Polyhedron Vol. 5, No. 12, PP. 2013-2020, 1986 Printed in Great Britain

0277-5387/86 S3.00+.00 0 1986 Pergamon Journals Ltd

BIS[BIS{@IPHENYLPHOSPHINYL)METHYL}ETHYL PHOSPHINATE]BIS(ETHANOL) COPPER(I1) PERCHLORATE :

SYNTHESIS, CRYSTAL AND MOLECULAR STRUCTURE

MARIJA HERCEG,* PAVICA BRONZAN-PLANINIC, HENRIKA MEIDER and

BORIS MATKOVIC

“Rudjer BogkoviC” Institute, 41001 Zagreb, Croatia, Yugoslavia

(Received 6 January 1986 ; accepted 8 May 1986)

Abstract-Bis~is{(diphenylphosphinyl)methyl}ethyl phosphinate]bis(ethanol) metal(I1) perchlorate complexes, where metal = Co, Ni or Cu, have been prepared by the reaction of metal perchlorates and bis[(diphenylphosphinyl)methyl]ethyl phosphinate, (RPOEt), in absolute ethanol. The crystal structure of the copper complex is triclinic, space group PI, a = 13.688(7) A, b = 14.424(10) A, c = 9.865(2) A, a = 110.43(4)“, /I = 90.13(2)“, y = 115.54(4)“, I’= 1619.8 A3, 2 = 1 and refined to R = 0.048 (R, = 0.057). The structure consists of complex cations surrounded by perchlorate anions. Two RPOEt ligands and two ethanols are coordinated to the copper atom situated at the centre of symmetry 0, 0, 0. The RPOEt ligand is bidentate [Cu-O distances 1.969(4) A, 2.312(4) A], but the third oxygen atom from phosphoryl bonds is hydrogen bonded [2.669(6) A], to the oxygen atom of ethanol molecule coordinated to the copper at 1.988(4) A. The conformations of the ligand and chelate rings, magnetic data, molar conductance values, infrared and electronic spectra are given.

The synthesis of some cobalt(D), nickel(H) and copper perchlorate’ and chloride 2,3 complexes with tripod organophosphorus compounds, was reported previously. The types of ligands, together with their abbreviations, are portrayed in Scheme 1.

The preparation of ligands RPOEt, RPPh and RPOH was reported before!T5 Bis[(diphenylphos- phinyl)methyl]ethyl phosphinate (RPOEt) is the ligand studied in the present work. It has three phosphoryl groups bridged by methylene groups. Another ligand consisting of three phosphoryl groups bridged by methylimido groups is dodeca- methyl diimidotriphosphoramide, named TRIPA,

[(CH3)2~2P(0) ’ NCH3 ’ [(CH3)2wP(o) * NCH3 *

P(“)[(CH3)2~2*a In the complexes : [Er(TRIPA)*

(No3)I(No3)2 and [Ca(TRIPA)(N03)2(H20)1 TRIPA acts as tridentate ligand.’

The ligands RPOEf RPPh and RPOH are poten- tially tridentate too. Conformation analyses revealed that RPPh acts preferentially as a bidentate ligand, but the possibility that this ligand is a tri- dentate complexing agent was not excluded.Y No

*Author to whom correspondence should be addressed.

structure of any complex with RPOEt, RPPh and RPOH has been reported yet.

Formulae of investigated complexes are:

[Co(RPOEt),(C,H,OH)~(ClO,),, mi(RPOEt), (C2HSOH)J(C104)2 and [Cu(RPOEt),(C,H,OH)d (ClO,),. These compounds were characterized by chemical analysis, infrared and electronic spectra, magnetic and conductivity measurements. X-ray structure determination has been carried out on

[Cu(RPoEt),(C,H,oH),1C10,),.

EXPERIMENTAL

The ligand, bis[(diphenylphosphinyl)methyl] ethyl phosphinate (RPOEt) was prepared ac- cording to the literature data.5

For conductivity measurements nitrobenzene was purified by the method of Taylor and Kraus.” All other solvents were analytical grade reagents dried over molecular sieves without further puri- fication.

