N-Heterocyclic Carbene-Stabilized Germanium and Tin Analogues of Heavier Nitriles: Synthesis, Reactivity, and Catalytic Application

Abstract

The synthesis of stable heavier analogues of nitriles as monomeric tetrylene−phosphinidenes Mes TerEP(IDipp) (E = Ge, Sn; Mes Ter = 2,6-Mes 2 C 6 H 3 , IDipp = C([N-(2,6-iPr 2 C 6 H 4 )CH] 2 ) was achieved by taking advantage of NHC (N-heterocyclic carbene, here IDipp) coordination to the low-valent phosphorus center. Multiple bonding character of the E−P bonds was examined experimentally and computationally. Both germanium and tin compounds undergo [2+2] cycloaddition with diphenylketene, whereas reaction of the tin derivative with tris(pentafluorophenyl)borane provided unique "push−pull" phosphastannene ( Mes Ter)(Ar)Sn = P(IDipp) (Ar = C 6 F 4 [B(F)(C 6 F 5 ) 2 ]). Going further, we demonstrated the potential of tetrylene−phosphinidene complexes in catalytic hydroboration of carbonyl compounds.

Low‐Valent Group 14 Phosphinidenide Complexes [({SIDipp}P)2M] Exhibit P–M pπ–pπ Interaction (M=Ge, Sn, Pb)

“…The group of Roesky was able to synthesize a cAAC‐stabilized silylene with two terminal phosphinidenide ligands ( I , Scheme ) . Very recently the group of Inoue the synthesis of germylene and stannylene phosphinidene NHC complexes [ Mes TerMP(IDipp)] ( II ) (M=Ge, Sn; Mes Ter=Bis‐2,6‐(2,4,6‐trimethylphenyl)phenyl), which show a multiple M−P bond character . Only a few oligomeric compounds with bridging phosphandiide ligands like the dimeric species [{M(μ‐P{C 6 H 3 ‐2,6‐(C 6 H 3 ‐2,6‐ i Pr 2 ) 2 }] 2 (M=Ge, Sn, Pb), the hexameric [Ge(μ‐PSi i Pr 3 )] 6 or the tetrameric [Sn(μ‐PSi t Bu 3 )] 4 as well as other cage‐like compounds are reported .…”

“…[14] Very recently the group of Inoue the synthesis of germylene and stannylene phosphinidene NHC complexes [ Mes TerMP(IDipp)] (II) (M = Ge, Sn; Mes Ter = Bis-2,6-(2,4,6-trimethylphenyl)phenyl), which show a multiple MÀP bond character. [21] Only a few oligomeric compounds with bridging phosphandiide ligands like the dimeric species [{M(m-P{C 6 H 3 -2,6-(C 6 H 3 -2,6-iPr 2 ) 2 }] 2 [22] (M = Ge, Sn, Pb), the hexameric [Ge(m-PSiiPr 3 )] 6 [23] or the tetrameric [Sn(m-PSitBu 3 )] 4 [24] as well as other cage-like compounds are reported. [23,[25][26][27] As far as we know, no compound of the type M(PR) 2 (M = Ge(+2), Sn(+2), Pb(+2)) is reported in literature.…”

N‐Heterocyclic Carbene Analogues of Nucleophilic Phosphinidene Transition Metal Complexes

“…[22] N-Heterocyclic carbene-stabilized germanium and tin analogueso fh eavier nitrileso ft he type [( Mes Ter)EP(IDipp)] (E = Ge, Sn; Mes Te r = 2,6-bis(2,4,6-trimethylphenyl)phenyl) were recently isolatedb yI noue and co-workers by reactingd imeric [( Mes Ter)ECl] 2 with 1,w hichr esembles the reaction with the dimeric metal chlorides as shown in Scheme 2. [23] Naturally, metal-phosphorusm ultiple bonding does not play any significant role in these late transition or p-block metal complexes, which is different from the bonding situationt hat will be uncovered for the phosphinidene-typec omplexes 4-8 presented in this contribution.…”

“…In addition, the group of von Hänisch employed the potassium salts [(SIMes)PK] (SIMes=bis(2,4,6‐trimethylphenyl)imidazolidin‐2‐ylidene) [13] and [(SIDipp)PK] for the preparation of main group metal complexes, [21] with the tetrylene derivatives [{(SIDipp)P} 2 M] (M=Ge, Sn, Pb) representing the most recent examples [22] . N‐Heterocyclic carbene‐stabilized germanium and tin analogues of heavier nitriles of the type [( Mes Ter)EP(IDipp)] (E=Ge, Sn; Mes Ter=2,6‐bis(2,4,6‐trimethylphenyl)phenyl) were recently isolated by Inoue and co‐workers by reacting dimeric [( Mes Ter)ECl] 2 with 1 , which resembles the reaction with the dimeric metal chlorides as shown in Scheme 2 [23] . Naturally, metal‐phosphorus multiple bonding does not play any significant role in these late transition or p ‐block metal complexes, which is different from the bonding situation that will be uncovered for the phosphinidene‐type complexes 4 – 8 presented in this contribution.…”

Isolation of N‐Heterocyclic Carbene‐Stabilized Phosphorus and Arsenic Mononitride

“…Similar heteroleptic P 2 and AsP species bearing neutral and anionic N‐heterocyclic carbenes were also prepared . These syntheses relied on the use of the carbene‐phosphinidene adduct [(IDipp)PSiMe 3 ], which can be conveniently used for the formation of phosphorus‐element and phosphorus‐metal bonds . The lighter nitrogen congener, the imidazolin‐2‐imine [(IDipp)NSiMe 3 ] ( 1 ), has also found widespread use in transition metal and main group element chemistry,, and accordingly, we envisaged that this compound might serve as a suitable starting material for the preparation of the heteroleptic dicarbene complexes [(IMes)EN(IDipp)] ( 4a : E = P, 4b : E = As).…”