JPP_NP0 ,_PUN like_PRP all_DT0 J-couplings_NN2 ,_PUN can_VM0 have_VHI a_AT0 positive_AJ0 or_CJC negative_AJ0 sign_NN1 ._SENT A_AT0 negative_AJ0 J_NP0 corresponds_VVZ to_PRP a_AT0 more_AV0 stable_AJ0 antiparallel_NN1 nuclear_AJ0 spin_NN1 alignment_NN1 ,_PUN while_CJS a_AT0 positive_AJ0 J_NP0 corresponds_VVZ to_PRP a_AT0 more_AV0 stable_AJ0 parallel_AJ0 nuclear_AJ0 spin_NN1 alignment_NN1 ._SENT Although_CJS most_DT0 31P_AJ0 NMR_NP0 experiments_NN2 can_VM0 give_VVI the_AT0 magnitude_NN1 of_PRF JPP_NP0 (_PUL i.e._AV0 ,_PUN ∣JPP∣_NP0 )_PUR ,_PUN few_DT0 can_VM0 give_VVI the_AT0 sign_NN1 ._SENT We_PNP sought_VVD to_TO0 understand_VVI the_AT0 signs_NN2 of_PRF the_AT0 experimentally_AV0 observed_AJ0 ∣JPP∣_NN1 in_PRP our_DPS data_NN0 sets_NN2 because_CJS the_AT0 sign_NN1 of_PRF JPP_NP0 was_VBD shown_VVN to_TO0 relate_VVI to_PRP the_AT0 structure_NN1 in_PRP other_AJ0 studies_NN2 of_PRF JPP_NN1 in_PRP metal_NN1 complexes_NN2 ._SENT To_TO0 obtain_VVI signs_NN2 for_PRP our_DPS data_NN0 set_NN1 ,_PUN quantum_NN1 chemical_AJ0 simulations_NN2 were_VBD used_VVN (_PUL see_VVB the_AT0 Supporting_AJ0 Information_NN1 for_PRP computational_AJ0 details_NN2 )_PUR ._SENT The_AT0 absolute_AJ0 values_NN2 of_PRF the_AT0 computed_AJ0 JPP_NN1 trend_NN1 linearly_AV0 with_PRP the_AT0 experimental_AJ0 values_NN2 (_PUL JPPexperimental_NP0 =_NP0 0.913∣JPPcomputed∣_NN1 +_NN1 2.24_CRD Hz_NN0 ;_PUN R2_CRD =_NP0 0.852_CRD )_PUR ,_PUN indicating_VVG that_CJT the_AT0 coupling_NN1 can_VM0 be_VBI computed_VVN with_PRP reasonably_AV0 good_AJ0 accuracy_NN1 ._SENT 
Two-bond_AJ0 couplings_NN2 ,_PUN such_DT0 as_PRP the_AT0 JPP_NN1 values_NN2 arising_VVG from_PRP the_AT0 through-Ni_AJ0 coupling_NN1 pathway_NN1 ,_PUN are_VBB expected_VVN to_TO0 have_VHI a_AT0 negative_AJ0 sign_NN1 ._SENT Simulations_NN2 show_VVB that_CJT this_DT0 is_VBZ not_XX0 always_AV0 true_AJ0 for_PRP Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 ,_PUN with_PRP many_DT0 complexes_NN2 having_VHG a_AT0 positive_AJ0 JPP_NN1 (_PUL Figure_NN1 2_CRD )_PUR ._SENT Generally_AV0 ,_PUN the_AT0 3C_AJ0 complexes_NN2 have_VHB more_AV0 a_AT0 negative_AJ0 JPP_NN1 in_PRP comparison_NN1 to_PRP 2C_AJ0 complexes_NN2 by_PRP ~_NP0 40_CRD Hz_NN0 ,_PUN and_CJC NiII_CRD complexes_NN2 have_VHB a_AT0 more_AV0 negative_AJ0 JPP_NN1 in_PRP comparison_NN1 to_PRP Ni0_CRD by_PRP ~_NP0 60_CRD Hz_NN0 regardless_AV0 of_PRF linker_NN1 length_NN1 ._SENT The_AT0 observation_NN1 that_CJT NiII_CRD complexes_NN2 have_VHB a_AT0 more_AV0 negative_AJ0 JPP_NN1 in_PRP comparison_NN1 to_PRP Ni0_CRD regardless_AV0 of_PRF linker_NN1 length_NN1 appears_VVZ to_TO0 contrast_VVI with_PRP the_AT0 relationships_NN2 observed_VVN with_PRP ∣JPP∣_NP0 ,_PUN where_AVQ 2C_AJ0 complexes_NN2 had_VHD the_AT0 smallest_AJS ∣JPP∣_NN1 for_PRP NiII_CRD