-LIGAND COMPLEXES AS SUPRAMOLECULAR

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ORGANOMETALLIC P

n

-LIGAND COMPLEXES AS SUPRAMOLECULAR

BUILDING BLOCKS

Dissertation zur Erlangung des

Doktorgrades der Naturwissenschaften (Dr. rer. nat.) der Naturwissenschaftlichen Fakultät IV - Chemie und Pharmazie

der Universität Regensburg

vorgelegt von

Laurence John Gregoriades aus Nicosia, Zypern

Regensburg 2006

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Diese Arbeit wurde angeleitet von Prof. Dr. Manfred Scheer.

Promotionsgesuch eingereicht am: 2 Februar 2006 Tag der mündlichen Prüfung: 7 März 2006

Vorsitzender: Prof. Dr. Henri Brunner

Prüfungsausschuss: Prof. Dr. Manfred Scheer Prof. Dr. Rainer Winter Prof. Dr. Ruth Gschwind

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Die vorliegende Arbeit wurde in der Zeit von September 2001 bis März 2004 am Institut für Anorganische Chemie der Universität Karlsruhe (TH) und von April 2004 bis Januar 2006 am Institut für Anorganische Chemie der Universität Regensburg unter Anleitung von Herrn Prof.

Dr. Manfred Scheer angefertigt.

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To my two families

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Regensburger Alchemie, Roswitha Neumann, 2006 (modified illustration of The Alchymist, In Search of the Philosopher’s Stone, Discovers Phosphorus, and prays for the successful Conclusion of his operation, as was the custom of the Ancient Chymical Astrologers, Joseph Wright of Derby, 1771, taken from http://www.ibiblio.org/wm/paint/auth/wright/).

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“One lesson we learn is that when pure science is being done, and sometimes long after it is done, it is usually impossible to predict what the consequences will be. This shows how important it is to support pure science even if it has no obvious consequences. The important criterion should be the quality of the work, not its possible practical applications.”

Keith J. Laidler, To Light Such a Candle, Oxford University Press, Oxford, 1998

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4.6. Synthesis of the Complexes Based on [Cp*Mo(CO)2(η³-P3)] 124 4.6.1. [Cu2(µ-Cl)2{Cp*Mo(CO)2(µ,η³:η²-P3)}2] (76a) 124 4.6.2. [Cu2(µ-Br)2{Cp*Mo(CO)2(µ,η³:η²-P3)}2] (76b) 124 4.6.3. [Cu(µ-I){Cp*Mo(CO)2(µ3,η³:η¹:η¹-P3)}]n (77) 125 4.6.4. [Ag{Cp*Mo(CO)2(µ3,η³:η²:η¹-P3)}2]n[Al{OC(CF3)3}4]n

(78) 126

4.7. Synthesis of the Complex Based on [Cp*Mo(CO)2(η³-As3)] 127 4.7.1. [Ag2{Cp*Mo(CO)2(µ,η³:η²-As3)}2

{Cp*Mo(CO)2(µ3,η³:η²:η²-As3)}2][〈Al{OC(CF₃)3}4〉₂] (81) 127 4.8. Synthesis of the Complexes Based on [Cp*Fe(η⁵-P5)] 128

4.8.1. [Ag{Cp*Fe(µ3,η⁵:η²:η¹-P5)}2]n[Al{OC(CF3)3}4]n (83) 128 4.8.2. [Agx{Cp*Fe(η⁵-P5)}y(NO2)x(NCCH3)z] (85) 130 4.8.3. [Au5{Cp*Fe(η⁵-P5)}2]n[(PF6)5n] (86) 130 4.8.4. [(AuCl)3{Cp*Fe(η⁵-P5)}]n(87) 130 4.9. Synthesis of the Complexes Based on [(Cp*Mo)2(µ,η⁶-P6)] 131

4.9.1. [Cu20(µ-Cl)16(µ3-Cl)4{(Cp*Mo)2(µ7,η⁶:η⁶:η¹:η¹:η¹:η¹:η¹-P6)}3

{(Cp*Mo)2(µ7,η⁶:η⁶:η²:η¹:η¹:η¹:η¹-P6)}(NCCH3)12]n (88) 131 4.9.2. [(Cp*Mo)2(µ,η⁶-P6)][Al{OC(CF3)3}4] (89) 132 4.9.3. [Ag{(Cp*Mo)2(µ3,η⁶:η⁶:η²-P6)}2][Al{OC(CF3)3}4] (90) 133 4.10. Synthesis of the Complexes Based on [(Cp*Mo)2(µ,η³-P3)

