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Transition metal complexes of dialkyl α-hydroxyiminophosphonates, a novel class of metal complexes
Polyhedron Vol. 12, No. 23, pp. 2887-2890, Printed in Great Britain
1993 0
0277-5387/93 IF6.00+ .W 1993 Pergamon Press Ltd
COMMUNICATION TRANSITION METAL COMPLEXES OF DIALKYL aHYDROXYIMINOPHOSPHONATES, A NOVEL CLASS OF METAL COMPLEXES S. W. ANNIE BLIGH,* NICK CHOI, DONOVAN ST C. GREEN, HARRY R. HUDSON, CATHERINE M. McGRATH, MARY McPARTLIN and MAX PIANKA
School of Applied Chemistry, University of North London, Holloway Road, London N7 8DB, U.K. (Received 6 September 1993 ; accepted 28 September 1993)
Abstract-A new range of dialkyl a-hydroxyiminophosphonates has been prepared and the first examples of metal complexes of this class of compound have been obtained ; X-ray crystal structure analysis of the dichlorobis(diethy1 E-(a)-hydroxyiminopropanephosphonate)nickel(II) complex shows a distorted octahedral coordination at the nickel atom giving two symmetry related diethyl-(@-a-hydroxyiminopropanephosphonate ligands and two chlorine donors.
Bioactive phosphorus containing molecules have long been used in the fields of agriculture’ and drug design, however their role as active ligands with biologically important metals2 has yet to be fully exploited. a-Hydroxyiminophosphonic acid derivatives are widely known not only as intermediates in the synthesis of the important aminophosphonic acidq3s4but also as phosphorylating agents,’ potential metalloenzyme inhibitors,6 and as having fungitidal activity.7 In this work the scope of these compounds has been extended considerably by the synthesis of a number of novel dialkyl derivatives. For the first time the potential of these dialkyl ahydroxyiminophosphonates as ligands has been demonstrated by the successful synthesis of a range of transition metal complexes. X-ray structure analysis confirms the formation of a five membered chelate ring on coordination of diethyl E-(a)hydroxyiminopropanephosphonate to nickel(I1). *Author to whom correspondence should be addressed. TCrystal data: C,,H,,NO,P, M = 285.28, orthorhombic, CI= 10.264(3), space n,2,2,, group b = 19.243(3), c = 7.803(2) A, U = 1541.17 A3, 2 = 4, F(OO0) = 608, D, = 1.229 g cm-‘, ~(Mo-K,) = 1.8 cm-‘, 1 = 0.71069 b;. Final R = 0.0774 (R,,, = 0.0763) for 1027 unique reflections with I/a(l) > 3.
The new dialkyl esters were prepared by adaptation of a literature method.8 Reaction of acylphosphonates with hydroxylamine, using 3 M HCl in the work up procedure, gives dialkyl u-hydroxyiminophosphonates with predominating Eisomers and in good yield (> 90%). 3’P(CDC13) NMR data of a number of these compounds are presented in Table 1. The 3’P assignment of the structural isomers was initially based on literature data’ for related compounds and has been confirmed by a single crystal structure analysis? of diisopropyl E(a)-hydroxyiminobenzylphosphonate L2 (Fig. 1). The solid state structure of L2 consists spiral chains formed by hydrogen bonding between the phosphoryl and oxime group of adjacent molecules (H(04). . *0( In)1 .6OA}. The structure of the individual molecules of L2, shown in Fig. 1, establishes a conformation ideally adapted to complex formation ; the potential donor atoms, the oxygen atom of the phosphoryl and the nitrogen atom of the oxime, being cis to each other resulting in a preformed “chelate-bite” of 2.886 8, in the solid state. Very few compounds of this type are crystalline, but there have been two recent characterizations of the E and Z form of dimethyl ahydroxyiminobenzylphosphonate9 and diisopropyl E- (rz)- hydroxyiminophthalimidopropylphosphon-
2887
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Communication Table 1. The new dialkyl a-hydroxyiminophosphonate 3’P NMR
with the E: Z ratio deduced from
“P NMR L L’ L2 L3 L4 LS L6
R ethylI isopropyl n-butyl n-butyl ethyl isopropyl
R ethyl phenyl methyl propyl cyclopropyl 2-ethoxycarbonylethyl
ate.” The equivalent bond lengths in these compounds do not differ significantly from those in L’, but in both the E isomers truns-conformations of the potential donor atoms are observed. Interestingly for a monoalkyl a-hydroxyiminophosphonates where metal complex formation has been reported, X-ray structure analysis of the uncoordinated mol-
E:Z
6E, 6Z
78122 80:20 loo:o 96:4 75:25 loo:o
12.03, 6.58 7.62,4.68 10.68 12.06, 7.08 9.76, 6.44 10.93
ecule also show a preformed chelate conformation similar to that in L’.” To date no examples of metal complexes of the bifunctional dialkyl a-hydroxyiminophosphonates have been reported, which is surprising considering that in addition to complexes of the monoalkyl esters,” both phosphoryl” and oxime13 functional
Fig. 1. The structure of diisopropyl E-(cr)-hydroxyiminobenzylphosphonate.