and_CJC 3C_CRD complexes_NN2 had_VHD the_AT0 largest_AJS ∣JPP∣_NN1 for_PRP NiII_CRD (_PUL Figure_NN1 1_CRD )_PUR ._SENT These_DT0 differences_NN2 between_PRP JPP_NP0 and_CJC ∣JPP∣_NP0 become_VVB consistent_AJ0 when_CJS it_PNP is_VBZ recognized_VVN that_CJT a_AT0 more_AV0 negative_AJ0 JPP_NN1 results_NN2 in_PRP a_AT0 smaller_AJC ∣JPP∣_NN1 when_CJS JPP_NP0 is_VBZ positive_AJ0 and_CJC a_AT0 larger_AJC ∣JPP∣_NN1 when_CJS JPP_NP0 is_VBZ negative_AJ0 ._SENT Therefore_AV0 ,_PUN ∣JPP∣_NP0 is_VBZ largest_AJS when_CJS both_AV0 the_AT0 linker_NN1 length_NN1 and_CJC oxidation_NN1 state_NN1 are_VBB associated_VVN with_PRP the_AT0 same_DT0 shift_NN1 in_PRP JPP_NP0 ,_PUN such_DT0 as_CJS in_PRP 2C_NN1 Ni0_CRD complexes_NN2 (_PUL both_AV0 shift_NN1 JPP_NN1 more_AV0 positive_AJ0 )_PUR and_CJC 3C_AJ0 NiII_CRD complexes_NN2 (_PUL both_AV0 shift_NN1 JPP_NN1 more_AV0 negative_AJ0 )_PUR ,_PUN explaining_VVG the_AT0 odd_AJ0 relationship_NN1 among_PRP JPP_NP0 ,_PUN linker_NN1 ,_PUN and_CJC oxidation_NN1 state_NN1 derived_VVN from_PRP Figure_NN1 1._CRD To_TO0 relate_VVI the_AT0 effects_NN2 of_PRF structure_NN1 and_CJC oxidation_NN1 state_NN1 on_PRP JPP_NP0 ,_PUN the_AT0 sign_NN1 of_PRF a_AT0 measured_AJ0 ∣JPP∣_NN1 therefore_AV0 needs_VVZ to_TO0 be_VBI considered_VVN (_PUL vide_VVB infra_AV0 )_PUR ._SENT 
After_CJS we_PNP identified_VVD that_CJT JPP_NP0 correlates_VVZ with_PRP the_AT0 ligand_NN1 structure_NN1 and_CJC oxidation_NN1 state_NN1 ,_PUN an_AT0 explanation_NN1 is_VBZ still_AV0 needed_VVN to_TO0 answer_VVI why_AVQ JPP_NP0 becomes_VVZ more_AV0 negative_AJ0 upon_PRP oxidation_NN1 from_PRP Ni0_CRD to_PRP NiII_CRD or_CJC upon_PRP increasing_VVG the_AT0 linker_NN1 length_NN1 from_PRP 2C_NN1 to_PRP 3C_NN1 ._SENT Given_VVN the_AT0 observed_AJ0 dependence_NN1 of_PRF ∣JPP∣_NN1 on_PRP linker_NN1 length_NN1 and_CJC oxidation_NN1 state_NN1 ,_PUN JPP_NP0 may_VM0 be_VBI described_VVN as_PRP equation_NN1 where_AVQ the_AT0 2JPP_AJ0 term_NN1 arises_VVZ from_PRP through-Ni_AJ0 coupling_NN1 and_CJC the_AT0 m+1JPP_NN1 term_NN1 arises_VVZ from_PRP through-linker_NN1 coupling_NN1 (_PUL m_ZZ0 =_AJ0 number_NN1 of_PRF carbons_NN2 in_PRP the_AT0 linker_NN1 )_PUR ._SENT The_AT0 effect_NN1 of_PRF changes_NN2 in_PRP oxidation_NN1 state_NN1 and_CJC linker_NN1 length_NN1 on_PRP the_AT0 values_NN2 of_PRF through-Ni_NN1 and_CJC through-linker_NN1 coupling_NN1 was_VBD therefore_AV0 explored_VVN further_AV0 with_PRP this_DT0 model_NN1 in_PRP mind_NN1 ._SENT 
Effect_NN1 of_PRF Ligand_NN1 Donation_NN1 on_PRP JPP_NP0 ._SENT 
