Resolution and Absolute Stereochemistry of 6,7-Dimethoxy-4-phenyl-1,2,3,4-tetrahydroisoquinoline. The Crystal Structure of the R-Hydrochloride Salt Form.
“… 2 Representative ladder motifs in secondary ammonium halides. (a) Type 1 ladder in PEFCUY, in which the third-shortest N + ···X - contact lies along the bisector of the H−N + −H angle and the hydrogen-bond motif (shaded) forms a cis,cis arrangement. (b) Type 2 ladder in BUHCIQ, in which the third-shortest N + ···X - contact lies to the backside of one N + −H bond and the hydrogen-bond motif forms a trans,trans arrangement.…”
The ring-laddering and ring-stacking concepts of structural inorganic chemistry, having been shown
previously to be useful for rationalizing the crystal structures of organic secondary ammonium halides, are shown
also to be applicable to describe the structural chemistry of tertiary and primary ammonium halides. General
examination of the directional preferences of N+···X- contacts in the crystal structures of 196 tertiary ammonium
halides (R3NH+X-) and 59 primary ammonium halides (RNH3
+X-) confirms that the shortest contacts in each
structure are N+−H···X- hydrogen bonds that are close to linear. The next shortest N+···X- contacts display preferred
directions of approach toward the centers of the faces of the pseudo-tetrahedral R3NH+ and RNH3
+ moieties.
Association of R3NH+X- ion pairs according to these preferences leads frequently to the formation of dimers, ladders,
and 2D nets in crystal structures of tertiary ammonium halides. Similar association of R3NH+X- ion pairs leads
frequently to the formation of ladders, 2D nets, cubanes, and extended stacks in crystal structures of primary
ammonium halides. The observed structural motifs, in particular the distribution of N+(−H)···X- distances, are
influenced by interactions between the R groups of the organic moieties, both within and between motifs.
“… 2 Representative ladder motifs in secondary ammonium halides. (a) Type 1 ladder in PEFCUY, in which the third-shortest N + ···X - contact lies along the bisector of the H−N + −H angle and the hydrogen-bond motif (shaded) forms a cis,cis arrangement. (b) Type 2 ladder in BUHCIQ, in which the third-shortest N + ···X - contact lies to the backside of one N + −H bond and the hydrogen-bond motif forms a trans,trans arrangement.…”
The ring-laddering and ring-stacking concepts of structural inorganic chemistry, having been shown
previously to be useful for rationalizing the crystal structures of organic secondary ammonium halides, are shown
also to be applicable to describe the structural chemistry of tertiary and primary ammonium halides. General
examination of the directional preferences of N+···X- contacts in the crystal structures of 196 tertiary ammonium
halides (R3NH+X-) and 59 primary ammonium halides (RNH3
+X-) confirms that the shortest contacts in each
structure are N+−H···X- hydrogen bonds that are close to linear. The next shortest N+···X- contacts display preferred
directions of approach toward the centers of the faces of the pseudo-tetrahedral R3NH+ and RNH3
+ moieties.
Association of R3NH+X- ion pairs according to these preferences leads frequently to the formation of dimers, ladders,
and 2D nets in crystal structures of tertiary ammonium halides. Similar association of R3NH+X- ion pairs leads
frequently to the formation of ladders, 2D nets, cubanes, and extended stacks in crystal structures of primary
ammonium halides. The observed structural motifs, in particular the distribution of N+(−H)···X- distances, are
influenced by interactions between the R groups of the organic moieties, both within and between motifs.
“…A complete three.dimensional X-ray investigation of the (+)-4(R)-enantiomer has been performed. The resolution and absolute stereochemistry of 6,7-dimethoxy-4-phenyl-1,2,3,4-tetrahydroisoquinoline will be published elsewhere (Mondeshka, Angelova, Stensland, Werner & Ivanov, 1990).…”
The ring-stacking and ring-laddering concepts of structural inorganic chemistry may be applied to rationalize motifs observed for secondary ammonium halides R(2)NH(2)X (X = Cl, Br) in the organic solid state. General examination of the directional preferences of N(+)...X(-) contacts in 166 crystal structures confirms that the shortest contacts (3.0-3.2 and 3.2-3.4 A, X = Cl, Br) are N(+)-H...X(-) hydrogen bonds lying approximately along the directions of the N(+)-H bond vectors. The next shortest N(+)...X(-) contacts display two preferred directions of approach: i) contacts in the distance range 3.2-3.5 (X = Cl) and 3.2-3.9 A (X = Br) lie close to the H-N(+)-H plane, along the direction of the bisector of the H-N(+)-H angle; ii) contacts in the distance range 4.0-4.2 (X = Cl) and 4.0-4.4 A (X = Br) lie close to the H-N(+)-H plane, along the direction of an axis extending to the rear of one of the N(+)-H bonds. Both directions of approach lead frequently to association of R(2)NH(2) (+)X(-) ion pairs into laddered motifs. Stacking association is also observed, giving rise in one case to discrete cubanes and in several other cases to extended stacked-cube arrangements. In each case, the distribution of N(+)...X(-) contacts reflects a balance between the directional properties of the N(+)-H...X(-) hydrogen bonds and (primarily steric) interactions between the R groups of the organic moieties. The ladder and stack motifs of the organic ammonium halides are in many cases directly comparable to those in alkali metal amides, [R(2)NM](n), and information derived from the extensive organic sample provides insight into the motifs adopted by the inorganic complexes.
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