Electronic effect of a perfluorinated β-diketiminate ligand on the bonding nature of copper carbonyl complexes

Abstract

<p>A combined experimental and computational study demonstrates the influence of fluorine substituents on the electronic properties of β-diketiminate ligands.</p>

Synthesis of Homo‐ and Heteroleptic Al, Ga and Zn Complexes Containing (Per)fluorinated β‐Diketiminate Ligands

“…The 1 H NMR spectra of the heteroleptic β ‐diketiminate zinc ethyl complexes 16 Fnac 2 ZnEt [ 19a ] and 17 Fnac 2 ZnEt ( 1 ) show virtually identical shifts for the methylene ( 16 Fnac 2 ZnEt δ 0.10; 1 δ 0.12) and methyl protons ( 16 Fnac 2 ZnEt δ 0.76; 1 δ 0.77), as is also observed for the methyl groups ( δ –0.91) of the heteroleptic aluminum complexes 16 Fnac 2 AlMe 2 [ 19a ] and 17 Fnac 2 AlMe 2 ( 2 ). In contrast, the 13 C NMR resonances of the methyl groups in the aluminum complexes ( 16 Fnac 2 AlMe 2 δ –12.7; 2 δ –14.0) slightly differ.…”

“…The 17 Fnac 2 ligands in complexes 1 and 2 show almost planar configurations of the C 3 N 2 M unit with the C 6 F 5 rings standing perpendicular to the ligand core as was previously observed for the corresponding 16 Fnac 2 ‐substituted complexes 16 Fnac 2 ZnEt and 16 Fnac 2 AlMe 2 , respectively. [ 19a ] The zinc atom in complex 1 adopts a trigonal planar coordination geometry with a minor deviation (0.046 Å) from planarity, whereas the aluminum atom in complex 2 is tetrahedrally coordinated. The Zn–C bond [1.940(2) Å] is slightly shorter than those reported for Dippnac 2 ZnEt [1.971(4) Å] [ 21 ] and 6 Fnac 2 ZnEt { 6 Fnac 2 = HC[C(CF 3 )N‐2,6‐ i Pr 2 –C 6 H 3 ]} [1.963(17) Å] [ 22 ] but comparable to that observed in 16 Fnac 2 ZnEt [1.9449(12) Å].…”

“…The Al–Me bond length in complex 2 [1.943(2) Å] is virtually identical with that observed for 16 Fnac 2 AlMe 2 [1.945(2) Å], but shorter than those reported for 10 Fnac 2 AlMe 2 [ 10 Fnac 2 = HC[C(CH 3 )NC 6 F 5 ] 2 , 1.957(3)/1.947(3) Å] [ 23 ] and Mesnac 2 AlMe 2 [1.960(3), 1.966(4) Å], [ 24 ] respectively. As was observed in the zinc complexes, the Al–N bond length also increases and the N–Al–N bond angles decrease with decreasing σ ‐donor capacity of the β ‐diketiminate substituent [Mesnac 2 AlMe 2 1.916(3)/1.926(3), 95.24(12)°; [ 24 ] 10 Fnac 2 AlMe 2 1.917(2)/1.926(2), 94.00(8)°; [ 23 ] 16 Fnac 2 AlMe 2 1.948(2)/1.942(2), 93.02(7)°; [ 19a ] and 17 Fnac 2 AlMe 2 (1.949(2)/1.956(2), 89.80(8)°], whereas the Me–Al–Me bond angles steadily increase [Mesnac 2 AlMe 2 112.63 (15)°; 10 Fnac 2 AlMe 2 118.89(14)°; 16 Fnac 2 AlMe 2 120.77(7)°; 17 Fnac 2 AlMe 2 123.74(2)°]. Deviations from planarity (defined by N1, N2, C1, C3) are observed for the Al atom [0.8779(28) Å] and the γ ‐carbon atom [0.2163(33) Å] in complex 2 .…”

“…Exact molar ratios of the reactions and reaction conditions were optimized by monitoring several small‐scale reactions, which were performed in J ‐Young NMR tubes in deuterated solvents under different reaction conditions, by in situ 1 H and 19 F NMR spectroscopy. ZnMe 2 and AlMe 3 were commercially available and used as received, whereas 16 Fnac 2 H, [ 19a ] 17 Fnac 2 H, [ 19b ] and Cp* 2 Zn [ 28 ] were prepared according to literature procedures.…”

“…The reactions typically occurred with MF elimination and subsequent decomposition via an aforementioned cyclization reaction pathway. [ 19b ] These findings severely limit the use of such (per)fluorinated β ‐diketiminate ligands in metal organic chemistry and show the necessity for other types of transmetalation reagents. We therefore became interested in the synthesis of group 12 (Zn) and group 13 metal (Al, Ga) complexes and report herein on the syntheses of heteroleptic zinc, aluminum and gallium complexes 17 Fnac 2 ZnEt ( 1 ), 17 Fnac 2 AlMe 2 ( 2 ) and 16 Fnac 2 GaMe 2 ( 3 ) as well as homoleptic zinc complexes ( 16 Fnac 2 ) 2 Zn ( 4 ) and ( 17 Fnac 2 ) 2 Zn ( 5 ) containing the (per)fluorinated 16 Fnac 2 – and 17 Fnac 2 – ligands.…”