High-Level Systematic ab Initio Comparison of Carbon- and Silicon-Centered SN2 Reactions Attila Á. Dékány, Gyula Z. Kovács, and Gábor Czakó* MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary * E-mail: gczako@chem.u-szeged.hu 5 SiH2F2 F -0.0000002120 0.4360269141 -1.2783994488 Si 0.0000000834 -0.4971026003 -0.0000010513 F -0.0000005507 0.4360289771 1.2783986387 H -1.2326561709 -1.2928909411 0.0000189713 H 1.2326682237 -1.2928722774 0.0000255913 5 SiH2Cl2 Cl 0.0000014166 0.3661917867 -1.6702897317 Si 0.0000003845 -0.8081338291 -0.0000000584 Cl 0.0000012966 0.3662023878 1.6702808424 H -1.2229576732 -1.6214082597 0.0001542604 H 1.2228515263 -1.6215705014 0.0001600380 5 SiH2Br2 Br -0.0000000124 0.2084199575 -1.8122849393 Si -0.0000000280 -1.0518316555 -0.0000024833 Br -0.0000000418 0.2084199356 1.8122853015 H -1.2220429561 -1.8681492683 0.0000185117 H 1.2220480383 -1.8681414369 0.0000219680 5 SiH2I2 I -0.0000000027 0.1516225849 -2.0168124479 Si -0.0000000139 -1.2232018582 -0.0000002523 I -0.0000000066 0.1516231365 2.0168119631 H -1.2185904445 -2.0483789617 0.0000336229 H 1.2185920024 -2.0483765848 0.0000344378 5 SiH2FCl F -0.6474693459 -0.0000002481 -1.5816188166 Si 0.5667979529 -0.0000000294 -0.5608945980 Cl -0.1785248330 -0.0000002030 1.3353920025 H 1.3449896164 -1.2277208643 -0.7651373506 H 1.3449726464 1.2277335011 -0.7651281065 5 SiH2FBr F -0.7053598147 -0.0000001178 -2.0922007393 Si 0.5799853218 -0.0000000292 -1.1612734475 Br -0.0700465300 -0.0000000631 0.9415017500 H 1.3436019273 -1.2273381196 -1.4218833885 H 1.3435919506 1.2273461585 -1.4218747921 5 SiH2FI F -0.7400202791 -0.0000000223 -2.4807275852 Si 0.5806670500 0.0000000161 -1.5968793404 I -0.0389698974 -0.0000000072 0.7548386350 H 1.3375652035 -1.2252394545 -1.8920191048 H 1.3375637466 1.2252403349 -1.8920174486 5 SiH2ClBr Cl -0.0000000355 0.4531177474 -2.2234284685 Si -0.0000000457 -0.8965207780 -0.6895681807 Br -0.0000000438 0.1571196464 1.2485590699 H -1.2223305442 -1.7062750867 -0.7792089323 H 1.2223365375 -1.7062667447 -0.7792045540 5 SiH2ClI Cl -0.0000000060 0.5085137595 -2.6430693793 Si -0.0000000042 -0.9311362347 -1.1891325113 I -0.0000000048 0.0916130974 1.0226928098 H -1.2207667783 -1.7377570878 -1.3309925226 H 1.2207677131 -1.7377557124 -1.3309915711 5 SiH2BrI Br -0.0000000150 0.2435352946 -2.2709807379 Si -0.0000000393 -1.1245966390 -0.5347884403 I -0.0000000192 0.1264190681 1.5576141529 H -1.2202988499 -1.9434959881 -0.5900173510 H 1.2203035487 -1.9434890270 -0.5900146858