Metal Carbonyls
MCQs for CSIR NET & GATE
Organometallic Compounds
Topicwise Assignment-3
Q1. Among the metals, Mn, Fe, Co and Ni, the ones those would react in its native form directly with CO giving metal carbonyl compounds are:
(b) Mn and Fe
(c) Fe and Ni
(d) Ni and Co
Q2. In the trans-PtCl2L(CO) complex, the CO stretching frequency for L= NH3, pyridine, NMe3 decreases in the order.
(b) NH3>pyridine>NMe3
(c) NMe3>NH3>pyridine
(d) pyridine>NMe3>NH3
Q3. For the reaction, trans-[IrCl(CO)(PPh3)2] + Cl2 → trans-[IrCl3(CO)(PPh3)2], the correct observation
(a) VCO (product) > VCO (reactants)
(b) VCO (product) < VCO (reactants)
(c) VCO (product) = VCO (reactants)
(d) VCO (product) = VCO (free CO)
Q4. Complexes of general formula, fac-[Mo(CO)3(phosphite)3] have the C-O stretching bands as given below.
VCO, cm-1: 2090(i); 2040(ii); 1977(iii); 1945(iv)
The correct combination of the phosphine and the stretching frequency is,
(a) (A-i), (B-ii), (C-iii), (D-iv)
(b) (A-ii), (B-i), (C-iv), (D-iii)
(c) (A-iv), (B-iii), (C-ii), (D-i)
(d) (A-iii), (B-iv), (C-i), (D-ii)
Q5. In metal-olefin interaction, the extent of increase in metal → olefin Ï€-back donation would
(b) change the formal oxidation state of the metal
(c) change the hybridization of the olefin carbon from sp2 to sp3.
(d) increase with the presence of electron donating substituent on the olefin.
Q6. Though cyclobutadiene (C4H4) is highly unstable and readily polymerizes in its free state, its transition metal complexes could be isolated because
(b) it gains stability due to formation of C4H42- on binding to transition metals.
(c) its polymerization ability reduces in presence of transition metal.
(d) it becomes stable in presence of transition metals due to formation of C4H42+.
Q7. The correct statement regarding terminal/bridging CO groups in solid Co4(CO)12 and Ir4(CO)12 is
(b) number of bridging CO groups in Co4(CO)12 is 4.
(c) number of terminal CO groups in Co4(CO)12 is 8.
(d) number of bridging CO groups in Ir4(CO)12 is zero.
Q8. The ligands that is/are fluxional in [(n5-C5H5)(n1-C5H5)Fe(CO)2] in the temperature range 21-298K, is (are)
(b) n1-C5H5
(c) n5-C5H5 and CO
(d) n1-C5H5 and CO
Q9. Complexes HM(CO)5 and [(n5-C5H5)M’(CO)3]2 obey the 18-electron rule. Identify M and M’ and their 1H NMR chemical shifts relative to TMS.
(b) M=Cr, 4.10; M’=Mn, -7.5
(c) M=V, -7.5; M’=Cr, 4.10
(d) M=Mn, 10.22; M’=Fe, 2.80
Q10. Amongst the following,
(A) [Mn(n5-Cp)(CO)3]; (B) [Os(n5-Cp)2]; (C) [Ru(n5-Cp)2]; (d) [Fe(n5-Cp2)]
The compounds with most shielded and deshielded Cp protons respectively, are
(b) D and B
(c) C and A
(d) C and B
Q11. [(n3-C3H5)Mn(CO)4] shows fluxional behaviour. The 1H NMR spectrum of this compound when it is in the non-fluxional state shows
(a) one signal
(b) two signals in the intensity ratio of 4:1
(c) three signals in the intensity ratio of 2:2:1
(d) five signals of equal intensity
Q12. The approximate positions of VCO bands (cm-1) in the solid-state infrared spectrum and the Fe-Fe bond order in [Fe(n5-C5H5)(μ-CO)(CO)]2 (non-centrosymmetric) respectively, are
(b) (2020, 1980, 1800) and two
(c) (2020, 1980) and one
(d) (2143) and one
Q13. Correct order of M-C bond length of metallocenes (A-C) is
(A) [Fe(n5-Cp2)] (B) [Ni(n5Cp2)] (C) [(n5Cp2)]
(b) B>C>A
(c) C>B>A
(d) A>C>B
Q14. The 1H NMR spectrum of [Ru(n4-C8H8)(CO)3] at 23 oC consists of a sharp single line. The number of signals observed at low temperature (-140 oC) in its spectrum is
(a) 8
(b) 6
(c) 4
(d) 2
Q15. For fluxional Fe(CO)5 (structure given below) in solution, the exchange of numbered CO groups will be between
(a) 2 and 5; 3 and 4
(b) 2 and 3; 4 and 5
(c) 2 and 3; 1 and 5
(d) 1 and 2; 4 and 5
Ans Key:
Q1.c Q2.a Q3.a Q4.a Q5.c Q6.b Q7.d Q8.b Q9.a Q10.a Q11.c Q12.a Q13.b Q14.c Q15.a