Selected bond lengths (A) and angles (“): P(l)-O(l), 1.456(6); P(1)-0(2), 1.545(7); P(1)-0(3), 1.549(7); P(l)-C(l), 1.807(9); 0(4)-N(l), 1.398(10); N(l)-C(l), 1.288(12); O(2)--P(lw(1) 117.2(4), O(3)-P(l)-O(l) 113.8(4),0(3)-P(1)---0(2) 102.7(4), C(l)-P(lfl(1) 114.6(4),C(l)-P(1)--0(2) 100.2(4), C(l)--P(lw(3) 106.6(4), C(l)-N(1)-0(4) 110.3(7), N(I)--C(l)-P(1) 111.3(7).
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Fig. 2. The structure of the cis dichloro NiL’,Cl, showing the E isomer-k form of the ligand. Selected bond lengths (A) and angles (“) : N&Cl, 2.346(4) ; Ni-O( l), 2.118(8) ; Ni-N( l), 2.036(9) ; P(l)-O(l), 1.478(8); P(1)-0(2), 1.550(9) and P(1)-0(3) 1.550(S); O(l)-Nix1 168.3(2), N(l)-Ni-Cl 89.6(3), N(l)-Ni-O(l) 80.9(3), Cl-Ni-Cl’ 96.0(2), O(l)-Ni-O(l’) 83.1(4), N(l)-Ni-N(I’) 176.6(3), P(l)--O(I)---Ni 115.1(4),C(21)-0(2)-P(1) 120.5(7),C(31)-0(3)-P(1) 120.4(9), O(4)-N(l)--Ni 120.2(7), C(I)-N(l)-Ni 125.3(8).
groups can coordinate to metal ions. In this study it has been found that reaction of methanolic solutions of the diesters and the transition metal salt MX2 gives MLzXz (M = Co and Ni ; L = L’-L6 ; X = Cl or N03). All the cobalt(I1) and nickel(I1) complexes were characterized by satisfactory elemental analyses, and by liquid secondary ion mass spectrometry (LSIMS) which gave base peaks corresponding to [M + H - Cl,]’ in all cases. The infra-red spectra of the ligands and their metal complexes indicated that the oxime stretch at v(C=N), 1614 cm-’ shifts to 1645 cm-’ on complexation and the two phosphoryl stretches at v(p--O), 1173 and 1234 cm-’
*Crystal data: C,4C12H32N2NiOsP2,A4 = 547.96, monoclinic, space group C2/c, a = 8.980(2), b = 13.435(3), c = 21.218(3) A, /I = 94.864(2)“, U = 2550.65 A’, Z = 4, 6000) = 1144, D,= 1.427 g cme3, ~(Mo-K,) = 11.0 cm-‘, 1 = 0.71069 A. Final R =0.0725 (R,= 0.0682) for 876 absorption corrected data with Z/e(Z)> 2.5.
condense and shift to 1164 and 1213 cm-‘. Magnetic moment measurements of CoL,X, are 4.6 to 4.7 BM and NiL2X2 are 3.1 to 3.2 BM, which are in the normal range for six coordinate complexes of cobalt(I1) and nickel(I1). The formulation of the complexes has been confirmed by a single crystal structure analysis* of NiL’&. This shows the cisdichloro molecule of exact C2 symmetry illustrated in Fig. 2, and confirms the E isomeric form of the phosphonate diester L’. The atom pairs O(l), O(1’) and N(l), N(l’) from the two symmetry related chelating ligands coordinate in cis and truns configurations, respectively. The five membered chelate rings adopt an envelope conformation with maximum deviation from planarity of 0.125 A for P(1). The oxime hydrogen atom is 2.26 8, from the coordinated chlorine atom, indicating strong intramolecular hydrogen bonding. The selective complexation of the E isomers provides a useful method to separate the two isomeric forms and their biological activity can therefore be studied individually. Work is in progress in pre-
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Communication
paring a range of lanthanide complexes for their potential applications as NMR shift and imaging agents. AcknowledgementsWe thank the PCFC for studentships (N. C. & C. M. M.), and the SERC for access to the Chemical Database Service at Daresbury.
