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Hydrophosphination is the insertion of a carbon-carbon multiple bond into a phosphorus-hydrogen bond (Scheme 1) forming a new phosphorus-carbon bond.^[1]

Scheme 1. The reaction of hydrophosphination.

Like other metal-catalyzed hydrofunctionalizations (addition of an E-H bond to an unsaturated), the rate and regiochemistry of the addition is influenced by the catalyst.

Free-radical hydrophosphination

Secondary phosphines add to alkenes in the presence of free-radical initiators.^[2]

Ultraviolet irradiation or conventional free-radical sources initiate radical hydrophosphinations. H-atom abstraction from P-H bond produces the phosphino radical, a seven electron species (Scheme 2).^[3]

Base-catalyzed hydrophosphination=

Strong bases catalyze the addition of secondary phosphines to vinyldiphenylphosphine:

HPR₂ + CH₂=CHPR'₂ → R2PCH₂CH₂PR'₂

Metal-catalyzed reactions

Metal-catalyzed hydrophosphinations typically include coordination of the primary or secondary phosphine to the metal, activation of the P-H bond (via oxidative addition or proton abstraction by an external base), P-C bond formation (through either insertion, Michael addition, or [2+2] cycloaddition), reductive elimination or addition of the abstracted proton and finally substitution of the newly made phosphine by the starting primary or secondary phosphine.^[4]^[5]

Early transition metal and lanthanide catalysts

Scheme 4. Proposed mechanism for Proposed mechanism for hydrophosphination of diphenylacetylene with phenylphosphine (PPhH2) catalyzed by a cationic titanium phosphinidene complex.

Metal complexes of d⁰ configuration are known.^[6]

Hydrophosphination of simple alkenes and alkynes is catalyzed by lanthanocene complexes.

^[7] The catalytic cycle for the hydrophosphination of α,ω-pentenylphosphine is shown in Scheme 3. Typical of most electron-poor early metal catalysts for hydrophosphination, this one includes the characteristic P-H bond cleavage and P-C and C-H bond formation steps. The primary phosphine undergoes a σ-bond metathesis with the bis(trimethylsilyl)methylene ligand forming the lanthanide-phosphido. This is then followed by a 1,2-insertion of the pendant terminal alkene or alkyne on the phosphine into the Ln-P bond. Finally, protonolysis of the Ln-C bond with the starting primary phosphine releases the new phosphine and regenerates the catalyst. Given that the metal is electron-poor, the M-C bond is polar enough to be protonolyzed by the substrate primary phosphine; this is characteristic of electron-poor, early metals.

Since many of the transition metal catalysts that are involved in hydrophosphination employ a phosphido intermediate, it is surprising that there are so few examples of catalysts that involve the metal-phosphinidene intermediate, M=PR. One such example is the Ti-catalyzed hydrophosphination of diphenylacetylene with phenylphosphine (Scheme 4) by Mindiola et al.^[8] This system involves a cationic catalyst precursor that is stabilized by the bulky 2,4,6-tri(isopropyl)phenyl- substituent on the phosphinidene and the close ionic association of methyltris(pentafluorophenyl)borate. This precursor undergoes exchange with phenylphosphine to make the titanium-phenylphosphinidene complex which is the catalyst. The Ti=PPh undergoes a [2+2] cycloaddition with diphenylacetylene to make the corresponding metallacyclobutene. The substrate, phenylphosphine, protonolyzes the Ti-C bond and after a proton shift regenerates the catalyst and releases the new phosphine.

Titanium-catalyzed 1,4-hydrophosphination of 1,3-dienes with diphenylphosphine has been demonstrated (Scheme 5).^[9] It is a rare example of a non-d⁰ early transition metal catalyst that catalyzes hydrophosphination. In the first step, the Ti²⁺ precursor undergoes an oxidative addition of the P-H bond in diphenylphosphine which generates the Ti³⁺ catalyst. The rest of the catalysis involve the usual steps: P-C bond formation via 1,2-insertion followed by C-H bond formation and P-H bond activation via protonolysis with the substrate secondary phosphine.

Late transition metal catalysts

Scheme 6. Proposed mechanism for hydrophosphination of enones catalyzed by the cationic palladium(II) catalyst.

Late transition metal hydrophosphination catalysts generally require alkenes and alkynes with electron withdrawing substituents.^[10]^[4]^[11]^[12] This is due to the fact that mechanism for the P-C bond forming step usually involves nucleophilic attack of the phosphorus to the unsaturated carbon. Generally speaking, these metal complexes will first be bound by a primary or secondary phosphine, which then undergoes proton abstraction to make a nucleophilic phosphido ligand. The proton abstraction usually occurs by an external base.This base acts as a co-catalyst which is common to late transition metal hydrophosphination catalysts.^[13]^[14]^[15]^[16] This complex catalyzes hydrophosphination of enones (Scheme 6). The bound secondary phosphine becomes deprotonated by the base triethylamine, forming the phosphido. Following this the phosphido attacks the β-carbon of the enone, which is bound to the palladium through its oxygen atom. The abstracted proton from the secondary phosphine is delivered to the enone oxygen. Substitution by another secondary phosphine regenerates the catalyst and releases the 1,2-addition product. Other common characteristics of such late metal catalysts that do not require oxidative addition of the P-H bond are: the metal in a 2+ oxidation state, and cationic complexes. These two features are important given that a base is needed because being cationic and in an oxidation state of 2+ increases the acidity of the coordinated primary or secondary phosphine proton and allows for weaker bases/conjugate acids to be used in catalysis.

