Reactivity of the osmium antimony cluster Os3(CO)10(MU H)(MU sbph2) with some group 16 compounds

Chapter 1: Organometallic chemistry of clusters containing osmium or ruthenium and the heavier group 15 elements 2.1... Chapter 1 Organometallic chemistry of clusters containing osmium

REACTIVITY OF THE OSMIUM-ANTIMONY CLUSTER Os3(CO)10(µ-H)(µ-SbPh2) WITH SOME GROUP 16

2010

Acknowledgements

First of all, I would like to thank my supervisors, A/P Fan Wai Yip, A/P Leong Weng Kee and A/P Richard Wong Chee Seng for their patient guidance and invaluable advice throughout the project

Next, I would like to thank all the members of the groups In particular, I would like to express my gratitude to Seah Ling, Kien Voon, Garvin, Xue Ping, Rakesh, Boon Ying and Kai Ning, for their help, support and fruitful discussions

I am also grateful to all the staff in the instrument labs for making data acquisition possible

Last but not least, I would like to thank my lovely family members for their prayers and motivation support that made the project complete

Chapter 1: Organometallic chemistry of clusters containing osmium

or ruthenium and the heavier group 15 elements

2.1 Reaction of Os3(CO)10(µ-H)(µ-SbPh2) with REER and PhEH p.16

4.3 Synthesis of organometallic clusters containing transition

metal- lanthanide bonds

(a) Synthesis of Os3(CO)11[P(CH2CH2C9H7)Ph2], 13

(b) Synthesis of Os3(CO)11[P(OC4H3)Ph2], 14

p.44

p.44 p.44 4.4.3 Reaction of Cp*2Sm(THF)2 with 13 or 14

(a) Reaction with Os3(CO)11[P(CH2CH2C9H7)Ph2], 13

(b) Reaction with Os3(CO)11[P(OC4H3)Ph2], 14

p.45 p.45 p.45 4.4.4 Synthesis of (THF)Yb[(C9H7CH2CH2)PPh2]3, 15 p.45

4.4.5 Reaction of (THF)Yb[(C9H7CH2CH2)PPh2]3 with

MOLECULAR NUMBERING SCHEME

The short line extending from Os (in the molecular structure diagrams) represents a

coordinative bond from carbon monoxide to osmium (Os-CO)

1 Os3(CO)10(µ-H)(µ-SbPh2)

Os

H Os

Os SPh

3b Os3(CO)10(µ-H)(µ-SePh)

Os

H Os

Os SePh

3c Os3(CO)10(µ-H)(µ-TePh)

Os

H Os

Os TePh

5a

5b

5c Unknown compounds from reaction of 1 or 2 with REER or REH

5d (R = Ph, Me, p-tolyl; E = S, Se, Te)

16 Unknown compounds from reaction of 11 with 15

Os Os

Os L

H

D HOs3(CO)10(µ-SbPh2)L

Os Os

Os H

L

E HOs3(CO)10(µ-SbPh2)L

Os Os

Os L

E R

H HOs3(CO)10(µ-SbPh2)( R2E2)or HOs3(CO)10(µ-SbPh2)(REH),

R = Ph or Me; E = S, Se or Te

Os Os

Os E

H

R

ER or H

Abbreviations

EA Elemental Analyses

ESI Electrospray Ionization

FAB Fast Atom Bombardment

Q-Tof Quadrupole Time-of-Flight

NMR Nuclear Magnetic Resonance

ORTEP Oak Ridge Thermal Ellipsoid Plot

THF Tetrahydrofuran

TLC Thin Layer Chromatography

LIST OF TABLES

p.26

LIST OF SCHEMES

bonds through ligand assistance

p.40

bonds through ligand assistance

p.41

Chapter 1 Organometallic chemistry of clusters containing osmium or

ruthenium and the heavier group 15 elements

Organometallic clusters are compounds with two or more metal atoms in which metal-metal bonding is present.1 Beginning from the 1970s, numerous novel clusters have been reported every year.2 The initial stimulus was the cluster-surface analogy, i.e., a metal cluster may serve as a structural model for the interaction of organic ligands on the surface of bulk metal The gradual evolution of cluster structure, magnetic behavior, and ionization potential with increasing cluster size is another reason for the interest in cluster compounds When several transition metal atoms bind together, they tend to agglomerate in order to form the maximum number of metal-metal bonds, instead of forming chains. 3