6. 7. 8. 9.
REFERENCES 1. D. G. Cameron, H. R. Hudson, I. A. 0. Ojo and M. Pianka, Phosphorus and Sulfur 1988, 40, 183 ; Handbook of Organophosphorus Chemistry (Edited by R. Engel), Dekker, New York (1992). 2. P. J. Sadler, Adv. Znorg. Chem. 1991, 36, 1. 3. S. Asano, T. Kitahara, T. Ogata and M. Mastsui, Agric. Biol. Chem. 1975, 37, 1193. 4. L. Maier and P. J. Diel, Phosphorus, Sulfur and Silicon 199 1,62, 15. 5. E. Breuer, R. Karaman, D. Gibson, H. Leader and
10. 11. 12. 13. 14.
A. Goldblum, J. Chem. Sot., Chem. Commun. 1988, 504. E. Breuer, M. Safadi, M. Chorev, A. Vincze and P. Bel, Tetrahedron 1991,47, 1257. N. K. Roy and H. K. Taneja, Intern. J. Agric. 1987, 5, 215. K. D. Berlin, R. T. Claunch and E. T. Gaudy, J. Org. Chem. 1968,33, 3090. E. Breuer, R. Karaman, A. Goldblum, D. Gibson, B. V. L. Potter and J. H. Cummins, J. Chem. Sot. Perkin Trans. Z 1988, 3047. E. Breuer, M. Safadi, M. Chorev and D. Gibson J. Org. Chem. 1990,55, 6147. D. Gibson and R. Karaman, Znorg. Chem. 1989,28, 1928. R. Babe&i, A. W. G. Platt and J. Fawcett, J. Chem. Sot., Dalton Trans. 1992, 675. C. Lopez, S. Alvarez, X. Solans and M. Font-Bardia, Polyhedron 1992, 11, 1637. K. D. Berlin, N. K. Roy, R. T. Claunch and D. Bade, J. Am. Chem. Sot. 1968,!Ml, 4494.
1993 0
0277-5387/93 IF6.00+ .W 1993 Pergamon Press Ltd
COMMUNICATION TRANSITION METAL COMPLEXES OF DIALKYL aHYDROXYIMINOPHOSPHONATES, A NOVEL CLASS OF METAL COMPLEXES S. W. ANNIE BLIGH,* NICK CHOI, DONOVAN ST C. GREEN, HARRY R. HUDSON, CATHERINE M. McGRATH, MARY McPARTLIN and MAX PIANKA
School of Applied Chemistry, University of North London, Holloway Road, London N7 8DB, U.K. (Received 6 September 1993 ; accepted 28 September 1993)
Abstract-A new range of dialkyl a-hydroxyiminophosphonates has been prepared and the first examples of metal complexes of this class of compound have been obtained ; X-ray crystal structure analysis of the dichlorobis(diethy1 E-(a)-hydroxyiminopropanephosphonate)nickel(II) complex shows a distorted octahedral coordination at the nickel atom giving two symmetry related diethyl-(@-a-hydroxyiminopropanephosphonate ligands and two chlorine donors.
Bioactive phosphorus containing molecules have long been used in the fields of agriculture’ and drug design, however their role as active ligands with biologically important metals2 has yet to be fully exploited. a-Hydroxyiminophosphonic acid derivatives are widely known not only as intermediates in the synthesis of the important aminophosphonic acidq3s4but also as phosphorylating agents,’ potential metalloenzyme inhibitors,6 and as having fungitidal activity.7 In this work the scope of these compounds has been extended considerably by the synthesis of a number of novel dialkyl derivatives. For the first time the potential of these dialkyl ahydroxyiminophosphonates as ligands has been demonstrated by the successful synthesis of a range of transition metal complexes. X-ray structure analysis confirms the formation of a five membered chelate ring on coordination of diethyl E-(a)hydroxyiminopropanephosphonate to nickel(I1). *Author to whom correspondence should be addressed. TCrystal data: C,,H,,NO,P, M = 285.28, orthorhombic, CI= 10.264(3), space n,2,2,, group b = 19.243(3), c = 7.803(2) A, U = 1541.17 A3, 2 = 4, F(OO0) = 608, D, = 1.229 g cm-‘, ~(Mo-K,) = 1.8 cm-‘, 1 = 0.71069 b;. Final R = 0.0774 (R,,, = 0.0763) for 1027 unique reflections with I/a(l) > 3.