Some late metal hydrophosphination catalysts rely on oxidative addition of a P-H bond. For example, a Pt(0) catalyst that undergoes oxidative addition of a secondary phosphine to form the corresponding Pt(II) phosphido complex (Scheme 7). Following this, alkenes such as acrylonitrile inserts into the Pt-P bond and then reductively eliminate to afford the hydrophosphinated acrylonitrile. This P-C bond forming step was found to occur through an outer-sphere, Michael-type addition because telomerization was occurring. The carbanion intermediate would attack another molecule of acrylonitrile affording a product that would be expected from many 1,2-insertions of the alkene.</ref>^[4]

As stated in the last example, the alkene inserted into the metal-phosphorus bond, but insertion into the metal-hydrogen bond is also possible (Scheme 7).^[17]^[18] The Ni(0) catalyst involves oxidation addition of a P-H bond to the metal, followed by insertion of the alkene into the M-H bond (Scheme 8). As a result of this, the product phosphine is produced through reductive elimination of a P-C bond rather than a P-H bond in Glueck's system.

A prospective hydrophosphination catalyst utilizes a ruthenium(II) complex (Scheme 9).^[19]^[20]^[21]^[22]^[23] Like the other late metal catalysts that require a base co-catalyst, this complex requires a base to deprotonate the coordinated secondary phosphine, generating a nucleophilic phosphido complex. The following reactivity varies from the other late metal catalysts in that P-C bond forming step involves a [2+2] cycloaddition with alkenes and alkynes forming metallacycles. The Ru-C bond of the metallacycle is then protonolyzed by the conjugate acid of the base co-catalyst. The newly formed phosphine is then substituted by the starting secondary phosphine to regenerate the catalyst and release the new phosphine. What makes this catalyst unique is that it forms metallacycles, or rather P-C bonds, with strongly and mildly activated, simple and electron-rich alkenes and alkynes, whereas the other catalysts discussed are rather limited; generally, early metals catalyzing unactivated substrates and late metals predominantly activated ones.

As stated, characteristic of the late metal catalysts for hydrophosphination that require a base co-catalyst is that they are in the 2+ oxidation state and cationic. Thus, efforts are also underway to use the similar halide-free, cationic ruthenium(II) complex for catalysis.

