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The monomeric solvent-free compound CaR 2 1 [R = C(SiMe 3 ) 3 ] is obtained as colourless air-and moisturesensitive crystals from the reaction between KR and CaI 2 ; in the solid the C-Ca-C axis is bent with Ca-C 2.459(9) Å and C-Ca-C 149.7(6)°; reactions of 1 with ethers ROEt give RH, ethene and Ca(OEt) 2 .

Complexes cis- [PtR,(dmso),] and cis- [PtRCl(dmso),] (dmso = dimethyl sulphoxide) are readily obtained from K, [PtCI,] and SnMe,R (R = aryl or Me) in dmso at 70-90 "C. Hydrogen-1 n.m.r. spectra show that the dmso ligands are bound through sulphur in solution and that the dmso ligand trans to R in cis-[PtRCl(dmso),] undergoes dissociation and exchange a t ambient temperature. With anionic reagents X-(X = Br, I, or SCN) the complex cis- [PtPhCl(dmso),] forms bridged complexes [Pt,Ph,(p-X),(dmso),].In addition to the diaryl complex, SnMe,-(C,H,OMe-2) forms the cyclometallated complex [Pt(C6H,0dH,-2) (dmso),]. The dmso ligands of all the complexes are readily displaced by phosphorus donors, AsPh,, SbPh,, or 2,2'-bipyridyl ; 'H} n.m.r. parameters are reported for the phosphorus-containing complexes.L~KYLTHIMI-'l.HYLTIN compounds (Snhle,R) have been shown to react with a number of chloro-complexes of platinum( 11) and the reactions with [PtCl,(cod)] (cod = cyclo-octa-1 ,Tj-diene) provide a convenient route to the complexes [PtR,(cod)], [PtRCl(cod)], and complexes derived from them by displacement of cod by a variety of N, Y , and As donors.l This route can he of particular value when the corresponding aryl-lithium or Grignard reagent is not available [for example, R = Cr(q-C,H,)(CO),] or is not obtainable in a pure form [for example, R = 1,2-dihydrobenzocyclobutenyl] . , However, this and other methods of introducing alkyl and aryl ligands into platinum(I1) complexes have the disadvantage of requiring that the common starting material K,[PtCl,] must first be converted into a complex [PtCl,L2] (L = $cod, PR,, etc.) which is normally isolated before being treated with an organometallic reagent to give the organoplatinum( 11) complex.We have now found that platinum(I1) methyl and aryl complexes may be obtained by a very simple procedure from K2[PtC1,] and organotin compounds using dime thy1 sulphoxide (dmso) as solvent. This and the related method starting from [PtCl,(dmso),] are described here, and we also describe a number of comparisons between these routes and the previously described reaction between the organotin compounds and [PtCl,(cod)] ; a preliminary account of some of this work has a~p e a r e d .~ RESULTSA N D DISCUSSION In a typical procedure (method A), K,[PtCl,] (0.002 mol) was dissolved in dmso (8 cm3) at room temperature, an excess of SnMe,R (R = Me or aryl; 0.004-0.01 mol) added, and the mixture stirred for several hours at 70-90 "C. After removal of dmso under vacuum the complexes [PtR,(dmso),] were readily isolated. Use of equimolar proportions of K,[PtCl,] and SnMe,R gave the complexes [PtRCl(dmso),]. The reaction mixtures were initially red owing to the presence of [PtC1,I2-, and during the course of a few minutes became yellow because of formation of cis-[PtCl,(dmso),]. The course of the reaction and yield were similar irrespective of whether t No reprints available.the tin conq)ound was introduced before or after this colour change. W i t m the product was colourless, the mixture after complet...

The alkyls EuR2 (R = C(SiMe3)3) and YbR2 (R = [C(SiMe3)2(SiMe2X)], X = Me, CHCH2, or CH2CH2OEt) have been obtained from reactions between KR and MI2, and the ytterbium analogues of Grignard reagents, Yb[C(SiMe3)2(SiMe2X)]I·OEt2 (X = Me, CH=CH2, Ph or OMe) from reactions between RI and Yb metal. The compounds YbR2 and EuR2 crystallize as solvent-free monomers with C−M−C = 136−137°. The alkylytterbium iodides crystallize from diethyl ether as solvated iodide-bridged dimers in which the coordination at Yb is four when X = Me but is increased to five by chelation from the group X when X = OMe. When X = CHCH2, the Yb···X interaction is weak. The reaction 2RYbI = R2Yb + YbI2 is not observed when X = Me, but takes place readily when X = Ph, CHCH2, or OMe and provides a route to the dialkyls MR2 when the alkylpotassium KR cannot be obtained, e.g., when X = OMe. The dialkyl Yb[C(SiMe3)2(SiMe2X)]2 with X = Me reacts with ethers R‘OEt (R‘ = Et, Bu, But) to give ethene and alkoxides RYbOR‘. The corresponding reaction does not take place when X = OMe and is very slow when X = CHCH2.

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Crystals of (RMe2Si)&K (R = Me, 1; R = Ph, 2), obtained from MeK and (RMezSi)&H, contain linear chains of alternate potassium cations and planar [(RMe&)&]-anions, with weak interactions between chains; in 1 the central carbon atoms of the anions are midway between the potassium cations, but in 2 cationanion pairs are linked by q6 coordination of phenyl groups.Methylpotassium has been carefully studied by X-ray powder methods and neutron diffraction,lJ but as far as we are aware there has hitherto been nosinglecrystal X-ray investigation of 4 donor-free organopotassium compound. We report the preparation and structures of compounds 1 and 2, which contain bulky organosilyl groups. (Me,Si),CK (PhMe,Si),CK 1 2 compound 1 can be obtained by either of the routeslf The colorless, exceedingly air-and moisture-sensitive +MeLi +KOBut -MeH -LiOBut (Me,Si),CH -(Me,Si),CLi -1 (a) +MeLi +(Messi)sCH -LiOBut -MeH

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