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Syntheses and crystal structures of mononuclear rhodium hydrido complexes from the reactions of [Rh(H)2(PPh3)2(EtOH)2]ClO4 with various nitrogen ligands
Polyhedron 21 (2002) 1613 /1620 www.elsevier.com/locate/poly
Syntheses and crystal structures of mononuclear rhodium hydrido complexes from the reactions of [Rh(H)2(PPh3)2(EtOH)2]ClO4 with various nitrogen ligands Xiao-Yan Yu a, Masahiko Maekawa b,*, Tomonori Morita b, Ho-Chol Chang a, Susumu Kitagawa a,*, Guo-Xin Jin c a
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan b Research Institute for Science and Technology, Kinki University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan c State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun 130022, People’s Republic of China Received 13 December 2001; accepted 11 February 2002
Abstract Reactions of the Rh hydrido complex [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) with nitrogen ligands such as 2-(4-thiazolyl)benzimidazole (tbz), pyridazine (pdz), imidazole (im) and pyrimidine (pmd) in CH2Cl2 afforded various mononuclear Rh hydrido complexes, [Rh(H)2(PPh3)2(tbz)]ClO4 (2), [Rh(H)2(PPh3)2(pdz)2]ClO4 ×/2CH2Cl2 (3), [Rh(H)Cl(PPh3)2(pdz)2]ClO4 ×/CH2Cl2 (4), [Rh(H)2(PPh3)2(im)2]ClO4 ×/2CH2Cl2 (5), [Rh(H)Cl(PPh3)2(im)2]ClO4 ×/CH2Cl2 (6), [Rh(H)2(PPh3)2(pmd)2]ClO4 ×/CH2Cl2 (7) and the Rh non-hydrido complex [RhCl2(pmd)4]ClO4 (8). The Rh complexes 2, 3, 5 and 6 were crystallographically characterized. The formation process was monitored by 1H NMR and UV /Vis spectra. In all the Rh hydrido complexes, the Rh atom is coordinated by two PPh3 ligands in trans- positions and two nitrogen ligands in the cis -positions. The remaining sites are occupied by one or two hydride atoms to form a saturated 18-electron framework in a slightly distorted octahedral geometry. For complex 2 an appreciable inter-molecular p interaction is observed between planes of tbz and PPh3 ligands, while an intra-molecular hydrogen bonding interaction between C /H and Cl atoms is found in complex 6. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Mononuclear complexes; Rhodium complexes; Hydrido complexes; Nitrogen ligands; Crystal structures
1. Introduction Considerable interest and many investigations have been so far devoted to mononuclear Rh hydrido complexes with tertiary phosphine ligands as highly effective catalysts for the hydrogenation and hydroformylation of olefins [1], which are for instance representative of Wilkinson’s complex RhCl(PPh3)3 [2]. Rh complexes with nitrogen heterocyclic ligands have been also known in relation to their catalytic activities [3], and their hydrido complexes are particularly expected to
* Corresponding authors. Fax: /81-6-6730-5896 (M.M.); fax: /8175-753-4979 (S.K.) E-mail addresses: [email protected] (M. Maekawa), [email protected] (S. Kitagawa).
produce a superior property. However, there are relatively few investigations of mononuclear Rh hydrido complexes including chloride and nitrogen ligands as analogous ones to Wilkinson’s complex [4]. Although Rh non-hydrido complexes with nitrogen ligands have been well investigated [5 /7], crystallographic studies of Rh hydrido complexes with nitrogen ligands have been limited. We have so far examined the reactions of the Rh hydrido complex [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) with nitrogen bridging ligands such as pyrazine (pyz) and 4,4?-bipyridine derivatives in various organic solvents [7]. It has been illustrated that these reaction processes are greatly related to the solvents and the structural feature of the nitrogen bridging ligands. Complex 1 formed the dinuclear Rh complex [Rh2(PPh3)2{(h6C6H5)Ph2P}]2](ClO4)2 ×/6CH2Cl2 in CH2Cl2, with the
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 2 8 - 8
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reductive elimination of hydrogen. The reaction of complex 1 with pyrazine (pyz) in CH2Cl2 afforded the triangular Rh3 complex [Rh3(PPh3)6(pyz)3](ClO4)3 ×/ CH2Cl2, in contrast to the formation of the dinuclear Rh hydrido complex [Rh2(H)4(PPh3)4(Me2CO)2(pyz)](ClO4)2 ×/EtOH in Me2CO. The reaction of complex 1 with 4,4’-trimethylenedipyridine (tmdp), having a long spacer, in CH2Cl2 provided the dinuclear Rh nonhydrido complex [Rh2(PPh3)4(tmdp)2](ClO4)2. In this study, as further investigations, the reactions of complex 1 with nitrogen ligands such as 2-(4-thiazolyl)benzimidazole (tbz), pyridazine (pdz), imidazole (im) and pyrimidine (pmd) in CH2Cl2 were examined according to Scheme 1. Several mononuclear Rh complexes were isolated and their structures were crystallographically characterized.
2. Experimental 2.1. General procedures All operations were carried out using standard Schlenk techniques under N2 atmosphere. All the organic solvents were distilled by general methods before use. RhCl3 ×/3H2O, 2-(4-thiazolyl)benzimidazole, pyridazine, imidazole and pyrimidine were commercially purchased from Steam and Aldrich and used without further purifications. [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) was synthesized according to the literature [8]. IR spectra were recorded on a Perkin /Elmer System 2000 FT IR spectrometer as a KBr pellet. UV /Vis spectra were recorded on a HITACHI U-3500/U-4000 spectrometer. 1H NMR spectra were measured at room temperature (r.t.) on a JEOL JNM-A 500 FT NMR
Scheme 1.
spectrometer. Trimethylsilane was used as an internal reference. 2.2. Preparation of Rh complexes with nitrogen ligands 2.2.1. [Rh(H)2(PPh3)2(tbz)]ClO4 (2) A 5 ml CH2Cl2 solution of [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) (41.1 mg, 0.05 mmol) was added to the tbz ligand (10.1 mg, 0.05 mmol) in CH2Cl2 (5 ml). After stirring for 30 min, the reaction solution was filtered. The yellow filtrates were introduced into 5 mm diameter glass tubes and were layered with hexane as the diffusion solvent. The glass tubes were sealed and allowed to stand at r.t. for 2 days. Light yellow crystals of complex 2 were collected. Yield: 43.7 mg (94%). IR (KBr pellet, cm 1): 2081 (Rh /H), 1435, 1095, 696 and 519. 1H NMR (CD2Cl2, 23 8C, ppm): d 11.98 (N /H of benzimidazole), 8.19 (2-H of thiazolyl), 8.08 (4-H of benzimidazole), 7.00 /7.59 (Ph of PPh3), 6.03 (5-H of benzimidazole), /15.60 (Rh /H) and /16.30 (Rh /H). Anal. Calc. for C46H39P2N3SRhO4Cl: C, 59.40; H, 4.23; N, 4.52. Found: C, 59.26; H, 3.97; N, 4.33%. 2.2.2. [Rh(H)2(PPh3)2(pdz)2]ClO4 ×/2CH2Cl2 (3) and [Rh(H)Cl(PPh3)2(pdz)2]ClO4 ×/CH2Cl2 (4) Complex 3 was prepared in the same manner as for complex 2, using the pdz ligand (8.0 mg, 0.10 mmol). Light yellow crystals of complex 3 were obtained 2 days later at the middle part of the glass tubes. Yield: 43.4 mg (82%). IR (KBr pellet, cm 1): 2046 (Rh /H), 1435, 1093, 697 and 521. 1H NMR (CD2Cl2, 23 8C, ppm): d 9.16 (3,6-H of prd), 8.57 (5-H of prd), 8.21 (4-H of prd), 7.20 /7.48 (Ph of PPh3), and /16.89 (Rh /H). Anal. Calc. for C46H44P2N4RhO4Cl5: C, 52.17; H, 4.19; N, 5.29. Found: C, 51.68; H, 4.11; N, 5.33%. The reaction solution was allowed to stand for a further 2 weeks and colorless crystals of complex 4 were collected at the upper part of the glass tubes. Yield: 4.0 mg (8%). IR (KBr pellet, cm 1): 2174 (Rh /H), 1435, 1093, 696 and 523. Anal. Calc. for C45H41P2N4RhO4Cl4: C, 53.59; H, 4.10; N, 5.56. Found: C, 53.32; H, 4.03; N, 5.86%. 2.2.3. [Rh(H)2(PPh3)2(im)2]ClO4 ×/2CH2Cl2 (5) and [Rh(H)Cl(PPh3)2(im)2]ClO4 ×/CH2Cl2 (6) Complex 5 was prepared in the same manner as for complex 3, using the im ligand (6.7 mg, 0.10 mmol). The reaction solution was allowed to stand at r.t. for 2 days and light yellow crystals of complex 5 were obtained at the middle part of the glass tubes. Yield: 38.1 mg (74%). IR (KBr pellet, cm 1): 2051 (Rh /H), 1435, 1095, 695 and 520. 1H NMR (CD2Cl2, 23 8C, ppm): d 10.09 (N / H of im), 7.21 /7.61 (Ph of PPh3), 6.71 (2-H of im), 6.57 (4-H of im), 6.31 (5-H of im) and /16.85 (Rh /H). Anal. Calc. for C44H44P2N4RhO4Cl5: C, 51.06; H, 4.28; N, 5.41. Found: C, 51.44; H, 4.42; N, 5.57%.
