New dithiocarbamate and xanthate complexes of nickel(II) with iminophosphines

Inorganica Chimica Acta 355 (2003) 33 /40 www.elsevier.com/locate/ica

New dithiocarbamate and xanthate complexes of nickel(II) with iminophosphines Jose´ L. Serrano a,*, Luis Garcı´a a, Jose´ Pe´rez a, Eduardo Pe´rez a, Gregorio Sa´nchez b, Joaquı´n Garcı´a b, Gregorio Lo´pez b, Gabriel Garcı´a b, Elies Molins c ´ rea de Quı´mica Inorga´nica, 30203 Cartagena, Spain Departamento de Ingenierı´a Minera, Geolo´gica y Cartogra´fica. A b Departamento de Quı´mica Inorga´nica, Universidad de Murcia, 30071 Murcia, Spain c Institut de Cie`ncia de Materials de Barcelona-CSIC. Campus Universitari de Bellaterra, E-08193 Cerdanyola, Barcelona, Spain a

Received 20 December 2002; accepted 24 April 2003

Abstract The synthesis of new cationic dithiocarbamate nickel(II) complexes with the mixed-donor bidentate ligands o -Ph2PC6H4 /CH/ NR is described. The derivatives of general formula [Ni(R2?dtc)(o -Ph2PC6H4CH /NR)][ClO4] [R?/iPr; R /Me (1), Et (2), iPr (3), t Bu (4); R? /iBu; R/Me (5), Et (6), iPr (7), tBu (8)] have been obtained by direct reaction between Ni(ClO4)2, the bis(dithiocarbamate) precursors [Ni(R2?dtc)2] and the corresponding iminophosphine. Analogous reaction using [Ni(R?xan)2] as starting materials allowed the preparation of complexes [Ni(R?xan)(o -Ph2PC6H4CH /NR)][ClO4] [R? /Et; R/Me (9), Et (10), iPr (11), tBu (12); R?/iPr; R /Me (13), Et (14), iPr (15), tBu (16)]. The new complexes have been characterized by partial elemental analyses, conductivity measurements and spectroscopic methods (IR, 1H and 31P{1H} NMR). The X-ray structures of complexes (1), (5) and (13) are reported, revealing that the iminophosphine acts as chelating ligand with coordination around the nickel atom distorted from the square-planar geometry. # 2003 Elsevier B.V. All rights reserved. Keywords: Nickel; Dithiocarbamate complexes; Xanthate complexes; Iminophosphines; Crystal structures; Cambridge Structural Database

1. Introduction Dithiocarbamates and related ligands [1] as well as transition-metal complexes in which a 1,1-dithio ligand forms a four-membered ring with the metal ion have been extensively investigated and thoroughly reviewed [2 /5]. Thus, we have described the preparation of some organometallic nickel(II) complexes containing these ligands [6,7], and a systematic study of nickel(II) xanthates [8] and dithiocarbamates [9] with monodentate or polydentate N- or P- donor ligands is being carried out in recent years. However, to the best of our knowledge, to date there are no reports of complexes with both the Ni(S2CX)  fragment (X /N or O) and mixed donor N S P bidentate ligands. In fact, examples of nickel(II) complexes stabilized by these so called N S P

* Corresponding author. E-mail address: [email protected] (J.L. Serrano). 0020-1693/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0020-1693(03)00342-6

ligands are relatively scarce [10 /13], although a growing interest is expected with regard to the potential use of some of them as ‘SHOP’-type catalysts [11]. The considerable attention received by N S P and, in general, polydentate ligands with both hard and soft donor atoms [14 /20], comes from their versatile coordination behaviour [21,22] and its potential hemilability [20,23], that make their complexes useful as the basis for molecule-based sensors [24 /26] and in the synthesis of inorganic macrocycles via the ‘weak-link approach’ [27,28]. As mentioned above for nickel(II), metal complexes containing hemilabile ligands have been found to be catalytically active in a range of reactions [23]. Thus, some complexes with N S P ligands are suitable for palladium-catalyzed allylic alkylation [29], oligomerization of olefins [30,31], homogeneous hydrogenation of double and triple C /C bonds [32] and copolymerization of CO/olefins [33 /35]. Among the most widely studied N S P ligands with these characteristics are the pyridylphosphines and the iminophosphines that we present in

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J.L. Serrano et al. / Inorganica Chimica Acta 355 (2003) 33 /40

this work, from which Group 10 metal complexes have been profusely reported since 1992 [36 /43]. In this sense, we have described in recent work the syntheses of some organometallic derivatives containing iminophosphine ligands [10,44 /46], and explored its coordination chemistry with these metals [47,48]. We report here the preparation of new dithiocarbamate and xanthate complexes of nickel(II) with iminophosphines by means of a simple synthetic route, unexplored with this kind of ligands.

