(a) Table 27.3 lists the calculated value of eff for Eu 3+ as 0. On what...

(a) Table 27.3 lists the ‘calculated’ value of μ_eff for Eu³⁺ as 0. On what basis is this value calculated? Explain why observed values of μ_eff for Eu³⁺ are greater than zero.

(b) The complex UO₂Cl₂(THF)₃ contains one labile THF ligand and readily forms a diuranium complex, A, that contains 7-coordinate U(VI) with trans-UO₂ units. A is a precursor to a number of mononuclear complexes. For example, one mole of A reacts with four moles of K[O-2,6-^tBu₂C₆H₃] to give two moles of B, and with four moles of Ph₃PO eliminating all coordinated THF to yield two moles of C. Suggest identities for A, B and C and state the expected coordination environment of the U(VI) centre in each product.

Table 27.3.

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Metal ion La ³+ Ce³+ P₁³+ Nd³+ Sm ³+ Eu ³+ Gd³+ Tb³+ Dy³+ 3+ Ho' Er³¹+ Tm³+ Yb³+ Lu³¹+ Colour Colourless Colourless Green Lilac Pink Yellow Pale pink Colourless Pale pink Yellow Yellow Rose pink Pale green Colourless Colourless Ground state electronic configuration [Xe]4f0 [Xe]4f1 [Xe]4f2 [Xe]4f3 [Xe]4f4 [Xe]4f3 [Xe]4f6 [Xe]4f? [Xe]4f8 [Xe]4f9 [Xe]4f10 [Xe]4g1 [Xe]4f12 [Xe]4f13 [Xe]4f14 Ground state term symbol ¹So 2Fs/2 3 HA *19/2 51A 6H5/2 ¹Fo 851/2 1F6 6H15/2 $18 4115/2 3H6 2F712 'So Magnetic moment, μ (298 K)/B Calculated from eq. 27.1 0 2.54 3.58 3.62 2.68 0.84 0 7.94 9.72 10.63 10.60 9.58 7.56 4.54 0 Observed 0 2.3-2.5 3.4-3.6 3.5-3.6 2.7 1.5-1.6 3.4-3.6 7.8-8.0 9.4-9.6 10.4-10.5 10.3-10.5 9.4-9.6 7.1-7.4 4.4-4.9 0