Alkyl Coordination in meso -(ONO) 2- Supported Uranium(IV) Complexes.

A series of U(IV) complexes bearing alkyl and chloride ligands in the trans configuration was synthesized and characterized. Starting with the diastereopure U(IV) trans -dichloride complex meso -( t Bu2P ONO)UCl 2 (dtbpy) ( 1 , t Bu2P ONO = 2,6-bis((di- tert -butylphosphino)methanolato)pyridine), four distinct alkyl groups were employed to prepare ( t Bu2P ONO)U(R)Cl(dtbpy), where R = (trimethylsilyl)methyl (neosilyl), 2a , R = 2,2-dimethyl propyl (neopentyl), 2b , and R = 2-methyl-2-phenyl propyl (neophyl), 2c . Alkylation occurs with specificity but generates a predominant species and a minor species corresponding to anti / syn regioisomers relative to the t Bu2 P groups of the ligand. For synthesis using R = methyl, the dimethyl complex ( t Bu2P ONO)U(Me) 2 (dtbpy), 2d , was prepared; the addition of 1 equiv of MeLi produced a mixture of products. Complexes 2a - 2d were characterized using single crystal X-ray diffraction (SC-XRD), UV-vis-nIR, and 1 H and 31 P NMR spectroscopies.