BORANE, DIBORANE, ETC.

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Reaction Between the Ether Complex of Boron Trifluoride and Lithium Hydride. Communication 1. Preparation of Pure Diborane

Russian Chemical Bulletin
Vol.5(8.) 1956 pp.925-934
DOI: 10.1007/BF01166405
http://www.springerlink.com/content/x8245352g00v5048/

Mikheeva,V;Fedneva,E

The simplest boron hydride- diborane- is one of the most stable compounds of this class and is one of the least active in its attack on the grease in joints and taps. Until recently, most of the methods for its synthesis gave complex mixtures of volatile substances containing relatively little diborane, and its isolation from these mixtures was a very difficult task.

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Diborane

Brauer

Diborane was first obtained from the mixture of boron hydrides resulting from the hydrolysis of magnesium boride; later it was produced by spark discharge in mixtures of BCl3 or BBr3 with H2 [1,2,3]. It now can be produced more easily and in larger quantities by the reaction of LiH, NaH or alkali borohydrides with BF3 diethyl etherate [4]. To obtain good yields, the alkali hydrides must be very finely powdered. Since alkali hydrides are hygroscopic and difficult to grind, the use of alkali borohydrides, are are fine powders to begin with, has certain advantages for laboratatory-scale synthesis. On the other hand, LiH is a particularly economical starting material for the production of larger quantities of B2H6.

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Preparation of Diborane from Lithium Hydride and Boron Trihalide Ether Complexes

Elliot,J;Boldebuck,E;Roedel,G

Abstract

J. Am. Chem. Soc.
Vol.74(20) 1952 pp.5047–5052
DOI: 10.1021/ja01140a017
http://pubs.acs.org/doi/abs/10.1021/ja01140a017

Abstract

The preparation of diborane from lithium hydride and boron trihalide etherates under different conditions is described and secondary reactions are discussed. The reaction between lithium hydride and boron trifluoride in ethyl ether has been shown to proceed by two different courses. If ether-soluble, active hydrogen-containing promoters are present, or if pressure is used to force the reaction between lithium hydride and diborane, the hydride is converted completely to lithium borohydride and lithium fluoride before diborane is evolved. In the absence of soluble promoters, diborane escapes continually from the solution, lithium borofluoride is formed and lithium borohydride does not accumulate. If less than a specified ratio of borohydride to hydride exists in the ether solution, the borohydride is consumed in the continuing reaction, and diborane is evolved. In tetrahydrofuran, a promoter is not required for the conversion of lithium hydride to lithium borohydride. Since the solubility of diborane is relatively high in tetrahydrofuran, conditions favor the production of borohydride by reaction of diborane with lithium hydride, as in the pressure reaction with ether as solvent.

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The Preparation of Boron Hydrides by the Reduction of Boron Halides

Hurd,Dallas
J. Am. Chem. Soc.
1949, Vol.71(1),  pp.20–22
DOI: 10.1021/ja01169a007

Abstract

It recently (1945) has been found that boron hydrides, specifically diborane and diborane monohalides, can be synthesized by the reduction of boron halide vapor with hydrogen in the presence of metals at elevated temperatures.

EXPERIMENTAL WORK ON HYDRIDES & BOROHYDRIDES

Hydrides and Borohydrides of Light Weight Elements and Related Compounds

Schlesinger,H;Wartik,Thomas;Moore,R;Schaeffer,Riley;Steindler,N;Urry,G

Final Report, 1950 AD097410
University of Chicago
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD097410&Location=U2&doc=GetTRDoc.pdf

Index

Introduction
    I. Borazole Studies
       A. Preparation of Borazole from Trihalogenoborazoles
          1. Reduction of trichloroborazole by lithium aluminium hydride
             - in the absence of solvents
             - various solvents tested
             - diethyl ether borazole azeotrope
             - separation of borazole from n-butyl ether and from lithium aluminium hydride
             - the effect of lithium hydride on the preceeding separation
          2. Reduction of trichloroborazole by lithium aluminium hydride plus lithium hydride
          3. Reduction of trichloroborazole by lithium borohydride
          4. Reduction of trichloroborazole by lithium borohydride plus lithium hydride
          5. Preparation and reduction of tribromoborazole
       B. Mono and Dichloro, and Mono and Dibromo- borazole
          (Preparation, Physical Properties, and Reduction)
       C. Thermal Decomposition of Borazole
   II. Further Studies on Tetrachlorodiborine and Related Compounds
       A. Tetrachloroborine
          1. Preparation
          3. Reactions
             a. with hydrogen
             b. with dimethylamine
             c. with trimethylamine
                - Properties of the trimethylamine addition product
                - Behaviour toward hydrogenating agents
                  lithium aluminium hydride
                  lithium borohydride
             d. with methane and hydrogen chloride
             e. Summary of reactions studied earlier
       B. Other Subchlorides
  III. Preparation of Calcium and Sodium Aluminium Hydrides
       A. Calcium Aluminium Hydride
       B. Sodium Aluminium Hydride
       C. Discussion
   IV. Thermal Decomposition of Lithium Borohydride
    V. Reactions of Hydrazine dihydrochloride with Lithium Borohydride
   VI. Publications

