Resonance Character of Copper/Silver/Gold Bonding in Small Molecule⋅⋅⋅MX (X=F, Cl, Br, CH₃, CF₃) Complexes

Abstract

The resonance character of Cu/Ag/Au bonding is investigated in B⋅⋅⋅M-X (M=Cu, Ag, Au; X=F, Cl, Br, CH3, CF3; B=CO, H2O, H2S, C2H2, C2H4) complexes. The natural bond orbital/natural resonance theory results strongly support the general resonance-type three-center/four-electron (3c/4e) picture of Cu/Ag/Au bonding, B:M-X↔B(+) -M:X(-) , which mainly arises from hyperconjugation interactions. On the basis of such resonance-type bonding mechanisms, the ligand effects in the more strongly bound OC⋅⋅⋅M-X series are analyzed, and distinct competition between CO and the axial ligand X is observed. This competitive bonding picture directly explains why CO in OC⋅⋅⋅Au-CF3 can be readily replaced by a number of other ligands. Additionally, conservation of the bond order indicates that the idealized relationship bB⋅⋅⋅M +bMX =1 should be suitably generalized for intermolecular bonding, especially if there is additional partial multiple bonding at one end of the 3c/4e hyperbonded triad.

What is NBO analysis and how is it useful?

“…Figure 2 also illustrates the striking complementarity of ω-bonding vs.r-longbonding contributions to total bond order (dotted line, circles), showing the interesting 'bond order conservation' principle [(b HAr + b ArY ) + b HAr ≈ 1] that is accurately maintained throughout the HNgY series. Such strong propensity for bond order conservation in resonance-type 3c/4e hyperbonding has been noted in previous studies of TM ligation [66] and other contexts [67]. From general resonance-theoretic conceptions of ω-bonding (4a) vs.r-long-bonding (4b) as described above, one can readily infer that this conservation principle originates in the 'mono-valency' of the on-axis p z -type valence orbital of the central Ng atom that is being shared in various ω/r bonding combinations with terminal H, Y valence orbitals of the triad, but must saturate at total available valency of one.…”

“…[15,59,66]) as well as in correlative-type studies to be described below (Section 3.3). [15,59,66]) as well as in correlative-type studies to be described below (Section 3.3).…”

π⋅⋅⋅H+⋅⋅⋅π Hydrogen Bonds and Their Lithium and Gold Analogues: MP2 and CASPT2 Calculations

“…The same ethylene complexes were analyzed later and their acetylene analogues were also considered . A theoretical study on the resonance character of bonding in B ⋅⋅⋅ M−X systems (M=Cu, Ag, Au; X=F, Cl, Br, CH 3 , CF 3 ; B=CO, H 2 O, H 2 S, C 2 H 2 , C 2 H 4 ) is partly in line with this study, since among different interactions also the Au ⋅⋅⋅ π contacts are considered here . One can also mention the T‐shaped FLi ⋅⋅⋅ C 2 H 4 and IAu ⋅⋅⋅ C 2 H 2 structures, the latter of which was analyzed both theoretically and experimentally by broadband rotational spectroscopy .…”

Understanding Regium Bonds and their Competition with Hydrogen Bonds in Au2:HX Complexes

“…From the theoretical perspective, several computational studies have been carried out in order to characterize this new interaction involving Au atom. B:AuX complexes, with B=OC, H 2 O, H 2 S, C 2 H 2 and C 2 H 4 and X=F, Cl, Br, have been studied at BP86 level . The complexes between acetylene and AuX (X= OH, F, Cl, Br, CH 3 , CCH, CN, and NC) with a π regium bond have been characterized at MP2 level .…”

“…B:AuX complexes, with B=OC, H 2 O, H 2 S, C 2 H 2 and C 2 H 4 and X=F, Cl, Br, have been studied at BP86 level. [16] The complexes between acetylene and AuX (X = OH, F, Cl, Br, CH 3 , CCH, CN, and NC) with a π regium bond have been characterized at MP2 level. [17] The regium and halogen bond complexes has been compared using MP2 and CCSD(T) computational methods.…”