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The preparation and coordination chemistry of iPr2P(E)NHP(E′)iPr2 (E, E′=Se; E=Se, E′=S; E=S, E′=O; E,E′=O
Inorganica Chimica Acta 290 (1999) 1 – 7
The preparation and coordination chemistry of i Pr2P(E)NHP(E%)iPr2 (E, E%=Se; E=Se, E% =S; E =S, E% =O; E,E%=O Dominico Cupertino a, David J. Birdsall b, Alexandra M.Z. Slawin b, J. Derek Woollins b,* b
a Zeneca Specialties, Blackley, Manchester M9 8ZS, UK Department of Chemistry, Loughborough Uni6ersity, Loughborough LE11 3TU, UK
Received 12 November 1998; accepted 29 January 1999
Abstract Reaction of iPr2PCl with (Me3Si)2NH gives iPr2PNHiPPr2 (not isolated) which was oxidised with sulfur/selenium/oxygen to give Pr2P(E)NHP(E%)iPr2 (E, E%=Se; E=Se, E%=S; E= S, E%= O; E,E%=O). These neutral LH molecules readily undergo deprotonation/complexation to form simple ML2 species and demonstrative examples with Zn, Cd, Pd, Pt are reported. The X-ray structure of two examples of iPr2P(E)NHP(E%)iPr2 (E, E%=Se, E,E%= O) are reported. The molecules pack into infinite chains via H…E Hydrogen bonds. The X-ray structures of three typical metal complexes which illustrate tetrahedral (Cd[(iPr2PSe)2]2) and square planar (Pt[N(iPr2PSe)2]2) coordination at the metal centre as well as the ability of the ME2P2N ring to adopt the pseudo-chair conformation (Pt[iPr2P(Se)NHP(S)iPr2]2) are also reported. © 1999 Elsevier Science S.A. All rights reserved. i
Keywords: Crystal structures; Coordination chemistry; Phosphorous ligands; Amino ligands; Seleno ligands; Oxygen ligands
The dithioimidodiphosphinates have been known for some considerable time [1] and there has recently been a resurgence of interest in their coordination chemistry as a consequence of the steric control that this ligand system may impart compared to, for example, acac. Both ourselves and others have reported extensively on the chemistry of Ph2P(S)NHP(S)Ph2 [2 – 5] and to a lesser extent its selenium homologue [6 – 8]. Recently, we described some complexes derived from i Pr2P(S)NHP(S)iPr2 [9]. One especially interesting feature [10] was that in the palladium complex Pd[N(iPr2PS)2]2 the six-membered PdS2P2N ring adopts a pseudo-boat conformation whereas in the platinum complex Pt[N(iPr2PS)2]2 the PtS2P2N ring is in a pseudo-chair conformation. Here, we report on studies to investigate the generality of this observation by extension of the chemistry to include selenium com* Corresponding author. Tel.: + 44-1509-263 171; fax: +44-1509223 925. E-mail address: [email protected] (J.D. Woollins)
pounds as well as mixed S/Se and mixed S/O compounds. This paper describes the preparation of a range of iPr2P(E)NHP(E%)iPr2 (E, E% = Se 1; E= Se, E% =S 2; E= S, E% = O 3; E,E% =O 4) together with examples of their coordination complexes with tetrahedral and square planar metal centres. The X-ray structures of 1, 4 and three metal complexes are described (Fig. 1).
1. Experimental Unless stated otherwise, all reactions were performed under an atmosphere of oxygen-free nitrogen using standard Schlenk procedures. All glassware was oven dried at 100°C or flame dried under vacuum before use. All solvents and reagents were purchased from Aldrich, Strem or Fisher and used as received. In addition toluene, THF, Et2O and petroleum ether (60– 80) were distilled from sodium-benzophenone under nitrogen, and CH2Cl2 from CaH2. CDCl3 (99+atom% D) was as supplied.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 0 2 0 - 1 6 9 3 ( 9 9 ) 0 0 0 8 7 - 0
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The resulting white precipitate was filtered off. Excess selenium was removed by dissolving the product in CH2Cl2 and filtering through celite, followed by removal of solvent in vacuo. The crude product was recrystallised from CH2Cl2 and hexane. Yield 4.25 g, 10.47 mmol, 65%. Microanalysis calculated for C12H29NP2Se2: C, 35.3; H, 7.1; N, 3.4. Observed: C, 35.5; H, 7.1; N, 3.6%. 31P{1H} NMR (CDCl3): 89.5 ppm, 1 J(71Se– 31P) 757 Hz. FT-IR (KBr disc): n(N–H) 3207(s); d(N–H) 1385(m); n(PNP) 903(s), 877(s); n(PSe) 488.5 cm − 1. FAB + ve MS: m/z 407 corresponds to HN(iPr2PSe)2.
1.2. iPr2P(Se)NHP(S) iPr2 (2) A solution of iPr2PNHPiPr2 was prepared as for 1. Selenium (1.27 g, 16 mmol) was added and the solution stirred overnight. Sulfur (0.48 g, 15 mmol) was then added and stirring continued for 6 h. The solvent was removed in vacuo and the off-white product recrystallised from CH2Cl2 and hexane. Yield 2.13 g, 5.9 mmol, 37%. Microanalysis calculated for C12H29NP2SeS: C, 40.0; H, 8.1; N, 3.8. Observed: C, 40.3; H, 8.5; N, 3.6%. 31P{1H} NMR (CDCl3): 92.1, 89.2 ppm, 2 J(31P– 31P) 35.2 Hz, 1J(71Se– 31P) 747 Hz. FT-IR (KBr disc): n(N–H) 3214(s); d(N–H) 1385(s); n(PNP) 904(s), 878(s); n(PSe) 473; n(PS) 560 cm − 1. FAB + ve MS: m/z 360 corresponds to iPr2P(Se)NHP(S)iPr2. Fig. 1. The X-ray structure of 1 and 4 showing (a) an isolated molecule and (b) the H-bonded chain structure which both molecules adopt in the solid state (the structures are not isomorphous but are quite similar). 31
P (36.2, 101.25 MHz) were recorded on Jeol FX90Q, Bruker AC250 FT spectrometers. Chemical shifts are reported relative to 85% H3PO4 on both spectrometers. IR spectra were recorded as KBr discs on a Perkin-Elmer System 2000 FTIR spectrometer. Microanalyses were carried out by the service at Loughborough University. FAB +ve mass spectra were recorded by the EPSRC mass spectrometry service at Swansea.
1.1. iPr2P(Se)NHP(Se) iPr2 (1) This method is based on a literature preparation of related compounds [11], the reaction was performed under nitrogen. A solution of iPr2PCl (4.87 g, 5.0 ml, 32 mmol) in toluene (100 ml) was added dropwise to a solution of HN(SiMe3)2 (2.58 g, 3.4 ml, 16.0 mmol) in hot (50°C) toluene (50 ml) over 30 min. Heating and stirring was continued for 3 h after which time the reaction was cooled to room temperature (r.t.) and selenium was added (2.53 g, 31 mmol). The reaction was then refluxed for a further 6 h and cooled to 0°C.
1.3. iPr2P(O)NHP(S) iPr2 (3) A solution of iPr2PNHPiPr2 was prepared as for 1. Sulfur (0.48 g, 15 mmol) was then added and stirred overnight. Hydrogen peroxide (30% solution 1.9 ml) was then added dropwise and stirring continued. The solvent was removed in vacuo and the white product recrystallised from CH2Cl2 and hexane. Yield 1.23 g, 4.14 mmol, 25%. Microanalysis calculated for C12H29NP2O2: C, 48.5; H, 9.8; N, 4.7. Observed: C, 48.1; H, 10.1; N, 4.8%. 31P{1H} NMR (CDCl3): 90.9, 54.8 ppm, 2J(31P– 31P) 21.9 Hz. FT-IR (KBr disc): n(N–H) 3442(s); d(N–H) 1387(m); n(PNP) 890(m), 882(m); n(PO) 1038(m); n(PS) 670(m) cm − 1. FAB +ve MS: m/z 298 corresponds to iPr2P(O)NHP(S)iPr2.
