Synthesis of Stable Potassium Phosphinophosphides and Reaction with Organosilyl Halides and Chlorophosphanes.

The synthesis of sterically demanding 2,6-bis(2,4,6-trimethylphenyl)phenyl (Ter)-stabilized and H-substituted diphosphanes TerHP-PR2 (4a-4c) via conversion of the phosphide TerPHK (2) with secondary chlorophosphanes ClPR2 (3a-3c, where R = iPr, Ph, and tBu, respectively) is described. The diphosphanes 4a-4c were deprotonated using KH in tetrahydrofuran, selectively yielding the potassium phosphinophosphides K[TerP-PR2] (5a-5c). These phosphinophosphides are stable in solution as well as in the solid state and can be further functionalized via salt-metathesis reactions. Reaction with organosilyl halides selectively yields the silylated diphosphanes Ter(SiR12R2)P-P(iPr)2 (6a and 6b, where R1 = R2 = CH3 and R1 = CH3, R2 = Ph, respectively), whereas conversion with chlorophosphanes selectively yields the triphosphanes R12P-P(Ter)-P(iPr)2 (7a and 7b, where R = iPr and Ph, respectively).

A Persistent Phosphanyl-Substituted Thioketyl Radical Anion.

Alkali metal salts, M+ [Ter(iPr)P-C(=S)-P(iPr)2 S].- (M=Na, K; 2_M; Ter=2,6-bis-(2,4,6-trimethylphenyl)phenyl) containing a room-temperature-stable thioketyl radical anion were obtained by reduction of the thioketone precursor, Ter(iPr)P-C(=S)-P(iPr)2 S (1), with alkali metals (Na, K). Single-crystal X-ray studies as well as EPR spectroscopy revealed the unequivocal existence of a thioketyl radical anion in the solid state and in solution, respectively. The computed Mulliken spin density within 2_M is mainly located at the sulfur (49 %) and the carbonyl carbon (33 %) atoms. Upon adding [2.2.2]-cryptand to the radical species 2_K to minimize the interionic interaction, an activation reaction was observed, yielding a potassium salt with a phosphanyl thioether based anion, [K(crypt)]+ [Ter(iPr)P-C(-S-iPr)-P(iPr)2 S]- (3) as the product of an intermolecular shift of an iPr group from a second anion. The products were fully characterized and application of the radical anion as a reducing agent was demonstrated.

Insertion of CS2 into a Phosphorus-Arsenic Single Bond and Investigations on Phosphane Arsanyldithiocarboxylates.

The synthesis and reactivity of sterically demanding phosphaarsanes TerR1P-AsR2 (3) is described. These species were selectively synthesized via metathesis reactions of Ter-stabilized [Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl] potassium phosphides TerR1PK (1) with the N-heterocyclic chloroarsane ClAs{N(tBu)CH2}2 (2). Conversion of the n-butyl-substituted phosphaarsane 3c with the reactive heterocumulene CS2 leads to an insertion into the P-As bond, yielding the phosphane arsanyldithiocarboxylate TerR1P-C(S)S-AsR2 (4c) as a new structural motif. Because full conversion of 3c with CS2 requires long reaction times, an alternative synthetic route is reported herein, involving the conversion of 2 with phosphane dithiocarboxylates TerR1-C(S)SK (5), enabling synthetic access to a wider range of phosphane arsanyldithiocarboxylates. These interpnictogen dithiocarboxylates show an interesting bonding situation with a significantly elongated As-S bond due to negative hyperconjugation within the molecule. All products along the reaction path were fully characterized.

Synthesis of Sterically Demanding Secondary Phosphides and Diphosphanes and Their Utilization in Small-Molecule Activation.

Sterically demanding secondary potassium phosphides (4) were synthesized and investigated. Reaction with halophosphanes (5) yields diphosphanes (6), whereas reaction with CS2 yields phosphanyl dithioformates (10). These can be further converted to the corresponding phosphanyl esters of dithioformic acid R2P-C(S)S-PR2 (8). One of these thioesters (8) was found to undergo a migration reaction, resulting in the formation of a phosphanylthioketone with an additional phosphanylthiolate group (9), which was used as a chiral ligand in gold coordination chemistry. The phosphanyl migration reaction was investigated by spectroscopic and theoretical methods, revealing a first-order reaction via a cyclic transition state. All species mentioned were fully characterized.

Reaction of potassium phosphide KP(iPr)Ter with chalcogens, heteroallenes and an acyl chloride.

The reactivity of the secondary phosphide KP(iPr)Ter (1) (Ter = 2,6-bis-(2,4,6-trimethylphenyl)phenyl) toward small molecules is reported. Phosphide 1 displays distinct nucleophilic character and reacts selectively with chalcogens (S8, Sex), heteroallenes (CO2, nPrNCS), and an acyl chloride (AdCOCl) to give the corresponding dichalcogenophosphinates (2a, 3), phosphanyl formate (5), thiocarbamoylphosphane (6a), or acylphosphane (7a), respectively. Furthermore the follow-up chemistry of these products was investigated. 2a was converted to a PSPS ligand (2b) which forms a Au(I) complex (2c) with (Me2S)AuCl. Likewise, a gold complex of 7a was prepared. All species were isolated and fully characterized.

[E(µ-NBbp)]2 (E = P, As) - group 15 biradicals synthesized from acyclic precursors.

The synthesis of Bbp stabilized biradicals of the type [E(µ-NBbp)]2 (E = P, As) (Bbp = 2,6-bis[bis(trimethylsilyl)methyl]phenyl) was investigated. Contrary to the established synthetic protocol for terphenyl substituted biradicals [E(µ-NTer)]2 by reduction of [ClE(µ-NTer)]2, the analogous Bbp substituted precursor [ClE(µ-NBbp)]2 could only be obtained in low yields. For this reason, a new synthesis had to be found to generate [E(µ-NBbp)]2. Instead of using cyclic [ClE(µ-NBbp)]2 we prepared the acyclic Bbp-N(ECl2)2 species starting from Bbp-NH2 and ECl3 and studied the reduction with magnesium chips, which led to the formation of the desired biradicals [E(µ-NBbp)]2. All species along the reaction path were fully characterized.