Axial ligand substitution and photoisomerization reactions in ruthenium(II) trans mixed-chelate complexes containing the ligands 1,2-phenylenebis(dimethylarsine) and 2,2'-bipyridine or 1,10-phenanthroline

Article abstract of DOI:10.1016/S0277-5387(00)00369-7

The nitrosyl complex in trans-[RuCl(pdma)(bpy)(NO)] [PF₆]₂ (pdma = 1,2-phenylenebis(dimethylarsine), bpy=2,2'-bipyridine) reacts at room temperature with stoichiometric NaN₃, followed by an excess of a neutral ligand L₁ in 2-butanone under reflux, to afford high yields of the mono-substituted derivatives trans-[RuCl(pdma)(bpy)L₁]PF₆ (L₁ = pyridine (py) 1, triphenylphosphine (PPh₃) 2, N-methylimidazole (mim) 3, acetonitrile (MeCN) 4, dimethylsulfoxide (dmso) 5 or pyrazine (pyz) 6). The related compound trans-[RuCl(pdma)(phen)(NO)][PF₆]₂ (phen = 1,10-phenanthroline) reacts similarly to yield trans-[RuCl(pdma)(phen)L₁]PF₆ (L₁ = py 8, PPh₃ 9, mim 10 or pyz 11). The pyrazine complexes in 6 and 11 react with MeI at room temperature in acetone to afford trans-[RuCl(pdma)(L-L)(mpyz⁺)][PF₆]₂ (mpyz⁺ = N-methylpyrazinium, L-L = bpy 7 or phen 12, respectively). 3 reacts with an excess of a neutral ligand L₂ in the presence of stoichiometric AgCF₃CO₂ in water/acetone under reflux to afford high yields of the di-substituted derivatives trans-[Ru(pdma)(bpy)mim(L₂)][PF₆]₂ (L₂ = mim 13, py 14 or MeCN 15) and 2 reacts similarly with AgCF₃CO₂ in water/MeCN to give trans-[RuCl(pdma)(bpy)PPh₃(MeCN)][PF₆]₂ (16). The complexes in 1-16 exhibit intense d(π)(Ru(II)) → π*(L-L) and d(π)(Ru(II)) → π*(L₁/L₂) (L₁/L₂ = py, pyz or mpyz⁺) metal-to-ligand charge-transfer absorption bands in the near-UV-visible region and are mildly photosensitive in solution. Solar irradiation leads to isomerization; for example 3 is converted into cis-[RuCl(pdma)(bpy)mim] PF₆ (17) over a period of ca. 100 h exposure to diffuse sunlight in acetone. Single crystal X-ray structures have been determined for 1, 2 · DMF, 3, 12 · 3MeCN, 14 · DMF and 17. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(00)00369-7

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 1193–1203
Axial ligand substitution and photoisomerization reactions in
ruthenium(II) trans mixed-chelate complexes containing the ligands 1,2-
phenylenebis(dimethylarsine) and 2,29-bipyridine or 1,10-phenanthroline
a
b
b
Benjamin J. Coe a, , Christopher I. McDonald , Samantha M. Couchman , John C. Jeffery ,
*
Leigh H. Rees b, Simon J. Coles c, Thomas Gelbrich c, Michael B. Hursthouse c
a Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
b Department of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
c EPSRC X-ray Crystallography Service, Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
Received 28 January 2000; accepted 25 February 2000
Abstract
The nitrosyl complex in trans-[RuCl(pdma)(bpy)(NO)][PF6]2 (pdmas1,2-phenylenebis(dimethylarsine), bpys2,29-bipyridine)
reacts at room temperature with stoichiometric NaN3, followed by an excess of a neutral ligand L1 in 2-butanone under reflux, to afford high
yields of the mono-substituted derivatives trans-[RuCl(pdma)(bpy)L1]PF6 (L1spyridine (py) 1, triphenylphosphine (PPh3) 2, N-meth-
ylimidazole (mim) 3, acetonitrile (MeCN) 4, dimethylsulfoxide (dmso) 5 or pyrazine (pyz) 6). The related compound trans-
[RuCl(pdma)(phen)(NO)][PF6]2 (phens1,10-phenanthroline) reacts similarly to yield trans-[RuCl(pdma)(phen)L1]PF6 (L1spy 8,
PPh3 9, mim 10 or pyz 11). The pyrazine complexes in 6 and 11 react withMeIat room temperatureinacetonetoaffordtrans-[RuCl(pdma)(L–
L)(mpyzq)][PF6]2 (mpyzqsN-methylpyrazinium, L–Lsbpy 7 or phen 12, respectively). 3 reacts with an excess of a neutral ligand L2
in the presence of stoichiometric AgCF3CO2 in water/acetone under reflux to afford high yields of the di-substituted derivatives trans-
[Ru(pdma)(bpy)mim(L2)][PF6]2 (L2smim 13, py 14 or MeCN 15) and 2 reacts similarly with AgCF3CO2 in water/MeCN to give trans-
[RuCl(pdma)(bpy)PPh3(MeCN)][PF6]2 (16). The complexes in 1–16 exhibit intense dp(RuII)™p*(L–L) and dp(RuII)™p*(L1/L2)
(L1/L2spy, pyz or mpyzq) metal-to-ligand charge-transfer absorption bands in the near-UV–visible region and are mildly photosensitive
in solution. Solar irradiation leads to isomerization; for example 3 is converted into cis-[RuCl(pdma)(bpy)mim]PF6 (17) over a period of
ca. 100 h exposure to diffuse sunlight in acetone. Single crystal X-ray structures have been determined for 1, 2PDMF, 3, 12P3MeCN, 14PDMF
and 17.
q2000 Elsevier Science Ltd All rights reserved.
Keywords: Photoisomerization; Ruthenium
1. Introduction
metal-to-ligand charge-transfer (MLCT) chromophores can
induce sequential, intramolecular electron or energy-transfer
processes. The design of potentially useful MLCT-based
molecular devices requires optimization of both electronic
and stereochemical properties, and a particular emphasis on
structurally well defined systems has emerged recently [5–
7]. With functionalized octahedral MLCT chromophores, a
trans disposition of attached donor/acceptor (‘quencher’)
units is likely to be advantageous in order to achievephenom-
ena such as long-lived charge-separation. One approach to
the preparation of such assemblies involves controlled ligand
substitutions at trans octahedral metal centres.
It has recently become apparent that ruthenium(II) com-
plexes of N-heterocyclic chelating ligandssuchas2,29-bipyr-
idine (bpy), 1,10-phenanthroline (phen) or 2,29:69,20-
terpyridine have potential for applications as components of
photoactive molecular-level devices [1,2]. Of particular cur-
rent interest is the discovery that relatives of the prototypical
complex [RuII(bpy)3]2q can act as efficientsensitizerswhen
covalently attached to the surfaces of semiconducting nano-
crystalline metal oxide electrodes in photovoltaic cells[3,4].
