Complexes of diisopropyl methylphosphonate with metal salts containing complexing anionic groups

J. inorg,nucl.Chem.,1970,Vol.32, pp. 83 to 90. PergamonPress. Printedin Great Britain

COMPLEXES OF DIISOPROPYL METHYLPHOSPHONATE WITH METAL SALTS CONTAINING COMPLEXING ANIONIC GROUPS* N. M. K A R A Y A N N I S , C. OWENS, L. L. PYTLEWSK1 and M. M. LABES Department of Chemistry, Drexel institute of Technology, Philadelphia, Pa. 19104 (First received 26 March 1969; in revised form 9 May 1969) Abstract-- Although the synthesis of complexes of diisopropyl methylphosphonate 1DI M P) with metal salts containing anions with coordinating ability presents severe difficulties in most cases, a number of complexes have been isolated and characterized by means of spectral, magnetic and conductance studies. These include nitrato and thiocyanato complexes of the types [UO21DIMP)~IO_~NO)2] and [M(D1MP)a(NCS)~](M = Mg,Ni), and quaternary crystalline complexes obtained from systems of the type MgCIz-MCI2-DIMP-H20 (M = Mn, Co, Ni, Cu, Zn). No stable or sufficiently pure complexes of DIMP with 3d or alkaline earth metal halides could be obtained. By utilization of equimolar amounts of anhydrous MgCI2 and MCI~ hydrate in the presence of DIMP, chloride ions are transferred from Mg(ll) to M(ll) and the chlorometallate anion is stabilized by the large complex cation which consists of Mg(II) coordinated to DIMP and water molecules and, in some cases, chloride ions. The complexes synthesized in this way were assigned the structures [Mg~DIMP)4~H~O)2] [MCI~](M = Mn, Co, Zn), [MgCI(D1MP)~(H20)~][NiCI3(DIMP)] and [MgCI(DIMP)(H20)4][CuCI:~] • DIMP. The latter complex is one of the few examples of a stable compound of the trichlorocuprate (II) anion. The structure of this compound involves one free D1MP molecule enclosed in cavities in the lattice, INTRODUCTION

PHOSPHINE oxides form crystalline complexes with metal halides, nitrates, thiocyanates and perchlorates [1-5]. We have recently reported a number of crystalline cationic complexes of metal perchlorates with diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate(DMMP)[6,7]. DIMP also forms crystalline complexes with Ti(IV) and Sn(II) and tlV) halides, uranyl nitrate and Mg(II) and Ni(II) thiocyanates, which can be easily isolated. However, we have not been able to isolate DIMP complexes with other metal halides, nitrates or thiocyanates in a sufficiently pure state. Alkoxyphosphoryl compounds are, in general, weaker ligands than phosphine oxides [7, 8]. Thus, for example, the bidentate ligand bisqdi-n-butylphosphinyl)methane is capable of displacing all of the chloride ions from around a transition *The support of U,S. Army Edgewood Arsenal under Contract No. D A A A 15-67-C-0644 is gratefully acknowledged. I. D, M. L. G oodgame and F. A, Cotton, J. them. Soc. 3735 ( 1961) and references therein. 2. K, lssleib and B. Mitscherling, Z. anorg, allg. Chem. 304, 73 (1960). 3. F. A. Cotton, D. M, L. Goodgame and R. H. Soderberg, Inorg. Chem. 2, 1162 (1963). 4. M.J. Frazer, W. Gerrard and R. Twaits, J. inorg, nucl. Chem. 25, 637 (1963). 5. D. R. Cousins and F. A. Hart, J. inorg, nucl. Chem. 30, 3009 (1968). 6. N. M. Karayannis. C, Owens, L. L. Pytlewski and M. M. Labes, J. inorg, nucl. Chem. 31, 2059 (1969). 7. N. M. Karayannis, C. Owens, L. L. Pytlewski and M. M. l_abes, J. inorg, nuel, Chem, 31, 2767 (1969). 8. S. N omura and R. Hara, A nalytica ehim. A eta 25, 212 ( 1961 ). 83