1.4. iPr2P(O)NHP(O) iPr2 (4) A solution of iPr2PNHPiPr2 was prepared as for 1. Hydrogen peroxide (30% solution, 3.8 ml) was added dropwise and stirred. The solvent was removed in vacuo and the white product recrystallised from CH2Cl2 and hexane. Yield 2.4 g, 8.37 mmol, 54%. Microanalysis calculated for C12H29NP2O2: C, 51.2; H, 10.3; N, 4.9. Observed: C, 50.9; H, 9.8; N, 4.6%. 31P{1H} NMR (CDCl3): 55.5 ppm. FT-IR (KBr disc): n(N–H)
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Table 1 Details of the X-ray data collections and refinementsa Compound
1
4
6
7
11
Empirical formula M Crystal system Space group Diffractometer/radiation a (A, ) b (A, ) c (A, ) a (°) b (°) g (°) U (A, 3) Z Dcalc. (M gm−3) m (mm−1) F(000) Measured reflections Independent reflections (Rint) Observed reflections Final R R%
C12H29NP2Se2 407.22 monoclinic P21/c SMART/Mo Ka 14.680(1) 10.524(1) 12.349(1) 90 105.91(1) 90 1835 4 1.47 4.19 824 7879 2649 (0.0173) 2649 0.0286, 0.0819
C12H29NP2O2 290.31 monoclinic P21/n SMART/Mo Ka 8.603(1) 10.269(1) 19.163(1) 90 92.53(1) 90 1691 4 1.14 0.225 636 7152 2436 (0.021) 2353 0.041, 0.107
C24H56N2P4PtSe4 1007.52 monoclinic C2/c SMART/Mo Ka 13.561(1) 21.554(1) 13.855(1) 90 112.89(1) 90 1952 4 1.79 7.85 1952 7981 2638 (0.095) 2585 0.0329, 0.0802
C24H56N2P4Se4Cd 924.86 triclinic P1( (no. 2) AFC7S/Cu Kab 13.080(4) 16.49(1) 9.487(7) 103.20(8) 109.67(4) 78.30(4) 1858 2 1.65 10.92 916 5820 5537 2901c 0.055, 0.057
C24H56N2P4PtS2Se2 913.72 monoclinic P21/c SMART/Mo Ka 10.623(1) 14.602(1) 12.090(1) 90 103.10(1) 90 1826 2 1.66 6.14 904 7179 2574 (0.1695) 2524 0.0446, 0.1022
a
All data collections were performed at 290 K. Data collection using SMART and Mo Ka gave the same cell but less satisfactory refinement. R values are for observed data [I =2.0s(I)] or c [I\3.0s(I)]. Complex 2 gave a cell which is isomorphous with 1 [a =12.175(2), b = 10.520(1), c= 14.615(3) A, , b= 105.6(2)°, P21/a. Complex 9 gave a cell which is isomorphous with 7 [a= 9.364(1), b= 12.969(1), c = 16.572(1) A, , a = 78.93(1), b=77.76(1), g= 68.99(1)°, P1( ]. Neither of these mixed S/Se structures could be refined because of disorder. b
3223(s); d(N–H) 1392(s); n(PNP) 945(s), 881(s); n(PO) 1150(s). FAB +ve MS: m/z 281 corresponds to i Pr2P(O)NHP(O)iPr2.
ppm, 2J(195Pt– 31P) 97.3 Hz, 1J(71Se– 31P) 536 Hz. FTIR (KBr disc): n(PNP) 1181(s); n(PSe) 477(m); d(NPSe) 412(w) cm − 1. FAB +ve MS: m/z 1008 corresponds to Pt[N(iPr2PSe)2]2.
1.5. Zn[( iPr2PSe)2]2 (5) 1.7. Cd[( iPr2PSe)2]2 (7) ZnCO3·2Zn(OH)2·H2O (0.028 g, 0.081 mmol) was added to a solution of 1 (0.10 g, 0.25 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 2 h. The cloudy/white mixture was filtered and the filtrate was reduced by two thirds and cooled overnight to give the product as clear crystals. Yield 0.125 g, 0.142 mmol, 87%. Microanalysis calculated for C24H56N2P4Se4Zn: C, 32.8; H, 6.3; N, 3.1. Observed: C, 32.8; H, 6.1; N, 3.0%. 31P{1H} NMR (CDCl3): 59.8 ppm, 1J(31P – 71Se) 539 Hz. FT-IR (KBr disc): n(PNP) 1225(s), 759(w); n(PSe) 426(m). FAB +ve MS: m/z 878 corresponds to Zn{N(iPr2PSe)2}2.
1.6. Pt[N( iPr2PSe)2]2 (6) Complex 1 (0.1 g, 0.268 mmol) was added to a solution of PtCl2COD (0.046 g, 0.134 mmol) in methanol (5 cm3), which was stirred for 2 h. The product, a yellow solid was collected by filtration. Yield 0.10 g, 0.122 mmol, 90%. Microanalysis calculated for C24H56N2P4Se4Pt: C, 28.6; H, 5.5; N, 2.8. Observed: C, 29.0; H, 5.0; N, 2.4%. 31P{1H} NMR (CDCl3): 50.1
CdCO3 (0.019 g, 0.12 mmol) was added to a solution of 1 (0.091 g, 0.23 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 3 h. The solution was reduced to 1 ml. Methanol was added to precipitate the off-white product. Yield 0.090 g, 0.098 mmol, 74%. Microanalysis calculated for C24H56N2P4Se4Cd: C, 31.2; H, 6.0; N, 3.0. Observed: C, 30.9; H, 5.9; N, 2.5%. 31 P{1H} NMR (CDCl3): 56.6 ppm, 2J(111/113Cd– 31P) 30.8 Hz, 1J(71Se– 31P) 563 Hz. FT-IR (KBr disc): n(PNP) 1229(s), 752(m); n(PSe) 425(m). FAB +ve MS: m/z 925 corresponds to Cd{N(iPr2PSe)2}2. Table 2 Selected IR data for imidophosphinates (cm−1) Compd
Formula
n(NH)
n(PNP)
n(PE)
1 2 3 4
i
3207, 3214, 3442, 3223,
903, 904, 890, 945,
488 473, 560 1038, 670 1150
Pr2P(Se)NHP(Se)iPr2 Pr2P(Se)NHP(S)iPr2 i Pr2P(O)NHP(S)iPr2 i Pr2P(O)NHP(O)iPr2 i
1385 1385 1387 1392
877 878 882 881
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
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Table 3 IR assignments for M[iPr2P(E)NP(E)iPr2]2 (M= Zn, Pt, Pd and Cd (cm−1)) Compd
Formula
n(PNP)
n(PE)
5 6 7 8 9 10 11 12
Zn[(iPr2PSe)2]2 Pt[N(iPr2PSe)2]2 Cd[(iPr2PSe)2]2 Pd[N(iPr2PSe)2]2 Zn[iPr2P(Se)NHP(S)iPr2]2 Pd[iPr2P(Se)NHP(S)iPr2]2 Pt[iPr2P(Se)NHP(S)iPr2]2 Zn[iPr2P(O)NHP(S)iPr2]2
1225, 1181 1229, 1182 1225, 1181 1222 1224,
426 477 425 477 426, 471 433, 469 421, 487 1023, 472
759 752 767
790
Table 5 Selected bond lengths (A, ) and angles (°) in 6 and 7 Cd[N(iPr2PSe)2]2 (7)
1.8. Pd[N( iPr2PSe)2]2 (8) KOtBu (0.019 g, 0.169 mmol) and 1 (0.069 g, 0.169 mmol) were added to a solution of PdCl2COD (0.024 g, 0.085 mmol) in methanol (2 ml) and stirred for 2 h. The blood red solution was evaporated to dryness and the product extracted into dichloromethane. The solvent was removed in vacuo to give a red solid product. Yield 0.045 g, 0.049 mmol, 59%. Microanalysis calculated for C24H56N2P4Se4Pd: C, 31.4; H, 6.1; N, 3.1. Observed: C, 31.6; H, 5.8; N, 2.8%. 31P{1H} NMR (CDCl3): 55.9 ppm, 1J(71Se– 31P) 590 Hz. FT-IR (KBr disc): n(PNP) 1182(s); n(PSe) 477(m). FAB +ve MS: m/z 918 corresponds to Pd{N(iPr2PSe)2}2.