The utility of organotransition metal complexes in these and
related devices rests upon the fact that photon absorption by
Although ‘chromophore-quencher’ complexes based on
trans-{RuII(bpy)2}2q centres have been prepared [8], these
undergo extremely facile photoinitiated ligand dissociation
* Corresponding author. Tel.: q44-161-275-4601; fax: q44-161-275-
4598; e-mail: b.coe@man.ac.uk
0277-5387/00/$ - see front matter q2000 Elsevier Science Ltd All rights reserved.
PII S0277-5387(00)00369-7
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and isomerizationreactions. Inattemptstoidentifyalternative
systems suitable for the preparation of stable trans MLCT
chromophoric assemblies, we have chosen to explore the
derivative chemistry of ruthenium(II) complexes of the che-
lating ligand 1,2-phenylenebis(dimethylarsine) (pdma).
The precursor trans-[RuIICl(pdma)2(NO)]2q [9] readily
undergoes nitrosyl substitution reactions to afford mono- and
dinuclear derivatives containing the non-chromophoric
trans-{RuIICl(pdma)2}q core [10,11], but subsequent
chloride substitutions are remarkably difficult [10]. We
have recently reported the mixed-chelates trans-[RuII-
Cl(pdma)(L–L)(NO)]2q (L–Lsbpy or phen) [12],
which were designed to act as versatile synthetic precursors
to functionalized trans assemblies via stepwise axial ligand
substitutions. The reactivity of these complexes and the pho-
tostability of the resulting products are the subjects of the
present report.
N2. All E1/2 values were calculated from (EpaqEpc)/2 at a
scan rate of 200 mV sy1
.
2.3. Preparations
2.3.1. trans-[RuCl(pdma)(bpy)py]PF6 (1)
A solution of trans-[RuCl(pdma)(bpy)(NO)][PF6]2
(50 mg, 0.056 mmol) and NaN3 (3.7 mg, 0.057 mmol) in
pyridine (10 cm3) was stirred at room temperature for 2 h,
then heated at reflux for 1 h. Addition of aqueous NH4PF6
yielded a deep red precipitate which was filtered off, washed
with water and dried. Yield: 39 mg, 87%. Anal. Found: C,
37.4; H, 3.65; N, 5.10. Calc. for C25H29As2ClF6N3PRu: C,
1
37.4; H, 3.65; N, 5.25%. H NMR (200 MHz, CD3CN): d
9.27 (2H, d, Js5.8 Hz, H6,69), 8.55 (2H, d, Js8.0 Hz,
H3,39), 8.17 (2H, t, H4,49), 8.05 (2H, m, C6H2), 7.82 (2H, t,
H5,59), 7.73–7.65 (5H, m, pyH2,4,6 and C6H2), 6.93 (2H, t,
pyH3,5), 1.78 (6H, s, 2AsMe), 1.62 (6H, s, 2AsMe). m/z:
658 ([MyPF6y]q) and 579 ([MyPF6yypy]q).
2. Experimental
2.3.2. trans-[RuCl(pdma)(bpy)PPh3]PF6 (2)
2.1. Materials and procedures
A solution of trans-[RuCl(pdma)(bpy)(NO)][PF6]2
(51 mg, 0.057 mmol) and NaN3 (3.7 mg, 0.057 mmol) in
acetone (5 cm3) was stirred at room temperature for 2 h. A
solution of PPh3 (594 mg, 2.27 mmol) in 2-butanone (10
cm3) was added, the acetone was removed in vacuo, and the
solution was heated at reflux for a further 2 h. The solvent
was reduced to a small volume in vacuo and diethyl ether
was added to give a golden-coloured precipitate which was
filtered off, washed with diethyl ether, and dried. The product
waspurifiedbyreprecipitationfromacetonitrile/diethylether
to afford a yellow solid. Yield: 45 mg, 80%. Anal. Found: C,
46.35; H, 3.80; N, 3.20; P, 6.05. Calc. for C38H39As2ClF6-
N2P2Ru: C, 46.3; H, 4.00; N, 2.85; P, 6.30%. 1H NMR (200
MHz, CD3CN): d 8.34 (2H, d, Js8.2 Hz, H6,69), 8.24 (2H,
d, Js5.2 Hz, H3,39), 8.07–7.98 (4H, m, H4,49 and C6H2), 7.77
(2H, m, C6H2), 7.32–7.23 (5H, m, H5,59 and 3PhH4), 7.13–
7.04 (6H, m, 3PhH3,5), 6.93 (6H, m, 3PhH2,6), 1.74 (6H, s,
2AsMe), 1.54 (6H, s, 2AsMe). m/z: 841 ([MyPF6y]q)
and 578 ([MyPF6yyPPh3]q). A reaction was also carried
out using the above method, but instead of heating at reflux
after the addition of PPh3, the solution was stirred at room
temperature for 93 h. This afforded 26 mg of 2 (46%, pure
by 1H NMR).
The compound RuCl3P2H2O was supplied by Johnson
Matthey plc and pdma was obtained from Dr P.G. Edwards,
University of Wales College of Cardiff. The salts trans-
[RuCl(pdma)(L–L)(NO)][PF6]2 (L–Lsbpy or phen)
were prepared according to published procedures [12]. All
other reagents were obtained commercially and used as sup-
plied. All reactions were conducted under an argon atmos-
phere. Products were dried overnight at room temperature in
a vacuum desiccator (CaSO4) prior to characterization.
2.2. Instrumentation
1H NMR spectra were recorded on a Varian Gemini 200
spectrometer and all shifts are referenced to SiMe4. The com-
plex fine splitting of the pyridine or 2,29-bipyridine proton
resonances is ignored and the signals are reported as simple
doublets or triplets. Elemental analyses were performed by
the Microanalytical Laboratory, University of Manchester.
Infrared spectra were obtained as KBr discs with an ATI
Mattson Genesis Series FTIR instrument. FAB mass spectra
were recorded using a Kratos Concept spectrometer with a
6–8 keV Xe atom beam and 3-nitrobenzyl alcohol as matrix.
Cyclic voltammetric measurements were carried out using
an EG&G PAR model 173 potentiostat/galvanostat with a
model 175 universal programmer. A single-compartmentcell
was used with the saturated calomel reference electrode
(SCE) separated by a salt bridge from the platinum-bead
working electrode and platinum-wire auxiliary electrode.
