Diruthenium Research
1
Synthesis, Structural, Electrochemical and Spectroscopic Characterization of Diruthenium (III,II) Complexes With Mixed Anionic Bridging Ligands Karl M. Kadish, a,* Tuan Phan, c Rachel Garcia, a Elizabeth Varughese, b E. Van Caemelbecke, a,b and John L. Bear a,* a Department of Chemistry, University of Houston, Houston, TX 77204 b Department of Chemistry, Houston Baptist University, Houston, TX 77074 c Department of Chemistry, Texas Southern University, Houston, TX 77004 Introduction Previous Ru 2 (L) 4 Cl complexes, where L = ap, 2-Fap, 2,6-F 2 ap 2,4,6-F 3 ap and F 5 ap with four identical unsymmetrical bridging ligands have been shown to posses different isomeric distributions. 1,2,3 In theory the four geometric isomeric forms are labeled (4,0), (3,1), (2,2) trans, or (2,2) cis. 1-7 There is typically one dominant isomeric form that the complex tends to prefer. For example Ru 2 (ap) 4 Cl exists primarily in the (4,0) form while Ru 2 (Fap) 4 Cl exists in the (3,1) form. 2,3 The preferred geometric conformation may depend on both steric and electronic factors, and this point was examined in this present study which reports the synthesis, structural, electrochemical, and spectroscopic properties of partially substituted ap or Fap diruthenium complexes of the type Ru 2 (ap) x (ac) 4-x Cl and Ru 2 (Fap) x (ac) 4-x Cl where x = 1,2,3 or 4. Ru Ru 2 (ac) (ac) 2 (Fap) (Fap) 2 Cl Cl Ru Ru 2 (ac) (ac) 3 (Fap)Cl (Fap)Cl Ru Ru 2 (Fap) (Fap) 4 Cl Cl Ru Ru 2 (ac)(Fap) (ac)(Fap) 3 Cl Cl ●TLC revealed the presence of four products after 6 hours. ●The remaining solid was subjected to column chromatography using silica gel and a mixture of v/v 7:3 ratio of hexanes to acetone respectively Summary ●The yield of a given Ru 2 (ac) x (L) 4-x Cl complex depends on the time the reaction is carried out. Intermediate species with less acetate ligands are more kinetically favored since Ru 2 (L) 4 Cl is formed after addition of only 2 equivalents of HL. ●The X-ray crystal structures of Ru 2 (ac) 2 (ap) 2 Cl and Ru 2 (ac) 2 (Fap) 2 Cl reveal: - Both Fap and ap bridging ligands adopt a trans configuration after replacing the acetate ligand - The different N(p)-Ru-Ru-N(a) torsion angle values of 6.86 and 1.68 for Ru 2 (ac) 2 (ap) 2 Cl suggest steric hindrance upon replacing the acetate by the pyridinate ligand. This trend was also expected for Ru 2 (ac) 2 (Fap) 2 Cl, but the two torsion angles have similar values in this compound. - The Ru-N(a) bond lengths trans to each other have different values in Ru 2 (ac) 2 (Fap) 2 Cl, but this trend is not observed for the fully substituted compound, Ru 2 (Fap) 4 Cl. -The N(p)-Ru-Ru-N(a) torsion angles and the bond lengths in Ru 2 (ac) 2 (Fap) 2 Cl suggest that the electronic effects prevail over steric effects, thus giving some insight as to which geometry is preferred by the ap-type ligands in the mixed ligand complex. -The similar orientation of the ap and Fap bridging ligands in Ru 2 (ac) 2 (ap) 