Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands

A series of ruthenium allenylidene
complexes bearing polyaromatic
substituents have been prepared starting from [Ru­(bdmpza)­Cl­(PPh3)2] (1) (bdmpza = bis­(3,5-dimethyl­pyrazol-1-yl)­acetato).
Reacting 1 with 1,1-bis­(3,5-di-tert-butyl­phenyl)-1-methoxy-2-propyne
results in the formation of two structural isomers of an allenylidene
complex [Ru­(bdmpza)­Cl­(CCC­(PhtBu2)2)­(PPh3)] (5A/5B), as well as the related carbonyl
complex [Ru­(bdmpza)­Cl­(CO)­(PPh3)] (4A/4B). Conversion of 9-ethynyl-9-fluorenol leads to the
corresponding allenylidene complex [Ru­(bdmpza)­Cl­(CC(FN))­(PPh3)] (7A/7B) (FN = fluorenyl). Based
on anthraquinone, a new synthetic route toward 10-ethynyl-10-hydroxy­anthracen-9-one
via the trimethylsilyl-protected propargyl alcohol is described, and
subsequent conversion of this compound to the allenylidene complex
([Ru­(bdmpza)­Cl­(CC(AO))­(PPh3)] (12A/12B) (AO = anthrone) is
reported. The synthetic route from 7H-benzo­[no]­tetraphen-7-one to the propargyl alcohol 7-ethynyl-7H-benzo­[no]­tetraphen-7-ol is described,
which is followed by the transformation into the allenylidene complex
[Ru­(bdmpza)­Cl­(CC(BT))­(PPh3)] (17A/17B) (BT = benzotetraphene).
The molecular structures of 4B, 7A, 7B, 12A, 12B, 13A,
and 17A have been characterized by single-crystal X-ray
crystallography, and these analyses suggest that 17A might
function as a “metal-tuned organic field effect transistor”.
The electrochemical properties of the allenylidene complexes have
been studied via cyclic voltammetry, and time-dependent DFT calculations
have been conducted to assign weak absorptions in the NIR region to
forbidden MLCT transitions.