Pt[N(iPr2PSe)2]2 (6)
Ring 1
Ring 2a
Bond lengths (A, ) M–Se(1) M–Se(2) Se(1)–P(1) Se(2)–P(2) P(1)–N(1) P(2)–N(1)
2.625(2) 2.636(2) 2.168(4) 2.176(4) 1.60(1) 1.58(1)
2.622(2) 2.628(4) 2.188(4) 2.178(4) 1.60(1) 1.56(1)
2.4642(6) 2.4616(6) 2.218(2) 2.205(2) 1.603(5) 1.623(5)
Bond angles (°) Se(1)–M–Se(2) M–Se(1)–P(1) M–Se(2)–P(2) Se(1)–P(1)–N(1) Se(2)–P(2)–N(1) P(1)–N(1)–P(2)
111.32(6) 101.5(1) 101.3(1) 119.3(4) 119.6(4) 142.6(7)
112.19(6) 101.7(1) 100.9(1) 118.9(4) 119.8(5) 144.4(7)
101.59(2) 111.09(5) 106.02(4) 117.3(2) 116.4(2) 127.6(3)
a
Ring 2 is numbered sequentially w.r.t. ring 1 thus Se(1) corresponds to Se(3) etc.
recrystallised from CH2Cl2/methanol. Yield 0.060 g, 0.077 mmol, 55%. Microanalysis calculated for C24H56N2P4Se2S2Zn: C, 36.7; H, 7.1; N, 3.6. Observed: C, 36.4; H, 6.6; N, 3.9%.%. 31P{1H} NMR (CDCl3): 65.7, 56.6 ppm, 2J(31P– 31P) 28.2 Hz, 1J(71Se– 31P) 505 Hz. FT-IR (KBr disc): n(PNP) 1225(s), 767(m); n(PSe) 426(s); n(PS) 471(s). FAB + ve MS: m/z 783 corresponds to Zn[iPr2P(Se)NHP(S)iPr2]2.
1.9. Zn[ iPr2P(Se)NHP(S) iPr2]2 (9)
1.10. Pd[ iPr2P(Se)NHP(S) iPr2]2 (10)
ZnCO3·2Zn(OH)2·H2O (0.025 g, 0.07 mmol) was added to a solution of 2 (0.075 g, 0.21 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 3 h. The cloudy/white mixture was filtered and the filtrate was reduced to a white solid. The product was
KOtBu (0.022 g, 0.191 mmol) and 2 (0.068 g, 0.191 mmol) were added to a solution of PdCl2COD (0.027 g, 0.096 mmol) in methanol (2 ml) and stirred for 45 min.
Table 4 Selected bond lengths (A, ) and angles (°) in 1 and 4 i
Pr2P(S)NHP(S)iPr2 [9]
i
Pr2P(Se)NHP(Se)iPr2 (1)
i
Pr2P(O)NHP(O)iPr2 (4)
Bond lengths (A, ) P(1)–E(1) P(2)–E(2) P(1)–N(1) P(1)–N(2) H···E(1%) N···E(1%)
1.949(1) 1.941(1) 1.684(2) 1.682(3) 2.60 3.57
2.1027(9) 2.0961(8) 1.693(3) 1.686(3) 2.80 3.66
1.486(2) 1.471(2) 1.671(2) 1.669(2) 2.11 2.90
Bond angles (°) E(1)–P(1)–N(1) N(1)–P(2)–E(2) P(1)–N(1)–P(2) N(1)–H···E(1%) E(1)–P(1)···P(2)–E(2)
114.76(10) 114.14(9) 131.6(1) 170 79
114.83(10) 114.82(10) 131.2(2) 173 80
113.42(11) 113.70(12) 130.0(2) 174 52
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
The deep red solid product was filtered off and recrystallised from CH2Cl2/methanol. Yield 0.065 g, 0.079 mmol, 83%. Microanalysis calculated for
5
C24H56N2P4S2Se2Pd: C, 34.9; H, 6.8; N, 3.4. Observed: C, 34.3; H, 6.5; N, 3.1%. 31P{1H} NMR (CDCl3): 64.9, 56.6 ppm, 2J(31P– 31P) 28.2 Hz, 1J(71Se– 31P) 525 Hz. FT-IR (KBr disc): n(PNP) 1181(s); n(PSe) 433(w); n(PS) 469(m) cm − 1. FAB + ve MS: m/z 824 corresponds to Pd[iPr2P(Se)NHP(S)iPr2]2.
1.11. Pt[ iPr2P(Se)NHP(S) iPr2]2 (11)
Fig. 2. The X-ray structure of 7.
KOtBu (0.022 g, 0.191 mmol) and 2 (0.068 g, 0.191 mmol) were added to a solution of PtCl2COD (0.035 g, 0.096 mmol) in methanol (2 ml) and stirred for 25 min. The yellow product was collected by filtration and recrystallised from CH2Cl2/methanol. Yield 0.050 g, 0.055 mmol, 59%. Microanalysis calculated for C24H56N2P4S2Se2Pt: C, 31.5; H, 6.1; N, 3.1. Observed: C, 31.5; H, 5.9; N, 2.6%. 31P{1H} NMR (CDCl3): 59.8, 48.8 ppm, 2J(31P– 31P) 21.9 Hz, 2J(195Pt– 31P) 95.7 Hz, 1J(71Se– 31P) 545 Hz. FT-IR (KBr disc): n(PNP) 1222(s); n(PSe) 421(w); n(PS) 487(w) cm − 1. FAB + ve MS: m/z 913 corresponds to Pt[iPr2P(Se)NHP(S)iPr2]2.
1.12. Zn[ iPr2P(O)NHP(S) iPr2]2 (12)
Fig. 3. The X-ray structure of 6.
ZnCO3·2Zn(OH)2·H2O (0.038 g, 0.12 mmol) was added to a solution of 3 (0.10 g, 0.34 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 3 h. The cloudy/white mixture was filtered and the filtrate was reduced to 1 ml. Addition of hexane gave the desired product as a white solid. Yield 0.125 g, 0.142 mmol, 87%. Microanalysis calculated for C24H56N2P4S2O2Zn: C, 44.1; H, 8.5; N, 4.2. Observed: C, 44.2; H, 8.5; N, 3.9%. 31P{1H} NMR (CDCl3): 60.8, 52.0 ppm, 2J(31P– 31P) 22.0 Hz. FT-IR (KBr disc): n(PNP) 1224(s), 790(w); n(PO) 1023(m); n(PS) 472(w) cm − 1. FAB + ve MS: m/z 658 corresponds to Zn[iPr2P(O)NHP(S)iPr2]2.
1.13. Crystallography
Fig. 4. The X-ray structure of 11 showing one of the 50% occupancy models of the trans system.
