Oxidation State Dependent Coordination Modes: Accessing an Amidate‐Supported Nickel(I) δ‐bis(C−H) Agostic Complex

Abstract

Amidate-supported two- and three-coordinate Ni complexes were synthesized by reduction of the corresponding Ni precursors. A dramatic change in binding mode is observed upon reduction from Ni to Ni . The Ni derivatives include an unprecedented Ni bis(C-H) agostic complex and a two-coordinate Ni complex.

The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d10 Nickel π‐Complexes

“…As noted previously, oxidation states of nickel diphosphines are often evaluated according to the magnitude of 2 J P,P in unsymmetrical complexes. In principle, differences reflect electron density at the bridging metal centre, although limitations include the requirement for inequivalent P atoms and a diamagnetic ground state . XAS offers the advantage of providing an independent experimental probe of oxidation states without the limitations of 2 J P,P values.…”

“…In principle, differences reflect electron density at the bridging metal centre, [108] although limitations include the requirement for inequivalentPatoms and ad iamagnetic ground state. [13,81] XAS offers the advantage of providing an independent experimental probe of oxidation states withoutt he limitations of 2 J P, P values. The XAS data of formally square-planar complexesy ield distinctive pre-edge features that track with oxidation of the metal centre.…”

“…We have recently become interested in exploring the fundamental organometallic chemistry of earth-abundant, first-row transition metals. For example, we are exploring the organometallicc hemistry of nickel, [10][11][12][13][14] which has undergone ar enaissance in recent years. [15][16][17][18][19][20][21] Our focus has been the structure and reactivityo fn ickel p-complexes, which have been reported in aw ide range of catalytic processes, including the coupling of CO 2 and ethylene, [5,[22][23][24][25][26][27][28][29][30][31][32] intermolecular Tischenkoc oupling, [33][34][35] benzoxasilole synthesis, [36,37] the aldol reaction, [38] allylic alkylation, [39] allylic amination, [40] allylic amidation, [41] epoxide functionalization, [42] and Suzuki-Miyaura coupling.…”

Structure and Isotope Effects of the β‐H Agostic (α‐Diimine)Nickel Cation as a Polymerization Intermediate

“…[14] At À96 8 8C, the b-agostic hydrogen atoms of 2 and of 4 exhibit 1 HNMR resonances at À13.2 and À12.0 ppm, respectively.The assignments of the 1 HNMR spectra are facilitated by COSY and HSQC experiments.T he b-agostic 1 Ha nd the b-non-agostic 1 Hr esonances broaden as the temperature increases and coalesce at À50 8 8C( Supporting Information, Figure S1). Although only the methylene carbon (C a )i si nitially labeled with 13 C, rapid hydride elimination and reinsertion during synthesis results in an equal distribution of the 13 Cl abel between C a and C b ( Supporting Information, Equation S5). [16] To determine the 1 J CH coupling constant for the agostic H, we prepared 2-13 Cu sing CH 3 13 CH 2 MgBr.…”

“…We measured the rates of b-H elimination-rotation-reinsertion using 13 CNMR line broadening techniques with 2-13 Ca tv arious temperatures (Supporting Information, Figure S5). We measured the rates of b-H elimination-rotation-reinsertion using 13 CNMR line broadening techniques with 2-13 Ca tv arious temperatures (Supporting Information, Figure S5).…”