Ruthenium and rhodium nitrosyl complexes containing dichalcogenoimidodiphosphinate ligands

Polyhedron 26 (2007) 4631–4637 www.elsevier.com/locate/poly

Ruthenium and rhodium nitrosyl complexes containing dichalcogenoimidodiphosphinate ligands Wai-Man Cheung a, Qian-Feng Zhang b, Chui-Ying Lai a, Ian D. Williams a, Wa-Hung Leung a,* a

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China b Department of Applied Chemistry, Anhui University of Technology, Maanshan, Anhui 243002, PR China Received 9 January 2007; accepted 15 March 2007 Available online 10 April 2007

Abstract Interaction of [Ru(NO)Cl3(PPh3)2] with K[N(R2PS)2] in refluxing N,N-dimethylformamide afforded trans-[Ru(NO)Cl{N(R2PS)2}2] (R = Ph (1), Pri (2)). Reaction of [Ru(NO)Cl3(PPh3)2] with K[N(Ph2PSe)2] led to formation of a mixture of trans[Ru(NO)Cl{N(Ph2PSe)2}2] (3) and trans-[Ru(NO)Cl{N(Ph2PSe)2}{Ph2P(Se)NPPh2}] (4). Reaction of Ru(NO)Cl3 Æ xH2O with K[N(Ph2PO)2] afforded cis-[Ru(NO)(Cl){N(Ph2PO)2}2] (5). Treatment of [Rh(NO)Cl2(PPh3)2] with K[N(R2PQ)2] gave Rh(NO){N(R2PQ)2}2] (R = Ph, Q = S (6) or Se (7); R = Pri, Q = S (8) or Se (9)). Protonation of 8 with HBF4 led to formation of trans-[Rh(NO)Cl{HN(Pri2PS)2}2][BF4]2 (10). X-ray diffraction studies revealed that the nitrosyl ligands in 2 and 4 are linear, whereas that in 9 is bent with the Rh–N–O bond angle of 125.7(3)°. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Ruthenium; Rhodium; Nitrosyl; Chalcogen ligands; Crystal structures

1. Introduction Nitrosyl is a versatile ligand for coordination and organometallic compounds [1–5]. The chemistry of metal nitrosyl complexes has become a focus of intensive research recently [6] due in part to the important roles of nitric oxide in biological systems [7]. In this connection, the study of metal nitrosyls that can release NO under photochemical conditions has attracted much attention [8,9]. Ru nitrosyls appear as promising candidates for NO generation because they are photolabile but thermally stable under physiological conditions. Of note, Prakash and coworkers synthesized a Ru nitrosyl compound with a polydentate amino-thiolate ligand that can release NO upon irradiation with visible light [10]. This prompts us

*

Corresponding author. Tel.: +852 23587360; fax: +852 23581594. E-mail address: [email protected] (W.-H. Leung).

0277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2007.04.002

to explore the chemistry of Ru nitrosyl complexes in sulfur-rich ligand environments. Dichalcogenoimidodiphosphinates, [N(R2PQ)2] (R = aryl, alkyl; Q = S, Se) (Scheme 1), which have been recognized as chalcogen analogues of acetylacetonate, can form stable complexes with a range of main group and transition metal ions [11–15]. Owing to their electron-donating ability and steric bulk, [N(R2PQ)2] can stabilize electronrich, unsaturated metal compounds. For example, we have synthesized the 16-electron Ru(II) complexes [Ru{N(R2PQ)2}2(PPh3)] that can bind to reactive species such as sulfur monoxide [16] and diazene [17]. Although Ru{N(Ph2PQ)2} complexes with p acid ligands such as CO [16] are known, analogous compounds containing nitrosyl have not been synthesized. In this paper, we describe the synthesis and crystal structures of Ru nitrosyl complexes supported by [N(R2PQ)2]. Analogous Rh compounds containing bent nitrosyl ligands have also been prepared.

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R

R P

Q

P

Q

N

R

R

R = aryl, alkyl Q = O, S, Se Scheme 1.

