Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit

Journal of Organometallic Chemistry 696 (2011) 2263e2268

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Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit Dai Oyama a, *, Takashi Hamada b, Tsugiko Takase a a b

Cluster of Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan Graduate School of Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan

a r t i c l e i n f o

a b s t r a c t

Article history: Received 25 September 2010 Received in revised form 16 November 2010 Accepted 18 November 2010

Two stereoisomers of cis-[Ru(bpy)(pynp)(CO)Cl]PF6 (bpy ¼ 2,20 -bipyridine, pynp ¼ 2-(2-pyridyl)-1,8-naphthyridine) were selectively prepared. The pyridyl rings of the pynp ligand in [Ru(bpy)(pynp)(CO)Cl]þ are situated trans and cis, respectively, to the CO ligand. The corresponding CH3CN complex ([Ru(bpy)(pynp)(CO) (CH3CN)]2þ) was also prepared by replacement reactions of the chlorido ligand in CH3CN. Using these complexes, ligand-centered redox behavior was studied by electrochemical and spectroelectrochemical techniques. The molecular structures of pynp-containing complexes (two stereoisomers of [Ru(bpy)(pynp) (CO)Cl]PF6 and [Ru(pynp)2(CO)Cl]PF6) were determined by X-ray structure analyses. Ó 2010 Elsevier B.V. All rights reserved.

Keywords: Ruthenium 1,8-Naphthyridine unit Polypyridyl ligand Carbonyl complex Crystal structure Redox property

1. Introduction Redox reactions are one of the most fundamental chemical reactions. In particular, much attention is currently focused on ligand-centered redox reactions in transition metal complexes [1e5]. The redox-active compounds based on polypyridyl units containing transition metals such as ruthenium(II), osmium(II) and rhenium(I) play important roles in the fields of solar energy conversion and the data storage of photo- or electronic information at the molecular level [6e9]. The naphthyridines consist of a group of diazanaphthalenes with one nitrogen in each ring [10]. Since Tanaka and co-workers described a detailed 1,8-naphthyridine-based redox reaction [11], attention has been paid to the redox-active properties of a variety of naphthyridine ligands. For example, the bidentate naphthyridine, 2-(2-pyridyl)-1,8-naphthyridine (pynp), is a useful ligand for mononuclear systems, which acts as a catalyst for water oxidation [12]. For complexes with the pynp ligand, there is a stereochemical question with regard to binding of the pynp ligand because it is unsymmetrical structure. It is, therefore, very interesting for the

* Corresponding author. Cluster of Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan. Tel./fax: þ81 24 548 8199. E-mail address: [email protected] (D. Oyama). 0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2010.11.031

complexes with pynp to study relationship between coordination geometries of them and their reactivities. In this paper, the stereospecific synthesis, structures and redox properties of complexes with pynp (cis-[Ru(bpy)(pynp)(CO)Cl]þ; bpy ¼ 2,20 -bipyridine) is described. We demonstrate a suitable synthetic method for the selective formation of stereoisomers and determine the molecular structures by X-ray structure analyses. Using the presented complexes, ligand-centered redox properties are studied by electrochemical and spectroelectrochemical techniques. 2. Results and discussion 2.1. Synthesis, characterization and structures of the complexes We have initially synthesized stereoisomers of cis-[Ru(bpy) (pynp)(CO)Cl]þ ([1]þ). As shown in Fig. 1, there are four possible geometries in the complex. In this series, however, only two types of the complex (a and b in Fig. 1) could be selectively prepared. Compound [1a]þ was prepared by reacting the [Ru(bpy)(CO)Cl2]2 dimer [13] with pynp [14,15] in 2-methoxyethanol, in accordance with a modified published method (Scheme 1) [16,17]. Reaction of the pynp-dimer ([Ru(pynp)(CO)Cl2]2) with bpy should give a different isomer to [1b]þ as shown in Scheme 1, because the order of the addition of the ligands confers geometric specificity [16,17]. To confirm this result, we also carried out the synthesis of the bis-pynp

