Binuclear rhodium and iridium complexes containing pentamethylcyclopentadienyl and pyrazolate ligands

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Abstract
The preparation of the methoxo-and hydroxo-bridged pentamethylcyclopentadienyliridium(III) complexes [{(C5Me5)Ir}2(µ-Pz)2(µ-OH)][BF4][Pz = pyrazolate (pz) or 3-methylpyrazolate (mpz)], [{(C5Me5)Ir}2(µ-Pz)(µ-OMe)2][A][A = ClO4 or BF4; Pz = pz, mpz, or 3,5-dimethylpyrazolate (dmpz)], and [{(C5Me5)Ir(Hdmpz)}2(µ-OH)2][BF4]2 from [Ir(C5Me5)(Me2CO)3][A]2 or [{(C5Me5)Ir}2(µ-OH)3][BF4]·H2O and their characterisation are reported. [{(C5Me5)Ir}2(µ-pz)2(µ-OH)][BF4] and [{(C5Me5)Ir}2(µ-pz)(µ-OMe)2][BF4] and their rhodium analogues react with HCl yielding the binuclear chloride complexes [{(C5Me5)M}2(µ-pz)2(µ-Cl)][BF4] and [{(C5Me5)M}2(µ-pz)(µ-Cl)2][BF4](M = Rh or Ir). Progressive addition of hydrochloric acid to the last rhodium complex leads to the mononuclear compounds [Rh(C5Me5)Cl(Hpz)2][BF4] and [Rh(C5Me5)Cl2(Hpz)] and, ultimately, to [{(C5Me5)RhCl}2(µ-Cl)2]. The complexes [{(C5Me5)M}2(µ-pz)2(µ-Cl)][BF4] and [{(C5Me5)M}2(µ-pz)(µ-Cl)2][BF4] were also prepared from the corresponding neutral complex [M(C5Me5)Cl2(Hpz)]; the mixed-metal complex [(C5Me5)Rh(µ-pz)(µ-Cl)2Ir(C5Me5)][BF4] was also prepared by this route. The di-µ-hydrido-rhodium complex [{(C5Me5)Rh}2(µ-pz)(µ-H)2][BF4] reacted with neutral ligands L (CO or ButNC) to give [{(C5Me5)Rh}2(µ-pz)L2][BF4]. Spectroscopic studies on these complexes and on the carboxylate complex [{(C5Me5)Rh}2(µ-O2CMe)(µ-CO)2][PF6](prepared from [{(C5Me5)Rh}2(µ-H)2(µ-O2CMe)][PF6] and CO) indicate that the CO and ButNC ligands are moving between terminal and bridging positions.

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