JPH06508890A - Use of organometallic compounds to deposit metals on substrates - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Use of organometallic compounds for depositing metals on substrates The present invention uses metals of Group 2 as metals. or elements of group 4, elements of subgroups 1 to 8, rare earth elements, or bismuth organometallic compounds containing for the production of thin films or for the deposition of metals. For the production of epitaxial layers, the organic It relates to the use of metal compounds while decomposing them.

consisting of pure elements or their combined forms with, for example, nitrogen, arsenic, or phosphorus; The deposition of this layer can be applied to electrical, optical, optoelectronic, switching devices, and compound semiconductors. , can be used in the production of lasers.

The properties of these films depend on the deposition conditions and the chemical composition of the deposited film. fluctuate.

These layers can be deposited from the solid phase, liquid phase, or gas phase.

Possible deposition methods from the gas phase include metal-organic vapor deposition (MOCVD), UV Photo-metal organic vapor phase (photo-MOVP) method, in which materials are decomposed by irradiation, laser compound vapor deposition (laser CVD) method, or metal-organic magnetron All known methods are included, such as the sputtering (MOMS) method. credibility The advantages compared to It is easy to operate and manufacture under atmospheric or low pressure conditions.

The MOCVD method is an organic metallization process in which metals are decomposed while being precipitated at temperatures below 1100°C. Use a compound. The typical equipment currently using MOCVD is organometallic Outlet called "bubbler" with feeding device for material, substrate to be coated A carrier gas that must be inert for reaction chambers and organometallic components containing consists of sources for resources. The "bubbler" is preferably an organometallic compound to a constant, relatively low temperature above the melting point of a substance but far below the decomposition temperature Maintained. The reaction chamber or decomposition chamber preferably has a much higher temperature. However, the temperature is below 1100℃, at which the organometallic compound is completely separated. The metal is precipitated. Steaming organometallic compounds using a carrier gas and introduced into the decomposition chamber together with the carrier gas. Easy amount of steam flow This allows for well-controlled growth of thin layers. ing.

Other methods of vapor phase deposition basically only provide the energy necessary for decomposition. is different from others.

Vapor phase deposition methods are complex in terms of technology, equipment, and many manufacturing parameters. It has the disadvantage of requiring control and monitoring.

When such a system for vapor phase deposition is not available, either liquid or solid phase can be used. A method involving the precipitation of these methods is much more convenient. In this case, use a reasonable organometallic compound. Prepare a substrate with a liquid or solid coating containing the organometallic Only heat treatment is necessary to decompose the compound.

Deposition of metals from the liquid phase is carried out, for example, by spin-on techniques. this child means applying an amount of a solution or formulation to the center of the substrate and, after stirring, This includes rotating the person at a preset speed. As a result As a result, a film of uniform thickness is formed on the substrate surface, and the thickness depends on the spin speed. The metal content is determined by the concentration of the organometallic compound and the viscosity of the formulation. Therefore, it can be decided in advance. After evaporation of solvent and decomposition of organometallic compounds After heating above the temperature, a metal layer can be obtained on the substrate.

Up until now, epitaxial layers have mainly been produced using trimethylgallium, trimethylalium, etc. carried out using metal alkyls such as aluminum or trimethylindium. It's here. These compounds are extremely sensitive to air and moisture and cannot be released spontaneously. Flammable, some compounds decompose at temperatures not much above room temperature. I'm sorry The synthesis, transportation, storage and use of these compounds require complex safety measures. shall be. Due to its sensitivity, disposal is problematic and recovery is virtually impossible. It is.

Attachment with Lewis bases such as trimethylamine and triphenylphosphine Addition compounds (e.g. GB21 23 422, EP-A 108469 or E P-A 176537) or within molecules of this type. regulated compounds (e.g. DE-A 36 31 469 and DE-A38 41, 643) which became known over time. There are limits to the use of This is because it is too volatile for vapor phase deposition.

The object of the invention is to be insensitive and simple to operate and to provide both liquid and gas phase The objective is to find suitable metal organyls for precipitation from .

Elements of groups 2 to 4 and subgroups 1 to 8 of the periodic law as metals, rare earths A multiply coordinated organometallic compound containing an element from the group of We, the inventors, have found that the above requirements are met extremely well.

