Preparation and properties of FeRu(CO) 5(L)(α-diimine) (α-diimineR-DAB, R-Pyca; LPR 3, CO); the reduction of the coordinated 1,4-diaza-1,3-butadiene to dianionic 1,2-diaminoethane by reaction with hydrogen

Abstract

FeRu(CO) 6( iPr-Pyca) ( 1a) reacts with hydrogen to give the highly reactive species H 2FeRu(CO) 5( iPr-Pyca) ( 2), which contains a bridging and a terminal hydride atom. Treatment of 2 with CX 4 affords HFeRu(X)(CO) 5( iPr- Pyca) (XCl ( 3a); I ( 3b)) in which the terminal hydride has been substituted. Complex 2 reacts back with carbon monoxide to give FeRu(CO) 6( iPr-Pyca) ( 1a), whereas treatment of 2 with PMe 2Ph gives FeRu(CO) 5(PMe 2Ph)( iPr-Pyca) ( 4b). Complexes 4 can easily be prepared from the hexacarbonyl complexes FeRu(CO) 6(α-diimine) (α-diimine iPr-Pyca ( 1a); iPR-DAB ( 1b)) and the appropriate phosphine, giving FeRu(CO) 5(PR 3)(α-diimine) (α-diimine iPr-Pyca, PR 3PPh 3 ( 4a); α-diimine iPr-Pyca, PR 3PMe 2Ph ( 4b); α- diimine iPr-DAB, PR 3PPh 3 ( 4c); α-diimine iPr-DAB, PR 3PMe 2Ph ( 4d)) in high yields. Reaction of FeRu(CO) 5(PPh 3)( iPr-DAB) ( 4c) with hydrogen at 90 °C yields FeRu(CO) 5(PPh 3)( iPr-N-CH 2CH 2-N- iPr) ( 5). The use of deuterium showed that the reduction proceeds stereoselectively, giving solely the trans-addition product FeRu(CO) 5(PPh 3)( iPr-N-C(H)(D)C(H)(D)-N- iPr) (5′). Complex 5 can easily be converted by carbon monoxide to FeRu(CO) 6( iPr-N-CH 2CH 2-N- iPr) ( 8). The conversion of 8 to 5 can be performed also, albeit less facile than the conversion of 5 to 8. The hydrogenation of both 1b and 4c was inhibited by carbon monoxide and free triphenylphosphine. In the latter case the new complexes FeRu(CO) 4(PPh 3) 2(α-diimine) (α-diimine iPr-Pyca (6a); iPr-DAB ( 6b)) were formed. A single crystal X-ray structure determination of 6a was obtained. Red crystals of 6a (C 49H 42N 2O 4P 2FeRu, M r=941.8, Z=2) are triclinic, space group P 1 and have cell constants a=11.625(3), b=14.269(3), c=15.963(2) Å, α=90.95(1), β=100.23(1) and γ=101.95(2)°. A total of 5886 reflections was used in the refinement which converged to a final R value of R=0.064. Reaction of MRu(CO) 6( iPr-DAB)(MFe ( 1b); Ru ( 1c)) with 40 bar of carbon monoxide at 90 °C afforded Ru(CO) 3( iPr-DAB) and M(CO) 5 (MFe, Ru). Interestingly it was found that reaction of Ru(CO) 3(DAB) with H 2Fe(CO) 4 also produced FeRu(CO) 6( iPr-N-CH 2CH 2-N- iPr) ( 8), whereas D 2Fe(CO) 4 afforded only the trans deuterated compound FeRu(CO) 6( iPr-N-C(H)(D)C(H)(D)-N- iPr) ( 8). Finally attention has been focussed on the elucidation of the mechanism of this trans addition of H 2/D 2 to the central CC bond of the coordinated 1,4-diaza-l,3-butadiene.