This invention relates to the preparation of metal carbides, nitrides, suicides, borides and phosphides and to other metallic products.

By way of example of methods used in the prior art, tungsten metal in finely divided form is mixed with carbon black and the mixture is heated typically to a temperature of about 1700° to 2300°C. This results in tungsten carbide which is usually mixed with a binder metal such as cobalt and is then subjected typically to shaping into the desired shape, presintering, shaping and sintering.

Other hard metal powders are produced in similar fashion except that carburization is done at the metal oxide stage rather than with the metal itself.

Such methods pose difficulties such as the need for very high temperatures. Further difficulties are also encountered. If it is desired, for example, to apply the carbide as a coating, it has to be done by chemical vapor deposition or physical vapor deposition which is limited to line of sight procedures.

It is an object of the present invention to provide better methods of producing metal carbides, nitrides, suicides, borides, phosphides, etc., also metal alloys, such methods providing one or more of the following advantages:

(1) Lower temperatures in the preparation of the metal compound or alloy M _a Xfc wherein M represents the metal or metals, X represents the combining element or elements and the subscripts a and b represent the atomic proportions of M and X.

(2) A simplified procedure.

(3) Greater control over the combining proportions, a and b.

(4) More facile methods of application of _a Xb to end products.

(5) Potential routes to materials or material morphologies that have heretofore been impossible or difficult to prepare.

These and other objects of the invention will be apparent from the ensuing description and the appended claims.

I have found that organometallic complexes of the selected metal (hereinafter called precursors) can be prepared which are soluble in common organic solvents or can be melted at relatively low temperatures. Solutions can be applied to the surface of a substrate, heated to vaporize the solvent and then pyrolyzed on the surface. Melts of solid precursors can be shaped into fibers, rods, etc. and pyrolyzed. The pyrolysis can be carried out at relatively low temperatures to provide the substance _a Xb. Yet the precursors are not so volatile that they cannot be pyrolyzed.

The organometallic precursor contains the metal M associated with the element X and with ligands. The element X may be bonded directly to M or it may be

contained in one or more of the ligands, such that upon pyrolysis the ligands are lost with the exception of X which is bound to, or which becomes bound to the metal M. Preferably the ligands are free of halogen or oxygen directly bonded to the metal M. When possible, the precursor is designed such that there are multiple bonds between M and X to increase the likelihood that these two elements will retain a bonding interaction during pyrolysis. M represents a single metal or two or more different metals and X represents one or more elements.

The ligands endow the precursor with solubility in organic solvents or provide a material which is solid and meltable. Therefore solutions or melts of the precursors can, for example, be applied to a surface by dipping or brushing. Solutions of the precursors, if sufficiently viscous and non-volatile, can be extruded in the form of rods, fibers, etc. The precursors may in certain cases be polymerized and the polymers may be shaped into the intended form before pyrolysis. Polymeric precursors may result directly from the method of preparation. The precursors can be pyrolyzed at relatively low temperatures. The method of application as coatings is not limited to line of sight.

Another aspect of the invention is the use of certain non-volatile precursors which upon pyrolysis leave the metal M in pure form; i.e. the complex forms the metal M and does not form a metal carbide, nitride, etc. This aspect of the invention is useful in depositing refractory metals such as tungsten on substrates such as steel, titanium, ceramics, silicon and gallium arsenide. An example of a suitable non-volatile precursor for cobalt is Cog(CO)is described in Advances in Organometallic Chemistry, Vol. 14, page 287 (1976).

1 In another embodiment of the invention the

2 component X is another metal rather than carbon, nitrogen,

3 silicon, boron or phosphorus and the end product is an

4 alloy. The use of precursors of the present invention to

5 produce alloys is useful where the alloy has a high melting

6 point and is to be deposited on a substrate which is low

7 melting or which would be damaged by contact with the

8 molten alloy.

9

10 Examples of M and X pairs are set forth in

11 Table I. X may be carbon, nitrogen, silicon, boron or

12 phosphorus. X may also be a metal other than M. M is a

13 transition metal, a lanthanide metal, an actinide metal

14 or tin. It will be understood that M may be more than one

15 metal and that X may be one or more of the elements C, N,

16 B, Si or P.

17

18 TABLE I

19

20 M X M X M X=Mτ

21 Ti C Fe N Ag RU

22 w C Hf N Ag Pd

23 Hf C Ta N Nb Sn

24 Fe C Ti B Co Nd

25 Cr C Fe B Co Fe

26 Ta C Fe Si Au Pd

27 Cr C Pd Si Au Ru

28 V C Ru Si Co Zn

29 Nb C Rh si

30 Ti N Co P

31 W N Fe P

32. 3 Examples of suitable solvents for the precursors 4 are CH2CI2, CHCI3, CO2, SO2, sulfolane, MeOH, 5 EtOH, Et2θ, glyme, diglyme, THF, freon, benzene, toluene, 6 DMSO, DMF, N-methylpyrolidone, hexane, and pentane. 7

The following specific examples will serve to illustrate the practice and advantages of the invention.