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The reaction solution was allowed to stand at r.t. for another 2 weeks and colorless crystals of complex 6 were collected at the upper part of the glass tubes. Yield: 1.0 mg (2%). IR (KBr pellet, cm 1): 2133 (Rh /H), 1434, 1094, 696 and 523. Anal. Calc. for C43H41P2N4RhO4Cl4: C, 52.46; H, 4.20; N, 5.69. Found: C, 52.51; H, 4.11; N, 5.53%.
2.2.4. [Rh(H)2(PPh3)2(pmd)4]ClO4 ×/CH2Cl2 (7) and [RhCl2(pmd)4]ClO4 (8) Complex 7 was prepared in the same manner as for complex 3, using the pmd ligand (8.0 mg, 0.10 mmol). Complex 7 was obtained as white precipitates. Yield: 36.0 mg (74%). IR (KBr pellet, cm 1): 2060 (Rh /H), 1584, 1435, 1094, 696 and 520. 1H NMR (CD2Cl2, 23 8C, ppm): d 9.17 (2-H of pmd), 8.73 (6-H of pmd), 8.28 (4-H of pmd), 7.26 /7.38 (Ph of PPh3), 7.01 (5-H of pmd) and /17.30 (Rh /H). Anal. Calc. for C45H42P2N4RhO4Cl3: C, 55.49; H, 4.35; N, 5.75. Found: C, 55.92; H, 4.20; N, 5.58%. Yellow crystals of complex 8 were collected 4 days later at the lower part of the glass tubes. Yield: 3.5 mg (12%). IR (KBr pellet, cm 1): 1595, 1411, 1122, 706 and 625. Anal. Calc. for C16H16N8RhO4Cl3: C, 32.37; H, 2.72; N, 18.88. Found: C, 32.68; H, 2.61; N, 18.69%.
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3. Results and discussion 3.1. Crystal structures 3.1.1. [Rh(H)2(PPh3)2(tbz)]ClO4 (2) In the reaction of complex 1 with the nitrogen ligand, the tbz ligand acted as a bidentate chelate ligand and led to the typical mononuclear Rh hydrido complex 2. Since no crystallographic structures of Rh complexes containing the tbz ligand have been reported, complex 2 is the first example of a Rh hydrido complex with the tbz ligand. Fig. 1 shows the cation moiety of complex 2 together with the atomic labelling scheme. The Rh atom is coordinated by two P atoms, two N atoms and two hydride atoms in a distorted octahedral environment. The two PPh3 ligands are nearly in trans-positions with a P(1) /Rh /P(2) angle of 167.06(8)8. The Rh coordination plane defined by two N atoms of the tbz ligand and two hydride atoms are coplanar with the mean deviation ˚ . Two heterocyclic rings of the tbz ligand are of 0.0365 A ˚ . The nearly coplanar with a mean deviation of 0.0707 A average Rh /P, Rh /N and Rh /H distances of 2.299, ˚ are similar to those of other analogous 2.197 and 1.58 A ˚ is hydrido complexes [14]. The H H distance of 2.08 A characteristic of hydrido complexes [15]. The N(1) /Rh / N(2) angle of 76.1(2)8 is within the range of values of other Rh complexes with bidentate nitrogen ligands [16]. Selected bond distances and bond angles are listed in Table 2.
2.3. X-ray crystallography For each complex, a suitable crystal was sealed into the glass capillary (0.7 mm, GLAS) and mounted on the crystal goniometer. The intensity data of all the single crystals were collected on the Rigaku/Mercury CCD system using graphite monochromated Mo Ka radiation ˚ ). The structures of complexes 2, 5 and 6 (l/0.710691 A were solved by the direct method (SIR-92 for 2 and 5; SIR-97 for 6) [9], and expanded using Fourier techniques [10]. The structure of complex 3 was solved by the heavy-atom Patterson method [11] and expanded using Fourier techniques [10]. The hydride hydrogen atoms were located and refined isotropically. All other hydrogen atoms were included but not refined. The nonhydrogen atoms were refined anisotropically. The final cycle of full-matrix least-squares refinement was based on 5251, 4348, 4418 and 6594 observed reflections (I / 3s(I )) for complexes 2, 3, 5 and 6, respectively. The unweighted and weighted agreement factors of and Rw /[a w (Fo2/Fc2)2/ R /ajjFoj/jFcjj/ajFoj 2 2 1/2 a w (Fo ) ] were used. The atomic scattering factors and anomalous dispersion terms were taken from ref. [12]. All calculations were performed using the TEXSAN crystallographic software package [13]. The detailed crystal data of all complexes are summarized in Table 1.
3.1.2. [Rh(H)2(PPh3)2(pdz)2]ClO4 ×/2CH2Cl2 (3) The structure of the cation moiety of complex 3 is presented in Fig. 2. The Rh atom is coordinated by two PPh3 ligands, two pdz ligands and two hydride atoms to afford a mononuclear Rh complex in a slightly distorted octahedral geometry. In each pdz ligands, one of the two N atoms is bonded to the Rh atom. The two pdz ligands, in cis- positions, are inclined against the N2RhH2 coordination plane at an angle of 31.2(2)8. On the other hand, two PPh3 ligands in trans -positions are bent toward the two hydrides with a P(1) /Rh /P(1?) angle of 163.89(5)8. The Rh /P, Rh /N and Rh /H distances of ˚ are similar to those of 2.3033(9), 2.181(3) and 1.44(4) A other Rh hydrido complexes [14]. The H H distance of ˚ is within the range of values found in other 2.03 A hydrido complexes [15]. Selected bond distances and angles are listed in Table 3. Metal complexes with the pdz ligand as a heterocyclic ligand have been relatively limited, in comparison with those with the pyrazine ligand [17]. Although recently there have been several crystallographic reports on complexes with pdz ligands [18], Rh complexes with the pyz ligand are few. The crystal structure of complex 3 is remarkable as a Rh hydrido complex with the pdz ligand.
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Table 1 Crystal data and measurement conditions for 2, 3, 5 and 6 Complexes
2
3
5
6
Formula M Crystal system Space group ˚) a (A ˚) b (A ˚) c (A b (8) ˚ 3) V (A Dcalc (g cm 3) F (000) Z m (Mo Ka) (cm 1) Number of reflections
RhP2N3ClO4C46H39S 930.20 monoclinic P 21/c 13.2040(9) 13.7074(9) 23.268(1) 99.3724(8) 4155.0(5) 1.487 1904 4 6.50 24430 (total) 9159 (unique) 5251 [I 3.00s (I )] 0.078 0.081
RhP2N4Cl5O4C46H44 1059.00 orthorhombic P 212121 15.362(6) 15.404(1) 10.048(2)
RhP2N4Cl5O4C44H44 1034.97 orthorhombic P 212121 15.020(2) 15.3277(3) 10.1368(2)
2377(1) 1.479 1080 2 7.53 14955 (total) 2854 (unique) 4348 [I 3.00s (I )] 0.042 0.055
2333.8(4) 1.473 1056 2 7.65 14544 (total) 2783 (unique) 4418 [I 3.00s (I )] 0.044 0.062
RhP2N4Cl4O4C43H41 984.49 Monoclinic P 21/n 22.608(1) 14.2621(5) 13.7827(5) 104.3593(7) 4305.3(3) 1.519 2008 4 7.65 27180 (total) 9470 (unique) 6594 [I 3.00s (I )] 0.054 0.068
Number of observations R Rw
Fig. 1. The crystal structure of the cation moiety of complex 2. Only Rh(1), N(1), N(2), N(3), S(1), P(1), P(2), C(11), C(17), C(23), C(29), C(35), C(41), H(1) and H(2) in the coordination sphere are labelled.
Fig. 2. The crystal structure of the cation moiety of complex 3. Only Rh(1), N(1), N(1?), N(2), N(2?), P(1), P(1?), C(5), C(11), C(17), C(5?), C(11?), C(17?), H(1) and H(1?) in the coordination sphere are labelled.
Table 2 ˚ ) and bond angles (8) of 2 Selected bond lengths (A Bond lengths Rh(1) P(1) Rh(1) N(1) Rh(1) H(1)
2.317(2) 2.192(7) 1.59(6)
Rh(1) P(2) Rh(1) N(2) Rh(1) H(2)
2.282(2) 2.203(6) 1.57(8)
Bond angles P(1) Rh(1) P(2) P(1) Rh(1) N(2) P(2) Rh(1) N(2) Rh(1) P(1) C(11) Rh(1) P(1) C(23) Rh(1) P(2) C(35) H(1) Rh(1) H(2)
167.06(8) 92.9(2) 97.1(2) 112.2(3) 113.6(3) 114.3(3) 82.0(3)
P(1) Rh(1) N(1) P(2) Rh(1) N(1) N(1) Rh(1) N(2) Rh(1) P(1) C(17) Rh(1) P(2) C(29) Rh(1) P(2) C(41)
93.5(2) 96.8(2) 76.1(2) 117.4(3) 111.9(2) 118.0(3)
Table 3 ˚ ) and bond angles (8) of 3 Selected bond lengths (A Bond lengths Rh(1) P(1) Rh(1) H(1)
2.3033(9) Rh(1) N(1) 1.44(4)
Bond angles P(1) Rh(1) P(1?) a P(1) Rh(1) N(1?) a P(1)1 Rh(1) N(1?) a Rh(1) P(1) C(5) Rh(1) P(1) C(17)
163.89(5) 92.3(1) 98.8(1) 112.0(2) 117.0(1)
a
P(1) Rh(1) N(1) P(1) a Rh(1) N(1) N(1) Rh(1) N(1?) a Rh(1) P(1) C(11) H(1) Rh(1) H(1?) a
Symmetry codes X1, Y1, Z .