Details of the data collections and refinements are given in Table 1. All data collections were performed at r.t. The SMART data collections consisted of at least a hemisphere of data collected using ‘thin’ slices (0.3°); these structures were solved and refined (on F 2) using SHELXTL [12]. The AFC structure was determined using v-scans (2u max. 120°) and solved and refined using TEXSAN [13]. It was interesting to note that a data collection for 7 using the SMART system did not refine well, whilst the data from the serial system were reasonably satisfactory. In 1 and 4 some disorder in one of the isopropyl groups was evident and two 50% occupancy systems were refined in each case, the protons on this isopropyl group were not included in the final refinement. The N–H
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D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
protons in 1 and 4 were allowed to refine freely whilst remaining H atoms were refined, using a riding model (SHELXTL) or in idealised positions (TEXSAN). In 11 the sulfur/selenium atoms were disordered and were refined with equal occupancies with symmetry considerations defining any particular molecule as having sulfur atoms trans to each other. All of the non-H atoms were refined anisotropically throughout. 2. Results and discussion The synthesis of iPr2P(E)NHP(E%)iPr2 was performed using a method previously reported for related systems [9,10]. The reaction scheme for the ligand preparation is shown in Eq. 1.
n(PNP) and n(N–H) peaks in the expected regions (Tables 2 and 3). In principle there are two tautomers possible for 1–4. Thus, upon going from Ph2(S)NHP(S)Ph2 to Ph2P(O)NP(OH)Ph2, the X-ray structures reveal a change in tautomeric form. However 1 and 4 both appear to adopt the same iPr2P(E)NHP(E%)iPr2 structure. In 1 the P–Se bond lengths (2.1027(9) and 2.0961(8) A, ) typical for PSe double bonds and the P–N bonds (1.693(3) and 1.686(3) A, ) are single. Similarly in 4 the PO bond lengths (1.486(2) and 1.471(2) A, ) reflect the double bond nature of the PO group, while the P–N bond lengths, though the shortest of any of the iPr2P(E)NHP(E%)iPr2 systems, are still effectively single in character (1.671(2) and 1.669(2) A, ) and equivalent to each other (Table 4). Both 1 and 4 adopt anti conformations with the PE groups rotated with respect to the P–N–P plane, the E(1)–P(1)···P(2)–E(2) torsion angle being 80° for the selenium compound (cf. 79° in the sulfur analogue) and 52° in the oxygen compound. As is typical the anti conformation is associated with chain-like packing of the molecules in the solid state. There is an N–H···E hydrogen bond in all the systems; which has the effect of lengthening the PE bond lengths for the hydrogen bonded E atoms. Since the ligands all contain an acidic NH proton they are readily deprotonated to form anionic chelate complexes. The reaction of 1–4 with the appropriate metal salts led to the formation of neutral complexes with the general formula ML2 (Eq. 2).
(1) The symmetric diseleno and dioxy ligands were obtained in good yields. The mixed sulfur/selenium and sulfur/oxygen ligands were obtained in lower yields due to unavoidable formation of the diseleno and dioxy ligands as by-products, though these were easily separated by recrystallisation. The difference in 31P NMR chemical shifts between PO (d 55.5 ppm), PS (d 92.1 ppm) and PSe (d 89.5 ppm) is typical and can readily be compared to the related compounds with the formula Ph2P(E)NHP(E%)Ph2. Whilst the assignments for the AX 31P NMR spectra of the mixed ligands could be confidently achieved by comparing the chemical shifts with those of the symmetric ligands reported here and previously. The 1H NMR spectra, FAB + mass spectra and CHN analysis were satisfactory for all compounds. The solid state IR spectra of the ligands show n(PE),
(2) The complexes were characterised by a combination of 1H, 31P NMR, IR, mass spectroscopy and elemental analysis. All gave satisfactory results. The 31P NMR spectra of 10 and 11 indicate only one isomer in solution although we were unable to assign the exact geometry (cis or trans) from the NMR data. In the solid state X-ray structure the sulfur atoms lie trans to each other in both compounds. The 1J(31P– 77Se) cou-
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
plings in 4 –9 are lower in magnitude than in the free ligand 1 and 2. This suggests a lowering of the P–Se bond order, as expected in a delocalised system. The deprotonation of the ligand on complexation leads to the loss of the n(N– H) band in the IR spectra. There is also the expected shift to a lower frequency of the 31P NMR signals as a consequence of deprotonation/complexation. As observed in related systems there is an increase in the frequency of the n(PNP) vibration in the complexes compared with the free ligand. The X-ray structure of Cd[N(iPr2PSe)2]2 (7) reveals (Table 5, Fig. 2) the expected tetrahedral geometry at the metal centre. The structure is isomorphous with the sulfur analogue. The CdSe2P2N ring adopts a pseudoboat conformation with the Cd(1) – Se(1) – P(1) –Se(2) being approximately co-planar (max. dev., 0.17 A, for Se(1)) and P(1)–N(1) – P(2) – Se(2) forming the other plane of a boat (max. dev., 0.12 A, for N(1)). The two planes are inclined by ca. 142°. Within statistical significance the same geometry is adopted for the other chelate ring of the structure. The X-ray structures of Pt[N(iPr2PSe)2]2 (6) (Table 5, Fig. 3) and Pt[iPr2P(Se)NHP(S)iPr2]2 (11) (Fig. 4) reveal the ability of the ligand system to adopt two alternate ring geometries which we noted previously [10] for Pt[N(iPr2PS)2]2 (pseudo-chair) and Pd[N(iPr2PS)2]2 (pseudo-boat). The structure of 11 is disordered with the sulfur and selenium atoms having 50% occupancy throughout, but there is no doubt about the conformation of the PtSSeP2N ring. In 6 the platinum atom lies on a crystallographic two-fold axis and is in a square planar environment (max. dev., for Pt – Se(1) – Se(2)– Se(1%)–Se(2%) 0.06 A, for Se(1)). The PtSe2P2N ring adopts a boat-like conformation Pt – Se(1) – P(2) –Se(2) (max. dev., of 0.24 A, for Se(2)) is inclined by 135° with respect to P(2)–Se(1) – P(1) – N(1) (max. dev., of 0.1 A, for N(1)). In 11 the mixed ligand complex, although disordered, crystallographic consideration means that the Se/S ligand in any particular molecule must always be trans. The PtSeSP2N ring adopts a pseudo-chair conformation (Fig. 4), but the disorder precludes de-
7
tailed discussion of the structure. However it should be noted that we previously observed that the change in conformation is accompanied by significant changes in the bonding [10] and we observed a similar effect here, thus, the P–N–P angle in 11 (136.3(4)°) is considerably enlarged compared to that observed (127.6(3)°) in 6.
Acknowledgements We are grateful to the JERI for an equipment grant.
