Polyhedral members of the Mg2nP2m family derived from dimeric magnesium trialkylsilylphosphandiide

From Diphosphane to Diphosphodiide Gold(III) Derivatives of 1,2-Diphosphinobenzene

Treatment of 1,2-diphosphinobenzene with [Au(C6F5)3(tht)] leads to the diphosphane derivative [{Au(C6F5)3}(1,2-PH2C6H4PH2)] (1), which further reacts with other pentafluorophenylgold(III) reagents in the presence of acetylacetonate as deprotonating agent to afford phosphane-phosphide complexes. The noncyclic PPN[{Au(C6F5)3}2(1,2-PHC6H4PH2)] (2; PPN = bis(triphenylphosphine)iminium) has been shown to be a useful starting material for the synthesis of higher nuclearity cyclic or noncyclic diphosphide or even diphosphodiide derivatives through similar reactions. The crystal structures of the trinuclear anionic NBu4[{Au(C6F5)3}(1,2-PHC6H4PH){Au(C6F5)2Cl}{mu-Au(C6F5)2}] (3) and the hexanuclear [{Au(C6F5)3}(1,2-PC6H4P){Au(C6F5)3}{mu-M(dppe)M}2] (M = Au (12), Ag (13)) have been established by X-ray diffraction methods, the last complexes having a bicyclic ring containing three intramolecular interactions between the M(I) centres.

Ligand Exchange Reaction Between an Alkylzinc Primary Amide and a Dialkylmagnesium Compound: Crystal Structures of [(thf)MeMg-μ-N(H)SiiPr3]2 and (tmeda)Mg[N(H)SiiPr3]2

The reaction of alkylzinc triisopropylsilylamide with dialkylmagnesium leads to a ligand exchange. Besides the starting materials, heteroleptic alkylmagnesium triisopropylsilylamide and homoleptic magnesium bis(triisopropylsilylamide) are detected by NMR spectroscopy. After the addition of 1,2-bis(dimethylamino)ethane (TMEDA) to the reaction mixture, (tmeda)Mg[N(H)SiiPr3]2 (1) precipitates as colorless cuboids (C24H60MgN4Si2, a = 2269.6(2), b = 1029.58(5), c = 1593.2(1) pm, beta = 120.826(8) degrees , monoclinic, C2/c, Z = 4). The amide nitrogen atoms are coordinated planarily with strongly widened Mg-N-Si bond angles of 139.2(1) degrees . The metalation of triisopropylsilylamine with dimethylmagnesium in THF yields quantitatively heteroleptic [(thf)MeMg-N(H)SiiPr3]2 (2) which crystallizes as colorless needles (C28H66Mg2N2O2Si2, a = 1982.4(2), b = 2034.1(1), c = 907.22(6) pm, beta = 95.021(9), monoclinic, P2(1)/n, Z = 4). Because of the bridging position of the triisopropylsilylamide anion, the tetracoordinate nitrogen atoms show rather long Mg-N bond lengths of 210.7 pm (average value).

Complexes of the Heavier Alkaline Earth Metals Ca, Sr, and Ba with O-Functionalized Phosphanide Ligands

Metathesis reactions between either SrI(2) or BaI(2) and 2 equiv of the potassium phosphanide [[(Me(3)Si)(2)CH]-(C(6)H(4)-2-OMe)P]K yield, after recrystallization, the complexes [[([Me(3)Si](2)CH)(C(6)H(4)-2-OMe)P](2)M(THF)(n)] [M = Sr, n = 2 (5); Ba, n = 3 (6)]. Similar metathesis reactions between MI(2) and 2 equiv of the more sterically demanding potassium phosphanide [[(Me(3)Si)(2)CH](C(6)H(3)-2-OMe-3-Me)P]K yield the chemically isostructural complexes [[([Me(3)Si](2)CH)(C(6)H(3)-2-OMe-3-Me)P](2)M(THF)(2)] [M = Ca (9), Sr (7), Ba (8)]. Compounds 5-9 have been characterized by multi-element NMR spectroscopy and X-ray crystallography. Complex 9 is thermally unstable and decomposes at room temperature to give the tertiary phosphane [(Me(3)Si)(2)CH](C(6)H(3)-2-OMe-3-Me)P(Me) and an unidentified Ca-containing product. Compounds 5 and 6 also decompose at elevated temperatures to give the corresponding tertiary phosphane [(Me(3)Si)(2)CH](C(6)H(4)-2-OMe)P(Me) and intractable metal-containing products. The decomposition of 5, 6, and 9 suggests that these compounds undergo an intramolecular methyl migration from the O atom in one phosphanide ligand to the P atom of an adjacent phosphanide ligand to give species containing dianionic alkoxo-phosphanide ligands.

Cage compounds of heterotrimetallic mixed phosphanediide/silanolate aggregates with an alkaline Earth metal-centered phosphorus octahedron

The lithiation of potassium triisopropylsilylphosphanide yields the corresponding phosphanediide. The subsequent metathesis reaction with SrI(2) and BaI(2) in the presence of hexamethyldisiloxane gives hexalithium hexapotassium strontium hexakis(triisopropylsilylphosphanediide)bis(trimethylsilanolate) (1) and the corresponding barium derivative (2), respectively. The alkaline earth metal atoms are surrounded octahedrally by the phosphanediide ligands. Six P(3) faces of the octahedron are capped by the K atoms, and the P-P edges of two opposite P(3) faces are bridged by the lithium atoms. The Li cations are also bonded to the Me(3)SiO substituents giving a coordination number of three for the alkali metals.

A homologous series of alkaline earth phosphanides: syntheses, crystal structures, and unusual dynamic behavior of (THF)(n)M[P(CH(SiMe(3))(2))(C(6)H(4)-2-CH(2)NMe(2))](2) (M = Mg, Ca, Sr, Ba)

The secondary phosphine R(Me(2)NCH(2)-2-C(6)H(4))PH reacts with Bu(2)Mg to give the homoleptic complex Mg[PR(C(6)H(4)-2-CH(2)NMe(2))](2) (1) [R = CH(SiMe(3))(2)]. The analogous heavier alkaline earth metal complexes (THF)(n)Ae[PR(C(6)H(4)-2-CH(2)NMe(2))](2) [Ae = Ca (2), n = 0; Ae = Sr (3), Ba (4), n = 1] have been synthesized by metathesis reactions between K[PR(C(6)H(4)-2-CH(2)NMe(2))] and 0.5 equiv of the respective alkaline earth metal diiodide. Compounds 1-4 have been characterized by X-ray crystallography and multielement NMR spectroscopy. In the solid state, compounds 1-4 are monomeric, complexes 1 and 2 adopting a distorted tetrahedral geometry and complexes 3 and 4 adopting a distorted square pyramidal geometry (1: orthorhombic, P2(1)2(1)2(1), a = 11.413(3) A, b = 12.072(3) A, c = 32.620(11) A, Z = 4. 2: monoclinic, P2(1)/c, a = 9.5550(4) A, b = 17.4560(7) A, c = 24.5782(10) A, beta = 91.673(2) degrees, Z = 4. 3: monoclinic, C2/c, a = 15.0498(9) A, b = 13.0180(8) A, c = 24.3664(14) A, beta = 104.593(2) degrees, Z = 4. 4: monoclinic, C2/c, a = 15.2930(10) A, b = 13.0326(9) A, c = 24.6491(17) A, beta = 105.542(2) degrees, Z = 4). In toluene solution, compounds 2-4 are subject to dynamic processes which are attributed to a monomer-dimer equilibrium for which bridge-terminal exchange of the phosphanide ligands in the dimer may be frozen out at low temperatures.