PURCHASE AGREEMENT

Exhibit 10.36

Conformed Copy

$250,000,000

BLACKROCK, INC.

2.625% Convertible Debentures Due 2035

PURCHASE AGREEMENT

February 16, 2005

Exhibit 10.36

SCHEDULE A

The following table sets forth the hypothetical stock price and the number of Additional Shares to be issuable per $1,000 principal amount of Debentures:

Exhibit 10.36

SCHEDULE B

BLACKROCK, INC.

2.625% Convertible Debentures Due 2035

No.                     

February 16, 2005

Morgan Stanley & Co. Incorporated

Citigroup Global Markets Inc.

Merrill Lynch, Pierce, Fenner & Smith Incorporated

UBS Securities LLC

Dear Sirs and Mesdames:

BlackRock, Inc., a Delaware corporation (the “ Company ”), proposes to issue and sell to the several purchasers named in Schedule I hereto (the “ Initial Purchasers ”)

$250,000,000 aggregate principal amount of its 2.625% Convertible Debentures Due 2035 (the “ Securities ”) to be issued pursuant to the provisions of an Indenture to be dated as of February 23, 2005 (the “ Indenture ”) between the Company and JPMorgan Chase Bank, N.A., as Trustee (the “ Trustee ”). The Securities will be convertible into shares of the Company’s Class A common stock, $0.01 par value (the “ Underlying Securities ”).

The Securities and the Underlying Securities will be offered without being registered under the Securities Act of 1933, as amended (the “ Securities Act ”), to qualified institutional buyers in compliance with the exemption from registration provided by Rule 144A under the Securities Act.

The Initial Purchasers and their direct and indirect transferees will be entitled to the benefits of a Registration Rights Agreement dated the Closing Date (as defined herein) between the Company and the Initial Purchasers (the “ Registration Rights Agreement ”).

In connection with the sale of the Securities, the Company has prepared a preliminary offering memorandum (the “ Preliminary Memorandum ”) and will prepare a final offering memorandum (the “ Final Memorandum ” and, with the Preliminary Memorandum, each a “ Memorandum ”) including or incorporating by reference a description of the terms of the Securities and the Underlying Securities, the terms of the offering and a description of the Company. As used herein, the term “Memorandum” shall include in each case the documents incorporated by reference therein. The terms “ supplement ”, “ amendment ” and “ amend ” as used herein with respect to a Memorandum shall include all documents deemed to be incorporated by reference in the Preliminary Memorandum or Final Memorandum that are filed subsequent to the date of such Memorandum with the Securities and Exchange Commission (the

“ Commission ”) pursuant to the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”).

1. Representations and Warranties . The Company represents and warrants to, and agrees with, you that:

(a) (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in either Memorandum complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder and (ii) the Preliminary Memorandum does not contain and the Final Memorandum, in the form used by the Initial Purchasers to confirm sales and on the Closing Date (as defined in Section 4), will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to statements or omissions in either Memorandum based upon information relating to any Initial Purchaser furnished to the Company in writing by such Initial Purchaser through you expressly for use therein.

(b) The Company has been duly incorporated, is validly existing as a corporation in good standing under the laws of the Delaware, has the corporate power and authority to own or lease its property and to conduct its business as described in each Memorandum and is duly qualified to transact business and is in good standing in each jurisdiction in which the conduct of its business or its ownership or leasing of property requires such qualification, except to the extent that the failure to be so qualified or be in good standing would not have a material adverse effect on the Company and its subsidiaries, taken as a whole.