2. Experimental 2.1. Materials and physical measurements C, H, N and S analyses were carried out with a Perkin/Elmer 240C microanalyser. IR spectra were recorded on a Perkin/Elmer spectrophotometer 16F PC FT-IR, using nujol mulls between polyethylene sheets. NMR data were recorded on a Bruker AC 200E or a Varian Unity 300 spectrometer. Conductance measurements were performed with a Crison 525 conductimeter (in acetone; c/5/104 M). The starting [Ni(R2?dtc)2] [49] and [Ni(R?xan)2] [50] complexes and the iminophosphine ligands [51] were prepared according to reported procedures. All other chemicals and solvents were supplied by Sigma-Aldrich Co. 2.2. Preparation of the complexes [Ni(R2?dtc)(o Ph2PC6H4CH /NR)][ClO4] (R? /iPr; R /Me (1), Et (2), iPr (3), tBu (4); R? /iBu; R /Me (5), Et (6), iPr (7), tBu (8)) The complexes were obtained by reacting Ni(ClO4)2, the bis(dithiocarbamate) precursor [Ni(R2?dtc)2] and the corresponding iminophosphine in ethanol according to the following general method. To an ethanolic suspension (10 ml) of fine pulverized Ni(ClO4)2 (0.062 g, 0.172 mmol) and fine pulverized [Ni(R2?dtc)2] (0.172 mmol) was added the calculated amount of iminophosphine (0.172 mmol) in ethanol solution previously prepared. The reaction was stirred at reflux temperature until dissolution of its components (5 h approximately) and filtered through celite while hot. Solvent was then partially evaporated under reduced pressure and the deep red solution cooled to 4 8C for 24 h. The red crystalline solids thus obtained were filtered off, washed with water and air dried. [Ni(iPr2dtc)(o -Ph2PC6H4CH /NMe)][ClO4] (1) was obtained in 74% yield. Anal . Calc. for C27ClH32N2O4PS2Ni: C, 50.8; H, 5.0; N, 4.4; S, 10.0. Found: C, 50.9; H, 5.2; N, 4.2; S, 10.1%. LM /143 V 1 cm2 mol1. IR (cm 1): 1620 (C /N str), 1524 (C /N str), 996 (C /S str). 1H NMR (Me2CO-d6): 1.39 (s-br, 12H,

