The Crystal and Molecular Structure of the Adduct Formed by the Reaction of Tributylphosphine and p-Chlorobenzylidenemalononitrile

Abstract

Crystals of the 1:l adduct of tributylphosphine withp-chlorobenzylidenemalononitrile are monoclinic, a = 13.719(2), b = 12.557(5), c = 14.229(3) ?L, P = 110.59(2)", Z = 4, space group P211c. The structure was determined with diffractometer data by direct methods and refined by block-diagonal leastsquares calculations to R = 0.10 for 1405 observed reflections. The structure is zwitterionic with the positive charge localized on the phosphorus atom and the negative charge mainly on the terminal -C(CN)2 group.Les cristaux de I'adduit 1:1 de la tributylphosphine avec le p-chlorobenzylidenemalononitrile sont monocliniques avec a = 13.719(2), b = 12.557(5), c = 14.229(3) ?L, P = 110.59(2)",Z = 4, le groupe spatial est P211c. La structure a ttk determinke B partir des donntes du diffractomktre par les mCthodes directes et les moindres carrks aprts raffinement juisqu'ii un R = 0.10 pour 1405 rkflexions observkes. La structure est zwittkrionique avec la charge positive localiske sur I'atome de phosphore e t la charge nkgative principalement sur le groupe -C(CN)2 terminal.[Traduit par l e journal]Can. J. Chem.. 51. 2794 (1973) All the reactions involving the interaction of nucleophiles with electronegatively substituted alkenes can be rationalized in terms of an initial attack of the nucleophile on the P-carbon atom of the alkene to form the intermediate (I), whose further reaction can give rise to a variety of products depending on the conditions (eq. 1 ; X is an electronegative sustituent) (1). The existence of species of type 1 has been verified in the case of substituted stilbenes for charged nucleophiles (2-4).When the nucleophile is uncharged, a special case of eq. 1 arises and a zwitterion should be formed, eq. 2. One case where an adduct of 1 : 1 stoichiometry has been experimentally observed in such an attack by a neutral nucleophile is the interaction of tributylphosphines with benzylidenemalononitriles (5). Horner and Klupfel (5) originally formulated the structure as the zwitterion (2). Since then, several other possible structures have been considered (6,7).A recent n.m.r. investigation (7) has concluded that the zwitterionic structure (2) was correct. Because of the direct relevance of these compounds to the theory of nucleophilic alkene substitution reactions, the structure analysis of the 1 : 1 adduct of tributylphosphine with p-chlorobenzylidenemalononitrile was undertaken in an attempt to confirm the results of the n.m.r. investigation. ExperimentalThe adduct crystallized from dioxan as yellowish irregular fragments. A small crystal was mounted a n d sealed in a thin-walled capillary (when left in the open the crystals showed evidence of decomposition and of being hydroscopic). Unit-cell and space group data were obtained from various rotation, Weissenberg, and precession photographs; accurate cell parameters were obtained by a least-squares procedure applied to the setting angles of 12 general reflections measured o n a diffractometer. Crystal DataCzzH32CIN2P (mol. wt. 390.9): monoclinic, a = Can. J. ...

Properties and reactions of ylidenemalononitriles

“…320"322 The crystal and molecular structure of the 1:1 adduct formed by the reaction of tributylphosphine and CS (7) has been determined with diffractometer data by direct methods. 323 The zwitterionic adduct has the positive charge localized on the phosphorus atom and the negative charge mainly on the terminal dicyanomethyl group.…”

Interactions and reactions in some 2,2′-disubstituted biphenyls—an open or shut case

“…In zwitterion 9, the anionic group, an enolate of a cyclic b-diketone, takes a pseudo-equatorial position with respect to the newly formed ring and is oriented at 54.61(5) • to the best plane through the whole ring system, but in the two independent molecules of zwitterion 8, the negatively charged dicyanomethide groups take pseudoaxial positions and are oriented at 69.37 (12) and 75.0(2) • to the best plane through each ring system. The molecules of zwitterion 9 are linked in chains along the a axis by hydrogen bonding between the carbonyl oxygens and an intervening water molecule (O ◊ ◊ ◊ H-O: 1.941 (19) and 1.870(19) A ˚) (Fig.…”