Beiträge zur Chemie des Phosphors, 62¹ Zur Frage des ³¹P-kernresonanzspektroskopischen Nachweises von monomerem und dimerem Phenylphosphor und der Ringgröße von Organyl-cyclophosphanen.

Abstract

The weak resonances at + 22 and + 49 ppm appearing in the 31P NMR spectrum of melts or solutions of (PPh)5 that have been attributed previously in the literature to “dimeric” and “monomeric phenylphosphorus” are caused by (PPh)6 and (PPh)4, respectively. This was proved by comparison with the 31P NMR parameters of related compounds and by 31P NMR spectroscopic investigation of authentic samples of (PPh)6 and (PPh)4, the latter of which was prepared in high yield from (Me3Si)PhP–PPh–PPh(SiMe3) and PhPCl2. (PEt)4 and mixed-substituted phenyl-ethyl-cyclotetraphosphanes exhibit similar chemical shifts as (PPh)4, corresponding mixed-substituted cyclohexaphosphanes have similar chemical shifts as (PPh)6. Generally, cyclophosphanes establish an equilibrium between (PR)n-species of different ring-size. Probably, the ring-interconversion proceeds via a multi-center mechanism. No 31P NMR spectroscopic evidence for the existence of free PPh or P2Ph2 under the conditions described could be detected. On thermolysis of (PEt)4 the existence of (PEt)3 was proved for the first time.

The structure and reactivity of arsenic compounds: Biological activity and drug design

“…The cyclic phosphorus compound (PhP)6 exhibits solventdependent equilibria with (PhP)5, e.g. in THF, CS2, C6H6, the only species present is the hexamer, whereas in CHCI3, the pentamer predominates [140]. When arsenomethane is treated with cacodyl, Me2As-AsMe2, an equilibrium mixture is obtained, involving the making and breaking of As-As bonds, the C~s bonds being stable [136].…”

Catalytic PH Activation by Ti and Zr Catalysts

“…[46,47] Literature precedent has shown disproportionation of (PhPH) 2 affords PhPH 2 , cyclic oligomers (RP) n and Ph(H)PA C H T U N G T R E N N U N G (PPh) n P(H)Ph (predominantly n = 3). [46] Upon prolonged heating three additional signals appeared which were assigned to (PPh) 4 , [48] (PPh) 5 [49] and (PPh) 6 . [48] By integration, (PPh) 5 is the major product although it is also known that (PPh) 4 and (PPh) 6 disproportionate to (PPh) 5 upon heating.…”

“…[46] Upon prolonged heating three additional signals appeared which were assigned to (PPh) 4 , [48] (PPh) 5 [49] and (PPh) 6 . [48] By integration, (PPh) 5 is the major product although it is also known that (PPh) 4 and (PPh) 6 disproportionate to (PPh) 5 upon heating. [50] In comparison, the analogous dehydrocoupling catalyzed by a Rh species yields (PhPH) 2 in 56 % yield on heating to 150 8C for 26 h. [41] In addition to the dehydrocoupling products, the 31 P NMR spectra of the above PhPH 2 reaction mixtures showed resonances including a doublet at d 136.6 ppm and triplet at À119.9 ppm with a J P,H coupling constant of 304 Hz and a singlet at d 41.0 ppm, all of which were attributed to…”

Reactions and Coordination Properties of the First Secondary Carbaboranyldiphosphane: 1,2-Bis(phenylphosphanyl)-1,2-dicarba-closo-dodecaborane(12)

“…When a mixture of stereoisomers of 1 (1a/1b ϭ 3:1) was treated with dimethylzirconocene in boiling toluene for 2 h (Scheme 1), the formation of three phosphorus-containing products Ϫ meso-[Cp 2 Zr(PPh) 3 ] (3) [13] [14] , (PPh) 4 (4) [15] , and (PPh) 5 (5) [16] (ratio 2.8:1.1:1.0) Ϫ was observed by 31 P-NMR spectroscopy. The 1 H-NMR spectrum of the reaction mixture showed the presence of unreacted dimethylzirconocene (ca.…”