FULL PAPER

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate 2Donor2Acceptor Inter-Ligand Interactions as Evident from Experimental and

TD-DFT Computational Analysis

Sandip Dey,[a] Vimal K. Jain,*[a] Axel Knoedler,[b] Wolfgang Kaim,[b] and Stanislav Zalis[c]

Keywords: Platinum / Selenium / NMR spectroscopy / Density functional calculations

Several platinum(II) complexes of 2-(dimethylamino)ethane-selenolate with the formulae, [PtCl(SeCH2CH2NMe2)(PR3)](1), [PtPh(SeCH2CH2NMe2)(PnBu3)] (2), [Pt2Ph2(Cl)(SeCH2-CH2NMe2)(PnBu3)2] (3), [Pt2Cl3(SeCH2CH2NMe2)(PR3)2] (4),[Pt(SeCH2CH2NMe2)2(P−P)] (5), [Pt2(SeCH2CH2NMe2)2-(P−P)2]++ (6), and [Pt(SeCH2CH2NMe2)(PPh3)]n[PF6]n (7) havebeen synthesized and characterized by elemental analysis,UV/Vis and NMR (1H, 31P, 77Se, 195Pt) spectroscopy. The ste-reochemistry of these complexes (1−7) has been deduced

Introduction

Platinum group metal chalcogenolates have attractedconsiderable attention during the last 15 years or so due totheir wide structural diversity[1] and relevance incatalysis,[225] and as a result of being precursors for thesynthesis of metal chalcogenides[628] for electronic de-vices.[9] The area of metal chalcogenolates has been domi-nated by molecules containing the M2SR linkage.[1] Inmost cases these molecules have been isolated as non-volat-ile, insoluble (or sparingly soluble) polymers, thus makingthem inconvenient as precursors for the synthesis of metalchalcogenides. Although several strategies have been ad-opted to suppress polymerisation, the use of hybrid ligandscontaining both soft chalcogen and hard N donor atomshas been quite successful, such as pyridine-2-thiolate[10] oraliphatic mercapto amines.[11214] The continued current in-terest in selenium containing inorganic materials[15] and inpursuance of our program on the design and developmentof molecular precursors, we explored some chemistry of in-ternally functionalized selenolates, viz. pySe[16] andMe2NCH2CH2Se2.[8] Herein we now report the synthesis,spectroscopy, electrochemistry, structures, and DT-DFTcalculations of platinum complexes derived from the latterligand.

[a] Novel Materials & Structural Chemistry Division, BhabhaAtomic Research Center (B.A.R.C.),Mumbai-400085, India

[b] Institut für Anorganische Chemie, Universität Stuttgart,Pfaffenwaldring 55, 70569 Stuttgart, Germany

[c] J. Heyrovsky Institute of Physical Chemistry, Academy ofSciences of the Czech Republic,Dolejskova 3, 18223 Prague, Czech Republic

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from NMR spectroscopic data. A weak absorption in the UV/Vis spectrum of 1 has been assigned to a ligand (Se)-to-li-gand (PR3) charge transfer (LLCT), supported by TD-DFTcalculations. The structures of [PtCl(SeCH2CH2NMe2)(PPh3)]and [Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)2] have been estab-lished by single crystal X-ray diffraction analysis. Each plat-inum atom in the latter is coordinated to four different li-gands and Me2NCH2CH2Se behaves as µ2-bridging and isalso simultaneously chelated to one of the platinum atoms.

Results and Discussion

Synthesis and Spectroscopy

Treatment of [Pt2Cl2(µ-Cl)2(PR3)2] with two equivalentsof NaSeCH2CH2NMe2, prepared by the reductive cleavageof the Se2Se bond in (Me2NCH2CH2Se)2 with sodiumborohydride, afforded dimethylaminoethylselenolate com-plexes of the type [PtCl(η2-SeCH2CH2NMe2)(PR3)] (1)[PR3 5 PEt3 (1a), PnPr3 (1b), PnBu3 (1c), PMe2Ph (1d), orPMePh2 (1e)] (Scheme 1). The analogous triphenylphos-phane complex, [PtCl(SeCH2CH2NMe2)(PPh3)] (1f) can bereadily prepared by the reaction of PtCl2(PPh3)2 with oneequivalent of NaSeCH2CH2NMe2.

The 1H NMR spectra of 1 showed the expected integra-tion and peak multiplicities. The selenolate proton reson-ances, i.e., SeCH2, NMe2, NCH2 were flanked with plat-inum satellites with 3J(Pt-H) being 24227, 14218, and36242 Hz, respectively. The observed magnitudes of 3J(Pt-H) can be compared with platinum complexes containingneutral RSeCH2CH2NMe2 ligands.[17,18] The 31P NMRspectra of 1 exhibited single resonances flanked with 195Ptsatellites. The magnitude of 1J(Pt-P), (343423662 Hz) in-dicates that the phosphane ligand is trans to the nitrogenatom of the chelated [SeCH2CH2NMe2]2 group.[16,19,20]

The 195Pt{1H} NMR spectra of these complexes displayeda doublet due to coupling with a single 31P nucleus. Thedoublet appeared in a narrow range of δ 5 24266 to24308. As is evident from Table 1, there is shielding of the195Pt resonances as the phosphane ligand is changed fromPMe2Ph to PMePh2 through PPh3. A similar trend is evid-ent for 77Se and 31P chemical shifts which, however, showeddeshielding. The 77Se NMR resonances for 1 appeared as atriplet owing to the coupling with the 195Pt nucleus. Theresonance for 1f, however, appeared as a broad signal and

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. ZalisFULL PAPER

Scheme 1

Table 1. 31P{1H}, 77Se{1H} and 195Pt{1H} NMR spectroscopic data (δ in ppm, J in Hz) for dimethylaminoethaneselenolate complexesof platinum(II)

Complex 195Pt{1H} 77Se{1H} 31P{1H}δ 1J(195Pt-31P) δ 1J(195Pt-77Se) 1J(195Pt-31P)

[PtCl(SeCH2CH2NMe2)(PEt3)] (1a) 24308(d) 3407 140.1 147 4.5 3434[PtCl(SeCH2CH2NMe2)(PnPr3)] (1b) 24283(d) 3400 138.5 129 24.7 3415[PtCl(SeCH2CH2NMe2)(PnBu3)] (1c) 24284(d) 3394 137.8 138 24.0 3416[PtCl(SeCH2CH2NMe2)(PMe2Ph)] (1d) 24266 3439 164(d) 123 221.8 3454

