Transition metal-boron bonds

Compounds containing transition metal-boron bonds are produced by the reaction of 2-CIB5H8 with NaM(CO)s when M = Re and Mn 190>. These compounds are formulated as 2-[(CO)5M]BsH8 on the basis of infra-red and nmr studies 190>. 

The nature of the transition metal-boron bond in [LXM = B-R] is obviously strongly influenced by the boron bonded substituent R. Descriptions based on calculations range from an almost purely... 

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... 

Hae] Haegg, G., Kiessling, R., Distribution Equilibria in Some Ternary Systems Mel-Me2-B and the Relative Strength of the Transition-Metal-Boron Bond , J. Inst. Met., 81, 57-60 (1952) (Phase Relations, Experimental, 6)... 

The efficiency of transmetalation from boron to palladium in the catalytic 1,4-addition of aryl or 1-alkenylboronic acids to enones encouraged us to extend the protocol to the addition of aryl- and 1-alkenylboronic adds to aldehydes in an aqueous solution (Eq. 4). The insertion of carbonyl groups into transition metal-carbon bonds has not received much attention, but the catalytic use of transition metals may allow such addition of various organometallics which are inert without a catalyst, the asymmetric addition using a chiral phosphine complex, or the reaction in an aqueous phase. 

The chemistry of metalloborane compounds is vast, although most are not prepared by oxidative addition of the B—H bond to a metal complex neither do they contain metal-hydrogen bonds. The synthesis of metalloborane hydrides involves many routes, the mechanisms of which are obscure. Reactions between borohydrides and transition-metal complexes involve hydride transfer without the formation of a metal-boron bond (see 1.10.7). 

The same bases have produced the extensive variety of metal complexes with the transition metals, the amines and carbonyls serving as representative examples. Recently several transition metal complexes have also been shown to exhibit Lewis base properties to BF or BH with the formation of metal-boron bonds. The first example of this was SHRIVER s preparation of (CgHgJ WH BF which contains a tungsten-boron bond (1). The contains an unshared pair of electrons which are donated to the electron... 

Metallaborane and borylene complexes are related to some extent because both types possess direct metal-boron bonds however, the nature of these interactions is varied. In metallaborane clusters, the framework is made up by nonclassical, electron-deficient, multicenter two-electron bonds, while the borylene ligand (BR) is related to one or more transition metal centers by classicrJ, electron-precise, two-center two-electron (2c-2e) bonds [280 -283]. Since the discovery of various bridged and terminal borylene complexes by Braunschweig and Aldrige, the chemistry of this subarea of transition metal complexes of boron has received significant attention from both structure/bonding and... 

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