For future reference I have now solved this problem. The list cannot reference an atom that has not yet appeared in the list - we cannot refer to atom 10 until after the line for atom 10. The MOL_1 file that works looks like
C6O6H4
Number of atoms: 14
1.63382 0.042977 0.094272 6 1 0 0 0 1 1
2.38958 -1.37571 0.403735 6 2 1 0 0 0 1
1.73699 -2.7079 -0.285838 6 3 2 1 0 0 0
0.10271 -2.7684 -0.338365 6 4 3 2 0 0 0
-0.672186 -1.35568 -0.625144 6 5 4 3 0 0 0
-0.71357 0.977572 0.386955 8 1 2 3 0 0 0
2.2838 1.1237 -0.061766 8 2 3 4 0 0 0
3.42504 -1.43726 1.13744 8 3 4 5 0 0 0
2.45886 -3.63999 -0.759309 8 4 5 6 0 0 0
-0.531577 -3.85589 -0.167049 8 5 6 5 0 0 0
-1.75036 -1.31346 -1.29631 8 6 1 2 0 0 0
2.75383 1.41776 1.09851 1 8 2 3 0 0 0
4.42358 -1.40471 0.661835 1 9 3 4 0 0 0
-0.476419 -4.50471 -0.594265 1 11 5 6 0 0 0