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N

bpy N

Np

pynp Nn

CO

CO

Ru Np Nn

N

a

nþ

N

CO Ru

hv

CO

N

N

2.2. Redox properties of the complexes Cyclic voltammograms (CVs) of the present complexes ([1]þ and [2] ) exhibited two successive one-electron reductions based on two bidentate ligands (Table 2 and Fig. S1): in [1]þ, the first cathodic wave (Epc1) is assigned to the pynp-centered reduction [22], whereas the second wave (Epc2) is assigned to the bpycentered reduction [9,19,23]. Unexpectedly, the CH3CN complex ([3]2þ) showed three reduction waves (Fig. S1), and the first two waves are located in a more positive region (ca. 0.1 V) than the corresponding Cl-complexes ([1]þ). These observations suggest that the CH3CN ligand is a better p-acceptor than the Cl ligand and these data support the results of the IR measurements (nCO values; Table 2). Although the third wave was not assigned, it probably results from a new species formed by an EC reaction process. The first cathodic waves of [1]þ, [2]þ and [3]2þ showed nearly reversible behavior by immediately return scanning, which indicates the existence of stable one-electron reduction species within the timescale of the CV. In addition, complexes [1a]þ, [1b]þ and [2]þ showed a reversible one-electron oxidation attributed to the RuIII/II couple. The RuIII/II couple of [3]2þ was not observed with the solvent window. Intramolecular cyclization, by taking advantage of a ligandlocalized redox reaction, serves for the reductive activation of the MeCO bond. For example, unusual cyclization of [Ru(bpy)2(CO) (napy)]2þ (napy ¼ 1,8-naphthyridine) was reported by Tanaka and co-workers [11,24]. One-electron reduction of the napy moiety has been ascribed to an intramolecular nucleophilic attack of the nonbonded nitrogen of napy to the carbonyl carbon. This attack results in the formation of the five-membered carbamoyl ring. þ

Cl

OC

+

N

Cl

CO

Ru

pynp

N

Ru

CO

[1a]+

Ru Np

N

Cl Cl

N

Nn

Cl

Nn

Cl

Np

Nn

CO Ru CO

Np Cl

hv

Np

Cl

CO

Ru OC

bpy

Nn

Ru Np

Cl

Nn

Cl N

pynp +

Np Nn

CO Ru

N = bpy N

Nn

Nn

[2]+

Cl

= pynp Np

+ CO

N

Np

* Nn and Np denote the naphthyridine nitrogen and the pyridine nitrogen, respectively. Scheme 1.

N

CO Ru NCMe Nn

Ru

Cl

MeCN

Np

Cl

Cl

2+

N

[Ru(CO)2Cl2]n

pynp

N

(L ¼ the monodentate ligand). Nn and Np denote the naphthyridine nitrogen and the pyridine

type complex ([Ru(pynp)2(CO)Cl]þ; [2]þ) according to Scheme 1. The IR and NMR spectra of all complexes are indicative for the preparation of a single compound. The corresponding CH3CN complex ([3]2þ) of [1a]þ was prepared by replacement reactions of the chlorido ligand in CH3CN using an Agþ ion. Although the synthesized complexes were all single species as determined from the spectroscopic measurements, we could not assign their structures due to their spectral resemblance. Consequently, X-ray analyses were performed to obtain detailed structural information of [1]þ and [2]þ. The crystal structure of [1a]þ is shown in Fig. 2, and selected bond lengths and angles are listed in Table 1. The geometry around the ruthenium center is a distorted octahedral. As expected, the pyridyl ring of the pynp ligand in [1a]þ is situated trans to the CO ligand. The 1,8-naphthyridine unit of the pynp ligand of [1a]þ is located beside the CO ligand with a dihedral angle of 5.3(4) (C20eN4eRu1eC24). A fairly short interatomic distance between the non-coordinating nitrogen atom of the pynp ligand and the carbon atom of CO in [1a]þ of 2.706(6)  A may imply a donoreacceptor interaction between them. On the other hand, the pyridyl ring of the pynp ligand in [1b]þ is situated cis to the CO ligand (Fig. 2). Although the quality of the crystals of [2]þ was not good enough for a detailed analysis of the bond lengths and angles [18], the pyridyl ring of the first-incorporated pynp ligand in [2]þ is also situated cis to the CO ligand (Fig. 3). Contrary to [1a]þ, however, the 1,8-naphthyridine unit of the second-incorporated pynp ligand in [2]þ is located on the opposite side to the carbonyl group. This result, therefore, indicates that there is no stereo selectivity in incorporating the second pynp ligand. The RueN and RueCO bond parameters of [1a]þ and [1b]þ are close to those of similar complexes (Table 1) [16,17,19e21]. N

