Cyclopentadienone-like Behavior of Fluorenone and 4,5-Diazafluoren-9-one

Abstract

The aromatic compounds fluorenone (1) and 4,5-diazafluoren-9-one (2) behave like cyclopentadienones in their reaction with [Cp*Co(C 2 H 4 ) 2 ] (3a), affording the sandwich-type complexes [Cp*Co(η 4 -1)] ( 4) and [Cp*Co(η 4 -2)] ( 5), respectively, whose structures have been determined by X-ray diffraction. Both complexes show double-bond fixation in their η 2 -coordinated sixmembered rings and belong to a new structure type of mononuclear organometallics. The cobalt-coordinated ligands 1 and 2 present in 4 and 5, respectively, may be replaced by two molecules of carbon monoxide. In accord with their cyclopentadienone-like nature, they are nucleophilic and undergo O-acylation with acetyl chloride, affording cobaltocenium species.

A Synthetic and X‐ray Crystallographic Study of Zinc and Platinum Complexes of 4,5‐Diazafluoren‐9‐one (Dafone) and Dicobalt Hexacarbonyl Derivatives of 9‐Phenylethynyl‐4,5‐Diazafluoren‐9‐ol: Chelation versus Monocoordination

“…As noted by a number of previous workers, [13][14][15][16][17][18][19][20][21][22] the rather long N···N distance in 4,5-diazafluoren-9-one (dafone) (6) frequently renders symmetrical chelate formation to be non-competitive, with monocoordination and incorporation of an additional ligand. The asymmetry of the M-N bond lengths is clearly apparent in both cis-and trans-(dafone) 2 MX 2 complexes, and is particularly evident in d 9 Cu II systems in which geometric distortions are amplified by Jahn-Teller effects.…”

“…Finally, to avoid interference from a potentially coordinating solvent such as dimethyl sulfoxide, an aqueous solution of K 2 PtBr 6 was treated with dafone in methanol; crystals of (dafone)PtBr 4 (14) were obtained. As shown also in Figure 9, the platinum atom is in a very slightly perturbed octahedral environment, and the cis-Br-Pt-Br and cis-BrScheme 4.…”

“…The structures of a number of dafone derivatives of Mn, [13] Co, [14] Ni, [15] Cu, [16] Zn, [17] Cd, [18] Pd, [19] Ru, [20] Eu, [21] and Sn [22] have been previously reported. Comparisons of the N···N distances with those (≈2.62-2.65 Å) in the widelystudied bipyridyl or 1,10-phenanthrolene systems, which have a noticeably smaller bite, must be made.…”

Coordination chemistry and applications of versatile 4,5-diazafluorene derivatives

“…Dafo has been used as a ligand for metals across the periodic table: Mn, 43 Co, 44,45 Ni, [46][47][48] Cu, 44,[48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] Zn, 7 Mo, 63 Ru, 9,[64][65][66][67][68][69][70][71][72][73] Pd, 17,44,[74][75][76][77][78][79][80][81][82][83][84][85][86][87] Ag, [88]…”

“…50,[94][95][96] In the vast majority of cases dafo behaves as a bidentate chelate ligand, however there are a few examples where dafo adopts either a monodentate κ 1 -N coordination mode, 7,17,50,54,56,88,89 a bis-monodentate bridging coordination mode, 17,59,60,79,81,97 or even an η 4 -cyclopentadienone-like coordination mode in the [Cp*Co(η 4 -dafo)] complex. 45…”