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Inorganica Chimica Acta 359 (2006) 1404–1412

Synthesis and characterization of some monoorganotin(IV)chloride adducts with internally functionalized oximes:

Crystal and molecular structures of nBuSnCl3 Æ HON@C(Me)Py-2 ÆC6H5Me and a trinuclear hydroxo bridged stannoxane

{nBuSnCl2(ON@C(Me)Py-2)OH}2SnnBuCl Æ 0.5HON@C(Me)Py-2

Vinita Sharma a, Sangeeta Agrawal a, Rakesh Bohra a,*, Raju Ratnani b, John E. Drake c,Ann L. Bingham d, Michael B. Hursthouse d, Mark E. Light d

a Department of Chemistry, University of Rajasthan, J.L.N. Marg, Jaipur 302004, Rajasthan, Indiab Department of Applied Chemistry, MDS University, Ajmer 305001, India

c Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ont., Canada N9B 3P4d Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK

Received 22 August 2005; accepted 16 September 2005Available online 16 November 2005

Abstract

Reactions of RSnCl3 (R = Et and nBu) with internally functionalized oximes in 1:1 and 1:2 stoichiometric ratios in anhydrous benzeneafforded non-ionic fibrous complexes of the general formula RSnCl3 Æ nHON@C(R 0)Ar [R = Et and Bu; R 0 = H, Me n = 1 and 2 (1–8);R 0 = only Me (9–11); Ar = 2-NC5H4, 2-OC4H3. Except for 1:1 furyl derivative, the value of 119Sn chemical shifts for all these derivativesin the 119Sn NMR spectra suggests hexa-coordination around tin atom. The crystal and molecular structures of one of the adducts nBuS-nCl3 Æ HON@C(Me)Py-2 Æ C6H5Me (2.tol.) and of a trinuclear hydroxo bridged stannoxane {nBuSnCl2(ON@C(Me)Py-2)OH}2SnnBu-Cl Æ 0.5 HON@C(Me)Py-2 (12), obtained on hydrolysis of nBuSnCl3 Æ 2HON@C(Me)Py-2 (6), revealed a distorted octahedralenvironment around tin with the participation of both nitrogen atoms (ring as well as oxime nitrogen atom of the same ligand moiety)in coordination. In compound (2.tol.), the existence of intramolecular hydrogen bonding between the hydroxyl proton of the ligand moi-ety and the chlorine atom stabilizes the geometry. Unique asymmetric Sn–O(H)–Sn and Sn–O–N–Sn bridges are present in compound(12), resulting in a linear trinuclear stannoxane framework.� 2005 Elsevier B.V. All rights reserved.

Keywords: Trinuclearstannoxanes; Internally functionalized; Intramolecular hydrogen bonding

1. Introduction

Organostannoxane chemistry has always intriguedchemists due to their synthetic challenges [1–3], uniquestructural features ranging from monomeric [4,5] to clusternetworks [2,6–9] and wide range of catalytic applications[10]. Recently, inorganic–organic hybrid materials are find-

0020-1693/$ - see front matter � 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.ica.2005.09.017

* Corresponding author. Tel./fax: +91 141 2700364.E-mail address: rkbohra@satyam.net.in (R. Bohra).

ing a special place in the field of material science, by pro-viding an opportunity to combine useful properties bothfrom the organometallic and also from the ligand [11,12].In our previous studies on organotin(IV) [13–15] and alsoon organogermanium(IV) and organolead(IV) [16] deriva-tives of internally functionalized oximes, we reported thatsubtle variations in the organo group or in the ligand moi-ety usually result in different structural patterns. It is wellknown that oximes are important multidentate organicacids not only due to their strong biological activities

Table 1Synthetic and analytical data for the adducts of monoorganotin(IV) chlorides with internally functionalized oximes

Compound Colour and physical state M. pt. (in �C) Elemental analysis Obs. (Calc.)

Cl M

EtSnCl3 Æ HON@C(Me)Py (1) Pinkish white solid 170 27.14 (27.25) 30.35 (31.41)nBuSnCl3 Æ HON@C(Me)Py (2) Pinkish white solid 165 25.26 (25.42) 28.35 (28.37)EtSnCl3 Æ HON@C(H)Py (3) Pink solid 155 28.21 (28.27) 31.50 (31.54)nBuSnCl3 Æ HON@C(H)Py (4) White solid 130 26.21 (26.31) 29.33 (29.35)EtSnCl3 Æ 2HON@C(Me)Py (5) Pink solid 135 19.94 (20.20) 22.55 (22.65)nBuSnCl3 Æ 2HON@C(Me)Py (6) Pinkish white solid 120 18.72 (19.18) 21.38 (21.40)EtSnCl3 Æ 2HON@C(H)Py (7) Yellow solid 60 21.28 (21.34) 23.75 (23.81)nBuSnCl3 Æ 2HON@C(H)Py (8) Pink solid 67 20.16 (20.20) 22.47 (22.54)BuSnCl3 Æ HON@C(Me)C4H3O (9) Yellow liquid 26.01 (26.11) 29.10 (29.14)EtSnCl3 Æ 2HON@C(Me)C4H3O (10) Yellow solid 100 21.13 (21.08) 23.48 (23.53)nBuSnCl3 Æ 2HON@C(Me)C4H3O (11) Yellow liquid 19.86 (19.97) 22.24 (22.29)

V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412 1405

[17,18], but also due to their capacity to easily form com-plexes with various metals [19–21].