CH3-dtc), 3.57 (s, 3H, CH3 /NP), 4.49 (s-br, 2H, CHdtc), 7.43 (m, 1H, H3), 7.63 (m, 11H, H4/Ph), 7.94 (m, 2H, H5, H6), 8.43 (s, 1H, Ha). 31P NMR (Me2CO-d6): 32.5 (s). [Ni(iPr2dtc)(o -Ph2PC6H4CH /NEt)][ClO4] (2) was obtained in 79% yield. Anal . Calc. for C28ClH34N2O4PS2Ni: C, 51.6; H, 5.2; N, 4.3; S, 9.8. Found: C, 51.8; H, 5.3; N, 4.4; S, 10.0%. LM /141 V 1 cm2 mol1. IR (cm1): 1614 (C /N str), 1518 (C /N str), 993 (C /S str). 1H NMR (Me2CO-d6): 1.34 (d, 6H, CH3dtc, J /6.6), 1.44 (m, 9H, CH3-dtc; CH3 /NP), 3.66 (m, 2H, CH2 /NP), 4.46 (s-br, 1H, CH-dtc), 4.71 (s-br, 1H, CH-dtc), 7.31 (m, 1H, H3), 7.63 (m, 11H, H4/Ph), 7.97 (m, 2H, H5, H6), 8.49 (d, 1H, Ha, J/2.4). 31P NMR (Me2CO-d6): 32.3 (s). [Ni(iPr2dtc)(o-Ph2PC6H4CH /NiPr)][ClO4] (3) was obtained in 70% yield. Anal . Calc. for C29ClH36N2O4PS2Ni: C, 52.3; H, 5.4; N, 4.2; S, 9.6. Found: C, 52.2; H, 5.3; N, 4.1; S, 9.7%. LM /130 V 1 cm2 mol1. IR (cm1): 1616 (C /N str), 1516 (C /N str), 993 (C/S str). 1H NMR (Me2CO-d6): 1.25 (d, 6H, CH3 / NP, J/6.6), 1.37 (s-br, 6H, CH3-dtc), 1.44 (s-br, 6H, CH3-dtc), 4.33 (m, 1H, CH /NP), 4.46 (s-br, 1H, CHdtc), 4.71 (s-br, 1H, CH-dtc), 7.28 (m, 1H, H3), 7.59 (m, 11H, H4/Ph), 7.98 (m, 1H, H5), 8.08 (m, 1H, H6), 8.48 (d, 1H, Ha, J /3.3). 31P NMR (Me2CO-d6): 33.6 (s). [Ni(iPr2dtc)(o -Ph2PC6H4CH /NtBu)][ClO4] (4) was obtained in 81% yield. Anal . Calc. for C30ClH38N2O4PS2Ni: C, 53.0; H, 5.6; N, 4.1; S, 9.4. Found: C, 53.2; H, 5.6; N, 4.3; S, 9.5.%. LM /127 V 1 cm2 mol1. IR (cm1): 1616 (C /N str), 1516 (C /N str), 993 (C/S str). 1H NMR (Me2CO-d6): 1.11 (m-br, 12H, CH3-dtc), 1.53 (s, 9H, CH3 /NP), 4.46 (s-br, 1H, CHdtc), 4.70 (s-br, 1H, CH-dtc), 7.29 (m, 1H, H3), 7.68 (m, 11H, H4/Ph), 8.02 (m, 1H, H5), 8.07 (m, 1H, H6), 8.52 (d, 1H, Ha, J /5.4). 31P NMR (Me2CO-d6): 33.1 (s). [Ni(iBu2dtc)(o-Ph2PC6H4CH /NMe)][ClO4] (5) was obtained in 71% yield. Anal . Calc. for C29ClH36N2O4PS2Ni: C, 52.3; H, 5.4; N, 4.2; S, 9.6. Found: C, 52.2; H, 5.5; N, 4.3; S, 9.7%. LM /100 V 1 cm2 mol1. IR (cm1): 1619 (C /N str), 1519 (C /N str), 999 (C /S str). 1H NMR (Me2CO-d6): 0.84 (d, 6H, CH3dtc, J/6.0) 0.94 (d, 6H, CH3-dtc J /6.0), 2.17 (m-br, 1H, CH-dtc), 2.27 (m-br, 1H, CH-dtc), 3.45 (d, 2H, CH2-dtc, J /7.0), 3.57 (s, 3H, CH3 /NP), 3.64 (d, 2H, CH2-dtc, J /7.1), 7.41 (m, 1H, H3), 7.71 (m, 11H, H4/ Ph), 7.94 (m, 2H, H5, H6), 8,43 (s, 1H, Ha). 31P NMR (Me2CO-d6): 32.4 (s). [Ni(iBu2dtc)(o-Ph2PC6H4CH /NEt)][ClO4] (6) was obtained in 73% yield. Anal . Calc. for C30ClH38N2O4PS2Ni: C, 53.0; H, 5.6; N, 4.1; S, 9.4. Found: C, 52.8; H, 5.6; N, 4.0; S, 9.2%. LM /140 V 1 cm2 mol1. IR (cm1): 1610 (C /N str), 1525 (C /N str), 998 (C/S str). 1H NMR (Me2CO-d6): 0.90 (m-br, 12H, CH3-dtc), 1.45 (t, 3H, CH3 /NP, J /7.2), 2.25 (m-br, 2H, CH-dtc), 3.53 (s-br, 2H, CH2-dtc), 3.70 (m, 4H,

