Structures of germylenes and stannylenes with chelating ligands: a DFT study

Abstract

Geometries of 20 germylenes and 18 stannylenes based on dialkanolamines, diethylenetri amines, and related compounds were optimized by the DFT method. It was found that the most of the germylenes and stannylenes studied are more stable as dimeric structures of different types. The dimerization is possible due to either additional Ge-O(N) interactions or Ge-Ge bonding. The factors leading to the stabilzation of one or another isomer are examined.Presently, investigation of compounds containing di valent Group 14 elements (Si, Ge, Sn, Pb) is a rapidly developing area of organometallic chemistry. "Heavy" car benes can be the starting substances for the synthesis of diverse organometallic compounds and intermediates, for instance, transition metal complexes and clusters, deriva tives with the metal-carbon and metal-heteroatom mul tiple bonds, small metallacycles, and analogs of carbeni um ions and radicals. Approaches to the synthesis of these compounds and studies of their reactivity were analyzed in reviews. 1-8 It is well known that such compounds (mainly silicon and germanium derivatives, and, to a lesser extent, tin compounds) are not so stable as their analogs contain ing metal atoms with the formal oxidation state +4.Several possible methods for stabilization of such com pounds have been reported to date. 2 The first method, viz., kinetic stabilization, assumes the insertion of bulky sub stituents that impede the approach of the reactant to the reaction center of the molecule into the groups bound to the germanium atom. The second and third methods, viz., thermodynamic stabilization, are realized for compounds in which (a) the metal atom is covalently bound to n or π donor substituents and (b) there is an additional tran sannular interaction with an electron donor.Therefore, diethanolamines RN(CH 2 CH 2 OH) 2 and diethylenetriamines RN(CH 2 CH 2 NR´H) 2 capable of forming three bonds (two covalent bonds and one coordi nation bond) with the metal atom seem to be appropriate ligands for stabilization of germylenes and stannylenes. Earlier, 8-16 it was found that dialkanolamines readily form compounds with germanium and tin atoms in the oxida tion state +4. However, analysis of literature data showed that such ligands were almost not used in chemistry of "heavy" carbenes, although they are suitable for efficient stabilization of the electron unsaturated center by all the three methods mentioned above, and the kinetic stabiliza tion is not excluded even in the case of dialkanolamines if the carbon atoms have bulky substituents.The syntheses of one germylene, MeN(CH 2 CH 2 O) 2 Ge, 17 and several stannylenes 18,19 were reported. The struc tures of these compounds were not studied by X ray dif fraction analysis. In addition, two stannylenes, MeN(CH 2 CH 2 NPr i ) 2 Sn and MeN(CH 2 CH 2 NSiMe 3 ) 2 Sn, were synthesized. The structure of the latter compound was studied 20 by X ray diffraction analysis. A series of works 21-25 on the synthesis of the Ge 2+ and Sn 2+ deriva tives based on Me 2 NCH 2 CH 2 OH suggest the ...

Trapping Molecular SnBr2(OH)2 by Tin Alkoxide Coordination: Syntheses and Molecular Structures of [MeN(CH2CMe2O)2SnBr2]2·SnBr2(OH)2 and RN(CH2CMe2O)2SnL [R = Me, n‐Octyl; L = Lone Pair, Cr(CO)5, W(CO)5, Fe(CO)4, Br2]

“…Hydrogen atoms are omitted for clarity. DFT calculations have shown that for 2,8dioxa-5-aza-1-stanna(II)bicyclo [3.3.0]octanes of the type RN(CH 2 CH 2 O) 2 Sn (R = H, Me, Ph) the cis isomer is more stable than the trans isomer with energy differences that range from 2.6 (R = H) to 1.3 kcal mol -1 (R = Ph), [6] but no calculations were performed for sterically more crowded stanna(II)bicyclo [3.3.0]octane derivatives. (5) Sn(1)···Sn(X) 3.6353(1) 3.6124 (3) 3.5966 (3) 3.4697 (3) 3.5229 (4) 3.3927 (4) 3.4440 (3) (27) 3.9435 (1) 2.239(9) Å; Sn-N: 2.413(10), 2.447(10) Å].…”

“…In the solid state, 9·0.5C 7 H 8 is a centrosymmetric dimer formed by intermolecular OǞSn interactions to give a fourmembered Sn 2 (7), 176.01 (6), and 148.00(10)°, (2) Sn (1)-O(21) 2.050 (7) Sn(1)-N (14) 2.245 (3) 2.247(6) Sn(1)-Br (1) 2.5601 (5) 2.5158(10) Sn(1)-Br (2) 2.5604 (5) 2.5340 (10) Sn (2)-O(11) 2.081 (5) Sn (2)-O(21) 2.116 (8) Sn (2)-O(27) 2.104 (5) Sn (2)-O(31) 2.091 (5) Sn (2)-Br (3) 2.5032(10) Sn(2)-Br (4) 2.5024(10) Sn(3)-Br (5) 2.5261(10) Sn(3)-Br (6) 2.5306 (10) Sn (3)-O(27) 2.073 (5) Sn (3)-O(31) 2.145 (5) Sn (3)-O(37) 2.018 (5) Sn (3)-N(34) 2.247 (6) Sn (1)···Sn(1A) 3.4080 (4) Sn (1)···Sn (2) 3.3365 (2) Sn (2)···Sn (3) 3.3397 (1) O(27)···O (17) 2.586 (8) O(21)···O (37) 2.609 (8) respectively. The intramolecular Sn (1) [11] The Sn(1)-Br(1) and Sn(1)-Br (2) Compound 10 can formally be interpreted as an insertion product of molecular SnBr 2 (OH) 2 into the intermolecular Sn-O bridge of the dimeric compou...…”

“…This is probably due to the steric effects of the methyl groups. DFT calculations have shown that for 2,8‐dioxa‐5‐aza‐1‐stanna(II)bicyclo[3.3.0]octanes of the type RN(CH 2 CH 2 O) 2 Sn (R = H, Me, Ph) the cis isomer is more stable than the trans isomer with energy differences that range from 2.6 (R = H) to 1.3 kcal mol –1 (R = Ph),6 but no calculations were performed for sterically more crowded stanna(II)bicyclo[3.3.0]octane derivatives. The tin atoms in 1′ , 1″ , and 2 are four‐coordinate and exhibit strongly distorted pseudo‐trigonal‐bipyramidal configurations with N(14), O(11A) ( 1′ , 2 ), N(24), O(21A) ( 1″ ) occupying the axial positions and O(11), O(17), lone pair ( 1′ , 2 ) and O(21), O(27), lone pair ( 1″ ) occupying the equatorial positions.…”

“…A solution of W(CO) 5 -(thf) in THF, which was prepared from W(CO) 6 (3.32 g, 9.43 mmol) in THF (250 mL) under UV irradiation, was added to a solution of 2 (3.68 g, 9.43 mmol) in THF (100 mL). After stirring the reaction mixture at room temperature for 2 h, the solvent was removed under vacuum, and the resulting yellow-brown solid was recrystallized from toluene.…”