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Unusual Stability despite a P‐bonded Proton: Phospha and Diphospha Ureas with the TrtP(H)‐Moiety
Author(s) -
Plack Volker,
Goerlich Jens R.,
Schmutzler Reinhard
Publication year - 1999
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/(sici)1521-3749(199906)625:6<919::aid-zaac919>3.0.co;2-7
Subject(s) - chemistry , medicinal chemistry , nucleophile , ammonia , moiety , nuclear magnetic resonance spectroscopy , isocyanate , bond cleavage , stereochemistry , organic chemistry , catalysis , polyurethane
As the first diphospha‐urea with P‐bonded protons, [TrtP(H)] 2 C=O ( 3 ) was found to be of amazing stability, which is thought to be due to the presence of the triphenylmethyl groups. Unlike known cyclic or non‐cyclic analogues, 3 showed next to no tendency to eliminate carbon monoxide. 3 was obtained by reaction of the dimeric phospha‐isocyanate (TrtPCO) 2 ( 1 ) with LiAlH 4 , in which the intermediary phosphaalkene 2 was observed. Caused by its two asymmetric phosphorus atoms, 3 appeared as a mixture of two isomers, meso‐3 and rac‐3 (ratio: 20 : 1). Theoretical considerations, and the analysis of the proton‐coupled 31 P NMR spectrum (spin system: AA′XX′), allowed the assignment of the signals to the two isomers. The action of anhydrous hydrogen chloride on 3 led to the cleavage of one P–C(:O)‐bond, and formation of an equimolar mixture of TrtPH 2 ( 5 ) and TrtP(H)C(:O)Cl ( 6 ). Cleavage of a P–C(:O)‐bond in 3 was also observed in its reaction with tetramethylguanidine (TMG) or ammonia. As proved by 31 P NMR spectroscopy in the case of TMG, the reaction proceeded via the phosphaalkene intermediate 8 . Acting as nucleophiles, TMG and ammonia substituted TrtP(H) in 3 , and the P,N‐ureas 9 and 10 , with TrtPH 2 ( 5 ) as a side product, were obtained.