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CH2 /NP/CH2-dtc), 7.27 (m, 1H, H3), 7.71 (m, 11H, H4/Ph), 7.94 (m, 2H, H5, H6), 8,49 (s, 1H, Ha). 31P NMR (Me2CO-d6): 31.6 (s). [Ni(iBu2dtc)(o -Ph2PC6H4CH /NiPr)][ClO4] (7) was obtained in 69% yield. Anal . Calc. for C31ClH40N2O4PS2Ni: C, 53.7; H, 5.8; N, 4.0; S, 9.2. Found: C, 53.8; H, 5.8; N, 4.2; S, 9.3%. LM /135 V 1 cm2 mol1. IR (cm 1): 1615 (C /N str), 1525 (C /N str), 997 (C /S str). 1H NMR (Me2CO-d6): 0.91 (s-br, 12H, CH3-dtc), 1.26 (d, 6H, CH3 /NP, J /6.3), 2.26 (m, 2H, CH-dtc), 3.51 (s-br, 2H, CH2-dtc), 3.62 (s-br, 2H, CH2dtc), 4.34 (m, 1H, CH /NP), 7.28 (m, 1H, H3), 7.72 (m, 11H, H4/Ph), 7.95 (m, 1H, H5), 8.07 (m, 1H, H6), 8,48 (d, 1H, Ha, J/3.0). 31P NMR (Me2CO-d6): 33.6 (s). [Ni(iBu2dtc)(o -Ph2PC6H4CH /NtBu)][ClO4] (8) was obtained in 75% yield. Anal . Calc. for C32ClH42N2O4PS2Ni: C, 54.3; H, 6.0; N, 4.0; S, 9.1. Found: C, 54.4; H, 6.1; N, 4.0; S, 9.1%. LM /145 V 1 cm2 mol1. IR (cm 1): 1608 (C /N str), 1524 (C /N str), 998 (C /S str). 1H NMR (Me2CO-d6): 0.89 (d, 6H, CH3dtc, J/6.9), 0.93 (d, 6H, CH3-dtc, J /6.3), 1.54 (s, 9H, CH3 /NP), 2.24 (m, 2H, CH-dtc), 3.50 (d, 2H, CH2-dtc, J /7.5), 3.60 (d, 2H, CH2-dtc, J /8.1), 7.27 (m, 1H, H3), 7.75 (m, 11H, H4/Ph), 8.01 (m, 1H, H5), 8.05 (m, 1H, H6), 8,52 (d, 1H, Ha, J/5.1). 31P NMR (Me2COd6): 33.2 (s). 2.3. Preparation of the complexes [Ni(R?xan)(oPh2PC6H4CH /NR)][ClO4] [R?/Et; R /Me (9), Et (10), iPr (11), tBu (12); R? /iPr; R /Me (13), Et (14), iPr (15), tBu (16)] The complexes were obtained by reacting Ni(ClO4)2, the bis(xanthate) precursor [Ni(R?xan)2] and the corresponding iminophosphine in ethanol according to the following general method. To an ethanolic solution (10 ml) of fine pulverized Ni(ClO4)2 (0.062 g, 0.172 mmol) and fine pulverized [Ni(R?xan)2] (0.172 mmol) was added the calculated amount of iminophosphine (0.172 mmol) in ethanol solution previously prepared. After 30 minutes stirring at room temperature the resulting solutions were concentrated under reduced pressure to half volume. The addition of diethyl ether caused precipitation of the new brown complexes, which were filtered off, washed with diethyl ether and air dried. [Ni(Etxan)(o -Ph2PC6H4CH /NMe)][ClO4] (9) was obtained in 69% yield. Anal . Calc. for C23ClH23NO5PS2Ni: C, 47.4; H, 4.0; N, 2.4; S, 11.0. Found: C, 47.6; H, 4.0; N, 2.6; S, 11.1%. LM /109 V 1 cm2 mol 1. IR (cm1): 1616 (C/N str), 1226 (C /O str), 1024 (C/S str). 1H NMR (Me2CO-d6): 1.43 (t, 3H, CH3-xan, J /7.0), 3.64 (s, 3H, CH3 /NP), 4.73 (cd, 2H, CH2-xan, J /7.0), 7.51 (m, 1H, H3), 7.71 (m, 11H, H4/Ph), 8.01 (m, 2H, H5, H6), 8.45 (s, 1H, Ha). 31P NMR (Me2CO-d6): 31.5 (s). [Ni(Etxan)(o -Ph2PC6H4CH /NEt)][ClO4] (10) was obtained in 65% yield. Anal . Calc. for

