closo-Monocarbaboranes as ligands for transition metals: synthesis and reactivity of exo-diphosphineplatinum-closo-monocarbaborane complexes; structure of [Pt{But 2P(CH2)2PBut 2}(closo-CB11H12)][CB11H12]

Blue Phosphorescent Zwitterionic Iridium(III) Complexes Featuring Weakly Coordinating nido-Carborane-Based Ligands

“…An additional but very weak resonance is observed for 2a – 2d , ∼2100 cm –1 , which is suggestive of a weak Ir−μ-H–B stretching band. Such M−μ-H–B interactions have been noted previously with carboranes. , In particular, Reed and Teixidor observed similar stretching frequencies in [CB 11 H 12 ] − - (∼2380 cm –1 ) and nido -carborane-based (2119–2077 cm –1 ) systems, respectively, and have also ascribed these bands to weak interactions of carboranyl B–H bonds with cationic metal centers. Hawthorne observed slightly lower B–H stretching frequencies (∼1965 cm –1 ) for a nido -carborane anion associated with Ir­(III) through two B−μ-H–Ir interactions .…”

“…A long Ir···B(11) distance of 2.528(6) Å is found, which is longer than the sum of the covalent radii of the two atoms (2.07 Å) based on literature values, suggesting no appreciable covalent metal–ligand bonding interaction. These distances are also systematically longer by ∼0.3 Å than those in Ir­(III)-based complexes in which B–H agostic interactions are normally invoked. , In addition, the Ir–H­(1A) bond distance (1.935(9) Å) also well exceeds the sum of the covalent radii (1.54 Å) of Ir­(III) and H atoms. The B(11)–H­(1A) bond distance of 1.007(2) Å is nearly identical to those of the other terminal B–H bonds on the boron cluster scaffold in 2a , suggesting that this bond (in addition to the analogous bonds in 2b – 2d ) is not strongly activated by the Ir­(III) center.…”

Silver Phosphanes Partnered with Carborane Monoanions: Synthesis, Structures and Use as Highly Active Lewis Acid Catalysts in a Hetero-Diels–Alder Reaction

“…[19±21] Given that only the antipodal [B (12)] and lower pentagonal belt [B(7)ÀB(11)] boron atoms appear significantly perturbed in the 11 B NMR spectrum on coordination of the {AgPPh 3 } fragment, we suggest a mechanism to explain the observed fluxionality that incorporates the metal phosphane precessing around the five triangular faces formed between B(7)ÀB (11) and B (12). This mechanism is similar to that previously observed for the movement of {Rh(cod)} [44] or {Pt(tBu 2 P(CH 2 ) 3 PtBu 2 )} [51] over the surface of [closo-CB 11 H 12 ] À . In the 31 P{ 1 H} NMR spectrum of 1, a peak centred at d 18.70 is observed as a pair of concentric doublets, due to 109 AgP and 107 AgP coupling, having an average value for J(AgP) average of 743 Hz.…”

Nonclassical Applications of closo-Carborane Anions: From Main Group Chemistry and Catalysis to Energy Storage

“…131 In the solid state, two cage B−H units interact with the metal center in an agostic "like" manner. Weller 27−32 and Spencer 33 binding mode in 74 conveys an extremely weak trans influence to the corresponding olefinic double bond, as the "double bond" is extremely elongated [1.451( 4) Å] to the point where a metallocyclopropane formalism better describes the system. This observation can be rationalized as the cluster being such a weak donor substituent that it is essentially not at all antibonding with respect to the trans-olefin, allowing for better d−π to π* overlap for backbonding.…”