Jean-Claude Bunzli - Square-planar rhodium(I) complexes with aromatic bent terdentate nitrogen ligands as candidates for rod-like extended materials

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      Publication Details (including relevant citation   information):

      Benech,J.M., Piguet,C., Bernardinellli,G., Bunzli,J.C.G.,   Hopfgartner,G. Journal of the Chemical Society-Dalton   Transactions 2001 (5) 684-689

      Abstract: The crystal structure of   2,6-bis(1-methylbenzimidazol-2-yl)pyridine (L-4) evidenced a   quasi trans-trans conformation of the unsubstituted nitrogen   atoms of the aromatic rings which is maintained in solution on   the NMR timescale. Reactions of L-4, or of its lipophilic   analogue 2,6-bis(1-octylbenzimidazol-2-yl)pyridine (L-5), with   [Rh(NBD)Cl](2) (NBD=bicyclo[2.2.1]hepta-2,5-diene) produced   poorly soluble dimetallic complexes [{Rh(NBD)Cl}(2)L-i] (i=4 or   5). The crystal structure of [{Rh(NBD)Cl}(2)L-5] revealed that   the terdentate aromatic unit adopts a distorted trans-trans   conformation and acts as a bridging ligand connecting two   [Rh(NBD)Cl] units through the nitrogen atoms of the benzimidazole   side arms. Solution studies (ES-MS, NMR) indicate that (i) the   dimetallic structure is maintained in solution, (ii) the   complicated fluxional behaviour observed at room temperature is   blocked at 210 K on the NMR timescale and (iii) the bent aromatic   core cannot act as a meridional terdentate chelate toward Rh-I.   The consequences of this co-ordination behaviour on the molecular   anisometry of extended complexes is discussed

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