SIC3021 Practical of Inorganic Chemistry III 2024 PDF

LABORATORY MANUAL SIC3021 PRACTICAL OF INORGANIC CHEMISTRY III 1  Emergency Telephone Numbers Further information in the details of the safety and health practice in the Universiti Malaya can be found at: Occupational Safety &...

LABORATORY MANUAL SIC3021 PRACTICAL OF INORGANIC CHEMISTRY III 1  Emergency Telephone Numbers Further information in the details of the safety and health practice in the Universiti Malaya can be found at: Occupational Safety & Universiti MalayaSafety Health and Environment Handbook (OSHE), Universiti Malaya The University has a statutory obligation to comply with the safety requirements and you, as a student, have a duty to abide by the regulations. The following notes are to guide you in good laboratory practice and to familiarize yourself with the safety aspects of your laboratory work. Emergency Telephone Numbers: National Emergency Number 999 (Mobile phone, dial 112) Universiti Malaya Security Office +603 7967 7070 Universiti Malaya Medical Centre (UMMC) +603 7949 2892 Emergency Department Universiti Malaya Students’ Health Clinic +603 7967 6445 Occupational Safety & Health and Environment +603 7967 6597 (OSHE) Department of Chemistry Office +603 7967 4204 Pantai Fire Station (Jalan Pantai Baru) +603 2282 4444 Pantai Police Station (Jalan Pantai Baru) +603 2282 2222 (The numbers given above are working telephone numbers, as of 5th October 2022) 2  CONTENTS NO. EXPERIMENT PAGE 1 SYNTHESIS OF NICKEL COMPLEX WITH MIXED 4 LIGAND SYSTEM 2 THE PREPARATION AND CHARACTERIZATION OF 6 MESITYLENETRICARBONYLMOLYBDENUM(0) 3 MAGNETIC SUSCEPTIBILITY 8 4 ELECTRONIC SPECTRA OF NICKEL(II) COMPLEXES 18 (A d8 SYSTEM) 3 Experiment 1 Practical of Inorganic Chemistry III SYNTHESIS OF NICKEL COMPLEX WITH MIXED LIGAND SYSTEM INTRODUCTION Hydrazones are prepared from the condensation of hydrazides with aliphatic or aromatic aldehyde- ketones. These compounds form metal complexes, featuring nitrogen, and oxygen donor atoms, showcasing intriguing stereochemical, electrochemical, and electronic properties. They have diverse applications across biological, inorganic, analytical, and catalytic processes. On the other hand, phosphine-based compounds find broad pharmacological utility, serving as antiviral, antioxidant, antifungal, anticancerogenic, antibacterial, and antitumor agents. In the realm of anticancer drug research, the stabilization of nickel(II) and palladium(II) complexes with bulky ligands like triphenylphosphine can prevent the formation of highly reactive species, enabling interactions with pharmacological targets such as DNA. Additionally, tertiary phosphine complexes of nickel, palladium, and platinum play a significant role in catalysis as homogeneous catalysts. Notably, nickel catalysis is particularly appealing due to its cost-effectiveness. LEARNING OUTCOME Students will be able to prepare and characterize mixed ligand metal complexes. METHODOLOGY a) Synthesis of dichlorobis(triphenylphosphino)nickel(II), NiCl2(PPh3)2 NOTE: PLEASE HANDLE GLACIAL ACETIC ACID WITH CARE AND DO IT IN THE FUME CUPBOARD In a round-bottom flask, melt 5.25 g of triphenylphosphine in a water bath. Weigh 2.38 g of NiCl2.6H2O and add 50 mL of glacial acetic acid to the nickel salt. A slurry will form. Pour the slurry into the stirring molten triphenylphosphine. Remove the flask from the bath and continue stirring at room temperature for 3 hours. Filter the product, wash with about 20 mL of hot glacial acetic acid to remove traces of free triphenylphosphine and keep in a vacuum desiccator. Run IR for the prepared compound. b) Synthesis of Schiff base, benzoic acid-(2-hydroxy-benzylidene)-hydrazide Dissolve 0.136 g of benzoylhydrazide in 30 mL of ethanol and pour the solution into a 250 mL round bottom flask. Dissolve 0.122 g of salicyldehyde in 20 mL of ethanol. While stirring the benzoylhydrazide solution, pour salicyldehyde into the first solution. Reflux the mixture for 4.5 hours. Then, cool the reaction mixture to room temperature. If solids do not appear, dry off the solvent on a rotary evaporator until yellow solid is seen. Pour water into the round bottom flask, swirl several times and filter the solid. Recrystallize the solid from hot ethanol to afford the pure ligand. Analyze the prepared Schiff base on IR and 1H NMR (in DMSO-d6). 