Chapter 5 Multiple Choice Questions

. Type question here
(i) U forms homoleptic alkyls UR_n only in the +4 oxidation state
(ii) Ce forms homoleptic alkyls CeR_n in oxidation states +3 and +4
(iii) [Ln{CH₂(SiMe₃)₂}₃] are all three-coordinate monomers
(iv) [Ln{CH₂(SiMe₃)₂}₃] are all four-coordinate dimers
(v) Homoleptic alkyls Ln/AnR_n are oxygen- and moisture-sensitive
(vi) Homoleptic alkyls Ln/AnR_n are oxygen-sensitive but not moisture-sensitive
(vii) [Yb{C(SiMe₃)₃}₂] has two-coordinate Yb with linear coordination geometry
(viii) [Yb{C(SiMe₃)₃}₂] forms three-coordinate dimers with trigonal planar coordination geometry
(ix) U forms homoleptic alkyls UR_n in all oxidation states from +3 to +6

(i), (iv), (v), and (viii) only are correct

(i), (iv), (v), and (ix) only are correct

(iv), (v), (viii), and (ix) only are correct

(iii), (v), and (ix) only are correct

. [Cp*₂Sm] (Cp* = h⁵-C₅Me₅) reacts with phenylacetylene (PhCCH) in thf solution to form:

[Cp*₂Sm(CCPh)]₂ + H₂

[Cp*Sm(CCPh)(thf)₂]₂ + 2HCp*

[Cp*₂Sm(HCCPh)]

. Isocyanide RNC reacts with [Cp₃M] (M = Pr or U) to form new complexes [Cp₃M(CNR)]. The IR spectrum of [Cp₃M(CNR)] shows an increase of 48 cm^-¹ in n(CN) where M=Pr and a decrease of 50 cm^-¹ in n(CN) where M=U. The explanation of the differences in n(CN) is:

RNC acts as a s-donor and p-acceptor where M=Pr, but only as a s-donor where M=U.

RNC acts only as a s-donor where M=Pr, but is reduced to RNC²^- where M=U.

RNC acts only as a s-donor where M=Pr, but as a s-donor and p-acceptor where M=U.

RNC is bonded through the N atom where M=Pr, but through the C atom where M=U as Pr³⁺ is a harder Lewis acid than U³⁺.

. Consider the following statements about cyclopentadienyl (Cp^-) and its Ln(III) complexes:
(i) Cyclopentadiene C₅H₆ is a weaker Brønsted acid than CH₄
(ii) Cp₃Ln are thermally very stable
(iii) Cp₃Ln are Brønsted acidic
(iv) Cp₃Ln are Lewis acidic
(v) Cp₃Lu forms discrete monomers in the solid state
(vi) Cyclopentadiene C₅H₆ is a stronger Brønsted acid than CH₄
(vii) Cp₃Ln are Brønsted basic
(viii) Cp₃Ln are thermally very unstable
Now select the correct statement below:

(i), (ii), (iv), and (vii) only are correct

(ii), (iv), (v), (vi), and (vii) are correct

(i), (iii), (iv), and (viii) only are correct

(ii), (iv), (vi), and (vii) only are correct

. Consider the following statements about f-element COT complexes (COT = C₈H₈):
(i) COT²^- is a planar 8 p electron ligand
(ii) COT²^- is a planar 10 p electron ligand
(iii) there is a f-component to bonding in [An(COT)₂] that involves donation from An to COT²^-
(iv) there is a f-component to bonding in [An(COT)₂] that involves donation from COT²^- to An
(v) there is a d-component to bonding in [An(COT)₂] that involves donation from COT²^- to An
(vi) there is a d-component to bonding in [An(COT)₂] that involves donation from An to COT²^-
(vii) [Pu(COT)₂] is paramagnetic
(viii) [U(COT)₂] reacts with PrCl₃ to form [Pr(COT)₂] and UCl₃
Now select the correct statement from the list below:

(ii), (iv), (v) and (vii) only are correct

(i), (iii), (iv) and (viii) only are correct

(ii), (iii), (iv), (vii) and (viii) are correct

(ii), (iii) and (v) only are correct

. Consider the following statements about lanthanoid bis(arene) complexes [Ln(h⁶-1,3,5-Bu^t₃-C₆H₃)₂]:
(i) The oxidation state of Ln is +2
(ii) The oxidation state of Ln is 0
(iii) The complexes are very thermally unstable
(iv) The complexes are synthesized by reaction of Ln atoms with 1,3,5-Bu^t₃-C₆H₃
(v) The complexes are synthesized by reaction of LnCl₃ with 1,3,5-Bu^t₃-C₆H₃ in the presence of a reducing agent
(vi) The most stable complex in the series is where Ln = Yb
(vii) The most stable complex in the series is where Ln = Gd
Now select the correct statement below:

(i), (v) and (vi) only are correct

(ii), (iii), (iv) and (vii) are correct

(ii), (iv) and (vii) only are correct

(i), (iii) and (v) only are correct

. Which of the following reactions is never observed in organolanthanoid chemistry?

b-alkyl elimination

alkene insertion

b-hydride elimination

oxidative addition

s-bond metathesis

. Consider the following statements about organolanthanoid catalysed alkene hydrogenation:
(i) [Cp*₂LuMe]₂ is the catalytically active species in alkene hydrogenation
(ii) If the substrate has more than one double bond, organo-Ln catalysts are generally selective for hydrogenation of the least hindered double bond
(iii) If the substrate has more than one double bond, organo-Ln catalysts are generally selective for hydrogenation of the most hindered double bond
(iv) Organo-Ln catalysts achieve lower turnover frequency but higher selectivity than d-transition metal catalysts
(v) Organo-Ln catalysts achieve higher turnover frequency than d-transition metal catalysts
(vi) Organo-Ln catalysts are widely used in industrial alkene hydrogenation processes
Now select the correct statement below:

(i), (ii), (v), and (vi) are correct

(i), (ii), and (v) only are correct

(ii), (v) and (vi) only are correct

(ii) and (v) only are correct

. Which of the following would be least likely to catalyse alkene polymerization?

[Cp*₂La(CH₂SiMe₃)] (Cp* = h⁵-C₅Me₅)

[(NN)ErMe]⁺ (NN = chelating monoanionic N-donor ligand)

[Cp*₂YbMe] (Cp* = h⁵-C₅Me₅)

[Cp*₂Lu{C(SiMe₃)₃}] (Cp* = h⁵-C₅Me₅)

. The following are being considered as catalysts/precatalysts for alkene hydroamination:
(i) Ln(OTf)₃ (OTf^- = CF₃SO₃^-) (ii) [Cp₂Ln(NEt₂)]
(iii) [Cp₂Ln(OⁱPr)]
(iv) [Cp₂Ln(CH₂SiMe₃)]
(v) [Cp₂LnH]
Select the most plausible selection of candidates from the list below:

(iv) only

(ii) and (v) only

(i), (iii) and (v) only

(ii), (iv), and (v) only

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