Combined kinetic and DFT studies on the stabilization of the pyramidal form of H3PO2 at the heterometal site of [Mo3M′S4(H2O)10]4+ clusters (M′ = Pd, Ni)

Abstract

4+ complexes, in which the rare pyramidal form of H 3 PO 2 is stabilized by coordination to the M' site of the clusters. The reaction proceeds with biphasic kinetics, both steps showing a first order dependence with respect to H 3 PO 2 . These results are interpreted in terms of a mechanism that involves an initial substitution step in which one tetrahedral H 3 PO 2 molecule coordinates to M' through the oxygen atom of the P=O bond, followed by a second step that consists in tautomerization of coordinated H 3 PO 2 assisted by a second H 3 PO 2 molecule. DFT studies have been carried out to obtain information on the details of both kinetic steps, the major finding being that the role of the additional H 3 PO 2 molecule in the second step consists in catalysing a hydrogen shift from phosphorus to oxygen in O-coordinated H 3 PO 2 , which is made possible by its capability of accepting a proton from P-H to form H 4 PO 2 + and then transfer it to the oxygen. DFT studies have been also carried out on the reaction at the Mo centres to understand the reasons that make these metal centres ineffective for promoting tautomerization.

Reaction mechanisms in solution

“…Kinetic and DFT studies have been carried out on the reaction of the [Mo 3 M 0 S 4 (H 2 O) 10 ] 4+ clusters (M 0 = Pd, Ni) with H 3 PO 2 to form the [Mo 3 M 0 (pyr-H 3 PO 2 )S 4 (H 2 O) 9 ] 4+ complexes, in which the rare pyramidal form of H 3 PO 2 is stabilized by coordination to the M 0 site of the clusters. 41 The reaction, studied with stopped-flow spectrophotometry, proceeds with biphasic kinetics, both steps showing a first order dependence with respect to H 3 PO 2 . The mechanism (Fig.…”

Hydrolysis of Element (White) Phosphorus under the Action of Heterometallic Cubane-Type Cluster {Mo3PdS4}

“…Heterometallic cubane-type cluster complexes with {M 3 PdS 4 } (M = Mo, W) core that were first described by Hidai's group in Japan [9,10], possess a number of attractive properties including unordinary reactivity and catalytic activity of the Pd site [11][12][13][14][15][16][17][18][19][20][21][22]. To cite the most recent example, {Mo 3 PdS 4 } cluster complexes react with fullerene C 60 to form hybrid compounds containing a fullerene molecule coordinated to palladium in the cluster core [23].…”

Kinetic, DFT and TD-DFT studies on the mechanism of stabilization of pyramidal H3PO3 at the [Mo3M′S4(H2O)10]4+ clusters (M′ = Pd, Ni)

“…2,6-10 On the other hand, some mononuclear complexes with tautomerized H 3 PO 3 have been also recently reported: trans-[Ru(NH 3 ) 4 (pyr-H 3 PO 3 )(H 2 O)] 2+ , 1 [CpRu(PPh 3 ) 2 (pyr-H 3 PO 3 )] + , 11 and [Ru(dppe) 2 (pyr-H 3 PO 3 )] 2+ . 12 We have previously shown 13, 14 that tautomerization of the related H 3 PO 2 acid occurs at the M¢ site of Mo 3 M¢S 4 clusters (M¢ = Ni, Pd) with biphasic kinetics, and a mechanism has been proposed in which the first resolved kinetic step corresponds to substitution of the water coordinated to the Pd centre to give a complex containing O-coordinated tet-H 3 PO 2 . Tautomerization of coordinated H 3 PO 2 occurs in the second step through a mechanism in which a second H 3 PO 2 molecule catalyzes an H-shift from phosphorus to oxygen through a deprotonation-protonation sequence, the process being completed with isomerization of the complex containing the O-coordinated pyr-H 3 PO 2 to the more stable one coordinated through the phosphorus.…”