Crystal structure of bis(μ2-3,5-dichloro-2-oxidobenzoato-κ4O,O′:O′,O′′)-hexakis(μ2-pivalato-κ2O:O′)-bis(pivalato-κ2O,O′)-tetrakis(1,10-phenanthroline-κ2N,N′)tetragadolinium(III), C102H108Cl4Gd4N8O22