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Alkali and alkaline-earth metal complexes of 4′-acetobenzo-15-crown-5 and 4′-acetobenzo-18crown-6 have been prepared and characterised by i.r. and n.m.r. spectroscopy. The crystal and molecular structure of 4′-aceto-benzo-18-crown-6·Sr[ClO4]2(the title complex) has been determined. No intermolecular interaction between the metal ion and the aceto-group has been observed. The reaction of several metal salts with 4′-(bromoaceto)benzo-15-crown-5 gives rise to internal nucleophilic displacement of the bromine by the anion to yield novel crown ethers.

Novel alkaline earth metal thiocyanate complexes are formed by the template condensation of furan-2,5-dicarbaldehyde with 1,11-diamino-3,6,9-trioxaundecane and 1,5-bis(2-aminophenoxy)-3-oxapentane; the X-ray structure of aqua-(3,15-diaza-6,9,12,20-tetraoxabicyclo[15,2,1]eicosa-2,15,17,19-tetraene)-di-isothio-cyanatostrontium(II) has been determined.

Crystals of the title compound are monoclinic, a= 25.685(15), b= 10.444(6), c= 18.818(11), β= 119.18(5)°, Z= 8 in space group C2/c, with the oxygens of water molecules present in the crystals lying along two-fold axes. The structure was determined by Patterson and electron-density methods and refined by least-squares techniques to R= 0.066 for 992 independent reflections. The fused ring system of the dibenzophospholium cation is almost planar and while the exocyclic C–P–C angles lie in the range 110–117°, the endocyclic angle is 93.9°. It is suggested that this low value is consistent with the presence of considerable ring strain, which is relieved either on phosphorane formation following nucleophilic attack at phosphorus, or on dealkylation of dibenzophospholium salts. The implications of ring strain in dibenzophospholium salts are discussed in connection with the possible aromaticity of the dibenzophospholes.

Novel alkaline earth metal thiocyanate complexes are formed by the template condensation of 1,11-diamino-3,6,9-trioxaundecane with pyridine-2,6-dicarbaldehyde; the X-ray structures of (3,15,21-triaza-6,9,12-trioxabicyclo [15.3.1]heneicosa-1(21), 2, 15, 17, 19-pentaene)di-isothiocyanatocalcium(II) and aqua-(3,15,21-triaza-6,9,12-trioxabicyclo[15.3.1]heneicosa-1(21),2,15,17,19-pentaene)di-isothiocyanatostrontium(II) have been determined and the ready exchange of alkaline earth cations for lead(II) in these complexes is reported.