Synthesis, crystal structure of ruthenium 1,2‐naphthoquinone‐1‐oxime complex and its mediated CC coupling reactions of terminal alkynes

Abstract

AbstractSubstituted decarbonylation reaction of ruthenium 1,2‐naphthoquinone‐1‐oxime (1‐nqo) complex, cis‐, cis‐[Ru| ζ2‐N(O)C10‐H6O|2(CO)2] (1), with acetonitrile gave cis‐, cis‐[Ru | ζ2‐ N(O)C10H6O|2(CO)(NCMe)] (2). Complex 2 was fully characterized by 1H NMR, FAB MS, IR spectra and single crystal X‐ray analysis. Complex 2 maintains the coordination structure of 1 with the two naphthoquinonic oxygen atoms, as well as the two oximato nitrogen atoms located cis to each other, showing that there is no ligand rearrangement of the 1‐nqo ligands during the substitution reaction. The carbonyl group originally trans to the naphthoquinonic oxygen in one 1‐nqo ligand is left in its original position [O(5)‐Ru‐C(1), 174.0(6)°], while the other one originally trans to the oximato group of the other 1‐nqo ligand is substituted by NCMe [N(1)‐Ru‐N(3), 170.6(6)°]. This shows that the carbonyl trans to oximato group is more labile than the one trans to naphthoquinonic O atom towards substitution. This is probably due to the comparatively stronger ± back bonding from ruthenium metal to the carbonyl group trans to naphthoquinonic O atom, than the one trans to oximato group, resulting in the comparatively weaker Ru–‐CO bond for the latter and consequently easier replacement of this carbonyl. Selected coupling of phenylacetylene mediated by 2 gave a single trans‐dimerization product 3, while 2 mediated coupling reaction of methyl propiolate produced three products: one trans‐dimerization product 4 and two cyclotrimeric products 5 and 6.