J-coupling_NP0 links_VVZ pairs_NN2 of_PRF nuclei_NN2 through_PRP bonding_NN1 electrons_NN2 ;_PUN thus_AV0 ,_PUN it_PNP is_VBZ expected_VVN that_CJT changes_NN2 to_PRP the_AT0 electron_NN1 density_NN1 in_PRP bonds_NN2 along_PRP the_AT0 coupling_NN1 pathway_NN1 can_VM0 affect_VVI J_NP0 ._SENT This_DT0 dependence_NN1 is_VBZ evidenced_VVN by_PRP the_AT0 electronic_AJ0 effects_NN2 observed_VVN for_PRP many_DT0 2JHH_NN1 and_CJC 2JCH_NN1 couplings_NN2 ._SENT For_PRP Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 ,_PUN the_AT0 2JPP_NN1 (_PUL i.e._AV0 ,_PUN through-Ni_NP0 )_PUR coupling_NN1 term_NN1 in_PRP eq_NN1 1_CRD would_VM0 likely_AV0 depend_VVI on_PRP the_AT0 electron_NN1 density_NN1 in_PRP the_AT0 P─Ni_AJ0 bonds_NN2 ._SENT Therefore_AV0 ,_PUN charge_NN1 transfer_NN1 analysis_NN1 using_VVG absolutely_AV0 localized_AJ0 molecular_AJ0 orbitals_NN2 was_VBD used_VVN to_TO0 understand_VVI P─Ni_AJ0 bonds_NN2 ,_PUN including_PRP the_AT0 effects_NN2 of_PRF P-donation_NN1 and_CJC back-bonding_NN1 (_PUL see_VVB the_AT0 Supporting_AJ0 Information_NN1 for_PRP computational_AJ0 details_NN2 )_PUR ._SENT 
The_AT0 charge_NN1 transfer_NN1 analysis_NN1 showed_VVD a_AT0 strong_AJ0 correlation_NN1 of_PRF JPP_NN1 with_PRP the_AT0 σ-bonding_AJ0 P-to-Ni_NN1 charge_NN1 transfer_NN1 (_PUL CTP-to-Ni_NP0 )_PUR (_PUL Figure_NN1 3_CRD )_PUR ,_PUN whereas_CJS the_AT0 back-bonding_NN1 Ni_NP0 to_PRP P_NP0 charge_NN1 transfer_NN1 showed_VVD a_AT0 worse_AJC correlation_NN1 with_PRP JPP_NP0 (_PUL Figure_NN1 S12_CRD )_PUR ._SENT The_AT0 relationship_NN1 of_PRF JPP_NP0 with_PRP CTP-to-Ni_NP0 indicates_VVZ that_CJT JPP_NP0 should_VM0 become_VVI more_AV0 negative_AJ0 with_PRP increased_AJ0 charge_NN1 donated_VVN to_PRP Ni_NP0 ._SENT Notably_AV0 ,_PUN the_AT0 slopes_NN2 of_PRF the_AT0 2C_AJ0 and_CJC 3C_AJ0 lines_NN2 of_PRF best_AV0 fit_AJ0 do_VDB not_XX0 differ_VVI significantly_AV0 (_PUL p-value_VVB =_NN0 0.3066_CRD )_PUR ,_PUN indicating_VVG that_CJT CTP-to-Ni_NP0 is_VBZ independent_AJ0 of_PRF the_AT0 linker_NN1 length_NN1 ._SENT This_DT0 independence_NN1 of_PRF CTP-to-Ni_NP0 from_PRP linker_NN1 length_NN1 signifies_VVZ that_CJT P-to-Ni_AJ0 charge_NN1 transfer_NN1 solely_AV0 affects_VVZ the_AT0 through-Ni_AJ0 2JPP_AJ0 term_NN1 in_PRP eq_NN1 1._CRD In_PRP principle_NN1 ,_PUN increased_AJ0 P-to-Ni_NN1 donation_NN1 can_VM0 arise_VVI from_PRP an_AT0 increasing_AJ0 Lewis_NP0 basicity_NN1 of_PRF P_NP0 ,_PUN an_AT0 increasing_AJ0 Lewis_NP0 acidity_NN1 of_PRF Ni_NP0 ,_PUN or_CJC an_AT0 increasing_AJ0 overlap_NN1 of_PRF Ni_NP0 and_CJC P_NP0 orbitals_NN2 ._SENT The_AT0 relationship_NN1 between_PRP JPP_NP0 and_CJC P-to-Ni_NP0 charge_NN1 transfer_NN1 also_AV0 provides_VVZ a_AT0 rationale_NN1 for_PRP why_AVQ JPP_NP0 varies_VVZ with_PRP oxidation_NN1 state_NN1 ,_PUN because_CJS NiII_CRD is_VBZ generally_AV0 more_AV0 Lewis_NP0 acidic_AJ0 than_CJS Ni0_CRD ,_PUN inducing_VVG more_DT0 charge_NN1 donation_NN1 from_PRP P_ZZ0 atoms_NN2 ._SENT 