(µ,η²-PS)] 133

4.10.1. [{Cu(µ-Cl)}3{(Cp*Mo)2(µ3,η³:η³:η¹-P3)(µ,η²- PS)}{(Cp*Mo)2(µ₃,η³:η³:η¹-P3)(µ₃,η²:η²:η¹-PS)}]n

(92a) 133

4.10.2. [{Cu(µ-Br)}3{(Cp*Mo)2(µ3,η³:η³:η¹-P3)(µ,η²- PS)}{(Cp*Mo)2(µ₃,η³:η³:η¹-P3)(µ₃,η²:η²:η¹-PS)}]n

(92b) 134

4.10.3. [{Cu(µ-I)}3{(Cp*Mo)2(µ3,η³:η³:η¹-P3)(µ,η²-PS)}

{(Cp*Mo)2(µ₃,η³:η³:η¹-P3)(µ₃,η²:η²:η¹-PS)}]n (92c) 135 4.10.4. [Ag{(Cp*Mo)2(µ3,η³:η³:η¹-P3)(µ,η²-

PS)}{(Cp*Mo)2(µ₃,η³:η³:η¹- P3)(µ₃,η²:η²:η¹-

PS)}]n[Al{OC(CF3)3}4]n(94) 136

5. Conclusions 137

5.1. Complexes Based on [Cp2M2(CO)4(η²-P2)] (M = Cr, Mo) 138 5.2. Complexes Based on [Cp^xM(CO)2(η³-E3)] (Cp^x = Cp, Cp*;

M = Cr, Mo; E = P, As) 140

5.3. Complexes Based on [Cp*Fe(η⁵-P5)] 143 5.4. Complexes Based on [(Cp*Mo)2(µ,η⁶-P6)] 144 5.5. Complexes Based on [(Cp*Mo)2(µ,η³-P3)(µ,η²-PS)] 146

5.6. Outlook 147

6. Notes and References 149

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7. Appendix 159 7.1. List of Abbreviations 159

7.2. List of the Reported Compounds 160 7.3. Crystallographic Data for the Reported Structures 162

7.3.1. [Cp*Mo(CO)2(η³-P3)] (7c) 162 7.3.2. [Cp*Fe(η⁵-P5)] (9a) 164 7.3.3. [Ag2{Cp2Mo2(CO)4(µ3,η²:η²:η²-P2)}2{Cp2Mo2(CO)4

(µ₄,η²:η²:η¹:η¹-P2)}2][(ClO4)2]•2CH3CN

(42d•2CH3CN) 166

7.3.4. [Ag2{Cp2Mo2(CO)4(µ3,η²:η²:η²-P2)}2{Cp2Mo2(CO)4

(µ₄,η²:η²:η¹:η¹-P2)}2][(PF6)2]•2CH3CN (42e•2CH3CN) 170 7.3.5. [Ag2{Cp2Mo2(CO)4(µ₃,η²:η²:η²-P2)}2{Cp2Mo2(CO)4

(µ4,η²:η²:η¹:η¹-P2)}2] [(SbF6)2]•4.5CH3CN

(42f•4.5CH3CN) 174

7.3.6. [Ag2{Cp2Mo2(CO)4(µ₃,η²:η²:η²-P2)}2{Cp2Mo2(CO)4

(µ4,η²:η²:η¹:η¹-P2)}2][〈Al{OC(CF3)3}4〉2]•CH2Cl2

(42g•CH2Cl2) 178

7.3.7. [Au2{Cp2Mo2(CO)4(µ₃,η²:η²:η²-P2)}2{Cp2Mo2(CO)4

(µ4,η²:η²:η¹:η¹-P2)}2][(PF6)2]•2C4H8O•2CH2Cl2

(42h•2C4H8O•2CH2Cl2) 184 7.3.8. [Ag2{Cp2Mo2(CO)4(µ₄,η²:η²:η¹:η¹-P2)}2(η²-NO2)2] (49) 188

7.3.9. [Au{Cp2Mo2(CO)4(µ3,η²:η²:η¹-P2)}Cl] (50) 191 7.3.10. [(Cp′′Rh)2{Cp2Mo2(CO)4(µ₄,η²:η²:η¹:η¹-P2)}(µ-

