Infrared-Driven Charge-Transfer In Transition Metal-Containing B12x122- (X = H, F) Clusters

Density functional theory (DFT) calculations and infrared multiple photon dissociation (IRMPD) spectroscopy are employed to probe [TM center dot(B12H12)]- and [TM center dot(B12H12)(2)](2-) clusters [TM = Ag(I), Cu(I), Co(II), Ni(II), Zn(II), Cd(II)]. A comparison is made between the charge-transfer properties of the clusters containing the hydrogenated dodecaborate dianions, B12H122-, and the fluorinated analogues, B12F122-, for clusters containing Cd(II), Co(II), Ni(II), and Zn(II). IRMPD of the [TM center dot(B12H12)](-) and [TM center dot(B12H12)(2)](2-) species yields B12H11- via hydride abstraction and B12H12- in all cases. To further explore the IR-induced charge-transfer properties of the B(12)X12(2) (-) (X = H, F) cages, mixed-cage [TM(B12H12)(B12F12)](2-) [TM = Co(II), Ni(II), Zn(II), Cd(II)] clusters were investigated. IRMPD of the mixed-cage species yielded appreciable amounts of B12F12- and B12H12- in most cases, indicating that charge-transfer to the central TM cation is a favorable process; formation of B12F12- is the dominant process for the Co(II) and Ni(II) mixed-cage complexes. In contrast, the Zn(II) and Cd(II) mixed-cage complexes preferentially produced fragments of the form BxHyFz-/2-, suggesting that H/F scrambling and/or fusion of the boron cages occurs along the IRMPD pathway.