Structure and stability of MCl4 carbene complexes (M = Si, Ge, Sn): Experiment and theory

The Field of Main Group Lewis Acids and Lewis Superacids: Important Basics and Recent Developments

“…Thus, the reorganization energies of group 14 metal halides may be one order of magnitude larger than that of group 13 metal halides. Large reorganization energies of MCl 4 (157-291 kJ mol À 1 ) are also observed in complexes with IDipp (1,3-bis(2,6diisopropylphenyl)imidazol-2-ylidene), [77] the trends in complex stability are similar to the noted above for complexes with pyridine. In contrast, corresponding bent dihalides MCl 2 have very small reorganization energies (8-13 kJ mol À 1 in complexes with IDipp, [77] 6 kJ mol À 1 in complex with Py [78] ) which changes the trend in dissociation energies: Si < Ge < Sn for tetrahalides, while Si > Ge > Sn for dihalides.…”

“…[131] The data on Lewis acidity of 9-boratriptycene vary depending on the used LA scale. Gutmann acceptor number of 9-boratriptycene (76.2 [131] ) is slightly smaller than that of B(C 6 F 5 ) 3 (76)(77)(78)(79)(80)(81)(82), indicating that 9boratriptycene is weaker LA than B(C 6 F 5 ) 3 with respect to triethylphosphineoxide. In contrast, IR spectroscopy data show that C�N shift in B(C 6 H 4 ) 3 CH • AN and C=O shift in B-(C 6 H 4 ) 3 CH • EtOAc adducts are larger than that in corresponding complexes of B(C 6 F 5 ) 3 .…”

“…[c] Basis set II is defined as 6-311 + + G(2d,2p) for H, C, N, Si; and def2-TZVPD for Ge, Sn. [77] of tetrahedral SiCl 4 to the geometry in eq-SiCl 4 • Py (Scheme 7,b) requires 220 kJ mol À 1 ; and 280 kJ mol À 1 to the square planar geometry in trans-SiCl 4 • 2NH 3 (Scheme 7,c). Thus, the reorganization energies of group 14 metal halides may be one order of magnitude larger than that of group 13 metal halides.…”

“…In contrast, corresponding bent dihalides MCl 2 have very small reorganization energies (8-13 kJ mol À 1 in complexes with IDipp, [77] 6 kJ mol À 1 in complex with Py [78] ) which changes the trend in dissociation energies: Si < Ge < Sn for tetrahalides, while Si > Ge > Sn for dihalides. [77] In the latter case the trend is due to decreasing of the DA bond energy with the increase of the atomic radii of the group 14 element.…”

“…[b] Dissociation into free LA and two LB. [c] Basis set II is defined as 6–311++G(2d,2p) for H, C, N, Si; and def2‐TZVPD for Ge, Sn [77] …”