References

^ Delacroix, O.; Gaumont, A. (2005). "Hydrophosphination of Unactivated Alkenes, Dienes and Alkynes: A Versatile and Valuable Approach for the Synthesis of Phosphines". Current Organic Chemistry. 9 (18): 1851–1882. doi:10.2174/138527205774913079.
^ Pietro Tundo; Liang-Nian He; Ekaterina Lokteva; Claudio Mota (4 October 2016). Chemistry Beyond Chlorine. Springer International Publishing. pp. 152–164. ISBN 978-3-319-30071-9.
^ Quin, L. D. A Guide to Organophosphorus Chemistry; John Wiley & Sons: New York, 2000; pp 28-29.
^ ^a ^b ^c Glueck, David S. (2010). "Recent Advances in Metal-Catalyzed C–P Bond Formation". C-X Bond Formation. Topics in Organometallic Chemistry. Vol. 31. pp. 65–100. doi:10.1007/978-3-642-12073-2_4. ISBN 978-3-642-12072-5.
^ Rosenberg, L. R. ACS Catal. 2013, 3, 2845.Rosenberg, L. (2013). "Mechanisms of Metal-Catalyzed Hydrophosphination of Alkenes and Alkynes". ACS Catalysis. 3 (12): 2845. doi:10.1021/cs400685c.
^ Greenberg, S.; Stephan, D. W. (2008). "Stoichiometric and catalytic activation of P–H and P–P bonds". Chemical Society Reviews. 37 (8): 1482. doi:10.1039/B612306F.
^ Motta, A.; Fragalà, I. L.; Marks, T. J. (2005). "Energetics and Mechanism of Organolanthanide-Mediated Phosphinoalkene Hydrophosphination/Cyclization. A Density Functional Theory Analysis". Organometallics. 24 (21): 4995. doi:10.1021/om050570d.
^ Zhao, G. Y.; Basuli, F.; Kilgore, U. J.; Fan, H. J.; Aneetha, H.; Huffman, J. C.; Wu, G.; Mindiola, D. J. J. Am. Chem. Soc. 2006, 128, 13575.Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha, H.; Huffman, J. C.; Wu, G.; Mindiola, D. J. (2006). "Neutral and Zwitterionic Low-Coordinate Titanium Complexes Bearing the Terminal Phosphinidene Functionality. Structural, Spectroscopic, Theoretical, and Catalytic Studies Addressing the Ti−P Multiple Bond". Journal of the American Chemical Society. 128 (41): 13575. doi:10.1021/ja064853o.
^ Perrier, A.; Comte, V.; Moise, C.; Le Gendre, P. Chem. – Eur. J. 2010, 16, 64.Perrier, A.; Comte, V.; Moïse, C.; Le Gendre, P. (2010). "First Titanium-Catalyzed 1,4-Hydrophosphination of 1,3-Dienes". Chemistry – A European Journal. 16: 64. doi:10.1002/chem.200901863.
^ Pringle, P. G.; Smith, M. B. (1990). "Platinum(0)-catalysed hydrophosphination of acrylonitrile". Journal of the Chemical Society, Chemical Communications (23): 1701. doi:10.1039/C39900001701.
^ Sadow, A. D.; Togni, A. J. Am. Chem. Soc. 2005, 127, 17012.Sadow, A. D.; Togni, A. (2005). "Enantioselective Addition of Secondary Phosphines to Methacrylonitrile: Catalysis and Mechanism". Journal of the American Chemical Society. 127 (48): 17012. doi:10.1021/ja0555163.
^ Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Chem. Commun. 2010, 46, 6950.Huang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P. H. (2010). "Palladium(ii)-catalyzed asymmetric hydrophosphination of enones: Efficient access to chiral tertiary phosphines". Chemical Communications. 46 (37): 6950. doi:10.1039/C0CC00925C. PMID 20730193.
^ Xu, C.; Jun Hao Kennard, G.; Hennersdorf, F.; Li, Y.; Pullarkat, S. A.; Leung, P. H. (2012). "Chiral Phosphapalladacycles as Efficient Catalysts for the Asymmetric Hydrophosphination of Substituted Methylidenemalonate Esters: Direct Access to Functionalized Tertiary Chiral Phosphines". Organometallics. 31 (8): 3022. doi:10.1021/om201115n.
^ Huang, Y. H.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y. X.; Leung, P. H. Organometallics 2012, 31, 4871.Huang, Y.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y.; Leung, P. H. (2012). "Palladacycle-Catalyzed Asymmetric Intermolecular Construction of Chiral Tertiary P-Heterocycles by Stepwise Addition of H–P–H Bonds to Bis(enones)". Organometallics. 31 (13): 4871. doi:10.1021/om300405h.
^ Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Inorg. Chem. 2012, 51, 2533.Huang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P. H. (2012). "Palladacycle-Catalyzed Asymmetric Hydrophosphination of Enones for Synthesis of C*- and P*-Chiral Tertiary Phosphines". Inorganic Chemistry. 51 (4): 2533. doi:10.1021/ic202472f. PMID 22289417.
^ Huang, Y.; Chew, R. J.; Li, Y.; Pullarkat, S. A.; Leung, P. H. (2011). "Direct Synthesis of Chiral Tertiary Diphosphinesvia Pd(II)-Catalyzed Asymmetric Hydrophosphination of Dienones". Organic Letters. 13 (21): 5862. doi:10.1021/ol202480r. PMID 21985055.
^ Shulyupin, M. O.; Kazankova, M. A.; Beletskaya, I. P. Org. Lett. 2002, 4, 761.Shulyupin, M. O.; Kazankova, M. A.; Beletskaya, I. P. (2002). "Catalytic Hydrophosphination of Styrenes". Organic Letters. 4 (5): 761. doi:10.1021/ol017238s.
^ Kazankova, M. A.; Shulyupin, M. O.; Borisenko, A. A.; Beletskaya, I. P. Russ. J. Org. Chem. 2002, 38, 1479.Kazankova, M. A.; Shulyupin, M. O.; Borisenko, A. A.; Beletskaya, I. P. (2002). "Synthesis of Alkyl(diphenyl)phosphines by Hydrophosphination of Vinylarenes Catalyzed by Transition Metal Complexes". Russian Journal of Organic Chemistry. 38 (10): 1479. doi:10.1023/A:1022552404812.
^ Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. Organometallics 2007, 26, 1473.Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. (2007). "A Highly Reactive Ruthenium Phosphido Complex Exhibiting Ru−P π-Bonding". Organometallics. 26 (6): 1473. doi:10.1021/om0700056.
^ Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. Angew. Chem. Int. Ed. 2010, 49, 3367.Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. (2010). "Concerted [2+2] Cycloaddition of Alkenes to a Ruthenium-Phosphorus Double Bond". Angewandte Chemie International Edition. 49 (19): 3367. doi:10.1002/anie.201000356.
^ Derrah, E. J.; McDonald, R.; Rosenberg, L. Chem. Commun. 2010, 46, 4592.Derrah, E. J.; McDonald, R.; Rosenberg, L. (2010). "The [2+2] cycloaddition of alkynes at a Ru–P π-bond". Chemical Communications. 46 (25): 4592. doi:10.1039/C002765K.
^ Gibson, G. L.; Morrow, K. M. E.; McDonald, R.; Rosenberg, L. Inorg. Chim. Acta. 2011, 369, 133.Gibson, G. L.; Morrow, K. M. E.; McDonald, R.; Rosenberg, L. (2011). "Diastereoselective synthesis of a "chiral-at-Ru" secondary phosphine complex". Inorganica Chimica Acta. 369: 133. doi:10.1016/j.ica.2010.12.058.
^ Burton (née Morrow), K. M. E.; Belli, R. G.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. manuscript in preparation.

[1] Delacroix, O.; Gaumont, A. (2005). "Hydrophosphination of Unactivated Alkenes, Dienes and Alkynes: A Versatile and Valuable Approach for the Synthesis of Phosphines". Current Organic Chemistry. 9 (18): 1851–1882. doi:10.2174/138527205774913079.

