The Chemistry of Cyclodiphosphazanes

Thompson, David Graham (1978) The Chemistry of Cyclodiphosphazanes. PhD thesis, University of Glasgow.

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A variety of bis (di ) alkylaminocyclodiphosph (Ill )azanes of the type, (R1R2NPNR3)2 (R1=alkyl, R2=alkyl or H, R3=alkyl or aryl), have been prepared. In most cases synthesis has been effected by aminolysis of the dichloro-derivatives, (ClPNR3)2, exceptions being (Me2NPNC6H40Me-p)2 which was prepared by dimethylaminolysis of the acyclic bis(dichlorophosphino)amine, (C6H40Me-p)N(PCl2)2, and (Me3SiNMe. PNBut)2, which was prepared by treating (ClPNBut)2 with heptamethyldisilazane. The novel cage compound, P(NBut)2PNMe.(CH2)2. KMe, has also been prepared, through the action of N,N'-dimethylethylene- diamine on (ClPNBut)2. The synthesis of Me2NP. NBut.PCl. NBut was repeated and other monodialkylamino-derivatives, R 1 2NP. NR2 . PCI. NR2 (R1=Me, R2=Ph; R1=Pri, R2=But), prepared by treating (ClPNR2)2 with two molar equivalents of the required amine. The action of excess antimony trifluoride or methylamine on Me2NP. NBut.PCl. NBu t afforded Me2NP. NBu t. PF. NBu t and Me2NP.NBut ,P(NHMe). NBu t respectively. A series of alkoxycyclodiphosph(lll)azanes of the type, ROP. NBu t. PX. NBu t (R=alkyl; X=Cl or OR), plus the cage-derivatives, P(NBut)2PO.(CH2)n. O (n=2 or 3) have been synthesised via alcoholysis of (ClPNBut)2 in the presence of triethylamine. Attempts at isolating (ButOPNBut)2 were unsuccessful owing to butene elimination forming Bu t OP. NBu t . P(0)H. NBu t. Many of the above cyclodiphosph(lll)azanes display geometrical isomerism and evidence is presented on the basis of n. m. r. , i. r. , Raman, and photoelectron spectroscopic data, dipole moment and basicity measurements, and X-ray diffraction studies to suggest that when t-butyl is attached to the ring-nitrogen the cis form is thermodynamically favoured, whereas when the smaller aryl-groups are attached, it is the trans form which is more stable. For the first time, thermodynamically unstable cyclodiphosphazane isomers trans-(XPNBut)2 (X=Me2N,MeO, and EtO)] have been isolated. The compounds, [Cl(x)PNBu t]2 (X=0 or S), were surprisingly unreactive towards dimethylamine; [Me2N(x)PNBut]2 finally being produced by treating (Me2NENBut)2 with t-butylhydroperoxide (X=0) and elemental sulphur (X=S). Unlike (ClPNBut)2, which is readily oxidised, (Me2NPNBut)2 is unaffected by dimethyl sulphoxide. These results prompted an investigation into the oxidation reactions of cyclodiphosph(lll)azanes. Cis and trans-(XPNBut)2 (X=Me2N or MeO) react stereospecifically with one or two molar equivalents of elemental sulphur and selenium to give the respective mono- and di- sulphides and selenides with retention of configuration at phosphorus. An X-ray diffraction study of cis- [Me2N(S)PNBut]2 confirmed the structural assignments. Neither cis nor trans-(MeOPNBut)2 reacted with elemental tellurium, but both cis and trans-(Me2NPNBut)2 afforded the monotelluride, trans-Me2NP.NBut . P(Te)NMe2.NBu t, which exhibited intermolecular tellurium exchange at an intermediate rate on the n. m. r. time-scale. No ditelluride could be isolated. Selenium exchange was not observed. However, mixing equimolar solutions of cis-(XPNBut)2 (X=Me2N or MeO) with cis or trans- [x(Se)PNBut]2 yielded the analogous cis. or cis and trans (l:l) monoselenides, XP. NBut. P(Se)X. NBut. Treatment of both cis and trans-(Me2NPNBut)2 with methyl iodide produced the quaternary salts, cis and trans-Me2NP. NBu t. P+ (Me)NMe2. NBut (retention of configuration at phosphorus). On the other hand, the action of methyl iodide on both cis and trans-(MeOPNBut)2 resulted in an Arbuzov-type rearrangement to MeOP. NBut . P(0)Me. NBu t and (after extended reaction periods) to cis and trans-[Me(0)PNBut]2 respectively. Similarly, treatment of cis-(EtOPNBut)2 with methyl iodide afforded Et0P. NBut. P(0)Me. NBut and ci3-[Me(0)PNBut]2. Tentative evidence is presented to suggest these Arbuzov-type rearrangements occur with inversion of configuration at phosphorus, Cis-[Me(o)PNBut]2 may also he produced by heating cis-(MeOPNBut)2 in an evacuated sealed tube. The thermodynamic instability of trans-(XPNBut)2 (X=Me2N or MeO) is paralleled by their enhanced nucleophilicity relative to the cis isomers, as was shown by qualitative observations of the considerably faster rates of reaction of the trans isomers towards sulphur, selenium and methyl iodide. The compounds, Et2N(X)P. NBut. P(Y)NEt2. NBut (X=S or Se, Y=lone-pair; X=Y=S or Se), C5H10N(Se)P. NBu t. P(X)NC5H10.NBut (X=lone-pair or Se), and P(Se),(NBut)2. PNMe,(CH2)2. NMe were produced similarly from their respective parent cyclodiphosph(lll)azanes. By contrast, the reactions of cis-Me2NP. NBut , PCI,NBut with one molar equivalent of dimethyl sulphoxide or elemental sulphur gave a 1:1 mixture of Me2N(0)P. NBut. P(0)Cl. NBut isomers plus starting material and a 1:1 mixture of Me2N(S)P,NBut ,PCl,NBut isomers respectively. The adduct, Me2NP. NBu t. P+ . NBnt AlCl4-, was formed (though not isolated) on reacting cis-Me2NP. NBut. PCI. NBut with aluminium trichloride.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1978
Depositing User: Enlighten Team
Unique ID: glathesis:1978-78785
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:54
Last Modified: 30 Jan 2020 14:54

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