Tungsten complexes of chiral C2-symmetric picchxn, picchxnMe2, and PDP ligands (N4 ligands; picchxn = trans-N,N'-bis(pyridin-2-ylmethyl)-1,2-diaminocyclohexane, picchxnMe2 = trans-N,N’-dimethyl-N,N’-bis(pyridin-2-ylmethyl)-1,2-diaminocyclohexane, and PDP = 2-[[2-(1-(pyridin-2-ylmethyl)pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine) have been synthesized. Two diastereomers of (κ3-picchxn)W(CO)3 and (κ3-picchxnMe2)W(CO)3 have been observed, while only one has been observed for (κ3-PDP)W(CO)3. Mononitrosylation yielding [(κ3-N4)W(NO)(CO)2]PF6, followed by an intramolecular substitution yields [(κ4-N4)W(NO)(CO)]PF6 complexes. Multiple cis-β diastereomers are kinetically favored for [(cis-β-PicchxnMe2)W(NO)(CO)]PF6, but only one is favored for [(cis-β-Picchxn)W(NO)(CO)]PF6 and [(cis-β-PDP)W(NO)(CO)]PF6; cis-α diastereomers of all complexes are thermodynamically favored. The isolation of a single cis-α or cis-β diastereomer is much more straightforward for [(κ4-picchxn)W(NO)(CO)]PF6 and [(κ4-PDP)W(NO)(CO)]PF6. This work suggests possible utility of complexes of N4 ligands in enantioselective synthesis.

Topological variations of tungsten complexes of N4 Ligands

2019 Spring National Meeting

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