Inorganic-Chemical Practical Course Spring Semester 2014 tris(ethylenediamine)cobalt(III) chloride ([Co(en)3]Cl3) H2 H2 N H2 N N Cl3 Co N N H2 H2 N H2 and [Co(dinosar)]Br3 NO2 HN NH HN Br 3 Co HN NH NH NO2 27/05/2014 Patrick Zwick B2 Patrick Zwick Exp 5 1 Aim of the experiment The aim of the experiment was the synthesis of tris(ethylenediamine)cobalt(III) chloride ([Co(en)3]Cl3) as well as the synthesis of 1,8-dinitro-3,6,10,13,16- hexaazabicyclo[6,6,6]eicosane cobalt(III) bromide ([Co(dinosar)]Br3). The cryptand ligand dinosar was built around the metal centre of tris(ethylenediamine)cobalt(III) using template methodology. The product [Co(en)3]Cl3 was analysed by 1H-NMR spectroscopy in two different solvents (D2O and DMSO-d6). The product [Co(dinosar)]Br3 was analysed by 1HNMR spectroscopy in comparison with the spectra given by the instruction[2]. 2 Introduction The synthesized products are Co(III) complexes. Cobalt(III) complexes favour a d 6 low spin octahedral configuration and are kinetically inert. This means that the ligands are not labile and therefore it is common to prepare the analogue Co(II) species first and convert it into the Co(III) complex by oxidation afterwards[4]. This was done for the first part of the experiment were first [Co(en)3]2+ was synthesized and was secondly oxidised to [Co(en)3]Cl3 by H2O2. The three bidentate ethylenediamine ligands form three 5 membered chelate rings in the metal complex which leads to greater stability. The tris(ethylenediamine)cobalt(III) chloride complex has (as all octahedral metal complexes with three bidentate ligands) two enantiomers (Δ 'right-handed' and Λ 'left-handed'). This enantiomers can racemate if a rearrangement over a trigonal bipyramidal- or a square-based pyramidal intermediate takes place while one of the bidentate ligands donor atoms is uncoordinated (cf. Fig. 1)[5]. The dinosar ligand that is produced in a M template synthesis in the second part of the trigonal bipyramidal experiment is a cryptant ligand[2]. It also forms three 5-membered rings M in [Co(dinosar)]Br3. The stability of this M left-handed right-handed complex is even greater than the stability M of [Co(en3)][Cl]3 since all donor atoms sit in one molecule. This cage-like cryptand square-based pyramidal Fig. 1: Enantiomers and possibility of ligands like dinosar can be used to formrearrangement in an octahedral metal complex complexes with unstable metal centres[6]. with three bidentate ligands 2 Patrick Zwick Exp 5 3 Experimental part 3.1 Synthesis of tris(ethylenediamine)cobalt(III) chloride CoCl2*6H2 O H2O2 H2 N NH2 HCl EtOH, H2O, 0 °C, 1h H2 H2 N H2 N N Cl3 Co N N H2 H2 N H2 CoCl2·6H2O C2H8N2 HCl [Co(en)3]Cl3 1 2 3 4 6.00 g 4.51 mL 4.25 mL, 6M 2.09 g 25.0 mmol 67.5 mmol 25.5 mmol 7.61 mmol 1.0 eq. 2.7 eq. 1.0 eq. 30,44% CoCl2·6H2O (1, 6.00 g, 25.0 mmol, 1.0 eq.) was dissolved in H2O (17.5 mL). Ethylenediamine (2, 4.51 mL, 67.5 mmol, 2.7 eq.) and aqueous HCl (3, 6M, 4.35 mL, 25.5 mmol, 1.0 eq.) were added to H2O (12.5 mL) and cooled on ice. The aqueous CoCl2 solution was added to the diethylenamin solution and H2O2 (5 mL, 30%) was added to this mixture while it was constantly stirred. The mixture was placed on a heat plate and boiled gently until there was only 30 mL left. Concentrated HCl (30 mL) and ethanol (60 mL) were added to the mixture. The mixture was allowed to cool down to RT over 30 min. After the mixture was cooled on ice, the precipitate was collected by filtration. The solid was washed with ethanol (2 x 10 mL) and diethyl ether (2 x 10 mL). The solid was air dried to obtain the product (4, 2.09 g, 7.61 mmol, 30%, Lit[3]: 65 %) as yellow crystals. H-NMR (250 MHz, 298 K, DMSO-d6, δ/ppm): 5.90 – 5.59 (m, 6 H, 2), 5.48 – 5.17 (m, 6 H, 1 2), 2.82 – 2.55 (m, 6 H, 1), 2.54 – 2.44 (m, 6 H, 1). 