2J(Se-P) 5 24[PtCl(SeCH2CH2NMe2)(PMePh2)] (1e) 24293(d) 3555 190.6(d) 104 26.8 3571

2J(Se-P) 5 30[PtCl(SeCH2CH2NMe2)(PPh3)] (1f) 24305 3658 218.6(br) 2 7.4 3662[Pt(Ph)(SeCH2CH2NMe2)(PnBu3)] (2) 24245 3845 2 2 23.1 3834[Pt2(Ph)2Cl(SeCH2CH2NMe2)(PnBu3)2] (3) 24295 3776 2 2 21.0 3783

24073 3761 2 2 24.2 3829[Pt2Cl3(SeCH2CH2NMe2)(PEt3)2] (4a) 2 2 2 2 5.1 3203

3.5 3355[Pt2Cl3(SeCH2CH2NMe2)(PMe2Ph)2] (4b) 2 2 2 2 221.0 3581

222.4 3359[Pt(SeCH2CH2NMe2)2(dppm)] (5a) 24251(t) 2429 78.0 294 252.9 2412[Pt(SeCH2CH2NMe2)2(dppe)] (5b) 24958(t) 2884 29.3 264 46.7 2859

J(Se-P) 5 11[Pt(SeCH2CH2NMe2)2(dppp)] (5c) 24913(t) 2783 53.5 279 21.8 2849[Pt2(SeCH2CH2NMe2)2(dppm)2][BPh4]2 (6a) 24065(d,d) 2738 255.0 472 239.3(d) 2286

J(P-P) 5 65244.8(d) 2745

J(P-P) 5 65[Pt2(SeCH2CH2NMe2)2(dppe)2][BPh4]2 (6b) 24680(d,d) 2852 276.6 385 47.3 2822

36.9 3158[Pt2(SeCH2CH2NMe2)2(dppp)2][BPh4]2 (6c) 24534(d,d) 2706 309.8 316 21.8(d) 2676

J(P-P) 5 31213.7(d) 3048

J(P-P) 5 31[Pt(SeCH2CH2NMe2)(PPh3)]n[PF6]n (7) 24071(d) 3323 49.8 2 5.3 3330

(major) (major)23854 3337 17.9 2 3.1 3353(minor) (minor)

hence platinum coupling could not be resolved. The magni-tude of 1J(195Pt-77Se) is comparable to that of the valuesreported for mononuclear platinum selenolates.[16,21,22] Theappearance of a single resonance in 77Se NMR spectra sug-gests that the phosphane is cis to the selenium atom as the2J(77Se-31P)cis couplings are usually small (. 10 Hz).[22,23]

However, such couplings are slightly larger for 1d and 1e(24 and 30 Hz, respectively) and could thus be resolved inthe 77Se NMR spectra.

Eur. J. Inorg. Chem. 2001, 2965229732966

Reaction of [Pt2Ph2(µ-Cl)2(PnBu3)2] with two equivalentsof NaSeCH2CH2NMe2, affords a mixture of products,[PtPh(SeCH2CH2NMe2)(PnBu3)] (2) and [Pt2Ph2(Cl)-(SeCH2CH2NMe2)(PnBu3)2] (3). Compound 3 appears tobe an intermediate product in the reaction, which on fur-ther reaction with NaSeCH2CH2NMe2 yields 2. The calcu-lated values of C, H, and N for the two are not significantlydifferent, hampering an unambiguous identification of 2and 3. The two can, however, be separated by repeated

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate FULL PAPERrecrystallization. The NMR spectroscopic data for 2 can becompared with 1 as described above. Although the magni-tude of 1J(Pt-P) is greater (418 Hz) than that of 1c, it is incompliance with ArPtII complexes in which the phosphaneis trans to nitrogen, e.g. [Pt2R2(µ-N2N)2(PR3)2] (R 5 Meor aryl, N2N 5 pyrazole).[24] The 31P and 195Pt NMRspectra of 3 exhibited two separate resonances attributableto ‘‘PtPhCl(PnBu3)’’ and ‘‘PtPh(Se2N)(PnBu3)’’ fragments.The magnitude of 1J(Pt-P) suggests that the phosphane li-gand is trans to Cl in the former and trans to N in thelatter fragment.[25] This stereochemistry is unambiguouslyestablished by X-ray structural analysis (see later).

The chloro analogue of 3, [Pt2Cl3(SeCH2CH2NMe2)-(PR3)2] (4) [PR3 5 PEt3 (4a), PMe2Ph (4b)] can be obtainedreadily by treatment of [Pt2Cl2(µ-Cl)2(PR3)2] with 1 in 1:2molar ratio. The 31P NMR spectra of a freshly preparedsolution exhibited two singlets each flanked with platinumsatellites. The signal of lower frequency may be attributedto the phosphane attached to the metal atom containing thechelating Se2N ligand. The magnitude of 1J(Pt-P) couplingassociated with this signal is reduced (ø 90 Hz) relative tothat of the corresponding mononuclear complex. The se-cond resonance at higher frequency may be assigned to thephosphane coordinated to the metal atom containing twochlorines and the selenium atom. Similar NMR spectro-scopic data have been reported for [Pt2Cl3(µ-Sepy)(PR3)2].[16] Although the spectra of 4b did not changewith time, 4a slowly isomerised in solution to establish anequilibrium with another species 4a9. Thus, a CDCl3 solu-tion of 4a, after 2 h, displayed four resonances (δ 5 5.1,3.4, 3.1, 2.4), each showing platinum satellites, the intensityof which changed with time until an equilibrium is reachedafter two days. No change occurs after a week. It is likelythat the ‘‘PtCl2(PR3)’’ fragment of 4a isomerises from cis-‘‘PtCl2’’ to the trans-‘‘PtCl2’’ configuration, a structure ob-served for palladium complex, [Pd2Cl3(Sepy)(PR3)2].[16]

Thus, the second set of resonances (δ 5 3.1, 1J(Pt-P) 53504 Hz; δ 5 2.4, 1J(Pt-P) 3218 Hz) may be attributed to4a9 in which ‘‘PtCl2’’ has a trans configuration.

