Asymmetric Halogeno-Bridged Complexes of the Late Transition Metals − A Computational and Experimental Study

Abstract

Metathesis reactions of dinuclear halo‐bridged complexes of the late transition metals have been studied by NMR. For selected combinations of 15 different complexes, it has been shown that asymmetric complexes are formed in a dynamic equilibrium. The equilibrium constants have been calculated and the trends therein are discussed. A theoretical analysis of halo‐bridged complexes containing (C3H5)MX, (H3P)MX2, [(H3P)2MX]+, and (ppy)2RhCl fragments (M = Pd, Pt; X = Cl, Br, I; ppy = anion of 2‐phenylpyridine) has been carried out to gain further insight into (i) the influence of the bridging halogen atoms on the equilibrium, (ii) the electron transfer, (iii) the thermodynamic stability and the dynamic equilibrium behaviour, and (iv) structural differences between symmetric and asymmetric halo‐bridged complexes.

RhCl3‐Mediated Coupling Reactions of tert‐Butyl Acetylene

“…A crystallographic analysis revealed that complex 2 is a chloro‐bridged Rh III dimer with a carbonyl ligand, a neopentyl ligand and an alkenyl ketone ligand6 (Figure 1). Complex 2 displays a crystallographic inversion center and accordingly a flat Rh(μ‐Cl) 2 Rh unit 7. The Rh–Cl bond lengths [2.497(2) and 2.510(2) Å] are in between what was observed for the dinuclear complexes [{Cp*RhCl(μ‐Cl)} 2 ] [2.4649(11) and 2.4522(10) Å]8 and [{Rh(μ‐Cl)(ptpy) 2 } 2 ] [ptpy = 2‐( p ‐tolyl)pyridinato] [2.548(2) and 2.5521(19) Å] 9.…”

Synthesis of Novel Heterotetrametallic (d6-d10-d8) Polyalkynyl Complexes Starting from Heterobimetallic Chloride-Bridged (d6-d8) Compounds

“…This structural feature contrasts with the planar cores previously found in the corresponding doubly chloride‐bridged symmetrical bimetallic species (NBu 4 ) 2 [(C 6 F 5 ) 2 Pt(μ‐Cl) 2 Pt(C 6 F 5 ) 2 ]8 and [{Rh(η 5 ‐C 5 Me 5 )Cl(μ‐Cl)} 2 ] 9. A recent theoretical study seems to confirm the observation that asymmetric chloro‐bridged complexes tend to have a bent structural arrangement 3p. Thus, the cationic mixed derivative [(bzq) 2 Rh(μ‐Cl) 2 Pt(PBu 3 ) 2 ] + is also considerably bent (29.4°)3o and similar nonplanar structures, albeit less severely distorted, have also been found in [(PMe 3 )Cp*Ir(μ‐Cl) 2 Pt(dppp)] 2+ (ca.…”

“…It is interesting to note that one of the most remarkable differences can be seen in the M′ 2 Cl 2 core. Thus, while the nickel and platinum anions exhibit typical3p,10 M′ 2 Cl 2 C 4 planar cores (both have a crystallographic centre of inversion), the anion [(C 6 F 5 ) 2 Pd(μ‐Cl) 2 Pd(C 6 F 5 ) 2 ] 2− found in 6 displays a slightly bent chloro‐bridge, with the dihedral angle defined by the corresponding palladium coordination planes being 13°. The resulting Pd ··· Pd distance of 3.464(2) Å is, as expected, longer than that found in the nickel derivative [Ni ··· Ni 3.28 Å] 14.…”

New Catalysts and Receptors by Self-Assembly and Combinatorial Chemistry

“…Over the last years, we have developed very efficient and versatile methods, which allow the synthesis of bimetallic complex-es, in which two different metal fragments are connected by either two [2][3][4][5] or three [6][7][8] halogeno-bridges [9]. Some of the complexes, which are suited for the synthesis of asymmetric complexes with three halogeno-bridges are shown in Scheme 1.…”