While_CJS JPP_NN1 trends_NN2 with_PRP P-to-Ni_NP0 charge_NN1 transfer_NN1 ,_PUN the_AT0 physical_AJ0 origin_NN1 of_PRF this_DT0 dependence_NN1 needed_VVD further_AJC elucidation_NN1 ._SENT According_VVG to_PRP Ramsey_NP0 ,_PUN J-coupling_NP0 occurs_VVZ via_PRP four_CRD different_AJ0 mechanisms_NN2 ._SENT The_AT0 Fermi_NP0 contact_NN1 mechanism_NN1 is_VBZ the_AT0 dominant_AJ0 J-coupling_AJ0 mechanism_NN1 for_PRP JPP_NP0 in_PRP other_AJ0 compounds_NN2 and_CJC was_VBD therefore_AV0 expected_VVN to_TO0 be_VBI dominant_AJ0 for_PRP complexes_NN2 in_PRP our_DPS data_NN0 set_NN1 ._SENT Indeed_AV0 ,_PUN calculations_NN2 of_PRF the_AT0 four_CRD different_AJ0 Ramsey_NP0 contributors_NN2 to_PRP JPP_NP0 indicated_VVD that_CJT the_AT0 Fermi_NP0 contact_NN1 contribution_NN1 dominated_VVD the_AT0 total_AJ0 JPP_NN1 (_PUL see_VVB the_AT0 Supporting_AJ0 Information_NN1 )_PUR ._SENT In_PRP the_AT0 Fermi_NP0 contact_NN1 mechanism_NN1 ,_PUN J-coupling_NP0 arises_VVZ via_PRP spin-pairing_NN1 of_PRF s_ZZ0 electrons_NN2 with_PRP a_AT0 nucleus_NN1 due_AJ0 to_PRP their_DPS nonzero_NN1 electron_NN1 density_NN1 at_PRP the_AT0 nuclei_NN2 of_PRF atoms_NN2 ._SENT Given_VVN this_DT0 ,_PUN and_CJC the_AT0 high_AJ0 3s_CRD character_NN1 of_PRF the_AT0 lone_AJ0 pairs_NN2 of_PRF trivalent_AJ0 P_ZZ0 atoms_NN2 ,_PUN it_PNP follows_VVZ that_CJT the_AT0 value_NN1 of_PRF JPP_NN1 should_VM0 be_VBI strongly_AV0 affected_VVN by_PRP the_AT0 donation_NN1 of_PRF P_ZZ0 lone_AJ0 pairs_NN2 into_PRP Ni_NP0 ._SENT 
This_DT0 relationship_NN1 between_PRP JPP_NP0 and_CJC CTP-to-Ni_NP0 tracks_NN2 with_PRP the_AT0 presence_NN1 of_PRF electron-withdrawing_AJ0 groups_NN2 on_PRP ligands_NN2 trans_NN2 to_PRP P_ZZ0 atoms_NN2 ,_PUN likely_AJ0 by_PRP affecting_VVG the_AT0 Lewis_NP0 acidity_NN1 of_PRF Ni_NP0 ._SENT Structurally_AV0 related_VVN NiII_CRD complexes_NN2 that_CJT differ_VVB in_PRP the_AT0 number_NN1 (_PUL e.g._AV0 ,_PUN 2-2025_CRD ,_PUN 2-2057_CRD ,_PUN 2-2087_CRD )_PUR or_CJC strength_NN1 (_PUL e.g._AV0 ,_PUN 2-2046e_NP0 ,_PUN 2-2056_CRD ,_PUN 2-2035_CRD )_PUR of_PRF withdrawing_VVG groups_NN2 on_PRP the_AT0 trans_NN2 ligands_NN2 demonstrate_VVB this_DT0 relationship_NN1 between_PRP CTP-to-Ni_NP0 and_CJC JPP_NP0 (_PUL Chart_NN1 1_CRD )_PUR ,_PUN with_PRP complexes_NN2 containing_VVG more-withdrawing_AJ0 groups_NN2 having_VHG a_AT0 more_AV0 negative_AJ0 JPP_NN1 and_CJC a_AT0 larger_AJC ∣JPP∣_NN1 ._SENT Complexes_NN2 of_PRF Ni0_CRD (_PUL e.g._AV0 ,_PUN 2-2046d_AJ0 ,_PUN 2-2046f_AJ0 ,_PUN 2-2291_CRD )_PUR also_AV0 exhibit_VVB the_AT0 trend_NN1 of_PRF a_AT0 more_AV0 negative_AJ0 JPP_NN1 with_PRP an_AT0 increased_AJ0 number_NN1 withdrawing_VVG groups_NN2 on_PRP the_AT0 trans_NN2 ligand_NN1 ,_PUN but_CJC because_CJS Ni0_CRD complexes_NN2 generally_AV0 have_VHB a_AT0 positive_AJ0 JPP_NN1 ,_PUN this_DT0 is_VBZ manifested_VVN as_PRP a_AT0 less_AV0 positive_AJ0 JPP_NN1 and_CJC smaller_AJC ∣JPP∣_NN1 ._SENT 
