Structure du dihydrogénodiphosphate de potassium anhydre, K2H2P2O7

(NH4)2[Ni(H2P2O7)2(H2O)2]

“…The two tetrahedra share an apex (O4) to form the H 2 P 2 O 7 2À diphosphate anion in a roughly eclipsed conformation. The average P-O distance of 1.545 Å is the same as for the isotypic Co member and is comparable to the average distances observed for other diphosphates: 1.533 Å in (NH 4 ) 2 Zn(H 2 P 2 O 7 ) 2 Á2H 2 O, 1.537 Å in K 2 H 2 P 2 O 7 (Larbot et al, 1983) and 1.543 Å in K 3 H(H 2 P 2 O 7 ) 2 (Dumas, 1978).…”

Dipotassium zinc bis(dihydrogendiphosphate) dihydrate, K2Zn(H2P2O7)2·2H2O

“…The K atoms are eightfold coordinated, with KÐO distances ranging from 2.757 (3) to 3.339 (4) A Ê . The average KÐO distance of 2.959 A Ê is slightly longer than those found in K 4 P 2 O 7 Á3H 2 O (2.812 A Ê ; Dumas & Galigue, 1974) and K 2 H 2 P 2 O 7 (2.908 A Ê ; Larbot et al, 1983).…”

“…To our knowledge, no mixed dihydrogendiphosphates of the form (A,T) x (H 2 P 2 O 7 ) y ÁzH 2 O (A = alkaline earth and T = transition metal) have been reported. Some simple alkali metal dihydrogendiphosphates are known: Na 2 H 2 P 2 O 7 Á6H 2 O (Collin & Willis, 1971), K 2 H 2 P 2 O 7 (Larbot et al, 1983), K 2 H 2 P 2 O 7 Á0.5H 2 O (Dumas et al, 1973), K 3 H(H 2 P 2 O 7 ) 2 (Dumas, 1978), K 3 Na(H 2 P 2 O 7 ) 2 (Dumas et al, 1980), Rb 2 H 2 P 2 O 7 Á0.5H 2 O (Averbuch-Pouchot & Durif, 1993a) and Cs 2 H 2 P 2 O 7 (Averbuch-Pouchot & Durif, 1993b). Acidic metal diphosphates have been implicated in some enzyme-catalysed reaction processes (Haromy et al, 1984) and are used as inhibitors in the formation and dissolution of apatite crystals in vitro (Mathew et al, 1993).…”

“…Data collection: SMART (Bruker, 1999); cell re®nement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and ATOMS (Dowty, 1999); software used to prepare material for publication: SHELXL97. (Larbot et al, 1983), K 2 H 2 P 2 O 7 .1/2H 2 O (Dumas et al, 1973), K 3 H(H 2 P 2 O 7 ) 2 (Dumas, 1978), K 3 Na(H 2 P 2 O 7 ) 2 (Dumas et al, 1980) (Averbuch-Pouchart & Durif, 1993b). Acidic metal diphosphates have been implicated in some enzyme-catalyzed reaction processes (Haromy et al, 1984) and are used as inhibitors in the formation and dissolution of apatite crystals in vitro (Mathew et al, 1993).…”

“…The structure of K 2 Zn(H 2 P 2 O 7 ) 2 •2H 2 O can be described in terms of layers parallel to (001) (Fig. 1) (2.908 Å; Larbot et al, 1983).…”