Stable, crystalline complexes containing the five-coordinate [CoL2X]+ species, where X = Cl, Br, or I and L is one of the bidentate ligands diphenyl(o-methylthiophenyl)phosphine (I, SP), diphenyl(o-methylselenophenyl)phosphine (II, SeP), or diphenyl(o-diphenylarsinophenyl)phosphine (III, AP), have been isolated and characterized by magnetism and conductivity measurements, electronic and infrared spectra, and elemental analyses. All of the complexes are deep red and possess one unpaired electron (pett = 2.1-2.5 BM). The electronic spectra exhibit three distinct bands below 22,000 cm-1 which may be assigned to ligand-field transitions.Research interest and activity in five-coordinate com-.plexes has accelerated dramatically during the past 4 years. Whereas five-coordination is now fairly common for nickel(II), when polydentate ligands containingbonding donor atoms, such as arsenic, phosphorus, sulfur, or selenium, are used,3-6 well-characterized examples of five-coordinate complexes of a d7 ion have not been observed so frequently. One authentic, low-spin example is [Co(HPPh2)3Br2].7 Also, Venanzi and co-workers8 have prepared five-coordinate co-(1964).
A new tetradentate ligand, tris( o-methylthiophenyl (phosphine, P(o-C6H4SCHs)3 (TSP, I), forms a series of crystalline, intensely-colored, trigonal-bipyramidal nickel(II) complexes containing the species [Ni(TSP)X] + (X = I, Br, Cl, or NTCS) or [Ni(TSP)L]2 + (L = thiourea, triphenylphosphine, or methyldiphenylphosphine). The two lowest energy electronic absorption bands in the visible and ultraviolet spectra have been assigned to the two 4A4 -2E(D) transitions. Under similar conditions, the analogous arsine compound, tris( o-methylthiophenyl (arsine, As^-CePUSCHsh (TSA), did not react with nickel(II) salts.
Tris-(o-diphenylphosphinopheny1)phosphine and the arsenic analogue form complexes with nickel(r1) of the type [NiX(chelate)]+ which are five-coordinate with trigonal-bipyramidal structure. Nitrate and perchlorate ions co-ordinate strongly to nickel in these complexes.RECENT investigations have shown that nickel(@ tends to form five-co-ordinate complexes more often than suspected hitherto. The majority of such compounds have been obtained by using phosphorus and arsenic donors. Thus o-phenylenebis( dimethylarsine) (I) (das) forms complexes of the type [MX(das),]+ in solution, and solid salts such as [MX(das),][PF,] have been iso1ated.l The terdentate ligand, bis-(3-dimethylarsinopropyl)methylarsine (11) (tas), gives complexes of the type [NiX2(tas)], the solid bromo-compounds having a distorted square-p yramidal structure. o-CBH,(AsMe2), Me*As(CH,*CH,-CH,*AsMe,),(11) (WWe report here the preparation and properties of a number of complexes with two quadridentate ligands, one of phosphorus (QP; IIIa) and the other of arsenic (QAS; IIIb).The complexes prepared and some of their physical properties are listed in Table 1. These are 1 : 1 electrolytes in nitrobenzene, and the conductance does not increase when iodomethane is added, indicating that all four arsine or phosphine groups are co-ordinated, and therefore that the complexes are five-co-ordinate. The complexes with two co-ordinating anions remain five-co-ordinate even in the solid state as shown by the virtual identity of the spectra of the series of complexes [NiBr(QAS)]Y (Y = Br, ClO,, BPh,), both in solution and in the solid state. They are of low spin, and their properties are very similar to the corresponding palladium(11) and platinum(I1) compound^.^ L = P; (IIIa) (QP) L = As; (IIIb) (QAS)
Six-and five-co-ordinate complexes of ruthenium(ir) with the unsymmetrical diphosphine ligand Ph2P(CH2)3PMe2 have been prepared. Phosphorus-31 n.m.r. spectroscopy indicates that octahedral complexes [RuCI,(P-P),],[RuH(CI)(P-P),], and [RuH(CO)(P-P),JCIO, (P-P = diphosphine ligand) have the all-trans arrangement with Me,P trans to Me,P and Ph2P trans t o Ph2P. The five-co-ordinate complexes [RuX(P-P),]BPh,, where X = CI or H, are not fluxional at room temperature and have a trigonal-bipyramidal structure with axial PMe2 groups and equatorial PPh, groups. Similar structures are proposed for analogous complexes of Ph,P(CH,),PMePh and of Ph2P(CH2),PPh2.
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