High nuclear CoIInCoIIIm coordination clusters with planar Con+m arrays have been reported for n = 7 (m = 0); n = 9 (m = 3) and n = 11 (m = 2). To the best of our knowledge the title compound {CoII10} thus represents the largest homovalent planar Co complex with n = 10 (m = 0) (see Figure 3).