ONE-DIMENSIONAL POLYMERIZATION OF M2(OAC)4 (M=CU, RH) UNITS USING 2-(AMINOMETHYL)PYRIDINE - PREPARATION AND CHARACTERIZATION OF [RH2(OAC)4(AMP)]N AND [CU4(OAC)8(AMP)2]N

Synthetic procedures are described for the preparation of polymeric complexes of the general formula [M2(OAc)4(amp)]n (M = Rh, Cu; amp = 2-(aminomethyl)pyridine). Reaction of Rh2(OAc)4(MeOH)2 (1) with one equivalent of amp in MeCN produces [Rh2(OAc)4(amp)]n.n/2MeCN (2.n/2MeCN) in good yield (73%). The dinuclear Rh(II) carboxylate core remains intact and has a metal-metal distance of 2.410(1)angstrom. The coordination sphere of Rh(1) is completed by a pyridine nitrogen atom of one amp ligand while the coordination sphere of Rh(2) is completed by the amine nitrogen atom of a second amp ligand. These amp groups then bridge to adjacent Rh2(4+) units to give a one-dimensional polymer [Rh2(OAc)4(amp)]n. Hydrogen bonding is evident between the amp amine groups and the carboxylate oxygen atoms [N(25)...O(3) = 2.964 angstrom). The peak with the highest m/z value in the FAB mass spectrum of 2 from a chloroform/p-nitrobenzylalcohol matrix corresponds to the fragment [Rh2(OAc)4]3(amp)2. Reaction of Cu2(OAc)4(H2O)2 (3) with one equivalent of amp in MeCN, followed by recrystallization from EtOH/Et2O, produces crystals of [Cu4(OAc)8(amp)2]n (4). The structure of 4 consists of well-separated, one-dimensional polymeric chains composed of alternating [Cu2(OAc)4] and [Cu2(OAc)2(amp)2]2+ units which are linked by syn, anti bridging acetates. The [Cu2(OAc)4] units closely resemble the starting material, with the two copper centres bridged by four eta1: eta1: mu AcO- ligands over a metal-metal separation of 3.282(1) angstrom. The axial coordination sites are occupied by an oxygen atom of the syn, anti bridging acetates. The [Cu2(OAc)2(amp)2]2+ units contain two monoatomically bridging acetate groups, with the coordination sphere of the metals completed by a chelating amp ligand and the second oxygen atom of the syn, anti bridging acetates. Hydrogen bonding between the amine group of the amp ligands and the mono-atomic bridging acetate groups is evident [N(22)...O(25) = 2.877 angstrom].