5511
(including methylene chloride and benzene). The three polymeric platinum halide anions of 2-5 are hitherto unknown for platinum and its congeners (pal(10) Postdoctoral Fellow of the National Institute of General ladium and nickel); furthermore, the anion of 3 and 4 Medical Sciences, No. 1 F02 GM37,585. (1 1) Predoctoral Fellow of the National Institute of General Medical represents a rare example of a compound possessing Sciences, No. 5 F 0 1 GM46,047. metal atoms with mixed valency (uiz., Pt(I1) and Pt(1V) Jerome A. Berson,* Dale M. McDaniel,“ Leonard R. Corwinll within the same discrete unit), while the novel anion Department of Chemistry, Yale University of 5 provides the first case determined by X-ray diffracNew Haven, Connecticut 06520 tion of a substituted benzene ring u bonded to more Received April 25, 1972 than one transition metal atom. This communication thereby illustrates the possible diversity and scope of the general reaction of anhydrous transition metal chloSynthesis and Structural Characterization of Three rides with triphenylmethyl chloride under varying New Platinum(1V) Halide Anions as conditions to give new anions of unusual stoichiometry. Triphenylcarbeniuml Salts. Isolation from Reaction of Our study of the reactions of [PtC1414with (C6H&CC1 Platinum Tetrachloride with Trityl Chloride in Benzene was predicated on the basis that the well-known [PtC16lzof a Novel [Pt4(C6H4)zC114]2 - Anion Containing anion may not be produced due to the inability of a +Phenylene Ligands2 [PtC16]- species to ionize (CRHS)SCC~ further. Since Pt(1V) invariably possesses an octahedral-like coSir: ordination, one may expect dimerization of [PtCLIWe wish to report the preparation and characterizato give the previously unknown [Pt2Cllo]2-anion. tion of [ ( c ~ H ~ ) ~ c ] + [ P t CH,CIz]Cl,. (11, [(C,H&C]+2The coordinating ability of the solvent used for the (2), [(C6Hj)3C]+2[Pt,CIi212- (31, [(CsH5)3CIfz[%C~IO]~reaction of [PtCl4I4with (C6H5),CC1 appears to deter[Pt3CL2]2-. 2CzH2C14 (4), and ’ [ ( C B H S ) ~ C ] ~ Z [ P ~ ~ ( Cmine ~ H ~the ) Z - nature and extent of the products isolated. Cl14]2-. 2CHzCI, (5) by the previously unreported reacA finely powdered slurry of [PtCl,], in CHzClz reacts tion of [PtC14]43with (C6H,),CC1 in various solvents completely under nitrogen with (C6Hj),C1 in slight excess of 1 : l mole ratio to give an orange solution (1) The term “carbenium” (rather than the inveterate “carbonium” ion, which will be used in this paper, has been suggested by G. A. Olah which yields yellow-orange crystals of 1 upon evapora[J. Amer. Chem. SOC.,94, 808 (1972)] for “classical” trivalent carbotion of solvent. A few deep red crystals of 2 and cations to differentiate them from “nonclassical” penta- or tetracoordiorange-red crystals of 3 invariably crystallize out with nated carbocations. (2) (a) This research resulted from an initial investigation included in 1. Slow evaporation of solvent from the red solution, the dissertation submitted by P. M. Cook to the Graduate School at which results from the above orange solution standing Colorado School of Mines in partial fulfillment of the requirements for for 48 hr or more, gives some crystals of 1 with increased the M.S. degree, 1968; (b) presented in part at the1 61st National Meeting of the American Chemical Society, Los Angeles, Calif., March amounts of 2 and 3. Although the yields of 2 and 3 1971, Abstracts, I N O R G 95. vary from 5 to 20 and 10 to 40%, respectively, excess (3) Although platinum tetrachloride has been reported from a powder of this suggestion from the status of a working hypothesis to that of a mechanistic proposal.
