Tetrakis diborons, reactions

A stoichiometric reaction of tetrakis(triphenylphosphine)platinum(0) with bis(pinacolato)diboron gives cis-diborylplatinum(n) complex in high yield (Scheme 3).38 The diborylplatinum complex then reacts with an alkyne, giving m-diboration product.40,41 These results indicate that the diboration proceeds through the general mechanism shown in Scheme 1 (E1 = E2 = Bpin), which involves the formation of diborylplatinum(n), insertion of an alkyne into the B-Pt bond, and reductive elimination. 

The reaction of the porphyrin ligand, TTP (tetra-p-tolylporphyrin) with BF3-OEt2 leads to the oxide fluoride complex, B2OF2(TTP) and the structure has been established using H, 13C, nB and 19F NMR spectroscopy and FAB mass spectrometry [9], The structure contains a B—O—B bridge in which each boron is bonded to fluorine and to a nitrogen of TTP. The structure of the diboron complex was confirmed by an X-ray crystal structure determination of the tetrakis-(p-chlorophenyl)porphyrin (TpCiPP) derivative. 

A fairly extensive metathetical chemistry of diboron compounds has been developed which provides the means for synthesis of specific derivatives from more commonly available starting materials such as tetrachloro-diborane(4) and the tetrakis(dialkylamino)diboron derivatives. Thus, reactions involving hydrolysis, aminolysis, alcoholysis, transamination, etc., are available for interconversions of diboron compounds by pathways analogous to those known in monoboron chemistry. Examples of such reactions include the following ... 

Reactions of this type are somewhat less satisfactory for preparation of mixed diboron derivatives containing boron-carbon bonds. Thus, while tetrakis(dimethylamino)diborane(4) is readily hydrolyzed to tetrahydroxy-diborane(4) in aqueous acid, l,2-bis(dimethylamino)-l,2-diethylborane(4) reacts with formation of hydrogen and cleavage of the boron-boron bond 14). Reaction of the dibutyl analog with a twofold excess of water gave the dimethylamine adduct of the boroxole... 

Relatively little is known of the reactions of diboron tetrahalides with aromatics apart from a study by Fox and Wartik (39) of the interaction of B2CI4 with benzene and naphthalene. With the former, dichlorophenyl-borane was obtained in high yield after long reaction times. With naphthalene, immediate formation of a loose complex was suggested by the formation of a bright yellow color. The reagents could be recovered from this complex by distillation, but after about 2 weeks at room temperature a product formulated as l,2,3,4-tetrakis(dichloroboryl)tetralin (IX) was obtained. 

This method is an adaption of the U. S. Borax Research group s procedure that Illustrates a practical and efficient method for the synthesis of tetra(alkoxo)diborons. Several (alkoxo)diborons, such as tetra(methoxo)-,3 bis(catecholato)-, and bis(pinacolato)diboron (1). are synthesized from tetrakis(dimethylamino)diboron. The diborons are excellent reagents for the synthesis of various organoboronic esters via the transition metal-catalyzed addition and cross-coupling reactions. ... 

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