Copper(III) and Vanadium(IV)-Oxo Corrolazines
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- 作者：Joseph P. Fox ; Bobby Ramdhanie ; Adelajda A. Zareba ; Roman S. Czernuszewicz ; and David P. Goldberg
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：October 18, 2004
- 年：2004
- 卷：43
- 期：21
- 页码：6600 - 6608
- 全文大小：183K
- 年卷期：v.43,no.21(October 18, 2004)
- ISSN：1520-510X
文摘
As part of our efforts to develop the transition metal chemistry of corrolazines, which are ring-contracted porphyrinoidspecies most closely related to corroles, the vanadium and copper complexes (TBP)8Cz(H)VIVO (1) and (TBP)8CzCuIII(2) of the ligand octakis(para-tert-butylphenyl)corrolazine [(TBP)8Cz] have been synthesized. The coordination behavior,preferred oxidation states, and general redox properties of metallocorrolazines are of particular interest. The corrolazineligand in 1 was shown to contain a labile proton by acid/base titration and IR spectroscopy, serving as a -2 ligandrather than as the usual -3 donor. The oxidation state of the vanadium center in 1 was shown to be +4, inagreement with the overall neutral charge for this complex. The EPR spectrum of 1 reveals a rich signal consistentwith a VIV(O) (d1, S = 1/2) porphyrinoid species (gxx = 1.989, gyy = 1.972, gzz = 1.962). The electrochemicalanalysis of 1 shows behavior closer to that of a porphyrazine than a corrolazine, with a positively shifted, irreversiblereduction at -0.65 V (vs Ag/AgCl). Resonance Raman and IR data for 1 confirm the presence of a triply bondedterminal oxo ligand with 
(V16O) = 975 cm-1 and (V18O) = 939 cm-1. The copper complex 2 exhibits a diamagnetic1H NMR spectrum, indicative of a bona fide square planar copper(III) (d8, low-spin) complex. Previously reportedcopper corroles have been characterized as copper(III) complexes which exhibit a paramagnetic NMR spectrum athigher temperatures, indicative of a thermally accessible triplet excited state ([(corrole
+)CuII]). The NMR spectrumfor 2 shows no paramagnetic behavior in the range 300-400 K, indicating that compound 2 does not have athermally accessible triplet excited state. These data show that the corrolazine system is better able to stabilize thehigh oxidation state copper center than the corresponding corroles. Electrochemical studies of 2 reveal two reversibleprocesses at +0.93 and -0.05 V, and bulk reduction of 2 with NaBH4 generates the copper(II) species [(TBP)8CzCuII]-(2a), which exhibits an EPR signal typical of a copper(II) porphyrinoid species.
(V16O) = 975 cm-1 and (V18O) = 939 cm-1. The copper complex 2 exhibits a diamagnetic1H NMR spectrum, indicative of a bona fide square planar copper(III) (d8, low-spin) complex. Previously reportedcopper corroles have been characterized as copper(III) complexes which exhibit a paramagnetic NMR spectrum athigher temperatures, indicative of a thermally accessible triplet excited state ([(corrole+)CuII]). The NMR spectrumfor 2 shows no paramagnetic behavior in the range 300-400 K, indicating that compound 2 does not have athermally accessible triplet excited state. These data show that the corrolazine system is better able to stabilize thehigh oxidation state copper center than the corresponding corroles. Electrochemical studies of 2 reveal two reversibleprocesses at +0.93 and -0.05 V, and bulk reduction of 2 with NaBH4 generates the copper(II) species [(TBP)8CzCuII]-(2a), which exhibits an EPR signal typical of a copper(II) porphyrinoid species.