Effect of peripheral donor substituents on the binding modes of phosphinomethanide ligands. Synthesis and crystal structures of alkali metal derivatives of an O-functionalised phosphinomethanide ligand

Abstract

The O-functionalised tertiary phosphine {(Me3Si)2CH}P(C6H4-2-CH2OMe)2 (9) is accessible via the reaction of {(Me3Si)2CH}PCl2 with two equivalents of in situ generated 2-LiC6H4CH2OMe. Phosphine 9 is readily deprotonated by Bu(n)Li to give the lithium phosphinomethanide [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Li] (13), which undergoes metathesis reactions with the alkoxides MOR [M = Na, K, R = Bu(t); M = Rb, R = 2-ethylhexyl] to give the heavier alkali metal phosphinomethanides [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]M]n in good yields [M = Na (14), n= 2; M = K (15), Rb (16), n=[infinity]]. Compounds 9, [{(Me3Si)2CH}P(C6H4-2-CH2OMe)2LiBr]2 (10), and 14-16 have been studied by X-ray crystallography; in the solid state 14 adopts a dimeric structure, whereas 15 and 16 crystallise as one-dimensional polymers.

Mixed donor-functionalised phosphinomethanide complexes of the alkali metals; synthesis, structures, and solution dynamics

“…The calculated structure of the ground state (12a) closely resembles the solid state structure of 12 obtained by X-ray crystallography. Although the calculated bond lengths in 12a are typically overestimated by between 0.03 and 0.1 A ˚, the angles within the core of the calculated structure are similar to those obtained crystallographically; for example the P-Na-O bite angles in 12 and 12a are 83.27 (7) and 83.50 • , respectively, while the P-Na-N bite angles are 84.24(9) and 86.74 • , respectively.…”

“…In addition, we have shown that the incorporation of donor-functionality at the periphery of a phosphinomethanide can have a pronounced effect on the coordination behaviour of these ligands. [3][4][5][6][7] The symmetrically-functionalised phosphinomethanide ligands [{(Me 3 Si) 2 C}P(C 6 H 4 -2-CH 2 Z) 2 ] -[Z = NMe 2 (1), OMe (2)] adopt a range of coordination modes in their complexes with the alkali metals. The peripheral amino groups in 1 enable this ligand to coordinate to alkali metal centres via a novel PN 2 -coordination mode, with no direct contact between the metal and the carbanion centre.…”

“…[[{(Me 3 Si) 2 C}P(C 6 H 4 -2-CH 2 NMe 2 ) 2 ]M(L) n ] x [M = Li (3), n = 0, x = 1; 3 M = Na (4), (L) n = (Et 2 O) 0.5 (DME) 0.5 , x = 1; 4 M = K (5), Rb (6), n = 0, x = •; 5 M = Cs (7), (L) n = (PhMe), 6 x = •] exhibit remarkable structural diversity in the solid state, ranging from non-solvated monomers to one-dimensional polymers.…”

“…The less sterically demanding methoxy groups of 2, in conjunction with the extra lone pair at the oxygen atom of this substituent, allow for increased inter-and intramolecular interactions in the alkali metal complexes of this ligand. 7 In contrast to the monomeric structure of 4, the sodium complex [[{(Me 3 Si) 2 C}P(C 6 H 4 -2-CH 2 OMe) 2 ]Na] 2 (8) adopts a dimeric structure in the solid state; each ligand binds the sodium ion via a PO 2 -coordination mode, with one O atom on each ligand bridging between two Na ions, forming a dimer with a Na 2 O 2 core. The ligand binding mode in the corresponding potassium and rubidium complexes (10)] is significantly different from the doubly chelating PN 2 /PO 2 coordination modes observed for 4-8.…”

Structural, Spectroscopic, and Computational Analysis of Heterometallic Thorium Phosphinidiide Complexes

“…Complex 3 is the only compound in which the alkali metal does not have an interaction with an arene ring of the mesityl, which may be the reason why it is an outlier, because the alkali metal–phosphinidiide bond lengths of 2.881(2), 3.2297(16), 3.5586(9), and 3.6467(14) Å are consistent with their respective effective nuclear charge. There are few compounds containing Rb–P − and Cs–P ,,− ,− bonds, with the M–P distances ranging from ∼3.32 to 3.57 (for Rb) Å and from ∼3.42 to 3.81 Å (for Cs), which encompass the distances observed in 4 and 5 .…”