Multiple Bonds Between Metal Atoms / 05-Tungsten Compounds

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exchange reactions, W2Cl4(PEt3)4 and W2Cl4(PBun3)4 react with PMe3, PMe2Ph, and PMePh2 to form a series of W2Cl4 mixed-phosphine complexes, W2Cl4(PEt3)3(PMe3), W2Cl4(PEt3)2(PMe3)2, W2Cl4(PEt3)3(PMe2Ph), W2Cl4(PEt3)2(PMe2Ph)2, W2Cl4(PEt3)3(PMePh2), W2Cl4(PBun3)3(PMe3), W2Cl4(PBun3)3(PMe2Ph), W2Cl4(PBun3)2(PMe2Ph)2, and W2Cl4(PBun3)3(PMePh2).97 The results of the phosphine ligand exchange studies suggest that the exchange reactions proceed by an interchange dissociative mechanism, with the entering group within the W24+ coordination sphere at the axial coordination site before the rate-determining phosphine displacement step.97

Another synthetic method86 involves the thermal decomposition of trans-WCl2(PMe3)4 and mer-WCl3(PMe3)3. The decomposition in refluxing dibutyl ether proceeds as follows:

trans-WCl2(PMe3)4				Bu2O	0.5W2Cl4(PMe3)4 + 2PMe3
				reflux
mer-WCl3(PMe3)3	Bu2O		0.25W2Cl4(PMe3)4 + 0.5WCl4(PMe3)3 + 0.5PMe3
	reflux

Interestingly, W2I4(CO)8 has not been useful for the preparation of complexes of the type W2I4(PR3)4,98even though the related molybdenum analog has been used to prepare Mo2X4(PR3)4 compounds. The asymmetrical compound 1,1-W2(C>CMe)2Cl2(PMe3)4 has been prepared33 from the reaction between W2Cl4(PMe3)4 and LiC>CMe in dimethoxyethane. Both the W–W bond length (2.268(l) Å) and the W–C bond length (2.13 Å) are consistent with the presence of significant W–C / interaction.33 W2(C>CMe)4(PMe3)4 and W2(C>CBut)4(PMe3)4 are prepared similarly using four equivalents of LiCCMe or LiCCBut and W2Cl4(PMe3)4 in dimethoxyethane solution.99 Only a slight lengthening of the W–W bond length for W2(C>CMe)4(PMe3)4 (2.276(1) Å) is observed upon the addition of the two alkynyl ligands.37

The first synthesis of W24+ complexes containing monodentate nitrogen based ligands was recently achieved. Unlike the W26+ complex W2(µ-H)(µ-Cl)Cl4(py)457,81 prepared from W2(mhp)4, the synthesis of W2Cl4(4-But-py)4 is performed by reduction of WCl4 by either KC8 or NaBEt3H at low temperature in THF, followed by the addition of the amine. A similar reaction occurs with either pyridine derivatives, 4-tert-butylpyridine and 3-n-butylpyridine,28 or primary amines resulting in W2Cl4(NH2R)4 complexes where R is Prn, But, or Cy.27 Unlike the monodentate phosphine derivatives,35,36,42,86,87 the crystal structure of W2Cl4(4-But-py)4 has an eclipsed centrosymmetric structure where the pyridine groups face each other across the dimetal unit.28 In contrast, complexes with primary amines retain a D2d geometry with a trans arrangement of the amine ligands analogous to that of mondentate phosphine ligands.27

The reactions of toluene solutions of W2Cl4(PBun3)4 with the bidentate phosphine ligands 1,2-bis(dimethylphosphino)ethane (dmpe),29,30 1,2-bis(diphenylphosphino)ethane (dppe),30,38 1,3-bis(diphenylphosphino)propane (dppp),36 1,2-bis(diphenylphosphino)amine (dppa),42 and 1,2-bis(diethylphosphino)ethane (depe),40 produce green _-W2Cl4(δ2-PP)2 isomers. With the exception of _-W2Cl4(δ2-dppa)2, the compounds have been structurally characterized. As an example the core of _-W2Cl4(δ2-dppp)2 is shown in Fig. 5.5.

Unique to this series of compounds is W2Cl4(dppe)2 where both the green (_) and brown (`) isomers of W2Cl4(dppe)2 have been isolated and structurally characterized.30,38 Notable is the lengthening of the W–W bond in going from the _ to the `-form of W2Cl4(dppe)2 (2.281(1) Å versus 2.314(1) Å). This is a consequence of the staggered rotational conformation in the `- isomer (twisted 31.3° from the eclipsed conformation) which leads to a weakening of the anglesensitive β-bond. Only the `-isomer has been isolated and characterized for the phosphine ligands Pri2P(CH2)3PPri2 (dippp),41 Ph2PNHPPh2 (dppa),42 and Ph2PCH2PPh2 (dppm).34 The purple complex `-W2Cl2(µ-dippp)2 has been prepared41 by reduction of a mixture of WCl4 and Pri2P(CH2)2PPri2 with Na/Hg. The W–W bond length is between those of the _- and `-

194Multiple Bonds Between Metal Atoms Chapter 5

isomers of W2Cl4(dppe)2 and, in accord with this result, the P–W–W–P torsional angle of this chiral molecule is 75.9°.41 The complex W2Cl4(µ-dppm)2 has been prepared by the reaction of W2Cl4(PBun3)4 with bis(diphenylphosphino)methane in a mixture of hexane and toluene.34 This air-sensitive compound exhibits a βΑβ* electronic transition at 730 nm. It is structurally similar to Mo2Cl4(µ-dppm)2, but has a longer M–M bond length (2.269(1) Å versus 2.138(1) Å) and unlike its molybdenum analog possesses a slightly twisted geometry (average ρ = l7˚).34 The only structurally characterized quadruply bonded W2Br4 complex, W2Br4(µ-dppm)2,31 has an eclipsed geometry that more closely resembles those of the Mo2X4(µ-dppm)2 compounds where X is Cl, Br, or I59,63,100-102 rather than that of W2Cl4(µ-dppm)2, with a torsional angle of 17.25º.34 The slightly shorter W–W bond length in W2Br4(µ-dppm)2 (2.263(1)Å) in comparison to W2Cl4(µ-dppm)2 (2.269(1)Å) is attributed to the torsion angle in W2Cl4(µ-dppm)2 that results in a weaker β bond.31,34,103

Fig. 5.5. The core of _-W2Cl4(δ2-dppp)2.

