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In a quest for efficient precursors for the synthesis of boratrane complexes of late transition metals, we have developed a useful synthetic method using [L′M(μ-Cl)Clx]2 as precursors (L′=η6-p-cymene, M=Ru, x=1; L′=COD, M=Rh, x=0 and L′=Cp*, M=Ir or Rh, x=1; COD=1,5-cyclooctadiene, Cp*=η5-C5Me5). For example, treatment of Na[(H3B)bbza] or Na[(H2B)mp2] (bbza=bis(benzothiazol-2-yl)amine; mp=2-mercaptopyridyl) with [L′M(μ-Cl)Clx]2 yielded [(η6-p-cymene)RuBH{(NCSC6H4)(NR)}2] (2; R=NCSC6H4), [{N(NCSC6H4)2}RhBH{(NCSC6H4)(NR)}2] (3; R=NCS-C6H4), [(η6-p-cymene)RuBH(L)2] (5; L=C5H4NS), and [Cp*MBH(L)2] (6 and 7; L=C5H4NS, M=Ir or Rh). In order to delineate the significance of the ligands, we studied the reactivity of [(COD)Rh(μ-Cl)]2 with Na[(H3B)bbza], which led to the formation of the isomeric agostic complexes [(η4-COD)Rh(μ-H)BHRh(C14H8N3S2)3], 4 a and 4 b, in parallel to the formation of 16-electron square-pyramidal rhodaboratrane complex 3. Compounds 4 a and 4 b show two different geometries, in which the Rh−B bonds are shorter than in the reported Rh agostic complexes. The new compounds have been characterized in solution by various spectroscopic analyses, and their structural arrangements have been unequivocally established by crystallographic analyses. DFT calculations provide useful insights regarding the stability of these metallaboratrane complexes as well as their M→B bonding interactions. [ABSTRACT FROM AUTHOR]

We report the synthesis and structural characterization of moderately air stable metal rich metallaboranes of iridium. Treatment of [Cp*IrCl 2 ] 2 with BH 3 ·thf at high temperature led to the isolation of a trimetallic [ nido -5-(Cp*Ir) 3 B 7 H 11 ], 1 . Compound 1 is isoelectronic and isostructural with decaborane-14 where three BH units in [B 10 H 14 ] have been replaced by Cp*Ir fragments. As far as we are aware, 1 is the first example of a iridadecaborane having three metals. In addition to the formation of 1 , a change in the reaction conditions enabled us to isolate a 7 sep [(Cp*Ir) 3 B 4 H 4 ], 2 . The geometry of 2 can be viewed as a condensed polyhedron composed of Ir 3 B 3 octahedron capped by a BH unit. All the compounds have been characterized by IR and 1 H, 11 B, and 13 C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. Quantum-chemical calculations by DFT methods for compounds 1 and 2 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO–LUMO gaps are consistent with the high stabilities of the iridium clusters compared to their known Rh and Co analogues. [ABSTRACT FROM AUTHOR]

Boron-heteroelement multiple bonding across Group 13-Group 16. • The boron-heteroelement multiple bonds are sparsely explored. • Hetero-element multiple bonding comprising boron and group 13–16 elements. • Various synthetic methodologies for the synthesis of B-E multiple bonded systems. • Experimental and where available, theoretical studies are discussed. Multiple bonding involving the heavier main-group elements has been of great interest for a long time. This interest stems from the structure-bonding-reactivity aspects of these unusual compounds. Despite many initial failures, success in this area was finally achieved by the discovery of new synthetic paradigms which involved the kinetic stabilization of these compounds. Among this family of compounds, compounds containing two different elements are still quite sparse. This review focuses on compounds involving a multiple bond between boron and another heteroelement. The various synthetic methods used to prepare such compounds, their spectroscopic features including NMR parameters and where available, single-crystal X-ray structural data and theoretical studies, are discussed. [ABSTRACT FROM AUTHOR]

Diborane(6), diborane(4) and diborene(2) complexes of various transition metals. • Diboranes are valuable compounds for numerous synthetic reactions. • The diborene(2) complexes having boron-boron double bond are sparsely explored unlike alkene complexes. • Diborane(4/6) and diborene(2) complexes stabilized in the coordination sphere of transition metals are reviewed here. • Various synthetic routes for the synthesis of diborane and diborene complexes are discussed. • Photophysical properties of diborene species have been also discussed here. Diborane(4) and diborane(6) molecules are demanding renewed interest due to their varied reactivity towards diverse substrates. The chemistry of molecules comprising electron-precise B-B bonds has witnessed swift developments in the recent years. In spite of the continuous interest and extensive efforts in the synthesis of diborane compounds, the formation of boron-boron bonds is still difficult and uncontrolled. On the other hand, the diborene molecules (R-B B-R′; R, R′ = H, phosphine, amine, NHC etc), are also of significant interest owing to their ability to regulate the property of biradicals by changing the substituents of the parent diborene(2), HB BH. In addition, transition metal diborene species exhibit fascinating photo-physical properties. In this review, we have delivered a background of B-B bond formation and a synopsis of the latest developments in the synthesis of boron-boron single and multiple bonds. The reactivity of diborane/diborene complexes towards various transition metals has also been discussed in detail. [ABSTRACT FROM AUTHOR]