Correlation of Coordination Geometries and Stability Factors in Organotin(IV) Derivatives of 4-Acylpyrazol-5-onates with their Fungicidal (Mycelial Control) and Insecticidal (Topical Toxicity, Larvicidal and Ovicidal) Activities

Abstract

The fungicidal and insecticidal activities of the 4-acetyl (HPMAP) and 4-benzoyl (HPMBP) derivatives of 3-methyl-l-phenylpyrazol-5-one and their complexes with diorganotins [Bu2Sn(PMAP)2, Bu2Sn(PMBP)2, Ph2Sn(PMAP)2 and Ph2Sn(PMBP)2] and triorganotins [Bu3SnPMAP, Ph3SnPMAP, Bu3Sn(PMBP)(H2O) and Ph3SnPMBP] have been determined and their ED50 (fungicidal activity) and LC50 (insecticidal activity) values are reported. An attempt has been made to correlate the type of coordination geometry around the tin atom [based on published 119Sn NMR and 119Sn Mössbauer data as well as on the crystal structures of Bu2Sn(PMBP)2 and Bu3Sn(PMBP)(H2O)] and the relative stabilities with the observed bioactivities in these compounds. The diorganotin complexes are more effective than the triorganotins as insecticides. The effect of disproportionation of R3SnL to give R4Sn and R2SnL2 is discussed with respect to insecticidal activity. The stability constants of the diorganotin compounds are reported, and they suggest that these compounds are sufficiently stable to prevent appreciable ligand exchange before their assimilation into the living tissues of the insects. © 1997 by John Wiley & Sons, Ltd.