Here, we report the synthesis and characterization ofsome monoorganotin(IV) chloride derivatives with inter-nally functionalized oximes, including the crystal andmolecular structure of nBuSnCl3 Æ HON@C(Me)Py-2 ÆC6H5Me. In order to explore their potential applicationsas precursors for hybrid materials, one of the compounds,[nBuSnCl3 Æ 2HON@C(Me)Py-2] (6), was partially hydro-lyzed and the resulting trinuclear hydroxo bridged stannox-ane cluster, {nBuSnCl2(ON@C(Me)Py-2)OH}2SnnBuCl Æ0.5 HON@C(Me)Py-2 (12), was characterized by X-ray dif-fraction analysis (see Table 1).

2. Experimental

nBuSnCl3 was used as supplied. All the solvents weredried prior to use. IR spectra were recorded as Nujol mullson a Bomem MB-102 FT-IR spectrophotometer and thedata are given in Table 2. 1H, 13C{1H} and 119Sn{1H}NMR spectra were recorded in 5 mm NMR tubes asfreshly prepared CDCl3 solutions on a Bruker DPX-300NMR spectrometer operating at 300, 75.47 and111.92 MHz, respectively (data are summarized in Table3). Spectra were referenced with the internal chloroformpeak (d 7.26 for 1H and 77.0 ppm for 13C) and external33% solution of Me4Sn in C6D6 for 119Sn. Tin was esti-

Table 2Some important IR data (cm�1) assigned for the adducts of monoorganotin(I

Compound mO–H mC@N

EtSnCl3 Æ HON@C(Me)Py 3430 1462nBuSnCl3 Æ HON@C(Me)Py 3410 1461EtSnCl3 Æ HON@C(H)Py 3250 1460nBuSnCl3 Æ HON@C(H)Py 3425 1455EtSnCl3 Æ 2HON@C(Me)Py 3445 1462nBuSnCl3 Æ 2HON@C(Me)Py 3450 1458EtSnCl3 Æ 2HON@C(H)Py 3436 1484nBuSnCl3 Æ 2HON@C(H)Py 3440 1460nBuSnCl3 Æ HON@C(Me)C4H3O 3110 1571EtSnCl3 Æ 2HON@C(Me)C4H3O 3100 1572nBuSnCl3 Æ 2HON@C(Me)C4H3O 3150 1568

a X = N or O.

mated as tin-dioxide and chloride was estimated by Vol-hard�s method.

2.1. Preparation of nBuSnCl3 Æ 2HON@C(Me)Py

A solution of BuSnCl3 (686 mg, 2.43 mmol) in benzenewas added to a solution of 2-acetyl pyridyloxime (331 mg,2.43 mmol) in benzene resulting in the slight exothermic for-mation of fibrous crystals of the complex. The mixture wasstirred for 1 h. The residue was filtered and dried in vacuoto give a pinkish white solid, which was recrystallized froma chloroform/hexane mixture [864 mg, 86% yield].

Similarly, all other alkyltin(IV) chloride adducts weresynthesized and their synthetic and analytical data aregiven in Table 1. Single crystals of 2.tol were obtained fromtoluene. One of the compounds, nBuSnCl3 Æ 2HON@C(Me)Py-2 (6), was partially hydrolyzed in CH2Cl2 togive a trinuclear stannoxane, {nBuSnCl2(ONC(Me)Py-2)OH}2SnnBuCl Æ 0.5HONC(Me)Py-2 (12). Both 2, withtoluene in the lattice, and 12 were characterized by X-raydiffraction analysis.

2.2. X-ray diffraction analyses

Colorless and pale-pink plate crystals of nBuSnCl3 ÆHON@C(Me)Py-2, C6H5Me, (2.tol.) and {nBuSnCl2-(ONC(Me)Py-2)OH}2SnnBuCl Æ 0.5HONC(Me)Py-2 (12),

V) chlorides derived from internally functionalized oximes

mN–O mSn–C mSn–Xa

vs 965s 587s 464wvs 970m 552m 465wvs 948s 514s 423ss 945m 525m 428svs 937s 559m 416mvs 940s 540m 418mvs 949s 561s 423ms 900m 530m 450mvs 969m 557m 467mvs 965vs 550m 414ss 930m 520m 460w

Table 3NMR data in CDCl3 for adducts of monoorganotin(IV) chlorides derived from internally functionalized oximes

Compound 1H NMR d ppm 13C {1H} NMR d ppm 119Sn{1H} d ppm

EtSnCl3 Æ HON@C(Me)Py 1.11 (t, 5.7 Hz (t), Sn–CCH3); 1.58 {q, 5.7 Hz(q), 2J(119/Sn–1H) = 34.2 Hz, Sn–CH2}; 2.41(oxime-Me); 7.38 (m, H-4); 7.89 (s, H-5); 7.96(s, H-3); 8.94 (d, 4.3 Hz (d), H-6); 9.20 (br,OH)

Due to poor solubility 13C{1H} NMR couldnot be resolved

�400.9

nBuSnCl3 Æ HON@C(Me)Py 0.97 (m, Sn–CCCCH3); 1.50 (m, Sn–CCCH2);1.90 (m, Sn–CCH2); 2.16 (m, Sn–CH2); 2.58(oxime-Me); 7.87 (m, H-4); 8.03 (d, 7.42 Hz(d), H-5); 8.30 (t, 7.7 Hz (t), H-3); 8.63 (m, H-6); 10.82 (br, OH)

11.6 (oxime-Me); 13.4 (Sn–CCCCH3); 25.3{1J(119Sn–13C) = 150.9 Hz, Sn–CH2}; 27.6{2J(119/117Sn–13C) = 76.0 Hz, Sn–CCH2};38.3 (Sn–CCCH2); 121.7 (C-5); 124.7 (C-3);142.6 (C-4); 143.8 (C-6); 145.0 (C-2 and C@N)

