Hydrolysis of Unactivated Esters and Acetonitrile Hydration by a Hydroxo−Dicopper(II) Complex

Frey, Steven T.; Murthy, Narasimha N.; Weintraub, Susan T.; Thompson, Laurence K.; Karlin, Kenneth D.

doi:10.1021/ic961439o

Cited by 45 publications

(20 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…the hydroxide group bound to the second, adjacent nickel ion. A final proton shift then establishes the very stable m-(amidato-N,O) bridges in 3 a ± c. Similar reaction mechanisms have previously been suggested for nitrile hydration at dinuclear iron(iii), [12] cobalt(iii), [27] copper(ii) [28] palladium(ii) [29] and rhenium(iii) [30] sites. It should be pointed out that no such reaction was observed for 1 under identical reaction conditions, which underlines the deactivation of the metal-bound hydroxide by its tight fixation in a bridging position between the two metal ions.…”

Section: Resultssupporting

confidence: 68%

“…However, examples for the bimetallic hydrolysis of unactivated carboxyesters and amides have hitherto remained rare. [8,28] It turns out that rather high temperatures have to be employed to achieve reasonable rates of reaction of 2 with DMF or DMA. Heating a solution of 2´(ClO 4 ) 2 the appearance of characteristic strong IR bands for the carboxylato bridges at 1592 cm À1 (10 a) and 1566 cm À1 (10 b) [n asym (CO 2 ); the n sym (CO 2 ) absorptions overlap with other bands and can not be assigned unambiguously].…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

et al. 1999

View full text Add to dashboard Cite

Using the possibility of tuning the metal ± metal distance in pyrazolatebased bimetallic complexes by the length of the chelating side arms attached to the heterocycle, we have synthesized related dinickel(ii) complexes in which either a hydroxide (1) or a H 3 O 2 unit (2) spans the two metal centers within the bimetallic pocket. Complex 1 exhibits strong antiferromagnetic coupling mediated by the bridging hydroxide unit (J À 56.9 cm À1 ), while 2 shows Curie ± Weiss behavior over a wide temperature range. The H 3 O 2 unit in 2 acts like the resting form of an active metalbound hydroxide and allows the study of cooperative transformations of small molecules at a dinickel(ii) site relevant to the active site of the metalloenzyme urease. Firstly, it mediates the hydration of various nitriles to give the respective m-amidato-N,O-bridged complexes 3 a ± c. Reaction of 2 with urea affords complex 5 with an N,O-bridging deprotonated urea, which when heated releases ammonia to yield the cyanato-bridged dinickel(ii) compound 4. This product is also obtained when 2 is treated with dimethylcyanamide. Unactivated amides dimethylformamide (DMF) and dimethylamide (DMA) are hydrolyzed by 2 only sluggishly, while the stoichiometric hydrolysis of esters such as ethyl acetate and ethyl propionate runs more cleanly to afford the carboxylato-bridged bimetallic complexes 10 b and c. Likewise, hydrolytic cleavage occurs with g-butyrolactone to give complex 10 d. We propose that these reactions proceed by cooperative action of the two metal ions within the bimetallic pocket of the dinickel(ii) core. Possible alternatives are addressed by investigation of analogous mononuclear nickel(ii) complexes 8 a and b in conjunction with a corresponding dimeric compound 9 and by the reaction of 2 with an excess of acetate to yield the dinickel(ii) complex 11, in which a formerly chelating side arm has been driven out of the coordination sphere. Complexes 1´(BPh 4 ) 2 , 2( BPh 4 ) 2 , 3c´(ClO 4 ) 2 , 4´(BPh 4 ) 2 , 8 b( ClO 4 ) 2 , 9´(ClO 4 ) 2 , 10 d´(ClO 4 ) 2 , and 11´(ClO 4 ) have been characterized structurally by X-ray crystallography.

show abstract

Section: Resultssupporting

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

et al. 1999

View full text Add to dashboard Cite

show abstract

“…Consequently, several synthetic Cu 2+ complexes with high Lewis acidity have been demonstrated to catalyze hydrolytic reactions [45,46,47]. A few Cu 2+ -substituted Zn hydrolases, including Aeromonas aminopeptidase (aAP) [48], astacin [53], and serralysin, also exhibit significant activities, which further corroborates the theory.…”

Section: Resultssupporting

confidence: 54%

Mechanistic studies of the astacin-like Serratia metalloendopeptidase serralysin: highly active (>2000%) Co(II) and Cu(II) derivatives for further corroboration of a "metallotriad" mechanism

