Quaternization and oxidation reactions of cyclodiphosphazane derivatives and their copper(i) and gold(i) complexes

Abstract

The reactions of cyclodiphosphazane derivatives cis-{^tBuN(H)P(μ-N^tBu)₂PN(H)^tBu} (1), cis-{MeN(C₄H₈N)P(μ-N^tBu)₂P(NC₄H₈Me)} (2) and {(Me₂NCH₂CH₂O)P(μ-N^tBu)₂P(OCH₂CH₂NMe₂)} (3) with methyl iodide and methyl triflate and their subsequent reactions with elemental sulfur and selenium are reported. Interestingly, the reactions of 1–3 with an excess of methyl iodide resulted in quaternising only one phosphorus atom in cis-[{^tBuNHP(μ-N^tBu)₂P(CH₃)NH^tBu}](I) (4), two exocyclic nitrogen atoms and one of the phosphorus atoms in cis-{(Me₂NC₄H₈N)P(μ-N^tBu)₂P(CH₃)(NC₄H₈NMe₂)}](I)₃ (7) and only two exocyclic nitrogen atoms in cis-[{(Me₃NCH₂CH₂O)P(μ-N^tBu)₂P(OCH₂CH₂NMe₃)}](I)₂ (8). The reaction of 1 with one equiv. of methyl triflate produced cis-[{^tBuN(H)P(μ-N^tBu)₂P(CH₃)N(H)^tBu}]OTf (5), whereas the same reaction in a 1 : 2 molar ratio afforded cis-{^tBuN(H)P(CH₃)(μ-N^tBu)₂P(CH₃)N(H)^tBu}(OTf)₂ (6). Compounds 4 and 5 showed poor solubility in water, whereas 7 and 8 were high melting crystalline solids with moderate to good water solubility. Treatment of 4 with either elemental sulfur or selenium gave both cis- and trans-chalcogenide derivatives. Similar reactions of 7 and 8 produced both mono- and bischalcogenides. Reactions between 4 or 7 and CuI yielded dinuclear complexes, cis-[{Cu₂(μ-I)₃(^tBuN(H)P)(μ-N^tBu)₂(P(CH₃)N(H)^tBu)]₂}(I)] (15) and cis-[{Cu₂(μ-I)₃[(Me₂NC₄H₈N)P(μ-N^tBu)₂P(CH₃)(NC₄H₈NMe₂)]₂}(I)₅] (16), while the reaction of 8 with CuI produced a coordination polymer [{Cu₂(μ-I)₃(μ-N^tBuP)₂(OCH₂CH₂NMe₃)₂}I]_∞ (17), containing triiodo-bridged [Cu₂(μ-I)₃] linkers. The molecular structures of several of these compounds were confirmed by single crystal X-ray diffraction studies. The Cu^I⋯Cu^I distance of 2.55 Å in 15 is quite short and is the same as that found in copper metal and also in complexes containing [Cu₂(μ-I)₃] linkers. All the metal complexes exhibit strong intra-, inter- or both intra- and inter-molecular hydrogen bonding interactions.