Reaction of PtCl2(P2P) with two equivalents of Na-SeCH2CH2NMe2 yields, mononuclear [Pt(SeCH2CH2-NMe2)2(P2P)] (5) [P2P 5 dppm (5a), dppe (5b), dppp(5c)] as yellow crystalline solids. The NMR spectra (31P,77Se, 195Pt) (Table 1) are similar to several organochalcogen-olates [Pt(ER)2(P2P)] reported by us.[16,21,23,26] These com-plexes have been assigned a cis configuration. Unlike 1, theMe2NCH2CH2Se in 5 acts in monodentate fashion i.e.,binding through selenium only. This mode of binding canreadily be identified from 1H NMR spectra. The NMe2 pro-tons in 5 appear at δ ø 2.0 with the absence of 195Pt coup-lings whereas in 1 they appear at δ ø 2.7 with 195Pt coup-lings. When the reaction is carried out in 1:1 stoichiometryin the presence of NaBPh4 (Scheme 1), a new series of bi-nuclear complexes, [Pt2(SeCH2CH2NMe2)2(P2P)2]-[BPh4]2 (6) [P2P 5 dppm (6a), dppe (6b), dppp (6c)] couldbe isolated. Complex 6 can also be prepared, as pale yellowfibrous crystals, by the reaction of 5 with[Pt(solvent)2(P2P)][BPh4]2. The 77Se NMR spectra exhib-

Eur. J. Inorg. Chem. 2001, 296522973 2967

ited single resonances suggesting that two bridging selenol-ate ligands are equivalent. The signals are deshielded withincreased 1J(Pt-Se) in comparison to the corresponding res-onance for 5. However the 31P{1H} (Figure 1) and195Pt{1H} (Figure 2) spectra showed two sets of resonances,and doublet of doublets, respectively; a pattern indicativeof non-equivalence of phosphorus nuclei of the P2P ligand.The spectra of 6a and 6c further showed phosphorus coup-ling, thus each signal appeared as a doublet (Figure 1). TheX-ray structures of several mononuclear compounds[M(ER)2(P2P)] (E 5 S or Se, M 5 Pd or Pt) have beenreported.[13,23] The structures reveal that in thiolates the twoM2S distances are nearly identical,[13,23] but for selenolatesthe two M2Se distances differ markedly[21,23,26] (e.g. Pt-(Sepy)2(dppe) Pt2Se 5 2.498, 2.433 A).[26] Similar differ-ences in Pt2E distances in binuclear complexes [Pt2X2(µ-ER)2(PR3)2] (ER 5 SeEt, SeCH2Ph)[19,27] are reported. Theselenolato ligands form an asymmetric Pt2Se2 ring[19,27]

whereas the thiolates give a symmetrical Pt2S2 fragment.[28]

On chelation of M(ER)2(P2P) with another metal centre,binuclear complexes such as [M2(ER)2(P2P)2]11 [11,13]

(M 5 Pd or Pt) are formed when E 5 S a symmetricalM2E2 bridge forms as shown by the X-ray structure of[M2(µ-SC5H9NMe)2(dppe)2][BPh4]2[13] where M2S dis-tances are nearly equivalent. Accordingly all phosphorusnuclei become chemically equivalent and display only one31P NMR resonance.[11,13,21,23] In case of binuclear cationicselenolate complexes, as observed for [Pt2Cl2(µ-SeR)2(PR3)2],[19,27] the M2Se bridge may be asymmetric (I)due to different M2Se distances consequently making the

Figure 1. 31P{1H} NMR spectrum of [Pt2(SeCH2CH2N-Me2)2(dppp)2][BPh4]2 (6c) in CDCl3

Figure 2. 195Pt{1H} NMR spectrum of [Pt2(SeCH2CH2N-Me2)2(dppp)2][BPh4]2 (6c) in CDCl3

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. ZalisFULL PAPERphosphorus nuclei magnetically different. The two in-equivalent phosphorus nuclei are coupled together to givedoublets in the 31P NMR spectra of 6a and 6c. The magni-tude of 2J(P-P) couplings are in accordance with the litera-ture values.[29] The absence of 2J(P-P) in 6b might be dueto different signs of 3J(P-P), 2J(P-P) coupling operatingthrough P2C2C2P and P2Pt2P routes, respectively.[30]

The intensity of two resonances (Figure 1) is significantlydifferent. This can be attributed to the difference in themagnitude of T1 of two sites, as reported earlier.[30]

Treatment of 1f with AgPF6 affords [Pt(SeCH2-CH2NMe2)(PPh3)]n[PF6]n (7). The 31P, 77Se, and 195Pt spec-tra exhibited two separate resonances in approximately a2:1 ratio. The 1J(Pt-P) in 31P and 195Pt NMR spectra arecomparable, indicating that both the species have similarconfiguration. Recently we have reported the structure of[{Pd(SeCH2CH2NMe2)Cl}n] which is a trimer (n 5 3) inwhich the chelated Se2N ligand bridges another palladiumatom through Se.[8] The observed two signals may be inter-preted for dimeric (II) and trimeric (III) forms in whicheach platinum is bonded to two Se atoms, one N and onePPh3 in nearly similar environments.

Absorption Spectra and ElectrochemistryThe absorption spectra of the complexes [PtCl-

(SeCH2CH2NMe2)(PR3)] in CH2Cl2 solution are charac-terised by a very weak band at 4002430 nm (Figure 3,Table 2). The band is hypsochromically shifted on replacingthe phenyl substituents on the PR3 group by donating alkylgroups. As will be confirmed by TD-DFT calculations (seebelow) this absorption is due to a ligand (Se)-to-ligand(PR3) charge transfer (LLCT) transition. The geometry ob-viously allows only rather poor orbital overlap, resulting invery weak yet well discernible bands (Figure 3). A similarband with ε 5 80 mol21·dm3·cm21 at 514 nm has been re-ported for the palladium analogue [PdCl(SeCH2CH2N-Me2)(PPh3)].[8] Allowed transitions occur only at higher en-ergies with λmax , 300 nm, in agreement with theory. Thedinuclear species [Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)2]does not allow a detectable Se-to-PnBu3 transition in thevisible or near UV region(Table 2).

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Figure 3. UV/Vis spectrum of [PtCl(SeCH2CH2NMe2)(PPh3)] (1f)in CH2Cl2

Table 2. UV/Vis absorption data of some platinum complexes re-corded in CH2Cl2

λmax (nm)Complex

[PtCl(SeCH2CH2NMe2)(PEt3)] (1a) 284, 405[PtCl(SeCH2CH2NMe2)(PMe2Ph)] (1d) 283, 405[PtCl(SeCH2CH2NMe2)(PMePh2)] (1e) 266 sh, 273 sh, 293 sh, 418[PtCl(SeCH2CH2NMe2)(PPh3)] (1f) 268 sh, 275 sh, 300 sh, 430

According to cyclic voltammetry in CH2Cl2/0.1mol·dm23 Bu4NPF6 the PtII complexes 1 and 3 are oxidisedirreversibly. The peak potentials for 1 show little variation(0.8320.89 V vs. ferrocene/ferrocenium), confirming that itis primarily the selenolate part (HOMO) which loses anelectron and not the PR3

2 ligating platinum centre. Thebridging selenolate in compound 3 is hard to oxidise as il-lustrated by the anodic peak potential of 1.13 V for irrevers-ible oxidation.