Therefore, the present invention provides an organometallic compound of the formula (RM+Z) For use in depositing metals on substrates by spin-on or vapor phase deposition. do.

However, in this formula R1 is hydrogen, alkyl having 1-8 carbon atoms, partially or completely; cycloalkyl having 3-8 carbon atoms, which may be fluorinated; is a cycloalkenyl or aryl group, M is Group 2 or 4, 1st, 2nd, 3rd, 4th, 5th, 6th, 7th or is also a metal of subgroup 8 or a metal from the rare earth group or bismuth , n is 1, 2.3 or 4 0 is 0, 1.2 or 3, n+o is related to the oxidation state of the metal 2 is -X-Y or -Xo, X is - (CHR 勺, - -NR"- A is cyclohexane, cyclohexene, cyclohexadiene or phenyl is a ring, B is cyclopentane, cyclopentene or cyclopentadiene ring , Y and Yo are independent of each other, respectively (CHHz)-NR' R', -(CH2), -PR' R', (CH*) @-A s R' R' or -(CHz)-SbR' R', and R2 is hydrogen, fluorine, or an alkyl group having 1-8 carbon atoms. However, there is a possibility that it is partially or completely fluorinated. R3 and R4 are independent of each other, each hydrogen, having 1-8 carbon atoms An alkyl group, even if the alkyl group is partially or completely fluorinated. Often cycloalkyl or cycloalkenyl groups having 3-8 carbon atoms Or it is an aryl group, m is l, 2.3 or 4, s, r, p and q are independent of each other and are Oll, 2 or 3, respectively. the law of nature, Furthermore, the compound of formula ■ is bound to one or more neutral ligands. is also possible, but in the case of M=Zn, X must be -(CHR"), - There is a condition.

The present invention further provides for the formation of thin films or layers by precipitation of metals from organometallic compounds. However, the organometallic compound used is Metal organolyl of formula I.

The invention further relates to novel compounds of formula I corresponding to formula II.

However, in the Kono style, the meaning shown in R', o, M, X', Y, Y' and n formula ■ Has taste.

Some of the compounds of formula I are known, for example dialkyl compounds of zinc or The corresponding coordination compound studies for cadmium and mercury compounds are , Thiele, etc., inorganic and general chemistry journals (Z, anorg, a l　l　g, Chem, ) 4dan (1980) 152 and E, rank goo 1- (Languth) et al., 530 (1985) 69.

Rank E for the production method of tetrakis(3-dimethylaminopropyl)zirconium Gate et al. describe this in the same magazine, 505 (1983) 127. of metal precipitation However, the use of these substances for this purpose is not described therein.

Compounds of formulas ■ and II are multiply coordinated and contain Group 5 nitrogen, phosphorus, arsenic or is stabilized within the molecule by transferring electrons from the atimone atom to the electron-deficient metal. It has become Therefore, it is particularly stable towards air and oxygen. spontaneous at room temperature It is extremely easy to operate and does not ignite or decompose. ) Omotoko 6-508890 (5) However, due to the influence of temperatures up to about 1100°C, metals can be deposited while Compounds of formula 0 and II that can be decomposed remove metals from both liquid and gas phases. It was found that this method is suitable for precipitating.

Compounds of formulas I and II contain stable yet easily removable leaving groups. Therefore, only a very small amount of carbon is contained in it, which affects the quality of the final product. It's a big advantage.

In formulas I, II and III heretofore and hereafter and in all dependent formulas, M is the second or Group 4 metal, preferably magnesium (Mg), calcium (Ca), Strontium (Sr), barium (Ba) germanium (Ge), tin (Sn) Or lead (Pb) or bismuth (Bi), a group 5 metal. These Particularly preferred among these are Ca, Ba, Sr%Sn, Bi, and pb.

M is also the first, second, third, fourth, fifth, sixth, seventh or seventh element of the periodic table of elements. Metals of subgroup 8 and therefore preferably copper (Cu), silver (Ag>, gold (Au), zinc Lead (Zn), cadmium (Cd), mercury (Hg), scandium (Sc), Thorium (Y), lanthanum (La), titanium (Ti), zirconium (Zr), Octunium (Hf), vanadium (V), niobium (Nb), tantalum (Ta ), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (M n), rhenium (Re), iron (Ir), cobalt (co), nickel (N i) rhodium (Rh), palladium (Pd) or platinum (Pt); Among them, Cd, Zn, Pb, Cu%Mn, Sn, Zr, Hg, Y, Ta, Ti, Particularly preferred are Ag, Au, Fe, Pd, Ni or Pd.

