Metal-1, 2,4 - Thiadiazole Phosphine Complexes Synthesis, Structure And Performance,

In this thesis, a few of 3,5-di-substituted-1,2,4-diazaphospholide complexes were studied by ¹H NMR, ¹³C NMR, ³¹P NMR, ¹³C and ¹⁵N CPMAS NMR, IR, elemental analysis and X-ray diffraction analysis.The preparation of N-, P-containing five-membered heterocyclic compound 1H-3,5-di-phenyl-1,2,4-diazaphosphole ([3,5-Ph₂dp]H) was optimized. The single crystals suitable for X-ray crystallographic diffraction analysis were obtained by solid recrystallization. X-Ray crystallography reveals two different cyclic dimeric structures linked by intermolecular disorder hydrogen bonds (N ... H), showing in the solid state a dynamic proton disorder. This comformation implys a dynamic equilibrium within both dimers. The conformations of the phenyl rings, the disorder of the NH protons, and the intermolecular hydrogen bond of [3,5-Ph₂dp]H in the solid state have been rationalized by [B3LYP/6-311++G(d,p)] calculations.The furhter reactions of H[3,5-R₂dp] (R = tBu, Ph) with varied alkali or transition metal species were carried out. Treatment of H[3,5-Ph₂dp] (Hdp = 1H-1,2,4-diazaphosphole) with nBuLi, K, or the reaction of K[3,5-tBu₂dp] with an excess amount of O₂, afforded the dimeric species [(η²,η¹-3,5-Ph₂dp)Li(THF)₂]₂, the polymeric complexes [(η²:η⁴-3,5-Ph₂dp)K(Et₂O)₂]_n, and[{(η²:η⁵-3,5-tBu₂dp)K(THF)} {η²(N,N)-η³(P,O,P)-3,5-tBu₂dp-(O,O)O₂K}]_n,respectively. The above alkali complexes bearing3,5-di-substituted-1,2,4-diazaphospholide ligands have been structurally characterizied, in which the versatile bonding ability of the ligands toward metal centers have been evidenced. Twoη²(N,N)-3,5-di-substituted-1,2,4-diazaphospholide complexes of tetrakis(3,5-di-pheny-1,2,4-diazaphopholide)-titanium(IV)[Ti(η²-3,5-Ph₂dp)₄]·3THF anddi-μ-chloro-(η⁴-bicyclo[2,2,1 ]hepta-2,5-diene)-bis(η²-3,5-di-tert-butyl-1,2,4-diazapho spholide)-ruthenium (II) [(η⁴-NBD)Ru(η²-3,5-tBu₂dp)₂] were prepared by the reaction of tetrakis(dimethylamido)titanium(IV) with 4 equivalents of 3,5-di-pheny-1,2,4-diazaphophole and by the treatment of di-μ-chloro-(η⁴-bicyclo[2,2,1]hepta-2,5-diene)ruthenium(II) [(NBD)RuCl₂] and 2 equivalents of 3,5-di-tert-butyl-1,2,4-diazaphospholide potassium, in which the metal atoms areη²(N,N)-bonding to the 1,2,4-diazaphospholides rationalized by DFT calculation. The complexes represent the firstη²-coordination mode of this ligand in any metal.The effect on palladium-catalyzed Heck reaction by two ruthenium complexes [(3,5-R₂dp)RuCp^*](R = tBu, Ph) was examined. They have been evidenced to be highly effective in the coupling of bromides, selected activated as well as neutral chlorides. The ruthenium complexes based onη⁵-1,2,4-diazaphospholide groups with an sp²-hybridized phosphorus atoms are likely to act as two-electron-donor ligandsη¹-bonded to the palladium ion through the phosphorus-atom lone pair.