Metal-boron interactions

Tris(acetonitrile)tricarbonylchromium and tris(acetonitrile)tricarbonyl-tungsten react with tris(dimethylamino)borane to give yellow, readily sublimable crystalline products of the type [(CH3)2N]3BM(CO)3. On the basis of their 11B nmr spectrum, -coordination of the aminoborane with a relatively strong, metal-boron interaction is suggested.8,9... 

This effect is due to strong metal-boron interactions leading to an increased coordination number of the B atoms and, additionally, to a much better electronic shielding of the B nuclei. 

Detailed studies have been carried out with metal-boron (Ni-B, Pd-B, Pt-B) and metal-phosphorous (Ni-P, Pd-P) films prepared by radiofrequency sputtering269-272. Pt hardly interacts with boron and shows the low selectivity of the pure metal269. Interaction between Ni or Pd and the metalloids results in a change in the electron density of... 

RB —> TM o-bonded model when R is a good 71-donor up to a strong TM —> BR 71-back donation when R is a weaker 71-donor.132 134 However, the most recent studies made the point that the sum of the covalent interactions gives a bond order less than unity, and argued the case for a mainly ionic transition metal-boron bond.133 135... 

The crystallographically determined structure of 15 confirms the presence of a butterfly arrangement of iron atoms within which the boron atom resides in contact with all four metal atoms [Fe—B = 2.044(6), 2.047(6), 1.966(6), and 1.974(6) A] and 0.31 A above the Fe —Fe vector the internal dihedral angle of the Fe4 butterfly is 114.0°. These parameters are compared in Table II with those of related clusters. Compound 15 was first isolated as a product from the reaction of Fe2(CO)6B2H6 with Fe2(CO)9 (60), and evidence for increased iron-boron interaction is observed in a dramatic change in nB-NMR spectral shift (8) from S — 24.2 to +116.0. 

The conjugate base of a cluster generated by deprotonation (see Section 5.1) is a Lewis base. Any metal-metal, metal boron, or boron boron bond is a potential Lewis base. The former have considerable nucleophilic character if anionic and effectively interact with electrophiles more complex than the proton. As the site of basicity is associated with framework bonding, this reaction type results in cluster building, for... 

In addition to the rj1, q2 and r 3 covalent transition metal tetrahydrobo-rates, another type of complexes exist where the interaction between M+ and BH4- is mainly electrostatic. These compounds which are quite common are defined as ionic tetrahydroborate complexes. They are characterised by the non-coordination of the tetrahydroborate and consequently by a long metal-boron distance. Several compounds of this class have been wrongly classified as monodentate covalent complexes. 

Boron atoms in transition metal clusters Denuding the boron atom of B-H interactions in transition metal boron clusters Transition metal boride clusters at the molecular level Recent advances in the chemistry of carborane metal complexes incorporating d and /block elements The interplay of alkylidyne and carbaborane ligands at metal centres. I. Synthesis of electronically unsaturated mixed-metal complexes. II. Proton-mediated reactions... 

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