Metalation of N-mesityl-P,P-diphenylphosphinic amide (1) in THF at room temperature with MgBu 2 and [(thf ) 2 Ca{N(SiMe 3 ) 2 } 2 ] yields [(thf ) n M{Ph 2 P(=O)-N-Mes} 2 {Ph 2 P-(=O)-NH-Mes} 2 ] [M/n = Mg/0 (2), Ca/2 (3)] regardless of the applied stoichiometry. These complexes are stabilized by weak intramolecular N-H···N hydrogen bridges. In both complexes only one NMR signal set is observed, however, for the magne- [a] Supporting Information (see footnote on the first page of this article): Experimental details, NMR spectra, temperature-dependent NMR spectra, crystallographic and refinement details.

Metalation of N -mesityl- P , P -diphenylphosphinic amide Ph 2 P(O)-NHMes (HL, I ) with MgBu 2 and Ae{N(SiMe 3 ) 2 } 2 (Ae = Ca, Sr, and Ba) yields alkaline-earth metal complexes with the compositions of [(thf) n Ae(L·HL) 2 ] [Ae/n = Mg/0 ( II ), Ca/2 ( III )] as well as of [Sr 2 L 3 (L·HL)(HL)] ( 1 ), [Ba 2 L 3 (L·HL)(HL)] ( 2 ), [Ba 3 L 6 ] ( 3 ), and [(thf) 2 Ba 3 L 6 ] ( 4 ). In III , 1 , 2 , and 3 , the alkaline-earth metal atoms are in severely distorted octahedral environments, and the structural distortions are partially caused by the small O-Ae-N bite angles of the chelating Ph 2 P(O)-NMes anions. The substructures (L·HL) contain N–H···N hydrogen bridges, stabilizing the arrangement of the ligands in complexes II , III , 1 , and 2 . In the trinuclear barium complex [Ba(μ-L) 3 Ba(μ-L) 3 Ba] ( 3 ), a rigid adjustment of the anionic L bases leads to a C 3 -symmetric molecule in the crystalline state with bridging oxygen atoms. Due to the small O–Ba–N bite angles of the chelating anions, vacant coordination sites are available at the outer barium centers. Coordination of thf bases in these gaps yields the complex [(thf)Ba(μ-L) 3 Ba(μ-L) 3 Ba(thf)] ( 4 ). However, THF is unable to deaggregate the trinuclear complexes into smaller barium-containing moieties. Increasing the radius of the alkaline-earth metals and increasing the nuclearity of these compounds lead to decreasing solubility in common organic solvents. NMR studies verify that the molecular structures of these alkaline-earth metal complexes are maintained in ethereal solvents and toluene.

Metalation of N‐mesityl‐P,P‐diphenylphosphinic amide with nBuLi in toluene yields tetranuclear lithium N‐mesityl‐P,P‐diphenylphosphinimidate ([Ph2P(OLi)=N−Mes]4, 1). Metalation of Ph2P(O)−N(H)Mes with a mixture of dibutylmagnesium and butyllithium in DME leads to formation of dinuclear [Ph2P{OLi(dme)}=N−Mes]2 (2). Excess of Ph2P(O)−N(H)Mes gives dinuclear [Li(O−PPh2=N−Mes){Ph2P(=O)−N(H)−Mes}]2 (3) with three‐coordinate alkali ions. The metathetical approach via reaction of 1 with anhydrous magnesium bromide in ethereal solution yields [{(thf)LiBr}2{(thf)Li(O−PPh2=NMes)(Et2O)Li(O−PPh2=NMes)}] (4). Heterobimetallic Li/Mg compounds are not accessible by these protocols. Reactions of 1 with DME, with excess of Ph2P(O)−N(H)Mes or with LiBr allows the straightforward conversion to compounds 2, 3 and 4.

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