A cyclo‐P₆ Ligand Complex for the Formation of Planar 2D Layers

Abstract

The all-phosphorus analogueo fb enzene, stabilized as middle deck in triple-decker complexes, is ap romising building block for the formation of graphene-like sheet structures. The reaction of [(CpMo) 2 (m,h 6 :h 6 -P 6 )] (1) with CuX (X = Br,I )l eads to self-assembly into unprecedented 2D networks of [{(CpMo) 2 P 6 }(CuBr) 4 ] n (2)a nd [{(CpMo) 2 P 6 }(CuI) 2 ] n (3). X-ray structural analyses show au nique deformation of the previously planar cyclo-P 6 ligand.T his includes bending of one Pa tom in an envelope conformation as well as ab isallylic distortion. Despite this, 2 and 3 form planar layers. Both polymers were furthermore analyzed by 31 P{ 1 H} magic angle spinning (MAS) NMR spectroscopy,r evealing signals corresponding to six non-equivalent phosphorus sites. Ap eak assignment is achieved by 2D correlation spectra as well as by DFT chemical shift computations.Ta iloreds yntheses of the inorganic analogues of organicm olecules, is af ascinating area of fundamental research. Following the so-called isolobal principle, [1] substitution of methine moieties by phosphorus atoms appearsq uite promising. In fact, 2016 marks the 50th anniversary of the first successful synthesis of ap hosphabenzenei nw hich one CH unit is replacedb y aPatom, [2] which set the stage for the ultimate goal, namely the preparation of carbon-free hexaphosphabenzene.S ince then,m any theoreticals tudies with respect to its aromaticity were reportedt hat outlined the instability of af ree cyclo-P 6 unit. [3] Nevertheless, its detection in an inert stabilizing matrix at low temperature might be feasible such that the challenge remains. As ynthetic approach demonstrated by the Scherer groupisthe stabilizationofthe P 6 ring by coordination to transition metals, thus affording at riple-decker complex [(Cp*Mo) 2 (m,h 6 :h 6 -P 6 )] (Cp* = h 5 -C 5 Me 5 )b earing ap lanar P 6 middle deck for the first time (Figure 1). [4] Triple-deckerc omplexesc ontaining the cyclo-P 6 unit could also be obtainedf or vanadium, [5] tungsten, [5] or niobium. [6] Quite recently,t he sandwich complex[ (CpMo) 2 (m,h 6 :h 6 -P 6 )] (1)w ith the parent Cp ligandsw as synthesized and characterized. [7] In the case of the Mo and Wc omplexes, the cyclo-P 6 ring has ap erfect D 6h symmetry, whereas Va nd Nb derivatives exhibit as light bisallylic distortion. [6a] It should be noted that the middled eck in [(Cp*Ti) 2 (m,h 3 :h 3 -P 6 )] has ac hair conformation (Figure 1). [8] In contrastt ob enzene, the presence of lone pairs at the phosphorus atoms converts these triple-decker complexes into excellent buildingb locks for supramolecular chemistry.P articularly intriguingis the possibility of graphene-like honeycomb networks resulting from reaction with Lewis acidic metal salts, an unmet challenge to date.We have appliedL ewis acidic coinage metal salts forl inkage of unsubstituted P n complexes [9] and also for [(Cp R Mo) 2 (m,h 6 :h 6 -P 6 )] (Cp R = Cp*, Cp Bn = h 5 -C 5 (CH 2 C 6 H 5 ) 5 ). [10] For example, the coordination of the bare cationsC u...

Discrete and Polymeric Organometallic‐Organic Hybrid Materials Based on the Diphosphorus Complex [Cp2Mo2(CO)4(η2‐P2)], CuI Salts, and 2,2′‐Bipyrimidine

“…In contrast to typical approaches in this area, in which nitrogen‐, oxygen‐, or sulfur‐donor‐containing organic ligands are employed to connect different metal centers, our group established an alternative approach by utilizing organometallic polyphosphorus (P n ) ligand complexes with flexible coordination modes as connectors between metal ions. This novel method allows for the synthesis of 1D and 2D coordination polymers, nano‐sized fullerene‐like supramolecular spherical aggregates, and a huge molecular organometallic capsule . An alternative approach by using three‐component reactions was also developed in our group.…”

Oxidation Chemistry of Inorganic Benzene Complexes

“…For Cu + , three different reaction products (oxidation, distorted tetrahedral, or square‐planar coordination complex) could be selectively obtained by choosing the appropriate solvent mixture of CH 2 Cl 2 and toluene . The Cp derivative [(CpMo) 2 (μ,η 6 :η 6 ‐P 6 )] forms supersandwich complexes based on weak Hg−P interactions with the trinuclear Lewis acid [( o ‐HgC 6 F 4 ) 3 ] and it forms two‐dimensional graphene‐like sheets with Cu I halides . Inside these layers, a distortion of the P 6 rings is observed, with one atom displaced out of the plane.…”

“…[18] The Cp derivative [(CpMo) 2 (m,h 6 :h 6 -P 6 )] forms supersandwich complexesb ased on weak HgÀPi nteractions with the trinuclear Lewis acid [(o-HgC 6 F 4 ) 3 ]a nd it forms two-dimensional graphene-like sheets with Cu I halides. [19,20] Inside these layers,ad istortion of the P 6 rings is observed, with one atom displaced out of the plane. The presented facts raise the question of how cyclo-E 6 tripledeckerc omplexes will react upon oxidation, how their reactivity compares to benzene, and if it is influenced by the nature of the Cp ligand or the nature of the pnictogen atoms Po rA s. To answer these questions, the redox behavior of the complexes[ (Cp R Mo) 2 (m,h 6 :h 6 -E 6 )] (E = P, Cp R = Cp(2a), Cp*(2b), Cp Bn (2c); E= As, Cp R = Cp*(3)),t he preparation of the singleelectron oxidation products and their detailed characterization, includings ingle-crystal X-ray diffraction analysis, are reported here.…”

Transition metal complexes of the naked pnictide elements

“…With CuBr or CuI, 2-dimensioal networks are formed with different Cu:E6M2 ratios ( Figure 95). 141 The structures show P6 units that remain planar and well as some in the CuBr complex that have significant deviations from planarity ( Figure 95A).…”