Structurally Characterized Organometallic Hydroxo ... - ACS Publications

Chem. Rev. 1994, 94, 895-910

885

Structurally Characterized Organometallic Hydroxo Complexes of the f- and d-Block Metals John W. Gilje’gt and Herbert W. Roesky’Tt Chemistry Deparfment, University of Hawaii, Honolulu, Hawaii 96822, and Institut fu Anorganische Chemie der Universi&t @ttIngen, 37077 Oiittlnpn, Germany Received November 22, 1993 (Revheti ManwcrJpt Received March 3, 1994)

Contents I. Introduction 11. Prologue

111. Scandium, Yttrium, Lanthanides, and Actinides IV. Titanium, Zirconium, and Hafnium V. Vanadium, Niobium, and Tantalum VI. Chromium, Molybdenum, and Tungsten VII. Manganese, Technecium, and Rhenium VIII. Iron, Ruthenium, and Osmium IX. Cobalt, Rhodium, and Iridium X. Nickel, Palladium, and Platinum XI. Copper, Silver, and Gold XII. Zinc, Cadmium, and Mercury XIII. Ackndwledgments XIV. References

895 895 895 897 90 1 902 903 904 907 908 909 909 909 909

I. Introduction

Organotransition metal hydroxides have been known for a long time, and there has been interest in them for many years, primarily because of their role in catalysis.’ However, this class of compounds has taken on increased importance with the growth of activity in materials-related chemistry. As organometallic precursors are now being used for the synthesis of oxide materials by sol-gel and related hydrothermal syntheses, an understanding organometallichydroxides, which occur as intermediates or themselves function as precursors, becomes important. The primary purpose of this review is to summarize the structures found in the organometallic hydroxide complexes of the d- and f-block elements. While preparative methods will be mentioned, many of the complexes have formed adventitiously and there are gaps in the chemical understanding. Nonetheless, common structural features occur throughout the periodic chart and we hope this review will aid the development of both the pure and applied chemistry of this series of compounds. We are unaware of another review of this area. However, terminal hydroxide complexes of the late transition metals and organometallic oxo-hydroxo compounds112are covered in reviews largely devoted to other topics. Z I. Prologue

A Lewis dot formula shows three electron pairs residing on oxygen in the hydroxide ion. As might be + University of Hawaii.

Universiut Gdttingen.

expected from this representation, the hydroxo ligand is capable of a variety of coordination modes utilizing one or several electron pairs. Thus, even the terminal M-OH linkages are complicated by possible contribution from three resonance forms: M-OH c+ M=OH c* MEOH In fact, M-OH units often possess short metal-oxygen distances which sometimes are interpreted in terms of metal-oxygen multiple bonding. While terminal hydroxo coordination is found in complexes of metals throughout the transition series, doubly and triply bridging geometries are more common. While there is no clear separation between the various metals, doubly bridging complexes are encountered relatively most frequently with the early transition and the f-block metals while the triple bridge is somewhat more common with the later metals. There are a variety of different structures for each type of hydroxide coordination, but among the triply bridging complexes “cubanes” are the most frequently encountered type and are common from group 6 to 12. In many cases the coordinated OH group is involved in hydrogen bonding. This can occur both in an intraand/or intercomplex fashion or to solvents of crystallization. When no other sites are accessible,very weakly basic molecules, with which the hydroxo complex has co-crystallized, may be involved. Undoubtably, the tendency of these compounds to hydrogen bond may influence their chemistry. However, this has not yet been investigated. The compounds mentioned in this review are listed in Table 1along with the metal-oxygen bond lengths.

I I I. Scandium, Yttrium, Lanthanides, and Actinides Hydrolysis is a common mode of decomposition for the organometallic complexes of the electropositive metals, and all of the known group 3, lanthanide, and actinide organometallic hydroxo complexes have been prepared by this route. The most common structural type of the organohydroxo complexes of the group 3 and lanthanide metals is the double-bridged [(CP)~MI~(P~-OH)~, where Cp may be C5H5 or a derivative. If the two Cp and two OH ligands are each considered to occupy a single coordination site, the metals are distorted tetrahedral and the Cp(centroid)zM planes are approximately perpendicular to the nearly planar M2(0)2 rings. [(CSH&YI~(P~-OH)~ was isolated from a mixture of (C5H5)2Y(B~t)(thf) and Ph-C=C-Ph, in which it presumably formed by hydrolysis and from which it co-crystallizes with P h c ~ c P h [. (~C ~ H & Y I ~ ( P ~ - O H ) ~ 0 1994 American Chemical Society

890 Chemlcal

Gil]e and Roesky

Reviews, 1994, Vol. 94. No. 4

YR (R= C5H5,CH3, or H) gave mixtures of products, as did the reaction of (C5H5)sY(thDwith a suspension ofNaOHin thf. When (NPC12).wasaddedtoscavange C5H5- a compound formulated as (CcH&Y(OH)(thD was isolated, but no structure was determined.3 With the lanthanides, [( [C~H~(S~M~~)ZI)ZS~IZ(C( OH), and I[CsH'(SiMe3)l2Yb)2(p*OH)2 are obtained by careful, oxidative hydrolysis:'

2{[C6H~,(SiMe3),l),Ln(L)+ 2H20

+

[{[C5H,(SiMe,)21)2Lnl,(rc,-OH), + 2L + H, Ln = Sm, n = 2,L = thf; Ln = Yb, n = 1,L = EhO John W. Gllh grew up In St. Paul, MN, and in 1961 received 8. Chem. degree from the University of Minnesota. He went on for graduate study at ttm University of Michigan, where he completed his Ph.D. in 1965, working with Robert W. Parry on boron hydride chemistry. In 1965 hejoinedthefacuityoftheUniversityofHawall where he Is now professor of chemistry. He has held visiting positionsal the University of Texas, Austin. (1972/1973). Imperial Collegeof ScIenc8andTechnology.London, (1979/1980), Technical Universityat Braunschweig.Germany. (198011981).andGiiningen University. Germany (1990). He received an Alexander von Humboldt Research Fellowship (1980) and was awarded a Distinguished Senior Scientist Award from the Alexander von Humboldt Foundation (1990). Currently he is serving as a Program Officer in Inorganic Chemistry at the National Science Foundation. His research interests include the moiecular chemistry of electropositive metals and phosphorus chemistry.

Herbert W. Rcesky was born in

1935 in Laukischken. He studied chemisbyatmeuniversityofG~ngen,Germany.whereheobtained his Diplom in 1961 and his Ph.D. in 1963. After one year of postdoctoral work at DuPont in Wilmington. DE, he made hls habilitation at Giiningen University. In 1971 he became full professor in Frankfurt and since 1980 he has been a full professorand director of the Institute of Inorganic Chemistry at Gningen University. During this time he has also been e vislting professor at Tokyo Instiiute of Technology and at Kyoto University in Japan. He Is

and ~ ( ~ C ~ H ~ ~ B u c ~ l )b~9L n 1 ~ ~ ~ ~ z - O H ~ ~

+

Ln[C5H4(But)13 2H,O

-

(~C5H,~Buc~12Ln),~~,-OH~, + 2C5H5(But) Ln = Nd or Dy In each of these reactions dilute solutions of water in an ether are used for the hydrolysis. The mean metaloxygen distances in these compounds are Sm-0 = 240,' Y b O = 229," Nd-0 = 232.9: and Dy-0 = 225.1 ~ m . ~ Another Y and an analogous Lu complex, I[O(CHzCH2C5H1)~1LnJ~(p2-Me~C3H-N2)(p~OH) (Ln = Y, Lu), form by