2 Cl and Ru 2 (ac) 2 (Fap) 2 Cl will suggest the same isomeric form for Ru 2 (ap) 4 Cl and Ru 2 (Fap) 4 Cl and therefore substitution of either the third or fourth acetate ligand is the crucial step to determine the exact isomeric form, i.e. (4,0) or (3,1) of the fully substituted compound. ●Electrochemical studies reveal a negative shift for the redox processes which is explained by the increase of electron density around the ruthenium atoms. ●The HOMO-LUMO gap decreases more as more acetates are substituted by Fap. Acknowledgement We gratefully acknowledge the Alliances for Graduate Education and the Professoriate (AGEP) for their community and financial support. We also appreciate the financial support from the Robert A. Welch Foundation: Houston Baptist University’s Welch Grant number BF-0016 University of Houston’s Welch Grant number E-0918 References (1) Bear, J. L.; Li, Y.; Han, B.; Van Caemelbecke, E.; Kadish, K. M. Inorg. Chem. 1997, 36, 5449. (2) Bear, J. L.; Wellhoff, J.; Royal, G.;Van Caemelbecke, E.; Eapen, S.; Kadish, K. M. Inorg. Chem. 2001, 40, 2282. (3) Chakravarty, A. R.; Cotton, F. A.; Tocher, D. Inorg. Chem. 1985, 24, 172. (4) Bear, J. L.; Lifsey, R. S.; Chau, L.K.; Ahsna, M. Q.; Korp, J. D.; Chavan, M.; Kadish, K. M. J. Chem. Soc., Dalton Trans. 1989, 93. (5) Bear, J. L.; Liu, L. M.; Kadish, K. M. Inorg. Chem. 1987, 26, 2927. (6) Bear, J. L.; Yao, C. L.; Liu, L. M.; Capdevielle, F. J.; Korp, J. D.; Albright, T. A.; Kang, S. K.; Kadish, K. M. Inorg. Chem. 1989, 28, 1254. (7) Chakravarty, A. R.; Cotton, F. A. Polyhedron 1985, 4, 1957. (8) Bear, J. L.; Chen, W.; Han, B.; Huang, S.; Wang, L.; Thuriere, A.; Van Caemelbecke, E.; Kadish, K. M.; Ren, T. Inorg. Chem. 2003, 42, Characterization Ongoing Studies We have reported recently that the combination of Ru 2 (ap) 4 Cl and CN - forms both the mono- and biscyano products of the type Ru 2 (ap) 4 CN and Ru 2 (ap) 4 CN 2 while the combination of Ru 2 (Fap) 4 Cl and CN - leads to four products formulated as Ru 2 (Fap) 4 CN, Ru 2 (Fap) 4 CN 2 , Ru 2 (Fap) 3 [µ-(o-NC)ap](µ-CN) and Ru 2 (Fap) 4 (µ-CN) 2 but in this case the exact type and yield of the products are temperature dependant. 8 We are now studying the reactivity of CN - with Ru 2 (ac) 2 (Fap) 2 Cl and Ru 2 (ac) 3 (Fap)Cl. 796.0 808.6 821.2 833.8 846.4 859.0 Mass (m/z) 0 3.1E+4 0 10 20 30 40 50 60 70 80 90 100 % Intensity 823.3943 821.3841 825.3611 820.3822 818.3811 819.3870 827.3510 817.3728 816.3716 815.3893 829.3641 838.3585 812.3750 669.0 679.2 689.4 699.6 709.8 720.0 Mass (m/z) 0 6083.1 0 10 20 30 40 50 60 70 80 90 100 % Intensity 694.3269 693.3230 698.3218 692.3102 697.3340 700.3215 691.3332 699.3193 690.3367 696.6970 689.3480 694.7258 697.8645 688.3528 701.3894 693.9579 687.3484 700.9946 707.2813 678.5524 703.9379 692.9114 684.2662 674.4416 689.7382 708.3513 711.4343 704.4412 671.5542 714.3500 677.4841 684.5297 925.0 935.8 946.6 957.4 968.2 979.0 Mass (m/z) 0 2970.6 0 10 20 30 40 50 60 70 80 90 100 % Intensity 