Using variable temperature 31P{1H} NMR spectroscopy as a probe, the position of the low lying triplet state in W2Cl4(µ-dppm)2 and W2Cl4(µ-dppe)2 was investigated.104 Based on a weakening of the β bond strength with increased torsion angles, the temperature dependence of the upfield chemical shifts to the singlet-triplet spin equilibrium allows the singlet-triplet state energy separation to be determined. For W2Cl4(µ-dppm)2 and W2Cl4(µ-dppe)2 with torsion angles of 17.3 and 58.7°, respectively, the energy separations between the 1β2 and 3ββ* states are -2650(20) and -1400(60) cm-1.104

The much greater ease of oxidation of W24+ complexes compared to the Mo24+ analogs is reflected in the marked differences between the electrochemical properties of W2Cl4(PBun3)4 and Mo2Cl4(PBun3)4. For example, while solutions of W2Cl4(PBun3)4 in THF and CH2Cl2 exhibit E1/2(ox) values of +0.04 V and -0.24 V versus SCE, respectively,87 the corresponding values for Mo2Cl4(PBun3)4 are +0.64 V and +0.38 V. The tungsten complex has been oxidized chemically to the paramagnetic and EPR-active salt [W2Cl4(PBun3)4]PF6 using [Ag(NCMe)4]PF6 as the oxidant.87 When W2Cl4(PBun3)4 is heated with acetic acid in glyme, oxidation occurs to yield the red trinuclear W4+ cluster W3O3Cl5(O2CCH3)(PBun3)3.30,87,105 The reaction between benzoic acid (2 equiv) and W2Cl4(PBun3)4 (1 equiv) in benzene produces W2(µ-H)(µ-Cl)(µ- O2CPh)2Cl2(PBun3)2,106 the product of the oxidative addition of HCl to W2(O2CPh)2Cl2(PBun3)2. This behavior contrasts with the relative ease of producing Mo2(µ-O2CR)2X2(PBun3)2 and Mo2(O2CR)4 by reactions of Mo2X4(PBun3)4 with carboxylic acids.

There are other well documented examples of oxidative addition reactions involving W–W quadruple bonds.107 The reaction of Cl2 with W2Cl4(dppe)2 affords W2(µ-Cl)2Cl4(dppe)2,61 while Cl2 (or CH2Cl2) oxidizes W2Cl4(µ-dppm)2 and W2Cl4(µ-dmpm)2 (prepared in situ from

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W2Cl4(PBun3)4 and Me2PCH2PMe2) to W2(µ-Cl)2Cl4(µ-dppm)2 and W2(µ-Cl)2Cl4(µ-dmpm)2.108 Similar reactions between W2Cl4(µ-dppm)2 and Ph2E2 (E = S or Se) yield complexes of the types W2(µ-Cl)(µ-EPh)Cl4(µ-dppm)2 and W2(µ-EPh)2Cl4(µ-dppm)2.109 The quantitative oxidative addition of CH3I to W2Cl4(µ-dppm)2 has been achieved using visible irradiation (η > 435 nm), whereas the thermal reactions of this complex with alkyl iodides yield W2Cl5I(µ-dppm)2 and W2Cl4I2(µ-dppm)2.110 The susceptibility of W2Cl4(µ-dppm)2 to oxidative addition is probably the explanation for why W2(µ-H)(µ-Cl)Cl4(µ-dppm)2 was obtained during unsuccessful attempts to prepare W2Cl4(µ-dppm)2 from the reaction between W2Cl4(PBun3)4 with dppm in toluene for 12 h.57 The target complex W2Cl4(µ-dppm)2 was later prepared by a similar procedure using toluene:hexane solvent mixtures and a reduction in reaction time to 4 h.34 Attempts to prepare W2Cl4(µ-dmpm)2 by the reaction of W2Cl4(PBun3)4 with Me2PCH2PMe3 in toluene/hexane solvent mixtures led111 instead to the W27+ complex [Cl2W(µ-Cl)(µ-dmpm)2(µ- PMe2)WCl(δ2-CH2PMe2)]Cl.

An unusual reaction occurs upon treating W2Cl4(PMe3)4 with H2 (3 atm) and Na/Hg in THF at 75 °C. The product appears to be W2(µ-H)(µ-PMe2)H4(PMe3)5; the W–W bond length is 2.588(1) Å, but the number of hydride ligands in this diamagnetic complex is not known for certain.112 Hydrogen present due to the use of the reducing agent NaBEt3H results in the formation of W2(µ-H)2(µ-O2CC6H5)2Cl2(PPh3)2 (2.3500(12) Å).113 A high yield (72%) bulk preparation of W2(µ-H)2Cl4(µ-dppm)2 results by reducing WCl4 with NaBEt3H in THF at low temperature and the subsequent addition of dppm. Without the isolation of an intermediate monodentate phosphine ligand complex such as W2Cl4(PBun3)4, the H2 formed as a by-product of the reduction oxidatively adds to the W24+ core.114 The W–W bond length of 2.3918(7) Å for W2(µ-H)2Cl4(µ-dppm)2 is only 0.12 Å longer than W2Cl4(µ-dppm)2 (2.269(1) Å).34,114 Only a 42.8% yield of the purple complex W2(µ-H)2Cl4(µ-dppa)2 is obtained when the same synthetic methodology is used with the bidentate phosphine ligand dppa is used instead of dppm.42 With a relatively short W–W bond length of 2.407(2) Å for W2(µ-H)2Cl4(µ-dppa)2, the 31P{1H} NMR spectra of W2(µ-H)2Cl4(µ-dppm)2 and W2(µ-H)2Cl4(µ-dppa)2 confirm the presence of a large HOMO-LUMO gap and the diamagnetism of complexes of this type.42