The M-OH distances are 220.2(2) and 215.4(3) pm for the Y and Lu complex, respectively.E The generation and subsequent reactions of hydrogen halide may complicate hydrolysis reactions of organometallic halides. A novel solution to this problem has been the use of Ph2SNH.HZO as a reagent to provide stoichiometric amounts of water and to absorb HC1 as it is formed. (C5Me5)zUC12(NHSPh2),a product from the reaction between (C&le&UCl~and HNSPhz, reacts with PhzSNH-H20in toluene:

member of the Academy of Sciences in Giiningen and of the Academy of Scientists "Leopoldina" in Halle. He has received many awards,e.g. the D.rer.nat.h.c. of Bielefeld University. AlfredStock-Memorial Award, and French Alexander-vonHumbo+itaward. More than 550 research publications. articles. patents and books document his activity.

consists of two (C&H5)2Yunits bridged by OH groups and with Y-0 distances of 233(2) and 236(2) pm. The PhC-CPh molecules are located between layers of [ ( C ~ H ~ ) ~ Y I ~ ( ~molecules, Z - O H ) ~which are oriented so that each 0-H is directed toward the C-C bond of an alkyne; the oxygen and carbon separations range between 344 and 355 pm, and a hydrogen binding interaction is proposed.3 Subsequent attempts to obtain [(C5H5)2YI~(p2-0H)2 by hydrolysis of ( C ~ H ~ T

(CsMe5)2U(OH)(NHSPhz)(C1) has a typical bent metallocene structure; the U-0 bond distance, 210(2) pm, decomis quite short.? (C5Mes)2U(OH)(NHSPh2)(C1) poses slowly in the solid state or within a few days in solution

Organometallic Hydroxo Complexes

-+

2(C5Me5),U(OH)(NHSPh2)(C1) (C5Me5),UC1,(NHSPh2) 2(C5Me5H)+ “U02(NHSPh,) or reacts further with PhzSNHaH20 to form a tetrauranium-oxo-hydroxo cluster:’

Chemical Reviews, 1994, Vol. 94, No. 4

897

The reaction of (C5Me5)2TiC12 with AgCF3S03 in moist thf produces [(CsMe5)2Ti(H20)21[CF3S0312.11 From aqueous solutions of this compound the monohydrate [(C5Me5)pTi(OH)(H2O)]CF3SO~H20 and dihydrate [(C5Me&Ti(OH) (H20)]CF3S03*2H20 have been isolated. All three compounds were characterized by X-ray diffraction and the Ti-OH distances are all nearly the same, 187-pm mean value for the three compounds. The first titanium hydroxide containing an 0-H-0 bond was prepared according to the following equations:12

The U-0 bond distances range from 196 to 236 pm and the OH groups are assigned on the basis of symmetry and bond distances. The U404(OH)2 core is a small segment of a common type encountered in uranium[(C5Mes)Ti(OH)OSi(But)2012 is a yellow crystalline oxide and uranium-oxy-halide chemistry. As the solid showing characteristic OH absorptions in the IR. complete hydrolysis of (C5Me&UC12would undoubtA side-on view of the structure shows an eightedly yield an oxide or oxy chloride, (C~Me5)2- membered ring in a boat form with one OH hydrogen U(OH)(NHSPh2)(Cl) and ( C ~ M ~ S ) ~ U ~ O ~ ( O H ) ~bonding C L - through a transannular bridge to the other, (NHSPh2)6can be viewed as intermediates in the which is not involved in hydrogen bonding: conversion of an organometallic precursor to an oxide.

*’ H

I V. Titanium, Zirconium, and Hafnium A. Titanium( I I I ) The reaction of the titanocene [(C~Hs)Ti(p2-H)l&(C5H4)21 with water in thf gives [(CSHS)T~(PZ-OH)I 2[~-CsH4)21:~

The crystal structure shows discrete molecules of [ (C~H~)T~(P~-OH)I~[P-(C~H~)~], with one OH in each molecule hydrogen bonded to a thf of solvation.

Ti\

‘0-

- -_-H-0 (ButI2

)i

\e- si -q

+

o\si/o IBut),

The hydrogen bridge increases the coordination number of O(1) and results in a long Ti(1)-O(1) bond, 187.2(2) pm. Normally the elimination of a water molecule would be expected, but in this case steric factors presumably prevent further reactions of the OH groups. On hydrolysis of (CsH&TiC12 in water at pH > 5 one cyclopentadienyl group is removed. Reaction of the product with formic acid gives the ionic trinuclear complex [T~~(C~~-O)(CL~-~H)~(C(~-HCOO)~(C [HC00]-.2HCOOH whose structure was determined by X-ray:13

B. Titanium( I V ) Several Ti(IV) complexes containing a terminal hydroxo ligand have been characterized by X-ray diffraction. [(C~M~~)~T~(OH)(HNCP~~)]BP~CE~~O, r prepared by the reaction of (CsMe5)2TiN=CPh2 with AgBPh4 in the presence of traces of m o i ~ t u r eshows ,~ H, pseudotetrahedral titanium coordination with a short Ti-OH distance, 185.3(7) pm, which indicates substantial Ti-0 double-bond character. The reaction of (CsMe&TiMe with AgBPh4 in thf gives the sterically congested [(CsMes)nTiMe(thf)lBPh4. The thf is easily displaced by donor molecules1° and in the presence of even traces of water [(CsMe&Ti(OH)(HzO)]BPh4*2thf forms. The Ti-OH bond length, 185.3(5) pm, is identical to that in the previous cation. The complex cation is oxygen centered, with Ti-0-Ti

Gilje and Roesky

898 Chemical Reviews, 1994, Vol. 94, No. 4

ref 3

6

7 7

8

9 10 11 11 12 13 14 15 16 16 17

18 18 19 20 21 22 23 24 25 26 27 28 28 29

195.0 213,218

29 30 31 32 33

195

55

see text

49 43

196 207.7 205 208 208.5 196.5, 191.7 208 223.7,214.0 227.2

see text see text see text see text

34 35 40 41 42 44 46 47 50 51 52 41 56

Chemical Reviews, 1994, Vol. 94,


No. 4 899

Table 1 (Continued) M-0 distance (pm)

219.4 208.7

ref

see text

48 37 50 39 53

205 see text

57 59 57

190 216.0,217.5 212.6 220.7 216.7

60 61 62 64 65

197.2 199.0

66 67

208 209 209 212 208.8 207 212 215 212 216

70 68 68 69 71 73 79 83

208 206

68 72

213 216 213 214 209 209 214

74 75 77 78 80 81 82 80

217.7

88

211 217.9 210.9 206.8

89 90 91 95

211.0 209.8 214 207 212

86 92 93 94 91

191.9 189 189.1 193.1,199.9

97 99 99 98

see text

216 Mn

Re

84

85

os

Rh

Ir

Ni

Pd

207.3 228,226.1,214.4

100 103

SO0

Gilje and Roesky


Table 1 (Continued)

angles around the central oxygen [106.9(2) to 107.6(2)'] being close tetrahedral. Each pair of Ti atoms is bridged by a formato and an hydroxo ligand. C. Zlrconlum

We are not aware of any hydroxide complexes of zirconium or hafnium in oxidation states other than IV. A number of hydroxide complexes of zirconium have been obtained from (CsH&ZrC12. With nitric acid in CHC13a dinuclear doubly OH-bridged complex [(C5H5)Zr(N03)2(~~2-OH)la.2thf is formed. The Zr atom has pentagonal-bipyramidal geometry with a C6H5 and an OH group occupying the axial positions and the equatorial plane containing two chelating NO3ligands and one OH group:14

?