Acetonitrile (HPLC grade) was used as received and tetra-
n-butylammonium hexafluorophosphate, twicerecrystallized
from ethanol and dried in vacuo, was used as supporting
electrolyte. Solutions containing ca. 10y3 mol dmy3 analyte
(0.1 mol dmy3 electrolyte) were deaerated by purging with
2.3.3. trans-[RuCl(pdma)(bpy)mim]PF6 (3)
A solution of trans-[RuCl(pdma)(bpy)(NO)][PF6]2
(50 mg, 0.056 mmol) and NaN3 (3.7 mg, 0.057 mmol) in
acetone (5 cm3) was stirred at room temperature for 2 h. N-
Methylimidazole (mim, 5 cm3) was added, the acetone was
removed in vacuo, and the solution was heated at ca. 1008C
for 1 h. After cooling to room temperature, addition of aque-
ous NH4PF6 and water afforded a red precipitate which was
filtered off, washed with water and dried. Reprecipitation
from acetone/diethyl ether gave a deep red solid. Yield: 42
mg, 94%. Anal. Found: C, 36.2; H, 3.75; N, 7.05. Calc. for
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C24H30As2ClF6N4PRu: C, 35.75; H, 3.75; N, 6.95%. 1HNMR
(200 MHz, CD3COCD3): d 9.53 (2H, d, Js5.2 Hz, H6,69),
8.72 (2H, d, Js8.0 Hz, H3,39), 8.21 (2H, t, H4,49), 8.12 (2H,
m, C6H2), 7.76 (2H, t, H5,59), 7.67 (2H, m, C6H2), 7.31 (1H,
s, C3H3N2), 6.95 (1H, s, C3H3N2), 6.36 (1H, s, C3H3N2),
3.54 (3H, s, Me), 1.83 (6H, s, 2AsMe), 1.72 (6H, s,
2AsMe). m/z: 660 ([MyPF6y]q) and 577 ([My
PF6yymim]q).
off and washed with water. The crude product was dissolved
in acetone and the solution wasfilteredtoremoveaninsoluble
tan residue. Addition of diethyl ether to the filtrate gave a
purple precipitate which was filtered off and washed with
diethyl ether. Repeated recrystallization from acetonitrile/
diethyl ether yielded the purple product. Yield: 11 mg, 18%.
Anal. Found: C, 32.0; H, 3.55; N, 5.95. Calc. for C25H31-
As2ClF12N4P2RuP0.5C2H3N: C, 31.7; H, 3.35; N, 6.40%. 1H
NMR (200 MHz, CD3COCD3): d 9.22 (2H, d, Js4.8 Hz,
H6,69), 8.99 (2H, d, Js5.3 Hz, mpyzq), 8.89 (2H, d, Js8.2
Hz, H3,39), 8.40 (2H, t, H4,49), 8.21 (4H, m, C6H2 and
mpyzq), 7.85 (2H, t, H5,59), 7.77 (2H, m, C6H2), 3.98 (3H,
s, Me), 1.90 (6H, s, 2AsMe), 1.88 (6H, s, 2AsMe). m/z:
819 ([MyPF6y]q) and 579 ([My2PF6yympyz]q).
2.3.4. trans-[RuCl(pdma)(bpy)(MeCN)]PF6 (4)
This was prepared in a similar manner to 1 by using ace-
tonitrile in place of pyridine. The reaction was cooled toroom
temperature, and the solvent removed in vacuo. The resulting
yellow/orange oil was dissolved in acetone (3 cm3), and
addition of aqueous NH4PF6 afforded an orange precipitate
which was filtered off, washed with water and dried. Repre-
cipitation from acetone/diethyl ether yielded an orangesolid.
Yield: 36 mg, 82%. Anal. Found: C, 35.8; H, 4.00; N, 5.00.
Calc. for C22H27As2ClF6N3PRuP0.5C3H6O: C, 35.55; H,
3.80; N, 5.30%. 1H NMR (200 MHz, CD3COCD3): d 9.50
(2H, d, Js5.9 Hz, H6,69), 8.73 (2H, d, Js7.4 Hz, H3,39),
8.27 (2H, t, H4,49), 8.14 (2H, m, C6H2), 7.83 (2H, t, H5,59),
7.69 (2H, m, C6H2), 2.28 (3H, s, Me), 1.67 (12H, s,
4AsMe). n(C^N) 2267 w cmy1. m/z: 620 ([MyPF6y]q)
and 578 ([MyPF6yyMeCN]q).
2.3.8. trans-[RuCl(pdma)(phen)py]PF6 (8)
This was prepared and purified in an identical manner to
1 by using trans-[RuCl(pdma)(phen)(NO)][PF6]2 (100
mg, 0.108 mmol) in place of trans-[RuCl(pdma)(bpy)-
(NO)][PF6]2. A red solid was obtained. Yield: 80 mg,
89%. Anal. Found: C, 39.3; H, 3.70; N, 5.05. Calc. for
C27H29As2ClF6N3PRu: C, 39.2; H, 3.55; N, 5.10%. 1H NMR
(200 MHz, CD3CN): d 9.66 (2H, d, Js5.2 Hz, H2,9), 8.72
(2H, d, Js8.2 Hz, H4,7), 8.24 (2H, s, H5,6), 8.11–8.01 (4H,
m, H3,8 and C6H2), 7.86 (2H, d, Js6.4 Hz, pyH2,6), 7.72
(2H, m, C6H2), 7.49 (1H, t, pyH4), 6.84 (2H, t, pyH3,5),
1.87 (6H, s, 2AsMe), 1.69 (6H, s, 2AsMe). m/z: 682
([MyPF6y]q) and 603 ([MyPF6yypy]q).
2.3.5. trans-[RuCl(pdma)(bpy)dmso]PF6 (5)
This was prepared and purified in an identical manner to
3, but using dmso in place of mim, to afford a yellow solid.
Yield: 33 mg, 74%. Anal. Found: C, 32.7; H, 3.90; N, 3.40;
S, 3.40. Calc. for C22H30As2ClF6N2OPRuS: C, 32.95; H,
3.75; N, 3.50; S, 4.00%. 1H NMR (200 MHz, CD3COCD3):
d 9.55 (2H, d, Js4.8 Hz, H6,69), 8.72 (2H, d, Js7.4 Hz,
H3,39), 8.34 (2H, t, H4,49), 8.09 (2H, m, C6H2), 7.90 (2H, t,
H5,59), 7.69 (2H, m, C6H2), 2.96 (6H, s, 2Me), 1.93 (12H,
s, 4AsMe). n(S_O) 1085 m cmy1. m/z: 657 ([My
PF6y]q) and 579 ([MyPF6yydmso]q).
2.3.9. trans-[RuCl(pdma)(phen)PPh3]PF6 (9)
This was prepared and purified in an identical manner to
2 by using trans-[RuCl(pdma)(phen)(NO)][PF6]2 (100
mg, 0.108 mmol) in place of trans-[RuCl(pdma)-
(bpy)(NO)][PF6]2. A yellow solid was obtained. Yield: 88
mg, 80%. Anal. Found: C, 47.2; H, 3.95; N, 3.00; P, 6.00.
Calc. for C40H39As2ClF6N2P2Ru: C, 47.55; H, 3.90; N, 2.75;
1
P, 6.15%. H NMR (200 MHz, CD3COCD3): d 9.09 (2H,
d, Js4.6 Hz, H2,9), 8.75 (2H, d, Js7.2 Hz, H4,7), 8.27 (2H,
s, H5,6), 8.23 (2H, m, C6H2), 7.82 (4H, m, H3,8 and C6H2),
7.31 (3H, t, 3PhH4), 7.08 (6H, t, 3PhH3,5), 6.75 (6H, t,
3PhH2,6), 1.94 (6H, s, 2AsMe), 1.70 (6H, s, 2AsMe). m/z:
864 ([MyPF6y]q) and 602 ([MyPF6yyPPh3]q).
