Duncan Carmichael

Dialkyl 1-Alkynylphosphonates: a Range of Promising Reagents

This review covers the preparations of 1-alkynylphosphonates by Michaelis–Arbuzov and Michaelis–Becker reactions, by nucleophilic substitutions at phosphorus (SNPV), and by elimination from 1-alkenylphosphonates. The reactivity and versatility of 1-alkynylphosphonates have made them valuable precursors for other phosphonates, and particularly for the synthesis of heterocycles by [2+2], [3+2], and [4+2] cycloaddition reactions.

New Trends in Phosphametallocene Chemistry

The increasing general awareness of phospholyl ligands within the chemical community rests upon two properties: they can replace cyclopentadienyls in metal complexes and their ŋ5-transition metal complexes can act as π-acceptor ligands for coordination chemistry. In this review three interrelated areas exploiting these characteristics are presented. They comprise new structures and reagents based upon main-group phospholyl complexes, the incorporation of phospholyl ligands into transition metal paramagnetic metallocenes, and the application of transition-metal phospholyl complexes in homogeneous catalysis.

Exploiting the Brønsted acidity of phosphinecarboxamides for the synthesis of new phosphides and phosphines.

We demonstrate that the synthesis of new N-functionalized phosphinecarboxamides is possible by reaction of primary and secondary amines with PCO− in the presence of a proton source. These reactions proceed with varying degrees of success, and although primary amines generally afford the corresponding phosphinecarboxamides in good yields, secondary amines react more sluggishly and often give rise to significant decomposition of the 2-phosphaethynolate precursor. Of the new N-derivatized phosphinecarboxamides available, PH2C(O)NHCy (Cy=cyclohexyl) can be obtained in sufficiently high yields to allow for the exploration of its Brønsted acidity. Thus, deprotonating PH2C(O)NHCy with one equivalent of potassium bis(trimethylsilyl)amide (KHMDS) gave the new phosphide [PHC(O)NHCy]−. In contrast, deprotonation with half of an equivalent gives rise to [P{C(O)NHCy}2]− and PH3. These phosphides can be employed to give new phosphines by reactions with electrophiles, thus demonstrating their enormous potential as chemical building blocks.

Use of the 2,5-bis-(tert-butyl)phospholide anion as an η5-ligand: stabilisation of η5-phospholyl complexes of ruthenium and rhodium

The 2,5-bis-(tert-butyl)phospholide anion promotes η5-complexation to late transition metals in cases where unhindered phospholyls may favour η1-ligation through the phosphorus lone pair.

η5‐Phospholylgallium: The First Monomeric Polyhapto Compound between a Phospholyl Ligand and a Main Group Metal

Monomeric polyhapto-bound phospholyl compounds were hitherto unknown for the main group elements. Use of a solution of metastable GaBr has allowed the synthesis of monomeric η5 -phospholylgallium, which has been characterized by X-ray structure analysis as the Cr(CO)5 complex 1.

An η2 transition state for the insertion of M(PR3)2 fragments (M = Pd or Pt) into the phosphorus–carbon bonds of pentacarbonyl(phosphirane)tungsten complexes

The reaction of (E)- and (Z)-[W(CO)5( [graphic omitted]HPh)] complexes with [M(PR3)2(C2H4)][M = Pd, (PR3)2= dppe (Ph2PCH2CH2PPh2); M = Pt, PR3= PPh3] has been studied and the following products [which result from insertion of the M(PR3)2 frogment into the phosphirane ring] have been fully characterised by NMR spectroscopy: (2R*,3S*,4S*)-(±)-, (2R*,3S*,4R*)-(±)- and (2R*,3S*,4R*)-(±)-[(dppe) Pd(CHPhCHPhPPh)W(CO)5]; (2S*,3S*,4S*)-(±)-, (2S*3R*4R*)-(±)- and (2S*,3S*,4R*)-(±)-[(Ph3P)2Pt(CHPhCHPhPPh)W(CO)5]; and trans-(2S*,3S*,4R*)-(±)-[(Ph3P)(OC)Pt-(CHPhCHPhPPh)W(CO)5]. The crystal and molecular structures of (Z)-[W(CO)5([graphic omitted]HPh)], (2R*,3S*,4R*)-(±)- and (R*,3S*,4S*)-(±)-[(dppe)Pd(CHPhCHPhPPh)W(CO)5] have been determined. The configurations of the products are interpreted in terms of a transition state in which a P–C bond is η2-co-ordinated to M(PR3)2 fragment.

Reactions of zero- and di-valent platinum metal complexes with phosphirene ring systems. Crystal structures of cis-[PtCl2(PEt3)(PPhCPhCPh)], cis-[Ptl(PPh3)(CPhCPhPPhMe)] and [(Et3P)2Pt(CPhCPhPPh)W(CO)5]

The phosphirene ring system Ph[graphic omitted]Ph 1 undergoes unidentate ligation and/or insertion reactions with a variety of platinum metal complexes. Insertion reactions also occur with the [W(CO)5] adduct of 1. Detailed NMR and single-crystal X-ray studies on [PtCl2(PEt3)([graphic omitted]Ph)] and [(Et3P)2Pt(CPhCPhPPh)W(CO)5] confirm the nature of both types of complexes. The compounds [{PtCl2(PEt3)}2] and Mel react with [Pt(PPh3)2(CPhCPhPPh)] to give [(Ph3P)2Pt(CPhCPhPPh)PtCl2(PEt3)] and [Ptl(PPh3)(CPhCPhPPhMe)], respectively, the latter being characterised by a single-crystal X-ray diffraction study.

Ruthenium(II) complexes of a 2,2′-biphosphinine

Abstract The biphosphinine complexes [RuC12(dmso)2(bp)] (2) and cis-[RuCl2(bp)2] (3) (bp=4,4’,5,5’-tetramethyl-2,2’-biphosphinine) have been prepared from [RuC12(dmso)4] and the free ligand. The crystal and molecular structure of 2, which crystallised in the space group C2/c with a=17.329(1), b=16.008(1), c=18.733(2) A,β=104.75(1)°, V=5025.2(1.4) A3 and Z=8 and refined to R=0.042,Rw=0.089, is presented and NMR data pertaining to both complexes is discussed. Analyses of the complexes suggest that the biphosphinine serves as a good π-acceptor ligand towards the ruthenium(II) centres.

Generation and interconversions of the di- and tri-nuclear platinum complexes [Pt2H2(dppe)2], [Pt2H3(dppe)2]+, and [Pt3H3(dppe)3]+. Crystal and molecular structure of [Pt3H3(dppe)3]+[BEt4]–, (dppe = Ph2PCH2CH2PPh2)

Multinuclear n.m.r. and crystallographic studies on [Pt2H2(dppe)2], [Pt2H3(dppe)2]+, and [Pt3H3(dppe)3]+ are described, the structure of the latter being unambiguously established for the first time.

An η2 transition state for the insertion of [Pd(dppe)] fragments into the phosphorus–carbon bonds of phosphiranepentacarbonyltungsten complexes. Crystal and molecular structures of (2R,3S,4R)- and (2R,3S,4S)-[Pd(dppe)(CHPhCHPhPPh)-W(CO)5], dppe = 1,2-bis(diphenylphosphanyl)ethane

Evidence for a transition state involving η2 co-ordination of a P–C bond to [Pd(dppe)] is obtained from an analysis of the insertion of [Pd(dppe)] fragments into (E)- and (Z)-[W(CO)5(PPh–CHPh–CHPh)] complexes.