From chemistry-request@server.ccl.net Thu Dec 24 17:49:22 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id RAA10957 for ; Thu, 24 Dec 1998 17:49:22 -0500 Received: from mcmail.cis.McMaster.CA (mattacf@mcmail.CIS.McMaster.CA [130.113.20.6]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id RAA09249 Thu, 24 Dec 1998 17:44:48 -0500 (EST) Received: from localhost (mattacf@localhost) by mcmail.cis.McMaster.CA (8.8.8/8.8.8) with SMTP id RAA06031; Thu, 24 Dec 1998 17:44:36 -0500 (EST) Date: Thu, 24 Dec 1998 17:44:36 -0500 (EST) From: "C.F. Matta" To: EILERT OFSTEAD cc: chemistry@www.ccl.net Subject: Re: CCL:Quantifying Agostic H--M Interactions? In-Reply-To: <0056650001255277000002L572*@MHS> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hi Eilert, Here is an important paper: P. L. A. Popelier and G. Logothetis "Characterization of an Agostic Bond on the Basis of the Electron Density", J. Organometallic Chem. 555, 101-111 (1998). Cheers. Cherif Matta Chemistry Dept. McMaster University Hamilton, Ontario Canada L8S 4M1 On Tue, 22 Dec 1998, EILERT OFSTEAD wrote: > > > I would be interested in the comments of CCL'ers regarding preferred strategies > for evaluating organometallic compounds which may have agostic interactions > present. In particular, I want to compare the relative stabilities of isomers > where only one has a probable agostic interaction. Both accuracy and > efficiency are of value here, so some compromise might be expected. My > interest includes both alkali metal and transition metal compounds. > > One would expect correlation effects to be important in these weak non-bonded > interactions, so post-HF methods are probably indicated (pain! avoid if > possible!), but since some of the DFT methods supposedly include correlation, I > have explored them tentatively as well. Scatter!!! With Li complexes, the > highest Li-H interaction **appears** to be indicated when using MP2/HF, but > when I try the more efficient LMP2 method available in Jaguar, eg, a > substantially higher stabilization seems indicated (+1 kcal. Real??). And DFT > methods consistently give somewhat lower apparent stabilization energies, > intermediate between MP2 and straight HF. What is a poor chemist to believe. > > Maybe that's life in the modeling world (at least in my short existence > there). So, recommendations, references, etc would be much appreciated. > > thanks, and best wishes for the Holidays, > > Eilert > eofstead@goodyear.com > ------------------ > > > --- > Administrivia: This message is automatically appended by the mail exploder: > CHEMISTRY@www.ccl.net: Everybody | CHEMISTRY-REQUEST@www.ccl.net: Coordinator > MAILSERV@www.ccl.net: HELP CHEMISTRY or HELP SEARCH | Gopher: www.ccl.net 73 > Anon. ftp: www.ccl.net | CHEMISTRY-SEARCH@www.ccl.net -- archive search > Web: http://www.ccl.net/chemistry.html > --- > >