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 synthesized and its complexation chemistry examined by the preparation of three representative coordination compounds. The novel chelate ligand 1,3-bis(N,N,N',N'-tetramethylguanidino)propane (btmgp, 1) has been synthesized by the reaction of N,N,N',N'-tetramethylguanidine (TMG) with 1,3-dibromopropane and subsequent deprotonation of the resulting guanidinium salt with sodium ethoxide. The bifunctional N-donor compound was treated with copper(I) iodide, copper(II) chloride and iron(II) iodide in a 1 : 1 molar ratio to yield the corresponding 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 environments (4).