1,3-Bis(N,N,N',N'-tetramethylguanidino)propane: synthesis, characterization and bonding properties of the first bidentate, peralkylated guanidine ligand

The first bidentate, peralkylated guanidine based ligand has been synthesiz ed and its complexation chemistry examined by the preparation of three repr esentative coordination compounds. The novel chelate ligand 1,3-bis(N,N,N', N'-tetramethylguanidino)propane (btmgp, 1) has been synthesized by the reac tion of N,N,N',N'-tetramethylguanidine (TMG) with 1,3-dibromopropane and su bsequent deprotonation of the resulting guanidinium salt with sodium ethoxi de. The bifunctional N-donor compound was treated with copper(I) iodide, co pper(II) chloride and iron(II) iodide in a 1 : 1 molar ratio to yield the c orresponding electroneutral complexes [CuI(btmgp)] 2, [CuCl2(btmgp)] 3 and [FeI2(btmgp)] 4. The structures of the dihydrochloride of 1 (1b) and of the complexes 2-4 have been determined by X-ray crystallography. A comparison of the molecular structures (2-4) shows that, in each case, btmgp acts as a bidentate ligand which is able to stabilize not only trigonal-planar (2), but also (distorted) square-planar (3) and tetrahedral coordination environ ments (4).