Copper is also known to exist in +3 oxidation state, which is believed to be involved in

Question:

Copper is also known to exist in +3 oxidation state, which is believed to be involved in some biological electron transfer reactions.
(a) Would you expect this oxidation state of copper to be stable? Explain.
(b) Name the compound K3CuF6 and predict the geometry of the complex ion and its magnetic properties.
(c) Most of the known Cu(III) compounds have square planar geometry. Are these compounds diamagnetic or paramagnetic?