The solid-state, solution and gas–phase interactions of diphosphane monooxide spacers with heavier group 8,9 transition metals and gallium in novel organometallic assemblies: An experimental and computational study

Six new mono-substituted carbonyl clusters [M3(CO)11(DPMO)] (M = Os, Ru; 1–4) and [Rh6(CO)15(DPMO)] (5, 6) were obtained from the reactions of non-symmetrical bifunctional diphosphane monoxides (DPMOs, Ph2P(CH2)nP(O)Ph2, n = 2, 3) with triangular clusters [Os3(CO)12] and [Ru3(CO)12], and octahedral cluster [Rh6(CO)15(NCMe)] under mild conditions. 1–6 were then subjected to electrophilic reactions with GaCl3, which resulted in coordination-based molecular assemblies [M3(CO)11(DPMO)(GaCl3)] (M = Ru, Os; 7–10) and [Rh6(CO)15(DPMO)(GaCl3)] (11, 12). 1–12 were characterised by 31P{1H} NMR, IR spectroscopy, and FAB mass spectrometry. The crystal structures of 1, 2 and 7 were determined by single-crystal X-ray analysis. 7 is the first solid-state characterised Os–Ga bridged complex. The latter and its constitutive fragment, 1, were studied by density functional calculations in the gas phase and in solution in order to better understand their structural features. Two different rotameric structures related by rotation about the P–C–C–P linkage of the DPMO ligand were established for 1 and 7. The bonding properties of 7 were analysed by means of a quantitative energy decomposition analysis (EDA). The EDA revealed a predominant electrostatic character for the interactions between the three units (carbonyl cluster, gallium halide and spacer) constitutive of 7.

Graphical abstractFunctionalisation of the pendant phosphane-oxide moiety of [Os3(CO)11(Ph2P(CH2)2P(O)Ph2)] with GaCl3 resulted in the formation of the first organometallic osmium–gallium mixed complex, [Os3(CO)11(Ph2P(CH2)2P(O)Ph2)(GaCl3)]. The structure of the latter was determined by X-ray crystallography, characterised by 31P{1H} NMR, IR spectroscopy, and FAB mass spectrometry, and its properties were examined using density functional theory (DFT, at the B3LYP level) in combination with a quantitative energy decomposition analysis (EDA). The condensed media were shown to have an effect on the structural features of [Os3(CO)11(Ph2P(CH2)2P(O)Ph2)(GaCl3)] and of the fragments constitutive of this osmium–gallium complex.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis and structural characterisation of coordination-based molecular assemblies of Ru, Os, and Rh. ► Non-symmetrical bifunctional diphosphanes as ligand spacers. ► Functionalisation of the pendant phosphane-oxide moiety with GaCl3. ► First organometallic Os-Ga bridged complex. ► Observation of rotameric structures related by rotation about the P–C–C–P linkage.