Review: Chemistry of the phosphinophosphinidene ^tBu₂PP, a novel π‐electron ligand

Abstract

In reactions with transition metal compounds, tBu2PPP(X)tBu2 (X = Br, Me) acts mainly as a precursor of the tBu2PP ligand, whereas tBu(Me3Si)PPP(Me)tBu2 acts as a precursor of the (Me3Si)PPtBu ligand. Up to now, only Pt(0) d10 ML2 metal centres were found to be able to stabilize the tBu2PP group in ‘pure form’ by means of η2‐coordination (side on). Several compounds of the [{η2 − tBu2PP}Pt(PR3)2] type were sufficiently stable to be isolated and characterized; however, not all of them gave single crystals suitable for X‐ray structure determinations. The X‐ray structures of these compounds and of [{µ − (1,2:2 − η − tBu2PP)Pt(PR3)2} {M(CO)5}] strongly suggest the ethene‐like form of 1,1‐di‐tert‐butyldiphosphene in these complexes. Such a form is also in agreement with RI DFT calculations with SVP basis for free tBu2PP. However, in trapping experiments with cyclic olefins and cyclic dienes tBu2PP exhibits, to some extent, electrophilic ‘singlet carbene’ properties. Copyright © 2002 John Wiley & Sons, Ltd.

Terminal, Anionic Carbide, Nitride, and Phosphide Transition‐Metal Complexes as Synthetic Entries to Low‐Coordinate Phosphorus Derivatives

“…[74][75][76][77] The tertbutyl substituted variant, tBu 2 PP, is known in complexes to electronically mimic olefins and in trapping experiments to have singlet phosphinidene character. [78] Singlet phosphinidenes are being sought, and the phosphino substituent has been proposed as one of the most viable for their stabilization. [79] Recently the terminally bonded phosphinophosphinidene complex [(h 1 -PPtBu 2 ){Cp 2 Zr(PPhMe 2 )}] was reported as the product of reaction between zirconocene dichloride and the reagent tBu 2 P-P(SiMe 3 )Li in the presence of excess [80] The reagent tBu 2 P-P(SiMe 3 )Li joins the tBu 2 P-P= P(X)tBu 2 (X = Br or Me) family as agents effective for the delivery of the PPtBu 2 unit to metal centers, in what has been termed "phosphinophosphinidene transfer".…”

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

“…[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.…”

“…[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 + [PNb(N[Np]Ar) 3 ] À (Np = neopentyl, Ar = 3,5-Me 2 C 6 H 3 ) that permits assembly [8] of R 2 PP ligands directly within the metal's protective coordination sphere.…”

Synthesis and Properties of Di-isopropylamino Derivatives of Diphosphanes and Triphosphanes: The X-Ray Structure of ( i Pr2N)2P–P(SiMe3)2

“…From the reaction of t Bu 2 P-P(SiMe 3 )Li with Cp 2 ZrCl 2 , we obtained the complex [µ-(1,2:2-η-t Bu 2 P=P){Zr(Cl)Cp 2 } 2 ] containing both a side-on and a terminally bonded t Bu 2 P-P ligand with two zirconium metal centers. In the presence of PPhMe 2 , this reaction yields [(η 1 − t Bu 2 P-P)Zr(PPhMe 2 )Cp 2 ]-a complex with terminally bonded t Bu 2 P-P. 3 Moreover we have found that t Bu 2 P-PLi-P t Bu 2 reacts with [(Et 3 P) 2 (M = Ni, Pd). 4 We intended to expand our studies on other lithium derivatives of triphosphanes R 2 P-PLi-PR 2 (R = t Bu).…”