Functionalization of Pentaphosphorus Cations by Complexation.

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P5 R2 ]+ cations with cyclopentadienyl metal complexes. The reaction of [CpAr Fe(µ-Br)]2 (CpAr =C5 (C6 H4 -4-Et)5 ) with [P5 R2 ][GaCl4 ] (R=iPr and 2,4,6-Me3 C6 H2 (Mes)) afforded bicyclo[1.1.0]pentaphosphanes (1-R, R=iPr and Mes), showing an unsymmetric "butterfly" structure. The same products 1-R were formed from K[CpAr ] and [P5 R2 ][GaCl4 ]. The cationic complexes [CpAr Co(η4 -P5 R2 )][GaCl4 ] (2-R[GaCl4 ], R=iPr and Cy) and [(CpAr Ni)2 (η3:3 -P5 R2 )][GaCl4 ] (3-R[GaCl4 ]) were obtained from [P5 R2 ][GaCl4 ] and [CpAr M(µ-Br)]2 (M=Co and Ni) as well as by using low-valent "CpAr MI " sources. Anion metathesis of 2-R[GaCl4 ] and 3-R[GaCl4 ] was achieved with Na[BArF24 ]. The P5 framework of the resulting salts 2-R[BArF24 ] can be further functionalized with nucleophiles. Thus reactions with [Et4 N]X (X=CN and Cl) give unprecedented cyano- and chloro-functionalized complexes, while organo-functionalization was achieved with CyMgCl.

Synthesis and Characterization of Bidentate Isonitrile Iron Complexes.

The divalent iron complexes trans-[FeBr2(BINC)2], [Cp*FeCl(BINC)] (Cp* = Me5C5), and [FeBr2(CNAr3NC)2] with the chelating bis(isonitrile) ligands BINC (bis(2-isocyanophenyl)phenylphosphonate) and CNAr3NC (2,2″-diisocyano-3,5,3″,5"tetramethyl-1,1':3',1″-terphenyl) have been prepared and characterized. Their subsequent reduction yields the di- and trinuclear compounds [Fe3(BINC)6], [Cp*Fe(BINC)]2, [Fe(CNAr3NC)2]2, and [K(Et2O)]2[Fe(CNAr3NC)2]2. The molecular structures of all new species were determined by X-ray crystallography and compared to those of related iron carbonyl complexes, demonstrating that the bidentate isonitrile ligands are capable surrogates for two CO ligands with only minimal distortion of the tetrahedral or octahedral geometry of the parent complexes. The complexes were further characterized by NMR and IR spectroscopy, and the electrochemical properties of selected compounds were analyzed by UV-vis-NIR spectroelectrochemistry.

Iron-Gallium and Cobalt-Gallium Tetraphosphido Complexes.

The synthesis and characterization of two heterobimetallic complexes [K([18]crown-6){(η4-C14H10)Fe(µ-η4:η2-P4)Ga(nacnac)}] (1) (C14H10 = anthracene) and [K(dme)2{(η4-C14H10)Co(µ-η4:η2-P4)Ga(nacnac)}] (2) with strongly reduced P4 units is reported. Compounds 1 and 2 are prepared by reaction of the gallium(III) complex [(nacnac)Ga(η2-P4)] (nacnac = CH[CMeN(2,6-iPr2C6H3)]2) with bis(anthracene)ferrate(1-) and -cobaltate(1-) salts. The molecular structures of 1 and 2 were determined by X-ray crystallography and feature a P4 chain which binds to the transition metal atom via all four P atoms and to the gallium atom via the terminal P atoms. Multinuclear NMR studies on 2 suggest that the molecular structure is preserved in solution.

An unusual Ni2Si2P8 cluster formed by complexation and thermolysis.

[LSi(η2-P4)] (L = CH[C(Me)N(Dipp)][C(CH2)N(Dipp)], Dipp = 2,6-diisopropylphenyl) forms well-defined 1 : 1 and 2 : 1 complexes with N-heterocyclic carbene nickel fragments. The cluster compound [(IDipp)Ni2P8(SiL)2] (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) is selectively formed by thermolysis of the complex [(IDipp)Ni(µ-η2:2-P4)SiL].

Construction of alkyl-substituted pentaphosphido ligands in the coordination sphere of cobalt.

Rare mono- and diorganopentaphosphido cobalt complexes are accessible by P-P condensation using the unprecedented, reactive cobalt-gallium tetraphosphido complex [K(dme)2{(MesBIAN)Co(µ-η4:η2-P4)Ga(nacnac)}] (2). Compound 2 was prepared in good yield by reaction of [K(Et2O){(MesBIAN)Co(η4-1,5-cod)}] [1, BIAN = bis(mesitylimino)acenaphthene diimine, cod = 1,5-cyclooctadiene] with [Ga(nacnac)(η2-P4)] (nacnac = CH[CMeN(2,6-iPr2C6H3)]2). Reactions with R2PCl (R = iPr, tBu, and Cy) selectively afford [(MesBIAN)Co(cyclo-P5R2)] (3a-c), which feature η4-coordinated 1,1-diorganopentaphosphido ligands. The mechanism of formation of these species has been studied by 31P{1H} NMR spectroscopy and DFT calculations. In the case of 3a (R = iPr), it was possible to identify the intermediate [(MesBIAN)Co(µ-η4:η2-P5iPr2)Ga(nacnac)] (4) by single-crystal X-ray diffraction. A related, monosubstituted organopentaphosphido cobalt complex [(MesBIAN)Co(µ-η4:η1-P5 tBu)GaCl(nacnac)] (5) was isolated by reacting dichloroalkylphosphane tBuPCl2 with 2. Heterobimetallic complexes such as 2 thus may enable the targeted construction of a range of new metal-coordinated polyphosphorus frameworks by P-P condensation.