5,5′‐Bi‐5H‐cyclopenta[2,1‐b;3,4‐b′]dipridinylidene, a New Bridging Ligand for Metal Complexes. Preliminary Communication

Abstract

5,5'-Bi-SH-cyclopenta[Z, 1-b ;3,4-b']dipyridinylidene (1) was synthesized in three steps from 9,lO-phenanthroline and characterized by UVjVIS and NMR spectroscopy, mass spectrometry, and cyclic voltammetry. Its ability to act as a bridging ligand is demonstrated by the synthesis of the complexes [R~(bpy)~(l)](PF& (6) and [{ Ru(bpy)2)2(1)1(PF6)4 (7) (bpy = 2,2'-bipyridWIntroduction. -Polynuclear diimine-type complexes of Ru" and 0s" are at present under investigation with respect to their intramolecular energy-and electron-transfer properties [l]. These properties depend strongly on the nature of the bridging ligand. Here, we report the synthesis and the characterization of a new bridging ligand: 5,5'-Bi-SH-cyclopenta [2,l-b ;3,4-b']dipyridinylidene (1). The unusual electronic properties of 1, as well as the preparation of two Ru" complexes, are discussed. The compound 1 was first reported in 1979 [2]; however, our data do not correspond with those published.

Synthesis, Structure and Chemistry of a Twisted Olefinic Bis-didentate Proligand: 5,5′-Bi-5H-cyclopenta[2,1-b : 3,4-b′]dipyridinylidene

“…The 1 H-NMR spectra of the two diamagnetic Zn II complexes show the expected shift of the ring protons to lower field on coordination. We have also prepared [6] 2 , the signals of the protons of the uncoordinated fragment of BDAF are abnormally broad. This line broadening is solvent dependent, and disappears in the binuclear complexes.…”

“…Method 3: The dehydrogenation of 4 by the action of DDQ has already been described in [6]. In addition to the data recorded there for 1, the following are relevant: IR: 1552w, 1260w, 1170m, 1110w, 1030w, 810m.…”

“…IR: 1560s, 1168s, 1123m, 890m, 740m, 456m. The preparations of the Ru II complexes have been described in [6].…”

“…To avoid the formation of geometric isomers (fac, mer), the tetradentate bridging ligand should be symmetric with respect to the axis of coordination. This requirement is fulfilled by 2,2'-bipyrimidine (bpym) [5], and by 9,9'-bi-4,5-diazafluorenylidene (bdaf) [6] (1), for example. In the course of work [7] on the oxidation of 4,5-diazaphenanthrene, we noticed a description of 1 as a colorless crystalline solid [8].…”

Synthesis and X-ray crystal structure of a bridging trispiran ligand

“…This latter compound is itself a bridging ligand and useful precursor to the corresponding unsaturated 9,9'-bi-4,5-diazafluorenylidene. 12 Conversion of 2 to its potassium salt and treatment with pentaerythrityl tetrabromide furnished the trispiran 4, albeit in somewhat disappointing yield (18%). This new compound was characterized by mass spectrometry and 1 H and 13 C NMR.…”