Progress Report XXXV
Progress Report XXXVI
Progress Report XXXVII
Progress Report XXXVIII

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Hydrides and Borohydrides of Light Weight Elements and Related Compounds

Schlesinger,H;Steindler,Martin;Urry,Grant;Hohnstedt,L;Kerrigan,J;Murib,J

Technical Report, 1952-1953
The University of Chicago
NR-356255/AD017260

Index

Introduction
    I. The Solubility of Diborane in Ethyl Ether and the Reaction between Lithium Borohydride and Borofluoride
       A. The Solubility of Diborane in Ethyl Ether
       B. The Reaction between Lithium Borohydride and Borofluoride
       C. Experimental Details
          (1) Apparatus
          (2) Procedure
          (3) Experimental Data for the Solubility Experiments
          (4) Sample Solubility Calculations
          (5) Experimental Data for Equilibrium Experiments
   II. Further Studies on the Sub-Chlorides of Boron
       A. Reactions of Tetrachlorodiborine
          (1) Etherates
          (2) The Reaction of Tetrachlorodiborine with Lithium Hydride
          (3) The Reaction of Tetrachlorodiborine with Diborane
          (4) The Reaction of Tetrachlorodiborine with Ethylene
       B. Reactions of Tetraboron Tetrachloride B4Cl4
          (1) Reaction with Dimethyl Zinc
          (2) Reaction with Methanol or Water
          (3) Structure of Tetraboron Tetrachloride
          (4) The Reaction of Tetraboron Tetrachloride with Diborane
          (5) Preparation of Tetraboron Tetrachloride
  III. Reactions of Hydrazine with Diborane and Related Compounds
       A. Preparation of the Adducts
          (1) General Considerations
          (2) Preparation of the Compound N2H4.2B(CH3)3
          (3) Preparation of the Compound N2H4.B2H2(CH3)4
          (4) Reactions of Hydrazine with Boron Trichloride
       B. Pyrolysis of the Compounds N2H4.2B(CH3)3 and N2H4.B2H2(CH3)4
          (1) Pyrolysis of Mixtures of Hydrazine and Trimethyl Boron
          (2) Pyrolysis of the Compound N2H4.B2H2(CH3)4
       C. Comparison of the Several Hydrazine Adducts and Their Pyrolysis Products
   IV. Pyrolysis of Mixtures of Diborane and Trimethyl Boron
    V. Other Experimental Work Undertaken During the Present Contract Year
       A. The Preparation of B-methyl, B-chloroborazoles
       B. Some Additional Experiments on the Reduction of Tetrachlorodiborine
       C. Additional Experiments on the Preparation of Sodium Aluminium Hydride
   VI. List of Publications

REVIEWS - BORON REAGENTS

Boron Reagents in Process Chemistry: Excellent Tools for Selective Reductions

Burkhardt,Elizabeth;Matos,Karl
Chem. Rev.
2006]Vol.106(7),  pp.2617–2650
DOI: 10.1021/cr0406918

Table of Contents

1. Introduction and Scope
2. Hydroboration
 2.1. Conversion to Alcohol
 2.2. Suzuki?Miyaura Substrate Formation
 2.3. Asymmetric Hydroboration
 3. Reduction to Alcohol
 3.1. Carboxylic Acid Reduction
 3.2. Aldehyde, Ketone, and Ester Reduction
 3.3. Lactone Reduction to Lactol
 3.4. Amide Reduction to Alcohol
 4. Reduction to Amines
 4.1. Amide Reduction
 4.2. Nitrile Reduction
 4.3. Nitro Group Reduction to Amine
 4.4. Reductive Amination
 4.4.1. Via Amine Boranes
 4.4.2. Via Sodium Triacetoxyborohydride
 5. Stereoselective Reactions with Boranes and Borohydrides
 5.1. Stereoselective Ketone Reduction
 5.2. Diastereoselective Reduction of ?-Hydroxyketone
 5.3. 1,2-Enone versus 1,4-Enone Reduction
 5.4. Enantioselective Ketone Reduction
 5.5. Enantioselective 1,2-Enone Reduction
 5.6. Enantioselective Imide and Imine Reduction
 6. Reductive Cleavage
 7. Conclusions
 8. List of Abbreviations
 9. Acknowledgments
10. Note Added after ASAP Publication
11. References

