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The Triphosphide ( t Bu 3 Si) 2 P 3 Na: Formation, X‐ray and Ab initio Structure Analyses, Protonation and Oxidation to Triphosphane ( t Bu 3 Si) 2 P 3 H and Hexaphosphanes ( t Bu 3 Si) 4 P 6 ☆
Author(s) -
Wiberg Nils,
Wörner Angelika,
Lerner HansWolfram,
Karaghiosoff Konstantin,
Fenske Dieter,
Baum Gerhard,
Dransfeld Alk,
von Ragué Schleyer Paul
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199806)1998:6<833::aid-ejic833>3.0.co;2-1
Subject(s) - chemistry , protonation , adduct , ab initio , crystallography , allylic rearrangement , molecule , ab initio quantum chemistry methods , nuclear magnetic resonance spectroscopy , stereochemistry , computational chemistry , ion , organic chemistry , catalysis
The violet THF adduct ( t Bu 3 Si) 2 P 3 Na(THF) 4 ( 1a ) of the triphosphide ( t Bu 3 Si) 2 P 3 Na ( 1 ) is prepared, (i) by protolysis of the tetraphosphide ( t Bu 3 Si) 2 P 4 Na 2 ( 2 ) with an equimolar amount of CF 3 CO 2 H in THF (transformation of 2 into 1 ), (ii) by the reaction of t Bu 3 SiNa and the oligophosphane ( t Bu 3 SiP 3 ) n in THF (building‐down of P n ), and (iii) by the action of t Bu 3 SiNa on PCl 3 in THF (building‐up of P n ). According to X‐ray structural analysis, the SiPPPSi skeleton of the anionic part [ t Bu 3 SiPPPSi t Bu 3 ] – of 1a is W‐shaped with two P–P 1 1 / 2 bonds; in addition, 1a contains a planar deltoid P 3 Na backbone with the 4 THF molecules coordinated to Na. The protolysis of 1a leads to cyclotriphosphane ( t Bu 3 Si) 2 P 3 H ( 11 ), and the oxidation of 1a leads to 1,1′‐bicyclotriphosphane ( t Bu 3 Si) 2 P 3 –P 3 (Si t Bu 3 ) 2 ( 12 ) as the main product and bicyclo[3.1.0]hexaphosphane ( t Bu 3 Si) 4 P 6 ( 13 ) as an isomer of 12 . The structures of 11 , 12 , and 13 as well as the structure of 1a have been unambiguously determined by 31 P‐NMR studies. Ab initio structure and energy calculations show that the acyclic P 3 H 2 – with allylic conjugation and P–P 1 1 / 2 bonds is thermodynamically more stable than the cyclic isomer whereas, in contrast, the neutral compound P 3 H 3 prefers the cyclic form. The exceptional downfield shift of the NMR signal of the central phosphorus in 1a is in agreement with DFT NMR calculations for a model compound [H 3 SiPPPSiH 3 ]Na with P–P 1 1 / 2 bonds.