Synthesis of group 9 and 10 metal complexes supported by chelating nitrogen-based ligands and mechanistic studies of their role in catalytic transformations

This dissertation describes the synthesis of late-transition metal complexes supported by chelating nitrogen-based ligands and their utility in bond activations and homogenous catalytic transformations. The two nitrogen-based ligand sets that are of central focus are the neutral bipyridine based tBu2bpy (4,4'-di-tert-butyl-2,2'-bipyridyl) and the monoanionic 3,5-diphenyl-2-(2-pyridyl)pyrrolide (PyPyr). The reactivity of rhodium, iridium, and platinum complexes supported by these ligands has been analyzed to determine to their role in activation of Si-H bonds and N-H bonds. These complexes impact as intermediates in catalytic transformations is also examined.;A series of platinum bis(triflate) complexes of the type L2Pt(OTf) 2 (L2 = tBu2bpy, tBuC6H4N=C(CH3)C(CH 3)=NC6H4tBu, S-BINAP, (C6H5)2PCH 2CH2P(C6H5)2, (C6F 5)2PCH2CH2P(C6F5) 2, OTf = OSO2CF3) were synthesized. Reactivity studies with L2Pt(OTf)2 uncovered that these complexes are catalysts for the intermolecular hydroamination of norbornene with arylsulfonamides and weakly basic anilines. Mechanistic studies are consistent with a mechanism involving sulfonamide coordination and generation of an acidic proton that is transferred to the norbornene. The resulting norbornyl cation is then attacked by free sulfonamide, and loss of proton from this adduct completes the hydroamination. A platinum-sulfonamide coordination complex readily undergoes deprotonation to give a mu-amido platinum-bridged dimer. Kinetic studies provide the rate law: rate = kobs[Pt][sulfonamide], which is consistent with a mechanism involving a metal-mediated transfer of a proton. These studies also involved use of Me3SiPh and Me3SnPh as non-nucleophilic proton traps.;The bis(ethylene) complex (PyPyr)Rh(C2H4) 2 was treated with HSiEt3, HSiPh3, and HSi tBuPh2 to produce the 16-electron Rh(V) bis(silyl)dihydrides (PyPyr)Rh(H)2(SiEt3)2, (PyPyr)Rh(H) 2(SiPh3)2, and (PyPyr)Rh(H)2(Si tBuPh2)2. The analogous Ir(V) bis(silyl)dihyride (PyPyr)Ir(H)2(SiPh3)2 has also been synthesized. X-ray crystallography reveals that the bis(silyl)dihydrides adopt a coordination geometry best described as a bicapped tetrahedron. Mechanistic studies of the silane exchange process involving (PyPyr)Rh(H)2(Si tBuPh2)2 and free HSiEt3 (to give (PyPyr)Rh(H)2(SiEt3)2) indicate that this process occurs by rate-limiting reductive elimination of HSi tBuPh2 from (PyPyr)Rh(H)2(Si3 BuPh2)2 to give the 14-electron Rh(III) intermediate (PyPyr)Rh(H)(SitBuPh2) that can be isolated as the dimer [(PyPyr)Rh(mu-H)(SitBuPh 2)]2.;Complexes of Pt(IV) containing the bidentate ligand PyPyr were prepared. The ethylene complex (PyPyr)Pt(C2H4)Cl was treated with HSiEt3 or HSiEtMe2 to produce the Pt(IV) silyldihydrides (PyPyr)Pt(H)2SiEt3 and (PyPyr)Pt(H)2SiEtMe 2, respectively. The solid-state structure of (PyPyr)Pt(H)2SiEt 3, determined by X-ray crystallography, reveals a dimeric structure that forms via pi-stacking between the PyPyr ligands. Addition of Lewis bases to (PyPyr)Pt(H)2SiEt3 resulted in either coordination to generate an octahedral Lewis base adduct (with DMAP) or silane elimination to give square planar Pt(II) Lewis base complexes (with phosphines). The compound (PyPyr)Pt(H)2SiEt3 was found to be an active hydrosilation catalyst for the hydrosilation of alkynes and olefins.;The rhodium and iridium complexes [(tBu 2bpy)2M(mu-Cl)]2 (M = Rh, Ir) containing the bidentate tBu2bpy ligand were prepared. The dimeric complexes reacted with HSiPh3 to give [( tBu2bpy)MH(SiPh3)(mu-Cl)]2 in good yields. Addition of PiPr3 to [(tBu2bpy)MH(SiPh3)(mu-Cl)] 2 gave the monomeric crystalline complexes of the type ( tBu2bpy)MH(SiPh3)Cl(P iPr3). Salt metathesis reactions with ( tBu2bpy)MH(SiPh3)Cl(P iPr3) produced (tBu 2bpy)MH(SiPh3)(R)PiPr 3 as monomeric octahedral complexes, where R = H, Me, and Ph. Thermolysis of (tBu2bpy)IrH(SiPh3)(Ph)P iPr3 in the presence of 1 equiv of HSiR3 (R = Ph, Et) at 100°C in C6H6 for 1 day generated (tBu2bpy)IrH2(SiPh 3)PiPr3 and PhSiR3 in >95% yield.;The platinum ethylene complex (PyPyr)Pt(C2H4)Cl was treated with 1 equiv of LiN(SiMe3)2, LiN iPr2, and LiNH(o-xylyl) to produce (PyPyr)PtH(CH2=CHN(SiMe3)2), (PyPyr)Pt(CH 2CH2NiPr2), and (PyPyr)Pt(CH2CH2NH(o-xylyl)), respectively. Addition of PiPr3 to (PyPyr)Pt(CH 2CH2NH(o-xylyl)) generated (PyPyr)Pt(P iPr3)(CH2CH2NH( o-xylyl)) in 95% yield. Addition of 1 equiv of a Lewis base (L) to (PyPyr)Pt(C2H4)Cl gave the Lewis base adduct (PyPyr)Pt(L)Cl (L = NEt3, NH2Ph, PiPr 3). Treatment of (PyPyr)Pt(PiPr 3)Cl with LiNH(o-xylyl) generated (PyPyr)Pt(P iPr3)(NH(o-xylyl)), which does not undergo ethylene insertion into the Pt-N bond under 1 atm of C2H 4 at 120°C over 3 days. These reactivity studies are consistent with a mechanism involving nucleophilic attack of an amide on a platinum olefin complex.