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metal ion and forms complexes of the general type [ML3][MCI4], (M = Fe(Ill), Co(II), Ni(II), n = 1, 3)[9]. However, bis-(diisopropoxyphosphinyl)-methane is a weaker donor and competes with chloride ions and water molecules in the first coordination sphere of a metal ion. This leads to products of unpredictable structure, i.e. [FeLCI2][FeCI4], CoClz. L . H20, 8CUC12.5L etc.[9]. On the other hand, interaction of neutral alkoxyphosphoryl compounds with metal halides at elevated temperatures leads to elimination of alkyl halide and formation of metal chelates of the corresponding mono-acid [10]. Thus, both factors discussed above account for the difficulties encountered during attempts at the synthesis of D I M P complexes with metal salts containing complexing anionic groups. Extraction studies of dipositive 3 d metal chlorides with trialkyl phosphates from aqueous LiCI solution, have shown that formation of [MCIa] 2- is favored with increasing LiCI concentration[11-13]. Further, the species extracted from the system CoC12-CaCl2-H20-tributyl phosphate(TBP), has been assigned the formula [Ca(TBP)2(H20)2][CoC14] on the basis of spectral evidence [14]. In complexes of the type A . 2 B . XPOCI3 (A = divalent metal halide, e.g. MgCI2, MnCI2; B = SbCls, FeC13, SnCI4; X = 6-8) the anions SbCIG-, FeCl4- and [SnCI~ • POCI3]- have been identified by means of far i.r. and visible spectral15]. Many of these compounds contain 1-2 uncoordinated POC13 molecules enclosed in cavities in the lattice[15]. Anionic chloro-complexes of the 3d metal ions are, reportedly, stabilized in concentrated aqueous solutions in the presence of metal chlorides in which the cation has a noble gas electronic core and is sufficiently polarizable to bind all the water molecules (e.g. Mg 2+) [16, 17]. It follows from the above discussion that addition of MgCI2 to D I M P solutions of transition metal halides would favor the transfer of chloride ions to the transition metal ion and lead to the formation of stable complexes. In fact, we have been able to synthesize a number of crystallirie complexes from systems of the type MgC12-MCI2D I M P - H 2 0 (M = Mn, Co, Ni, Cu, Zn). The present paper extends our studies on complexes of DIMP[6], to include the complexes of this ligand with metal salts having anionic groups with coordinating ability. EXPERIMENTAL Chemicals. Pure, water-free D I M P was provided by Edgewood Arsenal, Maryland, and utilized without further purification. The metal salts, triethylorthoformate and the various solvents utilized were the purest commercially available. Interaction o f metal halides with DIMP. Adducts of the type M X , -2DIMP (M -----Ti(IV), Sn(II), Sn(IV), X = C1, Br, l, n = 2, 4) are easily obtained by mixing dilute CC14 solutions of metal halide and D I M P (molar ratio of salt to ligand 1 : 2) and allowing the great bulk of the solvent to evaporate under reduced pressure. These compounds are currently the subject of extensive studies and will be dealt with in subsequent publications. Solutions of transition and alkaline' earth metal halides in D 1M P

9. J. A. Walmsley and S. Y. Tyree, lnorg. Chem. 2, 313 (1963). 10. E. Hayek and E. Rhomberg, Mh. Chem. 83, 1318 (1952); V. Gutmann and K. Fenkart, Mh. Chem. 99, 1452 (1968). 11. D. F. C. Morris, E. L. Short and D. N. Slater, Electrochim. A eta 8, 289 (1963). 12. D. F. C. Morris and E. R. Gardner, Electroehim.Acta8,823 (1963). 13. D. F. C. Morris and D. N. Slater, J. inorg, nucl. Chem. 27, 250 (1965). 14. B. Jezowska-Trzebiatowska, A. Bartecki and S. Kopacz, Zh. neorg. Khim. 13, 864 (1968). 15. W. L. Driessen and W. L. Groeneveld, Reel. Tray. chim. Pays-Bas. 87, 786 (1968). 16. C. A. Angell and D. M. Gruen, J . A m . chem. Soc. 88, 5192 (1966). 17. D. M. Gruen and C. A. Angell, lnorg, nucl. chem. Lett. 2, 75 (1966).