Main group-transition metal cluster compounds have been of great interest in the field

of organometallic chemistry due to their unique structural and reactivity patterns The introduction of main group elements into a transition metal cluster framework enhances its polarity and changes the reactivity chemistry from that of the homometallic system; this is the interplay between the differing properties of the elements Furthermore, there is a steady movement towards the view that the main group elements in many such compounds should be better regarded as an integral part

of the cluster core, rather than as ligands.4-6

Of the transition metals, among those most well-studied because of their propensity to form metal-metal bonded compounds are the heavier group 8 metals – ruthenium and osmium The chemistry of these two metals are often similar, differing mainly in their reactivity The next section will therefore examine the structural types that are known

for mixed metal clusters containing ruthenium or osmium and the heavier group 15

elements, viz., As, Sb and Bi

1.1 Structural feature

In contrast to the large number of structures known for Os-P and Ru-P clusters, there are very few examples of clusters containing osmium or ruthenium with the heavier group 15 elements Many of the clusters containing a heavier group 15 element have them present as a terminal ER3 (E = As, Sb, Bi) ligand Examples include

Os3(CO)10(AsPh3)2,7 Os3(CO)11(SbPh3),8 and Ru3(CO)9(SbPh3)(Ph2PCH2PPh2).9Clusters in which the E atom is bonded to two or more metal atoms are given in Table 1.1

In comparison with Os-P clusters, those containing a heavier group 15 element tend to adopt an open structure via M-M bond cleavage This may be due to the larger size of the heavier group 15 elements favoring bridging over a longer M…M distance As has been observed elsewhere, metal-metal bond lengths involving transition metals vary over a wide range and are very prone to steric and electronic effects of the substituents.10-11 The Ru-Ru bond lengths for the clusters in Table 1.1 span the range 2.731(1) to 3.1700(5) Å, i.e., a spread of 0.44 Å; the corresponding range for the Os-

Os bond is 2.7524(6) to 3.2332(12) Å, i.e., a spread of 0.48 Å The bridging hydride is

an example of ligand effects on metal-metal bond lengths The presence of a bridging hydride tends to lengthen the Os-Os bond, while a doubly hydride-bridged Os-Os bond tends to be contracted.10-11 The range from the M-E bond lengths are given in Table 1.2 The ranges reflect the covalent radii of the group 15 elements (1.19 Å, 1.38

Å and 1.46 Å for As, Sb and Bi, respectively.)

Table 1.1 Known EM clusters (M = Ru, Os; E = As, Sb, Bi)

HOs2(CO)6(AsMe2)(C6H4)

H2Os3(CO)11(AsR); R = H, Me Ph

Ru2(CO)6(µ-H)(AsMe2){C6H4Cr(CO)3}

-C6H4)L ; L = PPh3, PMe2Ph

Os3(CO)9(AsC6H4Me)(C6H3Me)

Os3(CO)8(AsC6H4Me)(C6H3Me){As(p-tolyl)3}

H2Os3(CO)9(AsC5H4SiMe3)

Os3(CO)9(µ-H)(SbPh2)(AsPh3)

Os3(CO)10(µ-H)(SbPh2)

Os3(CO)9(µ-H)(SbPh2)(C6H5)L ; L = PPh3, PMe2Ph

Ru3(CO)8(µ-H)(AsMe2){C6H4Cr(CO)3}

Ru3(CO)6(µ-CO)(AsPh2)(µ-OCC12H7)

H2Ru3(CO)8(AsPh3)(AsPh)

H2Ru3(CO)7(AsPh3)2(AsPh)

E E

Table 1.2 Ranges of the M-E bond lengths

Ru-As 2.366(1)-2.8568(4) Os-As 2.406(1)-2.5730(7)

Ru-Sb 2.5973(4)-2.7905(5) Os-Sb 2.5376(11)-2.8916(6)

Ru-Bi 2.756(1)-2.839(1) Os-Bi 2.799(2)-2.923(1)

1.2 Reactivity

Earlier work from our group has shown that osmium-antimony clusters often show novel reactivity patterns which are different from the phosphorus or arsenic analogues One of the more well-studied cluster among these is Os3(CO)10(µ-H)(µ-SbPh2), 1,

which can be obtained in reasonable yield from the salt elimination reaction of [Os3(µ-H)(CO)10(µ-CO)]- and an excess of Ph2SbCl in THF (Scheme 1.1) Two other products, Os3(CO)10(µ-SbPh2)2, A, with an SbPh2 bridging a closed Os-Os edge, and [Os3(CO)10(µ-H)(µ-SbPh2)]2, B, a dimeric version of cluster 1 which comprises two

