Stepwise Solid‐Phase Synthesis of Di‐ and Trinuclear Metal Complexes

Abstract

Monodisperse oligomers play a central role in understanding the chemistry and the physics of polymeric organic and inorganic materials.[1] The synthesis of monodisperse oligomers can be achieved by self-organization processes, random synthesis followed by separation processes, or by a step-bystep synthesis. All these strategies present their own advantages and disadvantages. Full control over chain length, end groups, and building-block sequence can be achieved using a stepwise approach. While this strategy is conceptually straightforward, it becomes increasingly tedious for higher oligomers owing to the purification steps needed. A particular elegant method for a repeated stepwise synthesis is the solidphase synthesis methodology which allows the purification of all intermediates by simple filtration. This strategy has been successfully applied to the synthesis of organic oligomeric compounds [2] while organometallic oligonuclear complexes have not been prepared in a stepwise manner by solid-phase synthesis. Mononuclear metal complexes have been prepared by solid-phase synthesis [3][4][5][6][7][8][9][10][11][12] for example, for biolabeling purposes or oligonucleotide-DNA/RNA binding studies and a dinuclear complex [13] has been synthesized by simultaneous double metalation of a peptide bound to a solid phase.We have already designed a system (polystyrene (PS)/ divinyl benzene-silyl ether linker-bidentate Schiff base ligand; 1 b in Scheme 1) which allows standard reactions of coordination and organometallic chemistry to be performed under solid-phase reaction conditions and the release of the final products from the insoluble matrix by fluoridolysis of the silyl ether linker. [14,15] The first application of this solid-phase reaction system to the synthesis of di-and trimetallic complexes is reported herein.The molybdenum carbonyl complexes reported herein possess several properties which make them suitable for solidphase synthesis approach, these are: 1) substitutionally inert metal-ligand bonds (molybdenum-carbonyl and molybdenum-isonitrile bonds), 2) carbonyl and isonitrile ligands which serve as sensitive analytical probes for IR spectroscopic analysis of the solid-phase system, [16,17] 3) highly colored complexes which permits UV/Vis spectroscopic analysis of

Polymer‐Supported Dioxido‐MoVI Complexes as Truly Functional Molybdenum Oxotransferase Model Systems

“…The immobilised bis(chelate) complex 1b is prepared analogously to 1a employing polymer-supported chelate ligands (Scheme 1 and Scheme 3; ligand loading 0.6-0.8 mmol g -1 polymer; polymer = polystyrene/2 % divinylbenzene). [27][28][29][30][31][32] The amount of molybdenum incorporated by 1b is compatible with the required 2:1 ligand/metal stoichiometry as shown by molybdenum uptake measurements. [23] Thus the molybdenum complexes are anchored to the polymeric backbone by two attachment points which should guarantee the desired site isolation effect (at least for some sites within the polymer).…”

“…Cleaving the Si-O bonds of 1b with fluoride ions releases the hydroxy analogue of 1a into solution confirming the correct formation of 1b. [27][28][29][30][31][32] PMe 3 is oxidised by 1b to OPMe 3 as shown by 31 The anchored Mo VI and Mo IV complexes 1b and 3b were subjected to one-electron reduction and oxidation, respectively (CEPT chemistry). Reaction of 1b with cobaltocene Co(C 5 H 5 ) 2 [33] gave polymer 4b which is EPR-active.…”

Oxidative Addition of RX to Soluble and Polymer‐Bound Molybdenum Carbonyl Complexes

“…For 3b a larger weight loss of 6.1% is observed at 200 °C, which can be accounted for by a loss of three carbon monoxide ligands and one chloro ligand, while the immobilised allyl complexes 4b − 6b only lose coordinated carbonyl ligands up to 200 °C (Table 6). Carbon monoxide loss has also been detected for immobilised Mo 0 carbonyl complexes 12. These data show that these complexes are formed quantitatively on the solid support and that allyl complexes are thermally more stable than the seven‐coordinate molybdenum‐tin complex.…”

Bioinspired functional analogs of the active site of molybdenum enzymes: Intermediates and mechanisms

“…The chelates HL were attached to the copolymer by silylether linkages. These linkers are stable toward hydrolysis but can be cleaved on purpose by fluoride ions to release and analyze the ligand or the respective complex in solution ("active site extraction" [129][130][131][132][133]). OAT from the polymer-anchored Mo(L 5 ) 2 (O) 2 to PMe 3 gives soluble OPMe 3 as shown by 31 [81].…”