Complexes of ligands derived from the condensation of 2-formyl- or 2-acetylpyridine with ethanolamine and the formation of two rearrangement products; X-ray crystal structures of Mn(L1) 2(NCS) 2, [Mn(L1)(NCS) 2] x, [Cu(L1)(H 2O) 2(ClO 4)] 2(ClO 4) 2, [Zn(L1)(H 2O) 2(ClO 4)] 2(ClO 4) 2 and [Mn(L3)(L4)] 2(ClO 4) 4·2EtOH (L1 = N-(2-hydroxyethyl)-2-pyridinecarboxaldimine, L3 = N-(2-hydroxyethyl)-methyl-2-pyridylketimine, L4 = ( Z)-1,3-di(2-pyridyl)but-2-enone)

Abstract

Four structurally diverse complexes of L1 ( N-(2- hydroxyethyl)-2-pyridinecarboxaldimine) have been synthesised and characterised. Mn(L1) 2(NCS) 2 is a monomer, orthorhombic, unit cell dimensions a= 9.786(4), b=12.748(4), c=17.615(6) Å, U= 2197(1) Å 3; [Mn(L1)(NCS)] x is a polymer, monoclinic, a=16.718(8), b=5.788(2), c=28.135(11) Å, β=91.61(3)°, U=2721(2) Å 3; [Cu(L1)(H 2O) 2- (ClO 4)] 2(ClO 4) 2 is a dimer, monoclinic, a= 15.132(11), b=9.235(8), c=23.030(17) Å, β= 102.32(5)°, U=3144(4) ° 3; [Zn(L1)(H 2O) 2- (ClO 4)] 2(ClO 4) 2 is also a dimer, monoclinic, a= 15.114(7), b=9.428(3), c=22.649(9) Å, β= 100.86(3)°, U=3170(2) Å 3. The formation of these complexes is discussed in relation to a proposed rearrangement scheme which accounts for the formation of a second, alternative product (L2) + (2-(2- hydroxyethyl)-3-(2-pyridyl)-imidazo [1,5- a]-pyridinium cation). Use of an equivalent methyl ketone precursor in place of the aldehyde led to formation of L3 ( N-(2-hydroxyethyl)-methyl-2-pyridylketimine) in situ. The dimeric manganese complex [Mn(L3)- (L4)] 2(ClO 4) 4·2EtOH (L4=( Z)-1,3-di(2-pyridyl)- but-2-enone) was structurally characterised, orthorhombic, a=23.987(7), b=12.697(3), c=19.355(5) Å, U=5895(3) Å 3, and a possible rearrangement scheme to form L4 is proposed.