Complexes of diisopropyl methylphosphonate

85

do not generally yield crystalline products at relatively low temperatures. At temperatures of 125 ° or higher chelates of isopropyl methylphosphonic acid are precipitated, with simultaneous evolution of isopropyl halide or hydrogen halide and propene. FeC13, VClz and CuClz form crystalline precipitates with D I M P in p-dioxane at 100 ° under reduced pressure. These compounds exhibit negative shifts of the P - O stretching frequency, which are characteristic of coordination through the phosphoryl oxygen[18]. However, analytical results and, in particular, metal to chlorine and carbon to phosphorus ratios indicate that the complexes are contaminated with substantial amounts of chelates of dealkylation products of DIMP. Negative vpo shifts have, reportedly, been observed during the gas-solid interaction of DIM P with divalent metal halides [ 19]. Attempts at synthesizing D I M P complexes with Ni(ll) halides, by allowing D I M P vapor to interact with the anhydrous metal salt under a vacuum of 5 × 10-;7 mm Hg, led to the formation of a mixture of the complex and unreacted metal halide. These complexes exhibit negative Vpo shifts (Vpo: D I M P 1241 cm-', N i C I z + D I M P 1218sh, l l 9 0 c m -t, NiBr2 + D I M P 1220sh, 1197 cm -1, N i l 2 + D I M P 1220sh, 1200 cm-'). However, they decompose rapidly when exposed to the atmosphere and could not be obtained in a pure state. Quaternary complexes from the systems MgCI.~-MCI.z-DIMP-H.,_O. These complexes were prepared by dissolving equimolar quantities of anhydrous MgCI2 and MCI2 hydrate (M = Mn, Co, Cu, Zn) in a 1 : 1 mixture of triethyl orthoformate-ethanol and adding 4 moles of D I M P per mole of MgCI2. The mixture is heated at 60 ° for 1 hr under stirring, The complex is precipitated upon cooling, under continuous stirring. For the preparation of the corresponding Ni(II) complex a five-fold excess of D I M P was utilized. A brown Fe(lI) analog was also isolated by the same procedure, but it was rather unstable and could not be obtained in a sufficiently pure state. The complexes are filtered, washed with ether and dried over magnesium perchlorate in an evacuated desiccator. It should be noted that the same reaction leads to viscous liquid final products when anhydrous MgCI2 and MCI~ are utilized as starting materials. Complexes of Metal Thiocyanates. Mg(ll) or Ni(l 1) thiocyanate is dissolved in DIMP and the solution is briefly heated (2-3 min) at 75 °. A crystalline precipitate is formed when the solution is allowed to stand at room temperature overnight. The complex is filtered, washed with ether and dried over Mg(CIO4)2 iia an evacuated desiccator. Under the same conditions no solid products were obtained with other metal thiocyanates (Fe(Ill), Co(lI), Cu(ll), Zn(II)). Complexes of metal nitrates. The uranyl nitrate complex was prepared by heating a triethyl orthoformate-DIMP solution of the salt at 40 °, under stirring, and, after cooling, allowing the solution to stand in the refrigerator overnight. Large yellow crystals are formed under these conditions, which are filtered, washed with cyclohexane and dichloromethane and dried over Mg(CIO4)2 in an evacuated desiccator. Single crystals of this complex were grown from CS2 by the procedure described elsewhere [6]. Under similar conditions Mn(NO3)2 and Cd(NO.~)2 yield crystalline precipitates, which are mixtures of the DIMP complexes and complexes of its dealkylation products, as indicated by analytical data. Other nitrates (Co(1 I), Ni(II), Cu(l I), La(I 1I)) yield viscous liquid final products, which show the characteristic negative PO shifts. Analyses of the solid complexes were performed by Schwarzkopf Microanalytical Laboratory, Woodside, New York. The syntheses reported here were repeated at least once with good reproducibility. Infrared spectra. I.R. spectra (4000-750 cm-') of the free ligand (liquid film) and Nujol mull of its metal complexes were obtained between IRTRAN 2 (zinc sulfide) windows on a Perkin-Elmer 621 spectrophotometer. Calibration of the spectra was effected by means of known frequency absorptions of polystyrene. The spectra of the thiocyanate and nitrate complexes are characterized by the absence of water bands. Electronic spectra. Solution and Nujol mull spectra of the new complexes were obtained with a Cary Model 14 spectrophotometer. Magnetic measurements. Magnetic susceptibilities were measured at room temperature {297°K) by the Faraday method. Mercuric tetrathiocyanatocobaltate(lI) was utilized as the magnetic susceptibility standard. Pascal's constants were used for the diamagnetic corrections[20]. Magnetic moments were calculated by use of the equation P-err= 2'84 ~/XM"°rr " T. 18. F. A. Cotton, R. D. Barnes and E. Bannister, J. chem. Soc. 2199 (1960). 19. G. G. Guilbault, Analytica. chim. Acta 39,260 (1967). 20. J. Lewis and R. G. Wilkins, Modern Coordination Chemistry, p. 403. Interscience, New York (1960).