Oxidative addition to the W–W quadruple bond occurs when acetonitrile is used as solvent in attempts to prepare W2Cl4(µ-dppm)2 and W2Cl4(µ-dppm)2(δ2-µ-CH3CN) is synthesized instead.115 As shown in Fig. 5.6, the N–C of the acetonitrile molecule is perpendicular to the W–W bond (2.4981(10) Å) and the C–C–N bond angle is no longer linear (116.3(7)°). The 31P{1H} NMR spectrum of the molecule has an AA'BB' pattern with multiplets centered at 4 and 15 ppm, indicating the acetonitrile is not fluxional on the NMR time scale.

Fig. 5.6. The core of W2Cl4(µ-dppm)2(δ2-µ-CH3CN).

196Multiple Bonds Between Metal Atoms Chapter 5

5.5Multiple Bonds in Heteronuclear Dimetal Compounds of Molybdenum and Tungsten

Quadruply bonded MoW heteronuclear dimetal complexes are relatively rare because of the difficulties in synthesizing the materials. This class of complexes has been the subject of reviews by Morris and Collman.116,117 The heteronuclear MoW tetracarboxylates have been synthesized by refluxing a 3:1 mixture of W(CO)6/Mo(CO)6 in o-dichlorobenzene with pivalic acid to form a 70:30 mixture of MoW(O2CC(CH3)3)4/Mo2(O2CC(CH3)3)4.118 The mixture can be separated by selective iodination to result in the precipitation of gray [MoW(O2CC(CH3)3)4]I (2.194(2) Å). Yellow MoW(O2CC(CH3)3)4 (2.080(1) Å)119 is sublimed after the MoW4+ product is obtained from the reduction of the MoW5+ precursor with zinc powder.118 Upon reaction with a saturated hydrochloric acid and addition of either CsCl or RbCl, oxidative addition at the dinuclear core occurs and the MoW6+ salts Cs3MoWCl8H or Rb3MoWCl8H (2.445(3) Å) are formed.119,120

Other bridging ligands such as the anion of 2-hydroxy-6-methylpyridine, 2,3,7,8,12,13,17,18-octaethylporphyrin, and meso-(4'-tolyl)octaethylporphyrin allow the preparation of MoW(mhp)4, MoW(OEP)4 and MoW(TOEP)4, respectively.121,122 Similar to the tetracarboxylate analog,118 the mhp derivative can be made by refluxing a mixture of Mo(CO)6, W(CO)6, and Hmhp in a ratio of 1:1.5:5, in diglyme/heptane, to produce a mixture of Mo2(mhp)4 and MoW(mhp)4.121 Oxidation with iodine, separation of the brown precipitate formed, and subsequent reduction with zinc amalgam results in MoW(mhp)4 in a 20% yield. The Mo–W bond length is 2.091 (1) Å.121 Substitution of Cr(CO)6 for Mo(CO)6 does not yield CrW(mhp)4. The compounds MoW(OEP)4 and MoW(TOEP)4 are prepared by refluxing a 1.25:6:1 ratio of the porphyrin, W(CO)6, and Mo(CO)6 in decalin.122 Unlike the preparation of MoW(O2CC(CH3)3)4 and MoW(mhp)4, a mixture of Mo2(OEP)4 or Mo2(TOEP)4, MoW(OEP)4 or MoW(TOEP)4, and W2(OEP)4 or W2(TOEP)4 were prepared and isolated by titration with ferrocenium hexafluorphosphate to allow the isolation of the cations [MoW(OEP)4]PF6 or [MoW(TOEP)4]PF6. Upon reduction with cobaltocene, the corresponding MoW4+ complexes were isolated. Based on 1H variable temperature NMR spectra, the rotation barrier for MoW(TOEP)4 is 10.6 kcal mol-1,122 slightly smaller than the value determined for W2(TOEP)2.92

The most extensive series of heteronuclear MoW complexes are those of composition MoWCl4(PR3)4 in which the quadruple bond is not supported by bridging ligands. For PR3 = PMePh2 or PMe2Ph derivatives, the best method of preparation is to react the mononuclear compounds Mo(δ6-PhPMePh)(PMePh2)3 or Mo(δ6-PhPMe2)(PMe2Ph)3 with WCl4(PPh3)2 in benzene.123,124 Substitution of WBr4(PPh3)2 for WCl4(PPh3)2 provides a synthetic route to MoWBr4(PMe2Ph)4 and MoWBr4(PMePh2)4.31

The lability of the phosphine ligands is illustrated by the following substitution reaction:124

MoWCl4(PMePh2)4 1 h, 40 oC, PMe3 (Me3P)2Cl2MoWCl2(PMePh2)2 3 h, 60 oC, PMe3

3P)2Cl2 MoWCl2(PMe3)2

These reactions reflect the expected trend in metal-phosphorus bond strengths, Mo–P < W–P. The PMe3 containing complexes MoWCl2(PMe3)2(PMePh2)2 and MoWCl2(PMe3)4 have similar electronic absorption spectra (recorded in benzene) to those of MoWCl4(PMePh2)4 and MoWCl4(PMe2Ph)4 with the βΑβ* transition in the region 650 to 635 nm.124 Also, the cyclic voltammograms of THF solutions of all four complexes resemble one another very closely with E1/2(ox) at +0.45 V and E1/2(red) at -1.8 V versus SCE. Other examples of (MoW)4+ mixed-

