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

• Published in: Organometallics 1997-04, Vol.16 (7), p.1418-1424
• Main Authors: Tamm, Matthias, Jentzsch, Thomas, Werncke, Wolfgang
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om9610556

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.