954.3988 950.4339 948.4099 953.4250 952.4289 947.4009 955.4121 946.4453 956.4240 971.3638 945.4575 968.3878 964.4180 944.4090 932.4727 963.4362 943.4206 543.0 550.8 558.6 566.4 574.2 582.0 Mass (m/z) 0 5.9E+4 0 10 20 30 40 50 60 70 80 90 100 % Intensity 569.2701 565.3088 563.2745 572.2518 561.2647 559.2550 571.2518 560.2672 568.8578 568.0084 556.2641 571.0099 566.7805 558.2723 573.2412 569.8525 563.8413 571.8615 574.1557 561.7983 554.2157 575.3276 559.8785 551.2537 557.2682 577.3043 Synthesis MeOH 80º C Ru 2 (ac) 4 Cl + X HL L= 2-Fap or ap Ru 2 (ac) 4- x (L) x Cl x = 1,2,3 or 4 Time, hr. 6 1 4 Electrochemistr y: X-Ray Crystallography: 30% 5% 20% 25% Ru Ru 2 (ac) (ac) 2 (Fap) (Fap) 2 Cl Cl · · acetone acetone (2) (2) 2.093 2.093 4 4 2.111 2.111 5 5 2.021 2.021 3 3 2.040 2.040 2 2 Ru Ru 2 (ac) (ac) 2 (ap) (ap) 2 Cl · Cl · acetone (1) acetone (1) 2.107 2.107 5 5 2.099 2.099 5 5 2.035 2.035 6 6 2.032 2.032 8 8 Ru 2 5+ /Ru 2 6+ Ru 2 5+ /Ru 2 4+ Potential (in V vs. SCE) A similar negative shift of Ru 2 5+ /Ru 2 6+ and Ru 2 5+ /Ru 2 4+ redox couples is observed when comparing Ru 2 (ac) 4 Cl, Ru 2 (ac) 2 (ap) 2 Cl and Ru 2 (ap) 4 Cl respectively. HOMO-LUMO - + 1.22 V 1.31 V 1.57 V * * using 1.12 UV-Visible Spectroscopy: Ru Ru 2 (ac) (ac) 2 (Fap) (Fap) 2 Cl Cl Ru Ru 2 (Fap) (Fap) 4 Cl Cl Ru Ru 2 (ac) (ac) 3 (Fap) (Fap) Cl Cl ORTEP from Bear et al. Inorg. Chem. 2001, 40, 2282-2286 (3,1) conformation: Ru 2 (Fap) 4 Cl ORTEP from Chakravarty et al. Inorg. Chem. 1985, 24, 172-177 (4,0) conformation: Ru 2 (ap) 4 Cl The lower energy band red shifts upon substitution of ac by Fap The following was observed with 3 equivalents of HFap: ●Reaction was stopped after 6 hours, excess ruthenium acetate was filtered and the filtrate liquid was evaporated. Ru Ru 2 (Fap) (Fap) 4 Cl Cl Ru Ru 2 (ac) (ac) 2 (Fap) (Fap) 2 Cl Cl Ru Ru 2 (ac) (ac) 3 (Fap)Cl (Fap)Cl The Ru(1)- N(x) bond length, where x= a is longer than the other Ru(2)- N(a) type bonds 0 1 -1 Shorter vs. 1 Similar magnitud e Longer vs. 1 The Ru(2)- N(y) bond length, where y=p is shorter than the other Ru(1)-N(p) type bonds The N(p)-Ru-Ru-N(a) torsion angles are significantly different for Ru 2 (ac) 2 (ap) 2 Cl but are similar in the case of Ru 2 (ac) 2 (Fap) 2 Cl ●The solution changed from a brown color to a green color. CH 2 Cl 2 ,0.1 M TBAP In CH 2 Cl 2 The percent yields listed above are average values after 6h; the percent yield of each product will vary with number of equivalents as well as time. The 3 rd Ru(1)-N(p) bond length (trans to Ru(1)-N(x)) is longer than the other Ru(1)- N(p) bond lengths
Transcript of Diruthenium Research
Synthesis, Structural, Electrochemical and Spectroscopic Characterization of Diruthenium (III,II) Complexes With Mixed Anionic Bridging Ligands
Karl M. Kadish,a,* Tuan Phan,c Rachel Garcia,a Elizabeth Varughese,b E. Van Caemelbecke,a,b and John L. Beara,*
aDepartment of Chemistry, University of Houston, Houston, TX 77204
bDepartment of Chemistry, Houston Baptist University, Houston, TX 77074
