Aerobically stable and substitutionally labile α-diimine rhenium dicarbonyl complexes

Abstract

New synthetic routes to aerobically stable and substitutionally labile α-diimine rhenium(i) dicarbonyl complexes offer a convenient entry in the chemistry of the cis-[Re(CO)2]+ core.

Efficient Direct Nitrosylation of α-Diimine Rhenium Tricarbonyl Complexes to Structurally Nearly Identical Higher Charge Congeners Activable towards Photo-CO Release

“…Consistent with what reported before, the CO stretching (νCO’s) frequencies of fac -[Re(CO) 2 (NO)(N-N)Br] + complexes 1 – 5 are substantially shifted to higher wavenumbers, which is unusual for carbonyls bound to the low valent metal [ 33 , 34 ]. In fact, the νCO’s are found in the region where rhenium(III) dicarbonyl complexes [ 35 ] (e.g., [Re III (CO) 2 Br 4 ] − )[ 36 ] are observed, and much higher than corresponding rhenium(II) species [ 37 ]. The symmetric νCO mode of the molecules is actually not far from that of CO gas (2143 cm −1 ).…”

“…We recently published synthetic procedures to aerobically stable and substitutionally labile α-diimine rhenium(I) dicarbonyl complexes of formula [Re I (CO) 2 (N-N)Br(py)] capable of exchanging the halide for other ligands [ 37 ]. Therefore, we next tried the reaction of the corresponding [Re I (CO) 2 (bpy)Br(py)] complex ( 8 ) with NOBF 4 .…”

“…All reagent and solvents were purchased from standard sources and used without further purification. Compound [Re(CO) 5 Br] was purchased from Sigma Aldrich, while complexes of formula fac -[Re I (CO) 3 (N-N)Br] [ 19 ], (Et 4 N)[Re II (CO) 2 Br 4 ][ 36 ], fac -[Re I (CO) 2 (N-N)(py)Br] [ 37 ], fac -[Re(CO) 3 (bpy)OH] [ 68 ] and fac -[Re(CO) 3 (bpy)(Me 2 N-py)](CF 3 SO 3 ) [ 46 ] were synthesized according to published procedures. Unless otherwise noted, solvents used in the preparation of all molecules were dry and O 2 -free.…”

“…The crude product was then dissolved in a minimal amount of methanol and precipitated with cold diethylether to give 7 as a white/beige solid ( 21 [Re(CO) 2 (py)(bpy)Br] (8). This complex was prepared by following a previously published procedure for similar species [37]. Brown solid, yield 80%.…”

Efficient direct nitrosylation of a-diimine rhenium tricarbonyl complexes to structurally nearly identical higher charge congeners activable towards photo-CO release

“…[Re III (CO) 2 Br 4 ] -) 36 are observed, and much higher than corresponding rhenium(II) species. 37 The symmetric νCO mode of the molecules is actually not far from that of CO gas (2143 cm -1 ). The evidence points to a significant reduction of Re-CO πbackbonding in favour of the stronger π-acceptor NO + .…”