Group-12 metal complexes with isomeric 1-(diphenylphosphino)-1′-[N-(pyridylmethyl)carbamoyl]ferrocenes: coordination polymersvs. finite multinuclear coordination assemblies

Abstract

The isomeric ferrocene phosphine-carboxamides, 1-(diphenylphosphino)-1′-{[N-(2-pyridyl)-methyl]carbamoyl}ferrocene (1) and 1-(diphenylphosphino)-1′-{[N-(4-pyridyl)methyl]carbamoyl}ferrocene (2) have been studied as ligands in group-12 metal bromide complexes. The reactions of 1 with CdBr₂·4H₂O and HgBr₂ at 1:1 mole ratio gave the discrete tetracadmium complex [Cd₂(μ-Br)₂(1-1κ²O,N²)₂{μ-1κ²O,N²:2κP-(C₅H₄N)CH₂NHC(O)fcPPh₂-CdBr₃}₂] (7; fc = ferrocene-1,1′-diyl) and the halogeno-bridged dimer [{Hg(μ-Br)Br(1-κP)}₂] (8), respectively. In the presence of acetic acid, the CdBr₂–1 system furnished a zwitterionic complex featuring protonated 1 as the P-monodentate donor, [CdBr₃{Ph₂PfcC(O)NHCH₂(C₅H₄NH)-κP}]·H₂O (6·H₂O). Under neutral conditions, compound 2, whose terminal donor groups are better arranged for the formation of extended assemblies, gave rise to one-dimensional coordination polymers [MBr₂{μ(P,N)-2}]_n (M = Cd, 4; M = Hg, 5). The crystal structures of 2·H₂O, its corresponding phosphine oxide (3·H₂O), and complexes 4, 5, 6·H₂O, 7 and 8 have been determined, revealing extensive hydrogen bonding interactions in the solid state.