%0 Journal Article %1 Hosmane.2000 %A Hosmane, Narayan S. %A Zhang, Hongming %A Maguire, John A. %A Wang, Ying %A Demissie, Temesgen %A Colacot, Thomas J. %A Ezhova, Maria B. %A Lu, Kai-Juan %A Zhu, Dunming %A Gray, Thomas G. %A Helfert, Sarah C. %A Hosmane, Suneil N. %A Collins, Jess D. %A Baumann, Frank %A Kaim, Wolfgang %A Lipscomb, William N. %D 2000 %J Organometallics %K DFT Group IA alkylation;magnesacarborane calcn calcn;mol crystal geometry magnesacarborane;heterocarborane magnesium metal metalation metallacarborane optimized prepn structure substituted substituted;DFT trimethylsilyl %N 4 %P 497--508 %R 10.1021/om990677z %T Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 28. Selective Alkylation and Reactivity of \dqCarbons Adjacent\dq and \dqCarbons Apart\dq Tetracarba-nido-dodecaborane(12) Derivatives toward Group 1 and Group 2 Metals. Synthetic, Spectroscopic, and Structural Investigations on Lithium-, Sodium-, Potassium-, Cesium-, and Magnesium-Complexed C4B8 Carboranes %V 19 %X The carbons apart tetracarbon carborane nido-2,6-(R)2-4,12-(SiMe3)2-2,4,6,12-C4B8H8 R = SiMe3 (I), Bu (II) and several of its B-alkylated derivs. react with Mg metal in THF solvent to produce magnesacarboranes e.g., (THF)2Mg(SiMe3)4(B-Bu-t)B4B7H7 (V) in yields ranging from 57\% to 74\%. The magnesacarboranes were characterized by chem. anal. and IR and 1H, 11B, and 13C NMR spectroscopy and by single-crystal x-ray diffraction. Two types of cages were found, one in (THF)2Mg(SiMe3)4(B-Me)C4B7H7 (IV) and the other in (L)2Mg(SiMe3)2(R)2(B-Y)C4B7H7 L = THF, R = SiMe3, Y = t-Bu (V); L = THF, R = SiMe3, Y = H (VI); (L)2 = TMEDA, R = Bu, Y = H (XI). Both cages showed electron-precise C and B atoms, as well as electron-deficient fragments. Approx. d. functional ab initio MO calcns. showed that the dianionic C4B8 cage can exist in a no. of energy-equiv. isomeric forms that can be trapped by a metal ion such as Mg. The reactions of I with the Group IA metals followed a different course in which two distinct steps occurred. The 1st step formed the paramagnetic intermediates which, in a slower step, reacted with a 2nd equiv. of the metal to give the diamagnetic (SiMe3)4C4B8H82-. For the lighter metals, this dianion picked up a proton to give (THF)4M(SiMe3)4C4B8H9 M = Li (VIII), Na (IX), K (X) in 35-54\% yield. In the case of Cs, no protonation occurred and the final product was a polymeric dicesiacarborane, exo-Cs(TMEDA)-1-Cs-(SiMe3)4C4B8H8n (VII), isolated in 41\% yield. All were characterized by chem. anal. and IR and 1H, 11B, and 13C NMR spectroscopy; VII and VIII were addnl. characterized by single-crystal x-ray diffraction studies. In VIII-X the Group IA metal was solvated by four THF mols. and was not involved in the cage, while in VII one Cs occupied an apical position above a C3B3 open face of one carborane and bonded to a B3 face of a neighboring carborane. The 2nd Cs, solvated by a TMEDA mol., occupies an exo-polyhedral position and was not part of the polymeric chain. One carbons adjacent magnesacarborane, exo-(m-H)3Mg(THF)3(SiMe3)2(Me)2C4B8H8 (XII), was also synthesized, in 81\% yield, by the reaction of the metal with the (SiMe3)2(Me)2C4B8H8 precursor. Single-crystal x-ray diffraction studies showed the compd. to be composed of an exo-polyhedral Mg(THF)32+ that is loosely bound to a (SiMe3)2(Me)2C4B8H82- cage. The carborane is best described as an 10-vertex arachno-(SiMe3)2C2B8H8 cage that subtends an electron-precise MeC:CMe fragment. on SciFinder(R)

@article{Hosmane.2000, abstract = {The carbons apart tetracarbon carborane nido-2,6-(R)2-4,12-(SiMe3)2-2,4,6,12-C4B8H8 [R = SiMe3 (I), Bu (II)] and several of its B-alkylated derivs. react with Mg metal in THF solvent to produce magnesacarboranes [e.g., (THF)2Mg(SiMe3)4(B-Bu-t)B4B7H7 (V)] in yields ranging from 57{\%} to 74{\%}. The magnesacarboranes were characterized by chem. anal. and IR and 1H, 11B, and 13C NMR spectroscopy and by single-crystal x-ray diffraction. Two types of cages were found, one in (THF)2Mg(SiMe3)4(B-Me)C4B7H7 (IV) and the other in (L)2Mg(SiMe3)2(R)2(B-Y)C4B7H7 [L = THF, R = SiMe3, Y = t-Bu (V); L = THF, R = SiMe3, Y = H (VI); (L)2 = TMEDA, R = Bu, Y = H (XI)]. Both cages showed electron-precise C and B atoms, as well as electron-deficient fragments. Approx. d. functional ab initio MO calcns. showed that the dianionic C4B8 cage can exist in a no. of energy-equiv. isomeric forms that can be trapped by a metal ion such as Mg. The reactions of I with the Group IA metals followed a different course in which two distinct steps occurred. The 1st step formed the paramagnetic intermediates which, in a slower step, reacted with a 2nd equiv. of the metal to give the diamagnetic [(SiMe3)4C4B8H8]2-. For the lighter metals, this dianion picked up a proton to give [(THF)4M][(SiMe3)4C4B8H9] [M = Li (VIII), Na (IX), K (X)] in 35-54{\%} yield. In the case of Cs, no protonation occurred and the final product was a polymeric dicesiacarborane, [exo-Cs(TMEDA)-1-Cs-(SiMe3)4C4B8H8]n (VII), isolated in 41{\%} yield. All were characterized by chem. anal. and IR and 1H, 11B, and 13C NMR spectroscopy; VII and VIII were addnl. characterized by single-crystal x-ray diffraction studies. In VIII-X the Group IA metal was solvated by four THF mols. and was not involved in the cage, while in VII one Cs occupied an apical position above a C3B3 open face of one carborane and bonded to a B3 face of a neighboring carborane. The 2nd Cs, solvated by a TMEDA mol., occupies an exo-polyhedral position and was not part of the polymeric chain. One carbons adjacent magnesacarborane, exo-(\textgreek{m}-H)3Mg(THF)3(SiMe3)2(Me)2C4B8H8 (XII), was also synthesized, in 81{\%} yield, by the reaction of the metal with the (SiMe3)2(Me)2C4B8H8 precursor. Single-crystal x-ray diffraction studies showed the compd. to be composed of an exo-polyhedral [Mg(THF)3]2+ that is loosely bound to a [(SiMe3)2(Me)2C4B8H8]2- cage. The carborane is best described as an 10-vertex arachno-(SiMe3)2C2B8H8 cage that subtends an electron-precise MeC:CMe fragment. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Hosmane, Narayan S. and Zhang, Hongming and Maguire, John A. and Wang, Ying and Demissie, Temesgen and Colacot, Thomas J. and Ezhova, Maria B. and Lu, Kai-Juan and Zhu, Dunming and Gray, Thomas G. and Helfert, Sarah C. and Hosmane, Suneil N. and Collins, Jess D. and Baumann, Frank and Kaim, Wolfgang and Lipscomb, William N.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/27710d451094991120cbf5e8998ea4d51/huebleriac}, doi = {10.1021/om990677z}, interhash = {2377abb8cc8cc5b2f0aeb71f97076b36}, intrahash = {7710d451094991120cbf5e8998ea4d51}, issn = {0276-7333}, journal = {Organometallics}, keywords = {DFT Group IA alkylation;magnesacarborane calcn calcn;mol crystal geometry magnesacarborane;heterocarborane magnesium metal metalation metallacarborane optimized prepn structure substituted substituted;DFT trimethylsilyl}, number = 4, pages = {497--508}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 28. Selective Alkylation and Reactivity of {\dq}Carbons Adjacent{\dq} and {\dq}Carbons Apart{\dq} Tetracarba-nido-dodecaborane(12) Derivatives toward Group 1 and Group 2 Metals. Synthetic, Spectroscopic, and Structural Investigations on Lithium-, Sodium-, Potassium-, Cesium-, and Magnesium-Complexed C4B8 Carboranes}, volume = 19, year = 2000 }