L

d

c

Fig. 1. Chemical structures of four stereoisomers in cis-[Ru(bpy)(pynp)(CO)L] nitrogen, respectively.

bpy

bpy

Np

b

Cl

N

L

pynp

CO Ru

Nn

L

Nn

Np

CO Ru

N bpy

pynp

N

Ru L

pynp

N

bpy

[1b]+

[3]2+

D. Oyama et al. / Journal of Organometallic Chemistry 696 (2011) 2263e2268

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O1 N5

C24

O1 N4

C24

N5

N1

Ru1

Ru1 N2

N2 N3

N3

N4 N1

Cl1

Cl1

Fig. 2. Structures of [1a]þ and [1b]þ with the atom numbering schemes. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. The asymmetric unit of the [1a]PF6 crystal contains two chemically identical ion pairs, only one of which is displayed. Only one component of the disordered CO group and Cl atom in [1b]þ is shown.

Table 1 Selected bond lengths ( A) and angles ( ) for [1a]PF6$1/2H2O and [1b]PF6$CH3CN. [1a]þ

[1b]þ

Bond lengths Ru1eCl1 Ru1eN1 Ru1eN2 Ru1eN3 Ru1eN4 Ru1eC24 C24eO1

2.4086(13) 2.064(4) 2.072(4) 2.109(3) 2.097(3) 1.867(5) 1.145(6)

Bond angles N1eRu1eN2 N3eRu1eN4 Ru1eC24eO1

78.84(16) 77.67(14) 174.8(4)

Ru1eCl1 Ru1eN1 Ru1eN2 Ru1eN3 Ru1eN4 Ru1eC24 C24eO1

2.369(2) 2.116(3) 2.077(3) 2.085(3) 2.130(3) 1.939(10) 1.031(12)

N1eRu1eN2 N3eRu1eN4 Ru1eC24eO1

77.84(13) 77.88(13) 175.8(9)

IR spectra of [1]þ, [2]þ and [3]2þ were measured under electrolysis conditions to investigate the possibility of the redoxinduced intramolecular structural changes in detail. The nCO band of not only [1b]þ and [2]þ, but also [1a]þ was found to shift from

O1 N6 N5 Ru1

C27 N1

1978 cm1 to 1943 cm1 upon the one-electron reduction of the complexes at 1.6 V (Table 2). Re-oxidation of the resultant solution at 0 V almost recovered the IR spectra of [1a]þ, [1b]þ and [2]þ. Compared with other similar ruthenium(II) carbonyl complexes [25], these red-shifts of the nCO bands by w35 cm1 correspond to the simple one-electron reduction of these complexes without any intramolecular structural changes. Compound [1a]þ does not form the metallacyclic compound though the CO ligand and the noncoordinating nitrogen atoms of pynp are situated adjacent to each other (2.706(6)  A by X-ray analysis). This results in the low acidity of the carbonyl carbon atom and prevents the nucleophilic attack of the non-coordinating nitrogen atom of pynp, even if the pynp moiety undergoes a one-electron reduction. The low nCO frequency (1978 cm1) in [1a]þ supports this result. It is generally known that the terminal carbonyl ligands undergo nucleophilic attacks when they exhibit nC^O frequencies over 2000 cm1 in ruthenium(II) complexes. For example, a variety of nucleophilic reagents R (R ¼ OH, H, CH3O) react with RueCO moieties to give the corresponding RueCO(R) in cis-[Ru (bpy)2(CO)2]2þ (nC^O: 2085, 2040 cm1) [23,26e28]. Therefore, electrolysis using [3]2þ, which has the higher acidity carbonyl carbon (nCO ¼ 2011 cm1), was performed. Nevertheless, essentially the same result was obtained: the nCO band of [3]2þ at 2011 cm1 shifts to 1979 cm1 following the one-electron reduction of the complexes (Fig. 4A and Table 2), and re-oxidation of the resultant solution