Cl)2][(BF4)2] •1.5CH2Cl2 (54•1.5CH2Cl2) 194 7.3.11. [(C14H8)Pt2{Cp2Mo2(CO)4(µ3,η²:η²:η¹-P2)}2(PEt3)4]

[(PF6)2] (57) 199

7.3.12. [(C14H8Cl)Pt{Cp2Mo2(CO)4(µ₃,η²:η²:η¹-

P2)}(PEt3)2][PF6]•CH2Cl2(59•CH2Cl2) 204 7.3.13. [Cu(µ-Cl){Cp2Cr2(CO)4(µ₄,η²:η²:η¹:η¹-P2)}]n (66a) 208 7.3.14. [Cu(µ-Br){Cp2Cr2(CO)4(µ₄,η²:η²:η¹:η¹-P2)}]n (66b) 211 7.3.15. [Cu(µ-I){Cp2Cr2(CO)4(µ4,η²:η²:η¹:η¹-P2)}]n•nCH3CN

(66c•nCH3CN) 214

7.3.16. [Ag{CpMo(CO)2(µ3,η³:η¹:η¹-

P3)}2]n[Al{OC(CF3)3}4]n•nCH2Cl2 (71•nCH2Cl2) 217 7.3.17. [Cu2(µ-Cl)2{Cp*Mo(CO)2(µ,η³:η²-P3)}2] (76a) 223 7.3.18. [Cu2(µ-Br)2{Cp*Mo(CO)2(µ,η³:η²-P3)}2] (76b) 226 7.3.19. [Cu(µ-I){Cp*Mo(CO)2(µ3,η³:η¹:η¹-P3)}]n (77) 229 7.3.20. [Ag2{Cp*Mo(CO)2(µ,η³:η²-

As3)}2{Cp*Mo(CO)2(µ3,η³:η²:η²- As3)}2][〈Al{OC

(CF3)3}4〉2]•2.5CH2Cl2 (81•2.5CH2Cl2) 232 7.3.21. [Ag{Cp*Fe(µ3,η⁵:η²:η¹-P5)}2]n[Al{OC(CF3)3}4]n

•nCH2Cl2(83•nCH2Cl2) 238 7.3.22. [Cu20(µ-Cl)16(µ3-Cl)4{(Cp*Mo)2

(µ7,η⁶:η⁶:η¹:η¹:η¹:η¹:η¹-P6)}3{(Cp*Mo)2

(µ7,η⁶:η⁶:η²:η¹:η¹:η¹:η¹-P6)}(NCCH3)12]n

•2nCH2Cl2 (88•2nCH2Cl2) 244 7.3.23. [Ag{(Cp*Mo)2(µ3,η⁶:η⁶:η²-P6)}2][Al{OC(CF3)3}4]

•CH2Cl2(90•CH2Cl2) 248 7.3.24. [{Cu(µ-I)}3{(Cp*Mo)2(µ₃,η³:η³:η¹-P3)(µ,η²-PS)}

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7.3.25. [Ag{(Cp*Mo)2(µ₃,η³:η³:η¹-P3)(µ,η²-PS)}{(Cp*Mo)2

(µ3,η³:η³:η¹-P3)(µ3,η²:η²:η¹-PS)}]n[Al{OC(CF3)3}4]n

•0.25nC7H8(94•0.25nC7H8) 256

8. Acknowledgements 263

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1. Introduction

Supramolecular chemistry^{[ ]}¹ has been masterfully implemented by Nature since the beginning of time and is most brilliantly embodied in the hydrogen-bonded structure of the substance that forms the essence of life itself, deoxyribonucleic acid (DNA, Figure 1.1). It is the chemistry involving the construction of molecular assemblies from discrete units by using weak, non-covalent interactions. In addition to hydrogen bonding, these interactions include van der Waals forces, Coulombic interactions and dipole-dipole interactions, and Nature skilfully manipulates these delicate tools to elegantly construct a plethora of other biomolecules and macromolecules. Furthermore, biological processes, for instance, oxygen transport and enzymolysis, are governed by the capacity of particular proteins to efficiently exercise control over metal coordination environments. In contrast to Nature, the scientific community’s involvement with supramolecular systems spans a mere four decades and its contributions are relatively modest. Nevertheless, it soon became evident that the study of supramolecules is not only of great interest to biologists and chemists, but also to physicists and engineers, and that it clearly defies the traditional boundaries of science, emerging as a true interdisciplinary field which is at the vanguard of current scientific research.

