Synthesis, characterisation and natural abundance 187Os NMR spectroscopy of hydride bridged triosmium clusters with chiral diphosphine ligands

Treatment of [Os3(μ-H)2(CO)10] with the chiral diphosphines BINAP, tolBINAP [(R)-2,2′-bis(di-4-tolylphosphino)-1,1′-binaphthyl], DIOP [(4R,5R)-(−)-O-isopropenylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane] affords [Os3(μ-H)2(CO)8(μ-L)] (L = BINAP (1), tolBINAP (2), DIOP (4)) in high yield. The X-ray structures for 1, 2 and 4 are reported, and structural and spectroscopic comparisons are made between these clusters and [Os3(μ-H)2(CO)8(μ-L)] (L = dppm (5), dppe (6), dppp (7)) which were synthesised similarly. Compounds 5 to 7 were previously synthesised by hydrogenation of 1,2-[Os3(CO)10(μ-L)] but the route from [Os3(μ-H)2(CO)10] is preferable. The H-bridged Os⋯Os distances are similar in 1, 2 and 4 indicating that these species are formally unsaturated 46-electron clusters. The P⋯P distances vary from 4.24 to 4.30 Å in 1 and 2, respectively, to 4.53 Å in 4 and there are related changes in the angles associated with the ligand set around the H-bridged osmium atoms. Introduction of the diphosphine ligands completely suppresses the ability to add CO, to insert acetylene to form a μ-η1,η2-vinyl compound, and to exchange hydride ligands with styrene-d8, which are reactions characteristic of [Os3(μ-H)2(CO)10]. Clusters 2 and 5–7 were also used to examine the potential of natural abundance 187Os NMR spectroscopy through techniques based on inverse detection by HMQC, HSQC and HMBC spectroscopy.

Graphical abstractClusters of the general formula [Os3(μ-H)2(CO)8(μ-P–P)] (P–P = R-BINAP, R-tolBINAP, R,R-DIOP) have been prepared and characterised. Natural abundance 187Os spectra of these and related clusters have been obtained using HMQC, HSQC and HMBC NMR spectroscopy.Figure optionsDownload full-size imageDownload as PowerPoint slide