[TundoHe2016-2] Pietro Tundo; Liang-Nian He; Ekaterina Lokteva; Claudio Mota (4 October 2016). Chemistry Beyond Chlorine. Springer International Publishing. pp. 152–164. ISBN 978-3-319-30071-9.

[3] Quin, L. D. A Guide to Organophosphorus Chemistry; John Wiley & Sons: New York, 2000; pp 28-29.

[Glueck-4] Glueck, David S. (2010). "Recent Advances in Metal-Catalyzed C–P Bond Formation". C-X Bond Formation. Topics in Organometallic Chemistry. Vol. 31. pp. 65–100. doi:10.1007/978-3-642-12073-2_4. ISBN 978-3-642-12072-5.

[5] Rosenberg, L. R. ACS Catal. 2013, 3, 2845.Rosenberg, L. (2013). "Mechanisms of Metal-Catalyzed Hydrophosphination of Alkenes and Alkynes". ACS Catalysis. 3 (12): 2845. doi:10.1021/cs400685c.

[6] Greenberg, S.; Stephan, D. W. (2008). "Stoichiometric and catalytic activation of P–H and P–P bonds". Chemical Society Reviews. 37 (8): 1482. doi:10.1039/B612306F.

[7] Motta, A.; Fragalà, I. L.; Marks, T. J. (2005). "Energetics and Mechanism of Organolanthanide-Mediated Phosphinoalkene Hydrophosphination/Cyclization. A Density Functional Theory Analysis". Organometallics. 24 (21): 4995. doi:10.1021/om050570d.

[8] Zhao, G. Y.; Basuli, F.; Kilgore, U. J.; Fan, H. J.; Aneetha, H.; Huffman, J. C.; Wu, G.; Mindiola, D. J. J. Am. Chem. Soc. 2006, 128, 13575.Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha, H.; Huffman, J. C.; Wu, G.; Mindiola, D. J. (2006). "Neutral and Zwitterionic Low-Coordinate Titanium Complexes Bearing the Terminal Phosphinidene Functionality. Structural, Spectroscopic, Theoretical, and Catalytic Studies Addressing the Ti−P Multiple Bond". Journal of the American Chemical Society. 128 (41): 13575. doi:10.1021/ja064853o.

[9] Perrier, A.; Comte, V.; Moise, C.; Le Gendre, P. Chem. – Eur. J. 2010, 16, 64.Perrier, A.; Comte, V.; Moïse, C.; Le Gendre, P. (2010). "First Titanium-Catalyzed 1,4-Hydrophosphination of 1,3-Dienes". Chemistry – A European Journal. 16: 64. doi:10.1002/chem.200901863.

[10] Pringle, P. G.; Smith, M. B. (1990). "Platinum(0)-catalysed hydrophosphination of acrylonitrile". Journal of the Chemical Society, Chemical Communications (23): 1701. doi:10.1039/C39900001701.

[11] Sadow, A. D.; Togni, A. J. Am. Chem. Soc. 2005, 127, 17012.Sadow, A. D.; Togni, A. (2005). "Enantioselective Addition of Secondary Phosphines to Methacrylonitrile: Catalysis and Mechanism". Journal of the American Chemical Society. 127 (48): 17012. doi:10.1021/ja0555163.

[12] Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Chem. Commun. 2010, 46, 6950.Huang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P. H. (2010). "Palladium(ii)-catalyzed asymmetric hydrophosphination of enones: Efficient access to chiral tertiary phosphines". Chemical Communications. 46 (37): 6950. doi:10.1039/C0CC00925C. PMID 20730193.

[13] Xu, C.; Jun Hao Kennard, G.; Hennersdorf, F.; Li, Y.; Pullarkat, S. A.; Leung, P. H. (2012). "Chiral Phosphapalladacycles as Efficient Catalysts for the Asymmetric Hydrophosphination of Substituted Methylidenemalonate Esters: Direct Access to Functionalized Tertiary Chiral Phosphines". Organometallics. 31 (8): 3022. doi:10.1021/om201115n.

[14] Huang, Y. H.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y. X.; Leung, P. H. Organometallics 2012, 31, 4871.Huang, Y.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y.; Leung, P. H. (2012). "Palladacycle-Catalyzed Asymmetric Intermolecular Construction of Chiral Tertiary P-Heterocycles by Stepwise Addition of H–P–H Bonds to Bis(enones)". Organometallics. 31 (13): 4871. doi:10.1021/om300405h.

[15] Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Inorg. Chem. 2012, 51, 2533.Huang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P. H. (2012). "Palladacycle-Catalyzed Asymmetric Hydrophosphination of Enones for Synthesis of C*- and P*-Chiral Tertiary Phosphines". Inorganic Chemistry. 51 (4): 2533. doi:10.1021/ic202472f. PMID 22289417.

[16] Huang, Y.; Chew, R. J.; Li, Y.; Pullarkat, S. A.; Leung, P. H. (2011). "Direct Synthesis of Chiral Tertiary Diphosphinesvia Pd(II)-Catalyzed Asymmetric Hydrophosphination of Dienones". Organic Letters. 13 (21): 5862. doi:10.1021/ol202480r. PMID 21985055.

