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An unstrained metal-containing macrocycle was ring-expanded by a ring-opening metathesis strategy, leading to the formation of a bimetallic dimeric macrocycle. The reaction is driven by coordination of a bulky ligand, 2,6-lutidine, on the fourth coordination site of the palladium center. In the absence of metal, or with a less bulky ligand, the ring-expansion reaction does not proceed.

The ability of (PNNH)CoCl2 (where PNNH is a phosphino and pyrazole substituted pyridine pincer) to serve as a precursor to coordinate the weak anion nitrate is investigated, giving a product with two coordinated nitrates, which demonstrate remarkable variability of nitrate binding in an overall six coordinate divalent cobalt complex. A synthetic variant with only one chloride per Co(II) is characterized, and retains coordination number 5. Comparison is made to rhodium, initially in oxidation state +1, including a carbonyl reporter ligand. The tridentate pincer displaces chloride and PPh3 from Rh(PPh3)2(CO)Cl to form the salt [(PNNH)Rh(CO)]Cl. That compound reacts with N-chloro succinimide with oxidation to trivalent rhodium, loss of carbon monoxide, but also with inadvertent chlorine substitution of pyrazole ring CH bond. As a comparison standard for PNNH ligand with a redox inert metal, (PNNH)ZnCl2 is characterized; bond lengths within the ligand allow the conclusion that the iron and cobalt analogs show no major back donation into the pincer ligand.

Ligand exchange at a sterically hindered palladium center was investigated for six different ligands. The palladium atom was coordinated to a tridentate, NNN pincer bis(amido)pyridine macrocycle to produce a square-planar complex, in which an acetonitrile molecule occupies one of the coordination sites. Kinetic studies showed that ligand exchange at the palladium center proceeds through an associative mechanism and, as a consequence, is impeded by the small size of the metallomacrocycle cavity. The ligand-exchange rate on the palladium center between acetonitrile and six different ligands has been investigated and compared to the exchange rate on the corresponding open form. Our results demonstrate that macrocyclization of ligands is a way to modify the rate of guest exchange in a square-planar metal complex.

The intermetallic molecules CuSb, AgSb, and AuSb were identified in the effusive molecular beam produced at high temperature under equilibrium conditions in a double-cell-like Knudsen source. Several gaseous equilibria involving these species were studied by mass spectrometry as a function of temperature in the overall range 1349-1822 K, and the strength of the chemical bond formed between antimony and the group 11 metals was for the first time measured deriving the following thermochemical dissociation energies (D°(0), kJ/mol): 186.7 ± 5.1 (CuSb), 156.3 ± 4.9 (AgSb), 241.3 ± 5.8 (AuSb). The three species were also investigated computationally at the coupled cluster level with single, double, and noniterative quasiperturbative triple excitations (CCSD(T)). The spectroscopic parameters were calculated from the potential energy curves and the dissociation energies were evaluated at the Complete Basis Set limit, resulting in an overall good agreement with experimental values. An approximate evaluation of the spin-orbit effect was also performed. CCSD(T) calculations were further extended to the corresponding group 11 arsenide species which are here studied for the first time and the following dissociation energies (D°(0), kJ/mol): 190 ± 10 (CuAs), 151 ± 10 (AgAs), 240 ± 15 (AuAs) are proposed. Taking advantage of the new experimental and computational information here presented, the bond energy trends along group 11 and 4th and 5th periods of the periodic table were analyzed and the bond energies of the diatomic species CuBi and AuBi, yet experimentally unobserved, were predicted on an empirical basis.