The_AT0 relationship_NN1 between_PRP JPP_NP0 and_CJC CTP-to-Ni_NP0 also_AV0 tracks_VVZ with_PRP the_AT0 donating_NN1 ability_NN1 of_PRF the_AT0 phosphine_NN1 ligand_NN1 (_PUL e.g._AV0 ,_PUN 2-2110_CRD and_CJC 2-2296_CRD of_PRF Chart_NN1 2_CRD )_PUR ,_PUN with_PRP more-donating_AJ0 phosphines_NN2 causing_VVG a_AT0 more_AV0 negative_AJ0 JPP_NN1 ._SENT However_AV0 ,_PUN for_PRP complexes_NN2 with_PRP large_AJ0 phosphines_NN2 ,_PUN JPP_NN1 values_NN2 were_VBD less_AV0 negative_AJ0 and_CJC CTP-to-Ni_AJ0 values_NN2 were_VBD smaller_AJC than_CJS those_DT0 of_PRF similar_AJ0 complexes_NN2 with_PRP smaller_AJC phosphines_NN2 ._SENT This_DT0 trend_NN1 is_VBZ opposite_AJ0 of_PRF what_DTQ is_VBZ expected_VVN ,_PUN given_VVN that_CJT large_AJ0 alkyl_NN1 substituents_NN2 (_PUL such_DT0 as_PRP tert-butyl_NN1 )_PUR are_VBB more_AV0 electron_NN1 rich_AJ0 than_CJS smaller_AJC alkyl_NN1 substituents_NN2 and_CJC should_VM0 therefore_AV0 impart_VVI greater_AJC P-to-Ni_AJ0 charge_NN1 transfer_NN1 ._SENT This_DT0 deviation_NN1 might_VM0 arise_VVI from_PRP the_AT0 increased_AJ0 steric_AJ0 bulk_NN1 of_PRF large_AJ0 ligands_NN2 ,_PUN causing_VVG P─Ni_AJ0 bonds_NN2 to_TO0 elongate_VVI ,_PUN as_CJS observed_VVN on_PRP comparing_VVG complexes_NN2 2-2020_CRD and_CJC 2-2143c_NP0 (_PUL Chart_NN1 2_CRD )_PUR ._SENT The_AT0 increased_AJ0 P─Ni_NN1 bond_NN1 length_NN1 in_PRP complexes_NN2 containing_VVG sterically_AV0 bulky_AJ0 ligands_NN2 may_VM0 cause_VVI a_AT0 decrease_NN1 in_PRP the_AT0 effective_AJ0 overlap_NN1 of_PRF P_NP0 and_CJC Ni_NP0 orbitals_NN2 ,_PUN causing_VVG a_AT0 lower_AJC CTP-to-Ni_NN1 and_CJC a_AT0 less_AV0 negative_AJ0 JPP_NN1 than_CJS expected_VVN on_PRP the_AT0 basis_NN1 of_PRF the_AT0 Lewis_NP0 structure_NN1 ._SENT 
While_CJS the_AT0 effect_NN1 of_PRF P-to-Ni_AJ0 charge_NN1 transfer_NN1 on_PRP JPP_NP0 is_VBZ useful_AJ0 for_PRP understanding_VVG the_AT0 NMR_NP0 spectra_NN2 of_PRF Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 ,_PUN the_AT0 trends_NN2 observed_VVN with_PRP P-to-Ni_NP0 charge_NN1 transfer_NN1 do_VDB not_XX0 explain_VVI the_AT0 differences_NN2 in_PRP JPP_NP0 for_PRP 2C_NN1 in_PRP comparison_NN1 to_PRP 3C_AJ0 complexes_NN2 ._SENT This_DT0 limitation_NN1 is_VBZ evidenced_VVN by_PRP the_AT0 ranges_NN2 of_PRF CTP-to-Ni_NP0 ,_PUN which_DTQ span_VVB similar_AJ0 values_NN2 for_PRP 2C_AJ0 complexes_NN2 (_PUL 28.2_CRD –_PUN 133.0_CRD me−_NP0 )_PUR and_CJC 3C_AJ0 complexes_NN2 (_PUL 28.4_CRD –_PUN 112.8_CRD me−_NP0 )_PUR but_CJC have_VHB trend_NN1 lines_NN2 with_PRP significantly_AV0 different_AJ0 y_ZZ0 intercepts_NN2 (_PUL p-value_VVB <_NN0 0.0001_CRD )_PUR ._SENT On_PRP the_AT0 basis_NN1 of_PRF eq_NN1 1_CRD ,_PUN the_AT0 negative_AJ0 shift_NN1 