The answer depends... If your inductor has only one input port, then indeed you can use the Z(1,1) Parameter to extract the inductance (Note: Im(Z) = 2*pi*Freq*L) However, if you have a two port device, you will need to use the Admittance to extract the inductance. The reason for this is that an S Matrix determines the distribution of power in a port with all other ports terminated. The Impedance matrix determines the impedance with all other ports OPEN (Inputs 1 Amp in port and measures voltage at all other ports) ! The Admittance matrix determines the admittance with all other ports SHORT (Inputs 1Volt and measures current at all other ports).
So, in short, if you have a two port inductor, use the relationship: Im(Y) = -1/(2*pi*Freq*L) to retrieve the Inductance. The reason is that if you use the Z matrix with a two port device, the open at the other port will induce such a strong parasitic capacitance that the inductance can not be determined. However, since the Admittance shorts the other port, the inductance is correct.
Have Fun!