Synthesis and Structures of Iron(II) Metallacycles Based on a PNPNP Framework

Abstract

A series of iron­(II) metallacycles based on a saturated PNPNP framework has been prepared by a simple metal-templated approach, incorporating various central phosphorus donor groups. The reaction of [Cp*­(CO)­Fe­{P­(OMe)2(NPh)}2]Li (Cp* = η5-C5Me5) with RPCl2 (R = Ph, OMe, NEt2) afforded a pair of isomeric metallacycle complexes, [Cp*­(CO)­Fe­{κ2-P 1,P 3-P1(OMe)2N­(Ph)­P2(R)­N­(Ph)­P3(OMe)2}]­PF6. For all cases of R, the configurational isomers were successfully separated, and their geometric arrangements were established through single-crystal X-ray analyses. UV light irradiation of the isomers bearing R = Ph provided the same product, [Cp*Fe­{κ3-P 1,P 2,P 3-P­(OMe)2N­(Ph)­P­(Ph)­N­(Ph)­P­(OMe)2}]­PF6, via intramolecular coordination of the central phosphorus atom to the iron center. The isomers also reacted with ClAu­(tht) (tht = tetrahydrothiophene) to provide the corresponding iron–gold bimetallic complexes via κ2-P 1,P 3-κ1-P 2-coordination of the PNPNP ligand, revealing their utility as building blocks for multimetallic architectures.