A new synthetic approach for spiro-𝛽-lactams by cyclization of cis-3-allyl-3-benzylthio-𝛽-lactams is presented. The reaction involves step-wise electrophilic addition-dealkylation sequence giving stereospecific synthesis of C-3-spiro-𝛽-lactams.

Two new complex salts containing 2,5-substituted benzoate ions, [Co(phen)₂CO₃]₂ (C₇H₃O₂FCl)Cl$\cdot$11H₂O (1) and [Co(phen)₂CO₃](C₇H₃NO₄Cl)$\cdot$6H₂O (2) (where phen = 1,10-phenanthroline, C₇H₃O₂FCl = 2-chloro-5-fluorobenzoate (cfbz) and C₇H₃NO₄Cl = 2-chloro-5-nitrobenzoate(cnbz)) were synthesized by reacting carbonatobis(1,10-phenanthroline)cobalt(III) chloride with appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H$\cdots$F and C-H$\cdots$O interactions amid other heteroatom interactions. The complex salts have been characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, multinuclear NMR), conductance and solubility product measurements. Single crystal X-ray structure determination revealed ionic structures of both the complex salts having discrete ions along with lattice water molecules. Crystal lattice is stabilized by a variety of hydrogen bonding interactions, i.e. O-H$\cdots$O, C-H$\cdots$O and C-H$\cdots$F involving second sphere coordination besides 𝜋-𝜋 interaction. Furthermore, packing analyses reveal that C-H…F interactions can manifest even in the presence of a large number of heteroatom interactions.