2. Experimental All manipulations were carried out under nitrogen by standard Schlenk techniques unless otherwise stated. Solvents were purified, distilled and degassed prior to use. NMR spectra were recorded on a Varian Mercury 300 spectrometer operating at 300, 121.5, and 282.5 MHz for 1 H, 31P, and 19F, respectively. Chemical shifts (d, ppm) were reported with reference to SiMe4 (1H), H3PO4 (31P), and CF3C6H5 (19F). Infrared spectra (KBr) were recorded on a Perkin–Elmer 16 PC FT-IR spectrophotometer. Elemental analyses were performed by Medac Ltd, Surrey, UK. The ligands K[N(R2PQ)2] (R = Ph, Q = O, S, or Se; R = Pri, Q = S or Se) [18–21] and [Ru(NO)Cl3(PPh3)2] [22] and [Rh(NO)Cl2(PPh3)2] [23] were prepared according to literature methods. Ru(NO)Cl3 Æ xH2O was purchased from Strem Ltd and used as received. 2.1. Preparation of trans-[Ru(NO)(Cl){N(R2PS)2}2] (R = Ph (1), Pri (2)) A suspension of [Ru(NO)Cl3(PPh3)2] (200 mg, 0.26 mmol) and 2 equiv. of K[N(Ph2PS)2] (256 mg, 0.53 mmol) in dmf (20 ml) was heated at reflux for 2–3 h, during which the color changed from dark green to orange. The solvent was pumped off, and the residue was washed with Et2O and then extracted with CH2Cl2. Recrystallization from CH2Cl2–Et2O–hexane afforded orange crystals. Compound 1: Yield: 83 mg (30%). Anal. Calc. for C48H40ClN3OP4RuS4 Æ CH2Cl2: C, 51.2; H, 3.7; N, 3.7. Found: C, 51.1; H, 3.9; N, 3.5%. 1H NMR (CDCl3): d 6.94–7.96 (m, C6H5). 31P{1H} NMR (CDCl3): d 38.20 (s). IR (KBr, cm1): 1834 [m(N„O)]. Compound 2: Yield: 28 mg (42%). 1H NMR (CDCl3): d 2.46–2.60 (m, 4H, CH(CH3)2), 2.10–2.23 (m, 4H, CH(CH3)2), 1.21–1.34 (m, 48H, CH(CH3)2). 31P{1H} NMR (CDCl3): d 60.84 (s). IR (KBr, cm1): 1841, 1826 [m(N„O)]. 2.2. Preparations of trans-[Ru(NO)(Cl){N(Ph2PSe)2}2] (3) and trans-[Ru(NO)(Cl){N(Ph2PSe)2}{Ph2P(Se)NPPh2}] (4) A mixture of [Ru(NO)Cl3(PPh3)2] (200 mg, 0.26 mmol) and 2 equiv. of K[N(Ph2PSe)2] (305 mg, 0.53 mmol) was