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Conductance measurements. The conductivities of 10 -3 M nitromethane solutions of the complexes were measured at 25 ° by using a Wayne Kerr Universal bridge and a cell calibrated with aqueous 0"0IN potassium chloride.

RESULTS

AND

DISCUSSION

Properties and analytical data of the complexes are given in Table 1, electronic spectra in Table 2 and i.r., magnetic and conductance data in Table 3. Nujol mull and D I M P solution electronic spectra of the complexes do not show appreciable differences, with the exception of the Cu(II) quaternary complex. The negative Vpo shifts observed in all cases, indicate coordination of DIMP to the metal ion through the phosphoryl oxygen [ 18]. Thiocyanato and nitrato complexes. These complexes are non-electrolytes as shown by the conductance measurements (Table 3). The thiocyanate or nitrate groups are, therefore, coordinated to the metal ion. The electronic spectrum of the Ni(II) thiocyanato complex is characteristic of a hexacoordinated configuration[21]. In the i.r. spectra of the Mg(II) and Ni(II) thiocyanato complexes, yen occurs at 2077 and 2096 cm -1, respectively. Although the C-S stretch overlaps with the band of D I M P at 787 cm -1 [6], it is obvious that it occurs at about 800 cm -1 from the appearance of a strong absorption at 792 cm -1 in the spectra of both complexes. In the metal perchlorate complexes of D I M P a weak to medium band is observed at ca 787 cm-116]. The occurrence of UCNat 2100-2040 cm -~ and Vcs at 860-780 cm -1 is characteristic of coordination to the metal ion through the nitrogen of the NCS group [22]. On the basis of the evidence discussed above the thiocyanato complexes are formulated as [M(DIMP)4(NCS)2] (M = Mg, Ni). It is interesting to note that the i.r. spectra of these complexes in the 1350850 cm -1 region indicate that, with the exception of the P-O stretch, no significant shifts of the free ligand bands occur upon complex formation. Thus D I M P shows absorption maxima(cm -~) in this region at 1309m(PCH3), 124Is(P-O), 1173m, 1139m, l106m, (all three characteristic of the ( P ) - O - C stretch in isopropyl esters), 1008vs, 980vs ((C)-O-P stretch), 912m, 895m (PCH3 occurring as a doublet)[6,23]. [Ni(DIMP)4(NCS)2] exhibits the following bands (cm -1) in the same region: 1309m, 1202s (P-O), 1173m, 1139m, l102m, 1010vs, 980vs, 915m, 899m. The i.r. spectrum of the uranyl nitrate complex shows the characteristic v4 and vl modes of coordinated nitrate (C2v symmetry)J24] at 1520 and 1276 cm -~, respectively, and the vz mode of the uranyl group at 927 cm -1. The other bands of coordinated nitrate overlap with D I M P absorptions. It is impossible to distinguish between coordination through one or two oxygen atoms for the nitrate group from i.r. evidence [24]. However, the two nitrate groups reportedly act as bidentate ligands in dioxodinitratobis-(triethyl phosphate) uranium(VI)[25]. A similar structure is, therefore, assigned to the D I M P analog, which is formulated as [UO2(DIMP)2(O2NO)~]. 21. N. S. Gill and R. S. Nyholm, J. chem. Soc. 3997 (1959). 22. A. Sabatini and I. Bertini, lnorg. Chem. 4, 1665 (1965); S. M. Nelson and T. M. Shepherd, J. inorg, nucl. Chem. 27, 2123 (1965). 23. L. C. Thomas and R. A. Chittenden, Spectrochim. A cta 20, 467,489 ( 1964); 21, 1905 (1965). 24. B. M. Gatehouse, S. E. Livingstone and R. S. Nyholm, J. chem. Soc. 4222 (1957). 25. J. E. Fleming and H. Lynton, Chem. Ind. 1409 ( 1959); 1415 (1960).