[17] Shulyupin, M. O.; Kazankova, M. A.; Beletskaya, I. P. Org. Lett. 2002, 4, 761.Shulyupin, M. O.; Kazankova, M. A.; Beletskaya, I. P. (2002). "Catalytic Hydrophosphination of Styrenes". Organic Letters. 4 (5): 761. doi:10.1021/ol017238s.

[18] Kazankova, M. A.; Shulyupin, M. O.; Borisenko, A. A.; Beletskaya, I. P. Russ. J. Org. Chem. 2002, 38, 1479.Kazankova, M. A.; Shulyupin, M. O.; Borisenko, A. A.; Beletskaya, I. P. (2002). "Synthesis of Alkyl(diphenyl)phosphines by Hydrophosphination of Vinylarenes Catalyzed by Transition Metal Complexes". Russian Journal of Organic Chemistry. 38 (10): 1479. doi:10.1023/A:1022552404812.

[19] Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. Organometallics 2007, 26, 1473.Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. (2007). "A Highly Reactive Ruthenium Phosphido Complex Exhibiting Ru−P π-Bonding". Organometallics. 26 (6): 1473. doi:10.1021/om0700056.

[20] Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. Angew. Chem. Int. Ed. 2010, 49, 3367.Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. (2010). "Concerted [2+2] Cycloaddition of Alkenes to a Ruthenium-Phosphorus Double Bond". Angewandte Chemie International Edition. 49 (19): 3367. doi:10.1002/anie.201000356.

[21] Derrah, E. J.; McDonald, R.; Rosenberg, L. Chem. Commun. 2010, 46, 4592.Derrah, E. J.; McDonald, R.; Rosenberg, L. (2010). "The [2+2] cycloaddition of alkynes at a Ru–P π-bond". Chemical Communications. 46 (25): 4592. doi:10.1039/C002765K.

[22] Gibson, G. L.; Morrow, K. M. E.; McDonald, R.; Rosenberg, L. Inorg. Chim. Acta. 2011, 369, 133.Gibson, G. L.; Morrow, K. M. E.; McDonald, R.; Rosenberg, L. (2011). "Diastereoselective synthesis of a "chiral-at-Ru" secondary phosphine complex". Inorganica Chimica Acta. 369: 133. doi:10.1016/j.ica.2010.12.058.

[23] Burton (née Morrow), K. M. E.; Belli, R. G.; Pantazis, D. A.; McDonald, R.; Rosenberg, L. manuscript in preparation.