Example 1. Preparation of Tungsten Carbide and Oxycarbide

Compound 1,

2Cp

1

is prepared as described by Ford and Laine in Journal of Organometallic Chemistry, Vol. 124, p. 29 (1977). Cp represents the cyclopentadienyl group. Precursor 1. is ^' placed in a quartz or nickel boat and is pyrolyzed in an atmosphere of nitrogen or argon at 500° to 950°C for 10 to 30 minutes. A 95 per cent conversion to 2C resulted where the boat was of nickel and where it was of quartz the product was tungsten oxycarbide, 2<C,0). In both cases the yield was about 95 per cent. The difference in results between nickel and. quartz containers is believed to be due to the fact that quartz supplies oxygen to form oxycarbide. it is believed that this could be prevented by coating the quartz container with tungsten.

Figure 1 of the drawings shows the X-ray powder diffraction pattern of the product of pyrolysis in a nickel boat.

The tungsten oxycarbide is useful to coat alloys n as electrode material in electrochemical reactions.

The tungsten carbide, W_C, is useful for hard, corrosion and wear resistant surfaces and can be used on cutting edges for machining tools.

The compound 1 is soluble in common organic solvents such as methanol, methylenedichloride, diethylether, etc. In solution form it can be applied to a substrate, for example, by brushing or dipping. Upon heating the solvent is evaporated and the compound 1. can be pyrolyzed to form a carbide or oxycarbide.

Compound 1. may also be used as such without dissolving it in a solvent and polymer derivatives can be formed into rods, fibers or other shapes and pyrolyzed.

Example 2. Preparation of Titanium Diboride

The organometallic precursor, Cp2Ti(BH4)2, was prepared by the method described by A. S. Lee, K. Isagawa, and Y. Otsuji, Chem. Lett. 1984, 363-366 by reaction of CP2TiCl2 with excess NaBH4 in THF. The resulting purple complex (purified by filtration and vacuum removal of solvent) is very air sensitive. The solid material is transferred to both nickel and quartz pyrolysis tubes in a dri-box and under argon and into a pyrolysis oven. After heating at 850° for 20 min.. X-ray powder analysis shows TiB2 and TiC present in 20 and 30% amounts, respectively. Very small particle sizes are obtained, less than 30 Angstrom units.

Example 3. Preparation of Ruthenium Silicide

^• Method 1 (Precursor 2 ) . To 8.9 mmol of octamethyltetra- silane are added 0.3 mmol of Ru3(CO)i2 ^{and the} solution is heated at 135°C in one atmosphere of hydrogen for 3 hours. A deep orange insoluble material precipitates and is washed with petroleum ether. The yield is 0.4 gram.

The material is insoluble in methylene chloride but is soluble in THF and methanol. It is very hygroscopic in air. Infrared analysis of the solution in THF shows peaks at 2060 (w), 2042 (w), 2038 (sh), 2023 (w) , 2004 (m) , 1978 (vs)cm~ . The product is believed to have the formula

L-(NHSiMe2)3NHRU3(CO) _U SiMe ₂ -J

2_

Method 2 (Precursor 3_) . To 7.5 mmol of tetramethyl- disilazane is added 0.08 mmol of Ru3(CO)]_2 ^and the solution is heated at 135° under 1 atmosphere of hydrogen for about 1 hour. The Ru (CO)χ2 disappears completely. The solution is evaporated. An oily orange residue remains in the flask. IR analysis (CH2CI2) of the metal carbonyl gives: 2121 (w) , 2101 (s), 2028 (vs) 2010 (vs), 1953 (sh)cm" ¹ . The formula of 3_ is believed to be

_p ___________ _^ _ ₁ L-Si e2R _U 3 ( o ) ₁₁ Si e2 H— '

3.

Method 3 (Precursor 4.). This precursor, [ (C2H5)3Si]2RU3(CO)ιo, is prepared by the method of Georg Suss-Fink described in his Habilitionsschrift entitled "Stochiometrische und Katalytische Aktivierungsreaktionen an dreikernegen Klustern des Osmiums und Rutheniums", University of Bayreuth, 1983.

Pyrolysis of each of 2 , 3_ and 4_ at 800°C for 2 hours yielded ruthenium suicide, RuSi. Figure 2 of the drawings represents the X-ray powder diffraction pattern of this product.

