Ovine III-thrift in nova scotia. Part 10. Palladium and rhodium complexes as reagents in the investigation of isocyanide metabolites of Trichoderma hamatum

Abstract

Spectroscopic studies indicate that the reaction of the methyl ester (1b) of the fungal metabolite 3-(3-isocyanocyclopent-2-enylidene)propionic acid (1a) with dichlorobis-µ-[methylenebis(diphenyl-phosphine)]-dipalladium(I)(6), to give the product of insertion of the isocyano function into the Pd–Pd bond, is accompanied by CC bond isomerisation. That the crystalline material thus obtained did contain the bridging isocyanide moiety as in the expected insertion product [7; RNC =(1b)] was confirmed by X-ray crystallographic analysis. Reaction of (1b) with di-µ-chloro-dichlorobis(η⁵-pentamethylcyclopentadienyl)dirhodium(III)(8) or bis(η⁵-pentamethylcyclopentadienyl)bis-(µ-thio-cyanato-N,S)-bis(thiocyanato-S)dirhodium(III)(9) gave the monomeric 1 : 1 adducts (10) and (11). The results of X-ray crystallographic analysis of (11), which displays greater thermal stability than the chloro analogue (10), support the assignment of structure (1b) to the isocyanide ligand, in agreement with earlier conclusions based on spectroscopic evidence