This is the structure of Lambda tris(catecholato)ferrate(III) anion. Coordinates were taken from "The Structure and Symmetry of Metal Tris Chelates" Reference prepared by Marion E. Cass and Henry S. Rzepa (available at http://www.people.carleton.edu/~mcass/trischelates/MTC-MI-C2js.html).
CC
SQ
SQ
CC
SQ
SQ
CC
SQ
SQ
The central iron node (formal charge +3).
The node elements with identifiers E9-N-11 (from the ligand structure E9-S-1-1), E9-N-23 (E9-S-1-2) and E9-N-35 (E9-S-1-3) form the first reference plane, which does not contain the central node element with the identifier E9-N-37. The node elements with identifiers E9-N-12 (E9-S-1-1), E9-N-24 (E9-S-1-2) and E9-N-36 (E9-S-1-3) form the second reference plane, which does not contain the central node element. The node elements in the first reference plane are to the left from the node elements in the second reference plane, when node elements from the same ligand structure are observed. It is assumed that the ligand structure is oriented towards the observer in such a way that the first reference plane is above and the second reference plane is below the central node element (seen from the observer point of view). This means that the ligand structures E9-S-1-1, E9-S-1-2 and E9-S-1-3 form the left-handed propeller twist and, therefore, the whole structure E9-S-1 has the Lambda absolute configuration (denoted by the "-" sense attribute value).
Note that id references order is fixed. The first id reference denotes the central node element, next three id references refer to the node elements forming the first reference plane and the last three id references refer to the node elements forming the second reference plane. The first reference plane can be chosen arbitrarily.