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@@ Line 17: / Line 17: @@
 ==Metal-catalyzed reactions==
-Metal-catalyzed hydrophosphinations typically include coordination of the primary or secondary phosphine to the metal, activation of the P-H bond (via oxidative addition or proton abstraction by an external base), P-C bond formation (through either insertion, Michael addition, or [2+2] cycloaddition), reductive elimination or addition of the abstracted proton and finally substitution of the newly made phosphine by the starting primary or secondary phosphine.<ref>Glueck, D. S. Top. Organomet. Chem. 2010, 31, 65.</ref><ref>Rosenberg, L. R. ACS Catal. 2013, 3, 2845.{{Cite journal | doi = 10.1021/cs400685c| title = Mechanisms of Metal-Catalyzed Hydrophosphination of Alkenes and Alkynes| journal = ACS Catalysis| volume = 3| issue = 12| pages = 2845| year = 2013| last1 = Rosenberg | first1 = L. }}</ref>
+Metal-catalyzed hydrophosphinations typically include coordination of the primary or secondary phosphine to the metal, activation of the P-H bond (via oxidative addition or proton abstraction by an external base), P-C bond formation (through either insertion, Michael addition, or [2+2] cycloaddition), reductive elimination or addition of the abstracted proton and finally substitution of the newly made phosphine by the starting primary or secondary phosphine.<ref name=Glueck>{{Cite book | doi = 10.1007/978-3-642-12073-2_4| chapter = Recent Advances in Metal-Catalyzed C–P Bond Formation| title = C-X Bond Formation| volume = 31| pages = 65–100| series = Topics in Organometallic Chemistry| year = 2010| last1 = Glueck| first1 = David S.| isbn = 978-3-642-12072-5}}</ref><ref>Rosenberg, L. R. ACS Catal. 2013, 3, 2845.{{Cite journal | doi = 10.1021/cs400685c| title = Mechanisms of Metal-Catalyzed Hydrophosphination of Alkenes and Alkynes| journal = ACS Catalysis| volume = 3| issue = 12| pages = 2845| year = 2013| last1 = Rosenberg | first1 = L. }}</ref>
 ===Early transition metal and lanthanide catalysts===
@@ Line 36: / Line 36: @@
 ===Late transition metal catalysts===
 [[File:Wiki7.png|thumbnail|left|Scheme 6. Proposed mechanism for hydrophosphination of enones catalyzed by the cationic palladium(II) catalyst.]]
-Late transition metal hydrophosphination catalysts generally require alkenes and alkynes with electron withdrawing substituents.<ref>{{Cite journal | doi = 10.1039/C39900001701| title = Platinum(0)-catalysed hydrophosphination of acrylonitrile| journal = Journal of the Chemical Society, Chemical Communications| issue = 23| pages = 1701| year = 1990| last1 = Pringle | first1 = P. G. | last2 = Smith | first2 = M. B. }}</ref><ref>{{Cite journal | doi = 10.1021/om990882e| title = Pt(Me-Duphos)-Catalyzed Asymmetric Hydrophosphination of Activated Olefins:  Enantioselective Synthesis of Chiral Phosphines| journal = Organometallics| volume = 19| issue = 6| pages = 950| year = 2000| last1 = Kovacik | first1 = I. | last2 = Wicht | first2 = D. K. | last3 = Grewal | first3 = N. S. | last4 = Glueck | first4 = D. S. | last5 = Incarvito | first5 = C. D. | last6 = Guzei | first6 = I. A. | last7 = Rheingold | first7 = A. L. }}</ref><ref>Sadow, A. D.; Togni, A. J. Am. Chem. Soc. 2005, 127, 17012.{{Cite journal | doi = 10.1021/ja0555163| title = Enantioselective Addition of Secondary Phosphines to Methacrylonitrile:  Catalysis and Mechanism| journal = Journal of the American Chemical Society| volume = 127| issue = 48| pages = 17012| year = 2005| last1 = Sadow | first1 = A. D. | last2 = Togni | first2 = A. }}</ref><ref>Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Chem. Commun. 2010, 46, 6950.{{Cite journal | doi = 10.1039/C0CC00925C| pmid = 20730193| title = Palladium(ii)-catalyzed asymmetric hydrophosphination of enones: Efficient access to chiral tertiary phosphines| journal = Chemical Communications| volume = 46| issue = 37| pages = 6950| year = 2010| last1 = Huang | first1 = Y. | last2 = Pullarkat | first2 = S. A. | last3 = Li | first3 = Y. | last4 = Leung | first4 = P. H. }}</ref> This is due to the fact that mechanism for the P-C bond forming step usually involves nucleophilic attack of the phosphorus to the unsaturated carbon. Generally speaking, these metal complexes will first be bound by a primary or secondary phosphine, which then undergoes proton abstraction to make a nucleophilic phosphido ligand. The proton abstraction usually occurs by an external base.This base acts as a co-catalyst which is common to late transition metal hydrophosphination catalysts.<ref>{{Cite journal | doi = 10.1021/om201115n| title = Chiral Phosphapalladacycles as Efficient Catalysts for the Asymmetric Hydrophosphination of Substituted Methylidenemalonate Esters: Direct Access to Functionalized Tertiary Chiral Phosphines| journal = Organometallics| volume = 31| issue = 8| pages = 3022| year = 2012| last1 = Xu | first1 = C. | last2 = Jun Hao Kennard | first2 = G. | last3 = Hennersdorf | first3 = F. | last4 = Li | first4 = Y. | last5 = Pullarkat | first5 = S. A. | last6 = Leung | first6 = P. H. }}</ref><ref>Huang, Y. H.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y. X.; Leung, P. H. Organometallics 2012, 31, 4871.{{Cite journal | doi = 10.1021/om300405h| title = Palladacycle-Catalyzed Asymmetric Intermolecular Construction of Chiral Tertiary P-Heterocycles by Stepwise Addition of H–P–H Bonds to Bis(enones)| journal = Organometallics| volume = 31| issue = 13| pages = 4871| year = 2012| last1 = Huang | first1 = Y. | last2 = Pullarkat | first2 = S. A. | last3 = Teong | first3 = S. | last4 = Chew | first4 = R. J. | last5 = Li | first5 = Y. | last6 = Leung | first6 = P. H. }}</ref><ref>Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Inorg. Chem. 2012, 51, 2533.