Os3(CO)10(µ-H)(µ-SbPh2) moieties linked via two SbPh2 bridges, are also obtained

Cluster A can also be obtained from the reaction of 1 and Ph2SbCl, and the Os-Os bond bridged by the SbPh2 moiety is fluxional.39

Cluster 1 undergoes nucleophilic addition reactions with two-electron donors L

(where L = EPh3, CO or tBuNC) via an Os-Os bond cleavage Depending on the identity of L, up to three isomers have been observed (Scheme 1.2).21-22 It has been established that tertiary phosphines and arsines tend to occupy equatorial positions while N and C donor ligands which are rod-like, such as nitriles and isonitriles, tend

to occupy axial positions; this has been attributed to stereoelectronic reasons;2 The axial position is electronically favored as it places poorer π-acid ligands trans to a CO,

as opposed to mutually trans COs if the ligand is in an equatorial position For phosphines and related sterically bulky ligands, the greater steric hindrance of the

axial position disfavors it In the reaction of cluster 1 with tBuNC, however, three isomers were observed, in which the isonitrile ligand occupied equatorial and axial positions.22 These adducts can undergo decarbonylation, especially at elevated

temperatures For example, the reaction of cluster 1 with AsPh3 at 65°C gave

Os3(CO)9(µ-H)(µ-SbPh2)(AsPh3), F, in which all the three Os-Os bonds remained

intact and the AsPh3 occupied an equatorial position on the unique unbridged osmium.21

Os

H Os

Os L

Os H

L SbPh2 +

L = EPh3, CO, tBuNC;

In contrast to the above, the reactivity of 1 with the chalcogens are unexplored The

contribution of transition metal-carbonyl compounds and the chalcogens introduces novel structural and reactivity features For example, it has been found that

Os3(CO)12-n(NCCH3)n (n = 1 or 2) reacted with R2E2 (R = Ph or Me; E = S, Se or Te)

to afford clusters Os3(CO)10(µ-ER)2, G, in two isomeric forms G1 and G2. 46-48 In line with our general interest in transition metal-main group element mixed-metal clusters,

