Uncovering Intramolecular pi-Type Hydrogen Bonds in Solution by NMR Spectroscopy and DFT Calculations.

Reaction between the phosphinito bridged diplatinum species [(PHCy2 )Pt(mu-PCy2 ){kappa(2) P,O-mu-P(O)Cy2 }Pt(PHCy2 )](Pt-Pt) (1), and (trimethylsilyl)acetylene at 273 K affords the sigma-acetylide complex [(PHCy2 )(eta(1) -Me3 SiC=C)Pt(mu-PCy2 )Pt(PHCy2 ){kappaP-P(OH)Cy2 }](Pt-Pt) (2) featuring an intramolecular pi-type hydrogen bond. Scalar and dipolar couplings involving the POH proton were detected by 2D NMR experiments. Relativistic DFT calculations of the geometry, relative energy, and NMR properties of model systems of 2 confirmed the structural assignment and allowed the energy of the pi-type hydrogen bond to be estimated (ca. 22 kJmol(-1) ).