M is also a metal from the rare earth group, thus cerium (Ce), Ozium (Pr), Neodymium (Nd), Promedium (Pm), Thermarium ( Sm), europium (Eu), gadolinium (Gd), terbium (Tb), Dysprosium (Dy), Holonium (Ho), Erbium (Er), Thuriu These are aluminum (Tm), tterbium (Yb), and lutetium (Lu). Of these Particularly preferred are Ce, Gd, Yb, P' and Nd.

The radicals R1, R3 and R4 each preferably have 1-8 carbon atoms, preferably A straight-chain or branched alkyl group having 1-5 carbon atoms. that archi The group is preferably straight-chain and therefore preferably methyl, ethyl, propyl, butyl. tyl, pentyl, hexyl, heptyl, octyl, isopropyl, Secondary butyl, tertiary butyl, 2-methylpentyl, 3-methylpentyl or Also 2-octyl.

Alkyl groups may be partially or fully fluorinated, e.g. monofluorinated. Uromethyl, difluoromethyl, trifluoromethyl, difluoroethyl, trifluoromethyl Must be fluoroethyl, pentafluoroethyl or trifluoropropyl. There is also.

R', R' and/or R4 are 3-8 carbon dissipated cycloalkyl or are cycloalkenyl groups, preferably they are cyclopropyl, cycloalkenyl, butyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexyl Nyl, cyclohexagenyl, cyclohebutyl, cyclohebutenyl, cycloheb tagenyl, cyclooctyl, cyclooctenyl, cyclooctagenyl, cyclo rooctagenyl, cyclooctatetraenyl, or particularly preferred is cyclopentagenyl.

Further, the compound of formula (II) or II is such that R', R' and/or R4 are aryl groups. Certain compounds are preferred. Aryl preferably means phenyl. Ru. This phenyl group may be present in substituted form. These substituents are intended for It does not have any significant effect on the intended use and does not have an unfavorable effect on the decomposition reaction. All substituents that do not have any effect are permitted.

The radicals R' and R3 and R4 may also appear repeatedly, then identical Sometimes it has one meaning, and sometimes it has a different meaning.

n+c) corresponds to the oxidation state of the specific metal used.For example, if M=Zn If so, then n+o=2, and if M=Zr, then n+o=4, and M=Ca Then, n+o=2. n is 1, 2.3 or 4, preferably 0 0, l or 2.

2 is the structural unit -X-Y or This creates dependent formulas II and III. Dependent formula II is derived from the new compound. Therefore, the present invention likewise relates to such novel compounds. Y and Yo are different Formulas II and III may have different meanings, so formulas II and III are and IIIa-IIId.

IIIa　R1゜-M+(C)LR28-Yln Engineering Ilb　R1゜-M+NR2 -Ylrl Among these, formulas 11a, IIb, IIc, IId, IIIa, l Particularly preferred are llb and lllc. Particularly preferred are formulas 11a, IIIa and and llIc.

In the case of M = Z n, the possible dependent expressions are rra, IIb, Ire, IId, l llb, llc and IIId. Among these, 1 formula 11a, IIb, Compounds IIc, llIb and llIc are preferred.

In the above and subsequent formulas and dependent formulas, A is preferably cyclohexane or is a phenyl ring. B is preferably cyclopentane or cyclopenta It's Jenling.

Y and Yo are independent of each other, and each represents (CH2)-NR' R' (CHa)--PR' R', (CHz) s A s R' R' or -(CH2), -3bR3R' It is.

Special! , Knee (CJ), -NR" R' and U- (CHI), -PR' R' The radicals are preferred, preferably Y=Y'.

R2 is preferably hydrogen or 1-8 carbon atoms, preferably 1-4 carbon atoms. It is an alkyl group which may be partially or completely fluorinated and has an elementary atom.