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C24ClH25NO5PS2Ni: C, 48.3; H, 4.2; N, 2.3; S, 10.7. Found: C, 48.1; H, 4.0; N, 2.2; S, 10.7%. LM /126 V 1 cm2 mol1. IR (cm1): 1623 (C/N str), 1226 (C/O str), 1022 (C/S str). 1H NMR (Me2CO-d6): 1.46 (m, 6H, CH3-xan; CH3 /NP), 3.72 (cd, 2H, CH2 /NP, J/7.2), 4.73 (cd, 2H, CH2-xan, J/6.9), 7.51 (m, 1H, H3), 7.71 (m, 11H, H4/Ph), 8.01 (m, 2H, H5, H6), 8.45 (s, 1H, Ha). 31P NMR (Me2CO-d6): 31.3 (s). [Ni(Etxan)(o-Ph2PC6H4CH /NiPr)][ClO4] (11) was obtained in 73% yield. Anal . Calc. for C25ClH27NO5PS2Ni: C, 49.2; H, 4.5; N, 2.3; S, 10.5. Found: C, 49.3; H, 4.2; N, 2.4; S, 10.3%. LM /99 V 1 cm2 mol1. IR (cm1): 1621 (C/N str), 1270 (C/O str), 1025 (C/S str). 1H NMR (Me2CO-d6): 1.23 (d, 6H, CH3 /NP, J /6.6), 1.40 (t, 3H, CH3-xan, J /7.1), 4.36 (m, 1H, CH /NP), 4.71 (cd, 2H, CH2-xan, J /7.1), 7.31 (m, 1H, H3), 7.73 (m, 11H, H4/Ph), 7.95 (m, 1H, H5), 8.07 (m, 1H, H6), 8.48 (s, 1H, Ha). 31P NMR (Me2COd6): 32.1 (s). [Ni(Etxan)(o-Ph2PC6H4CH /NtBu)][ClO4] (12) was obtained in 72% yield. Anal . Calc. for C26ClH29NO5PS2Ni: C, 50.0; H, 4.7; N, 2.2; S, 10.3. Found: C, 50.0; H, 4.6; N, 2.3; S, 10.4%. LM /105 V 1 cm2 mol1. IR (cm1): 1613 (C/N str), 1236 (C/O str), 996 (C /S str). 1H NMR (Me2CO-d6): 1.40 (t, 3H, CH3xan, J/6.1), 1.51 (s, 9H, CH3 /NP), 4.67 (cd, 2H, CH2xan, J/6.1), 7.31 (m, 1H, H3), 7.73 (m, 11H, H4/Ph), 8.02 (m, 2H, H5, H6), 8.55 (s, 1H, Ha). 31P NMR (Me2CO-d6): 32.2 (s). [Ni(iPrxan)(o-Ph2PC6H4CH /NMe)][ClO4] (13) was obtained in 65% yield. Anal . Calc. for C24ClH25NO5PS2Ni: C, 48.3; H, 4.2; N, 2.3; S, 10.7. Found: C, 48.4; H, 4.2; N, 2.5; S, 10.8%. LM /139 V 1 cm2 mol1. IR (cm1): 1634 (C/N str), 1250 (C/O str), 1020 (C/S str). 1H NMR (Me2CO-d6): 1.44 (d, 6H, CH3-xan, J /6,0), 3.64 (s, 3H, CH3 /NP), 5.60 (m, 1H, CH-xan), 7.51 (m, 1H, H3), 7.76 (m, 11H, H4/Ph), 7.94 (m, 2H, H5, H6), 8.45 (s, 1H, Ha). 31P NMR (Me2COd6): 31.6 (s). [Ni(iPrxan)(o-Ph2PC6H4CH /CH /NEt)][ClO4] (14) was obtained in 72% yield. Anal . Calc. for C25ClH27NO5PS2Ni: C, 49.1; H, 4.5; N, 2.3; S, 10.5. Found: C, 49.3; H, 4.5; N, 2.3; S, 10.5%. LM /104 V 1 cm2 mol1. IR (cm1): 1614 (C/N str), 1280 (C/O str), 1020 (C/S str). 1H NMR (Me2CO-d6): 1.47 (m, 9H, CH3-xa; CH3 /NP), 3.70 (m, 2H, CH2 /NP), 5.55 (m, 1H, CH-xan), 7.37 (m, 1H, H3), 7.80 (m, 11H, H4/Ph), 8.01 (m, 2H, H5, H6), 8.53 (s, 1H, Ha). 31P NMR (Me2CO-d6): 31.3 (s). [Ni(iPrxan)(o-Ph2PC6H4CH /NiPr)][ClO4] (15) was obtained in 71% yield. Anal . Calc. for C26ClH29NO5PS2Ni: C, 50.0; H, 4.7; N, 2.2; S, 10.3. Found: C, 50.1; H, 4.7; N, 2.4; S, 10.5%. LM /95 V 1 cm2 mol1. IR (cm1): 1617 (C/N str), 1276 (C/O str), 1026 (C/S str). 1H NMR (Me2CO-d6): 1.27 (d, 6H, CH3 /NP, J/6.3), 1.45 (d, 6H, CH3-xan, J/6.3), 4.39

