Article,

Formation, reactivity, and photorelease of metal bound nitrosyl in Ru(trpy)(L)(NO)n+ (trpy = 2,2':6',2''-terpyridine, L = 2-phenylimidazo4,5-f1,10-phenanthroline)

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Inorganic Chemistry, 47 (8): 3218--3227 (2008)
DOI: 10.1021/ic702160w

Abstract

Nitrosyl complexes with Ru-NO6 and Ru-NO7 configurations were isolated in the framework of Ru(trpy)(L)(NO)n+ trpy = 2,2':6',2''-terpyridine, L = 2-phenylimidazo4,5-f1,10-phenanthroline as the perchlorate salts 4(ClO4)3 and 4(ClO4)2, resp. Single crystals of protonated material 4-H+(ClO4)4·2H2O reveal a Ru-N-O bond angle of 176.1(7)° and triply bonded N-O with a 1.127(9) \AA bond length. Structures were also detd. for precursor compds. of 43+ as Ru(trpy)(L)(Cl)(ClO4)·4.5H2O and Ru(trpy)(L-H)(CH3CN)(ClO4)3·H2O. In agreement with largely NO centered redn., a sizable shift in n(NO) frequency was obsd. on moving from 43+ (1953 cm-1) to 42+ (1654 cm-1). The RuII-NO.bul. in isolated or electrogenerated 42+ exhibits an EPR spectrum with g1 = 2.020, g2 = 1.995, and g3 = 1.884 in CH3CN at 110 K, reflecting partial metal contribution to the singly occupied MO (SOMO); 14N (NO) hyperfine splitting (A2 = 30 G) was also obsd. The plot of n(NO) vs. E°(RuNO6 $\rightarrow$ RuNO7) for 12 analogous complexes Ru(trpy)(L')(NO)n+ exhibits a linear trend. The electrophilic Ru-NO+ species 43+ is transformed to the corresponding Ru-NO2- system in the presence of OH- with k = 2.02 $\times$ 10-4 s-1 at 303 K. In the presence of a steady flow of dioxygen gas, the RuII-NO.bul. state in 42+ oxidizes to 43+ through an associatively activated pathway (DSdpl = -190.4 J K-1 M-1) with a rate const. (k s-1) of 5.33 $\times$ 10-3. On irradn. with light (Xe lamp), the acetonitrile soln. of paramagnetic Ru(trpy)(L)(NO)2+ (42+) undergoes facile photorelease of NO (kNO = 2.0 $\times$ 10-1 min-1 and t1/2 $\approx$ 3.5 min) with the concomitant formation of the solvate RuII(trpy)(L)(CH3CN)2+ 2'2+. The photoreleased NO can be trapped as an Mb-NO adduct. on SciFinder(R)

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