New bonding mode of (dithioformato)phosphine ligand: synthesis, reactivity and crystal structure of [W(CO)5(PPh2CS2)]Et4N

1380 _{J . CHEM. S O C . , CHEM. C O M M U N . , 1993}

New Bonding Mode of (Dithioformato)phosphine Ligand: Synthesis, Reactivity and

Crystal Structure of [W(CO)5(PPh2CS2)]Et4N

Kuang-Hway Yih, Ying-Chih Lin,* Ming-Chu Cheng and Yu Wang

Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China

The phosphorus coordination of the diphenyl(dithioformato)phosphine ligand in [W(CO)5(PPh2CS2)]Et4N, 1 has been confirmed by an X-ray diffraction analysis; alkylation of 1 at the S atom results in the formation of W(CO)5[PPh2(CS2R)], 4 in high yield.

The chemistry of a zwitterionic trialkylphosphonium dithio- dinuclear complexes, bridging coordinations-7 in different carboxylate ligand, PR3+CS2-, with three possible coordina- fashions, are known. On the other hand, the chemistry of tion sites, has attracted considerable attention in recent anionic dialkylphosphinodithioformates, PR~CSZ-, is much years.1-8 Various bonding modes, which include monodentate less studied. The zirconium complex Zr(~-CSH5)2[q2- coordination,172 bidentate coordination by chelation3.4 and, in S2CP(SiMe3)2]C1 is the only example8 reported in the litera-

J . C H E M . SOC., C H E M . COMMUN., 1993 1381 I C C 0 0 O

1-

0

w'

-

W O q ' c o PhpHP' A'CO 0 0

OC.. I ,CO i OC.. I , S O

-

ii

vi

I

1 i v l 5a 2 4 a ; R = M e b; R = C3H5 C; R = C3H3

Scheme 1 Reagents and conditions: i, Me3N0, PhzHP, MeOH, 25 "C, 4 h; ii, BunLi, CS2, Et4NBr, MeCN, 25 "C, 1 min; iii, heat, THF,

2 h; iv, RX, CH2C12, 25 "C, 1 min (R = Me, X = I; R = C3H5, X = Br; R = C3H3, X = Br); v, (pip)2W(CO)4, MeCN, 80°C, 1 h; vi, BunLi, Et4NBr, MeCN, 25 "C (pip = piperidine)

ture. The two sulfur containing ligands bond to the metal centre exclusively through S-coordination in all of the reported complexes mentioned above. Herein we report a new coordination mode of the PR2CS2- ligand, which is bonded to the metal through phosphorus-coordination with a o,ql-bonding mode.

Treatment of W(CO)S(PPh2H) with Bu*Li and CS2 in the presence of Et4NBr afforded in 80% yield a red product, which was identified as [W(CO)s(PPh2CS2)]Et4N, 1.9 Satis- factory spectroscopic? and analytical data of 1 were obtained. In the 31P NMR spectrum of 1, a resonance at 6 59.08 with a