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phosphine ligand complexes are obtained when the reaction of Mo(δ6-PhPMe2)(PMe2Ph)3 with WCl4(PPh3)2 is carried out in the presence of excess PPh3. In this case, the mixed-phosphine ligand complex (PhMe2P)2Cl2MoWCl2(PMe2Ph)(PPh3) is formed first and then undergoes partial isomerization to (PhMe2P)(Ph3P)Cl2MoWCl2(PMe2Ph)2.125 The reactions of these isomers with THF lead to displacement of the PPh3 ligand.125

The 31P{1H} NMR spectra31,124,125 are consistent with structures of the corresponding Mo24+ and W24+ analogs with one Mo replaced by W, and X = Cl, Br and L = PR3. X-ray crystal structures have been reported for several of the complexes. A structure determination for MoWCl4(PMe3)2(PMePh2)2 revealed a Mo–W bond length of 2.207(1) Å.124 However, for MoWCl4(PR3)4, where PR3 = PMe3 (2.2092(7) Å),124 PMe2Ph (2.207(3) Å),125 or PMePh2 (2.210(4) and 2.207(4) Å),124 and MoWBr4(PMe2Ph)4 (2.209(1) Å),31 there is a disorder of the Mo and W atoms. For both MoWCl4(PMe2Ph)4 and MoWBr4(PMe2Ph)4, there is evidence of a 14 and 5% contamination of the crystals by Mo2Cl4(PMe2Ph)4 and Mo2Br4(PMe2Ph)4, respectively.31,125 The structural characterization of the isomers of composition MoWCl4(PMe2Ph)3(PPh3) has been carried out on a mixed crystal of these complexes.125

For the bidentate phosphine ligands dppe, dmpe, and dppm, the starting material MoWCl4(PMePh2)4 is reacted with the appropriate bidentate phosphine in either 1-propanol [dmpe and dppm] or methanol [dppe].126 _-MoWCl4(dppe)2, _-MoWCl4(dmpe)2 (2.234(4) Å), and MoWCl4(µ-dppm)2 (2.2110(7) Å) are formed by heating the corresponding reaction mixture, while MoWCl4(µ-dppe)2 (2.243(1) Å) is formed from _-MoWCl4(dppe)2 upon reflux in 1-propanol for 36 h. In contrast, MoWCl4(µ-dmpm)2 (2.193(2) Å)127 is prepared by stirring a solution of MoWCl4(PMePh2)4 and dmpm in a hexane/benzene solvent mixture for 1 h.126 As in the case of the monodentate phosphine derivatives, a disorder of the metal sites, Mo and W, is observed in the crystal structures.126, 127

5.6Paddlewheel Compounds with W25+ or W26+ Cores

A variety of compounds have been synthesized with either a W25+ or W26+ core and include triply bonded molecules such as W2(OC6F5)6(NHMe2)2, related molecules without bridging ligands, and edge-sharing or face-sharing bioctahedral geometries.14,42,61,87,94,113-115,128-141 When limited to ditungsten compounds with chelating anionic ligands, the paucity of W25+ or W26+ compounds is apparent. One of the two examples with a bridging carboxylate was synthesized in 1985 by the reaction of I2 in benzene with W2(O2CCMe3)4. The paramagnetic W25+ salt, [W2(O2CCMe3)4]I, retains the paddlewheel framework.18 Supported by three bridging pivalate ligands, the cation [W2(O2CBut)3(O2CBut)2]+ is synthesized by reaction of W2(O2CBut)6 with either Et3OBF4 or Me3SiO3SCF3 in CH2Cl2 at room temperature.142 The W26+ core has a distorted pentagonal pyramid geometry supported by three bridging and two chelating pivalate ligands. Loss of the anion of 2-hydroxy-6-methylpyridine results in formation of the paramagnetic orange-brown W25+ molecule W2(mhp)3Cl2 upon refluxing W2(mhp)4 in diglyme with AlCl3. Subsequent structural characterization of the dichloromethane solvate of W2(mhp)3Cl2 has shown that a very short W–W bond (Table 5.3) is retained (2.214(2) Å).82

A series of W25+ and W26+ compounds has been synthesized with the anion of 1,3,4,6,7,8- hexahydro-2H-pyrimido[1,2-a]pyrimidine (hpp). The W2(hpp)4Cl molecule has been structurally characterized as W2(hpp)4Cl and W2(hpp)4Cl0.5Cl0.5 with W–W bond lengths of 2.2131(8) Å and 2.209(1) Å, respectively.3 Surprisingly the W–Cl bond lengths vary rather significantly from 2.938(4) Å to 2.842(9) Å for W2(hpp)4Cl and W2(hpp)4Cl0.5Cl0.5. While W2(hpp)4Cl is prepared by layering a purple THF solution of W2Cl4(NH2Prn)4 over a THF solution of Lihpp, W2(hpp)4Cl0.5Cl0.5 is synthesized by reacting a THF solution of Lihpp with W2Cl4(NH2Prn)4 in toluene and layering the filtered solution with diethyl ether.

198Multiple Bonds Between Metal Atoms Chapter 5

Table 5.3. Structurally characterized paddlewheel type compounds with W25+ or W26+ cores

	Compound	W–W (Å)	ref.
	W25+
	W2(hpp)4Cl0.5Cl0.5	2.209(1)	3
	W2(hpp)4Cl	2.2131(8)	3
	W2(mhp)3Cl2	2.214(2)	82
	[W2(O2CBut)4]BF4	2.2762(14)	142
		2.2824(13)
	W26+
	W2(hpp)4Cl2·6CDCl3	2.2328(2)	73
	W2(hpp)4Cl2·4CH2Cl2	2.2497(8)	68
	W2(hpp)4Cl2	2.250(2)	3
	[NH2Me2]2W2[(p-tert-buylcalix[4]arene)2]	2.2926(1)	145
	[W2(p-tert-butylcalix[8]arene)Na2(MeCN)5]·5MeCN	2.2976(6)	143
	(NH2Me2)W2[(p-tert-buylcalix[4]arene)][(p-tert-buylcalix[4]arene)H]	2.3039(8	144,146
	[W2(p-tert-butylcalix[4]arene)2{µ-Na(pyridine)2}{µ-Na(pyridine)3}]·2THF	2.313(1)	24,147