2.3.6. trans-[RuCl(pdma)(bpy)pyz]PF6 (6)
This was prepared in an identical manner to 2, but using
pyrazine (181 mg, 2.26 mmol) in place of PPh3. Reprecipi-
tation from acetone/diethyl ether afforded a red solid. Yield:
37 mg, 78%. Anal. Found: C, 36.7; H, 3.50; N, 7.05. Calc.
for C24H28As2ClF6N4PRuP0.5C3H6O: C, 36.75; H, 3.75; N,
6.75%. 1H NMR (200 MHz, CD3CN): d 9.18 (2H, d, Js5.6
Hz, H6,69), 8.57 (2H, d, Js8.0 Hz, H3,39), 8.20 (2H, t, H4,49),
8.05 (2H, m, C6H2), 7.99 (2H, d, Js4.6 Hz, pyz), 7.86 (2H,
d, Js4.6 Hz, pyz), 7.73–7.66 (4H, m, H5,59 and C6H2), 1.77
(6H, s, 2AsMe), 1.66 (6H, s, 2AsMe). m/z: 659 ([My
PF6y]q) and 579 ([MyPF6yypyz]q).
2.3.10. trans-[RuCl(pdma)(phen)mim]PF6 (10)
This was prepared and purified in an identical manner to
3 by using trans-[RuCl(pdma)(phen)(NO)][PF6]2 (200
mg, 0.217 mmol) in place of trans-[RuCl(pdma)-
(bpy)(NO)][PF6]2. A red solid was obtained. Yield: 158
mg, 82%. Anal. Found: C, 38.85; H, 4.20; N, 6.35. Calc. for
C26H30As2ClF6N4PRuPC3H6O: C, 39.25; H, 4.10; N, 6.30%.
1H NMR (200 MHz, CD3COCD3): d 9.94 (2H, d, Js5.0
Hz, H2,9), 8.81 (2H, d, Js8.2 Hz, H4,7), 8.32 (2H, s, H5,6),
8.14 (4H, m, H3,8 and C6H2), 7.70 (2H, m, C6H2), 7.22 (1H,
s, C3H3N2), 6.85 (1H, s, C3H3N2), 6.33 (1H, s, C3H3N2),
3.42 (3H, s, Me), 1.92 (6H, s, 2AsMe), 1.81 (6H, s,
2.3.7. trans-[RuCl(pdma)(bpy)(mpyzq)][PF6]2 (7)
A solution of 6 (50 mg, 0.062 mmol) in DMF (1.5 cm3)
and MeI (0.5 cm3) was stirred at room temperature for 24 h.
The excess MeI was removed in vacuo, and addition of aque-
ous NH4PF6 afforded a purple precipitate which was filtered
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2AsMe). m/z: 684 ([MyPF6y]q) and 603 ([My
PF6yymim]q).
Js8.0 Hz, H3,39), 8.35 (2H, t, H4,49), 8.29–8.24 (4H, m,
pyH2,6 and C6H2), 7.96 (2H, t, H5,59), 7.82–7.76 (3H, m,
pyH4 and C6H2), 7.22–7.12 (3H, m, pyH3,5 and C3H3N2),
6.97 (1H, s, C3H3N2), 6.15 (1H, s, C3H3N2), 3.47 (3H, s,
Me), 1.91 (6H, s, 2AsMe), 1.80 (6H, s, 2AsMe). m/z:
849 ([MyPF6y]q), 703 ([My2PF6y]q), 624 ([My
2PF6yypy]q) and 543 ([My2PF6yypy–mim]q).
2.3.11. trans-[RuCl(pdma)(phen)pyz]PF6 (11)
This was prepared and purified in an identical manner to
6 by using trans-[RuCl(pdma)(phen)(NO)][PF6]2 (100
mg, 0.108 mmol) in place of trans-[RuCl(pdma)-
(bpy)(NO)][PF6]2. A red solid was obtained. Yield: 80
mg, 89%. Anal. Found: C, 37.75; H, 3.60; N, 6.50. Calc. for
C26H28As2ClF6N4PRu: C, 37.7; H, 3.40; N, 6.75%. 1H NMR
(200 MHz, CD3CN): d 9.68 (2H, d, Js4.4 Hz, H2,9), 8.76
(2H, d, Js6.0 Hz, H4,7), 8.26 (2H, s, H5,6), 8.13–8.02 (4H,
m, H3,8 and C6H2), 7.89 (4H, m, pyz), 7.73 (2H, m, C6H2),
1.86 (6H, s, 2AsMe), 1.73 (6H, s, 2AsMe). m/z: 683
([MyPF6y]q) and 603 ([MyPF6yypyz]q).
2.3.15. trans-[Ru(pdma)(bpy)(mim)MeCN][PF6]2 (15)
This was prepared in an identical fashion to 13 but using
acetonitrile (0.4cm3)inplaceofmim, withnoreprecipitation
of the crude product. An orange solid was obtained. Yield:
52 mg, 88%. Anal. Found: C, 32.7; H, 3.50; N, 7.70. Calc.
1
for C26H33As2F12N5P2Ru: C, 32.65; H, 3.50; N, 7.30%. H
NMR (200 MHz, CD3COCD3): d 9.46 (2H, d, Js5.4 Hz,
H6,69), 8.87 (2H, d, Js8.0 Hz, H3,39), 8.45 (2H, t, H4,49),
8.26 (2H, m, C6H2), 7.93 (2H, t, H5,59), 7.79 (2H, m, C6H2),
7.20 (1H, s, C3H3N2), 7.01 (1H, s, C3H3N2), 6.20 (1H, s,
C3H3N2), 3.50 (3H, s, C3H3N2–Me), 2.24 (3H, s, Me),
1.94 (6H, s, 2AsMe), 1.90 (6H, s, 2AsMe). m/z: 811 ([My
PF6y]q), 666 ([My2PF6y]q), 625 ([My2PF6yy
MeCN]q) and 544 ([My2PF6yyMeCNymim]q).
2.3.12. trans-[RuCl(pdma)(phen)(mpyzq)][PF6]2 (12)
This was prepared and purified in an identical manner to
7, but using 11 (50 mg, 0.061 mmol) in place of 6. A deep
purple solid was obtained. Yield: 29 mg, 48%. Anal. Found:
C, 32.8; H, 3.05; N, 5.50. Calc. for C27H31As2ClF12N4P2Ru:
C, 32.85; H, 3.15; N, 5.65%. 1H NMR (200 MHz,
CD3COCD3): d 9.66 (2H, d, Js5.2 Hz, H2,9), 8.99 (4H, m,
H4,7 and mpyzq), 8.44 (2H, s, H5,6), 8.27–8.12 (6H, m, H3,8
,
2.3.16. trans-[Ru(pdma)(bpy)(PPh3)(MeCN)][PF6]2 (16)
This was prepared and purified in an identical manner to
15 by using 2 (50 mg, 0.051 mmol) in place of 3. A yellow
solid was obtained. Yield: 37 mg, 64%. Anal. Found: C,
41.95; H, 3.75; N, 3.70; P, 7.85. Calc. for C40H42As2F12N3-
P3Ru: C, 42.25; H, 3.70; N, 3.70; P, 8.20%. 1H NMR (200
C6H2 and mpyzq), 7.79 (2H, m, C6H2) 3.93 (3H, s, Me),
1.99 (6H, s, 2AsMe), 1.97 (6H, s, 2AsMe). m/z: 843
([MyPF6y]q), 698 ([My2PF6y]q) and 602 ([My
2PF6yympyzq]q).