M.p.°C

Pale 81-82.5 green Deep 81-82 blue Blue70-5-72 green Bright 123-125 yellow White 83-84 White 47-49 Yellow 68-69 green Yellow 98-98.5

Color

22,29

34.03 41.84 40.23

25.39

34,26

34.25

34.39

Calc

22.07

33-41 42.17 39-71

25.19

33-56

33.37

33.79

Found

*The solid Mn(l 1) complex exhibits an intense yellow fluorescence.

[U O21DIMP)z{NOs)2]

MgClz.ZnCI2.4D1MP.2 H20 [Mg(DIMP)4(NCS)2] [Ni(DIMP)4INCS)~]

MgCI.2.CuCI2.2DI MP.4H~O

MgC12'NiCI~.4DIM P-2H20

MgCI2.CoCI~.4DIMP-2 HzO

MgCI2'MnCI2,4DIMP.2H20*

Complex

C%

4-60

7.34 7.% 7-65

6-39

7.39

7.39

7.42

Calc

4-60

7.48 7-95 7.38

6.16

7.00

7.21

7.42

Found

H% Found

9.18

3.67

2.48

2.48

8.21

8.31

1 2 . 5 4 1 1 . 7 9 2.46 2.82

9.35

1 2 . 6 2 12.61

1 2 . 6 2 12.05

2-48 2-61

3.34

2.48

2.55

2.46

Found

Mg%

Calc

1 2 . 6 7 1 2 . 4 7 2.49

Calc

Analytical data P%

31.31

6.68

6.55 31.55

7,01

9-21

5.64

6.64

5.47

6.61

9-59

5.98

6,00

5.62

3d metal or U% Calc Found

Table 1. Properties and analytical data of diisopropyl methylphosphonate complexes

Found

3.91

3-78

1 4 . 3 5 15-02

21.41 20.60

14.45 13.%

14.44 15.06

1 4 . 5 0 14.83

Calc

CI or N%

0

::r

0

O

88

No M. K A R A Y A N N I S et al. Table 2. Electronic spectra of diisopropyl methylphosphonate metal complexes Complex

MgCI2.MnCI2.4DIMP.2H20 MgCIz'CoCI2-4DIM P.2H20 MgCI2.NiCI2.4DIMP.2H20

MgCI~.CuC12.2DIMP.4H20

[Ni(DIMP)4(NCS)2]

Medium

X max, nm(~ max)

Nujol 10-2M in D I M P Nujol 10-'~M in D I M P Nujol 10-aM in D1MP

343sh, 365m, 380sh, 405sh, 432w, 455w 341 sh, 366(6.0), 455(0.56) 599sh, 618sh, 640s, b, 672s, b, 693s, b 595sh, 611 (318.8), 677(618), 697sh, 1570(60.7) < 300, 465vb, 609s, 680sh 490(29.5), 594sh, 626(102.2), 688(64.9), 1341(21.4) 312vs, 440vs, b, 890s, b 305(581 ), 363(431.9), 439(97.3), 475(98.8), 892(8.6), 1115(8.0)

Nujol 10-3M in DIMP 3 x 10-4 M in CH.~CN with added DIMP 10-aM in D I M P

310(3583),459(1184), 975(106.6), 1195(151.6) 326(54.4), 418(15.5), 678sh, 757(6-5), 1243(7.3)

sh: shoulder, v: very, s: strong, m: medium, w: weak, b: broad. Table 3. Infrared (upo), magnetic and conductance data on D I M P metal complexes