�406.4

EtSnCl3 Æ HON@C(H)Py 1.30 (t, 8.5 Hz (t), Sn–CCH3); 1.83 (q, 8.5 Hz(q), Sn–CH2); 7.73 (m, H-4); 7.83 (m, H-5);8.23 (m, H-3); 8.44 (s, CH); 8.86 (m, H-6);9.71 (br, OH)

Due to poor solubility 13C {1H} as well as the119Sn{1H} NMR could not be resolved

nBuSnCl3 Æ HON@C(H)Py 0.92 (m, Sn–CCCCH3); 1.46 (m, Sn–CCCH2);1.90 (m, Sn–CCH2); 2.12 (Sn–CH2); 7.21 (m,H-4); 7.83 (m, H-5); 8.23 (m, H-3); 8.31 (s,CH); 8.64 (m, H-6); 9.71 (br, OH)

13.4 (Sn–CCCCH3); 25.5{1J(119Sn–13C) = 186.8 Hz, Sn–CH2}; 27.7{2J(119Sn–13C) = 65.3 Hz, Sn–CCH2}; 38.3(Sn–CCCH2); 127.6 (C-5); 128.4 (C-3); 137.2(C-4); 142.3 (C-6); 145.4 (C-2 and C@N)

�401.6

EtSnCl3 Æ 2HON@C(Me)Py 1.08 (t, 5.7 Hz (t), Sn–CCH3); 1.55 (m, Sn–CH2); 2.38 (s, oxime-Me); 7.38 (m, H-4); 7.76(s, H-5); 7.89 (H-3); 8.78 (d, 5.1 Hz (d), H-6);9.73 (br, OH)

2.5 (Sn–CCH3); 10.08 (Sn–CH2); 11.7(oxime-Me); 121.1 (C-5); 124.1 (C-3); 137.1(C-4); 148.5 (C-6); 153.9 (C-2); 155.1 (C@N)

�221.2, �402.9

nBuSnCl3 Æ 2HON@C(Me)Py 0.93 (t, 6.6 Hz (t), Sn–CCCCH3); 1.46 (m, Sn–CCCH2); 1.86 (m, Sn–CCH2); 2.12 (m, Sn–CH2); 2.44 (oxime-Me); 7.38 (s, H-4); 7.84 (m,H-5); 7.87 (m, H-3); 8.65 (s, H-6); 9.71 (br,OH)

10.9 (oxime-Me); 13.3 (Sn–CCCCH3); 25.1{1J(119Sn–13C) = 158.5 Hz, Sn–CH2; 27.6({2J(119Sn–13C) = 76.0 Hz, Sn–CCH2); 38.2(Sn–CCCH2); 121.5 (C-5); 124.5 (C-3); 137.3(C-4); 144.8 (C-6); 152.1 (C-2); 148.9 (C@N)

�407.3

EtSnCl3 Æ 2HON@C(H)Py 1.04 (t, 6.2 Hz (t), Sn–CCH3); 1.58 (q, 5.7 Hz,Sn–CH2); 7.42 (m, H-4); 7.77 (m, H-5); 7.83(m, H-3); 8.31 (s, CH); 8.88 (s, H-6); 9.77 (br,OH)

Due to poor solubility 13C {1H} as well as the119Sn{1H} NMR could not be resolved

nBuSnCl3 Æ 2HON@C(H)Py 0.92 (t, 5.7 Hz, (t); Sn–CCCCH3); 1.30 – 2.10(m, Sn–CH2 CH2 CH2); 7.30 (s, H-4); 7.74 (m,H-5); 7.81 (m, H-3); 8.40 (s, CH); 8.75 (m, H-6); 9.81 (br, OH)

Due to poor solubility 13C {1H} NMR couldnot be resolved

�403.6

nBuSnCl3 Æ HON@C(Me)C4H3O 0.92 (t, 7.2 Hz, Sn–CCCCH3); 1.44 (m, Sn–CCCH2); 1.85 (m, Sn–CCH2); 2.18 (t, 7.7 Hz(t), Sn–CH2); 2.41 (oxime-Me); 6.57 (dd, 3.4and 1.6 Hz (d), H-4); 6.99 (d, 3.6 Hz (d), H-3);7.58 (s, H-5); 10.25 (br, OH)

13.1 (oxime-Me); 15.5 (Sn–CCCCH3); 25.2{1J(119Sn–13C) = 148.0 Hz, Sn–CH2}; 27.1{2J(119Sn–13C) = 64.4 Hz, Sn–CCH2; 36.9(Sn–CCCH2); 112.9 (C-4); 116.6 (C-3); 143.3(C-5); 144.9 (C-2); 146.8 (C@N)

�200.5

EtSnCl3 Æ 2HON@C(Me)C4H3O 1.37 (t, 8.6 Hz (t), Sn–CCH3); 1.98 {q, 8.5 Hz(q), 2J(119/117Sn–1H) = 34.2 Hz, Sn–CH2};2.28, 2.31 (each s, oxime-Me); 6.46, 6.54 (dd,2.5 Hz each (d), H-4); 6.78 {d, 2.8 Hz (d)} and6.84 (m) (H-3); 7.47 {d, 1.42 Hz (d)} and 7.63(H-5); 9.92 (br, OH)

2.1 Sn–CCH3; 11.8, 12.6 (oxime-Me); 19.4(Sn–CH2); 112.2, 113.6 (C-4); 114.1, 114.8 (C-3); 145.4, 146.8 (C-5); 147.2 (C-2); 147.5(C@N)

�337.6

nBuSnCl3 Æ 2HON@C(Me)C4H3O 0.84 (t, 6.0 Hz (t), Sn–CCCCH3); 1.33 (m, Sn–CCCH2); 1.79 (m, Sn–CCH2); 1.95 (t, 6.0 Hz(t), Sn–CH2); 2.39, 2.41 (each s, oxime-Me);6.52, 6.59 (m, H-4); 6.93, 7.52 (s, H-3); 7.63,8.08 (m, H-5); 10.08 (br, OH)

