Reversible metal-metal bond cleavage accompanied by the facile reversible addition of hydrogen to a Ru3 cluster. Synthesis and x-ray structures of Ru3(CO)8(.mu.-H)2(.mu.-tert-Bu2P)2 and Ru3(CO)8(.mu.-H)2(H)2(.mu.-tert-Bu2P)2

Abstract

The reversible formation and cleavage of a metal-metal bond is a key reaction in dinuclear and cluster chemistry.1 A few cases have been reported in which such a process is accompanied by the reversible addition of two electron donors such as CO or PR,.1 However, to our knowledge there have, so far, been no well characterized examples of the complete cleavage of a metal-metal bond accompanied by the reversible addition of H2 under mild conditions. There are relatively few examples of the reversible addition of H2 to a metal cluster2 (see Note Added in Proof, ref 10), and in the cases where the products have been fully characterized, no cleavage of metal-metal bonds occurs.2-3 We report here the first example of the facile, reversible addition of H2 to a metal cluster which is accompanied by a clearly recognized reversible metal-metal bond cleavage.Reaction of di-rezf-butylphosphine (f-Bu2PH) with Ru,(CO),2 in di-n-butylether (0.5 h) at 100 °C gives the purple bis-phosphido bridged trinuclear complex Ru3(CO)g(*i-H)2(»i-f-Bu2P)2 (1) in 55% yield.4 The diphenylphosphido analogue of 1 has been reported, and the two compounds have similar structures in the solid state5 (see below). Spectroscopic data for 1 (1R, 'H, 3IP, NMR) is in accord with the solid-state structure as determined by X-ray crystallography.6 The IR spectrum contains only terminal i>co absorptions, while the H NMR shows a triplet at h -17.19 (7p-H = 19.5 Hz) assigned to two equivalent hydride ligands. A similar resonance is observed in the spectrum of Ru3(CO)8(3x-H)2(3t-Ph2P)2, and the triplet pattern can be attributed to an AA'XX' type of spectrum.5 The 3IP|'H| NMR spectrum of 1 is a singlet at 6 256.05 consistent with phosphido groups bridging metal-metal bonds.7Purple hexane solutions of 1 rapidiy turn orange when exposed to H2 (1 atm) at ambient temperature. From these solutions orange crystals of the 50-electron complex Ru3(CO)g(3t-H)2-(H)2(m-J-Bu2P)2 (2) may be isolated by crystallization from hexane under a hydrogen atmosphere. This compound is stable with respect to loss of H2 in the solid state either under vacuum or a

Kinetics and Mechanism of Reversible Oxidative Addition of Hydrogen across the Metal−Metal Bond of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2. Steric Promotion of Metal−Metal Bond Cleavage But a CO Dissociative Mechanism

“…The new cluster (μ-H) 2 Ru 3 (CO) 8 (μ-PCyc 2 ) 2 was prepared by the procedure used for the di- tert -butylphosphido analog. The spectroscopic data are entirely analogous to those for (μ-H) 2 Ru 3 (CO) 8 (μ-PR 2 ) 2 , R = Ph 14 and t -Bu . The clusters (μ-H) 2 Ru 3 (CO) 8 (μ-PPh 2 ) 2 and (μ-H) 2 Ru 3 (CO) 8 (μ-PCyc 2 ) 2 do not react with hydrogen under the conditions examined.…”

“…In 1988 Jones et al described the reaction of hydrogen with (μ-H) 2 Ru 3 (CO) 8 (μ-P( t -Bu) 2 ) 2 , in which addition occurs quantitatively and reversibly across an unbridged metal−metal bond, producing (μ-H) 2 Ru 3 (H) 2 (CO) 8 (μ-P( t -Bu) 2 ) 2 (Figure ) …”

“…In 1988 Jones et al described the reaction of hydrogen with (µ-H) 2 Ru 3 (CO) 8 (µ-P(t-Bu) 2 ) 2 , in which addition occurs quantitatively and reversibly across an unbridged metal-metal bond, producing (µ-H) 2 Ru 3 (H) 2 (CO) 8 (µ-P(t-Bu) 2 ) 2 (Figure 1). 13 The reaction is of interest as one of the few examples of (1) addition of hydrogen across a metal-metal bond, especially a single bond, and (2) formation and elimination of two terminal hydrides on a cluster. We report here a study of the kinetics and mechanism of this novel reaction.…”

Reversible Binding of Dihydrogen in Multimetallic Complexes

“…[14] H 2 addition to the saturated 48-electron triangular cluster (µ-H) 2 Ru 3 (CO) 8 (µ-PtBu 2 ) 2 (16) results in the opening up of the cluster to form a linear, also electron-precise, Ru 3 trimetallic species (µ-H)H 2 Ru 3 (CO) 8 (µ-PtBu 2 ) 2 (17), with no overall loss of CO. Purging a solution with N 2 reforms the starting cluster 16, although in the solid state the cluster is stable to H 2 loss. [42] Detailed kinetic studies demonstrated that the mechanism involves CO loss (thus forming an unsaturated cluster) that precedes H 2 addition to a singlemetal centre with concomitant breaking of a Ru-Ru bond. Addition of CO affords the product that has made a net gain of H 2 .…”

Interplay of Electronic and Steric Effects of R2PH (R = tBu, o‐tolyl) in Reactions with Triruthenium Dodecacarbonyl

“…Other authors reported the same reaction behavior during the reaction of the ruthenium carbonyl with the bulky phosphane P t Bu 2 H (molar ratio 1:2) in refluxing dibutyl ether resulting in [Ru 3 (μ‐H) 2 (μ‐P t Bu 2 ) 2 (CO) 8 ] . 3 crystallized from CH 2 Cl 2 /diethyl ether at room temperature as yellow crystals belonging to the monoclinic space group P 2 1 / n with four molecules in the unit cell.…”