Syntheses, Structures, and Reactivity Studies of Half-Open Ruthenocenes and Their Oxodienyl Analogues

Abstract

Improved synthetic routes to Cp*Ru(Pdl) complexes (Pdl ) 2,4-dimethylpentadienyl and various oxodienyl ligands) including Cp*Ru(η 5 -2,4-Me 2 -C 4 H 3 O) (1), Cp*Ru[η 5 -2,4-(t-Bu) 2 -C 4 H 3 O] (1′), and Cp*Ru(η 5 -2,4-Me 2 -C 5 H 5 ) (1′′) have been developed, and the relative reactivities of the resulting complexes toward oxidative addition or ligand addition reactions have been examined. Thus, the oxopentadienyl complexes 1 and 1′ and the 2,4-dimethylpentadienyl complex 1′′ were found to undergo oxidative addition of SnCl 4 , Me 2 SnCl 2 , I 2 , Cl 2 (via CHCl 3 ), and O 2 , yielding Cp*Ru 5) readily, the oxodienyl products having η 3 -oxodienyl coordination occurring preferentially through an all-carbon allylic fragment, in line with ruthenium's soft nature. The O 2 reaction was of additional interest in that it also led to a product in which oxidation of the Cp* ligand to a C 5 Me 4 (CHO) ligand had occurred, giving (η 5 -C 5 Me 4 -CHO)Ru[η 5 -CH 2 C(Me)CHC(Me)O] (6). In contrast to the above, reactions of the 2,4-di(tertbutyl)oxodienyl or 2,4-dimethylpentadienyl ligand complexes were much less favorable, occurring much more slowly, if at all. For the reaction of CHCl 3 with the 2,4-dimethylpentadienyl complex, a small amount of an η 6 -toluene complex, [Cp*Ru(η 6 -C 7 H 8 )][Cp*RuCl 3 ] (11), was formed, apparently as a result of a carbon-carbon bond activation, giving a rearrangement of the dienyl ligand. The additions of Lewis bases to the oxodienyl complexes, leading to Cp*Ru[η 3 -CH 2 C(Me)CHC(Me)O]L species [L ) PPh 3 (7), PHPh 2 (8), PMe 3 (9), CO (10)], were most facile for small donors such as PMe 3 , while PPh 3 and CO additions were more reversible. Structural data have been obtained for representative examples of the above, i.e., complexes 1, 1′, 2, 5, 6, 7, and 11.

Selective, Cytotoxic Organoruthenium(II) Full‐Sandwich Complexes: A Structural, Computational and In Vitro Biological Study

“…Geometric parameters and bond lengths for each structure (4, 5 a, and 10-12) were found to be comparable with those previously published for complexes 1, 2, and 8, respectively (Table 3). [8,14] For each compound the phenyl and Cp* rings are co-planar, with the angle formed by the ring centroids and ruthenium atom equaling 180.028 (4), 179.968 (5 a), 176.448 (10), 177.778 (11), and 179.398 (12), respectively. The Cp*-arene interplanar separation is comparable for each complex, with an average distance of 3.52 .…”

Electrochemical oxidation of Cp*Ru(η5-2,4-dimethyl-pentadienyl) in acetonitrile. One-electron vs. two-electron generation of cationic acetonitrile coordinated complexes

“…The corresponding chemical shift of the quaternary carbon in the Cp* ligand of complex III appears at 110.0 ppm, which clearly suggests the higher oxidation state of the ruthenium atom [6]. From 1 H NMR data, it was found that the g 3 -pentadienyl ligand in complex III displayed typical chemical shifts for uncoordinated vinylic protons (H(C5)).…”

“…A comparative study of the chemical reactions of I and II has been undertaken, and there is clear evidence for the higher reactivity of the oxopentadienyl complex II towards oxidative addition, as well as in simple addition reactions [6].…”

“…The Cp*Ru(g 5 -2,4-dimethyl-pentadienyl) was synthesized and purified as previously described [6]. Tetrabutylammonium hexafluorophosphate 98% (n-Bu 4 NPF 6 ), lithium tetrafluoroborate 98% (LiBF 4 ), and phosphorous pentoxide 97% were obtained from Aldrich and used as received.…”

“…From 1 H NMR data, it was found that the g 3 -pentadienyl ligand in complex III displayed typical chemical shifts for uncoordinated vinylic protons (H(C5)). Meanwhile, the anti and syn hydrogens of the allylic fragment (H(C1)) showed enhanced electronic protection compared to the corresponding hydrogens of the g 5 -pentadienyl complex I [6].…”