12.0, 13.2 (oxime-Me); 15.7 (Sn–CCCCH3);25.3 {1J(119Sn–13C) = 158.5 Hz, Sn–CH2; 27.4{1J(119Sn–13C) = 67.0 Hz, Sn–CCH2; 39.2(Sn–CCCH2); 112.3, 113.3 (C-4); 114.4, 122.1(C-3); 143.4, 144.4 (C-5); 145.8, 146.3, (C-2);146.9 (C@N)

�324.6

1406 V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412

respectively, were mounted on glass fibers. Data was col-lected on a Bruker-Nonius KappaCCD area detector dif-fractometer, with / and x scans chosen to give a

complete asymmetric unit. Cell refinement [22] gave cellconstants corresponding to monoclinic cells, whosedimensions are given in Tables 4 and 5 along with other

Table 4Crystal data and structure refinement for nBuSnCl3[HON@C(Me)py-2] Æ C6H5Me (2.tol)

Empirical formula C18H25ON2Cl3SnFormula weight 510.44Temperature (K) 120(2)Wavelength (A) 0.71073Crystal system monoclinicSpace group P21/ca (A) 8.374(5)b (A) 22.77(3)c (A) 11.10(2)b (�) 92.7(1)V (A3) 2115(4)Z 4Dcalc (g/cm3) 1.603Absorption coefficient (mm�1) 1.596F(000) 1024Crystal size (mm3) 0.50 · 0.30 · 0.20h Range for data collection (�) 4.67–25.02Index ranges �9 6 h 6 9, �27 6 k 6 27,

�13 6 l 6 13Reflections collected 18398Independent reflections [Rint] 18402 [0.0000]Maximum and minimum transmission 0.7408 and 0.5025Refinement method full-matrix least-squares on F2

Data/restraints/parameters 18402/0/231Goodness-of-fit on F2 1.018Final R indices [F2 > 4r(F2)] R1 = 0.0762, wR2 = 0.1879R indices (all data) R1 = 0.1236, wR2 = 0.2205Largest differences in

peak and hole (e A�3)1.934 and �1.269

Table 5Crystal data and structure refinement for nBuSnCl2[ONC(Me)Py-2]OH}2SnnBuCl Æ 0.5HONC(Me)Py-2 (12)

Empirical formula C29.50H47O4.50N5Cl5Sn3

Formula weight 1077.04Temperature (K) 120(2)Wavelength (A) 0.71073Crystal system monoclinicSpace group P21/na (A) 17.981(2)b (A) 11.269(1)c (A) 21.820(2)b (�) 106.317(8)V (A3) 4243.3(8)Z 4Dcalc (g/cm3) 1.686Absorption coefficient (mm�1) 2.105F(000) 2120Crystal size (mm3) 0.10 · 0.06 · 0.02h Range for data collection (�) 2.97–27.57Index ranges 23 6 h 6 23, �14 6 k 6 14,

�28 6 l 6 28Reflections collected 57544Independent reflections [Rint] 9787 [0.0896]Maximum and minimum transmission 0.9591 and 0.8171Refinement method full-matrix least-squares on F2

Data/restraints/parameters 9787/52/420Goodness-of-fit on F2 1.048Final R indices [F2 > 4r(F2)] R1 = 0.0568, wR2 = 0.1109R indices (all data) R1 = 0.0895, wR2 = 0.1229Largest differences in

peak and hole (e A�3)1.756 and �1.408

V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412 1407

experimental parameters. An absorption correction wasapplied [23].

The structures were solved by direct methods [24] andrefined using the WINGX version [25] of SHELX-97 [26]. Allof the non-hydrogen atoms were treated anisotropically.In 12, the hydrogen atoms of the hydroxyl groups,O(2)–H(20) and O(4)–H(40), were located in the differencemap and refined with restraints on their bond lengths. Allother hydrogen atoms in 2.tol and 12 were included inidealized positions with isotropic thermal parameters setat 1.2 times that of the carbon atom to which they wereattached. In 12, the 60/40 disorder in two of the butylgroups was successfully modeled by placing restraints ondistances and thermal parameters. The free acid, HON-C(CH3)Py, in the lattice of 12 has an occupancy of 0.5.The final cycle of full-matrix least-squares refinementwas based on 18402 (for 2.tol.) and 9787 (for 12) ob-served reflections (12321 (for 2.tol.) and 7007 for (12)for F2 > 4r(F2)) and 231 (for 2.tol) and 420 (for 12) vari-able parameters and converged (largest parameter shiftwas 0.001 times its esd).

3. Results and discussion

Reactions of RSnCl3 with 2-acetyl pyridyl oxime or 2-pyridyl aldoxime in 1:1 and 1:2 molar ratios in benzenereadily afforded fibrous crystals of the adducts. Furtherreaction of BuSnCl3 with 2-acetyl pyridyl oxime in 1:3 mo-lar ratio yielded only 1:2 product;

RSnCl3 þ nHON@CðR0ÞPy! RSnCl3 � nHON@CðR0ÞPy

ðR ¼ Et;Bu; R0 ¼ H;Me; n ¼ 1 or 2; 1–8Þ.