N

M-O distance (pm)

ref

202.5 207.2 210 see text

2 101 102 104 105 106 107

see text see text

110 111

189.9

112

see text

113

aqueous sodium benzoate solution yields the trinuclear complex [Z~~(CL~-~)(CL~-~H)S(CLZ-CBHSCOO) [C6&,COO]-.O(C2H5)2. The complex cation is oxygen centered, and the Zr-0-Zr angles [107.3(1) to 108.9(2)OI at the central oxygen are close to the tetrahedral angle. Each pair of Zr atoms is bridged by a benzoato and a hydroxo ligand. The coordination octahedron around each Zr atom is completed by a C6H5 group+'

0

I N

L I

I

0

0

The reaction of (CsH5)2ZrC12 with CF3COOH in a two-phase CHC&/H20 system yields a dinuclear comin which the 18plex, [(C5H5)2Zr(OCOCF~)(~2-OH)12, electron Zr atoms are five-c00rdinate.l~ Salts of [(C~H~)~Z~~(CL~-OH)~(H~O)~I~+, a dihydroxy-bridged cation, have been obtained in the reaction of (C6H5)2ZrCl2 with AgCF3S03 or AgC104 followed by addition of water. X-ray structures of [(C5H&Zrz(p2-OH)z-

bh

(C5Me5)2Zr(OH)C1and (CsMe&Zr(OH)z were synthesized in high yield via treatment of (CsMe5)zZr(Bun)C1 and (C5Me&Zr(Me)z in hexane solution, respectively, with 1and 2 equiv of water. Confirmation of the two compounds as discrete, monomeric hydroxo compounds was provided by X-ray diffraction.ls Another structurally characterized complex containing a terminal Zr-OH is a hydroxo-N,N'-hydrazinoate produced by treatment of (CsMe&ZrMe(OH) with bis(p-t~lyl)diazomethane:~g

Base hydrolysis of (C~Me5)ZrCl3in thf yields [(C5-

Me~)ZrCll~(~~-O)(~~-OH)(~~-OH)~2thf. This cluster (H20)61(CF3S03)4.4thfand [(C~5)2Zr2(p2-OH)2(H20)61(C104)4.8thfshow that the Zr atoms have a distorted octahedral coordination geometry with a C5H5 group being trans to OH.16 Reaction of (C5H&ZrC12 with an

contains a nearly equilateral triangle of three Zr atoms capped above and below by p3-0 and KB-OHgroups and symmetrically edge bridged by three pz-OH groups which are coplanar with the three Zr atoms. The octahedral coordination sphere about Zr is completed by a terminal C1 and a C5Me5. Two chloride ligands


and one CsMes group lie on one side of the (-ZrO-I3 ring while the remaining C1 and the two CSMes groups are on the other, which produces a molecule with near Cs-m sy”etry.20121 The hydrolysis of (CsMes)ZrC13 with LiOH-HzO in This complex thf gives [ (CsMes)ZrCl2(H20)(1.12-OH)12. is also formed by hydrolysis of zirconium alkyls. 2(CSMes)ZrCl2R+ 4H2O

+

[(CsMes)ZrC12(H20)(~2-OH)12 + 2RH R = CH2C,Hs, SiMe, The dimer is [(CgHs)2Zr(NC-Prn)(1.12-OH)l2(BPh4)2contains a similar Zr2(1.12-OH)zunit.23 D. Hafnium We are not aware of any structural characterized organohafnium hydroxo complexes. V. Vanadium, Niobium, and Tantalum A majority of the structurally characterized hydroxo organometallic compounds of the group 5 metals are those of niobium. None have been reported for vanadium.


901

each Nb complete the coordination sphere. In this conformation two of the Nb atoms are bonded, while the third is not bonded to the others. The odd electron is coupled to a single Nb nucleus as indicated by a characteristic 10-line ESR spectrum. The very similar [(CSHS)N~C~I~(~~~-C~)~(I.~~0)is formed by hydrolysis of (CsH6)NbCL to [(CSHS)NbLrl2(1.12-0),where L4 is a combination of H2O and terminal or bridging C1 such that the niobium remains eight-coordinate and p e n t a ~ a l e n tfollowed ,~~ by reduction with aluminum, zinc powder, or sodium amalgam in thf. [( C S M ~ S ) N ~ C W ~(1.12-0H) ( ~ ~ ~ -(1.12-0) C ~ ) and polymeric [Nb&120~3thfl,are obtained by oxidation of (C~Mes)2NbC12 with 0 2 in the presence of H20.B Reduction of [(C~Me~)NbCl212(1.12-Cl)(cc2-OH)(1.12-0) by zinc powder in the presence of zinc oxide produces a double salt:

-

3[(CsMes)NbC1212(~2-C1)(~2-OH)(~2-0) + 2Zn + 2Zn0 [(C,Me,)Nb(1.1~-Cl)(1.1~-0)1~~ ~ ~ C s M e s ~ N b 1 3 ~ ~ 2 - C [Zn4C1,,I ~ ~ 2 ~ ~+2 - O ~ ~ ~ ~ 2

H2O Structurally [(C~Mes)Nb(ccrCl)012-0)13+ and [(CsMedNbl3(1.12-C1)2(~~~-OH)(1.12-0)3]+ are very similar only differing by the replacement of a bridging C1 in the A. Niobium first by an OH in the second. Hydrolysis of (C5Mes)NbCL with excess water leads The first structurally characterized niobium complex to a mixture of products.% Heating the crude mixture is the t r i n u ~ l e a r[(C~HS)N~OOCH]~(I.~TOH)~(I.~~-O)~*~~ which produces [(C~Me~)NbCl(cc2-0)33(1.13-0)(1.12-C1) (1.12-0) which was prepared by heating (CsHs)Nb(C0)3{ [ ( C S M ~ S ) N ~ I ~ ( O ~ H O ) H ) ~ ( I . ~ ~ (1.12-0)2(1.13O H) yields PPh3 with anhydrous HCOOH in xylene: 0)Cl)Cl upon treatment with water.%

In this d1 niobium compound the metal atoms are located at the vertices of an almost regular triangle with short Nb-Nb distances (314 pm, average). [(C&Me)Nb(CO)2C12]2undergoes decarbonylationB in refluxing thf to give a dark paramagnetic intermediate which reacts with atmospheric oxygen to produce another Nb(1V) trinuclear cluster [(CsH4Me)NbC113(1.12-C1)3(1.13-0H)(1.13-0). Within the triangular array there is one short, 282.7(1) pm, and two longer, 327.4(1) and 328.1(1) pm, Nb-Nb separations:2”lm

B. Tantalum There are few structures on hydroxotantalum complexes. (CSMe6)TaClr is quantitatively converted to [(C~Me~)TaCl2(OH)2]2(1.12-0) with excess of water. When this complex is heated in the solid state it loses water and HC1 to form [(C~Me~)Ta13(1.12-0)3(1.1~-0)(1.12Cl)Cla, which hydrolyzes in excess water to form the trinuclear cluster ([(C~M~S)T~~~(OH)P(I.~~-OH)(I. ( I . ( ~ - O ) ~ ( I . ~ ~ - OWhile ) C ~ this ] C ~is.not ~ ~the ~ formulation proposed in the original publication,90*31the compound almost certainly possesses the same structure as the analogous niobium complex.% (csMe~)Ta(H)2(~~-CHMez)PMes reacts with deoxygenated water in benzene to give the butterfly oxo The cluster [(CSM~S)T~(I.~~-O)~~(I.~~-O)~(I.~~tetranuclear core is surrounded by seven oxo ligands, four of which are doubly bridging, two of which cap the triangular faces of each wing, and one of which quadruply bridges the hinge and wing-tip tantalums:32

H-0’

\;a’/

‘0-H

10 ’

Each edge of the triangle is bridged by a chloride while a (p3-0) and a (p3-OH) triply bridge opposite faces of the Nb3 triangle. Terminal C&Me and C1 ligands on