cDepartment of Chemistry, Texas Southern University, Houston, TX 77004
IntroductionPrevious Ru2(L)4Cl complexes, where L = ap, 2-Fap, 2,6-F2ap 2,4,6-F3ap and F5ap with four identical unsymmetrical bridging ligands have been shown to posses different isomeric distributions.1,2,3 In theory the four geometric isomeric forms are labeled (4,0), (3,1), (2,2) trans, or (2,2) cis.1-7
There is typically one dominant isomeric form that the complex tends to prefer. For example Ru2(ap)4Cl exists primarily in the (4,0) form while Ru2(Fap)4Cl exists in the (3,1) form.2,3 The preferred geometric conformation may depend on both steric and electronic factors, and this point was examined in this present study which reports the synthesis, structural, electrochemical, and spectroscopic properties of partially substituted ap or Fap diruthenium complexes of the type Ru2(ap)x(ac)4-xCl and Ru2(Fap)x(ac)4-xCl where x = 1,2,3 or 4.
RuRu22(ac)(ac)22(Fap)(Fap)22ClClRuRu22(ac)(ac)33(Fap)Cl(Fap)Cl RuRu22(Fap)(Fap)44ClClRuRu22(ac)(Fap)(ac)(Fap)33ClCl
●TLC revealed the presence of four products after 6 hours.
●The remaining solid was subjected to column chromatography using silica gel and a mixture of v/v 7:3 ratio of hexanes to acetone respectively
Summary
●The yield of a given Ru2(ac)x(L)4-xCl complex depends on the time the reaction is carried out. Intermediate species with less acetate ligands are more kinetically favored since Ru2(L)4Cl is formed after addition of only 2 equivalents of HL.
●The X-ray crystal structures of Ru2(ac)2(ap)2Cl and Ru2(ac)2(Fap)2Cl reveal:
- Both Fap and ap bridging ligands adopt a trans configuration after replacing the acetate ligand
- The different N(p)-Ru-Ru-N(a) torsion angle values of 6.86 and 1.68 for Ru2(ac)2(ap)2Cl suggest steric hindrance upon replacing the acetate by the pyridinate ligand. This trend was also expected for Ru2(ac)2(Fap)2Cl, but the two torsion angles have similar values in this compound.
- The Ru-N(a) bond lengths trans to each other have different values in Ru2(ac)2(Fap)2Cl, but this trend is not observed for the fully substituted compound, Ru2(Fap)4Cl.
-The N(p)-Ru-Ru-N(a) torsion angles and the bond lengths in Ru2(ac)2(Fap)2Cl suggest that the electronic effects prevail over steric effects, thus giving some insight as to which geometry is preferred by the ap-type ligands in the mixed ligand complex.
-The similar orientation of the ap and Fap bridging ligands in Ru2(ac)2(ap)2Cl and Ru2(ac)2(Fap)2Cl will suggest the same isomeric form for Ru2(ap)4Cl and Ru2(Fap)4Cl and therefore substitution of either the third or fourth acetate ligand is the crucial step to determine the exact isomeric form, i.e. (4,0) or (3,1) of the fully substituted compound.
●Electrochemical studies reveal a negative shift for the redox processes which is explained by the increase of electron density around the ruthenium atoms.
●The HOMO-LUMO gap decreases more as more acetates are substituted by Fap.