2.3.13. trans-[Ru(pdma)(bpy)(mim)2][PF6]2 (13)
MHz, CD3COCD3): d 8.92 (2H, d, Js5.0 Hz, H6,69), 8.65
A solution of 3 (50 mg, 0.062 mmol), AgCF3CO2 (13.8
mg, 0.062 mmol) and mim (0.2 cm3) in acetone (5 cm3)
was heated at reflux for 75 min. Water (5 cm3) was added,
and reflux was continued for a further 3 h. The reaction
mixture was then filtered through celite to remove AgCl, and
addition of aqueous NH4PF6 and water yielded an orange
precipitate, which was filtered off, washed with water, and
dried. Reprecipitation from acetone/diethyl etheraffordedan
orange solid. Yield: 50 mg, 81%. Anal. Found: C, 34.0; H,
3.45; N, 8.50. Calc. for C28H36As2F12N6P2Ru: C, 33.7; H,
3.65; N, 8.45%. 1H NMR (200 MHz, CD3COCD3): d 9.61
(2H, d, Js4.8 Hz, H6,69), 8.78 (2H, d, Js8.0 Hz, H3,39),
8.36 (2H, t, H4,49), 8.25 (2H, m, C6H2), 7.91 (2H, t, H5,59),
7.78 (2H, m, C6H2), 7.22 (2H, s, 2C3H3N2), 6.96 (2H, s,
2C3H3N2), 6.25 (2H, s, 2C3H3N2), 3.49 (6H, s, 2Me),
1.80 (12H, s, 4AsMe). m/z: 852 ([MyPF6y]q), 707
([My2PF6y]q), 624 ([My2PF6y–mim]q) and 543
([My2PF6yy2mim]q).
4,49
(2H, d, Js7.6 Hz, 3,39), 8.30 (4H, m,
and C6H2),
H
H
7.89 (2H, m, C H ), 7.74 (2H, t, 5,59), 7.40 (3H, t, 3PhH4),
H
6
2
7.15 (6H, t, 3PhH3,5), 6.76 (6H, t, 3PhH2,6), 2.22 (3H, s,
Me), 1.96 (6H, s, 2AsMe), 1.66 (6H, s, 2AsMe). m/z:
991 ([MyPF6y]q), 845 ([My2PF6y]q), 583 ([My
2PF6yyPPh3]q) and 542 ([My2PF6yyPPh3y
MeCN]q).
2.3.17. cis-[RuCl(pdma)(bpy)mim]PF6 (17)
A solution of 3 (40 mg, 0.050 mmol) in acetone (20 cm3)
was exposed to sunlight for 100 h, during which time the
1
isomerization was completed (as shown by H NMR spec-
troscopy on a smaller sample in acetone-d6). The addition of
diethyl ether gave a precipitate which was filteredoff, washed
with diethyl ether and dried to afford a deep red solid. Yield:
31 mg, 78%. Anal. Found: C, 35.9; H, 4.00; N, 7.05. Calc.
for C24H30As2ClF6N4PRu: C, 35.75; H, 3.75; N, 6.95%. 1H
NMR (200 MHz, CD3COCD3): d 9.96 (1H, d, Js6.0 Hz,
bpy), 8.97 (1H, d, Js5.4 Hz, bpy), 8.56 (2H, t, bpy), 8.12
(1H, t, bpy), 8.10–7.99 (2H, m, C6H2), 7.93–7.80 (3H, m,
bpy and C3H3N2), 7.65–7.58 (2H, m, C6H2), 7.46 (1H, t,
bpy), 7.09 (1H, s, C3H3N2), 6.74 (1H, s, C3H3N2), 3.71
(3H, s, C3H3N2–Me), 1.92 (3H, s, AsMe), 1.56 (3H, s,
AsMe), 1.48 (3H, s, AsMe), 0.74 (3H, s, AsMe). m/z: 661
([MyPF6y]q) and 579 ([MyPF6yymim]q).
2.3.14. trans-[Ru(pdma)(bpy)(mim)py][PF6]2 (14)
This was prepared and purified in an identical fashion to
13 but using pyridine (0.4 cm3) in place of mim. A yellow/
orange solid was obtained. Yield: 43 mg, 66%. Anal. Found:
C, 36.5; H, 3.65; N, 6.65. Calc. for C29H35As2F12N5P2-
RuPC3H6O: C, 36.5; H, 3.95; N, 6.65%. 1H NMR (200 MHz,
CD3COCD3): d 9.69 (2H, d, Js4.6 Hz, H6,69), 8.76 (2H, d,
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1197
2.4. X-ray crystallography
Crystals of 1, 3, 12P3MeCN and 17 were grown by slow
diffusion of diethyl ether vapour into acetonitrile solutions of
the complex salts at 48C. Those of 2PDMF and 14PDMF
were obtained in similar manner, but using DMF solutions.
The approximate dimensions (mm) of the crystals chosen
for diffraction studies were as follows: 1 (0.15=0.15=
0.10), 2PDMF (0.40=0.10=0.10), 3 (0.40=0.20=0.05),
12P3MeCN (0.15=0.15=0.05), 14PDMF (0.30=0.20=
0.05), 17 (0.10=0.10=0.05).
Data collection details are as follows: for 1, 2PDMF and 3
data were collected on a SiemensSMART CCDarea-detector
diffractometer. Empirical absorption corrections were
applied by using multiple measurements of equivalent reflec-
tions, and the data were integrated by using SAINT [13].
For 12P3MeCN, 14PDMF and 17 data were collected on a
Nonius Kappa CCD area-detector diffractometer controlled
by the Collect software package [14]. The data were proc-
essed by Denzo [15] and corrected for absorption by using
the empirical method employed in Sortav [16,17] from
within the MAXUS suite of programs [18].
Fig. 1. Structural representation of the complex cation in the salt 1, with
hydrogen atoms omitted (50% probability ellipsoids).
Fig. 2. Structural representation of the complex cation in the salt 2PDMF,
with hydrogen atoms omitted (50% probability ellipsoids).
The structures of 1, 2PDMF and 3 were solved by direct
2
methods and refined by full-matrix least-squares on all Fo
data using Siemens SHELXTL 5.03 [13]. The same
approach was used for 12P3MeCN, 14PDMF and 17, but
using SHELXS-90 [19] and SHELXL-97 [20]. In all cases,
all non-hydrogen atoms were refined anisotropically with
hydrogen atoms included in idealized positions with thermal
parameters riding on those of the parent atom. Static disorder
y
is present in the PF6 anions of 1 and 17, and in the axial
ligands of 14PDMF (50% occupancy by py and mim in both
positions).
Representations of the complex cations in 1, 2PDMF, 3,
12P3MeCN, 14PDMF and 17 are given in Figs. 1–6. Crys-
tallographic data and refinement detailsarepresentedinTable
1, and selected bond distances and angles in Table 2.