4  c) Synthesis of organophosphine nickel(II) Schiff base complex, NiCl2(PPh3)2 + Schiff base Reflux NiCl2(PPh3)2 (0.653 g) with the Schiff base (0.226 g) in 40 mL of methanol in the presence of an equivalent amount of KOH for 5 hours. Cool the reaction mixture to room temperature. Filter the precipitate, wash with methanol and dry in a vacuum desiccator. Recrystallize to obtain the red crystal in dichloromethane. Run IR for the prepared compound. QUESTIONS 1. Rationalize the utilization of molten PPh3 over its solution. State the nature of the PPh3 in most organic solvents. 2. Explain the denticity of each ligand (PPh3 and Schiff base) towards formation of nickel complexes. Predict the possible geometries in your explanation. 3. Propose a mechanism for the nickel complex formation with the synthesized mixed ligands that is obtained in this experiment (proof from the spectroscopic data). REFERENCES 1. H.A. Tayim, A. Bouldoukian, F. Awad, J. Inorg. Nucl. Chem., 1970, 32, p 3799-3803. 2. P. Krishnamoorthy, P. Sathyadevi, P.T. Muthiah, N. Dharmaraj, RSC Adv., 2012, 2, p 12190– 12203. 5  Experiment 2 Practical of Inorganic Chemistry III THE PREPARATION AND CHARACTERIZATION OF MESITYLENETRICARBONYLMOLYBDENUM(0) INTRODUCTION Isolated organometallic compounds of the transition elements have been known for a long time(e.g., Zeize’s salt – 1827). However, it was not until the 1950’s, following the accidental discovery of ferrocene, that the organometallic chemistry of the transition metals became a major area of inorganic research. Perhaps the most versatile starting materials for the laboratory synthesis of transition metal organometallic compounds are the metal carbonyls. In this experiment, molybdenum hexacarbonyl is reacted directly with an organic aromatic (mesitylene). In general, the reaction can be represented as: Ar + Mo(CO)6 → ArMo(CO)3 + 3CO↑ LEARNING OUTCOME Students will be able to prepare and characterize air- and moisture-sensitive compounds. METHODOLOGY NOTE: THIS PREPARATION MUST BE PERFORMED IN A FUME HOOD. METAL CARBONYLS ARE VERY TOXIC. Assemble the apparatus as shown in the diagram using a 50 mL two-neck round bottom flask and a simple reflux condenser (water need not be circulated through the condenser: air cooling is sufficient). Add 1.8 g Mo(CO)6 to the flask followed by 10 mL of mesitylene, 10 mL decalin and 5- 10 mL of toluene or hexane (This facilitates the sublimed Mo(CO)6 to returnback to the reaction mixture during refluxing at 186oC).Flush the apparatus with a moderate stream of nitrogen for about 5 min. After the nitrogen flow is turned off and the stopcock closed, bring the mixture to a moderate boil with the heating mantle. Reflux for 2-3 hours (yield improves with stirring), then turn off the heat and immediately flush with nitrogen to prevent the mineral oil in the bubbler from being sucked back into the reaction vessel. 6 Allow the reaction mixture to cool to room temperature, then filter using a Buchner funnel. For purification, dissolve the filtered crude product in a minimum amount of CH2Cl2 (FUME CUPBOARD), pass the solution through a medium frit loaded with ~2-3 cm Celite (aspirator pump). Transfer the filtrate to a rotary evaporator and evacuate to dryness. Remove the resulting fine lemon-colored crystals with a spatula and weigh. Further purification of the recrystallized product may be achieved by vacuum sublimation (100ºC, high vacuum). (a) Characterization i. IR Spectrum. Record the IR spectrum of the product over the whole range and assign the important bands. Also record the IR spectrum of the compound in solution in CHCl3 in the region 1800-2000 cm-1. Comment on the differences between the two spectra in this region. ii. NMR Spectrum. Prepare 0.5 mL of a saturated solution of the product in the specially purified CHCI3 (obtainable from the Laboratory Assistant) and record the NMR spectrum. Comment on the spectrum particularly the information it provides about the structure and bonding of the complex. Explain why free mesitylene shows two peaks at 2.25 and 6.78 ppm (vs. TMS in CDCI3 of relative intensity 9:3). QUESTIONS 1. Use spectral data to determine the structure of the complex. 