1 H-NMR (250 MHz, 298 K, D2O, δ/ppm): 5.20 – 4.96 (m, 6 H, 2), 4.88 – 4.61 (m, 6 H, 2), 3.00 – 2.64 (m, 12 H, 1). 1a 1b H2 2a H H H N H2 N N H 2b Co Cl3 N N N H2 H2 H2 3 Patrick Zwick Exp 5 3.2 Synthesis of [Co(dinosar)]Br3 NO2 H2 H2 N H2 N N Co HN 1) H 2O, 40 °C, 1.5h O Cl3 CH 3NO2 Na 2CO3 *10H 2 O H N N N H 2 H 2 H2 HN NH Br 3 Co H 2) Acetic acid, HBr HN NH NH NO2 [Co(en)3]Cl3 Na2CO3·10H2O CH3NO2 CH2O [Co(dinosar)]Br3 5 6 7 8 9 1.81 g 4.05 g 5 mL 40 mL, 37 % 0.56 g 5.22 mmol 14.2 mmol 92.3 mmol 537 mmol 1.10 mmol 1.0 eq. 2.7 eq. 18 eq. 103 eq. 21,07% [Co(en)3]Cl3 (5, 1.81 g, 5.22 mmol, 1.0 eq.) and Na2CO3·10H2O (6, 4.05 g, 14.2 mmol, 2.7 eq.) were dissolved in water (90 mL). Acetonitrile (7, 5 mL, 92.3 mmol, 18 eq.) and formaldehyde (8, 47 %, 40 mL, 537 mmol, 103 eq.) were added and the mixture was briefly stirred. The mixture was heated to 40 °C for 1.5 h without stirring. The solution was stirred with a glass rod to induce crystalisation. The solution was cooled on ice and the precipitate was collected by filtration. The solid was dissolved with hot acetic acid (1M, 30 mL) and concentrated HBr (15 mL) was added immediately to the yellow solution. The solution was allowed to cool down to RT. The precipitate was collected by filtration, washed with MeOH / H2O (1:1, 1 x 15 mL), MeOH (1 x 15 mL), diethyl ether (1 x 15 mL) and was air dried to obtain the product (9, 0.56 g, 1.10 mmol, 21 %, Lit:[1]: 55 % ) as orange solid. H-NMR (250 MHz, 298 K, D2O, δ/ppm): 3.88 (dd, 2JHH = 13.7, 1.7 Hz 6 H, 1), 3.57 (dd, 1 2 JBH = 11.7, 9.1 Hz, 6 H, 2), 3.36 (dd, 2JHH = 13.9, 2.0 Hz, 6 H, 1), 2.94 (dd, 2JBH = 11.7, 9.2 Hz, 6 H, 2). 1b 1a NO2 H H 2a H HN NH HN H 2b Co HN NH Br3 NH NO2 4 Patrick Zwick Exp 5 4 Discussion A CoCl2*6H2 O H2O2 H2 N 1 NH2 HCl 2 EtOH, H2O, 0 °C, 1h 3 H2 H2 N H2 N N Cl3 Co N N H2 H2 N H2 4 NO2 H2 H2 N H2 N N B Co HN O Cl3 Na2CO3 *10H2 O CH3NO2 6 7 N N N H2 H2 H2 5 1) H2O, 40 °C, 1.5h 8 NH Br 3 Co H 2) Acetic acid, HBr H HN HN NH NH NO2 9 The synthesis (A) of tris(ethylenediamine)cobalt(III) chloride (4) was done as described in the reference[3]. Three ethylenediamine ligands were coordinated to a cobalt atom to form [Co(en)3]Cl2 which was then oxidised by H2O2 to form the product [Co(en)3]Cl3 (4). For the interpretation of the 1H-NMR spectra the protons had to be separated in two groups: homotope and diastereotope. It was shown that the protons bonded to the nitrogen atoms (1) and the protons bonded to cabon atoms (2) are diastereotope. So all protons are diastereotope. This comes by the chirality since the ethylendiamine ligands can coordinate to the metal centre forming Δ or Λ isomers. The DMSO-d6 spectrum shows four multiplets with integrals of each 6 protons due to the diastereotope protons. The D2O shows only three multiplets because the signals of 1a and 1b comes out as one signal with an integral of 12 protons. The integrals of the reference peak overlapped signals could be worked out by a comparison of the two spectra which actually was the reason for measuring the product in two solvents. The multiplets at 2.82 – 2.55 ppm and 2.54 – 2.44 ppm in The DMSO-d6 spectrum respectively 3.00 – 2.64 ppm in the D2O spectrum belongs to the diastereotope protons bonded to the nitrogen atoms (1a + 1b). The other two multiplets belong to the diastereotope protons (2a + 2b). The signals could not