The new dialkyl esters were prepared by adaptation of a literature method.8 Reaction of acylphosphonates with hydroxylamine, using 3 M HCl in the work up procedure, gives dialkyl u-hydroxyiminophosphonates with predominating Eisomers and in good yield (> 90%). 3’P(CDC13) NMR data of a number of these compounds are presented in Table 1. The 3’P assignment of the structural isomers was initially based on literature data’ for related compounds and has been confirmed by a single crystal structure analysis? of diisopropyl E(a)-hydroxyiminobenzylphosphonate L2 (Fig. 1). The solid state structure of L2 consists spiral chains formed by hydrogen bonding between the phosphoryl and oxime group of adjacent molecules (H(04). . *0( In)1 .6OA}. The structure of the individual molecules of L2, shown in Fig. 1, establishes a conformation ideally adapted to complex formation ; the potential donor atoms, the oxygen atom of the phosphoryl and the nitrogen atom of the oxime, being cis to each other resulting in a preformed “chelate-bite” of 2.886 8, in the solid state. Very few compounds of this type are crystalline, but there have been two recent characterizations of the E and Z form of dimethyl ahydroxyiminobenzylphosphonate9 and diisopropyl E- (rz)- hydroxyiminophthalimidopropylphosphon-
2887
2888
Communication Table 1. The new dialkyl a-hydroxyiminophosphonate 3’P NMR
with the E: Z ratio deduced from
“P NMR L L’ L2 L3 L4 LS L6
R ethylI isopropyl n-butyl n-butyl ethyl isopropyl
R ethyl phenyl methyl propyl cyclopropyl 2-ethoxycarbonylethyl
ate.” The equivalent bond lengths in these compounds do not differ significantly from those in L’, but in both the E isomers truns-conformations of the potential donor atoms are observed. Interestingly for a monoalkyl a-hydroxyiminophosphonates where metal complex formation has been reported, X-ray structure analysis of the uncoordinated mol-
E:Z
6E, 6Z
78122 80:20 loo:o 96:4 75:25 loo:o
12.03, 6.58 7.62,4.68 10.68 12.06, 7.08 9.76, 6.44 10.93
ecule also show a preformed chelate conformation similar to that in L’.” To date no examples of metal complexes of the bifunctional dialkyl a-hydroxyiminophosphonates have been reported, which is surprising considering that in addition to complexes of the monoalkyl esters,” both phosphoryl” and oxime13 functional
Fig. 1. The structure of diisopropyl E-(cr)-hydroxyiminobenzylphosphonate.
Selected bond lengths (A) and angles (“): P(l)-O(l), 1.456(6); P(1)-0(2), 1.545(7); P(1)-0(3), 1.549(7); P(l)-C(l), 1.807(9); 0(4)-N(l), 1.398(10); N(l)-C(l), 1.288(12); O(2)--P(lw(1) 117.2(4), O(3)-P(l)-O(l) 113.8(4),0(3)-P(1)---0(2) 102.7(4), C(l)-P(lfl(1) 114.6(4),C(l)-P(1)--0(2) 100.2(4), C(l)--P(lw(3) 106.6(4), C(l)-N(1)-0(4) 110.3(7), N(I)--C(l)-P(1) 111.3(7).
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Fig. 2. The structure of the cis dichloro NiL’,Cl, showing the E isomer-k form of the ligand. Selected bond lengths (A) and angles (“) : N&Cl, 2.346(4) ; Ni-O( l), 2.118(8) ; Ni-N( l), 2.036(9) ; P(l)-O(l), 1.478(8); P(1)-0(2), 1.550(9) and P(1)-0(3) 1.550(S); O(l)-Nix1 168.3(2), N(l)-Ni-Cl 89.6(3), N(l)-Ni-O(l) 80.9(3), Cl-Ni-Cl’ 96.0(2), O(l)-Ni-O(l’) 83.1(4), N(l)-Ni-N(I’) 176.6(3), P(l)--O(I)---Ni 115.1(4),C(21)-0(2)-P(1) 120.5(7),C(31)-0(3)-P(1) 120.4(9), O(4)-N(l)--Ni 120.2(7), C(I)-N(l)-Ni 125.3(8).