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Reduction of Organic Compounds with Diborane

Lane,Clinton
Chem. Rev.
1976, Vol.76(6),  pp.773–799
DOI: 10.1021/cr60304a005

Contents

   I. Introduction
  II. The Reagent
      A. Preparation
      B. Physical and Chemical Properties
      C. Reaction with Acidic Hydrogens
      D. Borane-Lewis Base Complexes
 III. Reductive Cleavage
      A. Alkenes and Alkynes
      B. Cyclopropanes
      C. Organic Halides
      D. Alcohols
      E. Ethers
      F. Epoxides
      G. Miscellaneous
  IV. Reduction of Organic Sulfur Compounds
   V. Reduction of Organic Nitrogen Compounds
      A. Imines
      B. Oximes
      C. Nitro Compounds and Related Derivatives
      D. Nitriles
  VI. Reduction of Organic Oxygen Compounds
      A. Aldehydes and Ketones
      B. Quinones
      C. Carboxylic Acids
      D. Carboxylic Acid Anhydrides
      E. Esters and Lactones
      F. Amides
 VII. Conclusions
VIII. References and Notes

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Organic Compounds Of Boron
Lappert,M
Chem. Rev.
1956, Vol.56(5),  pp.959-1064
DOI: 10.1021/cr50011a002



Summary

    I. Introduction
   II. Derivatives of Boric Acid
       A. Introduction
       B. Preparation of orthoborate
          1. Introduction
          2. Boron Trichloride
          3. Boron Trioxide
          4. Boron Acetate
          5. Orthoboric Acid
          6. Metallic Borates
          7. Orthoborates
          8. Other Methods
       C. Physical Properties of Orthoborates
       D. Chemical Properties of Orthoborates
          1. Thermal Stability
          2. Solvolysis Reactions and Reactions with Acids
          3. Halogenation Reactions
          4. Reaction with Ammonia and Amines
          5. Borate Complexes with Metal Salts
          6. Other Reactions
       E. Chelated Orthoborates and Borates of Polyhydric Alcohols
       F. Mixed Orthoborates
       G. Acyl Borates
       H. Metaborates
       I. Thioorthoborates
  III. Derivatives of HB(OH)₂ and HBO
       A. Introduction
       B. The Dialkylborines
       C. Preparation of Boronic Acids and Esters
          1. Introduction
          2. Oxidation of Trialkylborons
          3. Metal Alkyls or Aryls on Trialkyl Borates
          4. Hydrolysis or Alcoholysis or Alkyl- or Arylboron Dihalides (produced by the action of Metal Alkyls or Aryls on Boron Halides)
          5. Other Methods for Boronic Acids
          6. Special Methods for Boronic Esters
       D. Physical Properties of Boronic Acids and Esters
       E. Chemical Properties of Boronic Acids
          1. Acid Properties
          2. Boron-Carbon Cleavage Reactions (Oxidizing Agents)
          3. Boron-Carbon Cleavage Reactions (Metal Salts)
          4. Other Reactions
       F. Chemical Properties of Boronic Esters
       G. The Halogenoboronates



Hydroboration. III. The Reduction of Organic Compounds by Diborane, an Acid-type Reducing Agent

Brown,Herbert;Rao.B
J. Am. Chem. Soc.
1960, Vol.82(3), pp.681–686
DOI: 10.1021/ja01488a045

Abstract

Diborane is a powerful reducing agent for organic compounds, rapidly reducing at room temperatures aldehydes, ketones, epoxides, lactones, carboxylic acids, nitriles, azo compounds and t-amides. Esters are reduced more slowly, and acid chlorides, nitro compounds and sulfones do not react under these conditions. These reductions can be carried out either by passing diborane generated externally, into a solution of the organic compound in a suitable solvent, such as diglyme or tetrahydrofuran, or by adding boron trifluoride etherate to a solution of sodium borohydride and the compound in diglyme. The procedures make possible a number of selective reductions, such as the reduction of a carboxylic acid group or a nitrile group in the presence of a nitro group. The marked difference in the relative sensitivity of various groups to reduction by sodium borohydride and diborane is attributed to the acid-base characteristics of these reducing agents. Sodium borohydride is essentially a base, reaction occurring through nucleophilic attack of the borohydride ion on an electron deficient center of the reacting groups. On the other hand, diborane is a Lewis acid, and preferentially attacks the group at a position of high electron density. By a judicious use of diborane and alkali metal borohydrides, it became possible to reduce many groups in the presence of other groups, and to reverse the process at will.