heated in dmf (20 ml) at reflux for 3 h, during which the color changed from dark green to orange. The solvent was pumped off, and the residue was purified by column chromatography (silica gel) using CH2Cl2–hexane (1:1) as eluant. Complexes 3 and 4 were isolated as orange and reddish orange crystals, respectively. Compound 3: Rf = 0.11. Yield: 125 mg (38%). Anal. Calc. for C48H40ClN3OP4RuSe4 Æ CH2Cl2: C, 44.1, H, 3.2; N, 3.2. Found: 44.5; H, 3.1; N, 3.1%. 1H NMR (CDCl3): d 7.20–7.94 (m, 40H, C6H5). 31P{1H} NMR (CDCl3): d 28.98 (s). IR (KBr, cm1): 1834 [m(N„O)]. Compound 4: Rf = 0.23. Yield: 40 mg (13%). Anal. Calc. for C48H40ClN3OP4RuSe3 Æ 1.5CH2Cl2: 45.8; H, 3.3; N, 3.2. Found: C, 45.9; H, 3.3; N, 3.4%. 1H NMR (CDCl3): d 6.89–8.10 (m, 40H, C6H5). 31P{1H} NMR (CDCl3): d 71.49 (ddd, JPP = 40.0 Hz, JPP = 9.8 Hz, JPP = 6.2 Hz, PPh2), 55.66 (d, JPP = 40.0 Hz, P(Se)Ph2 trans to PPh2), 31.88 (dd, JPP = 3.5 Hz, JPP = 9.8 Hz), 26.91 (dd, JPP = 3.5 Hz, JPP = 6.2 Hz). IR (KBr, cm1): 1837 [m(N„O)]. 2.3. Preparation of cis-[Ru(NO)Cl{N(Ph2PO)2}2] (5) A suspension of Ru(NO)Cl3 Æ xH2O (25 mg, 0.098 mmol) and 2 equiv. of K[N(Ph2PO)2] (89 mg, 0.20 mmol) in acetone (15 ml) was heated at reflux for overnight. The solvent was removed, and the residue was extracted with CH2Cl2. Recrystallization from CH2Cl2– Et2O–hexane afforded pale reddish brown crystals. Yield: 47 mg (48%). Anal. Calc. for C48H40ClN3O5P4Ru Æ CH2Cl2: C, 54.3; H, 3.9; N, 3.9. Found: C, 54.1; 3.9; N, 3.8%. 1H NMR (CDCl3): d 6.85–7.93 (m, 40H, C6H5). 31P{1H} NMR (CDCl3): d 38.94 (d, JPP = 4.0 Hz), 34.74 (d, JPP = 3.3 Hz), 34.64 (d, JPP = 3.7 Hz), 31.52 (d, JPP = 3.7 Hz). IR (KBr, cm1): 1863 [m(N„O)]. 2.4. Preparation of [Rh(NO){N(Ph2PQ)2}2] (R = Ph, Q = S (6) or Se (7); R = Pri, Q = S (8)) A mixture of [Rh(NO)Cl2(PPh3)2] (50 mg, 0.069 mmol) and K[N(Ph2PQ)2] (0.14 mmol) in THF (10 ml) was heated at reflux for 1 h. The solvent was pumped off and the residue was washed with hexane. Recrystallization from CH2Cl2–hexane (6 and 7) or Et2O–hexane (8) afforded red crystals. Compound 6: Yield: 45 mg (63%). Anal. Calc. for C48H40N3OP4RhS4: C, 56.0; H, 3.9; N, 4.1. Found: C, 55.7; H, 3.9; N, 3.0%. 1H NMR (CDCl3): d 7.77–7.84 (m, 16H, C6H5), d 7.26–7.37 (m, 24H, C6H5). 31P{1H} NMR (CDCl3): d 37.85 (d, JRhP = 3.5 Hz). IR (KBr, cm1): 1655 [m(N„O)]. Compound 7: Yield: 46 mg (65%). Anal. Calc. for C48H40N3OP4RhSe4: C, 47.4; H, 3.3; N, 3.5. Found: C, 47.4; H, 3.3; N, 3.4%. 1H NMR (CDCl3): d 7.77–7.83 (m, 16H, C6H5), 7.26–7.39 (m, 24H, C6H5). 31P{1H} NMR (CDCl3): d 27.97 (d, JRhP = 4.1 Hz). IR (KBr, cm1): 1629 [m(N„O)].

W.-M. Cheung et al. / Polyhedron 26 (2007) 4631–4637

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Table 1 Crystallographic data and experimental details for trans-[Ru(NO)Cl{N(Pri2PS)2}2] (2), trans-[Ru(NO)(Cl){N(Ph2PSe)2}{Ph2P(Se)NPPh2}] (4), and [Rh(NO){N(Pri2PSe)2}2] (9) Compound

2

Empirical formula C24H56ClN3OP4RuS4 Formula weight 791.36 Crystal system triclinic Space group P 1 Z 1 ˚) a (A 8.4739(5) ˚) b (A 9.5191(5) ˚) c (A 13.1320(7) a (°) 106.086(1) b (°) 94.173(1) c (°) 113.566(1) ˚ 3) V (A 912.43(9) Dcalc (g cm3) 1.440 Temperature (K) 298(2) F(0 0 0) 414 l(Mo Ka) (mm1) 0.930 Total reflections 5848 Independent reflections 4759 Rint 0.0105 Ra1, wRb2 (I > 2r(I)) 0.0225, 0.0617 0.0238, 0.0624 R1, wR2 (all data) Goodness-of-fitc 1.021 P P a R1 = iFoj–jFci/ jFoj.  P P b wR2 =  w(jF2oj  jF2cj)2/ wjF2oj2 1/2.  P c 2 GoF = w(jFoj  jFcj) /(Nobs  Nparam) 1/2.

Compound 8: Yield: 35 mg (67%). Anal. Calc. for C24H56N3OP4RhS4: C. 38.0; H, 7.4; N, 5.6. Found: C, 38.4; H, 7.5; N, 5.3%. 1H NMR (C6D6): d 2.20–2.40 (m, 8H, CH(CH3)2), d 1.29–1.49 (m, 48H, CH(CH3)2). 31 P{1H} NMR (C6D6): d 63.17 (s). IR (KBr, cm1): 1630 [m(N„O)].

