We report here a thorough ¹H NMR study of Fe(acac)₂ solutions in a wide variety of noncoordinating and coordinating solvents, as well as the interaction of this complex with Et₃N, pyridine, PMe₂Ph, and R₂PCH₂CH₂PR₂ [R = Ph (dppe), Et (depe)] in C₆D₆. The study reveals that Fe(acac)₂ is readily transformed into Fe(acac)₃ in solution under aerobic conditions and that the commercial compound is usually contaminated by significant amounts of Fe(acac)₃. The ¹H NMR resonances of Fe(acac)₂ are rather solvent-dependent and quite different than those reported in the literature. The compound is unstable in CDCl₃ and stable in CD₂Cl₂, C₆D₆, CD₃CN, acetone-d⁶, DMSO-d⁶, THF-d⁸, and CD₃OD. The addition of the above-mentioned ligands (L) reveals only one paramagnetically shifted band for each type of acac and L proton, the position of which varies with the L/Fe ratio, consistent with rapid ligand exchange equilibria on the NMR time scale. A fit of the NMR data at a high L/Fe ratio allows the calculation of the expected resonances for all protons in the Fe(acac)₂L₂ molecules. The system with the bidentate depe ligand shows evidence for a slow ligand exchange at low depe/Fe ratios, proposed to involve a species with the cis-chelated mononuclear Fe(acac)₂(depe) structure, whereas the fast exchange at a higher ratio is proposed to involved a trans-Fe(acac)₂(κ¹-depe)₂ complex. Complex Fe(acac)₂(dppe) cannot be investigated in solution because of low solubility in a noncoordinating solvent and because of the poor dppe competition for binding in coordinating solvents. The compound was crystallized, and its X-ray structure reveals a 1-dimensional polymeric structure with dppe-bridged Fe centers having the trans-octahedral Fe(acac)₂(κ¹-dppe)₂ coordination environment.

Ir(CO)[CpFe{η⁵-C₅H₃(PPh₂)CH₂SR}]Cl [R = Ph and ^tBu], containing a κ²:P,S ligand, undergoes H₂ addition across the S–Ir–CO axis under kinetic control to form two distinct diastereoisomeric products, which then rearrange via S dissociation in a process that can be hijacked for useful catalysis, but ultimately form a single diastereoisomer of the thermodynamic product where the hydride ligands are trans to chloride and phosphine.

The crystal structure of MoO₂(SAP)(EtOH) is reported for the first time. The compound crystallizes in the monoclinic crystallographic system (P2₁/n, a = 11.0923(3) Å, b = 6.9590(2) Å, c = 19.4499(5) Å, β = 94.458(1)°, V = 1496.82(7) ų, Z = 4). The molybdenum atom adopts a distorted octahedral arrangement with cis Mo=O bonds, typical for cis-dioxomolybdenum(VI) complexes. The ethanol ligand is situated trans to one oxido ligand. Theoretical calculations in the gas phase were performed to examine the relative stability of MoO₂(L)(EtOH) and the [MoO₂(L)]₂ dimeric form (L = SAP, SAE).