Synthesis, Reactivity, and Structural Transformation of Mono- and Binuclear Carboranylamidinate-Based 3d Metal Complexes and Metallacarborane Derivatives

Abstract

A series of carboranylamidinate-based 3d metal complexes are reported. Treatments of 3d metal dichlorides (CoCl2, NiCl2(DME), CuCl2) with the lithium salts of carboranylamidines (Cab N H) generate the mononuclear C,N-coordinated complexes [(RNC(closo-1,2-C2B10H10)(NHR)]2M (1–6; M  Co, Ni, Cu; R = iPr, Cy) in moderate yields, respectively. These complexes have similar structures in the solid state, in which the metal atom is coordinated to two nitrogen atoms and bonded to two cage carbon atoms in a distorted-tetrahedral geometry. As a noninnocent ligand, Cab N H can be modified to produce carboranylamidinate thiol (Cab N SH) and nido derivatives Dcab N H (9, 10), respectively. Reaction of cupric acetate with 1 equiv of Cab N SH gave the binuclear complexes {[RNC(closo-1,2-C2B10H10)(NHR)]SCu}2 (R = iPr (7), Cy (8)) in 66 and 63% yields, respectively. The structure of 7 shows the formation of a Cu–Cu bond, and the geometry of the Cu2S2 core is planar. The zwitterionic nickel dicarbollide complexes (Dcab N )Ni(PPh3)Cl (11, 12) were prepared by reactions of the lithium salts of Dcab N H (9, 10) with NiCl2(PPh3)2 in THF. All complexes were characterized by elemental analysis and IR and NMR spectroscopy. The structures of 1, 3–5, 7, and 9–11 were further confirmed by single-crystal X-ray diffraction.

Carboranylamidinates

“…The molecular structures of 14a , 15a , 15b , and 16a were unambiguously determined by X‐ray diffraction. All four complexes were found to have similar structures in the solid state, in which the metal atom is coordinated to two nitrogen atoms and bonded to two cage carbon atoms in a distorted‐tetrahedral arrangement 20…”

“…According to an X‐ray diffraction study of 25a the products are dinuclear Cu I complexes comprising a Cu–Cu bond and two sulfur bridges. The intramolecular distance between the two copper atoms is 2.549(11) Å 20…”

“…Yet another exciting new possibility, i.e. the generation of nido ‐derivatives, has been outlined in a recent publication by Jin et al20 It was discovered that upon heating in neat methanol, the carboranylamidines 4a and 4b underwent facile degradation to selectively remove one boron atom and generate the new nido ‐ligands 28a and 28b , respectively (Scheme ). The products were recrystallized from a CH 2 Cl 2 /hexane mixture as colorless crystals in yields of 82 % and 80 %, respectively.…”

“…An X‐ray crystal structure determination of 29a confirmed that the nickel atom is η 5 ‐coordinated to the dicarbollide ligand, and the arrangement at the metal atom is that of a two‐legged piano stool with the nickel atom coordinated by the η 5 ‐C 2 B 3 , chlorine, and phosphorus atoms. The molecule is comprised of a nickel(II) phosphine unit, which is bonded to a C 2 B 3 face of a novel dicarbollylamidinate ligand 20…”

Reversible Photothermal Isomerization of Carborane‐Fused Azaborole to Borirane: Synthesis and Reactivity of Carbene‐Stabilized Carborane‐Fused Borirane

“…TheC u1-C1 distance of 1.900(4) compares to that of 1.935(8) in [CuMe 2 ] À , [18] 2.036 (4) in {1-C[NH( i Pr)]=N-( i Pr)-o-C 2 B 10 H 10 } 2 Cu, [19] and 1.920(2) in 1,1':2,2'-[Cu-(toluene)] 2 (C 2 B 10 H 10 ) 2 . [20] Theprevious result indicates that the B À C(carbene) bond in 2 is very strong and that CuCl cannot remove the carbene from the Bc enter.W ew ondered if aB rønsted acid could react with the coordinated carbene in 2.T reatment of 2 with 1equiv of HCl in ad ioxane solution afforded monochloroborane carbene adduct 4 with the cleavage of one BÀ C(cage) bond.…”