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(m, 1H, CH /NP), 5.55 (m, 1H, CH-xan), 7.37 (m, 1H, H3), 7.76 (m, 11H, H4/Ph), 7.99 (m, 1H, H5), 8.11 (m, 1H, H6), 8.53 (s, 1H, Ha). 31P NMR (Me2CO-d6): 32.8 (s). [Ni(iPrxan)(o -Ph2PC6H4CH /NtBu)][ClO4] (16) was obtained in 72% yield. Anal . Calc. for C27ClH31NO5PS2Ni: C, 50.8; H, 4.9; N, 2.2; S, 10.0. Found: C, 50.9; H, 4.9; N, 2.0; S, 10.1%. LM /102 V 1 cm2 mol1. IR (cm 1): 1610 (C /N str), 1268 (C /O str), 1028 (C /S str). 1H NMR (Me2CO-d6): 1.45 (d, 6H, CH3-xan, J /6.0), 1.55 (s, 9H, CH3 /NP), 5.56 (m, 1H, CH-xan), 7.35 (m, 1H, H3), 7.71 (m, 11H, H4/Ph), 8.04 (m, 1H, H5), 8.12 (m, 1H, H6), 8.53 (d, 1H, Ha, J /4.8). 31 P NMR (Me2CO-d6): 32.2 (s). 2.4. Crystal structure determination of [Ni(iPr2dtc)(o Ph2PC6H4CH /NMe)][ClO4] (1), [Ni(iBu2dtc)(o Ph2PC6H4CH /NMe)][ClO4] (5) and [Ni(iPrxan)(o Ph2PC6H4CH /NMe)][ClO4] (13) Crystals of (1) (0.55 /0.48 /0.20 mm3), (5) (0.50 / 0.25 /0.20 mm3) and (13) (0.50 /0.30 /0.20 mm3) suitable for X-ray diffraction studies were grown from dichloromethane/hexane, mounted on glass fibre and transferred to an Enraf-Nonius CAD4 diffractometer. The crystallographic data are summarised in Table 1. ˚ ); the scan Mo Ka radiation was used (l/0.71073 A method was v /2u corresponding to umax /30.4 (in 1 and 5) and umax /28.5 (in 13). Empirical c-scan mode absorption correction was made. The structures were solved by Patterson method (for 1) and direct methods (for 5 and 13) [52] and refined anisotropically on F2 [52]. Hydrogen atoms were included using a riding model.

3. Results and discussion 3.1. Dithiocarbamate complexes The reaction under continued ethanolic reflux (5 h) between Ni(ClO4)2, [Ni(R2?dtc)2] (R? /iPr or iBu) and the corresponding iminophosphine, yielded the new square-planar cationic complexes shown in Scheme 1. The nickel derivatives 1 /8 are air-stable, diamagnetic red solids that behave as 1:1 electrolytes [53]. The ionic nature of the perchlorate anion is confirmed by two strong bands at 1085 and 622 cm 1 ([n3(ClO4)] and [n4(ClO4)], respectively) observed in IR spectra [54]. Characteristic dithiocarbamate vibrations were also found in the 1525/1516 cm 1 [n (CN)] and 999 /993 cm 1 [n(CS)] regions. The presence of only one band in this later region supports the bidentate coordination of the dithio ligand [55], while the thioureide band near 1520 cm 1 indicates considerable double-bond character in the C /N bond. This behaviour may be attributed to the electron-releasing ability of the amines, which

forces high electron density towards the sulfur atoms, via the p system, thus producing the mentioned doublebond character and shifting the vibration to higher energy [n (C /N) /1690 /1640 cm 1; n (CN) /1350/ 1250 cm 1] [56]. A medium band attributed to the C / N stretching vibration of the iminophosphine is also observed in the 1620 /1608 cm1 region, shifted to lower frequencies than in the free ligands [44]. The 1H NMR spectra of the new complexes show the expected aromatic signals of the neutral R /N S P ligands. A typical iminic singlet or doublet resonance, depending on the strength of the coupling to the phosphorus atom [51], is found in the 8.43 /8.52 ppm region. In agreement with our previously reported results [10,46], this coupling increases as do the donating properties of the R group (Me B/EtB/iPrB/tBu), and appreciable HP coupling is also shown by the H(3) and H(6) protons [44]. The characteristic resonances of the R? (iPr or iBu) groups found in the aliphatic region also confirm the proposed formulae of the dithiocarbamate derivatives. In both series two sets of broad signals, with a variable rate of resolution depending on the complex, were observed at room temperature, as expected for two nonequivalent R? groups. Their 31P NMR spectra consist of singlets with chemical shifts in the range observed for related compounds [10,11].

3.2. Xanthate complexes In ethanol, Ni(ClO4)2, [Ni(R?xan)2] (R?/iPr or Et) and the corresponding iminophosphine react under mild conditions to give the corresponding cationic xanthate complexes (9/16) shown in Scheme 1. Measurements of their molar conductivity in acetone solutions indicate that xanthate complexes behave as 1:1 electrolytes [53]. Its IR spectra show the characteristic absorptions of perchlorate anion at 1080 and 624 cm 1, together with a medium band around 1620 cm 1 attributed to the C /N vibration of coordinated iminophosphines. The new complexes also exhibit bands in the 1280 /996 cm 1 region which are related to the vibrations of the S2COR group [57,58]. Those at approximately 1270 cm 1 are attributable to the stretching vibrations of the C /O /C group, while the bands around 1020 cm 1 belong to the n (C/S) vibration. Regarding to the 1H and 31P NMR spectra of new xanthate derivatives, they are quite similar to those shown by analogous dithiocarbamates. Well-defined aromatic (iminophosphine fragment) and aliphatic (xanthate fragment) regions appear in the former, and the expected singlets owing to coordinated iminophosphine are observed in the latter.