References [1] J.D. Woollins, J. Chem. Soc., Dalton Trans. (1996) 2893 and references therein. [2] P. Battacharyya, J.D. Woollins, Polyhedron 14 (1995) 3367. [3] J.R. Phillips, A.M.Z. Slawin, A.J.P. White, D.J. Williams, J.D. Woollins, J. Chem. Soc., Dalton Trans. (1995) 2467. [4] K.H. Ebert, R. Cea-Olivares, V. Garci-Motalvo, G. EspinosaPerez, M.R. Estrada, J. Novosad, J.D. Woollins, Z. Naturforsch., Teil B 51 (1996) 1145. [5] A.M.Z. Slawin, J. Ward, D.J. Williams, J.D. Woollins, J. Chem. Soc., Chem. Commun. (1994) 421. [6] P. Bhattacharyya, J. Novosad, J. Phillips, D.J. Williams, J.D. Woollins, J. Chem. Soc., Dalton Trans. (1995) 1607. [7] R. Cea-Olivares, V. Garcı´a-Montalvo, J. Novosad, J.D. Woollins, R.A. Toscanoa, G. Espinosa-Pe´rez, Chem. Ber. 129 (1996) 919. [8] (a) R. Cea-Olivares, J. Novosad, J.D. Woollins, A.M.Z. Slawin, V. Garcı´a-Montalvo, G. Espinosa-Pe´rez, P. Garcı´a y Garcı´a, J. Chem. Soc., Chem. Commun. (1996) 519. (b) V. Garcia-Montalvo, J. Novosad, P. Killian, J.D. Woollins, A.M.Z. Slawin, P. Garcia y, M. Lopez-Carduso, G. Espinosa-Perez, R. Cea-Olivares, J. Chem. Soc., Dalton Trans. (1997) 1025. [9] D. Cupertino, R.W. Keyte, A.M.Z. Slawin, D.J. Williams, J.D. Woollins, Inorg. Chem. 35 (1996) 2695. [10] D. Cupertino, R. Keyte, A.M.Z. Slawin, J.D. Woollins, D.J. Williams, Polyhedron 15 (1996) 4441. [11] F.T. Wang, J. Najdzionek, K.L. Leneker, H. Wasserman, D.M. Braitsch, Synth. React. Inorg. Met. Org. Chem. 8 (1978) 119. [12] SHELXTL, Siemens Analytical Instruments, Madison, WI, 1990. [13] TEXSAN, Crystal Structure Analysis Package, Molecular Structure Corporation, The Woodlands, TX, 1992.
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The preparation and coordination chemistry of i Pr2P(E)NHP(E%)iPr2 (E, E%=Se; E=Se, E% =S; E =S, E% =O; E,E%=O Dominico Cupertino a, David J. Birdsall b, Alexandra M.Z. Slawin b, J. Derek Woollins b,* b
a Zeneca Specialties, Blackley, Manchester M9 8ZS, UK Department of Chemistry, Loughborough Uni6ersity, Loughborough LE11 3TU, UK
Received 12 November 1998; accepted 29 January 1999
Abstract Reaction of iPr2PCl with (Me3Si)2NH gives iPr2PNHiPPr2 (not isolated) which was oxidised with sulfur/selenium/oxygen to give Pr2P(E)NHP(E%)iPr2 (E, E%=Se; E=Se, E%=S; E= S, E%= O; E,E%=O). These neutral LH molecules readily undergo deprotonation/complexation to form simple ML2 species and demonstrative examples with Zn, Cd, Pd, Pt are reported. The X-ray structure of two examples of iPr2P(E)NHP(E%)iPr2 (E, E%=Se, E,E%= O) are reported. The molecules pack into infinite chains via H…E Hydrogen bonds. The X-ray structures of three typical metal complexes which illustrate tetrahedral (Cd[(iPr2PSe)2]2) and square planar (Pt[N(iPr2PSe)2]2) coordination at the metal centre as well as the ability of the ME2P2N ring to adopt the pseudo-chair conformation (Pt[iPr2P(Se)NHP(S)iPr2]2) are also reported. © 1999 Elsevier Science S.A. All rights reserved. i
Keywords: Crystal structures; Coordination chemistry; Phosphorous ligands; Amino ligands; Seleno ligands; Oxygen ligands
The dithioimidodiphosphinates have been known for some considerable time [1] and there has recently been a resurgence of interest in their coordination chemistry as a consequence of the steric control that this ligand system may impart compared to, for example, acac. Both ourselves and others have reported extensively on the chemistry of Ph2P(S)NHP(S)Ph2 [2 – 5] and to a lesser extent its selenium homologue [6 – 8]. Recently, we described some complexes derived from i Pr2P(S)NHP(S)iPr2 [9]. One especially interesting feature [10] was that in the palladium complex Pd[N(iPr2PS)2]2 the six-membered PdS2P2N ring adopts a pseudo-boat conformation whereas in the platinum complex Pt[N(iPr2PS)2]2 the PtS2P2N ring is in a pseudo-chair conformation. Here, we report on studies to investigate the generality of this observation by extension of the chemistry to include selenium com* Corresponding author. Tel.: + 44-1509-263 171; fax: +44-1509223 925. E-mail address: [email protected] (J.D. Woollins)
pounds as well as mixed S/Se and mixed S/O compounds. This paper describes the preparation of a range of iPr2P(E)NHP(E%)iPr2 (E, E% = Se 1; E= Se, E% =S 2; E= S, E% = O 3; E,E% =O 4) together with examples of their coordination complexes with tetrahedral and square planar metal centres. The X-ray structures of 1, 4 and three metal complexes are described (Fig. 1).
1. Experimental Unless stated otherwise, all reactions were performed under an atmosphere of oxygen-free nitrogen using standard Schlenk procedures. All glassware was oven dried at 100°C or flame dried under vacuum before use. All solvents and reagents were purchased from Aldrich, Strem or Fisher and used as received. In addition toluene, THF, Et2O and petroleum ether (60– 80) were distilled from sodium-benzophenone under nitrogen, and CH2Cl2 from CaH2. CDCl3 (99+atom% D) was as supplied.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 0 2 0 - 1 6 9 3 ( 9 9 ) 0 0 0 8 7 - 0
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
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The resulting white precipitate was filtered off. Excess selenium was removed by dissolving the product in CH2Cl2 and filtering through celite, followed by removal of solvent in vacuo. The crude product was recrystallised from CH2Cl2 and hexane. Yield 4.25 g, 10.47 mmol, 65%. Microanalysis calculated for C12H29NP2Se2: C, 35.3; H, 7.1; N, 3.4. Observed: C, 35.5; H, 7.1; N, 3.6%. 31P{1H} NMR (CDCl3): 89.5 ppm, 1 J(71Se– 31P) 757 Hz. FT-IR (KBr disc): n(N–H) 3207(s); d(N–H) 1385(m); n(PNP) 903(s), 877(s); n(PSe) 488.5 cm − 1. FAB + ve MS: m/z 407 corresponds to HN(iPr2PSe)2.
1.2. iPr2P(Se)NHP(S) iPr2 (2) A solution of iPr2PNHPiPr2 was prepared as for 1. Selenium (1.27 g, 16 mmol) was added and the solution stirred overnight. Sulfur (0.48 g, 15 mmol) was then added and stirring continued for 6 h. The solvent was removed in vacuo and the off-white product recrystallised from CH2Cl2 and hexane. Yield 2.13 g, 5.9 mmol, 37%. Microanalysis calculated for C12H29NP2SeS: C, 40.0; H, 8.1; N, 3.8. Observed: C, 40.3; H, 8.5; N, 3.6%. 31P{1H} NMR (CDCl3): 92.1, 89.2 ppm, 2 J(31P– 31P) 35.2 Hz, 1J(71Se– 31P) 747 Hz. FT-IR (KBr disc): n(N–H) 3214(s); d(N–H) 1385(s); n(PNP) 904(s), 878(s); n(PSe) 473; n(PS) 560 cm − 1. FAB + ve MS: m/z 360 corresponds to iPr2P(Se)NHP(S)iPr2. Fig. 1. The X-ray structure of 1 and 4 showing (a) an isolated molecule and (b) the H-bonded chain structure which both molecules adopt in the solid state (the structures are not isomorphous but are quite similar). 31
P (36.2, 101.25 MHz) were recorded on Jeol FX90Q, Bruker AC250 FT spectrometers. Chemical shifts are reported relative to 85% H3PO4 on both spectrometers. IR spectra were recorded as KBr discs on a Perkin-Elmer System 2000 FTIR spectrometer. Microanalyses were carried out by the service at Loughborough University. FAB +ve mass spectra were recorded by the EPSRC mass spectrometry service at Swansea.