2. To what symmetry group does the complex belong? 3. Discuss the differences in the stretching frequencies of CO in Mo(CO)6 and the product. REFERENCES 1. G. E. Coates, M. L. H. Green and K. Wade: Organometallic Compounds Vol. 11. (The Transition Elements) 1968. 2. B. Nicholls and M. C. Whiting, J. Chem. Soc., (1959) 551. 3. F. A. Cotton, G. Wilkinson, C. A. Murillo, and. M. Bochmann., Advanced Inorganic Chemistry, 6th Edition, Wiley-Interscience: New York, 1999. 4. R. J. Angelici, J. Chem. Ed., 45 (1968) 119. 7 Experiment 3 Practical of Inorganic Chemistry III MAGNETIC SUSCEPTIBILITY INTRODUCTION Magnetic susceptibility is the degree of magnetization of a material in response to an applied magnetic field. If magnetic susceptibility is positive, then the material can be paramagnetic, ferromagnetic, ferrimagnetic, or antiferromagnetic. Measurements of magnetic properties have been used to characterize a wide range of systems from oxygen, metallic alloys, solid state materials, and coordination complexes containing metals. Most organic and main group element compounds have all the electrons paired and these are diamagnetic molecules with very small magnetic moments. All the transition metals have at least one oxidation state with an incomplete d subshell. Magnetic measurements, particularly for the first-row transition elements, give information about the number of unpaired electrons. The number of unpaired electrons provides information about the oxidation state and electron configuration. The aim of the experiment is (1) to acquaint the student with two of the experimental techniques involved in magnetochemical measurements, viz, the Gouy method for solids and the Evans’ method for solutions, and (2) to examine the magnetic behavior of a complex in the solid and solution state, and to gain information about stereochemical changes if any.The latest techniques include SQUID, (superconducting quantum interference device) a very sensitive magnetometer used to measure extremely subtle magnetic fields, based on superconducting loops containing Josephson junctions. Commercial SQUID magnetometers are available for temperatures between 300 mK and 400 kelvins, and magnetic fields up to 7 tesla. LEARNING OUTCOME Students will be able to correlate the magnetism of a metal complex with its electronic configuration and ligand strength. METHODOLOGY To a stirred solution of 4.0 g of manganese chloride (MnCl2.4H2O) and 10.2 g of sodium acetate (CH3COONa.3H2O) in water (150 mL) slowly add acetylacetone (18.8 mL). Follow by adding slowly, with stirring, a solution of potassium permanganate (0.80 g in 40 mL of water) and a few minutes later in small amounts, a solution of sodium acetate trihydrate (10.0 g in 40 mL of water). Heat on a water bath for 20 minutes at about 60°C, cool in ice-cold water and filter off the dark solid. Wash the product with ice- cold water, and dry in a vacuum desiccator over anhydrous calcium sulphate. Dissolve the dry chelate in warm toluene (20 mL), filter and re-precipitate the complex by cooling and adding petroleum ether (40-60°C) (about 75 mL). Dry in a vacuum desiccator. Calculate the percentage yield. 8  a) Measure the paramagnetic susceptibility of the complex as a solid (see Appendix 3A, p. 9-12). b) Run the NMR spectrum of a CHCl3 solution containing a known concentration of the complex (ca. 0.01 g/mL). Insert a capillary tube containing pure CHCl3 as external reference (see Appendix 3B). c) From the frequency separation of the proton resonance in the CHCl3, solution relative to the external reference of pure CHCl3, calculate the magnetic susceptibility of the complex in solution. Notes: NMR spectra of these solvent mixtures are provided. See Appendix 3C for the calculation of the mass susceptibility χoof these solvent mixtures. Diamagnetic correction of solvent: The frequency separation for the methyl resonance in the solvent mixture relative to the pure toluene capillary is a measure of the solvent susceptibility, hence this frequency shift is equivalent to a diamagnetic correction and must therefore be subtracted from the overall frequency separation measured for the metal complex. From the corrected frequency separation calculate ꭕg, ꭕM, and ꭕMcorr (corrected for the diamagnetism of the ligands, See Appendix 3D), and hence the solution Bohr Magneton Number, μeff. (seeAppendix 3B). QUESTIONS 1) Describe under what conditions spin-only formula will be useful to calculate µ of the complexes (Appendix 3A). 