Example 4. Preparation of Metal Nitrides and Phosphides

Metal nitride and metal phosphide precursors may be those described by Williams, Geoffrey and Whittle in J. Am. Chem. Soc. Vol. 107, pages 729-731 (1985), for example the nitrene compounds .5a and 5b described in Scheme 1 on page 729 or the phosphinidene analogue in which the nitrogen is replaced by phosphorus. Upon pyrolyzing at 800°C for 2 hours an iron nitride or phosphide will result. By substituting other metals for iron the corresponding nitrides and phosphides will result.

Among suitable precursors are the following which are described in the literature.

TABLE II, Carbide Precursors

Precursor Literature Reference

Fβ5(CO)i5C Adv. Organometallic Chem. (1976) 14, 285, 288-289

[Fe ₆ (C0) ₁₆ C]2-

[Co ₈ (CO) ₁₈ C]2-

RU6(CO)χ7C

[Rh ₆ (CO) ₁₅ C]2-

Rhg(CO) ₁₉ C

[Rh ₁₅ (CO) ₂ 8(C)2]~ RU5C(CO) 5 os ₅ c(co) ₁₅ J. Organometallic Chem. (1 52, C82-C83

Cθ2(C0) ₆ (RC=CR) Ibid (1983) 259, 253

(R s alkyl, aryl)

Ru ₆ C(CO) ₁₆ C ₆ H ₂ (CH ₃ )3 Adv. Organomet. Chem. (197 14, 285

RugC(CO)χ7

Cp ₂ VC=C-C(CH ₃ ) ₃ J. Organometallic Chem. (1 265. 249-255

Alkylidynetricobalt- J. Organometallic Chem. (l nonacarbonyl complexes 162, 89-98

Cp 2 ₂ W" ₂ 2I ^' r ₂ (CO) _fi ( Vμ _. - -J-C *-P* ^• h**)# -η ^J -C-Ph) Organometallics (1984) 3.,

Cp2Ti(PhCi=CPh) J. Organometallic (1983) 243, 157

Certain metal complexes containing two metals in the complex may be pyrolyzed to produce an alloy of the two metals. Examples are given in Table III.

TABLE III Alloy Precursors

Precursor Literature Reference

C CpYb ]Go( C ₅ H ₄ R) ₂ ( μ ₃ -CO ) ₄ J. Chem. Soc. Chem. Commun. (1984) 809

[Re ₄ CU2H ₁₆ L ₆ ](PF ₆ )2 J. Am. Chem. Soc. (1983) 105, 5137

Au ₂ R ₄ (μ ₃ -H)2(CO) ₁ 2(PPh ) J. Chem. Soc. Chem. Commun. (1983) 1332

Ln[Co(CO) ₄ ]2 Adv. Organometallic Chem.

[Ln = Sm/Eu/Yb] (1976) 12, 285, 288, 289

[Co ₅ Ni ₂ (CO) ₁₄ ] Adv. Organomet. Chem. (1976) 14., 285

[Co ₄ Ni ₂ (CO) ₁₄ ]2-

[Mo ₂ Ni ₃ (CO) ₁₆ 32-

(Cp) ₂ NbH2ZnCp Organometallics (1984 , 15<

Nitride Precursors

H2 U3 ( CO) gNH J. Chem. Soc. Chem. Commun. (1984) 186

[FeRU3N(CO)!2l ^" JACS (1984) 106, 4799

NOS(CH2Si β3)4 JACS (1984) 10 , 7493

[W(NPh)Me ₃ ] ₂ (μ-η ^:L ,η ^:L -NH ₂ NH ₂ ) JACS (1984) 106, 8316 (μ-η ² ,η ² NHNH)

Boride Precursors

(H)Fe ₃ (CO)9(μ ₃ -BH ₄ ) JACS (1984), 106.4633

HFe (CO)χ2BH2 Organometallics (1983) 2., 8

(C ₄ H ₄ B-Ph)Ru(CO) ₃ Angew. Chem. Int. Ed. (1983 2_2, 996

V ⁽ C5HsB-CH3 ⁾ 2 J. Organomet. (1984) 265, 2

1 The precursor may be in the form of a polymer.

2 A polymer has the advantage of being more easily shaped,

3 spun, etc. Examples of such polymers and their preparation

4 are as follows. 5

14

15 16

23

24 I will therefore be apparent that new and useful

25 methods of producing metal carbides, nitrides, borides,

26 suicides and phosphides, also metal alloys and pure

27 metals, have been provided. Also new and useful precursors

28 for the same and new methods and materials have been

29 provided for applying metal carbides, etc., metal alloys

30 and pure metals to solid substrates and for forming such

31 materials into useful shapes such as fibers, rods, etc. 32

33 34 35 36 37