1,1,6,6-Tetrakis(4-ethylphenyl)-1,2,3,4,5-hexapentaene

Abstract

Key indicators: single-crystal X-ray study; T = 90 K; mean (C-C) = 0.003 Å; R factor = 0.058; wR factor = 0.166; data-to-parameter ratio = 17.2.The title compound, (4-EtC 6 H 4 ) 2 C C C C C C(4-EtC 6 H 4 ) 2 or C 38 H 36 , was prepared from 1,1,6,6-tetrakis(4ethylphenyl)-2,4-hexadiyne-1,6-diol by reduction with SnCl 2 in an acidic medium. The molecule has a centre of symmetry at the mid-point of the cumulative double bonds, in which longer and shorter bonds alternate.

Transformation of a 1‐Zirconacyclopent‐3‐yne, a Five‐Membered Cycloalkyne, into a 1‐Zirconacyclopent‐3‐ene and Formal “1‐Zirconacyclopenta‐2,3‐dienes”

“…The treatment of a low‐valent zirconocene–bisphosphine complex, [Cp 2 Zr(PMe 3 ) 2 ],6 with 1,1,6,6‐tetrakis(4‐ethylphenyl)‐1,2,3,4,5‐hexapentaene ( 2 )7 at room temperature for 4 days gave the 2,5‐bisalkylidene‐1‐zirconacyclopent‐3‐yne compound 3 in 70 % yield [Eq. (2)].…”

“…The triple bond in 3 (C3C4) is significantly longer than that in the nonsubstituted 1‐zirconacyclopent‐3‐yne complex 1 (R=H; 1.237(5) Å),3e whereas the adjacent single bonds (C2C3 and C4C5) are slightly shorter in 3 than in 1 (1.406–1.408 Å in 1 ). These differences may reflect differences between the bond lengths of hexapentaene 2 and those of butatrienes: Compound 2 has a longer central bond (1.311(2) Å),7, 10 whereas butatrienes have a shorter central bond (1.22–1.28 Å). The alkylidene moieties are bent away from the metal center; the four carbon atoms C2–C5 and the Zr center are coplanar, and C1 and C6 are located 0.24 and 0.27 Å from this plane, respectively. …”

The Role of Bulkiness in Haptotropic Shifts of Metal–Cumulene Complexes

“…The carbon double bond attached to the Pt in 2a is significantly elongated in comparison to that of a similar free ligand (around 0.13 Å). [25] This C=C bond linked to the metal is statistically equal to the C=C bond in Ph 4 cumulene-[Rh(PPh 3 ) 2 Cl] (4a) (a difference of only 0.01 Å), [16] despite the fact that Pt is larger than Rh. The lengths of the M-C bonds that are contiguous to the center of the cumulene chain are also essentially equal.…”

“…Figure shows the crystal structures of 2a and 2b . The carbon double bond attached to the Pt in 2a is significantly elongated in comparison to that of a similar free ligand (around 0.13 Å) . This C=C bond linked to the metal is statistically equal to the C=C bond in Ph 4 cumulene–[Rh(PPh 3 ) 2 Cl] ( 4a ) (a difference of only 0.01 Å), despite the fact that Pt is larger than Rh.…”

Formation of Binuclear Zigzag Hexapentaene Titanium Complexes via a Titanacumulene [Ti=C=C=CH2] Intermediate

“…An unsubstituted isolated [5]cumulene C 6 H 4 is not available under preparative conditions yet it can be generated in situ and trapped with an appropriate substrate . In contrast, substituted hexapentaenes are easily available from the corresponding C 6 building blocks yet there have only been a few reports on the structural characterization of such molecules …”