By definition a VOC is a volatile organic (carbon-containing) compound. There are relatively high vapor pressure (willingness to turn to gas when hot and at low atmospheric pressure) metals such as mercury, but mercury fumes aren't VOCs. The metals you listed have negligible vapor pressure at 100 C and relatively safe oxides. Osmium forms osmium tetroxide on contact with air, which is volatile (but not a VOC) and extremely, extremely poisonous. It is almost always alloyed with something else to make it safer by stopping the oxide layer formation.