The gaseous free radicals, alkaline-earth metal monoalkylamides, monoacetylides, monoformamidates and monopyrrolidates, consisting of a metal atom (Ca or Sr) bonded to a single ligand, were synthesized in a Broida oven. The electronic and vibrational structures of these molecules were studied by low-resolution laser spectroscopy techniques. These inorganic molecules are ionic, well represented by the structure M⁺L⁻ (M = Ca, Sr: L = ligand). Three electronic transitions were identified for the metal monoalkylamides and the metal monoformamidates. The formamidate anion bonds to the metal in a bidentate fashion through the oxygen and nitrogen atoms. Two electronic transitions were observed for the metal monopyrrolidates. The pyrrolide anion ring bonds to the metal to provide these "open-faced sandwich" type molecules with pseudo-C₅ᵥ symmetry. For the metal monoacetylide molecules, only one electronic transition (Ā²Π-Ẋ²Σ⁺) was observed. Several vibrational frequencies were determined for these inorganic molecules from the low-resolution spectra. The Ā²Π-Ẋ²Σ⁺ transition of the calcium monoacetylide molecule was rotationally analyzed at high-resolution using the filtered laser excitation spectoscopy technique. The rotational line positions were fitted to a ²Π-²Σ⁺ Hamiltonian to obtain several rotational constants. The calcium-carbon bond length in CaCCH was calculated for the ground (2.248 Å) and excited (2.200 Å) electronic states. The vibration-rotation spectra of the gaseous bismuth hydride and bismuth deuteride molecules were recorded, using a diode laser system. The 1-0 fundamental band and several hot bands with Δv-1 were rotationally analyzed. The rotational line positions were fitted first, to a Dunham energy expression and then to a ³Σ⁻ Hamiltonian, to obtain ground state rotational constants. The bismuth-hydrogen (deuterium) bond distance was calculated to be 1.809 Å (1.807 Å).

The bonding in a series of ligand-bridged metal dimer complexes has been characterized by He(I) and He(II) photoelectron spectroscopy and approximate molecular orbital calculations. Bridging ligands such as carbonyl, nitrosyl, methylene and pyrazolyl in the complexes [CpFe(NO)]₂, [Cp*Fe(NO)]₂, [CpRu(NO)]₂, [Cp*Co(CO)]₂, [CpFe(CO)₂]₂, [Cp*Fe(CO)₂]₂, [CpFe(CO)]₂-μCO-μCH₂, [Cp*Fe(CO)]₂-μCO-μCH₂, [CpFe(NO)]₂- μCh₂, [CpRu(NO)]₂-μCH₂, [CpCo(CO)]₂-μCH₂, [CpRh(CO)]₂-μCH₂, [Ir(pyrazolyl)(CO)₂]₂, [Ir(3-methylpyrazolyl)(CO)₂]₂ and [Ir(3,5-dimethylpyrazolyl)(CO)₂]₂ are investigated and their effects upon metal-metal interactions are surveyed. Due to the presence of two d⁷ or d⁸ late metal atoms per molecule, these complexes display many overlapping ionization bands in a narrow valence ionization region. Attention has been given to modelling the photoelectron single ionization with asymmetric and symmetric Gaussians. The overlapping ionizations are successfully represented in terms of the model bandshapes. Thermodynamic relationships between bond dissociation and photoelectron ionization energies are also investigated. With relationships of this type, trends in bond energies may be correlated with ionization energies. Ligand inductive and bonding effects as well as small changes in molecular geometry cause shifts in the metal-based ionizations, which aid chemical understanding and interpretation of the molecular orbital picture. By comparing a series of related metal dimers, the assignment of related ionizations in the photoelectron spectra becomes apparent. Changes in ligand π accepting ability and changes in metal and formal oxidation states are also probed. Addition information is provided by vibrational fine structure in Cp₂Os, [CpFe(NO)]₂, and [Cp*Co(CO)]₂ and spin-orbit splitting in Cp₂Os. The metal-ligand backbonding combinations are found to be the most stable interactions and are responsible for the stability of the metal dimers. Metal-metal interactions are found to be relatively unimportant. Ligands with stronger π accepting abilities allow for more stabilized supported metal dimer complexes.