been differentiated to the protons (2a) and (2b) respectively (1a) and (1b) because there is to less information with only these 1H-NMR spectra. The non binomial triplet at 7.23 ppm belongs to some free protonated ethylenediamines which are not coordinated to the metal. The synthesis (B) of [Co(dinosar)]Br3 (9) also went well. This experimental part (B) was done as described in the reference[1]. For the interpreatation of the 1H-NMR spectrum, the protons 5 Patrick Zwick Exp 5 had to be separated in diastereotope an homotope again. It was shown that all protons bonded to a carbon atom (1a, 1b, 2a, 2b) are diastereotope and the protons bonded to a nitrogen atom do not even give a signal since they are exchanged by deuterium quickly. The 1H-NMR spectrum shows four doublets of doublets. The literature[1,2] showed that the peak at -11 ppm belongs to the former carbon atoms of ethylenedyamine and the peak at -15 ppm belongs to the bridging carbon atoms. The peak at 22 ppm in the HMQC spectrum belongs to the carbon carrying the nitro groups since it does not show any proton correlation. The proton signals at 3.88 ppm and 3.36 ppm (1a and 1b) correlate with the carbon signal at -11 ppm in the HMQC spectrum. This correlation shows that this protons sit at the bridging carbon atoms. The proton signals at 3.57 ppm and 2.94 ppm (2a and 2b) correlate with the carbon peak at -15 ppm in the HMQC spectrum. Therefore this protons sit at the former carbon atoms of ethylendiamine. The COSY spectrum shows that the proton signals at 3.88 ppm and 3.36 ppm (1a and 1b) are correlating and that the proton signals at 3.57 ppm and 2.94 ppm (2a and 2b) are correlating. This information shows that the diastereotope protons that sit on the same carbon atom are coupling to each other. The measured coupling constants confirm that theory since the coupling constants of the signals at 3.88 ppm and 3.36 ppm (1a and 1b) are the same and the coupling constants of the signals at 3.57 ppm and 2.94 ppm (2a and 2b) are the same, too. The signals of the diastereotope protons (1a, 1b and 2a, 2b) could not be differentiated with this spectrum. 5 Conclusion The aim of the experiment was reached. The synthesis of tris(ethylendiamine)cobalt(III) chloride and the conversion of the ligand to dinosar to build the final product [Co(dinosar)]Br3 went well. The purity of the products were proved by 1H-NMR spectroscopy and the data was discussed. All questions were answered and attached. 6 References [1] Harrowfield et al., J. Chem. Educ., 1985, 62, 804. [2] C. E. Housecroft, Task Sheet Experiment 5, 2014, 2 – 3. [3] Krause et al., J. Chem. Educ., 1976, 53, 667. [4] C. E. Housecroft, A. G. Sharpe, Inorganic Chemistry, Pearson, Harlow, 2012, 744 – 756. 6 Patrick Zwick Exp 5 [5] C. E. Housecroft, A. G. Sharpe, Inorganic Chemistry, Pearson, Harlow, 2012, 991 [6] Geue et al., J. Am. Chem. Soc., 1984, 106, 5478. 7 Answers to the questions 7.1 The reaction to make [Co(dinosar)]3+ is an example of a template synhtesis. Explain what this means. When the reactants are hold together in a template, so that a combination of them is allowed without many side reactions, it is called a template synthesis. In the specific case of this synthesis it was the NH2 groups of ethylenediamine that are coordinated by the cobalt centre close to each other in the tris(ethylenediamnie)cobalt(III) chloride template that react with nitromethane and formaldehyde to give the dinosar ligand in the final product. 