4

9

C48H40ClN3OP4RuSe3 1172.11 monoclinic P21/c 4 22.975(6) 20.593(5) 9.781(3)

C24H56N3OP4RhSe4 945.35 triclinic P 1 2 8.559(2) 9.770(2) 24.259(5) 85.945(4) 84.513(4) 66.311(3) 1847.8(7) 1.699 298(2) 940 1.699 17 135 6316 0.00214 0.0333, 0.0773 0.0402, 0.0798 1.036

93.915(4) 4617(2) 1.686 100(2) 2320 2.942 33796 10 844 0.0389 0.0365, 0.0750 0.0575, 0.0818 1.005

6.1; N, 4.3. Found: C, 30.1; H, 6.6; N, 4.2%. 1H NMR (CDCl3): d 6.80 (s, 2H, NH), 2.74–2.88 (m, 8H, CH(CH3)2), 1.20–1.46 (m, 48H, CH(CH3)2). 31P{1H} NMR (CDCl3): d 89.45 (s). 19F{1H} NMR (CDCl3): d 148.96 (s). IR (KBr, cm1): 1650, 1677 [m(N„O)]. 2.7. X-ray diffraction analysis

2.5. Preparation of [Rh(NO){N(Pri2PSe)2}2] (9) To a suspension of [Rh(NO)Cl2(PPh3)2] (50 mg, 0.069 mmol) in THF (10 ml) was added 2 equiv. of K[N(Pri2PSe)2] (61 mg, 0.14 mmol), and the reaction mixture was stirred at room temperature for 5 h. The solvent was removed and the residue was extracted with hexane– Et2O (1:1, v/v). Concentration and cooling at 10 °C afforded deep red crystals. Yield: 46 mg (65%). Anal. Calc. for C24H56N3OP4RhSe4: C, 30.5; H, 6.0; N, 4.5. Found: C, 30.6; H, 6.1; N, 4.3%. 1H NMR (C6D6): d 2.24–2.47 (m, 8H, CH(CH3)2), 1.28–1.57 (m, 48H, CH(CH3)2). 31P{1H} NMR (C6D6): d 54.38 (d, JRhP = 3.2 Hz). IR (KBr, cm1): 1618 [m(N„O)].

A summary of crystallographic data and experimental details for 2, 4, and 9 are summarized in Table 1. Intensity data were collected on a Bruker SMART APEX 1000 CCD diffractometer using graphite-monochromated Mo Ka ˚ ) at 100(2) K. The collected frames radiation (k = 0.71073 A were processed with the software SAINT. Structures were solved by the direct methods and refined by full-matrix least-squares on F2 using the SHELXTL software package [24]. Non-hydrogen atoms were refined anisotropically. Selected bond lengths and angles for complexes 2, 4 and 9 are listed in Tables 2–4, respectively. 3. Results and discussion

2.6. Preparation of [Rh(NO){NH(Pri2PS)2}2][BF4]2 (10)

3.1. Ruthenium nitrosyl compounds

To a solution of 8 (40 mg, 0.053 mmol) in Et2O (10 ml) was added 2 equiv. of HBF4 (54% in Et2O, 15 ll, 0.11 mmol) at 0 °C. The orange solid was collected and washed with Et2O. Recrystallization from CH2Cl2-Et2O afforded orange crystalline solid. Yield: 31 mg (62%). Anal. Calc. for C24H58B2F8N3OP4RhS4 Æ 0.5CH2Cl2: C, 30.2; H,

Treatment of [Ru(NO)Cl3(PPh3)2] with 2 equiv. of K[N(R2PS)2] in refluxing dmf afforded the nitrosyl compounds trans-[Ru(NO)Cl{N(R2PS)2}2] (R = Ph (1), Pri (2)) (Scheme 2), isolated as air-stable orange solids. The 31 P {1H} NMR spectra for both 1 and 2 exhibit a single resonance (at d 38.2 (s) and 60.84 (s) ppm, respectively),

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W.-M. Cheung et al. / Polyhedron 26 (2007) 4631–4637

Table 2 ˚ ) and angles (°) for trans-[Ru(NO)Cl{NSelected bond lengths (A (Pri2PS)2}2] (2) Ru(1)–S(1) Ru(1)–S(3) Ru(1)–N(1) N(1)–O(1) P(2)–S(2) P(4)–S(4) P(2)–N(2) P(4)–N(3)

2.4343(13) 2.4393(14) 1.810(5) 1.036(5) 2.0393(19) 2.031(2) 1.594(4) 1.582(5)

Ru(1)–S(2) Ru(1)–S(4) Ru(1)–Cl(1) P(1)–S(1) P(3)–S(3) P(1)–N(2) P(3)–N(3)