0‘

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Gilje and Roesky

in the CeH7SiMe3 and the source of the OH is uncertain.a Usualelectron-countingconventionsimply a Mo-Mo bond, which is also indicated by the Mo-Mo separation, 288.2(2) pm. The average Mo-0 distance, 208 pm, and Mo-0-Mo angle, 88.1', are consistent with this description. Closely related is [ ( C ~ H ~ ) M O ( ~ ~ - C ~ ) ~ ( ~ Z - O H ) M O (C7H7)1+, which was one of several products from reactions between LiCl and [(C7H7)Mo(toluene)I[PFel in methanol.41 The Mo-O,208.4 pm (av), and Mo-Mo, 309.1(1) pm, distances as well as the Mo-0-Mo angle, 95.8(3)', resemble those in [(C~H~)MO(~~-B~)(CLO-O Mo(C~H,)]+.41 ( C ~ H ~ ) ( C ~ ) ~ M O ( ~ ~ - O H ) ( ~ ~ - S M ~ ) ~isoMO(C~)(C~ lated from a reaction between (C5H6)MoC&and CH3SH in diethyl ether, consists of a (C5H5)MoC12moiety linked to (C5Hs)MoCl through one OH and two SMe In contrast to niobium, no hydroxo complexes in which bridges.42The Mo-Mo distance, 272.6(1) pm, indicates the oxidation state of tantalum is less than V have been metal-metal bonding. The molecule is asymmetric and structurally characterized. the (C&JC12Mo-O distance, 196.5(5)pm, is longer than (C5H5)ClMo-O, 191.7(5) pm. Interestingly, the opVI. Chromium, Molybdenum, and Tungsten posite trend occurs with the Mo-S bonds, where those There are many similarities between the chromium to (C5Hb)C12Moare about 15 pm shorter than the ones group metals, and it makes little sense to separate them to (C5H5)ClMo. in this discussion. Among these elements a few terminal A structure has been determined for (C5Hs)(ON)hydroxo organometallic complexes are encountered. Cr(&3eBut)(p2-0H)Cr(NO)(C5H5), a minor product However, doubly or triply bridging hydroxo ligands are from the reaction of (C5Hs)(ON)2CrClwith Mg(Sefar more common. B u ~ ) The ~.~ Cr-0 ~ distance, 196pm (av), and Cr-O-Cr Only two monometallic organo-hydroxo complexes angle, 93.9(2)', are comparable to those in (~2-0H)of the chromium group have been structurally charbridged Mo and W compounds, when size differences acterized. The Mo is octahedrally coordinated in between the metals is taken into account. The H atom [Cr(en)3+]3[(NC)4Mo(O)(OH)]3- with the oxo and hyon oxygen was located and refined in the X-ray droxo ligands being trans.34 While the proton was not structure. located in the structure, the two Mo-0 distances are Three as of yet uncharacterized compounds were 207.7(7) and 166.8(5) pm and the OH is assumed to obtained in a reaction of [(CsH&Mo(H)(Li)14with NO. have the longer bond. This distance is comparable to Prolonged treatment of each with aqueous HPF6 gives in 205.0(5) pm in [(C~H~)~MO(NH~M~)(OH)]+PF~[ (C5H5)Mo(P-C&-C~H~) (p2-H)(12-OH)Mo(C5Hd 1which the cation has a typical bent metallocene (PF6)2:& structure.36 [(NC)4Mo(O)(OH)I3- is prepared from [(NC)4Mo02Ik by an acid-base reaction with water in methanol,34 and [(C~H&MO(NH~M~)(OH)Iby hydrolysis of [(C5H5)2Mo(SMe2)Brl-in dilute, aqueous NH2Me.36 A terminal OH is also encountered in (OC)2Co(p2PPh2)2(p2-C-C6H4Me)W(C5H5)(OH), where the W-0 distance, 208.7(6)pm, is nearly the same asthe distances mentioned above. This compound is obtained from The OH group symmetrically bridges the two Mo atoms, the corresponding chloride by hydrolysis on deactivated Mo-0 = 208 pm (av), Mo-0-Mo = 94.3(6)', and a Moal~mina.3~ Mo bond is indicated. There are several examples of hydroxo bridges. K3Pyrazoleborate and -galate chemistry has led to three [(OC)~M(P~-OH)~M(CO)~] forms during alkaline hynovel organo Mo and W hydroxides. Attempts to form drolysis of M(CO)6, M = Mo or W,38 and an X-ray a methylallyl complex analogous to [Me~Ga(3,5-Mezstructure has been determined on the tungsten derivaHC~N~)~IMO(CO)~(M failed,& ~ C ~ Hrather ~) t i ~ e While . ~ ~ the W-W distance, 323.0(5) pm, implies Me Me a metal-metal bond, such bonding is not required to produce an 18-electron count about the metals and the short separation may reflect geometric constraints imposed by the necessity of minimizing 0-0repulsions between bridging OH groups. The mean W-0 distance, 216(2) pm, is long, the W-0-W angle, 97(1)", is relatively narrow, and the O.-O contacts, 245 pm, are H less than the sum of oxygen van der Waals radii, 280 forms, apparently by hydrolysis of an intermediate with Pm. [(C7H7)Mo(p~-Br) (P~-OH)~MO(C~H~)]+ was obtained "adventitious" water. The X-ray structure, in which from a reaction between MO(CO)~(C~H~)+BF~and hydrogen atoms were located and refined, reveals Cd7SiMe3 in the the bromine was probably an impurity distorted octahedral coordination about Mo and a The two terminal hydroxo ligands are attached to the wing-tip Ta atoms. Direct metal-metal bonds are not required to interpret the structure. The hydrolysis of (C6Me5)TaC&31and the air oxidation of (C5Me5)TaC12(CO)2*thP3 produces [(CsMedTaCl212(p2-0)(p2-OH)z. The molecule consists of two C5Me5TaCl2 units bridged by one oxo and two hydroxo ligands9


folded Mo(p2-OH)zMo ring (dihedral angle 28’) with the oxygen atoms being displaced toward the pyrazole ligand to which they are hydrogen bonded. Two different Mo-0 distances occur in the molecule: 223.7(2) pm, to the Mo to which the hydrogen-bonding pyrazolate ligand is coordinated and 214.0(2) pm to the other.@ Hydrolysis involving water of unknown origin also occurs in attempted preparations of [MeGa(3,5-MezHC~NZ)ZI(~Z-OH)M(CO)~(RC~H~), M = Mo or W; R = H or Me. A structure of the Mo compound with R = Me shows4I

An interesting feature of this structure is that the hydroxyl hydrogen has been precisely enough located to show that the oxygen is pyramidal. The Mo-0 distance, 227.2(4) pm, is somewhat longer than these involved in typical Mo(p2-OH)Mo bridges. An unusual bridging hydroxide forms in the hydrolysis of a (pyrazol-1-y1)boratecomplex


Q03

In addition to the cubane complexes there is a Cr4 compound with the adamantane structure. (CsMe6)zCrz(C0)4reacts with H20 in refluxingtoluene to produce [(C6Me6)4Cr4(rz-OH)sl2+in moderate yield.& A structure, determined on the BF4- salt, shows a tetrahedral arrangement of (MesC6)Crunits with each edge bridged by an OH. This deep blue ion is paramagnetic and has been formulated as a Cr(II1) complex. The Cr-0 distance is 195.7 pm (av) and Cr-0-Cr is 140.4(4)’. Finally, if ci~-[Mo(N~)~(PMe3)41 and COZare allowed to react in a 2:l acetone/toluene mixture for 15-20 days “small amounts” of red-orange Moq(p4-CO3)(CO)Z(O)Z(~z-~)z(cLz-OH)~ were (PM iso1ated.M ~ ~ ) ~ The structure of this unusual MoLMoVspecies is

