Heterotrimetallic and heterotetrametallic transition metal complexes

The synthesis of the ruthenium sigma-acetylides (eta(5)-C5H5)(LRu)-Ru-2-C C-bipy (4a, L = PPh3; 4b, L-2 = dppf; bipy = 2,2'-bipyridine-5-yl; dppf = 1,1'-bis(diphenylphosphino) ferrocene) is possible by the reaction of [(eta(5)-C5H5)L2RuCl] (1) with 5-ethynyl-2,2'-bipyridine (2a) in the presence of NH4PF6 followed by deprotonation with DBU. Heterobimetallic Fc-C C-NCN-Pt-C C-R (10a, R = bipy; 10b, R= C5H4N-4; Fc = (eta(5)-C5H5)(eta(5)-C5H4)Fe; NCN = [1,4-C6H2(CH2NMe2)(2)-2,6](-)) is accessible by the metathesis of Fc-C C-NCN -PtCl (9) with lithium acetylides LiC C-R (2a, R = bipy; 2b, R= C5H4N-4). The complexation behavior of 4a and 4b was investigated. Treatment of these molecules with [MnBr(CO)(5)] (13) and {[Ti](mu-sigma, pi-C, CSiMe3)(2)} MX (15a, MX = Cu(N, CMe) PF6; 15b, MX = Cu(N CMe) BF4; 16, MX = AgOClO3; [Ti] = (eta(5)-C5H4SiMe3)(2)Ti), respectively, gave the heteromultimetallic transition metal complexes (eta(5)-C5H5)L2Ru-C C-bipy[Mn(CO)(3)Br] (14a: L = PPh3; 14b: L-2 = dppf) and [(eta(5)-C5H5)L2Ru-C C-bipy{[Ti](mu-sigma, pi-C, CSiMe3)(2)}M]X (17a: L = PPh3, M = Cu, X = BF4; 17b: L-2 = dppf, M = Cu, X = PF6; 18a: L = PPh3, M = Ag, X = ClO4; 18b: L2 = dppf, M = Ag, X = ClO4) in which the appropriate transition metals are bridged by carbon-rich connectivities. The solid-state structures of 4b, 10b, 12 and 17b are reported. The main structural feature of 10b is the square-planar-surrounded platinum(II) ion and its linear arrangement. In complex 12 the N-atom of the pendant pyridine unit coordinates to a [mer, trans(NN'N) RuCl2] (NN'N = 2,6-bis-[(dimethylamino)methyl] pyridine) complex fragment, resulting in a distorted octahedral environment at the Ru(II) centre. In 4b a 1,10-bis(diphenylphosphino) ferrocene building block is coordinated to a cyclopentadienylruthenium-sigma-acetylide fragment. Heterotetrametallic 17b contains a (eta(5)-C5H5)(dppf) Ru-C C-bipy unit, the bipyridine entity of which is chelate-bonded to [{[Ti](mu-sigma, pi-C CSiMe3)(2)}Cu](+). Within this arrangement copper(I) is tetra-coordinated and hence, possesses a pseudo-tetrahedral coordination sphere. The electrochemical behavior of 4, 10b, 12, 17 and 18 is discussed. As typical for these molecules, reversible oxidation processes are found for the iron(II) and ruthenium(II) ions. The attachment of copper(I) or silver(I) building blocks at the bipyridine moiety as given in complexes 17 and 18 complicates the oxidation of ruthenium and consequently the reduction of the group-11 metals is made more dif. cult, indicating an interaction over the organic bridging units. The above described complexes add to the so far only less investigated class of compounds of heteromultimetallic carbon-rich transition metal compounds. (C) 2007 Elsevier B. V. All rights reserved.