Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands

Abstract

A series of ruthenium allenylidene complexes bearing polyaromatic substituents have been prepared starting from [Ru(bdmpza)Cl(PPh 3 ) 2 ] (1) (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetato). Reacting 1 with 1,1-bis(3,5-ditert-butylphenyl)-1-methoxy-2-propyne results in the formation of two structural isomers of an allenylidene complex [Ru(bdmpza)Cl(CCC(Ph t Bu 2 ) 2 )(PPh 3 )] (5A/5B), as well as the related carbonyl complex [Ru(bdmpza)Cl(CO)-(PPh 3 )] (4A/4B). Conversion of 9-ethynyl-9-fluorenol leads to the corresponding allenylidene complex [Ru(bdmpza)Cl(CC(FN))(PPh 3 )] (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))(PPh 3 )] (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))(PPh 3 )] (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. ■ INTRODUCTIONOrganometallic complexes containing allenylidene moieties are of considerable interest due to their characteristic chemical and physical properties. 1 The synthesis of cumulene based complexes has benefited immensely from the methodology published by Selegue. 2 The reaction of substituted propargyl alcohols with a variety of ruthenium based metal complexes allows for the direct formation of ionic and neutral complexes, and this has dramatically simplified the synthetic demand for such work. π-Conjugated systems based on ruthenium are important in systems that allow exchange of electrons via the cumulenylidene unit between remote terminal groups, 3 thus leading to interesting properties and potential applications in molecular-scale electronic, magnetic, and optical devices. 4 Special attention has been put on dinuclear compounds that can communicate along the allenylidene unit. The linking between the two metal centers can be achieved either via functionalization of the allenylidene with nitrogen based donor substituents, as in the bis(pyridyl)allenylidene−ruthenium(II) complex trans-[Cl(16-TMC)RuCCC(2-py) 2 ] + 5,9,5,9, py = pyridyl), 5 or via all carbon linked systems such as trans-[Cl(dppe) 2 Ru−CC−C(CH 3 )C(H)−C(CH 3 )CC Ru(dppe) 2 Cl]BF 4 , which results from the coupling of the diynyl and allenylidene moieties. 6 Nevertheless, classical mononuclear ruthenium allenylide...

Carbon-rich cyclopentadienyl ruthenium allenylidene complexes

“…We ascribe this oxidation event to the Ru 2+ /Ru 3+ redox couples due to previous observations for related carbon-rich allenylidene complexes reported by our group. 49,50 Moreover, this assignment agrees well with those of other authors. [57][58][59] In contrast, Skelton and Koutsantonis considered it unlikely that such oxidation processes may correspond to the Ru 2+ /Ru 3+ oxidation couple but preferred a ligand-centered oxidation instead.…”

“…However, these angles are closer to the ideal 1801 compared to the recently reported complex [Ru(bdmpza)Cl(PPh 3 )(QCQCQ(PCO))]. [49][50][51]55 The C a -C b bond lengths (1.251 Å (1); 1.256 Å (2) and 1.250 Å (5)) and the C b -C g distances (1.356 Å (1), 1.360 Å (2) and 1.378 Å (5)) are typical for the allenylidene unit when compared to other published allenylidene complexes. 14,21,[49][50][51]55 The Ru-C a bond distances of 1.895 Å (1), 1.907 Å (2) and 1.925 Å (5) are in good agreement with the distances of Ru-C cumulenylidene bonds.…”

“…14,21,[49][50][51]55 The Ru-C a bond distances of 1.895 Å (1), 1.907 Å (2) and 1.925 Å (5) are in good agreement with the distances of Ru-C cumulenylidene bonds. 14,21,[49][50][51]55 The experimental distances of the molecular structure of 2 are in good accordance to the theoretical values gained by DFT calculations (Table S2, ESI †).…”

“…[49][50][51]55 The C a -C b bond lengths (1.251 Å (1); 1.256 Å (2) and 1.250 Å (5)) and the C b -C g distances (1.356 Å (1), 1.360 Å (2) and 1.378 Å (5)) are typical for the allenylidene unit when compared to other published allenylidene complexes. 14,21,[49][50][51]55 The Ru-C a bond distances of 1.895 Å (1), 1.907 Å (2) and 1.925 Å (5) are in good agreement with the distances of Ru-C cumulenylidene bonds. 14,21,[49][50][51]55 The experimental distances of the molecular structure of 2 are in good accordance to the theoretical values gained by DFT calculations (Table S2, ESI †).…”

“…[40][41][42][43] Usually, electrophiles add to C-b of the allenylidene moieties, affording cationic carbyne complexes, 44 whereas nucleophiles attack at C-a or C-g. 27,[45][46][47][48] Recently, we reported on ruthenium allenylidene complexes [Ru(bdmpza)Cl(PPh 3 )(QCQCQCR 2 )] (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate; QCR 2 = polyaromatic residue) bearing polyaromatic moieties. [49][50][51] Most of these complexes show strong p-stacking interactions in solid state, which could be, therefore, promising candidates for metal-tuned FETs or ''organic'' metalsemiconductor field-effect transistors (OMESFETs). The synthesis followed the procedure first reported by Selegue 52 by using the corresponding propargyl alcohols.…”