Ligand design, coordination chemistry, and mechanistic studies of (phosphino)borates and their platinum, nickel, and copper complexes

Synthetic methods based on the delivery of a nucleophilic phosphine-containing carbanion to a borane electrophile are presented for substituted bis(phosphino)borates. A general preparative method is provided for substituted diarylchloroboranes. The reaction of phosphine containing carbanions with diarylchloroboranes results in selectively substituted bis(phosphino)borates. Ammonium and thallium bis(phosphino)borate salts are prepared by cation-exchange from the initially generated lithium salts.; The electronic properties of transition metals coordinated by bis(phosphino)borates are explored through NMR and IR spectroscopies. The spectroscopic features of (phosphino)borate-containing platinum(II) complexes indicate that phosphine substituents have a more significant electronic impact than borate substituents. Structural and spectroscopic comparisons of platinum(II) complexes indicate that the anionic bis(phosphino)borate ligand renders platinum(II) more electron-rich than structurally similar neutral phosphine donors. These results are corroborated by spectroscopic studies of molybdenum(0) complexes.; Comparative studies of structurally similar platinum(II) complexes convey the similarities and differences between zwitterionic and cationic systems. Examination of THF ligand self-exchange shows a mechanism change between the neutral and cationic species. Both bis(phosphino)borate- and neutral bis(phosphine)-ligated platinum methyl complexes undergo benzene C-H activation to form the corresponding phenyl complex; however, the rates of reaction and ultimate products differ. Isotopic studies indicate that the zwitterionic system forms observable intermediates prior to C-H activation, some of which are attributable to ligand metalation processes.; Structural and spectroscopic studies of a phenyl-substituted tris(phosphino)borate on platinum are presented. Alkyl- and hydride-containing platinum(II) and platinum(IV) species have been synthesized. The structural and spectroscopic features of these complexes are compared to related tris(pyrazolyl)borate systems on platinum.; The coordination and reaction chemistry of Ni(II), NI(I), and Ni(0) supported by an isopropyl-substituted tris(phosphino)borate are discussed. This system is compared to related phenyl-substituted tris(phosphino)borate nickel chemistry. Attempts to prepare Ni(III) and Ni(IV) complexes containing metal-ligand multiple bonds through group-transfer reactions are presented. Density functional theoretical studies are used to probe nickel complexes containing multiply-bonded ligands.; The coordination chemistry of copper(I) is explored using bis(phosphino)borates. Both aryl- and alkyl-substituted bis(phosphino)borates provide access to copper(I) complexes. A tert-butyl-substituted bis(phosphino)borate is particularly useful for preparing a family of three-coordinate compounds. The spectroscopic and structural features of these complexes are compared with similar, previously described examples.