Park

Ming

2002

J Biol Inorg Chem

View full text Add to dashboard Cite

Serralysin is a bacterial Zn-endopeptidase which has been considered a virulence factor to cause tissue damage and anaphylactic response. It contains a coordinated Tyr that is unique to the astacin-like Zn enzymes. The coordinated Tyr has been proposed to play an important role in the action of this endopeptidase family. Several metal-substituted derivatives of serralysin (including Mn2+, Co2+, Ni2+, Cu2+, and Cd2+ derivatives) are found to exhibit significant activities. Particularly, the Co- and Cu-substituted derivatives exhibit much higher activities than the native serralysin toward the hydrolysis of the tripeptide mimic benzoyl-Arg- p-nitroanilide, i.e., 35 and 49 times higher in k(cat) and 33 and 26 times in k(cat)/ K(m), respectively. Such remarkably higher activities of metal-substituted derivatives, especially the Cu derivative, than that of the native Zn enzyme are rare in the literature, reflecting the uniqueness of this enzyme among all Zn enzymes. The significantly different k(cat) yet similar K(m) values among the several metal derivatives suggests that the metal center is involved in catalysis, but not necessarily in the binding of the substrate, whereas the dramatically different inhibition constants for Arg-hydroxamate binding to the metal-substituted derivatives indicates direct binding of this inhibitor to the metal center. The activity-pH profiles of serralysin and its Co2+ and Cu2+ derivatives and the optical-pH profile of Cu-serralysin have been obtained, in which the decrease in activity at higher pH values was found to be associated with a dramatic increase in the Tyr-to-Cu2+ charge transfer transitions. This observation suggests that the binding of Tyr216 to the metal is inhibitory. A metal-centered mechanism is proposed for serralysin catalysis based on the results presented here, in which the detachment of the coordinated Tyr and formation of a H-bond with the transition-state complex are considered essential for the stabilization of the transition state.

show abstract

“…Strand scission of plasmid pBR322 was assayed in the presence of a reductant and several copper(II) coordination complexes, which had exhibited interesting reactivity with other unique substrates [22,23,24,25]. The most reactive of these complexes was a binuclear complex, [Cu 2 II (D 1 )(H 2 O) 2 ](ClO 4 ) 4 (1), in which the two coppers are coordinated by tris(pyridylmethyl)amine moieties that are linked through a -CH 2 CH 2 -bridge in the 5-pyridyl position (see Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

Oxidative strand scission of nucleic acids by a multinuclear copper(II) complex

et al. 2002

Self Cite

View full text Add to dashboard Cite

The compound [Cu(2)(II)(D(1))(H(2)O)(2)](ClO(4))(4).2H(2)O [D(1)=binucleating ligand with tris(2-pyridylmethyl)amine (TMPA) moieties linked in the 5-pyridyl position by a -CH(2)CH(2)- bridge] mediated efficient oxidative cleavage of pBR322 plasmid DNA under reducing conditions. A mononuclear analogue, [Cu(TMPA)(H(2)O)](ClO(4))(2), was less effective at linearizing supercoiled (Form I) plasmid DNA as compared to the binuclear complex. A new method for quenching the copper-dependent reactions has been developed to avoid plasmid scission by the binuclear complex and the standard gel loading buffer. EDTA was not sufficient for retarding copper reaction, but diethyldithiocarbamic acid was capable of inhibiting all reactivity. Investigation of oxidative cleavage of double-helical oligonucleotides by [Cu(2)(II)(D(1))(H(2)O)(2)](ClO(4))(4) confirmed the enhanced reactivity of the binuclear over the mononuclear complex and provided mechanistic insights into the nature of the reaction. Cleavage of DNA required both the binuclear complex and a reductant and likely proceeded through an O(2)-derived intermediate that does not include a diffusible hydroxyl radical. The greater efficiency of the binuclear complex relative to the mononuclear analogue is consistent with their relative abilities to activate dioxygen.

show abstract

Hydrolysis of Unactivated Esters and Acetonitrile Hydration by a Hydroxo−Dicopper(II) Complex

Cited by 45 publications

References 12 publications

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

Mechanistic studies of the astacin-like Serratia metalloendopeptidase serralysin: highly active (>2000%) Co(II) and Cu(II) derivatives for further corroboration of a "metallotriad" mechanism

Oxidative strand scission of nucleic acids by a multinuclear copper(II) complex

Contact Info

Product

Resources

About