{{Cite journal | doi = 10.1021/ic202472f| pmid = 22289417| title = Palladacycle-Catalyzed Asymmetric Hydrophosphination of Enones for Synthesis of C*- and P*-Chiral Tertiary Phosphines| journal = Inorganic Chemistry| volume = 51| issue = 4| pages = 2533| year = 2012| last1 = Huang | first1 = Y. | last2 = Pullarkat | first2 = S. A. | last3 = Li | first3 = Y. | last4 = Leung | first4 = P. H. }}</ref><ref>{{Cite journal | doi = 10.1021/ol202480r| pmid = 21985055| title = Direct Synthesis of Chiral Tertiary Diphosphinesvia ''Pd''(II)-Catalyzed Asymmetric Hydrophosphination of Dienones| journal = Organic Letters| volume = 13| issue = 21| pages = 5862| year = 2011| last1 = Huang | first1 = Y. | last2 = Chew | first2 = R. J. | last3 = Li | first3 = Y. | last4 = Pullarkat | first4 = S. A. | last5 = Leung | first5 = P. H. }}</ref> This complex catalyzes hydrophosphination of enones (Scheme 6). The bound secondary phosphine becomes deprotonated by the base triethylamine, forming the phosphido. Following this the phosphido attacks the β-carbon of the enone, which is bound to the palladium through its oxygen atom. The abstracted proton from the secondary phosphine is delivered to the enone oxygen. Substitution by another secondary phosphine regenerates the catalyst and releases the 1,2-addition product. Other common characteristics of such late metal catalysts that do not require oxidative addition of the P-H bond are: the metal in a 2+ oxidation state, and cationic complexes. These two features are important given that a base is needed because being cationic and in an oxidation state of 2+ increases the acidity of the coordinated primary or secondary phosphine proton and allows for weaker bases/conjugate acids to be used in catalysis.
+Late transition metal hydrophosphination catalysts generally require alkenes and alkynes with electron withdrawing substituents.<ref>{{Cite journal | doi = 10.1039/C39900001701| title = Platinum(0)-catalysed hydrophosphination of acrylonitrile| journal = Journal of the Chemical Society, Chemical Communications| issue = 23| pages = 1701| year = 1990| last1 = Pringle | first1 = P. G. | last2 = Smith | first2 = M. B. }}</ref><ref name=Glueck/><ref>Sadow, A. D.; Togni, A. J. Am. Chem. Soc. 2005, 127, 17012.{{Cite journal | doi = 10.1021/ja0555163| title = Enantioselective Addition of Secondary Phosphines to Methacrylonitrile:  Catalysis and Mechanism| journal = Journal of the American Chemical Society| volume = 127| issue = 48| pages = 17012| year = 2005| last1 = Sadow | first1 = A. D. | last2 = Togni | first2 = A. }}</ref><ref>Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Chem. Commun. 2010, 46, 6950.{{Cite journal | doi = 10.1039/C0CC00925C| pmid = 20730193| title = Palladium(ii)-catalyzed asymmetric hydrophosphination of enones: Efficient access to chiral tertiary phosphines| journal = Chemical Communications| volume = 46| issue = 37| pages = 6950| year = 2010| last1 = Huang | first1 = Y. | last2 = Pullarkat | first2 = S. A. | last3 = Li | first3 = Y. | last4 = Leung | first4 = P. H. }}</ref> This is due to the fact that mechanism for the P-C bond forming step usually involves nucleophilic attack of the phosphorus to the unsaturated carbon. Generally speaking, these metal complexes will first be bound by a primary or secondary phosphine, which then undergoes proton abstraction to make a nucleophilic phosphido ligand. The proton abstraction usually occurs by an external base.This base acts as a co-catalyst which is common to late transition metal hydrophosphination catalysts.<ref>{{Cite journal | doi = 10.1021/om201115n| title = Chiral Phosphapalladacycles as Efficient Catalysts for the Asymmetric Hydrophosphination of Substituted Methylidenemalonate Esters: Direct Access to Functionalized Tertiary Chiral Phosphines| journal = Organometallics| volume = 31| issue = 8| pages = 3022| year = 2012| last1 = Xu | first1 = C. | last2 = Jun Hao Kennard | first2 = G. | last3 = Hennersdorf | first3 = F. | last4 = Li | first4 = Y. | last5 = Pullarkat | first5 = S. A. | last6 = Leung | first6 = P. H. }}</ref><ref>Huang, Y. H.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y. X.; Leung, P. H. Organometallics 2012, 31, 4871.{{Cite journal | doi = 10.1021/om300405h| title = Palladacycle-Catalyzed Asymmetric Intermolecular Construction of Chiral Tertiary P-Heterocycles by Stepwise Addition of H–P–H Bonds to Bis(enones)| journal = Organometallics| volume = 31| issue = 13| pages = 4871| year = 2012| last1 = Huang | first1 = Y. | last2 = Pullarkat | first2 = S. A. | last3 = Teong | first3 = S. | last4 = Chew | first4 = R. J. | last5 = Li | first5 = Y. | last6 = Leung | first6 = P. H. }}</ref><ref>Huang, Y. H.; Pullarkat, S. A.; Li, Y. X.; Leung, P. H. Inorg. Chem. 2012, 51, 2533.