Therefore, R2 is preferably methyl, ethyl, propyl, butyl, trifluoromethane. Chyl, tetrafluoroethyl, pentafluoroethyl, heptafluoropropyl , as well as pentyl, hexyl, heptyl, octyl, nonafluorobutyl, and trifluorobutyl. Fluorohexyl or difluoropentyl. Furthermore, R2 is fluorine. You can.

When R2 appears repeatedly, its meaning may be the same or different. In that case, preferably the only R is not hydrogen.

m is 1.2.3 or 4, preferably 2 or 3.

r, p and q are independent of each other, respectively. , l, 2 or 3, preferably Preferably, it is 0.1 or 2. S is preferably l or 2, and or preferably 0.

The following group of compounds (1)-(40) has the formula 1. Particularly preferred of II or III A selection of examples is provided to help illustrate the most representative examples.

R3R4 NR1R2 NR3R4 R3R4N-CH2 R3R4 AsR3R' Y′ R3R4 (13) R1°-M+(CH2)2-FJR]R4].

(14) R1, -M+(CH2)J-NR]R4].

(151R10-M+(CH2), , -(CH,), -NR3R4].

(161R1゜-M+(CH,)]-PR]R4]n(33)　M(J[(CH 2), -NR3R4]2(34) Ca[(CH2)3-a3R4]2(35) Sr [(CH2)3 NR3R' 12 (36) Bar (CJ (2), - ? JR3R4] 2 (37)” [(CHz) 3-NR’R’13 (3B) C d[(CH2)3 NR3R'12(39) Hg[(CH2)3-NR3R' 12 (40) Zr [(CH2) 3-NR3R' 14 The compound of formula ■ is further Primary amines, secondary amines or tertiary amines or other diamines. Rui is the corresponding phosphane, siphosphane (d i Phosphane), arsane or siarsane (d iarsane) by binding to one or more neutral ligands of the type The coordination number varies depending on the size of the central atom and the size of the ligand. and 9.

Known compounds of formula ■ and new compounds of formula II are described in the literature (e.g. G, Behr (B aehr), P. Burbar, Methods of Organic Chemistry, Volume Xl11 /4, Georg Thieme Publisher, Stuttga Ruto (1970)) can be synthesized by the method known per se, and specific is known and can be synthesized under conditions suitable for the above reaction. itself public Variations of knowledge, especially those that are not mentioned in detail here, are also used in the method. It's okay.

In this way, compounds of formula I or II, such as metal (alkyl) chlorides, can be combined. corresponding Lewis base alkali metal organyl or Grignard compound. It can be synthesized by reacting in an inert solvent.

The reaction is preferably carried out in an inert solvent. Do not unfavorably affect the reaction. All solvents that are free and do not interfere with the reaction mechanism may be used for this purpose. The reaction temperature that can be used is substantially the temperature known in the literature for the synthesis of similar compounds. It corresponds to

The organometallic compounds according to the invention are extremely stable towards air, moisture and oxygen. It has been found that

Even after prolonged exposure to air, these compounds do not show any change and are stable at room temperature. It is stable, but may decompose at high temperatures while precipitating metals. difference Furthermore, it has only a low vapor pressure at room temperature, i.e. it is only slightly volatile. 1 For example, aliphatic or aromatic hydrocarbons or organic solvents such as ethers Its solubility in media is extremely high.

Due to these properties, the organometallic compounds of formula I can, in principle, be classified as organometallic compounds. Suitable for all methods of depositing metals by solution.

Organometallic compounds of the formula I are particularly suitable for the deposition of metals from the liquid or gas phase. It can be preferably used for.

This invention can be used to create thin films or epitaxial layers on any substrate. The method according to the present invention is based on a method of precipitation known per se from the liquid or gas phase. however, in these methods organometallic compounds of formula I are utilized. Ru.

Liquid phase deposition is carried out, for example, by depositing a substrate, for example a silicon wafer, containing an organometallic compound of formula I. In the simplest case, this involves dissolving the compound in an organic solvent. It is a liquid solution and can be carried out by coating. The above code The coating is preferably carried out by the known "spin-coating" method already described. It is also possible.

The reaction conditions for vapor phase deposition methods are known per se and have already been described herein. but chosen analogously to values known in the literature and familiar to those skilled in the art. It is also possible.