(c) Each subsidiary of the Company listed on Schedule II (the “subsidiaries”) hereto has been duly organized, is validly existing as a corporation or limited liability company, as the case may be, in good standing under the laws of the jurisdiction of its formation, has the corporate or limited liability company power and authority, as the case may be, to own or lease its property and to conduct its business as described in each Memorandum and is duly qualified to transact business and is in good standing in each jurisdiction in which the conduct of its business or its ownership or leasing of property requires such qualification, except to the extent that the failure to be so qualified or be in good standing would not have a material adverse effect on the Company and its subsidiaries, taken as a whole; all of the issued shares of capital stock or membership interests, as the case may be, of each subsidiary of the Company have been duly and validly authorized and issued and are owned directly or indirectly by the Company, free and clear of all liens,

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encumbrances, equities or claims and the issued shares of capital stock are fully paid and non-assessable.

(d) This Agreement has been duly authorized, executed and delivered by the Company.

(e) The authorized capital stock of the Company conforms as to legal matters to the description thereof contained in the Final Memorandum.

(f) The shares of common stock outstanding prior to the issuance of the Securities have been duly authorized and validly issued and are fully paid and non-assessable.

(g) The Securities have been duly authorized by the Company and, when executed and authenticated in accordance with the provisions of the Indenture and delivered to and paid for by the Initial Purchasers in accordance with the terms of this Agreement, will be valid and binding obligations of the Company, enforceable in accordance with their terms, subject to applicable bankruptcy, insolvency or similar laws affecting creditors’ rights generally and general principles of equity, and will be entitled to the benefits of the Indenture pursuant to which such Securities are to be issued and the Registration Rights Agreement.

(h) The Underlying Securities issuable upon conversion of the Securities have been duly authorized and reserved and, when issued upon conversion of the Securities in accordance with the terms of the Securities, will be validly issued, fully paid and non–assessable, and the issuance of the Underlying Securities will not be subject to any preemptive or similar rights.

(i) Each of the Indenture and the Registration Rights Agreement has been duly authorized, executed and delivered by, and is a valid and binding agreement of, the Company, enforceable in accordance with its terms, subject to applicable bankruptcy, insolvency or similar laws affecting creditors’ rights generally and general principles of equity and except as rights to indemnification and contribution under the Registration Rights Agreement may be limited under applicable law.

(j) The execution and delivery by the Company of, and the performance by the Company of its obligations under, this Agreement, the Indenture, the Registration Rights Agreement and the Securities will not contravene any provision of applicable law, statute, rule, regulation, or the certificate of incorporation or by-laws of the Company or any agreement or other instrument binding upon the Company or any of its subsidiaries that is material to the Company and its subsidiaries, taken as a whole, any

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judgment, order or decree of any governmental body, agency, court or self–regulatory organization having jurisdiction over the Company or any subsidiary, and no filing with or consent, approval, authorization, license or order of, or qualification or registration with, any governmental body, agency or self-regulatory organization is required for the performance by the Company of its obligations under this Agreement, the Indenture, the Registration Rights Agreement or the Securities, except such as may be required by the securities or Blue Sky laws of the various states or other jurisdictions in connection with the offer and sale of the Securities and by Federal and state securities laws with respect to the Company’s obligations under the Registration Rights Agreement.

(k) There has not occurred any material adverse change, or any development involving a prospective material adverse change, in the financial condition, or in the earnings, business or operations of the Company and its subsidiaries, taken as a whole, from that set forth in the Preliminary Memorandum provided to prospective purchasers of the Securities.

(l) There are no legal or governmental proceedings, actions, suits, inquiries or investigations pending or threatened to which the Company or any of its subsidiaries is a party or to which any of the properties of the Company or any of its subsidiaries is subject other than (i) proceedings accurately described in all material respects in each Memorandum and (ii) proceedings that would not have a material adverse effect on the Company and its subsidiaries, taken as a whole, or on the power or ability of the Company to perform its obligations under this Agreement, the Indenture, the Registration Rights Agreement or the Securities or to consummate the transactions contemplated by the Final Memorandum.

(m) The Company and its subsidiaries are in compliance with any and all applicable foreign, federal, state and local laws and regulations relating to the protection of human health and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants except where such non-compliance would not, singly or in the aggregate, have a material adverse effect on the Company and its subsidiaries, taken as a whole.