X-ray diffraction study to possess the solid-state SnI4 structure comprised of tetrahedral molecule^,^ we feel (in the absence to date of suitable single crystals for an X-ray crystallographic investigation) that our spectral data (presented below) provide conclusive evidence that this widely accepted possibility of such a simple monomeric species in the solid state can be definitely excluded. I n addition (inasmuch as we cannot find such a suggestion in the literature), we propose that platinum tetrachloride has a cubane-like tetrameric structure both in the solid and vapor states and offer the following arguments to support our proposal. (a) No Pt(1V) complexes are known to possess tetrahedral coordination as proposed for platinum tetrachloride; furthermore, a crystalline arrangement of discrete PtCh molecules would presumably give rise to a relatively volatile, paramagnetic complex which is not the case. Octahedral coordination can be achieved in [PtClalZ by chlorine bridge bonding either as in the known Pt(IV) cubane structures [Pt(CH3)3C1]4,6 [Pt(C~H5)3Cl]a,6and [PtC1(C3H6)C1],7 or as in [PtIa],* whlch contains an infinite zigzag chain of edge-linked PtCh octahedra. The structure of PtX3 (X = C1, Br)9 contains Pt(I1) in [Pt6XIZ] units and Pt(1V) in [PtXal, chains as in [PtIa],. Our spectral data indicate that the cubane structure is more likely. (b) The far-infrared spectrum10 of [PtCla], shows absorption bands characteristic of both terminal and bridging chlorine atoms;11 this spectrum is comparable to the spectra of [Pt(CHa)aCl]a and [PtCl(CaH~)Cl]a.7
V(Pt-Cl)t [Pt(CHa)aClla
G(Pt-Cl)t P(Pt-Cl)b G(R-Cl)b 220 140
[PtCKC3HdClla 330 d 180, 200 230 125 [PtChI, 337, 366, 376 182 215, 292 128 t = terminal chlorine, b = bridging chlorine, d = doublet The large difference in the assigned platinum-bridging chlorine stretching frequencies can be readily rationalized by the strong trans influence of the terminal alkyl ligands in the two known cubane-like Pt(IV) compounds. The ability of a rrans-methyl ligand to lower the Pt(1V)-C1 2 for stretching frequency is illustrated in PtCL(CH3)z [ P(CH+(CBH~)) which r(Pt-Cl) is 332 cm-1 when the methyl groups are cis to the chlorine atoms and 242, 265 cm-1 when the methyl groups are trans to the chlorine atoms.’* The same trans influence can be exerted on platinumbridging chlorine stretching frequencies as in PtzCla { P(CsHs)a] 2 which has v(Pt-Cl) equal to 320 cm-l when the chlorine atoms are trans to each
other but 260 cm-1 when the chlorine atom is trans to triphenylphosphine.13 (c) The mass spectrum of [PtClaIz consists of a parent m/e peak centered at 1348 due to [Pt4Cll6]+ and contains a rich fragmentation pattern completely consistent with a cubane structure. The only peaks found above the parent-ion peak are attributed to [PtsClls]+, [PtsClls]+, and [Pt&111]+ with only [PtsCh~]+having a high relative abundance; these three species are ascribed to a thermal rearrangement which is common for metal cluster systems. (d) Our X-ray powder film and powder diffractometry measurements of [PtCl& samples prepared by the method of Keller14 and also purchased from Alfa Inorganics, Inc., do not correspond to the powder patterns reported by Falqui.‘ Our patterns, which are all the same, cannot be indexed in the cubic crystal system. If [PtCl& crystallizes into more than one crystal system, the cubic crystal form reported by Falqui4 should have the cubane structure since her determined lattice length of a = 10.45 A is nearly identical with that of a = 10.55 A given‘ for [Pt(CH3)3Cl]d which also belongs to the cubic crystal system. Although the spatial requirement of a terminal methyl group about a platinum(1V) atom is almost exactly that of a terminal chlorine atom, a structure factor analysis of Falqui’s powder diffraction data shows that crystalline [PtCla], is not isomorphous with [Pt(CH&C1]4. A [PtL], type of structure is impossible in her cubic unit cell. (4) M. T. Falqui, Ann. Chim. (Rome),48, 1160 (1958). ( 5 ) R. E. Rundle and J. H . Sturdivant, J . Amer. Chem. Soc., 69, 1561 (1947). (6) R. N. Hargreaves and M. R. Truter, J. Chem. SOC.A , 90 (1971). (7) S.E. Binns, R. H. Cragg, R. D. Gillard, B. T. Heaton, and M. F. Pilbrow, ibid., 1227 (1969). (8) V. K. Brodersen, G. Thiele, and B. Holle, 2.Anorg. Allg. Chem., 369, 154 (1969). (9) U. Wiese, H. Schafer, H . G . Schnering, C. Brendel, and K. Rinke, Angew. Chem., Int. Ed. Engl., 9 (2), 158 (1970). (10) The far-infrared spectrum of a Nujol mull of [PtC14], was measured on a Digilab FTS-14 spectrometer through the courtesy of Dr. Peter Griffiths of Sadtler Research Labs, Philadelphia, Pa. (1 1) D. M. Adams and P. J. Chandler, Chem. Commun., 3, 69 (1966). (12) J. D. Ruddick and B. L. Shaw, J. Chem. SOC.A , 2801 (1969). (13) R. J. Goodfellow, P. L. Goggin, and L. M. Venanzi, ibid., 1897 ( 1967). (14) R . N. Keller in “Inorganic Syntheses,” Vol. 11, W. C. Fernelius, Ed., McGraw-Hill, New York, N. Y., 1946, p 253.
