Keywords: Nitrogen donor ligands / Guanidine ligands / Ligand designA series of bis-guanidine ligands designed for use in biomimetic coordination chemistry has been extended to a library matrix combining unprecedented substitutional flexibility within the guanidyl residues with a wide range of aliphatic and aromatic spacers connecting these functionalities. The underlying protocol can be used with predefined ureas as well as secondary amines to build up these units by reaction with phosgene if the ureas are otherwise unavailable. In the latter case, the resulting urea intermediates do not have to be isolated as the reaction proceeds further with additional phosgene to yield a chloroformamidinium chloride which is transformed into the bis-guanidine functionality by subsequent reaction with a suitable primary diamine in the presence of triethylamine as an auxiliary base. This concept has been used to synthesise and characterise more then two dozen different bis-guanidines based on 12 discrete monoguanidine units and seven different spacers. These spacers have been chosen such that the most important phenotypes have been dealt with and which range from rigid to more flexible scaffolds. In addition to spacers with no metal-bind-

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The transition metal complexes with the ligand 1,3‐bis(N,N,N′,N′‐tetramethylguanidino)propane (btmgp), [Mn(btmgp)Br2] (1), [Co(btmgp)Cl2] (2), [Ni(btmgp)I2] (3), [Zn(btmgp)Cl2] (4), [Zn(btmgp)(O2CCH3)2] (5), [Cd(btmgp)Cl2] (6), [Hg(btmgp)Cl2] (7) and [Ag2(btmgp)2][ClO4]2·2MeCN (8), were prepared and characterised for the first time. The stoichiometric reaction of the corresponding water‐free metal salts with the ligand btmgp in dry MeCN or THF resulted in the straightforward formation of the mononuclear complexes 1–7 and the binuclear complex 8. In complexes with MII the metal ion shows a distorted tetrahedral coordination whereas in 8, the coordination of the MI ion is almost linear. The coordination behavior of btmgp and resulting structural parameters of the corresponding complexes were discussed in an comparative approach together with already described complexes of btmgp and the bisguanidine ligand N1,N2‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)‐ethane‐1,2‐diamine (DMEG2e), respectively.

Abstract:To analyze the contribution of supramolecular interactions to helical architectures and to investigate whether ligand folding can be induced by only protons in a similar fashion in the absence of metal ions, a new 1,10-phenanthroline (phen)-based extended ligand,

Diastereomeric pairs of metallatetrahedron clusters of the type Re 2 (AgPR 3 ) 2 (µ-PCy 2 )(CO) 7 (ax-(ϩ)/(Ϫ)-camph) ((ϩ)-auxiliary, R = Ph 4a, 4b or Et: 6a, 6b and (Ϫ)-auxiliary, R = Ph 5a, 5b or R = Et: 7a, 7b) were prepared from the η 1 -carboxylate substituted dirhenium salt Li[Re 2 (µ-H)(µ-PCy 2 )(CO) 7 (ax-η 1 -(ϩ)/(Ϫ)-camph)] (camph = camphanate) and less than stoichiometric amounts of [Ag(PR 3 )BF 4 ] (R = Ph or Et) in solution at room temperature. The diastereomers were separated using PLC and identified by means of IR, 1 H and 31 P NMR, UV/VIS and CD spectroscopy. Using single crystal X-ray analysis the molecular structure of 4a/4b in material I and 4a/5a in II have been determined to assign the absolute configuration of the clockwise (C) and anticlockwise (A) configurated tetrahedral Re 2 Ag 2 framework in a ligand sphere of C 1 symmetry. These are the first structures which show a chelate like co-ordination of the carboxylic group of the camphanate ligand in a heterometallic cluster complex. Based on their CD spectra the absolute configuration of other chiral carboxylate substituted metallatetrahedra of the type Re 2 (MPR 3 ) 2 (µ-PCy 2 )(CO) 7 (ax-OC(O)R) (M = Au or Ag) can be assigned.