Electronic Structure Calculations on 1f

The ADF/BP calculated one-electron scheme of the[PtCl(SeCH2CH2NMe2)(PPh3)] complex is schematicallygiven in Figure 4. The composition of important molecular

Figure 4. ADF/BP calculated qualitative MO scheme of 1f

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate FULL PAPER

Table 3. ADF/BP calculated one-electron energies and percentagecomposition of selected highest occupied and lowest unoccupiedmolecular orbitals of [PtCl(SeCH2CH2NMe2)(PPh3)] (1f) expressedin terms of composing fragments

E [eV] PrevailingMO Pt PPh3 Se Cl NCharacter

Unoccupied 292a 21.87 PPh3 3 (d) 90 2 291a 22.06 PPh3 2 (d) 9490a 22.11 dPt 1 PPh3 1 Se 13 (d) 63 9 3 3Occupied89a 24.05 Se 1 dPt 29 (d) 2 58 10 288a 25.37 dPt 11 (s); 57(d) 1 7 23 287a 25.45 dPt 1 Cl 5 (s); 42(d) 3 4386a 25.70 Cl 1 Se 1 dPt 1(p); 19 (d) 25 5085a 26.16 Cl 1 Se 3(p); 4 (d) 4 46 3484a 26.25 dPt 78 (d) 10 3 283a 26.60 PPh3 6 (d) 72 10 3 2

orbitals is summarised in Table 3. The highest molecularorbital 89a is formed mainly from a Se p orbital with someadditional metal contribution. Pt 5d and Cl 3p orbitals con-tribute significantly to the next lower lying occupied MOs.The set of the lowest lying unoccupied molecular orbitals,90a, 91a, and 92a, is to a large extent located on the PPh3

fragment. The composition of the occupied MOs of the[PtCl(SeCH2CH2NMe2)(PH3)] model (Table 4) correspondsto those of the PPh3 complex. The lowest lying molecularorbital is delocalised; PH3 localised unoccupied MOs lie ata rather high energy. The excitation energies listed inTable 5 were calculated for the [PtCl(SeCH2CH2N-

Table 4. ADF/BP calculated one-electron energies and percentagecomposition of selected highest occupied and lowest unoccupiedmolecular orbitals of model complex [PtCl(SeCH2CH2NMe2)(PH3)] expressed in terms of composing fragments

MO E [eV] Prevailing Pt PH3 Cl SeCharacter

Unoccupied 249a 20.77 PH3 17(d) 68 1048a 20.83 PH3 7(d) 47 3047a LUMO 22.23 delocalized 28 (d) 20 11 28Occupied47a HOMO 24.30 Se 1 dPt 28 (d) 2 9 6246a 25.58 dPt 18 (s); 71(d) 2 4 745a 25.71 dPt 1 Cl 2 (s); 27(d) 2 61 544a 25.85 Cl 1 Se 1 dPt 1(p); 16 (d) 2 57 2443a 26.10 Se 1 Cl 7 (d) 1 36 5242a 26.40 dPt 85 (d) 11 2 2

Table 5. Selected calculated lowest TD DFT singlet excitation energies (eV) for [PtCl(SeCH2CH2NMe2)(PH3)]

ADF/BP G98/B3LYPState Main character Transition energy [eV] Oscillator strength Transition energy [eV] Oscillator strength

1A1 HOMO R LUMO 2.24 0.0004 2.53 0.00061A1 HOMO R LUMO 11 3.55 0.001 3.71 0.0021A1 HOMO 2 1 R LUMO 3.58 0.002 3.95 0.0051A1 HOMO R LUMO 1 2 3.67 0.010 4.08 0.0121A1 HOMO 24 R LUMO 4.71 0.082 5.09 0.190

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Me2)(PH3)] model with different DFT program configura-tions. In agreement with the experiments, there is one veryweak transition (HOMORLUMO, oscillator strength, 1023) at low energy, set apart by more than 1 eV fromthe following singlet transitions (Table 5). The calculatedexcitation energies of about 2.4 eV (corresponding to ca.500 nm) are in broad agreement with the 4002430 nm ob-served for various substituted derivatives (Table 2). Thisconspicuous absorption must be formulated mainly as li-gand (Se)-to-ligand (PR3) charge transfer, as has been pro-posed previously for palladium analogues.[8]

Crystal Structures of 1f and 3

An ORTEP plot of 1f with the crystallographic num-bering scheme is shown in Figure 5, and Table 6summarises essential data. The geometry around the pla-tinum atom is essentially square planar with the atoms P,Cl, Se, and N defining the coordination sphere. The phos-phane ligand is trans to the nitrogen atom of the chelatingselenolate group as inferred from the NMR spectroscopicdata. The five-membered chelate ring (Pt2Se2C2C2N)exists in a puckered conformation with the carbon atomsC(19) and C(20) lying on opposite sides of the mean plane.The structure of 1f is isomorphous to its palladium ana-logue, [PdCl(SeCH2CH2NMe2)(PPh3)][8] and various bondlengths and angles in the two structures are comparable.

Figure 5. Molecular structure of [PtCl(SeCH2CH2NMe2)(PPh3)](1f) with crystallographic numbering scheme

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. ZalisFULL PAPER

Table 6. Selected bond lengths [A] and bond angles [°] with esd’sfor [PtCl(SeCH2CH2NMe2)(PPh3)] (1f)

2.161 (5) N2C(20) 1.501 (8)Pt2NPt2P 2.2292 (15) N2C(21) 1.485 (8)Pt2Se 2.3773(7) N2C(22) 1.486 (8)Pt2Cl 2.3788 (15) C(19)2C(20) 1.502 (9)Se2C(19) 1.953 (6) P2C (av) 1.830N2Pt2P 174.57 (14) C(20)2N2C(21) 107.1 (5)N2Pt2Se 87.02 (14) C(20)2N2C(22) 109.5 (5)P2Pt2Se 91.07 (4) C(21)2N2C(22) 106.6 (5)N2Pt2Cl 90.61 (15) Pt2N2C(21) 114.9 (4)P2Pt2Cl 90.89 (6) Pt2N2C(22) 107.2 (4)Se2Pt2Cl 174.92 (4) Pt2N2C(20) 111.3 (4)Pd2Se2C(19) 95.9 (2) N2C(20)2C(19) 112.2 (5)

