Metallacycle Transfer Routes to Main-Group Phosphacycles

Abstract

The employment of phosphazirconacycles in metallacycle transfer reactions is a facile method for the synthesis of main-group phosphacycles. Reactions of Cp2Zr(PPh)3 (1), Cp2Zr(P(R*)C(Ph)CPh) (2), and Cp2Zr(P(Mes)P(Mes)C(Ph)CPh) (3) with various main-group dihalides results in cleavage of TM−MG bonds and formation of new MG−MG bonds. Triphosphanato complex 1 reacts with PhPCl2 or tBu2SnCl2 to yield (PPh)4 (4) and (t-Bu)2Sn(PPh)3 (7), respectively. Reaction of phosphametallacyclobutene 2 with PhPCl2 results in the formation of the unsymmetrically substituted 1,2-diphosphetene P(Ph)P(R*)C(Ph)CPh (5), while reaction with PhBCl2 yields PH(C6H2-(2-CH2C(CH3)2)-4,6-t-Bu2)B(Ph)CPhCPh (8), the product of ring expansion via CH activation. Phosphametallacyclopentene 3 reacts with PhPCl2 to furnish the unsymmetrically substituted 1,2,3-triphospholene P(Ph)P(Mes)P(Mes)C(Ph)CPh (6). Advantages to such metallacycle transfer reactions include (i) facile accessibility of main-group derivatives where conventional syntheses are laborious, tedious, and/or fraught with safety issues, (ii) selective control over molecular fragments, and (iii) new routes to novel main-group compounds.

Phosphaborenes: Accessible Reagents for the Synthesis of C−C/P−B Isosteres

“…Resonances in the 11 BNMR spectra (3a: d = 42.4 ppm; 3b: d = 44.1 ppm) are typical of those observed for base-coordinated phosphaborenes. [3,4] Single-crystal X-ray crystallographic studies of 3a and 3b ( Figure 1) confirmed the coordination of DMAP or ImMe 4 to the boron center and revealed short P = Bbond distances (3a: 1.8211 (16) ; 3b:1 .8309(16) )a nd small C-P-B bond angles,e ntirely consistent with previously reported basestabilized phosphaborenes.T he dative NÀBa nd CÀBb onds from the DMAP and ImMe 4 ligands (3a:1 .5685 (19); 3b: 1.609(2) )a re longer than in B and C,t hus reflecting the reduced Lewis acidity of the amino-substituted boron center.…”

“…Such as pecies was previously inferred, but not observed, as an unstable intermediate in the formation of ac yclic phosphinoborane from az irconacycle transfer reaction with PhBCl 2 . [16] The1 ,2-phosphaborete ring of 5 avoids planarity-and the antiaromatic 4p electron system that would result-by pyramidalization at the phosphorus center (sum of angles:3 078 8). Doubtless also contributing to the pyramidalization of the phosphorus center is the presence of aB ÀN pbond, indicated by the short BÀNb ond distance (1.3929- (19) ;F igure 2).…”

Syntheses and structures of [Me2Si{As(PtBu)3}2] and [(CyP)3SiMe2] (Cy=cyclohexyl, C6H11)

“…The structure of 4 is that of a four-membered, P 3 Si heterocycle of crystallographic Cs symmetry (Fig. 2), and is closely related to the previously reported tin(IV) heterocycle [( t BuP) 3 Sn t Bu 2 ] [12].…”

“…As in the structure of 3a, the P-Si [2.274(2) Å] and P-P [2.236(2) Å] bonds are as expected for single bonds [10]. Like [( t BuP) 3 Sn t Bu 2 ] [12] and [(RP) 3 As] À anions [2], the heterocyclic ring of 4 is puckered [dihedral angle of 134.7°at the P(1)Á Á ÁP(1A) vector].…”

Insertion Reactions of Neutral Phosphidozirconocene Complexes as a Convenient Entry into Frustrated Lewis Pair Territory

“…Zirconium phosphides display rich insertion chemistry; this reactivity can lead to useful synthetic applications, most notably the stoichiometric preparation of organophosphorus compounds or the catalytic hydrophosphination of olefins . Pioneering work by the groups of Issleib and Ellermann initiated early developments in this field, followed by extensive studies by the groups of Baker, Hey‐Hawkins,– Lappert and Stephan –. As a consequence of the considerable stock of knowledge gathered on zirconium phosphides prior to 2005, there have been comparatively few reports on new chemistry during the last decade, although the group of Waterman has made notable contributions on their application to dehydrocoupling reactions…”