Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 25. Syntheses, Structures, and Reactivities of GeCl₃-Substituted Half-Sandwich Germacarboranes, closo-1-Ge-2-(SiMe₃)-3-(R)-5-(GeCl₃)-2,3-C₂B₄H₃ (R = SiMe₃, Me, and H)

Abstract

Anhydrous GeCl4 reacts with the closo-stannacarboranes 1-Sn-2-(SiMe3)-3-(R)-2,3-C2B4H4 (R = SiMe3 (I), Me (II), and H (III)) in the absence of solvents to give the corresponding closo-germacarboranes 1-Ge-2-(SiMe3)-3-(R)-5-(GeCl3)-2,3-C2B4H3 (R = SiMe3 (IV), Me (V), and H (VI)) in yields of 43%, 22%, and 51%, respectively. Despite the presence of two potential Lewis-acid sites, the reactions of the germacarboranes with the bases C10H8N2, C8H6N4, and C15H11N3 produced exclusively 1-(L)-2-(SiMe3)-3-(R)-5-(GeCl3)-1,2,3-GeC2B4H3 (L = C10H8N2, R = SiMe3 (VII) and Me (VIII); L = C15H11N3, R = SiMe3 (XI)) or, when L = C8H6N4, the bridged complexes 1,1‘-(2,2‘-C8H6N4)-[1-Ge-2-(SiMe3)-3-(R)-5-(GeCl3)-2,3-C2B4H3]2 (R = SiMe3 (IX), Me (X)). The reaction of IV with (η5-C5H5)Fe(η5-C5H4CH2(Me)2N) produced a 1:1 mixture of the salt {[(η5-C5H5)Fe(η5-C5H4CH2]2N(Me)2}+{GeCl3}- (XII) and 1-Ge[(η5-C5H5)Fe(η5-C5H4CH2(Me)2N)]-2,3-(SiMe3)2-5-(NMe2)-2,3-C2B4H3 (XIII), a germacarborane in which a NMe2 group replaced the GeCl3 moiety on the carborane cage. All compounds were characterized by their infrared and 1H, 11B, and 13C NMR spectra, as well as chemical analysis. In addition, IV−VII, IX, and XII were characterized by single-crystal X-ray diffraction. The structures showed IV−VI to be half-sandwich complexes in which a Ge(II) was symmetrically bound to the C2B3 faces of the carboranes, with a Ge(IV) terminally bonded to the unique borons of the cages in a GeCl3 group. The structures of the Lewis-base adducts, VII and IX, showed that the nitrogens of the bases were symmetrically bonded to the Ge(II) atoms. Coordination by the bases resulted in a slip distortion of the capping metal atoms toward the boron side of the cages. Compounds XII and XIII are the final products of a sequence of reactions, one of which involves the displacement of a [GeCl3]- unit from the unique boron by a (η5-C5H5)Fe(η5-C5H4CH2(Me)2N) base, producing an intermediate that reacts further with another molecule of the base to give both XII and XIII. In no case was there any evidence of the Ge(IV) acting as a reactive Lewis-acid center. Ab initio molecular orbital calculations were used in rationalizing some of the synthetic and spectroscopic results obtained in this study.

Boranyl‐Functionalized [Ge9] Clusters: Providing the Idea of Intramolecular Ge/B Frustrated Lewis Pairs

“…[2,30] The DAB ligands in 2 a-Cu and 3 a-Cu bind to the [Ge 9 ] cluster through exo-cluster single bonds between one cluster vertex atom and the B atom, with GeÀB distances of 2.063(5) and 2.055(5) , respectively. The bond lengths are in the range of previously reported GeÀB bonds in germaborates, [31] germacarboranes [32] or germylenes. [25, 26b,c,e, 33] The [NHC Dipp Cu] + fragment coordinates one of the trigonal bases of the prism in an h 3 -fashion with Ge-Cu distances known for analogous complexes.…”

1,2‐Carbagerma‐closo‐dodecaborate as a Germanium Ligand in Coordination Chemistry – Synthesis, Structure and Reactivity

“…The Ge-C and Ge-B interatomic distances of 2.19-2.22 Å in the molecular structure of C are slightly shorter than the values of 2.22-2.28 Å found in crystal structures of small neutral closo-carbagermaboranes, 1-Ge-2,4-(SiMe 3 ) 2 -2,4-C 2 B 4 H 4 and 1-Ge-2,3-(SiMe 3 ) 2 -5-GeCl 3 -2,3-C 2 B 4 H 3 . [14] The similar Ge-C and Ge-B bond lengths determined indicate the possibility of cage disorder in the crystal, which results in difficulties in distinguishing between the CH and BH vertices. [15] The cage ordering found in the crystal of 1 may be attributed to interactions between the acidic N-H proton in the cation and the B7-B11-B12 triangular face in C. The three N-H···B distances are 2.62, 2.63 and 2.74 Å, where the N-H bond length is normalised at 1.009 Å.…”

Recent Advances in the Chemistry of Carboranes and Metallacarboranes

“…In addition, naphthalene also has a tendency to cocrystallize with any product or to substitute for a terminal B-H hydrogen, which often interferes with the reactivity of these dianionic ligands. The subsequent metalations of these ligands, in the conventional synthetic procedure, shown in Scheme 2, produce metallacarboranes of different geometries depending on the ratios of reactants involved [22][23][24][25][26][27][28][29][30][31]. The structures of the representive compounds are depicted in Figs.…”