Se2C(19)2C(20) 108.9 (4)

The molecular structure of [Pt2Ph2(Cl)(SeCH2CH2N-Me2)(PnBu3)2] (3), established by the X-ray diffractionmethod, is illustrated in Figure 6. Selected bond lengths andbond angles are given in Table 7. The structure consists oftwo distorted square planar platinum atoms which are heldtogether by a bridging selenolate centre. The two squareplanes of the platinum atoms are inclined to each otherthrough a Pt(1)2Se2Pt(2) angle of 111.69 (5)°. Each pla-tinum atom is coordinated to four different ligand atoms.The Pt(1) centre is coordinated to Ph, Cl, PBu3, and theselenium atom, the latter being mutually trans. The Pt(2)atom is bound to the chelating Me2NCH2CH2Se ligand andto the other PBu3 and Ph groups. The phosphane is transto the nitrogen atom whereas Se is trans to Ph. The Pt2Sedistances in 1f [2.3788(15) A] and 3 [2.4793(14) and2.4562(12) A] are significantly different, although these dis-tances are in agreement with the standard values. Thelonger Pt2Se distances in 3 compared with that of 1f reflectgreater trans influence of Ph and PBu3 than the chloride.

Figure 6. ORTEP plot of [Pt2Ph2Cl(SeCH2CH2NMe2)(PnBu3)2] (3)with crystallographic numbering scheme

Eur. J. Inorg. Chem. 2001, 2965229732970

Table 7. Selected bond lengths [A] and bond angles [°] with esd’sfor [Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)] (3)

2.4793(14) Pt(2)2Se 2.4562(12)Pt(1)2SePt(1)2P(1) 2.235(3) Pt(2)2P(2) 2.227(2)Pt(1)2Cl 2.432(3) Pt(2)2N 2.177(9)Pt(1)2C(11) 2.010(10) Pt(2)2C(5) 2.039(10)Se2C(1) 1.931(12) N2C(2) 1.542(18)C(11)2Pt(1)2P(1) 92.1(3) C(5)2Pt(2)2N 90.7(3)C(11)2Pt(1)2Cl 178.4(3) C(5)2Pt(2)2P(2) 88.5(3)P(1)2Pt(1)2Cl 88.20(11) P(2)2Pt(2)2N 178.9(2)C(11)2Pt(1)2Se 85.1(3) C(5)2Pt(2)2Se 174.0(3)P(1)2Pt(1)2Se 175.23(8) N2Pt(2)2Se 87.2(2)Cl2P(1)2Se 94.69(8) P(2)2Pt(2)2Se 93.64(7)Pt(1)2Se2Pt(2) 111.69(8) Pt(2)2N2C(2) 109.2(7)Pt(1)2Se2C(1) 101.7(4) Se2C(1)2C(2) 110.7(9)

Pt(2)2Se2C(1) 95.3(4)

The comparable trans influence of PBu3 and Ph groups isevident from the 1J(Pt-P) values from NMR spectra. Otherdistances, Pt2P, Pt2Cl, Pt2N, and Pt2C are well in agree-ment with those reported in the literature.[16,21,23,26]

Experimental Section

All the reactions were carried out under a nitrogen atmosphere indry, distilled analytical grade solvents to prevent oxidation of theoxygen sensitive selenolate ions. The complexes K2[PtCl4], cis-[PtCl2(PPh3)2], cis-[PtCl2(P2P)], trans-[Pt2Cl2(µ-Cl)2(PR3)2], andthe mixture of cis- and trans-[Pt2Ph2(µ-Cl)2(PnBu3)2] (P2P 5

dppm, dppe, dppp; PR3 5 PEt3, PnPr3, PnBu3, PMe2Ph, PMePh2)were prepared by the literature methods.[31,32,33] Melting pointswere determined in capillary tubes and are uncorrected. Microana-lyses were performed by the Analytical Chemistry Division ofB.A.R.C. 1H, 31P{1H}, 77Se{1H}, and 195Pt{1H} NMR spectrawere recorded on a Bruker DPX-300 NMR spectrometer operatingat 300, 121.49, 57.31, 64.52 MHz, respectively. Chemical shifts arerelative to internal chloroform peak (δ 5 7.26) for 1H, external85% H3PO4 for 31P, Me2Se for 77Se, and Na2PtCl6 for 195Pt. UV/Vis absorption spectra were recorded on a Bruins InstrumentsOmega 10 spectrophotometer. Cyclic voltammetry was carried outat 100 mV/s scan rate in dichloromethane/0.1 Bu4NPF6 using athree electrode configuration (glassy carbon working electrode, Ptcounter electrode, Ag/AgCl reference) and a PAR 273 potentiostatand function generator. The ferrocene/ferrocenium couple servedas internal reference.

Ground state electronic structure calculations on [PtCl-(SeCH2CH2NMe2)(PPh3)] have been done by density-functionaltheory (DFT) methods using the ADF2000.01[34,35] and Gaussian98[36] program packages. The lowest excited states were calculatedby the time dependent DFT (TD-DFT) method (both ADF andG98 programs) for the model system [PtCl(SeCH2CH2N-Me2)(PH3)]. Within the ADF program, Slater type orbital (STO)basis sets of double-ζ quality with polarisation functions within thephenyl rings and triple-ζ for the rest of the system were employed.The inner shells were represented by the frozen core approximation(1s for C, N 2p for Cl, 3p for Se, and 1s24d for Pt were keptfrozen). The following density functionals were used within ADF:The local density approximation (LDA) with VWN parameteris-ation of electron gas data or the functional including Becke’s gradi-ent correction[37] to the local exchange expression in conjunction

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate FULL PAPERwith Perdew’s gradient correction[38] to the LDA expression (ADF/BP). The scalar relativistic (SR) zero order regular approximation(ZORA) was used within the study. Within Gaussian-98 Dunning’spolarized valence double-ζ basis sets[39] were used for C, N, Cl,and H atoms; quasirelativistic effective core pseudopotentials anda corresponding optimized set of basis functions was employed forPt[40] and Se.[41] Becke’s three parameter hybrid functional with theLee, Yang, and Parr correction functional (B3LYP)[42] was used inGaussian 98 calculations (G98/B3LYP). The calculation on themodel system [PtCl(SeCH2CH2NMe2)(PH3)] was done with the ex-perimental geometry of the PPh3 complex with an optimized struc-ture of the PH3 ligand.