Physical measurements and the instrumentation employed have been already described.’ The cor- rection for the diamagnetism of the ligand was made with the use of Pascal’s constants.” All physical

2013

2014 M. HERCEG et al.

Ligand =

If R’ is OCaHS, the &and is bi~{diphenylphosphinyl)methyl]ethyl phosphinate (RFOEt)

If R’ is CIHS, the ligand is bis[(diphenylphosphinyl)rnethyl]phenylphosphine oxide (RFTh)

If R’ is OH, the ligand is bis[(diphenylphosphinyl)methyl]phosphinic acid (RPOH)

Scheme 1.

measurements were carried out immediately after recrystallization.

Preparation of complexes

The complexes [M(RPOEt),(C,H,OH)J(ClO,), (M = Co, Ni, Cu) were obtained by the reaction of metal(H) perchlorate and ligand, both dissolved in absolute ethanol and mixed together in a molar ratio of 1: 2. As all three complexes were obtained exactly in the same manner, only detailed prep- aration of [Cu(RPOEt)2(C,H,0H)rj(C10& is given : 0.371 g Cu(ClO& - 6Hz0 (1 mmol) was dis- solved in 4 cm3 of hot absolute ethanol, filtered and added slowly into a hot, filtered solution of 1.054 g RPOEt (2 mmol) in 10 cm3 abs. ethanol. After one day the product was filtered and washed with absolute ethanol and diethylether. The complexes were recrystallized by dissolving in hot 96% ethanol. The solution was refluxed for an hour, filtered and allowed to stand in a covered beaker for 2 days. The crystaIs were then collected by fil- tration and washed with small portions of abs. ethanol. The yield was about 80%. Found: Cu, 4.4; P, 13.4; Cl, 5.2. Calc. for [Cu(RPOEt), (CzH,OH),](CIO,),: Cu, 4.5; P, 13.3; Cl, 5.1%. Found: Co, 4.2; P, 13.3; Cl, 5.1. Calc. for [Co(RPOEt),(C,H,OH)d(ClO&: Co, 4.0; P, 13.3 ; Cl, 5.1%. Found: Ni, 4.1; P, 13.5; Cl, 5.1. Calc. for [Ni(RPOEt),(C,H,OH),](ClO,), : Ni, 4.2 ; P, 13.3; Cl, 5.1%.

Crystallography

Pale bluish, almost colourless crystals of [Cu (RPOEt)z(CzH,0H)2](C104)2, suitable for cry- stallographic study, were obtained by slow careful cooling of a hot 96% ethanolic solution of the recry- stallized complex. Pink crystals of the cor- responding cobalt complex and greenish crystals of Ni complex obtained in the same way, were not large enough for crystallographic study. However, X-ray powder patterns of the three compounds are similar and indicate a close structural relationship.

The crystals are unstable and were kept in a des- iccator over ethyl alcohol. Crystallographic par- ameters are given in Table 1. Three-dimensional intensity data were collected at room temperature with a Philips PW 1100 diffractometer. As a check on the stability of diffractometer and of the crystal three standard reflections (OOT ; Tl 1; 222) were monitored periodically. The intensities were cor- rected with ZOAK program” for Lorentz and polarization effects.

The structure was solved by vector and difference Fourier methods. The calculations included both f and fN for anomalous dispersion effects of Cu, Cl, P, 0 and C atoms.i3 The positions of H atoms were calculated from geometrical criteria and included in the structure factor calculations at the end of isotropic refinement. They were given the calculated isotropic temperature factors B(H) = 1.6B(C) - 2. Neither positional nor temperature parameters were refined for H atoms. All non-hydrogen atoms were refined anisotropically. The function mini- mized in least-squares refinement was w(]&l - ]F#. The weighting function applied was w = l/c?&), a weighting scheme of type 9 from the XRAY system. l4 The scattering factors of Cromer and Mann” were used for non-H and those of Stewart et aLL6 for H atoms. The final residuals are R = 0.048, R, = 0.057. The goodness of fit dropped from S = 1.531 to S = 1.007 by applying scale fac- tor for weights, SCALWT = 0.43.i4 The largest shift/error in the final cycle is 0.48. Calculations were performed on a Univac 1100 computer at the University Computing Centre, Zagreb with XRAY 76 system. I4 Final positional and thermal par- ameters and structure factors have been deposited as supplementary material.