Similar kind of reactions, with 2-acetyl furyl oxime,yielded products (9–11) as depicted below:

RSnCl3 þ nHON@CðMeÞC4H3O

! RSnCl3 � n0HON@CðMeÞC4H3O

ðwhen R ¼ Et; n ¼ 1 or 2 and n0 ¼ only 2;

when R ¼ nBu; n ¼ n0 ¼ 1 or 2Þ

Except for the butyltin(IV) derivatives with 2-furyloxime (yellow liquids), all these complexes are white orlight colored solids having solubility in polar solvents(comparatively less for ethyltin(IV) derivatives). Conduc-tance measurements of all these complexes in CHCl3 haveshown their non-ionic nature. Synthetic and physical dataof these derivatives are summarized in Table 1.

The IR spectra of all these derivatives have been inter-preted by comparing the data with those of the reactants.The OH band in the pyridyl derivatives is observed athigher wave numbers (3460–3400 cm�1), indicating weak-ening or breaking down of hydrogen bonding in the ligandon complexation. Shift in mC@N toward lower wave number(1460–1484 cm�1) suggests that the oxime-nitrogen atom ofthe ligand moiety is coordinating in all these pyridyladducts. This information may get support from the

Table 6Bond lengths (A) and angles (�) for nBuSnCl3[HON@C(Me)py–2] Æ C6H5Me (2.tol)

Sn(1)–Cl(1) 2.436(3) Sn(1)–Cl(2) 2.454(2)Sn(1)–Cl(3) 2.426(2) Sn(1)–C(1) 2.132(6)Sn(1)–N(1) 2.269(5) Sn(1)–N(2) 2.248(5)O(1)–N(1) 1.374(5) N(1)–C(5) 1.269(7)N(2)–C(7) 1.344(6) N(2)–C(8) 1.317(6)C(5)–C(6) 1.489(8) C(5)–C(7) 1.470(7)C(8)–C(9) 1.385(8) C(9)–C(10) 1.350(7)C(10)–C(11) 1.373(7) C(7)–C(11) 1.377(8)C(1)–C(2) 1.461(8) C(2)–C(3) 1.544(9)C(3)–C(4) 1.458(9) O(1)–Cl(1) 3.030(6)O(1)–H(1) 0.84 H(1)–Cl(1) 2.32

Cl(1)–Sn(1)–Cl(2) 90.71(7) Cl(1)–Sn(1)–Cl(3) 91.18(7)Cl(2)–Sn(1)–Cl(3) 164.72(5) C(1)–Sn(1)–Cl(1) 105.2(2)C(1)–Sn(1)–Cl(2) 92.7(2) C(1)–Sn(1)–Cl(3) 101.5(2)N(1)–Sn(1)–C(1) 169.2(2) N(2)–Sn(1)–C(1) 100.6(2)N(1)–Sn(1)–Cl(1) 84.3(1) N(2)–Sn(1)–Cl(1) 154.1(1)N(1)–Sn(1)–Cl(3) 83.1(2) N(2)–Sn(1)–Cl(3) 86.0(1)N(1)–Sn(1)–Cl(2) 82.0(2) N(2)–Sn(1)–Cl(2) 85.7(1)N(1)–Sn(1)–N(2) 69.8(2) C(7)–N(2)–C(8) 120.4(5)O(1)–N(1)–Sn(1) 122.0(3) C(7)–N(2)–Sn(1) 118.1(3)C(5)–N(1)–Sn(1) 121.5(4) C(8)–N(2)–Sn(1) 121.4(4)C(5)–N(1)–O(1) 116.5(5) C(2)–C(1)–Sn(1) 117.5(4)C(1)–C(2)–C(3) 112.8(5) C(2)–C(3)–C(4) 113.2(7)N(1)–C(5)–C(6) 124.0(5) N(2)–C(7)–C(5) 116.1(5)N(1)–C(5)–C(7) 114.3(5) N(2)–C(7)–C(11) 120.4(5)C(6)–C(5)–C(7) 121.7(5) N(2)–C(8)–C(9) 121.1(5)C(11)–C(7)–C(5) 123.5(5) C(8)–C(9)–C(10) 119.4(5)C(10)–C(11)–C(7) 119.3(5) C(9)–C(10)–C(11) 119.5(5)O(1)–H(1)–Cl(1) 141.9

Solvent

C(12)–C(13) 1.360(9) C(12)–C(17) 1.363(9)C(13)–C(14) 1.352(9) C(14)–C(15) 1.34(1)C(15)–C(16) 1.392(9) C(16)–C(17) 1.367(7)C(12)–C(18) 1.337(9)C(18)–C(12)–C(13) 114.9(8) C(18)–C(12)–C(17) 122.9(8)C(13)–C(12)–C(17) 122.2(6) C(14)–C(13)–C(12) 118.8(7)C(15)–C(14)–C(13) 121.4(7) C(14)–C(15)–C(16) 119.5(7)C(17)–C(16)–C(15) 120.1(6) C(12)–C(17)–C(16) 118.0(6)

1408 V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412

appearance of a new weak to medium intensity band in theregion 416–465 cm�1, assigned to mSn–N.

Weakening of the hydroxo bands in the furyltin(IV)complexes (3100–3150 cm�1) in comparison to the freeoxime (3250 cm�1), suggests that the donor center in thesecomplexes is the oxygen atom of the hydroxo group. Infavor of this conclusion, the mC@N appeared almost un-changed on complexation (1570 ± 2 cm�1 in complex;1575 cm�1 in free oxime) and a new medium to strongintensity absorption at 414–467 cm�1 may be assigned tomSn–O.

The 1H and 13C{1H} NMR spectra of all thesecomplexes have shown characteristic signals and multiplic-ities for R-Sn and for ligand protons and carbon atoms.However, in some cases due to the poor solubility of thecomplexes in CDCl3, the 13C NMR spectra could not beresolved.

