Rhodium(I) Complexes of a PBP Ambiphilic Ligand: Evidence for a Metal→Borane Interaction

Quasi-Thermoneutral P → B Interactions within Di- and Tri-Phosphine Boranes

Spectroscopic, structural, and theoretical evidence is provided for both open (no intramolecular P --> B interaction) and closed (with intramolecular P --> B interaction) forms of the di- and tri-phosphine boranes [o-(iPr(2)P)C(6)H(4)](2)BPh (2) and [o-(iPr(2)P)C(6)H(4)](3)B (3).

Synthesis, structure and coordination of the ambiphilic ligand (2-picolyl)BCy2

The new pyridine-borane compound (2-picolyl)BCy2, readily prepared from 2-picolyllithium and ClBCy2, adopts a head-to-tail dimeric structure in the solid state as indicated by X-ray diffraction analysis and according to NMR and DFT studies, the dimeric form equilibrates in solution with a strained monomeric structure; the ambiphilic behavior of the new compound is illustrated by its bridging coordination to the (p-cymene)RuCl2 unit.

On the Versatile and Unusual Coordination Behavior of Ambiphilic Ligands o-R2P(Ph)BR‘2

Monophosphine-boranes were shown to behave as bidentate ambiphilic ligands, whose structural versatility has been illustrated by the preparation of PdII and AuI complexes featuring unusual P --> M-Cl --> B and P --> M --> B interactions, respectively.

Transition-Metal Complexes of Boron—New Insights and Novel Coordination Modes

Since the publication of the last review in 1998, the transition-metal chemistry of boron has continued to raise unceasing interest. Boryl complexes, representing the most extensive subclass, have remained a focus of intense research, particularly for their implication in the metal-mediated functionalization of organic substrates. Absolute novelties such as borane complexes and terminal borylene complexes have been structurally authenticated. Upon further elaboration of these compounds, the known coordination modes of boron-based ligands have grown considerably. Combined structural and theoretical investigations have contributed to elucidate the fundamental electronic characteristics of the transition-metal-boron bond and are leading to applications of these compounds. The most useful synthetic strategies for the generation of transition-metal-boron bonds are highlighted here, and the most recent and intriguing compounds that have been reported are outlined and discussed.

Reactivity of the Metal→BX3 Dative σ-Bond: 1,2-Addition Reactions of the Fe→BX3 Moiety of the Ferraboratrane Complex [κ4-B(mimBut)3]Fe(CO)2

The ferraboratrane [kappa4-B(mim(Bu)t)3]Fe(CO)2 (mim(Bu)t = 2-mercapto-1-tert-butylimidazolyl), the first example of a complex which possesses a retrodative (i.e., metal-to-ligand) Fe-->B bond, is obtained via reaction of the tris(2-mercapto-1-tert-butylimidazolyl)hydroborato complex [Tm(Bu)t]FeCl with LiCH2SiMe3 followed by treatment with CO. Significantly, [kappa4-B(mim(Bu)t)3]Fe(CO)2 exhibits novel reactivity towards a variety of reagents that results in eradication of the Fe-->B bond via a formal 1,2-addition process and the formation of B-functionalized tris(mercaptoimidazolyl)borate derivatives, [XTm(Bu)t]FeY.

Palladium complexes with Pd→B dative bonds: Analysis of the bonding in the palladaboratrane compound [κ4-B(mimBut)3]Pd(PMe3)

The dinuclear complex {[mu-kappa(1),kappa(3)-B(mim(Bu(t)))(3)]Pd}(2), which features a Pd-->B dative bond, may be obtained by the reaction of [Tm(Bu(t))]K with Pd(OAc)(2); treatment of {[mu-kappa(1),kappa(3)-B(mim(Bu(t)))(3)]Pd}(2) with PMe(3) affords the mononuclear boratrane derivative [kappa(4)-B(mim(Bu(t)))(3)]Pd(PMe(3)), for which a molecular orbital analysis indicates that the palladium center possesses a d(8) configuration.