[{HC(CMeNAr)₂}₂Al₂P₄] (Ar=2,6‐iPr₂C₆H₃): A Reduction to a Formal {P₄}⁴⁻Charged Species

Abstract

The chemistry of white phosphorus has generated much interest over the past decades owing to its unique tetrahedral structure and variable bonding situation. Organophosphorus compounds can be used as reagents [1] and as ligands for innumerable complexes in catalytic processes.[2] The reactions of transition-metal complexes with white phosphorus have been extensively studied and have resulted in a large variety of P x ligands with unpredictable structures.[3] Among them, only one compound [Cp* 2 (CO) 2 Co 2 P 4 ] (Cp* = C 5 Me 5 ) [4] with a {P 4 } 4À species is reported. However, the reactions of the P 4 molecule with main-group complexes are limited to a few examples, [(AlCp*) 6 P 4 ], [5a] [(GaR) 3 P 4 ] (R= (SiMe 3 ) 3 C), [5b] and [Ga 2 P 4 tBu 6 ].[5c][LAl I ] (1) (L = HC(CMeNAr) 2 , Ar = 2,6-iPr 2 C 6 H 3 ) [6] with its nonbonding lone pair of electrons at aluminum indicates a singlet carbene-like character. It could be used in carbenetype reactions, as a Lewis base and moreover as a reducing reagent, which may show unprecedented chemical reactions. To our knowledge, the study of the chemical behavior of 1 is limited so far to coupling reactions. [7,8] Compounds containing the heavy elements of Group 13 and 15 are used as models in bonding theory [9] and as precursors for semiconducting materials.[10] Herein we report the reaction of 1 with white phosphorus to yield the first main-group complex of composition [(LAl) 2 P 4 ] (2) containing the {P 4 } 4À species. Treatment of two equivalents of 1 with white phosphorus at room temperature leads to 2 in good yield (Scheme 1). In contrast, the reaction of the tetrahedral aluminum(i) compound [(AlCp*) 4 ] with white phosphorus gave the electrondeficient cage compound [(AlCp*) 6 P 4 ], [5a] which consists of two face-sharing heterocubanes with two opposing corners unoccupied, and four P atoms from the complete cleavage of the P 4 molecule. Therefore we treated 1 with P 4 in a 4:1 ratio to explore the possibility of complete cleavage of all P À P bonds, however we obtained 2 and residual 1, based on the results of 1 H and 31 P NMR spectroscopic investigations. Clearly the bulky ligand L prevents the arrangement of a larger number of LAl moieties around the P atoms. When the reaction was carried out in a ratio of 1:1 between 1 and P 4 , 2 and residual P 4 together with some byproducts were obtained, again based on the results of 1 H and 31 P NMR spectroscopic investigations. Compound 2 is air sensitive and decomposes at 145 8C. 2 is sparingly soluble in pentane and hexane, however readily soluble in benzene, toluene, and diethyl ether. In CDCl 3 we observed the decomposition of 2.Compound 2 was characterized by 1 H, 13 C, and 31 P NMR spectroscopy using [D 6 ]benzene as the solvent, and by EI mass spectrometry and elemental analysis. The EI mass spectrum shows the molecular ion of 2. The 31 P NMR spectrum of 2 (d = 78.6 ppm) has a very different chemical shift compared to that of the free P 4 molecule (d = À519 ppm). No resonance signals were observed in C 6 D...

Bimetallic Activation of White Phosphorus

“…1 These units find their thermodynamic sink by either bridging two metal moieties 4 or undergoing electrophilic or nucleophilic attacks from ancillary ligands to form new P H, P C and P P bonds. 5 This bonding situation was observed in the unique cobalt complex [Co(Ph 2 PCH 2 PPh 2 PPPPPh 2 PCH 2 PPh 2 )]BF 4 (1) synthesized in Florence more than two decades ago from simple cobalt(II) hydrated salts, dppm (dppm = Ph 2 PCH 2 PPh 2 ) and white phosphorus in boiling THF/butanol mixture (Scheme 1). 6…”

d6 metal systems for white phosphorus activation

“…Two approaches have been considered in this respect, either reacting P 4 with carbenes and heavier carbene analogues or studying the reactivity of the intact molecule, mediated by the use of transition metal complexes. In the former approach tetraphosphorus frameworks, which contain P atoms with different connectivities and geometries have been obtained [19][20][21][22][23][24][25][26][27]. Such polyphosphorus units are endowed with high reactivity and, in principle, are useful to obtain organophosphorus derivatives, although up to now such possibilities have been scarcely considered and have not been accomplished yet in a catalytic fashion.…”

An Unexpected Pathway in the Cage Opening and Aggregation of P4

“…[1] In comparison, only a few reactions of white phosphorus with main-group complexes have been reported. Whereas the reactions of lowoxidation-state Group 13 species to some extent parallel those of transition-metal organometallic compounds, [2][3][4] the reactions of P 4 with more nucleophilic main-group complexes follow a distinctly different pathway, involving nucleophilic addition to the P 4 framework. [5][6][7][8] In the case of the 1:1 reaction of tBu 3 Ga with P 4 , attack of the tBu À ion across one of the P À P bonds gives a butterfly-shaped [tBuP 4 ]…”

“…The nortricyclic P 7 core arrangement found in 2 has been observed in a number of anionic and neutral P x nÀ cage structures. [9] However, the Cr 0 complex [{P 7 (PtBu 2 ) 3 }{Cr(CO) 4 } 2 ], [14] which contains a neutral, nortricyclic P 7 (PtBu 2 ) 3 ligand, is the closest analogue to 2.…”