In the 1H NMR spectra of alkyltin(IV) complexes withpyridyl oximes, the hydroxyl proton resonances aredeshielded (0.16–1.74 ppm) in comparison to the freeligand [19]. A significant shift in the ring proton resonancesof the 1:1 complexes (up to 0.52 ppm) in comparison to 1:2complexes (up to 0.16 ppm) has also been observed.Consistent with this, the 13C{1H} NMR spectra of 1:1derivatives exhibit a significant shift of the C-2, C-4 andC-6 carbon atoms of the pyridyl ring (up to 9.6 ppm).Further observation of a considerable shift in the C@Ncarbon resonances of all these derivatives (1.2–11.5 ppm)indicates coordination through the C@N nitrogen atom.

R-Sn protons exhibit characteristic signals and multi-plicities in the expected regions (0.92–2.18 ppm). In the13C NMR spectra of some of these derivatives, the alkylgroups are observed with coupling constants of the values1J(119Sn–13C) = 150.9–186.8 Hz and 2J(119Sn–13C) = 65.3–76.0 Hz.

The 119Sn{1H} NMR spectra of all the pyridyl-alkyl-tin(IV) adducts displayed a single resonance in the regiond �400.9 to �406.4 ppm, which falls in the range ofhexa-coordination at tin in mono-organotin(IV) complexes[27] and references therein. However, the presence of anequal intensity 119Sn chemical shift at �221.2 and�402.9 ppm in the 119Sn NMR spectrum of EtS-nCl3 Æ 2HON@C(Me)Py (5) suggests the existence of penta-hexa coordinated environment around tin atoms insolution. In 1:1 derivatives, the value of 119Sn chemicalshifts along with a significant shift in the ring proton/carbon resonances suggests participation of the ring nitro-gen in coordination. This conclusion was further corrobo-rated by the single crystal X-ray diffraction study of thecomplex, nBuSnCl3[HONC(Me)Py-2] Æ C6H5Me (2.tol.).

For all the 1:2 pyridyl adducts, the presence of only oneset of ligand resonances indicates that the ligand moietiesare in trans-positions to each other.

The chemical shift values for ligand protons in the 1HNMR spectra of the furyl derivatives show a deshielding ef-fect. The hydroxyl proton is shifted by 0.1–0.43 ppm in allthese derivatives, indicating coordination through the hy-

droxyl oxygen atom. Not much more shift (2.1–5.4 ppm)in the ring carbon resonances with a slight shift in theC@N carbon suggests non-participation of the ring oxygenas well as the C@N nitrogen atoms in coordination. This isin contrast to what was observed for pyridyl derivatives.

The value of the 119Sn chemical shift for the complex,nBuSnCl3 Æ HON@C(Me)C4H3O (d �200.5 ppm), suggestspenta-coordination around tin [27]. In the case of 1:2 com-plexes, the 119Sn chemical shifts are observed at d �324.6and �337.6 ppm, which falls in the range of hexa-coordina-tion around the tin atom. The lower value of these chemicalshifts for 1:2 complexes in comparison to their pyridyl ana-logs suggests weaker nucleophilicity of the 2-acetyl furyloxime. This information also gets support from the obser-vations that in the case of EtSnCl3 only the 1:2 complexforms, although the ligand was used in 1:1 molar ratio.The presence of two sets of ligand resonances in the 1Hand 13C{1H} NMR spectra of the 1:2 complexes indicatesthat the ligand moieties are cis to each other.

Table 7Selected distances (A) and angles (�) for nBuSnCl2[ONC(Me)Py-2]OH}2SnnBuCl Æ 0.5HONC(Me)Py-2 (12)a

Sn(1)–Cl(1) 2.473(2) Sn(2)–Cl(3) 2.524(2) Sn(3)–Cl(5) 2.397(2)Sn(1)–Cl(2) 2.445(2) Sn(2)–Cl(4) 2.417(2) Sn(3)–O(1) 2.107(4)Sn(1)–N(1) 2.241(5) Sn(2)–N(3) 2.238(5) Sn(3)–O(2) 2.122(4)Sn(1)–N(2) 2.211(5) Sn(2)–N(4) 2.224(5) Sn(3)–O(3) 2.103(4)Sn(1)–O(2) 2.087(4) Sn(2)–O(4) 2.075(4) Sn(3)–O(4) 2.159(4)O(2)–H(20) 0.83(6) O(4)–H(40) 0.84(6)H(20)� � �Cl(3) 2.38(5) H(40)� � �Cl(1) 2.51(7)O(2)� � �Cl(3) 3.207(5) O(4)� � �Cl(1) 3.253(5)Sn(1)–C(8) 2.127(6) Sn(2)–C(19A) 2.11(2) Sn(3)–C(23A) 2.10(2)C(8)–C(9) 1.512(6) C(19A)–C(20A) 1.512(6) C(23A)–C(24A) 1.512(6)C(9)–C(10) 1.518(7) C(20A)–C(21A) 1.518(7) C(24A)–C(25A) 1.518(7)C(10)–C(11) 1.511(7) C(21A)–C(22A) 1.512(7) C(25A)–C(26A) 1.512(7)N(1)–C(1) 1.349(8) N(3)-C(12) 1.358(8)N(1)–C(5) 1.331(8) N(3)–C(16) 1.327(8)N(2)–C(6) 1.290(8) N(4)–C(17) 1.281(8)O(1)–N(2) 1.342(6) O(3)–N(4) 1.354(7)C(1)–C(2) 1.377(9) C(12)–C(13) 1.379(9)C(1)–C(6) 1.468(9) C(12)–C(17) 1.474(9)C(2)–C(3) 1.385(9) C(13)–C(14) 1.389(9)C(3)–C(4) 1.37(1) C(14)–C(15) 1.38(1)C(4)-C(5) 1.392(9) C(15)–C(16) 1.371(9)C(6)–C(7) 1.493(8) C(17)–C(18) 1.485(9)