of_PRF JPP_NN1 of_PRF 3C_AJ0 complexes_NN2 in_PRP comparison_NN1 to_PRP 2C_AJ0 complexes_NN2 may_VM0 arise_VVI from_PRP differences_NN2 in_PRP the_AT0 through-linker_NN1 m+1JPP_NN1 coupling_NN1 due_AJ0 to_PRP the_AT0 difference_NN1 in_PRP linker_NN1 identity_NN1 ._SENT Alternatively_AV0 ,_PUN the_AT0 negative_AJ0 shift_NN1 of_PRF JPP_NN1 of_PRF 3C_AJ0 complexes_NN2 may_VM0 be_VBI due_AJ0 to_PRP the_AT0 through-Ni_AJ0 2JPP_AJ0 term_NN1 ,_PUN most_AV0 likely_AV0 due_AJ0 to_PRP differences_NN2 in_PRP P─Ni─P_AJ0 bite_NN1 angle_NN1 caused_VVN by_PRP the_AT0 linker_NN1 ._SENT 
Effect_NN1 of_PRF Linker_NP0 Length_NN1 on_PRP JPP_NP0 ._SENT 
Many_DT0 2J-coupling_AJ0 constants_NN2 are_VBB dependent_AJ0 on_PRP the_AT0 bond_NN1 angle_NN1 at_PRP the_AT0 central_AJ0 atom_NN1 ;_PUN therefore_AV0 ,_PUN the_AT0 relationship_NN1 of_PRF JPP_NN1 with_PRP P─Ni─P_NN1 bite_NN1 angle_NN1 was_VBD evaluated_VVN ._SENT If_CJS the_AT0 linker_NN1 affects_VVZ JPP_NN1 via_PRP the_AT0 through-Ni_NN1 (_PUL 2JPP_AJ0 )_PUR coupling_NN1 term_NN1 in_PRP eq_NN1 1_CRD ,_PUN there_EX0 would_VM0 be_VBI a_AT0 clear_AJ0 dependence_NN1 of_PRF JPP_NN1 on_PRP bite_NN1 angle_NN1 ._SENT However_AV0 ,_PUN a_AT0 low_AJ0 correlation_NN1 was_VBD observed_VVN between_PRP JPP_NN1 and_CJC bite_NN1 angle_NN1 for_PRP the_AT0 combined_AJ0 data_NN0 sets_NN2 (_PUL Figure_NN1 S16_CRD )_PUR ._SENT The_AT0 poor_AJ0 correlations_NN2 of_PRF JPP_NN1 with_PRP bite_NN1 angle_NN1 indicate_VVB that_CJT the_AT0 linker_NN1 does_VDZ not_XX0 affect_VVI the_AT0 through-Ni_AJ0 2JPP_AJ0 coupling_NN1 term_NN1 ._SENT This_DT0 finding_NN1 suggests_VVZ that_CJT differences_NN2 in_PRP JPP_NP0 between_PRP 2C_AJ0 and_CJC 3C_AJ0 complexes_NN2 instead_AV0 arise_VVB from_PRP differences_NN2 in_PRP the_AT0 through-linker_NN1 m+1JPP_NN1 coupling_NN1 terms_NN2 in_PRP eq_NN1 1._CRD 
The_AT0 through-linker_NN1 m+1JPP_NN1 coupling_NN1 describes_VVZ 3JPP_AJ0 and_CJC 4JPP_AJ0 for_PRP the_AT0 2C_AJ0 and_CJC 3C_AJ0 complexes_NN2 ,_PUN respectively_AV0 ,_PUN which_DTQ should_VM0 obey_VVI Karplus-type_AJ0 relationships_NN2 that_CJT depend_VVB on_PRP the_AT0 linker_NN1 geometry_NN1 ._SENT The_AT0 range_NN1 of_PRF 3JPP_AJ0 values_NN2 for_PRP complexes_NN2 in_PRP the_AT0 2C_AJ0 data_NN0 set_NN1 is_VBZ expected_VVN to_TO0 be_VBI small_AJ0 because_CJS there_EX0 is_VBZ little_DT0 conformational_AJ0 flexibility_NN1 available_AJ0 to_PRP bidentate_AJ0 ligands_NN2 with_PRP such_DT0 short_AJ0 linkers_NN2 when_CJS they_PNP are_VBB bound_VVN to_PRP metals_NN2 ._SENT Similarly_AV0 ,_PUN the_AT0 range_NN1 of_PRF 4JPP_AJ0 values_NN2 is_VBZ expected_VVN to_TO0 be_VBI small_AJ0 ,_PUN and_CJC therefore_AV0 the_AT0 average_AJ0 values_NN2 of_PRF m+1JPP_NN1 are_VBB sufficient_AJ0 for_PRP eq_NN1 1_CRD to_TO0 be_VBI useful_AJ0 ._SENT 