(n) The Company is not, and solely after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Final Memorandum will not be, required to register as an “investment company” as such term is defined in the Investment Company Act of 1940, as amended (the “ 1940 Act ”).

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(o) Neither the Company nor any affiliate (as defined in Rule 501(b) of Regulation D under the Securities Act, an “ Affiliate ”) of the Company has directly, or through any agent, (i) sold, offered for sale, solicited offers to buy or otherwise negotiated in respect of, any security (as defined in the Securities Act) which is or will be integrated with the sale of the Securities in a manner that would require the registration under the Securities Act of the Securities or (ii) offered, solicited offers to buy or sold the Securities by any form of general solicitation or general advertising (as those terms are used in Regulation D under the Securities Act) or in any manner involving a public offering within the meaning of Section 4(2) of the Securities Act.

(p) It is not necessary in connection with the offer, sale and delivery of the Securities to the Initial Purchasers in the manner contemplated by this Agreement to register the Securities under the Securities Act or to qualify the Indenture under the Trust Indenture Act of 1939, as amended.

(q) The Securities satisfy the requirements set forth in Rule 144A(d)(3) under the Securities Act.

(r) Each of the Company and its subsidiaries owns or possesses, or can acquire on reasonable terms, all adequate patents, patent rights, licenses, inventions, copyrights, know how (including trade secrets and other unpatented and/or unpatentable proprietary or confidential information, systems or procedures), trademarks, service marks and trade names necessary to carry on the business now operated by them, and neither the Company nor any of its subsidiaries has received any notice of infringement of or conflict with asserted rights of others with respect to any of the foregoing which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would have a material adverse affect on the Company and its subsidiaries, taken as a whole.

(s) The Company and each of its subsidiaries are insured by insurers of recognized financial responsibility against such losses and risks and in such amounts as are prudent and customary in the businesses in which they are engaged; neither the Company nor any of its subsidiaries has been refused any insurance coverage sought or applied for; and neither the company nor any of its subsidiaries has any reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage from similar insurers as may be necessary to continue its business at a cost that would not have a material adverse affect on the Company and its subsidiaries, taken as a whole, except as described in the Memorandum.

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(t) The Company and its subsidiaries possess all certificates, authorizations, licenses, approvals, consents, permits and other authorizations issued by the appropriate federal, state or foreign regulatory authorities necessary to conduct their respective businesses, and neither the Company nor any of its subsidiaries has received any notice of proceedings relating to the revocation or modification of any such certificate, authorization, licenses, approval, consent, permit or other authorization which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would have a material adverse affect on the Company and its subsidiaries, taken as a whole, except as described in the Memorandum.

(u) The Company and each of its subsidiaries maintain a system of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles and to maintain asset accountability; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

(v) The Company has established and maintained disclosure controls and procedures (as defined in Exchange Act Rules 13a-14 and 15d-14) that are adequate and effective and designed to ensure that material information relating to the Company, including its consolidated subsidiaries, is made known to its chief executive officer and chief financial officer by others within those entities.

(w) The consolidated financial statements incorporated by reference in the Memorandum, together with related schedules and notes, present fairly in all material respects the financial position of the Company and its consolidated subsidiaries at the dates indicated and the statement of operations and stockholders’ equity and cash flows of the Company and its consolidated subsidiaries for the periods specified, said financials have been prepared in accordance with generally accepted accounting principles (“ GAAP ”) applied on a consistent basis throughout the periods involved, except as disclosed therein; and the other financial information and data set forth in the Memorandum present fairly, in all material respects, the information shown therein and have been compiled on a basis consistent with that of the audited financial statements included or incorporated by reference in the Memorandum.

