Instability of Square Planar N₃-Ligand Iridium(I) Ethene Complexes

Abstract

New, five-coordinate, iridium(I) bis-ethene complexes [fac-(bpa-R)Ir I (ethene) 2 ] + (1 + : R ) H, 2 + : R ) Me, 3 + : R ) Bz; bpa-H ) N,N-di(2-pyridylmethyl)amine, bpa-Me ) N-methyl-N,N-di(2-pyridylmethyl)amine, bpa-Bz ) N-benzyl-N,N-di(2-pyridylmethyl)amine) were prepared. In contrast to their previously reported rhodium analogues, these iridium species do not readily lose one of their two ethene fragments to form square planar mono-ethene complexes [mer-(bpa-R)Ir I (ethene)] + . Heating complex 1 + results in N-H activation at the bpa-H ligand and formation of the dinuclear iridium(III) species [{(mer-µ 2 -bpa # )Ir III (ethyl)-(MeCN)} 2 ] 2+ (4 2+ ) with bridging amides (bpa # ) bpa-H deprotonated at NH amine ). Heating bpa-Bz complex 3 + results in aromatic C-H activation of the ligand benzyl group to form dinuclear iridium(III) species [{(bpa-Bz # )Ir III (µ 2 -H)} 2 ] 2+ (5 2+ ) with unsupported hydride bridges (bpa-Bz # ) bpa-Bz cyclometalated at the benzylic C2-position). The dimeric structure of 5 2+ easily breaks up in MeCN, giving the mononuclear species [(bpa-Bz # )Ir III (H)(MeCN)] + (6 + ). Complex 5 2+ is also light-sensitive: glass-filtered daylight converts it to a geometrical isomer, 7 2+ , in which the cyclometalated benzyl functionality of one of the two ligands has switched its position with a pyridyl donor.

Polymer Conjugates of Photoinducible CO‐Releasing Molecules

“…Bpma-type ligands usually coordinate facially, but they can also coordinate meridionally. [42][43][44][45] Additionally, in complexes 2 and 4 the OH func-tionality of the ligand could serve as a donor. Using X-ray analysis we evidenced that the Mn(CO) 3 core was facially coordinated by the bpma ligand.…”

Syntheses, structures, and spectroscopic properties of binuclear copper(II) complexes containing N,N-bis(2-pyridylmethyl)amine ligands

“…Like trispyrazolylborates, bpa-R can adopt both k 2 and k 3 coordination modes, but unlike trispyrazolylborates can coordinate in both facial and meridional k 3 modes [6]. A variety of transition metal complexes with bpa-R have been reported [7][8][9][10][11][12][13][14][15][16][17].…”

“…Like trispyrazolylborates, bpa-R can adopt both k 2 and k 3 coordination modes, but unlike trispyrazolylborates can coordinate in both facial and meridional k 3 modes [6]. A variety of transition metal complexes with bpa-R have been reported [7][8][9][10][11][12][13][14][15][16][17]. Coordination chemistry of copper is of continuing importance in relation to the structures and reactivity of the active sites in copper metalloproteins [18], but studies on copper(II) complexes with bpa-R are limited [19].…”

Synthesis, crystal structure, magnetic property, and nuclease activity of a binuclear iron(III) complex

“…A variety of transition metal complexes with bpa-R ligands have been reported [11][12][13][14][15][16][17][18][19][20][21]. Iron(III) centers linked by a bridging oxygen atom and two carboxylate bridges are well established in the structure of hemerythrin, a marine invertebrate respiratory protein, in its various forms [22][23][24].…”