SYNTHESIS OF 7-ALKYL ARYL-1,3,5-TRIAZA-7-PHOSPHONIA-ADAMANTANE CATIONS AND THEIR REDUCTIVE CLEAVAGE TO NOVEL N-METHYL-P-ALKYL/ARYL[3.3.1]BICYCLONONANE LIGANDS/

Two reaction pathways for the synthesis of 1,3,5-triaza-7-phosphoniaad amantane salts, RP[(CH2)(6)N-3](+)X(-) (1), were followed. Route 1 sta rts with commercial tetrakis(hydroxymethyl)phosphonium chloride, which is converted into P(CH2OH)(3) by treatment with a base. Subsequent qu aternization with alkyl halides RX and cyclization with formaldehyde a nd ammonia afford [R-TPA](+)X(-). This process is only applicable for R = Me (la) and Et (Ib), however, Route 2 is more general and starts w ith primary phosphanes RPH(2), which are converted into organotris (hy droxymethyl)phosphonium salts with formaldehyde and hydrochloric acid followed by ring closure with CH2O/NH3 to give compounds Ic-lf (R = t- Bu, c-Hex, Bz, and Ph, respectively, and X = Cl, I, PF6, or BPh(4)), R eductive cleavage of compounds 1 by sodium in liquid ammonia proceeds with either external (P-R) or internal (P-CH2) bond rupture. P-R cleav age affords the 1,3,5-triaza-7-phosphaadamantane (TPA), while cage cle avage leads to new bowl- or helmet-shaped ligand systems with peripher al amine and phosphane functions (2), Yields of the cage-opening react ion 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 p roposed for this reaction, the leaving group properties of R determini ng the direction of the cleavage. The crystal and molecular structures of compounds 2a and 2f were determined by X-ray diffraction studies. fro 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 smal l amounts, as detected by NMR spectroscopy. Isomer interconversion by P inversion is slow on the NMR time scale. Compounds 2a, 2b and 2f wer e oxidized with elemental sulfur and selenium to give the monosulfides and selenides, respectively (2aS, 2aSe, 2bS, 2bSe, 2fS, 2fSe). Oxidat ion 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 (Me(2)S)AuCl led to the 1:1 c omplexes 2aAuCl, 2bAuCl and 2fAuCl, with the AuCl units solely P-bonde d, as determined by X-ray diffraction of 2aAuCl and 2fAuCl. Compound 2 a forms an ionic 2:1 complex with AuCl, composed of the ions [(2a)(2)A u](+) Cl- (with unidentate ligands), while its reaction with [Me(2)AuC l](2) leads to [Me(2)Au(2a)](+) [Me(2)AuCl(2)](-) (with a chelating 2a ligand), as again confirmed by crystal structure analysis in both cas es. Ligands 2a, 2b and 2f also act as chelating ligands in their tetra carbonylmolybdenum complexes obtained in the reactions with (C7H8)MO(C O)(4).