Abstract
Metal complexes have long been recognized as fundamental in activating simple small molecules, which provide low-barrier reaction pathways through binding. One way to make highly reactive metal complexes is by reacting metal precursors with sterically demanding ligands that can create electronic unsaturation on the metal center, where activation can occur. A series of sterically crowded metal complexes have been synthesized by reactions of Pt(COD)2 with bulky tin ligands of the type HSnR3 [ R = But, Ph and C6H2Me3(mesitylene)]. These new complexes were studied for activation of small molecules like H2, CO, C2H2, C2H4, and catalytic H2- D2 exchange reactions at ambient conditions. The complex Pt(SnBut3)2(CNBut)2 was found to activate H2 and CO reversibly in solid state, as well as in solution. It also catalyzes the H2-D2 exchange at room temperature. Currently, the NHC carbene compounds as ligands are one of the most highly studied in organometallic chemistry. The role of NHC carbene ligands on the reactivity of Pt-Sn bimetallic complexes has also been studied. The Pt-Sn-NHC complex, [Pt(SnBut3)(IBut)(H)]2 was found to be highly reactive and efficient in the reversible activation of H2, and C2H4 at room temperature. This compound also activates CO at room temperature. The bimetallic complexes with inexpensive metals Ni & Sn were also synthesized and studied catalytically. The coordination chemistry of TEMPO radical with Ni metal was also explored. The 16 electron unsaturated "bow-tie" complex, Ni(η2-TEMPO)2 was found to be highly efficient in activation of C-H bond of alkynes and also found to be highly reactive towards other small molecules such as H2, CO, CO2, and other coordinating solvents such as THF and CH3CN. We were able to connect two Ni metal centers using an organic moiety in the complex Ni(η2-TEMPO)(κ1-TEMPOH)[κ1-κ1-CC(C6H4)CC]Ni(η2-TEMPO)(κ1-TEMPOH).