Experimental and Theoretical Investigations of Lithium and Magnesium Derivatives of Bis(tert-butylamido)cyclodiphosph(III/V)- and (V/V)azane Mono- and Ditellurides

Abstract

Deprotonation of bis(tert-butylamido)cyclophosph(III/III)azane with organolithium or organomagnesium reagents followed by oxidation with elemental tellurium is a viable approach to the preparation of metal cyclodiphosphazane mono- and ditellurides. The reaction of the cyclodiphosph(III)azane [tBu(H)NP(mu-NtBu)2PN(H)tBu] (1) with elemental tellurium in boiling toluene affords the monotelluride [tBu(H)N(Te)P(mu-NtBu)2PN(H)tBu] (9). A similar reaction involving the magnesium salt Mg[tBuNP(mu-NtBu)2PNtBu](THF)2 (2) also yields a monotelluride Mg[tBuN(Te)P(mu-NtBu)2PNtBu]-(THF)2 (10). By contrast, reaction of the lithium salt Li2[tBuNP(mu-NtBu)2PNtBu](THF)2 (3) with tellurium results in double oxidation and the formation of the ditellurides Li2[tBuN(Te)P(mu-NtBu)2P(Te)NtBu](THF)4 (11) and Li2-[tBuN(Te)P(mu-NtBu)2P(Te)NtBu](tmeda)2 (12). Compounds 9-12 have been characterized by multinuclear (1H, 7Li, 13C, 31P, and 125Te) NMR, while 9, 10, and 12 have also been characterized by X-ray crystallography. The structure of 9 reveals a typical cis/endo, exo arrangement, with no intermolecular contacts to tellurium. The seco-heterocubic structure, observed in 2, is retained in 10, with the ligand chelating magnesium in an N,N',N"-manner. Unique coordination behavior is exhibited by the ditelluride 12, in which the dianionic ligand is attached to the two lithium centers in both Te,Te' and Te,N bonding modes. Multinuclear NMR data are consistent with retention of the solid-state structures of 9-12 in solution at low temperatures. The reactivity of cyclodiphosph(III/III)azanes toward chalcogens is rationalized by using theoretical calculations (semiempirical PM3 level of theory), which show an inverse correlation between the charge at the phosphorus center and the ease of oxidation.

Chalcogenide Derivatives of Imidotin Cage Complexes

“…The lower reactivity of magnesium derivative 4 towards chalcogens, relative to that of lithium derivatives 2 (see below), parallels our earlier observations for the reactions of the [tBuNP(m-NtBu) 2 PNtBu] 2À anion towards tellurium. [13] The reaction of the anionic lithium-containing cubane 2 a with one equivalent of elemental chalcogen rapidly produces the monochalcogenide complexes 6 a and 6 b as depicted in Scheme 2. However, owing to the highly reactive nature of 2 a, it is difficult to prepare pure samples of the monochalcogenides using this method.…”

An Unusual Ditelluride: Synthesis and Molecular and Electronic Structures of the Dimer of the Tellurium‐Centered Radical [TePiPr2NiPr2PTe].

“…The phosphorus-tellurium bond length of 2.3798(8) Å is similar to that observed in related compounds containing a terminal P=Te bond. [17] The preferential formation of the P-H tautomer 4a may be contrasted with the series of monochalcogenides PPh2NHPh2P(E) (E = O, S, Se), which all exist exclusively as the N-H tautomer, both in solution and in the solid state. [18,19] Consequently, we prepared the monoselenide by stoichiometric oxidation of PiPr2NHiPr2P with selenium in n-hexane at 23 °C.…”

A Silver(I) Iodide Complex of a Tellurophosphorane

“…The characterization of 2 is significant since the monotelluride B is only available in 5% yield via telluration of the P(III)/PIII) precursor and it decomposes readily in solution. [8] …”

“…[4] We have previously shown that the phosphorus-tellurium bond is stabilized by a negative charge in the anionic ligands {[R 2 P(Te)] 2 N} − [5] and we reported the X-ray structures of hexameric and tetrameric Ag(I) complexes of this ligand for R = iPr and Ph, respectively. [6] In a sequel to that work we have now investigated the reaction of the P-Te dianion [tBuN(Te)P(-NtBu) 2 P(Te)NtBu)] 2− (A) [7] with silver(I) iodide and found, unexpectedly, that a AgI complex of the neutral monotelluride ([tBu(H)N(Te)P(-NtBu) 2 PN(H)tBu]) (B) [8] is formed.…”

“…1 J(P,Te) = 2024 Hz for B). [8] The broad signals are presumably due to the existence of rapid exchange equilibria, which is known to occur for the P(III) and P(V) sites in the tellurophosphane iPr 2 PCH 2 P(Te)PiPr 2 .…”