2.181(3)
98.8(1) 92.3(1) 92.7(2) 115.7(2) 89.0(3)
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of Rh hydrido complexes with the im ligand. To the best of our knowledge, this is the first crystal structure of a Rh hydrido complex with the im ligand.
Fig. 3. The crystal structure of the cation moiety of complex 5. Only Rh(1), N(1), N(1?), N(2), N(2?), P(1), P(1?), C(4), C(10), C(16), C(4?), C(10?), C(16?), H(1) and H(1?) in the coordination sphere are labelled.
3.1.3. [Rh(H)2(PPh3)2(im)2]ClO4 ×/2CH2Cl2 (5) The structure of the cation moiety of complex 5 is shown in Fig. 3. The structure of complex 5 essentially resembles that of complex 3. The Rh atom is coordinated by two PPh3 ligands, two im ligands and two hydride atoms in a distorted octahedral geometry. The two im ligands in cis- positions are slightly inclined against the N2RhH2 coordination plane at an angle of 27.7(2)8, which is smaller than that (31.2(2)8) of complex 3. The two PPh3 ligands are in trans -positions and the P(1) /Rh /P(1?) angle of 163.13(5)8 is similar to that (163.89(5)8) of complex 3. The Rh /P, Rh /N and Rh /H ˚ are close distances of 2.2955(9), 2.189(3) and 1.50(4) A to those of other Rh hydrido complexes [14]. The H H ˚ is in the range of those found in other distance of 2.07 A hydrido complexes [15]. Selected bond distances and angles are listed in Table 4. Our survey of Rh complexes with the im ligand and its derivatives described the tetranuclear complex [Rh(2Meim)(CO)2]4 (2-Meim /2-methylimidazole) [19a], the dinuclear complex [NBu4][Rh2(cod)2(dcbi)] ×/2i PrOH (dcbi /4,5-dicarboxyimida-zole) [19b], the mononuclear complexes [RhCl2(N-Meim)4]Cl ×/2H2O (Meim/N methyl-imidazole) [19c] and [imH][trans -RhCl4(im)2] [19d]. However, there are no reports of X-ray structures
3.1.4. [Rh(H)Cl(PPh3)2(im)2]ClO4 ×/CH2Cl2 (6) After light-yellow single crystals of complex 5 were obtained according to Scheme 1, colorless single crystals of complex 6 were collected from the same reaction solution 2 weeks later. The structure of the cation moiety of complex 6 is revealed in Fig. 4. The coordination sphere around the Rh atom consists of two PPh3 ligands, two im ligands, one Cl atom and one hydride atom, providing a distorted octahedral geometry. It is interesting that the two im ligands are located in the trans- positions and are separated by the Cl atom and the hydride atom. This structural feature is greatly different from that in complex 5. The P(1) /Rh /P(2) angle of 177.26(4)8 is much larger than those of 163.89(5)8 and 163.13(5)8 in complexes 3 and 5, respectively. Therefore the PPh3 ligands in the trans- positions are almost linearly located. The average Rh /P distance ˚ is longer than those of normal Rh and Ir of 2.362 A hydrido complexes [4,7]. The average Rh /N distances of ˚ are shorter than those of 2.181(3) and 2.189(3) 2.056 A ˚ in complexes 3 and 5, respectively. The Rh /Cl A ˚ is longer than those found in distance of 2.498(1) A other hydrido complexes [4] owing to the trans influence of the nitrogen ligands. Selected bond distances and angles are listed in Table 5. 3.2. Reactions of [Rh(H)2(PPh3)2(EtOH)2]ClO4 with nitrogen ligands in CH2Cl2 According to Scheme 1, the reactions of the Rh hydrido complex 1 with nitrogen ligands were attempted and their reaction processes were monitored by 1H NMR and UV /Vis spectra. The addition of the tbz
Table 4 ˚ ) and bond angles (8) of 5 Selected bond lengths (A Bond lengths Rh(1) P(1) Rh(1) H(1)
2.2955(9) Rh(1) N(1) 1.50(4)
Bond angles P(1) Rh(1) P(1?) a P(1) Rh(1) N(1?) a P(1)1 Rh(1) N(1?) a Rh(1) P(1) C(4) Rh(1) P(1) C(16)
163.13(5) 94.9(1) 96.6(1) 112.6(1) 117.1(1)
a
P(1) Rh(1) N(1) P(1) a Rh(1) N(1) N(1) Rh(1) N(1?) a Rh(1) P(1) C(10) H(1) Rh(1) H(1?) a
Symmetry codes: X2, Y , Z .
2.189(3)
96.6(1) 94.9(1) 93.3(2) 116.5(1) 87.0(3)
Fig. 4. The crystal structure of the cation moiety of complex 6. Only Rh(1), Cl(1), N(1), N(2), N(3), N(4), P(1), P(2), C(7), C(13), C(19), C(31), C(25), C(37) and H(1) in the coordination sphere are labelled.
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Table 5 ˚ ) and bond angles (8) of 6 Selected bond lengths (A Bond lengths Rh(1) Cl(1) Rh(1) P(2) Rh(1) N(3)
2.498(1) 2.364(1) 2.051(4)
Rh(1) P(1) Rh(1) N(1) Rh(1) H(1)
2.360(1) 2.061(4) 1.47(6)
Bond angles Cl(1) Rh(1) P(1) Cl(1) Rh(1) N(1) P(1) Rh(1) P(2) P(1) Rh(1) N(3) P(2) Rh(1) N(3) Rh(1) P(1) C(13) Rh(1) P(2) C(25) Rh(1) P(2) C(37) N(3) Rh(1) H(1)
90.94(4) 93.5(1) 177.26(4) 88.8(1) 89.8(1) 114.5(2) 115.2(2) 117.9(2) 86.0(2)
Cl(1) Rh(1) P(2) Cl(1) Rh(1) N(3) P(1) Rh(1) N(1) P(2) Rh(1) N(1) Rh(1) P(1) C(7) Rh(1) P(1) C(19) Rh(1) P(2) C(31) N(1) Rh(1) H(1)
91.46(4) 92.2(1) 91.6(1) 89.6(1) 114.5(2) 116.4(2) 112.4(1) 87.0(2)
ligand to complex 1 in CD2Cl2 initially showed two new quintet 1H NMR signals of hydride species at /15.60 and /16.30 ppm at r.t., together with the quintet 1H NMR signal of an hydride species at /22.16 ppm, which should be attributed to hydrides of complex 1. After about 1 h, the 1H NMR signal of complex 1 completely disappeared and the two new 1H NMR signals only remained. These facts indicate that Rh hydrido complex 2 with the tbz ligand was formed in CH2Cl2 solution. Similarly, on the reaction of complex 1 with pdz, im and pmd ligands, the 1H NMR signals of the hydride species could be observed at /16.89, /16.85 and /17.30 ppm for complexes 3, 5 and 7, respectively. On the other hand, as shown in the timecourse UV /Vis spectra (Fig. 5), complex 1 dissolved in CH2Cl2 at 23 8C displayed the color change from yellow to the dark brown solution of [Rh2(PPh3)2{(h6C6H5)Ph2P}]2]2 (lmax /410 nm (o /3056 cm 1 M1)) [7]. The further addition of tbz ligand to the CH2Cl2 solution exhibited the color change from dark-brown to a yellow solution (lmax /420 nm (o /2235 cm 1 M1)) and the formation of complex 2 was completed after about 50 min. On the basis of these structural studies in solution and the above-mentioned crystallographic
Fig. 5. The time-course UV /Vis spectra in CH2Cl2 at 23 8C. After the dissolving of complex 1: 10 (1) and ]/50 (2) min. After the addition of the tbz ligand to complex 1: 20 (3), 30 (4), 40 (5) and ]/50 (6) min. [c ]/1.7/10 4 M.
studies, it was concluded that the reaction of complex 1 with nitrogen ligands such as tbz, pdz, im and pmd ligands provided mononuclear Rh hydrido complexes without the reductive elimination of hydrogen. We previously demonstrated that the reactions of complex 1 with nitrogen bridging ligands such as pyrazine and 4,4?-bipyridine derivatives in CH2Cl2 could afford diand trinuclear Rh non-hydrido complexes[7] with the reductive elimination of hydrogen. The results in this study are greatly different from those previously found. Although the detailed reason is not obvious at the present, it is probably considered that nitrogen ligands such as tbz, pdz and im ligands are structurally difficult to bridge Rh centers owing to the steric repulsion against the phenyl group of the PPh3 ligand and should lead to mononuclear Rh hydrido complexes with nitrogen ligands, without the reductive elimination of hydrogen. As mentioned in the Section 2, when the reaction solution of the Rh hydrido complex 1 with pdz, im and pmd ligands was allowed to stand for more than 2 weeks, Rh complexes 4, 6 and 8 [20] with a coordinated Cl atom were collected in the same glass tubes, respectively. The reaction solution of complex 1 with the tbz ligand did not provide the corresponding Rh complex with a coordinated Cl atom since the tbz ligand played a role as a bidentate chelate ligand. In this study, the monitoring of their formation process by 1H NMR and UV /Vis spectra over 2 weeks has not been carried out and the structure of 6 could only be crystallographically characterized. At the present, although their formation mechanisms are not obvious in detail, it is considered that the Cl atom is probably derived from the CH2Cl2 solvent since it has been known that [RhCl(PPh3)2]2 was produced by the reaction of [Rh2(H)2(PPh3)4(Me4Si2O)2] with CH2Cl2 as the solvent [21].