Complex MgCI2 MnCI2 4DIMP 2H20 MgCI2 COC124DIMP 2H~O MgCI2 NiCI2 4DIMP 2H20 MgCI2 CuCI~ 2DIMP 4H~O MgCI2 ZnCI2 4DIMP 2HzO [Mg(DIMP)4(NCS)2I [Ni(DIMP)4(NCS)2] [U O2(DI M P)z(N 03)2]

vr,o,cm -1. 1215sh,1198 1215sh,1197 1212sh,1198, 1171 1239,1215 1217sh,1199 1212 1202 1167

AM,ohm-tcm2mole-~ (concentration) X~e°rr×I06 /~eft,BMT (10-aM),25°C (6× 10-~M),22°C 14218 9323

5.83 4.72

66.4* 72.2§

5257 1415 --4786 --

3.55 1.84 --3-38 --

63.4* 70.3* 74.6§ 8.4, 9.2* 14.6§

93-1, 81.1§, 109.7, 105.6, 108.7¢ 92.3*

sh: shoulder. *Vpo for DIMP, 1241 cm -1. TAt 297°K. *In CHsNOz + DIMP solution due to limited solubility of the complex in nitromethane. §In CH3NO2 solution.

The quaternary complexes. The sharp melting points of the quaternary complexes are indicative of their purity. The conductances of these complexes are slightly lower than those observed for 1 : 1 electrolytes in 10 - 3 - 5 × 10-5 M nitromethane solutions[21, 26]. Nevertheless, the colors, electronic spectra and magnetic moments (Tables 2 and 3) of the Mn(II), Co(II) and Ni(II) complexes clearly indicate that the transition metal ions are in an essentially tetrahedral environment [11-13, 21]. Analogous TBP complexes extracted from aqueous solutions in the presence of LiCI have been characterized as associated electrolytes in solution of the types [Li. X(TBP,H20)]+[MC13.2TBP] - and [Li-X(TBP,H20)]2 + [MC14] 2- (M = Mn, Co, Ni, Cu, Zn)[11-13]. Thus, the new complexes reported here may be formulated in a similar manner. 26. W. Byers, A. B. P. Lever and R. V. Parish, lnorg. Chem. 7, 1835 (1968).

