Triphospha-Dewar-benzenes

The reaction of triphospha-Dewar-benzene 654 with tri-/-butylazete 627 resulted in a mixture of two adducts 655 and 656 in a 2 1 ratio (Equation 250) <1997JOM(529)215>. 

Free 1,2,5-triphospha Dewar benzene derivative 95 is formed in two steps from 3 mol of 44a by oxidative decomplexation of the triphosphacyclohexa-l,4-diyl-2,5-diene ligand of the Hf complex 96 <1997CB1491>. An organometallic [2+1+1] cycloaddition reaction between the phosphinidene complex 97, 44a, and a coordinated CO gives access to the 1,2-diphosphacyclobutenone complex 98 (Scheme 31) <1998CEJ1917>. 

Hafnium complex 83 in the presence of hexachloroethane as mild chlorinating agent afforded a new triphospha Dewar benzene 84 in 49% yield as a pale-yellow powder (Equation 20) <1997CB1491>. 

A study of the reactivity of the carbonyl-functional phospha-alkenes (305) has also been reported. The triphospha-Dewar-benzene (306) has been shown to undergo cycloaddition reactions with alkynes to form the triphosphabishomo-prismane system (307). Cycloaddition of t-butylphospha-ethyne to the phosphatriafulvene (308) results in the formation of a single isomer of the diphosphaisobenzene (309), having an allene system within the ring. This... 

The synthesis of tri-/-butyl-lP,32, 5A -triphosphinine arose from studies of the behavior of t-butylphosphaethyne (206) in the coordination sphere of transition metals. The first indication of the transition metal template catalyzed trimerization of (206) was the isolation of the vanadium-complexed 1,3,5-triphospha-Dewar benzene (207) <87AG(E)908>. The formation of the tetra-phosphabarrelene complexed to zirconium (208) implied the intermediate formation of the com-plexed tri-(-butyltriphosphinine derivative. The free barrelene could be obtained by oxidative decomplexation using C2CI6 <95AG(E)8i>. 

Scheme 6-17 Trapping reactions of triphospha-Dewar-benzenes with tert-butylphosphaacetylene novel tetraphosphatetracycUc systems. DMSO, dimethyl sulfoxide.

Cyclotrimerization has been achieved with a variety of metals. The products may contain the trimer as a flat 1,3,5-triphospha-benzene unit (63), or as a folded Dewar-benzene type ligand (64). Recently, the pentamerization of a phosphaaUcyne has also been reported. ... 

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