Table 2 Electrochemical and IR data for the presented complexes.

N4

N2

Complexes

Cl1

[1a]þ

[1b]þ

[2]þ

1.10 1.43c 1.93

1.02 1.35 1.93

1.06 1.38 1.64

1975 1978 1943d

1973 1977 1942d

1972 1975 1941d

[3]2þ

a

N3

Potential/V Eox (RuIII/II)b Ered (1)b Ered (2)b Ered (3)b

Frequency/cm1 nC^O (KBr) nC^O (CH3CN) a b

Fig. 3. Structure of [2]þ with the atom numbering scheme. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level.

c d

In CH3CN, vs. Fcþ/Fc. E1/2 values. Epc values. Values of one-electron reduction species.

1.25 1.72 1.95 2008 2011 1979d

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an Ag/AgNO3 (0.01 M in CH3CN) reference electrode. All potentials are reported in volts versus ferrocenium/ferrocene couple (Fcþ/Fc) at 25  C under Ar. Infrared spectra under controlledpotential electrolysis conditions were obtained using a thin-layer cell sandwiched between two KBr crystals with an Au mesh working electrode, a platinum wire electrode and an Ag/AgNO3 reference electrode [25] .

Transmittance

A

*

2100

* 2000

1900

3.2. Materials

1800

1700

1600

Transmittance

B

All solvents were purchased as anhydrous solvents for organic synthesis and used without further purification. CH3CN for electrochemical experiments was further distilled over CaH2 under N2 just prior to use. 2-(2-Pyridyl)-1,8-naphthyridine (pynp), [Ru (CO)2Cl2]n, [Ru(bpy)(CO)2Cl2], [Ru(pynp)(CO)2Cl2] and [Ru(bpy)(CO) Cl2]2 were prepared according to known procedures or the modification of published methods [13e16,29e31]. 3.3. Preparation of [Ru(pynp)(CO)Cl2]2

*

2100

* 2000

1900

1800

1700

1600

Fig. 4. IR spectral changes of [3]2þ under controlled-potential electrolyses at 1.4 V (A) and at 0 V (B) in CH3CN. Asterisks denote solvent peaks.

The complex was prepared by the modification of a previously reported method [13]. [Ru(pynp)(CO)2Cl2] (54 mg, 0.124 mmol) was dissolved in dichloromethane (90 mL) and filtered. The filtrate was placed in a quartz flask with a stopper and irradiated with a 300 W xenon lamp for 19 h at room temperature, after which time a purple precipitate had formed. The precipitate was collected by filtration, washed with diethyl ether and dried in vacuo. The yield was 38 mg (75%). IR (KBr): 1957 cm1 (nC^O). 3.4. Preparation of cis-[Ru(bpy)(pynp)(CO)Cl]PF6 ([1a]PF6)