Fig. 3. Structural representation of the complex cation in the salt 3, with
hydrogen atoms omitted (50% probability ellipsoids).
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B.J. Coe et al. / Polyhedron 19 (2000) 1193–1203
Fig. 4. Structural representation of the complex cation in the salt12P3MeCN,
with disorder removed and hydrogen atoms omitted (50% probability
ellipsoids).
Fig. 6. Structural representation of the complex cation in the salt 17, with
hydrogen atoms omitted (50% probability ellipsoids).
chiometric azide at room temperature in acetone. The result-
ing intermediates, most likely trans-[RuIICl(pdma)(L–
L)N2]q, react with a range of neutral ligands to give clean
substitution ofthe position formerlyoccupiedbyNOq. These
reactions take place only slowly at room temperature, but
occur much more rapidly upon heating at ca. 808C in 2-
butanone.
Unlike the related complexes trans-[RuIICl(pdma)2L]q
(Lspy, mim, etc.) [10], the pdma/L–L trans mixed-che-
lates react with neutral ligands in the presence of AgCF3CO2
to substitute the chloride ligands, although heating isrequired
to give reasonably efficient reactions. For example, 15 was
also isolated from a reaction at room temperature, but in a
yield of only 14%. The efficacy of these substitutionreactions
depends to varying degrees upon the nature of the starting
complex and the incoming ligand. The best results were
obtained with salt 3, from which the derivatives 13–15 were
prepared. The presence of the trans geometry in the salts 1–
16 is confirmed by the 1H NMR spectra which each show a
single AA9BB9 pattern for the pdma ligand, either one or two
singlets for the AsMe groups and four signals for bpy or phen.
Fig. 5. Structural representation of the complex cation in the salt 14PDMF,
with hydrogen atoms omitted (50% probability ellipsoids).
3. Results and discussion
3.2. Photoisomerization reactions
3.1. Synthesis and characterization
Previous studies have shown that trans-{RuII(L–L)2}2q
(L–Lsbpy or phen) complexes readily photoisomerize to
their more stable cis isomers [8,26]. By contrast, when L–
Lspdma, no evidence for photoinstability has been found
[10]. Given these observations, it is perhaps unsurprising
that the new trans-{Ru(pdma)(L–L)}2q (L–Lsbpy or
phen) complexes show an intermediate degree of photosta-
bility. 1H NMR experiments in d6-acetone show that salts 1–
16 undergo complete isomerization to their cis forms, with
partial decomposition in some cases, following exposure to
It is well established that sufficiently electrophilic,linearly
coordinated nitrosyl ligands react with nucleophiles[21,22],
and the reaction with azide ion is a versatile means to convert
ruthenium(II) nitrosyls into substituted derivatives via dini-
trogen or solvento intermediates [10,11,23–25]. The n(NO)
values in trans-[RuIICl(pdma)(L–L)(NO)][PF6]2, 1878
cmy1 (L–Lsbpy) and 1874 cmy1 (L–Lsphen) [12], are
indicative of relatively electron-deficient nitrosyl ligands
[21,22], and these complexes hence react readily with stoi-
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1199
v
w
s
s
v
w
v
w
v
w
v
w
v
w
s
a
b
g
l
m
u
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1200
B.J. Coe et al. / Polyhedron 19 (2000) 1193–1203
Table 2
Table 2 (continued)
˚
Selected bond distances (A) and angles (8) for the complex salts 1, 2PDMF,
3, 12P3MeCN, 14PDMF and 17
N(1)–Ru(1)–N(5)
N(3)–Ru(1)–As(1)
173.0(7)
99.8(6)
N(4)–Ru(1)–As(1) 175.5(5)
N(3)–Ru(1)–As(2) 179.3(6)
N(4)–Ru(1)–As(2) 101.9(6)
As(1)–Ru(1)–As(2) 80.61(9)
N(4)–Ru(1)–N(5)
N(1)–Ru(1)–As(1)
N(5)–Ru(1)–As(1)
N(1)–Ru(1)–As(2)
N(5)–Ru(1)–As(2)
84.8(8)
94.5(5)
91.3(6)
92.4(5)
92.5(5)
1
Ru(1)–N(31)
Ru(1)–N(21)
Ru(1)–N(11)
2.088(3)
2.103(3)
2.108(3)
Ru(1)–As(1)
Ru(1)–As(2)
Ru(1)–Cl(1)
2.4117(6)
2.4186(5)
2.4254(10)
N(31)–Ru(1)–N(21) 87.36(11) N(11)–Ru(1)–As(2) 173.18(8)
N(31)–Ru(1)–N(11) 87.90(11) As(1)–Ru(1)–As(2) 82.123(13)
N(21)–Ru(1)–N(11) 77.88(11) N(31)–Ru(1)–Cl(1) 175.06(8)
N(31)–Ru(1)–As(1) 93.63(8) N(21)–Ru(1)–Cl(1) 90.49(8)
N(21)–Ru(1)–As(1) 178.74(8) N(11)–Ru(1)–Cl(1) 87.30(8)
N(11)–Ru(1)–As(1) 101.38(8) As(1)–Ru(1)–Cl(1) 88.45(2)
N(31)–Ru(1)–As(2) 97.77(8) As(2)–Ru(1)–Cl(1) 86.95(3)
N(21)–Ru(1)–As(2) 98.51(7)
17
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–As(2)
2.101(4)
2.122(4)
2.3836(7) Ru(1)–Cl(1)
Ru(1)–N(2)
Ru(1)–As(1)
2.056(4)
2.3686(7)
2.4377(14)
N(1)–Ru(1)–N(2)
N(2)–Ru(1)–N(3)
N(2)–Ru(1)–As(1)
78.46(18) N(1)–Ru(1)–N(3)
89.36(16) N(1)–Ru(1)–As(1)
91.04(12) N(3)–Ru(1)–As(1) 177.37(12)
85.04(16)
97.58(11)
N(1)–Ru(1)–As(2) 177.06(12) N(2)–Ru(1)–As(2) 100.13(12)
N(3)–Ru(1)–As(2)
N(1)–Ru(1)–Cl(1)
N(3)–Ru(1)–Cl(1)
92.38(12) As(1)–Ru(1)–As(2) 85.00(2)
92.83(13) N(2)–Ru(1)–Cl(1) 171.26(13)
90.69(12) As(1)–Ru(1)–Cl(1) 89.31(4)
2PDMF
Ru(1)–N(61)
Ru(1)–N(51)
Ru(1)–P(1)
2.093(2)
2.101(2)
2.2947(7) Ru(1)–Cl(1)
Ru(1)–As(1)
Ru(1)–As(2)
2.4160(4)
2.4278(4)
2.4629(7)
As(2)–Ru(1)–Cl(1) 88.60(4)
N(61)–Ru(1)–N(51) 78.23(8) P(1)–Ru(1)–As(2)
98.55(2)
diffuse sunlight for ca. 100 h. The isomerized samples show
no reversion to their trans forms after extended periods in the
dark. The1H NMR spectra ofthecisisomersarecharacterized
by increased numbers of signals due to reduced symmetry,
together with shifts of as much as 1 ppm for some of the
resonances. In particular, the lowest field bpy/phen doublets
are shifted downfield and some of the AsMe signals shift
upfield, upon trans™cis isomerization. In the case of the two
forms of [RuIICl(pdma)(bpy)mim]PF6 (3 and 17), the
isomerization was further confirmed by X-ray structuralstud-
ies (see later).
