Fe3+ + SCN- <-> FeSCN2+; log K = 3.02
Fe3+ + 2SCN- <-> Fe(SCN)2+; log K = 4.64
Fe3+ + 3SCN- <-> Fe(SCN)3; log K = 5.0
Fe3+ + 4SCN- <-> Fe(SCN)4-; log K = 6.3
Fe3+ + 5SCN- <-> Fe(SCN)52-; log K = 6.2
Fe3+ + 6SCN- <-> Fe(SCN)63-; log K = 6.1
Edit: Sorry, after pasting the data I realized you asked about isothio... No idea where to find them.