V I I . Manganese, Techneclum, and Rhenium

A. Manganese The characterized organomanganesehydroxides have structures based on the cubane core. When conducted in thf Mnz(CO)lo and Me3NO.2HzO give [Mn(C0)3( F ~ - O H ) ~Structures ] ~ . ~ ~ have been determined on bis adducts with toluene67 and ethylenediamine,68 with which it forms a hydrogen-bonded diamondoid network. [Mn(C0)3FX(~3-OH)4,]4 which was isolated from the reaction of Mn(C0)sX (X = C1 or Br) with T1F or AgF. A structure was determined on a crystal where x = 1.4. Apparently the fluorides and hydroxides are disordered.S9 A complex with higher nuclearity, Mn7(CO)l~(p3While the details of the reaction are beyond the scope OH)18,forms when benzophenone is present during the of this review, an initial coordination of water to the reaction of Mn&O)lo with M ~ ~ N O - ~ H This Z O .Mn7 ~~ metal is postulated.& A structure was determined for species consists of two cubane units joined through a the W derivative and the W-0 bond, 219.4(6) pm, is in common corner Mn atom. The geometries and Mn-0 the usual range. bond distances involving [Mn(C0)3(p3-OH)4]4,[MnFrom the viewpoint of this review, the preceding two compounds are particularly interesting as they are (C0)3Fx(p3-OH)~z14, and the outer six Mn atoms in among the very few examples of an OH group bridging Mn7(CO)l8(p3-OH)l8areessentially identical. However, coordination of the central Mn, which joins the two transition and main group metals. The most common structure encountered in the cubane units, in M ~ . I ( C O ) I ~ ( ~ ~is- Ointermediate H)~~ organo-hydroxo complexes of the group 6 metals is a between octahedral and trigonal prismatic and its Mn-O distances, 216.9(2) pm (av),are longer than the 205-pm cubane-like arrangement with metal and hydroxide Mn-0 separations seen in the other complexes and in oxygen atoms occupyingalternate corners of a distorted the outer atoms of the Mn7 species. This unique atom M404 cube. In general these clusters are electron is assigned as Mn(I1) on the basis of its structure and precise, with OH- utilizing three lone pairs to bond a charge balance c r i t e r i ~ n . ~ ~ three metals. The structurally characterized examples M o , WW), ~ ~ ~ ~ are [ ( O C ) ~ M ( ~ L ~ - O(M H)= ] ~ Crt9 ~ B. Technecium [(ON)(OC)ZMO(P~-OH)I 416’ [(C~H~)MO(P~-OH) 1 4 t 1 and [(OC)3W(p3-0H)(H)]4.53The cores of all of these are We are not aware of any structures for organometallic typical of A4B4 cubane complexes.” The Mo-0 and hydroxides of this element. W-0 bond lengths range between 215 and 228 pm while the Cr-0 range is 211-215 pm. C. Rhenium While details of the individual syntheses vary, the trans-(Dioxo)(tetracyano)rhenium(V), [ReOz(CN)4Is, M(C0)3compounds are formed by reactions of M(CO)s or related carbonyl derivatives with base,4M1*53the NO can be protonated to [ReO(OH)(CN)rl” which can be crystallized as the [PPb]+salt. The [ReO(OH)(CN)412complex from C(OC)~Mo(r~-OH)(H)l4, and NO.62 [ ( C ~ H ~ ) M O ( ~ ~ -formed, O H ) ] ~along with [ (C7H7)Moion has a distorted octahedral geometry. Bond distances are Re=O = 170(1), Re-OH = 190(1), and ( ~ z - C ~ ) ~ ( C ~ Z - O H ) M ~during ( C ~ Hattempts ~ ) ] ~ , to crystallize ( C ~ H ~ ) M O ( C I ) ( M ~ C ~ H S ) . ~ ~ Re-C (av) = 212(2) pm. The Re atom is displaced 8

904

Gilje and Roesky


pm out of the plane formed by the four carbon atoms toward the terminal oxo ligand, and the O=Re-OH unit is nearly linear, 175.7(5)0.m Photolysis of Re2(CO)e(PhzPCH2PPh2)in wet toluene or benzene leads to a 35 % yield of Re2(CO)6(~2-H)(Ph2PCH2PPh2)(p2-OH)and a 35 % yield of Rez(Co).~(Ph2P C H ~ P P ~ ~ ) ( P ~ -A Ocrystal H ) ~ . structure, which locates the OH, CH2, and hydride hydrogens, shows the first of these to be Ph2P

NCH2\

o

k

PPh2

o

The Re-0 distances are 217.7(5) and 216.0(5) pm and Re-0-Re is 88.6(2)', within the slightly asymmetric Re20(0H) ring.61 A Re3cluster containing a p&H, [Re3(~2-H)3(CO)g(p3-OH)]-, has been isolated as an NMe3 adduct from reactions of [Re3(p2-H)3(CO)g(p2-0)]e with Me&JH+Cl-, by protonation of [Re3(p2-H)3(CO)s(p2-O)12followed by treatment with NMe3, or by reaction of [Re3(p2H)4(C0)10]-with ONMe3. In the ONMe3 reaction the (pz-OH)comes either from water present in the amine oxide or by attack of a hydride on the oxygen of coordinated amine oxide. The structure of the anion is !E+,

with Re-0 = 212.6 (av), Re-Re = 297.9 pm (av), and Re-0-Re = 88.9O (av). The 0-H is hydrogen bonded to a triethylamine.62 [(OC)3Re(p3-OH)14,from the reaction of Re2(CO)lo or Re(C0)sClwith H2O at 200 0C,63possesses a distorted "cubane" structure. The Re atoms are approximately octahedral, and R e 4 = 220.7(8) pm, 0-Re-0 = 73.9', and Re-0-Re = 104.0(5)'. Each of the 0-H groups hydrogen bonds to a benzene molecule which lies perpendicular to a crystallographic 3-fold axis which passes through the OH group. Each benzene is involved in two of these hydrogen bonds and, as such, uses both faces in its interaction with 0-H groups.M A final organorhenium hydroxide is the unusual H

which formed by partial hydrolysis during the crystallization of ([ (OC)5Re130)BF4.The two compounds cocrystallize. The OH of F3B(p2-OH)Re(C0)5hydrogen bonds to a BF4- anion and Re-0 = 216.7 and B-0 = 147.6 pm.65 V II I. Iron, Ruthenium, and Osmium A. Iron

The two structurally characterized organoiron hydroxides are Fe2(Co)s(p2-PRR')(p2-OH)with R = R' =

p-C6H4MeS and R = CH(SiMe&, R' = H:67

Both structures are typical of Fez(CO)6(pz-X)2compounds but are unusual in that they have two different bridging groups. Fe&O)6(p2-P(H) [CH(SiMe3)21)(p2OH) possesses the additional unusual feature of cocrystallizing with F~~(CO)~(~~-CO)(~Z-H)(~Z-P[C (SiMe&l (OH)), which hydrogen bonds through its P-OH group to the O(H) of Fe2(CO)6(p2-P(H)[CH(SMe3hl )OLTOH).~In F ~ ~ ( C O ) ~ ( P ~[CH(SiMe3)21 -P(H) 1(p2-OH) the Fe-0 = 199.0(2) pm and Fe-0-Fe = 76.6(1)067and in Fe2(CO)6[c~2-P(C6H4Me)2l(p2-OH) the corresponding values are 197.2 pm (av) and 79.1(2)'.% F ~ ~ ( C O ) ~ ( ~ ~ (p2-OH) - P R Z ! )(R = p-CsH4Me) forms in low yield as a side product during direct reactions of Fez(C0)g with PRzH or in 60% yield by Fe(CO),(PR,H) Fe(CO),(PR,)Li

