%0 Journal Article %1 Hosmane.1997 %A Hosmane, Narayan S. %A Wang, Ying %A Zhang, Hongming %A Lu, Kai-Juan %A Maguire, John A. %A Gray, Thomas G. %A Brooks, Karen A. %A Waldhoer, Eberhard %A Kaim, Wolfgang %A Kremer, Reinhard K. %D 1997 %J Organometallics %K carborane coupling crystal dimer;EPR dimer;cyclic dimer;electrochem dimer;magnetic dimer;mol dimer;substituent dimer;titanacarborane effect prepn sandwich spin structure susceptibility titanium voltammetry %N 7 %P 1365--1377 %R 10.1021/OM960890K %T Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 21. Syntheses, Structures, EPR Spectra, and Reactivities of Bent-Sandwich and Half-Sandwich Titanacarboranes. Full Analysis of Spin-Spin Coupling in Two Structurally Characterized Titanium(III)-Carborane Dimers %V 16 %X The reaction of Cp2TiCl2 with the unsolvated dilithium compds. closo-exo-Li-1-Li-2-(R)-3-(SiMe3)-2,3-C2B4H4 (R = SiMe3, Me, H) produced dimeric mixed-sandwich titanacarboranes [commo-1-Cp-1-Ti(III)-2-(R)-3-(SiMe3)-2,3-C2B4H4]2 (R = SiMe3 (1), Me (2), H (3)) in yields of 60\%, 54\%, and 60\%, resp. The chem. oxidn. of these titanacarboranes in the presence of TiCl4 in THF resulted in the formation of the corresponding diamagnetic Ti(IV) species 1-(Cp)-1-(Cl)-1-(THF)-1-Ti-2-(R)-3-(SiMe3)-2,3-C2B4H4 (R = SiMe3 (7), Me (8), H (9)) in 86\%, 58\%, and 45\% yields, resp. When the bis(trimethylsilyl)-substituted dilithiacarborane precursor was reacted with TiCl3, only the monomeric full-sandwich chlorotitanacarborane [Li(TMEDA)]2[1-Cl-1,1'-Ti-(2,3-(SiMe3)2-2,3-C2B4H4)2] (4) was produced, while replacement of a SiMe3 group with a less sterically demanding Me group afforded the dimeric titanacarborane [Li(TMEDA)]2[1,1'-Ti-(2-Me-3-SiMe3-2,3-C2B4H4)2]2 (5A). On the other hand, when the TMEDA-solvated closo-exo-4,5-[(m-H)2Li(TMEDA)]-1-Li[(TMEDA)-2,4-(SiMe3)2-2,4-C2B4H4] was the precursor, reaction with TiCl3 yielded only the corresponding monomeric half-sandwich chlorotitanacarborane 1-(TMEDA)-1-Cl-1-Ti(III)-2,4-(SiMe3)2-2,4-C2B4H4 (6). In addn. to the X-ray analyses of 1, 5, 6, and 7, the Ti(III) compds. and an electrochem. generated Ti(IV)/Ti(III) mixed-valence complex (5B) were characterized by EPR spectroscopy. The dimers 1 and 5A exhibit unusually well-resolved triplet EPR features, which were fully analyzed and correlated with the structural results. Magnetic susceptibility measurements reveal a rather small d1-d1 exchange coupling const. of -45.8 cm-1 (antiferromagnetic interaction) for 1. The one-electron oxidn. of 5A produced an anion (S = 1/2) with rhombic EPR features, which was tentatively identified as a delocalized [Ti(+3.5)]2 mixed-valence species (5B). [on SciFinder(R)]

@article{Hosmane.1997, abstract = {The reaction of Cp2TiCl2 with the unsolvated dilithium compds. closo-exo-Li-1-Li-2-(R)-3-(SiMe3)-2,3-C2B4H4 (R = SiMe3, Me, H) produced dimeric mixed-sandwich titanacarboranes [commo-1-Cp-1-Ti(III)-2-(R)-3-(SiMe3)-2,3-C2B4H4]2 (R = SiMe3 (1), Me (2), H (3)) in yields of 60{\%}, 54{\%}, and 60{\%}, resp. The chem. oxidn. of these titanacarboranes in the presence of TiCl4 in THF resulted in the formation of the corresponding diamagnetic Ti(IV) species 1-(Cp)-1-(Cl)-1-(THF)-1-Ti-2-(R)-3-(SiMe3)-2,3-C2B4H4 (R = SiMe3 (7), Me (8), H (9)) in 86{\%}, 58{\%}, and 45{\%} yields, resp. When the bis(trimethylsilyl)-substituted dilithiacarborane precursor was reacted with TiCl3, only the monomeric full-sandwich chlorotitanacarborane [Li(TMEDA)]2[1-Cl-1,1'-Ti-(2,3-(SiMe3)2-2,3-C2B4H4)2] (4) was produced, while replacement of a SiMe3 group with a less sterically demanding Me group afforded the dimeric titanacarborane [Li(TMEDA)]2[1,1'-Ti-(2-Me-3-SiMe3-2,3-C2B4H4)2]2 (5A). On the other hand, when the TMEDA-solvated closo-exo-4,5-[(\textgreek{m}-H)2Li(TMEDA)]-1-Li[(TMEDA)-2,4-(SiMe3)2-2,4-C2B4H4] was the precursor, reaction with TiCl3 yielded only the corresponding monomeric half-sandwich chlorotitanacarborane 1-(TMEDA)-1-Cl-1-Ti(III)-2,4-(SiMe3)2-2,4-C2B4H4 (6). In addn. to the X-ray analyses of 1, 5, 6, and 7, the Ti(III) compds. and an electrochem. generated Ti(IV)/Ti(III) mixed-valence complex (5B) were characterized by EPR spectroscopy. The dimers 1 and 5A exhibit unusually well-resolved triplet EPR features, which were fully analyzed and correlated with the structural results. Magnetic susceptibility measurements reveal a rather small d1-d1 exchange coupling const. of -45.8 cm-1 (antiferromagnetic interaction) for 1. The one-electron oxidn. of 5A produced an anion (S = 1/2) with rhombic EPR features, which was tentatively identified as a delocalized [Ti(+3.5)]2 mixed-valence species (5B). [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Hosmane, Narayan S. and Wang, Ying and Zhang, Hongming and Lu, Kai-Juan and Maguire, John A. and Gray, Thomas G. and Brooks, Karen A. and Waldhoer, Eberhard and Kaim, Wolfgang and Kremer, Reinhard K.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/28d64a18b58c53a7c04f578955d998c62/huebleriac}, doi = {10.1021/OM960890K}, interhash = {7787750adbf04164c214ad99fefc0153}, intrahash = {8d64a18b58c53a7c04f578955d998c62}, issn = {0276-7333}, journal = {Organometallics}, keywords = {carborane coupling crystal dimer;EPR dimer;cyclic dimer;electrochem dimer;magnetic dimer;mol dimer;substituent dimer;titanacarborane effect prepn sandwich spin structure susceptibility titanium voltammetry}, number = 7, pages = {1365--1377}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 21. Syntheses, Structures, EPR Spectra, and Reactivities of Bent-Sandwich and Half-Sandwich Titanacarboranes. Full Analysis of Spin-Spin Coupling in Two Structurally Characterized Titanium(III)-Carborane Dimers}, volume = 16, year = 1997 }