Communications to the Edi?or
5512 Cl51 Cl41 C(61
C115'
CI(6'1
Figure 1. Architecture of the [Ptr(C6Ha)zC11c]~-anion which possesses crystallographic site symmetry C,-1; its geometry closely conforms t o D k 2 / m 2 / m 2 / m symmetry. Important average disstances within each of the twoo identical [Ptn(C6H4)Cl6]moietip are Pt-Cl(terminal), 2.274 (4) A; Pt-C1 (bridging), 2.352 (4) A ; Pt-C, 1.97 (2) A ; Pt (1). . .Pt(2), 3.258 ( 2 ) A. ThePt-Cl(bridging) ban$ connecting the two [Pt2(C6&)C16] moieties average 2.533
( 6 ) A.
triphenylmethyl chloride in the reaction mixture does not appear to greatly affect the relative yield of each product. Infrared spectra of 1-5 show the typical triphenylcarbenium ion spectrum l5 as well as absorption bands in the far-ir attributable to vibrational modes involving terminal and bridging chlorine ligands. Uv and lH nmr spectra also are typical of the triphenylcarbenium ion. l 6 X-Ray structural investigations of the five isolated combecause a characterization pounds were carried out of each anion by alternate methods was doubtful. The anion of 1 is indeed monomeric with one chlorine of the CH2C12molecule of crystallization occupying the sixth octahedral coordination site. Unfortu17c18
(15) D. W. A . Sharp and N. Sheppard, J . Chem. Soc., 674 (1957); R. E. Weston, Jr., A. Tsukamoto, and N. N. Lichten, Spectrochim.
nately, the crystal structure of 1 is disordered, and hence the positions of the uncoordinated chlorine of the CH2C12 molecule and the methylene carbon atom have not yet been unambiguously determined. The dimeric [PtzCllo]2- anion of 2 expectedly consists of two edge-shared octahedra of chlorine atoms with the two Pt(1V) atoms thereby joined by two bridging chlorine atoms. The [PtzCllo]2-anion has an idealized D2h geometry with th? Pt-Cl(bridging) bonds of average length 2.374 (1) A being significantly longer thano the Pt-Cl(termina1) ones of average length 2.298 (1) A. Other analogous [MzC110]71 systems characterized by X-ray diffraction include the [TizCllo]z-anion,1g NbzCllo,2o MozCllo, and RezCllo.2 2 The formation of 1 from the reaction of [PtCI4lr with (C6Hb)&C1 in CHzClz is apparently followed by slow dimerization to 2 . The slow rate of reaction could be due to the ability of CH2Cl2to strongly coordinate to the [PtClJ- anion, thus preserving octahedral coordination about the d6 Pt(1V) as well as fulfilling the effective atomic number rule common to Pt(1V) compounds. The [Pt3C112]2-anion of 3 has an idealized DZhgeometry which consists of three linearly arranged Pt atoms connected by chlorine-bridged bonds. Two terminal [PtC16]octahedra are each edge shared by the central Pt atom through two di-p-chloro linkages giving a square-planar geometry to the central Pt atom with a formal oxidation state of I1 instead of IV. The Pt(1V)-Cl(bridging) distances of average value 2.384 (3) A are significantly longer than the P;(II)-Cl (bridging) distances of average value 2.300 (3) A. This anion could result from the initial formation of a similar linear, chlorine-bridged [Pt3CIl4]2- anion which subsequently loses the two axial chlorine atoms on the central Pt atom as CI2 thereby reducing the centra1 Pt(1V) to the platinous (11) state. Such a reduction is reported t o take place in the case of the long-known, unstable chlorine-bridged bis(tri-n-propylphosphine) complex, Pt2Cls(PPra)2, to give the stable Pt2C14(PPr3)2dimer containing square-planar Pt(I1) atoms linked by bridging chlorine atoms.