The interconversion of quasi-planar butterfly and tetrahedral tetraruthenium cluster geometries: X-ray crystal structure of tetrahedral [H₂ru₄(CO)₁₀(µ-PPh₂)₂]

Abstract

The quasi-planar 64-electron butterfly cluster [ R U ~( C O ) ~~( ~-P P ~~) ~] reacts with dihydrogen under photolysis giving the 60-electron tetrahedral cluster [H2R~4(CO)10(p-PPh2)2], a transformation which can be reversed under a pressure of carbon monoxide; the two hydride ligands in the unsymmetric [H2R~4(CO)lo(p-PPh2)2] have been located via a single crystal X-ray analysis.

Reaction of the heterometallic cluster Os3Ru(μ-H)2(CO)13 with diphenylphosphine: phosphido-bridged tetrahedral and butterfly clusters

“…5. The two 31 P chemical shifts for the proposed structure for the minor isomer are also consistent with the 200-290 ppm range for a phosphido bridge across an Ru-Os edge (compounds 2 and 4, and the major isomer) compared with the <190 ppm for across an Os-Os edge (for the major isomer and 4), observed here and in other similar systems [12c, 13,16].…”

“…Since the 2 J PH will be dependent on this angle, it is reasonable to assign the resonance at À13.04 ppm ( 2 J PH = 23.9 Hz) to H (24). This leaves the most upfield resonance at À21.59 ppm assignable to H (13), which bridges an Os-Os edge. This is also consistent with earlier observations that the bridging hydride resonance in tetranuclear clusters is shifted increasingly upfield along the series Ru-Ru, Ru-Os and Os-Os [14].…”

“…The simplest mechanism involving simultaneous exchange among all three resonances is one that entails movement of the phosphido bridge; all reasonable exchanges involving hydrides only require mutual exchanges between two hydrides. However, an EXSY taken with s m = 0.1 s showed absence of the exchange crosspeak between the resonances due to H (24) and H (13). Since the crosspeak amplitudes are a function of the exchange rates [15], this indicates that the exchanges occur with different rates hence ruling out a concerted mechanism.…”

“…The chemistry of this cluster has otherwise been little investigated; so far, only its synthesis and structure [3], and its employment as a catalyst precursor supported on alumina for a number of catalytic reactions including alkene isomerisation and hydrogenation [4], and CO hydrogenation [5], have been reported. A much larger volume of work exists on the closely related clusters FeRu 3 (l-H) 2 (CO) 13 [6], and FeOs 3 (l-H) 2 (CO) 13 [7]. Cluster 1 is of interest to us because it is envisaged that the ruthenium vertex is expected to be more reactive than the osmium vertices.…”

“…We have recently reported a high-yield synthesis of the hetero group 8 tetranuclear cluster Os 3 Ru(l-H) 2 (CO) 13 (1), including its reactivity with PPh 3 [2]. The chemistry of this cluster has otherwise been little investigated; so far, only its synthesis and structure [3], and its employment as a catalyst precursor supported on alumina for a number of catalytic reactions including alkene isomerisation and hydrogenation [4], and CO hydrogenation [5], have been reported.…”