Structural Versatility of 5-Methyltetrazolato Complexes of (η⁵-Pentamethylcyclopentadienyl)iridium(III) Incorporating 2,2′-Bipyridine, <i>N</i>,<i>N</i>-Dimethyldithiocarbamate, or 2-Pyridinethiolate Ligands

Several new mono- and dinuclear η5-pentamethylcyclopentadienyl (Cp*) iridium(III) complexes bearing 5-methyltetrazolate (MeCN4−) have been synthesized and their molecular and crystal structures have been determined. For complexes incorporating 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen), both mononuclear κN2-coordinated and dinuclear μ-κN1:κN3-bridging MeCN4 complexes were obtained: [Cp*Ir(bpy or phen)(MeCN4-κN2)]PF6 (1 or 3) and [{Cp*Ir(bpy or phen)}2(μ-MeCN4-κN1:κN3)](PF6)3 (2 or 4), respectively. It was confirmed by X-ray analysis that the dinuclear complex in 2 has a characteristic structure with a pyramidal pocket constructed from a μ-κN1:κN3-bridging MeCN4− and two bpy ligands. In the case of analogous complexes with N,N-dimethyldithiocarbamate (Me2dtc−), yellow platelet crystals of mononuclear κN1-coordinated complex, [Cp*Ir(Me2dtc)(MeCN4-κN1)]·HN4CMe (5·HN4CMe), and yellow prismatic crystals of dinuclear μ-κN1:κN4-bridging one, [{Cp*Ir(Me2dtc)}2(μ-MeCN4-κN1:κN4)]PF6 (6), were deposited. The κN1- and κN1:κN4-bonding modes of MeCN4− in these complexes presumably arise from the compactness of the Me2dtc− coligand. 6 is the first example in which tetrazolates act as a μ-κN1:κN4-bridging ligand. Furthermore, the molecular and crystal structures of dinuclear complexes having μ-κ2S,N:κS-bridging 2-pyridinethiolate (2-Spy−) or 8-quinolinethiolate (8-Sqn−) ligands have been determined: [(Cp*Ir)2(μ-2-Spy or 8-Sqn-κ2S,N:κS)2] (7 or 8). These thiolato-bridging complexes were stable toward the addition of 5-methyltetrazole (HN4CMe), owing to the characteristic intramolecular stacking interaction between the pyridine or the quinoline rings. The 2-Spy complex of 7, however, reacted with an excess amount of Na(N4CMe), resulting in cleavage of the IrN(py) bond and coordination of MeCN4− in the μ-κN2:κN3-bridging mode: [(Cp*Ir)2(μ-2-Spy-κS:κS)2(μ-MeCN4-κN2:κN3)]PF6 (9). This bridging mode of MeCN4− was also observed in the triply bridging MeCN4 complex: [(Cp*Ir)2(μ-MeCN4-κN2:κN3)3]PF6 (10). In these various MeCN4 complexes, the structural parameters of the MeCN4 moiety were not perturbed by the difference in the bonding modes.