AcknowledgementWe gratefully acknowledge the Alliances for Graduate Education and the Professoriate
(AGEP) for their community and financial support.
We also appreciate the financial support from the Robert A. Welch Foundation:
Houston Baptist University’s Welch Grant number BF-0016
University of Houston’s Welch Grant number E-0918
References(1) Bear, J. L.; Li, Y.; Han, B.; Van Caemelbecke, E.; Kadish, K. M. Inorg. Chem. 1997, 36,
5449.
(2) Bear, J. L.; Wellhoff, J.; Royal, G.;Van Caemelbecke, E.; Eapen, S.; Kadish, K. M. Inorg. Chem. 2001, 40, 2282.
(3) Chakravarty, A. R.; Cotton, F. A.; Tocher, D. Inorg. Chem. 1985, 24, 172.
(4) Bear, J. L.; Lifsey, R. S.; Chau, L.K.; Ahsna, M. Q.; Korp, J. D.; Chavan, M.; Kadish, K. M. J. Chem. Soc., Dalton Trans. 1989, 93.
(5) Bear, J. L.; Liu, L. M.; Kadish, K. M. Inorg. Chem. 1987, 26, 2927.
(6) Bear, J. L.; Yao, C. L.; Liu, L. M.; Capdevielle, F. J.; Korp, J. D.; Albright, T. A.; Kang, S. K.; Kadish, K. M. Inorg. Chem. 1989, 28, 1254.
(7) Chakravarty, A. R.; Cotton, F. A. Polyhedron 1985, 4, 1957.
(8) Bear, J. L.; Chen, W.; Han, B.; Huang, S.; Wang, L.; Thuriere, A.; Van Caemelbecke, E.; Kadish, K. M.; Ren, T. Inorg. Chem. 2003, 42, 6230.
Characterization
Ongoing Studies We have reported recently that the combination of Ru2(ap)4Cl and CN- forms both the mono- and biscyano products of the type Ru2(ap)4CN and Ru2(ap)4CN2 while the combination of Ru2(Fap)4Cl and CN- leads to four products formulated as Ru2(Fap)4CN, Ru2(Fap)4CN2, Ru2(Fap)3[µ-(o-NC)ap](µ-CN) and Ru2(Fap)4(µ-CN)2 but in this case the exact type and yield of the products are temperature dependant.8 We are now studying the reactivity of CN- with Ru2(ac)2(Fap)2Cl and Ru2(ac)3(Fap)Cl.
796.0 808.6 821.2 833.8 846.4 859.0
Mass (m/z)
0
3.1E+4
0
10
20
30
40
50
60
70
80
90
100
% Intensi
ty
Voyager Spec #1[BP = 696.3, 45015]
822.3772
823.3943
821.3841
825.3611
820.3822
818.3811
819.3870
827.3510
817.3728
816.3716
815.3893 829.3641
838.3585812.3750
669.0 679.2 689.4 699.6 709.8 720.0
Mass (m/z)
0
6083.1
0
10
20
30
40
50
60
70
80
90
100
% Intensit
y
Voyager Spec #1[BP = 189.3, 11407]
695.3359
694.3269
693.3230
698.3218692.3102
697.3340
700.3215691.3332
699.3193
690.3367
696.6970689.3480694.7258
697.8645688.3528 701.3894693.9579
687.3484 700.9946 707.2813678.5524 703.9379692.9114684.2662674.4416 689.7382 708.3513 711.4343704.4412671.5542 714.3500677.4841 684.5297
925.0 935.8 946.6 957.4 968.2 979.0
Mass (m/z)
0
2970.6
0
10
20
30
40
50
60
70
80
90
100
% Intens
ity
Voyager Spec #1[BP = 189.3, 30950]
951.4343
954.3988950.4339
948.4099
953.4250
952.4289
947.4009 955.4121
946.4453
956.4240 971.3638945.4575968.3878964.4180