Phosphate

Phosphate Phosphate Phosphate

Phosphate Phosphate Phosphate Sugar

Sugar Sugar Sugar Sugar

Sugar Sugar Sugar

Amine base

Amine base Amine base Amine base Amine base Amine base

Figure 1.1. Schematic representation (left) and computer-generated structure (right, taken from http://de.wikipedia.org/wiki/Bild:DNA.jpg) of DNA. Hydrogen-bonding interactions between the amine bases of two separate sugar-phosphate strands result in the double helix structure.

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Despite the infancy of this field, supramolecular chemists have succeeded in creating a vast array of remarkable architectures by using, in particular, a simple yet effective synthetic concept based on metal centres and coordination chemistry, and have demonstrated the potential of such structures in molecular recognition and transport, catalysis, light harvesting, molecular electronics and the construction of molecular machines.^{[ ]}² The aforesaid concept, also referred to as

‘metal-directed synthesis’ or ‘metal-mediated self-assembly,’ is the most widely used strategy in the synthesis of supramolecules and involves the combination of coordinatively unsaturated metals and suitable ligands. In such reactions, weak dative bonding interactions generally lead to the often spontaneous self-assembly of a variety of coordination compounds ranging from discrete structures such as polygons, polyhedra, bowls and cages to extended arrays including 1D, 2D and 3D polymers, grids and networks (Figure 1.2). Moreover, this panoply of structures is usually accessible in high yields and under mild conditions, two decisive factors in synthetic chemistry.

Coordinatively unsaturated

metal centres Suitable ligands

Weak dative bonding interactions

Figure 1.2. Selected structures accessible by weak dative bonding interactions between coordinatively unsaturated metals and suitable ligands.

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The supramolecular structures mentioned above are most frequently synthesised using nitrogen, oxygen and sulphur donor ligands. The use of phosphorus donor ligands, on the other hand, is less common and generally limited to organophosphine ligands.^{[ ]}³ Organometallic Pn-ligand complexes,^{[ ]}⁴ that is, complexes containing substituent-free or ‘naked’ P atoms, have been shown to function as phosphorus donor ligands and are thus appealing candidates for use as building blocks in the construction of supramolecules. This fascinating class of compounds is a result of the pioneering work of Dahl and co- workers,^{[ ]}⁵ Ginsberg and Lindsell,^{[ ]}⁶ and Sacconi and co-workers.^{[ ]}⁷ Dahl and co-workers published their results at a time when dinitrogen complexes were already known and a subject of intense investigation, whereas analogous compounds of the heavier pnicogens were unknown. Although the published compounds [Co(CO)3(η³-As3)] 1^[5a]

and [Co2(CO)6(µ,η²-As2)] 2^[5b] (Figure 1.3) are actually Asn-ligand complexes,^[4c-g] they provided chemists with the incentive to synthesise analogous Pn-ligand complexes. The efforts of Ginsberg and Lindsell were soon rewarded in the early 1970s with the isolation of [ClRh(L)2(η²-P4)] 3a-d (Figure 1.4), complexes containing a dihapto- coordinated, and thus distorted, tetraphosphorus unit. Shortly after, Markò and co-workers isolated the compound [Co2(CO)6(µ,η²-P2)] 4,^{[ ]}⁸ the P analogue of compound 2, and it was not until the end of the 1970s that Sacconi and co-workers were able to isolate [(np3)Ni(η¹-P4)] 5^[7a]

(np3 = N(CH2CH2PPh2)3, Figure 1.4), a complex

Co

As As

As OC

CO CO

1 2 As

Co Co

As

CO CO CO OC

OC OC

Figure 1.3. The early Asn-ligand complexes of Dahl and co-workers.

Ph₂P N

Ni PPh2

PPh₂ P

P P

P 5 L

L Rh Cl

P P

P P 3a: L = PPh₃ 3b: L = P(p-CH₃C₆H₄)₃ 3c: L = P(m-CH3C6H4)3

3d: L = AsPh₃

Figure 1.4. The P4-ligand complexes of Ginsberg and Lindsell (3) and Sacconi and co-workers (5).

