The iron pivalate clusters [Fe3O(O2C tBu)6(H2O)3](O2C tBu)·HO2CtBu (1), [Fe 8(OH)4(O2CtBu)12(OC 6H4C6H5)8] (2) and [Fe3O(O2CtBu)6(C5H 5N)3] (3) have been used as single source precursors to synthesise iron oxide nanoparticles by a hot injection thermal decomposition method in oleylamine, hexadecanol, oleic acid, oleylamine/oleic acid with dodecanol or octyl ether as solvent. The effect of the different reaction parameters such as temperature, reaction time and capping agents on the phase and morphology were studied. The reaction time was studied for (1) by thermolysis in a mixture of oleylamine, oleic acid, hexadecanol and dodecanol (solvent) at 260 °C. The results obtained showed that a mixture of maghemite-C (Fe2O3) and magnetite (Fe3O 4) were obtained for aliquots withdrawn for reaction times of less than 30 minutes whilst only magnetite was obtained after one hour. The nanoparticles were characterised by p-XRD, TEM and magnetic measurements. TEM showed that monodispersed magnetite particles were obtained when the precursor was injected at the boiling point of the solvent. The diameter of the monodispersed nanoparticles obtained by the thermolysis of [Fe 3O(O2CtBu)6(H2O) 3](O2CtBu)·HO2C tBu (1) in oleylamine, hexadecanol, oleic acid with dodecanol or octyl ether as solvent were 4.3 ± 0.4 and 4.9 ± 0.5 nm respectively. Magnetic measurements revealed that all the particles are superparamagnetic. © The Royal Society of Chemistry 2013.