+ BuLi

+ Fe2(CO),

-

-

Fe(CO),(PR,)Li

thf chromatography --+

over alumina

Fe2(CO)6(~2-PR2) (/J~-OH) The sources of the OH- is unknown, but the relatively high yield argues against reactions involving minor impurities.@ Fe2(CO)&2-P(H) [CH(SiMe3)21)(~2-0H) is one of a large number of products formed in the reaction of [NEt,l2[Fe2(CO)el with clzPCH(SiMe3)~.~~ B. Ruthenlum and Osmium Apparently no monometallic organo hydroxides of ruthenium or osmium have been structurally characterized. Rather a number of remarkable clusters are encountered. In the simpler complexeswhich contain p2-OH ligands the M-0 distances are typically between about 207 and 210 pm, while in higher clusters about 212-216 pm is more typical. Within many complexes there are small differences in apparently similar M-0 bonds, and some structures contain several molecules per asymmetric unit, each with somewhat different bond lengths and angles. There are no significant differences between Ru-0 and Os-0 bond lengths, and the angles involving the OH groups often appear to be influenced more by the geometric constraints of the cluster than by intrinsic interactions between the hydroxo ligand and the metals to which it is most closely associated. The hydrolysis of [(arene)MC12]2 (M = Ru or Os) provides a variety of hydroxo complexes depending on the arene and the exact conditions of the reaction. With CeMe6, or p-MeCeH4CHMe2 the bulky 1,2,5-Me&& and aqueous Na2C03 or NaOH, [(arene)Ru(pa-OH)aRu(arene)]+ is obtainedF

-

NaSCOs

[(arene)RuCl,I,

(or NaOH)

(arene)Ru(p,-OH),Ru(arene)l+ With arene = C6H6 the reactions of [(C6H6)MC1212are more complex. In aqueous solution with approximately



equal metal and C032- concentrations a tetrameric cation forms:

005

Me

/[< o'c\o \-

0

1

(Bu"),P-R,6

I'

Me

0

p7 0

-R ~ - P I B u n l 3

t

It

+

M e COOH

t

0

-

0

[(C,&)RU(~~-OH)]~~+ contains a cubane core of alternating ruthenium and oxygen atoms.69 In contrast, a tetranuclear oxo-centered cation forms with excess NaOH or Na~C03: excea

NazCOs ,

.

'0' I

c=o

I In this compound two binuclear [(C~H~)M(~Z-OH)ZMMe (CeH6)l2+ units share a tetrahedrally coordinated oxide ion.68 The hydroxo hydrogen was located in the final differA triply OH bridged ion has been obtained by the ence map but was not refined. hydrolysis of a phenoxide complex:70 Structural confirmation is available for a number of hydroxo M3 carbonyl clusters. Among the simplest of these is Os&O)g(L)(pZ-OH) (pz-H) which is obtained from the as of yet structurally uncharacterized Os3(CO)&2-OH) (pz-H) by ligand exchange7, or by an unusual route from 0~3Hz(CO)g(PMezPh):'~ Perhaps this method succeeds because it avoids basic Os3 (CO),, I p - O H 1 ( p - H ) media employed in the reaction of [(C~H~)MC~ZIZ, and L = PPh, which may favor formation of the tetranuclear species. The [(arene)M(p~-OH)3M(arene)l+ complexes themselves can serve as precursors to binuclear hydroxo complexes. With pyrazole71

Ru OJ - OH13 R u

@

@""5-

IOC)'

L = PMe, P/:

Os, IC0l91L) l p - H ) 2

and with aldehydesT2

Another bimetallic ruthenium complex, which contains a single, doubly bridging hydroxide, forms in an oxidation using peracetic a ~ i d . ~ 3

H20 Me CH, C1O)Me +

CH, = C H C l O ) M e

An analogous reaction of OS~(CO)~O(~Z-OH) (p2-H)with PhzPCHzPPhz (dppm) produces Os3(CO)a(dppm)(p2OH)(pz-H) in which the dppm, OH, and H all bridge the same edge of the OS3 triar~gle.~e More unexpected pathways to M3 hydroxo clusters include an isomerization of the product of the reaction between 0s3(CO)lo(NCMe)~and Me&=NOH:

The structures of all of these clusters are normal. In each the Os-Os distances lie between about 270 and 300 pm, which are typical for Os-Os bonds. However, there are several trimetallic clusters in which the metals bridged by hydroxide are not directly bonded. Thus

906

Gilje and Roesky


(ps-OH)(p2-PPh2) where one of the Ru3 triangles is capped by the OH. The same RUBunit is edge bridged by PPh2 and capped on the side opposite the OH by the vinylidene group which itself complexes the remaining wing-tip Ru. The hydrogen on the OH was located in a difference map. The compound was formed by hydrolysis of R U ~ ( C O ) ~ ~ ( P ~ ~ P Cin=moist C P ~ thf.83 ~) While no M5hydroxo clusters have been characterized for the iron group several & complexes are known. Os3(CO)~(NMe3)(p2-OH)(p3-S)(p2-H), which is mentioned above, reacts with O S ~ ( C O ) ~ O (to ~ ~produce -S) 096(C0)18(112-OH)(p~q-S) (p3-S)(p2-H):80

in which the distance between the two osmiums bridged by OH is 337 pm, indicating there is no direct bond between these m e t a l ~ . ~ ~ J ~ In another trimetal cluster, F ~ R U ~ ( C O ) ~ ( P P ~ ~ ) ~ ( C L Z OH)2, the Ru-Ru edge is bridged by two OH groups and the ruthenium atoms are not bonded. This complex forms by chloride substitution in weakly basic solution: CI

Na2C03/acetone _.

Fe KO),

NBu,

OH lacetone

H

lPh,P)lOC),

I\ //\I

0

/o

The 0-H proton was located in a difference map, but was not refined. The hydride was not located but is assumed to bridge the longest Os-Os bond. UV radiation of a mixture of Ru3(CO)g(p3-CO)(pg-S) and RUQ(CO)~P in wet thf produces R U ~ ( C O ) I ~ ( ~ ~ - O H ) ~ (Il.4-8):

RU

\ /

Ru(CO), (PPh, 1

Fe(CO),

In Na&03/PrOH a lower yield is obtained, along with a side product which may be the mixed hydridohydroxo complex.79 One of the more successful methods of activating metal carbonyls involves the use of Me3NO which converts CO to C02. Me3N0.2H20 also has been successfullyemployed to prepare an osmium-hydridohydroxo complex: Os,

( p 35 )

+

2Me,NO. 2 H 2 0

-

IOCI‘

The hydroxyl hydrogens were located and refined and one hydrogen bonds to the second oxygen. Formal electron counting indicates this to be a 94-electron, rather than a 92-electron precise complex. Two lowenergy absorptions which are responsible for the compound’s blue color are attributed to the extra two electrons occupying antibonding orbitals within the core of the molecule.84 A final Me complex is [Ru3Cl3(CO)6(COEt)2(p3~ OH)]2.85 The three ruthenium atoms in each half of the dimeric unit are octahedrally coordinated. The octahedra share a common vertex occupied by a hydroxo group:

The osmiums which are bridged by OH are not bonded as indicated by their 370.7(6)-pm separation.80 Several M4 hydroxo clusters are known. With the exception of which was mentioned earlier, they all possess a “butterfly”conformation of the metal atoms in which, with one exception, the “wing tips” are connected by a bridging OH. [Os~(CO)12H~(p~-0H)]+[Os(C0)~(N03)~1has been obtained in high yield by reaction of Os4(CO)12H4 with N204. The first step apparently involves oxidation to [Os4(C0)12H4l2+,followed by a series of proton dissociations and the addition of water, whose source is unknown.8l In a similar process [Os4(C0)12H31- is oxidized by NO+PF6-in wet MeCN to several products including O S ~ ( C O ) ~ ~ H ~ & ~The -OH heavy-atom ).~ structures of [ O S ~ ( C O ) ~ ~ H ~ ( ~ ~and - O Os(C0)12H3(p2H)I+ OH) are the same. While the hydride locations are not unambiguouslyestablished, they are thought to lie along the “wing tips” of the Os4 butterfly. A different disposition of ligands about the M4 butterfly core is encountered in R U ~ ( C O ) ~ O ( C = C H P ~ ~ -