Mixed metal layers, compound semiconductors, electrical components, electronic components, optical components and opto-electronic components Alternatively, to produce a semiconductor laser, the formulation must be a compound of different metals. and compounds of other elements of the periodic table of elements, preferably compounds of elements of group It may contain.

One or more compounds suitable for the reaction conditions used are added during the decomposition process, in particular such as AsHs, As(CH3)5 or other doping agents. It is also possible to introduce compounds of arsenic, antimony or phosphorus. Also used here The doping agents used were mainly organometallic compounds of iron, magnesium, zinc, and chromium. Something can happen. Commonly used compounds include, for example, Zn (CH3)a , Mg (CHs)t, Fe (C@H5)2.

Addition of the compound of formula I itself as a doping agent in the precipitation step of other organometallic compounds It is also possible to

The layers produced by the method of the invention vary widely depending on the metal compound used. Can be used for a wide range of parts. For example, thin films produced according to the invention The system includes capacitors, sensors, superconductors, metal films, diodes, high Used in high speed transistors, electro-optical switches, optical storage and many other purposes It is possible. The following examples are intended to explain the invention in more detail. . All temperature indications are in degrees Celsius, m, p, melting point and s, p, boiling point.

and I dan yu Magnesium 24.3g (1.0 mol) and 3-dimethylaminopropylchlora Grini prepared in 500 ml of THF from 102.1 g (0.84 mol) of Dissolve 0.28 mol of barium chloride in THF IOOm1 at room temperature in Earle's reagent. solution is added dropwise and the mixture is heated to 70° C. for 2 hours. After cooling, remove the insoluble matter Filter off, remove the solvent and distill the residue under reduced pressure. As a result, bis(3-dimethyl Barium (Ruaminopropyl) is obtained.

Bis(3-diethylaminoprobyl)strontium and bis( 3-dimethylaminopropyl)calcium is obtained.

History ■Yu Magnesium 4.9g (0.2 mol) and 3-diethylaminoprobyl chloride Grignard prepared from 19.4 g (0.16 mol) of 100 ml of THF A solution of 0.05 mol of barium chloride in 100 ml of THF at room temperature was added to the reagent. After the reaction is complete, the mixture is stirred at room temperature for 24 hours, filtered, and dissolved. The medium is removed and the residue is distilled under reduced pressure. As a result, bis(3-diethylaminopropylene) lobil) barium is obtained.

In a similar way, Bis(3-diethylaminopropyl)strontium bis(3-diethylaminopropyl) provil) calcium, bis(3-dimethylaminopropyl) cadmium, bis (3-dimethylaminopropyl)mercury is obtained.

Delivery ■Yu In the same manner as in Example 1, bis(3-dimethylaminopropyl)cadmium (3 -dimethylaminopropyl) magnesium chloride and cadmium chloride? It is obtained as a colorless liquid with a boiling point of 62° C. and 70.3 mbar.

Achieving 5 Yuu In the same manner as in Example 1, bis(3-dimethylaminopropyl)mercury ( 3-dimethylaminopropyl) from magnesium chloride and mercuric chloride, colorless, 1151 obtained as a liquid with a boiling point of 96°C and 10.05 mbar Magnesium 6.1g (0.25 mol) and 3-dimethylaminopropylchlora Grignard reagent from 24.3 g (0.2 mol) of Id in 100 ml of THF was created. Approximately 80 ml of THF was then removed and the concentrated solution was added with pentane. 50 ml were mixed. The precipitated magnesium chloride was removed by filtration and the residue is distilled under reduced pressure. As a result, bis(3-dimethylaminopropyl)magnesium is obtained as white crystals with a boiling point of 10.05 mbar at 170°C. .

Bis(3-diethylaminoprobyl)magnesium can be converted in a similar manner.

and I51 8.71 g of 3-dimethylaminopropyllithium and 150 ml of diethyl ether 45.45 g of ZrCl was mixed into a solution dissolved in ZrCl at a temperature of -5℃ while shielding from light. The mixture was then stirred for 1 hour and the solvent was removed under reduced pressure. number of residues Extracted twice with n-pentane. The combined extracts were filtered, cooled to -78°C, and colorless. , acicular tetrakis(3-dimethylaminopropyl)zirconium was precipitated. .・ 11 Hill Yu Cr Cl 3.3 T HF 1 6 g in 200 ml of diethyl ether Add 12 g of 3-dimethylamine propyl lithium to the suspended suspension at 30°C for 4 hours. dropwise mix the ether solution. The mixture is stirred for a further 2 hours. After that The residue is extracted with n-pentane. Tris (3-di Red crystals of chromium (methylaminopropyl) precipitate from the extract.