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Organic Compounds Of Boron

Lappert,M

Chem. Rev.
1956, Vol.56(5),  pp.959-1064
DOI: 10.1021/cr50011a002

Summary

    I. Introduction
   II. Derivatives of Boric Acid
       A. Introduction
       B. Preparation of orthoborate
          1. Introduction
          2. Boron Trichloride
          3. Boron Trioxide
          4. Boron Acetate
          5. Orthoboric Acid
          6. Metallic Borates
          7. Orthoborates
          8. Other Methods
       C. Physical Properties of Orthoborates
       D. Chemical Properties of Orthoborates
          1. Thermal Stability
          2. Solvolysis Reactions and Reactions with Acids
          3. Halogenation Reactions
          4. Reaction with Ammonia and Amines
          5. Borate Complexes with Metal Salts
          6. Other Reactions
       E. Chelated Orthoborates and Borates of Polyhydric Alcohols
       F. Mixed Orthoborates
       G. Acyl Borates
       H. Metaborates
       I. Thioorthoborates
  III. Derivatives of HB(OH)₂ and HBO
       A. Introduction
       B. The Dialkylborines
       C. Preparation of Boronic Acids and Esters
          1. Introduction
          2. Oxidation of Trialkylborons
          3. Metal Alkyls or Aryls on Trialkyl Borates
          4. Hydrolysis or Alcoholysis or Alkyl- or Arylboron Dihalides (produced by the action of Metal Alkyls or Aryls on Boron Halides)
          5. Other Methods for Boronic Acids
          6. Special Methods for Boronic Esters
       D. Physical Properties of Boronic Acids and Esters
       E. Chemical Properties of Boronic Acids
          1. Acid Properties
          2. Boron-Carbon Cleavage Reactions (Oxidizing Agents)
          3. Boron-Carbon Cleavage Reactions (Metal Salts)
          4. Other Reactions
       F. Chemical Properties of Boronic Esters
       G. The Halogenoboronates
          1. Preparation
          2. Physical Properties
          3. Chemical Properties
       H. Boroxoles
          1. Introduction
          2. Preparation of Boronic Anhydrides
          3. Physical Properties and Structure of Boronic Anhydrides
          4. Chemical Properties of Boronic Anhydrides
          5. Other Boroxoles
       I. Thio Compounds
   IV. Derivatives of HOBH₂ and H₂BO₂
       A. Introduction
       B. The Boronous Acids
          1. Preparation
          2. Properties
       C. The Boronous Anhydrides
          1. Preparation
          2. Properties
       D. The Preparation of Boronous Esters
          1. Introduction
          2. Trialkylborons and Triarylborons
          3. Organometallic Compounds
          4. Esterification Methods
       E. Properties of Boronous Esters
          1. Physical Properties
          2. Chemical Properties
       F. The Dihalogenoboronites
          1. Preparation
          2. Physical Properties
          3. Chemical Properties
       G. Alkyl (and Aryl) Halogenoboronites
       H. Thio COmpounds
    V. Derivatives of Borine
       A. Introduction
       B. Preparation of Alkylborons and Arylborons
       C. Physical Properties of Alkylborons and Arylborons
       D. Chemical Properties of Alkylborons and Arylborons
          1. Introduction
          2. Oxidation
          3. Coordination Compounds
          4. Tetracovalent Boron Complexes
       E. Aminoborons and Aminoborines
          1. Introduction
          2. Triaminoborons
          3. Preparation of Aminoborines and Derivatives
          4. Physical Properties of Aminoborines and Derivatives
          5. Chemical Properties of Aminoborines and Derivatives
       F. Aminoboron Dihalides and Diaminoboron Halides
          1. Preparation
          2. Physical Properties
          3. Chemical Properties
       G. The Compounds B(R'R"N)BX
       H. Preparation of Alkyl (and Aryl) Boron Dihalides and Dialkyl (and Diaryl) Boron Halides
          1. Introduction
          2. Organometallic Compounds
          3. Trialkylborons and Aminodialkylborons
          4. Boronic and Boronous Acids and Derivatives
       I. Properties of Alkyl (and Aryl) Boron Dihalides and Dialkyl (and Diaryl) Born Halides
          1. Physical Properties
          2. Chemical Properties
   VI. References