1.1. iPr2P(Se)NHP(Se) iPr2 (1) This method is based on a literature preparation of related compounds [11], the reaction was performed under nitrogen. A solution of iPr2PCl (4.87 g, 5.0 ml, 32 mmol) in toluene (100 ml) was added dropwise to a solution of HN(SiMe3)2 (2.58 g, 3.4 ml, 16.0 mmol) in hot (50°C) toluene (50 ml) over 30 min. Heating and stirring was continued for 3 h after which time the reaction was cooled to room temperature (r.t.) and selenium was added (2.53 g, 31 mmol). The reaction was then refluxed for a further 6 h and cooled to 0°C.
1.3. iPr2P(O)NHP(S) iPr2 (3) A solution of iPr2PNHPiPr2 was prepared as for 1. Sulfur (0.48 g, 15 mmol) was then added and stirred overnight. Hydrogen peroxide (30% solution 1.9 ml) was then added dropwise and stirring continued. The solvent was removed in vacuo and the white product recrystallised from CH2Cl2 and hexane. Yield 1.23 g, 4.14 mmol, 25%. Microanalysis calculated for C12H29NP2O2: C, 48.5; H, 9.8; N, 4.7. Observed: C, 48.1; H, 10.1; N, 4.8%. 31P{1H} NMR (CDCl3): 90.9, 54.8 ppm, 2J(31P– 31P) 21.9 Hz. FT-IR (KBr disc): n(N–H) 3442(s); d(N–H) 1387(m); n(PNP) 890(m), 882(m); n(PO) 1038(m); n(PS) 670(m) cm − 1. FAB +ve MS: m/z 298 corresponds to iPr2P(O)NHP(S)iPr2.
1.4. iPr2P(O)NHP(O) iPr2 (4) A solution of iPr2PNHPiPr2 was prepared as for 1. Hydrogen peroxide (30% solution, 3.8 ml) was added dropwise and stirred. The solvent was removed in vacuo and the white product recrystallised from CH2Cl2 and hexane. Yield 2.4 g, 8.37 mmol, 54%. Microanalysis calculated for C12H29NP2O2: C, 51.2; H, 10.3; N, 4.9. Observed: C, 50.9; H, 9.8; N, 4.6%. 31P{1H} NMR (CDCl3): 55.5 ppm. FT-IR (KBr disc): n(N–H)
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
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Table 1 Details of the X-ray data collections and refinementsa Compound
1
4
6
7
11
Empirical formula M Crystal system Space group Diffractometer/radiation a (A, ) b (A, ) c (A, ) a (°) b (°) g (°) U (A, 3) Z Dcalc. (M gm−3) m (mm−1) F(000) Measured reflections Independent reflections (Rint) Observed reflections Final R R%
C12H29NP2Se2 407.22 monoclinic P21/c SMART/Mo Ka 14.680(1) 10.524(1) 12.349(1) 90 105.91(1) 90 1835 4 1.47 4.19 824 7879 2649 (0.0173) 2649 0.0286, 0.0819
C12H29NP2O2 290.31 monoclinic P21/n SMART/Mo Ka 8.603(1) 10.269(1) 19.163(1) 90 92.53(1) 90 1691 4 1.14 0.225 636 7152 2436 (0.021) 2353 0.041, 0.107
C24H56N2P4PtSe4 1007.52 monoclinic C2/c SMART/Mo Ka 13.561(1) 21.554(1) 13.855(1) 90 112.89(1) 90 1952 4 1.79 7.85 1952 7981 2638 (0.095) 2585 0.0329, 0.0802
C24H56N2P4Se4Cd 924.86 triclinic P1( (no. 2) AFC7S/Cu Kab 13.080(4) 16.49(1) 9.487(7) 103.20(8) 109.67(4) 78.30(4) 1858 2 1.65 10.92 916 5820 5537 2901c 0.055, 0.057
C24H56N2P4PtS2Se2 913.72 monoclinic P21/c SMART/Mo Ka 10.623(1) 14.602(1) 12.090(1) 90 103.10(1) 90 1826 2 1.66 6.14 904 7179 2574 (0.1695) 2524 0.0446, 0.1022
a
All data collections were performed at 290 K. Data collection using SMART and Mo Ka gave the same cell but less satisfactory refinement. R values are for observed data [I =2.0s(I)] or c [I\3.0s(I)]. Complex 2 gave a cell which is isomorphous with 1 [a =12.175(2), b = 10.520(1), c= 14.615(3) A, , b= 105.6(2)°, P21/a. Complex 9 gave a cell which is isomorphous with 7 [a= 9.364(1), b= 12.969(1), c = 16.572(1) A, , a = 78.93(1), b=77.76(1), g= 68.99(1)°, P1( ]. Neither of these mixed S/Se structures could be refined because of disorder. b
3223(s); d(N–H) 1392(s); n(PNP) 945(s), 881(s); n(PO) 1150(s). FAB +ve MS: m/z 281 corresponds to i Pr2P(O)NHP(O)iPr2.
ppm, 2J(195Pt– 31P) 97.3 Hz, 1J(71Se– 31P) 536 Hz. FTIR (KBr disc): n(PNP) 1181(s); n(PSe) 477(m); d(NPSe) 412(w) cm − 1. FAB +ve MS: m/z 1008 corresponds to Pt[N(iPr2PSe)2]2.
1.5. Zn[( iPr2PSe)2]2 (5) 1.7. Cd[( iPr2PSe)2]2 (7) ZnCO3·2Zn(OH)2·H2O (0.028 g, 0.081 mmol) was added to a solution of 1 (0.10 g, 0.25 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 2 h. The cloudy/white mixture was filtered and the filtrate was reduced by two thirds and cooled overnight to give the product as clear crystals. Yield 0.125 g, 0.142 mmol, 87%. Microanalysis calculated for C24H56N2P4Se4Zn: C, 32.8; H, 6.3; N, 3.1. Observed: C, 32.8; H, 6.1; N, 3.0%. 31P{1H} NMR (CDCl3): 59.8 ppm, 1J(31P – 71Se) 539 Hz. FT-IR (KBr disc): n(PNP) 1225(s), 759(w); n(PSe) 426(m). FAB +ve MS: m/z 878 corresponds to Zn{N(iPr2PSe)2}2.