t

Selected spectroscopic data: l H and 13C-{ lH} NMR are recorded at 298 K in CD3CN and given as 6 relative to SiMe4, 31P NMR data: H3P04 external standard. For 1: IR vlcm-l (KBr), v(C0): 2062m, 1979~, 1947~, 1 9 0 4 ~ ~ ; v(CS): 1027~, 9 9 0 ~ . 3'P NMR: 59.08 ('1W-p 238.24 Hz). 'H NMR: I.. 18 (tt, 12H, N-CH2-CH3, 3 J ~ - ~ 1.87, 3J~43 7.3 Hz), 3.10 (9, 8H, N-CH2-CH3, 3JH-H 7.3 Hz), 7.35 (m, 6H, Ph), 7.66 (m, 4H, Ph). l3C NMR: 7.6 (N-CH2-CH3), 53.0 (N-CHZ-CH~), 2: IR vlcm-1 (THF), v(C0): 1993m, 1879vs, 1859sh, 1833s. 31P (m, 6H, Ph), 7.69 (m, 4H, Ph). I3C NMR: 7.5 (N-CH2-CH3), 52.8 3a: IR vlcm-l (KBr), v(C0): 2071m, 1988s, 1957sh, 1911vs. 31P NMR: 64.26 (lJw-p 248.0 Hz). lH NMR: 2.71 ( s , 3H, CH3), 7.50 (m, 6H, Ph), 7.66 (m, 4H, Ph). l3C NMR: 21.9 (CH3), 198.1 (d), 198.1, 3b: IRvlcm-1 (KBr), v(C0): 2070m, 1988s, 1929vs. 3IPNMR: 64.49 5.19,5.25,5.34 (q,2H, S-CH2CHCH2), 5.78 (m, l H , S-CH2CHCH2), 7.53 (m, 6H, Ph), 7.68 (m, 4H, Ph). 13C NMR: 41.0 (S-CH2CHCH2), 3c: IR vlcm-l (KBr), v(C0): 2073m, 1957m, 1919vs. 31P NMR: 2.89), 4.04 (d, 2H, S-C&CCH, 35H-H 2.89), 7.48 (m, 6H, Ph), 7.69 (m, 4H, Ph). 13C NMR: 26.6 (s, SCH2CCH), 72.7 (s, SCH2CCH), 4a: IR vlcm-1 (KBr), v(C0): 1987m, 1854m, 1830vs, 1800vs, 1783s; 1.87, 35H-H 7.3 Hz), 1.59 (m, 6H, N-CH~-CH~-CHZ), 3.15 (4, 8H, N-CH2-CH3, 35H-H 7.3 Hz), 3.82 (m, 4H, N-CH-CH2-). l3C NMR: 6 199.6 (CO), 255.4 (CS2). NMR: 24.23 (lJW-p 187.4 Hz). 1H NMR: 1.17 (tt, 12H, N-CH2-CH3, 3JN-H 1.87, 3JH-H 7.3 HZ); 3.13 (4, 8H, N-CH2-CH3, 3 . f ~ 4 . 3 7.3), 7.43 (N-CH2-CH3), 205.8, 213.9, 214.0, 214.5, 215.2 (CO), 264.6 (CS2). 199.8, 200.3 (CO), 240.3 (CS2). (t , 'JW-P 248.6 Hz). 'H NMR: 3.96,4.00 (q,2H, S-CH2CHCH2), 5.14, 121.0 (S-CH2CHCH2), 129.6, (Ph), 130.6 (S-CH;?CHCH2), 198.0, 199.7, 200.2 (CO), 238.3 (CS2). 64.64 (t, *Jw-p 189.12 Hz). 'H NMR: 2.47 (t, l H , S-CH2CCH, 3JH-H 75.8 (s, SCHZCCH), 196.9 (d), 198.3, 198.8 (CO). V(CN): 1476m. 'H NMR (CD3CN): 1.21 (tt, 12H, N-CHZ-CH,, 3JN4.3 7.6 (N-CHZ-CH~), 24.7 (N-CH2-CH2-CH2), 26.0 (N-CHz-CHz), 47.5 (N-CH2-CH2), 52.9 (N-CH2-CH3), 204.0 (CO), 213.0 (CS2), 213.8 (CO). 4b: IR v/cm-l (MeCN), v(C0); 2072m, 1937vs. 31P NMR: -10.31 ('Jw-p 224.58 Hz). 'H NMR: 6.95 (d, ZH, PH, Jp-H 358 Hz), 7.47,7.67 (m, 10H, Ph).

Fig. 1 ORTEP drawing for the anion of [W(CO)s(PPh2CS2)]Et4N, 1

(Ph = C&), with thermal elli soids shown at the 50% probability level. Selected bond distances

(I)

and bond angles (") are as follows: W-P 2.553(1), P-C 1.872(5), C-S(l) 1.669(5), C-S(2) 1.650, W-S(l) 4.056( 2), W-S(2) 4.946( 2) ; C( 4)-W-P 97.5( 1 ) , W-P-C 112.2(2), P-C-S( 1) 11 2.7( 3), P-C-S( 2) 119.6(3).

tungsten satellite 238.24 Hz) indicates phosphorus coordination of the ligand. The unusual bonding mode for the PPh2CS2- ligand has been confirmed by an X-ray diffraction study.$ The structure of the anion of 1 is shown in Fig. 1. The

$. Crystal data for 1: C2&30No$S2W, space group Pi, a = 10.688(3),

b = 11.070(2), c , = 12.785 2 ) A , (Y = 88.26(1), p = 81.87(2), y =

4.32 mm-1, observed reflections 4557,28,,, = 2-49.8". The structure was solved by using the heavy atom method, a series of difference Fourier maps and refined by least-squares refinements with R = 0.028 and R , = 0.025. Hydrogen atoms were included in the structure factor calculations in their expected positions on the basis of idealized bonding geometry but were not refined by least-squares. Atomic coordinates, bond lengths and angles, and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre. See Notice to Authors, Issue No. 1.

