Stacked Complexes of Iridium and a Novel Form of Charge Compensation

Mixed valence metal chain compounds based on the monoanion [Ir(CO) 2 Tcbiim] - were investigated (Tcbiim = 4,4',5,5'-tetracyano-2,2'-biimidazole, a dianion). These compounds were prepared by inert atmosphere electrochemical oxidation with a variety of alkyl ammonium cation based electrolytes. Synthetic details are presented for the preparation of several asymmetric alkyl ammonium cations, and the subsequent electrolyte salt preparation. The technique for electrochemical oxidation is described in detail. Single-crystal X-ray solutions are presented for three complex Ir(I) salts: NEt 3 Me[Ir-(CO) 2 Tcbiim]. l /2CH 3 CN, NEt 2 Me 2 [Ir(CO) 2 Tcbiim], and a dication salt NEt 2 Me(CH 2 ) 4 NEt 2 Me[Ir(CO) 2 Tcbiim] 2 . The first of these crystallizes in the space group Pnnm with a = 6.918 Å, b = 22.223 Å, c = 15.101 Å, and Z = 4. A final agreement of R = 4.25% for 133 parameters with 972 retained data was obtained. The second crystallized in the space group P2 I 2 1 2 with a = 7.074 Å, b = 19.698 Å, c = 15.336 Å, and Z = 4. The obtained final agreement was R = 3.94% for 236 parameters with 1505 retained data. The dication structure was refined in the nonstandard space group P22 1 2 1 with a = 15.751 Å, b = 7.233 Å, c = 19.135 Å, and Z = 4. A final agreement of R = 5.1% for 130 parameters with 789 retained data was found. Solid-state packing for this series of compounds is discussed. Packing diagrams reveal molecular interactions responsible for earlier observations of thermochromic behavior. A series of insoluble mixed valence compounds formulated as [cat] 5 [Ir-(CO) 2 Tcbiim] 6 [an] where [cat] [an] denotes included supporting electrolyte were prepared. Conductivity data are presented. A reaction of [cat] 4 [Ir(CO) 2 Tcbiim] 6 with an isoelectronic analogue of the stacking unit [Pt(CN) 2 Tcbiim] 2- produced a unique one-dimensional alloy in single-crystal form. This compound, [NEt 3 Me] 3 [Ir(CO) 2 Tcbiim] 2 [Pt(CN) 2 Tcbiim].3CH 3 CN, crystallized in the space group P2 1 with a = 13.412 Å, b = 6.874 Å c = 13.409 Å, and β = 111.21°. Here, Z = 2, however; since there is one metal atom in the asymmetric unit, the stacking units are disordered along the stack. Perspective plots clearly reveal a metal atom chain. Final agreement of R = 4.01% was observed for 223 parameters with 2227 retained data. © 1988, American Chemical Society. All rights reserved.