3.3. Consideration on crystallographic study The four crystallographic studies revealed the significant structural differences among their bond distances and bond angles of complexes 2, 3, 5 and 6. In complex 6 with the Cl atom, the average Rh /N distance of 2.056 ˚ is shorter than those (2 (2.197(7) A ˚ ), 3 (2.181(3) A ˚) A ˚ )) of the other Rh complexes without and 5 (2.189(3) A the Cl atom. In contrast, the average Rh /P distance of ˚ ) is slightly longer than those of 2 complex 6 (2.362 A ˚ ), 3 (2.3033 A ˚ ) and 5 (2.2955 A ˚ ). The P /Rh /P (2.299 A angle of 6 (177.26(4)8) is rather larger than those of 2 (167.06(8)8), 3 (163.89(5)8), 5 (163.13(5)8) and other Rh hydrido complexes [4,7]. These changes should probably be caused by the repulsion between the bulky Cl atom and the trans-nitrogen ligands. The Rh /Cl distance of ˚ in complex 6 is also longer than those of 2.499(1) A
X.-Y. Yu et al. / Polyhedron 21 (2002) 1613 /1620
other Rh hydrido complexes [4] owing to the trans influence of the nitrogen ligands. It is suggested that complex 2 possesses a meaningful inter-planar interaction between the nitrogen ligand and the corresponding phenyl group of PPh3. The mean inter-planar distance between the benzimidazole portion of the tbz ligand and the phenyl group including the ˚ with a dihedral angle of 10.28, and C(11) atom is 3.409 A that between the thiazolyl group of the tbz ligand and ˚ with the phenyl group including C(29) atom is 3.422 A an angle of 27.18. A similar intra-molecular interaction has been known in previous reports [22]. This consideration is also supported by other structural parameters in complex 2: the Rh(1)/P(1) /C(11) bond angle of 112.2(3)8 is smaller than Rh(1)/P(1) /C(17) of 117.4(3)8 and Rh(1)/P(1) /C(23) of 113.6(3)8. The Rh(1)/P(2) /C(29) bond angle of 111.9(2)8 is smaller than Rh(1)/P(2) /C(41) of 118.0(3)8 and Rh(1)/P(2) / C(35) of 114.3(3)8. In complex 6, it should be noted that the intramolecular C /H Cl hydrogen bonds exist between the Cl atom and hydrogen atom at the 2-position in im ligands. The C(1) Cl(1) and C(4) Cl(1) distances are ˚ , respectively. Thus interactions 3.339(5) and 3.306(6) A are probably caused by the steric repulsion within the bulky PPh3 ligands. The possibility of Rh H agostic interaction and attractive Cl H /C hydrogen bonds in Rh complexes with the PPh3 ligand has recently been reported [23]. This suggestion is consistent with the results of the density functional analysis [23]: the intramolecular steric repulsion can force one of the phenyl rings of the PPh3 ligands toward the metal center.
4. Supplementary materials Crystallographic data for the X-ray crystal structural analyses have been deposited with the Cambridge Crystallographic Data Centre, CCDC, Nos. 169897 (2), 169896 (3), 169895 (5) and 169898 (6). Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: /44-1233-336033; e-mail: deposit@ ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements This work was partially supported by Grants-in-Aids from the Ministry of Education, Science, Culture, Sports and Technology in Japan and research funds from Kinki University. Miss. X.-Y. Yu is also grateful to the Ministry of Education, Science, Culture, Sports and Technology in Japan for financial support.
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References [1] (a) C. Bianchini, D. Fabbri, S. Gladiali, A. Meli, W. Phol, F. Vizza, Organometallics 15 (1996) 4604; (b) C. Bianchini, H.M. Lee, A. Meli, F. Vizza, Organometallics 19 (2000) 849; (c) A. van Rooy, E.N. Orij, P.C.J. Kamer, P.W.N.M. van Leeuwen, Organometallics 14 (1995) 34. [2] (a) J.F. Young, J.A. Osborn, F.H. Jardine, G. Wilkinson, Chem. Commun. (1965) 131; (b) J.A. Osborn, F.H. Jardine, J.F. Young, G. Wilkinson, J. Chem. Soc. (1966) 1711; (c) S.B. Duckett, C.L. Newell, R. Eisenberg, J. Am. Chem. Soc. 116 (1994) 10548. [3] P.A. Chaloner, M.A. Esteruelas, F. Joo´, L.A. Oro, Homogeneous Hydrogenation, Kluwer, Dordrecht, 1994. [4] (a) J.K. Huang, E.D. Stevens, S.P. Nolan, Organometallics 19 (2000) 1194; (b) F.T. Ladipo, J.S. Merola, Inorg. Chem. 29 (1990) 4172; (c) M.E. van der Boom, S.-Y. Liou, Y. Ben-David, M. Gozin, D. Milstein, J. Am. Chem. Soc. 120 (1998) 13415; (d) K. Osakada, T. Koizumi, T. Yamamoto, Angew. Chem., Int. Ed. 37 (1998) 349; (e) M. Mediati, G.N. Tachibana, C.M. Jensen, Inorg. Chem. 31 (1992) 1827. [5] (a) A.P. Sadimenko, S.S. Basson, Coord. Chem. Rev. 147 (1996) 247; (b) S. Trofimenko, Chem. Rev. 93 (1993) 943; (c) S. Trofimenko, Prog. Inorg. Chem. 34 (1986) 115; (d) C. Tejel, J.M. Villoro, M.A. Ciriano, J.A. Lo´pez, E. Eguiza´bal, F.J. Lahoz, V.I. Bakhmutov, L.A. Oro, Organometallics 15 (1996) 2967 (and references therein). [6] (a) R. Halesha, G.K.N. Reddy, S.P.S. Rao, H. Manohar, J. Organomet. Chem. 252 (1983) 231; (b) M. Maekawa, K. Sugimoto, T. Kuroda-Sowa, Y. Suenaga, M. Munakata, J. Chem. Soc., Dalton Trans. (2000) 4160. [7] (a) X.-Y. Yu, M. Maekawa, M. Kondo, S. Kitagawa, G.-X. Jin, Chem. Lett. (2001) 168; (b) X.-Y. Yu, M. Maekawa, T. Morita, H.-C. Chang, S. Kitagawa, G.-X. Jin, Bull. Chem. Soc. Jpn., 75 (2002) 267. [8] R.R. Schrock, J.A. Osborn, J. Am. Chem. Soc. 98 (1976) 2134. [9] (a) SIR-92, A. Altomare, M.C. Burla, M. Camalli, M. Cascarano, C. Giacovazzo, A. Guagliardi, G. Polidori, J. Appl. Crystallogr. 27 (1994) 435; (b) SIR- 97, A. Altomare, M.C. Burla, M. Camalli, M. Cascarano, C. Giacovazzo, A. Guagliardi, G. Polidori, R. Spagna, J. Appl. Crystallogr. 32 (1999) 115. [10] DIRDIF-94, P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, R. de Gelder, R. Israel, J.M.M. Smits, The DIRDIF-94 program system, Technical report of the crystallography laboratory, University of Nijmegen, 1994. [11] DIRDIF-94 PATTY, P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, R. de Gelder, R. Israel, J.M.M. Smits, The DIRDIF-94 program system, Technical report of the crystallography laboratory, University of Nijmegen, 1994. [12] D.T. Cromer, J.T. Waber, International Tables for X-Ray Crystallography, vol. IV, Kyonoch Press, Birmingham, 1974. [13] TEXSAN: Crystal Structure Analysis Package, Molecular Structure Corporation 1985 and 1999. [14] (a) M. Iglesias, C. del Pino, S. Martı´nez-Carrera, J. Organomet. Chem. 317 (1986) 363; (b) M. Iglesias, C. del Pino, J.L. Nieto, S. Martı´nez-Carrera, Inorg. Chim. Acta 145 (1988) 91; (c) J. Ott, L.M. Venanzi, C.A. Ghilardi, S. Midollini, A. Orlandini, J. Organomet. Chem. 291 (1985) 89. [15] P.G. Jessop, R.H. Morris, Coord. Chem. Rev. 121 (1992) 155.