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containing an intact P4 tetrahedron. Since then, the class of Pn-ligand complexes has developed into one rich with compounds of astonishing structural diversity and includes the tetrahedrane complexes [Cp^x2M2(CO)4(µ,η²-P2)] 6a-e^{[ ]}⁹ and [Cp^xM(CO)2(η³-P3)] 7a-f,^{[9a-e, ]}¹⁰ the complexes [Cp^xM(CO)2(η⁴-P4)] 8a,b,^{[ ]}¹¹ the sandwich complexes [Cp^xM(η⁵-P5)] 9a-h,^{[ ]}¹² and the triple-decker sandwich complexes [(Cp^xCr)2(µ,η⁵-P5)] 10a,b^{[ ]}¹³ and [(Cp^xM)2(µ,η⁶-P6)] 11a-d^[9e,g] (Table 1.1). The complexes 9a, 10b and 11c were the first of their kind to be Table 1.1. Selected examples of Pn-ligand complexes.

Structure Cp^x M Compound[Reference]

Cp Cr 6a^[9a,b]

Cp Mo 6b^[9c,d]

Cp* Mo 6c^[9e]

Cp W 6d^[9f]

P

M M

P

Cp^x CO CO Cp^x

OC

OC Cp* W 6e^[9g]

Cp Cr 7a^[9a,b]

Cp Mo 7b^[9c,d,10]

Cp* Mo 7c^[9e]

Cp´ Mo 7d^[10a]

Cp´´ Mo 7e^[10a]

M

P P

P OC

CO Cp^x

Cp* W 7f^[9g,10b]

Cp* Nb 8a^[11a]

M

P P

P OC

CO Cp^x

P Cp΄΄ Ta 8b^[11b]

Cp* Fe 9a^[12a-c]

Cp^Et Fe 9b^[12d]

Cp´´ Fe 9c^[10a,12e]

Cp´´´ Fe 9d^[12f]

Cp* Ru 9e^[12d,g]

Cp^Et Ru 9f^[12d,g]

Cp* Os 9g^[12g]

P P P P P

Cp^x M

Cp^Et Os 9h^[12g]

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Cp Cr 10a^[13a]

P P

P P M P

Cp^x M Cp^x

Cp* Cr 10b^[13b]

Cp* V 11a^[9g]

Cp^Et V 11b^[9g]

Cp* Mo 11c^[9e]

M Cp^x P

P P

PP M P

Cp^x

Cp* W 11d^[9g]

isolated and can undoubtedly be considered as milestones in the field of Pn-ligand complex research. Compounds 9a and 10b contain the cyclo- P5 anion and 11c hexaphosphabenzene, the all-phosphorus analogues of the cyclopentadienide anion and benzene, respectively, and thus beautifully demonstrate the isolobality of P atoms and CH fragments.

The compounds listed in Table 1.1 are all neutral, but there are also examples of ionic Pn-ligand complexes, such as the monocationic triple-decker sandwich complexes [CpFe(µ,η⁵-P5)FeCp^x]⁺ 12a,b^{[ ]}¹⁴ and the recently reported dianionic sandwich complex [Ti(η⁵-P5)2]²¯ 13^{[ ]}¹⁵ (Figure 1.5) which, surprisingly, is described as air-stable although it is formally a 16VE Ti⁰ complex. The discovery of the ‘carbon-free’

metallocene 13 is, without question, one of great significance and will undoubtedly fuel the efforts of chemists around the world who are striving to ‘bake’ new ‘bread’ for that ‘old sandwich,’ ferrocene.

12a: Cp^x = Cp*

12b: Cp^x = Cp^Et

13 P P P

P P Fe Cp^x Fe

Cp ⁺

P P P P P P P P

P P Ti

2-

Figure 1.5. Examples of ionic Pn-ligand complexes.

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As the family of Pn-ligand complexes began to expand, researchers in the field became interested in the reactivity of these intriguing compounds. Many Pn-ligand complexes have been isolated as adducts of the neutral Lewis-acidic 16 VE M(CO)5 (M = Cr, Mo, W) fragments, thus revealing the Lewis basicity of the P atoms in these compounds.^{[ ]}¹⁶ The ligating potential of these complexes is also evidenced in examples of greater elegance. Scherer and co-workers have demonstrated that the reaction of 6b with [Re2(CO)6(µ- Br)2(THF)2] in CH2Cl2 leads to 14.^[16b] Interestingly, in THF, 14 rearranges to 15 thus leading to the formation of a six-membered Re2P4

ring (Figure 1.6).