N(61)–Ru(1)–P(1)
N(51)–Ru(1)–P(1)
92.26(6) As(1)–Ru(1)–As(2) 84.727(12)
93.60(6) N(61)–Ru(1)–Cl(1) 84.45(6)
N(61)–Ru(1)–As(1) 168.98(6) N(51)–Ru(1)–Cl(1) 83.41(6)
N(51)–Ru(1)–As(1) 97.76(6) P(1)–Ru(1)–Cl(1) 175.93(2)
P(1)–Ru(1)–As(1)
98.27(2) As(1)–Ru(1)–Cl(1) 84.90(2)
N(61)–Ru(1)–As(2) 96.97(6) As(2)–Ru(1)–Cl(1) 84.24(2)
N(51)–Ru(1)–As(2) 167.13(6)
3
Ru–N(1)
Ru–N(21)
Ru–N(31)
2.087(3)
2.107(3)
2.107(3)
Ru(1)–As(1)
Ru(1)–As(2)
Ru(1)–Cl
2.4081(7)
2.4028(5)
2.4494(11)
N(1)–Ru–N(21)
N(1)–Ru–N(31)
N(1)–Ru–As(1)
N(1)–Ru–As(2)
N(1)–Ru–Cl
N(21)–Ru–N(31)
N(21)–Ru–As(1)
N(21)–Ru–As(2)
87.36(11) N(21)–Ru–Cl
87.32(11) N(31)–Ru–As(1)
96.99(8) N(31)–Ru–As(2)
93.20(7) N(31)–Ru–Cl
175.55(8) As(1)–Ru–Cl
77.47(11) As(1)–Ru–As(2)
99.48(8) As(2)–Ru–Cl
178.20(8)
90.41(8)
174.64(8)
100.84(8)
88.43(8)
87.18(3)
82.16(2)
88.91(3)
3.3. UV–visible studies
Electronic absorption spectra for all of the new complex
salts were recorded in acetonitrile and results are presented
in Table 3. All show relatively intense, broad dp(RuII)™
p*(bpy/phen) MLCT bands [27,28] in the region 360–460
nm. For the series trans-[RuIICl(pdma)(bpy)L1][PF6]n
(ns1 or 2, 1–5 and 7), the MLCT energy decreases as
the overall electron donor strength of L1 increases, in the
order L1sdmso-PPh3fmpyzq-MeCN-py-mim.This
ordering reflects a steady destabilization of the Ru-based
HOMO. Similar trends are observed for the phen com-
plexes in 8–10 and 12 and for the trans-[Ru(pdma)-
(bpy)mim(L2)][PF6]2 series 13–15. The disubstituted
derivatives 13–15 all have higher MLCT energies than their
parent complex in 3 because mim, py and MeCN are less
basic than chloride. For the same reasons, substitution of the
chloride ligand in 2 by MeCN to give 16 produces a blue shift
of ca. 0.25 eV.
12P3MeCN
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–N(4)
2.019(2)
2.120(2)
2.118(2)
Ru(1)–As(1)
Ru(1)–As(2)
Ru(1)–Cl(1)
2.4067(9)
2.4182(7)
2.4146(10)
N(1)–Ru(1)–N(4)
N(4)–Ru(1)–N(3)
N(4)–Ru(1)–As(1)
N(1)–Ru(1)–Cl(1) 176.24(6) N(4)–Ru(1)–Cl(1)
N(3)–Ru(1)–Cl(1)
N(1)–Ru(1)–As(2)
92.49(8) N(1)–Ru(1)–N(3)
78.39(9) N(1)–Ru(1)–As(1)
96.84(6) N(3)–Ru(1)–As(1) 171.62(6)
87.56(6)
84.04(6) As(1)–Ru(1)–Cl(1) 88.90(3)
90.59(6) N(4)–Ru(1)–As(2) 176.81(5)
92.28(8)
94.82(6)
N(3)–Ru(1)–As(2) 100.64(6) As(1)–Ru(1)–As(2) 83.74(3)
Cl(1)–Ru(1)–As(2) 89.31(3)
14PDMF
The complexes containing py or pyz co-ligands also show
dp(RuII)™p*(py/pyz) MLCT bands which in many cases
overlap with the dp(RuII)™p*(bpy/phen) absorptions. In
the complexes in 7 and 12, dp(RuII)™p*(mpyzq) bands
are observed at especially low energy owing to the strongly
p-accepting nature of the mpyzq ligand. The spectra of the
Ru(1)–N(3)
Ru(1)–N(4)
Ru(1)–As(1)
2.11(2)
2.11(2)
2.439(3)
Ru(1)–N(1)
Ru(1)–N(5)
Ru(1)–As(2)
2.10(2)
2.12(2)
2.447(3)
N(3)–Ru(1)–N(1)
N(1)–Ru(1)–N(4)
88.1(8)
89.2(8)
N(3)–Ru(1)–N(4)
N(3)–Ru(1)–N(5)
77.7(8)
87.0(8)
(continued)
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B.J. Coe et al. / Polyhedron 19 (2000) 1193–1203
1201
isomeric pair of complexes in 3 and 17 are somewhat differ-
3.4. Electrochemical studies
ent, with the dp(RuII)™p*(bpy) band maximum occurring
at higher energy by ca. 0.19 eV in the cis isomer. Besides
their MLCT bands, all of the complexes also show one or
more intense UV absorptions due to intraligand p™p*
excitations.
All of the new complex salts were studied by cyclic vol-
tammetry in acetonitrile and results are presented in Table 3.