1382

coordination geometry about the tungsten atom can be described as distorted octahedral. The CS2 unit is attached to the phosphorus atom through carbon with no bonding interaction between the tungsten metal centre and the sulfur atoms, the W-S(l) and W-S(2) distances are 4.056(2) and 4.946(2)

A,

respectively. Obviously, 1 was formed by a deprotonation step followed by a nucleophilic attack at the carbon atom of CS2. In the reaction of W(C0)4(NHCSHlo)2 with Bu*Li and CS2, the CS2 insertion into the W-N bond gave [W(C0)4(S2CNCSHlo)]Et4N 5a. The insertion of CS2 into the Pt-F bond of [Pt(PPh3)2F][HF2] gave [Pt(S2CF)(PPh&], where the dithiofluoroformate ligand coordinates to Pt through two S atoms.10 To our knowledge, complex 1 is the first example of phosphorous coordination of the PR2CS2- ligand.

The reaction of 1 with Me1 in CH2C12 gave a neutral complex W(C0)5[PPh2(CS2CH3)] 4a in 80% yield. The alkylation takes place at the sulfur atom. In the 13C NMR

spectrum of 4a, a singlet at 6 21.86 is attributed to the Me of the -CS2Me group.11 Lack of Jp-H coupling of this resonance contrasts with the observation of a doublet resonance (2Jp-c 14.7Hz)12 for the methyl group of the compound [W(q- C5H5) { SZC(Me)PMe3} (C0)2] where the methyl group is bound to the carbon atom. The 31P NMR spectrum of 4a shows a resonance at 6 64.26 (lJw-p 247.95 Hz), close to that of 1. Two other alkylation products W(CO)S[PPh2- (CS2CH2CH=CH2)], 4b and W(CO)S[PPh2(CS2CH2- G C H ) ] , 4c from allylic bromide and propynyl bromide, respectively, were prepared. The resonances in the 3lP NMR spectra of 4b and 4c are at 6 64.49 (~Jw-p 248.56 Hz) and 6 64.64 (lJw-p 189.12 Hz), respectively. Complex 4c decom- posed at room temp. in about 20 min.

Thermolysis of 1 in tetrahydrofuran (THF) gave a cationic product identified as [W(CO)4(PPh2CS2)]Et4N, 3 based on its analytical and spectroscopic data (see Scheme 1). The IR spectra of 3 exhibits four absorption bands at 1993,1879,1859 and 1833 cm-1, a typical pattern for a cis-M(CO)& unit in octahedral geometry. In the mass spectrum of 3, the molecular ion along with the CO fragmentations are detected with a highest observed peak at mlz 817 corresponding to the [W(C0)4(PPh2CS2][Et4N]2+ cation. The 31P NMR spectrum of 3 shows a resonance at 6 24.23, again with a tungsten satellite 187.4 Hz) indicating phosphorus coordination.

J . C H E M . SOC., C H E M . C O M M U N . , 1993

Compared with the 31P chemical shift of the compound 1, the relatively up-field shift of this resonance suggests different chemical environments for the PR2CS2- ligand in 1 and 3. A new chelation mode of the bidentate PR2CS2- ligand i.e. chelation through the phosphorus and one of the sulfur atoms is proposed. The structure and chemical reactivity of 3 are currently under investigation.

Attempts to prepare a dinuclear complex using the PR2CS2- unit of 1 as a bridging ligand led to cleavage of the P-CS2 bond. For example, in the reaction of 1 with [W(C0)4(NHC5H10)2], the CS2 of 1 inserted into the W-N bond of [W(C0)4(NCH5H10)2] to yield the known dithiocar- bamate complex [W(C0)4(q2-S2CNCSH1o)]Et4N 5a and the starting material W(CO)S(PPh2H) 5b.

We thank the National Science Council of Taiwan, the Republic of China for support.

Received, 20th April 1993; Corn. 3102283H

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