1. Preparation of [PtCl(SeCH2CH2NMe2)(PEt3)] (1a): To a freshlyprepared methanolic solution (5 cm3) of NaSeCH2CH2NMe2 [pre-pared from (Me2NCH2CH2Se)2 (99.7 mg, 0.32 mmol) and NaBH4

(25.4 mg, 0.67 mmol)] was added a dichloromethane solution (20cm3) of [Pt2Cl2(µ-Cl)2(PEt3)2] (247.7 mg, 0.32 mmol). The reactionmixture was stirred at room temperature for 4 h. The solvents were

Table 8. Physical, analytical and 1H NMR spectroscopic data for dimethylaminoethaneselenolate complexes of platinum(II)

Complex Recrystallisation M.p. Analysis:Found (calcd) 1H NMR spectroscopic datasolvent (0C) (%)(% yield) C H N δ

[PtCl(SeCH2CH2NMe2)- hexane (65) 63 23.6 5.3 2.6 1.40 [d,t, 7.6 Hz (t), 17 Hz (d) PCH2Me]; 1.86 [d,q, 7.6 Hz (q),(PEt3)] (1a) (24.0) (5.0) (2.8) 17 Hz (d) PCH2-]; 2.33 [t, 6.1 Hz, 3J(Pt-H) 5 27 Hz, SeCH2];

2.75 [d, 4J(P-H) 5 2.6 Hz, 3J(Pt-H) 5 17 Hz, NMe2]; 2.86[d, t, 1.7 Hz (d) 4J(P-H), J(H-H) 5 7 Hz; 3J(Pt-H) 5 36 Hz, NCH2]

[PtCl(SeCH2CH2NMe2)- hexane 87 28.3 6.0 2.8 1.04 (t, 7.2 Hz, PCH2CH2Me); 1.5221.67 (m, PCH2CH2-);(PnPr3)] (1b) (72) (28.8) (5.8) (2.6) 1.7521.87 (m, PCH2-); 2.33 [t, 6.2 Hz, 3J(Pt-H) 5 27 Hz, SeCH2];

2.74 [d, 4J(P-H) 5 2.5 Hz, 3J(Pt-H) 5 15 Hz, NMe2];2.85 [t, d, 4J(P-H) 5 1.5, 6 Hz (d), 3J(Pt-H) 5 37 Hz, NCH2-]

[PtCl(SeCH2CH2NMe2)- hexane 46 32.2 6.3 2.1 0.85 (t, 7.1 Hz, P CH2CH2CH2Me); 1.3021.50(PnBu3)] (1c) (80) (32.9) (6.4) (2.4) (m, PCH2CH2CH2-); 1.7221.80 (m, PCH2-); 2.24 [t, 6.2 Hz,

3J(Pt-H) 5 27 Hz, SeCH2]; 2.67 [d, 4J(P-H) 5 2.6 Hz,3J(Pt-H) 5 14 Hz, NMe2]; 2.78 [d, t, 4J(P-H) 5 1.5, 5 Hz (t),3J(Pt-H) 5 36 Hz, NCH2-]

[PtCl(SeCH2CH2NMe2)- CH2Cl2/hexane 156 27.3 3.9 2.5 1.80, 1.81 [each d, 2J(P-H) 5 11.2 Hz, 3J(Pt-H) 5 40 Hz, PMe2];(PMe2Ph)] (1d) (69) (27.7) (4.1) (2.7) 2.23 (br, SeCH2); 2.70 [d, 3J(P-H) 5 2.2 Hz, NMe2]; 2.85

[br, 3J(Pt-H) 5 38 Hz, NCH2]; 7.34 (br), 7.67 (br) (Ph)[PtCl(SeCH2CH2NMe2)- CH2Cl2/hexane 199(d) 34.5 3.7 2.2 2.23 [d, J(P-H) 5 11.2, 3J(Pt-H) 5 32 Hz, PMe]; 2.21 (SeCH2,(PMePh2)] (1e) (45) (35.1) (4.0) (2.4) merged with PMe resonance) 2.83 [d, 4J(P-H) 5 2.8 Hz,

3J(Pt-H) 5 18 Hz, NMe2]; 2.99 [d, t, 1.6 Hz (d) 4J(P-H),J(H-H) 5 6.1 Hz; 3J(Pt-H) 5 38 Hz, NCH2]; 7.3827.43 (m) (Ph)

[PtCl(SeCH2CH2NMe2)- CH2Cl2/acetone 235(d) 40.4 3.5 2.1 2.21 [t, 6.2 Hz 3J(Pt-H) 5 24 Hz, SeCH2]; 2.88 [d, 4J(P-H) 5(PPh3)] (1f) (72) (41.0) (3.9) (2.2) 2.8 Hz, 3J(Pt-H) 5 17 Hz, NMe2]; 3.08 [d, t, (d) 4J(P-H) 5

1.5 Hz, J(H-H) 5 6.2 Hz; 3J(Pt-H) 5 42 Hz, NCH2];7.3327.49 (m) 7.6827.49 (m) (Ph)

[PtPh(SeCH2CH2NMe2)- hexane 147 41.6 6.7 1.1 0.89 (t, 7.2 Hz, PCH2CH2CH2Me); 1.34 (m, PCH2CH2CH2-);(PnBu3)] (2) (40) (42.2) (6.8) (2.2) 1.50 (m, PCH2CH2-); 2.33 [d, 4J(P-H) 5 1.9 Hz, 3J(Pt-H) 5

27 Hz, NMe2]; 2.45 (t, 6 Hz, SeCH2); 2.99 [t, d, 4J(P-H) 52.2 Hz; J(H-H) 5 5.5 Hz, 3J(Pt-H) 5 38 Hz, NCH2-],6.8927.00 (m), 7.4527.48 (m) (Ph)

[Pt2Ph2(Cl)(SeCH2CH2NMe2)- 153 41.6 6.8 1.0 0.90 (m, PCH2CH2CH2Me); 1.2621.88 (m, PCH2CH2CH2-);(PnBu3)2] (3) (42.3) (6.6) (1.2) 2.01 (s, NMe2); 2.20 (br, SeCH2), 2.43 (br, NCH2),

