Synthesis Experiment 3

Synthesis, reactivity and spectra of Tris(Acetylacetonato)Cobalt(I II) Experiment 3

Introduction: The aim of the experiment is to synthesisze 𝑇𝑟𝑖𝑠(𝑎𝑐𝑒𝑡𝑦𝑙𝑎𝑐𝑒𝑡𝑜𝑛𝑎𝑡𝑜)𝑐𝑜𝑏𝑎𝑙𝑡(𝐼𝐼𝐼) ′[𝐶𝑜(𝑎𝑐𝑎𝑐)3 ]. The copper complex was then nitrated with 𝐶𝑜𝑝𝑝𝑒𝑟(𝐼𝐼)𝑛𝑖𝑡𝑟𝑎𝑡𝑒 𝑡𝑟𝑖ℎ𝑦𝑑𝑟𝑎𝑡𝑒 to form[𝐶𝑜(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ], the complexes were both analyzed in infrared, electronic spectra and NMR. The melting points for the complexes were measured. Method: The method was done as in the inorganic chemistry third year practical guide. Results: Table1: The table illustrating the percentage yield, structure of the complex and melting points C Yield (g) o m p o u n d f o r m u l a e [𝐶𝑜(𝑎𝑐𝑎𝑐) 2.33 3 ]

[𝐶𝑜(𝑎𝑐𝑎𝑐 0.55 − 𝑁𝑂2 )3 ]

Perc enta ge yield (%)

Melting pointd(℃)

31.1 0

204-210

39.9 0

196-200

Structure of complex

Calculation protocol for percentage yield:

𝐴𝑐𝑎𝑐 = 𝐶𝐻3 𝐶(𝑂)𝐶𝐻𝐶(𝑂𝐻)𝐶𝐻3 2𝐶𝑜𝐶𝑂3 + 6𝐴𝑐𝑎𝑐 + 𝐻2 𝑂2 → 2[𝐶𝑜(𝐴𝑐𝑎𝑐)3 ] + 2𝐶𝑂2 + 4𝐻2 𝑂 𝑛(𝐶𝑜𝐶𝑂3 ) =

𝑚 𝑚𝑀

=

2.5 118.941

= 0.0201𝑚𝑜𝑙𝐶𝑜𝐶𝑂3

(1: 1) 𝑚𝑜𝑙𝑒 𝑟𝑎𝑡𝑖𝑜 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 (2𝐶𝑜𝐶𝑂3 : 2[𝐶𝑜(𝐴𝑐𝑎𝑐)3 ]) The 𝑛([𝐶𝑜(𝐴𝑐𝑎𝑐)3 ]) = 0.0201𝑚𝑜𝑙𝑒 𝑚([𝐶𝑜(𝐴𝑐𝑎𝑐)3 ]) = 𝑛 × 𝑚𝑀 = 0.0201 × 359.281 = 7.552𝑔 %𝑦𝑖𝑒𝑙𝑑 =

𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙𝑚𝑎𝑠𝑠 𝑎𝑐𝑡𝑢𝑎𝑙

2.33

× 100% = 7552 × 100% = 30.85%

For nitrated complex [𝐶𝑜(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 ] 𝐶𝑢(𝑁𝑂3 )2 + 3𝐻2 𝑂 + 2(𝐶𝐻3 𝐶𝑂)2 𝑂 → 𝐶𝑢(𝐶𝐻3 𝐶𝑂) ∙ 3𝐻2 𝑂 + 2𝐶𝐻3 𝐶𝑂2 + 𝑁𝑂2 [𝐶𝑜(𝑎𝑐𝑎𝑐)3 ] + 3𝐶𝐻3 𝐶𝑂2 𝑁𝑂2 → [𝐶𝑢(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ] + 3𝐶𝐻3 𝐶𝑂2 𝑚

1

𝑛(𝐶𝑜(𝑎𝑐𝑎𝑐)3 ) = 𝑚𝑀 = 359.281 = 0.002783𝑚𝑜𝑙 𝑠𝑖𝑛𝑐𝑒 𝑖𝑡 𝑖𝑠 (1: 1)𝑟𝑎𝑡𝑖𝑜 𝐶𝑜(𝑎𝑐𝑎𝑐)3 : [𝐶𝑢(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ] Then 𝑛([𝐶𝑢(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ]) = 0.00278𝑚𝑜𝑙 So ([𝐶𝑢(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ]) = 𝑛 × 𝑚𝑀 = 0.00278 × 494.2729 = 1.376𝑔 %𝑦𝑖𝑒𝑙𝑑 =

𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙𝑦𝑖𝑒𝑙𝑑 𝑎𝑐𝑡𝑢𝑎𝑙𝑦𝑖𝑒𝑙𝑑

0.55

× 100%0 = 1.376 × 100% = 40%

Table 2: Table illustrating UV/visible spectra for two complexes formed. Complex formed

Color of complex Absorbed color Wavelength peak(nm) Dark green 520,18 Green [Co(acac)3] Dark green 520,18 Green [Co(acac-NO2)3] The peaks are not visible; the use of literature values was used for the completion of the results. Table 3: The IR data and the observed peaks Peaks , Possible Function groups C-H C=O Discussion

𝑤𝑎𝑣𝑒𝑛𝑢𝑚𝑏𝑒𝑟 𝑐𝑚−1 2966.37 1569.10

The experiment involves the synthesis of Tris(Acetylacetonato)cobalt(III), 𝐶𝑜(𝑎𝑐𝑎𝑐)2 and the nitration of the complex to form the nitrated compound (𝐶𝑜(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ), below is the balanced chemical reaction 2𝐶𝑜𝐶𝑂3 + 6𝑎𝑐𝑎𝑎 + 𝐻2 𝑂2 → 2[𝐶𝑜(𝑎𝑐𝑎𝑎)3 ] + 2𝐶𝑂2 + 4𝐻2 𝑂 The experiment procedure resulted in small yield of the products which is 38%, the most products got lost in the addition of the oxidizing agent the hydrogen peroxide which coursed the bubbling and the splitting of the reagent at the beginning of the practical. The color of the complex is dark green color with the literature absorbance wavelength which shows that the absorbed color of the complex is purple which a complementary color of the green color at that is given wavelength number. The melting point of the complex is at 204℃ − 210℃ and the literature melting point for the complex is at 201℃ − 213℃ these results shows that the complex has an impurity that’s why it has low melting point. The nitration of [𝐶𝑜(𝑎𝑐𝑎𝑎)3 ] to form(𝐶𝑜(𝑎𝑐𝑎𝑐 − 𝑁𝑂2 )3 ), below is a balance equation 𝐶𝑢(𝑁𝑂3 )2 ∙ 3𝐻2 𝑂 + 2(𝐶𝐻3 𝐶𝑂)2 𝑂 → 𝐶𝑢(𝐶𝐻3 𝐶𝑂) ∙ 3𝐻2 𝑂 + 2𝐶𝐻3 𝐶𝑂2 𝑁𝑂2 The yield of the products was 40% which is a low yield, this was brought by the process of recrystallization and the products were lost in the process, the use of chloroform to was going to help crystalize most of the products but it was not used. The color of the complex is green with the wavelength of 520nm from the literature and purple is the absorbed complementary color of the complex. The melting point of the complex is at 196℃ − 200℃, with the literature melting point at 197℃ − 198℃ so which this indicate that the product has impurities since it was not washed with ethanol to make them pure. Assignment Question 1: discussed above Question 2 Free ligands

[Co(acac)3]

[Co(acac-NO2)3]

Question 3 Chelation is a process which involves ligands with more two or more binding sides to bond to a metal. This process allows ligands with bi-dentate characters to bind to a central metal atom to form a ring like structure. Question 4 The spectrum bands and possible functional groups is indicated at table 3, the IR spectrum for nitrated compound [Co(acac-NO2)3] the spectrum is not included the analyses was not done for that

reason. The functional groups for [Co(acac)3] C-H is at 2966.37cm-1 and C=O is at 1569.10cm-1. The bands are not the same due to transmittance which is different, the NO2 band is not available in the spectrum but is at 822.16 according to literature books Shalhoub(1980) and this could have been nicely observed in IR spectrum of the nitrated complex which is not available. Question5 The HNMR show only for peaks which are proton based peaks. The peak at 1.90 shows a water molecule and it has two hydrogen atoms in it. The peak at 5.38 represents the solvent molecules containing the hydrogen’s atoms in it. There are two peaks up field which are 2.099m and 3.49pm and the show hydrogen’s from acac-ligands and methyl groups respectively. Question 6

Comments

The practical was centered on the analyses of the spectrums which is still new at level but gaining experience and the preparation of the crystals was success but the analyses took much of the time.

Bibliography Atkins, A., T, O., Rourke, J., M, W., & F, A. (2010). Shriver And Atkin's inorganic chemistry. New York: Oxford university press. Shalhoub. (1980). synthesis reaction and spectr. chemistry education, 525-526. Smith. (2011). Organic chermistry. New York: McGraw-Hill.