*S Numerous examplesz4 of compounds with mixed metal valency exist, but Pt(I1)Pt(IV) compounds usually occur either as a mixture of separate Pt(I1) and Pt(1V) units as found in PtC13Y or as alternating Pt(I1) and Pt(1V) species oriented in 25 chains as occurs in [Pt(en)2Br,][Pt(en)2Br4]. [PtCI4l4reacts completely with (C6H5):CC1 in 1,1,2,2tetrachloroethane to give 4 as the only detectable product. The ir spectrum of the red crystals obtained by evaporation is the same as that of the reaction solution. An X-ray diffraction study showed that both the cation and anion of 4 are identical with those of 3 but that 4 crystallizes into a different space group due to an accompanying solvent molecule of crystallization. The nonisolation of the monomeric anion is under-
Acta, 22,433 (1966). (16) M. Baez, V. Gutmann, and 0. Kunze, Monatsh. Chem., 93, 1142 (1962); G. B. Moodie, T. M, Connor, and R . Stewart, Can. J . Chem., 37, 1402 (1959). (17) (a) [(C6Hs)3C]+[PtClj.CH2ClnI- (1): monoclinic, P21/c; n = 11.343 (3) b = 14.498 (5) A, c = 15.442 (3) b;, 0 = 111.96 (1)'; pobsd = 1.96 g cm-3 cs. pealed = 1.98 g cm-3 for Z = 4. Least-squares refinement gave R I ( F ) = 8.4% and Rn(F) = 9.2% for 743 independent diffractotfletry data ( I > 241)). (b) [(CsHs)aC]+z[PtzCl~o]~(2): tric = 18.197 (6) 01 = clinic, P1; a = 10.152 (2) A, b = 13.030 (3) 100.39 (1)'; po&d = 2.06 g Cm-'L'S. 122.41 (I)', 0 = 87.27 (2)", y pealed = 2.05 g cm-3 for Z = 2. Least-squares refinement gave R I ( F ) = 3.3 % and Rz(F) = 4.7% for 2058 independent diffrytometry data ( I > 241)). (c) [ ( C B H S ) ~ C ] - . [ P ~ ~ C(3): ~ ~ ~triclinic, ]*P l ; a = 10.725 b = 12.645 (2) A, c = 8.712 (2) A, 01 = 95.34 (I)', @ = 98.98 (2) (I)', "( = 109.40 (1)'; pabed = 2.28 g Cm-3 6s. &Bled = 2.29 g cm-3 for Z = I . Least-squares refinement gave R I ( F ) = 4.2% and R d F ) = 4.9% for 1550 independent diffractometry data ( I > 2 4 ) ) . (d) [(CsHj)aCl+z[Pt~Cl~~]*-. 2C2HzCId (4): monoclinic, P21:c; a = 9.403 (2) b = 29.645 (4) A, c = 10.559 ( 2 ) A,13 = 105.99 (1)'; &bad = 2.14 g cm-3 cs. pcalcd = 2.15 g 6111-3 for Z = 2. Least-squares refinement gave R I ( F ) = 6.3 % and &(F) = 8.5 % for 1474 independent diffractometry data ( I > 2u(I)). (e) [ ( C ~ H S ) ~ C ] + Z [ P ~ ~ ( C ~ H ~ ) ~ C ~ ~ ~ I ~ - . ~ C H ~ C ~ Z (19) T. J. Kistenmacher and G. D. Stucky, Inorg. Chem., 10, 122 (5): monoclinic, P21/c; a = 12.173 (2) A, b = 21.376 (7) A, c = 12.400 (1971). (2) A,8 = 107.77 (1)'; pobsd = 2.28 g Cm-3 OS. &*led = 2.25 g for (20) A. Zalkin and D. E. Sands, Acta Crystallog?'.,11, 615 (1958). Z = 2. Least-squares refinement yielded R I ( F ) = 4 . 5 Z and R d F ) = (21) D. E. Sands and A. Zalkin, ibid., 12,723 (1959). 5.2% for 1658 independent diffractometry data ( I > 2u(1)). (22) I
