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Synthesis and characterization of platinum and palladium complexes featuring a rare secondary borane pincer motif

Synthesis and characterization of platinum and palladium complexes featuring a rare secondary borane pincer motif
Synthesis and characterization of platinum and palladium complexes featuring a rare secondary borane pincer motif
The synthesis and characterization of a series of platinum and palladium complexes containing a secondary borane Z-class ligand supported by 2-mercaptopyridine heterocycles is reported herein. Addition of 2 equiv of Na[H2B(mp)2] to [Pt(μ-Cl)(COEOMe)]2 (where COEOMe = 8-methoxycyclooct-4-en-1-ide) in the presence of 2 equiv of a tertiary phosphine (PR3 = PPh3, PCy3, PCyp3, P(o-tol)3, PPh2(o-tol), PPh2(2-(3-methyl)indolyl)) leads to the formation of the complexes [Pt{κ3-S,B,S-HB(mp)2}(PR3)] (1–6). Addition of 2 equiv of Na[H2B(mp)2] to [Pd(μ-Cl)(COEOMe)]2 in the presence of 2 equiv of a tertiary phosphine (PR3 = PPh3, PCy3, PCyp3, PPh2(o-tol)) leads to the formation of the complexes [Pd{κ3-S,B,S-HB(mp)2}(PR3)] (7–10). It was also demonstrated that the synthesis of the palladium complex 7 could be achieved from the palladium precursor [PdCl(Me)(COD)] (where COD = 1,5-cyclooctadiene) as an alternative synthetic strategy. In the above reactions, either the COEOMe fragment or the methyl fragment serves to act as a “hydride acceptor” facilitating the ultimate transformation of the borohydride-based ligand [H2B(mp)2]− to the corresponding secondary borane κ3-S,B,S coordinated HB(mp)2 pincer ligand. The complexes [Pd{κ3-S,B,S-HB(mp)2}(PR3)] and [Pt{κ3-S,B,S-HB(mp)2}(PR3)] are rare examples of metal–borane complexes where one hydrogen substituent remains at the boron center. These compounds have particularly short palladium– and platinum–boron distances, the shortest of the structurally characterized compounds being 2.067(6) Å for [Pd{κ3-S,B,S-HB(mp)2}(PPh2(o-tol))] and 2.076(10) Å for [Pt{κ3-S,B,S-HB(mp)2}(PCy3)], respectively (the shorter distances of two independent complexes in the unit cells of both structures).
0276-7333
2177-2187
Iannetelli, Angelo
3f6fd91d-6ac8-433e-9e46-1c0831be4ed7
Tizzard, Graham J.
8474c0fa-40df-43a6-a662-7f3c4722dbf2
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Owen, Gareth R.
88a0d18b-a3d5-46f5-b5a8-24c03a5eb66f
Iannetelli, Angelo
3f6fd91d-6ac8-433e-9e46-1c0831be4ed7
Tizzard, Graham J.
8474c0fa-40df-43a6-a662-7f3c4722dbf2
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Owen, Gareth R.
88a0d18b-a3d5-46f5-b5a8-24c03a5eb66f

Iannetelli, Angelo, Tizzard, Graham J., Coles, Simon J. and Owen, Gareth R. (2018) Synthesis and characterization of platinum and palladium complexes featuring a rare secondary borane pincer motif. Organometallics, 37 (13), 2177-2187. (doi:10.1021/acs.organomet.8b00306).

Record type: Article

Abstract

The synthesis and characterization of a series of platinum and palladium complexes containing a secondary borane Z-class ligand supported by 2-mercaptopyridine heterocycles is reported herein. Addition of 2 equiv of Na[H2B(mp)2] to [Pt(μ-Cl)(COEOMe)]2 (where COEOMe = 8-methoxycyclooct-4-en-1-ide) in the presence of 2 equiv of a tertiary phosphine (PR3 = PPh3, PCy3, PCyp3, P(o-tol)3, PPh2(o-tol), PPh2(2-(3-methyl)indolyl)) leads to the formation of the complexes [Pt{κ3-S,B,S-HB(mp)2}(PR3)] (1–6). Addition of 2 equiv of Na[H2B(mp)2] to [Pd(μ-Cl)(COEOMe)]2 in the presence of 2 equiv of a tertiary phosphine (PR3 = PPh3, PCy3, PCyp3, PPh2(o-tol)) leads to the formation of the complexes [Pd{κ3-S,B,S-HB(mp)2}(PR3)] (7–10). It was also demonstrated that the synthesis of the palladium complex 7 could be achieved from the palladium precursor [PdCl(Me)(COD)] (where COD = 1,5-cyclooctadiene) as an alternative synthetic strategy. In the above reactions, either the COEOMe fragment or the methyl fragment serves to act as a “hydride acceptor” facilitating the ultimate transformation of the borohydride-based ligand [H2B(mp)2]− to the corresponding secondary borane κ3-S,B,S coordinated HB(mp)2 pincer ligand. The complexes [Pd{κ3-S,B,S-HB(mp)2}(PR3)] and [Pt{κ3-S,B,S-HB(mp)2}(PR3)] are rare examples of metal–borane complexes where one hydrogen substituent remains at the boron center. These compounds have particularly short palladium– and platinum–boron distances, the shortest of the structurally characterized compounds being 2.067(6) Å for [Pd{κ3-S,B,S-HB(mp)2}(PPh2(o-tol))] and 2.076(10) Å for [Pt{κ3-S,B,S-HB(mp)2}(PCy3)], respectively (the shorter distances of two independent complexes in the unit cells of both structures).

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Accepted/In Press date: 26 June 2018
e-pub ahead of print date: 26 June 2018
Published date: 6 July 2018

Identifiers

Local EPrints ID: 422186
URI: https://eprints.soton.ac.uk/id/eprint/422186
ISSN: 0276-7333
PURE UUID: 86054860-3158-4fae-ab62-395d24668901
ORCID for Graham J. Tizzard: ORCID iD orcid.org/0000-0002-1577-5779
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

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Date deposited: 18 Jul 2018 16:30
Last modified: 19 Jul 2018 00:34

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Author: Angelo Iannetelli
Author: Simon J. Coles ORCID iD
Author: Gareth R. Owen

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