7.2 Explain why the stability of the following complexes decrease in the order: [Co(dinosar)]3+ > [Co(en)3]3+ > [Co(NH3)6]3+ The dinosar and the ethylenediamine ligands form chelating rings in the metal complex. Therefore this complexes are more stable than the ammonio complex since this ligand does not chelate at all. The complex with the dinosar ligand is more stable than the tris(ethylendiamine)cobalt complex because all six coordinated groups sit in the same molecule instead of three molecules as in [Co(en)3]3+. The dinosar ligand is quite inflexible and therefore more immutable in contrast to ethylenediamine. This effect also decreases from [Co(en)3]3+ to [Co(NH3)]3+. This is an entropie effect since e.g. six molecules get free but only three molecules get bonded to the complex in the ligand exchange from [Co(NH 3)]3+ to [Co(en)3]3+. 7.3 What types of isomers could the following compounds show? Not all complexes possess isomers. Draw the structures of all isomers and give names that tell the isomers apart (e.g. cis and trans). - octahedral [Rh(ox)3]3- - square planar [PtBr2(NMe3)2] - octahedral [TiCl3(THF)3] - octahedral [Ir(acac)3] - square planar [Rh(CO)(PPh3)2Cl] - octahedral [Ru(bpy)3]2+ - octahedral [Ru(phen)2Cl2] - tetrahedral [CoCl2Br2]27 Patrick Zwick Exp 5 O O O O O O O O O O O O O Rh 3 O 3 Rh O O O O O O O Br O Br O O Δ Λ O Cl Cl Ti Ti O O Me3 N NMe3 Br Cl O Cl O Pt Br NMe3 trans O O Ir O O NMe3 cis O Cl Pt O O O O O Ir O O O Cl fac mer Δ Λ 2 2 N N N N N N N N OC Cl Rh Ph3P OC PPh3 Ph3 P cis N Ru N PPh 3 Δ N N Cl Cl Cl Ru Λ N N N N N N Ru Cl cis + Δ N cis + Λ 2 Cl Cl Co Cl trans N N N Cl trans N Cl Rh N Ru Ru Br Br no isomers 8. Spectra The experimental spectra are attached to this protocol as followed: 8.1 250 MHz 1H-NMR spectrum of [Co(en)3]Cl3 in DMSO-d6 (p. 9). 8.2 250 MHz 1H-NMR spectrum of [Co(en)3]Cl3 in D2O (p. 10). 8.3 250 MHz 1H-NMR spectrum of [Co(dinosar)]Br3 in D2O (p. 11). 8 5500 5.32 5.74 6000 2.82 2.69 2.54 2.50 2.44 5.90 5.74 5.59 5.48 5.32 5.17 ac_praktI_.2900.1.fid PZ Exp5 [Co(en)2][(Cl)]3 in dmso-d6 400 5000 5.4 6.00 5.6 5.5 f1 (ppm) 5.3 200 4500 100 4000 0 3500 5.2 2.50 5.7 2.54 5.8 2.69 5.9 6.00 300 3000 1000 2500 800 2000 600 400 1500 200 2.75 2.70 16.13 2.80 1000 0 2.65 2.60 f1 (ppm) 2.55 2.50 500 2.45 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 16.13 6.00 6.00 0 5.5 5.0 f1 (ppm) 4.5 4.0 3.5 3.0 2.5 -500 2.0 1.5 1.0 0.5 0.0 -0.5 2.64 3.00 5.20 5.08 4.96 4.88 4.61 3000 2800 4.61 4.88 4.96 5.08 5.20 ac_praktI_.2892.1.fid 300 2600 2400 200 2200 100 4.9 4.8 f1 (ppm) 4.7 1800 4.6 2.64 5.0 15.22 5.1 0 3.00 5.2 6.00 2000 1600 400 1400 300 1200 200 1000 100 800 12.02 0 600 3.00 2.95 2.90 2.85 2.80 2.75 2.70 2.65 f1 (ppm) 400 200 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 f1 (ppm) -200 12.02 15.22 6.00 0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 -1.0 2.99 2.95 2.92 2.88 3.39 3.38 3.34 3.33 3.63 3.59 3.56 3.52 3.92 3.92 3.87 3.86 3.92 3.92 3.87 3.86 3.63 3.59 3.56 3.52 3.39 3.38 3.34 3.33 2.99 2.95 2.92 2.88 ac_praktI_.2916.1.fid PZ exp5 [Co(dinosar)][Br]3 in D2O 1H NMR (250 MHz, Deuterium Oxide) δ 3.88 (dd, J = 13.7, 1.7 Hz, 7H), 3.57 (dd, J = 11.7, 9.1 Hz, 6H), 3.36 (dd, J = 13.9, 2.0 Hz, 6H), 2.94 (dd, J = 11.7, 9.2 Hz, 6H). 3600 3400 3200 1400 3000 1200 2800 2600 1000 2400 800 2200 600 2000 B (dd) 3.57 A (dd) 3.88 400 1800 D (dd) 2.94 1600 C (dd) 3.36 200 1400 1200 3.9 3.8 3.7 3.6 3.5 1000 6.00 6.03 6.01 6.00 0 3.4 3.3 f1 (ppm) 3.2 3.1 3.0 800 2.9 600 400 12.0 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 f1 (ppm) 4.5 4.0 3.5 0 6.00 6.00 6.00 6.99 6.01 5.83 6.03 6.41 200 3.0 -200 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 -1.0