2) What conditions should be satisfied by a complex whose magnetic susceptibility we wishto determine in solution? Are there any restrictions to the type of reference solvent we could use? On the basis of your answer, discuss the feasibility of determining μeff for thefollowing: a. Fe(CN)63- in aqueous solution using the tert-butanol methyl resonance as reference. b. CuCl 42- in pyridine using the toluene methyl resonance as reference. c. Ni(DMG)2 in benzene using the methyl resonance of 4-methylpyridine as reference (DMG = dimethylglyoxime). REFERENCES 1. F. A. Cotton, G. Wilkinson, C. A. Murillo, and. M. Bochmann., Advanced Inorganic Chemistry, 6th Edition, Wiley-Interscience: New York, 1999. 2. M. Greenaway and L. E. Trail. J. Chem. Educ., (1983), 60 (8), p 681. 9 APPENDIX 3A THE MEASUREMENT OF MAGNETIC SUSCEPTIBILITY THEORY AND DEFINITIONS Magnetic susceptibility is defined as the ratio of the intensity of magnetism induced in a substance to the magnetizing force or intensity of field to which it is subjected. It provides important electronic structural information of the transition and rare earth metal complexes. Traditionally, measurement of magnetic susceptibility has been made using the Gouy and the Faraday methods. The original instruments were originally made from conventional laboratory balances and large permanent magnets. The magnets were brought towards the sample and the positive or negative change of apparent weight was noted. The balances and sample holder were free of ferromagnetic materials. The systems that evolved were very large relying on heavy magnets, fixed in position, and a moving sample. The late Professor Evans of Imperial College London introduced an innovative step to the measurement. Instead of measuring the apparent weight loss or gain of a suspended sample, the force acting upon a suspended magnet was detected, thereby turning the method on its head. The advantage realized by this step led to the development of the light and inexpensive magnetic susceptibility balance, which is the MSB-MKI. The model used in our laboratory is MSB-AUTO which has many improved features, and which still relies on the advantage first obtained by Professor Evans. The three most common ways that magnetic susceptibility values are expressed are with reference to the volume of sample, the weight of sample, and the moles of sample. These terms are commonly referred to as volume susceptibility, mass susceptibility, and molar susceptibility. The equations relating these terms are provided below: VOLUME SUSCEPTIBILITY The volume susceptibility, ꭕv designated is expressed by the following formula: where I is the intensity of magnetism included in the substance and H is the intensityof the applied external magnetic field The volume susceptibility can be quite variable due to changes in the density of the substance, particularly when the sample is a gas or solid. The mass susceptibility, χg, introduces a densityfactor in the following manner: 10 MASS SUSCEPTIBILITY ꭕv ꭕg = d where d is the density of the substance, Note that ꭕg has units of reciprocal density, cm3 g MOLAR SUSCEPTIBILITY The most common way of reporting a magnetic susceptibility value in the literature is by molar susceptibility, designated as χM. The relationship of molar susceptibility to mass susceptibility is shown below: χM= χg x MW where MW is the molecular weight of the substance. The χM is the best value to use when comparing different materials qualitatively or assessing the potential of a quantitative applications since the value of the term is not subjected to variations due to the method of measurement or to sample density. Since the Auto, like other methods, measures Volume