Unprecedented Isomerization of the “Rigid Rod” Organometallic {[M(dmb)2]+}n Polymers (M = Ag; dmb = 1,8-diisocyano-p-menthane) from “Linear” to “Staircase” to “Ladder”

Abstract

The design of new polymeric materials based upon organometallic and coordination compounds is becoming a topic of interest.1 Recently our group reported the preparation and characterization of the first examples of “rigid rod” organometallic polymers using the diisocyanide ligand, dmb, to form the {[M(dmb)2]Y}n materials (M ) Cu, Ag; Y ) PF6, BF4, NO3, ClO4, CH3CO2). The M atoms are tetracoordinated by isocyanide groups in a distorted tetrahedral fashion and are doubly bridged by dmb ligands which adopt a conformation where both -NtC groups point in the same direction (Scheme 1; rotamer I). This conformation dominates the chemistry of bi-, tri-, and polymetallic compounds of dmb.3 dmb exhibits a C-C single bond allowing rotations which can lead to two types of rotamers (Scheme 1; rotamers I and II). We now wish to report two new structural forms of the {[Ag(dmb)2]Y}n polymers that are found in equilibrium at room temperature which can be obtained under certain crystallization conditions. The three conformation isomers are built upon a combination of rotamers I and II.