944.4090932.4727 963.4362943.4206
543.0 550.8 558.6 566.4 574.2 582.0
Mass (m/z)
0
5.9E+4
0
10
20
30
40
50
60
70
80
90
100
% Intensit
y
Voyager Spec #1[BP = 566.3, 58532]
566.3083 569.2701565.3088
563.2745
572.2518561.2647
559.2550
571.2518
560.2672
568.8578
568.0084
556.2641571.0099
566.7805
558.2723 573.2412569.8525563.8413
571.8615574.1557
561.7983554.2157 575.3276
559.8785551.2537 557.2682577.3043
Synthesis
MeOH80ºC
Ru2(ac)4Cl + X HL
L= 2-Fap or ap
Ru2(ac)4-x(L)xCl
x = 1,2,3 or 4
Time, hr.61 4
Electrochemistry:
X-Ray Crystallography:
30% 5%20%25%
RuRu22(ac)(ac)22(Fap)(Fap)22Cl Cl · · acetoneacetone
(2)(2)
2.09342.0934
2.11152.1115
2.02132.0213
2.04022.0402
RuRu22(ac)(ac)22(ap)(ap)22Cl · Cl ·
acetone (1)acetone (1)
2.10752.1075
2.09952.0995
2.03562.0356
2.03282.0328
Ru25+/Ru2
6+
Ru25+/Ru2
4+
Potential (in V vs. SCE)
A similar negative shift of Ru25+/Ru2
6+ and Ru25+/Ru2
4+ redox couples is observed when comparing Ru2(ac)4Cl, Ru2(ac)2(ap)2Cl and Ru2(ap)4Cl respectively.
HOMO-LUMO
-+
1.22 V
1.31 V
1.57 V*
*using 1.12
UV-Visible Spectroscopy:
RuRu22(ac)(ac)22(Fap)(Fap)22ClCl
RuRu22(Fap)(Fap)44ClCl
RuRu22(ac)(ac)33(Fap)(Fap) Cl Cl
ORTEP from Bear et al. Inorg. Chem. 2001, 40, 2282-2286
(3,1) conformation: Ru2(Fap)4ClORTEP from Chakravarty et al. Inorg. Chem. 1985, 24, 172-177
(4,0) conformation: Ru2(ap)4Cl
The lower energy band red shifts upon substitution of ac by Fap
The following was observed with 3 equivalents of HFap:
●Reaction was stopped after 6 hours, excess ruthenium acetate was filtered and the filtrate liquid was evaporated.
RuRu22(Fap)(Fap)44ClCl
RuRu22(ac)(ac)22(Fap)(Fap)22ClCl
RuRu22(ac)(ac)33(Fap)Cl (Fap)Cl
The Ru(1)-N(x) bond length, where x= a is
longer than the other Ru(2)-N(a)
type bonds
01 -1
Shorter vs. 1
Similar magnitude
Longer vs. 1
The Ru(2)-N(y) bond length, where y=p is
shorter than the other Ru(1)-N(p)
type bondsThe N(p)-Ru-Ru-N(a) torsion angles are significantly different for
Ru2(ac)2(ap)2Cl but are similar in the case of Ru2(ac)2(Fap)2Cl
●The solution changed from a brown color to a green color. CH2Cl2,0.1 M TBAP
In CH2Cl2The percent yields listed above are average values after 6h; the percent yield of each product will vary with number of equivalents as well as time.
The 3rd Ru(1)-N(p) bond length (trans to Ru(1)-N(x)) is longer than the other
Ru(1)-N(p) bond lengths
![Promoted by [tpyRu(IV)#O]L The Mechanism of Water ...storage.googleapis.com/.../55fe607841f89TPavbpr/057-Llobet.pdf · diruthenium complex recently reported by Llobet,11 denoted [2,2]3+](https://static.fdocuments.in/doc/165x107/5aa5d6c37f8b9a1d728db3f7/promoted-by-tpyruivol-the-mechanism-of-water-complex-recently-reported.jpg)