With_PRP these_DT0 considerations_NN2 in_PRP mind_NN1 ,_PUN a_AT0 three-parameter_AJ0 model_NN1 was_VBD found_VVN to_TO0 be_VBI sufficient_AJ0 to_TO0 describe_VVI JPP_NN1 for_PRP 2C_AJ0 and_CJC 3C_AJ0 complexes_NN2 ._SENT The_AT0 best_AJS fit_NN1 for_PRP the_AT0 three_CRD parameters_NN2 (_PUL one_CRD slope_NN1 ,_PUN one_CRD intercept_NN1 ,_PUN and_CJC one_CRD correction_NN1 for_PRP 3C_AJ0 linkers_NN2 )_PUR together_AV0 enables_VVZ eq_NN1 1_CRD to_TO0 become_VVI equation_NN1 where_CJS CTP-to-Ni_NP0 is_VBZ the_AT0 numerical_AJ0 value_NN1 of_PRF charge_NN1 transfer_NN1 from_PRP P-to-Ni_NP0 from_PRP a_AT0 charge_NN1 transfer_NN1 analysis_NN1 and_CJC L_ZZ0 is_VBZ a_AT0 parameter_NN1 that_CJT describes_VVZ the_AT0 difference_NN1 in_PRP average_AJ0 through-linker_NN1 m+1JPP_NN1 ._SENT Equation_NN1 2_CRD shows_VVZ a_AT0 good_AJ0 R2_CRD =_NP0 0.9267_CRD and_CJC RMS_NN1 error_NN1 of_PRF 11.8_CRD Hz_NN0 for_PRP the_AT0 combined_AJ0 data_NN0 set_NN1 of_PRF 203_CRD complexes_NN2 for_PRP which_DTQ JPP_NP0 and_CJC CTP-to-Ni_NP0 values_NN2 could_VM0 be_VBI calculated_VVN (_PUL Figure_NN1 4_CRD )_PUR ._SENT 
Implications_NN2 for_PRP the_AT0 Analysis_NN1 of_PRF 31P_NP0 NMR_NP0 Spectra_NN2 ._SENT 
Equation_NN1 2_CRD can_VM0 be_VBI used_VVN to_TO0 interpret_VVI 31P_NP0 NMR_NP0 spectra_NN2 of_PRF Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 ,_PUN even_AV0 when_CJS the_AT0 sign_NN1 of_PRF JPP_NN1 is_VBZ not_XX0 directly_AV0 available_AJ0 through_PRP measurements_NN2 ._SENT For_PRP example_NN1 ,_PUN in_PRP the_AT0 case_NN1 where_AVQ quantum_NN1 chemical_AJ0 simulations_NN2 are_VBB available_AJ0 ,_PUN a_AT0 computed_AJ0 value_NN1 of_PRF CTP-to-Ni_NP0 can_VM0 be_VBI used_VVN with_PRP eq_NN1 2_CRD to_TO0 find_VVI JPP_NP0 ,_PUN for_PRP a_AT0 comparison_NN1 to_PRP ∣JPP∣_NN1 observed_VVN in_PRP spectra_NN2 ._SENT Except_CJS for_PRP ∣JPP∣_NP0 ≲_NP0 10_CRD Hz_NN0 ,_PUN where_CJS the_AT0 sign_NN1 would_VM0 be_VBI ambiguous_AJ0 ,_PUN the_AT0 sign_NN1 will_VM0 be_VBI apparent_AJ0 if_CJS the_AT0 absolute_AJ0 value_NN1 of_PRF the_AT0 computed_AJ0 JPP_NN1 for_PRP the_AT0 simulated_AJ0 Ni_NP0 complex_NN1 is_VBZ near_PRP the_AT0 experimentally_AV0 observed_AJ0 ∣JPP∣_NN1 ._SENT 
The_AT0 further_AJC utility_NN1 of_PRF eq_NN1 2_CRD comes_VVZ from_PRP its_DPS description_NN1 of_PRF the_AT0 behavior_NN1 of_PRF JPP_NN1 ._SENT The_AT0 negative_AJ0 dependence_NN1 of_PRF JPP_NP0 on_PRP P-to-Ni_NP0 charge_NN1 transfer_NN1 enables_VVZ one_PNI to_TO0 deduce_VVI the_AT0 sign_NN1 of_PRF JPP_NN1 in_PRP a_AT0 series_NN0 of_PRF Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 with_PRP varying_AJ0 ligand_NN1 electronics_NN1 ._SENT For_PRP example_NN1 ,_PUN for_PRP a_AT0 sequence_NN1 of_PRF Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 with_PRP