2þ

recovered the IR spectra of [3] (Fig. 4B). This result leads to another influence, the ligand flexibility, for the redox-induced intramolecular metallacyclization reaction in this complex system. Redox-induced metallacyclization occurred in [Ru(bpy)2(CO)(napy)]2þ, although the complex has a lower nCO value (2003 cm1) than that of [3]2þ (2011 cm1). It would be important for the metallacyclization reaction to have a flexible monodentate ligand in order to effectively attack the neighboring carbonyl carbon. As a result, [3]2þ does not involve the redox-induced intramolecular metallacyclization reaction despite satisfying both steric and electronic conditions. This work revealed that two stereoisomers exhibited similar redox properties. On the other hand, the reactivity of the presented bidentate pynp complexes is quite different from that of the reported monodentate napy complex, though both ligands have the same 1,8-naphthyridine unit. 3. Experimental 3.1. Physical measurements Elemental analyses were carried out at the Research Center for Molecular-Scale Nanoscience, Institute for Molecular Science. Infrared spectra were obtained as KBr pellets with a JASCO FT-IR 4100 spectrometer. Mass spectra were obtained with a Bruker Daltonics microTOF mass spectrometer. NMR spectra were recorded on a JEOL JMN-AL300 spectrometer. Electronic absorption spectra were obtained on a JASCO V-570 UV/VIS/NIR spectrophotometer. Electrochemical measurements were conducted on an ALS/Chi model 620A electrochemical analyzer. Measurements on complexes were made in CH3CN containing tetra-n-butylammonium perchlorate (TBAP, 0.1 M) as a supporting electrolyte, in a one-compartment cell consisting of a platinum working electrode, a platinum wire counter electrode and

A mixture of [Ru(bpy)(CO)Cl2]2 (125 mg, 0.176 mmol) and pynp (77 mg, 0.372 mmol) was heated under reflux in 2-methoxyethanol (20 mL) for 3 h. The mixture was evaporated to dryness under reduced pressure and the remaining solid was dissolved in water (40 mL). The solution was filtered and added to an excess of KPF6. The precipitate was collected by filtration and washed with water and diethyl ether. The product was then dried in vacuo. The crude product was recrystallized from acetonitrile/diethyl ether to give large crystals of [Ru(bpy)(pynp)(CO)Cl]PF6. The yield was 140 mg (59%). Anal. Calc. for C24H17N5OClPF6Ru: C, 42.84; H, 2.55; N, 10.41. Found: C, 42.51; H, 2.75; N, 10.38%. ESI-MS (CH3CN): m/z ¼ 528 (Mþ), 500 (M  COþ). 1H NMR (CD3CN): d 9.70 (d, 1H), 9.62 (d, 1H), 9.38 (dd, 1H), 9.02 (t, 1H), 8.94 (d, 2H), 8.81e8.45 (m, 4H), 8.19e7.96 (m, 4H), 7.86 (t, 1H), 7.58 (dd, 1H) and 7.41 (t, 1H) ppm. 13C NMR (CD3CN): d 200.72 (CO), 156.92, 155.63, 155.18, 154.41, 153.99, 153.55, 149.69, 143.25, 141.32, 140.89, 140.32, 139.94, 139.62, 139.05, 129.36, 128.62, 127.63, 127.41, 126.22, 124.94, 123.72, 121.64 and 121.27 ppm. 3.5. Preparation of cis-[Ru(bpy)(pynp)(CO)Cl]PF6 ([1b]PF6) A similar reaction between [Ru(pynp)(CO)Cl2]2 and bpy under the same conditions described above gave rise to [Ru(bpy)(pynp) (CO)Cl]PF6 ([1b]PF6) with a 44% (90 mg) yield. Anal. Calc. for C24H17N5OClPF6Ru: C, 42.84; H, 2.55; N, 10.41. Found: C, 42.66; H, 2.78; N, 10.40%. ESI-MS (CH3CN): m/z ¼ 528 (Mþ), 500 (M  COþ). 1 H NMR (CD3CN): d 9.80 (d, 1H), 9.58 (dd, 1H), 8.98 (d, 1H), 8.82 (s, 1H), 8.73 (m, 1H), 8.50e8.33 (m, 6H), 8.07e7.98 (m, 3H), 7.76 (t, 1H), 7.54 (m, 1H) and 7.36 (t, 1H) ppm. 13C NMR (CD3CN): d 200.34 (CO), 158.82, 157.87, 155.65, 155.18, 154.72, 154.01, 148.70, 141.93, 140.70, 139.02, 138.52, 129.09, 128.83, 128.62, 127.76, 127.45, 127.14, 125.41, 125.23, 124.05, 123.77, 121.64 and 121.35 ppm.