RESULTS AND DISCUSSION

Description of the structure

Figure 1 is an ORTEP plot of the structure with atom numbering scheme. Selected bond distances

Bis[(diphenylphosphinyl)methyl]ethyl phosphinate ligand

Table 1. Crystallographic parameters

2015

Formula Formula weight Space group

a (8) b (A) c (A) a (“)

?? V &) Z

&(g cm-3) & (g cm-3)

F(O, 090) /J (cm-‘) 2 (A) Data collection instrument Orientation reflections

No., range, 29” Crystal size (mm) Scan method Data collection range, 20” No. of unique data

measured Total with Fi 2 308 No. of parameters refined R RW

(G5lJw,*p,c1*cu 1399.5 PT 13.688(7) 14.424( 10) 9.865(2) 110.43(4) 90.13(2) 115.54(2) 1619.8 1 1.435 1.38 (pycnometer,

decalin as liquid) 727 6.4 0.7107 Philips PW 1100

22,416 0.4 x 0.16 x 0.06 O-28 4-60

3970 3640 394 0.048 0.057

GoJ%&p&c0 1394.9 PT 13.753(4) 14.449(5) 9.860(4) 110.65(3) 90.12(3) 115.71(4) 1623.8 1 1.426

725 39.8 1.5418 Philips PW 1100

18,10-25

and bond angles are given in Tables 2 and 3, respect- ively ; C-C distances and C-C-C angles in per- ipheral phenyl rings are available as supplementary material.*

The structure consists of complex cations sur- rounded by perchlorate anions. Two RPOEt ligands and two ethanols are coordinated to the copper atom. The polyhedron around the copper is tetrahedrally distorted octahedron. The RPOEt

* Supplementary material, available from the Editor, includes : tables of atom parameters, equivalent isotropic and anisotropic temperature factors, observed and cal- culated structure factors, bond distances and angles within peripheral phenyl rings and those including hydro- gen atoms, as well as equations of least-squares planes. Atomic coordinates have also been deposited with the Cambridge Crystallographic Data Centre.

ligand is bidentate, but the third phosphoryl oxygen atom is hydrogen bonded to the oxygen atom of ethanol molecule coordinated to the copper.

One terminal and the central p---O group of RPOEt ligand are coordinated to the copper at two unequal distances [1.969(4) and 2.312(4) A] thus permitting an extended conformation of the ligand, with the torsion angle about one of the central bonds, C(91 )-P(3), of 171.9(3)“, the O(ljCu-O(3) chelate angle of 90.0(l)’ and O(1). . - O(3) bite of 3.036(4) A. The conformation about the other central bond, P(3jC(93), is gauche, with a torsion angle -78.6(4)“, the O(3) - * *O(5) distance is 3.269(5) 8, and the P(ljP(3jP(5) virtual angle is 120.14(6)“. The valence angle on the bridging carbon atom which is involved in the six-membered chelate ring, P(ljC(91 jP(3) is larger than the corresponding angle in the non coordinated part of the ligand, P(3jC(93 )-P(5), 113.9(3),O vs 112-l(3)“. The

2016 M. HERCEG et al.

Fig. 1. Molecular geometry and atom-labelling scheme for the molecule [Cu(RPOEt)z(CzH,OH)21(C104)2.

intracation hydrogen bond, O(5). . . H-O(7) of 2.669(6) 8, with H-O(7) of 1.092(4) w and the angle on H of 179.6(2)’ may be responsible for this.

Taking into account the O(5) - * - H-O(7) hydro- gen bond, there are two chelate rings in one asymmetric unit, around the copper atom. The conformation of the six-membered Cu-0( 1)-P (l)-C(91)-P(3)-0(3) ring may be described following Cremer and Pople17 by the amplitude of pucker Q = 0.633(4) A and pseudorotational

Table 2. Some important bond distances (A)

Cu-o( 1) cu-o(3) Cu-G(7)

W)-C(lE) G(9)-C(5E) C(lE)-C(3E) C(5E)-C(7E) CKl)-wll) Cltl)--o(12) CW)-wl3) Cl(l)-wl4)

1.969(4) 2.312(4) 1.988(4) 1.448(5) 1.476(6) 1.490(9) 1.468(11) 1.370(9) 1.345(10) 1.320(10) 1.332(14)

1.496(5) 1.796(5) 1.782(6) 1.796(4) 1.475(5) 1.568(4) 1.808(4) 1.798(6) 1.492(3) 1.809(6) 1.794(7) 1.791(6)

phase angles cp = 176.4(3)’ and 8 = 78.5(3)“. P(1) and O(3) lie on one side and O(1) and P(3) on the other side of the least-squares plane through the P(3), O(3), O(l), P(1) atoms of the ring. The deviation of ring atoms from this plane is - 0.009(2) A for P( 1) ; 0.009(2) A for P(3), 0.030(4) 8, for O(1) and -0.029(4) 8, for O(3).*’ Cu and C(91) are well above the plane, 0.337(2) 8, and 0.689(5) ,& respectively. After Boeyensrg this con- formation is near boat B.,, (cp = 180.0”, 8 = 90.00). The torsion angles are given in Table 4.

