The reaction of [Ge{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Cl] (1) with LiBut or LiC⋮CPh in Et2O afforded substituted products [Ge(R){N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}] [R = But (2) or C⋮CPh (3)], respectively. However, the one-pot reaction of 1 with PhC⋮CH and BunLi in Et2O afforded lithium germinate [{(PhC⋮C)3Ge}3GeLi(Et2O)3] (4). Compound 1 can also undergo ligand transfer reaction with LiAlH4 to give [AlH{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}2] (5). Treatment of 1 with excess NaBH4 in THF afforded germanium(II) hydride-borane adduct [Ge(BH3){N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}H] (6). The reaction of 1 with MI (M = Cu and Au) gave the first examples of Ge(II)−M(I) adducts [Ge(CuI){N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Cl]4 (7) and [Ge(AuI){N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Cl] (8). Compounds 2−8 have been characterized by X-ray analysis.
Reaction of [Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )]Li 2 with Ti(dNR)Cl 2 (Py) 3 afforded the corresponding titanium imido complexes [η 5 :σ-Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )]Ti(dNRComplexes 2 and 3 were also prepared by an imido exchange reaction of 1 with RNH 2 (R ) 2,6-Me 2 C 6 H 3 , 2,6-i Pr 2 C 6 H 3 ). Similarly, [η 5 :σ-Me 2 C(C 9 H 6 )(C 2 B 10 H 10 )]Ti-(dN t Bu)(Py) (4) was prepared from the reaction of [Me 2 C(C 9 H 6 )(C 2 B 10 H 10 )]Li 2 with Ti-(dN t Bu)Cl 2 (Py) 3 . The reactivity of 1 toward a series of unsaturated organic compounds was examined. Complex 1 underwent imido/oxo exchange reactions with carbonyl compounds such as Ph 2 CO, PhCHO, and PhNCO to generate the corresponding imines or carbodiimide and oxotitanium oligomers. The resulting insoluble oxotitanium oligomer was trapped by Me 3 SiCl, resulting in the formation of a chloride complex, [η 5 :σ-Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )]Ti-(OSiMe 3 )Cl (5). Interaction of 1 with CS 2 gave t BuNdCdN t Bu and t BuNdCdS with a molar ratio of 1:3 as well as an insoluble sulfidotitanium complex. 1 was able to catalyze the hydroamination of phenyl acetylene with amines to afford both Markovnikov and anti-Markovnikov products. The product ratio was dependent upon the steric hindrance of the amines used. High regioselectivity was observed for sterically demanding amines such as t-BuNH 2 . The anti-Markovnikov [2+2] cycloaddition intermediate [η 5 :σ-Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )]-Ti(η 3 -N t BuCHdCPh) (6) was successfully isolated from a stoichiometric reaction of 1 with phenyl acetylene in toluene. The molecular structures of 3-6 were further confirmed by single-crystal X-ray analyses.
Interaction of [Me3NH][7,8-CH2OCH2-7,8-C2B9H10] with M(NR2)4 gave the simple amine elimination products [η5-(CH2OCH2)C2B9H9]M(NMe2)2(NHMe2) (M = Zr (2a), Hf (2b)) or the unexpected C−O bond cleavage products [σ:η1:η5-(OCH2)(Me2NCH2)C2B9H9]Ti(NR2) (R = Me (3a), Et (3b)). The higher oxophilicity of the Ti center provides the driving force for the latter reactions. It is suggested that the C−O bond cleavage is prior to the amine elimination in the formation of 3a,b. This serves as a convenient and practical method for the preparation of constrained-geometry half-sandwich metallacarboranes with two different functional sidearms. Complex 3a can undergo a clean amine exchange reaction to produce new constrained-geometry titanacarborane amides. Reactions of 3a with unsaturated molecules CyNCNCy, SCS, Xyl−NC, PhC⋮N, Bu n NCS, Ph2CCO, and PhNCO gave monoinsertion products. They, except for [σ:η1:η5-(OCH2)(Me2NCH2)C2B9H9]Ti[η3-CyNC(NMe2)NCy] (7), do not react with amines. In sharp contrast, 7 can react readily with Me2NH to regenerate 3a and release guanidine, which leads to the discovery of new catalytic guanylation of amines. All new complexes were fully characterized by various spectroscopic techniques and elemental analyses. Most of them were further confirmed by single-crystal X-ray analyses.
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