Susceptibility and the literature is quotedin Molar Susceptibility, the conversion between the two values is quite common in magneto chemical studies. The initial step in the conversion, that is obtaining a χg value from χν, is donewithin the Auto provided the length and weight of the sample are known and can be entered into the unit. Calculation of magnetic moment The molar susceptibility obtained has to be corrected for the inherent diamagnetic contribution (χdia) from the ligands and metal ions using the table of Pascal’s constants. i.e. χ Μcorr = χ exp - χdia The relationship between molar susceptibility and effective magnetic moment, µeff is It can also be shown that the effective magnetic moment, µeff is given by, 11 µeff = √ n(n+2) B.M. [Note: A system obeying Curie law would have no or negligible orbital contribution towards the magnetic moment]. For the details on the operation of the MSB-AUTO magnetobalance, please refer to the operating manual. Cleaning and storage of sample tube [Note: The sample tube used in this magnetobalance is a high precision tube made of silica. It is expensive and should be treated with care!] The good maintenance of the sample tubes is essential for good results. Sample tubes can be cleaned with conventional detergents and/or organic solvents, depending on the nature of their sample. In difficult cases, strong acids, viz. HCl or HNO3 may be required. Pipe cleaners have proven to be a useful tool. Similarly, an aerosol can of ethylene dichloride, supplied with a plastic capillary spout (available for degreasing electronic components) has proven invaluablein removing oil from the tubes when analyzing for wear metals. The tube should be stored in a dust-free environment and its susceptibility should be measuredbefore introducing a sample. As a final precaution, the outside of the tube should be wiped witha dust free wiper just prior to introducing it to the balance, particularly if it has been allowed to lay on the bench. Packing sample into the tube The tube is packed as follows. The solid to be measured is ground to a fine powder in a mortar and pestle. HgCo(NCS)4 forms very fine crystals and can usually be used without grinding. Note that the greatest source of error in Gouy measurements is in homogeneous packing. It is essential that an effective routine for the packing of the powder into the tube is developed and adhered to. Good packing requires time and patience. A small amount of the compound is picked up from the mortar, placed in the flares mouth of thetube, and tapped to the bottom of the tube. The closed end of the tube is tapped for about a minute on two sheets of filter paper on a wooden bench. (See a demonstrator about this). This process is continued until the tube is filled to the mark - make sure that the sample does not pack down with further tapping. Wipe away any excess compound from the mouth of the tubeto remove excess moisture. 12 Standard to calibrate the balance Several standards can be used for checking the calibration of the balance. Perhaps one of the most reliable trouble free standard is water (106 χg = - 0.720), since it is readily available in pure form. A singly distilled water sample should suffice. HgCo(SCN)4 (105 χg = +1.644 at 20oC) is considered one of the best solid standards. At other temperature, use the relation dχg = -0.05 x 10-6 cgs/K dτ to obtain the exact χg value. The ethylenediamine salts of nickel, Ni (en)3 S2O3 (105 χg = +1.104) is also a useful secondarystandard. Many solid samples of paramagnetic substances, if properly dried and ground and packed,usually give within 2% of their literature value. If it is necessary to recalibrate, please refer to Section 5.2 of the original operator’s manual. 