Constructing a short C–H · · · O hydrogen bond: the crystalline complex of triphenylsilylacetylene with triphenylphosphineoxide. A very unusual crystal structure with Z = 7 and Z′ = 3.5
Abstract
The crystalline complex of triphenylsilylacetylene
(Ph3Si–C![[triple bond, length as m-dash]](https://www.rsc.org/images/entities/char_e002.gif)
C–H) and
triphenylphosphineoxide (Ph3P![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
O) contains four
symmetry independent molecular dimers which are connected by
CC–H · ·
· OP hydrogen bonds. These hydrogen bond
have
H · · ·
O separations between 1.99 and 2.05 Å, and are the
shortest reported for acetylenic donors. This reflects the fact that the
hydrogen bonds are formed between one of the strongest known C–H
donors and one of the strongest O acceptors. The red-shift of the
acetylenic IR C–H stretching vibration compared to an apolar
solution is -149 cm-1, the largest reported for a
known crystal structure. The crystal packing in space group
P![[1 with combining macron]](https://www.rsc.org/images/entities/char_0031_0304.gif)
is complex with the very rare unit cell content of
3.5 formula units per asymmetric crystal unit
(Z′ = 3.5).
C–H) and
triphenylphosphineoxide (Ph3PO) contains four
symmetry independent molecular dimers which are connected by
CC–H · ·
· OP hydrogen bonds. These hydrogen bond
have
H · · ·
O separations between 1.99 and 2.05 Å, and are the
shortest reported for acetylenic donors. This reflects the fact that the
hydrogen bonds are formed between one of the strongest known C–H
donors and one of the strongest O acceptors. The red-shift of the
acetylenic IR C–H stretching vibration compared to an apolar
solution is -149 cm-1, the largest reported for a
known crystal structure. The crystal packing in space group
P is complex with the very rare unit cell content of
3.5 formula units per asymmetric crystal unit
(Z′ = 3.5).
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