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[16] (a) L. Dadci, H. Elias, U. Frey, A. Ho¨rnig, U. Koelle, A.E. Merbach, H. Paulus, J.S. Schneider, Inorg. Chem. 34 (1995) 306; (b) A. Zucca, S. Stoccoro, M.A. Cinellu, G. Minghetti, M. Manassero, J. Chem. Soc., Dalton Trans. (1999) 3431.; (c) B.A. Jackson, L.M. Henling, J.K. Barton, Inorg. Chem. 38 (1999) 6218. [17] P.J. Steel, Coord. Chem. Rev. 106 (1990) 221. [18] (a) J. Cano, G. De Munno, F. Lloret, M. Julve, Inorg. Chem. 39 (2000) 1611; (b) T. Otieno, S.J. Rettig, R.C. Thompson, J. Trotter, Inorg. Chem. 34 (1995) 1718; (c) T. Felzer, A. Lentz, T. Debaerdemacker, O.Z. Abou-El-Wafa, Z. Naturforsch., Teil. B 45 (1990) 199 (and references therein). [19] (a) A. Tiripicchio, M. Tiripicchio Camellini, R. Uson, L.A. Oro, M.A. Ciriano, M.T. Pinillos, J. Organomet. Chem. 224 (1982) 207; (b) J.C. Bayo´n, G. Net, P.G. Rasmussen, J.B. Kolowich, J. Chem. Soc., Dalton Trans. (1987) 3003; (c) Z.D. Matovic, S.R. Trifunovic, G. Ponticelli, L.P. Battaglia, G. Pelizzi, I.A. Efimenko, D.J. Radanovic, Inorg. Chim. Acta 278 (1998) 209;
[20]
[21] [22]
[23]
(d) G. Mestroni, E. Alessio, A. Sessanta o Santi, S. Geremia, A. Bergamo, G. Sava, A. Boccarelli, A. Schettino, M. Coluccia, Inorg. Chim. Acta 273 (1998) 62. The crystal data could be only collected in complex 8: complex 8, formula C16H16N8RhO4Cl3, M 593.62, crystal system tetragonal, space group P 4/n , a/ 10.592(2), b/10.592(2) and c/9.5780(6) ˚ , V /1074.6(3) A ˚ 3, Dcalc /1.834 g cm 3, Z /2, m (Mo Ka) A 1 12.08 cm and number of total reflections 6412. M.D. Curtis, W.M. Butler, J. Greene, Inorg. Chem. 17 (1978) 2928. (a) S. Onaka, Y. Katsukawa, M. Yamashita, Chem. Lett. (1998) 525.; (b) N.G. Spitsina, V.V. Gritsenko, O.A. S’yachenko, B.B. Safoklov, Y.M. Shul’ga, E.B. Yagubskii, Russ. Chem. Bull. 49 (2000) 367; (c) H.-C. Chang, T. Ishii, M. Kondo, S. Kitagawa, J. Chem. Soc., Dalton Trans. (1999) 2467. (a) R. Cini, A. Cavaglioni, Inorg. Chem. 38 (1999) 3751; (b) J. Fawcett, J.H. Holloway, G.C. Saunders, Inorg. Chim. Acta 202 (1992) 111.
Syntheses and crystal structures of mononuclear rhodium hydrido complexes from the reactions of [Rh(H)2(PPh3)2(EtOH)2]ClO4 with various nitrogen ligands Xiao-Yan Yu a, Masahiko Maekawa b,*, Tomonori Morita b, Ho-Chol Chang a, Susumu Kitagawa a,*, Guo-Xin Jin c a
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan b Research Institute for Science and Technology, Kinki University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan c State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun 130022, People’s Republic of China Received 13 December 2001; accepted 11 February 2002
Abstract Reactions of the Rh hydrido complex [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) with nitrogen ligands such as 2-(4-thiazolyl)benzimidazole (tbz), pyridazine (pdz), imidazole (im) and pyrimidine (pmd) in CH2Cl2 afforded various mononuclear Rh hydrido complexes, [Rh(H)2(PPh3)2(tbz)]ClO4 (2), [Rh(H)2(PPh3)2(pdz)2]ClO4 ×/2CH2Cl2 (3), [Rh(H)Cl(PPh3)2(pdz)2]ClO4 ×/CH2Cl2 (4), [Rh(H)2(PPh3)2(im)2]ClO4 ×/2CH2Cl2 (5), [Rh(H)Cl(PPh3)2(im)2]ClO4 ×/CH2Cl2 (6), [Rh(H)2(PPh3)2(pmd)2]ClO4 ×/CH2Cl2 (7) and the Rh non-hydrido complex [RhCl2(pmd)4]ClO4 (8). The Rh complexes 2, 3, 5 and 6 were crystallographically characterized. The formation process was monitored by 1H NMR and UV /Vis spectra. In all the Rh hydrido complexes, the Rh atom is coordinated by two PPh3 ligands in trans- positions and two nitrogen ligands in the cis -positions. The remaining sites are occupied by one or two hydride atoms to form a saturated 18-electron framework in a slightly distorted octahedral geometry. For complex 2 an appreciable inter-molecular p interaction is observed between planes of tbz and PPh3 ligands, while an intra-molecular hydrogen bonding interaction between C /H and Cl atoms is found in complex 6. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Mononuclear complexes; Rhodium complexes; Hydrido complexes; Nitrogen ligands; Crystal structures
1. Introduction Considerable interest and many investigations have been so far devoted to mononuclear Rh hydrido complexes with tertiary phosphine ligands as highly effective catalysts for the hydrogenation and hydroformylation of olefins [1], which are for instance representative of Wilkinson’s complex RhCl(PPh3)3 [2]. Rh complexes with nitrogen heterocyclic ligands have been also known in relation to their catalytic activities [3], and their hydrido complexes are particularly expected to
* Corresponding authors. Fax: /81-6-6730-5896 (M.M.); fax: /8175-753-4979 (S.K.) E-mail addresses: [email protected] (M. Maekawa), [email protected] (S. Kitagawa).
produce a superior property. However, there are relatively few investigations of mononuclear Rh hydrido complexes including chloride and nitrogen ligands as analogous ones to Wilkinson’s complex [4]. Although Rh non-hydrido complexes with nitrogen ligands have been well investigated [5 /7], crystallographic studies of Rh hydrido complexes with nitrogen ligands have been limited. We have so far examined the reactions of the Rh hydrido complex [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) with nitrogen bridging ligands such as pyrazine (pyz) and 4,4?-bipyridine derivatives in various organic solvents [7]. It has been illustrated that these reaction processes are greatly related to the solvents and the structural feature of the nitrogen bridging ligands. Complex 1 formed the dinuclear Rh complex [Rh2(PPh3)2{(h6C6H5)Ph2P}]2](ClO4)2 ×/6CH2Cl2 in CH2Cl2, with the
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 2 8 - 8
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reductive elimination of hydrogen. The reaction of complex 1 with pyrazine (pyz) in CH2Cl2 afforded the triangular Rh3 complex [Rh3(PPh3)6(pyz)3](ClO4)3 ×/ CH2Cl2, in contrast to the formation of the dinuclear Rh hydrido complex [Rh2(H)4(PPh3)4(Me2CO)2(pyz)](ClO4)2 ×/EtOH in Me2CO. The reaction of complex 1 with 4,4’-trimethylenedipyridine (tmdp), having a long spacer, in CH2Cl2 provided the dinuclear Rh nonhydrido complex [Rh2(PPh3)4(tmdp)2](ClO4)2. In this study, as further investigations, the reactions of complex 1 with nitrogen ligands such as 2-(4-thiazolyl)benzimidazole (tbz), pyridazine (pdz), imidazole (im) and pyrimidine (pmd) in CH2Cl2 were examined according to Scheme 1. Several mononuclear Rh complexes were isolated and their structures were crystallographically characterized.