13 APPENDIX 3B EVANS' METHOD FOR MAGNETIC SUSCEPTIBILITIES (Extracted from J. Chem. Ed., 46, 1969, 167) This method is based on the principle that the position of a given proton resonance in the spectrum of a molecule is dependent on the bulk susceptibility of the medium in which the molecule is found. The shift of a proton resonance line of an inert substance due to the presence of paramagnetic ions is given by the theoretical expressions5. (1) where δν is the shift, νo is the applied field, χv is he volume susceptibility of the solution containing paramagnetic ions, and χ’ is the volume susceptibility of the reference solution. Forexample, if an aqueous solution of paramagnetic substance with 3% of t-butyl alcohol as aninert reference substance is placed in the inner tube of a concentric cell, and an identical solution without the paramagnetic substance is placed in the annular section of the cell, two resonance lines will usually be obtained for the methyl protons of the t-butyl alcohol due to the difference in the volume susceptibilities of the solutions. This is in accord 5 with eqn. (1). The gram susceptibility, χg of the dissolved substance is given by the expression. (2) where δν is the frequency separation between the two lines in cycles/sec, νo is the frequencyat which the 3 proton resonances are being studied in cycles/sec, m is the mass of substance contained in 1 cm of solution, χo is the mass (gram) susceptibility of the solvent (-0.72 x 10-6 cc g-1 for dilute t-butyl alcohol solutions), do is the density of the solvent, and ds that of the solution. For highly paramagnetic substances, the last term can often be neglected5. The molarsusceptibility, the effective magnetic moment and the "spin only" number of unpaired electrons may be calculated by the same procedure used for the Gouy measurements (See Appendix 3A). 14 APPENDIX 3C MASS SUSCEPTIBIILITY OF SOLVENT MIXTURES For a mixture of non-interacting components, Use of this equation and the table below would enable us to calculate the mass susceptibility ofthe solvent mixtures used in this experiment. TABLE SOLVENT MASS SUSCEPTIBILITY DENSITY χo x 10-6 (c.g.s. or Gaussian units) (gcm-3) Benzene -0.702 0.876 Toluene -0.7176 0.863 Pyridine -0.622 0.981 Chloroform -0.497 1.49 15 APPENDIX 3D DIAMAGNETIC CORRECTIONS When making diamagnetic corrections, an addition to the measured value is made for eachatom present in the molecule. The relevant diamagnetic susceptibilities are given in the table below: TABLE DIAMAGNETIC CORRECTIONS (c.g.s. units) (All values x 10-6/g atom) Element / ion Diamagnetic correction values H -2.93 C -6.00 C (aromatic) 6.24 O (alcohol) -4.61 O (carbonyl) +1.73 N (C=N) -5.57 Mn3+ -10.0 Ni2+ -12.8 16 APPENDIX 3E Consider at equilibrium we have n mol of each of the square planar and tetrahedral forms present,each with a MOLAR magnetic susceptibility of χM, then for the equilibrium: We can write, But since Now i.e., µeff2 = constant x χM at a given temperature, thus we can write Assuming that the maximum Bohr Magneton Number, µeff, for a tetrahedral [Ni(salen)2] complexin solution is about 3.3 (See Reference 1), it is then possible to obtain an expression for K which can be solved using the observed value for µeff, (obs) which you calculate from your data. 17 Experiment 4 Practical of Inorganic Chemistry III ELECTRONIC SPECTRA OF NICKEL(II) COMPLEXES, A d8 SYSTEM INTRODUCTION Tanabe-Sugano (TS) diagrams are correlation diagrams that depict energies of electronic states of the complexes (or Terms) as a function of the strength of the ligand field. Ligand field is the electric field that is created by the ligands around a metal ion when the complex is formed. The strength of the ligand field is measured by the parameter Dq, which is related to the octahedral crystal field splitting by 10Dq = ∆o. The energy of an electronic state in a TS diagram is denoted by E. Figure 1 shows d8 diagram. In the diagrams the term energies, E, are expressed as E/B and plotted against ∆O/B, where B is the Racah parameter. E/B Figure 1: TS diagram for d8 system (Shiver & Atkins, 2010). 