7.3827.57 (m, Ph)[Pt2Cl3(SeCH2CH2NMe2)- hexane 187 21.1 4.2 1.7 1.16 (m, PCH2Me); 1.8222.16 (m; PCH2-); 2.63 (br, SeCH2);(PEt3)2] (4a) (80) (21.7) (4.6) (1.6) 2.79 (br, NMe2) 3.02 (br, NCH2).[Pt2Cl3(SeCH2CH2NMe2)- hexane 102 25.7 3.5 1.3 1.64, 1.83, 1.88, 2.04 (each d, 11.5 Hz PMe2), 2.55 [d, 4J(P-H) 5(PMe2Ph)2] (4b) (87) (26.0) (3.5) (1.5) 2.3 Hz], 3.00 [d, 4J(P-H) 5 2.8 Hz, NMe2 1:1], 3.58 (br., NCH2),

2.64 (br, SeCH2), 7.3227.54(m), 7.7627.83 (m) (Ph)[Pt(SeCH2CH2NMe2)2- acetone/hexane 154 44.2 4.8 3.0 1.96 (s, NMe2); 2.42 (br, SeCH2); 2.59 (br, NCH2); 4.35(dppm)] (5a) (62) (44.9) (4.8) (3.2) [t, 2J(P-H) 5 10.4 Hz; 3J(Pt-H) 5 44 Hz, PCH2-];

7.3927.47 (m), 7.8227.89 (m) (Ph)[Pt(SeCH2CH2NMe2)2- acetone/hexane 184 44.8 4.9 3.0 2.03 (s, NMe2); 2.1522.56 (m, NCH2, SeCH2, PCH2); 7.51 (br),(dppe)] (5b) (60) (45.6) (4.9) (3.1) 7.8827.96 (m) (Ph)[Pt(SeCH2CH2NMe2)2- acetone/hexane 162 44.7 4.8 2.0 1.88 (s, NMe2); 1.9422.96 (overlapping resonance due to NCH2,(dppp)] (5c) (75) (46.2) (5.1) (3.1) SeCH2, PCH2) 7.2927.82 (m, Ph)[Pt2(SeCH2CH2NMe2)2- CH2Cl2/hexane 84 60.6 5.0 1.1 2.47 (br, NMe2); 2.74 (br, SeCH2); 2.82 (br, NCH2); 4.04(dppm)2][BPh4]2 (6a) (65) (60.6) (5.0) (1.3) [t, 2J(P-H) 5 11 Hz PCH2-]; 6.7526.93 (m), 7.2327.62 (m) (Ph)[Pt2(SeCH2CH2NMe2)2- acetone/hexane 126 60.3 5.2 1.4 1.8021.95 (br, PCH2); 2.34 (s, J(Pt-H) 5 16 Hz NMe2);(dppe)2][BPh4]2 (6b) (72) (61.0) (5.1) (1.3) 2.61 (br, SeCH2); 3.05 [br, 3J(Pt-H) 5 45 Hz NCH2];

6.7726.91 (m), 7.1827.31 (m), 7.3727.69 (m) (Ph)[Pt2(SeCH2CH2NMe2)2- acetonehexane 195 60.5 5.1 1.1 1.68 (br, PCH2); 2.17 (s, NMe2); 2.25 (br, CH2-CH2P), 2.49(dppp)2][BPh4]2 (6c) (60) (61.3) (5.2) (1.3) (br, SeCH2); 3.07 [br, J(Pt-H) 5 46 Hz, NCH2];

6.8727.06 (m); 7.4227.64 (m) (Ph)[Pt(SeCH2CH2NMe2)- 2.79 (s, NMe2 1 NCH2 base of the peak broadened);(PPh3)]n[PF6]n (7) 2.30 (br, SeCH2); 7.3427.70 (m) Ph.

Eur. J. Inorg. Chem. 2001, 296522973 2971

evaporated under reduced pressure and the residue was extractedwith dichloromethane (337 cm3), the solution was passed througha Florisil column and the solvent removed in vacuo. The residuewas recrystallised from hexane (yield 210 mg, 65%). All othermononuclear complexes [PtCl(SeCH2CH2NMe2)(PR3)] (PR3 5

PnPr3, PnBu3, PMe2Ph, PMePh2) were prepared in a similar man-ner. Pertinent data are summarized in Table 8.

2. Preparation of [PtCl(SeCH2CH2NMe2)(PPh3)] (1f): Preparedanalogously as described in method 5 by using [PtCl2(PPh3)2](268.8 mg, 0.34 mmol) NaSeCH2CH2NMe2 [prepared from(Me2NCH2CH2Se)2 (54.4 mg, 0.18 mmol) and NaBH4 (14.0 mg,0.37 mmol)]. The residue was washed thoroughly with diethyl etherto remove liberated triphenylphosphane and then recrystallisedfrom CH2Cl2/acetone mixture as yellow-orange crystals (yield158 mg, 72%).

3. Preparation of [PtPh(SeCH2CH2NMe2)(PnBu3)] (2) and[Pt2Ph2Cl(SeCH2CH2NMe2) (PnBu3)2] (3): Prepared analogously

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. ZalisFULL PAPERas described in method 1 from [Pt2Ph2(µ-Cl)2(PnBu3)2] (99.5 mg,0.10 mmol) and NaSeCH2CH2NMe2 [prepared from(Me2NCH2CH2Se)2 (32 mg, 0.11 mmol) and NaBH4 (8.9 mg,0.23 mmol)]. The 31P and 195Pt NMR spectra of this product exhib-ited three resonances. The product on recrystallization from hexanegave colourless crystals of [PtPh(SeCH2CH2NMe2)(PnBu3)] (yield29 mg, 24%). The supernatant solution on repeated recrystalliza-tion from hexane containing ø 5% benzene afforded[Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)2] (54 mg, 48%).

4. Preparation of [Pt2Cl3(SeCH2CH2NMe2)(PEt3)2] (4a): Solid[PtCl(SeCH2CH2NMe2)(PEt3)] (17.7 mg, 0.04 mmol) was mixedwith [Pt2Cl2(µ-Cl)2(PEt3)2] (13.5 mg, 0.02 mmol) in CDCl3 (0.5cm3) in an NMR tube. After a few days the solution was dried invacuo, the pale yellow product was washed with hexane and driedin vacuo (yield 25.0 mg, 80%).