groups can coordinate to metal ions. In this study it has been found that reaction of methanolic solutions of the diesters and the transition metal salt MX2 gives MLzXz (M = Co and Ni ; L = L’-L6 ; X = Cl or N03). All the cobalt(I1) and nickel(I1) complexes were characterized by satisfactory elemental analyses, and by liquid secondary ion mass spectrometry (LSIMS) which gave base peaks corresponding to [M + H - Cl,]’ in all cases. The infra-red spectra of the ligands and their metal complexes indicated that the oxime stretch at v(C=N), 1614 cm-’ shifts to 1645 cm-’ on complexation and the two phosphoryl stretches at v(p--O), 1173 and 1234 cm-’
*Crystal data: C,4C12H32N2NiOsP2,A4 = 547.96, monoclinic, space group C2/c, a = 8.980(2), b = 13.435(3), c = 21.218(3) A, /I = 94.864(2)“, U = 2550.65 A’, Z = 4, 6000) = 1144, D,= 1.427 g cme3, ~(Mo-K,) = 11.0 cm-‘, 1 = 0.71069 A. Final R =0.0725 (R,= 0.0682) for 876 absorption corrected data with Z/e(Z)> 2.5.
condense and shift to 1164 and 1213 cm-‘. Magnetic moment measurements of CoL,X, are 4.6 to 4.7 BM and NiL2X2 are 3.1 to 3.2 BM, which are in the normal range for six coordinate complexes of cobalt(I1) and nickel(I1). The formulation of the complexes has been confirmed by a single crystal structure analysis* of NiL’&. This shows the cisdichloro molecule of exact C2 symmetry illustrated in Fig. 2, and confirms the E isomeric form of the phosphonate diester L’. The atom pairs O(l), O(1’) and N(l), N(l’) from the two symmetry related chelating ligands coordinate in cis and truns configurations, respectively. The five membered chelate rings adopt an envelope conformation with maximum deviation from planarity of 0.125 A for P(1). The oxime hydrogen atom is 2.26 8, from the coordinated chlorine atom, indicating strong intramolecular hydrogen bonding. The selective complexation of the E isomers provides a useful method to separate the two isomeric forms and their biological activity can therefore be studied individually. Work is in progress in pre-
2890
Communication
paring a range of lanthanide complexes for their potential applications as NMR shift and imaging agents. AcknowledgementsWe thank the PCFC for studentships (N. C. & C. M. M.), and the SERC for access to the Chemical Database Service at Daresbury.
6. 7. 8. 9.
REFERENCES 1. D. G. Cameron, H. R. Hudson, I. A. 0. Ojo and M. Pianka, Phosphorus and Sulfur 1988, 40, 183 ; Handbook of Organophosphorus Chemistry (Edited by R. Engel), Dekker, New York (1992). 2. P. J. Sadler, Adv. Znorg. Chem. 1991, 36, 1. 3. S. Asano, T. Kitahara, T. Ogata and M. Mastsui, Agric. Biol. Chem. 1975, 37, 1193. 4. L. Maier and P. J. Diel, Phosphorus, Sulfur and Silicon 199 1,62, 15. 5. E. Breuer, R. Karaman, D. Gibson, H. Leader and
10. 11. 12. 13. 14.
A. Goldblum, J. Chem. Sot., Chem. Commun. 1988, 504. E. Breuer, M. Safadi, M. Chorev, A. Vincze and P. Bel, Tetrahedron 1991,47, 1257. N. K. Roy and H. K. Taneja, Intern. J. Agric. 1987, 5, 215. K. D. Berlin, R. T. Claunch and E. T. Gaudy, J. Org. Chem. 1968,33, 3090. E. Breuer, R. Karaman, A. Goldblum, D. Gibson, B. V. L. Potter and J. H. Cummins, J. Chem. Sot. Perkin Trans. Z 1988, 3047. E. Breuer, M. Safadi, M. Chorev and D. Gibson J. Org. Chem. 1990,55, 6147. D. Gibson and R. Karaman, Znorg. Chem. 1989,28, 1928. R. Babe&i, A. W. G. Platt and J. Fawcett, J. Chem. Sot., Dalton Trans. 1992, 675. C. Lopez, S. Alvarez, X. Solans and M. Font-Bardia, Polyhedron 1992, 11, 1637. K. D. Berlin, N. K. Roy, R. T. Claunch and D. Bade, J. Am. Chem. Sot. 1968,!Ml, 4494.