Formation of Phosphaalkyne Trimers: A Mechanistic Study

Abstract

The geometric and electronic structures of phosphaethyne trimers were studied using density functional theory (B3LYP/cc-pVTZ) as well as CBS-QB3, CCSD(T), and complete active space selfconsistent field (CASSCF) computations. The effect of the substituents was also investigated. Our aim was to identify the low-energy equilibrium structures with synthetic interest; therefore, we were determining minima without any restriction on the chemical structure. The global minimum of the C 3 P 3 H 3 potential energy surface is confirmed to be the 1,2,3-triphosphinine. The next energetically stable isomer is a potentially synthesizable target with a P 3 ring, which is only 34 kJ/mol above the global minimum. Formation of phosphaethyne trimers by reaction of phosphaethyne and 1,4diphosphatriafulvene has been determined. This suggests that the thermodynamically controlled product is the 1,3,5-triphosphinine, while 1,3,6-triphosphafulvene is the kinetically favored product. For the latter a biradical reaction pathway also exists. Analysis of the effect of the substituents shows that the reaction barriers increase with the size of the substituent. Using the bulky 2,4,6-tri-tertbutylphenyl (supermesityl) substituent, the relative stabilities of 1,3,5-triphosphinine and 1,3,6triphosphafulvene are reversed, and the latter is expected to be the most stable phosphaalkyne trimer with bulky substituents. The head-to-tail reaction of phosphaethyne and phosphanylidene carbenoid yields 1,3,6-triphosphafulvene with very small barriers, while 1,4-diphosphafulvene is expected to be a byproduct. The results are in good agreement with the experimental findings.

Reply to “Comment on ‘Tuning Magnetic Moments by 3d Transition-Metal-Doped Au6 Clusters’”

“…This structure is reoptimized using the PW91 functional (B3PW91 key word) with a scalar relativistic effective core potential Stuttgart/Dresden (SDD) basis set, implemented in the Gaussian03 package . Both PBE/VPSR (DMOL3) and B3PW91/SDD (G03) computations show the ring structure of Sc@Au 6 prefers the D 2 h symmetry at 0.01 Å tolerance (see Figure b,c), even the cluster is performed in its D 6 h symmetry, the geometry optimizations will still lead to the D 2 h symmetry owing to the Jahn−Teller effect, in agreement with the computations of Höltzl et al This indicates that the PSM model presented by Höltzl et al can be used to describe and predict the electronic structure of the M@Au 6 system.…”

“…The main assumption of the PSM is that molecular orbitals corresponding to the itinerant electrons have shapes similar to that of the atomic orbitals which can be denoted by capital S, P, D. With the model of PSM, the total magnetic moment of the high D 6 h symmetry Mn@Au 6 cluster and the local magnetic moment of the Mn atom, which were indeed found in our work, are simply explained by the closed electronic shell. The results of other M@Au 6 clusters obtained in our work can also be explained by PSM …”

“…Höltzl et al reported the phenomenological shell model of metal clusters (PSM) in their comment on our recent paper to provide a consistent rationalization for the observed variation of the geometries and magnetic properties of M@Au 6 . The main assumption of the PSM is that molecular orbitals corresponding to the itinerant electrons have shapes similar to that of the atomic orbitals which can be denoted by capital S, P, D. With the model of PSM, the total magnetic moment of the high D 6 h symmetry Mn@Au 6 cluster and the local magnetic moment of the Mn atom, which were indeed found in our work, are simply explained by the closed electronic shell.…”

“…For the case of Sc@Au 6 , we reported the lowest energy structure of this cluster had a D 6 h symmetry computed at PW91/VPSR level of theory . However, Höltzl et al pointed out the D 6 h symmetry was unexpected since this compound had 9 shell electrons with a 1S 2 1P x 2 1P y 2 1D x y 2 1D x 2 − y 2 1 electron configuration according to the PSM model. It should be noted that Sc@Au 6 has D 6 h symmetry at 0.1 Å tolerance in our previous work, if the tolerance is set at 0.01 Å, this cluster shows D 2 h symmetry (see Figure a).…”

Theoretical Design of Novel Trinuclear Sandwich Complexes with Central M3 Triangles (M = Ni, Pd, Pt)

“…Therefore, the present systems hold substantial d-aromaticity characters. Note that aromaticities involving d orbitals are rather intriguing, since they may give rise to novel multiple (σ, π, and δ) aromaticity character due to the more complicated nodal structures of the d atomic orbitals.…”