S(1)–Ru(1)–S(2) S(1)–Ru(1)–S(3) S(1)–Ru(1)–S(4) N(1)–Ru(1)–S(1) N(1)–Ru(1)–S(3) Cl(1)–Ru(1)–S(1) Cl(1)–Ru(1)–S(3) N(1)–Ru(1)–Cl(1) P(1)–N(2)–P(2)

99.90(5) 79.58(5) 176.64(5) 95.92(12) 90.85(13) 85.04(5) 88.38(5) 178.65(14) 134.4(3)

S(3)–Ru(1)–S(4) S(2)–Ru(1)–S(4) S(2)–Ru(1)–S(3) N(1)–Ru(1)–S(2) N(1)–Ru(1)–S(4) Cl(1)–Ru(1)–S(2) Cl(1)–Ru(1)–S(4) Ru(1)–N(1)–O(1) P(4)–N(3)–P(3)

2.4369(14) 2.4441(14) 2.3392(14) 2.026(2) 2.0494(19) 1.586(5) 1.591(5) 101.26(5) 79.15(5) 178.08(6) 91.04(13) 87.33(13) 89.74(5) 91.73(5) 177.3(5) 136.4(3)

Table 3 ˚ ) and angles (°) for trans-[Ru(NO)(Cl){N(Ph2PSelected bond lengths (A Se)2}{Ph2P(Se)NPPh2}] (4) Ru(1)–Se(1) Ru(1)–Se(3) Ru(1)–N(1) N(1)–O(1) P(2)–Se(2) P(1)–N(2) P(3)–N(3)

2.5765(7) 2.5060(6) 1.719(3) 1.139(3) 2.1856(10) 1.593(2) 1.579(2)

Ru(1)–Se(2) Ru(1)–P(4) Ru(1)–Cl(1) P(1)–Se(1) P(3)–Se(3) P(2)–N(2) P(4)–N(3)

Se(1)–Ru(1)–Se(2) Se(3)–Ru(1)–P(4) Se(1)–Ru(1)–P(4) N(1)–Ru(1)–Se(1) N(1)–Ru(1)–Se(3) Cl(1)–Ru(1)–Se(1) Cl(1)–Ru(1)–Se(3) N(1)–Ru(1)–Cl(1) P(2)–N(2)–P(1)

90.45(2) 89.60(3) 167.44(2) 96.99(8) 89.42(8) 85.72(2) 88.72(2) 176.53(9) 135.90(17)

Se(2)–Ru(1)–P(4) Se(1)–Ru(1)–Se(3) Se(2)–Ru(1)–Se(3) N(1)–Ru(1)–Se(2) N(1)–Ru(1)–P(4) Cl(1)–Ru(1)–Se(2) Cl(1)–Ru(1)–P(4) Ru(1)–N(1)–O(1) P(3)–N(3)–P(4)

2.5321(7) 2.3717(10) 2.3527(10) 2.1652(10) 2.1932(10) 1.572(2) 1.616(2) 94.73(3) 83.94(2) 171.708(16) 97.34(8) 93.69(9) 84.77(2) 83.37(3) 175.9(3) 123.90(16)

R Ru(NO)Cl3(PPh3)2

Se(1)–Rh(1)–Se(2) Se(1)–Rh(1)–Se(3) Se(1)–Rh(1)–Se(4) N(1)–Rh(1)–Se(1) N(1)–Rh(1)–Se(3) Rh(1)–Se(1)–P(1) P(1)–N(2)–P(2)

2.5232(6) 2.5163(6) 1.905(3) 2.1872(9) 2.1848(9) 1.597(3) 1.605(3) 98.758(14) 169.368(17) 77.687(14) 97.65(10) 92.98(10) 104.77(3) 132.61(17)

Rh(1)–Se(2) Rh(1)–Se(4) N(1)–O(1) P(2)–Se(2) P(4)–Se(4) P(2)–N(2) P(4)–N(3) Se(3)–Rh(1)–Se(4) Se(2)–Rh(1)–Se(4) Se(2)–Rh(1)–Se(3) N(1)–Rh(1)–Se(2) N(1)–Rh(1)–Se(4) Rh(1)–N(1)–O(1) P(4)–N(3)–P(3)

2.4897(7) 2.5104(6) 1.122(4) 2.2103(10) 2.1979(10) 1.598(3) 1.593(3) 100.784(15) 161.527(19) 79.319(14) 99.86(9) 98.58(9) 125.7(3) 132.93(17)