The W26+ molecule, W2(hpp)4Cl2, is synthesized by the reaction of WCl4 in THF with one equivalent of NaEt3BH in the presence of Lihpp. The green-brown compound has been reported with W–W bond lengths of 2.250(2) Å and 2.2497(8) Å for the complexes W2(hpp)4Cl2, shown in Fig. 5.7,3 and W2(hpp)4Cl2.4CH2Cl2,68 respectively. An alternate synthesis involves the reaction of eight equivalents of the free ligand Hhpp with the triply bonded compound W2Cl2(NMe2)4 in a melt for 12-15 h with evolution of HNMe2.73 A crystal structure of the CDCl3 adduct W2(hpp)4Cl2·6CDCl3 contains a W–W bond length of 2.2328(2) Å.73

Fig. 5.7. The structure of W2(hpp)4Cl2. The W···Cl separation of over 3.0 Å is too long to be a significant bonding interaction.

The majority of W26+ compounds result from the reaction of tungsten species with calixarene ligands.24,143-147 The reaction of WCl6 with the ligand p-tert-butylcalix[8]areneH8 and subsequent reduction with sodium amalgam in toluene yields the orange-brown complex [W2(p-tert-butylcalix[8]arene)Na2(MeCN)5]·5MeCN with a tungsten-tungsten triple bond length of 2.2976(6) Å and a torsion angle of 39.4°,143 similar to the compound [W2(p-tert- butylcalix[4]arenetetrol)2(µ-Na(pyridine)2{µ-Na(pyridine)3}] with a tungsten-tungsten bond distance of 2.313(1) Å.24,147

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The triply bonded compound W2(NMe2)6 reacts with p-tert-buylcalix[4]arene in toluene and retains the tungsten-tungsten triple bond to form [NH2Me2]2W2[(p-tert-buylcalix[4]arene)2] (2.2926(1) Å).145 Reaction of [NH2Me2]2W2[(p-tert-buylcalix[4]arene)2] and W2[{(p-tert- buylcalix[4]arene)H}2] (formed by the reaction of (p-tert-buylcalix[4]arene)H4 and W2(OBut)6 in benzene) result in the triply bonded compound (NH2Me2)W2[(p-tert-buylcalix[4]arene)[(p- tert-buylcalix[4]arene)H] (2.3039(8) Å).144,146

References

1.P. Mountford and J. A. G. Williams, J. Chem. Soc., Dalton Trans. 1993, 877.

2.F. A. Cotton, R. H. Niswander and J. C. Sekutowski, Inorg. Chem. 1979, 18, 1152.

3.F. A. Cotton, P. Huang, C. A. Murillo and D. J. Timmons, Inorg. Chem. Commun. 2002, 5, 501.

4.F. A. Cotton, P. E. Fanwick, R. H. Niswander and J. Sekutowski, J. Am. Chem. Soc. 1978, 100, 4725.

5.F. A. Cotton, R. H. Niswander and J. C. Sekutowski, Inorg. Chem. 1978, 17, 3541.

6.A. R. Chakravarty, F. A. Cotton and E. S. Shamshoum, Inorg. Chem. 1984, 23, 4216.

7.F. A. Cotton, W. H. Ilsley and W. Kaim, Inorg. Chem. 1980, 19, 1450.

8.F. A. Cotton, W. H. Ilsley and W. Kaim, Inorg. Chem. 1979, 18, 3569.

9.F. A. Cotton and W. Wang, Inorg. Chem. 1984, 23, 1604.

10.F. A. Cotton, W. H. Ilsley and W. Kaim, Inorg. Chem. 1980, 19, 1453.

11.F. A. Cotton, L. R. Falvello, S. Han and W. Wang, Inorg. Chem. 1983, 22, 4106.

12.F. A. Cotton and T. Ren, J. Am. Chem. Soc. 1992, 114, 2237.

13.M. H. Chisholm, H. T. Chiu and J. C. Huffman, Polyhedron 1984, 3, 759.

14.K. M. Carlson-Day, J. L. Eglin, L. T. Smith and R. J. Staples, Inorg. Chem. 1999, 38, 2216.

15.D. Baxter, R. Cayton, M. H. Chisholm, J. C. Huffman, E. Putilina, S. Tagg, J. Wesemann, J. Zwanziger and F. Darrington, J. Am. Chem. Soc. 1994, 116, 4551.

16.F. A. Cotton and W. Wang, Inorg. Chem. 1982, 21, 3859.

17.A. P. Sattelberger, K. W. McLaughlin and J. C. Huffman, J. Am. Chem. Soc. 1981, 103, 2880.

18.D. J. Santure, J. C. Huffman and A. P. Sattelberger, Inorg. Chem. 1985, 24, 371.

19.D. J. Santure, J. C. Huffman and A. P. Sattelberger, Inorg. Chem. 1984, 23, 938.

20.F. A. Cotton, L. R. Falvello and W. Wang, Inorg. Chim. Acta 1997, 261, 77.

21.D. J. Santure, K. W. McLaughlin, J. C. Huffman and A. P. Sattelberger, Inorg. Chem. 1983, 22, 1877.

22.J. L. Eglin, L. T. Smith and R. J. Staples, Inorg. Chim. Acta 2003, 351, 217.

23.F. A. Cotton and S. A. Koch, J. Am. Chem. Soc. 1977, 99, 7371.

24.L. Giannini, E. Solari, C. Floriani, N. Re, A. Chiesi-Villa and C. Rizzoli, Inorg. Chem. 1999, 38, 1438.

25.D. M. Collins, F. A. Cotton, S. A. Koch, M. Millar and C. A. Murillo, Inorg. Chem. 1978, 17, 2017.

