Heterobimetallic and Mixed-Valence Chloro-Bridged Complexes with Orthometalated Rhodium(III) and Iridium(III) Fragments

Abstract

The synthesis and characterization of heterobimetallic and mixed‐valence complexes in which orthometalated [(ppy)2MCl] (M = Rh, Ir; ppy = 2‐phenylpyridine anion) and [(bzq)2RhCl] (bzq = benzo[h]quinoline anion) fragments are linked via chloro‐bridges with rhodium(I), iridium(I), palladium(II), and platinum(II) fragments is reported. These complexes are formed in nearly quantitative yields by metathesis reactions from the respective homodimeric compounds. The structures of [(ppy)2Rh(μ‐Cl)2Rh(cod)] (cod = η4‐1,5‐cyclooctadiene) and [(ppy)2Rh(μ‐Cl)2Pt(PBu3)‐Cl] were determined by X‐ray structure analyses.

Silyl–Thioether Multidentate Ligands – Synthesis of RhIII Complexes via RhI/RhIII Mixed‐Valent and Cyclooctenyl Intermediates

“…This pale‐yellow, binuclear Rh I /Rh III complex (Figure 2B) consists of a pseudo‐octahedral Rh III center and a pseudo‐square‐planar Rh I center. The rhodium atoms are bridged by two Cl atoms 36,37. The Rh–Cl distances reflect the differing oxidation states, as expected for a Rh I /Rh III dichlorido‐bridged complex.…”

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

“…In complex 1 , the Pt−Rh distance of 3.407(1) Å suggests that the observed puckering does not lead to any significant metal−metal bonding interaction. However, this distance is markedly shorter than those observed in the respective homobimetallic species [{(C 6 F 5 ) 2 Pt(μ‐Cl)} 2 ] 2− [3.528(1) Å]8 and [{Rh(η 5 ‐C 5 Me 5 )Cl(μ‐Cl)} 2 ] [3.719(1) Å]9 and in the mixed Rh III −Pt II ortho ‐metallated derivatives [(ppy) 2 Rh(μ‐Cl) 2 PtCl(PBu 3 )] (3.61 Å)3l and [(bzq) 2 Rh(μ‐Cl) 2 Pt(PBu 3 ) 2 ] + (3.63 Å) 3o. Clearly, the value mentioned above is more akin to that found in the chloride/alkynide hetero‐bridged compound [(PEt 3 )Cp*Rh(μ‐Cl)(μ‐C≡CPh)Pt(C 6 F 5 ) 2 ] [3.371(1) Å] 4g…”

“…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. 11°)3g and [(ppy) 2 Rh(μ‐Cl) 2 PtCl(PBu 3 )] (13.2°) 3l. However, other theoretical and structural analyses of square‐planar d 8 metal complexes of the type [L 2 M(μ‐Cl) 2 ML 2 ] seem to suggest that attractive metal−metal interactions are one of the main factors responsible for the observed bending 10.…”

“…Treatment of a red solution of [MCp*Cl 2 (PEt 3 )] (M = Rh, Ir) in acetone with 1 equivalent of the solvated platinum or palladium complex [ cis ‐M′(C 6 F 5 ) 2 (thf) 2 ] immediately gave an orange solution, from which the corresponding complexes 1−4 could be isolated as orange solids in high yields (i, Scheme 1). It should be mentioned that several neutral [(ppy) 2 M(μ‐Cl) 2 M′(PR 3 )Cl] (M = Rh, Ir; M′ = Pt, Pd; ppy = 2‐phenylpyridine anion; R = Bu, Et) or cationic [(chel)M(μ‐Cl) 2 M′(PEt 3 ) 2 ](BF 4 ) (M = Rh, Ir; M′ = Pt, Pd; chel = anion of 2‐phenylpyridine, benzo[4]quinoline, C 6 H 5 CHRNMe 2 , or η 3 ‐allyl) heterobinuclear (d 6 ‐d 8 ) chloride‐bridged complexes have been very recently prepared by metathesis reactions from the respective chloro‐bridged homodimeric compounds 3l,3o. In addition, related dicationic [(PMe 3 )(η 5 ‐C 5 Me 5 )M(μ‐Cl) 2 PtL 2 ] 2+ (OTf) − 2 (M = Rh, Ir; L 2 = dppp, 2 PPh 3 ) complexes have been prepared by a similar route starting from the bis(triflate) species [MCp*(PMe 3 )(OTf) 2 ] (M = Rh, Ir) and the corresponding dichloroplatinum derivatives 3g…”

“…The chemistry of bimetallic complexes has aroused much interest and has led to great development in the field of organometallic chemistry 1. In this area, there have been many reports detailing the preparation and chemistry of symmetrical or asymmetrical dichloro‐bridged homobinuclear complexes,2, 3l mainly because they play a prominent role as starting materials in organometallic chemistry and because of their relevance in catalysis. In marked contrast, the heterobinuclear analogues L m (μ‐Cl) 2 M′L n 3a−3e are very scarce and their chemistry remains essentially undocumented, although efforts to develop this chemistry have recently been reported 3f−3p…”