P

S

R

R

NO S

N

dmf, reflux

S

P

S

P

N

Ru

R

Cl

R

R

R i

R = Ph (1), Pr (2) Scheme 2.

consistent with the trans geometry of the compounds. The IR spectrum of 1 shows a strong N–O band at 1834 cm1, which is similar to that for trans-[Ru(NO)Cl(S2CNEt2)2] (1840 cm1) [25]. The splitting for the m(NO) band (1826 and 1841 cm1) for 2 is probably due to a solid-state effect. Photolysis of 2 in THF led to a green species that did not exhibit any m(NO) bands in the IR spectrum, indicating that the loss of the nitrosyl ligand. Unfortunately, we have not been able to crystallize this green complex. Reaction of [Ru(NO)Cl3(PPh3)2] with 2 equiv. of K[N(Ph2PSe)2] in refluxing dmf led to a mixture of trans[Ru(NO)Cl{N(Ph2PSe)2}2] (3) and trans-Ru(NO)Cl{N(Ph2PSe)2}{Ph2P(Se)NPPh2}] (4) (Scheme 3), which could be separated by column chromatography using CH2Cl2– hexane as eluant. Apparently, the formation of 4 involved the Ru-assisted selenium atom abstraction of one [N(Ph2PSe)2] ligand in 3, possibly by PPh3. It may be noted that in a previous paper, we reported that interaction of [Ru(@CHPh)Cl2(PCy3)2] (Cy = cyclohexyl) with K[N(Ph2PSe)2] resulted in selenium atom abstraction from the [N(Ph2PSe)2] ligand and the formation of trans-[Ru(@CHPh){Ph2P(Se)NPPh2}2] along with trans[Ru(@CHPh){N(Ph2PSe)2}2] [26]. Chalcogen atom abstraction occurred for the [N(Ph2PSe)2] ligand but not in the sulfide analogue presumably because of the weaker P@Se bond strength compared with that of P@S. The IR N–O stretching frequency of 3 (1834 cm1) is similar to that of 1. The 31P {H} NMR spectrum of 3 displays at singlet at d 28.98 ppm, indicative of the trans geometry of the molecule. In the 31P {1H} NMR spectrum of 4, the doublet

Table 4 ˚ ) and angles (°) for [Rh(NO){N(Pri2PSe)2}2] (9) Selected bond lengths (A Rh(1)–Se(1) Rh(1)–Se(3) Rh(1)–N(1) P(1)–Se(1) P(3)–Se(3) P(1)–N(2) P(3)–N(3)

2 K[N(R2PS)2]

R P

Ph

Ph NO Ph Ph Se Se P 2 K[N(Ph2PSe)2] N N Ru dmf P Se P Se reflux Cl Ph Ph Ph Ph P

Ru(NO)Cl3(PPh3)2

3 Ph P +

N

Ru P

Ph

Ph NO Se Se

N Se P Cl Ph Ph Ph 4

Scheme 3.

Ph P

Ph

W.-M. Cheung et al. / Polyhedron 26 (2007) 4631–4637

of doublets of doublets at d 71.49 ppm (3JPP = 40, 2 JPP = 9.8 and 3JPP = 6.2 Hz) is assigned to the PPh2 group, whereas the doublet at d 55.66 ppm (3JPP = 40 Hz) is assigned to the P(Se)Ph2 group opposite to the PPh2 group. The remaining two P(Se)Ph2 groups appear as two doublets of doublets at d 26.91 (4JPP = 3.5, 3 JPP = 6.2 Hz) and 31.88 ppm (4JPP = 3.5, 3JPP = 9.8 Hz) ppm, respectively. No reaction was found between [Ru(NO)Cl3(PPh3)2] and K[N(Ph2PO)2]. Refluxing Ru(NO)Cl3 Æ xH2O with K[N(PPh2PO)2] in acetone gave cis-[Ru(NO)Cl{N(Ph2PO)2}2] (5) (Scheme 4), isolated as air-stable brown crystals. Unlike the sulfide and selenide analogues, the NO and Cl ligands in 5 are cis to each other, as evidenced by the 31P {1H} NMR spectrum that displays four doublets at d 38.94, 34.74, 34.64 and 31.52 ppm (J  3–4 Hz). The IR NO stretching frequency for 5 (1863 cm1) is higher than those of 1 and 3, suggesting that the P@O group is less electron-releasing than chloride. 3.2. Rhodium nitrosyl compounds Treatment of [Rh(NO)Cl2(PPh3)2] with K[N(R2PQ)2] in THF afforded [Rh(NO){N(R2PQ)2}2] (R = Ph, Q = S (6) or Se (7); R = Pri, Q = S (8) or Se (9)) (Scheme 5), isolated as air-stable red crystals. The 31P {1H} NMR spectra of 6, 7, and 9 display doublets at d 37.85, 27.97, and 54.38 ppm, respectively, with JRhP values of 3–4 Hz, whereas a singlet at d 63.17 ppm was found for 8. The IR N–O stretching frequencies for 6–9 of 1618–1655 cm1 are within the range expected for bent nitrosyl compounds [2], although they are higher than that for [Rh(NO)Cl2(PPh3)2] (1559 cm1) [23]. The m(NO) for [Rh(NO){N(R2PQ)2}2] was found to Ph