26.F. A. Cotton, G. N. Mott, R. R. Schrock and L. G. Sturgeoff, J. Am. Chem. Soc. 1982, 104, 6781.

27.F. A. Cotton, E. V. Dikarev and S. Herrero, Inorg. Chem. Commun. 1999, 2, 98.

28.F. A. Cotton, E. V. Dikarev, J. D. Gu, S. Herrero and B. Modec, Inorg. Chem. 2000, 39, 5407.

29.F. A. Cotton, M. W. Extine, T. R. Felthouse, B. W. S. Kolthammer and D. G. Lay, J. Am. Chem. Soc. 1981, 103, 4040.

30.F. A. Cotton, T. R. Felthouse and D. G. Lay, J. Am. Chem. Soc. 1980, 102, 1431.

31.F. A. Cotton, J. L. Eglin and C. A. James, Inorg. Chem. 1993, 32, 681.

32.F. A. Cotton, J. G. Jennings, A. C. Price and K. Vidyasagar, Inorg. Chem. 1990, 29, 4138.

33.T. C. Stoner, S. J. Geib and M. D. Hopkins, J. Am. Chem. Soc. 1992, 114, 4201.

34.J. M. Canich and F. A. Cotton, Inorg. Chim. Acta 1988, 142, 69.

35.F. A. Cotton, J. L. Eglin and C. A. James, Acta Crystallogr. 1993, C49, 893.

36.J. L. Eglin, E. J. Valente, K. R. Winfield and J. D. Zubkowski, Inorg. Chim. Acta 1996, 245, 81.

200Multiple Bonds Between Metal Atoms Chapter 5

37.K. D. John, V. M. Miskowski, M. A. Vance, R. F. Dallinger, L. C. Wang, S. J. Geib and M. D. Hopkins,

Inorg. Chem. 1998, 37, 6858.

38.F. A. Cotton and T. Felthouse, Inorg. Chem. 1981, 20, 3880.

39.K. M. Carlson-Day, J. L. Eglin, C. Lin, T. Ren, E. J. Valente and J. D. Zubkowski, Inorg. Chem. 1996, 35, 4727.

40.K. M. Carlson-Day, J. L. Eglin, K. M. Huntington and R. J. Staples, Inorg. Chim. Acta 1998, 271, 49.

41.M. D. Fryzuk, C. G. Kreiter and W. S. Sheldrick, Chem. Ber. 1989, 122, 851.

42.J. L. Eglin, L. T. Smith, R. J. Staples, E. J. Valente and J. D. Zubkowski, J. Organomet. Chem. 2000, 596, 136.

43.T. A. Stephenson, E. Bannister and G. Wilkinson, J. Chem. Soc. 1964, 2538.

44.T. A. Stephenson and D. Whittaker, Inorg. Nucl. Chem. Lett. 1969, 5, 569.

45.F. A. Cotton and M. Jeremic, Synth. Inorg. Metal-Org. Chem. 1971, 1, 265.

46.G. Holste, Z. anorg. allg. Chem. 1973, 398, 249.

47.A. Bino, F. A. Cotton, Z. Dori, S. Koch, H. Kueppers, M. Millar and J. C. Sekutowski, Inorg. Chem. 1978, 17, 3245

48.A. Bino, K. F. Hesse and H. Kueppers, Acta Crystallogr. 1980, B36, 723.

49.D. J. Bergs, M. H. Chisholm, K. Folting, J. C. Huffman and K. A. Stahl, Inorg. Chem. 1988, 27, 2950.

50.D. J. Santure and A. P. Sattelberger, Inorg. Synth. 1989, 26, 219.

51.G. M. Bancroft, E. Pellach, A. P. Sattelberger and K. W. McLaughlin, J. Chem. Soc., Chem. Commun. 1982, 752.

52.D. L. Lichtenberger and J. G. Kristofzski, J. Am. Chem. Soc. 1987, 109, 3458.

53.G. S. Girolami and R. A. Andersen, Inorg. Chem. 1982, 21, 1318

54.F. A. Cotton and D. G. Lay, Inorg. Chem. 1981, 20, 935.

55.D. J. Santure and A. P. Sattelberger, Inorg. Chem. 1985, 24, 3477

56.G. S. Girolami, V. V. Mainz and R. A. Andersen, Inorg. Chem. 1980, 19, 805.

57.P. E. Fanwick, W. S. Harwood and R. A. Walton, Inorg. Chem. 1987, 26, 242.

58.F. A. Cotton, L. R. Falvello, W. S. Harwood, G. L. Powell and R. A. Walton, Inorg. Chem. 1986, 25, 3949.

59.F. A. Cotton, K. R. Dunbar and R. Poli, Inorg. Chem. 1986, 25, 3700.

60.J. D. Chen, F. A. Cotton and L. R. Falvello, J. Am. Chem. Soc. 1990, 112, 1076.

61.P. A. Agaskar, F. A. Cotton, K. R. Dunbar, L. R. Falvello and C. J. O’Connor, Inorg. Chem. 1987, 26, 4051.

62.F. A. Cotton, L. M. Daniels, G. L. Powell, A. J. Kahaian, T. J. Smith and E. F. Vogel, Inorg. Chim. Acta 1988, 144, 109.

63.M. D. Hopkins, W. P. Schaefer, M. J. Bronikowski, W. H. Woodruff, V. M. Miskowski, R. F. Dallinger and H. B. Gray, J. Am. Chem. Soc. 1987, 109, 408.

64.J. V. Brencˇicˇ and F. A. Cotton, Inorg. Chem. 1970, 9, 351.

65.R. H. Cayton, M. H. Chisholm, J. C. Huffman and E. B. Lobkovsky, J. Am. Chem. Soc. 1991, 113, 8709.

66.M. J. Byrnes and M. H. Chisholm, Chem. Commun. 2002, 2040.