we embarked on an exploration of the chemistry of 1 with some compounds of the

E R

1.3 References

1 Mingos, D M P.; Wales, D J Introduction to Cluster Chemistry, 1990

2 Deeming, A J In Comprehensive Organometallic Chemistry II; Abel, E W.; Stone,

F G A.; Wilkinson, G.; Eds.; Elsevier: Oxford, 1995; Vol 7, Chap 12, pp

5 Whitmire, K H Adv Organomet Chem 1998, 42, 1

6 Leong, W K Bull Sing N I C 1996, 24, 51

7 Bradford, C W.; Nyholm, R S J Chem Soc., Dalton Trans 1973, 529

8 J N Nicholls, M D Vargas, Inorg Synth 1989, 28, 232

9 Shawkataly, O.; Ramalingam, K.; Fun, H K.; Abdul Rahman, A.; Razak, I A J

Cluster Sci 2004, 15, 387

10 Pomeroy, R K In Comprehensive Organometallic Chemistry II; Abel, E W.; Stone,

F G A.; Wilkinson, G.; Eds.; Elsevier: Oxford, 1995; Vol 7, Chap 15, pp

14 Guldner, K.; Johnson, B F G.; Lewis, J J Organomet Chem 1988, 355, 419

15 Cullen, W R.; Rettig, S J.; Zhang, H Organometallic 1993, 12, 1964

16 Arce, A J.; Deeming, A J J Chem Soc., Dalton Trans 1982, 1155

17 Cooksey, C J.; Deeming, A J.; Rothwell, I P J Chem Soc., Dalton Trans 1981,

1718

18 Guldner, K.; Johnson, B F G.; Lewis, J.; Owen, S M.; Raithby, P R J

Organomet Chem 1988, 341, C45

19 Tay, C T.; Leong, W K J Organomet Chem., 2001, 625, 231

20 Chan, K H; Leong, W K.; Mak, K H Garvin Organometallic, 2006, 25, 250

21 Chen, G.; Leong, W K J Chem Soc., Dalton Trans 1998, 2489

22 Chen, G.; Leong, W K J Organomet Chem 1999, 574, 276

23 Deng, M.; Leong, W K Organometallics 2002, 21, 1221

24 Chen, G.; Leong, W K Organometallic 2001, 20, 2280

25 Chen, G.; Deng, M.; Lee, C K.; Leong, W K.; Tan, J.; Tay, C T J Organomet

Chem 2006, 691, 387

26 Chen, G.; Deng, M.; Lee, C K.; Leong, W K Organomeallic 2002, 21, 1227

27 Knox, S A R.; Lloyd, B R.; Morton, D A V.; Nicholls, S M.; Orpen, A G.;

Vinas, J M.; Weber, M.; Williams, G K J Organomet Chem 1990, 394, 385

28 Ang, H G.; Ang, S G.; Du, S W J Organomet Chem 1999, 590, 1

29 Johnson, B F G.; Lewis, J.; Massey, A D.; Braga, D.; Grepioni, F J Organomet

Chem 1989, 369, C43

30 Jackson, P A.; Johnson, B F G.; Lewis, J.; Massey, A D.; Braga, D.; Gradella, C.;

Grepioni, F J Organomet Chem 1990, 391, 225

31 Arce, A J.; Deeming, A J.; DeSanctis, Y.; Garcia, A M.; Manzur, J.; Spodine, E

34 De Silva, R M.; Mays, M J.; Solan, G A J Organomet Chem 2002, 664, 27

35 Süss-Fink, G.; Guldner, K.; Herberhold, M.; Gieren' A.; Huebner, T J Organomet

Chem 1985, 279, 447

36 Chen, G.; Leong, W K J Cluster Sci 2006, 17, 111

37 Ang, H G.; Hay, C M.; Johnson, B F G.; Lewis, J.; Raithby, P R.; Whitton, A J

J Organomet Chem 1987, 330, C5

38 Gremaud, G.; Jungbluth, H.; Stoeckli-Evans, H.; Süss-Fink, G J Organomet Chem

1990, 388, 351

39 Chen, G.; Leong, W K J Chem Soc., Dalton Trans 2000, 4442

40 Lee, Y W.; Ph.D thesis, National University of Singapore, 1995

41 Ang, H G.; Ang, S G.; Du, S.; Sow, B H.; Wu, X J Chem Soc., Dalton Trans

1999, 2799

42 Cullen, W R.; Rettig, S J; Zheng, T C Organometallic 1995, 14, 1466

43 Field, J S.; Haines, R J.; Smit, D N J Organomet Chem 1982, 240, C23

44 Deng, M.; Leong, W K J Chem Soc., Dalton Trans 2002, 1020

45 Chen, G.; Leong, W K Organometallic 2001, 20, 5771

46 Johnson, B F G In Transition Metal Clusters; Johnson, B F G.; Ed.; Wiley:

Chichester, 1980; Chap 1

47 Arce, A J.; Arrojo, P.; De Sanctis, Y Polyhedron 1992, 11, 1013

48 Zhang, J.; Leong, W K J Chem Soc., Dalton Trans 2000, 1249

Chapter 2 Reaction of Os 3 (CO) 10 (µ-H)(µ-SbPh 2 ), 1 with group 16 compounds

As mentioned in the previous chapter, antimony-containing osmium clusters are known to undergo nucleophilic addition.1-2 While triosmium clusters are known to react with group 16 elements, in contrast, the reactivity of antimony-containing osmium clusters with group 16 elements has not been explored In this section, the synthesis and reactivity of the cluster Os3(CO)10(µ-H)(µ-SbPh2), 1 with some group

16 compounds are reported

The cluster Os3(CO)10(µ-H)(µ-SbPh2), 1 reacted with an equimolar of REER or PhEH (R = Ph, Me; E = S, Se, Te) in hexane at room temperature to afford a yellow solid (5);

TLC separation of the supernatant gave several bands in low yields, of which the two

major ones (3 and 4) have been characterised (Scheme 2.1)

Os

H Os

Os RE

Os

ER

Unknown Hex RT

5a: R = Ph, E = S 5b: R = Ph, E = Se 5c: R = Ph, E = Te 5d: R = Me, E = Se

The identities of Os3(CO)10(µ-H)(µ-SPh) (3a), Os3(CO)10(µ-H)(µ-SePh) (3b),

Os3(CO)10(µ-H)(µ-TePh) (3c) and Os3(CO)10(µ-H)(µ-SeMe) (3d) were made on the

basis of their IR spectra in the carbonyl region and bridging hydride resonance in their 1

H NMR spectra, which matched those reported earlier;3-5 the IR spectrum for 3a

2000 2050

2100 2150

The profiles of the CO stretching vibrations of 4a and 4b were similar, indicating that

they were analogous products (Figure 2.2) The pattern was also different from that for the two known clusters Os3(CO)10(µ-SbPh2)(µ-EPh2) (E = P or Sb, 4e and 4f,

respectively), in particular, an extra peak at 2031 cm-1 or 2029 cm-1 was observed for

2000 2050

2100 2150

tabulated values for 4b, 4e and 4f.6