0

c 0

0



The complex is prepared by the reaction of Ru(C3Hs)cl(c0)3with C H d H 2 in benzene. The Ru-OH distances are 216 pm (av). IX. Cobalt, Rhodium, and Irldlum A. Cobalt We are unaware of any structurally characterized organocobalt hydroxides. B. Rhodium and Iridium Ir(CH2EMe3)(CO)(PPh3)2 (E = C or Si) can be hydrolyzed to Ir(OH)(CO)(PPh3)2. Befitting a derivative of Vaaka's compound, the coordination about Ir is trans-square planar. The Ir-0 distance, 211.0(9) pm, is close to the sum of the covalent radii of 0 and Ir.= This is the only structure of a terminal hydroxo complex of Rh or Ir. There are a number of neutral or cationic dirhodium or iridium complexes containing bridging hydroxo groups. [(C3H5)2RhC1]2reacts with KO2 in CH2Cl2 to form ( C ~ H ~ ) ~ R ~ ( C L - O Hin )~ 70R% ' ~yield. (C~H The ~)~ reaction is thought to proceed through a dioxygen intermediate which abstracts hydrogen from the solvent, forming the final product.s7 In (CaH&Rh(pOH)2Rh(C3H5)2 rhodium is cis-octahedral if the coordination sphere is defined by the terminal carbons in the allyl groups and the two bridging hydroxide oxygen atoms. The average metrical parameters in the Rh202 core are Rh-0 = 217.7 pm, O-Rh-O = 81.8', Rh-O-Rh = 98O.= Cationic [(C5Me5)(L)Rh(p-OH)2Rh(CsMe5)(L)12+ forms with a variety of pyridine type ligands by

SO7

The hydroxo ligands in [(CsMes)Rh(p2-0H)3Rh(C~Mes)]' can be substituted by acid-base reactions

-

[(C,Me,)Rh(p2-OH),Rh(c6Me5)]+ + 2HL [(C6Me5)Rh(p2-OH)(r2-L)2Rh(C5Me6)l+ + 2H20 and the structure of one of these has been solved; the

r

1

Rh-O distance is 211.0(4) pm and the Rh-O-Rh angle is 111.7(2)O.OO Air oxidation of Ir2(C~H12)&12produces (CSH12)(Cl)Ir(p2-O)(p2-OH)2~(C~H12)(Cl) in low yield. In this complex the octahedrally coordinated metal atoms are joined by three bridging oxygens, two of which have been assigned as OH and one an 0. While an unambiguous determination of the bridging groups was not possible the two symmetry-related groups whose Ir-0 distances, 209.8(1) pm, exceed the remaining 11-0 separation, 202.4(8) pm, are thought to be the hydroxo A bis-iridium p2-oxo complex undergoes a dramatic, rearrangement upon heating in benzene or toluene to produce a &-OH) linkage: A

-

[(C5Me6)Rh(c12-OH)3Rh(C5Me6)l C10, + HClO,

+ 2L

[(C5Me5)(L)Rh(c12-OH)2Rh(C6Me6)(L)l (ClO,), + H2O

A structure has been determined for the pyridine adduct. The coordination around the rhodium atoms is pseudo-octahedral with the CNe5 occupying three fac positions, pyridine one, and the hydroxides the remaining two sites. Distances and angles are Rh-O = 211 pm (av), O-Rh-O = 76.8(2)O, and Rh-O-Rh = 103.1(2)'. The bridging OH groups are hydrogen bonded to the C104-.89 The very similar complex with L = 3,bdimethylpyrazole, Me2CHN2H, has also been structurally investigated. In this compound Rh-O = 217.9 pm (av), O-Rh-O = 129.8' (av), and Rh-O-Rh = 99.3O.OO There are several complexes in which two Rh or Ir atoms are connected by triple bridges, at least one of which is an OH. Tris-p2-hydroxo structures are known for [(C5Me5)M(p2-OH)3M(CsMes)]+Xwith M = Rh and X = OH- and for M = Ir and X = MeCOZ-. Assuming the CsMes ligands each occupy three coordination sites the metal atoms are pseudo-octahedral and the two C5Mes rings are approximately parallel. Mean distances are Rh-O = 210.9 and 11-0 = 212.0 pm, and angles are Rh-O-Rh = 89.5O, O-Rh-O = 75.0°, Ir-0-Ir = 92.8O, and O-Ir-0 = 73.3O. In both cases the bridging hydroxides are hydrogen bonded to the anion and, in the Rh compound,to waters of cry~tallization.~~

R,

The reaction occurs when R is 3-MeCeH4 or P h and a structure has been determined for the Ph derivative. The Ir-0 distance of 214 pm is considerably longer than either of the two Ir-0 distances in the starting oxo complex" Finally, two very similar Rh and Ir "A frame" complexes, prepared by trans

- [MICI)ICO)(R,PCH,PR,)I,

+OH-

-

have been structurally c h a r a c t e r i ~ e d . ~The . ~ ~ basic structures of the two anions are very similar: 11-0 = 207(2) pm, 114-h = 99.4(8)' and Rh-O = 206.8(4) pm, Rh-0-Rh = 99.1(1)". In the structure of the Ir complex the OH hydrogen was located in the difference map, but was not refiied. In both complexes the

908 Chemical Reviews, 1994, Vol. 94,

Gilje and Roesky

No. 4

hydroxide hydrogen bonds, in the Ir caseF4 to a C1counterion and, with Rh,g5to an acetone of solvation.

I(MeC,H,CH,l(Me,P)

Nilp-OH)],

+

NiR,ltmedl

PMe,

-

ti I

X. Nickel, Palladium, and Platlnum

/ .0\

/ Ni

A. Nickel

MeC6H4Ch,

Structures have been reported for four organohydroxide complexes of nickel. Three of these were prepared by metathesis reactions and a rational synthetic route has been designed for the fourth, which originally was found as a minor side product in another reaction. The treatment of trans-Ni(PMea)~(R)(X), R = alkyl, with HzO or OH- yields alkylnickel dimers containing bridging hydroxides. While a variety of alkyl groups have been utilized96-98 a structure is only available for R = CH&H4Me, which was synthesized by

M~c,H,cH(

-

2(MeC,H,CH2) (Me,P),Ni(NC,H,Me,) + 2H,O (MeC,H,CH,) (Me3P)Ni(rz-OH),Ni(PMe3) (CH2C6H4Me)+ 2PMe, 2HNC4H,Me,

+

The Ni atoms are approximately square planar, and the Niz(0H)z core is folded (dihedral angle = 133.6’) with the oxygen atoms oriented toward and apparently hydrogen bonded to a 2,5-dimethylpyrrole molecule of crystallization. The Ni-0 separation is 191.9 pm (av). An anionic doubly OH bridged complex is also obtained by metathesis:

Distances and angles within the planar NiZ(0H)z core are Ni-0 = 189 pm (av), Ni-0-Ni = 99.2(4)’, and Ni0-Ni = 80.8(4)0.w The hydroxides in this anion are labile, and mono or disubstituted derivatives can be obtained from reactions with various bases. A monohydroxo complex forms from the reaction with pyrazole, C ~ H ~ N Z H :

A structure on the [But4N]+ salt shows the fivemembered ring, containing the two Ni atoms, has an envelope conformation. The average Ni-0 distance is 189.1(4) pm.% The final structurally characterized Ni complex is ) Z ~ Loriginally ~ ’ O H ) was Z Ni3(C H ~ C ~ H ~ M ~ ) ~ ( P M ~ ~ which obtained as a minor side product during the work up of reactions between NiC12(PMe& and Mg(CHzCsH4Me)(Cl). Subsequently it was prepared in 70-8095 yields byg8

\

/

CH C H Me 2 6

!‘\p,qe3 /Ni/PMe,

0’ ‘CH2C,H,Me I

H

Each Ni is approximately square planar with the three planes’ edges joined through the (p3-OH) groups. The Ni-0 distances to the nickel which is also bonded to two alkyl groups are 199.9 (av) and 193.1pm (av) to the other two.

