In the book "Inorganic reaction in water", the symbol "κ" is used to describe the bonding in some complexes, the meaning of the symbol is well discussed here. However, the compound whose formula is K6[{Co(CN)5}2(μ-SO2-1κS:2κO)] has vague detail "1κS:2κO". What is the structural formula of this compound?
From K3[CoBr(CN)5] and K2SO3, followed by methanol, arises yellow K4[Co(CN)5(SO3)]⋅4H2O. Aqueous K3[Co(CN)5] and SO2, followed by methanol, may yield orange K6[{Co(CN)5}2(μ-SO2–1κS:2κO)]⋅4H2O.
I assume that you know that $\mu$ indicates the presence of a ligand bridge in the complex between two metallic centers.
From the IUPAC Golden Book:
An affix in the name of a polydentate chelate complex indicating single ligating atom attachments of a polyatomic ligand to a coordination centre. A right superscript numerical index indicates the number of such attachments. Example: $$\ce{Ni[(CH3)2PCH2CH2P(CH3)2]Br2}$$ $$\text{dibromobis[1,2-ethanediylbis(dimethylphosphine)-}κ^2\text{P] nickel(II)}$$
So, $\kappa$ is used to describe the apticity of a polidentate ligand, that is how many functional groups of a ligand coordinate a certain central ion and which atoms are involved.
In the IUPAC example the ligand is bidentate and 2 phosphorous atoms are involved in the chelation.
In your case, you have two cobalt ions bridged by an $\ce{SO2}$ molecule. However it seems a little odd to me that your reference reports formulas without the correct charge balance... stating that there is a cobalt complex with coordination number 5 and with neutral charge. Are you sure this is the correct formula?
Anyway, reading literally what is written in your question: there are 2 metallic centers bridged by an $\ce{SO2}$ molecule and in which 1-sulfur atom, and 2-oxygen atoms coordinate respectively the first cobalt ion and the second cobalt ion. I think, however, that such a complex is not possible and this could probably be just the stoichiometry of a unit cell for the crystal lattice.