The second ring could be considered as eight membered, Cu-O(3)-P(3)-C(93)-P(5)-0(5) * * * H-O(7), or seven membered if geometrically determined H atom is excluded. This seven mem- bered ring is rather puckered. There is a significant deviation of the ring atoms from the least-squares plane through the O(5), O(7), Cu and O(3) atoms of the ring. The atom O(5) is 0.028(5) A, CuO.O15(3) 8, on one side and the atom O(7) is 0.047(5) A, O(3) 0.026(5) A on the other side of the plane. The other ring atoms are P(3) 1.046(3) A, C(93) 0.493(6) A above and P(5) 0.463(3) 8, below the plane. Torsion angles are given in Table 4. The O(3) * * - O(7) bite distance is 2.948(5) A and the corresponding angle on the copper atom is 86.2(l)“. The longest copper-

Bis[(diphenylphosphinyl)methyl]ethyl phosphinate ligand 2017

Table 3. Some important bond angles (deg)

O(l)-Cu--o(3) 90.0( 1) C(91)-P(3FC(93) 105.7(3) O(l)-Cu-o(3) 90.0(l) 0(5)-P(5)-C(93) 112.1(2)

W)-Cu--o(7) 92.2(2) 0(5)_P(5W(5) 110.9(2) O(l>-cu~(7) 87.8(2) 0(5)-P(5)-C(7) 110.8(3) 0(3)--cu--0(7) 86.2(l) C(93F-P(5)-C(5) 105.7(3) 0(3)-Cu-o(7)’ 93.8(l) C(93)_P(5_(7) 109.2(3) O(l)-P(lW(91) 112.6(2) C(5)-P(5)--c(7) 107.9(3) O(l)-P(lW(1) 112.1(3) P(3>-0(9W(5E) 119.3(4) O(l)-P(lW(3) 110.2(2) 0(9)-U5EW(7E) 109.8(5) C(91)_P(1W(l) 106.1(3) Cu-O(7)-C(lE) 125.0(3) C(91)-P(l>-c(3) 108.1(3) W7)--c(1E)--c(3E) 110.5(4) C(l)_P(l)-CO) 107.4(2) 0(11)--c1(1Hv12) 109.6(5) 0(3)-P(3)-w9) 115.5(2) O(ll)--cl(l)-wl3) 113.5(6) O(3)-P(3W(91) 113.6(2) O(l l)-wFw4) 111.0(9) 0(3)_P(3W(93) 112.4(2) 0(12)-w>-o(~3) 110.9(8) O(9)-P(3)--c(91) 102.8(2) w2)-w-w4) 105.7(8) O(9)-P(3W(93) 105.7(2) w13)--c1(lHw4) 105.8(8)

a The atoms marked with a prime correspond to positions obtained by using the transformation -x, -y, -z.

oxygen bond distance [2.312(4) A] involves the cen- tral phosphoryl bond which is the shortest one [ 1.475(5) A]. The two peripheral phosphoryl bonds are equal, 1.496(5) and 1.492(3) A. The bond dis- tances and angles of the ligand (Tables 2 and 3) are close to the values found before in the crystal structures of diphenylphosphinic acid,” diphen- ylthiophospinic acid,” sodium salt of monomethyl ester of fosfomycin,** or sodium salts of bis(di- phenylphosphinyl) methane.23J4 The smooth differences in P-C bonds along the backbone of the ligand (Table 2) seem to have similar causes as, for instance, the differences in P-O bonds along the backbone of P,O:i anion in the crystal struc-

tures of condensed triphosphates or the differences in P-N,,,+,,, bonds in TRIPA * Hz0 (Table 5).

As is usual in phosphine oxides and related com- pounds, distortion of phosphorus coordination tetrahedra is observed i.e. the C,S--P-C,S angle decreases to 105.7(3)O while QP-O angle increases to 115.5(2)“. The two angles involving oxygen from the ethoxy group, 0-P-C+ are quite different, 102.8(2)0 vs 105.7(2)“.