18 The lowest energy term is set to 0, and all other states are defined relative to the ground state. The terms for d8 configuration include 3F, 1D, 3P, 1G and 1S. Since the 3F is the ground state we will assume that the two transitions observed in the absorption spectrum arise from the 3F and 3P states. (Note that spin allowed transitions (ΔS = 0) will be the most intense). Electron-electron repulsion splits the term into components with different energies as shown in Figure 2. Figure 2: Splitting of free-ion terms in octahedral field (Shriver & Atkins, 2010). The purpose of the experiment is to extract the value of the ligand-field splitting parameters from the electronic absorption spectrum of a complex with more than one d electron, when electron- electron repulsions are important. The strategy involves fitting the observed transitions (UV visible spectra) to the correlation lines in a Tanabe-Sugano diagram and identifying the values of ∆O and B. LEARNING OUTCOME Students will be able to explain the effect of ligand strength on the electronic spectra of metal complex by using the Tanabe-Sugano diagram. METHODOLOGY Preparation of Nickel(II) Complexes: *obtain complex 1 from the lab assistant and prepare complexes 2, 3, 4 and 5. 1. [Ni(bipy)3]SO4.6H2O Warm an aqueous solution containing 15 g of 2,2-bipyridyl and 6 g of NiCI2.6H2O. Cool and filter. Dissolve 5 g of the chloride and add 5 cm3 of a 1 M solution of Na2SO4. Ni(bipy)3SO4 crystallizes out. Reference: J. Chem. Soc., 1971 (A), 1637, 1640. 19  2. [Ni(en)3]Cl2.2H2O Add 3.0 mL of 70% aqueous ethylenediamine tt a solution of 2.38 g (0.01 mol) NiCl2.6H2O in 100 mL of water. Filter the purple solution to remove the small amount of anhydrous iron oxide which precipitates and is then evaporated to a volume of 40 to 50 mL on a steam bath. Add two drops of ethylenediamine, and cool the solution in an ice bath. Collect the orchid-colored crystals by suction, wash twice with 95% ethanol, and air-dried. The yield is ca. 2.86 g (80%). Several more grams may be recovered from the mother liquor by adding ethanol and cooling. 3. [Ni(NH3)6]Cl2 Dissolve 2 g NiCl2.6H2O in 3 mL water. Add 6 mL NH3 and heat for 10 min. but do not boil. (Use fume- hood.) Then cool the solution in an ice bath and slowly add 6 mL ethanol while stirring. Filter with suction. Wash the precipitate with ethanol and acetone; and air-dried. Record your yield. 4. [Ni(DMSO)6]Cl2 Dissolve 2 g of NiCl2.6H2O in minimum ethanol (approx. 3-4 mL) and mix with the same volume of ether, followed by 4.0 mL of dimethylsulfoxide (DMSO). Cool the mixture in the refrigerator until crystals are formed. Filter and dry in a vacuum desiccator. Reference: J. Inorg. Nucl. Chem., (1961), 16, 219. 5. K4[Ni(NCS)6].4H2O Dissolve 0.01 mole of Ni(SO4).7H2O and KSCN in water (Work out appropriate amounts). Evaporate to dryness. Extract with absolute alcohol. Filter off the K2SO4 and concentrate on the alcoholic solution to obtain the complex. Reference: Inorg. Chem. 4 (1965), 715, 823. Prepare solutions as described in Table 1. Table 1: Solutions of complexes to be prepared. Complex Solvent and Blank Concentration 1. [Ni(bipy)3]SO4.6H2O Water 0.05 M 2. [Ni(en)3]Cl2.2H2O 20% en 0.05 M 3. [Ni(NH3)6]Cl2 Aqueous NH3 0.05 M 4. [Ni(DMSO)6]Cl2 DMSO 0.05 M 5. K4[Ni(NCS)6].4H2O 10 M KSCN in water 0.05 M bipy = 2,2-bipyridyl ; en = ethylenediamine ; DMSO = dimethylsulfoxide Record the spectrum of each solution in the region 200 – 1100 nm and calculate ∆O and B, for each ligand. 20 QUESTIONS 1. Determine all the spin-allowed electronic transition for d8 system. 2. Arrange the ligands in the spectrochemical series, that is in order of increasing ∆o. 3. Assign the 2 bands in the observed spectrum of complex 5 and estimate the frequency of the missing band. 4. Estimate the frequency of the absorption maximum for the 3A2g → 3T1g(P) transition in complex 1. Why is it not possible to get this directly from the spectrum? (Do not include limitations of instrumentation as a valid reason). 5. The energy versus ∆ correlations for 3T1g (P) and 3T1g(F) deviate from linearity, why? REFERENCES 1. C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, 5th edn., Pearson Prentice Hall, 2018. 2. M. Weller, T. Overton and J. Rourke, Inorganic Chemistry, 7th edn, Oxford University Press, 2018. 3. F. A. Cotton, G. Wilkinson, C. A. Murillo, and. M. Bochmann. Advanced InorganicChemistry, 6th Edition, Wiley-Interscience: New York, 1999. 4. Cotton, J. Chem. Educ.1964, 41, 466. 5. Sutton, J. Chem. Educ. 1960, 37, 498. 6. Manch & Fernelius. J. Chem. Educ. 1961, 38, 192. 7. Forster & Goodgame. Inorg. Chem. 1965, 4, 823. 8. R. S. Drago. Physical Methods in Inorganic Chemistry, Rheinhold, New York, 1965. 21