Synthesis and Characterization of Triosmium Clusters Containing the Bidentate Ligand Ph₂PCH₂CH₂SMe:  Detection of an Isomerization Reaction Involving Bridging and Chelating Ligand Coordination Modes

Abstract

Diphenylphosphinoethylene methyl sulfide, Ph 2 PCH 2 CH 2 SMe, reacts with [Os 3 (CO) 11 -(NCMe)] yielding [Os 3 (CO) 11 (Ph 2 PCH 2 CH 2 SMe)]. Treatment of [Os 3 (CO) 10 (NCMe) 2 ] with 1 equiv of the P,S ligand initially yields the cluster 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)], in which the phosphine and the thioether moieties coordinate to different metal atoms of the metal triangle; addition of two or more equivalents of the ligand yields 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)] and [Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe) 2 ]. The cluster 1,2-[Os 3 (CO) 10 (µ-Ph 2 -PCH 2 CH 2 SMe)] is metastable and undergoes a slow isomerization reaction at room temperature to form 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)], in which the ligand chelates one Os atom. Computational modeling of 1,2-and 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)] indicates that the two clusters are of similar stability, with the latter isomer being of slightly lower energy. The dynamic behavior of the clusters have been investigated by variable-temperature 13 C{ 1 H} and 31 P{ 1 H} NMR, and the kinetics of the isomerization reaction have been measured. The latter indicate that the isomerization proceeds via an associative mechanism which is proposed to involve an intramolecular nucleophilic attack by the coordinated sulfur on an osmium atom. The solid state structures of [Os 3 (CO) 11 (Ph 2 PCH 2 CH 2 SMe)], 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)], and 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)] are reported.

The structure of a triosmium carbonyl cluster-phenylarsine oxide derivative

“…The 13 C NMR carbonyl region reveals nine signals in the range of 179e160 ppm, which were assigned by comparison with those reported in the literature [25,31,34], and the low field resonances were assigned to C-2, C-4, and C-7. This assignment is based on the general trend that axial carbonyl resonances shift to lower fields than those of equatorial and by considering that As(1) is more electronegative than As(2), as was observed in IR spectroscopy [26,33].…”

Polyhedral Flexibility in the Sulfido-Capped Cluster H2Ru3(CO)9(μ3-S) on Reaction with 2-(Diphenylphosphino)thioanisole (PS) and Reversible Tripodal Rotation of the Chelated PS Ligand in H2Ru3(CO)7(κ2-PS)(μ3-S)

“…IR (CH 2 Cl 2 , initial isomeric mixture) ν(CO) 1994 (br), 2039 (s), 2071 (s) cm −1 . H 2 Ru 3 (CO) 7 (κ 2 -P eq ,S eq )(μ 3 -S) (kinetic product): 1 H NMR (500 MHz, CDCl 3 ) δ −20.11 (1H, broad dd, 2 J HP 9.54, 2 J HH 1.79 Hz, hydride), −17.26 (1H, dd, 2 J HP 34.00, 2 J HH 1.79 Hz, hydride), 2.75 (3H, s, SCH3), 7.30−7.65 (13H, m, aryl), 7.85 (1H, dd, J HH 7.75, 1.79 Hz, aryl). 31 X-ray Crystallography.…”

“…47 Isomerization Kinetics. The kinetics to equilibrium for 2-(P eq ,S eq ) ⇌ 2-(P ax ,S eq ) were investigated by 1 Young valve that allowed the sample to be freeze−pump−thawdegassed prior to active measurement. The NMR experiments were conducted in the NMR probe, and the progress of the reaction was followed as a function of the intensity of the hydride resonances until the ratio of the two isomers reached equilibrium.…”

“…Typically, heterobidentate hemilabile donors react with metal clusters to give chelated or bridged products depending on the nature of the ligand and the energetics associated with the different product isomers, and this phenomenon was first described by Nordlander and co-workers in 2001 for the reaction of the triosmium cluster 1,2-Os 3 (CO) 10 (MeCN) 2 with the hemilabile donor (2-methylthioethyl)diphenylphosphine (PS′). 1 The bridged cluster Os 3 (CO) 10 (μ-PS′) is formed as a kinetic product of substitution that undergoes a slow, nondissociative isomerization to the thermodynamically favored chelated cluster Os 3 (CO) 10 (κ 2 -PS′) (Scheme 1). 2 Here the thiomethyl moiety promotes an in-plane migration of ligands about the Os−Os bond by changing from a 2e to 4e donor that enables the coordination of adjacent metal centers.…”

“…Both species exhibit a distinct pair of bridging hydrides that comprise the AB portion of an ABX spin system and whose geminal coupling to the ancillary phosphine facilitates the stereochemical assignment of the phosphine moiety relative to the hydrides. The kinetic product displays a pair of doublet of doublets (dd) centered at δ −20.11 and −17.26 where the small 1.8 Hz splitting observed derives from hydride−hydride coupling, as verified by 1 H COSY. 11 The resonance at δ −17.26 exhibits a large 2 J PH coupling of 34.0 Hz in full support for a trans orientation of the phosphine to one of the hydrides.…”