Cl(1)–Sn(1)–Cl(2) 168.29(6) Cl(3)–Sn(2)–Cl(4) 165.14(6) Cl(5)–Sn(3)–O(4) 165.5(1)Cl(1)–Sn(1)–N(1) 90.4(1) Cl(3)–Sn(2)–N(3) 87.3(1) Cl(5)–Sn(3)–O(1) 95.5(1)Cl(1)–Sn(1)–N(2) 80.9(1) Cl(3)–Sn(2)–N(4) 80.5(1) Cl(5)–Sn(3)–O(2) 88.2(1)Cl(1)–Sn(1)–O(2) 89.8(1) Cl(3)–Sn(2)–O(4) 88.2(1) Cl(5)–Sn(3)–O(3) 86.0(1)Cl(2)–Sn(1)–N(1) 84.9(1) Cl(4)–Sn(2)–N(3) 87.4(1) O(1)–Sn(3)–O(2) 83.8(2)Cl(2)–Sn(1)–N(2) 87.4(1) Cl(4)–Sn(2)–N(4) 84.7(1) O(1)–Sn(3)–O(3) 168.7(2)Cl(2)–Sn(1)–O(2) 89.8(1) Cl(4)–Sn(2)–O(4) 90.8(1) O(1)–Sn(3)–O(4) 91.7(2)N(1)–Sn(1)–N(2) 71.9(2) N(3)–Sn(2)–N(4) 72.0(2) O(2)–Sn(3)–O(4) 80.0(2)N(1)–Sn(1)–O(2) 154.0(2) N(3)–Sn(2)–O(4) 155.1(2) O(2)–Sn(3)–O(3) 85.0(2)N(2)–Sn(1)–O(2) 82.4(2) N(4)–Sn(2)–O(4) 83.1(2) O(3)–Sn(3)–O(4) 84.6(2)Cl(1)–Sn(1)–C(8) 99.5(2) Cl(4)–Sn(2)–C(19A) 103.6(5) Cl(5)–Sn(3)–C(23A) 102.3(6)Cl(2)–Sn(1)–C(8) 92.1(2) Cl(3)–Sn(2)–C(19A) 91.0(4) O(1)–Sn(3)–C(23A) 89.5(8)N(1)–Sn(1)–C(8) 103.5(2) N(3)–Sn(2)–C(19A) 100.4(6) O(2)–Sn(3)–C(23A) 168.1(8)N(2)–Sn(1)–C(8) 175.4(2) N(4)–Sn(2)–C(19A) 168.7(4) O(3)–Sn(3)–C(23A) 101.2(8)O(2)–Sn(1)–C(8) 102.1(2) O(4)–Sn(2)–C(19A) 104.1(6) O(4)–Sn(3)–C(23A) 90.3(6)Sn(1)–C(8)–C(9) 120.5(4) Sn(2)–C(19A)–C(20A) 122(1) Sn(3)–C(23A)–C(24A) 115(1)C(8)–C(9)–C(10) 112.8(5) C(19A)–C(20A)–C(21A) 112.8(5) C(23A)–C(24A)–C(25A) 112.8(5)C(11)–C(10)–C(9) 113.4(5) C(20A)–C(21A)–C(22A) 113.4(5) C(24A)–C(25A)–C(26A) 113.4(5)Sn(1)–O(2)–Sn(3) 125.6(2) Sn(2)–O(4)–Sn(3) 124.9(2) Sn(3)–O(2)–H(20) 107(5)Sn(1)–O(2)–H(20) 106(5) Sn(2)–O(4)–H(40) 100(6) Sn(3)–O(4)–H(40) 125(6)O(2)–H(20)–Cl(3) 178(5) O(4)–H(40)–Cl(1) 147(5)N(2)–O(1)–Sn(3) 124.5(3) N(4)–O(3)–Sn(3) 124.3(4)C(5)–N(1)–C(1) 119.8(6) C(16)–N(3)–C(12) 119.2(5)C(5)–N(1)–Sn(1) 123.0(4) C(16)–N(3)–Sn(2) 124.5(4)C(1)–N(1)–Sn(1) 116.3(4) C(12)–N(3)–Sn(2) 116.3(4)C(6)–N(2)–O(1) 117.7(5) C(17)–N(4)–O(3) 117.0(5)C(6)–N(2)–Sn(1) 119.8(4) C(17)–N(4)–Sn(2) 120.0(4)O(1)–N(2)–Sn(1) 122.0(4) O(3)–N(4)–Sn(2) 123.0(4)N(1)–C(1)–C(2) 121.3(6) N(3)–C(12)–C(13) 121.3(6)N(1)–C(1)–C(6) 115.5(6) N(3)–C(12)–C(17) 115.8(5)C(2)–C(1)–C(6) 123.2(6) C(13)–C(12)–C(17) 122.9(6)C(1)–C(2)–C(3) 118.7(6) C(12)–C(13)–C(14) 118.8(6)C(4)–C(3)–C(2) 120.0(7) C(15)–C(14)–C(13) 119.4(6)C(3)–C(4)–C(5) 118.4(6) C(16)–C(15)–C(14) 118.6(6)N(1)–C(5)–C(4) 121.7(6) N(3)–C(16)–C(15) 122.8(6)N(2)–C(6)–C(1) 115.6(5) N(4)–C(17)–C(12) 115.7(6)N(2)–C(6)–C(7) 122.4(6) N(4)–C(17)–C(18) 123.6(6)C(1)–C(6)–C(7) 122.0(6) C(12)–C(17)–C(18) 120.7(6)

a The bond lengths and angles for the free acid and the disordered butyl groups of lesser occupancy are not included.

