined with anisotropic displacement
parameters. The hydrogen atoms bonded to C(1) were included
in calculated positions (C᎐H 0.96 Å) with a fixed isotropic
displacement parameter 1.2Ueq of C(1).
CCDC reference number 186/917.
See http://www.rsc.org/suppdata/dt/1998/1477/ for crystallo-
graphic files in .cif format.
Acknowledgements
We thank Dr. G. A. Griffith and R. Murphy for assistance with
recording the NMR spectra, Dr. G. Eaton for recording the
mass spectra and the Royal Society (E. G. H.) for support.
References
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1996, 3215.
The structure of complex 2 was solved by Patterson and
Fourier methods and refined on F 2 using SHELXL 96.17 All
J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484
1483

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Received 19th January 1998; Paper 8/00515J
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J. Chem. Soc., Dalton Trans., 1998, Pages 1477–1484