Phosphine-Stabilized Pnictinidenes

The reaction of the intramolecular germylene‐phosphine Lewis pair (o‐PPh₂)C₆H₄GeAr* (1) with Group 15 element trichlorides ECl₃ (E=P, As, Sb) was investigated. After oxidative addition, the resulting compounds (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)ECl₂ (2: E=P, 3: E=As, 4: E=Sb) were reduced by using sodium metal or LiHBEt₃. The molecular structures of the phosphine‐stabilized phosphinidene (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)P (5), arsinidene (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)As (6) and stibinidene (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)Sb (7) are presented; they feature a two‐coordinate low‐valent Group 15 element. After chloride abstraction, a cyclic germaphosphene [(o‐PPh₂)C₆H₄(Ar*)GeP] [B(C₆H₃(CF₃)₂)₄] (8) was isolated. The ³¹P NMR data of the germaphosphene were compared with literature examples and analyzed by quantum chemical calculations. The phosphinidene was treated with [iBu₂AlH]₂, and the product of an Al−H addition to the low‐valent phosphorus atom (o‐PPh₂)C₆H₄(Ar*)Ge(H)P(H)Al(C₄H₉)₂ (9) was characterized.

Ring Expansions of Nonpolar Polyphosphorus Rings

The reaction of the phosphinidene complex [Cp*P{W(CO)₅ }₂ ] (1 a) (Cp*=C₅ Me₅ ) with the anionic cyclo-P_n ligand complex [(η³ -P₃ )Nb(ODipp)₃ ]^- (2, Dipp=2,6-diisopropylphenyl) resulted in the formation of [{W(CO)₅ }₂ {μ₃ ,η^3:1:1 -P₄ Cp*}Nb(ODipp)₃ ]^- (3), which represents an unprecedented example of a ring expansion of a polyphosphorus-ligand complex initiated by a phosphinidene complex. Furthermore, the reaction of the pnictinidene complexes [Cp*E{W(CO)₅ }₂ ] (E=P: 1 a, As: 1 b) with the neutral complex [Cp'''Co(η⁴ -P₄ )] (Cp'''=1,2,4-tBu₃ C₅ H₂ ) led to a cyclo-P₄ E ring (E=P, As) through the insertion of the pentel atom into the cyclo-P₄ ligand. Starting from 1 a, the two isomers [Cp'''Co(μ₃ ,η^4:1:1 -P₅ Cp*){W(CO)₅ }₂ ] (5 a,b), and from 1 b, the three isomers [Cp'''Co(μ₃ ,η^4:1:1 -AsP₄ Cp*){W(CO)₅ }₂ ] (6 a-c) with unprecedented cyclo-P₄ E ligands (E=P, As) were isolated. The complexes 6 a-c represent unique examples of ring expansions which lead to new mixed five-membered cyclo-P₄ As ligands. The possible reaction pathways for the formation of 5 a,b and 6 a-c were investigated by a combination of temperature-dependent ³¹ P{¹ H} NMR studies and DFT calculations.

Reaction of Pentelidene Complexes with Diazoalkanes: Stabilization of Parent 2,3-Dipnictabutadienes

