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

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 center dot 4H(2)O and HgBr2 at 1: 1 mole ratio gave the discrete tetracadmium complex [Cd-2(mu- Br)(2)(1- 1 kappa O-2, N-2)(2){mu-1 kappa O-2, N-2: 2 kappa P-(C5H4N)CH2NHC(O)fcPPh(2)- CdBr3}(2)] (7; fc = ferrocene- 1,1' - diy1) and the halogeno- bridged dimer [{Hg(mu-Br)Br( 1-kappa P)}(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{Ph(2)PfcC(O)NHCH2(C5H4NH)-kappa P}]center dot H2O (6 center dot 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{mu(P,N)-2}](n) ( M = Cd, 4; M = Hg, 5). The crystal structures of 2 center dot H2O, its corresponding phosphine oxide (3 center dot H2O), and complexes 4, 5, 6 center dot H2O, 7 and 8 have been determined, revealing extensive hydrogen bonding interactions in the solid state.