Scheme 1. (i) Ref. [24]; (ii) Ref.  [23]; (iii) 5.54 g of 1 and 2.97 g of 2; (iv) 1.72 g Mn(O₂CMe)₂·4H₂O and 1.75 g of 3, water; (v) saturated NaCl solution; (vi) 5.0 g LDH-[C₆H₅COO] and 1.71 g of 5, water, and stirred.

Fig. 1. (A) IR spectra of (a) free sulfonato-salen, (b) Na₂[Mn(Cl)(L)], and (c) Na₂[Mn(OAc)(L)] and (B) (a) Na₂[Mn(Cl)(L)], (b) LDH-[Mn(Cl)(L)], and (c) LDH-[C₆H₅COO].

Fig. 2. X-ray powder patterns of (a) LDH-[C₆H₅COO] and (b) LDH-[Mn(Cl)(L)].

Fig. 3. TGA (upper) and first derivative curves (lower) of (A) Na₂[Mn(Cl)(L)], (B) LDH-[C₆H₅COO], and (C) LDH-[Mn(Cl)(L)].

Fig. 4. Probable energy-level diagram of Mn(III) in square-pyramidal coordination.

Fig. 5. UV–vis spectra of (a) LDH-[Mn(Cl)(L)], (b) free chiral sulfonato–manganese(III) complex (5) and (c) LDH-[C₆H₅COO] in Nujol mull.

Fig. 6. Calculated structure of the sulfanato–Mn(III) salen ion (5)

Fig. 7. Comparison of conversion, selectivity, and de (%) of (R)-limonene over (a) LDH hosted Mn–salen complex and (c) zeolite-immobilized Mn(salen-2) [38], and for (−)-α-pinene over (b) LDH hosted Mn–salen complex, (d) zeolite-immobilized Mn(salen-2) [38], and (e) zeolite-immobilized Co(salen)  [38].

Fig. 8. IR spectra of (a) fresh Na₂[Mn(Cl)(L)], (b) fresh LDH-[Mn(Cl)(L)] and LDH-[Mn(Cl)(L)] catalyst after (c) first run, (d) second run, and (e) third run.

Table 1. Characterisation of catalyst precursors, the LDH-host precursor, and hosted Mn(III) complex

Table 2. Epoxidation of (R)-limonene and (−)-α-pinene using molecular oxygena

Table 3. Influence of solvent and choice of oxidant on the epoxidation of (R)–limonene and (−)-α-pinenea

Table 4. Performance of reused catalyst in the epoxidation of (R)-limonene and (−)-α-pinene