Ru(NO)Cl3(PPh3)2

2 K[N(Ph2PO)2] acetone, reflux

Ph NO O Cl N Ru O Ph P O P Ph Ph Ph O P N Ph Ph P

5 Scheme 4.

R Rh(NO)Cl2(PPh3)2

2 K[N(R2PS)2] thf

R

R R Q P N N Rh P Q Q P R R R R P

NO

Q

Q = S, R = Ph (6) R = Pr i (7) Q = Se, R = Ph (8) R = Pr i (9) Scheme 5.

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decrease in the order R: Pri > Ph, Q: Se > S. This suggests that the selenium ligand is a stronger donor than the sulfur counterpart. Unlike 1, no reaction was found when 6 in THF was irradiated with UV light. Attempts have been made to activate the nitrosyl ligand of the Rh nitrosyl compounds by treatment with nucleophiles and electrophiles. No reactions were found when 6 was reacted with MeLi or LiBEt3H. Treatment of 6 with PMe3 in CDCl3 gave OPMe3 identified by 31 P NMR spectroscopy along with an uncharacterized Rh species that showed the absence of m(NO) in the IR spectrum. We have not been able to crystallize this Rh-containing product. Reaction of 7 with HBF4 in Et2O afforded an orange precipitate 10 analyzed as dicationic [H27][BF4]2. The IR spectrum of 10 shows m(NO) at 1650 and 1677 cm1, indicating that the bent nitrosyl ligand remained intact. The 31P {1H} NMR spectrum of 10 displays a singlet at d 89.45 ppm that is considerably more downfield than that for 7, but similar to that for HN(Pri2PS)2 (d 91.2 ppm). The observation of a single 31P signal suggests that 10 has a square pyramidal geometry with 2 equivalent [N(Pri2S)2] ligands at the equatorial positions. In addition to the resonances due to the isopropyl protons, the 1H NMR spectrum displays a broad NH resonance at d 6.80 ppm that underwent deuterium exchange upon treatment with D2O. On the basis of the spectroscopic data, 10 is formulated as a dicationic Rh nitrosyl compound containing two protonated dithioimidodiphosphinate ligands, [Rh(NO){HN(Pri2PS)2}] [BF4]2. 3.3. Crystal structures The solid-state structure of 2 is shown in Fig. 1; selected bond lengths and angles are listed in Table 2. The geometry about Ru is pseudo octahedral with the nitrosyl ligand opposite to the chloride. The Ru–N–O linkage is linear (177.3(5)°) as expected for the {MNO}6 configuration using the Enemark–Feltman notation [27]. The Ru–N dis˚ is rather long compared with those of tance of 1.810(5) A reported Ru(II) nitrosyl compounds (e.g. 1.643(8) and ˚ for [Ru(NO)(bdt)2] (bdt = 1,2-benzenethio1.687(8) A ˚ for trans-[Ru(TPP)(NO)(OH)] late) [28] and 1.751(5) A (TPP = tetraphenylporphyrin dianion [29]). The Ru–S dis˚ ) are comparable to those in [Ru{Ntances (av. 2.4387 A ˚ ) [16]. Similar to other (Pri2PS)2}2(PPh3)] (av. 2.405 A M–[N(R2PS)2] complexes, the P–S distances (2.026(2)– ˚ ) in 2 are longer than those in HN(Pri2PS)2 2.049(2) A ˚ ) [20] whereas the P–N distances (1.941(1) and 1.949(1) A ˚ (1.586(5)–1.594(4) A) are shorter than those in the latter ˚ ). The P–N–P angles in 2 (1.682(3) and 1.684(2) A (134.4(3)° and 136.4(3)°) are slightly larger than that in HN(Pri2PS)2 131.6(1)°) [20]. The solid-state structure of 4 is shown in Fig. 2; selected bond lengths and angles are listed in Table 3. The geometry around Ru is pseudo octahedral with the nitrosyl group opposite to the chloride. The nitrosyl ligand is linear with the Ru–N–O angle of 175.9(3)°. The Ru–N distance in 4

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W.-M. Cheung et al. / Polyhedron 26 (2007) 4631–4637

Fig. 1. Molecular structure of trans-[Ru(NO)Cl{N(Pri2PS)2}2] (2). The ellipsoids are drawn at 30% probability level.