P

Mo Mo

P

CO CO Cp

OC OC

Cp

Re Br Re OC

OC CO Br CO CO CO

CO Re

P

Mo Mo

P OCOC

Cp

OCOC

Cp Re

P Mo

Mo P

COCO Cp CO

Cp OC

OC CO Br

BrOC CO CO

14 15

Figure 1.6. The first compounds reported containing the Pn-ligand complex 6b as a ligand.

Stoppioni and co-workers have shown that the Pn-ligand complexes [(tppme)M(η³-P3)] (tppme = CH3C(CH2PPh2)3; M = Co, Rh, Ir) react with CuÎ, AgÎ and AuÎ salts of weakly coordinating anions (WCAs) to yield the trinuclear cationic complexes [{(tppme)M(η³- P3)}2M´]⁺ 16a-f^{[ ]}¹⁷ (M´ = Cu, Ag, Au; Figure 1.7) in which coordination of M´ to two P─P edges, each from a different cyclo-P3

unit, is observed. Furthermore, reaction of [(tppme)Ir(η³-P3)] with CuBr has been shown by Ghilardi and co-workers to lead to the remarkable ionic compound [{(tppme)Ir(η³-P3)}3Cu5Br4][CuBr2] 17 (Figure 1.7), in which the Cu atoms are found in three different coordination environments.^{[ ]}¹⁸ In the cation of 17, the Cu atoms are in trigonal and tetrahedral coordination modes, whereas in [CuBr2]¯, the coordination mode is essentially linear. The same authors have also reported the ‘super-sandwich’ [{(tppme)Co(η³-P3)}2(CuBr)6] 18 (Figure 1.7) in which a hexagonal Cu6Br6 moiety is sandwiched between two [(tppme)Co(η³-P3)] complexes.^{[ ]}¹⁹

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[P] = PPh₂ 16a: M = Co, M' = Cu 16b: M = Co, M' = Ag 16c: M = Co, M' = Au 16d: M = Rh, M' = Ag 16e: M = Rh, M' = Au 16f: M = Ir, M' = Au

[P]

M

P P P

[P]

[P] [P]

M P

P P M'

Cu [Ir]

P P

P [Ir]

P P

P Cu

Br

Cu [Ir]

P P P Cu Br

Cu

Br Br

+ +

[Ir] = (tppme)Ir 17

Cu

Br Br [Co]

P P

P [Co]

P P P Cu Cu

Cu Cu Br

Cu Br Br

Br

[Co] = (tppme)Co 18

Figure 1.7. Compounds containing the Pn-ligand complexes [(tppme)M(η³-P3)] (M = Co, Rh, Ir).

Pn-ligand complexes have been subjected to various other reactivity studies. Due to their analogy with ferrocene, investigations on the complexes [Cp^xFe(η⁵-P5)] 9a-d (Table 1.1) have been particularly intensive. Compounds 9a,b react with [CpFe(η⁶-C6H6)]PF6

to yield the cationic triple-decker complexes 12a,b (Figure 1.5).^[14] In addition, 9a has been shown to react with [M(CO)3(NCMe)3] (M = Cr, Mo) under formation of the binuclear complexes [Cp*Fe(µ,η⁵- P5)M(CO)3] 19a,b^{[ ]}²⁰ (Scheme 1.1), while reaction with [{Cp*Ir(CO)}2] yields the compounds 20-22^{[12c, ]}²¹ (Scheme 1.1), depending on the reaction conditions. In complex 20, the cyclo-P5 unit coordinates in a η² side-on fashion to the Ir atom and the planarity of this unit is maintained, whereas in 21 and 22, distortion from planarity and, in the case of 22, even bond cleavage is observed. Distortion from planarity and bond cleavage of the cyclo-P5 unit is also observed in 23- 25^{[21, ]}²² (Scheme 1.1), the products resulting from the reaction of 9a with [Cp´´Ta(CO)4]. A range of polynuclear clusters has also been isolated by the reaction of 9a with [{Cp^xCo(CO)}2],^{[ ]}²³ [Cp*Mo(CO)3CH3]^{[ ]}²⁴ and [{Cp´´Ru(CO)2}2]^{[ ]}²⁵ and are shown in Scheme 1.2. Most of these clusters demonstrate that the cyclo-P5 unit of 9a has undergone fragmentation.

-LIGAND COMPLEXES AS SUPRAMOLECULAR

ORGANOMETALLIC P