(x) The Company and its subsidiaries have good and marketable title in fee simple to all real property and good and marketable

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title to all personal property owned by them which is material to the business of the Company and its subsidiaries, in each case free and clear of all liens, encumbrances and defects except such as are described in the Memorandum or such as do not materially affect the value of such property and do not interfere with the use made and proposed to be made of such property by the Company and its subsidiaries; and any real property and buildings held under lease by the Company and its subsidiaries are held by them under valid, subsisting and enforceable leases with such exceptions as are not material and do not interfere with the use made and proposed to be made of such property and buildings by the Company and its subsidiaries, in each case except as described in the Memorandum.

(y) Each of BlackRock Advisors, Inc., BlackRock Institutional Management Corporation, BlackRock Financial Management, Inc., BlackRock (Japan), Inc., BlackRock Capital Management, Inc., BlackRock HPB Management, LLC, State Street Research Management Company, BlackRock Realty Advisors, Inc. and BlackRock International Ltd. (together, the “ Investment Adviser Subsidiaries ”) is duly registered as an investment adviser under the Investment Advisers Act of 1940, as amended (the “ Advisers Act ”) and none of the Investment Adviser Subsidiaries is prohibited by any provision of the Advisers Act or the 1940 Act, or the respective rules and regulations thereunder, from acting as an investment adviser. The Investment Adviser Subsidiaries are the only direct or indirect subsidiaries of the Company required to be registered as investment advisers under the Advisers Act. Each of the Investment Adviser Subsidiaries is duly registered, licensed or qualified as an investment adviser in each jurisdiction where the conduct of its business requires such registration and is in compliance with all federal, state and foreign laws requiring any such registration, licensing or qualification or is subject to no material liability or disability by reason of the failure to be so registered, licensed or qualified in any such jurisdiction or to be in such compliance. None of the Company or its other direct or indirect subsidiaries is required to be registered, licensed or qualified as an investment adviser under the laws requiring any such registration, licensing or qualification in any jurisdiction in which it or such other subsidiaries conduct business or is subject to material liability or disability by reason of the failure to be so registered, licensed or qualified.

(z) Each of BlackRock Investments, Inc. and State Street Research Investment Services (the “ Broker Dealer Subsidiaries ”) is duly registered, licensed or qualified as a broker-dealer under the Exchange Act, and under the securities laws of each jurisdiction where the conduct of its business requires such registration and is in compliance with all federal, state and foreign laws requiring such registration, licensing or

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qualification or is subject to no material liability or disability by reason of the failure to be so registered, licensed or qualified in any such jurisdiction or to be in such compliance. Each of the Broker Dealer Subsidiaries is a member in good standing of NASD and each other self-regulatory organization where the conduct of its business requires such membership. Neither the Company nor any of the Company’s other direct or indirect subsidiaries is required to be registered, licensed or qualified as a broker-dealer under the laws requiring any such registration, licensing or qualification in any jurisdiction in which it or such other subsidiaries conduct business or is subject to any material liability or disability by reason of the failure to be so registered, licensed or qualified except where the failure to be so registered, licensed or qualified would not have a material adverse affect on the Company and its subsidiaries, taken as a whole.

(aa) Each of the Investment Adviser Subsidiaries and the Broker Dealer Subsidiaries is, has been and will upon consummation of the transactions contemplated herein be, in compliance with, and each such entity has received no notice of any kind of any violation of, (A) all laws, regulations, ordinances and rules (including those of any non-governmental self-regulatory agencies) applicable to it or its operations relating to investment advisory or broker-dealer activities, as the case may be, and (B) all other laws, regulations, ordinances and rules applicable to it and its operations, except, in either case, where any failure to comply with any such law, regulation, ordinance or rule would not have, individually or in the aggregate, a material adverse effect on the Company and its subsidiaries taken as a whole.

(bb) Each entity for which the Investment Adviser Subsidiaries acts as investment adviser and, to the best knowledge of the Investment Adviser Subsidiaries, each entity for which the Investment Adviser Subsidiaries acts as sub-adviser and, in each case, which is required to be registered with the Commission as an investment company under the 1940 Act (a “ Fund ”) is, and upon consummation of the transactions contemplated