D. Oyama et al. / Journal of Organometallic Chemistry 696 (2011) 2263e2268 Table 3 Crystallographic data for [1a]PF6$1/2H2O and [1b]PF6$CH3CN.

Chemical formula Formula weight Crystal system Space group Unit cell parameters a ( A) b ( A)  c (A) a ( ) b ( ) g ( ) V ( A3) Z m(Mo Ka) (cm1) No. of measured reflections No. of observed reflections Refinement method Parameters R1 (I > 2s(I))a wR2 (all data)b S a b

[1a]PF6$1/2H2O

[1b]PF6$CH3CN

C24H18N5O1.5ClPF6Ru 681.93 Monoclinic P21/c (no. 14)

C26H20N6OClPF6Ru 713.97 Triclinic P1 (no. 2)

7.9697(2) 26.9006(6) 24.6978(6)

8.3700(2) 12.5848(4) 13.9805(4) 90.5926(9) 93.5756(8) 102.8130(8) 91.7744(8) 5284.6(2) 1435.05(7) 8 2 8.282 7.663 50,105 14,197 11,992 6486 Full-matrix least-squares on F2 713 377 0.0563 0.0516 0.1736 0.1680 1.096 1.078

R1 ¼ S(kFoj  jFck)/SjFoj. P P wR2 ¼ f ðFo2  Fc2 Þ2 = ðFo2 Þ2 g1=2 . w

w

3.6. Preparation of cis-[Ru(pynp)2(CO)Cl]PF6 ([2]PF6) A similar reaction between [Ru(pynp)(CO)Cl2]2 and pynp under the same conditions described above gave rise to [Ru(pynp)2(CO)Cl] PF6 with a 77% (162 mg) yield. Anal. Calc. for C27H18N6OClPF6Ru: C, 44.79; H, 2.51; N, 11.61. Found: C, 44.39; H, 2.76; N, 11.22%. ESI-MS (CH3CN): m/z ¼ 579 (Mþ), 551 (M  COþ). 1H NMR (CD3CN): d 9.89 (d, 1H), 9.81 (d, 1H), 9.29 (dd, 1H), 9.08e8.76 (m, 6H), 8.54e8.20 (m, 5H), 7.98e7.93 (m, 2H) and 7.59e7.54 (m, 2H) ppm. 13C NMR (CD3CN): d 192.26 (CO), 157.73, 155.01, 154.77, 154.24, 149.65, 142.84, 142.09, 140.47, 139.69, 139.19, 139.13, 139.09, 139.07, 138.26, 127.85, 127.80, 127.54, 126.36, 125.97, 125.36, 125.21, 125.04, 124.68, 121.45, 121.15 and 120.93 ppm. 3.7. Preparation of cis-[Ru(bpy)(pynp)(CO)(CH3CN)](PF6)2 ([3](PF6)2) A mixture of [1a]PF6 (35 mg, 0.052 mmol) and an aqueous AgNO3 solution (13 mg, 0.077 mmol/2 mL) in CH3CN (20 mL) was refluxed for 6 h. The gray precipitate of AgCl was removed by filtration through a Celite column and the orange filtrate was concentrated to ca. 2 mL under reduced pressure. Addition of a saturated aqueous solution of KPF6 (2 mL) to the solution resulted in an orange precipitate. The precipitate was collected by filtration, and washed with cold water and diethyl ether. The yield was 26 mg (61%). Anal. Calc. for C26H20N6OP2F12Ru$5H2O: C, 34.18; H, 3.31; N, 9.20. Found: C, 34.31; H, 3.41; N, 9.32%. ESI-MS (CH3CN): m/z ¼ 246.5 (M  CH3CN2þ). 1H NMR (CD3CN): d 9.45 (d,1H), 9.40 (dd,1H), 9.14 (d, 1H), 8.92 (d,1H), 8.81e8.62 (m, 4H), 8.41e8.26 (m, 4H), 8.00e7.82 (m, 2H), 7.57 (d, 1H), 7.50 (dd, 1H) and 7.26 (d, 1H) ppm. 3.8. X-ray Crystallography of [1a]PF6, [1b]PF6 and [2]PF6 Crystals for X-ray analyses of the complexes were obtained by vapor diffusion of diethyl ether into an acetonitrile solution of the complexes. A suitable single crystal for the measurement was mounted on a glass fiber. Data were collected at 23  C ([1a]PF6 and [1b]PF6) or 100  C ([2]PF6) on a Rigaku RAXIS-RAPID diffractometer A). All with graphite monochromated Mo Ka radiation (l ¼ 0.71075  data were collected and processed using the PROCESS-AUTO program