Complexes of diisopropyl methylphosphonate

89

The X-ray powder diffraction patterns of the Mn(II), Co(II) and Zn(lI) complexes are almost identical. The Vpo of these complexes occurs as a sharp band at 1197-1199 cm -1 with a shoulder at 1215-1217 cm -1. Similar i.r. patterns have been observed in the products of the gas-solid interaction of D I M P with metal chlorides [19]. However, the magnitude of the Vpo shift shows considerable variations with change of metal ion (MnCI2 1220sh,1198; CuCI2 1200sh,1185; ZnCI~ 1205sh,1173; HgCI2 1228,1174119]; NiCI2 1218sh,1190 cm -~ (this work)). Thus, the occurence of Upo at the same frequencies in the three complexes under discussion is indicative of coordination of all D I M P molecules to Mg(II). The splitting of the PO stretch in two bands is attributed to two chemically inequivalent sets of ligands in the [Mg(DIMP)4(H20)2] cationic group[26]. Coordination of water to Mg(II) is indicated from the fact that, in all the quaternary complexes, the intensity of the i.r. water bands does not diminish after prolonged vacuum desiccation over Mg(C104)2. N o free D I M P bands are observed in the i.r. spectra of the Mn(II), Co(II) and Zn(II) complexes. The electronic spectra in the Mn(ll) and Co(II) complexes are characteristic of the corresponding [MCI4] ~- anions, as far as band positions and intensities are concerned[11, 14, 21]. On the basis of the above discussion the Mn(II), Co(II) and Zn(II) complexes are formulated as [Mg(DIMP)4(H20)2][MC14]. The conductances of these complexes in nitromethane solution (Table 3) are considerably lower than those expected from 2 : 2 electrolytes [27]. It should be noted, in this connection, that the molar conductances of [ML~][MCI4] (M = Co,Ni, L = bis-(di-n-butylphosphinyl)methane) in nitrobenzene are also lower than those corresponding to 1 : 1 electrolytes, owing to molecular association in solution[9]. In general, conductance data on 2:2 electrolytes of this type are rather scarce in the literature. The Vpo in the Ni(II) complex is split in three bands occurring at 1212sh, 1198 and 1171 cm -1. The first two bands are assigned to D I M P molecules coordinated to Mg(II), as is obvious from their occurrence at the same frequencies as in the complexes discussed above. The band at 1171 cm -~ is assigned to one D I M P molecule coordinated to Ni(II). In fact, although the electronic spectrum and magnetic moment of the complex point to an essentially tetrahedral configuration for the Ni(II) ion, the spectrum is different from that of [NiCI4] 2[11, 13]. This anion is formed in TBP solutions only in the presence of a large excess of chloride ions[13]. The electronic spectrum of the Ni(II) complex is, however, very similar to that of the species characterized as [Li.xTBP]*[NiCI:~ •yTBP]- by Morris and Slater [13]. Apparently, in the case of the complex under discussion only one chloride ion is transferred from Mg(II) to Ni(II), under the experimental conditions (molar ratio of chloride ion to Ni(II) 2: 1). Thus, the formulation of the complex as [MgCI(DIMP)3(HeO)2][NiCI3(DIMP)] is justified on the basis of the evidence presented above. Cu(II) formed, rather unexpectedly, a complex of a different type than the other divalent 3d metal ions. From the i.r. spectrum (Table 3) it is obvious that one D I M P molecule is not coordinated ( 1239 cm-') while the other is coordinated to Mg(II) (1215 cm-~). Coordination of D I M P to Cu(II) is ruled out, since if this was the case ~'POshould appear at a lower frequency (below 1200 cm-1)[19]. The 27, F. A. Cotton and D. M. L. Goodgame, J. A m. chem. Soc~ 82, 5771 (1960).

90

N.M.

K A R A Y A N N | S et al.

absence of a very strong band at c a . 400 nm in the electronic spectrum excludes the presence of [CUC1412-[12, 28]. The presence of [CuCla.DIMP]- is also excluded on the basis of the i.r. evidence. The solid state and acetonitrile solution (with added D I M P for the complete dissolution of the complex) spectra of the Cu(II) complex provide definitive evidence for the presence of the [CuCl3]anion [29]. In fact, the spectrum of this ion shows absorption maxima in acetonitrile solution at 261, 315,465 and 900 nm having extinction coefficients of the same order of magnitude as those observed in the present work [29]. Thus, under the experimental conditions, transfer of one chloride ion from Mg(I1) to Cu(II) leads to the stabilization of the rather uncommon [CuCla]-. On the basis of the above discussion the complex is formulated as [MgCI(DIMP)(H~O)4][CuC13] •DIMP. The free ligand molecule is, presumably, enclosed in cavities in the lattice [15]. In D I M P solution the [CuCl3]- anion is apparently solvated and the resulting spectrum is very complicated (Table 2) and indicative of the presence of more than one species. In conclusion, the complexes of D I M P with metal salts containing complexing anionic groups are relatively unstable and decompose at moderately elevated temperatures. Stable crystalline D I M P complexes with salts of this type were obtained only in a few cases. In all other cases the complexes either could not be isolated or were contaminated with substantial amounts of decomposition products. However, systems of the type MgCI2.MCI~.DIMP.H20 (M----Mn, Co, Ni, Cu, Zn) yield stable quaternary complexes. In this case one or two chloride ions are transferred from Mg(II) to the 3d metal ion and the resulting anionic chlorometallate complex is stabilized by the large countercation [11-17]. Further characterization studies of the metal complexes of phosphonate esters reported here and in previous papers [6, 7], including far i.r. and Raman solution spectra, are to be undertaken as soon as the proper instrumentation becomes available. 28. C. Furlani and G. Morpurgo, Theor. chim.Acta 1, 102 (1963). 29. W. Schneider and A. V. Zelewsky, Heir. chim..4 cta 46, 1848 (1963).