Fig. 3. Molecular structure of [Rh(NO){N(Pri2PSe)2}2] (9). The ellipsoids are drawn at 30% probability level.

tron configuration [27]. It may be noted that the isoelectronic Co compound [Co(NO)(S2CNEt2)2] also has square pyramidal geometry with an apical bent nitrosyl ˚ is comparable ligand [31]. The Rh–N distance of 1.905(3) A ˚ ) [30]. The Rh to that in [Rh(NO)Cl2(PPh3)2] (1.91(1) A atom is displaced above the Se4 mean plane by ca. ˚ . The average Rh–Se distance is 2.5099 A ˚ . The P– 0.317 A ˚ ) and P–N (1.593(3) and Se (2.1848(9)–2.210(1) A ˚ ) distances and P–N–P angles (134.4(3)° and 1.605(3) A 136.4(3)°) compare well with those in 4. 4. Conclusion

Fig. 2. Molecular structure of trans-[Ru(NO)(Cl){N(Ph2PSe)2}{Ph2P(Se)NPPh2}] (4). The ellipsoids are drawn at 30% probability level.

˚ ) is typical of Ru(II) nitrosyl compounds [7]. The (1.719(3) A ˚ ) is comparable to that in Ru–P distance (2.372(1) A ˚ ) [25]. The [Ru(@CHPh){Ph2P(Se)NPPh2}2] (av. 2.383 A ˚ ) is longer than the Ru–Se Ru–Se (trans to P) (2.5765(7) A ˚ ) due to the trans (trans to Se) (2.5060(6) and 2.5321(7) A influence of the PPh2 group. The N–P distance in the ˚ ) is slightly longer than [Pri2P(Se)NPPri2] ligand (1.616(2) A ˚ ). The P–N–P the N–P(Se) distances (1.573(2)–1.593(2) A i i  angle in the [Pr2P(Se)NPPr2] ligand (123.9(2)°) is obviously smaller than that in the [N(Pri2PSe)2] ligand (135.9(2)°). The solid-state structure of 9 is shown in Fig. 3; selected bond lengths and angles are listed in Table 4. The geometry around Rh is pseudo square pyramidal with the nitrosyl ligand occupying the apical position. The Rh–N–O angle is 125.7(3)° that is characteristic for bent nitrosyl compounds [1,2]. A similar bond angle was found for [Rh(NO)Cl2(PPh3)2] (125(1)°) [30]. The bending of the Rh–N–O linkage is in accordance with the {RhNO}7 elec-

In summary we have synthesized and structurally characterized Ru and Rh nitrosyl compounds with [N(R2PQ)2] (Q = O, S, Se) ligands. X-ray crystallography revealed that the nitrosyl ligand in the Ru compounds is linear whereas that in the Rh analogue is bent. Interaction of [Ru(NO)Cl3(PPh3)2] with K[N(Ph2PSe)2] resulted in selenium atom abstraction of the ligand and formation of trans-[Ru(NO)(Cl){N(Ph2PSe)2}{Ph2P(Se)NPPh2}]. Treatment of [Rh(NO){N(Pri2PS)2}2] with HBF4 led to protonation of the dithioimidodiphosphinate ligands and formation of dicationic [Rh(NO){HN(Pri2PS)2}2][BF4]2. Acknowledgements The work was supported by the Hong Kong Research Grants Council (Project Nos. 602104 and 602203). We thank Dr. Herman Sung for solving the crystal structures. Q.-F. Zhang thanks the Science and Technological Fund of Anhui Province, PR China, for the Outstanding Youth Award (06046100). Appendix A. Supplementary material CCDC 632255, 632256 and 632257 contain the supplementary crystallographic data for 2, 4 and 9. These data can be obtained free of charge via http://www.ccdc.cam.

W.-M. Cheung et al. / Polyhedron 26 (2007) 4631–4637

ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.poly.2007.04.002.

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