Carboxylate- and Phosphate Ester-Bridged Dimagnesium(II), Dizinc(II), and Dicalcium(II) Complexes. Models for Intermediates in Biological Phosphate Ester Hydrolysis

Abstract

Carboxylate-bridged dimagnesium(II) complexes were synthesized and characterized by employing the dinucleating ligand XDK, where H 2 XDK is m-xylylenediamine bis(Kemp's triacid imide). The reaction of 1 or 2 equiv of sodium diphenyl phosphate with [Mg 2 (XDK)(CH 3 OH) 4 (H 2 O) 2 (NO 3 )](NO 3 ), 1(NO 3 ), afforded [Mg 2 (XDK){µ-η 2 -(PhO) 2 PO 2 }(CH 3 OH) 3 (H 2 O)(NO 3 )]‚3CH 3 OH (2‚3CH 3 OH) and [Mg 2 (XDK){µ-η 2 -(PhO) 2 PO 2 }{η 1 -(PhO) 2 PO 2 }(CH 3 -OH) 3 (H 2 O)]‚CH 3 OH (3‚CH 3 OH), respectively. These are the first structurally characterized phosphate esterbridged dimagnesium(II) complexes. The reaction of 1 with 1 equiv of bis(4-nitrophenyl) hydrogen phosphate resulted in protonation of one of the carboxylate ligands and liberation of one magnesium(II) ion to give [Mg-(HXDK) 2 (H 2 O) 2 ] (4), an octahedral complex containing two short, low barrier intramolecular OH‚‚‚O hydrogen bonds. The phosphate ester exchange rate of free and bound diphenyl phosphate in 3 in methanol solution was measured by variable-temperature 31 P{ 1 H} NMR spectroscopy and compared to that of structurally analogous dizinc(II), [Zn 2 (XDK){µ-η 2 -(PhO) 2 PO 2 }{η 1 -(PhO) 2 PO 2 }(CH 3 OH) 2 (H 2 O)] (5), and dicalcium(II), [Ca 2 (XDK){µ-η 2 -(PhO) 2 PO 2 }{η 1 -(PhO) 2 PO 2 }(CH 3 OH) 3 (H 2 O)]‚CH 3 OH, (6‚CH 3 OH), complexes. The synthesis and structural characterization of 6 is presented, along with a discussion of the differences between the carboxylate-and phosphate ester-bridged dimagnesium(II), dizinc(II), and dicalcium(II) centers. Crystallographic data are as follows. 1(NO 3 ): monoclinic, P2 1 /c, a ) 11.240(3) Å, b ) 13.019(2) Å, c ) 30.208(7) Å, ) 99.11(1)°, V ) 4365(2) Å 3 , Z ) 4, R ) 0.045, and R w ) 0.054 for 5021 independent reflections with I > 3σ(I). 2‚3CH 3 OH: monoclinic, P2 1 /c, a ) 16.611(5) Å, b ) 16.059(6) Å, c ) 21.930(9) Å, ) 93.34(6)°, V ) 5840(4) Å 3 , Z ) 4, R ) 0.069, and R w ) 0.085 for 3759 independent reflections with I > 2σ(I). 3 . CH 3 OH: monoclinic, P2 1 /n, a ) 18.912(4) Å, b ) 16.254(2) Å, c ) 21.646(5) Å, ) 112.26(2)°, V ) 6158(2) Å 3 , Z ) 4, R ) 0.060, and R w ) 0.072 for 5184 independent reflections with I > 3σ(I). 4: monoclinic, P2 1 /n, a ) 15.210(5) Å, b ) 15.772(3) Å, c ) 13.093(3) Å, ) 96.35(3)°, V ) 3122(1) Å 3 , Z ) 2, R ) 0.069, and R w ) 0.070 for 1840 independent reflections with I > 2σ(I). 6 . CH 3 OH: monoclinic, P2 1 /n, a ) 16.5471(3) Å, b ) 24.3415(6) Å, c ) 16.5865(3) Å, ) 104.2530(10)°, V ) 6475.

DNA hydrolysis promoted by di- and multi-nuclear metal complexes

“…To date very few functional dinuclear Mg 2+ complexes have been developed. Carboxylate-bridged dimagnesium complex is the first dinuclear Mg 2+ complex with a bridging phosphate [81]. The Yang group reported that the Mg complex of diethylenetriamine (dien) appeared in a Cl − -bridged dimer form of [Mg 2 (dien) 2 Cl 3 ] + and is a remarkably simple yet effective promoter for the hydrolytic cleavage of DNA [82].…”

Mechanistic Investigation into the Cleavage of a Phosphomonoester Mediated by a Symmetrical Oxyimine‐Based Macrocyclic Zinc(II) Complex

“…Previous research found that metal cations such as Mg 2+ , Ca 2+ , Fe 3+ , and Zn 2+ usually existed in the active site of natural hydrolysis enzymes 5–7. Further research with artificial metal complexes containing metal ions such as alkali metal ions (Li + , Na + , K + ),8, 9 alkaline‐earth metal ions (Mg 2+ , Ca 2+ ),10–12 transition‐metal ions (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Mo 2+ etc. ),12–26 and lanthanide metal ions (La 3+ , Ce 3+ , Eu 3+ , Tb 3+ etc.…”

“…Further research with artificial metal complexes containing metal ions such as alkali metal ions (Li + , Na + , K + ),8, 9 alkaline‐earth metal ions (Mg 2+ , Ca 2+ ),10–12 transition‐metal ions (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Mo 2+ etc. ),12–26 and lanthanide metal ions (La 3+ , Ce 3+ , Eu 3+ , Tb 3+ etc. )27–30 was conducted.…”

Iron(III)- and copper(II) complexes of an asymmetric, pentadentate salen-like ligand bearing a pendant carboxylate group

“…alkoxo or phenoxo) bridging units have been utilised to construct homo-and heterodinuclear complexes [18][19][20][21]. Up to date, only a few examples are known for the bridging coordination of an endogenous carboxylate [22][23][24][25].…”