67.F. A. Cotton, S. A. Koch, A. J. Schultz and J. M. Williams, Inorg. Chem. 1978, 17, 2093

68.F. A. Cotton, P. Huang, C. A. Murillo and X. Wang, Inorg. Chem. Commun. 2003, 6, 121.

69.B. E. Bursten, F. A. Cotton, A. H. Cowley, B. E. Hanson, M. Lattman and G. G. Stanley, J. Am. Chem. Soc. 1979, 101, 6244.

70.F. A. Cotton and D. J. Timmons, Polyhedron 1998, 17, 179.

71.W. H. deRoode, K. Vrieze, E. A. Koerner von Gustorf and A. Ritter, J. Organomet. Chem. 1977, 135, 183.

72.J. D. Schagen and H. Schenk, Crystallogr. Struct. Commun. 1978, 7, 223.

73.M. H. Chisholm, J. Gallucci, C. M. Hadad, J. C. Huffman and P. J. Wilson, J. Am. Chem. Soc. 2003, 125, 16040.

Tungsten Compounds 201

Eglin

74.F. A. Cotton, N. E. Gruhn, J. Gu, P. Huang, D. L. Lichtenberger, C. A. Murillo, L. O. VanDorn and

C.C. Wilkinson, Science 2002, 298, 1971.

75.D. DeMarco, T. Nimry and R. A. Walton, Inorg. Chem. 1980, 19, 575.

76.L. B. Anderson, F. A. Cotton, D. DeMarco, A. Fang, W. H. Ilsley, B. W. S. Kolthammer and

R.A. Walton, J. Am. Chem. Soc. 1981, 103, 5078.

77.F. A. Cotton, L. R. Falvello, M. F. Fredrich, D. DeMarco and R. A. Walton, J. Am. Chem. Soc. 1983, 105, 3088.

78.F. A. Cotton, D. DeMarco, B. W. S. Kolthammer and R. A. Walton, Inorg. Chem. 1981, 20, 3048.

79.W. S. Harwood, D. DeMarco and R. A. Walton, Inorg. Chem. 1984, 23, 3077.

80.J. Savard and H. Alper, Can. J. Chem. 1988, 66, 2483.

81.R. T. Carlin and R. E. McCarley, Inorg. Chem. 1989, 28, 2604.

82.T. R. Ryan and R. E. McCarley, Croatica Chem. Acta 1995, 68, 769.

83.D. M. Collins, F. A. Cotton, S. Koch, M. Millar and C. A. Murillo, J. Am. Chem. Soc. 1977, 99, 1259.

84.F. A. Cotton, S. Koch, K. Mertis, M. Millar and G. Wilkinson, J. Am. Chem. Soc. 1977, 99, 4989.

85.F. A. Cotton and B. J. Kalbacher, Inorg. Chem. 1977, 16, 2386.

86.P. R. Sharp and R. R. Schrock, J. Am. Chem. Soc. 1980, 102, 1430.

87.R. R. Schrock, L. G. Sturgeoff and P. R. Sharp, Inorg. Chem. 1983, 22, 2801.

88.F. A. Cotton, L. R. Falvello, G. N. Mott, R. R. Schrock and L. G. Sturgeoff, Inorg. Chem. 1983, 22, 2621.

89.C. Mertis and N. Psaroudakis, Polyhedron 1989, 8, 469.

90.J. C. Kim, V. L. Goedken and B. M. Lee, Polyhedron 1996, 15, 57.

91.J. P. Collman, J. M. Garner and L. K. Woo, J. Am. Chem. Soc. 1989, 111, 8141.

92.J. P. Collman, J. M. Garner, R. T. Hembre and Y. Ha, J. Am. Chem. Soc. 1992, 114, 1292.

93.M. M. Balakrishnarajan, P. Kroll, M. J. Bucknum and R. Hoffmann, New J. Chem. 2004, 28, 185.

94.F. A. Cotton and S. K. Mandal, Inorg. Chem. 1992, 31, 1267.

95.M. D. Hopkins, V. M. Miskowski and H. B. Gray, J. Am. Chem. Soc. 1988, 110, 1787.

96.F. A. Cotton, J. L. Hubbard, D. L. Lichtenberger and I. Shim, J. Am. Chem. Soc. 1982, 104, 679.

97.M. H. Chisholm and J. M. McInnes, J. Chem. Soc., Dalton Trans. 1997, 2735.

98.F. A. Cotton, L. R. Falvello and R. Poli, Polyhedron 1987, 6, 1135.

99.T. Stoner, W. P. Schaefer, R. E. Marsh and M. D. Hopkins, J. Cluster Science 1994, 5, 107.

100.S. A. Best, T. J. Smith and R. A. Walton, Inorg. Chem. 1978, 17, 99.

101.E. H. Abbott, K. S. Bose, F. A. Cotton, W. T. Hall and J. C. Sekutowski, Inorg. Chem. 1978, 17, 3240.

102.F. L. Campbell, F. A. Cotton and G. L. Powell, Inorg. Chem. 1985, 24, 177.

103.M. C. Milletti, Polyhedron 1993, 12, 401.

104.F. A. Cotton, J. L. Eglin, B. Hong and C. A. James, Inorg. Chem. 1993, 32, 2104.

105.F. A. Cotton, T. R. Felthouse and D. G. Lay, Inorg. Chem. 1981, 20, 2219.

106.F. A. Cotton and G. N. Mott, J. Am. Chem. Soc. 1982, 104, 5978.

107.T.-L. C. Hsu, S. A. Helvoigt, C. M. Partigianoni, C. Turro and D. G. Nocera, Inorg. Chem. 1995, 34, 6186.

108.J. A. M. Canich, F. A. Cotton, L. M. Daniels and D. B. Lewis, Inorg. Chem. 1987, 26, 4046.

109.J. A. M. Canich, F. A. Cotton, K. R. Dunbar and L. R. Falvello, Inorg. Chem. 1988, 27, 804.