2. Experimental 2.1. General procedures All operations were carried out using standard Schlenk techniques under N2 atmosphere. All the organic solvents were distilled by general methods before use. RhCl3 ×/3H2O, 2-(4-thiazolyl)benzimidazole, pyridazine, imidazole and pyrimidine were commercially purchased from Steam and Aldrich and used without further purifications. [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) was synthesized according to the literature [8]. IR spectra were recorded on a Perkin /Elmer System 2000 FT IR spectrometer as a KBr pellet. UV /Vis spectra were recorded on a HITACHI U-3500/U-4000 spectrometer. 1H NMR spectra were measured at room temperature (r.t.) on a JEOL JNM-A 500 FT NMR
Scheme 1.
spectrometer. Trimethylsilane was used as an internal reference. 2.2. Preparation of Rh complexes with nitrogen ligands 2.2.1. [Rh(H)2(PPh3)2(tbz)]ClO4 (2) A 5 ml CH2Cl2 solution of [Rh(H)2(PPh3)2(EtOH)2]ClO4 (1) (41.1 mg, 0.05 mmol) was added to the tbz ligand (10.1 mg, 0.05 mmol) in CH2Cl2 (5 ml). After stirring for 30 min, the reaction solution was filtered. The yellow filtrates were introduced into 5 mm diameter glass tubes and were layered with hexane as the diffusion solvent. The glass tubes were sealed and allowed to stand at r.t. for 2 days. Light yellow crystals of complex 2 were collected. Yield: 43.7 mg (94%). IR (KBr pellet, cm 1): 2081 (Rh /H), 1435, 1095, 696 and 519. 1H NMR (CD2Cl2, 23 8C, ppm): d 11.98 (N /H of benzimidazole), 8.19 (2-H of thiazolyl), 8.08 (4-H of benzimidazole), 7.00 /7.59 (Ph of PPh3), 6.03 (5-H of benzimidazole), /15.60 (Rh /H) and /16.30 (Rh /H). Anal. Calc. for C46H39P2N3SRhO4Cl: C, 59.40; H, 4.23; N, 4.52. Found: C, 59.26; H, 3.97; N, 4.33%. 2.2.2. [Rh(H)2(PPh3)2(pdz)2]ClO4 ×/2CH2Cl2 (3) and [Rh(H)Cl(PPh3)2(pdz)2]ClO4 ×/CH2Cl2 (4) Complex 3 was prepared in the same manner as for complex 2, using the pdz ligand (8.0 mg, 0.10 mmol). Light yellow crystals of complex 3 were obtained 2 days later at the middle part of the glass tubes. Yield: 43.4 mg (82%). IR (KBr pellet, cm 1): 2046 (Rh /H), 1435, 1093, 697 and 521. 1H NMR (CD2Cl2, 23 8C, ppm): d 9.16 (3,6-H of prd), 8.57 (5-H of prd), 8.21 (4-H of prd), 7.20 /7.48 (Ph of PPh3), and /16.89 (Rh /H). Anal. Calc. for C46H44P2N4RhO4Cl5: C, 52.17; H, 4.19; N, 5.29. Found: C, 51.68; H, 4.11; N, 5.33%. The reaction solution was allowed to stand for a further 2 weeks and colorless crystals of complex 4 were collected at the upper part of the glass tubes. Yield: 4.0 mg (8%). IR (KBr pellet, cm 1): 2174 (Rh /H), 1435, 1093, 696 and 523. Anal. Calc. for C45H41P2N4RhO4Cl4: C, 53.59; H, 4.10; N, 5.56. Found: C, 53.32; H, 4.03; N, 5.86%. 2.2.3. [Rh(H)2(PPh3)2(im)2]ClO4 ×/2CH2Cl2 (5) and [Rh(H)Cl(PPh3)2(im)2]ClO4 ×/CH2Cl2 (6) Complex 5 was prepared in the same manner as for complex 3, using the im ligand (6.7 mg, 0.10 mmol). The reaction solution was allowed to stand at r.t. for 2 days and light yellow crystals of complex 5 were obtained at the middle part of the glass tubes. Yield: 38.1 mg (74%). IR (KBr pellet, cm 1): 2051 (Rh /H), 1435, 1095, 695 and 520. 1H NMR (CD2Cl2, 23 8C, ppm): d 10.09 (N / H of im), 7.21 /7.61 (Ph of PPh3), 6.71 (2-H of im), 6.57 (4-H of im), 6.31 (5-H of im) and /16.85 (Rh /H). Anal. Calc. for C44H44P2N4RhO4Cl5: C, 51.06; H, 4.28; N, 5.41. Found: C, 51.44; H, 4.42; N, 5.57%.
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The reaction solution was allowed to stand at r.t. for another 2 weeks and colorless crystals of complex 6 were collected at the upper part of the glass tubes. Yield: 1.0 mg (2%). IR (KBr pellet, cm 1): 2133 (Rh /H), 1434, 1094, 696 and 523. Anal. Calc. for C43H41P2N4RhO4Cl4: C, 52.46; H, 4.20; N, 5.69. Found: C, 52.51; H, 4.11; N, 5.53%.
2.2.4. [Rh(H)2(PPh3)2(pmd)4]ClO4 ×/CH2Cl2 (7) and [RhCl2(pmd)4]ClO4 (8) Complex 7 was prepared in the same manner as for complex 3, using the pmd ligand (8.0 mg, 0.10 mmol). Complex 7 was obtained as white precipitates. Yield: 36.0 mg (74%). IR (KBr pellet, cm 1): 2060 (Rh /H), 1584, 1435, 1094, 696 and 520. 1H NMR (CD2Cl2, 23 8C, ppm): d 9.17 (2-H of pmd), 8.73 (6-H of pmd), 8.28 (4-H of pmd), 7.26 /7.38 (Ph of PPh3), 7.01 (5-H of pmd) and /17.30 (Rh /H). Anal. Calc. for C45H42P2N4RhO4Cl3: C, 55.49; H, 4.35; N, 5.75. Found: C, 55.92; H, 4.20; N, 5.58%. Yellow crystals of complex 8 were collected 4 days later at the lower part of the glass tubes. Yield: 3.5 mg (12%). IR (KBr pellet, cm 1): 1595, 1411, 1122, 706 and 625. Anal. Calc. for C16H16N8RhO4Cl3: C, 32.37; H, 2.72; N, 18.88. Found: C, 32.68; H, 2.61; N, 18.69%.
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3. Results and discussion 3.1. Crystal structures 3.1.1. [Rh(H)2(PPh3)2(tbz)]ClO4 (2) In the reaction of complex 1 with the nitrogen ligand, the tbz ligand acted as a bidentate chelate ligand and led to the typical mononuclear Rh hydrido complex 2. Since no crystallographic structures of Rh complexes containing the tbz ligand have been reported, complex 2 is the first example of a Rh hydrido complex with the tbz ligand. Fig. 1 shows the cation moiety of complex 2 together with the atomic labelling scheme. The Rh atom is coordinated by two P atoms, two N atoms and two hydride atoms in a distorted octahedral environment. The two PPh3 ligands are nearly in trans-positions with a P(1) /Rh /P(2) angle of 167.06(8)8. The Rh coordination plane defined by two N atoms of the tbz ligand and two hydride atoms are coplanar with the mean deviation ˚ . Two heterocyclic rings of the tbz ligand are of 0.0365 A ˚ . The nearly coplanar with a mean deviation of 0.0707 A average Rh /P, Rh /N and Rh /H distances of 2.299, ˚ are similar to those of other analogous 2.197 and 1.58 A ˚ is hydrido complexes [14]. The H H distance of 2.08 A characteristic of hydrido complexes [15]. The N(1) /Rh / N(2) angle of 76.1(2)8 is within the range of values of other Rh complexes with bidentate nitrogen ligands [16]. Selected bond distances and bond angles are listed in Table 2.
2.3. X-ray crystallography For each complex, a suitable crystal was sealed into the glass capillary (0.7 mm, GLAS) and mounted on the crystal goniometer. The intensity data of all the single crystals were collected on the Rigaku/Mercury CCD system using graphite monochromated Mo Ka radiation ˚ ). The structures of complexes 2, 5 and 6 (l/0.710691 A were solved by the direct method (SIR-92 for 2 and 5; SIR-97 for 6) [9], and expanded using Fourier techniques [10]. The structure of complex 3 was solved by the heavy-atom Patterson method [11] and expanded using Fourier techniques [10]. The hydride hydrogen atoms were located and refined isotropically. All other hydrogen atoms were included but not refined. The nonhydrogen atoms were refined anisotropically. The final cycle of full-matrix least-squares refinement was based on 5251, 4348, 4418 and 6594 observed reflections (I / 3s(I )) for complexes 2, 3, 5 and 6, respectively. The unweighted and weighted agreement factors of and Rw /[a w (Fo2/Fc2)2/ R /ajjFoj/jFcjj/ajFoj 2 2 1/2 a w (Fo ) ] were used. The atomic scattering factors and anomalous dispersion terms were taken from ref. [12]. All calculations were performed using the TEXSAN crystallographic software package [13]. The detailed crystal data of all complexes are summarized in Table 1.
3.1.2. [Rh(H)2(PPh3)2(pdz)2]ClO4 ×/2CH2Cl2 (3) The structure of the cation moiety of complex 3 is presented in Fig. 2. The Rh atom is coordinated by two PPh3 ligands, two pdz ligands and two hydride atoms to afford a mononuclear Rh complex in a slightly distorted octahedral geometry. In each pdz ligands, one of the two N atoms is bonded to the Rh atom. The two pdz ligands, in cis- positions, are inclined against the N2RhH2 coordination plane at an angle of 31.2(2)8. On the other hand, two PPh3 ligands in trans -positions are bent toward the two hydrides with a P(1) /Rh /P(1?) angle of 163.89(5)8. The Rh /P, Rh /N and Rh /H distances of ˚ are similar to those of 2.3033(9), 2.181(3) and 1.44(4) A other Rh hydrido complexes [14]. The H H distance of ˚ is within the range of values found in other 2.03 A hydrido complexes [15]. Selected bond distances and angles are listed in Table 3. Metal complexes with the pdz ligand as a heterocyclic ligand have been relatively limited, in comparison with those with the pyrazine ligand [17]. Although recently there have been several crystallographic reports on complexes with pdz ligands [18], Rh complexes with the pyz ligand are few. The crystal structure of complex 3 is remarkable as a Rh hydrido complex with the pdz ligand.