All three oxygen atoms from P=O groups lie on the same side of the plane through the three phosphorus atoms at various distances, O(1) at -1.489(5) A, O(3) at -1.473(5) 8, and O(5) at -0.399(5) A, with 0(1).**0(3) and 0(3)...0(5)

Table 4. Torsion angles (deg)

6-membered chelate ring cu-o(l)-P(1~(91) Ow-P(1>-c(91)_P(3) P(l)-C(9l)_P(3Hx3) C(9l>-P(3W(3>--cu P(3>--0(3~--0(1) 0(3)-Cu-w)_P(l)

BPOEt ligand

C(lt_P(l)-c(9l)_P(3) C(3)_P(lM(91)-P(3) P(l)-C(9l)_P(3)-C(93) P(l)-C(91)_P(3FP(9)

13.9(4) -51.2(4)

48.1(4) - 10.6(4) - 18.4(3)

16.9(3)

71.8(4) - 173.2(3)

171.9(3) - 77.4(4)

‘I-membered ring

~--0(3)-P(3>--c(93) 0(3)-P(3W(93)_P(5) P(3)--c(93tiP(5)--0(5) C(93)-P(5)-0(5). . . O(7) P(5wx5). . . O(W 0(5)~~~0(7)-Cu--0(3) wFCu-w3~P(3)

C(9Q-P(3)--C(93)_P(5) P(3)--c(93)_P(5)-C(5) P(3>-c(93)_P(5W(7)

- 130.6(2) 45.9(3) 34.1(4)

- 68.3(4) 30.7(4)

- 3.9(2) 73.8(3)

-78.6(4) 155.0(3)

-89.1(3)

2018 M. HERCEG et al.

Table 5. Bond distances and angles along the backbone of the ligands P,O&, TRIPA and RPOEt

Compound

Longer P-Xstidwa Shorter P--X,,, P-Xi,,,,-P bonds bonds angles

(A) (A) (deg) Ref.

Nag901,, * 6HzO

NaSMnP3010* 12HzO*

NapCuP,OlO* 12HzO*

Na3C!dP301,, - 12HzO*

1.67(l) 1.67(l)

1.619(5) 1.629(8)

1.629(3) 1.629(3)

1.640(5) 1.620(5)

TRIPA - Hz0 1.689(2) 1.695(2)

tCu(~OEt),(C,H,OH)zl(ClO~)z 1.808(4) 1.809(6)

1.60(l) 1.60(l)

1.588(4) 1.591(5)

1.578(3) 1.590(3)

1.593(5) 1.599(5)

1.671(2) 1.667(2)

1.796(5) 1.798(6)

124.4(l) 123.4(l)

135.5(4) 133.4(4)

133.3(2) 132.5(2)

135.2(3) 136.8(3)

126.6(l) 125.8(l)

113.9(3) 112.1(3)

25

26

27

28

29

this paper

“X is 0, N or C. * Mn, Cu and Cd compounds seem to be isostructural.

distances of 3.036(4) 8, and 3.269(5) A, respectively. The plane through phenyl ring C(1) to C(15) is almost parallel to the plane through O(3) P(3), O(9) [dihedral angle of 4.7(3)“], and perpendicular to the plane through P(l), P(3), P(5) [dihedral ‘angle of 89.5(2)“]. The acute angle between the plane through phenyl ring C(3) to C(35) and the plane through C(1) to C(15) is 73.9(2)“. The plane through the phenyl ring C(5) to C(55) is roughly parallel to the plane through O(5), O(7), O(3), Cu, O(3)‘, O(7)‘, O(5)’ [Table 3, dihedral angle of 9.3(2)“]. The acute angle between the plane through phenyl ring C(7) to C(75) and the plane through C(5) to C(55) is 74.4(3)“.

The cation-anion interactions seem to be rather weak. Cation-anion distances shorter than 3.6 A are given in Table 6.

Physical properties

Magnetic data of the cobalt(I1) and nickel(I1) complexes (Table 7) are indicative of spin-free octa-

hedral compounds. The effective moment of the copper complexes is more or less independent of the stereochemistry.

Molar conductance values observed (Table 7) are close to those expected for 2 : 1 electrolytes.

