Ruthenium(II) Complexes with (2,4,6-Cycloheptatrien-1-ylidene)ethenylidene Ligands:  Strongly Polarized Allenylidene Complexes

Abstract

The syntheses of cationic ruthenium(II) allenylidene complexes [(1a−e)PF6] of the type [CpRu(CCCR2)(PPh3)2]PF6 (1a, R2C: = cycloheptatrienylidene; 1b, R2C: = 2,7-dimethyl-4,5-benzocycloheptatrienylidene; 1c, R2C: = 2,7-diphenyl-4,5-benzocycloheptatrienylidene; 1d, R2C: = dibenzo[a,e]cycloheptatrienylidene; 1e, R2C: = 4,5-dihydrodibenzo[a,e]cycloheptatrienylidene) are reported. In the series 1a−e, the decreasing ability of R2C: to stabilize a positive charge results in a tuning of the electronic and optical properties by changing the relative contributions of the two canonical forms [Ru+]CCCR2 (A) and [Ru]C⋮CCR2 + (B), which is studied particularly by NMR and UV/visible spectroscopy. The first molecular hyperpolarizabilitiy β of (1b)PF6 has been determined by hyper Raleigh scattering. The X-ray crystal structures of (1b)PF6, (1d)PF6·CH2Cl2, and the acetylide complex CpRu(C⋮C−C7H7-2,4,6)(PPh3)2 are presented.

The First Thioallenylidene Complexes from Ruthenium-Butatrienylidene Intermediates

“…Judging, however, from the col-"true" energy difference between the vibrationally relaxed ours (alkyloxy-substituted allenylidene complexes are orground and excited states determined by electrochemical ange, while all-carbon substituted analogues are violet to methods. The energy difference ∆E op Ϫ ∆E ec provides a purple) [8,9] and the optical data for the closely related measure of the vibrational excitation associated with the [CpRu(PPh 3 ) 2 ] ϩ derivatives, [14] we conclude that the optical transition and therefore of the degree of structural HOMOϪLUMO gap decreases in the series NR 2 > OR > reorganization required upon excitation, and is param-SR > CR 3 , thus providing a rationale for the observed eterized as the structural factor ∆χ (Equation 1). [13] trends in the 13 C-NMR data.…”

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

“…This has been explained in terms of a larger contribution from the alkynyl-type resonance form II as opposed to the genuine cumulenylidene-type resonance form I (Scheme 2) when the metal center is more electron-rich and the substituents at C-γ are less able to support a positive charge adjacent to them. [1,2,4,20,21] In the light of the stability of the ferrocenylmethylene carbenium ion [22] the ferrocenyl substituent may be expected to stabilize the alternative alkynyl resonance form III, as indicated in Scheme 2, in line with the results from IR spectroscopy. We note here that Le Bozec et al arrived at a similar conclusion in their study of [(C 6 Me 6 )-Cl(PMe 3 )RuϭCϭCϭC(Ph)(Fc)] ϩ PF 6 Ϫ , closely related to 3a and 3b.…”

[Co2(CO)6(Alkynyl)] Complexes of Dibenzosuberyl and Dibenzosuberenyl Carbocations: Dibenzotropylium or Dibenzoheptafulvene?

“…In particular,w en ote that dibenzosuberenone is severely puckered, [24] but becomes ap lanar zwitterion when coordinated to AlCl 3 in 17. [25] Considering now metal complexes, we see that the planar sevenmembered ring in [Mn(CO) 2 P(OMe) 3 (C 7 H 6 ÀCCÀC 5 H 4 )]BF 4 (18) [26] excludes significant p delocalisation from the co-linear alkyne linker.I nc ontrast, in [Ru(C 5 H 5 )(PPh 3 ) 2 (C 15 H 10 =C=C=)]PF 6 (19), the linear Ru=C=C=Cg rouping brings about puckering of the central ring and also af olding back of the two benzo wingtips through 138 relative to the plane defined by C4a-C5a-C9a-C11a. [27]…”