Preparation and electrochemical investigation of monomeric complexes of molybdenum(0-VI) with the ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (L). Crystal structure of [MoIVLBr3](PF6)

Spectroscopic Properties, Electrochemistry, and Reactivity of Mo0, MoI, and MoII Complexes with the [Mo(bpa)(CO)3] Unit [bpa = bis(2-picolyl)amine] and Their Application for the Labelling of Peptides

“…These Mo II complexes could be reduced once more at a potential of around Ϫ1.0 V, again yielding complexes 1 and 2. For the complexes [Mo(R 3 -tacn)(CO) 3 ] (R ϭ Me or benzyl), electrochemical formation of [Mo(R 3 -tacn)(CO) 3 Br] ϩ was reported, but the corresponding rereduction to yield the Mo 0 complexes was not observed between ϩ2.0 V and Ϫ2.0 V. [25,48] One difference in reactivity between [Mo(bpa)(CO) 3 Br] ϩ and [Mo(tacn)(CO) 3 Br] ϩ is that the latter compound could be crystallized from aerobic aqueous solutions, [35] whereas the former reacted further to yield the dinuclear Mo V complex [Mo 2 (bpa) 2 (O) 2 (µ-O) 2 ](Br,PF 6 ).…”

“…[63] Bis(2-picolylamine) and Mo(CO) 6 were purchased from Aldrich. The compounds Nbenzylbis(2-picolyl)amine, [64] [Mo( [9]aneN 3 )(CO) 3 ], [35] [Mo([9]-aneN 3 (CO) 3 Br]Br 3 , [35] [Mo(Me 3 [9]aneN 3 )(CO) 3 ], [48] and [Mo-(CO) 3 (EtCN) 3 ] [65] were synthesized according to literature procedures.…”

“…With the aid of controlled potential coulometry, the number of transferred electrons for this reduction process was shown to be two, again yielding the neutral compounds 1 and 2. The bpa derivatives differ from the tacn analogues in this respect, because the corresponding reduction peak of the seven-coordinated species for the tacn complexes was not observed in the range from Ϫ2.0 V to ϩ2.0 V. [25,48] Additional evidence for the chemical reversibility of the two-electron oxidation of 1 and 2 was also obtained from UV and IR spectroelectrochemical investigations (see below).…”

“…Formation of seven-coordinated Mo II species has also been reported for fac-Mo(CO) 3 complexes with two different tacn derivatives. [25,48] After generation of the seven-coordinated species [Mo(bpa)(CO) 3 Br] ϩ and [Mo(Bzbpa)(CO) 3 Br] ϩ , single reduction peaks were observed at more negative potentials, namely at Ϫ1.20 V vs. Fc/Fc ϩ for [Mo(bpa)(CO) 3 Br] ϩ and Ϫ0.95 V vs. Fc/Fc ϩ for [Mo(Bzbpa)(CO) 3 ] ϩ , as shown in Figure 4 for complex 2.…”

Molybdenum Complexes Bearing the Tris(1‐pyrazolyl)methanesulfonate Ligand: Synthesis, Characterization and Electrochemical Behaviour

“…[68] The first oxidation potential of the Mo 0 complex 1 (-0. 35 3 ] n , in which L is a tridentate N-donor ligand [Tp (n = -1), [70] Tpm Me (n = 0), [71] 1,4,7-trimethyl-1,4,7-triazacyclononane (n = 0), [72] or 1,4,7-tribenzyl-1,4,7-triazacyclononane (n = 0)], [70] thus reflecting [66][67][68][73][74][75] the relative donor/acceptor abilities of these different L ligands. The more negative value (-0.53 V vs Fc/Fc + ) is reported [70] 3 ], [71] whereas that of 1 is intermediate, in accord with the order of the net electron-donor ability of the corresponding tripodal ligands.…”