B. Palladium and Platlnum A Pt complex, (dppe)PtMe(OH), whose Pt-0 bond distance is 202.5(8) pm has been mentioned in a review article, without details.,

[(C~F~)ZP~(~Z-OH)ZP~(C~F~)~I” can be prepared by a route analogous to that for [ ( C ~ F ~ ) Z N ~ ( ~ Z - O H ) Z N ~ (C6F6)z12-:loo

with platinum this method fails as coordinated benzonitrile undergoes nucleophilic attack by hydroxide. However, the bis(pz-OH) platinum complex has been obtained by chloride metathesis:lol

All three [B~NIz[(C~FS)ZM(~Z-OH)ZM(C~FS)ZI compounds (M = Nilo2,Pd”, PtlOl) are isomorphous, with square-planar metals forming a planar MzOz ring. The metrical parameters are nearly the same for the Pd (Pd-0 207.3 pm (av), 0-Pd-0 81.2(4)’, Pd-0-Pd 98.8(4)’) and Pt compounds (Pt-0 207(2) pm, 0-Pt-0 78.6(5)’, Pt-0-Pt 101.4(6)’) and are similar to those in the Ni compound when allowance is made for the different sizes of the metals. The reactions of [(CsFs)zPt(r~-OH)zPt(CsF5)1” with azoles are very similar to those of [(C~F~)ZN~(PZ-OH)ZNi(CsF&]”. A structure has been determined for [ B u ~ N I z [ ( C ~ F ~ ) Z P ~ ( ~ Z -(~w,0~H-) MP ~ t -Z C ~ H N Z ) (C6F5)2].lo2The central five-membered PtzNzO ring is puckered, the average Pt-0 distance is 210 pm (av) and the overall structure closely resembles the nickelpyrazolate complex. A tripalladium complex, I[(&mq)Pd]3013-Ph2PCHC02 Et) (P~-OH)]+PF~-, has been characterized from

Chemical Reviews, 1994, Voi. 94, No. 4


2(Me3Si),CZnC1+ 2Hz0

-

909

(Me3Si),CZn(p,-OH),ZnC(SiMe,)3

C

,Pi b

Li

(N

C

=8-q.

The OH is thought to originate from traces of water in solvents or on the silica gel used to purify the compound. There are three different Pd-0 distances: 228(1) pm to the Pd which is also bonded to phosphorus, 226.1(8) pm to the carbon-bonded Pd, and 214.4(9) pm to the P d which is coordinated by two oxygens. The differences in bond lengths may be due to differences in the trans ligand.lO3 In 1947 a structure of “tetramethylplatinum” was pub1ished.lM Later the crystals used in this early study were shown to be [Me3Pt(p3-OH)14.1°5 In 1968X-ray” and neutron diffraction107 studies appeared on [MesPt(p3-OH)]4, precipitated from solutions containing Me3Pt+upon the addition of base. While none of these is precise by modern standards, they establish that [MesPt(p3-OH)]~possesses a cubane like structure with Pt-0 bond distances of about 220-222 pm. In the neutron structure the hydrogen atoms have been located and the 0-H bond, 93(8) pm, is directed away from the Pt404~luster.~07 XI. Copper, Silver, and Gold A. Copper and Silver There is much interest in hydroxo-bridged copper complexes, which are important in establishing magnetic interactions between d9ions.lW Nonetheless, there do not appear to be any structures available for organocopper hydroxides. Likewise organosilver hydroxides have not been structurally investigated.

B. Gold Structures are known for two organogold hydroxides. In both, square-planar gold atoms are joined through double hydroxobridges. { [PhC=C(Ph)C(Ph)=C(Ph)]Au(pz-OH))z,isolated from the reaction of LiC(Ph)=C(Ph)C(Ph)=C(Ph)Li and AuC13,lW is planar with the exception of the phenyl groups.ll0 In contrast, the four square-planar gold atoms in [MezAu(p~-OH)l~ are tilted with respect to one another giving the molecule apThe Au-0 distances in both proximate S 4 compounds are varied and range between 184 and 227 pm in [Me2Au(p2-0H)l4 and 209 and 226 pm in {[PhC=C(Ph)C(Ph)=C(Ph)IAu(p2-OH)jz. However, both structures were determined using photographic data and final R values are above l o % , so detailed analysis of the metrical data is probably not valid. X I I . Zinc, Cadmium, and Mercury

An alkylzinc hydroxide has been obtained by the hydrolysis of (Me3Si)&ZnCl with NaOH in wet thf

In contrast to other organozinc hydroxides, (MeaSi)sCZn(p~-OH)zZnC(SiMe3)3 is stable in moist air. The C-Zn(p2-OH)zZn-C fragment is planar (Zn-0 = 189.9(9) pm, 0-Zn-0 = 77.5(3)’, and Zn-0-Zn = 102.3(3)0).112 A tetrameric, distorted cubane, somewhat unstable cadmium hydroxide forms in the hydrolysis of (C$& Cd in moist toluene: 4Cd(C,F,)z

+ 4HzO

-

toluene

[ ( C $ ‘ ~ ) C ~ ( P ~ - O+H4C, ) IF~.$

Cd-0 distances range from 220 to 229 pm and the Cd0-Cd angles are about 100’ while the 0-Cd-0 angles are near 8Oo.ll3 No organomercury hydroxo complex has been structurally characterized. X I I I. Acknowiedgments

The support of the Materials Research Program at the University of Hawaii, the Deutche Forschungsgemeinschaft, and the VW-Foundation is gratefully acknowledged. X I V. References (1) Bottomley, F.; Sutin, L. Ado. Organomet. Chem. 1988,28, 339. (2) Bryndza, H. E.; Tam, W. Chem. Reo. 1988,88, 1163. (3) Evans, W. J.; Hozbor, M. A.; Bott, S. G.;Robineon, G.H.; Atwood, J. L. Znorg. Chem. 1988,21, 1990. (4) Hitchcock, P. B.;Lappert,M. F.; Prashar, S.J. Organomet. Chem. 1991, 413, 79. (5) H e r r ” , W . A.; Anwander, R.; Kleine, M.; bfele, K.; Riede, J.; Scherer, W. Chem. Ber. 1992,125, 2391. (6) Schumann, H.; Loebel, J.; Pickardt, J.; Qian, C.; Xie, 2.Organometallics 1991, 10, 215. (7) Ariyaratne, K. A. N. S.Ph.D. Thesis, University of Hawaii, 1992. (8) Guggenberger,L. J.;Tebbe, F. N. J. Am. Chem.SOC.1976,98,4137. (9) Bochmann, M.; Jaggar, A. J.; Humthouse, M. B.; Mazid, M. Polyhedron 1990,9, 2097. (10) Bochmann, M.; Jaggar, A. J.; Wileon, L. M.; Hursthouse, M. B.; Motevalli, M. Polyhedron 1989,8,1838. (11) Thewalt, U.; Honold, B. J. Organomet. Chem. 1988,348, 291. (12) Liu, F.; Roesky, H.W.; Schmidt, Ha-G.;Noltemeyer, M. Organometallics 1992, 11, 2965. (13) Dbppert, K.; Thewalt, U. J. Organomet. Chem. 1986,301,41. (14) Lasser, W.; Thewalt, U. J. Organomet. Chem. 1984,275,63. (15) Klima, S.;Thewalt, U. J. Organomet. Chem. 1988,354, 77. (16) Lasser, W.; Thewalt, U. J. Organomet. Chem. 1986,311, 69. (17) Thewalt, U.; Dbppert, K.; Lasser, W. J. Organomet. Chem. 1986, 308, 303. (18) Bortolin, R.; Patel, V.; Munday, J.; Taylor, N. J.; Carty, A. J. J. Chem. Soc., Chem. Commun. 1986,456. (19) Santarsiero, B. D.; Moore, E. J. Acta Crystallogr. 1988, C44,433. (20) Babcock, L. M.; Day, V. W.; Klemperer, W. G.J. Chem.SOC.,Chem. Commun. 1988,519. (21) Babcock, L. M.; Day, V. W.; Klemperer, W. G.Znorg. Chem. 1989,

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910


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