110.C. M. Partigianoni and D. G. Nocera, Inorg. Chem. 1990, 29, 2033.

111.F. A. Cotton, J. A. M. Canich, R. L. Luck and K. Vidyasagar, Organometallics 1991, 10, 352.

112.K. W. Chiu, R. A. Jones, G. Wilkinson, A. M. R. Galas and M. B. Hursthouse, J. Chem. Soc., Dalton Trans. 1981, 487.

113.K. M. Carlson-Day, T. E. Concolino, J. L. Eglin, C. Lin, T. Ren, E. J. Valente and J. D. Zubkowski,

Polyhedron 1996, 15, 4469.

114.T. E. Concolino, J. L. Eglin, E. J. Valente and J. D. Zubkowski, Polyhedron 1997, 16, 4137.

115.J. L. Eglin, E. M. Hines, E. J. Valente and J. D. Zubkowski, Inorg. Chim. Acta 1995, 229, 113.

116.R. H. Morris, Polyhedron 1987, 6, 793.

202Multiple Bonds Between Metal Atoms Chapter 5

117.J. P. Collman and R. Boulatov, Angew. Chem. Int. Ed. 2002, 41, 3948.

118.V. Katovic, J. L. Templeton, R. J. Hoxmeier and R. E. McCarley, J. Am. Chem. Soc. 1975, 97, 5300.

119.V. Katovic and R. E. McCarley, J. Am. Chem. Soc. 1978, 100, 5586.

120.V. Katovic and R. E. McCarley, Inorg. Chem. 1978, 17, 1268.

121.F. A. Cotton and B. E. Hanson, Inorg. Chem. 1978, 17, 3237

122.J. P. Collman, S. T. Harford, S. Franzen, T. A. Eberspacher, R. K. Shoemaker and W. H. Woodruff,

J.Am. Chem. Soc. 1998, 120, 1456.

123.R. L. Luck and R. H. Morris, J. Am. Chem. Soc. 1984, 106, 7978.

124.R. L. Luck, R. H. Morris and J. F. Sawyer, Inorg. Chem. 1987, 26, 2422.

125.F. A. Cotton, L. R. Falvello, C. A. James and R. L. Luck, Inorg. Chem. 1990, 29, 4759.

126.F. A. Cotton and C. A. James, Inorg. Chem. 1992, 31, 5298.

127.F. A. Cotton, K. R. Dunbar, B. Hong, C. A. James, J. H. Matonic and J. L. C. Thomas, Inorg. Chem. 1993, 32, 5183.

128.R. G. Abbott, F. A. Cotton and L. R. Falvello, Inorg. Chem. 1990, 29, 514.

129.M. H. Chisholm, I. P. Parkin, W. E. Streib and K. S. Folting, Polyhedron 1991, 10, 2309.

130.M. H. Chisholm, K. S. Kramer, J. D. Martin, J. C. Huffman, E. B. Lobkovsky and W. E. Strieb,

Inorg. Chem. 1992, 31, 4469.

131.F. A. Cotton, E. V. Dikarev and W.-Y. Wong, Inorg. Chem. 1997, 36, 80.

132.F. A. Cotton, E. V. Dikarev, N. Nawar and W.-Y. Wong, Inorg. Chem. 1997, 36, 559.

133.F. A. Cotton, E. V. Dikarev and W.-Y. Wong, Inorg. Chem. 1997, 36, 902.

134.F. A. Cotton, E. V. Dikarev, N. Nawar and W.-Y. Wong, Inorg. Chim. Acta 1997, 262, 21.

135.F. A. Cotton, E. V. Dikarev and W.-Y. Wong, Polyhedron 1997, 16, 3893.

136.M. H. Chisholm, K. Folting and D.-D. Wu, Acta Crystallogr. 1998, C54, 225.

137.J. T. Barry, S. T. Chacon, M. H. Chisholm, V. F. DiStasi, J. C. Huffman, W. E. Streib and

W.G. Van Der Sluys, Inorg. Chem. 1993, 32, 2322.

138.S. T. Chacon, M. H. Chisholm, W. E. Streib and W. G. Van Der Sluys, Inorg. Chem. 1989, 28, 5.

139.F. A. Cotton, J. L. Eglin and C. J. James, Inorg. Chem. 1993, 32, 687.

140.K. M. Carlson-Day, J. L. Eglin, E. J. Valente and J. D. Zubkowski, Inorg. Chim. Acta 1996, 244, 151.

141.K. M. Carlson-Day, J. L. Eglin, E. J. Valente and J. D. Zubkowski, Inorg. Chim. Acta 1999, 284, 300.

142.T. A. Budzichowski, M. H. Chisholm, J. C. Huffman, K. S. Kramer and M. G. Fromhold, Inorg. Chim. Acta 1993, 213, 141.

143.V. C. Gibson, C. Redshaw and M. R. J. Elsegood, Chem. Commun. 2002, 1200.

144.M. H. Chisholm, K. Folting, W. E. Streib and D.-D. Wu, Inorg. Chem. 1999, 38, 5219.

145.U. Radius and J. Attner, Eur. J. Inorg. Chem. 1998, 299.

146.M. H. Chisholm, K. Folting, W. E. Streib and D.-D. Wu, Chem. Commun. 1998, 379.

147.L. Giannini, E. Solari, A. Zanotti-Gerosa, C. Floriani, A. Chiesi-Villa and C. Rizzoli, Angew. Chem. Int. Ed. Engl. 1997, 36, 753.

148.V. Calvo-Pérez, T. P. Fehlner and A. L. Rheingold, Inorg. Chem. 1996, 35, 7289.

149.T. P. Fehlner, V. Calvo-Pérez and W. Cen, J. Electr. Spectrosc. Related Phenom. 1993, 66, 29.

150.P. E. Fanwick, W. S. Harwood and R. A. Walton, Inorg. Chem. 1987, 26, 242.