5. Preparation of [Pt(SeCH2CH2NMe2)2(dppe)] (5b): To a stirredmethanolic solution (5 cm3) of NaSeCH2CH2NMe2 [prepared from(Me2NCH2CH2Se)2 (92.8 mg, 0.31 mmol) and NaBH4 (23.8 mg,0.63 mmol)] solid [PtCl2(dppe)] (201.5 mg, 0.30 mmol) was added.To this mixture dry acetone (20 cm3) was added whereupon a yel-low solution formed which was stirred for 3 h at room temperature.The solvents were stripped off under vacuum and the residue wasextracted with acetone (337 cm3) and filtered. The filtrate was re-duced to a minimum volume (5 cm3), a few drops of hexane wereadded to yield yellow crystals of the title complex (yield 163 mg,60%).

The complexes [Pt(SeCH2CH2NMe2)2(P2P)] (P2P 5 dppm, dppe)were prepared in an analogous manner.

6. Preparation of [Pt2(SeCH2CH2NMe2)2(dppm)2][BPh4]2 (6a): a) Adichloromethane suspension of (20 cm3) of [PtCl2(dppm)](248.9 mg, 0.38 mmol) was added to a stirred methanolic solution(5 cm3) of NaSeCH2CH2NMe2 [prepared from (Me2NCH2CH2Se)2

(59.2 mg, 0.20 mmol) and NaBH4 (15.5 mg, 0.41 mmol)]. After 1 hof stirring a methanolic solution of NaBPh4 (133.5 mg, 0.39 mmol)

Table 9. Crystal data and structure refinement for [PtCl(SeCH2CH2NMe2)(PPh3)] (1f) and [Pt2Ph2Cl(SeCH2CH2NMe2)(PnBu3)2] (3)

1f 3

Empirical formula C22H25ClNPSePt C43H68ClNP2SePt2

Molecular mass 643.90 1165.55Crystal system, Monoclinic, Triclinic,Space group P21/n P1Unit cell dimensions:a [A] 9.4299(19) 9.3083(19)b [A] 19.972(4) 15.859(3)c [A] 11.704(2) 16.587(3)α [°] 108.96(3)β [°] 95.19(3) 97.55(3)γ [°] 93.32(3)V [A3] 2175.6(8) 2282.5(8)Z 4 4Dc [Mg·m23] 1.966 1.924Absorption coefficient µ [mm21] 8.326 7.938F(000) 1232 1300Range for data collection [°] 2.03 to 30.00 1.55 to 30.00Refinement method Full-matrix least-squares on F2.0 Full-matrix least-squares on F2.0Reflections collected/unique 7797/6351 14091/13328Data/restraints/parameters 6351/0/244 13328/0/419Goodness of fit on F2 0.937 1.092Final R indices R1 5 0.0444, wR2 5 0.1151 R1 5 0.0357, wR2 5 0.0838R indices (all data) R1 5 0.0574, wR2 5 0.1263 R1 5 0.0996, wR2 5 0.1798Largest diff. peak and hole [e·A23] 2.000 and 25.602 2.340 and 22.075

Eur. J. Inorg. Chem. 2001, 2965229732972

was added and the whole mixture was stirred for 3 h. Solvents wereevaporated in vacuo and the residue was extracted with dichloro-methane and passed through a Florisil column. The solvent wasevaporated in vacuo, the residue was washed with hexane andrecrystallised from a CH2Cl2/hexane mixture (yield 261 mg, 65%).Other cationic complexes [Pt2(SeCH2CH2NMe2)2(P2P)2][BPh4]2(P2P 5 dppe, dppp) were prepared in a similar way.

b) To a methanolic suspension (8 cm3) of [PtCl2(dppm)] (215.7 mg,0.33 mmol) a methanolic solution (3 cm3) of NaBPh4 (114.2 mg,0.33 mmol) was added and stirred for 1 h whereupon a pale yellowsolution formed. To this a freshly prepared methanolic solution ofNaSeCH2CH2NMe2 [prepared from (Me2NCH2CH2Se)2 (51.4 mg,0.17 mmol), NaBH4 (13.2 mg, 0.35 mmol)] and 20 cm3 of dichloro-methane was added and stirred. After 3 h the solvents were strippedoff under vacuum. The residue was extracted with dichloromethane(337 cm3) and passed through a Florisil column. The volume ofthe solution was reduced to 5 cm3. Recrystallisation from CH2Cl2/hexane mixture gave yellow solid (yield 216 mg, 62%).

7. Preparation of [Pt(SeCH2CH2NMe2)(PPh3)]n[PF6]n (7): An acet-one solution (15 cm3) of AgPF6 (51 mg, 0.21 mmol) was addedto solid [PtCl(SeCH2CH2NMe2)(PPh3)] (116 mg, 0.20 mmol) withstirring. Silver chloride immediately precipitated with concomitantcolour change from orange to pale yellow. The reactants werestirred at room temperature for 4 h. Precipitated AgCl was filteredthrough celite and the solvent was evaporated in vacuo. The yellowresidue was examined by NMR spectroscopy.

Crystallography: X-ray data of an orange crystal of[PtCl(SeCH2CH2NMe2)(PPh3)] (1f) (0.230.230.2 mm) and acolourless crystal of [Pt2Ph2Cl(SeCH2CH2NMe2)-(PnBu3)2] (3) (0.330.330.3 mm) were collected at 173(2) K on aSiemens P3 diffractometer using graphite monochromated Mo-Kα

radiation (λ 5 0.71073 A), employing the ω-2θ scan technique. Theunit cell parameters (Table 9) were determined from 25 reflectionseach, measured by random search routine. The intensity data were

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate FULL PAPERcorrected for Lorentz polarisation and absorption effects. Thestructures were solved using direct methods, the mononuclear com-plex proved to be isostructural with the previously reported palla-dium analogue.[8] The non-hydrogen atoms were refined aniso-tropically except for the methyl carbon atoms C(23) and C(43).These two atoms were treated within a disorder model [0.62 and0.38 for C(23) and C(23A), 0.93 and 0.07 for C(43) and C(43A)];each of the adjacent methylene carbon atoms C(22) and C(42) wasrefined using two different sets of hydrogen atoms. Three of the n-butyl groups and the phenyl ligands exhibit high standard devi-ations, presumably due to thermal motion.

AcknowledgmentsWe thank Dr. J. P. Mittal and Dr. P. Raj for encouragement of thiswork. We are also grateful to Dr. P. K. Mathur, Head, AnalyticalChemistry Division, BARC for providing the microanalysis of thecompounds. Support for this work from BMBF (Project IND 99/060), the DFG, FCI (Frankfurt am Main), the Ministry of Educa-tion of the Czech Republic, and the DLR (Bonn) for KONTAKTProject CZE 00/013 is gratefully acknowledged.

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