varying_AJ0 P-donating_AJ0 abilities_NN2 ,_PUN 1-D_NN1 31P_NP0 NMR_NP0 spectroscopy_NN1 will_VM0 give_VVI a_AT0 series_NN0 of_PRF JPP_NN1 values_NN2 ._SENT If_CJS ∣JPP∣_NP0 increases_VVZ as_PRP the_AT0 phosphine_NN1 ligands_NN2 become_VVB more_AV0 donating_VVG ,_PUN the_AT0 observed_AJ0 JPP_NN1 values_NN2 are_VBB likely_AV0 negative_AJ0 ._SENT If_CJS ∣JPP∣_NP0 decreases_VVZ with_PRP more-donating_AJ0 phosphines_NN2 ,_PUN the_AT0 JPP_NN1 values_NN2 are_VBB likely_AV0 positive_AJ0 ._SENT A_AT0 similar_AJ0 screening_NN1 can_VM0 be_VBI performed_VVN by_PRP keeping_VVG the_AT0 phosphine_NN1 ligand_NN1 the_AT0 same_DT0 and_CJC incorporating_VVG withdrawing_VVG groups_NN2 on_PRP the_AT0 trans_NN2 ligands_NN2 ,_PUN because_CJS a_AT0 more_AV0 negative_AJ0 JPP_NN1 is_VBZ expected_VVN for_PRP an_AT0 increased_AJ0 withdrawing_AJ0 ability_NN1 of_PRF trans_NN2 ligands_NN2 ._SENT Once_CJS the_AT0 sign_NN1 is_VBZ deduced_VVN ,_PUN the_AT0 trends_NN2 in_PRP Figure_NN1 2_CRD suggest_VVB that_CJT the_AT0 sign_NN1 of_PRF JPP_NN1 can_VM0 be_VBI used_VVN to_TO0 make_VVI an_AT0 oxidation_NN1 state_NN1 assignment_NN1 ._SENT Given_VVN the_AT0 complexities_NN2 involved_VVN in_PRP determining_VVG the_AT0 sign_NN1 of_PRF JPP_NP0 via_PRP NMR_NP0 spectroscopy_NN1 ,_PUN this_DT0 approach_NN1 —_PUN while_CJS indirect_AJ0 —_PUN may_VM0 prove_VVI to_TO0 be_VBI the_AT0 simplest_AJS option_NN1 in_PRP many_DT0 cases_NN2 ._SENT Additionally_AV0 ,_PUN the_AT0 incorporation_NN1 of_PRF a_AT0 term_NN1 (_PUL i.e._AV0 ,_PUN L_ZZ0 )_PUR accounting_NN1 for_PRP differences_NN2 in_PRP through-linker_NN1 coupling_NN1 may_VM0 enable_VVI a_AT0 description_NN1 of_PRF other_AJ0 complexes_NN2 with_PRP varied_AJ0 linker_NN1 lengths_NN2 or_CJC linker_NN1 identities_NN2 ,_PUN such_DT0 as_PRP BINAP_NN1 and_CJC SPIRAP_NN1 ,_PUN provided_CJS a_AT0 value_NN1 of_PRF L_ZZ0 can_VM0 be_VBI determined_VVN for_PRP the_AT0 linker_NN1 ._SENT 
CONCLUSION_NN1 
JPP_NP0 is_VBZ a_AT0 convenient_AJ0 NMR_NP0 parameter_NN1 for_PRP elucidating_VVG the_AT0 structure_NN1 of_PRF Ni_NP0 bidentate_NN1 phosphine_NN1 complexes_NN2 ._SENT For_PRP 2C_AJ0 complexes_NN2 ,_PUN ∣JPP∣_NP0 <_NP0 30_CRD Hz_NN0 and_CJC ∣JPP∣_NN1 >_NN1 40_CRD Hz_NN0 are_VBB indicative_AJ0 of_PRF NiII_CRD and_CJC Ni0_CRD ,_PUN respectively_AV0 ,_PUN while_CJS the_AT0 reverse_NN1 is_VBZ true_AJ0 for_PRP 3C_AJ0 complexes_NN2 ._SENT This_DT0 seemingly_AV0 odd_AJ0 relationship_NN1 among_PRP ∣JPP∣_NP0 ,_PUN oxidation_NN1 state_NN1 ,_PUN and_CJC linker_NN1 length_NN1 becomes_VVZ more_AV0 easily_AV0 understood_VVN after_PRP examining_VVG the_AT0 sign_NN1 of_PRF JPP_NP0 ,_PUN where_AVQ a_AT0 more_AV0 negative_AJ0 JPP_NN1 is_VBZ observed_VVN with_PRP a_AT0 higher_AJC oxidation_NN1 state_NN1 for_PRP both_DT0 linker_NN1 lengths_NN2 ._SENT 