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Table 1 Crystal data and structure refinement details for compounds (1), (5) and (13) 1

5

13

Empirical formula

C27H32ClN2NiO4PS2 ×/12/CH2Cl2

C29H36ClN2Ni4PS2

C24H25ClNNiO5PS2

Formula weight Temperature (K) Absorption coefficient (mm1) Crystal system Space group ˚) a (A ˚) b (A ˚) c (A a (8) b (8) g (8) ˚ 3) V (A Z Dcalc (Mg m 3) F (0 0 0) Tmax, Tmin Reflections collected Independent reflections Observed reflections Parameters Refinement method R1 a wR2 b Sc ˚ 3) Maximum, Minimum Dr (e A

680.26 293(2) 0.943 triclinic P/1¯ 11.593(8) 13.210(9) 13.354(3) 109.80(4) 112.66(4) 98.90(6) 1677.2 (8) 2 1.347 706 0.840, 0.666 10 518 10 071 [Rint /0.0358] 4692 370 full-matrix least-squares on F2 0.0710 0.2006 0.952 1.072, /0.745

665.85 293(2) 0.907 orthorhombic Pbca 19.111(3) 13.839(2) 24.161(2) 90 90 90 6390.0(15) 8 1.384 2784 0.935, 0.809 10 690 9652 [Rint /0.0555] 4086 361 full-matrix least-squares on F2 0.0493 0.1257 0.906 0.690, /0.421

596.70 293(2) 1.068 monoclinic Cc 23.448(3) 8.946(2) 14.170(2) 90 114.262(11) 90 2709.8(8) 4 1.463 1332 0.862, 0.813 3545 3545 [Rint /0.0000] 1907 316 full-matrix least-squares on F2 0.0512 0.1266 0.904 0.436, /0.391

a

R1 /ajjFoj/jFcjj/ajFoj for reflections with I /2s (I ). wR2 /{a[w (Fo2 /Fc2)2]/a[w (Fo2)2]}1/2 for all reflections; w 1 /s2(F2)/(aP )2/bP , were P/(2Fc2/Fo2)/3 and a and b are constants set by the program. c S /{a[w (Fo2 /Fc2)2]/(n/p )}1/2; n is the number of reflections and p the total number of parameters refined. b

3.3. X-ray structures of (1), (5) and (13)

Scheme 1.

Complexes 1 (Fig. 1), 5 (Fig. 2), and 13 (Fig. 3), show a distorted square planar coordination. This fact is apparent from deviations of atoms from least square plane NiS2PN (Table 2). Complexes 1 and 13 exhibit a tetrahedral distortion while complex 5 displays a square pyramidal one. The Cambridge Structural Database (CSD) [59] v. 5.23 was searched for all the Ni(II) structures containing the chelated fragment Ni(S2CX), Ni being a tetracoordinated atom. The number of hits obtained were 75 for X /N, 27 for X /O, 18 for X /C and 6 for X /S. In the dithiocarbamate and xanthate complexes the S /Ni / S chelating ring exhibits a narrow range of 76.6 /81.28, and the values shown by our complexes are included within it (Table 3). The dithiocarbamate complexes present a mean value for the S /C distances of 1.735 ˚ , while in the xanthate complexes this value is 1.696 A ˚. A The distances presented by the complexes reported in this paper are very similar to these (Table 3). Also the

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Table 2 Deviations of atoms from the least square plane NiS2PN Complex

1

5

13

Ni(1) S(1) S(2) P(1) N(1) rms

0.0602(13) /0.1158(12) 0.0907(16) /0.1126(11) 0.0774(15) 0.0937

/0.0597(8) /0.0182(8) 0.0454(10) /0.0161(7) 0.0486(10) 0.0414

0.0260(22) /0.1806(23) 0.1618(30) /0.1707(22) 0.1635(30) 0.1519

Table 3 ˚ ), angles (8) and torsion angles (8) Selected bond lengths (A

i



Fig. 1. Structure of the [Ni( Pr2dtc)(o -Ph2PC6H4CH /NMe)] cation in the single crystal structure of 1. All hydrogen atoms and the dichloromethane of crystallization have been omitted for clarity.

