741735-94-4Relevant articles and documents
The coordination chemistry of "[BP3]NiX" platforms: Targeting low-valent nickel sources as promising candidates to L3Ni=E and L3Ni≡E linkages
MacBeth, Cora E.,Thomas, J. Christopher,Betley, Theodore A.,Peters, Jonas C.
, p. 4645 - 4662 (2008/10/09)
A series of divalent, monovalent, and zerovalent nickel complexes supported by the electron-releasing, monoanionic tris(phosphino)borate ligands [PhBP 3] and [PhBPiPr3] ([PhBP3] = [PhB(CH2PPh2)3]-, [PhBP iPr3] = [PhB(CH2PiPr 2)3]-) have been synthesized to explore fundamental aspects of their coordination chemistry. The pseudotetrahedral, divalent halide complexes [PhBP3]NiCl (1), [PhBP3]Nil (2), and [PhBPiPr3]NiCl (3) were prepared by the metalation of [PhBP3]Tl or [PhBPiPr3]Tl with (Ph 3P)2NiCl2, Nil2, and (DME)NiCl 2 (DME = 1,2-dimethoxyethane), respectively. Complex 1 is a versatile precursor to a series of complexes accessible via substitution reactions including [PhBP3]-Ni(N3) (4), [PhBP3] Ni(OSiPh3) (5), [PhBP3]Ni(0-p-tBu-Ph) (6), and [PhBP3]Ni(S-p-tBu-Ph) (7). Complexes 2-5 and 7 have been characterized by X-ray diffraction (XRD) and are pseudotetrahedral monomers in the solid state. Complex 1 reacts readily with oxygen to form the four-electron-oxidation product, {[PhB(CH2P(O)Ph2) 2(CH2PPh2)]-NiCl} (8A or 8B), which features a solid-state structure that is dependent on its method of crystallization. Chemical reduction of 1 using Na/Hg or other potential 1-electron reductants generates a product that arises from partial ligand degradation, [PhBP 3]Ni(η2-CH2PPh2) (9). The more sterically hindered chloride 3 reacts with Li(dbabh) (Hdbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene) to provide the three-coordinate complex [κ2-PhBPiPr 3]Ni(dbabh) (11), also characterized by XRD. Chemical reduction of complex 1 in the presence of L-type donors produces the tetrahedral Ni(I) complexes [PhBP3]Ni(PPh3) (12) and [PhBP 3]Ni(CNtBu) (13). Reduction of 3 following the addition of PMe3 or tert-butyl isocyanide affords the Ni(I) complexes [PhBP iPr3]Ni(PMe3) (14) and [PhBPiPr 3]Ni(CNtBu) (15), respectively. The reactivity of these [PhBP3]NijL and [PhBPiPr3]Ni jL complexes with respect to oxidative group transfer reactions from organic azides and diazoalkanes is discussed. The zerovalent nitrosyl complex [PhBP3]Ni(NO) (16) is prepared by the reaction of 1 with excess NO or by treating 12 with stoichiometric NO. The anionic Ni(O) complexes [[κ2-PhBP3]Ni(CO)2][nBu 4N] (17) and [[κ2-PhBPiPr 3]Ni(CO)2][ASN] (18) (ASN = 5-azoniaspiro[4.4]nonane) have been prepared by reacting [PhBP3]Tl or [PhBPiPr 3]Tl with (Ph3P)2Ni(CO)2 in the presence of R4NBr. The photolysis of 17 appears to generate a new species consistent with a zerovalent monocarbonyl complex which we tentatively assign as {[PhBP3]Ni(CO)}{nBu4N}, although complete characterization of this complex has been difficult. Finally, theoretical DFT calculations are presented for the hypothetical low spin complexes [PhBP3]Ni(NtBu), [PhBPiPr 3]Ni(NtBu), [PhBPiPr3]Ni(NMe), and [PhBPiPr3]Ni(N) to consider what role electronic structure factors might play with respect to the relative stability of these species.