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Table 1 Crystal data and measurement conditions for 2, 3, 5 and 6 Complexes
2
3
5
6
Formula M Crystal system Space group ˚) a (A ˚) b (A ˚) c (A b (8) ˚ 3) V (A Dcalc (g cm 3) F (000) Z m (Mo Ka) (cm 1) Number of reflections
RhP2N3ClO4C46H39S 930.20 monoclinic P 21/c 13.2040(9) 13.7074(9) 23.268(1) 99.3724(8) 4155.0(5) 1.487 1904 4 6.50 24430 (total) 9159 (unique) 5251 [I 3.00s (I )] 0.078 0.081
RhP2N4Cl5O4C46H44 1059.00 orthorhombic P 212121 15.362(6) 15.404(1) 10.048(2)
RhP2N4Cl5O4C44H44 1034.97 orthorhombic P 212121 15.020(2) 15.3277(3) 10.1368(2)
2377(1) 1.479 1080 2 7.53 14955 (total) 2854 (unique) 4348 [I 3.00s (I )] 0.042 0.055
2333.8(4) 1.473 1056 2 7.65 14544 (total) 2783 (unique) 4418 [I 3.00s (I )] 0.044 0.062
RhP2N4Cl4O4C43H41 984.49 Monoclinic P 21/n 22.608(1) 14.2621(5) 13.7827(5) 104.3593(7) 4305.3(3) 1.519 2008 4 7.65 27180 (total) 9470 (unique) 6594 [I 3.00s (I )] 0.054 0.068
Number of observations R Rw
Fig. 1. The crystal structure of the cation moiety of complex 2. Only Rh(1), N(1), N(2), N(3), S(1), P(1), P(2), C(11), C(17), C(23), C(29), C(35), C(41), H(1) and H(2) in the coordination sphere are labelled.
Fig. 2. The crystal structure of the cation moiety of complex 3. Only Rh(1), N(1), N(1?), N(2), N(2?), P(1), P(1?), C(5), C(11), C(17), C(5?), C(11?), C(17?), H(1) and H(1?) in the coordination sphere are labelled.
Table 2 ˚ ) and bond angles (8) of 2 Selected bond lengths (A Bond lengths Rh(1) P(1) Rh(1) N(1) Rh(1) H(1)
2.317(2) 2.192(7) 1.59(6)
Rh(1) P(2) Rh(1) N(2) Rh(1) H(2)
2.282(2) 2.203(6) 1.57(8)
Bond angles P(1) Rh(1) P(2) P(1) Rh(1) N(2) P(2) Rh(1) N(2) Rh(1) P(1) C(11) Rh(1) P(1) C(23) Rh(1) P(2) C(35) H(1) Rh(1) H(2)
167.06(8) 92.9(2) 97.1(2) 112.2(3) 113.6(3) 114.3(3) 82.0(3)
P(1) Rh(1) N(1) P(2) Rh(1) N(1) N(1) Rh(1) N(2) Rh(1) P(1) C(17) Rh(1) P(2) C(29) Rh(1) P(2) C(41)
93.5(2) 96.8(2) 76.1(2) 117.4(3) 111.9(2) 118.0(3)
Table 3 ˚ ) and bond angles (8) of 3 Selected bond lengths (A Bond lengths Rh(1) P(1) Rh(1) H(1)
2.3033(9) Rh(1) N(1) 1.44(4)
Bond angles P(1) Rh(1) P(1?) a P(1) Rh(1) N(1?) a P(1)1 Rh(1) N(1?) a Rh(1) P(1) C(5) Rh(1) P(1) C(17)
163.89(5) 92.3(1) 98.8(1) 112.0(2) 117.0(1)
a
P(1) Rh(1) N(1) P(1) a Rh(1) N(1) N(1) Rh(1) N(1?) a Rh(1) P(1) C(11) H(1) Rh(1) H(1?) a
Symmetry codes X1, Y1, Z .
2.181(3)
98.8(1) 92.3(1) 92.7(2) 115.7(2) 89.0(3)
X.-Y. Yu et al. / Polyhedron 21 (2002) 1613 /1620
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of Rh hydrido complexes with the im ligand. To the best of our knowledge, this is the first crystal structure of a Rh hydrido complex with the im ligand.
Fig. 3. The crystal structure of the cation moiety of complex 5. Only Rh(1), N(1), N(1?), N(2), N(2?), P(1), P(1?), C(4), C(10), C(16), C(4?), C(10?), C(16?), H(1) and H(1?) in the coordination sphere are labelled.
3.1.3. [Rh(H)2(PPh3)2(im)2]ClO4 ×/2CH2Cl2 (5) The structure of the cation moiety of complex 5 is shown in Fig. 3. The structure of complex 5 essentially resembles that of complex 3. The Rh atom is coordinated by two PPh3 ligands, two im ligands and two hydride atoms in a distorted octahedral geometry. The two im ligands in cis- positions are slightly inclined against the N2RhH2 coordination plane at an angle of 27.7(2)8, which is smaller than that (31.2(2)8) of complex 3. The two PPh3 ligands are in trans -positions and the P(1) /Rh /P(1?) angle of 163.13(5)8 is similar to that (163.89(5)8) of complex 3. The Rh /P, Rh /N and Rh /H ˚ are close distances of 2.2955(9), 2.189(3) and 1.50(4) A to those of other Rh hydrido complexes [14]. The H H ˚ is in the range of those found in other distance of 2.07 A hydrido complexes [15]. Selected bond distances and angles are listed in Table 4. Our survey of Rh complexes with the im ligand and its derivatives described the tetranuclear complex [Rh(2Meim)(CO)2]4 (2-Meim /2-methylimidazole) [19a], the dinuclear complex [NBu4][Rh2(cod)2(dcbi)] ×/2i PrOH (dcbi /4,5-dicarboxyimida-zole) [19b], the mononuclear complexes [RhCl2(N-Meim)4]Cl ×/2H2O (Meim/N methyl-imidazole) [19c] and [imH][trans -RhCl4(im)2] [19d]. However, there are no reports of X-ray structures
3.1.4. [Rh(H)Cl(PPh3)2(im)2]ClO4 ×/CH2Cl2 (6) After light-yellow single crystals of complex 5 were obtained according to Scheme 1, colorless single crystals of complex 6 were collected from the same reaction solution 2 weeks later. The structure of the cation moiety of complex 6 is revealed in Fig. 4. The coordination sphere around the Rh atom consists of two PPh3 ligands, two im ligands, one Cl atom and one hydride atom, providing a distorted octahedral geometry. It is interesting that the two im ligands are located in the trans- positions and are separated by the Cl atom and the hydride atom. This structural feature is greatly different from that in complex 5. The P(1) /Rh /P(2) angle of 177.26(4)8 is much larger than those of 163.89(5)8 and 163.13(5)8 in complexes 3 and 5, respectively. Therefore the PPh3 ligands in the trans- positions are almost linearly located. The average Rh /P distance ˚ is longer than those of normal Rh and Ir of 2.362 A hydrido complexes [4,7]. The average Rh /N distances of ˚ are shorter than those of 2.181(3) and 2.189(3) 2.056 A ˚ in complexes 3 and 5, respectively. The Rh /Cl A ˚ is longer than those found in distance of 2.498(1) A other hydrido complexes [4] owing to the trans influence of the nitrogen ligands. Selected bond distances and angles are listed in Table 5. 3.2. Reactions of [Rh(H)2(PPh3)2(EtOH)2]ClO4 with nitrogen ligands in CH2Cl2 According to Scheme 1, the reactions of the Rh hydrido complex 1 with nitrogen ligands were attempted and their reaction processes were monitored by 1H NMR and UV /Vis spectra. The addition of the tbz
Table 4 ˚ ) and bond angles (8) of 5 Selected bond lengths (A Bond lengths Rh(1) P(1) Rh(1) H(1)
2.2955(9) Rh(1) N(1) 1.50(4)
Bond angles P(1) Rh(1) P(1?) a P(1) Rh(1) N(1?) a P(1)1 Rh(1) N(1?) a Rh(1) P(1) C(4) Rh(1) P(1) C(16)
163.13(5) 94.9(1) 96.6(1) 112.6(1) 117.1(1)
a
P(1) Rh(1) N(1) P(1) a Rh(1) N(1) N(1) Rh(1) N(1?) a Rh(1) P(1) C(10) H(1) Rh(1) H(1?) a
Symmetry codes: X2, Y , Z .
2.189(3)
96.6(1) 94.9(1) 93.3(2) 116.5(1) 87.0(3)
Fig. 4. The crystal structure of the cation moiety of complex 6. Only Rh(1), Cl(1), N(1), N(2), N(3), N(4), P(1), P(2), C(7), C(13), C(19), C(31), C(25), C(37) and H(1) in the coordination sphere are labelled.