1.6. Pt[N( iPr2PSe)2]2 (6) Complex 1 (0.1 g, 0.268 mmol) was added to a solution of PtCl2COD (0.046 g, 0.134 mmol) in methanol (5 cm3), which was stirred for 2 h. The product, a yellow solid was collected by filtration. Yield 0.10 g, 0.122 mmol, 90%. Microanalysis calculated for C24H56N2P4Se4Pt: C, 28.6; H, 5.5; N, 2.8. Observed: C, 29.0; H, 5.0; N, 2.4%. 31P{1H} NMR (CDCl3): 50.1
CdCO3 (0.019 g, 0.12 mmol) was added to a solution of 1 (0.091 g, 0.23 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 3 h. The solution was reduced to 1 ml. Methanol was added to precipitate the off-white product. Yield 0.090 g, 0.098 mmol, 74%. Microanalysis calculated for C24H56N2P4Se4Cd: C, 31.2; H, 6.0; N, 3.0. Observed: C, 30.9; H, 5.9; N, 2.5%. 31 P{1H} NMR (CDCl3): 56.6 ppm, 2J(111/113Cd– 31P) 30.8 Hz, 1J(71Se– 31P) 563 Hz. FT-IR (KBr disc): n(PNP) 1229(s), 752(m); n(PSe) 425(m). FAB +ve MS: m/z 925 corresponds to Cd{N(iPr2PSe)2}2. Table 2 Selected IR data for imidophosphinates (cm−1) Compd
Formula
n(NH)
n(PNP)
n(PE)
1 2 3 4
i
3207, 3214, 3442, 3223,
903, 904, 890, 945,
488 473, 560 1038, 670 1150
Pr2P(Se)NHP(Se)iPr2 Pr2P(Se)NHP(S)iPr2 i Pr2P(O)NHP(S)iPr2 i Pr2P(O)NHP(O)iPr2 i
1385 1385 1387 1392
877 878 882 881
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Table 3 IR assignments for M[iPr2P(E)NP(E)iPr2]2 (M= Zn, Pt, Pd and Cd (cm−1)) Compd
Formula
n(PNP)
n(PE)
5 6 7 8 9 10 11 12
Zn[(iPr2PSe)2]2 Pt[N(iPr2PSe)2]2 Cd[(iPr2PSe)2]2 Pd[N(iPr2PSe)2]2 Zn[iPr2P(Se)NHP(S)iPr2]2 Pd[iPr2P(Se)NHP(S)iPr2]2 Pt[iPr2P(Se)NHP(S)iPr2]2 Zn[iPr2P(O)NHP(S)iPr2]2
1225, 1181 1229, 1182 1225, 1181 1222 1224,
426 477 425 477 426, 471 433, 469 421, 487 1023, 472
759 752 767
790
Table 5 Selected bond lengths (A, ) and angles (°) in 6 and 7 Cd[N(iPr2PSe)2]2 (7)
1.8. Pd[N( iPr2PSe)2]2 (8) KOtBu (0.019 g, 0.169 mmol) and 1 (0.069 g, 0.169 mmol) were added to a solution of PdCl2COD (0.024 g, 0.085 mmol) in methanol (2 ml) and stirred for 2 h. The blood red solution was evaporated to dryness and the product extracted into dichloromethane. The solvent was removed in vacuo to give a red solid product. Yield 0.045 g, 0.049 mmol, 59%. Microanalysis calculated for C24H56N2P4Se4Pd: C, 31.4; H, 6.1; N, 3.1. Observed: C, 31.6; H, 5.8; N, 2.8%. 31P{1H} NMR (CDCl3): 55.9 ppm, 1J(71Se– 31P) 590 Hz. FT-IR (KBr disc): n(PNP) 1182(s); n(PSe) 477(m). FAB +ve MS: m/z 918 corresponds to Pd{N(iPr2PSe)2}2.
Pt[N(iPr2PSe)2]2 (6)
Ring 1
Ring 2a
Bond lengths (A, ) M–Se(1) M–Se(2) Se(1)–P(1) Se(2)–P(2) P(1)–N(1) P(2)–N(1)
2.625(2) 2.636(2) 2.168(4) 2.176(4) 1.60(1) 1.58(1)
2.622(2) 2.628(4) 2.188(4) 2.178(4) 1.60(1) 1.56(1)
2.4642(6) 2.4616(6) 2.218(2) 2.205(2) 1.603(5) 1.623(5)
Bond angles (°) Se(1)–M–Se(2) M–Se(1)–P(1) M–Se(2)–P(2) Se(1)–P(1)–N(1) Se(2)–P(2)–N(1) P(1)–N(1)–P(2)
111.32(6) 101.5(1) 101.3(1) 119.3(4) 119.6(4) 142.6(7)
112.19(6) 101.7(1) 100.9(1) 118.9(4) 119.8(5) 144.4(7)
101.59(2) 111.09(5) 106.02(4) 117.3(2) 116.4(2) 127.6(3)
a
Ring 2 is numbered sequentially w.r.t. ring 1 thus Se(1) corresponds to Se(3) etc.
recrystallised from CH2Cl2/methanol. Yield 0.060 g, 0.077 mmol, 55%. Microanalysis calculated for C24H56N2P4Se2S2Zn: C, 36.7; H, 7.1; N, 3.6. Observed: C, 36.4; H, 6.6; N, 3.9%.%. 31P{1H} NMR (CDCl3): 65.7, 56.6 ppm, 2J(31P– 31P) 28.2 Hz, 1J(71Se– 31P) 505 Hz. FT-IR (KBr disc): n(PNP) 1225(s), 767(m); n(PSe) 426(s); n(PS) 471(s). FAB + ve MS: m/z 783 corresponds to Zn[iPr2P(Se)NHP(S)iPr2]2.
1.9. Zn[ iPr2P(Se)NHP(S) iPr2]2 (9)
1.10. Pd[ iPr2P(Se)NHP(S) iPr2]2 (10)
ZnCO3·2Zn(OH)2·H2O (0.025 g, 0.07 mmol) was added to a solution of 2 (0.075 g, 0.21 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 3 h. The cloudy/white mixture was filtered and the filtrate was reduced to a white solid. The product was
KOtBu (0.022 g, 0.191 mmol) and 2 (0.068 g, 0.191 mmol) were added to a solution of PdCl2COD (0.027 g, 0.096 mmol) in methanol (2 ml) and stirred for 45 min.
Table 4 Selected bond lengths (A, ) and angles (°) in 1 and 4 i
Pr2P(S)NHP(S)iPr2 [9]
i
Pr2P(Se)NHP(Se)iPr2 (1)
i
Pr2P(O)NHP(O)iPr2 (4)
Bond lengths (A, ) P(1)–E(1) P(2)–E(2) P(1)–N(1) P(1)–N(2) H···E(1%) N···E(1%)
1.949(1) 1.941(1) 1.684(2) 1.682(3) 2.60 3.57
2.1027(9) 2.0961(8) 1.693(3) 1.686(3) 2.80 3.66
1.486(2) 1.471(2) 1.671(2) 1.669(2) 2.11 2.90
Bond angles (°) E(1)–P(1)–N(1) N(1)–P(2)–E(2) P(1)–N(1)–P(2) N(1)–H···E(1%) E(1)–P(1)···P(2)–E(2)
114.76(10) 114.14(9) 131.6(1) 170 79
114.83(10) 114.82(10) 131.2(2) 173 80
113.42(11) 113.70(12) 130.0(2) 174 52
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
The deep red solid product was filtered off and recrystallised from CH2Cl2/methanol. Yield 0.065 g, 0.079 mmol, 83%. Microanalysis calculated for
5
C24H56N2P4S2Se2Pd: C, 34.9; H, 6.8; N, 3.4. Observed: C, 34.3; H, 6.5; N, 3.1%. 31P{1H} NMR (CDCl3): 64.9, 56.6 ppm, 2J(31P– 31P) 28.2 Hz, 1J(71Se– 31P) 525 Hz. FT-IR (KBr disc): n(PNP) 1181(s); n(PSe) 433(w); n(PS) 469(m) cm − 1. FAB + ve MS: m/z 824 corresponds to Pd[iPr2P(Se)NHP(S)iPr2]2.
1.11. Pt[ iPr2P(Se)NHP(S) iPr2]2 (11)
Fig. 2. The X-ray structure of 7.
KOtBu (0.022 g, 0.191 mmol) and 2 (0.068 g, 0.191 mmol) were added to a solution of PtCl2COD (0.035 g, 0.096 mmol) in methanol (2 ml) and stirred for 25 min. The yellow product was collected by filtration and recrystallised from CH2Cl2/methanol. Yield 0.050 g, 0.055 mmol, 59%. Microanalysis calculated for C24H56N2P4S2Se2Pt: C, 31.5; H, 6.1; N, 3.1. Observed: C, 31.5; H, 5.9; N, 2.6%. 31P{1H} NMR (CDCl3): 59.8, 48.8 ppm, 2J(31P– 31P) 21.9 Hz, 2J(195Pt– 31P) 95.7 Hz, 1J(71Se– 31P) 545 Hz. FT-IR (KBr disc): n(PNP) 1222(s); n(PSe) 421(w); n(PS) 487(w) cm − 1. FAB + ve MS: m/z 913 corresponds to Pt[iPr2P(Se)NHP(S)iPr2]2.
1.12. Zn[ iPr2P(O)NHP(S) iPr2]2 (12)
Fig. 3. The X-ray structure of 6.
