Synthesis and characterization of molybdenum oxo complexes of two tripodal ligands: reactivity studies of a functional model for molybdenum oxotransferases

Abstract

Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented.

Experimental and theoretical study of a truly functional biomimetic molybdenum oxotransferase analogue system

“…5a is calculated to be thermodynamically more stable than 5b (by 20.1 kJ mol À1 ; Table S4). This is in agreement with experimentally determined crystal structure analyses of typical L n Mo V 2 O 3 complexes [20,21] [20,21]). The scaled [9] calculated asymmetric Mo@O vibrations of 5a (split by coupling with CH deformation vibrations into 960 and 955 cm À1 ) nicely match the experimentally observed one at 960 cm À1 [5].…”

Synthesis, characterization and catalytic activity of dioxidomolybdenum(VI) complexes of tribasic pentadentate ligands

“…Electronic spectra of the ligand and complexes were recorded in methanol or DMSO using a Shimadzu 1601 UV-vis spectrophotometer. 1 H NMR spectra were recorded on a Bruker Avance 500 MHz spectrometer with the common parameter settings in DMSO-d 6 . The δ values are quoted relative to TMS as an internal standard.…”

“…The oxygen atom transfer properties of these complexes play a significant role in investigating the functioning mechanism of molybdenum transferase enzymes, which also consist of a cis-[Mo VI O 2 ] moiety as the active site [6][7][8][9][10][11][12]. The tendency of molybdenum to form stable complexes with oxygen, nitrogen and sulfur donor containing ligands has led to the development of high-valent molybdenum Schiff base complexes which are effective catalysts both in homogeneous and heterogeneous reactions [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Self-assembly of calix[4]arene amine derivatives

“…DPA has found several uses in biological aspects resulting from the uptake of metal ions 114 and its synthesis is relatively straight forward ( Figure 59) 115 . Its synthesis involves the drop-wise addition of 2-pyridinecarboxaldehyde in ethanol to a solution of 2-(aminomethyl)-pyridine also in ethanol, to form the imine which is then reduced by sodium borohydride in ethanol to give the desired product.…”