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Table 5 ˚ ) and bond angles (8) of 6 Selected bond lengths (A Bond lengths Rh(1) Cl(1) Rh(1) P(2) Rh(1) N(3)
2.498(1) 2.364(1) 2.051(4)
Rh(1) P(1) Rh(1) N(1) Rh(1) H(1)
2.360(1) 2.061(4) 1.47(6)
Bond angles Cl(1) Rh(1) P(1) Cl(1) Rh(1) N(1) P(1) Rh(1) P(2) P(1) Rh(1) N(3) P(2) Rh(1) N(3) Rh(1) P(1) C(13) Rh(1) P(2) C(25) Rh(1) P(2) C(37) N(3) Rh(1) H(1)
90.94(4) 93.5(1) 177.26(4) 88.8(1) 89.8(1) 114.5(2) 115.2(2) 117.9(2) 86.0(2)
Cl(1) Rh(1) P(2) Cl(1) Rh(1) N(3) P(1) Rh(1) N(1) P(2) Rh(1) N(1) Rh(1) P(1) C(7) Rh(1) P(1) C(19) Rh(1) P(2) C(31) N(1) Rh(1) H(1)
91.46(4) 92.2(1) 91.6(1) 89.6(1) 114.5(2) 116.4(2) 112.4(1) 87.0(2)
ligand to complex 1 in CD2Cl2 initially showed two new quintet 1H NMR signals of hydride species at /15.60 and /16.30 ppm at r.t., together with the quintet 1H NMR signal of an hydride species at /22.16 ppm, which should be attributed to hydrides of complex 1. After about 1 h, the 1H NMR signal of complex 1 completely disappeared and the two new 1H NMR signals only remained. These facts indicate that Rh hydrido complex 2 with the tbz ligand was formed in CH2Cl2 solution. Similarly, on the reaction of complex 1 with pdz, im and pmd ligands, the 1H NMR signals of the hydride species could be observed at /16.89, /16.85 and /17.30 ppm for complexes 3, 5 and 7, respectively. On the other hand, as shown in the timecourse UV /Vis spectra (Fig. 5), complex 1 dissolved in CH2Cl2 at 23 8C displayed the color change from yellow to the dark brown solution of [Rh2(PPh3)2{(h6C6H5)Ph2P}]2]2 (lmax /410 nm (o /3056 cm 1 M1)) [7]. The further addition of tbz ligand to the CH2Cl2 solution exhibited the color change from dark-brown to a yellow solution (lmax /420 nm (o /2235 cm 1 M1)) and the formation of complex 2 was completed after about 50 min. On the basis of these structural studies in solution and the above-mentioned crystallographic
Fig. 5. The time-course UV /Vis spectra in CH2Cl2 at 23 8C. After the dissolving of complex 1: 10 (1) and ]/50 (2) min. After the addition of the tbz ligand to complex 1: 20 (3), 30 (4), 40 (5) and ]/50 (6) min. [c ]/1.7/10 4 M.
studies, it was concluded that the reaction of complex 1 with nitrogen ligands such as tbz, pdz, im and pmd ligands provided mononuclear Rh hydrido complexes without the reductive elimination of hydrogen. We previously demonstrated that the reactions of complex 1 with nitrogen bridging ligands such as pyrazine and 4,4?-bipyridine derivatives in CH2Cl2 could afford diand trinuclear Rh non-hydrido complexes[7] with the reductive elimination of hydrogen. The results in this study are greatly different from those previously found. Although the detailed reason is not obvious at the present, it is probably considered that nitrogen ligands such as tbz, pdz and im ligands are structurally difficult to bridge Rh centers owing to the steric repulsion against the phenyl group of the PPh3 ligand and should lead to mononuclear Rh hydrido complexes with nitrogen ligands, without the reductive elimination of hydrogen. As mentioned in the Section 2, when the reaction solution of the Rh hydrido complex 1 with pdz, im and pmd ligands was allowed to stand for more than 2 weeks, Rh complexes 4, 6 and 8 [20] with a coordinated Cl atom were collected in the same glass tubes, respectively. The reaction solution of complex 1 with the tbz ligand did not provide the corresponding Rh complex with a coordinated Cl atom since the tbz ligand played a role as a bidentate chelate ligand. In this study, the monitoring of their formation process by 1H NMR and UV /Vis spectra over 2 weeks has not been carried out and the structure of 6 could only be crystallographically characterized. At the present, although their formation mechanisms are not obvious in detail, it is considered that the Cl atom is probably derived from the CH2Cl2 solvent since it has been known that [RhCl(PPh3)2]2 was produced by the reaction of [Rh2(H)2(PPh3)4(Me4Si2O)2] with CH2Cl2 as the solvent [21].
3.3. Consideration on crystallographic study The four crystallographic studies revealed the significant structural differences among their bond distances and bond angles of complexes 2, 3, 5 and 6. In complex 6 with the Cl atom, the average Rh /N distance of 2.056 ˚ is shorter than those (2 (2.197(7) A ˚ ), 3 (2.181(3) A ˚) A ˚ )) of the other Rh complexes without and 5 (2.189(3) A the Cl atom. In contrast, the average Rh /P distance of ˚ ) is slightly longer than those of 2 complex 6 (2.362 A ˚ ), 3 (2.3033 A ˚ ) and 5 (2.2955 A ˚ ). The P /Rh /P (2.299 A angle of 6 (177.26(4)8) is rather larger than those of 2 (167.06(8)8), 3 (163.89(5)8), 5 (163.13(5)8) and other Rh hydrido complexes [4,7]. These changes should probably be caused by the repulsion between the bulky Cl atom and the trans-nitrogen ligands. The Rh /Cl distance of ˚ in complex 6 is also longer than those of 2.499(1) A
X.-Y. Yu et al. / Polyhedron 21 (2002) 1613 /1620
other Rh hydrido complexes [4] owing to the trans influence of the nitrogen ligands. It is suggested that complex 2 possesses a meaningful inter-planar interaction between the nitrogen ligand and the corresponding phenyl group of PPh3. The mean inter-planar distance between the benzimidazole portion of the tbz ligand and the phenyl group including the ˚ with a dihedral angle of 10.28, and C(11) atom is 3.409 A that between the thiazolyl group of the tbz ligand and ˚ with the phenyl group including C(29) atom is 3.422 A an angle of 27.18. A similar intra-molecular interaction has been known in previous reports [22]. This consideration is also supported by other structural parameters in complex 2: the Rh(1)/P(1) /C(11) bond angle of 112.2(3)8 is smaller than Rh(1)/P(1) /C(17) of 117.4(3)8 and Rh(1)/P(1) /C(23) of 113.6(3)8. The Rh(1)/P(2) /C(29) bond angle of 111.9(2)8 is smaller than Rh(1)/P(2) /C(41) of 118.0(3)8 and Rh(1)/P(2) / C(35) of 114.3(3)8. In complex 6, it should be noted that the intramolecular C /H Cl hydrogen bonds exist between the Cl atom and hydrogen atom at the 2-position in im ligands. The C(1) Cl(1) and C(4) Cl(1) distances are ˚ , respectively. Thus interactions 3.339(5) and 3.306(6) A are probably caused by the steric repulsion within the bulky PPh3 ligands. The possibility of Rh H agostic interaction and attractive Cl H /C hydrogen bonds in Rh complexes with the PPh3 ligand has recently been reported [23]. This suggestion is consistent with the results of the density functional analysis [23]: the intramolecular steric repulsion can force one of the phenyl rings of the PPh3 ligands toward the metal center.
4. Supplementary materials Crystallographic data for the X-ray crystal structural analyses have been deposited with the Cambridge Crystallographic Data Centre, CCDC, Nos. 169897 (2), 169896 (3), 169895 (5) and 169898 (6). Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: /44-1233-336033; e-mail: deposit@ ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements This work was partially supported by Grants-in-Aids from the Ministry of Education, Science, Culture, Sports and Technology in Japan and research funds from Kinki University. Miss. X.-Y. Yu is also grateful to the Ministry of Education, Science, Culture, Sports and Technology in Japan for financial support.
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[21] [22]
[23]
(d) G. Mestroni, E. Alessio, A. Sessanta o Santi, S. Geremia, A. Bergamo, G. Sava, A. Boccarelli, A. Schettino, M. Coluccia, Inorg. Chim. Acta 273 (1998) 62. The crystal data could be only collected in complex 8: complex 8, formula C16H16N8RhO4Cl3, M 593.62, crystal system tetragonal, space group P 4/n , a/ 10.592(2), b/10.592(2) and c/9.5780(6) ˚ , V /1074.6(3) A ˚ 3, Dcalc /1.834 g cm 3, Z /2, m (Mo Ka) A 1 12.08 cm and number of total reflections 6412. M.D. Curtis, W.M. Butler, J. Greene, Inorg. Chem. 17 (1978) 2928. (a) S. Onaka, Y. Katsukawa, M. Yamashita, Chem. Lett. (1998) 525.; (b) N.G. Spitsina, V.V. Gritsenko, O.A. S’yachenko, B.B. Safoklov, Y.M. Shul’ga, E.B. Yagubskii, Russ. Chem. Bull. 49 (2000) 367; (c) H.-C. Chang, T. Ishii, M. Kondo, S. Kitagawa, J. Chem. Soc., Dalton Trans. (1999) 2467. (a) R. Cini, A. Cavaglioni, Inorg. Chem. 38 (1999) 3751; (b) J. Fawcett, J.H. Holloway, G.C. Saunders, Inorg. Chim. Acta 202 (1992) 111.