1. A metal complex compound useful as an infrared absorbent prepared by coordinating two bidentate ligands selected from the following groups to a center metal selected from the group consisting of nickel, copper, cobalt, palladium and platinum and neutralizing such a complex with a cation ##STR164## wherein, R.sup.3 to R.sup.6 each independently represents a hydrogen atom, halogen atom, cyano group, hydroxyl group, or a substituted or unsubstituted alkyl, aryl, cycloalkyl or heterocyclic group which may be bonded through a divalent connecting group to a benzene ring, or a group of nonmental atoms forming a substituted or unsubstituted five-membered or six membered ring by bonding of R.sup.3 and R.sup.4, R.sup.4 and R.sup.5, or R.sup.5 and R.sup.6 ; R.sup.3 to R.sup.6 may be the same or different.