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[32]. All the calculations were carried out with the CrystalStructure crystallographic software package [33] except for refinement, which was performed using SHELXL-97 [34]. The structures were solved by direct methods [35,36]. Multi-scan absorption corrections were applied [37]. The CO group and Cl atom in [1b]þ were disordered at two sites, having approximate occupancies of 80:20. Thus, leastsquares calculations including the disordered atoms and the structure were successfully refined. Non-coordinated hydrogen atoms of water were not included in the structures of [1a]þ and [2]þ. Crystallographic parameters of [1a]PF6 and [1b]PF6 are summarized in Table 3. Acknowledgement We thank Professor Koji Tanaka of the Institute for Molecular Science (IMS) for his helpful advice and discussion. D.O. gratefully acknowledges the financial support of the IMS, the Joint Studies Program (2009e2010). Appendix A. Supplementary material CCDC 778924 and 778925 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Center via www. cccdc.cam.ac.uk/data-request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jorganchem.2010.11.031. References [1] J.L. Boyer, J. Rochford, M.-K. Tsai, J.T. Muckerman, E. Fujita, Coord. Chem. Rev. 254 (2010) 309. [2] J.L. van der Vlugt, J.N.H. Reek, Angew. Chem., Int. Ed. 48 (2009) 8832. [3] J.L. Boyer, T.R. Cundari, N.J. DeYonker, T.B. Rauchfuss, S.R. Wilson, Inorg. Chem. 48 (2009) 638. [4] E.C. Constable, Coord. Chem. Rev. 252 (2008) 842. [5] W. Kaim, G.K. Lahiri, Angew. Chem., Int. Ed. 46 (2007) 1778. [6] M.H.V. Huynh, D.M. Dattelbaum, T.J. Meyer, Coord. Chem. Rev. 249 (2005) 457. [7] M.D.K. Nazeeruddin, M. Grätzel, Comprehensive Coordination Chemistry II, vol. 9, Elsevier, Oxford, UK, 2004, pp. 719e758. [8] F. Barigelletti, L. Flamingnni, Chem. Soc. Rev. 29 (2000) 1. [9] V. Balzani, A. Juris, M. Venturi, S. Campagna, S. Serroni, Chem. Rev. 96 (1996) 759. [10] M.A. Ciriano, L.A. Oro, Comprehensive Coordination Chemistry II, vol. 1, Elsevier, Oxford, UK, 2004, pp. 55e61. [11] H. Nakajima, K. Tanaka, Chem. Lett. (1995) 891. [12] H.-W. Tseng, R. Zong, J.T. Muckerman, R. Thummel, Inorg. Chem. 47 (2008) 11763. [13] G.B. Deacon, C.M. Kepert, N. Sahely, B.W. Skelton, L. Spiccia, N.C. Thomas, A.H. White, J. Chem. Soc., Dalton Trans. (1999) 275. [14] C.S. Campos-Fernandez, L.M. Thomson, J.R. Galan-Mascaros, X. Ouyang, K.R. Dunbar, Inorg. Chem. 41 (2002) 1523. [15] S.K. Patra, N. Sadhukhan, J.K. Bera, Inorg. Chem. 45 (2006) 4007. [16] C.M. Kepert, G.B. Deacon, N. Sahely, L. Spiccia, G.D. Fallon, B.W. Skelton, A.H. White, Inorg. Chem. 43 (2004) 2818. [17] D. Oyama, A. Asuma, T. Takase, Inorg. Chem. Commun. 