The range of cyclo and poly(phosphazene) derivative has been significantly expanded by exploiting the reactivity of organic, organometallic and inorganic functionality resident in a preformed cyclo or poly(phosphazene). The alkyne unit has significant potential for further synthetic elaboration but has been underutilized in phosphazene chemistry. This contribution will focus on alkynlphosphazenes and selective aspects of their reactivity with an emphasis on recent results. Traditionally the only significant route to alkynlphosphazenes has been via the interaction of an organolithium reagent with a fluorophosphazene and we have used this approach to prepare several such derivatives. We have overcome the limitation to fluorophosphazenes by preparing, via standard coupling methodologies, p-ethynlphenol. The corresponding phenolate has been reacted with cyclo and poly(chlorophosphazenes) to give the ethnylphenoxy derivatives. Ab initio and DFT calculations show that no direct mesomeric alkyne/phosphazene π system interactions occur and that the phenoxy π system is likewise electronically isolated from the phosphazene. The reaction of the alkynlphosphazenes with dicobalt octacarbonyl produces the well known alkyne/dicobalt hexacarbonyl cluster which we have examined in a variety of phosphazene environments. Detailed electrochemical studies show a reversible one electron reduction to the radical anion which can be observed by esr spectroscopy. This reduction process can also be observed in carbon chain polymer with an alkynlphosphazene substituent thus providing well characterized redox polymers. The alkynlphosphazene / cobalt carbonyl cluster was also obtained in both cyclo and poly(phosphazene) ethynlphenoxy derivatives. The polymeric species undergoes a thermal decomposition process at modest temperatures to provide a dispersion of cobalt nanoparticles in a polymer matrix. The thermal decomposition process of the poly( ethynlphosphazenes) prior to the incorporation of the dicobalt carbonyl cluster show that the alkyne functionality leads to significant increases in thermal stability and char yields.