Diorganophosphanylphosphinidenes as Complexed Ligands: Synthesis via an Anionic Terminal Phosphide of Niobium

Abstract

Compounds with multiple bonding between adjacent phosphorus atoms are of interest both as free molecules and as complexed ligands.[1] As one proceeds formally from triply bonded P 2 , via intermediate states of reduction, all the way to two equivalents of PH 3 , several interesting PÀP bonded systems (and isomers thereof) may be considered. Phosphanylphosphinidene, PPH 2 , a neutral isomer of HP = PH (diphosphene) is an intriguing parent species in this regard and its geometric and electronic structure have been the subject of several theoretical investigations. [2][3][4][5] Organic derivatives of phosphanylphosphinidene have generated interest as complex ligands capable of h 2 -binding to transition-metal centers.[2] A prototypical example is the structurally characterized complex [(h 2 -tBu 2 PP)Pt(PPh 3 ) 2 ].[6]That organic phosphanylphosphinidenes, exemplified by tBu 2 PP, are novel p-electron ligands in a manner reminiscent of alkenes or alkynes is recognized and was the subject of a recent review article. [7] Fritz and co-workers have pioneered the synthesis of such derivatives by utilization of the "phosphanylphosphinidene transfer" reagent, tBu 2 PP = PX(tBu 2 ) (X = Me or Br), [6,7] which represented, until now, the only synthetic entry to complexes of phosphanylphosphinidenes.Herein we report an alternative synthetic entry to complexed organic derivatives of phosphanylphosphinidene. Our method takes advantage of our ability to synthesize an unprecedented anionic, niobium, terminal phosphide complex, Na (1) [9] presented us with a unique entry into low-coordinate[*] J.

A Terminal Nitride‐to‐Phosphide Conversion Sequence Followed by Tungsten Phosphide Functionalization Using a Diphenylphosphenium Synthon

“…Previously reported routes to terminal phosphide complexes include metathesis of phosphaalkynes with [W 2 (O t Bu) 6 ],25–27 ancillary‐ligand exchange at an existing terminal metal phosphide moiety,14 activation of P 4 to yield complexed phosphide as a terminal ligand either directly or via intermediate bimetallic complexes containing μ‐P 1 or μ:η 2 ,η 2 ‐P 2 ligands,2, 5, 20, 21, 28, 29 and by treating [(N 3 N)WCl] (N 3 N=[(Me 3 SiNCH 2 CH 2 ) 3 N] 3− ) with either LiP(H)Ph (2 equiv) or LiP(SiMe 3 ) 2 (2 equiv) 22. 30 Complete intermetal exchange of a phosphide ligand represents a new addition to this list.…”

“…Formation of 7 ‐OTf likely proceeds by the reaction of weakly nucleophilic 5 with an electrophilic phosphenium species generated by the reaction of Me 3 SiOTf and PClPh 2 38. The synthesis of 7 ‐OTf through Me 3 SiCl elimination closely relates to the synthesis of the Group 5 η 2 ‐phosphanylphosphinidene complexes [(η 2 ‐R 2 PP)Nb{N(Np)Ar} 3 ] ( 8 , R= t Bu; 9 , R=Ph),2, 39 and complements the work of Fritz and co‐workers with their synthesis of Group 10 η 2 ‐phosphanylphosphinidene complexes by t Bu 2 PP group transfer 40. 41…”

Selective [3+1] Fragmentations of P4 by “P” Transfer from a Lewis Acid Stabilized [RP4]− Butterfly Anion

“…[23] Only the major form of the disordered tert-butyl group is shown. Selected bond lengths []and torsion angles [ o ]: P1-P2/P3 2.2096(5)/2.2139(5), P2-P3 2.1755 (6), P1-C1 1.8766 (14), P2-C22 1.9210 (16), P3-C19 1.9149-(16), C23-C24 1.332 (2), C21-C20 1.538 (2);P1-P2-P3-C19 101.35 (6).…”

“…[2] Increased control is possible with as tepwise strategy,i nw hich P 4 is converted into an "activated" product to enable subsequent selective functionalization. Exemplary are the P 4 -derived R 2 P 5 + cages A reported by Weigand and co-workers (Scheme 1a), [3] thec arbene-stabilized diphosphene B reported by Bertrand and co-workers, [4] thet ransition-metal-activated m,h 1:1 -P 4 -coordinated diruthenium dication C of Stoppioni and co-workers, [5] the terminal niobium phosphide D reported by Figueroa and Cummins, [6] and the bimetallic,b utterflytype bicyclo [1.1.0]tetraphosphabutanes E reported by the research groups of Scheer (M = Fe), [7] Scherer (M = Fe), [8] and Wolf (M = Ni). [9][10][11] We discovered that the nucleophilic addition of sterically encumbered aryl lithium reagents to P 4 in the presence of triarylborane Lewis acids (LAs) grants access to stable Li + salts 1 of the elusive [RP 4 ] À butterfly anion (Scheme 1b).…”

Phosphines and Related Tervalent Phosphorus Systems

“…751 Among new terminal phosphinidene metal complexes described are those involving titanium, 752 vanadium, 753 chromium, 754 cobalt, rhodium and iridium, 755,756 and iron, ruthenium and osmium. 757,758 Also reported are niobium complexes of diorganophosphinophosphinidenes, R 2 P-P: , 759 and a molybdenum complex in which an arylphosphinidene acts as a ten-electron donor. 760 The stabilisation of phosphenium cations, R 2 P: 1 , and other low coordination number phosphorus(III) species, by coordination to phosphorus has continued to be an active topic.…”