Long‐Range Electronic Coupling in Various Oxidation States of a C₄‐Linked Tris(β‐diketonato)ruthenium Dimer

Abstract

Despite an increasingly varied experimental data basis [1] and sophisticated theoretical approaches [2] there is still only a rudimentary understanding of which factors govern the extent of interaction between metal centers in formally symmetrical mixed-valent compounds. Such compounds can be considered as intermediates in ™degenerate∫ inner-sphere metal-to-metal electron transfer. The interplay between metal configurations, the metal±ligand interface, and the properties of the ligand bridge has to be considered. Although the mere metal±metal distance has often been used as a guideline [3] in the absence of other, less accessible parameters, it is clear from several experiments [1] that the electronic properties of the ligands mediating the metal±metal interaction may be more relevant than the metal±metal separation. However, the correlation between metal configurations and the bridge type also requires consideration, especially when using alternatives to the often studied d 5 /d 6 combination, [1, 3] familiar from prototypes, such as the Creutz±Taube ion [3a] [(H 3 N) 5 Ru-(m-pz)Ru(NH 3 ) 5 ] 5+ (pz = pyrazine) or partially oxidized biferrocenyl species. [4] Herein we describe the extraordinarily varied results for two different mixed-valent configurations that are accessible by single-electron transfer from the structurally characterized diruthenium(iii) complex 1. [5] The distinguishing feature of the ligand bridge is an unsaturated, cumulene-like, C 4 spacer which, in contrast to other C 4 -bridged dinuclear systems, [6] interacts with the metals through conventional Werner-type coordination, namely through b-diketonato chelate ligation. [5] The complex 1 could be characterized crystallographically, [7] it has an almost linear C 4 chain with localized singlebond/triple-bond alternation (Figure 1). At 13.1359(6) ä the metal±metal separation is much longer than in directly C 4connected diruthenium complexes (ca. 8.0 ä), [6] and the chelate rings are virtually perpendicular (90.98).

Synthesis and characterization of bis(bipyridine)ruthenium(II) complexes with bromo or protected ethynyl β-diketonato ligands

“…Hoshino et al have shown that the introduction of alkyne group at the c-position of a b-diketonato chelate ring can lead to several oligomers or polymers with interesting properties [1,[4][5][6]. Nevertheless the way they prepare their building blocks is long and tedious [4].…”

“…A terminal alkyne can form a bridging group between two metal atoms or organometallic moieties [1][2][3]. Hoshino et al have shown that the introduction of alkyne group at the c-position of a b-diketonato chelate ring can lead to several oligomers or polymers with interesting properties [1,[4][5][6].…”

Bis(diphenylphosphino)acetylene as bifunctional ligand in cycloplatinated complexes: Synthesis, characterization, crystal structures and mechanism of MeI oxidative addition

“…The 1 H, 13 C, 31 P and 195 Pt NMR spectra were recorded on a Bruker Avance DRX 500 MHz spectrometer in CDCl 3 as solvent. The operating frequencies and references, respectively, are shown in parentheses as follows: 1 H (500 MHz, TMS), 13 C (125 MHz, TMS), 31 P (202 MHz, 85% H 3 PO 4 ), and 195 Pt (107 MHz, aqueous Na 2 PtCl 4 ).…”

“…The NMR spectra of complex 3. (A): 1 H in the Me region; (B): 31 P NMR and (C) 13 C NMR in the Me region. The peak labeled * in 1 H NMR is due to water of CDCl 3 solvent.…”

“…The methylplatinum(II) complexes, 1 and 2, were reacted cleanly with an excess of MeI in CH 2 Cl 2 at room temperature to give air-stable solid products having the general formula [Pt 2 I 2-Me 4 (C^N) 2 (m-dppac)] (C^N ¼ ppy, 3; bhq, 4). The synthesized Pt(IV) complexes were fully characterized using 1 H, 13 C, 31 P and 195 Pt NMR spectroscopy and elemental analysis. Complex 3 was further identified by single crystal X-ray structure determination.…”