V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412 1409

1410 V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412

The molecular structures of 2.tol and 12 have beenunambiguously established by single crystal X-ray diffrac-tion analyses. Distances and bond angles are given inTables 6 and 7, respectively, and the molecules are dis-played in the ORTEP diagrams in Figs. 1 and 2. Additionalmaterial available from the Cambridge CrystallographicData Centre comprises the final atomic coordinates andthermal parameters for all atoms and a complete listingof bond distances and angles. In the structure of 2.tol,

Fig. 1. ORTEP plot of the molecule nBuSnCl3[HON@C(Me)py-2] Æ C6H5M

Fig. 2. ORTEP plot of nBuSnCl2[ONC(Me)Py-2]OH}2SnnBuCl. Only the highacid is omitted for clarity. The non-hydrogen atoms are drawn with 50% prob

the central tin atom Sn(1) is coordinated with ring nitrogenN(2) and with oxime nitrogen N(1) of the same ligandmoiety having tin–nitrogen distances less than the sum ofthe van der Waal�s radii of tin and nitrogen atoms(Sn(1)–N(1); 2.269(5), Sn(1)–N(2); 2.248(5) A) [28]. Thesedistances are also less than the Sn–N distances present incorresponding tetraorganodistannoxanes, indicatingstronger coordinating interactions in the structure [13,15].The C(1) atom of the butyl group is in cis-position with

e. The non-hydrogen atoms are drawn with 50% probability ellipsoids.

er occupancy forms of the disordered butyl groups are shown and the freeability ellipsoids.

V. Sharma et al. / Inorganica Chimica Acta 359 (2006) 1404–1412 1411

Cl(1), although the angle C(1)–Sn(1)–Cl(1) is increased(105.2(2)�) due to intramolecular hydrogen bondingbetween H(1) and Cl(1) (2.32 A) resulting in a distortedoctahedral environment on central tin atom. A comparisonof the O(1)–H(1) distances with the free ligand [13] and alsowith a hybrid complex [{Me2Sn(ON@C(Me)C5H4-N)}2O}]2 Æ 2[2-NC5H4(Me)C@NOH] [15] reveals that thehydrogen bonding interaction is weaker in this case (0.83in 2.tol, 1.01(5) in tetramethyldistannoxane derivative and1.02(2) A in free ligand). The remaining two chlorine atomsCl(2) and Cl(3) are in trans-positions to each other (Cl(2)–Sn(1)–Cl(3); 164.72(5)�). All three tin–chlorine distancesare different.

It is worthwhile to mention here that the structure of atrinuclear hydroxo bridged stannoxane {nBuSnCl2(ON@C(Me)Py-2)OH}2SnnBuCl Æ 0.5 HON@C(Me)Py-2 (12)exhibits interesting structural features which are ratheruncommon. In the structure of 12, the tin atoms areinvolved in a linear stannoxane framework with asym-metric Sn–O–Sn bridging. The presence of both an Sn–O(H)–Sn bridge and an Sn–O–N–Sn bridge betweentwo Sn atoms appears to be unique even though the bondlengths and angles are as expected. The terminal Sn(1)and Sn(2) tin atoms adopt a distorted octahedral environ-ment with the coordinating interaction of both the ringand oxime nitrogen atoms of the ligand moiety beingwith the central tin atom Sn(3). It is interesting to men-tion here that the degree of coordinating interactionbetween tin and nitrogen atoms is greater in these com-plexes in comparison to their corresponding tetraorgan-odistannoxanes [13,15]. The central tin atom Sn(3) isagain in a distorted octahedral environment and theligand moieties are in trans-position to each other[O(1)–Sn(3)–O(3); 168.7(2)�]. The other two oxygen atomsare cis [O(2)–Sn(3)–O(4); 80.02]. This small angle is asso-ciated with a distinctive feature of this structure with twosignificant O–H� � �Cl hydrogen bonds, O(2)–H(20)� � �Cl(3) and O(4)–H(40)� � �Cl(1).

4. Conclusions

Except in the 1:1 complexes of furyl ketoxime withnBuSnCl3, in all these derivatives the tin atoms are in dis-torted octahedral environment. In the structure of 2.tol.,both the nitrogen atoms (ring as well as the oxime nitro-gens) are taking part in coordination and occupying cispositions to each other. Unique unsymmetrical Sn–O(H)–Sn and Sn–O–N–Sn bridges are present in the structureof trinuclear hydroxo bridged stannoxane 12 that was ob-tained on the hydrolysis of 6. All three tin atoms arehexa-coordinated with distorted octahedral environment.There are few examples where the functionalized heteroatom takes part in intramolecular bond formation as foundin the cis octahedral structure of 2.tol. Further the structureof the hydrolytic intermediate {nBuSnCl2(ONC(Me)Py-2)OH}2SnnBuCl Æ 0.5HONC(Me)Py-2 (12) clearly indicatesthe formation of polymeric network during hydrolysis,

providing a suggestive route to inorganic–organic hybridmaterials.

5. Supplementary material

Crystallographic data for the structures reported in thispaper have been deposited with the Cambridge Data Cen-tre for compound 2.tol., No. 267338 and compound 12 No.267339. Copies of this information may be obtained free ofcharge from The Director, CCDC, 12 Union Road,Cambridge CB2 1Ez, UK (fax: + 44 1223 336033; e-mail:deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).

Acknowledgements

We are thankful to DST and UGC-Delhi, for financialsupport. V.S. is thankful to UGC-Delhi for providingPost-doctoral fellowship. M.B.H. thanks the UK Engineer-ing and Physical Sciences Council for support of the X-rayfacilities at Southampton. J.E.D. thanks the University ofWindsor for financial support.

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