PH3 as a Phosphorus Source for Phosphinidene–Carbene Adducts and Phosphinidene–Transition Metal Complexes

Abstract

The parent phosphinidene-carbene adduct NHC=PH is a versatile synthon in main group chemistry and can act as an electronically flexible ligand for transition metals. Previously, it could only be synthesized with sterically demanding N-aryl substituents. This paper describes simple methods for the synthesis of NHC=PH adducts with varying steric demand from elemental phosphorus or easily accessible phosphorus sources. Furthermore, the reactivity of NHCs towards PH3 was investigated. It was shown how a NHC inserts into the P-H bond of PH3, which opens up a route to NHC=PH adducts from an imidazolium salt and PH3. The adducts were used in the simple syntheses of bis(phosphinidene) mercury(<small>II</small>) and group 6 pentacarbonyl parent phosphinidene complexes. Their electronic and structural properties were investigated to elucidate the influence of the NHC on the phosphinidene and identify possible applications.

N‐Heterocyclic Carbene–Phosphinidene Adducts: Synthesis, Properties, and Applications

“…NHC=PR carbonyl complexes 69 of the group 6 transition metals can also be prepared directly from the metal hexacarbonyls [M(CO) 6 ] (M = W, Mo, Cr) using UV light, as was shown by Bispinghoff and Grützmacher for 6· PH (Scheme ) . Using parent phosphinidene adduct 5· PH that bears the less hindered 1,3‐dimesitylimidazol‐2‐ylidene ( 5 ) even the bimetallic carbonyl complex could be detected.…”

“…Treatment of the N‐arylated imidazolium salt [ 6 ‐H][Cl] with Na(OCP) for 4 hours in refluxing THF afforded after work‐up 6· PH ( δ 31 P = –136.7) in 71 % yield (Scheme ) . Analogously, the parent phosphinidene adducts 7· PH (87 %; δ 31 P = –134.5) and 10· PH (34.5 %; δ 31 P = –127.2) were prepared (Scheme ), yet this method does not tolerate N‐alkylated imidazolium salts, such as [ 1 ‐H][Cl] and [ 3 ‐H][Cl] …”

“…[22] Analogously, the parent phosphinidene adducts 7·PH (87 %; δ 31 P = -134.5) [27] and 10·PH (34.5 %; δ 31 P = -127.2) [28] were prepared (Scheme 16), yet this method does not tolerate N-alkylated imidazolium salts, such as [1-H][Cl] and [3-H][Cl]. [37] Scheme 16. Synthesis of carbene-phosphinidene adducts by phosphide transfer reactions from Na(OCP).…”

“…[50] NHC=PR carbonyl complexes 69 of the group 6 transition metals can also be prepared directly from the metal hexacarbonyls [M(CO) 6 ] (M = W, Mo, Cr) using UV light, as was shown by Bispinghoff and Grützmacher for 6·PH (Scheme 45). [37] Using parent phosphinidene adduct 5·PH that bears the less hindered 1,3-dimesitylimidazol-2-ylidene (5) even the bimetallic carbonyl complex could be detected. Thus, addition of one equivalent of [W(CO) 5 (THF)] to 5·PH afforded monometallic 70, which upon addition of an excess of [W(CO) 5 (THF)] led to a mixture of 70 and bimetallic 71 that was spectroscopically characterized (Scheme 46).…”

Synthesis and Structures of RhI and IrI Complexes Supported by N‐Heterocyclic Carbene‐Phosphinidene Adducts

“…In addition to (NHC)PR (R = Ph or sterically bulky aryl group) adducts, parent phosphinidene adducts of the type (NHC)PH have been prepared by several groups. The groups of Grützmacher and von Hänisch isolated a series of octahedral metal(0) carbonyl complexes [{(IDipp)PH}M(CO) 5 ] (M = Cr, Mo, W) and [{(IMes)PH}W(CO) 5 ] . Bertrand et al developed a sterically encumbered N‐heterocyclic carbene supported parent phosphinidene adduct (IPr*)PH [IPr* = 1,3‐bis{2,6‐bis(diphenylmethyl)‐4‐methylphenyl}imidazolin‐2‐ylidene] from the reaction of Na(OCP) and the corresponding imidazolium salt .…”