The reaction of the phosphinidene complex [Cp*P{W(CO)₅ }₂ ] (1 a) with diphenyldiazomethane leads to [{W(CO)₅ }Cp*P=NN{W(CO)₅ }=CPh₂ ] (2). Compound 2 is a rare example of a phosphadiazadiene ligand (R-P=N-N=CR'R'') complex. At temperatures above 0 °C, 2 decomposes into the complex [{W(CO)₅ }PCp*{N(H)N=CPh₂ )₂ ] (3), among other species. The reaction of the pentelidene complexes [Cp*E{W(CO)₅ }₂ ] (E=P, As) with diazomethane (CH₂ NN) proceeds differently. For the arsinidene complex (1 b), only the arsaalkene complex 4 b [{W(CO)₅ }₂ {η^1:2 -(Cp*)As=CH₂ }] is formed. The reaction with the phosphinidene complex (1 a) results in three products, the two phosphaalkene complexes [{W(CO)₅ }₂ {η^1:2 -(R)P=CH₂ }] (4 a: R=Cp*, 5: R=H) and the triazaphosphole derivative [{W(CO)₅ }P(Cp*)-CH₂ -N{W(CO)₅ }=N-N(N=CH₂ )] (6 a). The phosphaalkene complex (4 a) and the arsaalkene complex (4 b) are not stable at room temperature and decompose to the complexes [{W(CO)₅ }₄ (CH₂ =E-E=CH₂ )] (7 a: E=P, 7 b: E=As), which are the first examples of complexes with parent 2,3-diphospha-1,3-butadiene and 2,3-diarsa-1,3-butadiene ligands.

The 2-Arsaethynolate Anion: Synthesis and Reactivity Towards Heteroallenes

The synthesis and isolation of the 2-arsaethynolate anion, AsCO(-) , and its subsequent reactivity towards heteroallenes is reported. Reactions with ketenes and carbodiimides afford four-membered anionic heterocycles in formal [2+2] cycloaddition reactions. By contrast, reaction with an isocyanate yielded a 1,4,2-diazaarsolidine-3,5-dionide anion and the unprecedented cluster anions As10 (2-) and As12 (4-) . These preliminary reactivity studies hint at the enormous potential synthetic utility of this novel anion, which may be employed as an arsenide (As(-) ) source.

Insight into the Reaction of a Dinuclear Phosphinidene Complex with Nitriles

The phosphinidene complex [Cp*P{W(CO)5}2] (1; Cp*=C5 Me5 ) reacted with malononitrile to give the 1,2-dihydro-1,3,2-diazaphosphinine derivative 2. The reaction of 1 with 1,4-benzodinitrile gave [1,4-{{W(CO)5}2 P-N=C(Cp*)}2 (C6 H4)] (3), the first example of a cumulene-like aminophosphinidene complex. The reaction of 1 with aniline gave the aminophosphinidene complex [(Ph)N(H)P{W(CO)5}2] (4). To compare the reactivity of benzonitrile and aniline with 1, the phosphinidene complex 1 was reacted with three different isomers of aminobenzonitrile (2-, 3-, and 4-aminobenzonitrile). These reactions gave an insight into the reaction pathway of 1 with benzonitrile derivatives. Compounds 5, 6 a, 6 b, and 7, which are derivatives of 1,2-dihydro-1,3,2-diazaphosphinine or benzo-2H-1,2-azaphospholes, were, as well as all other products, characterized by mass spectrometry, NMR and IR spectroscopy, and X-ray structure analysis.

Stepwise Formation of a 1,3-Butadiene Analogue of Mixed Heavier Group 15 Elements

The reaction of the phosphinidene complex [Cp*P{W(CO)5}2] (1 a) with di-tert-butylcarboimidophosphene leads to the P-C cage compound 6 and the Lewis acid-base adduct [Cp*P{W(CO)5}2(CNtBu)] (2 a). In contrast, the arsinidene complex shows a different reactivity. At low temperatures, the arsaphosphene complex [{W(CO)5}{η(2)-(Cp*)As=P(tBu)}{W(CO)5}] (3) is formed. At these temperatures, 3 reacts further with a second equivalent of carboimidophosphene to form [{W(CO)5}{η(2)-{(Cp*)(tBu)P}As=P(tBu)}{W(CO)5}] (5), probably by the insertion of a phosphinidene unit (tBuP) into an As-C bond. In contrast, at room temperature 3 reacts further by a radical-type reaction to form [{(tBu)P=As-As=P(tBu)}{W(CO)5}4] (4). Compound 4 is the first example of a neutral, 1,3-butadiene analogue containing only mixed heavier Group 15 elements. It consists of two P=As double bonds connected by arsenic atoms.