Phosphine complexes diboranes

Synthesis of pinacol arylboronates 190 200 via cross-coupling reaction of bis(pinacolato)diborane(4) with chloroarenes catalyzed by palladium(O)-tricyclohexyl-phosphine complexes has been demonstrated by Ishiyama et al. (Scheme 31).115... 

The complexes of boranes and boron trihalides with simple phosphorus compounds have been extensively investigated, possibly because of the presence of B- P coupling. Reaction of phosphine with diborane gave the monomeric complex H3P.BH3 with a B signal - -60 8 p.p.m. [from (MeO)3B] which was a quartet of doublets with B- P coupling of 27 c./sec. and the B- H coupling of 103... 

Methods of preparation of phosphine boranes include the reaction of phosphines with diborane (9.7), the addition of boron trihalides to phosphines (9.8) and the action of heat on certain arylphos-phonium borohydride salts (9.9). Phosphines and phosphites rupture trialkylamine borane complexes, replacing B-N with B-P. 

Mdssbauer spectra of bonding and structure in, 15 184-187 reactions with diborane, 16 213 stabilization of, 5 17, 18-19 cyanates, 17 297, 298 cyanide complexes of, 8 143-144 cyclometallated bipyridine complex, 30 76 diazene complexes, 27 231-232 dinitrogen complexes, 27 215, 217 diphosphine complexes of, 14 208-219 dithiocarbamates, 23 253-254 -1,2-dithiolene complexes, 22 323-327 hydrogen bonding, 22 327 halide complexes with phosphine, etc., 6 25 hexaflouride, structure, 27 104 hydride complexes, 20 235, 248-281, see also Transition metal-hydride complexes... 

The reaction of Os3(CO)i2 with H2 at 110°C. produces a reactive, unsaturated hydrido cluster Os3(/u.-H)2(CO)io. This dark purple complex is analogous to diborane and has the two hydrides bridging a very short Os s bond. It can add phosphines, phosphites, arsines, pyridine, and isocyanides to form Os3H2(CO)ioL (Scheme 25). The hydrido cluster adds alkenes and alkynes. Initially, an addition complex with a r-bonded alkene or alkyne is formed. Hydride addition to the unsaturated ligand follows. 

Conditions for the successful synthesis of full-shell clusters are first, the possibility of unhindered collisions of the metal atoms, and second, the prevention of a local ligand excess, leading to smaller clusters and complexes. The only method of fulfilling these conditions hitherto described is the use of diborane(6) as a reducing agent for metal halides and additionally as a Lewis acid to bind phosphine to such an extent that only very small amounts of free ligand molecules are present in solution. 

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