{{Cite journal | doi = 10.1021/ic202472f| pmid = 22289417| title = Palladacycle-Catalyzed Asymmetric Hydrophosphination of Enones for Synthesis of C*- and P*-Chiral Tertiary Phosphines| journal = Inorganic Chemistry| volume = 51| issue = 4| pages = 2533| year = 2012| last1 = Huang | first1 = Y. | last2 = Pullarkat | first2 = S. A. | last3 = Li | first3 = Y. | last4 = Leung | first4 = P. H. }}</ref><ref>{{Cite journal | doi = 10.1021/ol202480r| pmid = 21985055| title = Direct Synthesis of Chiral Tertiary Diphosphinesvia ''Pd''(II)-Catalyzed Asymmetric Hydrophosphination of Dienones| journal = Organic Letters| volume = 13| issue = 21| pages = 5862| year = 2011| last1 = Huang | first1 = Y. | last2 = Chew | first2 = R. J. | last3 = Li | first3 = Y. | last4 = Pullarkat | first4 = S. A. | last5 = Leung | first5 = P. H. }}</ref> This complex catalyzes hydrophosphination of enones (Scheme 6). The bound secondary phosphine becomes deprotonated by the base triethylamine, forming the phosphido. Following this the phosphido attacks the β-carbon of the enone, which is bound to the palladium through its oxygen atom. The abstracted proton from the secondary phosphine is delivered to the enone oxygen. Substitution by another secondary phosphine regenerates the catalyst and releases the 1,2-addition product. Other common characteristics of such late metal catalysts that do not require oxidative addition of the P-H bond are: the metal in a 2+ oxidation state, and cationic complexes. These two features are important given that a base is needed because being cationic and in an oxidation state of 2+ increases the acidity of the coordinated primary or secondary phosphine proton and allows for weaker bases/conjugate acids to be used in catalysis.
 [[File:Pt cycle.png|thumbnail|left|Scheme 7. Proposed mechanism for hydrophosphination catalyzed by Pt(II) phosphido complex.]]
 [[File:Nickel catalyst.png|thumbnail|right|Scheme 8. Proposed mechanism for hydrophosphination catalyzed by Ni(0) catalyst.]]
-Some late metal hydrophosphination catalysts rely on oxidative addition of a P-H bond. For example, a Pt(0) catalyst that undergoes oxidative addition of a secondary phosphine to form the corresponding Pt(II) phosphido complex (Scheme 7). Following this, alkenes such as acrylonitrile inserts into the Pt-P bond and then reductively eliminate to afford the hydrophosphinated acrylonitrile. This P-C bond forming step was found to occur through an outer-sphere, Michael-type addition because telomerization was occurring. The carbanion intermediate would attack another molecule of acrylonitrile affording a product that would be expected from many 1,2-insertions of the alkene.<ref>Scriban, C.; Glueck, D. S.; Zakharov, L. N.; Kassel, W. S.; DiPasquale, A. G.; Golen, J. A.; Rheingold, A. L. Organometallics 2006, 25, 5757.{{Cite journal | doi = 10.1021/om060631n| title = P−C and C−C Bond Formation by Michael Addition in Platinum-Catalyzed Hydrophosphination and in the Stoichiometric Reactions of Platinum Phosphido Complexes with Activated Alkenes| journal = Organometallics| volume = 25| issue = 24| pages = 5757| year = 2006| last1 = Scriban | first1 = C. | last2 = Glueck | first2 = D. S. | last3 = Zakharov | first3 = L. N. | last4 = Kassel | first4 = W. S. | last5 = Dipasquale | first5 = A. G. | last6 = Golen | first6 = J. A. | last7 = Rheingold | first7 = A. L. }}</ref><ref>Scriban, c.; Kovacik, L.; Glueck, D. S. Organometallics, 2005, 24, 4871.{{Cite journal | doi = 10.1021/om050433g| title = A Protic Additive Suppresses Formation of Byproducts in Platinum-Catalyzed Hydrophosphination of Activated Olefins. Evidence for P−C and C−C Bond Formation by Michael Addition| journal = Organometallics| volume = 24| issue = 21| pages = 4871| year = 2005| last1 = Scriban | first1 = C. | last2 = Kovacik | first2 = I. | last3 = Glueck | first3 = D. S. }}</ref><ref>Wicht, D. K.; Kourkine, I. V.; Lew, B. M.; Nthenge, J. M.; Glueck, D. S. J. Am. Chem. Soc. 1997, 119, 5039.{{Cite journal | doi = 10.1021/ja970355r| title = Platinum-Catalyzed Acrylonitrile Hydrophosphination via Olefin Insertion into a Pt−P Bond| journal = Journal of the American Chemical Society| volume = 119| issue = 21| pages = 5039| year = 1997| last1 = Wicht | first1 = D. K. | last2 = Kourkine | first2 = I. V. | last3 = Lew | first3 = B. M. | last4 = Nthenge | first4 = J. M. | last5 = Glueck | first5 = D. S. }}</ref>
+Some late metal hydrophosphination catalysts rely on oxidative addition of a P-H bond. For example, a Pt(0) catalyst that undergoes oxidative addition of a secondary phosphine to form the corresponding Pt(II) phosphido complex (Scheme 7). Following this, alkenes such as acrylonitrile inserts into the Pt-P bond and then reductively eliminate to afford the hydrophosphinated acrylonitrile. This P-C bond forming step was found to occur through an outer-sphere, Michael-type addition because telomerization was occurring. The carbanion intermediate would attack another molecule of acrylonitrile affording a product that would be expected from many 1,2-insertions of the alkene.</ref><ref name=Glueck/>
 As stated in the last example, the alkene inserted into the metal-phosphorus bond, but insertion into the metal-hydrogen bond is also possible (Scheme 7).<ref>Shulyupin, M. O.; Kazankova, M. A.; Beletskaya, I. P. Org. Lett. 2002, 4, 761.{{Cite journal | doi = 10.1021/ol017238s| title = Catalytic Hydrophosphination of Styrenes| journal = Organic Letters| volume = 4| issue = 5| pages = 761| year = 2002| last1 = Shulyupin | first1 = M. O. | last2 = Kazankova | first2 = M. A. | last3 = Beletskaya | first3 = I. P. }}</ref><ref>Kazankova, M. A.; Shulyupin, M. O.; Borisenko, A. A.; Beletskaya, I. P. Russ. J. Org. Chem. 2002, 38, 1479.{{Cite journal | doi = 10.1023/A:1022552404812| year = 2002| last1 = Kazankova | first1 = M. A.| journal = Russian Journal of Organic Chemistry| volume = 38| issue = 10| pages = 1479| last2 = Shulyupin | first2 = M. O.| last3 = Borisenko | first3 = A. A.| last4 = Beletskaya | first4 = I. P.|title=Synthesis of Alkyl(diphenyl)phosphines by Hydrophosphination of Vinylarenes Catalyzed by Transition Metal Complexes}}</ref> The Ni(0) catalyst involves oxidation addition of a P-H bond to the metal, followed by insertion of the alkene into the M-H bond (Scheme 8). As a result of this, the product phosphine is produced through reductive elimination of a P-C bond rather than a P-H bond in Glueck's system.