All exhibit reversible or quasi-reversible RuIII/II oxidation
waves, together with ligand-based reduction processeswhich
Table 3
Electrochemical and UV–vis data for complex salts in acetonitrile
Complex salt
E1/2 (V vs. SCE) (DEp (mV)) a
lmax (nm)
Assignment
RuIII/II
Ligand waves
(´ (dm3 moly1 cmy1)) b
1 trans-[RuCl(pdma)(bpy)py]PF6
0.88 (60)
y1.49 (70)
440sh (4100)
342 (7600)
296 (21800)
246 (14800)
398 (4400)
298 (17600)
458 (3900)
344 (4700)
296 (19400)
248 (12100)
430 (4000)
292 (20600)
244 (12400)
378 (3900)
292 (14900)
246 (11000)
430 (10000)
294 (25200)
248 (20800)
572 (20200)
402 (5400)
288 (22900)
438 (7400)
266 (45200)
398 (4900)
268 (35500)
448 (9200)
268 (33000)
410 (6700)
268 (33600)
572 (16900)
394 (5200)
268 (36000)
412 (3700)
292 (20400)
246 (12400)
398 (4400)
288 (20600)
244 (14500)
390 (6100)
288 (20700)
246 (14200)
364 (6000)
288 (15900)
428 (6200)
320sh (7700)
290 (24600)
dp™p*(bpy)
dp™p*(py)
p™p*
p™p*
2 trans-[RuCl(pdma)(bpy)PPh3]PF6
3 trans-[RuCl(pdma)(bpy)mim]PF6
1.29 (60)
0.68 (70)
y1.30 (170)
y1.54 (90)
dp™p*(bpy)
p™p*
dp™p*(bpy)
p™p*
p™p*
p™p*
4 trans-[RuCl(pdma)(bpy)(MeCN)]PF6
5 trans-[RuCl(pdma)(bpy)dmso]PF6
6 trans-[RuCl(pdma)(bpy)pyz]PF6
0.96 (60)
1.47 c
y1.53 (70)
y1.38 (70)
dp™p*(bpy)
p™p*
p™p*
dp™p*(bpy)
p™p*
p™p*
1.04 (70)
1.29 (90)
dp™p*(pyz/bpy)
p™p*
p™p*
7 trans-[RuCl(pdma)(bpy)(mpyzq)][PF6]2
y0.48 (80)
y1.52 d
dp™p*(mpyzq)
dp™p*(bpy)
p™p*
y1.72 d
8 trans-[RuCl(pdma)(phen)py]PF6
9 trans-[RuCl(pdma)(phen)PPh3]PF6
10 trans-[RuCl(pdma)(phen)mim]PF6
11 trans-[RuCl(pdma)(phen)pyz]PF6
12 trans-[RuCl(pdma)(phen)(mpyzq)][PF6]2
0.88 (80)
1.28 (80)
0.67 (80)
1.02 (90)
1.30 (110)
y1.48 (110)
dp™p*(phen)
p™p*
y1.24 (60)
y1.55 (100)
y1.42 (130)
dp™p*(phen)
p™p*
dp™p*(phen)
p™p*
dp™p*(pyz/phen)
p™p*
y0.44 (70)
y1.37 (170)
dp™p*(mpyzq)
dp™p*(phen)
p™p*
13 trans-[Ru(pdma)(bpy)(mim)2][PF6]2
14 trans-[Ru(pdma)(bpy)(mim)py][PF6]2
15 trans-[Ru(pdma)(bpy)mim(MeCN)][PF6]2
1.06 (110)
1.25 (140)
1.28 (150)
y1.36 (80)
y1.32 (80)
y1.39 (70)
dp™p*(bpy)
p™p*
p™p*
dp™p*(bpy)
p™p*
p™p*
dp™p*(bpy)
p™p*
p™p*
16 trans-[Ru(pdma)(bpy)PPh3(MeCN)][PF6]2
17 cis-[RuCl(pdma)(bpy)mim]PF6
1.82 (120)
0.67 (80)
y1.23 (50)
y1.56 (80)
dp™p*(bpy)
p™p*
dp™p*(bpy)
p™p*
p™p*
a Measured in solutions ca. 10y3 mol dmy3 in analyte and 0.1 mol dmy3 in NBun4PF6 at a platinum-bead working electrode with a scan rate of 200 mV sy1
.
Ferrocene internal reference E1/2s0.41 V, DEps90 mV.
b Solutions (5–7)=10y5 mol dmy3
.
c Epa for an irreversible oxidation process.
d Epc for an irreversible reduction process.
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B.J. Coe et al. / Polyhedron 19 (2000) 1193–1203
range from reversible to irreversible. Within the series
trans-[RuIICl(pdma)(bpy)L1][PF6]n (ns1 or 2, 1–7) the
RuIII/II E1/2 values become more positive as the overall
electron donor strength of L1 decreases, in the order
L1smim)py)MeCN)pyz)mpyzqfPPh3)dmso. As
expected, this trend parallels that observed in the
dp(RuII)™p*(bpy) MLCT data (see earlier). The RuIII/II
E1/2 values of the phen complexes in 8–12 are essentially
identical to those of their bpy counterparts, and the same
dependence upon L1 is evident. Similarly, in the disubstituted
complex salts trans-[RuII(pdma)(bpy)mim(L2)][PF6]2
(13–15) the RuIII/II E1/2 values shift to more positive poten-
tials as the electron donor strength of L2 decreasesin theorder
mim)py)MeCN. The complex in 16 has an especially
anodic RuIII/II E1/2 due to the combined p-electron-with-
drawing abilities of the MeCN and PPh3 ligands. The cyclic
voltammograms of 3 and 17 are essentiallyidentical,showing
that isomerization doesnot affecttheredoxpropertiesofthese
complexes.
showing that the pdma ligand exerts a rather greater STE on
bpy than does chloride. The Ru–As bond distances of
2.3836(7) A (trans to bpy) and 2.3686(7) A (trans tomim)
indicate that the STE of bpy on pdma is slightly larger than
that of mim.
˚
˚
4. Conclusion
Stepwise substitutions of the axial nitrosyl and chloride
ligands are readily achieved in the mixed-chelates trans-
[RuIICl(pdma)(L–L)(NO)][PF6]2 (L–Lsbpy or phen).
However, the resulting products are mildly photosensitive in
solution and isomerize irreversibly to their cis forms. The
preparation of chromophore-quencher complexes based on
trans-{RuII(pdma)(L–L)}2q centres is therefore unlikelyto
be a worthwhile objective.
Supplementary data
3.5. Structural studies
Supplementary data (fractional atomic coordinates, ani-
sotropic thermal parameters, and full listings of bond lengths
and angles) are available from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: q44-1223-336033; e-mail: deposit@ccdc.
cam.ac.uk) on request, quoting the deposition numbers
CCDC 139504 (1), CCDC 139505 (2PDMF), CCDC
139506 (3), CCDC 139507 (12P3MeCN), CCDC 139508
(14PDMF) and CCDC 139509 (17).
Single-crystal X-ray structures were determined for 1,
2PDMF, 3, 12P3MeCN, 14PDMF and 17. Representations
of the complex cations are shown in Figs. 1–6. Thecomplexes
in 1, 2PDMF and 3 show the expected trans arrangement of
the pdma and bpy ligands. In 2PDMF, the steric bulk of the
PPh3 causes the pdma and bpy ligands to bend slightly
towards the chloride, giving an average E–Ru–Cl (EsAs or
N) bond angle of 84.25(9)8. The corresponding average
bond angles in 1 and 3 are 88.3(1) and 88.7(1)8, respec-
tively, showing very little distortion of the octahedral coor-
dination geometries. The Ru–Cl bond distances increase in
Acknowledgements
˚
the order 1-3-2PDMF, with a difference of ca. 0.04 A
between 1 and 2PDMF. This trend reveals the structural
trans-effect (STE) order with respect to trans chloride of
py-mim-PPh3.
Thanks are due to the Nuffield Foundation for financial
support and to the EPSRC for provision of a studentship
(CIM). We are grateful to Johnson Matthey plc for a gen-
erous loan of ruthenium trichloride.
The structure of 14PDMF confirms that the trans geometry
of 3 is maintained upon substitution of the chloride with a
pyridine ligand, and the trans structure is also found in
12P3MeCN. In the latter salt, the Ru–N(mpyzq) distance
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