Metalation of N‐mesityl‐P,P‐diphenylphosphinic amide Ph2P(=O)–N(H)Mes (1) with n‐butyllithium, sodium amide and potassium hydride yields the corresponding alkali metal N‐mesityl‐P,P‐diphenylphosphoryl amides of lithium (2), sodium (3), and potassium (4). The lithium complex 2 forms a dimer with an eight‐membered (Li–O–P–N)2 ring. The sodium derivative 3 crystallizes as a dinuclear centrosymmetric complex with a central Na2O2 ring. The potassium congener 4 precipitates as a tetranuclear compound with an inner K4O4 heterocubane cage. In these complexes the phosphoryl amido ligands act as bidentate Lewis bases and form strained four‐membered M–O–P–N rings. Due to this fact, the endocyclic M–O bonds of the M2O2 rings vary within a large range.

a b s t r a c tIn this work, the inhibitory effect of a commercial anti-scalant (Veolia Hydrex s 9209) on the calcium minerals of carbonate, sulfate and hydrocalumite (Ca/Al) clay deposition from seawater has been investigated. Different concentration factors and anti-scalant doses were studied by analyzing the water hardness and turbidity. The inhibitory effect of the investigated anti-scalant was efficient even at lower concentrations. The percentage inhibition decreases with increasing the temperature and increases with increasing the dose/amount of the anti-scalant. The carbonate scale inhibition was 499% and 98-99% at 50 and 70°C, respectively. The percentage inhibition of sulfate from hemihydrate was ranged from 80% to 87% for 2 and 8 ppm anti-scalant at 50°C. The inhibition of Ca/Al hydrocalumite deposition increases from 70% to 90% upon increasing the dose from 3 to 5 ppm, respectively. A recommended useful dose of antiscalant for seawater is 5 ppm.