[Christine1]

Is anyone has the literature value or know the value for the effective magnetic moment of potassium bisoxalato cuprate(II) dihydrate?

Thanks heaps

[cheese (MSW)]

Here’s what I could find for you.  I hope you have access to a good library.  The Inorg  CHem paper should be available to you electronically.
The magnetic moment is less than the spin only value (1.73 BM) because of weak coupling of the unpaired electrons on the copper atoms.
Magnetism of potassium dioxalatocuprate(II) dihydrate and ammonium dioxalatocuprate(II) dihydrate
    By Jeter, D. Y.; Hatfield, W. E.
    From Inorganica Chimica Acta (1972), 6(3), 523-5.
The magnetic susceptibilities of the K and ammonium salts of dioxalatocuprate(II) dihydrate were measured at 2.9-296°K.  The EPR spectra give evidence for weak spin-spin coupling which is confirmed by the magnetic susceptibility data.  The mechanism for the weak interaction is transmitted by the oxalate bridges.
Crystal structure and magnetism of sodium bis(oxalato)cuprate(II)dihydrate, Na2Cu(C2O4)2.2H2O. A deductive proposal for the structure of copper oxalate, CuC2O4.xH2O (O .ltoreq. .times. .ltoreq. 1)
A. Gleizes, F. Maury, J. Galy Inorg. Chem., 1980, 19 (7), pp 2074–2078.
Last section: “It is interesting to compare these results with those which can be deduced from the study of the complexes K2Cu(C2-04),.2H20 and (NH4)zCu(C204)2~2H20 (ref above).   The authors of this work have found that these complexes followed a Curie-Weiss law with 8 = 0.7 K and 8 = 0.6 K, respectively. If those deviations from the Curie law are attributed to an intrachain coupling, one can deduce J = -0.7
 cm-1 and J = -0.6 cm-1,respectively. Thus, the couplings in the potassium and the ammonium salts appear to be even weaker than in the sodium salt. This discrepancy is to be related to the structural differences between these compounds. K2Cu(C204)2.2H20 and NH4 ) 2C~ (CZ0 4 ) 2 ~ 2aHre2 i0so str~ctural.B~u t, unlike what happens in Na2C~(CZ04)2-2Ht2h0e,ir structures are not made of columnar stacks of units [ C U ( C ~ O ~ b) u~t ]c~on- t ain units [ C U ( C ~ O ~ , H ~ Oan)d~ u]n~it-s [ C U ( C ~ O ~ d) i~sp]o~se-d in such a way (Figure that the interaction occurs through weak oxalate bridges over distances of more than 5 A, whereas in the sodium salt the structural arrangement allows for direct,
even if weak, 6 type overlap of the magnetic orbitals.”   (formatting is off)