Problems 85 3.9 Which of the following species contain a C4 axis and 3.27 Six of the nine vibrati...
Problems 85 3.9 Which of the following species contain a C4 axis and 3.27 Six of the nine vibrational degrees of freedom of SiF are IR active. Why are IR absorptions observed only at 389 and 1030 cm for this compound? 3.10 How many mirror planes do each of the following molecules contain: (a) SF" (b) H2S; (c) SF" (d) 3.28 AICİ6 belongs to the D2hpoint group: SOF: () SO () SO,? 3.11 (a) What structure would you expect Si2Hs to possess? (b) Draw the structure of the conformer most favoured in terms of steric energy. (c) Does this conformer possess an inversion centre? (d) Draw the structure of the conformer least favoured in terms of steric energy. (e) Does this conformer possess an inversion centre? 3.12 Which of the following species contain inversion centres? (a) BF: (b) SiF4 (c) XeF4 (d) PFs How many degrees of vibrational freedom does (e) [XeFsl: (f) SFo: (g) C2F4 (h) H2C C-CH2 .14 To which point group does NF belong? (d) this ion? (b) Use the Dh character table in Appendix 3 to determine the symmetries of the IR active stretching 3.13 Explain what is meant by an oo-fold axis of rotation. modes of vibration. 3.15 The point group of [AuC2] is Dooh What shape is 3.29 The IR spectra of salts of [A o exhibit absorptions around 540 and 570 em Usinga group theory approach, confirm that only one of 16 Determine the point group of SPsC The point group of Br is C2y Draw the structure of BrF, and compare your answer with the predictions of the VSEPR model. these absorptions arises from a stretching mode. 3.30 Determine how many CO stretching modes are possible for trans-M(CO)X What are their 18 In worked example 2.7, the structure of the [XeFs) symmetries, and how many are IR active ion was predicted. Confirm that this structure is consistent with Dsh symmetry 3.31 In 1993, the [Pt(CO)l2+ ion was reported for the first time [G. Hwang et al. (1993) Inorg. Chem., vol. 32 19 Assign a point group to each member in the series 4667]. One strong absorption at 2235 cm in the IR spectrum was assigned to vco and this was absent in the Raman spectrum. In the Raman spectrum, two absorptions co at 2257 and 2281 cm (absent in the IR spectrum) were observed. Show that these data are consistent with (a) cCl, (b) CClyF, (c) CCI2F2. (d) CCIF and 3.20 (a) Deduce the point group of SF (b) Is SOF4 in the 3.21 22 Determine the number of degrees of vibrational 323 How many normal modes of vibration are IR active Which of the following point groups possesses the highest number of symmetry elements: (a) Oi (b) Ta: (c) I? [P(CO)412 having Dh symmetry. 3.32 Explain how you could distinguish between freedom for each of the following: (a) SO2: (b) SiHO HCN: (d) H20 (e) BF cis-M(CO)bX2 and trans-M(COX2 by using nformation from the CO stretching region of IR spectra. Include in your answer a derivation of number of vco modes for each molecule. for (a) H.OSa n
Problems 85 3.9 Which of the following species contain a C4 axis and 3.27 Six of the nine vibrational degrees of freedom of SiF are IR active. Why are IR absorptions observed only at 389 and 1030 cm for this compound? 3.10 How many mirror planes do each of the following molecules contain: (a) SF" (b) H2S; (c) SF" (d) 3.28 AICİ6 belongs to the D2hpoint group: SOF: () SO () SO,? 3.11 (a) What structure would you expect Si2Hs to possess? (b) Draw the structure of the conformer most favoured in terms of steric energy. (c) Does this conformer possess an inversion centre? (d) Draw the structure of the conformer least favoured in terms of steric energy. (e) Does this conformer possess an inversion centre? 3.12 Which of the following species contain inversion centres? (a) BF: (b) SiF4 (c) XeF4 (d) PFs How many degrees of vibrational freedom does (e) [XeFsl: (f) SFo: (g) C2F4 (h) H2C C-CH2 .14 To which point group does NF belong? (d) this ion? (b) Use the Dh character table in Appendix 3 to determine the symmetries of the IR active stretching 3.13 Explain what is meant by an oo-fold axis of rotation. modes of vibration. 3.15 The point group of [AuC2] is Dooh What shape is 3.29 The IR spectra of salts of [A o exhibit absorptions around 540 and 570 em Usinga group theory approach, confirm that only one of 16 Determine the point group of SPsC The point group of Br is C2y Draw the structure of BrF, and compare your answer with the predictions of the VSEPR model. these absorptions arises from a stretching mode. 3.30 Determine how many CO stretching modes are possible for trans-M(CO)X What are their 18 In worked example 2.7, the structure of the [XeFs) symmetries, and how many are IR active ion was predicted. Confirm that this structure is consistent with Dsh symmetry 3.31 In 1993, the [Pt(CO)l2+ ion was reported for the first time [G. Hwang et al. (1993) Inorg. Chem., vol. 32 19 Assign a point group to each member in the series 4667]. One strong absorption at 2235 cm in the IR spectrum was assigned to vco and this was absent in the Raman spectrum. In the Raman spectrum, two absorptions co at 2257 and 2281 cm (absent in the IR spectrum) were observed. Show that these data are consistent with (a) cCl, (b) CClyF, (c) CCI2F2. (d) CCIF and 3.20 (a) Deduce the point group of SF (b) Is SOF4 in the 3.21 22 Determine the number of degrees of vibrational 323 How many normal modes of vibration are IR active Which of the following point groups possesses the highest number of symmetry elements: (a) Oi (b) Ta: (c) I? [P(CO)412 having Dh symmetry. 3.32 Explain how you could distinguish between freedom for each of the following: (a) SO2: (b) SiHO HCN: (d) H20 (e) BF cis-M(CO)bX2 and trans-M(COX2 by using nformation from the CO stretching region of IR spectra. Include in your answer a derivation of number of vco modes for each molecule. for (a) H.OSa n
3.28 Al,Clo belongs to the D2n point group: 3.32 E 3.33 (a) How many degrees of vibrational freedom does Al2Cl6 possess? (b) Use the D2h character table in Appendix 3 to determine the symmetries of the IR active stretching modes of vibration. D I E C₂(2) C ) C(x) i olxy) (x2) olyz) コート ---7777 iiii
3.28 Al,Clo belongs to the D2n point group: 3.32 E 3.33 (a) How many degrees of vibrational freedom does Al2Cl6 possess? (b) Use the D2h character table in Appendix 3 to determine the symmetries of the IR active stretching modes of vibration. D I E C₂(2) C ) C(x) i olxy) (x2) olyz) コート ---7777 iiii