ISSN:
0009-2940
Keywords:
1,3,5-Triaza-7-phospha-adamantane
;
Reductive cleavage of phosphonium salts
;
Ambidentate P,N-ligands
;
P,N-[3.3.1]bicyclononane systems
;
Phosphanes
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Two reaction pathways for the synthesis of 1,3,5-triaza-7-phosphoniaadamantane salts, RP[(CH2)6N3]+X- (1), were followed. Route 1 starts with commercial tetrakis(hydroxymethyl)phosphonium chloride, which is converted into P(CH2OH)3 by treatment with a base. Subsequent quaternization with alkyl halides RX and cyclization with formaldehyde and ammonia afford [R-TPA]+X-. This process is only applicable for R = Me (1a) and Et (1b), however. Route 2 is more general and starts with primary phosphanes RPH2, which are converted into organotris(hydroxymethyl)phosphonium salts with formaldehyde and hydrochloric acid followed by ring closure with CH2O/NH3 to give compounds 1c-1f (R = t-Bu, c-Hex, Bz, and Ph, respectively, and X = Cl, I, PF6, or BPh4). Reductive cleavage of compounds 1 by sodium in liquid ammonia proceeds with either external (P-R) or internal (P-CH2) bond rupture. P-R cleavage affords the 1,3,5-triaza-7-phosphaadamantane (TPA), while cage cleavage leads to new bowl- or helmet-shaped ligand systems with peripheral amine and phosphane functions (2). Yields of the cage-opening reaction are highest for R = Ph (2f), moderate for R = Me and Et (2a, 2b), and poor with the remaining R groups (2c-2e). A radical mechanism is proposed for this reaction, the leaving group properties of R determining the direction of the cleavage. The crystal and molecular structures of compounds 2a and 2f were determined by X-ray diffraction studies. Exo positions were found for the N-Me and P-R groups. The isomers with the R group in the endo position are also present in solution in small amounts, as detected by NMR spectroscopy. Isomer interconversion by P inversion is slow on the NMR time scale. Compounds 2a, 2b and 2f were oxidized with elemental sulfur and selenium to give the monosulfides and selenides, respectively (2aS, 2aSe, 2bS, 2bSe, 2fS, 2fSe). Oxidation with H2O2 led to degradation. Compound 2a was quaternized at the P atom by treatment with Mel to give the corresponding phosphonium salt. Treatment with equimolar quantities of (Me2S)AuCl led to the 1:1 complexes 2aAucl, 2bAuCl and 2fAuCl, with the AuCl units solely P-bonded, as determined by X-ray diffraction of 2aAuCl and 2fAuCl. Compound 2a forms an ionic 2:1 complex with AuCl, composed of the ions [(2a)2Au]+ Cl- (with unidentate ligands), while its reaction with [Me2AuCl]2 leads to [Me2Au(2a)]+ [Me2AuCl2]- (with a chelating 2a ligand), as again confirmed by crystal structure analysis in both cases. Ligands 2a, 2b and 2f also act as chelating ligands in their tetracarbonylmolybdenum complexes obtained in the reactions with (C7H8)Mo(CO)4.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19951280907
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