The intensity, position and shape of the absorp- tion bands in the electronic spectra (Table 7) are typical of octahedral cobalt(I1) and nickel(I1) com- plexes. The broad asymmetric band in the near IR region in the spectrum of copper(I1) complex appearing at 855 nm can be compared with the spectra of known tetragonally distorted octahedral copper(I1) complexes.

Infrared spectral data (Table 8) are in good agree- ment with the X-ray structural determinations. The most important absorption bands in the spectra of the ligand and its complexes in the range of 4000- 620 cm-’ are those of P=O, than OH and C-O vibrations from the coordinated ethanol and of CIOrion vibrations. The spectrum of the ligand exhibits three strong absorption bands assigned to P=O stretching vibrations. The maximum at 1245

Table 6. Cation-anion distances“ (A)

O( 11) * . . C(53)’ 3.373(15) O(12). . . C(93) 3.562(11) 0( 11). . . C(5E) 3.515(9) 0(13)~..C(31)” 3.446(13) O( 11) . * * C(75) 3.518(11) 0(13)*..C(14)“’ 3.523(10) O(12). . . C(93)” 3.410(14) 0(13)-.*C(91)n 3.584(16) o(12)~~~c(91)n 3.490(14) 0(14)*~*c(ll)” 3.456(19)

“Key: (I)x,y, l+z; (II) -x, l-y, -z; (III) -x, l-y, l-z.

Bis[(diphenylphospbinyl)methyl)ethyl phosphinate ligand

Table 7. Electronic spectra, conductometric and magnetic measurements

2019

Compound

[Cu(~CEt),(C,H,OH)WQ), [Ni(~OEt)K~H,OH)&ClW~ [Co WQEt)&H,OHU(ClW~

c010ur U (W Ab (cm* ohm-’ mol-‘) KS (B-M.)

white 855 46.56 1.95 greenish 413,780, 1420 46.86 3.32 pink 480,530 46.92 4.92

“Recorded as nujol mulls. b Measured in 10m3 M nitrobenzene solutions, at 295 K.

Table 8. Main IR vibrational bands (cm-‘) and relative assignments

Compound W-W v(C--o)

v(p---o) (coordinated ethanol) v(Cl0;)

RPOEt 1245s, sp 122os, sp 119os, sp

121os, sp 303Om 104Om 109ovs 1178s, sp 1015m 935w 1162s, sp 625m

[CoW’OEt),(C,H,OH)zl(ClQ& 12OOs, sp 118Os, sp 1165s, sp

3130m 1047m 109Ovs 1015m 935w

625m

1198s, sp 118Os, sp 117os, sp

3130m 1047m 109ovs 1015m 935w

625m

cm-’ assigned to the P=O stretching vibration of the central phosphoryl group, and the maximum appearing at 1220 cm-’ are shifted to lower wave numbers (121 O-l 162 cm-‘). Data observed indicate that in all isolated metal complexes the central p---O group as well as one of the exterior p---O groups are involved in complex formation. Positions of

the maxima of the central p---O group vibrations indicate stronger bonding of the ligand to the cobalt@) and nickel@) than to the copper@) ion. The maximum assigned to P-_ocZHS vibrations appearing in the spectrum of the ligand RPOEt at 1035 cm-’ is not shifted in the spectra of the complexes. That means that this group is not

ow----------- ’ A0 ,,b, &o ’ Wavenumber (cm-‘)

Fig. 2. IR absorption spectrum of [Co(RPOEt),(C2H,0H),J(C10.J2.

2020 M. HERCEG et al.

involved in complex formation. Maxima of the OH vibrations assigned to the coordinated ethanol indi- cate stronger coordination of ethanol in the copper(I1) (3030 cm-‘) than in the nickel(U) and cobalt(II) (3130 cm-‘) complexes. The weaker coordination of ethanol in the cobalt(I1) and nick- el(I1) complexes is the reason for the rather high instability of these complexes and the faster replace- ment of ethanol by water than in the case of the copper(E) compound. The most important absorp- tion bands of [Co(RPOEt)2(C2HSOH)~(C104)2 are presented in Fig. 2.

Acknowle&ements-This work was supported by grant from the Foundation of Scientific Research of SR Croatia. We thank Dr TonEi Bali&%mii: for conducting some of the preliminary studies and Mr Milenko Bruvo for collecting the data on Philips PW 1100 diffractometer at University of Zagreb.

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