Title: Phosphido-Bridged Trinuclear Platinum Clusters: A DFT Study

Abstract

The compound H(PEt3)3Pt3(μ-PPh2)3 is the unique example of a 46e− phosphido-bridged triangular cluster, but its X-ray assigned stereochemistry appears questionable. In particular, the H-free P3Pt3(μ-P)3 metal core is identical to that of the 44e− cation [(PEt3)3Pt3(μ-PPh2)3]+ in two salts of the same publication. Also, the lack of a distortional effect due to the upright and strongly-bound hydride ligand is suspicious and intriguing aspects emerge from the inconsistent electronic structure. Although H(PEt3)3Pt3(μ-PPh2)3 is fully validated by IR and NMR spectra, DFT optimizations never reproduced the proposed experimental structure but highlighted a different stereochemistry still consistent with the spectroscopic response. Here, a formal Pt(II) ion is essentially isolated and has square-planar coordination, completed by two trans-axial ligands (H and Et3P) out of the Pt3 plane. Given the chemical reliability of the in silicomolecule, the crystals of the experimental structure have likely contents other than the hydridic cluster and a co-crystallized Ph2PH molecule. As a working hypothesis, the Pt-H and P-H linkages of the distinct components may have reacted together with H2 release, and subsequent cristallization of the salt whereas the ion pair [(PEt3)3Pt3(μ-PPh2)3]+/[Ph2P]−. This would explain the equal geometries of the putative 46e− cluster and the H-free 44e− cation. In the lack of any experimental X-ray dataset, the proposed crystal formulation could not be fully validated, but in the paper various aspects support its reliability.