Continuation of front page (51) Int, C1,5 identification code Office serial number CO7F 3108 7 457-4H 3/10 7457-4H 7100A 8018-4H 11100A 9155-4H C23C16/30 8116-4 18108 8414-4K (72) Inventor: Wuertherman, Federal Republic of Wilfried Germany 1000 Berlin 12 Krume Strasse 25 I (72) Inventor Zois, Thomas Federal Republic of Germany 2900 Oldenburg Sommerwerke (72) Inventor: Justo, Oriper Federal Republic of Germany 1000 Berlin 37 am Loergarten 45

Claims (1)

[Claims] Claim 1: For depositing metal on a substrate by spin-on or vapor phase deposition. Formula I R■-M-[-Z]nI Use of organometallic compounds. However, in this formula R1 is hydrogen, alkyl having 1-8 carbon atoms, and some or all of them may be fluorinated, cycloalkyl or cycloalkyl having 3-8 carbon atoms. is a loalkenyl or aryl group, M is a metal of the second or fourth group, the first, second, third, fourth, fifth, sixth, seventh or 8 subgroup metals or metals from the rare earth group or bismuth; n is 1, 2, 3 or 4; o is 0, 1, 2 or 3; n+o is related to the oxidation state of the metal Z is -X-Y or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and X is -(CHR2 ) m−′ -NR2-' ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ X′ has ▲mathematical formulas, chemical formulas, tables, etc.▼, ▲has mathematical formulas, chemical formulas, tables, etc.▼ ， ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ A is cyclohexane, cyclohexene, cyclohexadiene or phenyl is ng, B is a cyclopentane, cyclopentene or cyclopentadiene ring , Y and Y' are mutually independent, and each -(CH2)s-NR3R4 -(CH2)s-PR3R4 -(CH2)s-AsR3R4 or -(CH2)s-SbR3R4, R2 is hydrogen, fluorine or partially or completely fluorine having 1-8 carbon atoms. is an alkyl that may be primed, R3 and R4 are independent of each other, hydrogen, partially or fully fluorinated, having 1-8 carbon atoms, respectively. cycloalkyl or cycloalkyl having 3-8 carbons; It is a loalkenyl group or an aryl group, m is 1, 2, 3 or 4, s, r, p and q are independent of each other and are 01, 2 or 3, respectively; Furthermore, the compound of formula I is bound to one or more neutral ligands. is possible, provided that if M=Zn, then X is not -(CHR2)m-. There is a condition that it is possible. Claim 2: An organometallic compound of the formula I according to claim 1 for the deposition of an epitaxial layer. use of things. Claim 3: The organometallic compound used is a compound of formula I according to claim 1. Characterized by the precipitation of metals from organometallic compounds, there is a thin film on the substrate. or the method of manufacturing the layers. Claim 4: Electrical system, dielectric system, electronic system, optical system, and The reaction conditions used are suitable for producing optoelectronic systems. Special feature is that more than 10% of arsenic, antimony or phosphorus compounds are supplied during the precipitation process. 2. A method according to claim 1, wherein the method comprises: Claim 5: In addition to the organometallic compound of formula I, a doping agent is added during the precipitation step. 5. A method according to claim 4, characterized in that: Claim 6 The organometallic compound of formula I according to claim 1 is used for precipitation of other organometallic compounds. 5. Process according to claim 4, characterized in that it is added as a doping agent during the step. Claim 7 Compound of formula II ▲There are mathematical formulas, chemical formulas, tables, etc.▼II However, in this formula R1, o, M, X', Y, Y' and n have the meanings given in formula I in claim 1. do. Claim 8 The compound further comprises one or more neutral ligands through a coordinate bond. 8. A compound of formula II according to claim 7, characterized in that: