Chemistry ofC-Trimethylsilyl-Substituted Heterocarboranes. 27. Synthetic, Spectroscopic, Structural, and Reactivity Studies on d⁰Hafnacarboranes of 2,3-C₂B₄-Carborane Ligands

Abstract

The sodium/lithium compounds closo-exo-Li(THF)-1-Na(THF)-2-(SiMe3)-3-(R)-2,3-C2B4H4 (R = SiMe3, Me, H), were found to react with several different hafnium reagents to produce half- and full-sandwich and mixed-ligand chlorohafnacarboranes in good yields. The reaction of the sodium/lithium compounds with HfCl4 in 2:1 molar ratios produced the full-sandwich complexes 1-Cl-1-(THF)-2,2‘-(SiMe3)2-3,3‘-(R)2-4‘,5,5‘,6-Li(THF) n -[1,1‘-comm o-Hf(2,3-C2B4H4)2] (R = SiMe3, n = 2 (I); R = Me, n = 1 (II); R = H, n = 1 (III)) in yields of 77%, 65%, and 71%, respectively. When R = SiMe3, a 1:1 molar ratio of carborane to HfCl4 gave the half-sandwich species [Li(THF)2][1,1,1-(Cl)3-closo-1-Hf-2,3-(SiMe3)2-2,3-C2B4H4] (V) in 77% yield. On the other hand, both 2:1 and 1:1 reaction ratios of carborane (R = Me) to Cp*HfCl3 gave only the mixed-ligand sandwich compound 1,1‘-(Cl)2-2-(SiMe3)-3-(Me)-4,5-Li(THF)-1,1‘-commo-Hf[(η5-C5Me5)(η5-2,3-C2B4H4)] (IV) in 82% yield. All compounds were characterized by infrared spectroscopy, 1H, 13C, and 11B NMR spectroscopy, and chemical analysis. Compounds I−III were characterized further by single-crystal X-ray diffraction. The structures show the hafnacarboranes to have bent-sandwich structures in which a Hf atom, in a formal +4 state, was sandwiched between two carborane ligands and was also bonded to a Cl atom and a THF molecule to give a distorted-tetrahedral arrangement about the metal.

Cyclopentadienyl vs Indenyl Substituents. Organolanthanide Complexes and Biscarborane Compounds Derived from a Versatile Ligand, Me2Si(C9H7)(C2B10H11)

“…The 11 B NMR spectrum consists of many broad, unresolved resonances, which differs from those of 2 and [Me 2 Si(C 9 H 6 )(C 2 B 10 H 11 )] K 3 . The IR spectrum shows a unique doublet centered around 2508 cm -1 , typical of the ionic interaction of a positive metal center and an anionic carboranyl ligand. ,6b, It is reasonable to suggest that the solid-state structure of 8 is similar to that of [η 5 :η 6 -Me 2 Si(C 9 H 6 )(C 2 B 10 H 11 )]Sm(THF) 2 prepared from an unexpected redox reaction between SmI 2 and [Me 2 Si(C 9 H 6 )(C 2 B 10 H 11 )]Na in THF 6b…”

Evolution of C2B4Carborane Chemistry: from Early Years to the Present

“…The fact that [Me 3 SiCH 2 ] - replaced the THF in the primary coordination sphere of the zirconium demonstrates the inertness of the Cl that is coordinated to the zirconium; this is quite different from the behavior of corresponding chlorozirconocenes . The corresponding commo- chlorohafnacarboranes, formed by the reaction of HfCl 4 and carborane in a 1:2 molar ratio, were found to have structures similar to that of the chlorozirconacarborane shown in Figure (see Scheme ) . A 1:1 ratio fo HfCl 2 to carborane produced the half-sandwich [Li(THF) 2 ][1,1,1-(Cl) 3 - closo- 1-Hf-2,3-(SiMe 3 ) 2 -2,3-C 2 B 4 H 4 ].…”

Advances in the metallacarborane chemistry of f-block elements

“…41 Most of the small cage lanthanacarboranes have involved the use of the "carbons adjacent" (2,3-C 2 B 4 ) isomer; the "carbons apart" (2,4-C 2 B 4 ) isomer also forms metallacarboranes. 41,42 Although isolated full-and half-sandwich lanthanacarboranes in the "carbons apart" cage system had been reported, 42, 43 44 A general synthetic procedure is outlined in Scheme 4. While the solid-state structures of the dimeric Nd, Gd, Dy, Ho and Lu sandwich metallacarboranes were determined by X-ray crystallography, only one of them (where Ln = Gd) is shown in Fig.…”