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A Zwitterionic Phosphonio‐1, 2, 4‐Diazaphospholide and Neutral 1, 2, 4‐Diazaphosphole — A Comparative Study of Molecular Structures and Co‐ordination Properties
Author(s) -
Szarvas Laszlo,
Bajko Zoltan,
Fusz Stefan,
Burck Sebastian,
Daniels Jörg,
Nieger Martin,
Gudat Dietrich
Publication year - 2002
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200211)628:11<2303::aid-zaac2303>3.0.co;2-f
Subject(s) - chemistry , crystallography , deprotonation , adduct , borane , protonation , moiety , lithium (medication) , single crystal , lone pair , stereochemistry , molecule , ion , organic chemistry , endocrinology , catalysis , medicine
The bis‐phosphonio‐1, 2, 4‐diazaphospholide salt ( 1 [Cl]) reacts with complex boron hydrides under selective extrusion of one PPh 3 moiety to give borane adducts of a novel zwitterionic phosphonio‐1, 2, 4‐diazaphospholide. Both the Et 3 B adduct 2b and the free zwitterionic heterocycle 3 , which was liberated by further reaction of 2b with NEt 3 , were characterized by spectroscopic data and 2b , as well, by a single crystal X‐ray diffraction study. The comparison of the structural data with those of a neutral 1, 2, 4‐diazaphosphole and a lithium‐1, 2, 4‐diazaphospholide which was formed by deprotonation of the parent 1, 2, 4‐diazaphosphole 4a discloses trends in endocyclic bonding distances which can be rationalized in terms of a charge dependent shift in the π‐electron distribution. First studies of the co‐ordination properties reveal for both 2b and 4a a marked preference to bind two M(CO) 5 ‐fragments (M = Cr, W) via the lone‐pairs of the phosphorus and one nitrogen atom; mononuclear complexes with P ‐co‐ordinated heterocycles are formed as intermediates. A single crystal X‐ray diffraction study of the dinuclear complex [Cr 2 (CO) 10 (μ 2 ‐C 2 H 3 N 2 P‐κ P , κ N )] ( 10a ) together with spectroscopic studies (including 183 W NMR studies of tungsten complexes) suggests that M→L back donation is more efficient for P ‐ than for N ‐bound metal fragments. No evidence for π‐co‐ordination of the 1, 2, 4‐diazaphosphole ring to a Cr(CO) 3 fragment was obtained.