11 (2008) 1097. [18] Crystal data for [2]PF6$H2O: C27H20N6O2ClPF6Ru, Fw ¼ 741.98, triclinic, space group P-1 (#2), a ¼ 8.9584(9), b ¼ 12.4532(12), c ¼ 12.7664(14)  A, a ¼ 79.962 A3, Z ¼ 2, Dcalc ¼ 1.786 g cm3, (3), b ¼ 83.133(3), g ¼ 81.149(3) , V ¼ 1379.4(2)  6102 unique reflections (Rint ¼ 0.120), R1 (I > 2s(I)) ¼ 0.0959, wR2 (all reflections) ¼ 0.2520. [19] D. Oyama, A. Asuma, T. Hamada, T. Takase, Inorg. Chim. Acta 362 (2009) 2581. [20] J.M. Clear, J.M. Kelly, C.M. O’Connell, J.G. Vos, C.J. Cardin, S.R. Costa, J. Chem. Soc., Chem. Commun. (1980) 750. [21] R. Bhattacharyya, R.S. Drago, K.A. Abboud, Inorg. Chem. 36 (1997) 2913. [22] C.S. Campos-Fernandez, X. Ouyang, K.R. Dunbar, Inorg. Chem. 39 (2000) 2432. [23] D. Ooyama, T. Tomon, K. Tsuge, K. Tanaka, J. Organomet. Chem. 619 (2001) 299. [24] T. Tomon, T. Koizumi, K. Tanaka, Angew. Chem., Int. Ed. 44 (2005) 2229. [25] H. Nakajima, Y. Kushi, H. Nagao, K. Tanaka, Organometallics 14 (1995) 5093. [26] H. Ishida, K. Tanaka, M. Morimoto, T. Tanaka, Organometallics 5 (1986) 724. [27] H. Tanaka, B.-C. Tzeng, H. Nagao, S.-M. Peng, K. Tanaka, Inorg. Chem. 32 (1993) 1508. [28] K. Toyohara, H. Nagao, T. Mizukawa, K. Tanaka, Inorg. Chem. 34 (1995) 5399.

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[29] P.A. Anderson, G.B. Deacon, K.H. Haarmann, F.R. Keene, T.J. Meyer, A.H. White, Inorg. Chem. 34 (1995) 6145. [30] M. Haukka, J. Kiviaho, M. Ahlgren, T.A. Pakkanen, Organometallics 14 (1995) 825. [31] D. Oyama, T. Hamada, Acta Crystallogr. E64 (2008) m442. [32] PROCESS-AUTO. Rigaku Corporation, Tokyo, Japan, 1998. [33] CrystalStructure, Ver. 3.8: Crystal Structure Analysis Package. Rigaku and Rigaku Americas, The Woodlands, Texas, USA, 2007.

[34] G.M. Sheldrick, SHELXL-97, University of Göttingen, Göttingen, Germany, 1997. [35] SIR 92: A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. Burla, G. Polidori, M. Camalli J. Appl. Crystallogr. 27 (1994) 435. [36] SIR 97: A. Altomare, M. Burla, M. Camalli, G. Cascarano, C. Giacovazzo, A. Guagliardi, A. Molitern, G. Polidori, R. Spagna J. Appl. Crystallogr. 32 (1999) 115. [37] T. Higashi, ABSCOR. Rigaku Corporation, Tokyo, Japan, 1995.