Making use of a combination of ab initio calculated geometries, orbital energies, and orbital spatial distributions as well as experimental information about bond lengths, bond energies, vibrational frequencies, and dipole moments, the nature of the terminal PO bond in phosphates such as (MeO) 3 PO was probed and compared to the case in MeOsPdO where P is trivalent and a PO π bond is thus assumed to exist. We find that the MeOsP and terminal PO bond lengths in (MeO) 3 PO are essentially the same as in MeOsPdO and the terminal PO lengths are substantially shorter than single PsOMe bond lengths. We also find that the HOMO orbital energies in the two compounds are within 0.1 eV of one another and that these orbitals have spatial characteristics much like one would expect of a bonding π orbital connecting two atoms from different rows of the periodic table. Using this data, making a comparison to the more familiar bonding arising in N 2 , CO, and BF, and taking note of the dipole moments in compounds known to possess dative bonds, we conclude that it is best to represent the terminal PO bond in phosphates in terms of valence-bond structures such as (MeO) 3 PdO in which the formal charges are P 0 O 0 and where a single PO π bond exists. However, when it comes to characterizing the PO antibonding π* orbitals, significant differences arise. Electronic structure methods were able to identify the π* orbital of MeOsPdO and to determine its energy (the MeOsPdO -anion is even bound). Similar attempts to identify the PO π* orbital in the unbound (MeO) 3 PdO -anion lead us to conclude that this anion state is probably so strongly coupled to the continuum (i.e., to states corresponding to (MeO) 3 PdO plus a free electron) that it is so short lived as to be undetectable in experiments.

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The complexes [(Cp)Ru(CO)3]+ and [(Ind)Ru(CO)3]+ were subjected to chemical, electrochemical, and spectroelectrochemical investigations in an attempt to gauge their similarity to [(Cp)Fe(CO)3]+ and [(Ind)Fe(CO)3]+. While the Fe complexes exhibited reversible electrochemical behaviorthe indene analogue exhibiting a so-called “inverse indenyl effect”the Ru complexes exhibited limited electrochemical reversibility, even at −30 °C and higher scan rates. The formation of the hydride complexes [(Cp)Ru(CO)2H] and [(Ind)Ru(CO)2H] was observed via 1H NMR and IR. The X-ray crystal structure of [(Ind)Ru(CO)3]+ is presented here for the first time.