Borane ligand functionality

This paper reviews the chemistry of metalloborane derivatives that contain borane or heteroatom borane groups which function as monohapto ligands. These compounds can be divided into three classes according to the number of electrons formally donated by the borane ligand to the metal. The electron pair acceptor class, represented by the compound Na[(OC)5Mn BHg], has received little attention thus far. The one-electron donor class, exemplified by the complex, l,2-(CH3)2-3- (C5H5)Fe(CO)2]-BioC2Ho, has a rich chemistry of metal-carbon and metal-boron derivatives. The third class includes two-electron donor derivatives that are represented by the compound (CHs)f,N[7,8-BoHioCHP - CrfCO),]. 

It is now apparent that there are as many diverse structural types in this area as there are in the more established field of organo-transition metal chemistry. There are now many known examples where the borane or hetroatom borane moiety functions as a mono-, di-, tri-, tetra- or penta-hapto ligand. This paper is limited to borane and heteroatom borane groups which function as monohapto ligands. 

Thus far we have seen that Schiff base ligands tend to promote six-coordination, but an unusual reaction has been found to occur between TiCl2(salen) and borohydride. No reduction at titanium is seen, but rather, addition of BtLr to the imino function of the ligand occurs to give a dimeric seven-coordinate titanium(IV) compound, (24), containing amine-boranes as... 

Bis(phosphoranimine) ligands, chromium complexes, 5, 359 Bis(pinacolato)diboranes activated alkene additions, 10, 731—732 for alkyl group functionalization, 10, 110 alkyne additions, 10, 728 allene additions, 10, 730 carbenoid additions, 10, 733 diazoalkane additions, 10, 733 imine additions, 10, 733 methylenecyclopropane additions, 10, 733 Bisporphyrins, in organometallic synthesis, 1, 71 Bis(pyrazol-l-yl)borane acetyl complexes, with iron, 6, 88 Bis(pyrazolyl)borates, in platinum(II) complexes, 8, 503 Bispyrazolyl-methane rhodium complex, preparation, 7, 185 Bis(pyrazolyl)methanes, in platinum(II) complexes, 8, 503 Bis(3-pyrazolyl)nickel complexes, preparation, 8, 80-81 Bis(2-pyridyl)amines... 

Piotrowicz, S. R., Harvey, G. R., Boran, D. A., Weisel, C. P., and Springer-Young, M. (1984). Cadmium, copper, and zinc interactions with marine humus as a function of ligand structure. Mar. Chem., 14, 333-346. 

---