ZnCO3·2Zn(OH)2·H2O (0.038 g, 0.12 mmol) was added to a solution of 3 (0.10 g, 0.34 mmol) in dichloromethane (20 ml), and the mixture was refluxed for 3 h. The cloudy/white mixture was filtered and the filtrate was reduced to 1 ml. Addition of hexane gave the desired product as a white solid. Yield 0.125 g, 0.142 mmol, 87%. Microanalysis calculated for C24H56N2P4S2O2Zn: C, 44.1; H, 8.5; N, 4.2. Observed: C, 44.2; H, 8.5; N, 3.9%. 31P{1H} NMR (CDCl3): 60.8, 52.0 ppm, 2J(31P– 31P) 22.0 Hz. FT-IR (KBr disc): n(PNP) 1224(s), 790(w); n(PO) 1023(m); n(PS) 472(w) cm − 1. FAB + ve MS: m/z 658 corresponds to Zn[iPr2P(O)NHP(S)iPr2]2.
1.13. Crystallography
Fig. 4. The X-ray structure of 11 showing one of the 50% occupancy models of the trans system.
Details of the data collections and refinements are given in Table 1. All data collections were performed at r.t. The SMART data collections consisted of at least a hemisphere of data collected using ‘thin’ slices (0.3°); these structures were solved and refined (on F 2) using SHELXTL [12]. The AFC structure was determined using v-scans (2u max. 120°) and solved and refined using TEXSAN [13]. It was interesting to note that a data collection for 7 using the SMART system did not refine well, whilst the data from the serial system were reasonably satisfactory. In 1 and 4 some disorder in one of the isopropyl groups was evident and two 50% occupancy systems were refined in each case, the protons on this isopropyl group were not included in the final refinement. The N–H
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D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
protons in 1 and 4 were allowed to refine freely whilst remaining H atoms were refined, using a riding model (SHELXTL) or in idealised positions (TEXSAN). In 11 the sulfur/selenium atoms were disordered and were refined with equal occupancies with symmetry considerations defining any particular molecule as having sulfur atoms trans to each other. All of the non-H atoms were refined anisotropically throughout. 2. Results and discussion The synthesis of iPr2P(E)NHP(E%)iPr2 was performed using a method previously reported for related systems [9,10]. The reaction scheme for the ligand preparation is shown in Eq. 1.
n(PNP) and n(N–H) peaks in the expected regions (Tables 2 and 3). In principle there are two tautomers possible for 1–4. Thus, upon going from Ph2(S)NHP(S)Ph2 to Ph2P(O)NP(OH)Ph2, the X-ray structures reveal a change in tautomeric form. However 1 and 4 both appear to adopt the same iPr2P(E)NHP(E%)iPr2 structure. In 1 the P–Se bond lengths (2.1027(9) and 2.0961(8) A, ) typical for PSe double bonds and the P–N bonds (1.693(3) and 1.686(3) A, ) are single. Similarly in 4 the PO bond lengths (1.486(2) and 1.471(2) A, ) reflect the double bond nature of the PO group, while the P–N bond lengths, though the shortest of any of the iPr2P(E)NHP(E%)iPr2 systems, are still effectively single in character (1.671(2) and 1.669(2) A, ) and equivalent to each other (Table 4). Both 1 and 4 adopt anti conformations with the PE groups rotated with respect to the P–N–P plane, the E(1)–P(1)···P(2)–E(2) torsion angle being 80° for the selenium compound (cf. 79° in the sulfur analogue) and 52° in the oxygen compound. As is typical the anti conformation is associated with chain-like packing of the molecules in the solid state. There is an N–H···E hydrogen bond in all the systems; which has the effect of lengthening the PE bond lengths for the hydrogen bonded E atoms. Since the ligands all contain an acidic NH proton they are readily deprotonated to form anionic chelate complexes. The reaction of 1–4 with the appropriate metal salts led to the formation of neutral complexes with the general formula ML2 (Eq. 2).
(1) The symmetric diseleno and dioxy ligands were obtained in good yields. The mixed sulfur/selenium and sulfur/oxygen ligands were obtained in lower yields due to unavoidable formation of the diseleno and dioxy ligands as by-products, though these were easily separated by recrystallisation. The difference in 31P NMR chemical shifts between PO (d 55.5 ppm), PS (d 92.1 ppm) and PSe (d 89.5 ppm) is typical and can readily be compared to the related compounds with the formula Ph2P(E)NHP(E%)Ph2. Whilst the assignments for the AX 31P NMR spectra of the mixed ligands could be confidently achieved by comparing the chemical shifts with those of the symmetric ligands reported here and previously. The 1H NMR spectra, FAB + mass spectra and CHN analysis were satisfactory for all compounds. The solid state IR spectra of the ligands show n(PE),
(2) The complexes were characterised by a combination of 1H, 31P NMR, IR, mass spectroscopy and elemental analysis. All gave satisfactory results. The 31P NMR spectra of 10 and 11 indicate only one isomer in solution although we were unable to assign the exact geometry (cis or trans) from the NMR data. In the solid state X-ray structure the sulfur atoms lie trans to each other in both compounds. The 1J(31P– 77Se) cou-
D. Cupertino et al. / Inorganica Chimica Acta 290 (1999) 1–7
plings in 4 –9 are lower in magnitude than in the free ligand 1 and 2. This suggests a lowering of the P–Se bond order, as expected in a delocalised system. The deprotonation of the ligand on complexation leads to the loss of the n(N– H) band in the IR spectra. There is also the expected shift to a lower frequency of the 31P NMR signals as a consequence of deprotonation/complexation. As observed in related systems there is an increase in the frequency of the n(PNP) vibration in the complexes compared with the free ligand. The X-ray structure of Cd[N(iPr2PSe)2]2 (7) reveals (Table 5, Fig. 2) the expected tetrahedral geometry at the metal centre. The structure is isomorphous with the sulfur analogue. The CdSe2P2N ring adopts a pseudoboat conformation with the Cd(1) – Se(1) – P(1) –Se(2) being approximately co-planar (max. dev., 0.17 A, for Se(1)) and P(1)–N(1) – P(2) – Se(2) forming the other plane of a boat (max. dev., 0.12 A, for N(1)). The two planes are inclined by ca. 142°. Within statistical significance the same geometry is adopted for the other chelate ring of the structure. The X-ray structures of Pt[N(iPr2PSe)2]2 (6) (Table 5, Fig. 3) and Pt[iPr2P(Se)NHP(S)iPr2]2 (11) (Fig. 4) reveal the ability of the ligand system to adopt two alternate ring geometries which we noted previously [10] for Pt[N(iPr2PS)2]2 (pseudo-chair) and Pd[N(iPr2PS)2]2 (pseudo-boat). The structure of 11 is disordered with the sulfur and selenium atoms having 50% occupancy throughout, but there is no doubt about the conformation of the PtSSeP2N ring. In 6 the platinum atom lies on a crystallographic two-fold axis and is in a square planar environment (max. dev., for Pt – Se(1) – Se(2)– Se(1%)–Se(2%) 0.06 A, for Se(1)). The PtSe2P2N ring adopts a boat-like conformation Pt – Se(1) – P(2) –Se(2) (max. dev., of 0.24 A, for Se(2)) is inclined by 135° with respect to P(2)–Se(1) – P(1) – N(1) (max. dev., of 0.1 A, for N(1)). In 11 the mixed ligand complex, although disordered, crystallographic consideration means that the Se/S ligand in any particular molecule must always be trans. The PtSeSP2N ring adopts a pseudo-chair conformation (Fig. 4), but the disorder precludes de-
7
tailed discussion of the structure. However it should be noted that we previously observed that the change in conformation is accompanied by significant changes in the bonding [10] and we observed a similar effect here, thus, the P–N–P angle in 11 (136.3(4)°) is considerably enlarged compared to that observed (127.6(3)°) in 6.
Acknowledgements We are grateful to the JERI for an equipment grant.
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