A new family of flexible scorpionate ligands based on 2-mercaptopyridine

Abstract

A new family of flexible scorpionate ligands based on 2-mercaptopyridine is reported. The tris- and bis-substituted ligands, K[HB(mp)₃] (1) and Na[H₂B(mp)₂] (2) (mp = 2-mercaptopyridine) have been prepared and fully characterised. The structural characterisation of 1 reveals an unprecedented μ₃-κ³-SS′H-η¹η¹η²-κ²-S″C-η¹η¹-κ¹-S′-η¹ coordination mode. The coordination of both 1 and 2 to copper(I) complexes containing triphenylphosphine and tricyclohexylphosphine co-ligands is investigated suggesting κ³-SSS coordination modes for [Cu{HB(mp)₃}(PR₃)] {where R = Ph (3); R = Cy, (4)} and κ³-SSH coordination modes for [Cu{H₂B(mp)₂}(PR₃)] {where R = Ph (5); R = Cy (6)} the latter confirmed by structural characterisation of 5. A structural comparison with the sulfur based scorpionates, HB(mt)₃ and H₂B(mt)₂ (mt = methyl-2-mercaptoimidazole) is made in terms of the degree of tautomerisation of the heterocyclic rings.