˚ )/angle/torBond length (A sion angle (8)

1

5

13

Ni(1)/N(1) Ni(1)/P(1) Ni(1)/S(1) Ni(1)/S(2) S(1)/C(21) S(2)/C(21) N(2)/C(21) N(2)/C(22) N(2)/C(25) a C(21)/O(1)

1.937(4) 2.1495(13) 2.2333(14) 2.1669(15) 1.726(6) 1.721(6) 1.291(7) 1.497(7) 1.505(7)

1.910(3) 2.1546(10) 2.2575(10) 2.1554(10) 1.726(3) 1.725(3) 1.301(4) 1.485(4) 1.479(4)

1.950(8) 2.162(2) 2.226(3) 2.159(3) 1.653(9) 1.711(9)

N(1)/Ni(1)/P(1) N(1)/Ni(1)/S(1) N(1)/Ni(1)/S(2) P(1) /Ni(1)/S(1) P(1) /Ni(1)/S(2) S(1)/Ni(1)/S(2) C(21)/S(1)/Ni(1) C(21)/S(2)/Ni(1) S(1)/C(21)/S(2) Fig. 2. Structure of the [Ni(iBu2dtc)(o -Ph2PC6H4CH/NMe)] cation in the single crystal structure of 5. For clarity, all hydrogen atoms have been omitted.

Ni(1)/P(1)/C(7)/C(2) P(1) /C(7) /C(2)/C(1) C(7) /C(2) /C(1)/N(1) C(2) /C(1) /N(1)/Ni(1) C(1) /N(1)/Ni(1)/P(1) N(1)/Ni(1)/P(1) /C(7) a

Fig. 3. Structure of the [Ni(iPrxan)(o -Ph2PC6H4CH /NMe)] cation in the single crystal structure of 13. For clarity, all hydrogen atoms have been omitted.

1.305(12) 92.36(13) 98.13(13) 175.69(13) 166.13(6) 91.84(5) 77.88(6) 86.44(19) 88.70(19) 106.7(3) 30.2(4) /1.7(7) /17.5(9) /1.6(9) 26.5(5) /35.2(2)

88.85(9) 97.63(9) 173.01(9) 173.02(4) 94.53(4) 78.75(4) 84.49(12) 87.74(11) 108.52(19)

88.8(2) 96.0(2) 170.8(3) 168.70(11) 96.97(10) 79.66(9) 82.9(3) 83.7(3) 113.2(5)

43.8(3) 38.7(7) /1.8(4) 4.7(11) /23.2(5) /30.0(15) /9.9(5) /3.5(15) 46.7(3) 41.5(9) /54.44(15) /50.2(4)

C(26) in 5.

values of the S /C /S angle in complexes 1, 5 and 13 are close to those found in the CSD for dithiocarbamate and xanthate (range of 105.4 /118.28) complexes. The ˚ C /X mean distance is 1.355, 1.300, 1.431 and 1.635 A when X /N, O, C and S, respectively; the corresponding values for structures in this paper are again similar, particularly in the xanthate case (Table 3). Most of the NiS2PN fragments found in the CSD are planar (dihedral angle under 58, Fig. 4) meanwhile the values shown for complexes 1, 5 and 13 are 9.1(2), 10.6(2) and 10.5(6)8, respectively. In dithiocarbamate structures, 62 correspond to complexes with the same donor atom trans to both sulfur atoms, the two Ni /S distances being similar. Thirteen structures show different donor atoms trans to sulfur as the ones reported in this paper. In these cases

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39

Fig. 4. Dihedral angle (8) between the planes defined by S/Ni/S and S /C/S.

the Ni /S distances are clearly unequal, with a range of ˚ (mean value of 0.034 A ˚ ). differences of 0.011 /0.060 A As shown in Table 3, the differences found in complexes 1 and 5 are over this range. In xanthate structures only three square planar having different donor atoms trans to sulfur were found in the CSD, and the differences in Ni /S distances range from ˚ . Complex 13 also shows a stronger 0.031 to 0.052 A contrast in the mentioned distances than the other structures (Table 3). With regard to the iminophophine chelate ring, the three crystal structures described in this work show a distorted screw-boat conformation [60] as can be ascertained from the six torsion angles (Table 3).

4. Supplementary material Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC no. 199028 (1), 199026 (5) 199027 (13). Copies of this information may be obtained from The Director, CCDC, 12 Union Road, Cambridge, CB 1EZ, UK (fax: /44-1233-336-033; e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk).

Acknowledgements Financial support of this work by Centro de Coordinacio´n de la Investigacio´n de la Regio´n de Murcia (project PI-61/00813/FS/01) and Direccio´n General de Investigacio´n (project BQU2001-0979-C02-02) is gratefully acknowledged.

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