Inorganic Chemistry, Vol.41, No.15, 3886-3893, 2002
A homologous series of alkaline earth phosphanides: Syntheses, crystal structures, and unusual dynamic behavior of (THF)(n)M[P{CH(Si-Me-3)(2)}(C6H4-2-CH2NMe2)](2) (M=Mg, Ca, Sr, Ba)
The secondary phosphine R(Me2NCH2-2-C6H4)PH reacts with Bu2Mg to give the homoleptic complex Mg{PR(C6H4-2-CH2NMe2)}(2) (1) [R = CH(SiMe3)(2)]. The analogous heavier alkaline earth metal complexes (THF)(eta)Ae{PR(C6H4-2-CH2NMe2)}(2) [Ae = Ca (2), n = 0; Ae = Sr (3), Ba (4), n = 1] have been synthesized by metathesis reactions between K{PR(C6H4-2-CH2NMe2)} 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) Angstrom, b = 12.072(3) Angstrom, c = 32.620(11) Angstrom, Z = 4. 2: monoclinic, P2(1)/c, a = 9.5550(4) Angstrom, b = 17.4560(7) Angstrom, c = 24.5782(10) Angstrom, beta = 91.673(2)degrees, Z = 4. 3: monoclinic, C2/c, a = 15.0498(9) Angstrom, b = 13.0180(8) Angstrom, c = 24.3664(14) Angstrom, beta = 104.593(2)degrees, Z = 4. 4: monoclinic, C2/c, a = 15.2930(10) Angstrom, b = 13.0326(9) Angstrom, c = 24.6491(17) Angstrom, 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.